Research On Control Algorithm And Monitor Platform Of Dual Input Micro Inverter

Centralized inverter and distributed inverter are two developing directions of PV grid connected technology.With rapid growth of photovoltaic family users and rapid development of building integrated technology,high efficiency micro inverter has become a research hotspot.At present,the main reason that restricts the use of micro inverters is that the power level is not match with the cost.The multichannel input micro inverter is relatively moderate in power and cost,and becomes the development direction of the next step of the micro inverter.The object of this paper is dual input micro inverter,focusing on its hardware circuit design,MPPT,grid-connected control,multi-inverter communication and island protection.Finally,a prototype of dual input micro inverter is developed and an experimental platform is set up.The main works of this paper are as follows:(1)The hardware overall schemes of the dual input micro inverter is determined.According to topology’s efficiency,size,power selected “active clamp interleaving flyback + full bridge” as the main circuit topology,and analysis the working model;Analysis and design of the main topology and key hardware system;Demonstrate multi-inverter communication scheme,analysis and design the hardware circuit of ZigBee and power line carrier communication.(2)An adaptive step sizes MPPT algorithm based on fuzzy control is proposed.After analyzing the shortcomings of the physical model of photovoltaic solar panels and the traditional disturbance observation method,combined with fuzzy control theory and perturbation observation method,an adaptive step sizes MPPT algorithm is proposed.The simulation results show that the algorithm traces to the maximum power point in 0.02 s and the range of power fluctuation is within 0.5 W.(3)A grid connected control algorithm based on quasing proportional resonance is proposed.The state averaging method is used to model the small signal of the main circuit,and the existing problems of the current grid control algorithm are analyzed.Finally,a parallel network control algorithm based on quasing proportional resonance control is proposed,which realizes the control process without static error and the bandwidth is adjustable.The simulation results show that the output current harmonic rate of the algorithm is only 1.81%.(4)The strategy of multi machine communication and island protection in distributed system is studied.Designed a communication method based on data packet for multi-inverter communication.In view of the problem of island protection in multi inverter grid connected system,propose a hybrid islanding detection method.The simulation results show that the algorithm can enter the island protection in 340 ms,and the harmonic current rate is 5.40% when the grid connected.(5)The experiment platform built for the dual input micro inverter,to verify the performance of each part.The experimental results show that the dual inputs micro-inverter’s hardware system is with good performance.The efficiency of the main circuit is over 95%.Adaptive step size MPPT algorithm has remarkable effect,and tracking efficiency is up to 99.15%.The grid-connected control algorithm has good performance,harmonic distortion and power factor of the grid current at rated power is 5.328% and 99.5%;the design of communication algorithm based on data packet can realize multi-inverter communication function.