| Rectifier is wildly used as AC/DC for transforming electric power in industrial production. Traditional rectifiers consist of uncontrollable rectifier with diode as commuter and phase-controlled rectifier with SCR as commuter. Both the traditional rectifiers have been applied for a long time, the technology is relatively mature. However, they make serious harmonic pollution, low power factor and the output DC voltage suffers instability problems. These shortcomings seriously affect the fficiency of energy conversion. To overcome the shortcomings of the conventional rectifier, PWM rectifier came into being. Compared with the conventional rectifier, PWM rectifier can gain side current sinusoidal and operate with unity power factor with fast response to current. Besides, the energy of PWM rectifier flows two-way.In this thesis, the principle and topology of PWM rectifier are researched, and the mathematical model of PWM rectifier is derived. On this basis, control methods for voltage-type PWM rectifier are studied, especially direct current control technology and energy feedback control techniques. Finally, simulation models of three-phase voltage-type PWM rectifier are builded in MATLAB.In order to avoid the complex coordinate transformation, and solve the uncertainty of load parameter, the adaptive control method for voltage-type PWM rectifier is proposed. The adaptive control method introduces control theory into the study of PWM rectifier technology by analyzing the mathematical model. When the load is uncertain, the method in this thesis can adapt to load parameters change and ensure the robustness of control systems. Besides, the method can provide high control precision. The control structure of adaptive method is designed with current tracking mode. The complex coordinate transformations are avoided by constructing a three-phase current dynamic basis. Finally, the design of the load adaptive control scheme is simulated; simulation results show the effectiveness of the control scheme.The theoretical research and practical system design for voltage type PWM rectifier are made in this thesis, unity power factor characteristics and current and fast dynamic response characteristics of the voltage type PWM rectifier are verified. Load-adaptive method proposed in this thesis can adapt to the changes in the load parameters and avoid the complex coordinate transformation. The control scheme is simple, with good value and application prospect. |
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