| 1. |
- Ahmed, Noman, et al.
(författare)
-
A computationally efficient continuous model for the modular multilevel converter
- 2014
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Ingår i: IEEE Journal of Emerging and Selected Topics in Power Electronics. - : IEEE. - 2168-6777. ; 2:4, s. 1139-1148
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Tidskriftsartikel (refereegranskat)abstract
- Simulation models of the modular multilevel converter (MMC) play a very important role for studying the dynamic performance. Detailed modeling of the MMC in electromagnetic transient simulation programs is cumbersome, as it requires high computational effort and simulation time. Several averaged or continuous models proposed in the literature lack the capability to describe the blocked state. This paper presents a continuous model, which is capable of accurately simulating the blocked state. This feature is very important for accurate simulation of faults. The model is generally applicable, although it is particularly useful in high-voltage dc applications.
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| 2. |
- Antonopoulos, Antonios, et al.
(författare)
-
Modular multilevel converter AC motor drives with constant torque from zero to nominal speed
- 2014
-
Ingår i: IEEE transactions on industry applications. - 0093-9994 .- 1939-9367. ; 50:3, s. 1982-1993
-
Tidskriftsartikel (refereegranskat)abstract
- Modular multilevel converters are shown to have a great potential in the area of medium-voltage drives. Low-distortion output quantities combined with low average switching frequencies for the semiconductor devices create an ideal combination for very high-efficiency drives. However, the large number of devices and capacitors that have to conduct the fundamental-frequency current require more complex converter control techniques than its two-level counterpart. Special care needs to be taken for starting and operation at low speeds, where the low-frequency current may cause significant unbalance between the submodule capacitor voltages and disturb the output waveforms. In this paper, principles for converter operation with high torque in the whole speed range are investigated. Experimental results from a down-scaled 12-kVA prototype converter running a loaded motor at various speeds between standstill and the rated speed are also provided.
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| 3. |
- Bakas, Panagiotis, et al.
(författare)
-
Design considerations and comparison of hybrid line-commutated and cascaded full-bridge converters with reactive-power compensation and active filtering capabilities
- 2019
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- This paper compares two hybrid topologies that combine the line-commutated converter (LCC) with cascaded full-bridge (FB) converters. The latter are utilized for compensating the reactive power and filtering the current harmonics of the LCC. The method that was developed for dimensioning these hybrid topologies is presented in detail. This method is utilized for calculating the arm voltage and current waveforms, which are used to estimate other important quantities, such as conduction losses and energy variations. Finally, the studied converters are compared in terms of voltage/current ratings, semiconductor requirements, conduction losses, and energy variations.
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| 4. |
- Bakas, Panagiotis, et al.
(författare)
-
Hybrid alternate-common-arm converter with director thyristors - Impact of commutation time on the active-power capability
- 2019
-
Ingår i: 2019 21st European Conference on Power Electronics and Applications, EPE 2019 ECCE Europe. - Genova, Italy : Institute of Electrical and Electronics Engineers Inc.. - 9789075815313 - 9781728123615
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Konferensbidrag (refereegranskat)abstract
- This paper investigates the impact of the thyristor commutation time on the peak currents and the active-power capability of the hybrid alternate-common-arm converter (HACC). This converter employs director thyristors for the alternate connection of a common arm in parallel to the main arms. The parallel connection enables current sharing among the arms, which allows the HACC to transfer higher output power without increasing the peak arm current. It is shown that the active-power capability of the HACC is doubled for a certain current-sharing factor, which, however, is altered by the thyristor commutation time. Therefore, the impact of the commutation time on the active-power capability of the HACC is investigated theoretically. Finally, this analysis is verified by simulation results.
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| 5. |
- Bakas, Panagiotis, et al.
(författare)
-
Hybrid alternate-common-arm converter with high power capability : Potential and limitations
- 2020
-
Ingår i: IEEE transactions on power electronics. - : IEEE. - 0885-8993 .- 1941-0107. ; 35:12, s. 12909-12928
-
Tidskriftsartikel (refereegranskat)abstract
- This paper studies a new hybrid converter thatutilizes thyristors and full-bridge (FB) arms for achieving higherpower capability than the full-bridge (FB) modular multilevel converter (MMC) with reduced semiconductor requirements. The study covers the theoretical analysis of the energy balancing,the dimensioning principles, the maximum power capability, and the limitations imposed by the discontinuous operation of theconverter. Based on the analysis of these aspects, the theoretical analysis is concluded by identifying the design constraints that need to be fulfilled for achieving the maximum power capabilityof the converter. It is concluded that the maximum power capability can be achieved for a certain range of modulation indices and is limited by both the commutation time of the thyristors andthe power angle. Finally, simulation and experimental results that confirm the theoretical analysis and the feasibility of the studied converter are presented and discussed.
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| 6. |
- Bakas, Panagiotis, et al.
(författare)
-
Hybrid Converter With Alternate Common Arm and Director Thyristors for High-Power Capability
- 2018
-
Ingår i: 2018 20th European Conference on Power Electronics and Applications (EPE’18 ECCE Europe).
-
Konferensbidrag (refereegranskat)abstract
- This paper presents the basic operating principles of a new hybrid converter that combines thyristors and full-bridge (FB) arms for achieving high active-power capability. This converter consists of a modular multilevel converter (MMC) equipped with additional common arms, which alternate between the upper and lower dc poles. This alternation is achieved by the thyristors that are utilized as director switches and allow the parallel connection of the common arms and the arms of the MMC. The main contributions of this paper are the analysis of the operating principles, the simulation verification of the functionality of the proposed converter, and the comparison of the latter with the full-bridge modular multilevel converter (FB-MMC).
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| 7. |
- Bakas, Panagiotis
(författare)
-
Hybrid Converters for HVDC Transmission
- 2019
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The line-commutated converter (LCC) and the voltage-source converter (VSC) are the two main converter technologies utilized in high-voltage direct current (HVDC) transmission applications. Depending on the application requirements, one technology might be more advantageous than the other. On the one hand, the LCC features technological maturity, high efficiency, and high power-transfer capability, but it lacks the ability to independently control active and reactive power and to ride through ac faults. On the other hand, the VSC overcomes the shortcomings of the LCC and offers more functionality, as it features the ability to independently control active and reactive power, ac-fault ride through capability, black-start capability, and superior harmonic performance. Yet, it is less mature, less efficient, and has lower power-transfer capability than the LCC. Thus, the combination of the LCC and the VSC topologies could yield hybrid converters that leverage the complementary characteristics of both technologies and thus are optimized for HVDC applications. Therefore, the main objective of this thesis is to investigate existing and derive new hybrid converters that combine the complementary characteristics of the LCC and VSC technologies.The hybrid converters investigated in this thesis are divided in two main categories, namely: (a) current-source; and (b) voltage-source hybrid converters. The former category includes hybrid converters that are based on the LCC structure and utilize a VSC part either for compensating the reactive power consumed by the LCC, or for active filtering of the LCC current harmonics, or for independently controlling active and reactive power, or for achieving a combination of these functionalities. Four different current-source hybrid converters have been investigated and compared in terms of functionality, conduction losses, and semiconductor requirements.The second category includes more complex circuits that combine thyristors and modular VSC elements in ways that enable these hybrid converters to operate as VSCs and to achieve high active-power capability. Two new voltage-source hybrid converters are analyzed and compared in terms of active-power capability, semiconductor requirements, and controllability. This study reveals that the hybrid alternate-common-arm converter (HACC) is the most interesting circuit; thus, an in-depth analysis is performed for this converter. The theoretical analysis shows that, under certain operating conditions, the HACC can transfer twice the active power of the full-bridge modular multilevel converter (FB-MMC) with lower semiconductor rating per unit of active power. Yet, if the total commutation time of the thyristors and/or the power angle are increased beyond certain values, the active-power capability of the HACC is reduced. Finally, simulation and experimental results are provided in order to verify the theoretical analysis and prove the feasibility of the HACC.
