Distributed Electric Aircraft Propulsion Architectures with Fault Protection Strategy
Recent advancements in the turbo-electric Distributed Electric Aircraft propulsion (DEAP) systems highlight the necessity of reliable, robust, and lower-weight electrical power systems architectures. Traditional radial architectures of DEAP with multiple propulsion motors using the single-bus feeder suffer from the isolation of several propulsion motors for a fault in the main busbar. This thesis introduces enhanced fault-tolerant architectures, which are designed to overcome the above issues with traditional radial architecture, without the need of isolating several propulsion motors for a fault in the system. The proposed fault-tolerant architectures, including an H-type architecture, enhance the system's fault tolerance, and robustness. A key focus of this research in this thesis is the development of a protection coordination strategy for the DEAP system that includes, current limiting and I2t based strategies. DEAP systems utilize the DC bus system at higher voltage levels than conventional systems ranging from +/- 0.5 kV to +/-5 kV. In addition to partial discharge effects, there are other challenges, particularly associated with effectively limiting short-circuit fault currents due to the low cable impedance. Due to this, the fault current rises sharply, requiring an enhanced protection strategy. To accomplish this, an algorithm is proposed utilizing an I2t and the current limiting-based strategies to protect the system from short circuit faults along with the backup protection, in case the circuit breaker fails to operate. A fault in the system causes an abnormal amount of thermal energy inside the cable. The thermal energy accrued within the cable due to the fault leads to an increase in temperature beyond the thermal limits and breaks down the insulation. The thermal stress on a conductor is indicated by the current squared over time I2t, associated with the energy causing the thermal breakdown of the cable. Therefore, to evaluate the short circuit capability, this thesis utilizes a 250 MCM utility cable, and the thermal analysis is carried out using the ANSYS Fluent software. The corresponding I2t curves were shown to help circuit breakers protect the system before the thermal energy damages the insulation of the cable.
Circuit breakers, protection coordination, propulsion motors, Distributed Electric Aircraft Propulsion (DEAP), current limiting strategy, I2t protection, Backup protection, thermal analysis.
Networked Digital Library of Theses and Dissertations