| 1. |
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| 2. |
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| 3. |
- Krismer, Florian, et al.
(författare)
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Analysis and practical relevance of CM/DM EMI noise separator characteristics
- 2017
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Ingår i: IEEE transactions on power electronics. - : IEEE Press. - 0885-8993 .- 1941-0107. ; 32:4, s. 3112-3127
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Tidskriftsartikel (refereegranskat)abstract
- This work investigates sources of measurement errors that result for common mode/differential mode (CM/DM) separators in a practical measurement environment, with a particular focus on the recently presented input impedance criterion for CM/DM separators, derives the respective analytical expressions, and employs a detailed analytical model to verify the obtained findings. Furthermore, a method is derived, which determines the worst-case measurement error by reason of cross coupling for given measured DM and CM output voltage components. Based on an example, this work illustrates how the obtained expressions can be advantageously used in a computer program to automatically decide whether a particular spectral measurement component represents a useful measurement result or if it is strongly affected by cross coupling (CM to DM and DM to CM). Finally, the paper presents the realization and accompanying experimental results of an active CM/DM separator, which allows for low realization effort and features competitive separation capabilities (DMTR/CMRR > 50 dB and CMTR/DMRR > 42 dB for frequencies up to 10 MHz).
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| 4. |
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| 5. |
- Risseh, Arash, 1980-, et al.
(författare)
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Design of a Thermoelectric Generator for Waste Heat Recovery Application on a Drivable Heavy Duty Vehicle
- 2017
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Ingår i: SAE International Journal of Commercial Vehicles. - : SAE International. - 1946-391X .- 1946-3928. ; 10:1, s. 26-44
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Tidskriftsartikel (refereegranskat)abstract
- The European Union’s 2020 target aims to be producing 20 % of its energy from renewable sources by 2020, to achieve a 20 % reduction in greenhouse gas emissions and a 20 % improvement in energy efficiency compared to 1990 levels. To reach these goals, the energy consumption has to decrease which results in reduction of the emissions. The transport sector is the second largest energy consumer in the EU, responsible for 25 % of the emissions of greenhouse gases caused by the low efficiency (<40 %) of combustion engines. Much work has been done to improve that efficiency but there is still a large amount of fuel energy that converts to heat and escapes to the ambient atmosphere through the exhaust system. Taking advantage of thermoelectricity, the heat can be recovered, improving the fuel economy. A thermoelectric generator (TEG) consists of a number of thermoelectric elements, which advantageously can be built into modules, arranged thermally and electrically, in a way such that the highest possible thermal power can be converted into electrical power. In a unique waste heat recovery (WHR) project, five international companies and research institutes cooperated and equipped a fully drivable Scania prototype truck with two TEGs. The entire system, from the heat transfer in the exchangers to the electrical power system, was simulated, built and evaluated. The primary experimental results showed that approximately 1 kW electrical power could be generated from the heat energy. In this paper the entire system from design to experimental results is presented.
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| 6. |
- Smedby, Karin E., et al.
(författare)
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GWAS of Follicular Lymphoma Reveals Allelic Heterogeneity at 6p21.32 and Suggests Shared Genetic Susceptibility with Diffuse Large B-cell Lymphoma
- 2011
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Ingår i: PLoS Genetics. - : Public Library of Science (PLoS). - 1553-7390 .- 1553-7404. ; 7:4, s. e1001378-
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Tidskriftsartikel (refereegranskat)abstract
- Non-Hodgkin lymphoma (NHL) represents a diverse group of hematological malignancies, of which follicular lymphoma (FL) is a prevalent subtype. A previous genome-wide association study has established a marker, rs10484561 in the human leukocyte antigen (HLA) class II region on 6p21.32 associated with increased FL risk. Here, in a three-stage genome-wide association study, starting with a genome-wide scan of 379 FL cases and 791 controls followed by validation in 1,049 cases and 5,790 controls, we identified a second independent FL-associated locus on 6p21.32, rs2647012 (ORcombined = 0.64, P-combined= 2x10(-21)) located 962 bp away from rs10484561 (r(2)< 0.1 in controls). After mutual adjustment, the associations at the two SNPs remained genome-wide significant (rs2647012: ORadjusted = 0.70, P-adjusted= 4x10(-12); rs10484561: ORadjusted = 1.64, P-adjusted= 5x10(-15)). Haplotype and coalescence analyses indicated that rs2647012 arose on an evolutionarily distinct haplotype from that of rs10484561 and tags a novel allele with an opposite (protective) effect on FL risk. Moreover, in a follow-up analysis of the top 6 FL-associated SNPs in 4,449 cases of other NHL subtypes, rs10484561 was associated with risk of diffuse large B-cell lymphoma (ORcombined = 1.36, P-combined = 1.4x10(-7)). Our results reveal the presence of allelic heterogeneity within the HLA class II region influencing FL susceptibility and indicate a possible shared genetic etiology with diffuse large B-cell lymphoma. These findings suggest that the HLA class II region plays a complex yet important role in NHL.
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| 7. |
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| 8. |
- Thelin, Peter, et al.
(författare)
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Analytical Calculation of the Airgap Flux Density of PM Synchronous Motors with Buried Magnets Including Axial Leakage, Tooth and Yoke Saturations
- 2000
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Ingår i: Proc. of the International Conference on Power Electronics and Variable Speed Drives, London, September 2000.. - : IEE. ; , s. 218-223
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Konferensbidrag (refereegranskat)abstract
- It has been shown earlier that the airgap flux density of PM motors with buried magnets can be calculated with a satisfactory result, if saturated iron bridges, axial leakage flux (from 2D-FEM) and teeth saturation are taken into account. In this paper, instead of using 2D-FEM, an analytical expression for the axial reluctance is derived. By including the saturation of rotor and stator yokes, the model is even further improved. The result is a complete analytical model, which takes into account all phenomena mentioned above, and improves the agreement with experimental values.
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| 9. |
- Thelin, Peter, et al.
(författare)
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Calculation of the Airgap Flux Density of PM Synchronous Motors with Buried Magnets including Axial Leakage and Teeth Saturation
- 1999
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Ingår i: Proc. of the Electrical Machines and Drives Conference, Canterbury, UK, September 1999. - : Institution of Electrical Engineers (IEE). ; , s. 339-345
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Konferensbidrag (refereegranskat)abstract
- It has been shown earlier that the airgap flux density of unsaturated PM motors with buried magnets can be calculated analytically, with a satisfactory result, compared to 2D-FEM calculations. By taking axial leakage flux, and stator and rotor teeth saturation into account an improved expression for the airgap flux density, showing better agreement with experiments, is obtained.
