Modeling Smart Inverters for Hardware-in-the-loop tests in Low-Voltage Distribution Systems

Wide-scale deployment of Smart Inverters (SIs) can only happen if their impacts on power systems can be clearly understood. For this reason, thorough power flow and system stability studies are required. Traditional power system simulation software does not include proper models for SIs. Furthermore, dynamic behavior of SIs is not very well known to develop such models. Consequently, hardware in the loop tests with digital real-time simulators seem to be the best option, due to their high fidelity. That being said, interface between the simulated and real-world plays a very significant role. Since the real world is sampled and these samples are utilized to map reality inside digital real-time simulator, any mistake may render the test unstable. On the other hand, real-time simulation has very strong timing requirements and this becomes a deciding factor on how much detail can be modeled. Since the bridge inverters have several components that operate in time steps that are much smaller than conventional power systems, digital realtime simulators have very limited capacity. Using simplified inverter models has been investigated in the past and shown to be acceptable in steady-state situations. This paper investigates use of such models for protection studies in low-voltage networks.