Research And Design On The Controller Of Three-phase Grid-connected Photovoltaic Generation System

The technology of photovoltaic generation is not only an important part of energy resource, but also has the potentiality to become the major energy resource in the future. Three-phase grid-connected photovoltaic generation system convert solar energy into electrical energy, taking three-phase way connection with power grid. This way can maximize the use of solar energy because of its characteristics can and make the grid more convenient management and operation of power, will be the main form of solar energy utilization. But there are still some problems:high cost of power generation, power generation efficiency is low, and security protection and the way connecting with power grid to be improved. Thus, in this paper distributed three-phase grid-connected photovoltaic generation system as the research object, in order to use of solar energy more safely and efficiently, a deep research on the controller of distributed three-phase grid-connected photovoltaic generation system is made, and presents the design scheme.In this paper, the relevant concepts of photovoltaic generation include composition and classification is studied. The controller of three-phase grid-connected photovoltaic generation system is divided into four main functional parts:the maximum power point tracking control part, grid-connected output power control part, grid-connected current control part and isolated island effect control strategy part. Four parts separately conducted in-depth theoretical analysis and research:issues for the PV array characteristics of control, the general design of the photovoltaic array simulation model structure and design based on the incremental conductance method to achieve maximum power point tracking block diagram; For the problem that the traditional grid-connected strategy can’t compensate the reactive power generate by the load,this paper design an improved grid-connected strategy, not only can the amount of functional and effective input power can compensate for the introduction of non-functional because the amount of load to achieve the grid current and grid voltage with the same frequency; Three-phase current tracking control system for use in open-loop static error SVPWM, anti-disturbance and dynamics of such deficiencies, and design a network based on the current track SVPWM control scheme to deadbeat control as a feedback link that allows fast and accurate output current follow the reference current; For the lack of the common isolated island effect control strategies, passive islanding detection methods are improved, the introduction of wavelet analysis in the identification process, the design of the island based on wavelet transform effect control strategies to quickly identify the general passive detection tests were not recognized by the common passive islanding detection methods.The simulation model of the maximum power point tracking control, grid-connected output power control, grid-connected current control and isolated island effect control are built on the platform of MATLAB/Simulink. The simulation results confirm the feasibility of the control strategies proposed in this paper.