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| 10. |
- Thelin, Peter, et al.
(författare)
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Comparison between Different Ways to Calculate the Induced No-Load Voltage of PM Synchronous Motors using Finite Element Methods
- 2001
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Ingår i: Proc. of the 4th IEEE International Conference on Power Electronics and Drive Systems (PEDS'01), Bali, Indonesia, October 2001, vol. 2.. ; , s. 468-474
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Konferensbidrag (refereegranskat)abstract
- In this paper two different ways of calculating the induced no-load voltage of permanent magnet synchronous motors (PMSM), by the use of a finite element method (FEM) program, have been compared. Neither of the two calculation methods require a FEM software package that can perform time-stepping. The number of required static FEM-calculations is limited to just a few, or even to one. The calculations are performed on five motor geometries. The results are compared to values obtained from time-stepping FEM-calculations, and to the measured induced no-load voltages of the five manufactured prototype motors. It can be seen that the least time-consuming method is accurate enough in most of these cases. The exceptions, in this study, are when there are relatively large airgaps and/or when the stator teeth are saturated.
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| 11. |
- Thelin, Peter, et al.
(författare)
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Development and Efficiency Measurements of a Compact 15 kW 1500 r/min Integral Permanent Magnet Synchronous Motor
- 2000
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Ingår i: Proc. of the IEEE Industry Applications Society Annual Meeting, Roma, Italy, October 2000.. ; , s. 155-162
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Konferensbidrag (refereegranskat)abstract
- This paper presents the development of a 15 kW, 1500 r/min integral motor, with the same outer dimensions as an equivalent standard induction motor, but with the possibility of operating with speed control and at a higher efficiency. To make a compact integral motor, a permanent magnet rotor is used, the coils of the line-filter and the coil of the DC-link have been integrated with the stator core, only a small DC-link capacitor is employed, and the motor is controlled without a shaft sensor. Temperature and efficiency measurements on the manufactured prototype machine are performed and the results are very promising.
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| 12. |
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| 13. |
- Thelin, Peter, et al.
(författare)
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Rotor Cage Losses of an Inverter-Fed PMSM investigated with FEM
- 2003
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Ingår i: Proceedings of the European Conference on Power Electronics and Applications, EPE´03.
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Konferensbidrag (refereegranskat)abstract
- In the design of a compact inverter-fed buried permanent magnet synchronous motor, the high-frequency losses of the sparse rotor cage - which are difficult to predict - were assumed to be small. To investigate these ohmic high-frequency losses of the rotor cage, fixed-speed time-stepping 2D-FEM calculations have been carried out. The losses due to only the magnets, magnets and sinusoidal currents, high-frequency currents etc., and the actual currents are presented. The actual current wave-forms were obtained from measurements on the manufactured prototype motor.
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| 14. |
- Thelin, Peter, et al.
(författare)
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Suggestions Regarding the Pole-Number of Inverter-Fed PM-Synchronous Motors with Buried Magnets
- 1998
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Ingår i: Proc. of the International Conference on Power Electronics and Variable Speed Drives 1998. - : Institution of Electrical Engineers (IEE). ; , s. 544-547
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Konferensbidrag (refereegranskat)abstract
- When designing an inverter-fed PM-motor, one is quite free to choose a number of poles which utilizes the machine in a good way. A common rule of thumb is to choose a high pole-number for low-speed motors and vice versa, but there are no sharp borderlines between the different areas. This paper gives a suggestion regarding the pole-number for a desired power and speed of the motor.
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| 15. |
- Zhang, Yafan, et al.
(författare)
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Investigation of a Finned Baseplate Material and Thickness Variation for Thermal Performance of a SiC Power Module
- 2014
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Ingår i: 2014 15th International Conference on Thermal, Mechanical and Multi-Physics Simulation and Experiments in Microelectronics and Microsystems, EuroSimE 2014. - : IEEE Computer Society. - 9781479947904
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Konferensbidrag (refereegranskat)abstract
- A simplified transient computational fluid dynamics model of an automotive three-phase double-side liquid cooled silicon carbide power inverter, including pin-fin baseplates, has been developed and qualified for parametric studies. Effective heat transfer coefficients have been extracted from the detailed pin-fin baseplate model for two coolant volume flow rates 2 l/min and 6 l/min, at the coolant temperature 105 degrees C. The inverter model includes temperature dependent heat losses of SiC transistors and diodes, calculated for two driving cycles. Baseplate materials such as copper, aluminum-silicon carbide metal matrix composite, aluminium alloy 6061 as well as virtual materials have been evaluated in the parametric studies. Thermal conductivity, specific heat and density have been varied as well as thickness of the finned baseplates (1 to 3 mm). A trade-off between temperature of SiC chips and baseplate weight has been investigated by means of Pareto optimization. The main results of the parametric studies include a weak dependence (1 to 3 degrees C) of the chip temperature on baseplate thickness. Furthermore, switching e.g. between copper and AlSiC results in 5 to 8 degrees C increase of the chip temperature, at 65 to 70 % baseplate weight reduction.
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| 16. |
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| 17. |
- Zhang, Yafan
(författare)
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Multiphysics Characterization of SiC Power Modules
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis proposes several novel silicon carbide power module design concepts. The goal has been to address the problems with the present designs. The electrical, thermal, and thermomechanical performances of the demonstrators have been evaluated along with presentations of methodologies of experimental and numerical characterizations.Compact high-temperature power modules with adequate cooling systems are attractive to automotive applications. Therefore, a novel thermal design of a double-sided liquid/air cooled silicon carbide power module (1200 V, 200 A) has been proposed. The concept integrates a dc-link capacitor, a gate driver board, and finned cooling channels. The cooling concept has been evaluated for three application scenarios based on a validated computational fluid dynamics model. Moreover, a simulation methodology has been developed to quantify the effect of different materials and thicknesses of the cold plates on the temperature of the silicon carbide power dies.For medium- and high-power applications, contemporary research concludes that the reliability of the existing packaging technology needs to be improved. Therefore, this work proposes a novel press-pack silicon carbide power module concept. The concept enables bondless package and allows for an order of magnitude higher clamping force on the heatsinks than what can be applied on the dies. First, experimental and numerical methodologies for thermomechanical performance characterization of a press-pack structure have been investigated. By using digital image correlation technique, the deformation of each stacked material layer has been obtained. The developed experiment has led to an analytical estimation of friction coefficients on the contact interfaces. The co-influence of the design parameters on the thermomechanical performance of the press-pack structure has been analyzed through a parametric study based on a finite element model. Second, the novel double press-pack silicon carbide power module concept has been evaluated in a demonstrator in terms of parasitic inductance, thermal resistance, and thermomechanical stress.Furthermore, many of the power module designs only stay at the stage of proof-of-concept due to the cost of retooling of the manufacturing facility. Embedded power modules which employ advanced printed circuit board processing and die embedding technologies, enable a solution with possibility of low cost and mass production. Therefore, a novel design concept of a three-phase embedded power module (1200 V, 20 A) has been proposed. Simulation-driven design development has been implemented and lead to a fabricated demonstrator. The electromagnetic, thermal, and thermomechanical performances of the concept have been evaluated by simulations and compared to a commercially available power module.
