Research On Control Strategies And Application Of Three-phase Voltage Source Pwm Rectifier

Using energy without pollution and efficiently is widely concerned around the world now. Traditional diode rectifier and phase-controlled rectifier need lots of reactive power provided by power grid, which will bring serious harmonic pollution to grid, affect the grid operating safely and other electronic equipment operating normally, and the effective utilization of energy will be reduced too. PWM rectifier has many advantages such as low current harmonics of grid side, unity power factor, reversibility of energy, DC voltage controlled, and so on,which will realize the "green conversion"of energy. PWM rectifier can solve the problem of harmonics and reactive power essentially, and has broad application prospects in the fields of high-power uninterruptible power supply, four-quadrant AC drives, traditional power system generation product, reactive power compensation, solar power generation and other areas as well as AC and DC driving system. In this paper, the control strategies and application of three-phase voltage source PWM rectifier is studied deeply, the main content as follows:1. In this paper, mathematical models of three-phase voltage source PWM rectifier are established respectively in the three-phase stationary coordinate, two-phase stationary coordinate and the synchronous rotating coordinate. The principle of space vector PWM technique is introduced, and simplified algorithm of SVPWM is also provided, which can not only avoid trigonometric functions and nonlinear computing, but increase the computing speed.2. Feedforward decoupling control strategy based on the dq coordinate and predictive current control strategy based on two-phase stationary coordinate both are mainly studied in this paper. The principle of feedforward decoupling control strategy is analyzed, and the designing methods of voltage outer-loop and current inner-loop are also discussed. This paper focuses on predictive current control strategy of which the control principle and the reason of static phase error existing in the AC side current are studied. And the paper presents improved predictive current control strategy, which solves the problem of static phase error existing in the AC side current in traditional predictive current control strategy using periodic phase information of voltage.3. This paper establishes mathematical model of multiple parallel three-phase voltage source PWM rectifier in two-phase synchronous rotating coordinate. The zero-sequence circulating control and current sharing control of multiple direct parallel are studied. And the paper presents zero-sequence circulating control strategy which adding zero-sequence circulating control loop in controlling system through controlling the zero vector duty cycle of SVPWM to achieve zero-sequence circulating current control. Moreover, maximum current automatic master-slave control strategy is used for current sharing control in parallel system, which improves redundancy. The paper also discusses the controlling of N parallel system basing on controlling technology of double parallel system.4. The application of three-phase voltage source PWM rectifier in high-power UPS is studied in this paper. The paper describes the key technology in the project design of three-phase voltage source PWM rectifier, and analyzes the test results of the prototype.The40kVA three-phase voltage source PWM rectifier we designed can meet the provisions of the UPS parameters, for example, input power factor is0.981, AC side current harmonic THD=2.49%.