Theory And Application Of High-speed Dc Vacuum Switch Based On Active Commutation Circuit

With the rapid adoption and large-scale application of the clean energy and renewable energy, it is contributing to the DC system in the direction of the interconnected network. In order to operate the power grid flexibly and open the fault circuit rapidly, DC Switch is particularly important and will be very broad application prospect. MVDC Collector Grid and Integrated Power System based on DC zonal electric distribution are urgent need for a reliable, full-featured, friendly environment, reasonable coast DC switch. The active commutation type of DC vacuum switch with the both characteristics of vacuum interruption and active commutation also has the characteristics of fast-break, low-cost, and miniaturization, and so it is the development direction of the switchgear in MVDC power grid.There are a series of technical bottlenecks to develop the DC vacuum switch based on active commutation circuit. To solve these problems, this paper analyzes the forcing current to zero characteristics of the vacuum arc and its influencing factors; proposes a complete calculation method of commutation circuit parameters and solutions for the interruption problems of small DC current and bi-directional DC current; designs a prototype of12kV rated high-speed vacuum switch based on electromagnetic repulsion driving and permanent magnet force latching; finally, considering the ship electrical applications, develops a prototype of5kV rated high-speed DC vacuum switch and finishes the test under laboratory conditions.The forcing current to zero characteristics of the main interruption unit, which is one of the most important design bases, determines the parameters selection of commutation circuit and the operation time of each component. This paper expounds the essence of the vacuum arc commutation interruption, analyzes the working conditions of DC fault current commutation interruption; using the one-dimensional heat conduction equation, analyzes the characteristics of the anode surface temperature in the process of DC fault current forcing current to zero and its influencing factors; using the particle conservation equation, analyzes characteristics of the gap metal vapor density in the same process and its influencing factors; utilizing the3D finite element model of the cup-typed AMF contacts, analyzes its characteristics in the same process.The parameters design of commutation circuit is the hard-core of the active DC vacuum switch research. This paper is based on the characteristics of the active commutation technology, in full working conditions, analyzes the commutation circuit parameters effects on the descent rate dl/dt before the zero-crossing of the main commutation unit current and the recovery voltage rise rate dV/dt after the zero-crossing; basing on the characteristics of the active commutation, proposes a complete calculation method of commutation circuit parameters; referring to the problems of small DC current commutation, proposes a double commutation branches DC switch topology using interlock interactive switch structure; referring to the requirement of bi-directional current interruption ability, proposes a four interlocking commutation switch to solve the operation time problems of commutation switch.The design of the fast actuator is the principal problem to be faced in the development of the DC switch. This paper is based on the main switch opening characteristics requirement due to commutation DC switch, proposes a high-speed vacuum switch structure based on electromagnetic repulsion driving and permanent magnet force latching; analyzes the characteristics of structure parameters of electromagnetic repulsion device and proposes the design guidelines; designs a prototype of12kV rated high-speed vacuum switch and finishes the characteristics test, after improving the structure of permanent magnet force latching device and adding the fuction of the reverse current buffer, the6mm stroke only needs2.8ms.Finally, for DC5kV onboard IPS applications, we develops a prototype of the high-speed DC vacuum switch; the test of prototype is finished under college laboratory conditions. The results indicate that its main parameters can meet the requirements of the onboard IPS.