Key Synchronization Control Technologies For Permanent Magnet Vacuum Circuit Breakers

The initial phase angle of the system current or voltage is uncertain at the moment when the breaker opens and closes the power equipment.The process of opening and closing is easy to produce inrush current and over-voltage,which has a great impact on the equipment and system.Synchronous control technology is also known as phase selection control technology.Its essence is to control the switch contact to complete the opening and closing operation at the best phase of voltage or current according to different load characteristics,so as to shorten or even avoid the electromagnetic transient process of opening and closing of the switch,improve the opening and closing energy of the circuit breaker and the stability of the system,which has become one of the front topics of current switch intelligence.This paper analyzes the importance of synchronous control and its realization mechanism.Firstly,the structure and working principle of permanent magnet circuit breaker are studied and analyzed.It has simple structure,few moving parts,high reliability and maintenance free,which lays a material foundation for the realization of synchronous control.Secondly,the operation process of synchronous opening and closing control is described,the principle of synchronous control technology is analyzed,and the influence of external factors such as control voltage,ambient temperature,pre breakdown characteristics on the realization of synchronous control technology is discussed.Through MATLAB simulation,it is verified that the synchronous control technology can restrain the over-voltage and inrush current when closing three typical capacitors,no-load lines and no-load transformers,and the necessity and feasibility of synchronous control are confirmed.Then,aiming at the two main problems of realizing the synchronous control technology at present: the accurate prediction of the opening and closing target voltage,the current zero crossing point and the operation time of the operating mechanism are studied respectively.In the aspect of synchronous closing,after denoising the interference signal,the FIR digital filter is designed to accurately extract the fundamental component,and the linear interpolation method is used to extract the zero point of the target signal.In the aspect of synchronous breaking,phase controlled breaking of fault current is the most difficult.In this paper,breaking of single-phase ground fault current is taken as the research object.After the mathematical model of fault current is simplified by Taylor series,the adaptive least mean square error algorithm is used to calculate the characteristic parameters of fault current,and then accurately predict the current zero crossing time when the arc goes out in the process of breaking.Matlab simulation verifies the fault The effectiveness and feasibility of the current phase controlled breaking algorithm.Finally,this paper proposes a prediction model of action time of operating mechanism based on Optimized BP neural network by CGA.The cloud genetic algorithm with outstanding global optimization ability is integrated into BP neural network.By optimizing the initial weight and threshold value of BP neural network when establishing the model,the shortcomings of BP network,such as too many iterative steps,slow convergence speed,easy to fall into local minimum but not global optimization,are remedied.The cloud theory that can effectively deal with fuzzy information is introduced into genetic algorithm to form cloud genetic algorithm In the process of calculation,the probability of crossover and mutation is not invariable,but is in dynamic adaptive change.Matlab simulation shows that compared with the standard BP neural network model,the cga-bp network model proposed in this paper can predict the action time of the operating mechanism faster,with smaller error and higher accuracy.