A Voltage-Based Approach Without Extra Hardware for Open-Circuit Fault Diagnosis in Closed-Loop PWM AC Regenerative Drives

The widespread use of electric drives has led to an increasing interest in their condition monitoring and fault diagnostics. With respect to power-switch open-circuit fault diagnosis, the majority of the proposed voltage-based approaches require additional hardware, increasing the system cost. As a result, industry acceptance may be low. This paper proposes a new voltage-based approach-without additional sensors-for open-circuit fault diagnosis in closed-loop controlled pulsewidth-modulation (PWM) ac voltage source converters, by using the information contained in the reference voltages available from the control system. The robustness against false alarms of the proposed technique is improved by employing a voltage observer, in order to estimate the actual converter voltages. It has been proven that the algorithm is insensitive to parameter errors; thus, its effectiveness is not compromised. In order to assess the applicability of the diagnostic technique, it is integrated into the control system of a permanent-magnet-synchronous-machine drive, with regenerative capabilities, together with three of the most widely used PWM control strategies: hysteresis current control, direct torque control, and space vector modulation. The technique performance is analyzed in detail by means of several experimental results.