Research On Discontinuous PWM Inverter Modulation Strategy

Along with the application of PWM technology in the field of Power Electronics, Two level and three level continuous SVPWM modulation algorithm has been deeply studied by experts and scholars at home and abroad, and it has been widely used in many industrial production processes. At the same time, the discontinuous PWM modulation algorithm began to appear. By studying a large number of science and technology papers at home and abroad, The continuous PWM modulation method of three level inverters was fully analyzed, and also was the discontinuous PWM modulation method. Finally, a discontinuous PWM modulation algorithm applied for three level NPC inverters was proposed in this paper.This paper first did a detailed study of continuous SVPWM modulation algorithm. By analyzing the several common three-level discontinuous PWM modulation methods, problems about the neutral point voltage, and about the PN voltage transform in motor-load were found out. So a three level discontinuous PWM modulation algorithm-DSVPWM5 is proposed. By introducing a voltage control vector (?),through which DSVPWM5 can adjust the discontinuous interval width to balance the neutral point voltage.To avoid the PN jump in motor-load, analysis of all possible PN jumps were done considering all possibles of the voltage control vector φ in DSVPWM5. Whenever and wherever happens the PN jump, DSVPWM5 can switch to the other PWM method to avoid the PN jump. Then the DSVPWM5 was also verified in Matlab/Simulink simulation analysis. A double-loop control system is designed for the inverter using the proposed three level discontinuous PWM modulation algorithm. The double-loop control system for a permanent magnet synchronous motor is built on the Matlab/Simulink platform to verify the discontinuous PWM modulation algorithm based on motor load.Under laboratory conditions, using IGBT as switch devices, a control platform based on DSP is built, and the proposed three level discontinuous PWM modulation algorithm is verified on a 40 kW synchronous motor system.