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| 18. |
- Zhang, Yafan, et al.
(författare)
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Thermal evaluation of a liquid/air cooled integrated power inverter for hybrid vehicle applications
- 2013
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Ingår i: 2013 14th International Conference on Thermal, Mechanical and Multi-Physics Simulation and Experiments in Microelectronics and Microsystems, EuroSimE 2013. - New York : IEEE. - 9781467361385 - 9781467361378 ; , s. 6529944-
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Konferensbidrag (refereegranskat)abstract
- A thermal design of an integrated double-side cooled SiC 50kW-1200V-200A power inverter for hybrid electric vehicle applications has been proposed to enable cooling in two different automotive operating environments: under-hood and controlled temperature environment of passenger compartment. The power inverter is integrated with air/liquid cooled cold plates equipped with finned channels. Concept evaluation and CFD model calibration have been performed on a simplified thermal prototype. Computational experiments on the detailed model of the inverter, including packaging materials, have been performed for automotive industry defined application scenarios, including two extreme and one typical driving cycles. For the studied application scenarios the case temperature of the SiC transistors and diodes have been found to be below 210°C. The maximum steady-state temperature of the DC-link capacitor has been below 127 °C for the worst-case scenario including liquid cooling, and up to 140 °C for the worst-case scenario with air-cooling.
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| 19. |
- Abbas, Khizra, et al.
(författare)
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Autonomous Gate Drivers Tailored for Triangular Current Mode-Based Zero-Voltage Switching Two-Level Three-Phase Inverters for Electric Vehicle Drive Systems
- 2024
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Ingår i: Energies. - : MDPI AG. - 1996-1073. ; 17:5
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Tidskriftsartikel (refereegranskat)abstract
- The demand for highly efficient and dynamic electric vehicles (EVs) has increased dramatically. The traction inverter, a pivotal component in an EV powertrain, plays a crucial role. This study is dedicated to designing a traction inverter with focus on achieving high efficiency and elevated power density and mitigating electromagnetic interference (EMI) issues. To realize these objectives, autonomous gate drivers (AGDs) are proposed and designed using LTspice simulation software. The aim is to achieve zero voltage switching (ZVS) at both turn-on and turn-off through the utilization of triangular current mode (TCM) control on the gate driver. The AGDs implement a current modulation scheme by sensing the current and voltage and generating gate-source voltage signals with minimal delays. The implemented current modulation scheme by the AGDs results in an efficiency exceeding 99% for a 10 kW power rating. The sinusoidal output waveforms not only contribute to extending the motor lifespan by mitigating sharp-edge voltages but also bring advantages such as reduced switch stress, decreased EMI, and simplified thermal management.
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| 20. |
- Abbas, Khizra, et al.
(författare)
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Autonomously Modulating Gate Drivers For Triangular-Current Mode (TCM) Zero-Voltage Switching (ZVS) Buck Converter
- 2023
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Ingår i: <em>Proceedings of 22nd International Symposium on Power Electronics, Ee 2023</em>. - : Institute of Electrical and Electronics Engineers Inc..
-
Konferensbidrag (refereegranskat)abstract
- This paper introduces a novel approach to designing autonomous gate drivers for soft-switched buck converters. The objective is to reduce switching losses, enhance converter efficiency, and reduce electromagnetic interference (EMI). The uniqueness of this converter is that the pulse-width modulation is performed autonomously on the gate driver. The gate driver makes quick decisions on switching times, capitalizing on the minimal time delay between measurements and switching. In the proposed buck converter configuration, the gate driver senses both the current and voltage across the switches to avoid delay. When a slightly negative voltage is detected across the switch, it rapidly turns on, resulting in a zero-voltage switching (ZVS). With an external snubber capacitor placed across the switches, the turn-off switching losses are zero (ZVS). Hence, both the turn-on and turn-off of the switch are soft. To enable the switch to turn off, a reference value of the switch current needs to be sent out to the gate driver using a galvanically isolated current sensor. Through this approach, the efficiency of the 7 kW buck converter has been calculated to exceed 99% without including the filter losses. Additional benefits include reduced switch stresses, diminished electromagnetic interference (EMI), and simplified thermal management.
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| 21. |
- Abbas, Khizra, et al.
(författare)
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Autonomously Modulating Gate Drivers For Triangular-Current Mode (TCM) Zero-Voltage Switching (ZVS) Buck Converter
- 2023
-
Ingår i: Proceedings of 22nd International Symposium on Power Electronics, Ee 2023. - : Institute of Electrical and Electronics Engineers (IEEE).
-
Konferensbidrag (refereegranskat)abstract
- This paper introduces a novel approach to designing autonomous gate drivers for soft-switched buck converters. The objective is to reduce switching losses, enhance converter efficiency, and reduce electromagnetic interference (EMI). The uniqueness of this converter is that the pulse-width modulation is performed autonomously on the gate driver. The gate driver makes quick decisions on switching times, capitalizing on the minimal time delay between measurements and switching. In the proposed buck converter configuration, the gate driver senses both the current and voltage across the switches to avoid delay. When a slightly negative voltage is detected across the switch, it rapidly turns on, resulting in a zero-voltage switching (ZVS). With an external snubber capacitor placed across the switches, the turn-off switching losses are zero (ZVS). Hence, both the turn-on and turn-off of the switch are soft. To enable the switch to turn off, a reference value of the switch current needs to be sent out to the gate driver using a galvanically isolated current sensor. Through this approach, the efficiency of the 7 kW buck converter has been calculated to exceed 99% without including the filter losses. Additional benefits include reduced switch stresses, diminished electromagnetic interference (EMI), and simplified thermal management.
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| 22. |
- Abbas, Khizra, et al.
(författare)
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Comprehensive Insight into the Operational Dynamics of TCM-Based Zero-Voltage Switching (ZVS) Two-Level Three-Phase Inverters for Electric Vehicle (EV) Motor-Drive Applications
- 2024
-
Ingår i: 2024 IEEE Texas Power and Energy Conference, TPEC 2024. - : Institute of Electrical and Electronics Engineers (IEEE).
