Power hardware in the loop simulation with feedback current filtering for electric systems

Power Hardware-in-the-Loop (PHIL) simulations are suited for electric component tests and electric tests of hardware interacting with complex systems that are simulated. PHIL simulations combine the advantages of a pure software simulation and a hardware system test. At the present time, PHIL simulations unfortunately are not "plug and play", some important considerations have to be made before a PHIL experiment can be is carried out in a laboratory. This contribution focuses on an improvement on how the hardware part of a PHIL simulation is coupled with the real time computing system by introducing an additional current filter in the feedback path. The filter drastically improves the stability margin of the simulation setup. This method is applied to a use case involving a photovoltaic inverter connected to a low voltage grid with a linear and a nonlinear load. The low voltage grid and the loads are simulated and the photovoltaic inverter connected as real hardware to the simulation environment. The PHIL simulation would not run stably without the introduced feedback filter. With feedback current filtering the PHIL experiment can be stabilized and an insight in the interaction of the nonlinear load and the photovoltaic inverter can be gained. The feedback filter has to be parameterized appropriately; it is a compromise between stability margin and accuracy of the PHIL setup.