Application of Fuzzy Self-tuning PID Control Strategy in Soft Start of Asynchronous Motor
As a dragging machine, electric motors are widely used in industrial and mining enterprises, transportation, and defense industries. When the motor is directly started, the instantaneous inrush current is very large. If the motor is often started, excessive current will cause severe heat generation of the motor, shorten the service life of the motor, and also adversely affect the power grid, affecting the power supply of the power grid and the same power grid. Other loads [1, 2]. With the rapid development of power electronics technology, it has become a reality to use the thyristor as the main circuit component and the single-chip microcomputer to control the core of the intelligent starting device to complete the motor starting process. Aiming at the problem that the traditional motor soft starter is improperly selected due to the improper initial PID parameters or the environment is affected by the external environment, this paper studies a fuzzy self-tuning PID (FSA-PID) instead of the traditional PID. Strategy in the design of motor soft starters. Combining the fuzzy control idea with the conventional PID controller absorbs the advantages of both fuzzy control and conventional PID control. It is mainly used to solve the problem that the control object parameters that are difficult to solve by the traditional method are changed in a wide range, and the control performance is better than the conventional PID controller, and the reliability is higher. The fuzzy self-tuning PID principle, the soft starter principle and the software and hardware design process of the system are introduced. Finally, the working process of the motor soft starter is realized by computer simulation. The result proves the correctness and effectiveness of the proposed strategy.
The hardware of the control system consists of AT89C52 single-chip microcomputer system, voltage synchronization signal sampling and processing circuit, current detection circuit and pulse trigger circuit. The voltage signal from the synchronous transformer is sent to the AT89C52 external interrupt after being driven by the voltage comparator, photoelectric isolation and power. The current detecting circuit measures the actual working current of the motor with a current transformer. After being rectified, filtered, amplified, A/D converted and optically isolated, it is sent to the single-chip microcomputer, and the nonlinearity is compensated by software. The current signal is used as the calculation thyristor. The basis of the conduction angle size, and used for fault detection and digital tube display.
The self-tuning PID control strategy is applied to the design of the motor soft starter to make the controller intelligent and enhance the robustness of the system, thus solving the mechanical impact of current and torque on the motor itself during the starting and stopping of the motor and the grid. Problems such as negative effects are contained. The simulation results show the correctness of the strategy and further broaden the application field of fuzzy control.
