Online Strategizing Distributed Renewable Energy Resource Access in Islanded Microgrids

Electricity networks are evolving rapidly with the large‐scale integration of power electronic (PE)‐interfaced distributed renewable energy resources (DRERs). With this rapid deployment of PE‐interfaced renewables, requirements set for the PE‐interfaced DRERs have also evolved to maintain grid security and reliability. Fault ride‐through (FRT) is an essential requirement which should be adhered by DRERs, which will ensure security and reliability of the power system during grid faults. This paper critically reviews the existing FRT standards (grid‐code requirements) and FRT strategies implemented/ proposed for major DRERs, such as wind energy conversion systems (WECSs), solar photovoltaic (PV) systems, and microgrids. According to the review, robust FRT strategies are implemented/proposed DRERs, however, the FRT grid codes are presently developed with the perspective of both synchronous and renewable generation operating in the power system. However, this current approach should be augmented considering 100% PE‐based renewable energy scenarios, and emerging issues, such as high penetration of PE‐interfaced small‐scale renewable generators (e.g., domestic solar‐PV systems) and recurring grid faults, to achieve a sustainable renewable energy future.This article is categorized under: Concentrating Solar Power > Systems and Infrastructure Wind Power > Systems and Infrastructure Photovoltaics > Systems and Infrastructure

This paper presents a real-time implementation of multi-agent based game theory reverse auction model for microgrid market operation featuring conventional and renewable distributed energy resources (DER). Studies were conducted for a grid connected microgrid consisting of a synchronous generator, two inverter-based generation units and a combined load. The Multi-agent based platform was applied to monitoring, controlling and per-forming the reverse auction process of the DER. A competitive game-theory reverse auction model was investigated to schedule the DER unit commitment with hour-ahead market approach for the twenty-four hours of the day. The proposed methodology was realistically implemented and operated at Florida International University, Smart Grid Test system. The investigation shows that the proposed algorithm and the industrial based hardware structure can be implemented in existing electric utility grid as new assets of the system are added.

Given the huge concerns all over the world regarding carbon emissions from fossil fuels, energy crisis and global warming, the renewable distributed energy resources (DERs) are going to be integrated in electricity grids, which will make the energy supply more reliable and decrease transmission losses. Regrettably, one of the main practical defies in smart grid planning, control and operation with DERs is the voltage regulation at the distribution field level. This problem motivates the deployment of sensors and actuators in electricity grids so that the voltage regulation can be controlled at the desired level. To do that the measurements from the renewable microgrid state information is transmitted to an energy management center via the internet of things (IoT) based communication network. In other words, the proposed IoT communication infrastructure provides an opportunity to address the voltage regulation challenge by offering the two-way communication links for microgrid state information collection and estimation. Based on this smart grid communication infrastructure, we propose a Kalman filter based state estimation method for voltage regulation of the microgrid. Finally, the effectiveness of the Kalman filter based state estimation method is illustrated using the linear state space model of a microgrid incorporating DERs.

Several studies and field tests have shown the potential of conservation voltage reduction (CVR) to decrease peak demand, energy consumption, and system losses. Nonetheless, the energy savings achievable by CVR is dependent on the load model, which could be constant power, current, impedance, or any combination of these models. Also, the use of distributed energy resources (DERs) at the distribution level presents a challenge to successful CVR implementation as these resources could cause voltage fluctuations in the system. This paper studies the impact of load models on CVR implementation in a distribution system feeder interfaced with renewable DERs. Load flow analyses are carried out using constant power (PQ) and constant impedance (Z) load models, respectively, and the resulting effects on feeder losses and energy consumption are observed as CVR is implemented. In addition, the impacts of DERs and voltage regulation devices on the feeder voltage profile are analyzed. The feeder losses showed opposite trends with constant PQ and Z loads as CVR is implemented. Overall, the results showed varied impacts of load models and DER output on feeder losses, energy consumption, and bus voltages in the distribution network.

