减小电容容值的H桥级联型STATCOM电容取值分析与直流电压控制

Capacitor Value Selection Analysis and DC Voltage Control for Cascaded H-Bridge STATCOM With Reduced Capacitance Value

减小电容容值的H桥级联型静止同步补偿器(cascade H-bridgestatic synchronous compensator,CHB-STATCOM)采用薄膜电容可提升装置可靠性,但容值减小会对直流侧电压峰值和波动量、装置输出感性电流范围造成影响,且调制标幺方式和直流侧电压控制目标与传统STATCOM不同,为此,对减小电容容值的级联型STATCOM电容取值进行分析并建立一种直流电压控制方案。推导直流侧电容容值与电容电压的解析关系,以调制输出范围为约束条件,电容峰值电压一定时,求得电容取值与直流侧电压波动量、STATCOM输出感性电流范围的关系,并进行分析。推导功率单元电容电压与其瞬时功率的关系,对比不同被控量下控制系统数学模型,选取直流电压控制的被控量,建立直流电压的三级控制方案。仿真及实验结果验证了电容取值分析与控制方案的有效性。研究结果可为减小电容容值的级联型STATCOM电容取值提供理论参考,可满足电容电压的控制要求。

The cascaded H-bridge static synchronous compensator(CHB-STATCOM)with reduced capacitance value adopts thin film capacitor to improve reliability of the device.However,the reduced capacitance value affects peak voltage,and fluctuation voltage in DC side,and inductive current range.The modulation standard and voltage control target on DC side are different from traditional CHB-STATCOM.Therefore,the influence of CHBSTATCOM capacitor value is analyzed and a DC voltage control scheme is proposed.The analytic relationship between the capacitance value and DC side voltage is deduced.Under a certain DC voltage peak,the relationship of the capacitance value with the DC voltage fluctuation and the output inductive current range is obtained with modulation output scope as constraint.Based on this analytical relationship,analysis is carried out.The relationship between the capacitance voltage of the power module and its instantaneous power is also derived.Mathematical models of control system are compared under different controlled variables.DC voltage control variable is selected and a three-level control scheme of DC voltage is established.Simulation and experiment results verify effectiveness of the theoretical analysis and control scheme.The study provides insight for the CHB-STATCOM to reduce capacitance value,so control objectives of capacitor voltage can be satisfied.