Research Of The Rectifier Based On The SVPWM Modulation And High Power Factor

The high power factor rectifier studied in this thesis is based on the three-phase voltage neutral point clamped three-level rectifier topology structure, establishing the rectifier’s mathematical models in the different coordinate systems. Compared with the traditional diode rectifier, the PWM rectifier has many advantages such as the grid-free pollution, adjustable power factor and energy bidirectional flow, which make the PWM rectifier become hotspots and tendency on the power electronic technology research. Besides, the three-level topology structure has a relatively strong competitive advantage between the practicality and the control complexity in the middle and high voltage power applications. Accordingly, the three-level structure of the PWM rectifier has got more and more attentions, researches and applications.The thesis adopts the space vector pulse width modulation (SVPWM), and the improved way of the sector judgment in the 60 degree coordinate system is compared with the way of the sector judgment based on modulation ratio with the angle. This paper uses gh 60 degree coordinate system, and puts forward to the switching sequences in the different sectors based on the switching action sequence requirements, so that it can list the computational formulas of the vector time. The thesis does not only the comparisons between the indirect current control and the direct current control, but also compares the direct current control with direct power control in the voltage oriented control. The thesis designs the voltage outer loop of the direct current control to stabilize the DC voltage and control the power direction and values of the rectifier, furthermore, it designs current inner loop to control the netside currents to follow the sine input voltages, so that the unity power factor and the two-way transmission of energy of the PWM converter can come true. Considing the case of the voltage and current coupling in the two-phase synchronous rotation coordinate system, this thesis puts forward to the feedforward decoupling control strategy. At the same time, this thesis also introduces the working principle of the system in the direct power control. These two ways are compared for the advantages and disadwantages by means of the simulation research. In view of the inherent problems on the two capacities of the three-level neutral point clamped rectifier topology structure, this thesis analyses in details and puts forward to the time balance factor to control the operational time of the plus-minus small vectors by means of checking the capacities’ voltages and the three-phase current values in the netside and the neutral point voltage shifting control strategy based on the charge conservation theory aimed at decreasing the neutral point current’s influences to the neutral point voltage in the maxmum extent and making the neutral voltage be zero in the ideal state. This thesis also introduces the designs of the inductance, capacitor, and switch devices. Considering that activated currents produce relatively great reactive current distortions in the netside, this thesis disposes of the question based on the control algorithm. The digital phase-locked loop based on the instantaneous wattless theory in the rectifier is applied to providing the frequencies and phases in the netside of the rectifier.The thesis designs the hardware circuits and software flow patterns based on the SVPWM and high power factor rectifier. Besides, it does numbers of experiments about the rectifiers by means of the Matlab/Simulink simulation software to analysis the simulation waves. At last, the thesis arrivals at the conclusion that the simulation results prove the correctness of the theories.