Multi-rate control mode for maintaining fidelity in Quasi-Static-Time-Simulations

Quasi-Static-Time-Series (QSTS) simulation is a technique widely used in planning and research to evaluate the power system's behavior in daily, yearly and other time frames. This simulation technique has become increasingly relevant due to the interconnection of Distributed Energy Resources (DER) and unconventional loads into the power grid. It models the control actions performed by devices such as voltage regulators, capacitor banks and smart inverters among others, and captures their behavior in time. The EPRI Open source Distribution System Simulator (OpenDSS) includes all these features with its control models and its built-in time-based simulation modes. However, depending on the simulation needs users may select different simulation step sizes and control mode when working with QSTS simulations, adding systematic errors if not considered properly. This paper introduces the Multi-Rate control mode recently developed and implemented in OpenDSS. This control mode removes the error added when performing QSTS at different step sizes, keeping the simulation fidelity in accordance to the QSTS parameters set by OpenDSS users.