Design Of Household Grid-connected Photovotaic Power System

Today, electric energy has become the major secondary energy in the world. The increasingly deteriorating threats like the shortage of energy and the pollution of environment which are brought in by using conventional energies, including coal, petroleum and natural gas etc., to produce electricity, push the way of developing and harassing renewable energy resources to be the commanding height for the future energy development strategy. The solar energy, as a new kind of high efficiency and clean energy resources, is destined to be the number one choice for the future power generation. In the past, photovoltaic power generation mostly focused on the off-grid and was primarily used in the remote and electroless areas. Presently, photovoltaic market has embarked on its direction of the urban grid-connected power generation and the building integrated photovoltaic, and gradually ushers into the transition from the traditional supplementary energy resources to the new alternative ones. Building on this, a household grid-connected photovoltaic power system of high efficiency and high power factor is designed in this article.This system adopts the double topology made up of DC/DC and DC/AC circuit. Firstly, several maximum power point tracking technologies are comparative analysis to lessen the low conversion efficiency of solar cells. Considering that the shadow effect of PV array lead to low output voltage level, the paper come up with a new boost chopper of high voltage gain, combined with perturbation and observation method to control MPPT. Secondly, the control method of PV grid-connected inverter includes double closed-loops:an outer voltage loop and an inner current one. With voltage loop controlled by PI controller stabilizing DC bus voltage and current loop controlled by SPWM realizing the unity power factor running. Afterwards, the production mechanism, the potential harms and the detection method of the island detection of the grid-connected inverter are further researched in this paper. An improved active frequency drifting method is put forward to avoid the failure of island detection caused by different load characteristics. Finally, all of the theoretical analyses above have been simulated through MATLAB/Simulink.Following the theoretical analyses and simulation, the circuit design of the system hardware and flow chart of software are preliminarily finished based on TMS320F2812. For further research, also complete the design of menu program, data acquisition, SPWM program and part of tests.