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.

Electrification of ships is one of the hot topics in the marine industry. This is due to the stringent guidelines by the International Maritime Organisation (IMO) for curbing the green house gas emissions from the marine sector. In this paper, the state-space modeling approach is used to model bipolar dc grids on ships. A ferry is used as a test case. The modeling is done for the radial and zonal architecture with similar components. The dynamic simulation and stability analysis of the two architectures reveal that zonal architecture is potentially more stable than the radial architecture.

Solid-state circuit breakers (SSCB) show great promise to become the key element in the protection of low-voltage direct current microgrids. SSCBs operate in the microsecond range and employ semi-conductor devices that have strict safe operation area limits. Therefore, the design of the SSCB needs to consider the effects of fault detection delays and semi-conductor safe operation area limitations. This paper derives SSCB design criteria that consider the effect of different detection methods with different detection delays under varying system constraints. The design space is investigated in a sensitivity analysis, which provides insights into the operation boundaries of SSCB and explains how a combination of fault detection methods can reduce the SSCB size. The insights from the theoretical and sensitivity analysis are used to propose an SSCB design flowchart. SSCB prototype is developed and tested in different scenarios under nominal grid voltage and current. The derived design constraints can be used for efficient SSCB design and also to evaluate the effects of different protection schemes on the required SSCB size.

This paper presents a protection framework for low voltage dc grids, which segments these grids into zones and tiers according to their fault current potential and provided protection. Furthermore, the technology and applications of different protection devices are examined. It is demonstrated that the utilization of fast fault interruption and fault limiting inductors are vital for the protection of low voltage dc grids. Moreover, a design of a solid-state circuit breaker is presented, and this devices is experimentally verified. The experimental results showed that the total time for the detection and interruption of faults can be lower than $1 \mu \mathrm{s}$ with solid-state protection devices.

Since the voltages and currents in dc grids do not have a natural zero-crossing, the protection of these grids is more challenging than the protection of conventional ac grids. Literature presents several unit and non-unit protection schemes that rely on communication, or knowledge about the system's topology and parameters in order to achieve selective protection in these grids. However, communication complicates fast fault detection and interruption, and a system's parameters are subject to uncertainty and change. This paper demonstrates that, in low voltage dc grids, faults propagate fast through the grid and interrupted inductive currents commutate to non-faulted sections of the grid, which both can cause circuit breakers in non-faulted sections to trip. A decentralized plug-and-play protection scheme is proposed that ensures selectivity via an augmented solid-state circuit breaker topology and by utilizing the proposed time-current characteristic. It is experimentally shown that the proposed scheme provides secure and selective fault interruption for radial and meshed low voltage dc grids under various conditions.

Due to the distributed nature of future electrical power systems, decentralized control is essential for these grids. This paper shows that converters that have identical voltage thresholds switch off simultaneously even if some could have remained operational. Therefore, inadequate system and energy utilization can occur when decentralized demand or supply response is utilized. The Grid Sense Multiple Acces (GSMA) algorithm proposed in this paper ensures that, after a change occurs in the system, a subset of the converters remains connected to the grid, without the need of utilizing any form of communication. This is achieved by introducing an exponential backoff time between failed connection attempts. Furthermore, several simulations and experiments are conducted to illustrate and validate the behavior of the GSMA algorithm, showing that it can be applied to dc grids in order to improve system and energy utilization.

This paper presents a steady-state model and associated power flow equations that can be applied to any dc grid. State-of-art power flow methods and two newly proposed methods are discussed and applied to the proposed steady-state model. A standardized IEEE test feeder is used to benchmark the power flow methods with respect to accuracy, convergence and computational efficiency. It is shown that the two new methods have a superior performance compared to the existing techniques for the steady-state analysis of most common dc grids, providing up to a 93 % increase in computational efficiency for the system that was analyzed in this paper. Therefore, it is demonstrated in this paper that these power flow techniques can be used for the operation, planning, optimization, market simulation, and security assessment of practical dc grids.

Due to the sharp growth in the adaptation of electric vehicles (EV) in the Netherlands and the objectives of the Dutch Climate Accord is to encourage electric mobility, in the coming decades a substantial number of new EV charging facilities needs to be provided. Efficient planning of EV charging infrastructure is coupled with the notion of range anxiety, which is likely to be severely high in case of soon-to-be EV drivers. This study aims to estimate the cost of developing a new charging infrastructure under five scenarios of range anxiety in Amsterdam East. Employing a Linear Integer Programming optimization model, on the basis of geographic data on car registration, existing EV chargers, and electricity substations, it is obtained that if drivers use 90% of their battery before using a charging facility, the existing charging infrastructure needs to be expanded by only 31% to accommodate almost seven times larger number of EVs–the threshold set by the European Union (EU) legislation on the deployment of alternative fuel infrastructure. If drivers use only 30% of the batteries; however, an increase of 167% in infrastructure is inevitable (accounting for almost five million euro of cost). Second, at any point along the range anxiety spectrum, if the interval between charging session increases for 1 day, the overall cost decreases by more than 30%. These findings are discussed, and two policy approaches are proposed: (1) information technology approach; (2) demand-response approach, on the basis of EU legislation on energy efficiency and deployment of alternative fuel infrastructure.

To tackle the challenges of future distribution systems, dc is being reconsidered. However, broad adoption of dc distribution systems requires additional research into the modeling, stability, protection and control of these systems. Previous research presents modeling methods that only consider monopolar configurations and do not take mutual couplings into account. Therefore, this paper presents a state-space method that can be applied to any dc distribution system, regardless of configuration and mutual couplings. Moreover, it shows how the state-space matrices can be derived in a programmatic manner. Furthermore, the models are validated using an experimental dc microgrid set-up. Due to the mathematical nature, the presented modeling method can be applied easily, and the stability and control can be analyzed algebraically.

Constant power loads combined with low inertia form a major challenge for future distribution grids. This paper presents a state-space representation to model dc distribution systems. Two methods are discussed to analyze the (small-signal) stability of these dc distribution systems; an algebraic method and a Brayton-Moser method. The system models and the methods for stability analysis were verified using an experimental dc microgrid set-up. Furthermore, it was found that the instability of dc distribution systems can be classified into two categories: equilibrium instability and oscillatory instability.

The number of electric vehicles in the Netherlands has sharply increased over the past decade. This has caused a need for the allocation of a substantial amount of new electric vehicle chargers around the country, which in turn has been acknowledged by a variety of legislative bodies. However, the approach of how these new charging infrastructures need to be spatially distributed has yet to be decided, including the distance that an electric vehicle charger could be allocated from the final destination of its driver. The hypothesis of this study is that if residents walk a longer distance to/from these charging stations, the chargers could be shared by a greater number of electric vehicle owners, and the total cost of the new charging infrastructure could be reduced. By using linear integer programming, the minimum cost of allocating new fast-charging stations in a central, densely populated area of Amsterdam, accounting for 7% of the city’s population, is calculated. The results show that if residents were to walk for five minutes (roughly 400 metres) instead of two and half minutes (roughly 200 metres), the overall cost of new electric vehicle chargers could be reduced by more than 1 million euros. The study also found that both the cost of new charging stations and their efficiency of use are vastly affected by the portion of the charging infrastructure that is saved for people visiting the area. The findings of this study are discussed in detail, including the proposal of potential further studies.

Scalable and robust low-voltage direct current (LVdc) distribution 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 laboratory-scale microgrid.

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.