This study uses a rail vehicle auxiliary power system (APS) to feed the rail vehicle air conditioning, air compressor, etc. which requires a three−phase 380 VAC/60Hz power source. Rail vehicle receives a 750 VDC from
a third rail or an overhead conductor. This DC source is converted into a three−phase AC source through the APS three−phase inverter. This three-phase inverter (TPI) is a traditional inverter that has been designed by using six switches. The controlling signal to these switches can be provided by using different control strategies that help to regulate the switching time of the switches by regulating the pulse width of the signal. The TPI of the rail vehicle APS mostly uses the traditional square wave (SW) control strategy. The traditional SW control strategy can reduce high-frequency interference and avoid affecting railway side signals. However, the traditional SW control strategy produces higher voltage harmonics and a larger volume of the power converter. Therefore, certain strategies have been developed to overcome these shortcomings.
The Fourier Expansion Series Quick Adjustment (FESQA) control strategy has been proposed in this study. This control strategy is based on the square wave and the Fourier expansion series detection of the APS three-phase output voltage level and the amount of the harmonic present in it. Then the proposed FESQA control strategy quickly adjusts the duty cycle of each control pulse to reach the best value which is used to drive the switches of the TPI. The TPI generates a three-phase alternating current power which is isolated and filtered by the transformer and output filter (Lo and Co). Three-phase 380 VAC/ 60 Hz from the APS output is then used to provide power for the rail vehicle electrical equipment.
MATLAB/Simulink has been used to simulate the APS circuit model. Hardware implementation of the prototype of APS has also been performed in the laboratory to validate the proposed FEQSA control strategy. From the simulation and hardware result, it is obvious that the total harmonic distortion (THD) is enormously reduced by using the proposed control strategy and the output voltage Vo is more stable and closer to the required output voltage even with the change in the input voltage. Moreover, the size of the APS output filter using the proposed FESQA control strategy is smaller than the traditional control strategy. This will not only reduce the system volume but also reduce the system cost.

This study uses a rail vehicle auxiliary power system (APS) to feed the rail vehicle air conditioning, air compressor, etc. which requires a three−phase 380 VAC/60Hz power source. Rail vehicle receives a 750 VDC from
a third rail or an overhead conductor. This DC source is converted into a three−phase AC source through the APS three−phase inverter. This three-phase inverter (TPI) is a traditional inverter that has been designed by using six switches. The controlling signal to these switches can be provided by using different control strategies that help to regulate the switching time of the switches by regulating the pulse width of the signal. The TPI of the rail vehicle APS mostly uses the traditional square wave (SW) control strategy. The traditional SW control strategy can reduce high-frequency interference and avoid affecting railway side signals. However, the traditional SW control strategy produces higher voltage harmonics and a larger volume of the power converter. Therefore, certain strategies have been developed to overcome these shortcomings.
The Fourier Expansion Series Quick Adjustment (FESQA) control strategy has been proposed in this study. This control strategy is based on the square wave and the Fourier expansion series detection of the APS three-phase output voltage level and the amount of the harmonic present in it. Then the proposed FESQA control strategy quickly adjusts the duty cycle of each control pulse to reach the best value which is used to drive the switches of the TPI. The TPI generates a three-phase alternating current power which is isolated and filtered by the transformer and output filter (Lo and Co). Three-phase 380 VAC/ 60 Hz from the APS output is then used to provide power for the rail vehicle electrical equipment.
MATLAB/Simulink has been used to simulate the APS circuit model. Hardware implementation of the prototype of APS has also been performed in the laboratory to validate the proposed FEQSA control strategy. From the simulation and hardware result, it is obvious that the total harmonic distortion (THD) is enormously reduced by using the proposed control strategy and the output voltage Vo is more stable and closer to the required output voltage even with the change in the input voltage. Moreover, the size of the APS output filter using the proposed FESQA control strategy is smaller than the traditional control strategy. This will not only reduce the system volume but also reduce the system cost.

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