三相光伏逆变器多机并联谐振抑制控制策略

摘要

大型光伏电站必须采用三相并网方式以保障电网三相平衡, 而采用传统PI加电压前馈控制方式, 当接在并网变压器同一绕组达到一定数量后, 逆变器并网电流会发生震荡, 严重时甚至会因为超过安规THD而发生逆变器脱网, 严重影响光伏电站的运行.通过研究逆变器多机并联系统电网侧输出电流的谐振特性, 提出以虚拟电阻串电容替代实际硬件电路的控制策略, 不仅有效抑制多机并联谐振问题且保证了逆变器的高效.最后, 通过仿真与实验研究了最优虚拟阻值的选取, 且验证了该控制策略的实际应用性.%The three-phase grid-connected mode must be adopted in large PV power station to ensure the three-phase balance of the power network. By using the traditional PI method, when connected to the same winding of grid-connected transformer to a certain number, the grid-connected current of the inverter will vibrate. Seriously, the inverter will de-grid because it will be over the safety THD, which will seriously affect the operation of PV power station. By studying the resonant characteristics of the output current of the multi-inverter parallel system, a virtual resistor series capacitor method is proposed in this paper, which can suppress the resonance effectively. Finally, the optimal virtual resistance is studied, and the practical application of control strategy is proved.