High Power Factor Reversible PWM Rectifiers And Their Digital Control

Eliminating harmonic pollution and improving power factor are the quite important task in the field of power electronics. In this thesis power factor correction and reversible property are studied and the existing two kinds of reversible PWM rectification topologies and control strategy are analyzed. These two kinds of reversible PWM rectifier mainly include two-level three-phase PWM rectifier and three-level(TL) three-phase diode-clamped PWM rectifier. The space vector PWM(SVPWM) is employed to achieve low harmonic distortion and raise the utilizable ratio at DC side.Firstly, the operation basis and its control strategy for three-phase two-level PWM rectifier are dicussed and analyzed in detail. Here, the fast algorithm called pre-discomposition matrix is presented for SVPWM. This method can avoid the nonlinear algorithm and save the resource of DSP. Also the predictive current controller is proposed in three-phase two-level PWM rectifier in the two-phase fixed reference frame. The combination of the predictive current control and pre-discomposition SVPWM can realize high-frequency digital control, raise power density and minish the size. Due to that the control quantities are still sine wave in two-phase fixed reference frame, the system exists static error and the voltage ripple at DC side. Therefor no AC-line voltage sensors with SVPWM is studied and the new algorithm for no AC-line voltage sensors is proposed.Based on the studies of operation principle and mathematical models for three-phase three-level PWM converter, the TL SVPWM is analyzed and the pre-discomposition matrix method in two-level SVPWM is extended to TL SVPWM. So the linear algorithm for TL SVPWM is gotten and the run efficiency of DSP routine and the computing precision are improved greatly. The neutral point(NP) balancing problem is impersonal for TL PWM converter, the NP balance guarantees the high power factor and the safety of switches and DC capacitors. Hence, the current-sensorless hysteresis control strategy is proposed for NP balance. This control technique can keep the balance between the two DC capacitors in steady state but not perfectly in dynamic condition. So the control index method based on fuzzy controller is proposed. Fuzzy controller can automatically and intelligently adapt the value of the control index and change the operation time duration of the small vectors, to implement the NP balancing wonderfully whether in steady state or dynamic state.The current-decoupled controller is introduced into the control strategy for TL PWM converter just as two-level one. The decoupled TL PWM converter resembles the speed regulation for DC motor. From this, the design method for engineering is proposed in the thesis. This design method can shorten the design period and avoid the blindness for looking for control parameters.Besides, the reversible operation for two-level and TL PWM rectifiers is discussed in the thesis. The basis of the reversible operation in these two kinds of topology is same based on VOC. i.e. it is the output of the voltage regulator that deside the operating state of the PWM converters.Two kinds of PWM rectifier profiles are designed based on DSP TMS320F2808. The experimental and simulation waveforms verify these proposed control strategies and algorithms in this thesis.