| 1. |
- Ahmed, Noman, et al.
(author)
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A computationally efficient continuous model for the modular multilevel converter
- 2014
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In: IEEE Journal of Emerging and Selected Topics in Power Electronics. - : IEEE. - 2168-6777. ; 2:4, s. 1139-1148
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Journal article (peer-reviewed)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.
(author)
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Modular multilevel converter AC motor drives with constant torque from zero to nominal speed
- 2014
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In: IEEE transactions on industry applications. - 0093-9994 .- 1939-9367. ; 50:3, s. 1982-1993
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Journal article (peer-reviewed)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. |
- Norrga, Staffan, 1968-, et al.
(author)
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Decoupled steady-state model of the modular multilevel converter with half-bridge cells
- 2012
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Conference paper (peer-reviewed)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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| 4. |
- Norrga, Staffan, 1968-, et al.
(author)
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Frequency-Domain Modeling of Modular Multilevel Converters With Application to Maximizing the Operating Region
- 2012
-
In: IECON 2012 - 38th Annual Conference on IEEE Industrial Electronics Society. - : IEEE. - 9781467324212 ; , s. 4967-4972
-
Conference paper (peer-reviewed)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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| 5. |
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| 6. |
- Bakas, Panagiotis, et al.
(author)
-
Design considerations and comparison of hybrid line-commutated and cascaded full-bridge converters with reactive-power compensation and active filtering capabilities
- 2019
-
Conference paper (other academic/artistic)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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| 7. |
- Bakas, Panagiotis, et al.
(author)
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Hybrid alternate-common-arm converter with director thyristors - Impact of commutation time on the active-power capability
- 2019
-
In: 2019 21st European Conference on Power Electronics and Applications, EPE 2019 ECCE Europe. - Genova, Italy : Institute of Electrical and Electronics Engineers Inc.. - 9789075815313 - 9781728123615
-
Conference paper (peer-reviewed)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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| 8. |
- Bakas, Panagiotis, et al.
(author)
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Hybrid alternate-common-arm converter with high power capability : Potential and limitations
- 2020
-
In: IEEE transactions on power electronics. - : IEEE. - 0885-8993 .- 1941-0107. ; 35:12, s. 12909-12928
-
Journal article (peer-reviewed)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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| 9. |
- Bakas, Panagiotis, et al.
(author)
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Hybrid Converter With Alternate Common Arm and Director Thyristors for High-Power Capability
- 2018
-
In: 2018 20th European Conference on Power Electronics and Applications (EPE’18 ECCE Europe).
-
Conference paper (peer-reviewed)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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| 10. |
- Bakas, Panagiotis
(author)
-
Hybrid Converters for HVDC Transmission
- 2019
-
Doctoral thesis (other academic/artistic)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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| 11. |
- Bessegato, Luca, et al.
(author)
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A Method for the Calculation of the AC-Side Admittance of a Modular Multilevel Converter
- 2018
-
In: IEEE transactions on power electronics. - 0885-8993 .- 1941-0107.
-
Journal article (peer-reviewed)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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| 12. |
- Bessegato, Luca, et al.
(author)
-
Ac-side admittance calculation for modular multilevel converters
- 2017
-
In: 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
-
Conference paper (peer-reviewed)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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| 13. |
- Bessegato, Luca, et al.
(author)
-
Control and Admittance Modeling of an AC/AC Modular Multilevel Converter for Railway Supplies
- 2019
-
In: IEEE transactions on power electronics. - 0885-8993 .- 1941-0107.
-
Journal article (peer-reviewed)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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| 14. |
- Bessegato, Luca, et al.
(author)
-
Effects of Control on the AC-Side Admittance of a Modular Multilevel Converter
- 2019
-
In: IEEE transactions on power electronics. - : IEEE Press. - 0885-8993 .- 1941-0107. ; 34:8, s. 7206-7220
-
Journal article (peer-reviewed)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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| 15. |
- Bessegato, Luca, 1989-
(author)
-
Modeling of Modular Multilevel Converters for Stability Analysis
- 2019
-
Doctoral thesis (other academic/artistic)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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| 16. |
- Ciftci, Baris, et al.
