Research On Grid-connected Inverter With Harmonic Compensation For Distributed Power System

With the development of human society, the demands of electric power are also increasing. Onthe one hand, the green energy is going to instead of traditional fossil energy to deal with the energycrisis and environmental pollution; On the other hand, in order to meet the need of production and life,the intelligent power grid which is strong and reliable is under the construction. Therefore, thedistributed power system based on new energy power generation is got more and more attention.However, the construction of distributed power grid inevitably encounters power quality problemswith the limits of technical conditions and construction conditions. One of the most importantproblems is the harmonic pollution of power grid. Harmonic can lead to energy loss and evenequipments damage. Therefore, it is necessary to solve the harmonic pollution problem in theconstruction of distributed power system.In this background, comparing the similarities between shunt active power filter which caninhibit harmonics, and the necessary grid-connected inverter in the distributed power system, thispaper researches a grid-connected inverter with APF function for distributed power system. Theinverter is designed to supply power while compensate the harmonic of load with the surplus capacityof the inverter, which makes the harmonic in the power grid suppressed effectively without anyincrease in the cost of the system.Based on the new type of grid-connected inverter, the model of the grid-connected inverter isin-depth analyzed theoretically, and a unified control strategy with decoupled active and reactivepower based on grid voltage orientation is proposed in this paper. This control strategy can realize thegrid connection as while as the harmonic compensation, which ensures the quality of the power.Through the Matlab/Simulink modeling simulation, both the system and the control strategy areproved right. Based on the theory and simulation results, a30kW inverter experiment platform is built,and the DSP program is also designed. The experimental results show that the new type ofgrid-connected inverter can output grid connection current while the harmonic caused by thenonlinear load and unbalanced load can be effectively compensated, which effectively ensures thepower quality and achieves the design goal.At the same time, the experiments show that the compensation performance of the system needsto be improved. Therefore, the LCL filter is designed to instead of the original single L filter in thesystem. Through the analysis of the inverter’s new model with LCL filter and the filteringperformance influence factors, the parameter design method is given. By the simulation in Matlab/Simulink, the system performance after optimization design is proved to be improved, whichverifies the design idea.