基于电压平衡器的固态变压器及其控制策略研究

Research on Solid-state Transformer Based on Voltage Balancer and Its Control Strategy

固态变压器是交直流混合配电网的核心装置。针对低压直流配电网一般采用双极性供电的特点,提出了一种基于电压平衡器的固态变压器拓扑。所提拓扑的中间级DC/DC包括输入半桥、双有源桥和电压均衡3部分,结合其运行模式给出了各部分的控制策略。为了分析系统的大信号稳定性并加快仿真速度,给出了中间级DC/DC子模块的大信号回转器模型,并采用仿真方法验证了所提拓扑和控制策略的有效性。所提出的基于电压均衡器的固态变压器具有多个电压端口,能够与中高压电网及低压电网相连,提供自身用电或组网运行。

A solid-state transformer(SST)is the core device of AC/DC hybrid distribution network.Considering that a low-voltage DC distribution network usually uses bipolar power supply,an SST topology based on voltage balancer is proposed in this paper.The intermediate-stage DC/DC converter of the proposed topology consists of three parts,i.e.,half bridge,dual active bridge,and voltage balancer.Combined with its operation mode,the control strategies for each part are given.To analyze the system’s large-signal stability and accelerate the simulation speed,a large-signal gyrator model of the intermediate-stage DC/DC sub-module is also presented.The effectiveness of the proposed topology and control strategy is verified by simulations.The proposed SST based on voltage balancer has multiple voltage ports,which can be connected to medium-and high-voltage power grid as well as low-voltage power grid,and provide power supply for itself or the network operation.