Study On Impacts Of Large-scale PV Integration On Sub-Synchronous Oscillation

Renewable energy has grown rapidly over the past years in China.China ranks as first for installed capacity of wind and photovoltaic(PV)generation.Due to the increasing penetration of renewable energy,sub-synchronous oscillation(SSO)problem is becoming more complex,which will threaten the stability of the power system.However,there are few researches on SSO caused by photovoltaic generation connected to power system.Therefore,it is essential to study on impacts of large-scale PV integration on SSO problem.On the basis of this problem,this paper launched a study on the large-scale PV integration to grid.Firstly,a detailed operating principle about the PV generation is explained,including PV array,MPPT algorithm,inverter and its control strategy.Based on this,an equivlant electromagnetic transient model is established for SSO study.This model can ensure great calculation speed and accuracy,by appropriate aggregation modeling theory.And simulation results verify the accuracy of this model.Secondly,the small-signal stability of PV generation connected to the grid is analyzed.The small-signal model of the studied system is built and derivation euqations are given.To calculate the eigenvalue of the system state matrix,the characteristics of the oscillation mode and damp are discussed.The origins of the oscillation mode are found out by participation factor calculation.Finally,the SSO of large-scale PV integration power sytem is analyzed by using time domain simulation method.The influence of series compensation lines to the SSO of large-scale PV integration power sytem is investigated.And simulation results show that the series compensation lines may cause SSO problem.Meanwhile,the influence of short circuit ratio to the SSO of large-scale PV integration power sytem is studied.Simulation results show that the weakend AC power system may cause SSO,which threatens the stability of power system.