-
Konferensbidrag (refereegranskat)abstract
- This paper introduces a novel triangular-current mode (TCM), zero-voltage switching (ZVS) two-level three-phase inverter, specifically designed to enhance the performance of the electric vehicle (EV) drive system. The primary objective is to enhance the inverter efficiency by minimizing turn-on and turn-off switching losses while mitigating electromagnetic interference (EMI) by generating sinusoidal output waveforms. The distinctive feature of this inverter lies in its gate driver, which executes the current modulation scheme. Achieving ZVS during turn-on involves the gate driver sensing the switch voltage and turning it on at zero voltage, utilizing TCM. For turn-off ZVS, the gate driver monitors the switch current, turning it off when it exceeds a predefined reference value. With a carefully placed snubber capacitor, turn-off ZVS is achieved. The implemented current modulation scheme yields an efficiency exceeding 99% for a 10 kW power rating. The sinusoidal output waveforms not only enhance motor lifespan by safeguarding against sharp-edge voltages but also offer benefits like reduced switch stress and simplified thermal management.
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| 23. |
- Abdelhakim, A., et al.
(författare)
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Single-Stage Boost Modular Multilevel Converter (BMMC) for Energy Storage Interface
- 2020
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Ingår i: 2020 22nd European Conference on Power Electronics and Applications, EPE 2020 ECCE Europe. - : Institute of Electrical and Electronics Engineers (IEEE).
-
Konferensbidrag (refereegranskat)abstract
- Single-stage DC-AC power converters are gaining higher attention due to their simpler structure compared to the two-stage equivalent solution. In this paper, a single-stage DC-AC converter solution is proposed for interfacing a low voltage (LV) DC source with a higher voltage AC load or grid, where this converter has a modular structure with multilevel operation. The proposed converter, which is called boost modular multilevel converter (BMMC), comprises the boosting capability within the inversion operation, and it is mainly dedicated for interfacing LV energy storage systems, such as fuel cells and batteries, and it allows the use of LV MOSFETs (« 300 V), in order to utilize their low ON-state resistance, along with LV electrolytic capacitors. This converter is introduced and analysed in this paper, where simulation results using PLECS, considering a 10 kW three-phase BMMC, are presented in order to verify its functionality.
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| 24. |
- Ahmed, Noman, et al.
(författare)
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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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| 25. |
- Ahmed, Noman, et al.
(författare)
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Continuous modeling of open-loop control based negative sequence current control of modular multilevel converters for HVDC transmission
- 2013
-
Ingår i: Eur. Conf. Power Electron. Appl., EPE. - 9781479901166
-
Konferensbidrag (refereegranskat)abstract
- Negative sequence currents are obtained during ac-side asymmetrical faults of converters in highvoltage direct current (HVDC) transmission systems. Consequently, second order harmonics in the dc-side voltage and current, unbalanced ac-side currents, and power oscillations can be observed. This paper presents a negative sequence current control (NSCC) scheme that eliminates second order harmonic ripples in the voltage and current of the dc-side during unbalanced grid conditions. Controllers for this purpose are investigated using a continuous model of the modular multilevel converter (M2C). The proposed scheme utilizes an open-loop controller for lower level control of the M2C. The continuous model used also has the capability to model blocking and deblocking events which may be used during protective actions. Simulation results reveal that the proposed NSCC scheme is effective in suppressing dc-side voltage and current ripples. Moreover, it keeps the ac-side phase currents balanced during asymmetrical fault conditions.
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| 26. |
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| 27. |
- Ahmed, Noman, et al.
(författare)
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Efficient Modeling of an MMC-Based Multiterminal DC System Employing Hybrid HVDC Breakers
- 2015
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Ingår i: IEEE Transactions on Power Delivery. - : IEEE. - 0885-8977 .- 1937-4208. ; 30:4, s. 1792-1801
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Tidskriftsartikel (refereegranskat)abstract
- The feasibility of future multiterminal dc (MTDC) systems depends largely on the capability to withstand dc-side faults. Simulation models of MTDC systems play a very important role in investigating these faults. For such studies, the test system needs to be accurate and computationally efficient. This paper proposes a detailed equivalent model of the modular multilevel converter (MMC), which is used to develop the MTDC test system. The proposed model is capable of representing the blocked-mode operation of the MMC, and can be used to study the balancing control of the capacitor voltages. In addition, the operation of the MMC when redundant submodules are included in the arms can also be studied. A simplified model of a hybrid high-voltage dc breaker is also developed. Hence, the developed test system is capable of accurately describing the behavior of the MMC-based MTDC system employing hybrid HVDC breakers, during fault conditions. Using time-domain simulations, permanent dc-side faults are studied in the MTDC system. In addition, a scheme to control the fault current through the MMC using thyristors on the ac side of the converter is proposed.
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| 28. |
- Ahmed, Noman, 1974-
(författare)
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Efficient Modeling of Modular Multilevel Converters for HVDC Transmission Systems
- 2018
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The drive towards getting more and more electrical energy from renewable sources, requires more efficient electric transmission systems. A stronger grid, with more controllability and higher capacity, that can handle power fluctuations due to a mismatch between generation and load is also needed. High-voltage dc (HVDC) provides efficient and economical power transmission over very long distances, and will be a key player in shaping-up the future electric grid. Due to its outstanding features, the modular multilevel converter (MMC) has already been widely accepted as a key converter topology in voltage-source converter (VSC)-based HVDC transmission systems.In order to study the feasibility of future MMC-based HVDC grids, adequate simulation models are necessary. The main objective of the thesis is to propose MMC reduced-order simulation models capable of accurately replicating the response of an MMC during all relevant operating conditions. Such models are the basic building blocks in developing efficient simulation models for HVDC grids. This thesis presents two MMC equivalent simulation models, the continuous model (CM) and the detailed equivalent model (DEM). Compared to the CM, the DEM is also capable of demonstrating the individual sumodule behavior of an MMC. These models are validated by comparing with the detailed MMC model as well as with experimental results obtained from an MMC prototype in the laboratory. The most significant feature of the models is the representation of the blocking capability of the MMC, presented for the first time in the literature for an MMC equivalent simulation model. This feature is very important in replicating the accurate transient behavior of an MMC during energization and fault conditions. This thesis also investigates the performance of the MMC with redundant submodules in the arms. Two different control strategies are used and compared for integrating redundant submodules.The proposed MMC models are used in developing point-to-point and multiterminal HVDC (MTDC) systems. A reduced-order model of a hybrid HVDC breaker is also developed and employed in the MTDC system, making the test system capable of accurately replicating the behavior of the MMCbased MTDC system employing hybrid HVDC breakers. The conclusion of the analysis of dc-side faults in a MTDC system is that fast-acting HVDC breakers are necessary to isolate only the faulted part in the MTDC system to ensure the power flow in rest of the system is not interrupted.A generic four-terminal HVDC grid test system using the CM model is also developed. The simulated system can serve as a standard HVDC grid test system. It is well-suited to electromagnetic transient (EMT) studies in a limited version of commercially available EMT-type software. The dynamic performance of the HVDC grid is studied under different fault conditions.