(author)
-
Wireless control of modular multilevel converter autonomous submodules : 23rd European Conference on Power Electronics and Applications
- 2021
-
In: Proceedings 23rd European Conference on Power Electronics and Applications. - : Institute of Electrical and Electronics Engineers (IEEE).
-
Conference paper (peer-reviewed)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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| 17. |
- Ciftci, Baris, 1987-
(author)
-
Wireless Control of Modular Multilevel Converter Submodules
- 2022
-
Doctoral thesis (other academic/artistic)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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| 18. |
- Ciftci, Baris, et al.
(author)
-
Wireless control of modular multilevel converter submodules under ac-side faults
- 2021
-
Conference paper (peer-reviewed)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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| 19. |
- Ciftci, Baris, et al.
(author)
-
Wireless Control of Modular Multilevel Converter Submodules With Communication Errors
- 2022
-
In: IEEE Transactions on Industrial Electronics. - : Institute of Electrical and Electronics Engineers (IEEE). - 0278-0046 .- 1557-9948. ; 69:11, s. 11644-11653
-
Journal article (peer-reviewed)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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| 20. |
- Ilves, Kalle, et al.
(author)
-
A submodule implementation for parallel connection of capacitors in modular multilevel converters
- 2013
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In: Power Electronics and Applications (EPE), 2013 15th European Conference on.
-
Conference paper (peer-reviewed)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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| 21. |
- Ilves, Kalle, et al.
(author)
-
Analysis and operation of modular multilevel converters with phase-shifted carrier PWM
- 2013
-
In: 2013 IEEE Energy Conversion Congress and Exposition, ECCE 2013. - : IEEE. - 9781479903351 ; , s. 396-403
-
Conference paper (peer-reviewed)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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| 22. |
- Ali, Muhammad Taha, et al.
(author)
-
Analysis and Mitigation of SSCI in DFIG Systems With Experimental Validation
- 2020
-
In: IEEE transactions on energy conversion. - : IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC. - 0885-8969 .- 1558-0059. ; 35:2, s. 714-723
-
Journal article (peer-reviewed)abstract
- Sub-synchronous oscillations (SSOs) in doubly-fed induction generator (DFIG)-based series compensated power systems are mainly caused by sub-synchronous control interaction (SSCI). SSCI is the most recently found type of sub-synchronous resonances. In this article, SSCI is elaborated and investigated by performing eigenvalue analysis on a mathematically modeled DFIG system. The occurrence of SSCI is observed and the results of eigenvalue analysis are validated through a down-scaled 7.5-kW experimental setup of a grid-connected DFIG. Based on the analysis, the proportional control parameters of the rotor-side converter (RSC) are found to be very sensitive towards the sub-synchronous modes of the system. The results obtained from both the simulation and the experimental analysis show that if the sensitive proportional parameters of the RSC are tuned properly, then the DFIG system can become immune to the SSCI for any level of series compensation.
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| 23. |
- Ali, Muhammad Taha, et al.
(author)
-
Mitigation of Sub-Synchronous Control Interaction in DFIGs using a Power Oscillation Damper
- 2017
-
In: 2017 IEEE Manchester PowerTech, Powertech 2017. - : Institute of Electrical and Electronics Engineers (IEEE). - 9781509042371
-
Conference paper (peer-reviewed)abstract
- The aim of this research work is to analyse subsynchronous control interaction (SSCI) in doubly-fed induction generators (DFIGs) and to design a supplementary control technique for the mitigation of SSCI. A mathematical model of the DFIG is derived and linearized in order to perform an eigenvalue analysis. This analysis pinpoints the parameters of the system which are sensitive in making sub-synchronous modes unstable and hence are responsible for causing SSCI. A power oscillation damper (POD) is designed using a residue method to make the DFIG system immune to the SSCI. The POD control signal acts as a supplementary control, which is fed to the controller of the grid-side converter (GSC). The POD signal is applied to different summation junctions of the GSC controller in order to determine the best placement of the POD for effective mitigation of SSCI and for the increased damping of the system.
