Overmodulation control method without three-phase current sensor for permanent magnet synchronous motor

Abstract

The invention relates to an overmodulation control method without a three-phase current sensor for a permanent magnet synchronous motor. The method comprises the following steps: (1) according to reference voltage, calculating action time T'; (2) judging whether the T' is smaller than Tmin / 2 or not, continuing (3) if the T' is smaller than Tmin / 2, otherwise, preventing a B phase from moving, and causing an A phase to move leftwards and a C phase to move rightwards, wherein the Tmin / 2 is the minimum sampling time of single resistance sampling; (3) judging whether the reference voltage approaches to the upper boundary or the lower boundary of a sector where the reference voltage is positioned, continuing (4) if the reference voltage approaches to the upper boundary of the sector, and continuing (5) if the reference voltage approaches to the lower boundary; (4) causing the T' to be equal to the Tmin / 2, causing the A phase to move leftwards to the boundary, and causing the B phase to move rightwards; and (5) causing the T' to be equal to the Tmin / 2, causing the C phase to move rightwards to the boundary, and causing the B phase to move leftwards. When the method is adopted, during overmodulation, the single resistance sampling can be accurately finished, and the three phases move while the reference voltage is revised. Therefore, the modification amount of the reference voltage is minimum, and the method has a wide application range.

Description

technical field [0001] The invention relates to the technical field of motor control, in particular to the technical field of permanent magnet synchronous motor bus current acquisition, and specifically refers to an overmodulation control method for permanent magnet synchronous motors without a three-phase current sensor. Background technique [0002] Whether the stator three-phase current detection is accurate has a great influence on the actual motor control. Usually, the Hall current sensor is used to sample the three-phase current. Although the current sensor is convenient to use and has high precision, it is expensive and has a large circuit size. In the control of low-power permanent magnet synchronous motors, the cost limit is relatively strict, so some methods are to install a sampling resistor on each of the three lower bridge arms of the inverter circuit. Sampling the current is not suitable for the modulation method without zero vector, and the three resistors req...

AI Technical Summary

Problems solved by technology

When the modulation ratio is low, the three-phase PWM waveforms should all be close to 50%, which results in insufficient time for T1 and T2 to complete the ADC sampling in their respective time periods

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