基于两输入/输出闭环传函的PMSG网侧变流器次同步频率分量响应特性分析

Analysis of Response Characteristics of PMSG-GSC Controller to Subsynchronous Frequency Component Based on TITO Closed Loop Transfer Function

永磁直驱风电场发生次同步振荡时,由于风机变流控制系统对馈入的次同步频率分量的响应作用,会产生多个次/超同步频率电压,幅值过高时甚至影响风场的电能质量及动态无功补偿装置等的正常运行。采用两输入两输出(TITO)闭环传递函数方法揭示了直驱风电场次/超同步频率电压的产生机理及其解析计算方法。首先,针对永磁直驱风机并网系统,推导其两输入两输出闭环传递函数。在此基础上,分析变流控制系统参数及交流系统参数对响应特性的影响,并与采用单输入单输出闭环传递函数及开环传递函数所得分析结果对比,结果表明TITO闭环传递函数更准确地体现变流控制系统次同步频率分量响应特性,计算电压幅值更准确。最后采用时域仿真方法验证了次/超同步频率电压的存在以及参数变化对电压幅值的影响。

When subsynchronous oscillation(SSO)is induced in permanent magnet synchronous generator (PMSG)-based wind farms,multiple sub-/super-synchronous frequency voltages are generated with response of PMSG grid side converter(GSC)controller to subsynchronous frequency component.The voltages with high enough amplitude will affect power quality of wind farm and normal operation of dynamic reactive power compensator.Two-inputand two-output(TITO)closed-loop.transfer function is adopted to reveal the producing mechanism and analytic calculation method for sub-/super-synchronous frequency voltages in PMSG-based wind farms.Firstly,for the grid-connected PMSG,a TITO closed-loop transfer function is constructed.On this basis,the effect of converter controller parameters and AC system parameters on the response characteristics is analyzed. Analysis result is then compared with that calculated by single-input and single-output closed-loop transfer function, open-loop transfer function,respectively.Comparison result shows that the TITO closed-loop transfer function more accurately reflects the response characteristics o.f converter to subsynchronous frequency component,andthevoltage amplitudes is calculated more accurately.Finally,the presence ofsub-/super-synchronous voltages and the effect of parameters are verified with time domain simulation.