Modeling and Control of Single-Phase Power Electronic Converters and Islanded Microgrids using the Dynamic Phasor Method

Abstract

The structure and behaviour of electrical grids are rapidly changing due to the increasing grid integration of inverter-based resources (IBRs) and the adoption of electric vehicles in low-voltage distribution grids. The changes emphasize the need for a holistic modification of methods used in modeling and simulating power systems. The electromagnetic transients (EMT) simulations based on detailed switching time-domain models, represent the true dynamics of power systems and converters. However, EMT simulations require long execution times. With the increasing integration of IBRs in the power system, static phasor-type simulations may be inaccurate because of reduced system inertia and strong interaction of the control schemes of IBRs with line dynamics. The dynamic phasor (DP) method is an alternative method to develop computationally efficient and accurate power system models. The DP method gives the user the freedom to select dominant harmonics and dynamics to model which in turn, enables the use of large step sizes to accelerate simulations. In the literature, little attention has been paid to DP-based modeling of single-phase low-voltage systems. Considering the upsurge in the deployment of residential microgrids, developing robust and well-validated DP models of single-phase power converters and microgrids is pertinent. This thesis augments the library of DP models by extending the DP method to the modeling of nonlinear (Lyapunov) and linear controller-based single-phase grid-following and grid-forming inverters, H-bridge active rectifiers, droop-controlled microgrids, diode-bridge rectifiers, and non-isolated DC-DC converters. Additionally, this thesis proposes the DP model of a synchronization unit suitable for (re)connecting a grid-forming inverter to a microgrid. To ensure that the proposed DP models have similar dynamic and steady-state responses as the detailed switching models, this thesis proposes a methodological approach of developing small-signal and large-signal DP models for control design purposes. The fidelity of the proposed DP models are validated with experimental and detailed switching model results. Simulation results confirm the high fidelity of the proposed DP models to produce results with comparable accuracy as the detailed switching models while using less simulation execution time. The proposed DP models will be useful to researchers and engineers interested in conducting fast-paced and accurate study of power electronics-dominated low-voltage grids.