Exponential Curve-Based Control Strategy for Auxiliary Equipment Power Supply Systems in Railways

An exponential curve-based (ECB) control strategy has been proposed in this paper. The proposed ECB control strategy is based on the growth and decay of charge in the series RC circuit and the harmonic elimination by detecting the Fourier expansion series of the auxiliary equipment power supply system’s (AEPSS) three-phase output voltage level. It can quickly adjust each duty cycle to the best value for driving the isolated three-phase inverter (ITPI) and produce a three-phase 380 V_AC/60 Hz output. A comparison of the AEPSS output performance using the traditional voltage cancellation method (VCM) and the proposed ECB control strategy was performed. The hardware implementation of the system was performed on the prototype developed in the laboratory. These control strategies are tested under three conditions, i.e., (i) V_i = 550 V_DC. (ii) V_i = 750 V_DC. (iii) V_i = 800 V_DC. The total harmonic distortion (THD) is 13.7%, 14.5%, and 14.9%, and the output voltage V_o is 372.3 V_AC, 377.3 V_AC, and 385.3 V_AC using the traditional control strategy at three test conditions, respectively. However, the THD is 7.2%, 7.8%, and 8.0%, and the output voltage V_o is 382.2 V_AC, 381.2 V_AC, and 381.9 V_AC using the proposed ECB control strategy under the test conditions. It is obvious from the hardware results that the output voltage harmonics and output voltage level for the proposed ECB control strategy are superior to the traditional VCM. The voltage produced from the AEPSS using the proposed ECB control strategy is more stable and has better quality. In addition, the filter size is also reduced.