Research On Mppt Strategy Applied Of Single-stage Grid-connected Photovoltaic System

As the reduction of global energy resources, the development of new energy sources has become the common focus. Recently, the rise of photovoltaic has brought new hope for the generation growing shortage of energy. PV is the most important new energy resources because of the huge storage, widely used, environmental protection As a result, research of PV is meaningful and useful for the future energy problems.In this paper, the object of study is the can dispatch-type photovoltaic battery charging system and not a scheduling-style 3KW single-stage Grid-connected PV system. Paper mainly design the MPPT algorithm with MATLAB simulation and experimental, complete the software and hardware system implementation. The research platform is PIC18F23K20 and TMS320F2812. The software environment is MPLAB and CCStduio 3.3.Firstly, paper summarizes the main circuit topology of DC/DC about the battery charging system. Analysis the the working principle based on Buck circuit and Sepic circuit as well as half-bridge PWM control mode. Design the main circuit parameter of inductance, energy storage capacitance and choose the suitable MOSFET. The experiment results validate the design, and in a certain photovoltaic power supply input the battery charging system can work stable. For the 3KW single-stage Grid-connected PV inverter system, analysis the bipolar PWM control mode of the main circuit, design the parameter of input smoothing capacitor and output filter inductance. MATLAB simulation and experimental realization can validate that 3KW inverter system have a stability work station at a fixed load, and THD<5%.Secondly, paper mainly introduces the MPPT algorithm. For the PV battery charging system, research on the MPPT algorithm about converter duty cycle regulation based on the character of battery and work status of the circuit. From the research result shows that the system can catch the 90% energy from the input. For the 3KW single-stage Grid-connected PV inverter system, the paper mainly introduce the MPPT algorithm about power voltage method and new power voltage method based on the research of the PV cell mathematical model and transient characteristics of work. By doing transient analysis of pre-stage circuit about MPPT algorithm and introducing the theory of the cumulative balance of current, variable step size based on current cumulative compensation is proposed, the simulation model of system is established, and the experiment is implement. Experimental results show that this algorithm has a dynamic characteristic and MPPT stability. The quality of current transferred to the grid is excellent.For the island effect of 3KW PV inverter system, introduce the meathod of active detection and passive detection. Resolve the security and reliability of power grids to avoid the island effect through test the overvoltage and undervoltage of the output voltage.Lastly, finish the design of the software and hardware experiment system. Design of the experiment system is reasonable and reliable, the experimental data is suitable. PV battery charging system can work stability at status of MPPT,the charging efficiency is 85%.3KW single-stage PV grid system connected to the network successfully, and the grid current THD <5%.