PhD student Yue Cao with adviser P. Krein

Increased power levels in more electric aircraft (MEA) bring opportunities to optimize energy flow in multi-physics domains to benefit the power system’s stability and aircraft fuel economy. This project introduces thermal energy inherent in the cabin air and aircraft fuel as a dynamic management solution to offset stochastic load power in the MEA power system. Focus is on power electronics-controlled environmental control system (ECS) drives, which can provide dynamic thermal inertia and act as an effective electric swing bus to mitigate power variability. The generator’s output power becomes substantially more constant as a result, decreasing the demand from fast generator responses or dedicated energy storage such as batteries. In practice, the motor drives operate on a suitable bandwidth in the sense of filtering unwanted frequencies in the stochastic energy band. The lower update frequency limits air temperature variations in the cabin, and the higher update frequency, combined with ramp-rate and acoustic limits, lets the ECS respond without generating annoying noise. This modified thermal storage integrated VSM allows sub-second power dynamics to be filtered by the motor-tied thermal storage. The combination is illustrated in simulation and with experimental results based on realistic load power demand over a mission profile using the Boeing 787 as a platform.

Figure 3: Five-hour flight mission (top): single generator output power (middle: cabin temperature (bottom)

Figure 3 shows one generator’s output power with and without the ECS thermal storage mitigation of load power variability following a five-hour predefined flight mission. Cabin temperature is plotted for both scenarios. Note periods when up to 3 °C changes occur due to long and large power variations, while during the majority of the mission there are only minor temperature fluctuations. This research is supported by Rolls-Royce Corporation and the NSF Engineering Research Center for Power Optimization of Electro Thermal Systems (POETS).