The Control Of Stability About UPFC/BESS Access To New Energy System Of Large Power Grid

In recent years,rapid development of wind,solar and other new energy power generation technology,and the power generation capacity has been constantly improved.The consumptive capacity of renewable clean energy is low in power grid,and the phenomena of abandoned wind and light often occur.Among the flexible AC transmission system,UPFC has a powerful function,which can effectively improve the stability limit of the power grid,control the power flow and damping oscillation of the transmission line.In order to solve the fluctuation and intermittence of new energy power system,respond to the changes of power source,network load,and full response on "clean energy consumptive country,enhance the ability of flexible control of power transmission and distribution network,and meet the diversified demand of user",put forward new energy system of large power grid,and promote the consumption of new energy power based on FACTS and energy storage.(1)The basic theory and research status of the FACTS device is introduced,and the function application and control algorithm of UPFC is summarized in this paper.the background of UPFC/BESS and structure of new energy system of large power grid is expounded,and UPFC/BESS as the representative of both energy storage and FACTS is proved to be an effective method to solve the problem of fluctuation and intermittence in new energy system.(2)A new energy system model with UPFC,wind power generation,photovoltaic power generation,synchronous generator set,energy storage system and load is established.On the basis of the analysis of the UPFC structure and the equivalent circuit,the expression of the power transmission power and the stable operating range of the UPFC are obtained.Design the control strategy of synchronous generator,wind turbine,UPFC and energy storage system,the dynamic simulation of power balance through the PSCAD/EMTDC,and the results show that the new energy power system can effectively improve the receiving ability of new energy.(3)A new type of flexible transmission device UPFC/BESS based on UPFC and BESS is designed.The mathematical model of UPFC/BESS is established,and the power output balance equation of UPFC and BESS is derived.Based on WAMS technology,the flexible tracking control strategies of UPFC/BESS for transmission power instantaneous balance,medium and long term peak valley and gradient control are put forward,so that UPFC/BESS can dynamically balance active and reactive power of new energy system of large power grid under the most serious power imbalance.The simulation results show that UPFC/BESS can quickly adjust the power imbalance of the source,grid and load,and effectively suppress the power fluctuation of the new energy power.(4)The mathematical models of UPFC/BESS frequency control,system frequency characteristics and virtual synchronous generator are deduced.Then,a frequency virtual synchronous generator control strategy for UPFC/BESS access to new energy system of large power grid is designed.The Simulation analysis and comparison of the virtual synchronous generator control with droop,virtual inertia and conventional control show that the virtual synchronous generator control can provide virtual inertia and damping for system,can effectively maintain the system frequency stability,and promote the consumption of new energy power.