Electrical load emulator for unbalanced loads and with power regeneration

The paper presents a method of emulating electrical loads using power electronic Voltage Source Inverters (VSIs). The loads include machines such as induction motors and three phase diode rectifiers as well as larger electrical systems. The emulation of unbalanced four-wire loads has been achieved using a four-leg VSI. The load emulator is effectively a dynamically controllable source or sink which is capable of bidirectional power exchange with either a grid or another power electronic converter system. Using load emulation, the feasibility of connecting a particular machine to a grid or converter under various load conditions can be examined without the need for any electromechanical machinery. The additional feature of the load emulation technique described in the paper is the feedback of power absorbed by the emulator back to the grid. This feedback of power has been termed as power regeneration and has been achieved by another VSI in current controlled mode with the references generated using instantaneous p-q-r theory. The consistency of the experimental results with the simulation results proves the ability of emulator and the proposed testing approach.