Research On The Single Phase Z-Source Grid-Connected Inverter

Z-source inverter is a new type of inverter structure emerged inrecent years. It can make up for the defects of traditional invertertopology. In order to validate the effectiveness of the inverter structureand facilitate further development based on the topology of theengineering application, in this dissertation, the single phase Z-sourcegrid-connected inverter was studied.Firstly, the dissertation reviewed the application of traditionalinverters, described the defects of the traditional inverter structure andelaborated the basic working principle and control method of theZ-source inverter. Then, using two modeling methods, namely statespace averaging method and PWM switching signal flow graph method,the mathematical model of the Z-source inverter was made. After acomparative analysis of the small signal model for the control systemdesign, a lead compensation controller for the Z-network boost controland a quasi-PR controller for the current control were designed. Asimulation model was built in Matlab/Simulink to verify the effect of thecontrol strategy. Finally, experiments carried out using a1kW laboratoryprototype confirmed the correction and feasibility of the theory.The small-signal models obtained by the two modeling methods areapproximately the same. The lead compensation controller can stablecapacitance voltage in simulation. The quasi PR controller can make thegrid-connected current having zero error with the specified current andhaving the same frequency and phase with the grid voltage. The laboratory prototype of single-phase Z-source grid-connected inverterdelivered6A peak current to grid. The current had the same frequencyand phase with the grid voltage to achieve a unity power factoroperation. Both waveforms of the grid current and the voltage of theZ-network capacitor matched the results of simulation.According to the research results, the single phase Z-sourcegrid-connected inverter is correct in theory and the control methods arevalid. Meanwhile, it has laid a foundation for the further expansionresearch in the field of photovoltaic power generation.The innovation of this paper is that:1) respectively using statespace averaging method and the PWM switching signal flow diagrammethod, two different small signal model of the Z-source inverter isbuilt. After simulation and analysis, the final mathematical model for thecontrol system design is obtained.2) design a single-phase Z-sourcegrid-connected inverter control system, particularly the leadcompensation controller of the Z-network boost control. The simulationresults prove that the controller is able to stabilize the capacitor voltagewhen the DC power supply voltage jumps suddenly.3) design asingle-phase Z-source grid-connected inverter prototype system,including the hardware part and the software part. The prototype canwork in normal operation.