Many modelling methods for the analysis of dc distribution grids only consider monopolar configurations and do not allow for mutual couplings to be taken into account. The modelling method presented in this paper aims to deal with both of these issues. A state-space approach is chosen for its flexibility and computational speed. The derived approach can be applied to any dc distribution system regardless of its configuration and takes into account mutual couplings between phase conductors. Moreover, the state-space matrices can be derived in a programmatic manner. The derived model is verified empirically and by a reference model created in Simulink using PowerLib blocks. Subsequently, an illustrative system is analyzed, which shows the utility of the presented method in analyzing the dynamics of dc distribution systems. The presented method is especially useful for the analysis, design, and optimization of, for example, the stability and control systems of dc distribution systems.

This article proposes an analytical methodology to evaluate the performance of the main partial power processing (PPP) architectures in terms of the improvements in the system’s conversion efficiency. This analysis considers the influence of the system’s voltage gain, the auxiliary dc/dc converter’s efficiency, and the possibility of bidirectional power flow. Herein, the key PPP architectures are, thus, modeled and benchmarked. The presented results attest to the series configuration as the most efficient PPP circuit solution, with no limits on the system voltage gain, contrary to the generalized results found in today’s literature. To assess these results and the significance of the proposed analysis, a well-known, simple, and cost-effective flyback topology has been designed and tested for a series PPP circuit solution able to effectively interface a 5-kW battery energy storage system (BESS) to a 700-V dc grid. A relatively high power conversion efficiency and compact hardware are achieved due to the reduced size requirements on the input and output filtering stages. Above all, while explaining the PPP concept, this study shows that even converter circuits known for their low power efficiency can be used to derive highly efficient systems. A design approach is, thus, provided to facilitate the design of the presented PPP circuit, and measurements are, finally, carried out to compare the obtained results with the expected ones derived from the developed analytical models.

Scalable and robust low voltage direct current distribution (lvdc) networks require solutions allowing flexible power flow control and reliable short-circuit protection. In this paper, the continuous full-order large and small signal models of a partially rated power flow control converter (PFCC) are derived utilizing the generalized averaging method. The large signal model of the PFCC is coupled with a model of the lvdc grid. Due to the state-space representation the combined model of the PFCC and the lvdc grid is suitable for easy algorithmization, and efficient simulation. These advantages make them essential tools for studying and optimizing of scalable lvdc systems with decentralized power flow control based on the PFCC. The PFCC models provide insights into controller design and stability analysis. The models are experimentally validated, and the functionality of the PFCC is demonstrated in a laboratoryscale microgrid.

Employing bipolar dc distribution systems introduces the possibility of imbalance in the system. To analyze these systems it is crucial to create novel modelling techniques. This paper presents a method to decompose dc distribution systems into symmetrical components. The presented method simplifies the analysis of balanced, unbalanced, and fault conditions of bipolar dc distribution systems. Equivalent circuits for several network components in the symmetrical domain are derived and are shown to be independent under symmetrical conditions. Furthermore, a dynamic analysis is performed in the symmetrical domain showing that the method simplifies the analysis of dc distribution systems. Additionally, the symmetrical domain equivalent circuits of several fault conditions are derived.

Instability caused by low inertia and constant power loads is a major challenge of DC distribution grids. Previous research uses oversimplified models or does not provide general rules for stability. Therefore, a comprehensive approach to analyze the stability of DC distribution systems is desired. This paper presents a method to algebraically analyze the stability of any DC distribution system through the eigenvalues of its state-space matrices. Furthermore, using this method, requirements are found for the stability of three example systems. Additionally, a sensitivity analysis is performed, which considers the effect of several system parameters on the stability and disputes some overgeneralized conclusions of previous research. Moreover, various simulations are performed to illustrate the dynamic behavior of a stable and an unstable DC distribution system.

Changes in distribution grids pose significant challenges with respect to the control and management of these grids. Stability and decentralized control are vital to ensure the availability and accessibility of plug-and-play dc distribution grids that are (temporarily) without communication. Therefore, this paper presents guidelines for these grids that ensure global stability and a decentralized control strategy that implements these stability guidelines. The stability guidelines are derived using a Brayton-Moser representation of the system to arrive at a Lyapunov candidate function. Furthermore, the decentralized control strategy implements these stability guidelines and ensures that the voltages in the system remain within a specified range. Additionally, several simulations are performed to illustrate the stability of the system and the behavior of the control strategy under different scenarios.