电网短路状态下并网逆变器的谐振控制

为了改善电网短路故障情况下直驱式永磁风电系统的并网逆变器控制性能，提出基于比例积分谐振控制器的并网逆变器直接功率控制算法，通过设置基频谐振控制器实现网侧变流器输出电压、电流信号的无静差跟踪，同时在直流母线侧通过2倍工频谐振控制器可以抑制电网故障状态下直流母线的电压波动．与传统网侧逆变器的交直轴电流双闭环PI控制相比，该算法无须分离正负序电流分量，从而避免了电流滤波环节带来的系统带宽减小的弊端．在PSCAD／EMTDC环境下建立基于背靠背变流器的1．5MW永磁直驱风力发电系统仿真模型，仿真结果表明：当电网短路导致电压不平衡时，结合能量卸荷电路能够抑制直流母线电压的升高，限制了电网过电流，可以实现网侧逆变器的单位功率因数控制，增强了风电机组的故障穿越能力．同时搭建了10kV·A样机系统，试验波形证明了系统设计与控制策略的正确性和先进性．

Resonant controlling grid-connected converter under grid short-circuit fault

To improve the performance of directly driven wind turbine system with permanent magnet synchronous generator(DWT-PMSG) under grid short-circuit fault,a resonant control(RC) strategy was introduced into coordinate direct power control(DPC) scheme of grid side converter.Two RC controllers were developed based on the proportional-resonant regulator,which are tuned at the double fundamental frequency and grid frequency respectively to eliminate the direct current(DC) link voltage ripples and power pulsations produced by transient unbalanced grid faults.The quasi unity power factor was obtained without any necessity of grid voltage phase detecting,decoupling control or rotating transformation and diminishment of the overall control bandwidth of whole system,which indicates RC has better control precision and adaptability than traditional proportional integral(PI) control in wind energy conversion system.A 1.5 MW DWT-PMSG with back-to-back converter during grid single-phase short-circuit fault was simulated in the PSCAD/EMTDC environment.By adding an energy consumption crowbar,the redundant energy at DC side during grid faults will be consumed,which demonstrates the validity of the model and its analysis.The generator-converter arrangement and switching strategy are also verified by the 10 kV·A laboratory experiment.