Power management in a DC microgrid supported by energy storage

This paper investigates optimal power management in dc microgrids, with its applications to dc dual-source trolleybus systems. High mobility of buses and their impact on power supply networks introduce challenging power management issues. This paper incorporates line power losses in power management strategies and introduces a new distributed optimal power management methodology. A multi-objective optimization model is developed. Using only neighborhood information exchange among feeder lines in the network, the new consensus-type control accommodates both feeder current allocation and power loss reduction with fast convergence. One critical finding of this paper is that our local recursive optimization algorithms achieve the global optimal solution asymptotically. Under random noise on information exchange, convergence and optimality of the proposed method are established rigorously. The power system configurations of the Beijing dual-source trolleybus system are used for simulation case studies on the new power management methods. Feasibility, accuracy, and comparison with global optimization results are demonstrated.

A DC microgrid with DC bus signaling (DBS) for power management offers a promising and cost-effective solution for reliable electricity access in rural and remote communities, particularly in developing nations. In this article, a three-layer modularized model of a microgrid is presented, with emphasis on the “Basic DC Microgrid Model” (Layer 1), which ensures effective power management in the microgrid at all times. Through the framework of the Layer 1 model, various energy management scenarios (EMSes) can be implemented, by varying the voltage regulation priorities of the entities. This allows us to achieve different system objectives such as reduced battery requirement or less dependence on the AC Grid. Two of the EMSes are discussed, implemented, and examined through both digital simulations and experimental tests on a laboratory prototype. The results show that the DBS scheme achieves real-time power management in a DC microgrid and that different EMSes can be easily implemented to realize varied system-level objectives.

Microgrids are receiving tremendous attention due to increasing need to integrate Distributed Generations (DG) and to provide reliable power to critical loads. Proper power management in microgrid is required to regulate the system voltage and frequency, maintain power quality, and manage DGs. A microgrid system has been studied in this paper, which includes two natural gas generators, an energy storage device, solar PV, and a wind turbine. The DGs are modeled in details using PSCAD software and the practical constraints of the components are considered. The Virtual Droop Control (VDC) method for microgrid power management is proposed and described in details. The proposed technique has been applied to adjust the active and reactive power of each component in order to manage the system. Unit commitment algorithm has also been implemented to improve the system efficiency.

Energy management in DC microgrid with an efficient voltage compensation mechanism

An adaptive droop control with constant voltage regulation is proposed for the power and voltage management of a DC microgrid (DCMG) with multiple power sources, such as a utility grid (UG), a distributed generator (DG), an energy storage system (ESS), and an electric vehicle (EV). In the proposed scheme, the droop characteristics for the UG, ESS, and EV are adaptively changed according to electricity price conditions and state-of-charge (SOC) levels in order to optimize the DCMG operation flexibility as well as electricity cost. The proposed control method not only ensures the power-sharing of DCMG reliably without the use of a communication link, but also regulates the DC bus voltage stably at the nominal value. To achieve this, the proposed scheme consists of primary control and secondary control. The primary control is used to achieve power-sharing in the decentralized DCMG, while the secondary control is used to overcome the disadvantage of conventional droop control, i.e., to remove DC bus voltage deviations. Decentralized power management is also presented to enhance the DCMG system reliability in the presence of uncertainties such as DG generation power, the ESS and EV SOC levels, the grid and EV availabilities, the load demand, and electricity price conditions. The effectiveness of the proposed scheme is demonstrated in a comprehensive simulation and experiment under various conditions. The test results clearly confirm the control flexibility and overall performance of the proposed control scheme for decentralized DCMG system.

The integration of more-electric technologies, such as energy storage systems (ESSs) and electric propulsion, has gained attention in recent years as a promising approach to reduce fuel consumption and emissions in the maritime industry. In this context, hybrid power systems (HPSs) with direct current (DC) distribution are currently gaining a commendable interest in research and industrial applications. This paper examines the impact of using HPS with DC distribution and a battery energy storage system (BESS) over a conventional AC power system for short haul roll-on/roll-off (RORO) ferries. An electric ferry with a HPS is modeled in this study and the power management system is simulated using the Matlab/Simulink software. The result is validated using measured load profile of a ferry. The performance of the DC HPS is compared with the conventional AC system based on fuel consumption and emission reductions. An approach to estimate the fuel consumption of the diesel engine through calculation of specific fuel oil consumption (SFOC) is also presented. This study uses two optimization techniques: a classical power management method namely Rule-Based control (RB) and a meta-heuristic power management method known as Grey Wolf Optimization (GWO) to optimally manage the power sharing of the proposed HPS. Fuel consumption and emission indicators are also used to assess the performance of the two power management methods. The simulation results show that the HPS provides a 2.91% and 7.48% fuel consumption reduction using RB method and GWO method respectively. It is apparent from the result that the HPS has more fuel savings while running the diesel generator sets (DGs) at higher operational efficiency. It is interesting that the proposed HPS using both power management methods provided a 100% emission reduction at berth. Finally, it was found that using a meta-heuristic optimization algorithm provides better fuel and emission reductions than a classical method.

