Permanent magnet synchronous motor vector control scheme in inverter air conditioning fan

　　Anti-typhoon starting capability

　　For outdoor fans of air conditioners, since the fans are outdoors, it must be ensured that they can work normally under the influence of various natural conditions, especially under the influence of strong winds, the fans can start, run or alarm normally. For the vector control of permanent magnet synchronous motor without position sensing, the normal operation stage can work normally under strong typhoon due to the characteristics of fast dynamic response. However, without position sensing, an open-loop starting process is required to establish the rotor position and speed signals, and this starting process torque is relatively small, which makes it difficult to ensure reliable starting of the wind machine under the influence of strong typhoons.

　　In order to resist typhoons, in addition to increasing the starting torque as much as possible, the solution also adds a typhoon-resistant starting function module to ensure that the fan can successfully start or give a strong typhoon alarm signal. When the fan is shut down, the speed and direction of the fan under strong wind are related to the size and direction of the wind, and whether the fan can be started successfully is mainly related to the wind speed of the fan before starting. In this way, the initial speed and direction of the fan before starting need to be detected by the program first, and then the different starting process is processed according to the monitoring results, which can be divided into three cases as follows.

　　● Direct start

　　When the fan is in positive rotation and the speed is greater than a certain value, it directly enters the operation mode.

　　● Strong typhoon alarm, stop normal starting

　　When the fan speed is too high to ensure the normal starting of the fan, a strong typhoon alarm is issued and the fan stops normal starting.

　　● Normal start

　　In other cases except 1) and 2), the fan can ensure successful starting and start the fan according to the normal starting procedure.

　　After the simulated strong typhoon test, the system was able to start and run safely, and the performance of starting and running in strong wind environment was also verified in the actual outdoor environment test.

　　Motor phase loss detection

　　In order to ensure the normal starting and running of the fan, the motor phase loss detection is performed before each motor start, and the corresponding function function detects whether the three phase lines of the fan are connected normally and whether the 3-phase inverter bridge is intact, and if phase loss is detected, the fan start is stopped and a phase loss alarm is reported to ensure that the fan can succeed after entering the start program each time, and at the same time, the system has the corresponding error diagnosis capability.

　　Conclusion

　　The vector control scheme of permanent magnet synchronous motor introduced in this paper has the features of stable and reliable system operation, high efficiency, low cost, energy saving and low noise, which can fully meet the actual requirements of air conditioning fan.