PWM Rectifier Impedance Modeling for the UGM-INKA Hybrid Train

The hybrid train developed through the collaboration between UGM and INKA, utilizes the dc bus voltage to incorporate multiple energy sources, such as fuel cells, generators, and batteries. The hybrid train's dc voltage regulation requires a PWM rectifier to connect the generator to the dc bus and ensure voltage stability. The PWM rectifier needs an inductor on the input side as a filter, and a capacitor on the output side as a buffer to operate efficiently. In its practical application, the impedance value supplied by the generator may not satisfy or surpass the demands, causing the system to become unstable. This paper presents a model to determine the required inductance and capacitance values for the PWM rectifier. A 380 V three-phase ac generator with a power specification of 180 kW maintains the rectifier's dc output voltage at a constant 600 V. The inductance values were tested under various values and conditions. Based on the simulation results, the voltage-current ripple and drop increased with larger inductor values and decreased with smaller values. At 100% load, the voltage drop is 20.54% with the maximum limit inductor and 13.96% with the minimum limit inductor. The voltage ripple reached 2.65% at its upper limit and 0.47% at its lower limit. Meanwhile, the current ripple on the upper limit inductor measures 2.68%, and 0.54% on the lower limit. These results indicate that the proposed impedance model is suitable for implementation in a 180 kW PWM rectifier and ensures dc voltage stability.