Research On Impact Of Photovoltaic Power Station Connection On Regional Power Network Relay Protection And Its Countermeasures

In recent years,in order to deal with two major problems of energy and environment restricting the development of human society,many countries have begun to seek new solutions,and in this context,large-scale photovoltaic(PV)power generation comes into being.A large number of PV power stations connecting to traditional power grid increases the flexibility of the system operation,but at the same time,it also increases the complexity of the system structure,and brings new challenges to the regional power grid relay protection.Research on impact of PV power station connection on regional power network relay protection and its countermeasures are studied in this paper and the main work achievements can be summarized as follows:Firstly,the control strategies of PV grid-connected inverter are studied in this paper,including maximum power tracking control and two common contr ol strategies of PV inverter,and one is the traditional control strategy,and the other is the dynamic reactive power voltage support control strategy.Secondely,a simulation model of PV inverter is built in DIg SILENT /Power Factory software,and simulations are conducted for the fault current characteristics of PV inverter under different fault degree;And a typical grid model of PV power station connecting to 110 k V system through transmission line is built,and simulation for PV power station fault voltage and current characteristics under different fault types and weak power characteristics are conducted.Meanwhile,current phase characteristic of both sides of PV power station transmission line under different control strategies are also studied by simulation.And then,two kinds of conditions of grid-connected PV inverter output short circuit current reaching the limit and not are considered,and theoretical calculation formulas of all current protection are derived with PV power station connecting to typical distribution network from three aspects of the position of the short circuit point,the capacity of PV power station and the access position.And the influence rules of PV power station connection on current protection are summarized,and the correctness of the theoretical analysis is verified by simulation and methods for improvement are given.Finally,theoretical analysis why PV power station has impact on transmission line distance protection is conducted,and a PV power station transmission line adaptive distance protection improvement method through the use of information on both sides of the line is presented,and the correctness of the theoretical analysis and the feasibility of the proposed countermeasures are verified by simulation.