Research On MPPT And Control Strategy Of Small-scale Photovoltaic Grid-connected Inverter

Nowadays, solar energy as a new energy is vigorously, developed to solve the problemof energy, environment and development. More attention is paid to solar electrical energygeneration. Considering that the solar energy is volatility and stochastic, intermittent.Photovoltaic power generation system must adopt an effective control technology to ensurethe solar energy electricity could be reasonable transmission and management. Therefore, theresearch of aiming at the maximum power point tracking inverter in photovoltaic powergeneration system (MPPT) and grid connected control technology has the important practicalsignificance and practical value.The generation principle and the equivalent circuit model of photovoltaic cells is studieddeeply. A simulation model of photovoltaic cells is established. The main factors which affectthe output characteristics of photovoltaic cells are analysed. In order to solve the phenomenonof oscillation which appears in the traditional perturbation and observation method, withsmall inverter grade two non isolated circuit topology structure, put forwards an improvedperturbation and observation method which can real-time adjust the length of the step toachieve the maximum power point tracking. The traditional method in accordance with the"1/2" standard on tracking step adjustment, namely the system operating point every timeover the maximum power point, step to reduce1/2, the simulation results show that thealgorithm is effective to solve the problem of oscillation at the maximum power point,improve the output efficiency of the photovoltaic battery.This paper studies the structure of grid-connected inverter and the mathematical model,analyzes the control method, and determines double closed-loop control. In order to meet thetracking precision and the ability of resisting the disturbance, the characteristics ofproportional law (P), control strategy of PI (PI), control strategy of PR (PR) and controlstrategy of QPR (QPR) are in-depth compared. The result shows that QPR control has a bettertracking precision and ability of resisting disturbance. Therefore, QPR is applied to the innerloop control current of grid, the simulation of QPR is established. The simulation results showthat the control strategy of QPR improves the wave of grid-connected current. The controlstrategy of QPR is applied to the test prototype of miniature grid-connected inverter, the resultshows that the control strategy of QPR has a performance.