Reserch On Three Level Traction Inverter Pwm Method Of Full Speed Range

Limited by switching losses, system cooling and many other factors, the switching frequency of traction inverter would not surpass1kHz. With a low switching frequency, the traction inverter output waveform’s harmonic content at high frequency will be great. These harmonics will increase the additional loss of traction motors and harmonic torque which cause a large impact to the traction performance of high-speed train. To solve this problem, this paper studies on the model of high-speed train traction inverter-motor systems and designs a full field modulation multi-mode method which combines low-speed SVPWM asynchronous modulation and high-speed SHEPWM synchronous modulation through the operating principle analysis of the three-level SVPWM and selective harmonic elimination PWM (SHEPWM).It is difficult to solve the SHE nonlinear equations. Taking the advantage of the global convergence of PSO algorithm and the precise convergence of Newton’s method, an effective PSO-Newton hybrid algorithm was developed. In addition, considering that narrow pulse may appear in the optimal pulse pattern when the modulation index is high, a simple narrow pulse elimination method was developed in this article. The PSO-Newton hybrid algorithm was used to solve4segments of SHEPWM synchronization modulation in high speed zone. In the Matlab/Simulink, the specific harmonic elimination effect of each segments of SHEPWM synchronization modulation was simulated and verified.Then, the traction inverter and traction motor simulation model in Matlab/Simulink environment was built to test the performance of the full field modulation method, which means the motor would keep smoothly during the switching different modulation modes, and the traction motor stator current and torque didn’t change suddenly. Under the given speed command, the traction motor can accelerate smoothly to the given speed value, the traction motor voltage and current had a good sinusoidal and the torque ripple was small.Finally, the control method of vector control and modulation was programmed in TMS320F2812. Using hardware-in-loop real-time simulation based on dSPACE+TMS320F2812, the correctness of the designed full field modulation method was verified. The results showed that the motor’s phase current was much similar to the sine wave, while the whole system was stable. The presented modulation method had a good control performance for the traction inverter.