Independent speed variable frequency generator for more electric aircraft using brushless doubly-fed machines (BDFM)

Independent speed variable frequency generator for more electric aircraft using brushless doubly-fed machines (BDFM)

The Need

Technology continues to advance and with it, a push for higher performance of electrical components and devices, especially in the transportation industry. For example, in the past few decades, considerable efforts have been taken towards aircraft electrification. Traditional hydraulic and pneumatic power are replaced by electrical power on B787, and a 3% higher fuel efficiency is reached. The state-of-the-art more electric aircraft Boeing 787 uses a 3-stage synchronous generator which has limitations on overall performance because of the complex three-stage structure; but are not replaceable because electric powertrains cannot provide enough power density and efficiency to fully decarbonize a single-aisle aircraft.

The Technology

Turboelectric distributed propulsion (TeDP) is considered as a promising solution to the future of more electric aircraft propulsion and replacing 3-stage synchronous generators. At The Ohio State University, a team of researchers has proposed a turboelectric distributed propulsion (TeDP) using brushless doubly-fed machines (BDFMs) for aviation applications. Three 120-kW BDFMs, and three SiC-based two-level 75-kW three-phase inverters has been designed, while vector control and field-oriented control are implemented to operate BDFMs in generating and motoring mode respectively. A designed controller can fulfill the communication and control requirements of the TeDP system.The proposed aircraft generation system using BDFMs have the following advantages over the state of the art: 1) One device provides the same functions as the state-of-the-art 3-stage synchronous generator 2) Much simplified structure 3) No electronics on the rotating parts 4) No need for rare earth materials

Commercial Applications

  • Transportation
  • Airlines
  • Power/Energy Industries


  • Simplicity (compared to current devices)
  • No rare earth materials
  • No electronics or rotating parts

Research Interests

Julia Zhang is an Assistant Professor at Ohio State in the Electrical & Computer Engr. Department and a former Ford Control Engineer. She received her Ph.D. in Electrical Engineering from Ohio State. Her current research focuses on design, modeling, controls of AC electric machines and drives, vehicle noise, vibration and harness issues caused by electric machines and drives, and high voltage engineering.

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