Abstract
In conventional position sensorless permanent magnet (PM) machine drives, the rotor position is obtained from the phase-locked loop (PLL) with the regulation of spatial signal in estimated back electromotive force (EMF) voltages. Due to the sinusoidal distribution of back-EMF voltages, a small-signal approximation is assumed in the PLL in order to estimate the position. That is, the estimated position is almost equal to the actual position per sample instant. However, at high speed when the ratio of sampling frequency, fsample, over the rotor operating frequency, fe, is low, this approximation might not be valid during the speed and load transient. To overcome this limitation, a position estimation is proposed specifically for the high-speed operation of a PM machine drive. A discrete-time EMF voltage estimator is developed to obtain the machine spatial signal. In addition, an arctangent calculation is cascaded to the PLL in order to remove this small-signal approximation for better sensorless drive performance. By using the discrete-time EMF estimation and modified PLL, the drive is able to maintain the speed closed-loop at 36 krpm with only 4.2 sampling points per electrical cycle on a PM machine, according to experimental results.
Highlights
Permanent magnet (PM) machines are widely used in motion applications with high power densities, e.g., pumps, compressors and fans
PM machine drives at high speed have demonstrated advantages in applications with a size constraint [1,2,3]
For electromotive force (EMF)-based drives, the EMF voltage is estimated according to the voltage and current block, EMF voltage can be estimated from either the open-loop calculation based on the machine relationship with the knowledge of machine resistance and inductance
Summary
Permanent magnet (PM) machines are widely used in motion applications with high power densities, e.g., pumps, compressors and fans. Beyond 10% rated speed position estimation using the spatial signal in EMF voltages results in a comparable performance to saliency-based drives [14,15,20]. Estimation methods are preferred at high speed for the sensorless drive, because no voltage injection is filter. The rotor position is results in athe comparable performance to saliency-based drives [14,15,20] Under this effect, EMF-based calculatedposition by obtaining spatial signal in the speed estimated voltage. EMF-based estimationthe methods are preferred at high for the EMF sensorless drive, because no voltage injection is required to fully utilize the DC bus voltage
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