DC/DC与DC/AC级联变流器阻抗协调控制策略

在back-to-back级联变流器系统中，前级子变流器的输出阻抗与后级子变流器的输入阻抗相互影响，如果系统参数设计不合理，将会恶化系统稳定性。该文提出了一种阻抗协调控制策略，将级联系统的前级子变流器和后级子变流器的低频阻抗均呈现为阻性阻抗，使得低频相移为0，从而提高back-to-back级联变流器系统的稳定性。基于双H桥DC/DC变流器和三相两电平逆变器级联拓扑结构，对所提控制策略与传统控制策略进行了比较。基于阻抗特性的稳定性判据显示，在低频范围内，所提控制策略可以促进前级功率源变流器和后级负载变流器面向中间直流母线侧呈现阻性阻抗，从而显著降低阻抗匹配作用产生的相移，有助于提高系统的稳定性。最后通过仿真和实验验证了所提出控制策略的有效性。

Impedance-Coordination Control Strategy in Back-to-Back Converter Systems

In back-to-back cascaded converter systems, the output impedance of front sub-converter will interact with the input impedance of the rear sub-converter. If the system parameters are not designed properly, it will worsen system stability. In this paper, the concept of impedance-coordination control is proposed. Low-frequency impedances of the front and rear sub-converters in the cascade system are modified to be resistive so that the low-frequency phase shift is zero, which may improve the stability of back-to-back cascaded converter system. Based on the cascaded topology of dual H-bridge DC/DC converters and three-phase two-level inverters, this paper compares the proposed control with conventional control strategies. The impedance-based stability evaluations show that, in low frequency range, the proposed control can promote both the front source converter and rear load converter to present resistive impedance towards dc link, then phase shift of the impedance interaction can be greatly reduced, which contributes to a better stability. Simulation and experiment verify the effectiveness of the proposed control strategy.