On frequency response modeling of interconnected microgrids: Two different perspectives

Abstract

This paper deals with the frequency response modeling of interconnected microgrids. The frequency response model is used for frequency and tie-line power control analysis and synthesis. The proposed frequency response model is obtained using two different perspectives: (1) based on frequency sensitivity analysis, (2) based on the inertia concept. Besides, the dynamic of back-to-back converters and controllable active power sources are also included to obtain a generalized frequency response model with desirable performance. Indeed, it can be observed that in the first method, some circuit parameters can be neglected in the frequency response model. This finding is effective in providing a more simplified model. In the second method, the frequency response model has been presented as an innovative approach. In a way, we have selected the nature of distributed generations as an indicator of source classification in the model. This model is also enhanced by considering the inertia dynamics and controllable power source and has a better performance to show the network status. Since the microgrid frequency response model only covers the low-frequency dynamics, the fast dynamics of inner control loops as well as the modulation units and sensors are not considered. The proposed frequency response model can be used for frequency stability analysis studies as well as frequency and tie-line power control analysis and synthesis. Comprehensive simulation studies are carried out using the MATLAB simulation environment to compare and evaluate the developed models. Further, the proposed models are verified via PSCAD/EMTDC, considering two microgrids interconnected through back-to-back converters. The results showed that the proposed models are suitable and efficient for frequency response studies.