The Research Of Improved Three-Phase Voltage-Type PWM Rectifier And The Design Of Digital Controller

With the continuous development of the industrialization,harmonic pollution of electricalequipments has great influence on power equality, harmonic elimination has become a majorsubject in the field of power electronics. The three-phase PWM rectifier has become aresearch hotspot in the field of harmonic elimination, with its merits of little harmonics ofAC-side inputting current, high inputting power factor, bidirectional power flow, stableoutputting DC voltage.In high-power applications, three-phase PWM rectifier has the problems of short circuiton arms of bridge of inverter because of the electromagnetic interference or overhigh di/dtand du/dt of IGBT and circulation problems between the modules when adopting multipleparallel methods. In order to solve these problems, an improved three-phase PWM rectifierhas been proposed in this dissertation.The first part of this dissertation introduces the circuit structure of improved three-phasePWM rectifier and its operating principle when working on short circuit and paralleloperation, and the simulation models of the improved three-phase PWM rectifier andtraditional three-phase PWM rectifier based on MATLAB are established and the simulationresult prove the feasibility and advantage of the improved three-phase PWM rectifier. Thenthe mathematical models of the ABC three-phase static coordinate system and itstransformation to dq synchronization reference frame are also established.Secondly, in order to eliminate the drawback that the unbalanced voltages seriouslyinfluences the performance of the traditional feedforward decoupling control strategy, animproved feedforward decoupling control strategy is proposed. The proportional coefficientand the integral coefficient of the PI regulator are acquired by analyzing the control diagramof the outer voltage loop and the inner current loop.The simulation models of the improved feedforward decoupling control circuit andtraditional feedforward decoupling control circuit based on MATLAB are established and thesimulation result proves the validity of control algorithm. Merits and defects of hysteresiscontrol, triangularwave comparison control, feedforward decoupling control and vectorcontrol are analyzed, and three new control strategies, feedforward decoupling control basedon hysteresis comparison, feedforward decoupling control based on the triangle wavecomparison and triangle wave comparison control based on space vector, are proposed. Thesimulation models based on MATLAB are established and the simulation results prove thevalidity of these new control strategies.Finally, the system of the improved three-phase voltage source PWM rectifier isdesigned. This dissertation specifically introduces the design of main power circuit, thehardware and software of control system circuit. The experimental results prove the validityand advantage of this improved three-phase voltage source PWM rectifier and its controlstrategy.