Distributed Energy Resource Systems Research Articles

Fault tolerant control of electronically coupled distributed energy resources in microgrid systems

This paper proposes a sensor fault tolerant control (FTC) strategy for electronically-coupled distributed energy resource (DER) units in grid-connected microgrid systems. First, a fault dependent dynamical model of the DER unit incorporating sensor faults is proposed. The FTC strategy is then developed using a sliding mode observer (SMO) which has an inherent robustness property. The rational for using a SMO is the need to detect and reconstruct any fault that may occur in output measurements of the system as a result of sensor failure. The fault signals are reconstructed by using a robust approach that encompasses uncertainties in the system, such as frequency variation. This paper also represents the cyber attack as an unknown sensor fault, and consequently the DER current sensor measurements manipulated by a data integrity attack can be detected and reconstructed. The reconstructed fault signals are then used to modify the faulty sensor measurements, which are fed to the voltage source converter (VSC) controller. This ensures accurate generation of pulse width modulation (PWM) signals and consequently accurate tracking of real and reactive power references. Different case studies are tested on a detailed nonlinear model of the DER system. The impact of faults on the DER performance and the effectiveness of the proposed FTC scheme are evaluated through extensive simulation studies. Experimental verification of the method is provided to further validate the proposed approach.

Stochastic dominant-subordinate-interactive scheduling optimization for interconnected microgrids with considering wind-photovoltaic-based distributed generations under uncertainty

This study develops a dominant-subordinate-interactive stochastic programming (DSISP) model for the wind-photovoltaic-based distributed energy resource systems in Lize Financial Business District of Beijing, China. During the synergistic optimization process with 24-h prediction outputs of solar and wind power as constraints, the dominant level puts more emphasis on renewable energy utilization, while the minimization both of pollutant emissions and system cost are modeled as a multi-objective programming (MOP) problem placed at the subordinate level. Results indicate that: (a) renewable energy technologies would exert an increasing paramount role in power systems, with an average share of 15.54% through a whole year; (b) a higher violation risk would lead to a decreased strictness of the constraints for facility capacity availabilities, and then to a higher system cost, more green electricity generation, and lower non-renewable electricity generation. As a consequence, thermal supplies especially in winner days would depend strongly on gas-fired boiler, which would result in more pollutant emissions as a violation risk increases. Moreover, the performance of the DSISP model is enhanced by comparing with three single-objective programs and the MOP approach. Results demonstrate that the DSISP model can provide much comprehensive and systematic strategies as considering the bi-level structure within the systems.

Fractional-Order Sliding-Mode Control of Islanded Distributed Energy Resource Systems

This paper proposes a voltage control strategy for islanded operation of dispatchable electronically coupled distributed energy resource (DER) systems, for remote (off grid) electrification systems. The proposed control strategy is based on fractional-order sliding-mode control, offers black-start functionality, maintains the quality of the output voltage of the host DER system in spite of unbalanced and/or distorted load currents, and ensures protection of the power-electronic interface to external faults. Moreover, the fractional derivative order of the controller can be used as an additional tuning parameter. Performance of the proposed control strategy is demonstrated through time-domain simulation of single- and multi-DER islanded networks, starting from black-start and subjected to various operating scenario, and it is also compared to the performance of a proportional-integral (PI)-based control strategy.

Optimal design of distributed energy resource systems based on two-stage stochastic programming

Multiple uncertainties exist in the optimal design of distributed energy resource (DER) systems. The expected energy, economic, and environmental benefits may not be achieved and a deficit in energy supply may occur if the uncertainties are not handled properly. This study focuses on the optimal design of DER systems with consideration of the uncertainties. A two-stage stochastic programming model is built in consideration of the discreteness of equipment capacities, equipment partial load operation and output bounds as well as of the influence of ambient temperature on gas turbine performance. The stochastic model is then transformed into its deterministic equivalent and solved. For an illustrative example, the model is applied to a hospital in Lianyungang, China. Comparative studies are performed to evaluate the effect of the uncertainties in load demands, energy prices, and renewable energy intensity separately and simultaneously on the system’s economy and optimal design. Results show that the uncertainties in load demands have a significant effect on the optimal system design, whereas the uncertainties in energy prices and renewable energy intensity have almost no effect. Results regarding economy show that it is obviously overestimated if the system is designed without considering the uncertainties.