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| 29. |
- Ahmed, Noman, et al.
(författare)
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Efficient Modeling of Modular Multilevel Converters in HVDC-Grids Under Fault Conditions
- 2014
-
Ingår i: 2014 IEEE PES General Meeting | Conference & Exposition. - : IEEE Computer Society. - 9781479964154 ; , s. 6939166-
-
Konferensbidrag (refereegranskat)abstract
- High-voltage direct current (HVDC) grids using modular multilevel converters (M2Cs) have strongly been considered for the integration of distant renewable energy sources and also as a backbone to the existing ac-grids. The dynamic performance of the M2C is of particular interest in these grids. For electromagnetic transient (EMT) programs, modeling of HVDC-grids using detailed M2C models is unrealistic, as it requires extremely high computational effort and simulation time. In this paper an HVDC-grid test system is developed using a continuous simulation model of the M2C. The model is also capable of describing the blocking events of the M2C. Using time-domain simulations in PSCAD/EMTDC, the dynamic performance of the M2C in HVDC-grids under fault conditions is investigated. Simulation results reveal that the continuous M2C model can efficiently be used to study the dynamic performance of the M2C in HVDC-grids with high computational speed, under different fault conditions.
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| 30. |
- Ahmed, Noman, et al.
(författare)
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HVDC SuperGrids with modular multilevel converters - The power transmission backbone of the future
- 2012
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Ingår i: International Multi-Conference on Systems, Signals and Devices, SSD 2012. - : IEEE. - 9781467315906 ; , s. 6198119-
-
Konferensbidrag (refereegranskat)abstract
- In order to transmit massive amounts of power generated by remotely located power plants, especially offshore wind farms, and to balance the intermittent nature of renewable energy sources, the need for a stronger high voltage transmission grid is anticipated. Due to limitations in ac power transmission the most likable choice for such a grid is a high-voltage dc (HVDC) grid. However, the concept of the HVDC grid is still under active development as different technical challenges exist, and it is not yet possible to construct such a dc grid. This paper deals with prospects and technical challenges for future HVDC SuperGrids. Different topologies for a SuperGrid and the possibility to use modular multilevel converters (M2Cs) are presented. A comprehensive overview of different submodule implementations of M2C is given as well as a discussion on the choice between cables or overhead lines, the protection system for the dc grid and dc-side resonance issues.
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| 31. |
- Ahmed, Noman, 1974-, et al.
(författare)
-
M2C-BASED MTDC SYSTEM FOR HANDLING OF POWERFLUCTUATIONS FROM OFFSHORE WIND FARMS
- 2011
-
Ingår i: Proceedings of IET RPG-2011. - : IET. - 9781849195362
-
Konferensbidrag (refereegranskat)abstract
- In this paper a modular multilevel converter (M2C) basedmulti-terminal direct current (MTDC) system is proposed forthe connection of offshore wind farms. Each M2C ismodelled with 36 sub-modules per arm with a total of 216sub-modules consisting of half bridges. An open-loopconverter control method is employed for the M2Cs. Powersynchronizationcontrol is used instead of a phase-locked loop(PLL) for synchronization. A voltage controller isimplemented with power-synchronization control as an innerloop. By means of numerical simulations in PSCAD, it isshown that the system is self stabilizing both at steady stateand following power fluctuations of the wind farm.
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| 32. |
- Ahmed, Noman, et al.
(författare)
-
Performance of the modular multilevel converter with redundant submodules
- 2015
-
Ingår i: IECON 2015 - 41st Annual Conference of the IEEE Industrial Electronics Society. - : Institute of Electrical and Electronics Engineers (IEEE). - 9781479917624 ; , s. 3922-3927
-
Konferensbidrag (refereegranskat)abstract
- The modular multilevel converter (MMC) is the state-of-the-art voltage-source converter (VSC) topology used for various power-conversion applications. In the MMC, submodule failures can occur due to various reasons. Therefore, additional submodules called the redundant submodules are included in the arms of the MMC to fulfill the fault-safe operation requirement. The performance of the MMC with redundant submodules has not been widely covered in the published literature. This paper investigates the performance of the MMC with redundant submodules in the arms. Two different control strategies are used and compared for integrating redundant submodules. The response of the MMC to a submodule failure for the two strategies is also studied. Moreover, the operation of the MMC with redundant submodules is validated experimentally using the converter prototype in the laboratory.
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| 33. |
- Ahmed, Noman, et al.
(författare)
-
Prospects and challenges of future HVDC SuperGrids with modular multilevel converters
- 2011
-
Ingår i: Proceedings of the 2011-14th European Conference on Power Electronics and Applications (EPE 2011). - 9781612841670 - 9789075815153
-
Konferensbidrag (refereegranskat)abstract
- In order to transmit massive amounts of power generated by remotely located power plants, especially offshore wind farms, and to balance the intermittent nature of renewable energy sources, the need for a stronger high voltage transmission grid is anticipated. Due to limitations in AC power transmission the most likable choice for such a grid is a high voltage DC (HVDC) grid. However, the concept of the HVDC grid is still under active development as different technical challenges exist, and it is not yet possible to construct such a DC grid. This paper deals with prospects and technical challenges for the future HVDC SuperGrids. Different topologies for a SuperGrid and the possibility to use modular multilevel converters (M2Cs) are presented. A comprehensive overview of different sub-module implementations of M2C is given. An overview of short circuit behaviour of the M2C is also given, as well as a discussion on the choice between cables or overhead lines and DC-side resonance issues.
