Design And Research Of Three-Level Rectifier Based On SVPWM

With the development of industry and economy, a series of new problem emerges, such as reactive power and harmonic pollutions on electric grid, deteriorated environment, and energy crises. Under this background, together with the development and increasingly mature of multilevel technology, the research of the three-phase PWM convertor is becoming popular in this years Improving the power factor of the grid and eliminating the harmonic pollution have become the trend of the technology development of converter.As the diode-clamped three-level PWM convertor can provide sinusoidal input current which contains low harmonic components, its power factor can be very high and it provide bidirectional flow energy and so on. In this paper the control system of the diodel clamed three-level PWM convertor will be researched in detail. Firstly this paper analyzes the principle and topological structure of the PWM converter, and derives the mathematical model on the basis of the principle,and then decide the control strategy.In this thesis, the control strategy being studied in the double closed-loop PI control.The double closed-loop PI control is the common control method, including the outer loop of the DC voltage and the inner loop of the current. The outer loop controls the DC voltage as a constant, and the inner loop controls the current in accordance with the current instruction given by the voltage outer loop, achieving the sine wave current and the unity power factor control.Three-phase symmetric sinusoidal voltages can synthesize a rotate space voltage vector. In this paper, the problem of how to attain space voltage vector by SVPWM modulation strategy in three-level PWM convertor is didcussed.To study the above control strategy, building the system model of the voltage PWM converter in the MATLAB/Simulink environment, and designing the controller with the control strategy to finish the simulation experiment. The simulation result can verify the correctness and the effectiveness of the control strategy. At the same time, in the simulation process, this can provide the reference for the design of the actual circuit.At last, the paper introduces the design of the hardware circuit.This circuit takes the chip TMS320F28335as the controller and chooses the double closed-loop PI control as the control strategy. The circuit includes the detection circuit, the human-machine interface circuit, and the protection circuit.