Optimal planning and operation of aggregated distributed energy resources with market participation

This paper analyzes the optimal planning and operation of aggregated distributed energy resources (DER) with participation in the electricity market. Aggregators manage their portfolio of resources in order to obtain the maximum benefit from the grid, while participating in the day-ahead wholesale electricity market. The goal of this paper is to propose a model for aggregated DER systems planning, considering its participation in the electricity market and its impact on the market price. The results are the optimal planning and management of DER systems, and the appropriate energy transactions for the aggregator in the wholesale day-ahead market according to the size of its aggregated resources. A price-maker approach based on representing the market competitors with residual demand curves is followed, and the impact on the price is assessed to help in the decision of using price-maker or price-taker approaches depending on the size of the aggregated resources. A deterministic programming problem with two case studies (the average scenario and the most likely scenario from the stochastic ones), and a stochastic one with a case study to account for the market uncertainty are described. For both models, market scenarios have been built from historical data of the Spanish system.The results suggest that when the aggregated resources have enough size to follow a price-maker approach and the uncertainty of the markets is considered in the planning process, the DER systems can achieve up to 50% extra economic benefits, depending on the market share, compared with a non-aggregated business-as-usual approach (not implementing DER systems).

Coordinated online voltage management of distributed generation using network partitioning

Due to the increasing penetration level of renewable energy resources in distribution systems, a new approach for voltage and reactive power control needs to be developed to deal with the fluctuations caused by intermittent changes of these resources. This paper, at first proposes a systematic approach which splits distribution networks into several separate control areas to control the voltage profile of each area in an admissible time calculation which is necessary for online operation. Then to solve the voltage regulation problem, a new method based on particle swarm optimization (PSO) algorithm is proposed to be applied to each center using only zonal data and also to calculate the optimum reactive power set points of the distributed generations (DG) units in the related area. Finally, the results of the proposed method on IEEE 123-bus unbalanced test system in comparison with another method based on interior point algorithm in both decentralized and centralized manner demonstrate the ability and efficiency of the proposed method for online control of smart grids voltage profile.

Economic and environmental optimization for distributed energy resource systems coupled with district energy networks

This study aims to optimize DER (distributed energy resource) system with respect to economic and environmental objectives. In particular, we developed a mixed-integer linear programming model with multiple objectives at a neighbourhood level containing residential and office buildings. The equipment and layout of the district energy (power, heating, and cooling) networks were selected from several potential energy devices and paths using a mathematical model. The objectives of the model were to minimize the total annual cost and CO2 (carbon dioxide) emission and achieve the optimal design and operation to meet the yearly energy demands. Moreover, the economic and environmental benefits under different weights of the objective function were evaluated by sensitivity analysis. The results show that at a neighbourhood level, the DER system has significant environmental and economic benefits. The system could spontaneously select the most appropriate operation strategy using the developed mathematical model. In multiobjective scenarios, with the increase in the weight of environmental factor, the emission decreases and the cost increases gradually. When considering a single objective, the minimization of cost or carbon emission leads to a poor cost performance.

A Review of Technologies and Evaluation Softwares for Distributed Energy Source System

This study reviews the technologies and evaluation softwares for the Distributed Energy Resource System (DERs), which is considered as a realistic and economical way to realize the clean utilization of energy. For the the technologies of DERs, there summarizes the characteristics and global development of CHP (Combined Heat and Power), renewable generation, energy storage and cell fuels. In addition, this study sums up 15 kinds of softwares for evaluating DERs from the aspects of their developers, application scope, properties and so on. The results in this study provide the necessary information for the technologies and evaluation softwares for designing and optimization of DERs.

