Benefits Of Microgrids Research Articles

A Grid-Connected Microgrid Optimal Allocation Method Considering Self-Balancing Rate

Microgrid optimal allocation is the primary problem that needs to be solved in the stage of microgrid planning and design. Whether the optimal allocation scheme is reasonable or not will directly determine the safe operation and economic benefits of microgrid. Unreasonable allocation scheme will lead to higher power supply costs and poor performance, and can not even reflect the inherent superiority of microgrid. In this paper, based on some indicators such as the self-balancing rate, the power fluctuation rate of the tie line, and the proportion of spontaneous self-use, the effect of the different operation strategies of the wind/light/storage grid-type microgrid is analyzed firstly. Then, an optimal allocation method for grid-connected microgrid is proposed. Furthermore, based on the economic scheduling operation strategy, considering the initial investment cost, replacement cost, operation maintenance cost, residual value and purchase electricity cost, the optimal allocation scheme with different self-balancing rate is compared.

Recent trends in power management strategies for optimal operation of distributed energy resources in microgrids: A comprehensive review

The current era in sustainable development is focused on the rapid integration of renewable energy sources driven by a wide range of socio-economic objectives. Due to the inherent property of time-varying weather conditions, the intermittent sources, that is, Solar PV and Wind Energy, are considered as variable energy resources. The uncertainty and variability problem of these sources has brought many complications to distributed network operators to operate and control the complex or multi-microgrids with limited fast-ramping resources in order to maintain the power system flexibility. It led many researchers to find an alternative strategy since the conventional approaches are no longer adequate to handle the economic implications of operational decision making. At first, the brief review of various deterministic and probabilistic approaches, stochastic programming and robust optimisation strategies to address the uncertainty of variable energy resources are discussed. Furthermore, in the energy management point of view, the optimal scheduling problem of distributed sources of the microgrid is considered, and a brief review of optimisation models, advanced control strategies and demand response strategies to maximise economic benefits of microgrids are also elaborately presented. Finally, the multiagent-based distributed and decentralised control strategies for seamless integration of distributed generator units are reviewed under various configurations of the power grid along with communication network topologies.

The influence of grid connection of electric vehicles on microgrid and its coordinated control under the background of new energy power generation

To explore the influence of grid connected electric vehicle on microgrid and its collaborative control under the background of new energy power generation, in this study, the constraints of electric vehicle are established from two aspects of electric vehicle travel characteristics and battery charging and discharging characteristics. In view of the variety of controllable resources in microgrid, multi-agent microgrid coordination control architecture is used to control the multi-layer coordination of microgrid, and simulation is built to analyze four different scenes. The results show that in the microgrid load, it is found that the valley peak difference is the smallest when both the electric vehicle and the conventional load participate in the demand response (scene 4). In the change of SOC and charge discharge power of battery energy storage system, it is found that four scenes make the energy storage function of “low storage and high generation” play an effective role. In the economic and environmental benefits of microgrid daily operation, it is found that the daily operation cost and environmental benefits of scene 4 are significantly lower than that of scene 1. Therefore, in this study, the coordinated optimization method of integrating electric vehicle into microgrid based on multi-agent microgrid can effectively solve the coordinated optimization of multi controllable resources of microgrid, and provide experimental basis for the subsequent development and optimization of microgrid.

Integrating reliability and resilience to support the transition from passive distribution grids to islanding microgrids

Reliability and resilience are the main drivers for the transition of distribution networks from passive systems to active microgrids; as such, quantifying the potential benefits of microgrids in the design phase can support the transition of passive distribution networks into microgrids. To support this transition, this paper presents a mathematical optimization model which integrates techno-economic, resilience and reliability objectives. Storage and distributed generation are optionally installed to complement renewable generation, enabling the microgrid to supply priority demands during stochastic islanding events with uncertain duration. Islanding due to external events is combined with a detailed model of internal faults for comprehensive quantification and optimization of microgrid resilience and reliability. Minimizing the interruption costs yields optimal capacities and placements of distributed energy resources and new lines for reconfiguration. The proposed method produces microgrid designs with up to 95% reliability and resilience gain and moderate cost increase in two benchmark distribution networks using data from the United States Department of Energy. The developed methodology is scalable to large networks owing to the tailored Column-and-Constraint-Generation approach, reducing the computational time by 92% compared to state-of-the-art Benders decomposition for a 123 bus network.

