Leg Conversion Method for the Continuous Control of a Railway Vehicle Propulsion Inverter

In this study, we propose a whole-leg scheme for the continuous control of a railway vehicle propulsion inverter. The three-leg method is commonly used to obtain the output AC power from the input DC voltage in a railway vehicle propulsion inverter. When the power semiconductor of an inverter operating in a three-leg manner fails, a problem occurs in the power supply. Therefore, this study proposes a method that automatically converts into the two-leg method without replacing the power semiconductor when it fails while the inverter is driven with the three-leg method. This leg conversion method can prevent problems in supplying power by converting the power that can be obtained from an inverter operating with the three-leg method into that obtained from an inverter operating with the two-leg method. In addition, to verify the effectiveness of the leg conversion method, a demonstrative experiment was conducted after a simulation, and an actual inverter was fabricated. Consequently, the experimental results confirmed that in an inverter operating with the three-leg method, even if the power semiconductor failed, it could be converted for operation with the two-leg method to supply power normally.