Modeling and Analysis of The Control of Individual Stacks of a Multi-Stack Piezoelectric Actuator for Hybrid DC Circuit Breakers
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Ghosh, Amrita
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Abstract
Hybrid circuit breakers (HCBs) are a potential protection solution for medium-voltage direct current (MVDC) power systems (1 kV – 100 kV). These HCBs require fast mechanical switches (FMS) with efficient actuators. Using piezoelectric actuators in an FMS has been a topic of discussion in previous works. Piezoelectric actuators are expected to enable fast, reliable, and controllable actuation for HCBs. During the HCB contact separation, higher oscillations will bring the contacts closer and reduce the voltage withstand capability of the HCB. Hence, both achieving a small actuation time and reduced overshoot in the displacement curve is necessary to ensure that the circuit breaker does not have to dissipate a large amount of energy and to reduce the probability of restriking. In order to accelerate the actuation, if the driving voltage of the piezo rises too fast, resonance may occur leading to increased oscillations and overshoot. This thesis aims to explore control mechanisms that would provide an acceptable trade-off between fast actuation and reduced oscillations by studying how individual piezoelectric stacks of an actuator can be controlled. Two control methods namely – sequential triggering method and input shaping method are presented. A digital simulation model is also built and validated. The two control methods are also experimentally tested and the results are analyzed. These control methods, when applied individually, show improved undershoot and overshoot characteristics in the displacement travel curve of the actuator. When the two control methods are combined and applied, the response is shown to be critically damped with a switching time of 426 μs which is highly desirable for HCB application.
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2023-05-01
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