Energy trading in microgrids for synergies among electricity, hydrogen and heat networks

The emerging paradigm of interconnected microgrids advocates energy trading or sharing among multiple microgrids. It helps make full use of the temporal availability of energy and diversity in operational costs when meeting various energy loads. However, energy trading might not completely absorb excess renewable energy. A multi-energy management framework including fuel cell vehicles, energy storage, combined heat and power system, and renewable energy is proposed, and the characteristics and scheduling arrangements of fuel cell vehicles are considered to further improve the local absorption of the renewable energy and enhance the economic benefits of microgrids. While intensive research has been conducted on energy scheduling and trading problem, a fundamental question still remains unanswered on microgrid economics. Namely, due to multi-energy coupling, stochastic renewable energy generation and demands, when and how a microgrid should schedule and trade energy with others, which maximizes its long-term benefit. This paper designs a joint energy scheduling and trading algorithm based on Lyapunov optimization and a double-auction mechanism. Its purpose is to determine the valuations of energy in the auction, optimally schedule energy distribution, and strategically purchase and sell energy with the current electricity prices. Simulations based on real data show that each individual microgrid, under the management of the proposed algorithm, can achieve a time-averaged profit that is arbitrarily close to an optimum value, while avoiding compromising its own comfort.

Climate change impact of integrating a solar microgrid system into the Swedish electricity grid

Microgrids are small-scale electricity networks that integrate distributed electricity generation with consumers and, potentially, with storage devices. There is growing interest in these systems, as they can offer solutions for electrification of remote areas, deployment of distributed renewable energy resources, and decarbonization of electricity supply. However, the potential benefits of microgrids in terms of climate change mitigation have not yet been thoroughly assessed. In this study, Life Cycle Assessment was performed to determine the climate change impact of integrating a solar microgrid system in western Sweden into the Swedish electricity grid. To determine whether replacement of grid electricity with electricity from the microgrid can lower greenhouse gas (GHG) emissions, average and marginal GHG emission factors (EFs) for electricity use were estimated with explicit spatial and temporal resolution, using historical data on electricity generation and trade, and life cycle EFs for electricity generation technologies. The assessment, with both marginal and average EFs, showed that integration of the microgrid into the Swedish electricity grid did not provide GHG emissions abatements, as the electricity from the microgrid displaced grid electricity with lower carbon intensity. It was found that a microgrid without batteries would have lower climate change impact, but would still fail to lower overall GHG emissions. Moreover, it was demonstrated that the methodological approach used for estimation of EFs and the definition of spatial boundaries could influence the obtained results.

Missing discourse on microgrids – The importance of transmission and distribution infrastructure

The current discourse on microgrids is mostly limited to enhancing resiliency and misses the importance of existing transmission and distribution (T&D) infrastructure. Using a conceptual framework and ten microgrid case studies, we illustrate that T&D infrastructure affects the anticipated benefits of microgrids. Currently microgrids are often constructed in lieu of T&D improvements. In the long run, microgrids can work with existing T&D infrastructure to improve the reliability, efficiency and environmental sustainability of the electrical grid.

Adaptive protection scheme for microgrids based on SOM clustering technique

Microgrids are penetrating into the power systems at an unprecedented rate. The reason is the mutual economic and environmental benefits of microgrids, both for power grid utility and the consumers. Some special features of microgrids such as, the two main operational conditions called, islanded and grid-connected modes, and being composed of various types of distributed energy resources along with different uncertainties cause some tough challenges to protection and control systems. From the protection aspect, the coordination of overcurrent relays protection will become a difficulty, due to the extensive changes in the fault current levels sensed by these devices. In this paper, a new adaptive protection coordination scheme based on Self-Organizing Map (SOM) clustering algorithm is proposed for digital overcurrent relays equipped with several setting groups. Considering the similarity of mis-coordinated relay pairs for the clustering purpose, the proposed protection scheme focuses on solving the mis-coordination between main/backup relay pairs. As a case study, a modified IEEE 33-bus test system is used as a microgrid. In the case study, a synchronous distributed generation and two electric vehicle charging stations are installed. The results suggest that not only the proposed method is fully capable and flexible to significantly improve the mis-coordination of overcurrent relay pairs, but it can also ameliorate the operating time of relay.