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| 8. |
- Bessegato, Luca, et al.
(författare)
-
A Method for the Calculation of the AC-Side Admittance of a Modular Multilevel Converter
- 2018
-
Ingår i: IEEE transactions on power electronics. - 0885-8993 .- 1941-0107.
-
Tidskriftsartikel (refereegranskat)abstract
- Connecting a modular multilevel converter to anac grid may cause stability issues, which can be assessed byanalyzing the converter ac-side admittance in relation to the gridimpedance. This paper presents a method for calculating theac-side admittance of modular multilevel converters, analyzingthe main frequency components of the converter variables individually.Starting from a time-averaged model of the converter,the proposed method performs a linearization in the frequencydomain, which overcomes the inherent nonlinearities of theconverter internal dynamics and the phase-locked loop usedin the control. The ac-side admittance obtained analytically isfirstly validated by simulations against a nonlinear time-averagedmodel of the modular multilevel converter. The tradeoff posedby complexity of the method and the accuracy of the result isdiscussed and the magnitude of the individual frequency componentsis shown. Finally, experiments on a down-scaled prototypeare performed to validate this study and the simplification onwhich it is based.
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| 9. |
- Bessegato, Luca, et al.
(författare)
-
Ac-side admittance calculation for modular multilevel converters
- 2017
-
Ingår i: 2017 IEEE 3rd International Future Energy Electronics Conference and ECCE Asia, IFEEC - ECCE Asia 2017. - : Institute of Electrical and Electronics Engineers (IEEE). - 9781509051571 ; , s. 308-312
-
Konferensbidrag (refereegranskat)abstract
- Power electronic converters may interact with the grid, thereby influencing dynamic behavior and resonances. Impedance and passivity based stability criteria are two useful methods that allow for studying the grid-converter system as a feedback system, whose behavior is determined by the ratio of grid and converter impedances. In this paper, the ac-side admittance of the modular multilevel converter is calculated using harmonic linearization and considering five specific frequency components of the converter variables. The proposed model features remarkable accuracy, verified through simulations, and insight into the influence of converter and control parameters on the admittance frequency characteristics, which is useful for understanding grid-converter interaction and designing the system.
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| 10. |
- Bessegato, Luca, et al.
(författare)
-
Control and Admittance Modeling of an AC/AC Modular Multilevel Converter for Railway Supplies
- 2019
-
Ingår i: IEEE transactions on power electronics. - 0885-8993 .- 1941-0107.
-
Tidskriftsartikel (refereegranskat)abstract
- Modular multilevel converters (MMCs) can be configured to perform ac/ac conversion, which makes them suitable as railway power supplies. In this paper, a hierarchical control scheme for ac/ac MMCs for railway power supplies is devised and evaluated, considering the requirements and the operating conditions specific to this application. Furthermore, admittance models of the ac/ac MMC are developed, showing how the suggested hierarchical control scheme affects the three-phase and the single-phase side admittances of the converter. These models allow for analyzing the stability of the interconnected system using the impedance-based stability criterion and the passivity-based stability assessment. Finally, the findings presented in this paper are validated experimentally, using a down-scaled MMC.
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| 11. |
- Bessegato, Luca, et al.
(författare)
-
Effects of Control on the AC-Side Admittance of a Modular Multilevel Converter
- 2019
-
Ingår i: IEEE transactions on power electronics. - : IEEE Press. - 0885-8993 .- 1941-0107. ; 34:8, s. 7206-7220
-
Tidskriftsartikel (refereegranskat)abstract
- The stability of a modular multilevel converter connected to an ac grid can be assessed by analyzing the converter ac-side admittance in relation to the grid impedance. The converter control parameters have a strong impact on the admittance and they can be adjusted for achieving system stability. This paper focuses on the admittance-shaping effect produced by different current-control schemes, either designed on a per-phase basis or in the $dq$ frame using space vectors. A linear analytical model of the converter ac-side admittance is developed, including the different current-control schemes and the phase-locked loop. Different solutions for computing the insertion indices are also analyzed, showing that for a closed-loop scheme a compact expression of the admittance is obtained. The impact of the control parameters on the admittance is discussed and verified experimentally, giving guidelines for designing the system in terms of stability. Moreover, recommendations on whether a simplified admittance expression could be used instead of the detailed model are given. The findings from the admittance-shaping analysis are used to recreate a grid-converter system whose stability is determined by the control parameters. The developed admittance model is then used in this experimental case study, showing that the stability of the interconnected system can be assessed using the Nyquist stability criterion.
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| 12. |
- Bessegato, Luca, 1989-
(författare)
-
Modeling of Modular Multilevel Converters for Stability Analysis
- 2019
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Modular multilevel converters (MMCs) have recently become the state-of-the-art solution for various grid-connected applications, such as high-voltage direct current (HVDC) systems and flexible alternating current transmission systems (FACTS). Modularity, scalability, low power losses, and low harmonic distortion are the outstanding properties that make MMCs a key technology for a sustainable future. The main objective of this thesis is the modeling of grid-connected MMCs for stability analysis. The stability of the interconnected system, formed by the converter and the ac grid, can be assessed by analyzing the converter ac-side admittance in relation to the grid impedance. Therefore, a method for the calculation of the ac-side admittance of MMCs is developed. This method overcomes the nonlinearities of the converter dynamics and it can be easily adapted to different applications. Moreover, the effects of different control schemes on the MMC ac-side admittance are studied, showing how the converter admittance can be reshaped. This is a useful tool for system design, because it shows how control parameters can be selected to avoid undesired grid-converter interactions. This thesis also studies ac/ac MMCs for railway power supplies, which are used in countries with a low-frequency railway grid, such as Germany (16.7 Hz) and Sweden (16 2/3 Hz). A hierarchical control scheme for these converters is devised and evaluated, considering the requirements and the operating conditions specific to this application. Furthermore, admittance models of the ac/ac MMC are developed, showing how the suggested hierarchical control scheme affects the three-phase and the single-phase side admittances of the converter. For computing the insertion indices, an open-loop scheme with sum capacitor voltage estimation is applied to the ac/ac MMC. Lyapunov stability theory is used to prove the asymptotic stability of the converter operated with the proposed control method. This specific open-loop scheme is also adapted to a modular multilevel matrix converter, which performs three-to-three phase direct conversion. Finally, this thesis presents the design of a down-scaled MMC prototype for experimental verification, rated at 10 kW with 30 full-bridge submodules. The hardware and the software are designed to be easily reconfigurable, which makes the converter suitable for different research projects focused on MMCs. Experiments on this down-scaled MMC are used to support and validate the key results presented throughout the thesis.