Distributed energy systems integration and demand optimization for autonomous operations and electric grid transactions

Distributed power systems in the U.S. and globally are evolving to provide reliable and clean energy to consumers. In California, existing regulations require significant increases in renewable generation, as well as identification of customer-side Distributed Energy Resources (DER) controls, communication technologies, and standards for interconnection with the electric grid systems. As DER deployment expands, customer-side DER control and optimization will be critical for system flexibility and demand response (DR) participation, which improves the economic viability of DER systems. Current DER systems integration and communication challenges include leveraging the existing DER and DR technology and systems infrastructure, and enabling optimized cost, energy and carbon choices for customers to deploy interoperable grid transactions and renewable energy systems at scale.This paper presents a cost-effective solution to these challenges by exploring communication technologies and information models for DER system integration and interoperability. This system uses open standards and optimization models for resource planning based on dynamic-pricing notifications and autonomous operations within various domains of the smart grid energy system. It identifies architectures and customer engagement strategies in dynamic DR pricing transactions to generate feedback information models for load flexibility, load profiles, and participation schedules. The models are tested at a real site in California—Fort Hunter Liggett (FHL). The results for FHL show that the model fits within the existing and new DR business models and networked systems for transactive energy concepts. Integrated energy systems, communication networks, and modeling tools that coordinate supply-side networks and DER will enable electric grid system operators to use DER for grid transactions in an integrated system.

Technical grid connection guides for distributed electricity generation systems: a new DERlab database has come alive

The increasing share of distributed energy resources (DER) in electricity production requires new sources and techniques in grid support services to keep the quality and reliability of power supply high. Addressing this matter, DER systems are required to follow technical grid connection requirements determined by distribution system operators (DSOs). Currently, these requirements widely differ from country to country. Recent studies suggest developing unified grid connection requirements for DER on the international level. This unification currently is the main activity for DSOs and standardisation organisations in the field of grid-connected DER. To support this activity, the present article (i) offers a status report on recent studies relevant to the harmonisation of DER grid connection requirements, and (ii) identifies and discusses current DER grid connection guides, namely standards of international and European standardisation organisations, as well as regulations of national DSOs from Austria, Germany, Ireland, Latvia, Switzerland (German-speaking part) and the United Kingdom. The guides are collected and grouped according to the technical area and technology in a database: http://dergridrequirements.net. The database is a tool for finding relevant DER grid connection guides for a specific region, technical area and/or technology. The target audience of the database is DER system developers.

Design and implementation of communication architecture in a distributed energy resource system using IEC 61850 standard

A distributed energy resource (DER) system uses renewable generation and energy storage to provide power and ancillary services directly to users in the distribution system, and benefits the power grid by offering a solution to the energy crisis and mitigating the waste pollution to the environment. A key challenge in implementing a DER system is how to ensure the standardization of its communication network. The goal of this paper is to study and propose a common approach to standardize the communication network in the DER system using IEC 61850 and includes a design and implementation of the communication architecture. Two prototypical testbeds for the DER system have been developed in the SMERC laboratory and at KIER, with the aim to demonstrate a case study using the proposed approach. The testbeds contain various DERs such as photovoltaics, energy management systems, and electric vehicles. The procedure of integrating the IEC 61850 standard includes the system architecture configuration, data set design, test file write-up, and deployment of the gateway/client for communication. In the data set design, the specification of logical nodes, data object names, data attributes and common data classes are explained in detail. The research results and data collected from the current testbeds indicate a quality integration of the IEC 61850 standard with stable power flow and unified communication architecture in the DER system. Copyright © 2015 John Wiley & Sons, Ltd.

An MILP (mixed integer linear programming) model for optimal design of district-scale distributed energy resource systems

This study focuses on the optimal design of district-scale DER (distributed energy resource) systems in which energy is produced outside energy-consuming buildings and sent to the buildings through the energy distribution networks. A MILP (mixed integer linear programming) model is constructed. The model can achieve simultaneous optimization of locations (i.e., site for energy generation), synthesis (i.e., type, capacity, and number of equipment as well as structure of the energy distribution networks), and operation strategies of the entire system. The model is built in consideration of discreteness of equipment capacities, equipment partial load operation and output bounds as well as the influence of ambient temperature on gas turbine performance. The objective function is the total annual cost for investing, maintaining, and operating the system. The model is applied to an urban area in Guangzhou (China), and its validity and effectiveness is verified. Results show that the adoption of the proposed DER system provides significant economic benefits in respect to the conventional energy system.