Day-Ahead Optimization Scheduling for Islanded Microgrid Considering Units Frequency Regulation Characteristics and Demand Response

With the increase of distributed generation penetration, the economic operation of microgrid has been fully developed. For islanded microgrid, due to the lack of large grid support and the limited capacity of the distributed generation (DG), the energy supply of microgrid may not meet the need of users in real time. Therefore, it is of great significance to solve the problem of insufficient power supply of islanded microgrid and improve the economy of its operation. Firstly, this paper analyses the frequency characteristics of DG, and establishes power models oriented to the frequency regulation characteristics of microgrid and introduces the mathematical model of DG. Then, an islanded microgrid day-ahead optimization scheduling model considering frequency regulation characteristics of units and demand response (DR) is proposed. The frequency characteristics of controllable units and DR are considered in the model, and different strategies are selected to analyze their impact on microgrid economy. The example shows that the optimization scheduling model of microgrid established in this paper can reduce the power supply pressure during peak load periods, alleviate the problem of insufficient power supply, and effectively improve the overall benefit of microgrid, which verifies the rationality of the model.

An Intelligent Adaptive Overcurrent Protection System for an Automated Microgrid in Islanded and Grid-Connected Operation Modes

As the penetration of distributed generation sources increases at the distribution level, the necessity of designing microgrids is highlighted. Microgrids can operate in either islanded (separated from the utility grid) or grid-connected mode. Apart from the technical and economic benefits of microgrids, they may cause some protection issues in distribution systems. The most important of these issues is the difference between the short circuit levels in islanded and grid-connected operation modes. In this paper, an intelligent overcurrent relay that can adapt to the microgrid operation mode is proposed; that is, the relay detects the microgrid operation mode by means of an adaptive algorithm. The proposed adaptive method optimizes the accuracy and speed of the algorithm for detecting the microgrid operation mode. Then, the optimal settings that have been already stored in the relay are activated according to the microgrid operation mode. All internal processes of the relay use the voltage and current sampled at the relay location. As a result, the relay can be used in all networks without communication infrastructures. Finally, the proposed method is implemented in a sample microgrid. The superiority of the intelligent relay performance over conventional overcurrent relays is shown by numerical results.

A REVIEW ON HYBRID AC/DC MICROGRIDS: OPTIMAL SIZING, STABILITY CONTROL AND ENERGY MANAGEMENT APPROACHES

Electricity is the greatest gift of science to humanity reached for civilization where electricity is used for all purposes. However, in recent times a paradigm shift is evolving in the generation of electrical energy from the concept of using major generating plants to minor generating units allied to the distribution systems in the form of microgrids with alternative energy sources called renewables. Around the world renewable energy use is on the rise and these alternate energy sources can generate pollution-free electrical energy to the society. Although these are new centers and units with diminishing cost, there are still many challenges in operation and control of islanded and grid-connected microgrids configured in both AC and DC. Uniting the benefits of microgrids of AC and DC, Hybrid AC-DC Microgrids (HACDC) were developed.Thus, it is relatively imperative to investigate the optimal size, stability control, and strategies of economic efficiency operation of HACDC microgrid. Hence a great review on optimal sizing methods, stability control, and energy management strategies using various iterative and intelligence techniques published in different articles proposed by many authors were presented in this paper.

