Real time digital harmonic modeling and simulation: an advanced tool for understanding power system harmonics mechanisms

Off-line computation and sometimes full transient time domain simulation has been the tool of choice for modeling power system harmonic phenomena in the past. Due to significant advances in real-time digital network simulation technologies, both in decreasing time step size and increased model complexity, this tool becomes more attractive for advanced harmonic analysis. This paper proposes the use of hardware-in-loop (HIL) simulations to investigate complex practical power quality problems. The principle of HIL experiments in power system simulations is explained. Taking the cycloconverter based all-electric ship propulsion system of the US coast guard icebreaker "Healy" as an example a unique HIL experiment is described. Distorted voltages measured at the "Healy\´s" 6.6 kV AC bus are compared with simulation results. It is concluded, that real-time simulation with HIL capability leads to better understanding of power quality problems, particularly on closed coupled systems such as ship power systems.