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| 13. |
- Ciftci, Baris, et al.
(författare)
-
Wireless control of modular multilevel converter autonomous submodules : 23rd European Conference on Power Electronics and Applications
- 2021
-
Ingår i: Proceedings 23rd European Conference on Power Electronics and Applications. - : Institute of Electrical and Electronics Engineers (IEEE).
-
Konferensbidrag (refereegranskat)abstract
- The wireless control of modular multilevel converter (MMC) submodules might offer advantages for MMCs with a high number of submodules. However, the control system should tolerate the stochastic nature of the wireless communication, continue the operation flawlessly or, at least, avoid overcurrents, overvoltages, and component failures. The previously proposed control methods enabled to control the submodules wirelessly with consecutive communication errors up to hundreds of control cycles. The submodule control method in this paper facilitates the MMC to safely overcome communication errors that last longer and when the MMC experiences significant electrical disturbances during the errors. The submodules are proposed to operate autonomously by implementing a replica of the central controller in the submodules and drive the replicas based on the local variables and the previously received data. The simulation and experimental results verify the proposed control method.
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| 14. |
- Ciftci, Baris, 1987-
(författare)
-
Wireless Control of Modular Multilevel Converter Submodules
- 2022
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The modular multilevel converter (MMC) has extensively been used in high-voltage, high-power applications such as high-voltage dc transmission systems and flexible alternating current transmission systems. The control of MMC submodules is conventionally realized using wired communication systems. However, MMCs in high-power applications consist of up to thousands of submodules. Significant issues arise with the wired communication systems in the MMC valve halls of these applications, including considerable workforce and time requirements for the cable deployment.The main objective of this thesis is to propose a wireless control method for MMC submodules. Wireless communication has fundamental differences from wired communication regarding latency and reliability. Since the control of submodules is a time-critical process, the MMC internal control and modulation methods used with wired communication systems are not directly applicable to wireless communication systems.A wireless control method is proposed for the MMC submodules. The proposal is based on the distributed control of MMCs, where the control and modulation tasks are shared between a central controller and the submodule controllers. The fundamental data to transmit wirelessly is the insertion indices for each of the MMC arms and the synchronization signal for the modulation carriers generated in the submodules. The amount and the cycle time of the time-critical wireless data are in the range of tens of bytes and hundreds of microseconds and are independent of the total number of submodules. The proposal is experimentally verified on a laboratory-scale MMC.The original proposal is enhanced against the communication errors such that the submodules suffering from the errors can continue their modulation smoothly and uninterruptedly. If continuing the modulation is not feasible in case of very long-lasting communication errors, the submodules switch to a safe operation mode to avoid faults in the MMC. Moreover, wireless control of submodules with ac-side faults is analyzed. The MMC rides through the ac-side faults even with a complete loss of communication before or after the fault instant.A wireless communication network based on 5G New Radio is designed theoretically for an example full-scale MMC valve hall according to the proposed wireless control method. It is evaluated that the latency and reliability of the proposed communication solution can correspond to the proposed wireless control method requirements. Finally, the electromagnetic interference from the MMC submodules is measured as below 500 MHz, which does not affect a wireless communication held in the multi-GHz range.
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| 15. |
- Ciftci, Baris, et al.
(författare)
-
Wireless control of modular multilevel converter submodules under ac-side faults
- 2021
-
Konferensbidrag (refereegranskat)abstract
- Wireless control of modular multilevel converter (MMC) submodules has been offered recently with potentially lower cost and higher availability advantages for the converter station. In this paper, the wireless control of MMC submodules under ac-side faults is investigated. The central controller of the MMC is equipped for the unbalanced grid conditions. Local current controllers in the submodules are operated autonomously in case of loss of wireless communication during the fault. A set of simulations with single line-to-ground, line-to-line, and three-phase-to-ground faults reveal that the MMC rides through the faults in all the cases with the expected communication conditions or when the communication is lost before or after the fault instant.
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| 16. |
- Ciftci, Baris, et al.
(författare)
-
Wireless Control of Modular Multilevel Converter Submodules With Communication Errors
- 2022
-
Ingår i: IEEE Transactions on Industrial Electronics. - : Institute of Electrical and Electronics Engineers (IEEE). - 0278-0046 .- 1557-9948. ; 69:11, s. 11644-11653
-
Tidskriftsartikel (refereegranskat)abstract
- Wireless control of modular multilevel converter (MMC) submodules can benefit from different points of view, such as lower converter cost and shorter installation time. In return for the advantages, the stochastic performance of wireless communication networks necessitates an advanced converter control system immune to the losses and delays of the wirelessly transmitted data. This paper proposes an advancement to the distributed control of MMCs to utilize in wireless submodule control. Using the proposed method, the operation of the MMC continues smoothly and uninterruptedly during wireless communication errors. The previously proposed submodule wireless control concept relies on implementing the modulation and individual submodule-capacitor-voltage control in the submodules using the insertion indices transmitted from a central controller. This paper takes the concept as a basis and introduces to synthesize the indices autonomously in the submodules during the communication errors. This new approach allows the MMC continue its operation when one, some, or all submodules suffer from communication errors for a limited time. The proposal is validated experimentally on a laboratory-scale MMC.
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| 17. |
- Ilves, Kalle, et al.
(författare)
-
A submodule implementation for parallel connection of capacitors in modular multilevel converters
- 2013
-
Ingår i: Power Electronics and Applications (EPE), 2013 15th European Conference on.
-
Konferensbidrag (refereegranskat)abstract
- The modular multilevel converter is a suitable converter topology for high-voltage high-power applications and consists of series-connected submodules. Typically, these submodules are half-bridges with dc capacitors. A voltage ripple in the submodule capacitors is inevitable due to the current flowing in the arms. The converter should therefore be controlled in such a way that the capacitor voltages are kept balanced and close to their nominal values over time. This paper presents a new submodule circuit which alleviates the balancing of the capacitor voltages. The proposed submodule circuit consists of two capacitors and eight switches, forming a three-level submodule. Ideally, the voltage and current rating of the switches can be chosen such that the combined power rating of the semiconductors is the same as for equivalent half-bridge submodules. The proposed submodule circuit provides the possibility of connecting the two capacitors in parallel when the intermediate voltage level is used. This will reduce the capacitor voltage ripple, especially at low switching frequencies and thus allow for a reduction of the size, weight, and cost of the submodule capacitors. The proposed submodule circuit is validated by both simulation results and experiments on a laboratory prototype. It is found that the parallel connection of the submodule capacitors will, in fact, significantly improve the balancing of the capacitor voltages.
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| 18. |
- Ilves, Kalle, et al.
