Typical Design and Simulation Experimental Study of DC Micro-grid Control System

This paper's investigation is based on a solid state transformer (SST) interfaced DC microgrid (MG) system. Correspondingly, a hierarchical power and energy management strategy is proposed for this system. The proposed power management strategy includes three control levels: 1) primary control, distributed control for system power balance without communication; 2) secondary control for system seamless switching from islanding mode to SST-enabled mode; 3) tertiary control for system energy management. Different from the previous methods, the multiple control objectives control is implemented in the tertiary control layer. Thus, the tertiary control can not only control the DC MG system output power, but manage the battery state (charge or discharge) in DC MG based on its state of charge (SOC). Lastly, several typical case studies are carried out and the simulation results verify the proposed power and energy management strategy.

Nowadays, DC microgrids have become more popular than AC microgrid systems due to their high efficiency, as they can reduce the requirement of the conversion stages. Also, they can integrate with renewable energy sources easily. Additionally, DC microgrids are more stable, reliable, and less complex in design. Nevertheless, DC microgrid fault detection and identification present a significant challenge due to the limited research available in this field. Out of the several faults in the DC microgrid (like pole to pole, pole to ground, and arc fault), arc fault is a more serious fault because Arc discharge raises the temperature, which can harm the circuit and increase the risk of a fire. The DC microgrid system's ability to operate safely will be impacted when a High Impedance Series Arc Fault arises, so to provide protection to the line from the arc fault, we need to detect and identify the fault accurately. However, because the fault current generated in the DC microgrid by an arc fault is nonlinear, it is difficult to detect the fault in a DC network using conventional techniques, such as CBs or fuses. In order to detect and diagnose the major arc fault more effectively and precisely, a new approach is presented here that builds an observer model using the Geometric Control Theory's idea of subspaces, such as unobservable and invariant subspaces, among others. This paper aims to design an observer that will generate residual signatures for each of the faults and show zero results for a consecutive fault.

This paper presents a control design methodology that addresses high penetration of variable generation or renewable energy sources and loads for networked AC /DC microgrid systems as an islanded subsystem or as part of larger electric power grid systems. High performance microgrid systems that contain large amounts of stochastic sources and loads is a major goal for the future of electric power systems. Alternatively, methods for controlling and analyzing AC/ DC microgrid systems will provide an understanding into the tradeoffs that can be made during the design phase. This method develops both a control design methodology and realizable hierarchical controllers that are based on the Hamiltonian Surface Shaping and Power Flow Control (HSSPFC) methodology that regulates renewable energy sources, varying loads and identifies energy storage requirements for a networked AC/DC microgrid system. Both static and dynamic stability conditions are derived. A renewable energy scenario is considered for a networked three DC microgrids tied into an AC ringbus configuration. Numerical simulation results are presented.

This paper presents a plug-in electric vehicle (PEV) charging unit supplied by PV, wind and the battery in an autonomous mode of DC microgrid (MG) system. With the traditional control methods of PEV, the EV is charged without considering generation and the load limits. The control strategy proposed for PEV in this article is to increase the maximum rate of charging capacity of an EV only if generation exceeds the load demand using new current-loop control technique. The variation of photovoltaic irradiance, DC and AC loads, battery charging and discharging characteristics are considered which are directly coupled to a medium voltage DC bus. This tends to be an attractive option for increasing the efficiency and operation of electric vehicle charging station. The power reference based droop controller is designed for the battery to provide an efficient power management of a DC MG system by regulating the DC link voltage with less deviation. The effectiveness of the proposed MG system with Escape Ford EV vehicle has been validated by MATLAB/Simulink. The reported simulation results show that the approach presented is capable of governing the PEV charging unit and regulation of DC bus voltage.

Various power plants have been applied to increase electrification in remote areas, one of which is the Centralized Off-Grid PV system with AC micro grid. Although it has been widely used, this system has several drawbacks, including network losses, land, and synchronization with other power plants. A Power Conditioner System (PCS) based distributed generation system with DC micro grid has been proposed to overcome that deficiency. This DC microgrid system consists of multiple Solar DC Towers, each with solar panels, batteries and PCS connected to their respective loads. In the previous papers, an evaluation of the performance of individual PCS has been carried out in several aspects. In contrast, the performance of the entire DC micro grid system when working in multi-point has not been thoroughly tested. In this paper, the performance of a DC microgrid is evaluated in a multi-point system with PV as the primary source. A prototype of a DC microgrid system with two Solar DC Towers has been developed. The system's performance against solar irradiation and its overall efficiency has been tested. The system has also been tested to meet load requirements under various conditions from various sources, including taking and sending power to the DC micro grid with power-sharing mode. The evaluation shows that this DC microgrid system can work appropriately with good system performance, although it can still be improved in the future.

