Study On The Effect Of Photovoltaic (PV) Grid On The Current Distribution Network And Adaptive Protection Method

In today’s society increasingly scarce energy, the environment pollution is becoming more and more serious. Solar energy received wide attention from all walks of life and study because of its non-pollution environmental protection and renewable sustainable advantages. Also obtained the rapid development of photovoltaic application in independent photovoltaic power generation and power grid photovoltaic power supply two aspects. However, Photovoltaic(PV) power into the distribution network, will change the original distribution network topology. Network trend direction and short circuit current will also be real-time changes with photovoltaic power supply capacity and incorporated into the location of the different situation. All of these will affect the traditional three-step current protection, Even cause protection refusing action or misoperation.According to the principle of photovoltaic power generation, in the MATLAB simulation software to build a mathematical model for photovoltaic cell and analysis of the characteristics of photovoltaic cells output curve. Analyzed of light intensity and temperature’s influence on the photovoltaic battery output current and output power. In photovoltaic cell maximum power point tracking control method, this paper analyzes the tracking principle of variable step length conductance increment method. Combined with fixed voltage method and variable step length conductance increment method, constant pressure startup conductance increment method is proposed. In the MATLAB simulation software, two levels of photovoltaic(PV) grid topology is studied to build three-phase photovoltaic(PV) grid simulation model. The characteristics of photovoltaic(PV) grid is studied according to the results of the simulation.This paper analyzes the traditional three-step current protection movement condition and the scope of protection. setting up photovoltaic power distribution network model performs the simulation analysis in the PSCAD simulation software. Were studied in different fault cases, through the short circuit current protection, photovoltaic power in different capacity and different position after the access to the distribution network. This paper analyzed the influence on original distribution network protection device because ofphotovoltaic(PV) power supply connection.Based on the theory of photovoltaic(PV) grid power system analysis, This paper presents the adaptive current protection setting scheme using the composite sequence network voltage protection. The first step is to determine fault occurred in the upstream or downstream by extracting the fault point voltage and the positive sequence fault current phase difference. The second step is to determine the fault types by the zero sequence and negative sequence component, and setting values for the protection scheme. The third step is to calculate the current setting value in the protection installation using the composite sequence network voltage, and adaptive protection action. This protection scheme is verified by simulation, which can realize the adaptive online protection setting according to the photovoltaic(PV) power into position, capacity and failure position is different, also can effectively improve the local scope of protection.