(författare)
-
Analysis and operation of modular multilevel converters with phase-shifted carrier PWM
- 2013
-
Ingår i: 2013 IEEE Energy Conversion Congress and Exposition, ECCE 2013. - : IEEE. - 9781479903351 ; , s. 396-403
-
Konferensbidrag (refereegranskat)abstract
- The modular multilevel converter is a suitable topology for high-voltage high-power applications since the cascaded submodules can generate high-voltage waveforms with excellent harmonic performance at low switching frequencies. Many publications have been presented on the modulation and control of this converter type, some of which are based on phase-shifted carrier modulation. This paper presents an analysis of how the switching frequency affects the capacitor voltages, circulating current and alternating voltage at phase-shifted carrier modulation. It is found that integer multiples of the fundamental frequency should be avoided as they can cause the capacitor voltages to diverge. Suitable switching frequencies are then defined for which the arm and line quantities will be periodic and symmetric in the upper and lower arms. The theoretical results are then validated by both simulations and experimental results.
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| 19. |
- Norrga, Staffan, 1968-, et al.
(författare)
-
Decoupled steady-state model of the modular multilevel converter with half-bridge cells
- 2012
-
Konferensbidrag (refereegranskat)abstract
- Modular multilevel converters, based on cascading of halfbridge converter cells, can combine low switching frequency with low harmonic interference. They can be designed for high operating voltages without direct series connection of semiconductor elements. This has led to a rapid adoption within high-power applications such as HVDC, STATCOM and railway interties. Analysing the operation of these converters in the frequency domain poses a few challenges due to the presence of significant low-order harmonic voltages in the cell capacitors. This paper presents a frequency-domain model of the MMC converter with halfbridge cells, based on a two-stage approach. First, the circuit equations are decoupled by a simple linear transformation, whereby the circuit schematic can be separated into a dc-side and an ac-side part. Second, the switching operation within the phase arms is modelled in the frequency domain by iterated convolution. The model is verified against a timedomain simulation of a converter with ratings valid for HVDC applications. It is shown that the proposed methodology, where all calculations are made in the frequency domain, can accurately reproduce the results from the simulation.
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| 20. |
- Norrga, Staffan, 1968-, et al.
(författare)
-
Frequency-Domain Modeling of Modular Multilevel Converters With Application to Maximizing the Operating Region
- 2012
-
Ingår i: IECON 2012 - 38th Annual Conference on IEEE Industrial Electronics Society. - : IEEE. - 9781467324212 ; , s. 4967-4972
-
Konferensbidrag (refereegranskat)abstract
- Modular multilevel converters (MMC), based on cascading of half-bridge converter cells, can combine low switching frequency with low harmonic interference. They can be designed for high operating voltages without direct series connection of semiconductor elements. This has led to a rapid adoption within high-power applications such as high voltage direct current transmission, railway interties and medium voltage industrial motor drives. Analyzing the operation of these converters in the frequency domain poses a few challenges due to the presence of significant low-order harmonic voltages in the cell capacitors. This paper treats a frequency-domain methodology for computing inner variables of the MMC with half-bridge cells, based on a two-stage approach. First, the circuit equations are decoupled by a simple linear transformation, whereby the circuit schematic can be separated into a dc-side and an ac-side part. Second, the variables of the cell strings are computed in the frequency domain by iterated convolution. It is shown that the proposed methodology, where all calculations are made in the frequency domain, can accurately reproduce the results from a PSCAD simulation. Furthermore, the model is successfully employed as part of an optimization algorithm for maximizing the power handling capability of the converter by appropriately controlling the circulating current and zero-sequence ac-side voltage. Results from this work point to significant possibilities for improvement.
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| 21. |
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| 22. |
- Ahmed, Noman, et al.
(författare)
-
Validation of the continuous model of the modular multilevel converter with blocking/deblocking capability
- 2012
-
Ingår i: AC and DC Power Transmission (ACDC 2012), 10th IET International Conference on. - : Institution of Engineering and Technology. - 9781849197007
-
Konferensbidrag (refereegranskat)abstract
- This paper presents the continuous model for the Modular Multilevel Converter (M2C). The model operates in two modes, either operating as a voltage source in deblocked mode or as a rectifying diode bridge in blocked mode. The model is validated by comparison with a detailed M2C model having 36 submodules per arm, using different control strategies. The comparison is based on time-domain simulations in PSCAD/EMTDC. The continuous model shows a very good agreement with the detailed model.
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| 23. |
- Angquist, Lennart, et al.
(författare)
-
Low-Cost Ultra-Fast DC Circuit-Breaker Power electronics integrated with mechanical switchgear
- 2018
-
Ingår i: 2018 IEEE INTERNATIONAL CONFERENCE ON INDUSTRIAL TECHNOLOGY (ICIT). - : IEEE. - 9781509059492 ; , s. 1708-1713
-
Konferensbidrag (refereegranskat)abstract
- The paper describes a concept for fast-acting circuit-breaker using vacuum interrupter (VI) assisted by a power-electronic converter with low output voltage. The converter excites a passive resonant circuit to create current zero-crossing in the arc in the VI to make it extinguish the current. A fast-acting actuator using a Thomson coil separates the contacts in a few milliseconds. The principle is outlined, and a laboratory prototype is described. In experiments 10 kA was successfully interrupted against 9 kV in 3 ms.
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| 24. |
- Arévalo-Soler, Josep, et al.
(författare)
-
Dynamic Converter Control Role Configuration in Grid of Grids
- 2023
-
Ingår i: 2023 25th European Conference on Power Electronics and Applications, EPE 2023 ECCE Europe. - : Institute of Electrical and Electronics Engineers (IEEE).
-
Konferensbidrag (refereegranskat)abstract
- The control role of power converters conforming an HVDC link is generally static, i.e. changing the control role of the power converters is not considered in the power system operation. In this paper a lab-scaled demonstration on the control role reconfiguration while an AC/DC/AC link is in operation is presented.
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| 25. |
- Augustin, Tim, et al.
(författare)
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Modelling of HVDC breakers for HVDC grid simulations
- 2017
-
Ingår i: IET Conference Publications. - : Institution of Engineering and Technology.
-
Konferensbidrag (refereegranskat)abstract
- This paper deals with the modelling of high-voltage direct current (HVDC) breakers in PSCAD. The models are aimed at HVDC grid simulation and are kept as simple as possible. An overview is given over recently proposed HVDC breaker concepts. Assumptions and simplifications are explained as well. The main result is that even these simplified models are too detailed for grid simulations. The reason for this is that from a grid perpective the only thing that matters is when the metal-oxide varistor is inserted. The models can be used to estimate interruption times.
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| 26. |
- Augustin, Tim, et al.
