en Rolling Stock Rolling Stock پژوهشي Research <div style="text-align: justify;"><span style="font-size:10.0pt"><span style="line-height:115%"><span style="font-family:&quot;Times New Roman&quot;,serif">Nowadays, 2 to 4 inverters are installed in a metro train to feed the non-traction electrical loads (auxiliary loads). Increasingly, the reliability of this Auxiliary power supply systems (APSS) is paramount, ensuring uninterrupted operation of vital subsystems such as lighting, ventilation. In this paper, a novel approach to enhance the reliability and performance of APSS is presented. Following an introduction to the conventional APSS structure, a new framework is proposed through four key steps: 1) Data input, 2) Revamped classification of auxiliary loads based on technical parameters, 3) Strategic allocation of power sources to load groups, and 4) Enhancement of reliability indices. Through a detailed case study (Tehran metro&rsquo;s trains), the superiority of the new APSS is demonstrated, showcasing improved control features, heightened reliability, enhanced fault tolerance, and reduced implementation costs. The analysis and results reveals a significant improvement in reliability, with the new APSS exhibiting a maximum non-reliability rate of 0.13%, compared to 0.47% for the conventional system. Furthermore, the findings highlight the new APSS&#39;s ability to maintain power supply to high-priority load groups even after multiple faults</span></span></span></div> Metro Car, Auxiliary loads, Inverter, Reliability, APSS 99 114 http://ijrare.iust.ac.ir/browse.php?a_code=A-10-88-22&slc_lang=en&sid=1 Mohammad Babaeyzadeh m.babaeyzadeh@gmail.com 180031947532846002987 180031947532846002987 No School of Railway Engineering, Iran University of Science and Technology, Tehran, Iran Seyed Saeed Fazel fazel@iust.ac.ir 180031947532846002988 180031947532846002988 Yes School of Railway Engineering, Iran University of Science and Technology, Tehran, Iran Davood Arab Khaburi Khaburi@iust.ac.ir 180031947532846002989 180031947532846002989 No Department of Electrical Engineering, Iran University of Science and Technology, Tehran, Iran