Research On Grid-Connected Photovoltaic Inverter With The Low Harmonic LCL Filter

In recent years, since the energy shortage and environmental pollution, develop clean energy has become hot spot in today’s energy research. Use of solar energy has received the widespread attention for their different, limitless reserve and pollution-free characteristics. Photovoltaic power generation has become a hot topic of the power industry. Photovoltaic grid power generation system is the main form of solar power in the future. In the photovoltaic grid power generation system, inverter link is an important part of the system. This paper focuses on the part of the study, the main research content is as follows:Firstly, this paper introduces some basic structure of photovoltaic power generation systems, photovoltaic power generation systems are emphatically analyzed the structure of the core components of grid inverter, classification, etc. Choose the suitable three-phase full bridge inverter circuit as a photovoltaic grid inverter. In order to obtain high quality grid current in three-phase full bridge inverter backend with LCL filter as level after filtering. LCL filter performance is good, but the resonance problems. So it is particularly important to design the parameters to keep the stability of the system. Based on the equivalent inductance, power control and the resonant frequency have three aspects to design the parameters of the filter. LCL filter because of its merits, is more and more widely in high power application, but its inherent resonance point. In order to solve this problem, this paper, according to the topology of the LCL filter with LCL filter is established the mathematical model of three-phase photovoltaic grid inverter, analyzes its working principle, from two aspects of passive damping and active damping control analysis LCL photovoltaic grid inverter control scheme. Through the adoption of different position of the current as the amount of feedback control system, the analysis of the effect of different amount of feedback on the system stability, this paper proposes a new grid inverter control strategy, the grid current loop, capacitive current double closed loop control of the inner ring. Establish a mathematical model of three phase static coordinate system, obtained the model under two phase rotating coordinate system, by decoupling, d, q axis current independent control, realize the current double closed loop control, and USES the SVPWM modulation manner.Simulation model had been set up in MATLAB/Simulink environment, the LCL parameters and selection of control strategy is validated. The simulation results show that based on the grid current loop, capacitive current double closed-loop control to achieve high power factor of the inner ring tracking grid, and the system can remain stable, and the LCL filter can effectively filter out higher harmonic current, improve the quality of grid current, has great theoretical and practical significance. Finally, the hardware parts of the system design, including the design of the main circuit, the sampling circuit is designed to protect the driving circuit design and circuit design.