By using the “torque-power angle self-balancing†characteristic of the motor, a single-current-loop closed-loop start of the motor and a smooth switching of the position-sensorless control based on the sliding mode observer to the sliding mode observer are realized. At the same time, the influence of the current drop rate on the switching process is analyzed. By adopting the variable slope method, the smoothness and rapidity of the switching process are ensured. The simulation results show that this method is effective and feasible to solve the above problems.
Compared with other motors, synchronous reluctance motors have a series of advantages such as low cost, no copper loss, high efficiency, small torque ripple, high temperature magnetization loss, and weak magnetic field expansion, which are highly efficient motors.
For a high-performance motor speed control system, it is usually necessary to install a mechanical sensor on the rotor coaxial to detect the rotor position angle and speed information, so as to achieve double closed loop control of the speed, current, but this also brings to the control system A series of drawbacks [1]. For example, it increases the cost and complexity of the hardware system; the detection signal is also vulnerable to the external environment to reduce the reliability of the system; at the same time, in the harsh environment, the hardware is easily damaged, further increasing the maintenance cost and instability of the system. .
For this reason, the research of position sensorless control has become a hot topic in recent years. Many scholars have proposed some estimation methods such as motor salient-pole effect, back-EMF, state observer, sliding mode observer, and Kalman filter [2]. However, since the motor has a low signal-to-noise ratio at startup and at low speeds, the above method does not work well in self-starting and low-speed operation of the motor.
Therefore, the literature [3-5] proposed a boost and frequency up-start method. However, this method makes the motor run under the condition that both the speed and the current are open loop. Therefore, the current is not controllable and the overcurrent problem easily occurs. Literature [6-7] proposed a high-frequency signal injection method. This method requires continuous injection of a high-frequency current into the system, which can easily cause harmonics and torque ripple. At the same time, the process is complex and difficult, so the dynamic performance is not ideal.
In view of the above problems, this paper adopts the If-Frequency Method self-starting control strategy. This method adopts single-current loop closed-loop control in the motor starting and low-speed operation phase, and smoothly switches to the sliding-mode observer-based positionless in the middle-high speed. Sensor control to achieve sensorless control of the synchronous reluctance motor over the full speed range.
Self-starting method of position sensorless control of synchronous reluctance motor
in conclusion
In this paper, the "torque-power angle self-balancing" characteristic of the motor is used to realize the self-starting of the synchronous reluctance motor without position sensor control by adopting the If current-frequency method. At the same time, a variable slope method is adopted in the course of the stator current drop. The flow frequency method control can be smoothly transitioned to a position sensorless control based on a sliding mode observer, thereby realizing the position sensorless control of the synchronous reluctance motor in the full speed range. The simulation results can be concluded as follows:
1) Adopting the If-Frequency Frequency method not only can realize the self-start of the synchronous reluctance motor without position sensor control, but also can effectively prevent the current from flowing in the starting and switching process due to the closed-loop control of the stator current.
2) Under different loads, the motor can be started smoothly only by adjusting the appropriate given acceleration and stator current, and at the same time it can effectively prevent the motor from losing synchronization during the start-up process.
3) In the constant-speed and down-flow phase, the stator current adopts the decreasing slope of the variable slope, which can effectively guarantee the rapidity and stability of the switching process.
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