Optimal distributed energy resources and the cost of reduced greenhouse gas emissions in a large retail shopping centre

Abstract This paper presents a case study on optimal options for distributed energy resource (DER) technologies to reduce greenhouse gas emissions in a large retail shopping centre located in Sydney, Australia. Large retail shopping centres take the largest share of energy consumed by all commercial buildings, and present a strong case for adoption of DER technologies to reduce energy costs and emissions. However, the complexity of optimally designing and operating DER systems has hindered their widespread adoption in practice. This paper examines and demonstrates the value of DER in reducing the carbon footprint of the shopping centre by formulating and solving a multiobjective optimisation problem using the Distributed Energy Resources Customer Adoption Model (DER-CAM) tool. An economic model of the shopping centre is developed in DER-CAM using on-site-specific demand, tariffs, and performance data for each DER technology option available. Four key optimal DER technology investment scenarios are then analysed by comparing: (1) solution trade-offs of costs and emissions, (2) the cost of reduced emissions attained in each investment scenario, and (3) investment benefits with respect to the business-as-usual scenario. The analysis shows that a moderate investment in combined cooling, heat and power (CCHP) technology alone can reduce annual energy costs by 8.5% and carbon dioxide-equivalent emissions by 29.6%. A larger investment in CCHP technology, in conjunction with on-site solar photovoltaic (PV) generation, can deliver nearly 72% reductions in emissions at a 47% increase in total energy costs. The study demonstrates the effectiveness and flexibility of this type of modelling approach for the analysis, design, and ongoing assessment of new DER technologies under changing market conditions, supporting a more robust adoption of DER technologies in the commercial building sector.

Optimal design of distributed energy resource systems coupled with energy distribution networks

This study focuses on the optimal design of DER (distributed energy resource) systems coupled with heating, cooling, and power distribution networks. A superstructure-based MILP (mixed integer linear programming) model is constructed. The model can achieve simultaneous optimization of synthesis (i.e., type, capacity, number, and location of equipment as well as structure of the energy distribution networks) and operation strategies of the entire system. The model is built in consideration of discreteness of equipment capacities, equipment partial load operation and output bounds as well as the influence of ambient temperature on gas turbine performance. The objective function is the annual total cost for investing, maintaining, and operating the system. To provide an illustrative example, the model is applied to an urban area in Guangzhou, China. Comparative studies are performed to quantify the impact of distributed generation and the introduction of energy distribution networks and/or storages. Results show that the adoption of the DER system provides significant economic benefits. The introduction of energy distribution networks and/or storages has significant and similar effects on optimal system configuration and can improve the system's economic efficiency because of the elimination of some of the strong coupling relation between demands and generators.

Economic, Climate Change, and Air Quality Analysis of Distributed Energy Resource Systems

Abstract This paper presents an optimisation model and cost-benefit analysis framework for the quantification of the economic, climate change, and air quality impacts of the installation of a distributed energy resource system in the area surrounding Paddington train station in London, England. A mixed integer linear programming model, called the Distributed Energy Network Optimisation (DENO) model, is employed to design the optimal energy system for the district. DENO is then integrated into a cost-benefit analysis framework that determines the resulting monetised climate change and air quality impacts of the optimal energy systems for different technology scenarios in order to determine their overall economic and environmental impacts.

Optimum Siting and Sizing of Distributed Energy Resources Taking into Consideration Hourly Operating Strategies

In this paper, a distributed energy resource (DER) system plan and evaluation model is extended to include the design of district heating network. In the model, production and consumption of electric power and heat, power transmissions, transport of fuels to the production plants, transport of water in the district heating pipelines and storage of heat are taken into account. The problem is formulated as a mixed integer linear programming (MILP) model where the objective is to minimize the overall cost of the DER system. The solution gives the DER structure, i.e., which production units, heat transport lines and storages should be built as well as their locations, together with design parameters for plants and pipelines.

