Power IGBTs Application in AC-Wire DC-Motor Locomotive Thyristor-Based Power Circuit for Regenerative Brake Energy Efficiency Increase

As the entire Baikal-Amur Mainline and the eastern part of Trans-Siberian Railway in Russia are electrified with 25 kV 50 Hz AC, current Russian heavy freight and long-distance passenger rail operation largely relies on domestic AC-fed electric locomotives with DC motors. These locomotives universally apply thyristor-based power converters for energy rectification and inversion. While being considered efficient enough not to require immediate modernization, this traction system has long been causing concerns regarding its energy performance, namely, a low power factor during regenerative brake mode. However, introducing progressive converters based on modern semiconductor devices (such as IGBTs) as a possible solution may prove not to be economically and logistically reasonable if applied industry-wise, especially in terms of obsolete locomotive series which are still in operation. This induces a certain interest in alternative means of AC-to-DC thyristor-based electric drive energy efficiency increase that can offer comparable positive effects at lower expenditures. A developing method of this sort is presented in this paper. The method implies shunting the standard thyristor bridge with a single IGBT branch that serves as a fully controllable electronic switch and allows for a revised, more efficient thyristor control algorithm. A significant increase in regenerative brake power factor has been confirmed by mathematical simulation also presented in the paper.