Research And Design Of Three-phase Three-wire VIENNA Rectifier

Science and technology are increasingly developed in modern society,rectifiers as thefirst variable energy devices are widely used in the production of fields in society,but they willcause serious pollution problems to grid system such as decreasing the quality of the gridvoltage and power efficiency.So,how to deal with the power grid pollution has attracted theattention of a large number of people especially in promoting energy conservation days.Rectifier based on PWM can make it achieve sinusoidal input current, low current harmonicand run at unity power factor,so three-phase PWM rectifier has been widely used as the powerfactor correction unit in devices.Three-phase three-wire VIENNA rectifier is a three-levelrectifier,and compared to traditional three-phase two-level half-bridge converter, it has fewerfull-controlled switches and wider applications,in addition,it has no problem of dead time.Three-phase three-wire VIENNA rectifier is a strongly coupled and nonlinear system.Itscontrol system based on SVPWM is more complex for its combinational level logic state ismore than two-level rectifier. This paper is mainly to complete the research and engineeringdesign of digital controlling of three-phase three-wire VIENNArectifier,as follows:Firstly, the paper introduces the research process of three-phase and three-level PWMrectifier,it analyzes the working principles of VIENNA rectifier in single-phase andthree-phase circuit, and it also proposes a switch with three logical values. On the bases ofworking principles and coordinate transformation matrix,it establishes the mathematicalmodel of three-phase three-wire VIENNA rectifier in three-phase stationary and two-phasesynchronously rotating coordinate system,it also gives matrix equations of the model.Secondly, the paper proposes a control strategy of double loop PI upon voltage loop andcurrent loop,feed forward decoupling strategy is used.The controller tunes parametersaccording to the typical system designing,and it gives the reference formulas.Thirdly, the paper gives the introduction of three-phase three-wire VIENNA rectifierwith space vector modulation and three methods to analyze the principle of SVPWM.Itproposes a method of neutral-point voltage level balance controlling based on SVPWM.It alsogives the design of component parameter and control circuit in hardware system according toexperimental parameters and it also analyzes the flow charts of the software system.Finally,the simulation of three-phase three-wire VIENNA rectifier is done in theMATLAB platform,and the experimental device is built,it gives the experimental results.