光伏并网系统的谐波不稳定产生机理及影响规律

The Mechanism and Influence of Harmonic Instability for Photovoltaic Grid-Connected System

针对光伏、风力发电等电压源型逆变器与供电系统交互引起的谐波不稳定问题,采用基于阻抗分析法的输入导纳判据揭示这类谐波不稳定的产生机理及其影响规律。通过建立光伏并网系统等效电压源型逆变器阻抗模型,可从有源阻尼和无源阻尼两个角度分析谐波不稳定现象产生的原因。同时,基于Matlab/Simulink仿真平台搭建了光伏并网仿真系统,考察关键因素(PI控制参数Kp、总时间延迟Td、无源阻尼Rd、网侧电感Lg)对谐波不稳定的影响规律。仿真结果表明,谐波不稳定现象会在参数所对应的一个阈值范围内发生(该范围下电压源型逆变器阻尼为负),而输入导纳判据可以求解参数不稳定范围,从而判定谐波不稳定现象发生与否,仿真与理论分析相符。

The harmonic instability problem would arise from the interaction between power supply system and voltage source inverter(VSI)in the fields of photovoltaic(PV)or wind power generation.This paper studies the mechanism and influence laws of the harmonic instability via Input Admittance Criterion(IAC)of impedance-based analysis.The equivalent VSI impedance model of PV grid-connected system has been conducted to demonstrate the factors of harmonic instability in terms of active and passive damping.The model of PV grid-connected system is established on the basis of Matlab/Simulink platform to check the impacts of the critical factors on the behaviors of the harmonic instability(i.e.,proportional parameters Kp,total time delay Td,passive damping Rd and grid-side inductance Lg).Simulation results indicate that the harmonic instability occurs when the value of VSI damping is negative within the threshold range.The unstable domain is calculated by IAC to predict the harmonic instability.