Study On The Parameter Optimization Of Small Signal Model And Grid-connected Control Of Z-source Inverter

In recent years, with the increasingly prominent of traditional energy contradictionbetween supply and demand, and the global energy crisis, at the same time, people’sattention to environmental protection puts forward severe challenges to the traditionalenergy structure. Therefore, much attention has been paid to new energy powergeneration. In many types of new energy power generation applications, solar and windenergy are the most green and environmental renewable energy, so they are the focus ofgovernments to encourage and development. However, These two types of renewableenergy exists the problem of intermittent, volatility and low voltage grade, the inherentdisadvantages of traditional bridge inverter makes it difficult to play a goodperformance in these situations. The propose of Z-source inverter takes a good solutionto the application of traditional bridge inverter in these cases, its special impedancenetwork and allowing the bridge shoot-through provides a new mechanism for therealization of the single stage boost/buck voltage inverter. Therefore, the study Z-sourceinverter not only has important theoretical significance but also has considerablepractical value.This paper firstly summarizes the shortcomings of traditional bridge inverter andlimitation in the application of new energy power generation, and introduces the workmechanism briefly, then analyzes the Z-source inverter research status of impedancenetwork modeling and grid-connected control in detail, in the end, points out thenecessity of researching on Z-source inverter modeling and control from the perspectiveof application.Through analysis of the Z-source inverter working principle in-depth, the statespace average method is adopted to establish the impedance network capacitancevoltage small signal model, which gives the transfer function from direct duty ratio tothe resistance network capacitance voltage, combined with the classical control theoryroot locus method, analyzing the influence of impedance network inductance andcapacitance and parasitic parameters and shoot-through duty ratio to system zero pole,which paves the way for the parameter selection of passive component.In the study on parameter optimization of impedance network based on thecapacitive voltage small signal model, by comparing the output of step responsebetween Z-source inverter simulation circuit and capacitor voltage small signal model when duty ratio mutation, which validate the correctness of the model. On this basis,according to the influence on the dynamic performance of capacitor voltage stepresponse duet to the change of impedance network passive component parameters,optimize the parameters selection of inductance and capacitance, which provides atheoretical guidance for the design of impedance network parameters.In the study on grid-connected control of Z-source inverter after the parametersoptimization, firstly established the model of impedance network and three-phaseinverter bridge concerned on Z-source grid-connected inverter respectively based onstate space average method, then the mathematical model of three-phase Z-sourcegrid-connected inverter are given under two phase rotating coordinate system, andaccording to the principle of decoupling and capacitor voltage constant, design thedouble closed loop control system of Z-source grid-connected inverter based oncapacitive voltage outer loop, grid-connected current inner ring; finally the circuitsimulation model of three-phase Z-source grid-connected inverter is set up based on thecontrol strategy, and the Z-source grid-connected inverter working performance underthe condition of steady-state output, input voltage mutation and grid-connected currentmutation are analyzed in the simulation.Finally, the study on the experiment of single-phase Z-source grid-connectedinverter is set up. On the basis of analysis and selection on impedance network passivecomponents, filter inductor and power switch device, designs the control system whichconsists of voltage and current detection circuit, shoot-through signal generating circuit,grid-connected current control circuit and driver circuit, then set the experimentalplatform of single-phase Z-source grid-connected inverter, finally validates the designparameters of single-phase Z-source grid-connected inverter and the control system hasgood performance through the analysis of experimental results.