Research on Segmented Duty Cycle Control Strategy of Motor Operating Mechanism of High Voltage Circuit Breaker

In order to improve the breaking performance of high-voltage circuit breakers and effectively suppress the bounce and mechanical impact caused by contact collision during closing, this study proposes a PWM control strategy based on segmented duty cycle for the motor operating mechanism of 126kV high-voltage circuit breakers. By analyzing the kinematic and mechanical characteristics of the transmission system, a simulation model under 200V operating voltage was established on the MATLAB/Simulink (R2022a) simulation platform to verify the driving performance of the permanent magnet brushless DC motor under load conditions. The control system with TMS320F28335 as the core processor is constructed. The HEDSS Hyde photoelectric encoder, CHF-400B current sensor and LK-H022 laser displacement sensor are used to realize the real-time control and monitoring of motor current, rotor position and contact bounce. The rebound displacement of the moving contact before the end of the closing process is detected to reflect the contact bounce. The switched capacitor circuit and segmented duty cycle PWM control strategy are developed. The rigid closing signal is defined as the moment of contact between the moving and static contacts. Based on the starting characteristics of the motor, the opening distance and over-range motion range of the moving contact of the circuit breaker and the characteristics of the rigid closing signal, the motor angle interval is divided into three stages : starting ( 0-10° ), opening distance ( 10° -36° ) and over-range ( 36° -64° ). The genetic algorithm is used to establish a multi-objective function with the closing speed, closing time and contact bounce at the rigid closing point as the optimization objectives. The optimal duty cycle value of each corner interval is determined by optimization calculation. Under the condition that the weight coefficient is set to 1, a variety of control schemes are formulated, and the influence of each scheme on the closing characteristics of the circuit breaker is compared and analyzed by simulation and experiment. The experimental results show that using the switched capacitor circuit scheme, the closing time and the maximum closing speed are 54ms and 2.74m/s respectively, the closing time is shortened by 35.9%, the maximum closing speed is increased by 33.7%, and the contact bounce is 0.39mm. In Scheme 4, the duty ratios of the starting, opening and over-travel stages are 1,0.4 and 0.8, respectively. The closing time and the maximum closing speed are 51ms and 2.7m/s, respectively. The closing time is shortened by 37.1%, the maximum closing speed is increased by 25.9%, and the contact bounce is only 0.02mm, which is much lower than the IEC 62271-1 standard, and the balance is achieved in improving the operating speed and suppressing the contact bounce. This research provides a theoretical basis for the performance optimization of the motor operating mechanism of the high voltage circuit breaker, and provides a new idea for the stable operation of the power system protection.