Speed-sensorless vector control for permanent-magnet synchronous motors based on instantaneous reactive power in the wide-speed region

The paper proposes an implementation of the new sensorless speed-control scheme for a permanent-magnet synchronous motor (PMSM). In the proposed algorithm, the current observer estimates the line currents and the estimated speed can be yielded from the voltage equation because the information of speed is included in back EMF. However, the speed-estimation error between the estimated and the actual speed arises because of the measurement errors of the motor parameters and the sensing errors of the line currents and input voltages. Because the parameters such as machine inertia or a viscosity-friction coefficient depend on the mechanical load which is not constant in most applications, there are many restrictions in the actual implementation. To minimise the speed-estimation error, the estimated speed error is compensated by the instantaneous reactive power. Moreover, to increase productivity, a flux-weakening control algorithm is added to the proposed sensorless algorithm in the high-speed region. The proposed algorithm improves robustness by removing the mechanical equations in the observer and improves performance by adding flux weakening control in the high-speed region.