Abstract
In order to meet the fast operation demands of DC circuit breakers, a high-speed vacuum mechanical switch (VMS) driven by a repulsive force actuator is focused. To improve the drive speed and energy conversion efficiency (ECE) of the actuators, the dynamic characteristics of the double sided coil repulsive force actuators are investigated, and two generalized optimization design methods focusing on the aspect ratio of the driving coils (defined as ARF) and the electrical parameters (defined as EF) are developed. FEM simulation models' simulation and tests of VMS prototypes are conducted to verify the optimization methods. Results prove that the ARF method could improve the ECE of a VMS from 1.05% to 7.55%, and EF method could improve ECE of the same VMS from 1.05% to 6.61%, the combination of ARF and EF could improve the value of VMS's ECE to 10.50%, thus proving the validity and accuracy of the optimization methods.
Highlights
With the development of a voltage-source converter (VSC)-based HVDC system, the DC fault current rises dramatically, which requires the DC circuit breakers (DCCBs) to interrupt as fast as possible.1,2 There are mainly two types of DC circuit breakers that may satisfy the interruption requirements of the system: one is the mechanical DCCB which interrupts the fault current by a high-speed mechanical AC switch and a forced current zero circuit; the other is the so called hybrid DC circuit breaker with mechanical- and solid-state switch.3–6 In both the mentioned DCCBs, there are mechanical switches, which are required to be opened to a certain distance 2-5 ms after the DC fault happens
To improve the drive speed and energy conversion efficiency (ECE) of the actuators, the dynamic characteristics of the double sided coil repulsive force actuators are investigated, and two generalized optimization design methods focusing on the aspect ratio of the driving coils and the electrical parameters are developed
Results prove that the Aspect Ratio Factor (ARF) method could improve the ECE of a vacuum mechanical switch (VMS) from 1.05% to 7.55%, and Electrical Factor (EF) method could improve ECE of the same VMS from 1.05% to 6.61%, the combination of ARF and EF could improve the value of VMS’s ECE to 10.50%, proving the validity and accuracy of the optimization methods
Summary
With the development of a voltage-source converter (VSC)-based HVDC system, the DC fault current rises dramatically, which requires the DC circuit breakers (DCCBs) to interrupt as fast as possible. There are mainly two types of DC circuit breakers that may satisfy the interruption requirements of the system: one is the mechanical DCCB which interrupts the fault current by a high-speed mechanical AC switch and a forced current zero circuit; the other is the so called hybrid DC circuit breaker with mechanical- and solid-state switch. In both the mentioned DCCBs, there are mechanical switches, which are required to be opened to a certain distance 2-5 ms after the DC fault happens. Two ways are usually employed to calculate the dynamic mechanical characteristics of the repulsive actuators: the equivalent circuit model and the finite element method (FEM).. Two ways are usually employed to calculate the dynamic mechanical characteristics of the repulsive actuators: the equivalent circuit model and the finite element method (FEM).9,12–17 The former is with relatively low accuracy, but easier to be used in the optimal design, the latter is considered more accurate, but not so easy to be used in concert with the optimization design method. Electrical circuit parameters and the shape of the coils are proved to be the key factors that influence the efficiency of the repulsive actuators, no papers have given a specific guiding theory of the design optimization based on the mentioned two factors. Simulations and tests of prototypes are conducted to verify the calculation and optimization
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