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| 24. |
- Ali, Muhammad Taha, et al.
(author)
-
Optimal tuning and placement of POD for SSCI mitigation in DFIG-based power system
- 2019
-
In: 2019 IEEE Milan PowerTech, PowerTech 2019. - : Institute of Electrical and Electronics Engineers (IEEE). - 9781538647226
-
Conference paper (peer-reviewed)abstract
- The phenomenon of sub-synchronous control interaction (SSCI) in doubly-fed induction generators (DFIGs) is investigated and the optimal tuning and placement of a power oscillation damper (POD) for its mitigation is proposed in this paper. The effect of the POD on the DFIG system is studied by placing it at all the summation junctions of rotor-side converter (RSC) and grid-side converter (GSC) controllers, turn by turn. Five local signals are examined as different input signals to the POD out of which three local signals gave promising results. These signals include the DFIG's active power, the magnitude of the DFIG's apparent power, and the magnitude of the current through the transmission line. Residues are calculated for each POD placement and for each input to the POD. The calculated residues are studied along with the root-locus plots to see the effect of the POD on the mitigation of SSCI and the stability of the DFIG-based system.
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| 25. |
- Bessegato, Luca, 1989-, et al.
(author)
-
Control and Admittance Modeling of an AC/AC Modular Multilevel Converter for Railway Supplies
- 2020
-
In: IEEE transactions on power electronics. - : IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC. - 0885-8993 .- 1941-0107. ; 35:3, s. 2411-2423
-
Journal article (peer-reviewed)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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| 26. |
- Bessegato, Luca, et al.
(author)
-
Control of Direct AC/AC Modular Multilevel Converters Using Capacitor Voltage Estimation
- 2016
-
In: 2016 18TH EUROPEAN CONFERENCE ON POWER ELECTRONICS AND APPLICATIONS (EPE'16 ECCE EUROPE). - : IEEE.
-
Conference paper (peer-reviewed)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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| 27. |
- Bessegato, Luca, et al.
(author)
-
Control of Modular Multilevel Matrix Converters Based on Capacitor Voltage Estimation
- 2016
-
In: IEEE 8th International Power Electronics and Motion Control Conference (IPEMC-ECCE Asia), 2016. - : IEEE. - 9781509012107 ; , s. 3447-3452
-
Conference paper (peer-reviewed)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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| 28. |
- Björk, Joakim, 1989-
(author)
-
Fundamental Control Performance Limitations for Interarea Oscillation Damping and Frequency Stability
- 2021
-
Doctoral thesis (other academic/artistic)abstract
- With the transition towards renewable energy and the deregulation of the electricity markets, the power system is changing. Growing electricity demand and more intermittent power production increase the need for transfer capacity. Lower inertia levels due to a higher share of renewables increase the need for fast frequency reserves (FFR). In this thesis, we study fundamental control limitations for improving the damping of interarea oscillations and frequency stability.The first part of the thesis considers the damping of oscillatory interarea modes. These system-wide modes involve power oscillating between groups of generators and are sometimes hard to control due to their scale and complexity. We consider limitations of decentralized control schemes based on local measurements, as well as centralized control schemes with limitations associated to actuator dynamics and network topology. It is shown that the stability of asynchronous grids can be improved by modulating the active power of a single interconnecting high-voltage direct current (HVDC) link. One challenge with modulating HVDC active power is that the interaction between interarea modes of the two grids may have a negative impact on system stability. By studying the controllability Gramian, we show that it is possible to improve the damping in both grids as long as the frequencies of their interarea modes are not too close. It is demonstrated how the controllability, and therefore the achievable damping, deteriorates