基于有功指令共享的两级式光伏并网系统低电压穿越控制策略

Active-power-command-sharing low-voltage ride-through control strategy for two-stage PV grid-connected system

传统低电压穿越控制下,两级式光伏并网系统的前级和后级变换器控制相互独立。因此前级变换器需要根据直流母线电压波动被动地调整其输出功率,动态响应速度较低。针对这一问题,提出了一种基于有功功率指令共享的两级式光伏并网系统低电压穿越控制策略。该策略可以根据网侧电压降落深度动态调整后级变换器的有功功率指令,同时使光伏阵列根据该有功功率指令主动调整输出功率,保持直流母线电压恒定。通过仿真和实验将所提控制策略与现有的低电压穿越控制策略进行对比分析,结果表明:所提控制策略下光伏阵列的输出电压、电流的波动明显减小,且2台变换器输出功率动态响应加快,验证了所提控制策略的有效性。

Under the traditional low-voltage ride-through(LVRT)control,the front-end and the back-end con⁃verters of the two-stage photovoltaic(PV)grid-connected system are independent of each other.Therefore,the front-end converter needs to adjust its output according to DC bus voltage fluctuation,which is passive and the dynamic response speed is low.Aiming at this problem,an active-power-command-sharing LVRT control strategy for two-stage PV grid-connected system is proposed.The proposed strategy can dynamically adjust the active power command of the back-end converter according to grid-side voltage drop depth,while makes PV arrays initiatively reduce their generated power according to the active power command,and keep the DC bus voltage constant.The proposed strategy is compared with the existing LVRT control strategy by simulation and experiment,the results show that the output voltage and current fluctuations of PV arrays are significantly reduced,while the output power dynamic response of two converters is accelerated signifi⁃cantly,which verifies the efficiency of the proposed strategy.