Variable Frequency Speed Control System of Permanent Magnet Synchronous Motor Based on Hybrid Control
Xiao Qinghao and Tang Ningping, researchers of the School of Electrical Engineering and Automation of Fuzhou University, wrote in the first issue of "Electrical Technology" in 2019, aiming at two different types of variable frequency speed control methods for permanent magnet synchronous motors. Hybrid control type variable frequency speed control method combining control and automatic control.
The method combines the high-precision and self-controlled variable frequency speed regulation of the frequency control of the frequency control to improve the dynamic and steady state performance of the control system. A simulation model that automatically switches between the two is established in the Matlab/Simulink platform. Simulation results show that the method is effective and feasible.
The permanent magnet synchronous motor has the advantages of simple structure, reliable operation, high power density and high efficiency, and is easy to constitute a high-performance speed control system. In addition, with the development of power electronics technology, motor control technology, computer technology and the price of permanent magnet materials, it is widely used in many fields such as household appliances, vehicles, industrial control, aerospace, etc., and is very much in electric drive systems. Important application value.
In the variable frequency speed control system, there are two different control modes, one is that he controls the frequency conversion speed regulation, and the other is the self-controlled frequency conversion speed regulation, and the two control methods have their own advantages.
He controls the frequency conversion speed regulation, which is also known as the constant voltage frequency ratio control method. By giving the frequency of the stator current of the motor, the air gap rotating magnetic field corresponding to the frequency is generated, and the motor rotation speed and the air gap rotating magnetic field are strictly synchronized, thereby ensuring He controlled the high precision of frequency control. In addition, his control frequency conversion speed control system also has the advantages of simple control circuit structure and convenient adjustment.
However, there are inherent disadvantages in this control mode, namely the out-of-step problem. Self-controlled variable frequency speed regulation, whose output frequency is controlled by a rotor position detector on the motor shaft, and constitutes a closed loop system that automatically tracks the rotor position by the stator current frequency. This method can fundamentally eliminate the hidden danger of rotor oscillation and out-of-step. This is because the output frequency of the inverter device that supplies power to the stator winding of the motor is controlled by the rotor position detector and is always kept synchronized, thus avoiding the sudden change of load and the like. The phenomenon of out of step, but the control system is relatively complicated. In addition, due to the position detector accuracy, regulator control parameters and other factors, there will be a certain static error.
Combining the advantages of the above two control methods, this paper proposes a hybrid control type permanent magnet synchronous motor speed control method based on the combination of his control and automatic control [9-11], in order to better play two kinds of frequency control The advantages of the way. By establishing the corresponding system model and simulation experiment on Matlab/Simulink simulation platform, the simulation results show that the method is effective and feasible.
in conclusion
This paper proposes an automatic switching hybrid speed control method combining his control and automatic control by analyzing the characteristics of his control and self-control. The speed control method adopts the double-closed loop control mode of the speed and current at the start, which realizes the quick start of the motor, has strong load capacity, avoids the risk of losing the step, and has good dynamic performance.
When the switching condition is met, it switches to the other control mode, the switching process is smooth and fast, and no transient inrush current occurs. Under his control and control operation, the system has higher steady-state accuracy and a certain load capacity. When the load torque changes in the control stable region, the "torque-power angle self-balancing" characteristic of the motor is used, and the system can return to the steady state after a short self-adjustment; and when the given speed changes, the fast switching To the automatic control mode, to avoid the occurrence of out-of-synchronization, and to switch to the control of the control after the switching condition is met, thereby realizing the automatic switching between the control and the automatic control.
Under this method, the two control modes can smoothly and smoothly switch, and the characteristics of high steady-state precision, self-control dynamic fastness, and no loss of step are fully utilized, and the steady state and dynamic performance of the system are improved. This method also has certain defects. In the automatic control mode, the position sensor is needed to increase the speed signal, and the sensorless control is not completely implemented. The method has certain application value in the occasions where the rotational speed needs to be quickly adjusted and the rotational speed precision is high in steady state operation, such as textile chemical fiber and glass industry.
