Abstract
This paper presents a new electric powertrain for solar powered unmanned aerial vehicle (UAV). The proposed system structure is based on the development of the power supply system for both the Solong and Zyphyr aircraft models. The proposed UAV model incorporates the Zyphry UAV use of an AC line feeder instead of DC power lines to power the propellers. The proposed powertrain includes solar panels, an energy management system based on lithium sulfide battery, inverter, AC bus-line and active output filter (AOF). AOF topology is composed of a high switching frequency H-bridge inverter with a reduced size LC filter. The utilization of AOF system reduces the size and weight of the power transmission system and significantly improves its conversion efficiency by introducing an emulated series resistance with the H-bridge stage to ensure high quality pure sinusoidal waveform of the line voltage. This emulated series resistance produces an injected voltage across it to diminish unwanted harmonics created from the non-linear load. A simulation model and experimental setup are created to simulate the proposed system and the system is tested under non-linear load condition with closed-loop feed-back control strategy. The obtained simulation and experimental results demonstrate that high-quality sinusoidal line voltage waveforms can be obtained using the active resistance compensation technique with total harmonic distortion factor less than 3%. Moreover, power losses analysis and conversion efficiency calculation of the proposed system are performed and compared with that of the conventional three-phase PWM inverter, which proved that the power losses are reduced by 31%.
Highlights
The main goal of using an electric powertrain system operating at a frequency of 400 Hz in aerospace applications instead of conventional low frequency of 50/60 Hz is to reduce the size and weight of the power transmission system [1]
The results demonstrate that high-quality line voltages are obtained using the active resistance compensation technique with a total harmonic distortion less than 3%
For the case of non-linear load, the line current is operated in discontinuous conduction mode keeping acceptable load voltage quality and the load voltage quality is slightly degraded due to low order harmonics generated by the line current of the non-linear load
Summary
The main goal of using an electric powertrain system operating at a frequency of 400 Hz in aerospace applications instead of conventional low frequency of 50/60 Hz is to reduce the size and weight of the power transmission system [1]. Active output filter (AOF) have been proposed for variable speed constant frequency aircraft system with six-step inverter to eliminate the need of coupling transformer, increasing the conversion efficiency and reduce the overall passive elements sizing in aerospace application [34], [35]. This paper introduces a new electric powertrain system based on the concept of AOF for solar powered UAV to employ an effective filtration system instead of the use of traditional passive filters This allows the main inverter that operates at the total rated power to operate at low switching frequency, improves the overall efficiency of the powertrain system. The proposed systems using 400 HZ switching frequency main inverter and AOF systems are employed in UAV for further reduction in the size of the power transmission system under non-linear load conditions with closed loop control
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