The DC Bus Voltage Control Based on Virtual Inertia for SST

Abstract

Three-stage solid state transformer adopts three independent control units, so when the system power changes, the regulation of DC bus voltage stabilization is important. A DC bus voltage control Strategy based on virtual inertia is proposed for AC/DC converter in this paper. On the basis of traditional voltage/current double closed-loop controller, the virtual inertia control loop and the DC current feed-forward loop are introduced. In order to effectively suppress the voltage fluctuation of the DC bus in the case of the fluctuation of the system power, the inertia of the DC bus is enhanced by adding virtual capacitance. In order to reduce the influence on the DC voltage caused by load current changing, the voltage stability of the DC bus is enhanced by adding the DC current feed-forward link. Single phase shift control of load current feed-forward is adopted for DAB, which decreases the fluctuation of the DC bus voltage and increases the dynamic response time of the DC bus voltage. Finally, the simulation results verify the effectiveness of the proposed control strategy.