Position Sensorless Control of PMSMs Using Improved INFORM Method with a Single Current Sensor at Low Speed

This paper presents position sensorless control by High Frequency (HF) voltage injection methods with a DC-Link current sensor for Permanent Magnet Synchronous Machines (PMSMs) in the fields of low-cost driven at low speed. For single current sensor, three phase currents can be reconstructed via a single current sensor. However, due to the duration of the effective voltage vector in the low-modulation index, three phase current cannot be reconstructed entirely. When INdirect Flux detection by On-line Reactance Measurement (INFORM) method is applied with a DC-Link current sensor, due to three voltage vectors injected falling into unmeasurable index in the complex plane, instead of most used Pulse Width Modulation (PWM) phase shift, this paper proposes to make three injected voltage vectors exceed the unmeasurable area by improved INFORM method, which needed to inject three voltage vectors with an initial phase. Accordingly, a novel current sampled method by a DC-Link current sensor is proposed for the improved INFORM method. Ultimately, position sensorless control and phase current reconstruction are solved simultaneously, and the accuracy of position observed is improved. A series analysis of simulation verify the effectiveness of the presented algorithm.