Three-phase Pwm Rectifier

The conventional rectifiers produce harmonic problem in power system. While three-phase PWM voltage source rectifiers (VSR) can provide constant dc bus voltage and get low harmonic distortion of input current. It also has line power feedback capability. This paper mainly introduces three-phase VSR, including its principle, the topology, the mathematical model, the control strategies, and its hardware. The mathematical model of VSR is the essential means to investigate the VSR. Low frequency models and high frequency models are set up in ABC coordinate, α β coordinate, and dq coordinate, respectively. This paper focuses on two control strategies, one is voltage-oriented control (VOC), and the other is direct power control (DPC).Method of VOC includes indirect current control and direct current control, and their principles are introduced. This paper sets up a simulation model and presents a method of digital realization. A experiment about direct current control is done, and we find that the harmonics of line voltage deeply affect the distortion of input current. In order to weaken the distortion of input current, several practical means are presented.The advantages of DTC are simple structure, fast dynamic response, and the ability to resist disturbance. The concept of instantaneous power, the principle of DTC, and the method of selection of voltage vector are presented. When we use the conventional switching-table, the reactive power of system has uncontrollable region, and the input current is affected also. So a new type of switching-table is set up, and it is proved to be effective by experiment. At last, this paper compares these two methods: VOC and DTC.Moreover, the design of inductance and capacitance in VSR, the main function about DSP2407, the design of two-order active filter, and the using of intelligent power module (IPM) are introduced in this paper.