级联型多电平动态电压恢复器直流侧电压控制方法

DC voltage control of cascaded inverter-based dynamic voltage restorer

针对级联型多电平无串联注入变压器拓扑结构的动态电压恢复器(DVR),详细定量分析DVR的稳态工作特性。分析表明调节补偿电压相角,可以实现稳定直流电容电压。提出通过调节DVR注入电压相角实现快速补偿电网电压跌落的同时保持直流侧电压稳定的控制策略。该控制策略在最小能量补偿模式的基础上,将比例积分控制引入到注入电压生成方法中,DVR从电网吸收或发出有功功率,储能电容随之充电或放电以使电压恢复到额定值。为了减小直流电容间的电压偏差,进而提出采用闭环PI控制解决级联型多电平逆变器工作时H桥单元之间的电容电压均衡问题的方法。仿真结果验证了理论分析的正确性和所设计方法的可行性。

For the cascaded multilevel DVR（Dynamic Voltage Restorer） based on transformerless topology, its steady state characteristics are analyzed quantitatively. Analyses show that DC capacitor voltage can be stabilized by adjusting the injected voltage phase angle. A control strategy is presented,which compensates rapidly the system voltage sags while keeps the DC voltage stable by adjusting the injected voltage phase angle. PI controller is introduced into the injected voltage generation based on the minimal energy compensation model. The DVR absorbs or delivers active power from or to grid to maintain the DC capacitor voltage at its reference. In order to minimize the DC voltage deviation,the PI closed- loop control is used to balance the power among H-bridges of cascaded inverters. The correctness of theoretical analysis and the feasibility of the proposed design scheme are verified by simulation results.