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Coordinative Control Strategy for Power Electronic Transformer Based Battery Energy Storage System
Battery energy storage, Coordinative control, LQR, Power electronic transformer, State-feedback, SOC balancing
Abstract Power electronic transformer (PET) based on the cascaded H-bridge (CHB) and isolated bidirectional DC/DC converter (IBDC) is capable to accommodate large scale battery energy storage system (BESS) in the medium-voltage grid, named as power electronic transformer based battery energy storage system (PET-BESS). This paper investigates the PET-BESS and proposes a coordinative control strategy for it. In the proposed method, the CHB controls the power flow and battery state-of-charge (SOC) balancing, while the IBDC maintains the dc-link voltages with feedforward implementation of power reference and switch status of CHB. State-feedback and linear quadratic riccati (LQR) methods have been adopted in CHB to control the grid current, active and reactive power. A hybrid PWM modulating method is utilized to achieve SOC balancing, where battery SOC sorting is involved. The feedforward path of power reference and CHB switch status substantially reduces the dc-link voltage fluctuations under dynamic power variations. The effectiveness of the proposed control has been verified by both simulation and experimental results, not only the performance of the PET-BESS under bidirectional power flow has been improved, but also the battery SOC values have been adjusted to converge.
Keyword Yuwei Sun, Jiaomin Liu, Yonggang Li, Chao Fu, and Yi Wang
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