A Low-Frequency Junction Temperature Swing Suppression Method Based on Varying Switching Frequency for Single-Phase PWM Rectifiers

Single-phase PWM rectifier is an important part in traction drive system. The low-frequency junction temperature swing of the power devices caused by the frequent changes of train operating condition, has a substantial impact on the reliability and service life of the system. In this paper, an active thermal control strategy based on varying switching frequency is presented to reduce the amplitude of the low-frequency junction temperature swing. Firstly, the power level is defined using the reference output power, and the relationship between the junction temperature information and switching frequency at each power level is revealed. The curve fitting method is adopted to obtain the fitting parameters among them. On this basis, a 3D lookup table is established according to these parameters, including the power level, switching frequency and junction temperature information. Then, a suitable switching frequency can be selected according to the 3D lookup table, to suppress the junction temperature swing during the dynamic condition. Finally, simulation result is presented to validate the effectiveness of the proposed method.