as the frequency difference becomes small. With a modal frequency difference of 5%, the damping can be improved by around 2 percentage points whereas a modal frequency difference of 20% allows for around 8 percentage points damping improvement. The results are validated by simulating two HVDC-interconnected 32-bus power system models. We also consider the coordinated control of two and more HVDC links. For some network configurations, it is shown that the interaction between troublesome interarea modes can be avoided. The second part considers the coordination of frequency containment reserves (FCR) in low-inertia power systems. A case study is performed in a 5-machine model of the Nordic synchronous grid. We consider a low-inertia test case where FCR are provided by hydro power. The non-minimum phase characteristic of the waterways limits the achievable bandwidth of the FCR control. It is shown that a consequence of this is that hydro-FCR fails at keeping the frequency nadir above the 49.0 Hz safety limit following the loss of a HVDC link that imports 1400 MW. To improve the dynamic frequency stability, FFR from wind power is considered. For this, a new wind turbine model is developed. The turbine is controlled at variable-speed, enabling FFR by temporarily borrowing energy from the rotating turbine. The nonlinear wind turbine dynamics are linearized to facilitate a control design that coordinate FFR from the wind with slow FCR from hydropower. Complementary wind resources with a total rating of 2000 MW, operating at 70–90% rated wind speeds, is shown to be more than enough to fulfill the frequency stability requirements. The nadir is kept above 49.0 Hz without the need to install battery storage or to waste wind energy by curtailing the wind turbines.
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| 29. |
- Björk, Joakim, et al.
(author)
-
Fundamental Performance Limitations in Utilizing HVDC to Damp Interarea Modes
- 2019
-
In: IEEE Transactions on Power Systems. - : IEEE. - 0885-8950 .- 1558-0679. ; 34:2, s. 1095-1104
-
Journal article (peer-reviewed)abstract
- This paper considers power oscillation damping (POD) using active power modulation of high-voltage dc transmissions. An analytical study of how the proximity between interarea modal frequencies in two interconnected asynchronous grids puts a fundamental limit to the achievable performance is presented. It is shown that the ratio between the modal frequencies is the sole factor determining the achievable nominal performance. To illustrate the inherent limitations, simulations using a proportional controller tuned to optimize performance in terms of POD are done on a simplified two-machine model. The influence of limited system information and unmodeled dynamics is shown. The analytical result is then further validated on a realistic model with two interconnected 32-bus networks.
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| 30. |
- Björk, Joakim, et al.
(author)
-
Influence of Sensor Feedback Limitations on Power Oscillation Damping and Transient Stability
- 2022
-
In: IEEE Transactions on Power Systems. - : Institute of Electrical and Electronics Engineers (IEEE). - 0885-8950 .- 1558-0679. ; 37:2, s. 901-912
-
Journal article (peer-reviewed)abstract
- Fundamental sensor feedback limitations for improving rotor angle stability using local frequency or phase angle measurement are derived. Using a two-machine power system model, it is shown that improved damping of inter-area oscillations must come at the cost of reduced transient stability margins, regardless of the control design method. The control limitations stem from that the excitation of an inter-area mode by external disturbances cannot be estimated with certainty using local frequency information. The results are validated on a modified Kundur four-machine two-area test system where the active power is modulated on an embedded high-voltage dc link. Damping control using local phase angle measurements, unavoidably leads to an increased rotor angle deviation following certain load disturbances. For a highly stressed system, it is shown that this may lead to transient instability. The limitations derived in the paper may motivate the need for wide-area measurements in power oscillation damping control.
