PMSM Sensorless Vector Control System Of Variable Structure For Air Conditioning Compressor

In recent years, air conditioner compressor for frequency conversion air conditioning based on the induction motor gradually becomes the market mainstream.Although catering to the people on the properties of energy conservation, emissions reduction and efficiency requirements to a certain extent, it is still difficult to get rid of large starting current and low power factor of the induction motor. Permanent magnet synchronous motor(PMSM) obviously improve the efficiency, power factor and obtain better energy saving effect due to the rotor of permanent magnet without excitation, therefore PMSM becomes the new focus in the field of frequency conversion air conditioning research. But in the drive of air conditioning compressor vector control system, the periodic fluctuations of the load torque causes the speed volatility of the cycle, when running at low speed, the air conditioning system framework of high vibration and noise caused by speed fluctuation is especially obvious. Phenomenon is particularly obvious, at the same time reducing the efficiency of the system. Based on the analysis of the motor fluctuations caused such periodic load disturbance, the paper primarily studies sensorless vector control system of permanent magnet synchronous motor for air conditioning compressor, while the permanent magnet synchronous motor vector control system requires more accurate rotor position information. The air conditioning compressor in high temperature and high pressure environment determines we can not detect the position with the traditional sensor, so finding a simple and reliable sensorless control method is particularly important.Considering the hysteresis of switching time and space in the traditional sliding mode observer, the estimated current will swing up and down the actual value. In order to further improve the permanent magnet synchronous motor position precision, the paper uses saturation function instead of the switch function, which weakens the chattering effectively through the appropriate selection of boundary layer. In addition, the electromotive force for speed estimation is obtained by low pass filter in traditional sliding mode observer, and the low pass filter can cause the phase delay.At the same time the delay and low pass filter is closely related to the phase response, the lower the cutoff frequency, the greater the corresponding natural frequency phase delay. The cut-off frequency is constant, so we have to use the phase delay table to store the large capacity phase shift values in traditional sliding mode observer, it inevitably limits its application to a certain extent. therefore, the paper designs cutoff frequency of a new type low pass filter changing with speed, and it effectively solves the problem. Secondly, using the phase lock loop technique in the observer to estimate the counter electromotive force, for the calculation of magnetic pole position, eliminating the calculation noise.Finally, the dissertation studys the comparative simulation in the conventional sliding mode observer and a new sliding mode observer of the current, speed estimation values and position error based on the permanent magnet synchronous motor vector control system. And on this basis of this, the paper complete the core TMS320F28335 adapted to drive the air conditioning compressor permanent magnet synchronous motor drive hardware circuit design and software application development. While the completion of the new sliding mode observer designed in the experimental platform for low-speed and high-speed permanent magnet synchronous motor position accurately identified.The simulation results and experimental data show the feasibility and effectiveness of the improved sensorless permanent magnet synchronous motor vector control system, and it is of significance in engineering practice.