基于电压冗余状态的链式STATCOM直流侧电容电压平衡控制策略

Balancing control of DC capacitor voltage for cascaded H-bridge STATCOM based on voltage redundant states

分析了链式STATCOM电流和开关状态对直流侧电压的影响,当变流器电流I>0、模块输出电压为正时,直流电容充电,电压升高;当模块输出电压为负时,直流电容放电,电压降低;当电流I<0时情况相反。在此基础上,提出了一种新的基于交换冗余开关状态的直流侧电压平衡控制策略,将阀组内直流侧电压高的模块的开关状态向直流侧电压降低的开关状态交换,同时把直流侧电压低的模块的开关状态向直流侧电压升高的开关状态交换,改变电容的充放电时间,维持直流侧电压的平衡。所提控制策略易于实现,简单可行,仿真实验结果证明其能很好地维持直流侧电压平衡。

The impact of the current and switch state of cascaded STATCOM on DC-side voltage is analyzed.When converter current I 0 and module output voltage U0,DC capacitor is charged and its voltage rises;when I0 and U0,DC capacitor is discharged and its voltage drops;when I0,the situation is opposite.A DC voltage balancing strategy based on swap redundant switching states is thus proposed,which changes the switch state of the module with high DC voltage into the switch state causing voltage dropping while changes the switch state of the module with low DC voltage into the switch state causing voltage rising.The charge/discharge time of capacitor is thus changed and the DC-side voltage balance is maintained.The proposed control strategy is simple and easy to realize and its effectiveness is verified by simulative results.