Validating Simulation Analysis of Solar PV System Assessment for Residential Buildings using Homer Software

The local supply and supply scheme called micro grid will become a significant chance due to the latest development of small scale distributed generators such as OV on demand side. Renewable energy structure has been far reaching due to ecological demands. The essence of the structure for renewable energy is very efficient in using distributed generation within the structure of the power scheme. The low voltage DC distribution system is becoming essential as the amount of DC applications is increasing in our regular needs. Power provided through the AC distribution mechanism of low voltage requires both AC/DC converter to delivers the DC batteries. MGs would be fitted battery like energy storage devices. Since PVs and batteries primarily operates through DC, it is possible to emphasize the benefit of the DC distribution scheme over AC production. This article recommends an ideal MG layout including AC and DC distribution device choice. This article also describes qualitatively the benefit of micro grid with DC production, termed as DCMG through housing client studies assuming different kinds of home appliances.

Multi-objective optimal dispatching of microgrid based on improved genetic algorithm

Aiming at the optimization problem of micro-grid energy dispatch, the environmental benefit, system operation and maintenance cost, start-stop cost and main grid electricity price are proposed as the objective function, and the influence of the actual operation constraints of micro-grid system and the distributed non-scheduled new energy are taken into account at the same time. The multi-objective optimal dispatching model of microgrid is constructed, and the model is solved based on improved genetic algorithm. The numerical simulation results show that compared with the traditional single-target scheduling method of microgrid, the optimal scheduling method of this paper is beneficial to the micro-grid in the process of scheduling decision-making to achieve the overall coordination of economic, environmental and social benefits of microgrid.

Multiperiod Planning of Distribution Networks Under Competitive Electricity Market With Penetration of Several Microgrids Part II: Case Study and Numerical Analysis

This paper aims at investigating the effectiveness of the proposed model in Part I. For this, an IEEE 33-bus distribution system is selected, and the proposed algorithm is performed on it. Simulation results obtained from this system show that placing microgrids (MGs) in the distribution network has benefits for all participants; because the proposed model, in addition to considering the objectives of distribution system operator (DSO), finds the potential places to form MGs such that the obtained benefits of MGs are also provided for investments on establishing MGs at these places. The obtained results of this model are applicable for both DSO and MG investors.

Resilient design of large-scale distribution feeders with networked microgrids

Electrical distribution systems are often vulnerable to severe weather. Upgrades, such as microgrids, system hardening, and line redundancy, can greatly reduce the number of electrical outages during such extreme events. More recently, the networking of microgrids has received attention as a solution to further improve the resilience of distribution feeders. Although these upgrades have the potential to improve resilience, a barrier to their execution is a lack of tools and approaches that support systematic exploration of the underlying parameters of these upgrades and their cost vs. resilience tradeoffs.To address this gap, we develop a method for designing resilient distribution grids, including networked microgrids, by posing the problem as a two-stage stochastic program. When resilience is defined as the ability of a network to supply load immediately following a storm event, we show that a decomposition-based heuristic algorithm scales to a 1200-node distribution system. We also vary the study parameters, i.e., the cost of microgrids relative to system hardening and target resilience metrics. In this study, we find regions in this parametric space that correspond to different resilient distribution system architectures, such as individual microgrids, hardened networks, and a transition region that suggests the benefits of microgrids networked via hardened circuit segments.

Techno-economic Evaluation of Utilizing a Small-Scale Microgrid

Microgrid deployment has offered technical and economical benefits such as improving grid reliability, maximizing penetration of intermittent renewable energy sources, reducing the cost of energy production, etc. However, to realize those advantages, the costs of microgrid implementation may be bloated as microgrid need additional investment for the enabling technologies. Therefore, an appropriate approach to determine the economic viability of microgrid to quantify the values of microgrid benefits is needed. This study performs a techno-economic analysis of a small-scale grid-connected microgrid deployment which consists of photovoltaic (PV) and energy storage system. The analysis is done by considering the possible bussines models available in Indonesia where the microgrid test case is located, i.e, net metering for electricity bill, feed-in tariff for utilizing renewable energy, demand response (DR) implementation by exploiting battery roles in response of price variation during peak and off-peak period and assuming compensation is given every time microgrid is in islanded mode due to fault event occur in the main grid. The feasibility of each model is indicated by the microgrid’s net present value (NPV) and internal rate of return (IRR). The results show that further incentives from the utility or Government is required to make the small-scale microgrid deployment economically sustainable.

