EPE Association: EPE 2016 - LS1a: Modular Multilevel Converters

EPE 2016 - LS1a: Modular Multilevel Converters
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 2016 ECCE Europe - Conference > EPE 2016 - Topic 02: Power Converter Topologies and Design > EPE 2016 - LS1a: Modular Multilevel Converters

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   AC/AC Modular Multilevel Converters in Wind Energy Applications: Design Considerations
By Jakub KUCKA [View]
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Abstract: Modular multilevel topologies are possible candidates for medium-voltage wind turbines because of their scalability and possible redundancy. This paper concentrates on their design and investigates the influence of generator-to-grid voltage ratio, generator nominal frequency, module-capacitance minimising control approaches, third harmonic injection and fault ride-through capability requirement on the main design parameters (installed switching power, energy variation at module capacitors and efficiency). For different design scenarios, different topologies are concluded as being optimal.

   Analysis and Reduction of Capacitor Ripple Current in Modular Multilevel Converter for Variable Speed Drives
By SHAMBHU SAU [View]
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Abstract: The rms value of capacitor ripple current is one of the important parameters for capacitor selection in Modular Multilevel Converter (MMC) based medium voltage adjustable speed drives. In this paper, an expression for the rms value of ripple current of each submodule capacitor in MMC is derived analytically. The analysis reveals that like capacitor ripple voltage, the ripple current also increases at lower operating speed. It is shown that this current can be reduced by reducing the dc-bus voltage with the operating speed. Furthermore, in this method, the capacitor ripple voltage is also reduced without the need of injecting any circulating current at lower operating speed. To verify the claims, the simulation study is carried out in Matlab/Simulink and the results are compared for different values of dc-bus voltage at various operating speeds.

   Improved control strategy of the Modular Multilevel Converter for high power drive applications in low frequency operation
By Mauricio ESPINOZA [View]
[Download]

Abstract: Modular Multilevel Converters (M2C) are considered an attractive solution for high power drives. However, its operation at low rotational speeds can produce undesired voltage fluctuations in the M2C capacitors. In this paper, two methodologies to improve the converter performance in this speed range are analysed and tested. The first strategy proposes the control of the inner converter currents combining a synchronous dq rotating frame and resonant controllers to improve the current tracking and to reduce the voltage fluctuations. The second strategy achieves the reduction of the voltage fluctuations by adjusting the DC Port voltage as a function of the machine frequency. Both methods are validated by simulation and experimental work, where a 18 cell M2C prototype is applied to drive an induction machine.

   Insulation Coordination for a Modular Multilevel Converter Prototype
By Alexandre CHRISTE [View]
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Abstract: This paper provides a detailed overview of the dielectric design and insulation coordination applied to a medium voltage modular multilevel converter prototype. The complete system has ratings of 0.5MVA and is designed for connection to a 10 kVdc supply with a system voltage of 6.6 kVac. The choice of air as insulating and cooling medium requires careful considerations regarding the clearance and creepage distances with respect to the selected materials. The design considerations from the submodule to the cabinet level are presented in the paper, considering safety standards and their requirements for a selected over-voltage category and pollution degree. The final dielectric design is verified experimentally with dielectric ac withstand test and partial discharge measurements.

EPE 2016 - LS1a: Modular Multilevel Converters
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 2016 ECCE Europe - Conference > EPE 2016 - Topic 02: Power Converter Topologies and Design > EPE 2016 - LS1a: Modular Multilevel Converters
	[return to parent folder]

	AC/AC Modular Multilevel Converters in Wind Energy Applications: Design Considerations By Jakub KUCKA	[View] [Download]
Abstract: Modular multilevel topologies are possible candidates for medium-voltage wind turbines because of their scalability and possible redundancy. This paper concentrates on their design and investigates the influence of generator-to-grid voltage ratio, generator nominal frequency, module-capacitance minimising control approaches, third harmonic injection and fault ride-through capability requirement on the main design parameters (installed switching power, energy variation at module capacitors and efficiency). For different design scenarios, different topologies are concluded as being optimal.

	Analysis and Reduction of Capacitor Ripple Current in Modular Multilevel Converter for Variable Speed Drives By SHAMBHU SAU	[View] [Download]
Abstract: The rms value of capacitor ripple current is one of the important parameters for capacitor selection in Modular Multilevel Converter (MMC) based medium voltage adjustable speed drives. In this paper, an expression for the rms value of ripple current of each submodule capacitor in MMC is derived analytically. The analysis reveals that like capacitor ripple voltage, the ripple current also increases at lower operating speed. It is shown that this current can be reduced by reducing the dc-bus voltage with the operating speed. Furthermore, in this method, the capacitor ripple voltage is also reduced without the need of injecting any circulating current at lower operating speed. To verify the claims, the simulation study is carried out in Matlab/Simulink and the results are compared for different values of dc-bus voltage at various operating speeds.

	Improved control strategy of the Modular Multilevel Converter for high power drive applications in low frequency operation By Mauricio ESPINOZA	[View] [Download]
Abstract: Modular Multilevel Converters (M2C) are considered an attractive solution for high power drives. However, its operation at low rotational speeds can produce undesired voltage fluctuations in the M2C capacitors. In this paper, two methodologies to improve the converter performance in this speed range are analysed and tested. The first strategy proposes the control of the inner converter currents combining a synchronous dq rotating frame and resonant controllers to improve the current tracking and to reduce the voltage fluctuations. The second strategy achieves the reduction of the voltage fluctuations by adjusting the DC Port voltage as a function of the machine frequency. Both methods are validated by simulation and experimental work, where a 18 cell M2C prototype is applied to drive an induction machine.

	Insulation Coordination for a Modular Multilevel Converter Prototype By Alexandre CHRISTE	[View] [Download]
Abstract: This paper provides a detailed overview of the dielectric design and insulation coordination applied to a medium voltage modular multilevel converter prototype. The complete system has ratings of 0.5MVA and is designed for connection to a 10 kVdc supply with a system voltage of 6.6 kVac. The choice of air as insulating and cooling medium requires careful considerations regarding the clearance and creepage distances with respect to the selected materials. The design considerations from the submodule to the cabinet level are presented in the paper, considering safety standards and their requirements for a selected over-voltage category and pollution degree. The final dielectric design is verified experimentally with dielectric ac withstand test and partial discharge measurements.