Zero-Voltage Vector Based Method under Non-Zero Initial Current Condition for Flying Start of Sensorless PMSM Drive

When restarting a permanent magnet synchronous motor (PMSM) with unknown rotational speed, accurate estimation of the initial rotor position and speed must precede the application of appropriate voltage vectors. The zero-voltage vector (ZVV) based method, commonly employed for initial position estimation in medium-to-high speed PMSM flying-start applications, requires the motor's response current to decay to zero before applying subsequent pulses. As this condition is difficult to satisfy within limited timeframes during high-speed operation, this work proposes a novel ZVV-based method operating under non-zero initial current conditions. Through modeling of transient short-circuit current induced by ZVV pulses, a universal position estimation framework applicable to arbitrary initial current states is established, thus eliminating operational constraints of conventional ZVV-based methods and enhancing high-speed estimation accuracy, particularly in flux-weakening operation.