The virtual machine [power electronic conversion equipment testing]

Power electronic conversion equipment intended for use within an electric drive is usually tested by the attachment of electrical motors or generators. The paper presents an approach to overcome testing difficulties in the form of a virtual machine. The virtual machine is composed of a bi-directional power converter, a real-time simulator and a closed loop control system. These elements combine to produce a programmable load/source which can be connected directly to the power electronic inverter as a replacement for an electrical machine. It is recognised that there may be some confusion between the inverter and the converters which form the virtual machine, accordingly in the paper inverter is taken to mean the inverter being tested and converter is used to describe the power electronics in the virtual machine. The virtual machine is effectively a power level active impedance. It is important to realise that the virtual machine is capable of bi-directional power flow and also transient and steady state operation. These features allow it to emulate the characteristics of a wide range of electrical machines and their associated mechanical loads. The complexity of the emulation is limited only by the capability of the bi-directional power converter and the real-time simulation which controls it.