链式STATCOM直流侧电压平衡控制策略研究

Balancing Control Method of DC Voltage of Cascade STATCOM

针对STATCOM电容直流电压不稳定问题进行了分析,提出了一种增加附加充放电电路方式的STATCOM电容电压控制策略。采用附加电路对链式STATCOM电容进行充电及稳压控制,其中附加电路多绕组变压器的使用,有效地隔离了附加电路各链节直接的电的联系,消除了附加电路和装置主电路同时投入时电压瞬时降为零的现象,使得附加电路的控制策略可以完全和主电路控制策略独立;附加电路既可以直接接到大电网中,也可以采用与电网分离的独立供电电源,甚至可以采用大容量的UPS,可以较好地实现装置启动、快速功率切换等。装置动态响应能力亦有所增强,同时当主电路出现较大电压波动时,仍可以保证STATCOM电容电压的稳定,正常地输出无功。

This paper studies the unsiable problem of capaeitor voltage in the DC-link of STATCOM, and proposes a new control strategy with additional circuits, which are used to control charge and voltage stability. The use of additinnal cireuit muhi-wimling transformer effectively isolates the direct electrical contact between the additional circuits and the main circuits of devices, and avoids the occurrenee of instantaneous zero capacitance voltage when the additional circuits and the main circuits of devices are put into operation concurrently. This method makes the control strategy of additional eireuit independent of＇ the control strategy of the main circuit. The additional circuit can either connects to the large power grids, or use independent stand-alone power supply separated from the grid, or the large capaeity UPS, which can prefe.rably achieve devices starting, tast power switching and so on. In addition, the dynamic response of the devices can also be enhanced, and the STATCOM capacitor vohagc stability and normal reactive output can be ensured at the same time, when the main eireuits have larger vohage tluetuatinns.