大型光伏电站谐波谐振机理研究

Harmonic Resonance Mechanism Study of Large-Scale Photovoltaic Power Plants

大型光伏电站与理想电网之间不可忽略的电网阻抗使光伏电站与电网之间以及光伏电站内各并联逆变器之间产生交互作用,这种交互作用会引发大型光伏电站的谐波谐振。为研究大型光伏电站的谐波谐振机理,建立了系统解耦模型,将多逆变器并联系统转化为单逆变器系统进行研究。在解耦模型基础上推导出系统谐振频率、阻尼比以及稳定裕度与电网阻抗及并联逆变器个数之间的函数关系,分析了电网阻抗及并联逆变器个数对系统稳定裕度的影响,从闭环增益角度揭示了大型光伏电站谐波谐振机理。研究结果表明,电网阻抗不会引起系统有源阻尼失效,谐波谐振现象是由电网阻抗引起的系统稳定裕度降低而导致的。仿真及实验结果验证了理论分析的正确性。

Grid impedance that cannot be ignored between Large-Scale Photovoltaic Plants(LSPV)and the grid makes interaction among LSPV,grid and parallel inverters in LSPV.The interaction leads to system harmonic resonance.In order to study the LSPV resonance mechanism,a decoupling model that transforms multi-inverters parallel system into equivalent single inverter system is established.Then functions related to grid impedance,parallel inverters number,resonant frequency,damping ratio,stability margin are derived based on proposed decoupled model.A deep analysis on impact for system stability caused by grid impedance and the number of parallel inverters is also given.The harmonic resonance mechanism of LSPV is revealed from the point of closed-loop gain.Grid impedance will not disablea ctive damping and resonance is caused by stability margin reduction related to grid impedance.The study is validated through simulations and experiment.