考虑电网不对称故障的链式STATCOM并网点电压前馈策略

Grid Voltage Feed-forward Strategy for Cascaded STATCOM Considering Grid Asymmetry Faults

在电网电压出现不对称故障时,链式静止同步补偿器(STATCOM)仍然需要输出三相对称电流用以维持系统稳定,此时传统的电压前馈策略将导致相间直流电压出现较大的不平衡,影响系统安全运行。针对此问题,提出了一种并网点电压前馈的策略,该策略将传统比例前馈的电网电压中性点移动到电网线电压所形成三角形的正等角中心,从而使得变流器输出电压与电流相互垂直,大大减小了 STATCOM 三相之间的有功功率交换,有效提高电网不对称故障下直流电压的稳定性。仿真实验和样机现场运行结果验证了所提控制方法的有效性和可行性。

When an asymmetric fault occurs in the grid, the cascaded static synchronous compensator(STATCOM) still needs to output symmetrical current to maintain the stability of the system. At this time, the traditional grid voltage feed-forward strategy will lead to unbalanced active power among three phases, which will cause a large imbalance of DC voltage between the three phases, seriously affecting the safe operation of the system. To solve this problem, a new grid voltage feed-forward strategy is proposed in this paper. In the strategy, the neutral point of the traditional proportional feed-forward voltage is moved to the positive isogonal center of the triangle formed by the grid voltage, so that the output voltage and current of the converter are perpendicular to each other. Thus, the active power exchange between the three phases of the cascaded STATCOM is greatly reduced, and the stability of the DC voltage under asymmetric faults is effec tively improved. Simulation and experimental results verify the effectiveness and feasibility of the proposed control method.