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| 31. |
- Björk, Joakim, 1989-
(author)
-
Performance Quantification of Interarea Oscillation Damping Using HVDC
- 2019
-
Licentiate thesis (other academic/artistic)abstract
- With the transition towards renewable energy, and the deregulation of the electricity market, generation patterns and grid topology are changing. These changes increase the need for transfer capacity. One limiting factor, which sometimes leads to underutilization of the transmission grid, is interarea oscillations. These system-wide modes involve groups of generators oscillating relative to each other and are sometimes hard to control due to their scale and complexity. In this thesis we investigate how high-voltage direct current (HVDC) transmission can be used to attenuate interarea oscillations. The thesis has two main contributions.In the first contribution we show how the stability of two asynchronous grids can be improved by modulating the active power of a single interconnecting HVDC link. One concern with modulating HVDC active power is that the interaction between interarea modes of the two grids may have a negative impact on system stability. By studying the controllability Gramian, we show that it is always possible to improve the damping in both grids as long as the frequencies of their interarea modes are not too close. For simplified models, it is explicitly shown how the controllability, and therefore the achievable damping improvements, deteriorates as the frequency difference becomes small.The second contribution of the thesis is to show how coordinated control of two (or more) links can be used to avoid interaction between troublesome interarea modes. We investigate the performance of some multivariable control designs. In particular we look at input usage as well as robustness to measurement, communication, and actuator failures. Suitable controllers are thereby characterized.
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| 32. |
- Ciftci, Baris, et al.
(author)
-
Wireless Control of Modular Multilevel Converter Submodules
- 2021
-
In: IEEE transactions on power electronics. - : Institute of Electrical and Electronics Engineers (IEEE). - 0885-8993 .- 1941-0107. ; 36:7, s. 8439-8453
-
Journal article (peer-reviewed)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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| 33. |
- Gong, H., et al.
(author)
-
Admittance-Dissipativity Analysis and Shaping of Dual-Sequence Current Control for VSCs
- 2022
-
In: IEEE Journal of Emerging and Selected Topics in Power Electronics. - : Institute of Electrical and Electronics Engineers (IEEE). - 2168-6777 .- 2168-6785. ; 10:1, s. 324-335
-
Journal article (peer-reviewed)abstract
- This paper analyzes the admittance-dissipativity of dual-sequence current control for grid-connected voltage-source converters (VSCs). The output admittance model of dual-sequence current control is first developed in the stationary reference frame by using complex vectors. Impacts of digital filters used within current control and voltage-feedforward (VFF) control loops, and of the delay compensation at the fundamental frequency, are then evaluated. It is found that the cascaded use of sequence-decomposition filter (SDF) and the low-pass filter (LPF) in the VFF control loop adds a non-dissipative region in the output admittance, and the fundamental-frequency delay-compensation further worsens the dissipativity. An analytical design method for the LPF is then developed to mitigate the non-dissipative region, which lowers the instability risks and improves the stability robustness of dual-sequence current control under different grid conditions. Lastly, simulations and experimental results corroborate theoretical analyses.
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| 34. |
- Gong, Hong, et al.
(author)
-
Rethinking Current Controller Design for PLL-Synchronized VSCs in Weak Grids
- 2022
-
In: IEEE transactions on power electronics. - : Institute of Electrical and Electronics Engineers (IEEE). - 0885-8993 .- 1941-0107. ; 37:2, s. 1369-1381
-
Journal article (peer-reviewed)abstract
- This article revisits the design of the current controller for grid-connected voltage-source converters (VSCs), considering the dynamic impacts of the phase-locked loop (PLL), weak grids, and of voltage feedforward (VFF) control. First, a single-input single-output transfer-function-based model is proposed to characterize the interactions of control loops. It is analytically found that the proportional gain of the current controller essentially aggravates the instability effect of PLL in weak grids, while the cutoff frequency of the low-pass filter used with the VFF loop has a nonmonotonic relationship with the PLL-induced instability. Then, based on these findings, a guideline for redesigning the current controller of PLL-synchronized VSCs is developed, which enables a codesign of the current controller and VFF controller. Finally, simulation and experimental results confirm the validity of theoretical analyses.
