Research On Optimal Reserve Dispatch Model Considering Inverse-time Line Protection And Contingency Scenarios

The reserve configuration of power system is the precondition of safe operation,the guarantee of system security and reliability,and the optimization of system operation safety and economy.With the increasing demand of social economy and the gradual expansion of the scale of the system,the uncertain factors in the operation of the system are increasing,such as load fluctuation,line fault,unit outage,etc.The contingency will lead to active power deficiency system,pose a great threat to the security of the system,which may result in a large area blackout,and will affect the development of the national economy.With the rapid development of photovoltaic power generation grid connected system relieve the energy crisis in a certain extent,but due to the inherent uncertainty of photovoltaic power generation and intermittent,caused a greater impact on the safe and stable operation of the system.Therefore,in order to ensure the safe and stable operation of the system,it is necessary to configure a large capacity of standby to deal with unexpected accidents.The traditional reserve configuration usually takes the maximum capacity of the unit or a certain percentage of the maximum load,which can ensure the safe and stable operation of the system,but its economy is poor.The paper combined with the line thermal stability of inverse-time characteristic relaxation on the line,and on the basis of the reserve optimization under contingency,on the premise of safety,improve the economy.First of all,the meaning,classification and some basic methods of reserve configuration are introduced in this paper,such as deterministic method,probabilistic method,cost benefit analysis method,stochastic optimization method,and introduced the definition and classification of line protection,inverse-time characteristics,and combined with the standby response speed of current protection features of circuit is improved and the corresponding inverse-time limit line can withstand extreme degree,and were selected for this study,analyzed the effects of grid connected photovoltaic system on system and standby configuration.Secondly,the reserve optimization model under unexpected contingencycombined with the improvedinverse-time characteristicwasestablished in this paper.The model aim to minimize the cost of generation and reserve under satisfying constraints of general unit,network security and line thermal stability limit,combines the improved inverse-time characteristic of the line protection and the reserve response speed to optimize the reserve under the unexpected accident.Then,in order to ensure the safety of the system and waste light minimization,enhance economy under photovoltaic grid connected,the risk index of load loss and the risk index of waste light and interruptible load are introduced,and the reserve optimization model of photovoltaic grid connected combined with inverse-time characteristic of line protection under different contingencies is established in this paper.The model aim to minimize the cost of generation and reserve under the constraints of the system power balance,the unit output power constraint,the unit ramp rate constraint,the line power flow and thermal stability constraints,the minimum downtime of the unit,the risk of loss of load and the risk of waste light,upper and lower limit of interruptible load,minimum interruption time constraint,Interrupt frequency and combines the improved inverse-time characteristic of the line protection and the reserve response speed to optimize the reserve under different unexpected accident.Finally,The nonlinear model is linearized or nearly linearized,and a commercial mixed integer linear programming solver(CPLEX)is used to solve the problem in IEEE 30 systems and improved IEEE 30 systems include photovoltaic in this paper.Numerical results show that the power system combined with the inverse time characteristic of the line protection,actualize the different response speed of the reserve coordination dispatching.Under the premise of ensuring the security of the system,the model improves the economic efficiency of the system,and provides a new idea for power system reserve optimization problem.