改进的STATCOM相内直流电容电压平衡控制策略

An Improved DC Capacitor Voltage Balance Control Strategy Among Phases for STATCOM

在三角形接线方式下,分析级联H桥变流器静止同步补偿器(STATCOM)直流侧电容电压稳态数学模型,重点研究电压内环对直流侧电容电压控制的影响。同时,分析不加电压内环与传统电压内环的控制策略。在此基础上,提出利用变流侧电流反馈来叠加误差信号,以实现每个H桥调制波微小的移相,省去了锁相环,算法简单易行。仿真实验证明:在STATCOM补偿无功与谐波电流时,该策略都能使各H桥直流侧电容电压达到很好的平衡,稳态误差小。最后,搭建了电压660V、容量300kvar的试验样机进行补偿特性分析,试验结果表明该策略的正确性与有效性。

With a link structure of the delta-type, the steady-state mathematical model for DC side capacitor voltage is analyzed for cascaded H-bridge converters based on static synchronous compensator （STATCOM）. Special attention is paid to the influence of the voltage loop on the balanced and stable control strategy for the DC capacitor voltage. Meanwhile, strategies without a voltage inner loop and traditional voltage inner loop are researched in detail. On this basis, to achieve a slight phase shift of H-bridge modulated wave, a strategy for superposing the error signal by current feedback on the inverter side is proposed. The algorithm is simplified by forgoing the phase lock loop. Simulation results show that using the proposed control strategy, the DC capacitor voltage of H-bridges is stable and the steady-state error is reduced while STATCOM is used to compensate for reactive power and harmonic current. Finally, a cascaded STATCOM （660 V, 300 kvar） experimental prototype is developed to analyze the compensation characteristics. The correctness and effectiveness of the strategy are confirmed.