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| 35. |
- Harnefors, Lennart, 1968, et al.
(author)
-
Asymmetric Complex-Vector Models with Application to VSC-Grid Interaction
- 2020
-
In: IEEE Journal of Emerging and Selected Topics in Power Electronics. - 2168-6777 .- 2168-6785. ; 8:2, s. 1911-1921
-
Journal article (peer-reviewed)abstract
- The properties of complex space-vector models for asymmetric three-phase systems are investigated in this article. Most importantly, three alternative methods for the stability analysis of the asymmetric closed-loop systems are presented. The end results avoid the usage of matrix manipulations. It is shown how the theory can be applied to modeling and stability analysis of a grid-connected voltage-source converter (VSC). The methods are compared using numerical examples.
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| 36. |
- Harnefors, Lennart, 1968, et al.
(author)
-
Current controller design for passivity of the input admittance
- 2009
-
In: 2009 13th European Conference on Power Electronics and Applications, EPE '09; Barcelona; Spain; 8 September 2009 through 10 September 2009. - 9781424444328 ; , s. 1-8
-
Conference paper (peer-reviewed)abstract
- Current controller design for three-phase voltage-source converters, by which a passive input admittance is ideally obtained, is considered. Two design alternatives, with and without voltage feedforward, respectively, are shown to give similar performance. It is demonstrated how additional parts can be added to the controller while preserving the passivity property. This is applied particularly to resonant controllers.
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| 37. |
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| 38. |
- Harnefors, Lennart, 1968, et al.
(author)
-
Input-admittance calculation and shaping for controlled voltage-source converters
- 2007
-
In: IEEE Transactions on Industrial Electronics. - : Institute of Electrical and Electronics Engineers (IEEE). - 0278-0046 .- 1557-9948. ; 54:6, s. 3323-3334
-
Journal article (peer-reviewed)abstract
- A controlled power electronic converter can cause local instabilities when interacting with other dynamic subsystems in a power system. Oscillations at a certain frequency cannot, however, build up if the converter differential input admittance has a positive conductance (real part) at that frequency, since power is then dissipated. In this paper, input-admittance expressions for a voltage-source converter are derived. It is seen how the admittance can be shaped in order to get a positive real part in the desired frequency regions by adjusting the controller parameters.
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| 39. |
- Harnefors, Lennart, 1968, et al.
(author)
-
Regenerating-mode stabilization of the "statically compensated voltage model''
- 2007
-
In: IEEE Transactions on Industrial Electronics. - : Institute of Electrical and Electronics Engineers (IEEE). - 0278-0046 .- 1557-9948. ; 54:2, s. 818-824
-
Journal article (peer-reviewed)abstract
- Reversal of rotation under load of sensorless induction motor drives is very challenging, as there is often an unstable region in the low-speed regenerating mode. In this paper, a variant of the classical "voltage model," i.e., the "statically compensated voltage model," is modified for stable regenerating-mode operation with accurate model motor parameters. The mechanisms behind two low-speed instability phenomena are thereafter, explored, and methods for avoiding instability with inaccurate model parameters are developed. Experimental results verify the theory and show adequate performance.
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| 40. |
|
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| 41. |
- Li, S., et al.
