Study On The Influence Of Large-scale Photovoltaic Plants On Dynamic Security Region

New energy power generation,represented by solar power generation,has developed vigorously and achieved fruitful research results.The research methods of Dynamic Security Region(DSR)are also very mature.Large-scale photovoltaic power plants connected to the grid will inevitably affect the security and stability of the power system.This paper studies the impact of large-scale photovoltaic power plants connected to the grid on the dynamic security region of the power system.The time domain simulation is carried out by power system analysis software PSD-BPA,and DSR is solved by MATLAB.The main research contents and conclusions are as follows:1.A large number of simulations of typical power systems show that the boundary of dynamic security region with large-scale photovoltaic plant(LPV-DSR)can still be described by hyperplane within the allowable scope of engineering.The accuracy of the proposed LPV-DSR boundary is verified by time domain simulation of some operating points near the LPV-DSR boundary.2.Comparing the LPV-DSR under the four control strategies,the boundary of the LPV-DSR is approximately parallel to the original system DSR.The reactive power control mode has a great influence on the transient stability of power system.As long as the reactive power control mode is constant reactive power control,the DSR boundary is contracted,that is,the transient stability of power system becomes worse;as long as the reactive power control mode is constant voltage control,the DSR boundary is extended,that is,the transient stability of power system becomes better.In the active power control mode,the constant active power control mode is slightly better than the constant DC side voltage control mode.It is concluded that the combination of constant active power control and constant voltage control is the best control strategy for the converter which is beneficial to the transient stability of the system.3.Under the same control strategy,the range of DSR of the system varies monotonously with the increase of photovoltaic output when the photovoltaic power plant is combined with thermal power unit or hydropower unit or wind power,and the DSR boundaries under different photovoltaic output are approximately parallel.If the total output power of combined generation remains unchanged,the range of DSR is larger when there are traditional generators or wind turbines,therefore,adding thermal power units or hydropower units or wind power units to the grid-connected PV nodes can improve the transient stability of the system.The DSR range of the system varies monotonously with the increase of the number of grid-connected photovoltaic power stations in the superposition and substitution mode.When the demand is not high,the DSR boundary of the power system can be regarded as approximately parallel when replacing multiple motors.