A fault diagnosis and fault tolerant control method for DC-link circuit using notch filter in power traction converter

Abstract

The converter with a single-phase rectifier, a DC-link circuit and a three-phase inverter is widely applied in high-speed railway electrical traction drive system. An unexpected failure in DC-link circuit may trigger the protection of the traction control units (TCU) by detecting the amplitude of the voltages and currents. However, the TCU cannot detect the short circuit fault of the inductor in LC resonant circuit, due to the less obvious fault characteristics. It may generate a fluctuating DC-link voltage, a severe beat phenomenon of the motor current, which cause ripple torque and howling noise of the motor. Thus, this paper analyzes the different fault modes and effects of the DC-link circuit and presents a fast fault diagnosis method by using notch filter. Moreover, a fault tolerant control method based on frequency compensation is adopted. It requires no additional hardware but only some measurements which are available in control system. Some contrasting experimental results confirm the effectiveness and accuracy of the proposed method. It is shown that such fault diagnosis and tolerant control method keeps the traction system operating with a good performance which is important to avoid catastrophic consequences.