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| 34. |
- 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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| 35. |
- Ambatipudi, Radhika, 1982-
(författare)
-
High Frequency (MHz) Planar Transformers for Next Generation Switch Mode Power Supplies
- 2013
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Increasing the power density of power electronic converters while reducing or maintaining the same cost, offers a higher potential to meet the current trend inrelation to various power electronic applications. High power density converters can be achieved by increasing the switching frequency, due to which the bulkiest parts, such as transformer, inductors and the capacitor's size in the convertercircuit can be drastically reduced. In this regard, highly integrated planar magnetics are considered as an effective approach compared to the conventional wire wound transformers in modern switch mode power supplies (SMPS). However, as the operating frequency of the transformers increase from several hundred kHz to MHz, numerous problems arise such as skin and proximity effects due to the induced eddy currents in the windings, leakage inductance and unbalanced magnetic flux distribution. In addition to this, the core losses whichare functional dependent on frequency gets elevated as the operating frequency increases. Therefore, this thesis provides an insight towards the problems related to the high frequency magnetics and proposes a solution with regards to different aspects in relation to designing high power density, energy efficient transformers.The first part of the thesis concentrates on the investigation of high power density and highly energy efficient coreless printed circuit board (PCB) step-down transformers useful for stringent height DC-DC converter applications, where the core losses are being completely eliminated. These transformers also maintain the advantages offered by existing core based transformers such as, high coupling coefficient, sufficient input impedance, high energy efficiency and wide frequencyband width with the assistance of a resonant technique. In this regard, several coreless PCB step down transformers of different turn’s ratio for power transfer applications have been designed and evaluated. The designed multilayered coreless PCB transformers for telecom and PoE applications of 8,15 and 30W show that the volume reduction of approximately 40 - 90% is possible when compared to its existing core based counterparts while maintaining the energy efficiency of the transformers in the range of 90 - 97%. The estimation of EMI emissions from the designed transformers for the given power transfer application proves that the amount of radiated EMI from a multilayered transformer is lessthan that of the two layered transformer because of the decreased radius for thesame amount of inductance.The design guidelines for the multilayered coreless PCB step-down transformer for the given power transfer application has been proposed. The designed transformer of 10mm radius has been characterized up to the power level of 50Wand possesses a record power density of 107W/cm3 with a peak energy efficiency of 96%. In addition to this, the design guidelines of the signal transformer fordriving the high side MOSFET in double ended converter topologies have been proposed. The measured power consumption of the high side gate drive circuitvitogether with the designed signal transformer is 0.37W. Both these signal andpower transformers have been successfully implemented in a resonant converter topology in the switching frequency range of 2.4 – 2.75MHz for the maximum load power of 34.5W resulting in the peak energy efficiency of converter as 86.5%.This thesis also investigates the indirect effect of the dielectric laminate on the magnetic field intensity and current density distribution in the planar power transformers with the assistance of finite element analysis (FEA). The significanceof the high frequency dielectric laminate compared to FR-4 laminate in terms of energy efficiency of planar power transformers in MHz frequency region is also explored.The investigations were also conducted on different winding strategies such as conventional solid winding and the parallel winding strategies, which play an important role in the design and development of a high frequency transformer and suggested a better choice in the case of transformers operating in the MHz frequency region.In the second part of the thesis, a novel planar power transformer with hybrid core structure has been designed and evaluated in the MHz frequency region. The design guidelines of the energy efficient high frequency planar power transformerfor the given power transfer application have been proposed. The designed corebased planar transformer has been characterized up to the power level of 50W and possess a power density of 47W/cm3 with maximum energy efficiency of 97%. This transformer has been evaluated successfully in the resonant converter topology within the switching frequency range of 3 – 4.5MHz. The peak energy efficiency ofthe converter is reported to be 92% and the converter has been tested for the maximum power level of 45W, which is suitable for consumer applications such as laptop adapters. In addition to this, a record power density transformer has been designed with a custom made pot core and has been characterized in thefrequency range of 1 - 10MHz. The power density of this custom core transformer operating at 6.78MHz frequency is 67W/cm3 and with the peak energy efficiency of 98%.In conclusion, the research in this dissertation proposed a solution for obtaining high power density converters by designing the highly integrated, high frequency(1 - 10MHz) coreless and core based planar magnetics with energy efficiencies inthe range of 92 - 97%. This solution together with the latest semiconductor GaN/SiC switching devices provides an excellent choice to meet the requirements of the next generation ultra flat low profile switch mode power supplies (SMPS).
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| 36. |
- Anpalahan, Peethamparam, et al.
(författare)
-
Design Steps towards a High Power Factor Transverse Flux Machine
- 2001
-
Ingår i: Proc. of the European Conference on Power Electronics and Applications (EPE), Graz, Austria, August 2001.
-
Konferensbidrag (refereegranskat)abstract
- This article describes a topology of three-phase transverse flux machine and the derivation of ananalytical model which does not exist in the literature. Three dimensional finite element analysis isalso used to get more accurate results. Steps carried out to obtain a better power factor are presented.
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| 37. |
- Antonopoulos, Antonios, 1984-
(författare)
-
Control, Modulation and Implementation of Modular Multilevel Converters
- 2011
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Denna avhandling behandlar analys och styrning av den modulära multinivå omvandlaren (M2C). M2C är en lovande omvandlarteknologi för högspända högeffekttillämpningar. Anledningen till detta är låg distorsion i utstorheterna kan uppnås med låg medelswitchfrekvens per switch och utan utgångsfilter. Med M2C har utspänningen så lågt övertonsinnehåll att drift av högeffektmotorer är möjlig utan reduktion av märkeffekten. Emellertid innebär det stora antalet styrda switchar att styrningen blir mer komplex än för motsvarande tvånivåomvandlare. Styrningen av M2C måste måste konstrueras så att submodulernas kondensatorspänningar balanseras och är stabila oberoende av driftfall. En aktiv mekanism för val av submoduler, som är integrerad i modulatorn, har visat sig vara effektiv för att ombesörja den interna balanseringen av omvandlararmarna. Utöver balanseringen av de individuella kondensatorerna krävs en strategi för styrning av den totalt upplagrade energin i omvandlaren. Med utgångspunkt i en analytisk beskrivning av omvandlaren föreslås styrlagar för både öppen styrning och sluten reglering, vilka genom både simuleringar och med hjälp av experiment har visat sig vara stabila i hela arbetsområdet. Den potentiella växelverkan mellan den inre omvandlarstyrningen och en yttre strömreglering undersöks också. Både simuleringar och experiment bekräftar att eventuell interaktion inte innebär några avsevärda problem vare sig för omvandlaren eller motorn. En hårdvaruimplementering av en nedskalad trefasig 10kVA-omvandlare har genomförts för att verifiera modellering och styrning. Implementeringen av styrningen beskrivs i detalj. Styrningen är anmärkningsvärt snabb och kan utökas till godtyckligt antal nivåer. Den kan därför användas för en fullskaleimplementering i MW-klassen.
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| 38. |
- Antonopoulos, Antonios, 1984-, et al.
