Un-terminated Blackbox Modeling for Electric Machines

With the increasing penetration of power electronics in modern power systems, such as more electrified aircraft and ships, small-signal impedance-based design and stability evaluation have become widely accepted at the system level. This method is preferred because it does not require detailed information about the physical components and control loops, allowing for "blackbox" characterization. Typically, impedance measurement is conducted at the interfaces among subsystems and encompasses all dynamics from upstream or downstream, necessitating time-consuming re-measurements after any system variation. To overcome the need for re-measurements and maintain intellectual property for the original equipment manufacturer (OEM) through the blackbox approach, the un-terminated terminal behavior model (TBM) is introduced in this paper. This model pertains solely to the devices under test, remaining unaffected by the source side’s output impedance and the load side’s input impedance. In the rotor flux-orientated d-q domain, this paper presents analysis and procedures for source-load impedance decoupling to measure the un-terminated TBM for electric machines. Experimental tests were conducted on an interior permanent magnet synchronous machine to identify its blackbox un-terminated TBM. An induction machine serves as a torque perturbation source emulating loads or a governor, and a power hardware-in-the-loop (PHIL) system provides electrical power supply with voltage perturbation.