(författare)
-
Transient Behaviour of VSC-HVDC Links with DC Breakers Under Faults
- 2017
-
Ingår i: 2017 19th European Conference on Power Electronics and Applications (EPE'17 ECCE EUROPE). - : Institute of Electrical and Electronics Engineers (IEEE). - 9789075815276
-
Konferensbidrag (refereegranskat)abstract
- In future high-voltage direct current (HVDC) systems, a large number of HVDC breakers will be required.In this paper, the influence of HVDC breakers on the transient performance of point-to-point HVDC links in both asymmetrical and symmetrical monopolar configuration with half-bridge modular multilevel converters is studied with simulations in PSCAD. As HVDC breakers, the active resonant breaker and ABB’s hybrid breaker are considered. The analyzed scenarios include DC line faults, DC bus faults, and AC faults between the converter and the transformer. The highest DC breaking capability is required during DC line faults in the asymmetric and symmetric monopole. The converter stress is highest for DC bus faults and unbalanced converter AC faults in the asymmetric monopole and for DC bus pole-to-pole faults in the symmetric monopole. During DC pole-to-ground faults in the symmetric monopole, the HVDC breaker combined with DC side arrestors yields the lowest overvoltage stress on the cable of the healthy pole. The fault current shapes depend strongly on the interaction of the converter and the travelling waves on the lines, and differ from the fault current shapes in typical HVDC breaker test circuits. Furthermore, the active resonant breaker and the ABB hybrid breaker perform similarly in the used benchmarks due to the very fast DC line fault detection.
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| 27. |
- Baudoin, Antoine, et al.
(författare)
-
Experimental results from a Thomson-coil actuator for a vacuum interrupter in an HVDC breaker
- 2019
-
Ingår i: The Journal of Engineering. - : INST ENGINEERING TECHNOLOGY-IET. - 2051-3305. ; :17, s. 3527-3531
-
Tidskriftsartikel (refereegranskat)abstract
- Recent developments in high-voltage direct current transmission technology and the plans for multi-terminals motivate research efforts on the fast DC breaker. A novel concept to interrupt current up to several kiloamperes within a few milliseconds is presently under development, using a vacuum interrupter together with power electronics to create an artificial zero-crossing in the current through the switch. To achieve this objective, one critical component in the concept is an ultra-fast linear mechanical actuator. A prototype has been developed based on a Thomson coil. The experimental results are presented and show how a contact gap in a vacuum interrupter was effectively created in a controlled manner. Current of several kiloamperes was successfully interrupted within 3ms, thanks to the high-speed operation of the linear actuator.
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| 28. |
- Bessegato, Luca, 1989-, et al.
(författare)
-
Control and Admittance Modeling of an AC/AC Modular Multilevel Converter for Railway Supplies
- 2020
-
Ingår i: IEEE transactions on power electronics. - : IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC. - 0885-8993 .- 1941-0107. ; 35:3, s. 2411-2423
-
Tidskriftsartikel (refereegranskat)abstract
- Modular multilevel converters (MMCs) can be configured to perform ac/ac conversion, which makes them suitable as railway power supplies. In this paper, a hierarchical control scheme for ac/ac MMCs for railway power supplies is devised and evaluated, considering the requirements and the operating conditions specific to this application. Furthermore, admittance models of the ac/ac MMC are developed, showing how the suggested hierarchical control scheme affects the three-phase and the single-phase side admittances of the converter. These models allow for analyzing the stability of the interconnected system using the impedance-based stability criterion and the passivity-based stability assessment. Finally, the findings presented in this paper are validated experimentally, using a down-scaled MMC.
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| 29. |
- Bessegato, Luca, et al.
(författare)
-
Control of Direct AC/AC Modular Multilevel Converters Using Capacitor Voltage Estimation
- 2016
-
Ingår i: 2016 18TH EUROPEAN CONFERENCE ON POWER ELECTRONICS AND APPLICATIONS (EPE'16 ECCE EUROPE). - : IEEE.
-
Konferensbidrag (refereegranskat)abstract
- This paper applies a control method based on current control and sum-capacitor-voltage estimation to the direct ac/ac modular multilevel converter. As capacitor voltages are estimated, their measurements are not needed in the high-level control, which simplifies the communication between the main controller and the submodules of the converter. The stability of the internal dynamics of the converter, using the aforementioned control method, is studied using Lyapunov stability theory, proving that the system is globally asymptotically stable. The behavior of the converter is simulated focusing on three-phase 50 Hz to single-phase 16 (2)/(3) Hz conversion, which is typical for railway power supply systems of some European countries. Simulation results are in agreement with the expected behavior of the converter, both in steady-state and dynamic situations.
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| 30. |
- Bessegato, Luca, et al.
(författare)
-
Control of Modular Multilevel Matrix Converters Based on Capacitor Voltage Estimation
- 2016
-
Ingår i: IEEE 8th International Power Electronics and Motion Control Conference (IPEMC-ECCE Asia), 2016. - : IEEE. - 9781509012107 ; , s. 3447-3452
-
Konferensbidrag (refereegranskat)abstract
- In this paper, a control method based on capacitor voltage estimation is applied to the modular multilevel matrix converter topology. By using such control method, capacitor voltage measurement is not needed in the high-level control. A state-space model of the converter and the control method is developed. Lyapunov stability theory is used to prove global asymptotic stability of the internal dynamics of the converter. Simulation results showing the behavior of the converter in steady-state and dynamic situations are presented.
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| 31. |
- Bessegato, Luca, et al.
(författare)
-
Design of a Modular Multilevel Converter Prototype for Research Purposes
- 2018
-
Konferensbidrag (refereegranskat)abstract
- As modular multilevel converters gradually become the preferred topology for many high-voltage andhigh-power applications, they are widely studied among researchers, who need experimental results tovalidate their studies. This paper discusses the design of a down-scaled modular multilevel converterprototype for research purposes, equipped with 30 full-bridge submodules and 10 kW rating. The designof this prototype is aimed at safety, flexibility, orderliness, and compactness. The challenges posed by theimplementation of the converter prototype are examined, discussing the design of the prototype structure,the communication scheme, the full-bridge submodules, and the control hierarchy. The control systemis based on Xilinx Zynq system-on-chip, which integrates programmable logic and processing system,allowing for extensive computational capability as well as simple reconfiguration. Experimental resultsshowing the prototype in operation at nominal ratings are presented along with the devised graphical userinterface.
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| 32. |
- Blinov, Andrei, et al.
(författare)
-
High Gain DC-AC High-Frequency Link Inverter With Improved Quasi-Resonant Modulation
- 2022
-
Ingår i: IEEE Transactions on Industrial Electronics. - : Institute of Electrical and Electronics Engineers (IEEE). - 0278-0046 .- 1557-9948. ; 69:2, s. 1465-1476
-
Tidskriftsartikel (refereegranskat)abstract
- This article presents a high gain pure sine- wave inverter based on the full-bridge dc-ac high-frequency link cycloconverter topology for telecom or general-purpose applications. The improved quasi-resonant modulation method allows reduction of ringing and turn-off losses of the dc-side switches. This is achieved with minimal energy circulation and requires no multi-mode operation or extra auxiliary clamping circuits. The soft switching can be provided even if relatively large lossless snubber capacitors are connected across the input side transistors. Moreover, two of the switches at the ac side operate at fundamental frequency, while the rest feature zero current turn-off. A 48 V-DC to 230 V-AC, 1.2 kW sine-wave inverter prototype was developed to verify the proposed concept.
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| 33. |
- Blinov, Andrei, et al.
