The Strategy For Diverse Power Source Participating In Power System Restoration

Although the reliability and stability of power system is strengthening,there are still risks of large-scale blackout accident.Consquently,the fast restoration of blackout system is a very important control and decision problem in operation of power system.It's necessary to study on power system restoration method after a blackout,in order to ensure the power system restoration as soon as possible.Diesel generators and hydroelectric generators are usually adapted as black start units to restore thermal units,however,due to the number and start up time limitations of thermal units,the number of black start units which can be recovered quickly is important for us to improve the efficiency of power system restoration.In recent years,there have appeared different kinds of new power sources with the continuous development of power system,such as fast cut back units,high voltage direct current,renewable energy and so on.These power sources can start by itself or be recovered quickly,which can speed up the restoration of power system.Meanwhile,it is necessary for us to formulate corresponding restoration strategies based on the characteristics of different power sources.Therefore,this paper studied on power system restoration strategy and method of fast cut back units,high voltage direct current and renewable energy,the main research work of this paper is as follows:1.Because the FCB function of thermal units can,t be implemented for all units,it,s necessary to dynamically sectionalize the system with FCB units based on Girvan Newman(GN)algorithm.An improved GN algorithm was built to divide blackout system by using Laplaces metrics eigenvalues of power network to identify the number of subsystem.Meanwhile,the black start unit,the power balance and the dividing speed of subsystem were taken into account in network division.Simulation results in IEEE New England system and part of Jiangsu power system show that the method proposed in this paper could partition the system with FCB units effectively.2.A new optimization model of restoration path including HVDC was formulated according to technical requirements of power system restoration with HVDC.Firstly,based on the characteristics of HVDC system during restoration,a new optimization model of restoration path including HVDC was formulated.Due to the large amount of calculation for restoration path optimization,a new algorithm based on ordinal optimization theory was proposed to accelerate search speed of restoration path.Moreover,the simplified calculation method of voltage constraints while starting HVDC system and power flow eonstraints were formulated,and a rough estimation model of objective function was built.The optimization results can meet HVDC startup requirements,which can also validate that ordinal optimization theory can speed up restoration path optimization and power system restoration.3.A robust optimization model for determining the forward dispatch schedule of wind farms based on information gap decision theory(IGDT)was established since that the volatility of wind power makes it difficult to participate in power system restoration.Models of wind farm output and the influence on restored system were established based on the analysis of output power characteristics of wind farms.Then,considering the active power impact on recovered system when wind Power participates in power system restoration,a robust optimization model based on IGDT was formulated for power dispatch optimization.Simulation results demonstrate that the security constraints of the restored system can be kept within security limits when wind farm dispatch is optimized by the proposed method,what's more,the total active power of wind farms can reach the expected minimum goal.4.Considering that double-fed wind generators with reactive power regulation ability can reduce the voltage deviation and power loss during power system restoration,which can maintain the power flow stability of recovered system.This paper established a mixed integer reactive power optimization model of double-fed wind generators,where the optimization target is minimizing the voltage deviation and power loss of recovered system.Simulation results demonstrate that reactive power output scheme based on the proposed model can reduce voltage deviation and power loss.