(author)
-
Modeling, Analysis, and Advanced Control in Motion Control Systems - Part III
- 2017
-
In: IEEE Transactions on Industrial Electronics. - : Institute of Electrical and Electronics Engineers Inc.. - 0278-0046 .- 1557-9948. ; 64:4, s. 3268-3272
-
Journal article (peer-reviewed)abstract
- The April 2017 of IEEE Transactions on Industrial Electronics presents a Special Section on Modeling, Analysis, and Advanced Control in Motion Control Systems. This part of the Special Section consists of 17 papers which cover different applications on motion control systems. An article provides a novel disturbance observer- based nonlinear triple-step controller to attenuate the influence of cogging torque in low-speed condition for a permanent magnet dc motor. Considering that the cogging torque is a fast time-varying disturbance and changes harmonically, a reduced-order nonlinear observer is designed to estimate it. Another aticle considers the contouring control design problem for an industrial X–Y linear-motor-driven stage system. Based on the global task coordinate frame, combining iterative learning control with adaptive robust control together, a kind of learning adaptive robust control method is developed to suppress parametric uncertainties and disturbances. One article develops a novel controller based on adaptive servomechanism to achieve precise tracking for pneumatic muscle actuators whose model has nonlinear and time-varying characteristics. The driving force allocation and control problem for electric vehicles with multiple driving motors are studied in another paper. One paper focuses on a control system design for the oil well sonic logging device. The removal of ringing is desirable for acoustic logging as too much ringing can interfere with the processing of formation data.
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| 42. |
- Nikouei, Mojgan, et al.
(author)
-
Torque-Ripple Minimization for Permanent-Magnet Synchronous Motors Based on Harmonic Flux Estimation
- 2018
-
In: 2018 20Th European Conference On Power Electronics And Applications (Epe'18 Ecce Europe). - : IEEE. - 9789075815283
-
Conference paper (peer-reviewed)abstract
- This paper presents a control algorithm to reduce the torque ripple in permanent-magnet synchronous motors. This control algorithm is based on the on-line estimation of harmonic flux linkage. Together with the on-line estimation of the flux linkage, a proportional-integral-resonant controller is introduced to suppress the torque ripple.
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| 43. |
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| 44. |
- Petersson, Andreas, 1974, et al.
(author)
-
Comparison Between Stator-Flux and Grid-Flux-Oriented Rotor Current Control of Doubly-Fed Induction Generators
- 2004
-
In: IEEE Power Electronics Specialists Conference. - 0275-9306. ; 1, s. 482-486
-
Conference paper (peer-reviewed)abstract
- Grid-flux (or grid-voltage)-oriented rotor current control of the doubly-fed induction generator is investigated in this paper. It is shown that by using a grid-flux-oriented system, the stability and damping of the system is independent of the d component of the rotor current, in contrast to a stator-flux-oriented system. Also for the stator-flux-oriented system, a certain value of the d component of the rotor current causes the system to become unstable. Hence, with a grid-flux-oriented system it is possible to produce as much reactive power as desired from a stability point of view. The theoretical results are verified experimentally with good result.
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| 45. |
- Petersson, Andreas, 1974, et al.
(author)
-
Evaluation of Current Control Methods for Wind Turbines Using Doubly-Fed Induction Machines
- 2005
-
In: IEEE Transactions on Power Electronics. - 0885-8993 .- 1941-0107. ; 20:1, s. 227-235
-
Journal article (peer-reviewed)abstract
- In this paper, different rotor current control methods are investigated with the objective of eliminating the influence of the back electromotive force (EMF), which is that of, in control terminology, a load disturbance, on the rotor current. It is found that the method that utilizes both feed-forward of the back EMF and so-called "active resistance" manages best to suppress the influence of the back EMF on the rotor current, particularly when voltage sags occur, of the investigated methods. This method also has the best stability properties. In addition it is found that this method also has the best robustness to parameter deviations.
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| 46. |
- Petersson, Andreas, 1974, et al.
(author)
-
Flicker Reduction of Stall-Controlled Wind Turbine Using Variable Rotor Resistance
- 2004
-
In: Nordic Wind Energy Conference.
-
Conference paper (peer-reviewed)abstract
- In this paper, a flicker reduction control for stall-controlled wind turbines with induction generators, using variable rotor resistance, is derived. The objective is to reduce torque fluctuations and flicker emission by using a variable rotor resistance. However, the rotor resistance can only be varied within a limited range. This puts a limit to the achievable reduction in flicker emission and torque fluctuation which is investigated in this paper.
