基于长传输线的并网系统谐波谐振抑制策略研究

SUPPRESSION OF HARMONIC PROPAGATION IN GRID-CONNECTED SYSTEM BASED ON LONG TRANSMISSION LINE

在基于长传输线的光伏并网系统中,传输线中存在的寄生电感和电容会导致光伏并网系统出现多个谐振点以及线路末端公共连接点(point of common coupling,PCC)电压升高的问题。同时,当电网电压中存在背景谐波电压时,背景谐波的传播放大和逆变器谐振交互会导致并网电压电流波形畸变更加严重。为解决上述问题,该文提出一种复阻抗型有源阻尼器(complex-impedance active damper,CI-AD)与无源网络结合的控制策略,从串并联谐振机理的角度分析谐波阻抗特性曲线选取合适的电压电流增益,可同时抑制背景谐波传播放大和并网系统谐振,并且降低PCC电压,改善入网电流质量。仿真验证所提方案的正确性和有效性。

In a photovoltaic(PV)grid-connected system based on long transmission lines,the existence of parasitic inductance and capacitance on a transmission line may lead to multiple resonance point and induces the voltage of the line end to increase in PV grid-connected system.At the same time,when there is background harmonic in the grid voltage,the propagation of the background harmonics and the resonant interaction of the inverter will cause the waveform distortion of the grid voltage to be more serious.In order to solve the the above problems,this paper presents a control strategy combining the complex impedance type active dampers(CI-AD)with the passive network.From the perspective of the parallel and parallel resonance mechanism,the harmonic impedance characteristic curve is analyzed to select the appropriate voltage and current gain,both the background harmonic propagation amplification and the system resonance can be suppressed,PCC voltage and grid-connected current are improved as well.The simulation verifies the correctness and validity of the proposed strategy.