(författare)
-
Evaluation of Control and Modulation Methods forModular Multilevel Converters
- 2010
-
Ingår i: Proc. Int. Power Electronics Conf. (IPEC). - 9781424453955 ; , s. 746-753
-
Konferensbidrag (refereegranskat)abstract
- The modular multilevel converter is a promising converter technology for various high-voltage high-power applications. Despite the apparent simplicity of the circuit, the inherent dynamics of the converter and the balancing of the sub-module capacitor voltages impose high requirements on the control system, which can be implemented in quite different ways. To illustrate this, and to provide a guidance for future research on the subject, this paper presents an evaluation of four different control and modulation methods. The investigation is based on experiments on a down-scaled 10 kVA converter having 10 submodules per phase leg. The main items to be investigated are dynamics within the sub-modules, arm voltages and circulating currents. It is found that the suggested open-loop control method provides the fastest arm-voltage response and that the balancing approach based on a sorting algorithm is substantially faster and less complicated to implement than the method using a dedicated voltage controller for each sub-module.
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| 39. |
- Antonopoulos, Antonios, et al.
(författare)
-
Experimental evaluation of the impact of harmonics on induction motors fed by modular multilevel converters
- 2014
-
Ingår i: Proceedings - 2014 International Conference on Electrical Machines, ICEM 2014. - 9781479943890 ; , s. 768-775
-
Konferensbidrag (refereegranskat)abstract
- Inverter-based electrical-machine drives suffer from significantly higher losses compared to sinusoidal-supply-based alternatives, fed directly from the grid. Using multilevel inverters it becomes possible to partially mitigate the effects of the switched supply waveform, while keeping the advantages of variable-speed operation. This paper aims to evaluate the increase of the losses occurring in an induction motor (IM) fed by a modular multilevel converter (M2C), when compared to grid-connected operation, in order to evaluate the impact of the inverter-generated harmonics in the machine. It is confirmed that the losses created in the motor due to the harmonic content of the inverter-generated waveforms are very low, and almost equivalent to a purely sinusoidal supply. The investigation includes an analysis of the harmonic content from experimental waveforms obtained by an 11-kW IM laboratory setup, and it is further supported by measurements of the temperature rise in the IM-stator windings. It is concluded that the M2C could create the conditions even for high-power motors to be operated without any derating.
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| 40. |
- Antonopoulos, Antonios, et al.
(författare)
-
Global Asymptotic Stability of Modular Multilevel Converters
- 2014
-
Ingår i: IEEE Transactions on Industrial Electronics. - : IEEE. - 0278-0046 .- 1557-9948. ; 61:2, s. 603-612
-
Tidskriftsartikel (refereegranskat)abstract
- Modular multilevel converters require that the controller is designed so that the submodule capacitor voltages are equalized and stable, independent of the loading conditions. Assuming that the individual capacitor-voltage sharing is managed effectively, an open-loop strategy has been designed to ensure that the total amount of energy stored inside the converter always will be controlled. This strategy, using the steady-state solutions of the dynamic equations for controlling the total stored energy in each converter arm, has proven to be effective. The intention of this paper is to explain in a rigorous way the mechanism behind the suggested strategy and to prove that, when this open-loop strategy is used, the system becomes globally asymptotically stable. Experimental verification on a three-phase 10-kVA prototype is presented.
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| 41. |
|
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| 42. |
- Antonopoulos, Antonios, et al.
(författare)
-
Modular multilevel converter ac motor drives with constant torque form zero to nominal speed
- 2012
-
Ingår i: 2012 IEEE Energy Conversion Congress and Exposition, ECCE 2012. - : IEEE. - 9781467308014 ; , s. 739-746
-
Konferensbidrag (refereegranskat)abstract
- Modular multilevel converters (M2Cs) 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 the ideal combination for very high-efficiency drives, both from an electric motor and an inverter point of view. With M2Cs the output voltage has such a low harmonic content that high-power motors can be operated without any derating. However, the large number of devices and the existence of capacitors that have to conduct the fundamental frequency current, requires more complex converter control techniques than its two-level counterpart. Special care needs to be taken under starting and operation with low frequency, where the low-frequency current may cause significant unbalance between the submodule capacitor voltages, disturb the output waveforms, and eventually cause the converter to trip. In this paper, principles for converter operation with high torque in the whole speed range, from standstill to rated speed will be investigated. The converter-control method utilizes estimation of the capacitor voltage variation, based on equations describing steady-state conditions. Experimental results from a down-scaled 12 kVA prototype converter running a loaded motor from zero up to the rated speed are provided in the paper.
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| 43. |
- 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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| 44. |
- Antonopoulos, Antonios, et al.
(författare)
-
On Dynamics and Voltage Control of the Modular Multilevel Converter
- 2009
-
Ingår i: 2009 13th European Conference on Power Electronics and Applications, EPE '09. - : IEEE. - 9781424444328 ; , s. 3353-3362
-
Konferensbidrag (refereegranskat)abstract
- This paper discusses the impact of modulation on stability issues of the Modular Multilevel Converter (M2C). The main idea is to describe the operation of this converter system mathematically, and suggest a control method that offers stable operation in the whole operation range. A possible approach is to assume a continuous model, where all the modules in each arm are represented by variable voltage sources. and as a result, all pulse width modulation effects are disregarded. After simulating this model and testing different control methods, useful conclusions on the operation of the M2C have been extracted. The control methods are then implemented on a model with discrete half-bridge modules, in order to compare the results and to validate continuous model approach. When assuring that this model functions as expected, the goal of this paper is to conclude into a self-stabilizing voltage controller. A controller is proposed, which eliminates circulating currents between the phase legs and balances the arm voltages regardless of the imposed alteranting current.
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| 45. |
- Antonopoulos, Antonios, 1984-, et al.
(författare)
-
On Interaction between Internal Converter Dynamics and Current Control of High-Performance High-Power AC Motor Drives with Modular Multilevel Converters
- 2010
-
Ingår i: Proc. IEEE Energy Conversion Congress and Exposition (ECCE). ; , s. 4293-4298
-
Konferensbidrag (refereegranskat)abstract
- The modular multilevel converter (M2C) is a promising converter technology for various high-voltage highpower applications. The reason to this is that low-distortion output quantities can be achieved with low average switching frequencies per switch and without output filters. With the M2C the output voltage has such a low harmonic content that highpower motors can be operated without any derating. However, the apparent large number of devices, requires more complex converter control techniques than a two-level counterpart. Even though there have been several ways suggested to control the converter itself, it is still a challenge to investigate the interaction of these controllers with an external motor current controller. It is shown in the paper that the anticipated interaction will not result in any problems neither for the converter nor for the motor control itself.
