Improved Virtual Capacitor Control Strategy of Multi-Port Isolated DC-DC Converter in DC Microgrid
Zhang Hui1,2, Liang Yuxin1, Sun Kai2, Chen Huan2, Du Mingqiao1
1. School of Electrical Engineering Xi'an University of Technology Xi'an 710048 China;
2. State Key Laboratory of Safety Control and Simulation of Power System and Power Generation Equipment Tsinghua University Beijing 100084 China
At present, distributed micro-source has urgent demand for high up/down ratio, electrical isolation and high efficiency converter. Aiming at the low inertia of DC microgrid and poor bus voltage quality, an improved virtual capacitor (IVC) control strategy for a multi-port isolated DC-DC converter (MPIC) is proposed. Firstly, MPIC is used to replace the traditional Buck-Boost circuit to achieve the electrical isolation of the micro sources inside the energy storage system. Secondly, through analog frequency modulation control of the virtual synchronous generator in the AC microgrid, IVC control suitable for MPIC is obtained. Then a small signal model of the energy storage interface converter (ESC) under its IVC control is established, and the dynamic characteristics of the DC bus voltage under load disturbance are analyzed in depth. The voltage overshoot phenomenon generated during the disturbance process is eliminated by feedforward compensation, and the parameters such as voltage tracking coefficient, virtual capacitance and damping coefficient are given. Finally, simulation and experimental results verify the proposed control strategy.
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2021, Vol. 36 
