The Research Of Photovoltaic Grid-connected Detection And Control System

As the earth’s energy exhausting, people pay more and more attention to the development and utilization of renewable energy sources, solar energy as a clean pollution-free renewable sources of energy, will no doubt become the main part of the energy utilization in the future. Photovoltaic grid-connected generation is to convert solar energy into electricity, sending electricity to the grid through the inverter.The purpose of this article is to research photovoltaic grid-connected system, which realizes maximum use of solar energy, and through some methods such as detection control, to realize the successful grid-connection of photovoltaic inverter. The whole system mainly includes:photovoltaic array, DC transformation, inverter, control circuit, detection circuit, etc.In the aspect of achieving maximum use of solar energy, we mainly use the maximum power point tracking (MPPT) technology, making photovoltaic cell work at maximum power point, so as to realize the stability of the photovoltaic cells output and full use of solar energy. And to realize the grid-connection of photovoltaic inverter, we need to make the inverter output voltage and the grid voltage meet the conditions of the same amplitude, the same frequency and the same phase, and to minimize harmonic after grid-connection. In this article, we mainly use phase-locked loop technology, through the control of the voltage and the detection of power grid voltage phase to realize the same amplitude, the same frequency and the same phase of the inverter output voltage and the grid voltage. Handling of harmonic, this article uses the harmonic detection based on instantaneous reactive power theory, which transforms the three-phase voltage and current for coordinate, and through the low-pass filter phase-locked loop, accurately calculate the harmonic current. Fault detection is mainly aimed at analyzing and researching the fault of inverter on the DC side and AC on the grid-connected side, to ensure the safe and stable operation of the system.This article uses MATLAB for model simulation and analysis of photovoltaic grid-connected detection system. It establishes the simulation model of photovoltaic cells, and verifies its correctness; finds a suitable system of MPPT control methods through simulation and analysis of MPPT; finally carries on the simulation to grid-connection through the detection of voltage and current, which verifies that the whole system has reached the conditions of grid-connection.