Integrative Simulation of Inverter-Based PV Systems and Unbalanced Distribution System with Adaptive Step Size Framework in OpenDSS

As the penetration of inverter-based photovoltaic (PV) systems with various grid support functionalities increase rapidly, it becomes critical to examine their dynamic impacts on the distribution system. For dynamic studies in OpenDSS, the software provides a fixed-step size simulation framework, and users need to build their own model in a dynamic-link library (DLL) along with the integration algorithm. Model complexities may require the program to run at a small step size, which increases the unnecessary computational burden and results in a long simulation time. This paper proposes a new integrative simulation framework with adaptive step size in OpenDSS and the user-defined DLL. This new framework can increase the simulation efficiency significantly through adjusting the dynamic simulation step size in OpenDSS by evaluating the numerical integration accuracy within the DLL. The results show that the average step size utilized by the proposed simulation framework is over 9 times the fixed step size used by the original framework for the same dynamic simulation. Computational time consumption can also be saved by 70% using the proposed simulation framework.