适应于弱电网的永磁直驱风电机组虚拟惯量协调控制策略

摘要

Large-scale integration of wind turbines(WTs)results in the reduction of the power system inertia and weakens the system"s frequency regulation capability.Therefore,the virtual inertia control has been applied in the permanent magnet synchronous generator(PMSG)based wind turbines for grid frequency support,which introduces the frequency signal into the WT"s power or torque control.In the virtual inertia control,a phase locked-loop(PLL)is commonly needed to realize grid synchronization of the WTs.However,when connected to weak grids,the dynamics of the PLL can be deteriorated,which may even cause instability of the WTs.To deal with this problem,a virtual inertia coordinated control scheme is proposed for PMSG-based WTs,which utilizes the dynamics of the DC-link capacitor to realize self-synchronization instead of the PLL. Thus,it can ensure the desired stability of PMSG-based WTs when integrated into weak grids.Besides,based on the proposed control scheme,the WTs can release the stored kinetic energy in the rotating mass to supply inertia support under frequency disturbances.Corresponding grid connected self-synchronization and inertia simulation mechanisms are discussed in detail and simulations by MATLAB/Simulink verify effectiveness of the proposed coordinated control scheme.%大规模的风电机组并网使电力系统面临惯量减小与调频能力不足的问题,而风机的虚拟惯量控制是解决这一问题的重要手段.当前,永磁直驱风电机组的虚拟惯量控制主要通过将电网频率引入其功率控制或转矩控制中,来实现风机对电网的功率支撑,风电机组仍采用锁相环实现与电网的同步.但在弱电网下,锁相环的动态性能将恶化,甚至会导致风机的失稳.为此,提出一种适应于弱电网的永磁直驱风电机组虚拟惯量协调控制策略,该控制策略可利用直流电容动态实现直驱风电机组网侧逆变器的并网自同步,从而使直驱风电机组无需经过锁相环并网并且能适应于弱电网运行.此外,该控制策略可利用存储于风机的旋转动能为电网提供虚拟惯量.详细讨论了相应的并网自同步机理及惯量模拟机理,并基于MATLAB/Simulink仿真验证了该协调控制策略的有效性.