A 6.6-kV transformerless battery energy storage system based on a cascade multilevel PWM converter: Experimental verification by a 200-V, 10-kW, 3.6-kWh laboratory model

In this paper we present an energy storage system using a cascade PWM converter 11-14 and secondary batteries

Shigenori Inoue


Scholarcy highlights

  • The growing concern about energy problems has given impetus to research on distributed generation systems using natural energy sources such as wind power and solar power
  • The cascade PWM converter was operated at a power factor of 1, and the system voltage vSu0 and system current iu were in phase
  • In the real-scale system connected to a 6.6-kV power network, the voltage drop on the IGBT and the antiparallel diode is only about 0.3% of the DC voltage, and we may expect much smaller total harmonic distortion than in the laboratory model 13
  • The laboratory model used in this study was designed for simulation of secondary battery charge/discharge control by a cascade PWM inverter connected to the power grid, and power losses that occur during charge/discharge could not be reproduced
  • A distinctive feature of the proposed system is that NiMH battery packs are connected to the DC side of every cell of the cascade PWM converter
  • Prior to the experiment, the cascade PWM converter was stopped and the nine battery packs had nonuniform state of charge values of up to 5%
  • We describe SOC-balancing control that combines SOC balancing between phases and between stages, and the verification of its effectiveness

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