Model-Based Design and Real-Time Testing of Commercial More-Electric Aircraft Power Systems

This paper focuses on model-based design and real-time testing of a commercial more-electric aircraft power system. Important design considerations are first discussed in detail and the models for system design and testing are presented. The paper also elaborates on a distributed, real-time simulation platform for power system testing and evaluation. This platform is based upon FPGA (Field Programmable Gate Array) that handles on-chip computation in real time with latency of 32 FPGA clock cycles (potentially within 200 nanoseconds). Also, high-fidelity, physics-based models can capture a variety of electromagnetic transients, electromechanical dynamics, aerodynamics, controls, and thermal dynamics at time scales ranging from microseconds to seconds. By using this real-time platform, a representative commercial more-electric aircraft power system was designed and studied to verify the power adequacy, transient performance, and power quality. Simulation results show that starting two large induction motors simultaneously may drive the bus voltage out of the limits (upper and lower limits); however, separating the starting of 2 motors by 100 milliseconds can help to maintain the voltage within the limits. The voltage variation due to inrush currents under motor starting increases with the generator frequency. Studies about unbalanced loading conditions show that there exists an approximate linear relationship between the voltage unbalance (%) and phase power unbalance ratio. As the generator frequency increases, the voltage unbalance (%) increases when the power unbalance remains the same. The voltage unbalance under a capacitive load seems to be lower than that under a resistive load, while under an inductive load is looks higher than that under a resistive load. These studies demonstrate that through proper machine design and control, the generator is capable of maintaining the bus voltage due to direct-start inrush currents of induction motors driving large pumps within the required ranges and handle the unbalanced to a certain extent. In these studies, real-time simulation results match offline simulation results and experimental data about the generator and motors very well.