(författare)
-
Soft-Switching Modulation Method for Full-Bridge DC-AC HF-Link Inverter
- 2019
-
Ingår i: 45th annual conference of the ieee industrial electronics society (IECON 2019). - : IEEE. - 9781728148786 ; , s. 4417-4422
-
Konferensbidrag (refereegranskat)abstract
- This paper presents an improved modulation method for the cycloconverter stage of high frequency-link DC-AC inverters. By applying the quasi-resonant commutation mode during the entire operating period, the fast and reliable discharge of DC-side capacitances can be provided even if the output current is close to zero. This allows to ensure zero voltage switching (ZVS) conditions for the DC-side transistors, while applying small external snubber capacitors to reduce their turn-off losses. The proposed modulation strategy was significantly simplified and requires no external active auxiliary circuits or multi-mode operation. Moreover, two of the AC-side switches can operate at the fundamental frequency, while the rest operate with zero current switching (ZCS). The proposed modulation method is verified with mathematical analysis, simulation model and experimental prototype of full-bridge HF-link inverter.
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| 34. |
- Chaffey, Geraint, et al.
(författare)
-
Design of backup protection for the DC interconnection of adjacent point-to-point HVDC systems
- 2022
-
Ingår i: Proceedings 16th International Conference on Developments in Power System Protection, DPSP 2022. - : Institution of Engineering and Technology (IET). ; , s. 25-30
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- In order to provide additional flexibility in future power systems, it could be beneficial to connect existing point-to-point highvoltage direct-current (HVDC) systems at the DC-side into a multiterminal network. Such a network would allow increased operational flexibility, continued operation in case of maintenance, and could reduce the end-to-end losses in the overall system. The protection of such a system, however, poses interesting challenges with constraints which differ slightly from typical HVDC grid protection studies. This paper focuses on the trade-offs surrounding the backup protection strategy following failure of a DC circuit breaker in the primary protection role. For this particular application, where a control retrofit should be avoided, the focus is on enabling quicker recovery rather than attempting to maintain continuous operation on a charged and healthy network. Therefore, the functional requirements on the backup switchgear are in some respects reduced compared to that required for primary protection. The benefits of reduced voltage switchgear for this backup protection application are therefore investigated.
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| 35. |
- Chaffey, Geraint, et al.
(författare)
-
Requirements for functional testing of HVDC protection IEDs
- 2019
-
Konferensbidrag (refereegranskat)abstract
- Development of Intelligent Electronic Devices (IED) for HVDC protection is underway, driven in part by the prospective demands of future multiterminal HVDC systems. There is, however, no consensus on how to test the functionality of an HVDC protection IED. Successful operation of a future multivendor HVDC protection system requires functional specifications and harmonised test procedures for protection system components, including the protection IED. This paper presents an introduction to functional testing methods for HVDC protection IEDs. Evaluating the protection algorithm characteristic using synthetic waveforms is first performed, i.e. ’functional type testing’. Given that test procedures are in part dependent on the protection algorithm, tests are developed and presented for several algorithms. The behaviour of the IED in a power system simulation is then examined during generalised yet representative fault transients, i.e. equivalent to ’dynamic validation type testing’ of AC protection algorithms. The combination of functional and dynamic validation type testing allows the generalised functionality of the IED to be evaluated - testing the algorithm, hardware and software implementation, and overall performance. To provide examples of test procedures, an open-source HVDC IED prototype is tested in a hardware-in-the-loop configuration using a real-time simulator. The operation and accuracy of the protection characteristics are first examined, before the IED performance under representative waveforms is determined. Through tests of several non-unit line protection algorithms, it is shown that, depending on the algorithm applied, the IED is dependable for simulated faults within the protection zone, and secure during external faults. Moreover,the test configurations and procedures required to evaluate the functionality and the criteria for success are developed.
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| 36. |
- Chaffey, Geraint, et al.
(författare)
-
The Impact of Point-to-Point VSC-HVDC Protection on Short-Term AC System Voltage
- 2018
-
Ingår i: 2018 IEEE pes innovative smart grid technologies conference europe (ISGT-EUROPE). - : IEEE.
-
Konferensbidrag (refereegranskat)abstract
- Whilst point-to-point HVDC systems are presently protected from DC-side faults using circuit breakers at the AC-side of the converter stations, converters are unable to provide reactive power support to the AC system during the fault clearance. Implementing DC circuit breakers within the HVDC system could result in several benefits, including the near-continuous provision of reactive power to the AC systems. This paper compares HVDC system protection sequences using AC-side and DC-side protection, and evaluates the impact of these protection strategies on the AC voltage under varying AC-system configurations and varying power flow conditions.
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| 37. |
- Ciftci, Baris, 1987-, et al.
(författare)
-
A Proposal for Wireless Control of Submodules in Modular Multilevel Converters
- 2018
-
Konferensbidrag (refereegranskat)abstract
- The modular multilevel converter is one of the most preferred converters for high-power conversion applications. Wireless control of the submodules can contribute to its evolution by lowering the material and labor costs of cabling and by increasing the availability of the converter. However, wireless control leads to many challenges for the control and modulation of the converter as well as for proper low-latency high-reliability communication. This paper investigates the tolerable asynchronism between phase-shifted carriers used in modulation from a wireless control point of view and proposes a control method along with communication protocol for wireless control. The functionality of the proposed method is validated by computer simulations in steady state.
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| 38. |
- Ciftci, Baris, et al.
(författare)
-
Simple Distributed Control for Modular Multilevel Converters
- 2019
-
Ingår i: 2019 21st European Conference on Power Electronics and Applications, EPE 2019 ECCE Europe. - Brussels : European Power Electronics and Drives Association. - 9789075815306
-
Konferensbidrag (refereegranskat)abstract
- The central control of MMC becomes demanding in computation power and communication bandwidth as the number of submodules increase. Distributed control methods can overcome these bottlenecks. In this paper, a simple distributed control method together with synchronization of modulation carriers in the submodules is presented. The proposal is implemented on a lab-scale MMC with asynchronous-serial communication on a star network between the central and local controllers. It is shown that the proposed control method works satisfactorily in the steady state. The method can be applied as is to MMCs with any number of submodules per arm.
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| 39. |
- Ciftci, Baris, et al.
(författare)
-
Wireless Communication in Modular Multilevel Converters and Electromagnetic Interference Characterization
-
Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- The wireless control of modular multilevel converter (MMC) submodules was recently proposed. The success of the control depends on specialized control methods suitable for wireless communication and a properly designed wireless communication network in the MMC valve hall while aiming for low latency and high reliability. The wireless communication in the hall can be affected by the electromagnetic interference (EMI) of MMC submodules, voltage and current transients. In this article, firstly, a wireless communication network based on 5G New Radio is designed for an example full-scale MMC valve hall. After that, radiated EMI characteristics of MMC submodules with different voltage and current ratings and two dc circuit breakers are measured. The effects of EMI on wireless communication in the multi-GHz frequency band are tested. The interference from the components is confined below 500 MHz, and the wireless communication with 5825 MHz center frequency is not affected by the interference.
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| 40. |
- Ciftci, Baris, 1987-, et al.
