The Research Of Hybrid PWM Strategy Based On FPGA

With the continuous development of science and technology, high-speed rail and motor train with their comfort and convenience which meet the need of people has become the main means of transportation. In rail transit technology, as one of the core technologies, the performance of traction PWM technology is directly related to the stability, security and comfort of the system. This paper relies on the "12th Five Year" key projects of national science and technology support program"the hybrid EMU key technology research and typical prototype manufacture"and joint fund project" high-speed railway electric traction system safety prediction and control" (U1134204), and researches on the pulse width modulation technique and proposes a set of strategies based on FPGA hybrid pulse width modulation, and verifies them through extensive simulation and experiment.The basic principle and performance of pulse width modulation technology are studied. The basic principle of Intermediate 60 ° SPWM, Selected Harmonic Minimum PWM and Current Harmonic Minimum PWM are researched with the calculation method of switching angle introduced. Then the CHMPWM is compared with Intermediate 60° SPWM and SHEPWM in three aspects of realization mode, current harmonic and torque ripple. In the last, the conclusion that the CHMPWM has the advantages of good harmonic performance and small torque ripple is obtained and a hybrid pulse width modulation scheme is proposed.The smooth transition problem in the hybrid pulse width modulation strategy is analyzed. The basic principles to ensure smooth transition are analyzed, including continuous fundamental wave and small armonic content mutation in switching time.The advantage of FPGA in the realization of mixed pulse width modulation is compared with DSP, which is using high speed characteristics to ensure the fundamental continuity. The advantage of CHMPWM in smooth transitionis is compared with SHEPWM, which is ensuring a small mutation of harmonic content in switching time. The hybrid pulse width modulation strategy based on FPGA is simulated and verified by MATLAB.The digital implementation method of hybrid PWM strategy is introduced in detail. The realization mechanism of asynchronous SPWM, synchronous SPWM and CHMPWM in FPGA is analyzed. The FPGA design of mixed PWM strategy is introduced. At last, the FPGA design is simulated and verified by the simulation software in Quartus, and the simulation results are consistent with the theory.The hybrid EMU ground test platform is built, on which the hybrid module Tmodulation based on FPGA is experimentally verified. The simulation results are consistent with the theory, which verifies the correctness and effectiveness of the hybrid PWM strategy based on FPGA proposed in this paper.