H桥级联型静止同步补偿器容值减小产生的相间电压不平衡分析与抑制机理

Analysis and Suppression Mechanism for Clustered Voltage Imbalance Generated by Capacitance Reduction of CHB-STATCOM

采用小容值薄膜电容的H桥级联型静止同步补偿器(cascaded H-bridge static synchronous compensator,CHB-STATCOM)直流侧电压控制以直流侧电压平方值为被控量,在补偿功率发生跃变时相间电压不平衡加剧,传统相间电压平衡控制动态效果不佳。基于容值减小的CHB-STATCOM控制原理,推导各相直流侧电压平方值与跃变功率、电容容值的数学关系,揭示相间电压不平衡的原因,讨论直流侧电压峰值与电容电压纹波的关系。建立指令功率渐变的给定方法,分析指令功率渐变时间与相间电压不平衡的关系,揭示指令功率渐变时间对CHB-STATCOM补偿功率变化时相间电压不平衡的抑制机理。仿真和实验验证了理论分析与相间电压不平衡抑制机理的有效性。研究结论可为该类型的相间电压不平衡抑制提供理论基础。

The cascaded H-bridge static synchronous compensator(CHB-STATCOM)adopts small capacitance film capacitors,and its DC-side voltage control takes the DC-side voltage squared as the controlled quantity.The clustered voltage imbalance is aggravated when the compensation power jumps,and the traditional clustered voltage balancing control is dynamically ineffective.In this paper,based on the control principle of CHB-STATCOM with capacitance reduction,the mathematical relationship between the square of the DC voltage of each phase and the capacitor's jumping power and capacitance value is deduced.This study reveals the causes of clustered voltage imbalance and discusses the relationship between the peak DC side voltage and the capacitor voltage ripple.The given method of command power fading is established,the relationship between command power fading time and clustered voltage imbalance is analyzed,and the suppression mechanism of command power fading time on clustered voltage imbalance when CHB-STATCOM compensates for the power change is revealed.The simulation and experiment are conducted,and the effectiveness of the theoretical analysis and the clustered voltage imbalance suppression mechanism is verified.The study's conclusions can provide a theoretical basis for the clustered voltage imbalance suppression of this type.