This study is focused on two areas: the design of a Battery Energy Storage System (BESS) for a grid-connected DC Microgrid and the power management of that microgrid. The power management is performed by a Microgrid Central Controller (MGCC). A Microgrid operator provides daily information to the MGCC about the photovoltaic generation profile, the load demand profile, and the real-time prices of the electricity in order to plan the power interchange between the BESS and the main grid, establishing the desired state of charge (SOC) of the batteries at any time. The main goals of the power management strategy under study are to minimize the cost of the electricity that is imported from the grid and to maximize battery life by means of an adequate charging procedure, which sets the charging rate as a function of the MG state. Experimental and simulation results in many realistic scenarios demonstrate that the proposed methodology achieves a proper power management of the DC microgrid.

This paper presents a comprehensive study on power management and control strategies for hybrid renewable energy microgrids. The research focuses on a DC microgrid system that integrates photovoltaic (PV) arrays with a hybrid energy storage system (HESS) comprising batteries and supercapacitors. The proposed system addresses key challenges in renewable energy integration, including power fluctuations, energy balance maintenance, and DC bus voltage stability. We develop and analyze a multilayer control strategy for power sharing among the PV system, battery, and supercapacitor components. This strategy enables supercapacitors to handle fast transients while batteries manage steady-state power variations, enhancing overall system stability and extending battery lifespan by preventing overcharging and deep discharging. Three maximum power point tracking (MPPT) techniques—Perturb and Observe (P&O), Incremental Conductance (INC), and Fuzzy Logic Control (FLC)—are implemented and compared through MATLAB/SIMULINK simulations under varying irradiance conditions. The comparative analysis reveals that while P&O and INC methods offer simplicity and ease of implementation, the FLC approach achieves higher accuracy in maximum power tracking despite increased operational complexity. The simulation results confirm the effectiveness of the proposed control methods in ensuring DC-bus voltage stability and power balance throughout the system. This research contributes valuable insights for improving the scalability, resilience, and performance of microgrid systems with hybrid renewable energy sources and storage solutions.

A hierarchical power management scheme is proposed in this paper for a typical DC Microgrid. Different from other Microgrids, the DC Microgrid can interface to the distribution system by Solid-State transformer (SST). The hierarchical power management strategy includes three control levels: 1) primary control for DC Microgrid to implement distributed operation 2) secondary control for the DC Microgrid bus voltage recovery to achieve seamless mode switch 3) tertiary control to manage the battery charge and discharge. The DC Microgrid can operate in islanding mode, including the individual control for distributed renewable energy source (DRER) and distributed energy storage device (DESD). In addition, the DC microgrid can operate in SST-enabled mode to interface to the distribution system. The DC Micorgrid can seamlessly switch between islanding mode and SST-enable mode. The consideration of state of charge (SOC) for battery is also involved into the tertiary control. To this end, a lab test-bed is constructed to verify the system performance. Lastly, several typical case studies are carried out and the experimental results verify the proposed power management strategy.

DC microgrids can be created by integrating renewable energy resources at the distribution level. There are numerous advantages to using a grid-connected microgrid to meet the rising electricity demand. An isolated DC microgrid with solar PV arrays, wind turbines, and battery energy storage systems is shown to be connected to the grid in this study. The AC/DC bi-directional converter linked to the DC microgrid serves as the primary control for the Master controller. The PWM signal generated by the transformations is used to start and change the converter's mode of operation. Batteries can be used as a slave to the grid's power management in a DC microgrid. The case study of Islanding and Grid-connected are analyzed and simulated using MATLAB/Simulink. The study's findings offer some preliminary pointers for achieving long-term well-being. In order to achieve the best possible power system goals, a variety of factors may need to be carefully considered.

This paper proposes the coordinated control of a hybrid AC/DC power system with renewable energy source, energy storages and critical loads. The hybrid microgrid consists of both AC and DC sides. A synchronous generator and a PV farm supply power to the system's AC and DC sides, respectively. A bidirectional fully controlled AC/DC converter with active and reactive power decoupling technique is used to link the AC bus with the DC bus while regulating the system voltage and frequency. A DC/DC boost converter with a maximum power point tracking (MPPT) function is implemented to maximize the energy generation from the PV farm. Current controlled bidirectional DC/DC converters are applied to connect each lithium-ion battery bank to the DC bus. Lithium-ion battery banks act as energy storage devices that serve to increase the system stability by absorbing or injecting power to the grid as ancillary services. The proposed system can function in both grid-connected mode and islanding mode. Power electronic converters with different control strategies are analyzed in both modes in detail. Simulation results in MATLAB Simulink verify that the proposed topology is coordinated for power management in both AC and DC sides under critical loads with high efficiency, reliability, and robustness under both grid-connected and islanding modes.

