Research On Design Optimization And Control Technique Of New Permanent Magnet Actuator For Vacuum Circuit Breaker

Vacuum circuit breakers(VCBs)are widely used in power system construction because of their strong arc extinguishing ability,long electrical life,environmentally friendly and free maintenance.With the improvement of related theories and technologies,it is developing towards the direction of high voltage.In this dissertation,the permanent magnet actuator(PMA)for high voltage VCBs is taken as the object to study its design,optimization theory and control technology,which will help to improve the design and control level of VCBs in China,and then promote the development of power grid and its intelligent construction.Based on the comprehensive analysis of the topology structures,optimization design methods and control strategies of PMAs for high voltage VCBs,two new PMAs for 126 k V VCBs and 10 k V buffered reclosing VCBs are proposed and designed in this dissertation.A sequential multi-step optimization method and a multi-objective optimization algorithm based on adaptive surrogate modeling technique are put forward to optimize them efficiently.A piecewise control strategy for closing process is then put forward to improve their dynamic characteristics.The main research work and achievements of this dissertation are as follows:(1)The background and significance of this research are introduced.The research state-of-the-art of the topologies,optimization design methods and control strategies of operating actuators for high voltage VCBs are comprehensively reviewed.(2)A novel PMA for 126 k V VCB is proposed and its structural characteristics and working principle are described.The static characteristics of the proposed PMA are calculated and analyzed through solving the magnetostatic field equations by using the finite element method.A new method to solve the multi-physical domain problem coupling the electromagnetic field,electric circuit and mechanical movement is proposed and applied to calculate the dynamic characteristics of the novel PMA.(3)A sequential multi-step optimization method is proposed to implement the rapid and comprehensive optimization of the new PMA suitable for 126 k V VCBs,in which the optimization process is divided into three sub-optimization modules,namely,breaking spring system,closing holding mechanism and closing driving mechanism.The establishment procedures of the optimization models and algorithms used in each sub-module are described in detail,and the optimization results are analyzed and verified by some experiments on a prototype.(4)A multi-objective optimization algorithm based on adaptive surrogate modeling technique is proposed to lead the optimization to converge to the optimal solutions quickly.In the earlier stage,the surrogate models are constructed and evaluated,and gradually updated to improve the global accuracy of the models.In the later stage,the surrogate models are updated based on the approximate multi-objective optimization results to progressively enhance the local accuracy of the models near the optimal solutions area.The proposed multi-objective optimization algorithm is applied to the optimization of the new PMA for 126 k V VCBs.A satisfactory optimal solution set can be obtained with less computation time,further improving the overall performance of the PMA.(5)Based on the closing velocity optimal selection theory for 126 k V VCB,a design method of the best preset displacement curve for closing operation of the proposed PMA is given.A segmented control strategy for closing process is proposed,a simulation model of the closing control system is established,and the effect of closed-loop tracking control is tested.The influence of factors on the opening time dispersion of the PMA are simulated and analyzed.Some experiments are conducted to verify the effectiveness of the proposed control strategy.(6)A novel PMA for 10 k V buffered reclosing VCB is proposed and the specific steps of its initial design are given.The static and dynamic characteristics in the conventional closing and opening operations and the pulse reclosing operation are solved and analyzed based on the finite element method and the field-circuit-motion coupled method.The design results are verified by some experiments on a prototype.The influences of different energizing timings in the main and auxiliary mechanism coils on the characteristics of pulse closing are studied by means of experiments,obtaining a set of optimal timing parameters.