Research On Motor Drive System Of Air-conditioning Compressor

With economic growth and technic improvement, air conditioning technique transfers from initially fixed frequency to variable frequency which has become the mainstream in the next decades. Behind this is the increasing attention towards the environment, and the increase of consciousness of energy saving and environmental protection. Permanent magnet synchronous motor, compared to the induction motor has higher power factor and efficiency, and also has better characteristics of high power density, high reliability and so on. It is widely used in the field of household air conditioners and commercial air conditioning. At the same time, because of the existence of permanent magnets, it makes the motor system work without excitation, which makes the energy saving effect more outstanding, therefore PMSM is becoming the hotspot in the next generations. Because that in the environment of high temperature and high pressure, air conditioning compressor cannot work by traditional photoelectric encoder, thus it requires a simpler and more reliable control strategy without position sensor.This paper mainly studied the control strategy in the rotating motor in the air conditioning compressor system, using interior permanent magnet synchronous motor. Interior permanent magnet synchronous motor compared to surface permanent magnet synchronous motor has a more complicated math model. This paper firstly discussed the model of permanent magnet synchronous motor in vector control model, and secondly, because of the requirement of reducing noise in household air conditioner, this paper adapt a simple and quiet I-F starting strategy for motor drag and acceleration. Then, under the traditional control strategy Id-equals-to-zero, the derivation is described on traditional observer and full order observer by calculating back EMF, and carries on the comparison of the simulation of the two methods. It is concluded that the full order observer has better performance on the angle and speed estimation, at the same time, because there is no low-pass filtering part in the proposed method compared to the traditional method, the follow performance of full order observer shows great advantage. In synovial near rate, the saturation function instead of traditional switch function is used to reduce the harmonic back EMF. The performance is better. In the process of I-F drag and synovial membrane switch when the speed reaches a stable value, it is made stable in the process. And the speed transferring can be realized smoothly.To detect the electric position at the same time, this paper uses phase-locked loop to synchronously follow up the motor rotor and get the speed information. And by the speed filter after speed detection, real speed message can be obtained directly. Instead of the traditional arc tangent calculation method, this method can be more accurate observer to detect angle and speed information. At the same time, bandwidth of the phase-locked loop on the method is analyzed, and the zero pole configuration is given rules, it can increase the robustness of the disturbance of the system greatly.In this paper, in order to use the interior permanent magnet synchronous motor magnetic resistance torque more effectively, the model of interior permanent magnet synchronous motor was deduced under the MTPA( maximum torque per ampere) control strategy. Traditional control scheme for the electromagnetic torque was given by the relationship of active current and reactive current with the torque. This method will make the system more complicated in calculation, so based on the relationship between the active and reactive current this paper proposes a novel method that is simplified by Taylor formula, and the algorithm is more suitable for the engineering application. Finally, experiments have been done based on the 700 W IPMSM motor platform in order to verify the simulation. DSP28335 chip was used to control the power module, and the experiment finally verified the rationality and validity of the control strategy and theoretical analysis.