(författare)
-
Wireless Communication in Modular Multilevel Converters and Electromagnetic Interference Characterization
- 2022
-
Ingår i: IEEE Access. - : Institute of Electrical and Electronics Engineers (IEEE). - 2169-3536. ; , s. 38189-38201
-
Tidskriftsartikel (refereegranskat)abstract
- The wireless control of modular multilevel converter (MMC) submodules was recently proposed. The success of the control depends on specialized control methods suitable for wireless communication and a properly designed wireless communication network in the MMC valve hall while aiming for low latency and high reliability. The wireless communication in the hall can be affected by the electromagnetic interference (EMI) of MMC submodules, voltage and current transients. In this article, firstly, a wireless communication network based on 5G New Radio is designed for an example full-scale MMC valve hall. After that, the radiated EMI characteristics of the MMC submodules with different voltage and current ratings and two dc circuit breakers are measured. The effects of EMI on wireless communication in the multi-GHz frequency band are tested. The interference from the components is confined below 500 MHz, and the wireless communication with 5825 MHz center frequency is not affected by the interference.
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| 41. |
- Ciftci, Baris, et al.
(författare)
-
Wireless Control of Modular Multilevel Converter Submodules
- 2021
-
Ingår i: IEEE transactions on power electronics. - : Institute of Electrical and Electronics Engineers (IEEE). - 0885-8993 .- 1941-0107. ; 36:7, s. 8439-8453
-
Tidskriftsartikel (refereegranskat)abstract
- Wireless control of modular multilevel converter (MMC) submodules offers several potential benefits to exploit, such as decreased converter costs and ease in converter installation. However, wireless control comes with several challenging engineering requirements. The control methods used with wired communication networks are not directly applicable to the wireless control due to the latency and reliability differences of wired and wireless networks. This article reviews the existing control architectures of MMCs and proposes a control and communication method for wireless submodule control. Also, a synchronization method for pulsewidth modulation carriers is proposed suitable for wireless control. The imperfections of wireless communication, such as higher latency and packet losses compared to wired communication, are analyzed for the operation of MMCs. The latency is fixed with a proper controller and wireless network design. The converter is rendered immune to the packet losses by decreasing the closed-loop control bandwidth. The functionality of the proposal is verified, for the first time, experimentally on a laboratory-scale MMC using a simple wireless network. It is shown that wireless control of MMC submodules with the proposed approach can perform comparably to the wired control.
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| 42. |
- Hassanpoor, Arman, et al.
(författare)
-
Evaluation of different carrier-based PWM methods for modular multilevel converters for HVDC application
- 2012
-
Ingår i: IECON 2012 - 38th Annual Conference on IEEE Industrial Electronics Society. - : IEEE. - 9781467324212 ; , s. 388-393
-
Konferensbidrag (refereegranskat)abstract
- The outstanding features of modular multilevel converters (M2C) make it attractive for high voltage direct current (HVDC) systems. In order to achieve high efficiency in HVDC converter stations, the switching frequency and the capacitor voltage ripple of the converter should be minimized. A suitable modulation algorithm should achieve an optimal tradeoff between these two requirements. This paper evaluates different carrier-based PWM algorithms and discusses the most challenging technical aspects of an efficient M2C. It is observed that decoupling the waveform synthesis from the selection of which cell to switch at each instant has beneficial impact on operation performance. The evaluation is done by time-domain simulation considering a grid connected, three-phase M2C converter and an advanced control system. Results of this study can be used for implementing more economical HVDC converters.
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| 43. |
- Hassanpoor, Arman, et al.
(författare)
-
Switching pulse pattern optimisation for modular multilevel converters
- 2014
-
Ingår i: 40th Annual Conference of the IEEE Industrial Electronics Society, IECON 2014. ; , s. 4722-4728
-
Konferensbidrag (refereegranskat)abstract
- Modular multilevel converters (MMCs) are widely used in different applications such as high voltage direct current (HVDC) applications. The HVDC station loss is highly related to the converter switching pulse pattern which is generated by modulation algorithm and cell selection methods. This paper formulates the switching pulse pattern generation, as a versatile optimisation problem. The problem constraints and objectives are formulated for HVDC applications and compared with similar problems in the field of computer science. To overcome the computational complexity in solving the introduced optimisation problem, a heuristic method is proposed for cell selection algorithm. The method utilizes the current level in order to obtain lossless switching at zero-current crossings. The study of the proposed method, in a time-domain simulation platform, shows that the method can reduce the switching converter losses by 60% compared to carrier-based modulation, maintaining the same capacitor voltage ripple. Although this paper focuses on HVDC, the mathematical model is applicable for any MMC application.
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| 44. |
- Hassanpoor, Arman, et al.
(författare)
-
Tolerance-band modulation methods for modular multilevel converters
- 2013
-
Konferensbidrag (refereegranskat)abstract
- Modular multilevel converters (M2C) are increasingly used in high voltage direct current (HVDC) systems. The efficiency of M2Cs is highly related to the modulation method which determines the switching frequency and capacitor voltage ripple in the converter station. A new approach to modulation of M2C is presented in this paper. Tolerance-band methods are employed to obtain switching instants, and also cell selection. The proposed methods overcome the modulation problem for converters with few numbers of cells and also reduce the sorting efforts for cell balancing purposes while maintaining the cell-capacitor voltage limits. The evaluation is done by time-domain simulation by which the performance of each method is studied in both steady-state and transient cases. It is observed that using tolerance band methods not only reduces the switching frequency but also allows for handling severe fault cases in a grid connected system. Use of this method can reduce the switching losses and also allow for reduction of the cell capacitor size.
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| 45. |
- Heinig, Stefanie, et al.
(författare)
-
Auxiliary Power Supplies for High-Power Converter Submodules : State of the Art and Future Prospects
- 2022
-
Ingår i: IEEE transactions on power electronics. - : Institute of Electrical and Electronics Engineers (IEEE). - 0885-8993 .- 1941-0107. ; 37:6, s. 6807-6820
-
Tidskriftsartikel (refereegranskat)abstract
- Recent developments in medium-voltage (MV) silicon and silicon carbide (SiC) power semiconductor devices are challenging state-of-the-art converter and auxiliary power supply (APS) designs. The APS is an important converter component, which energizes the gate-drive units and, therefore, has an influence on the overall reliability and efficiency of the converter system. There has, however, been comparably little research on how the APS of high-power converter submodules can be realized, in particular, for high-voltage applications. New, or improved, solutions may build on state-of-the-art topologies in the near future, but utilize MV SiC technology in the APS circuit itself to enable improved efficiency, reliability, simplicity, and compactness. Externally-fed APS concepts could provide several further advantages. Their various benefits on converter and system level may enable them to be a competitive solution for future APS concepts. Especially, light-based power supply systems are considered most useful since they offer extreme voltage isolation capability and immunity to electromagnetic interference. This article presents a review of the wide range of solutions for APSs, possible implementation options, and the most important design considerations. The different solutions are evaluated in a qualitative fashion, providing an overview of available APS concepts with regard to the requirements for high-power converter applications.
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| 46. |
- Heinig, Stefanie, et al.
