高压链式STATCOM的最近电平调制策略研究

Nearest Level Modulation Method of Cascaded STATCOM Under High Voltage

三角形接线方式是高压级联多电平静止同步补偿器(static synchronous compensator,STATCOM)的较优接线方式,但接入电压为线电压,因此,在同样绝缘栅双极型晶体管(insulated-gate bipolar transistor,IGBT)器件下,每条换流链需要更多的链节。以三角形接线为例,采用不平衡aβ坐标系下的单相锁相环和分相控制策略产生调制波,该调制波通过最近电平调制产生脉宽调制(pulse width modulation,PWM)脉冲。通过仿真和物理模拟系统试验,说明最近电平调制在三角形接线下最近电平调制的可行性。最后,通过比较载波移相调制方法和最近电平调制方法,说明最近电平调制虽然会在小电流情况下引入少量间谐波,但其无需附加均压控制,更适合链节数量更多的情况;因此,最近电平调制有利于提高STATCOM的电压等级和容量。

Cascaded static synchronous compensator (STATCOM) takes many advantages under delta connection in high voltage. However, due to converter chains suffering the line voltage, more links are needed to use the same insulated-gate bipolar transistor (IGBT). This article, considering the specialty of delta connection, involves the single phase-locked loop under unbalanceabaxis and control strategy of independent phase control (IPC) to generate modulation waves. This modulation waves generate pulse width modulation (PWM) pulses by nearest level modulation (NLM). Finally, by comparing NLM and carrier phase shifting PWM (CPS-PWM), it is superior to using NLM in large number of links, though it can produce minor inter harmonics when the current is small. Thus, it is benefit for STATCOM to run by NLM under a higher voltage and larger capacity.