For the last couple of decades, Permanent Magnet Synchronous Machines (PMSMs) have attracted great attention in various industry applications such as hybrid electric vehicle systems, direct drive wind power generation applications, direct drive washing machines and servo systems etc. due to their high power density, wide range of constant power operation and good torque-speed response. This work focuses on developing and implementing simple yet reliable sensorless vector control algorithms for PM machines for the full speed range including zero speed.
Speed or position sensors used to obtain the rotor position information for high performance vector control of PM machines add more complexity to the hardware system, have poor immunity to electromagnetic noise and reduce the reliability of the system. Two sensorless algorithms are investigated in this work: 1) High frequency carrier signal injection based sensorless algorithm for zero and low speed operation; 2) Voltage model based sensorless algorithm for the middle and high speed operation. Initial rotor position is identified using the magnetic saturation effect.
Difference in the d- and q-axis inductances results in additional reluctance torque in Interior Permanent Magnet (IPM) synchronous machines, which makes them very suitable for operation with a constant output power over a very wide speed range theoretically. It is known that the field weakening control is required to achieve the constant power operation. Literature review indicates that stable control of IPM machines in the deep field weakening operation region still remains an issue to achieve the largest possible speed range. A single-current-regulator algorithm which gives a fixed command for the q-axis voltage and only controls the d-axis current is investigated in this work. The criteria of selecting the optimal q-axis voltage in terms of variable speeds and load conditions are proposed to achieve better operating efficiency and robustness of the system in the deep field weakening operation region.
The sensorless vector control algorithms and the single-current-regulator algorithm with optimal q-axis voltage control are tested on a 50 kW IPM machine system across the full range of speed and load to substantiate the theoretical work.