Robust Coordination of Distributed Generation and Price-Based Demand Response in Microgrids

Microgrid is an effective means to integrate distributed generation (DG) resource. However, uncertain renewable DG such as wind turbine and photovoltaic outputs and load demands can introduce tremendous difficulties for energy management in microgrids. To mitigate such difficulties, price-based demand response (PBDR) can adjust the loads to adapt to the renewables. On the other hand, dispatchable DG such as microturbines can coordinate with the PBDR to further manage the power balance and achieve economic benefits. In this paper, a two-stage robust microgrid coordination strategy is proposed: a PBDR is scheduled a day ahead and microturbine outputs are modified hourly. A two-stage robust optimization model is proposed to address the coordination problem with guaranteed robustness against the uncertainties of renewable DG and load demands. Simulation results show PBDR and multiple DG units can coordinate effectively to accommodate the renewable and demand uncertainties while maximizing the microgrid benefits.

A stochastic optimal power flow for scheduling flexible resources in microgrids operation

Microgrid operations are challenging due to variability in loads and renewable energy generation. Advanced tools capable of taking uncertainty into account are essential to maximize microgrid benefits when operating microgrid owned DERs. This paper proposes a novel optimization model for day-ahead economic dispatch of flexible resources within a microgrid environment, considering uncertainty of PV and loads.This model is conceived to support the microgrid supervisory control layer, providing a security-constrained day-ahead strategy to operate three types of microgrid flexible resources: PV, electric storage and controllable loads. The work presented in this paper introduces a novelty in microgrid operations by presenting a stochastic version of the day ahead scheduling of microgrid DERs to deal with uncertainties associated with PV, load and temperature while considering microgrid network limits and end-user comfort as optimization constraints. An annual analysis quantifies the benefits of to the microgrid-owner of a stochastic formulation over a deterministic one both in terms of ensuring end-user comfort and decreasing operation costs.

Robust multi-objective optimization for energy production scheduling in microgrids

ABSTRACTIn order to achieve better economic and environmental benefits of microgrids (MGs) under multiple uncertainties in renewable energy resources and loads, a novel energy production scheduling method is proposed based on robust multi-objective optimization with minimax criterion. Firstly, a mixed integer minimax multi-objective formulation is developed to capture uncertainties as well as minimize economic and environmental objectives. Secondly, the primal problem is decomposed into a bi-level optimization problem, which attempts to seek robust scheduling scheme set under the worst-case realization of uncertainties in a multi-objective framework. Finally, a hierarchical meta-heuristic solution strategy, including multi-objective cross entropy algorithm and δ+ indicator, is designed to solve the reconstructed problem. Numerical results demonstrate that the proposed scheduling method can effectively attenuate the disturbance of uncertainties as well as reduce energy costs and emissions, as compared with single-objective robust optimization and multi-objective optimization scheduling approaches. This study could offer useful insights which help decision-makers balance robustness and comprehensive benefits in the operation of MGs.

Multi-agent Cooperative Operation Model and Profit Allocation of PV-based Microgrid

The new electric power reform scheme allows the users of distributed generation or microgrid systems to participate in electricity trade, which is beneficial to the improvement of economic benefits of microgrid. Generally, microgrid is composed of several economic members, including photovoltaic operators, storage operators, users and so on. Based on the analysis on the impetus of operation consortia, market transaction mode and their cooperative game model among the economic members in microgrid are proposed. The time-sharing scheduling model of PV-based microgrid decides the operation status of members to maximize the benefits of the whole alliance, and the revenue of each member in the alliance is allocated by the Shapley Value method. As can be seen, the revenue of photovoltaic operators, storage operators and users are increased in cooperation mode with the increase of the considerable revenue of alliance, and achieve the parties’ mutual balance. Besides, the computational complexity is relatively low, which contributes to the large-scale development of PV-based microgrid.