Research On Control Strategy Of Three Phase Z-source Grid-connected Inverter

The earth's fossil fuels reserves are now getting depleted as the demand of energy for human activities is growing and increasingly depletive after hundred years mining.Meanwhile environmental problem caused by greenhouse gases and harmful gases in the traditional energy utilization become more and more serious.So searching for rich and clean energy resource has become an urgent problem for every country all over the world,as energy reserves direct relation the degree realizes of the rapid development of one country in the future.With its rich solar energy resources,clean pollution-free,Solar Energy gradually goes into people's scope and is quickly favored by most researchers of every country.Solar must be converted into electricity that can be used conveniently on a large scale.Therefore,the basic and main utilization of solar energy is photovoltaic.The inverter is key component to realized using of electricity generated by photovoltaic cells on a large scale.The traditional voltage source inverter application has heavy limitation because it is buck inverter and whenever the upper and lower devices of each phase leg couldn't be gated simultaneously.However,the two power switches in the same leg of the inverter shorting directly is allowed to exist in Z-source inverter which add a Z-type network.Meanwhile the buck and step-down control for inverter is convenient to realize by changing modulate function through shorting directly state,thus Z-source inverter have been widely applied to three-phase PV grid-connected systems.A three-loop control strategy is proposed in this paper to assure the accuracy and response speed of the grid-connected current and get higher energy transformation efficiency.In this paper,the principle of Z-source inverter adding Z-type network operation is described in detail and the new SVPWM modulation is imported in controlling part,then the principle and different algorithms of SVPWM modulation are described.Furthermore,algorithm implementation and simulation are detailed.Otherwise,the selection method of parameters in the main circuit is analyzed and explained.At last,every part of simulation model is built based on MATALB/SIMULINK to set up a whole set of simulation model of system.The simulation result coincides with the theoretical computation,verifies the correctness of the control strategy and theoretical analysis.