AC voltage generation in rail applications (auxiliary services), usually employs optimized PWM feedforward schemes in order to control the inverter. In this kind of applications the THD reduction of the filtered output voltage together with the reduced weight of the static converters are the main goals to be reached. In order to achieve these objectives, the most commonly used optimized PWM techniques are going to be compared in terms of Total Harmonic Distortion (THD), Weighted Total Harmonic Distortion (WTHD) and IGBT losses. Based on the results obtained from the aforementioned comparison, an improved modulator is proposed that is based on combining different modulation strategies. This fact allows reducing the converter weight and size and also the optimization of the THD, WTHD and IGBT losses. The comparison results as well as the new modulator performance are included. Additionally, the theoretical proposal has been validated through experimental results.
phase modulation; ac generators; voltage; ppulse width modulation; active filters; pulse width modulation inverters; power generation; total harmonic distortion; ppower cables; rails