An optimal DC bus voltage control method to improve the junction temperature of IGBTs in low speed operations of traction applications

Traction drives frequently operate at large torque and low speed states, which results in large junction temperature fluctuations and high peak value of inverter power devices. Therefore, the reliability of IGBTs will decrease significantly without suitable thermal control. In order to reduce power losses and junction temperature in low speed operation, the main studies of this paper are as follows: Firstly, an electro-thermal-load model of the traction inverter is established to analyze the junction temperature in different load operating conditions. Then, a control method of minimizing the IGBT power losses by regulating DC bus voltage is proposed. The results show that power losses and junction temperature of IGBTs have been decreased effectively without degrading the system performance in low frequency operations. Simulink and IPOSIM simulations are also employed to verify the correctness of the proposed method.