A microgrid is a well known solution to increase the technical and economical capability of distributed generations. Recently, DC microgrids, as small‐scale DC networks, have attracted more attention due to lower losses and simple control structure. Stability of DC microgrids can be an important issue under high penetration of constant power loads (CPLs). In this study, stability analysis of the DC microgrid system including hybrid wind/battery and CPLs is studied, and then three different types of stabilising compensators are presented in two groups to increase the stability margin and to stabilise the system under high penetration of CPLs. The proposed stabilising compensators modify the voltage reference, current reference and duty cycle by adding active damping signals in the external, middle and internal parts of the interfaced converter control loops. These active damping signals are obtained by the feedback of the output voltage and current and modify the DC microgrid control structure. To evaluate the system stability under different stabilising compensators, small signal and frequency response analyses are done with and without active damping signals. Simulation results based on a detailed DC microgrid model are given to verify the effectiveness of the proposed compensators.
Summary
This paper deals with the improvement of stability margin, dynamic behavior, and steady state performance of a direct current (DC) microgrid system consisting of wind energy sources, battery energy storage, and back up generation source. The DC microgrid control system should set the DC bus voltage at the allowable range and provide proper load sharing among generation sources. Accurate load sharing, proper voltage regulation, and dynamic stability of the system at presence of constant power loads (CPLs) are the main problems that may be raised in operation of DC microgrid systems. In order to address these issues, this paper proposes a generalized droop‐based compensator that not only stabilizes the DC microgrid dynamics at high penetration of CPLs, but also addresses the issues such as inaccurate load sharing and improper voltage regulation. The proposed generalized droop‐based compensator comprises three parts: the first part enhances the DC microgrid stability even at high penetration of CPL, the second part compensates the transmission lines voltage drops and improves the function of voltage regulation, and the third part performs proper load sharing among different generation sources. At the end, capability of the proposed compensator is examined by frequency response analysis and time domain simulations.
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