This paper proposes an effective scheme for real-time operation and protection of microgrids based on the distributed dynamic state estimation (DDSE) that is applied to a single renewable distributed energy resource (DER) or other components. First, the DDSE can be used for setting-less component protection that applies dynamic state estimation on a component under protection with real-time measurements and dynamic models of the component. Based on the results, the well-known chi-square test yields the confidence level that quantifies the goodness of fit of models to measurements, indicating the health status of the component. With this approach, renewable DERs in microgrids can be protected on an autonomous and adaptive basis. Meanwhile, the estimated state variables of each component are converted to phasor data with time tags, and then collected to the distributed energy resources management (DERMS) of microgrids. These aggregated phasor data that are once filtered by the DDSE are input to the static state estimation in the DERMS along with unfiltered data sent from conventional meters, relays, and digital fault recorders, ultimately generating real-time operating conditions of microgrids. This paper also provides numerical simulations for comparing the DDSE-based approach with the conventional centralized state estimation in terms of data accuracy and computational speeds.

A multi-level multi-objective strategy for eco-environmental management of electricity market among micro-grids under high penetration of smart homes, plug-in electric vehicles and energy storage devices

Summary In this paper a new framework is introduced to develop a coupled active and reactive market in distribution networks. Distributed energy resources (DERs) such as synchronous machine–based distributed generations and wind turbines offer their active and reactive powers to the proposed market. For the considered DERs, multicomponent reactive power bidding structures are introduced based on their capability curves. Also, the hourly speed variations of wind turbines are considered in the proposed model. A distribution company buys active and reactive powers from a wholesale market and sells them via this market. The demand side is active, and responsive loads or aggregators can participate in the market using a demand bidding/buyback program. The objective function of the proposed market is to minimize the active and reactive power costs of DERs and distribution companies, the penalty cost of CO2 emission, and the cost of running a demand bidding/buyback program. The effectiveness of the proposed method is examined on a 22-bus 20-kV radial distribution test system.

As more and more distributed renewable energy resources are integrated to the grid, the traditional consumers have become the prosumers who can sell back their surplus energy to the others who are in energy shortage. This peer-to-peer (P2P) energy transaction framework benefits the end users, financially and in term of energy security; and the network operators, in term of flexibility in DRES management, peak load shifting and regulation of voltage/frequency. Environmentally, P2P energy transaction also helps to reduce carbon footprint, reduces DRES payback period and incentivizes the installation of DRES. The current centralized market model is no longer suitable and it is therefore necessary to develop an adapted decentralized architecture for the advanced P2P energy transaction framework intra/inter-micro grid. In this paper, we discuss several distributed ledger approaches for such framework: Blockchain, Block Lattice and Directed Acyclic Graph (the Tangle). The technical advantages of these architectures as well as the persistent challenges are then considered.

The power system that we have today has gone through several transformations over the years. These changes are due to either advancement in science and technology or changes in customer demands. Today we have the vision for a future electrical power system known as the ‘Smart Grid’. This power system has several functional and operational capabilities which are envisioned to solve the reliability, generation deficit and cost issues in the power system. Majority of the power systems in the world are still being operated as the traditional power system with one-way communication and one-way power flow. Transitioning to a Smart Grid (SG) influences the protection schemes and principles of the power system as the smart grid is to incorporate Distributed Generation (DG) units and other Distributed Energy Resources (DERs) hence there is going to be a bi-directional flow of power and information. Therefore, there is also a need for development and advancement in the protection schemes. Over the years there have been a lot of transformational stages in the protection schemes for power system operation. Understanding the protection needs is important for power system operators to know the reason why certain protection schemes cannot work on new and modern power systems as they seek to transform their utilities to the future electrical grid known as the smart grid. This paper presents the transitional stages that power system protection has gone through and the requirements needed for smart grid protection.

