基于功率跟踪曲线切换的变速风电机组虚拟惯量控制

Virtual Inertia Control of Variable-speed Wind Turbines Based on the Switching of Power Point Tracking Curves

提出一种基于功率跟踪曲线切换的变速风电机组虚拟惯量控制方法:在电网正常时,风电机组接近最大功率跟踪曲线工作并储存动能;当电力系统频率发生跌落时,风电机组切换至另一近最大功率跟踪曲线工作,并释放转子动能。采用次优曲线切换机制可极大削弱惯量响应过程中原控制系统外环对df/dt前馈控制环节的抵消作用,提高惯量响应的动态性能。通过合理选择次优功率跟踪曲线,可减少因惯量控制导致的风能利用效率的降低。仿真中所选取的次优功率跟踪曲线可保证风电机组在惯量控制过程中,捕获的风功率始终不低于最大跟踪功率的98%。

A virtual inertia control method for variable-speed wind turbines is proposed based on the switching of power point tracking curves.In this method,when power grids are in normal states,the wind turbines operate with the nearly maximum power point tracking（MPPT）curve,and the kinetic energy is stored;when the frequency of power grids drops,the wind turbines switch to another nearly MPPT curve to operate,and kinetic energy is released to support grid frequency.The adoption of the suboptimal curve switching mechanism can significantly reduce the interaction between the df/dt feed-forward control loop and the original control loops,hence improving the dynamic response performance of the virtual inertia control.By the proper selection of the suboptimal power point tracking（SOPPT）curves,the reduction of wind power conversion efficiency caused by inertia control can be reduced.In the simulation cases,the captured wind power is always ensured no less than 98%times of the MPPT power during the inertia control of wind turbines.