Research On Single Stage Grid-Connected Photovotaic Inverter

With the energy shortage and environmental pollution getting serious, people have paid more and more attention to the development and utilization of renewable energy. Developing single-stage three-phase grid-connected photovoltaic inverter of great efficiency, stablility and security is the technical foundation for building high-capacity solar power station, which is an important part of photovoltaic power generation. Therefore, this paper mainly conducts the research on control system for single-stage three-phase grid connected photovoltaic inverters.Firstly, this paper deduces the three-phase voltage source inverter (VSI) mathematical model under abc and dq coordinate system, and analyses the inner loop current control,outer loop voltage control and the maximum power point tracking (MPPT) control, and a80KW the single-stage PV inverter simulation model has been built.Because of the utilization of device is not high, the paper presents that as long as the algorithm is modified, this inverter also can be realized active filter based on the theoretical analysis of PV inverter and active power filter (APF). It verifies three operating modes of PV inverter with APF by simulating.To solve the negative effect when Large-scale PV power station is disconnected to the grid suddenly under the conditions of grid disturbance or fault, this paper focuses on photovoltaic inverter technology-Low Voltage Ride Through (LVRT).The simulation result of single-stage photovoltaic grid inverters of double-loop control at the situation that grid voltage drops finds that the output current is over the range seriously. A strategy of LVRT technologies based on dual positive and negative sequence current loop and coordinated controlling of active and reactive current is proposed to ensure the AC currents of the PV inverter under maximum value permitted. Meanwhile, the PV inverter can sent out reactive power to support the voltage of PCC, so it possesses the ability of LVRT. The Simulation results show the effectiveness of the control strategy.