Microgrid protection schemes play a vital role in ensuring the reliability and efficiency of power distribution in urban and rural areas, especially as renewable distributed energy resources are increasingly integrated. This paper aims to provide a comprehensive analysis of existing microgrid protection schemes, discussing their advantages and limitations and highlighting key challenges and opportunities for future research. As microgrid systems become increasingly common, the management of power flow in small-community networks equipped with intelligent electronic devices, non-linear loads, and multiple distributed generation sources becomes more complicated. In order to address these challenges, coordination of protective schemes is required to prevent overload and damage to equipment. Firstly, the study discusses microgrid definitions and functional categories, highlighting their benefits and drawbacks. An analysis of microgrid protection literature includes adaptive protection systems as intelligent methods to address coordination challenges. Secondly, this review classifies microgrid protection techniques as modified, new knowledge-based and conventional schemes and provides a systematic analysis of optimization approaches. The study also examines the essential problems associated with the coordination of protective relays within microgrids. Finally, examining the current state of microgrid protection to identify the key research directions and opportunities for future development in this rapidly advancing field. The findings of this comprehensive analysis highlight the importance of effective microgrid protection in ensuring a stable and sustainable energy future.

This paper proposes a new multi-segment adaptive droop control method, applied in islanded AC microgrids with distributed energy storage systems (DESSs) and hybrid PV/Battery units, for balancing their state of charge (SoC). The power/frequency characteristic curves are adjusted locally in real-time, based on the SoC level of the respective battery. Aim of the control is to maintain a comparable number of charging/discharging cycles among the batteries, while preserving the power balance in the islanded microgrid. The control strategies are implemented in each battery without relying on communications or a central management algorithm. The microgrid frequency is used as communication parameter in order to adjust the charging/discharging rate of each storage system. Detailed simulation results verify the effectiveness of this method in an islanded microgrid consisting of several loads, powered by PVs, hybrid PV/Battery units and DESSs.

The increasing penetration of distributed energy resources (DERs) into power systems has transformed the landscape of energy distribution, bringing both opportunities and significant challenges. This study examines the impact of DER integration on power system stability, focusing on voltage stability, frequency stability, and transient stability. A comprehensive review of 50 high-quality studies from peer-reviewed journals and reputable conference proceedings was conducted, utilizing advanced modeling, simulation, and empirical analysis methods. The findings reveal that the intermittent nature of renewable DERs, such as solar and wind, leads to voltage fluctuations, necessitating advanced control strategies to maintain stability. Additionally, the displacement of traditional synchronous generators by inverter-based DERs reduces system inertia, posing severe frequency stability challenges that require innovative solutions like synthetic inertia and fast frequency response mechanisms. Transient stability issues are also exacerbated by DER integration, highlighting the need for advanced inverter controls and enhanced fault ride-through capabilities. Energy storage systems (ESS) are identified as crucial for buffering the variability of renewable DERs, providing essential services such as frequency regulation and voltage support. However, high costs and scalability issues remain barriers to widespread ESS adoption. The study underscores the importance of supportive regulatory and policy frameworks in facilitating the seamless integration of DERs while maintaining grid stability. Effective policies that promote smart grid technologies and DER-friendly regulations are essential for ensuring a stable, resilient, and sustainable power grid. This research contributes to a deeper understanding of the complex dynamics introduced by DERs and offers insights into developing robust strategies to address stability challenges in modern power systems.

DC micro-grids are the key technology for integrating distributed renewable energy resources (DERs) in the decentralized generation system since most of them are DC inherent. Energy storage systems play important role in stabilizing DC micro grids. In recent years hybrid energy storage systems (HESSs) draw a tremendous attention because of their excellent dynamics. In this paper, novel DC-DC single-inductor double-input bidirectional converter is presented for integrating the HESS to the DC micro-grid. The steady-state analysis of proposed converter is presented. Small-signal model of the converter is derived out and control strategy is demonstrated. Finally, detailed simulations are carried out in MATLAB SIMULINK. The capability of proposed converter for proper power-sharing between the battery and the super capacitor is validated through simulations.

This paper presents a control strategy for microgrids in smart grid environment. A hierarchical control strategy is developed to ensure stability and to optimize operation of microgrid. Communication, control and advanced metering infrastructure of smart grids are used to facilitate this control strategy. The control strategy incorporates storage device, electric car, various distributed energy resources and loads. Proposed control strategy considers microgrid operation in island and grid-connected mode. Island microgrid is stabilized by managing storage devices, dispatchable energy units and controllable loads. The control strategy is based on demand participation while stability of system has the highest priority. Theoretical discussion beyond presented algorithms reveal evidently the effectiveness of the proposed control method.

Guest Editorial: Situational awareness of integrated energy systems