Research On The System Of Z-source Photovoltaic Grid-connected Inverter

With the energy crisis, the environmental pollution problems have come into being,in recent years the solar photovoltaic industry has developed rapidly. The research ongrid-connected inverter technology of photovoltaic power generation aroused widespr--ead concern. The circuit topology of raditional PV inverter is complex, inefficient. TheUniversity of Michigan Professor Fangzheng Peng raised Z-source inverter in2002.This paper propsed a new control system of photovoltaic power grid-connected basedon it. The new control system is Z-source photovoltaic grid-connected inverter system.In this paper, do the following researches:First analyzing of the topology and working principle of Z-source inverter. AZ-source network added between the DC power supply and the inverter and the the Zsource network is constituted by two capacitors and two inductors cross with the sameparameters. Applying in circuit principle analyzing main circuit topology of theZ-source photovoltaic grid-connected inverter and set up mathematical model based onautomatic control principle. the Z-source PV grid system simplifies the mathematicalmodel with the two parts of the Z-source network and inverter models.In this paper, propsed a control technology of a space vector pulse widthmodulation (SVPWM) based on the whole control schema of the Z-source inverter.Through the zero state and the traditional zero state role in the working effect for theload. In each carrier period zero state time replaced directly part of the traditional thezero state generating SVPWM control for Z-source inverter. So obtain the space vectorPWM control, and it is more efficient and reliable.Finally, the paper determined the MPPT control method of perturbation and obser- -vation method based on the output characteristics of the photovoltaic cell array. Fromthe simulation of figure, just only select the suitable disturbance step length, then theimproved perturbation and observation(P&Ob) method has good tracking characteristic.The output is always near the maximum power point, so improving the power generati--on efficiency.Set up the voltage-type Z-source inverter system simulation platform bySimPowerSystems of MATLAB/SIMULINK. Though the simulation experiments,simulation results show that the Z-source photovoltaic grid-connected inverter systemhas incomparable superiority. The output AC of inverter have good sinusoidal voltagecharacteristics to meet and network harmonic voltage and current characteristics, finallyit verify the excellent performance of the control system.