Research On Low Voltage Ride Through Technology Of Photovoltaic Inverter

Nowadays, photovoltaic power generation is an effective method to alleviate the pressure of energy at the same time, the adverse effects of the access grid system of the existing power grid has also attracted wide attention. The process of power grid voltage fault in the grid system will make an instant from the power grid fault intensified. So, the research of photovoltaic inverter through low-voltage performance has certain practical value to improve the stability of power grid.Photovoltaic grid connected inverter as the main body of the implementation of control strategy, both at home and abroad on the expansion of the existing research results quite, the familiar these studies as the foundation, and then combined with low voltage ride through control strategy development needs, establish the control method suitable for the inverter's mathematical model and basic grid, focus on the power grid voltage transient fault two types of electrical parameters, find out the formulation under different fault type design to solve the core problem, of the inverter system are determined to deal with the low voltage ride through(LVRT control method. To limit the output current of the inverter size as the premise, put forward according to the grid voltage drop depth for active power output, power current deployment, according to the principle of reactive power compensation of the recovery voltage inverter realize the value of three phase voltage synchronous dips in the low voltage ride through(LVRT). Considering the unbalanced three-phase voltage of negative sequence component to control part of the output power and waveform modulation interference, established a through the grid voltage signal separation filter and accurately extract the positive sequence voltage component phase-locked control module, dual second order integral synchronous coordinate frame phase-locked loop based on, in order to assist the inverter system in asymmetric voltage sags of low voltage ride through(LVRT).In order to verify the proposed grid and low voltage ride through(LVRT strategy of correctness and practicability. Firstly, this paper in the MATLAB simulation platform, build a model, parameter setting and control module, the simulation is carried out to verify, to simulate the normal grid and voltage sags and waveform simulation test the inverter system can normal grid and low voltage ride through(LVRT) process can not exceeding current output continues to run, unbalanced voltage sags output current is stable, symmetry, crossing, inverter system can quickly normal grid connected power supply. Through the design of 500 kW photovoltaic inverter prototype, build experimental platform of grid connected inverter indicator, low voltage ride through(LVRT) index were the actual prototype is built to verify, from monitors and probe show up observation, the data and waveforms have reached the expected results, which further confirmed the correctness of the control strategy is established in this paper.