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| 46. |
- Antonopoulos, Antonios, 1984-
(författare)
-
On the Internal Dynamics and AC-Motor Drive Application of Modular Multilevel Converters
- 2014
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis is an effort to investigate the operation and the performanceof modular multilevel converters (M2Cs). Proven to be the most promisingtopology in high-voltage high-power applications, it is necessary to put aneffort in understanding the physical laws that govern the internal dynamicsof such converters, in order to design appropriate control methods. AlthoughM2Cs belong to the well-studied family of voltage-source converters (VSCs),and claim a modular structure, their control is significantly more complicatedcompared to two- or three-level VSCs, due to the fact that a much highernumber of switches and capacitors are needed in such a topology. This thesishighlights the important parameters that should be considered when designingthe control for an M2C, through analyzing its internal dynamics, and alsosuggests ways to control such converters ensuring stable operation withoutcompromising the performance of the converter.Special focus is given on ac motor-drive applications as they are very demandingand challenging for the converter performance. Interactions betweenthe internal dynamics and the dynamics of the driven motor are experimentallyinvestigated. The problem of operating the converter when connectedto a motor standing still is visited, even under the condition that a greatamount of torque and current are requested, in order to provide an idea forthe converter requirements under such conditions. Finally, an optimization ofthe converter operation is suggested in order to avoid overrating the convertercomponents in certain operation areas that this is possible.All analytical investigations presented in this thesis are confirmed by experimentalresults on a laboratory prototype converter, which was developedfor the purposes of this project. Experimental verification proves the validityof the theoretical investigations, as well as the correct performance of thecontrol methods developed during this project on a real, physical converter,hoping that the results of this thesis will be useful for large-scale implementations,in the mega- or even giga-watt power range.
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| 47. |
- Antonopoulos, Antonios, et al.
(författare)
-
Optimal selection of the average capacitor voltage for modular multilevel converters
- 2013
-
Ingår i: 2013 IEEE Energy Conversion Congress and Exposition, ECCE 2013. - : IEEE. - 9781479903351 ; , s. 3368-3374
-
Konferensbidrag (refereegranskat)abstract
- Variable-speed drives have reduced voltage requirements when operating below the base speed. In a modular-multilevel-converter-based (M2C-based) motor drive it is then possible to operate with reduced voltage in the submodule capacitors, than at the base speed. In this sense, a greater capacitor-voltage ripple can be accommodated, without exceeding the maximum peak-capacitor voltage. This paper presents an analytical investigation for the optimal selection of the average capacitor voltage for M2Cs, when the motor is operating with rated torque, below the base speed. This method does not require any power exchange between the converter arms, so it keeps the conduction losses at the minimum level. Additionally, the method decreases the switching losses, due to the decreased capacitor-voltage level. The overall ratings of the converter remain the same as in the base-speed operation. It is shown that this method can be applied at a speed range between the base speed and down to approximately one third of it, i.e, an operating range that covers the requirements for typical pump- and fan-type applications. The results obtained from the analytical investigation are experimentally verified on a down-scaled laboratory prototype M2C.
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| 48. |
- Antonopoulos, Antonios, 1984-, et al.
(författare)
-
Optimal Selection of the Average Capacitor Voltage for Variable-Speed Drives With Modular Multilevel Converters
- 2015
-
Ingår i: IEEE transactions on power electronics. - 0885-8993 .- 1941-0107. ; 30:1, s. 227-234
-
Tidskriftsartikel (refereegranskat)abstract
- Variable-speed drives have reduced voltage requirementswhen operating below the base speed. In a modularmultilevel-converter-based (M2C-based) motor drive it is thenpossible to operate with reduced voltage in the submodulecapacitors, than at the base speed. In this sense, a greatercapacitor-voltage ripple can be accommodated, without exceedingthe maximum peak-capacitor voltage. This paper presents ananalytical investigation for the optimal selection of the averagecapacitor voltage for M2Cs, when the motor is operating withrated torque, below the base speed. This method does not requireany power exchange between the converter arms, so it keepsthe conduction losses at the minimum level. Additionally, themethod decreases the switching losses, due to the decreasedcapacitor-voltage level. The overall ratings of the converterremain the same as in the base-speed operation. It is shownthat this method can be applied at a speed range betweenthe base speed and down to approximately one third of it,i.e, an operating range that covers the requirements for typicalpump- and fan-type applications. The results obtained from theanalytical investigation are experimentally verified on a downscaledlaboratory prototype M2C.
|
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| 49. |
- Antonopoulos, Antonios, et al.
(författare)
-
Stability Analysis of Modular Multilevel Converters With Open-Loop Control
- 2013
-
Ingår i: 39th Annual Conference of the IEEE Industrial Electronics Society, IECON 2013. - : IEEE. - 9781479902248 ; , s. 6316-6321
-
Konferensbidrag (refereegranskat)abstract
- Modular multilevel converters (M2Cs) require that the controller is designed so that the submodule capacitor voltages are equalized and stable, independent of the loading conditions. Provided that the individual capacitor voltage sharing is managed effectively, an open-loop strategy can been designed to ensure that the total amount of energy stored inside the converter always will be controlled. This strategy, using the steady-state solutions of the dynamic equations for controlling the total stored energy in each converter arm, has proven to be effective. The intention of this paper is to explain in a rigorous way the mechanism behind the suggested strategy, and to prove that, when this open-loop strategy is used, the system becomes globally asymptotically stable.
|
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| 50. |
- Asoodar, Mohsen, et al.
(författare)
-
A Computationally Efficient Model for Large-Scale Energy Storage Systems With Active Voltage Balancing in Modular Multilevel Converters
- 2023
-
Ingår i: 2023 IEEE Applied Power Electronics Conference And Exposition, APEC. - : Institute of Electrical and Electronics Engineers (IEEE). ; , s. 2973-2978
-
Konferensbidrag (refereegranskat)abstract
- In this paper, a novel method for modeling and simulation of large-scale energy storage systems (ESS) is provided. Specifically, the model is developed for large-scale series connected supercapacitors (SCs) intended for power electronic applications. This method is especially useful for high voltage applications where a large number of series connected energy storage units (ESUs) are required. The proposed solution reduces a multi-node string of series connected SCs-together with their corresponding voltage balancing circuit-to a single unit with two electrical nodes. The proposed model is connected to the dc link of a three phase grid-connected modular multilevel converter (MMC). In this system, the effectiveness of the proposed model and the proposed voltage balancing scheme is demonstrated for a string comprising ten thousand series connected ESUs. The efficacy of the proposed model and the balancing algorithm is proven by simulations in the MATLAB/Simulink environment.
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