Power conditioning unit is the key power supply unit in the spacecraft. The use of grid-connected power supply technology can realize the redundant protection of the power supply system of spacecraft. DC microgrid is an effective architecture that solves the interconnection of multiple DC power supply systems. Droop control is a commonly used control method in DC microgrid. In this paper, a new distributed DC microgrid architecture for aerospace is proposed, and the operation mode and control strategy of proposed DC microgrid system are described in detail. Next, the working principle of the grid-connected controller is introduced. According to the operating characteristics of the mentioned DC microgrid system, the operation status of three working modes of the grid-connected controller is analyzed and control strategy is also designed. At the same time, an adaptive droop control based on PCU bus voltage information is proposed, and the specific control method is explained. Afterwards, stability and simulation analysis are carried out according to the operation mode and control strategy of the microgrid system, and finally an experimental platform was built to verify the proposed design scheme and control strategy.KeywordsPower Conditioning UnitDC microgridAdaptive droop controlSpacecraft power supply system

To meet the fast-growing energy demand and manage the distributed resource, an intelligent energy management system plays a vital role in the electric power system. The next-generation electric power system, known as the smart grid, will incorporate a large number of renewable energy resources that fundamentally change the energy management paradigm. To manage efficiently the energy supply and demand in the power grid, further improvement in the reliability and efficiency of electrical grids can be achieved by utilizing dc distribution in microgrid systems. DC microgrid is an attractive technology in the modern electrical grid system because of its natural interface with renewable energy sources, electric loads (e.g. data center load, electrical vehicle charging load, residential dc load), solid state transformer and energy storage systems. In this paper we discussed the functional expectation of the dc microgrid, system architecture, communication structure and distributed grid intelligent system. This paper highlights the recent technology update in dc microgrid system. This paper also discusses benefits and challenges of using dc grid.

Research and development on DC microgrid is increasingly being done recently. This development aims to reduce or even replace the electrical energy generated from fossil energy. Therefore, DC microgrid is present to be the solution of future electric energy by using renewable energy. Many energy sources are used in microgrid systems, but the most widely used is photovoltaic (PV) to convert solar energy into electrical energy. Unfortunately, the system using PV is very limited in its usage time, so it needs a backup energy source to help with the power needs of the load when there is no sun. In addition, most PV systems also use maximum power point tracking (MPPT) using an algorithm to maximize power from PV. The use of MPPT in PV system has a positive impact that can improve the efficiency of power on microgrid but on the other hand this MPPT system can cause problems that is unstable voltage and can exceed DC bus voltage. Therefore it needs constant voltage control to keep the voltage on the DC bus remains stable and located at a set point that has been determined. So in this research will propose fuzzy logic controller (FLC) to keep the voltage on DC bus remain constant. The FLC will be applied to the converter buck while the MPPT control using the flower pollination algorithm (FPA) will be applied to the coupled inductor SEPIC converter.

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 microgrid can be defined as a grid of interconnected distributed energy resources, loads and energy storage systems. In microgrid systems containing renewable energy resources, the coordinated operation of distributed generation units is important to ensure the stability of the microgrid. A microgrid needs a successful control scheme to achieve its design goals. Undesirable situations such as distorted voltage profile and frequency fluctuations are significantly reduced by installing the appropriate hardware such as energy storage systems, and control strategies. The multi-agent system is one of the approaches used to control microgrids. The application of multi-agent systems in electric power systems is becoming popular because of their inherent benefits such as autonomy, responsiveness, and social ability. This study provides an overview of the agent concept and multi-agent systems, as well as reviews of recent research studies on multi-agent systems’ application in microgrid control systems. In addition, a multi-agent-based controller and energy management system design is proposed for the DC microgrid in the study. The designed microgrid is composed of a photovoltaic system consisting of 30 series-connected PV modules, a wind turbine, a synchronous generator, a battery-based energy storage system, critical and non-critical DC loads, the grid and the control system. The microgrid is controlled by the designed multi-agent-based controller. The proposed multi-agent-based controller has a distributed generation agent, battery agent, load agent and grid agent. The roles of each agent and communication among the agents are designed properly and coordinated to achieve control goals, which basically are the DC bus voltage quality and system stability. The designed microgrid and proposed multi-agent-based controller are tested for two different scenarios, and the performance of the controller has been verified with MATLAB/Simulink simulations. The simulation results show that the proposed controller provides constant DC voltage for any operation condition. Additionally, the system stability is ensured with the proposed controller for variable renewable generation and variable load conditions.