(författare)
-
Auxiliary Power Supplies for High-Power Converter Submodules: State-of-the-Art and Future Prospects
- 2020
-
Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Recent developments in high-voltage (HV) silicon and silicon carbide (SiC) power semiconductor devices are challenging state-of-the-art converter and auxiliary power supply (APS) designs. There has been comparably little research on how the APS of converter submodules can be realized. The APS is, however, an important converter component, which energizes the gate-drive units and, therefore, has an influence on the overall reliability and efficiency of the converter system. The wide range of possible solutions for APSs motivates an overview of state-ofthe- art and alternative concepts. Such a review is presented in this article, along with a qualitative evaluation regarding APS requirements for high-power converter applications.Moreover, future prospects of internal and external APS designs are discussed. Internal solutions may build on state-of-the-art topologies in the near future, but utilize HV SiC technology in the APS circuit itself to enable improved efficiency, reliability, simplicity, and compactness. The active voltage-divider-based APS is a promising concept if the required power is relatively low. Series-connected bootstrap circuits or snubber-based power tapping could provide a reduction of complexity and cost.It is recognized that several advantages are achievable by employing external APS concepts. Light-based power supply systems, comparably expensive today but under rapid development and with optimistic cost predictions, are considered most useful in this respect. Their extreme voltage isolation capability and immunity to electromagnetic interference, combined with various benefits on converter and system level, enable them to be a competitive solution for future APS concepts
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| 47. |
- Heinig, Stefanie, et al.
(författare)
-
Implications of Capacitor Voltage Imbalance on the Operation of the Semi-Full-Bridge Submodule
- 2019
-
Ingår i: IEEE transactions on power electronics. - : Institute of Electrical and Electronics Engineers (IEEE). - 0885-8993 .- 1941-0107. ; 34:10, s. 9520-9535
-
Tidskriftsartikel (refereegranskat)abstract
- Future meshed high-voltage direct current grids require modular multilevel converters with extended functionality. One of the most interesting new submodule topologies is the semi-full-bridge because it enables efficient handling of DC-side short circuits while having reduced power losses compared to an implementation with full-bridge submodules. However, the semi-full-bridge submodule requires the parallel connection of capacitors during normal operation which can cause a high redistribution current in case the voltages of the two submodule capacitors are not equal. The maximum voltage difference and resulting redistribution current have been studied analytically, by means of simulations and in a full-scale standalone submodule laboratory setup. The most critical parameter is the capacitance mismatch between the two capacitors. The experimental results from the full-scale prototype show that the redistribution current peaks at 500A if the voltage difference is 10V before paralleling and increases to 2500A if the difference is 40V. However, neglecting very unlikely cases, the maximum voltage difference predicted by simulations is not higher than 20-30V for the considered case. Among other measures, a balancing controller is proposed which reduces the voltage difference safely if a certain maximum value is surpassed. The operating principle of the controller is described in detail and verified experimentally on a down-scaled submodule within a modular multilevel converter prototype. It can be concluded that excessively high redistribution currents can be prevented. Consequently, they are no obstacle for using the semi-full-bridge submodule in future HVDC converters.
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| 48. |
- Heinig, Stefanie
(författare)
-
Main Circuits, Submodules, and Auxiliary Power Concepts for Converters in HVDC Grids
- 2020
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In order to enable the massive introduction of renewable energies the need for high-voltage direct current (HVDC) grids is anticipated. Large, globally interconnected HVDC networks will likely be the most cost-efficient means to balance electricity demand and available generation. In a meshed system it is important to ensure reliability, robustness, failure management, and fast protection of equipment. In case of a failure somewhere in the grid, the remaining system must be kept operational. State-of-the-art converter implementations are either not adapted to future system requirements or lead to increased losses, cost, and converter footprint. Therefore, this thesis examines several aspects of how to improve the HVDC converter design and functionality with the ultimate aim of developing reliable, highly efficient, cost-effective, more compact and lightweight converters.Advancements are made on several levels of the converter hardware hierarchy. Main circuits, submodule (SM) topologies, and auxiliary power supply (APS) concepts are investigated and new solutions are proposed. On main-circuit level, different voltage-source converters (VSCs) are evaluated in terms of their energy storage elements. This is useful to compare the physical volume of capacitors required by each topology and, thus, to address the need to develop more compact converter stations. The theoretical analysis indicates that the required energy storage of the alternate arm converter (AAC) is smaller compared to the modular multilevel converter (MMC).On SM level, new topologies are evaluated with the goal to find topologies, which enable efficient handling of dc-side short circuits, reduction of power loss, and lower SM capacitance. The semi-full-bridge (SFB) SM is identified as one of the most promising topologies from this point of view and is investigated in detail. A control concept for capacitor balancing and several options for improved operation of the SFB are presented. Furthermore, a novel SM cluster topology is proposed which features low conduction losses and increased protection against explosion.The availability of a reliable APS system is crucial for equipment in future HVDC grids. Therefore, APS solutions are investigated considering design complexity, reliable performance, and power consumption. This thesis presents a novel combined optical power and data transmission concept which is tailored to the specific requirements of HVDC converters employing high-voltage (HV) silicon carbide (SiC) devices. The proposed concept offers a robust solution for isolated APS and signal transmission across any voltage barrier.
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| 49. |
- Heinig, Stefanie, et al.
(författare)
-
Reduction of Switching Frequency for the Semi-Full-Bridge Submodule Using Alternative Bypass States
- 2018
-
Ingår i: 2018 20TH EUROPEAN CONFERENCE ON POWER ELECTRONICS AND APPLICATIONS (EPE'18 ECCE EUROPE). - : IEEE. - 9789075815283
-
Konferensbidrag (refereegranskat)abstract
- As regards modular multilevel converter submodules, a different number of switches may be involved in the transitions between voltage levels depending on the submodule type and choice of switching states. In this paper, an investigation of the average switching frequency associated with different choices of bypass states is performed for the semi-full-bridge submodule. Theoretical considerations and simulation results show that the average switching frequency per device can be halved by using the proposed alternative bypass state. Moreover, the switching losses can be reduced by up to 60%. Finally, a comparative study with the full-bridge submodule has been conducted.
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| 50. |
- Heinig, Stefanie, et al.
(författare)
-
Single-Fiber Combined Optical Power and Data Transmission for High-Voltage Applications
- 2020
-
Ingår i: Proceedings of the 46th Annual Conference of the IEEE Industrial Electronics Society, IECON 2020. - : Institute of Electrical and Electronics Engineers (IEEE).
-
Konferensbidrag (refereegranskat)abstract
- In this paper, power-over-fiber technology is used for combined power and data transfer applying amplitude-modulated light representing a pulse-width modulated signal that could be used for control of, for instance, power semiconductor devices in high-power converters. Even though the concept is generally applicable, an experimental verification aiming for a gate-driver of a switch in a modular multilevel converter is presented. In order to achieve a good resilience against electromagnetic noise, a concept where the modulated light is demodulated as a comparably powerful current signal is employed. A 5 MHz boost converter steps up the voltage to 15-20 V, such that silicon or silicon-carbide based power devices could be controlled. From the results, it can be concluded that it is possible to achieve transmission of a control signal with a latency of less than 500 ns for a gate drive unit of a high-power converter. The concept can easily be scaled up to powers of several watt.
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