Evaluation of OPAL-RT Simulator through Simulation of Microgrid with High Penetration of DER

Abstract: This thesis was written in collaboration with the department of electrical engineering at Uppsala University. It evaluates and tests the potentials and limitations of using the OPAL-RT simulator as a tool for designing and developing control strategies used in microgrids with a high penetration of distributed energy resources. As the world gradually transitions to a more decentralized power system with less conventional power production, new strategies to ensure reliable and robust power transmission and distribution must be developed.    The objectives of this thesis were to develop a model of a microgrid that can be used as a base for developing control strategies to limit slow voltage variations in microgrids with high penetration of distributed energy resources. When a template model and strategy for conducting this type of research had been developed the thesis started to focus on the Real-Time simulator. The power system part of the microgrid was converted into a Real-Time compatible model and was allocated to be run on one of the CPU cores of the simulator. In an iterative process, the power system was built and run on the simulator to get results concerning the size of the power system that can be simulated using the CPU cores where the limiting factor is the computational power of the cores. Since the power electronics found in the inverter part of the voltage source converter is operating at a very high switching frequency the inverter must be simulated on the simulator's FPGA. The last objective was to integrate the CPU model and the FPGA model into one model where two different time steps were used.  The results show that one CPU can simulate the 18-bus power system developed during this thesis. It is also assessed that the CPU is capable of simulating a considerably bigger system if no calculations or control strategies are present in the system. The FPGA is functioning and can simulate high-frequency switching power electronics in Real Time.    The conclusions are that Real Time simulators in general as well as the OPAL-RT simulator studied here at Uppsala University will be of great importance for the continuation of research connected to control strategies.