Research And Simulation Of High Power Factor Three Phase Controlled Rectifier

Over the years, with the continuous and rapid economic development, thedemand for electrical energy in the manufacturing sector is growing, it has beenrecognized that the environment itself is a power system, people are increasinglydemanding high-quality electricity. Conventional phase-controlled rectifier usesthyristor rectifier, its network power factor is low, side current distortion can causeserious harmonic pollution. On the other hand, traditional rectifier device has lowoperating frequency, and lower efficiency of energy transmission. This thesis designsa three-phase voltage-type PWM rectifier, the rectifier device can achieve unitypower factor on grid side, and the DC output voltage is stable.According to the characteristics of three-phase VSR topology, this thesisanalyzes the basic principle of the rectifier. With a detailed analysis of the maincircuit switching process, using switching function methods, I establish mathematicalmodels in abc stationary reference frame, αβ stationary frame and dq rotatingcoordinate system. It provides a mathematical basis for the further control strategy.Considering the performance of the system on the input side, this thesisdiscusses the current direct and indirect current control method of three-phase VSR,compares direct current control schemes of fixed switching frequency under differentcoordinate systems. Finally I select the program under dq rotating coordinate system,it can satisfy higher static and dynamic performance. By analyzing the three-phaseVSR control strategy, for the grid voltage disturbances and the coupling ofmathematical model of a three-phase VSR under dq rotating coordinate system, thisthesis introduces a control strategy based on the double-loop feedforward decouplingand design the main rectifier circuit and the control parameters.Since the actual grid voltage amplitude and phase may cause a certain degree ofdistortion due to different factors, the traditional hardware phase lock or single-phasedigital phase lock can’t lock the input current quickly and accurately when the gridvoltage and frequency drift. This thesis designs a new digital phase lock loop, it cantrack the phase and frequency of the grid voltage quickly, so the system can work inunity power factor status. Then, I establish a system model of a three-phase VSR in matlab/simulinksoftware platform, construct double-loop control and digital phase-locked loop modelbased on coordinate transformation, set corresponding parameters based ontheoretical studies and calculations, verify the feasibility of the system’s operation andtheory through software simulations.Finally, I design the corresponding hardware and software system in the actualsystem. Hardware circuit includes a sampling of current and voltage, IGBT typeselection and drive circuit design. Drive circuit uses an optocoupler to drive apush-pull circuit, it can drive IGBT power modules more efficiently. Software partanalyzes the double-loop feedback process flowchart, and the actual system designverify the feasibility of the theory.