The cyclical nature and high investment costs of the wind and photovoltaic renewable energy sources are the two critical issues seeking attention for the use of such systems in backup or isolated applications. This paper aims to present the experimental and economic analysis of a wind–photovoltaic-based hybrid direct current microgrid (DCMG) system for backup power and off-grid isolated power generation system for emergency purposes. The two distributed generating units comprising photovoltaic panels and wind generator were designed and developed for the experimental study. A lead-acid battery is also added as an energy storage system to enhance the system supply. The electric load of this system comprise of 42 DC light emitting diode (LED) lamps of 12 Watt each and a 25 Watt DC fan. The charge controller provides the control and protection features for the designed system. The complete system design and fabrication of this system have been undertaken at Mehran University of Engineering & Technology (MUET, Jamshoro, Pakistan). The compatibility of the designed system has been analysed by comparing the Levelized Cost of Energy (LCOE) with a conventional gasoline generator system of the same capacity. The capital, running and lifetime costs of DCMG are found to be 1.29, 0.15 and 0.29 times those of the gasoline generator, respectively. Moreover, it is found that per unit cost of gasoline generator is $0.3 (i.e., PKR 31.4) which is almost 3.4 times higher than that of the hybrid DCMG system. The performance and cost evaluation of the designed system indicate its broad potential to be adopted for commercialisation to meet backup power and off-grid power requirements. This study concludes that proposed DCMG system is a not only low cost, but also a pollution-free alternative option compared to the existing traditional small gasoline generator system.

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.

Today, DC Microgrid gain more attraction due to increasing electronic digital devices application such smart-phones, smart-tvs, and other digital apparatus which are operated in DC form. In the common grid, the electric power from AC source is converted to DC voltage for powering the digital devices as load. Hence, there are power conversions from AC-DC and potentially loss energy during conversions. DC Microgrid consisted of sources, loads, distribution lines and energy storages. In small capacity DC Microgrid, the stability of the system is vulnerable by dynamic load change. During load demands fluctuations, the DC Microgrid voltage is also dynamically fluctuated and can reach over the designated rate. To solve this problem, the PID controller is introduced in the DC-DC converter for maintaining the voltage rate at designated value regardless the load demands. In this paper, the DC Microgrid is consisted of photovoltaics as DC sources, XL-6019 as DC-DC converter, Arduino as controller, voltage and current sensors, distribution lines and loads. The proposed method is evaluated via experimental results. The responses of the proposed method in the DC Microgrid system are presented, evaluated, discussed, and compared between with and without applied method. The experimental results indicate that the proposed method has ability to reduce the voltage profile fluctuations during load demands changes and in short time.

The design and implementation of the battery energy storage system in DC micro-grid systems is demonstrated in this paper. The battery energy storage system (BESS) is an important part of a DC micro-grid because renewable energy generation sources are fluctuating. The BESS can provide energy while the renewable energy is absent in the DC micro-grid. The circuit topology of the proposed BESS will be introduced. The design of the voltage controller and the current controller for the battery charger/discharger are also illustrated. Finally, experimental results are provided to validate the performance of the BESS.

Energy management in DC microgrid is complex and challenging due to the stochastic nature of renewable energy sources and load demand. Coping with the deficit power, peak demand, and power converter control operations are a few major concerns. The photovoltaic (PV) system and battery energy storage system (BESS) utilization need special attention for the reliable and efficient operation of the DC microgrid. Hence, this article proposes the centralized energy management scheme (CEMS) in the DC microgrid to address the abovementioned challenges. The CEMS coordinates among the various physical layer components and computational layer (i.e., control layer) of the DC microgrid. It utilizes the multioptimization for energy management during the peak and <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">off</small> -peak load demand, optimal usage of PV-BESS, and performs the optimal load shedding operation. Furthermore, an optimal utilization of the PV-BESS problem is formulated and solved using linear programming to avoid excess usage of AC grid power. In deficit PV power, the optimal load shedding operation is formulated as mixed-integer linear programming problem to ensure the DC bus voltage regulation and power balance. The proposed CEMS demonstrates the effective operation of the PV system in maximum power point tracking, <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">off</small> -MPPT mode (i.e., voltage control), and BESS's charging/discharging operation. It is showcased that the hierarchical control structure of CEMS improves the performance, efficiency, and reliability of the DC microgrid operation. Hence, a 48 V and 1.2 kW PV-BESS-based DC microgrid system is developed to show the efficacy of the proposed algorithm under different scenarios in MATLAB/Simulink. The real-time simulator results of the developed system, obtained using OPAL-RT OP4510, confirmed the effectiveness and reliability of the proposed scheme.