Research On Controlling Strategy Of Three Phase Z-source Rectifier

The three-phase PWM rectifier is widely used in new energy sources and DCmotor driving and many other areas, for it can realize sinusoidal input current, andcan run under unity power factor. But the three-phase PWM rectifier can onlyachieve Boost conversion, and has poor anti-interference ability, so it is limited inmany applications. Z-sourse is led into the three-phase PWM rectifier andconstitutes the Z-sourse rectifier in order to overcome its inherent shortcomings.Z-sourse rectifier can achieve the traditional PWM rectifier’s function, as well asimplements buck conversion of the output voltage. It expands the range ofapplications of PWM Rectifier widely, so it has great significance to study workingmechanism and control method of the Z-sourse rectifier.The existing research on the Z-sourse rectifier is basically on design andrealization of the main circuit, and the research on analysis and design of the controlsystem is exile. In this paper, the Z-sourse rectifier will be equivalent to two controlsystems with a PWM rectifier in AC side, and a Z-sourse Buck net transform in DCside. The modeling method of Z-sourse Buck net is the key research, thesmall-signal control model is got, and the transfer function from direct duty cycle tothe output voltage is deduceded. These laid the foundation for the analysis anddesign of the control system of the Z-sourse rectifier.A three closed-loop is designed by using the simplified transfer function, witha double closed-loop of current and voltage in AC side, and a single closed-loop ofvoltage in DC side. Methords to calculate the parameters of PI regulators in everycontrol loop are given, as well as the main circuit paramenters’ calculation methords.By using MATLAB simulation software, the control system of the Z-sourse rectifieris simulated. With TMS320F2812as the core controller, a2kW experimentalplatform is set up, and experimental verification is completed. The results of thesimulation and the experiment show that the established model of the Z-sourserectifier and the analysis of the control system are correct and feasible.When use a single closed-loop of voltage in DC side to control the Z-sourserectifier, the output voltage has poor stability and large ripple. In regard to thisproblem, the paper puts forward a double closed-loop controlling system to theZ-sourse net with a inductor current-inner-loop, and a voltage-outer-loop. Thedesign methods of the paramenters in the PI regulators are analyzed. By utilizingthe simulation model in Chapter3and the experimental platform, the simulationanalysis and the experimental verification of the double closed-loop are finished,and the properties of triple closed-loop and quadruple closed-loop system are juxtaposed and analyzed.