Evaluation of electromechanical systems dynamically emulating a candidate hydrokinetic turbine

Implications of conducting hardware-in-the-loop testing of a specific hydrokinetic turbine on controllable motor-generator sets or electromechanical emulation machines (EEMs) are explored. The emulator control dynamic equations are presented, methods for scaling turbine parameters are developed and evaluated, and experimental results are presented from three EEMs programmed to emulate the same vertical-axis fixed-pitch turbine. Although hardware platforms and control implementations varied, results show that each EEM is successful in emulating the turbine model at different power levels, thus demonstrating the general feasibility of the approach. However, performance of motor control under torque command, current command, or speed command differed. In a demonstration of the intended use of an EEM for evaluating a hydrokinetic turbine implementation, a power takeoff controller tracks the maximum power-point of the turbine in response to turbulence. Utilizing realistic inflow conditions and control laws, the emulator dynamic speed response is shown to agree well at low frequencies with numerical simulation but to deviate at high frequencies.