A Time Domain Frequency Separation, TDFS-Model Approach Including Reactive Power of a Novel Electromechanical Actuator for MEA Applications

Future More Electric Aircraft (MEA) technology focuses on increasing the use of electrical equipment to a larger extent, e.g. replacing conventional hydraulic and pneumatic actuators with more electric components to reduce weight, cost and maintenance. Advances in enabling technologies of electric power generation, distribution, and consumption have made the use of electric actuators more competitive. Electric actuation can be based on Electro Hydrostatic (EHA), Electro Mechanical (EMA), or Magnetostrictive Actuator (MA) concepts. The governing idea in the TDFS model approach is to separate the high (electrical) and low (mechanical) frequency parts of the model and thereafter only consider the low frequency part. Electrical components as current and/or voltage converters/inverters are then described in terms of RMS-vales of currents and voltages and efficiencies or in circuit diagrams in form of load dependent resistors and in electromachines by means of load dependent loss resistances equivalent with their electromechanical efficiencies. Step-down and step-up voltage converters are described as fictive DC/DC transformers. The reactive power drawn by the motor is accounted for by a parallel electrical branch comprising a Current sink. This approach makes it possible to reduce the complexity of power system models of tentative systems to such extent that the resulting computational tool easily can be used for studies of the whole system performance during entire flight missions and/or for optimization. The electrical machine of the studied actuator is a permanent magnet synchronous machine intended for operation at relatively low speed and high torque. The continuous output power is 1 [kW] with a voltage level of 270 VDC at the DC-bus. This machine shows promising performance for more electric aircraft applications. The modeling approach in this paper shows that it is possible to perform simulations on entire flight missions. This feature constitutes a valuable tool for decision making, when different technologies are to be compared. The use of described actuator model is illustrated for an Unmanned Airborne Vehicle (UAV) application.