考虑SVG补偿装置的大型光伏并网系统振荡分析与抑制

Oscillation Analysis and Suppression of Large-scale Grid-connected Photovoltaic System Considering SVG Equipment

大型光伏电站由于远离负荷中心,长距离输电线路所产生的电网阻抗不可忽略,电网阻抗对于多逆变器相并联的大型光伏电站中某一个光伏发电单元而言将会等效放大数倍,从而造成并网点电压降低导致系统不稳定。光伏电站中的静止无功发生器(static var generator,SVG)等无功补偿装置可以用来降低电网阻抗对于并网点电压的影响。然而,研究发现,在补偿容量逐渐增大的情况下,无功补偿装置与逆变器系统之间的相互影响将会使系统出现振荡现象,而在逆变器控制回路内采用串联校正方式可以有效消除这种现象,从而保证系统的稳定运行。仿真结果与实验验证了理论分析的正确性。

In general,the large-scale PV station locates in rural areas far from the loads center,so,the grid impedance caused by long transmission line should not be ignored.It will be equivalently amplified several times for one certain generation unit,which usually causes the voltage decline and further unstable phenomenon.This influence of gird impedance on the connecting voltage can be eliminated by the static var generator(SVG)compensator in PV station.However,after further study,the system will become unstable due to the interaction between the PV inverter and the reactive compensation equipment with the increase of reactive power demanded by the grid impedance.In order to maintain the system stable and with better performance,the cascade lead correction was adopted to refine the system character.Finally,the correctness was verified by simulation and experiment.