Extending the Power Capability With Dynamic Performance of a Power-Hardware-in-the-Loop Application-Power Grid Emulator Using "Inverter Cumulation"

The increasing use of complex grid-connected technological components in safety-critical applications like public transportation or distributed power systems requires a precise evaluation of the reliability and robustness of these pieces of equipment during their development. Direct on-field tests of high-power systems are generally not possible. A conventional method of getting around this problem consists in using software-based simulation to analyze the behavior of the electric equipment under test (EUT) under normal and transient operation conditions of the grid. However, signal-level simulation is not able to perfectly reproduce every detail of a physical phenomenon. This publication describes a cost-effective realization of a power-hardware-in-the-loop (PHiL) grid emulation system combining two inverters with different electrical characteristics (type of semiconductor, switching frequency, dc link, etc.). The proposed grid emulator is a controllable power source not only capable of emulating low-frequency (50 Hz) transient faults as voltage sags but also high-order harmonic components usually present in the voltage waveforms of the utility grid (e.g., noise). A downscaled 5-kVA laboratory prototype has been implemented and the experimental results shown in this paper demonstrate the emulator's ability to combine high power with high dynamics.