Research And Manufacture Of The Multi-phase SPWM Controller Based On CPLD

This essay mainly analysised the two forms of phase-shift in PWM of level phase-shift and vertical phase-shift in serial units mid-voltage frequency converter, and concluded both the benefits and shortcomings of them. Both of them can output multi-levels voltage waves that approximated to the sine wave ,and light the harmonic pollution to the net and light the impulse to the net and motors, but with some shortcomings in itselves, (a) in case of vertical phase-shift when the modulate amplitude is smaller, the outputs between the units is different, need to distribute every power unit's output dynamically; (b) in case of level phase-shift, when the distance between the tri-angle waves is larger, the sample precision is lower and cannot meet the requirment. On basis of overcoming these shortcomings, we suggested a theory producing multi-paths SPWM by using vector rotating method that based on CPLD, this method keeps the benefits of the level phase-shift and vertical phase-shift but with simpler calculation and better output wave forms and faster response and better reliability.The essay discussed in detaily the following contents:(1) Described the two kinds of PWM modulation methods of carrier phase-shift in serial units mid-voltage frequency converter, and done simulation to the PWM modulation of carrier level phase-shift and vertical phase-shift ,analysised the output wave forms that under different modulation. The simulation and the system tests showed that both the carrier level phase-shift and vertical phase-shift PWM modulation can enhance the switching frequencies, and increase the numbers of output levels, and light the harmonics and promote the output wave forms, but with shortcomings in itselves. Due to this reason, suggested one method of vector rotating to resolve the problem of producing multi-paths SPWM in mid-voltage frequency converter, and given a detailed theoretically analysis.