Control method of permanent magnet synchronous brushless direct-current motor in low frequency

Abstract

The invention relates to the air conditioner control technology, and provides a control method of a permanent magnet synchronous brushless direct-current motor in low frequency. The control method of the permanent magnet synchronous brushless direct-current motor in low frequency is used for solving the problems that when a compressor works, axis error estimation is inaccurate, and position detection of the compressor is out of step. The control method of the permanent magnet synchronous brushless direct-current motor in low frequency comprises the steps that (1) a system collects phase current of the permanent magnet synchronous brushless direct-current motor through a current detection unit, transmits the phase current to a coordinate transformation unit to obtain a d-axis current component Id and a q-axis current component Iq of the phase current, and transmits the d-axis current component Id and the q-axis current component Iq to an axis error estimation unit; (2) the system calculates an error delta theta between the actual position of a motor rotor and an estimated position of the motor rotor according to the obtained parameters such as the d-axis current component Id and the q-axis current component Iq; (3) after the system compares a current working frequency f of the permanent magnet synchronous brushless direct-current motor with a first frequency f1 and a second frequency f2, the system calculates a speed presumption unit input value delta theta PLL, and calculates the current estimated rotating speed omega c of the rotor, and a current estimated position theta c of the motor rotor is determined through a phase presumption unit. According to the control method of the permanent magnet synchronous brushless direct-current motor in low frequency, the axis error delta theta is reduced artificially, namely, amplitude limiting processing is carried out on the axis error, the effect of restraining control is achieved, and the control method of the permanent magnet synchronous brushless direct-current motor in low frequency is applicable to the permanent magnet synchronous brushless direct-current motor.

Description

technical field [0001] The invention relates to air-conditioning control technology, in particular to a low-frequency control method for a permanent magnet synchronous DC brushless motor. Background technique [0002] The position sensorless vector control method of the permanent magnet synchronous brushless DC motor, one of the key technologies is the position detection of the motor rotor and the estimation of the operating frequency, especially at low frequencies, due to the accumulation of liquid in the compressor and insufficient oil return. Problems such as bearing lubrication will make the operation of the compressor unstable, cause fluctuations in the detection current, and cause inaccurate estimation of the axis error Δθ. Estimated value of the motor's current rotor position θ c Calculate the current estimated rotational speed ω of the motor by using the axis error Δθ c , ω c Through the phase estimation unit according to the formula: [0003] θ ...

AI Technical Summary

Problems solved by technology

[0006] The technical problem to be solved by the present invention is to provide a permanent magnet synchronous DC brushless motor for the control problems such as the out-of-step detection of the compressor position due to the inaccurate and large shaft erro

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