Research Of The Grid-connected Photovoltaic Inverter Control Strategy Based On DSP

Nowadays, the environmental pollution and exhaustion of energy crisis is becomingmore and more serious. As a kind of less pollution and large reserves of renewable energy, thedevelopment and utilization of solar energy gets more and more people’s attention. Amongthem, the photovoltaic grid-connected application as an important step in the utilization ofsolar energy, has been a hot spot that most countries compete against each other to develop,and has formed a certain scale of development.This paper focuses on signle-phase photovoltaic grid-connected inverter system. Thetopology structure, control strategy, maximum power point tracking, island effects have beendeeply reasearched. On this basis, I designed a3KW inverter prototype. The main contentsare as follows:(1)The development status and trends of the photovoltaic inverter are analyzed.Combined with the existing main circuit topology structure of single-phase photovoltaicgrid-connected inverter, a boost plus inverter double stage topology is proposed. The workingprinciple of the boost circuit and full-bridge inverter circuit are analyzed, and the filterparameters of the DC side and AC side are designed.(2)The photovoltaic cells are vulnerable to light, temperature and other environmentalfactors, the output power characteristics are obvious nonlinear. Based on the analysis of themodel of photovoltaic cells, combined with several maximum power point tracking algorithm,power perturbation and observation (P&O) method and incremental conductance method areresearched and simulated. The results show that the incremental conductance method is morestability and faster.(3)The tracking control of grid-connected current is the key technology. This context hasstudied the voltage-current dual-loop with grid voltage feed-forward control stragety,and thesingle pulse wide module (SPWM) algorithm and proportional-integral (PI) algorithm. Themathematical model of the system control was established.(4) Grid phase-locked and anti-islanding effect are key pots of grid-connected inverter.On the basis of the grid voltage phase-locked, with the passive and active detection methodsof anti-islanding, it can quickly track the grid phase, and prevent the island effect effectively. (5)In the analysis and research above, a single-phase photovoltaic grid-connectedinverter experimental prototype based the TMS320LF28035is buildt, the main hardwarecircuit and the control software are designed. The3KW prototype is tested, the experimentalresults and data analysis tested the validity of the above control strategy,the system achievedthe desired goal.