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| 47. |
- Petersson, Andreas, 1974, et al.
(author)
-
Modeling and Experimental Verification of Grid Interaction of a DFIG Wind Turbine
- 2005
-
In: IEEE Transactions on Energy Conversion. - 1558-0059 .- 0885-8969. ; 20:4, s. 878- 886
-
Journal article (peer-reviewed)abstract
- The response of the doubly fed induction generator (DFIG) wind turbine system to grid disturbances is simulated and verified experimentally. The results are compared to the response that a fixed-speed wind turbine would have given. A voltage sag to 80% (80% remaining voltage) is handled very well, which is not the case for a fixed-speed wind turbine. A second-order model for prediction of the response of DFIG wind turbines is derived, and its simulated performance is successfully verified experimentally. The power quality impact by the DFIG wind turbine system is measured and evaluated. Steady-state impact, such as flicker emission, reactive power, and harmonic emission, is measured and analyzed. It is found that the flicker emission is very low, the reactive power is close to zero in the whole operating range, and the current THD is always lower than 5%.
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| 48. |
- Pirsto, Ville, et al.
(author)
-
Intersample Modeling of the Converter Output Admittance
- 2021
-
In: IEEE Transactions on Industrial Electronics. - : Institute of Electrical and Electronics Engineers (IEEE). - 0278-0046 .- 1557-9948. ; 68:11, s. 11348-11358
-
Journal article (peer-reviewed)abstract
- The stability of the converter-grid interconnection can be studied by analyzing the product of the converter output admittance and the grid impedance. For reliable stability analysis, it has been of interest to obtain accurate converter output admittance models for a wide range of frequencies, ideally also around and above the Nyquist frequency of the converter system. This article presents a modeling method for the output admittance of power converters defined in the Laplace domain that takes into account the discrete nature of the control system. The modeling method is based on analyzing the intersample behavior of sampled-data systems, a class of systems that includes the modern digitally controlled power converters. The proposed method is compared to conventional admittance modeling methods, and its accuracy is validated by means of simulations and experiments.
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| 49. |
- Stamatiou, Georgios, 1984, et al.
(author)
-
Analytical Derivation of the DC-Side Input Admittance of the Direct-Voltage Controlled Modular Multilevel Converter
- 2017
-
In: IET Generation, Transmission and Distribution. - : Institution of Engineering and Technology (IET). - 1751-8687 .- 1751-8695. ; 11:16, s. 4018-4030
-
Journal article (peer-reviewed)abstract
- The input admittance of a converter, connected to other dynamic subsystems, is a useful tool to investigate whether poorly damped oscillations or even unstable conditions might occur at certain frequencies. This is of interest in applications employing the modular multilevel converter (MMC), where the internal dynamics of the converter and the increased number of control loops greatly affect the MMC’s dynamic behaviour, compared to other types of converters. In this paper, the dc-side input admittance of the direct-voltage controlled MMC is derived analytically and verified via small-signal perturbation in a detailed nonlinear time-domain simulation model. The MMC’s input admittance is parametrically studied and compared to the dc-side input admittance of an equivalent two-level converter.
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| 50. |
- Wallmark, Oskar, 1976, et al.
(author)
-
Loss Minimization of a PMSM Drive for a Hybrid Electric Vehicle
- 2004
-
In: Proc. 11th International Power Electronics and Motion Control Conference. ; 6, s. 160-164
-
Conference paper (peer-reviewed)abstract
- This paper considers minimization, by means of control, of losses in permanent-magnet synchronous motor (PMSM) drives in hybrid-electric vehicle (HEV) applications. A case study is presented to investigate the impact of loss minimization for an experimental PMSM drive, developed for propulsion in a series HEV. The case study shows that the additional inverter losses, due to the extra field weakening added, reduce the potential to minimize losses considerably.
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