The Research Of An Inverter Air-Conditioner's Outdoor Controller

In recent years the inverter air-conditioner has been a mainstream product in the market as its good performance and highly efficiency. But in domestic market,most of inverter air-conditions which apply the inductance motor prevent the performance to improve because of the disadvantages such as bigger start-up current and lower power factor. This kind of motor can not satisfy air-condition market's need under the condition of energy crisis. A new kind of motor called permanent magnet synchronous motor ( PMSM) will become the best choice of inverter air-condition compressor motor for its higher running efficiency and no excitation current. Compare with the air-conditioner with the inductance motor, the one with PMSM can save 10%-15% energy.In the process of motor running, we need test the position of rotor to complete field orientation control. There are three main factors in the following which determined that we can not use a mechanical sensor to get rotor's position.â‘ The high cost of the sensor.â‘¡For inverter air-conditioner, the motor is sealed in the compressor, which means the mechanical sensor is difficult to maintain.â‘¢The compressor is full of corrosive and high-pressed refrigeration, additional temperature change and mechanical vibration, all will reduce the stability and reliability of mechanical sensor. So it's very important to find a simpler and lower cost sensorless control method.According to the design an outdoor controller of the air-conditioner with PMSM use IRMCF 341 motor controlling chip, carry out the following works:(1). Deeply analyzed the mathematics model of PMSM in different coordinates and mutual conversion methods. Introduce the field orientation control principle and voltage space vector pulse width modulation (SVPWM) technology.(2). Put forward the rotor position method of rotor magnet flux calculation with phase lock loop. First calculate stator magnet flux by stator voltage and current, then induct it to phase lock loop to get the estimated value of rotor's position and velocity. Also put forward improved method and error corrector which are for the problems such as DC offset and parameter change. Meanwhile, deeply analyze three steps start-up strategy which applied in this system.(3). Design an inverter air-condition outdoor controller with IRMCF 341 motor controlling chip, according to the methods above. Erect the experiment platform, and make use of the regulated controlling parameters for motor rotary speed, magnet flux and position errors to make the system satisfied with the design requirements.