This comprehensive review critically analyses the complex correlation between DC microgrids and the incorporation of Distributed Generation (DG). It offers a full evaluation of fundamental principles, advanced control strategies, technology advancements, and practical implementations in real-world scenarios. This research examines the ability of Direct Current (DC) microgrids to effectively integrate and optimize various DG sources within the context of a paradigm shift towards decentralized energy solutions. The paper critically examines the obstacles and opportunities associated with renewable energy systems and different DG technologies. It provides essential insights for researchers, engineers, and politicians who are involved in the complex process of integrating distributed energy into existing systems. This review serves as a crucial resource that contributes to the understanding of DG in DC microgrids. It plays a significant role in developing conversations surrounding energy solutions that are both resilient and sustainable. This paper not only discusses the difficulties related to the integration of DG, but also emphasizes practical examples that demonstrate the flexibility and effectiveness of DC microgrid designs. This study serves as a crucial resource for stakeholders who aim to use the potential of DC microgrids, since it encompasses a comprehensive analysis of power electronics, energy storage, and sophisticated control systems. By combining critical evaluation with practical implementation, this review offers valuable insights and guidance in the field. The complete investigation plays a significant role in advancing the integration of DG, which is essential for creating a resilient and sustainable energy environment. It provides basic information that is needed for achieving effective integration. This review paper provides a comprehensive examination of the integration of DG within DC microgrids. From laying the groundwork with fundamental principles to scrutinizing challenges, technological advancements, and practical applications, this review aims to offer a holistic understanding of the dynamic landscape where DC microgrids intersect with distributed energy generation.

The power system network is complex and diverse in nature because of the random and irregular existence of renewable sources, various types of varying and constant loads. Under these circumstances, the stabilization of DC link voltage and obtaining reduced power fluctuations are the main control aspect of DC microgrid (MG) system. This paper explores a Kalman filter (KF) based voltage–current control algorithm for the battery unit to control the medium voltage direct current (MVDC) bus voltage accurately with trivial oscillations as compared to the traditional VI algorithm. The stability and monitoring of DC microgrids are greatly influenced by gathering sufficient and precise information. Since installing several sensors on DC MGs is costly and increases DC MG ripple. In this work, an extended Kalman filter (KF) is used to estimate the current of the lead-acid battery. Hence the current represents an important factor in guaranteeing safe operations. Where the Kalman Filter, which improves the estimation efficiency, to reach a good performance in the current prediction. By updating the proposed approach provides smooth and noise-less operation from the measured DC voltage. The control strategy established for electric vehicle (EV) in this paper is to improve the overall charging ability of the EV only if the system’s total power is greater than the load level by means of the current loop management technique. The feasibility of the designed MG system with the established battery management mechanism and the Escape Ford EV performance is studied using MATLAB/Simulink platform.

A Solid-State Transformer as Enabling Technology for Microgrids for Integration into the Power Distribution System: An Overview

The dynamic evolution of renewable energy sources (RESs) with utilization of power electronics converters (PECs) caused the situation, where many energy generation units works parallel in local systems named microgrids (MGs). This distributed generation systems with many few kW micro-sources have to provide energy for linear and non-linear loads in grid connected mode of operation, but also in islanded mode of operation, which requires more advanced monitoring and energy management algorithms to ensure power balance and good voltage quality. The issues of power management in islanded AC microgrids are studied by many research centres and novel solutions are necessary to improve the reliability of MGs. In literature, there is still a gap for development of harmonic power sharing method in MG with most often used non-linear loads. Together with active and reactive power management algorithms the harmonic power sharing algorithm need to be implemented in control system to obtain complete solutions. The most often used approach in MG is hierarchical control structure, which includes the basic control loops at primary level, independent for each of PECs and outer control loops at secondary level, which allow to improve voltage amplitude and frequency in point of common coupling, as well as power sharing between PECs. Moreover, the hierarchical control structure is a great opportunity to implement a distributed control algorithm, which is able to execute many operations in the same time. Based on this idea, the novel proportional harmonic power sharing algorithm has been developed. It causes the harmonic power sharing between PECs proportionally to active powers, improving the output current waveforms of converters by decreasing the amplitude of selected current harmonics. The principles of hierarchical droop control and reactive power management has been presented in this paper. The developed solution has been implemented in simulation research together with proportional reactive power sharing algorithm. In order to present the advantage of harmonic power sharing, the results have been compared with non-controlled harmonic power.