A DC-Flux-Injection Method for Fault Diagnosis of High-Resistance Connection in Direct-Torque-Controlled PMSM Drive System

This paper proposes a dc-flux-injection method for fault diagnosis of high-resistance connection (HRC) in a direct-torque-controlled permanent magnet synchronous machine (PMSM) drive system. In this method, the flux linkage bias is superimposed in the flux control loop of the direct torque control system, and then the dc current offset is excited in the stator windings. By superimposing two different pairs of flux linkage biases, a binary linear equation group about the resistance deviations can be established based on the stator currents and zero-sequence voltage component. By solving the equation group, the resistance deviations can be calculated for the HRC fault detection, faulty phase location, and fault severity estimation. Both the simulation and experimental results validate the effectiveness of the proposed method. In addition, the proposed method is immune to the symmetrical variations of stator resistance and interturn fault of the PMSM.