Virtual Power Plant. Environmental Technology Management Tools of The Settlement Processes

The Distributed Energy Resource (DER) systems represent a possible option for the implementation of the Low Carbon Cities development scenario, consistently with EU orientations. Many surveys, especially of engineering and information technology origin, are contributing to DER systems spread through testing the Virtual Power Plan (VVP): a technological system aimed at synchronously managing the information and energy fluxes, and able to have an effect on the urban metabolism balance and on the energy chain organizational model. In the event of a wider VVP spread, consequences for the urban structure social and technical conversion process might be envisioned. Such systems gain importance in terms of starting urban renewal processes, introducing new rules for the local energy and environmental infrastructures. In this way, it is envisioned the need for a deeper comprehension of the VVP innovative functionalities, this comprehension being significant for all the branches of knowledge which are interested in developing methods and tools for the Environmental Technology Management and Planning of the settlement processes. The author, who is interested in producing and organizing an energy, distributed, renewable and interactive model, shows, through a critical analysis of the Electricity Networks Europe program study cases, the operating potential of the new system, emphasizing the consequences on the settlement process development, thus providing a first definition of the strategic features for the VVP technical and social implementation.

Multi-objective operation optimization and evaluation of large-scale NG distributed energy system driven by gas-steam combined cycle in China

• A multi-objective operation optimization model for large-scale DER system is built. • We evaluate performances of three optimization modes under different daily periods. • VOC and joint optimization modes perform best in flat and peak periods, respectively. • PER of three optimization modes increase with the rising of absorption chiller COP. • NPV decreases quickly and DPP increases fast with the increase of NG price. Many pilot projects of large-scale distributed energy resources (DER) system have been constructed recent years in China and operation strategies make a great impact on their benefits and further development. This paper presents a multi-objective (joint) optimization model for the large-scale DER system of Guangzhou Higher Education Mega Center to obtain the optimal operation strategies under different daily periods: peak periods, flat periods, and valley periods. The prime mover used in this investigation is a gas-steam combined cycle based on combined gas turbines and steam turbines, and the DER system is evaluated under three different operation optimization modes: joint optimization mode of variable operational cost (VOC) and primary energy rate (PER), VOC optimization mode, and PER optimization mode. The primary energy consumption (PEC), PER, operational costs, and investment benefits of the DER system under different operation strategies of above three optimization modes are evaluated comparing with the buildings using conventional technologies. Results indicate that the VOC optimization mode provides the best combined cooling, heating, and power (CCHP) performance during flat periods by yielding the lowest PEC (133.78 kton/year) and operational cost (million $ 35.98/year), and the joint optimization mode shows the best performance during peak periods by producing the lowest PEC (80.42 kton/year) and similar low operational costs (million $ 21.74/year) to VOC optimization mode (million $ 20.89/year).

PSO Based Fuzzy Stochastic Long-Term Model for Deployment of Distributed Energy Resources in Distribution Systems With Several Objectives

This paper presents a particle swarm optimization (PSO) based fuzzy stochastic long term approach for determining optimum location and size of distributed energy resources (DERs). The Monte Carlo simulation method is used to model the uncertainties associated with long-term load forecasting. A proper combination of several objectives is considered in the objective function. Reduction of loss and power purchased from the electricity market, loss reduction in peak load level, and reduction in voltage deviation are simultaneously considered as the objective functions. At first these objectives are fuzzified and designed to be comparable with each other, then they are introduced to a PSO algorithm in order to obtain the solution which maximizes the value of integrated objective function. The output power of DERs is scheduled for each load level. An enhanced economic model is also proposed to justify investment on DER. IEEE 30-bus radial distribution test system is used as an illustrative example to show the effectiveness of the proposed method.

Installed capacity optimization of distributed energy resource systems for residential buildings

Our work aims to reduce residential energy consumption and expense by presenting a methodology for integrating electricity and hot water supply, and determining the optimum installed capacities of the selected distributed energy resource systems, which consist of a photovoltaic system, a solar water heating system and a fuel cell system. Initially, we build the dynamic model respectively for every individual system on the basis of their respective working principles. Then we propose operation strategies of electric power and hot water separately for the integration of the models. Followed, we apply a genetic algorithm to optimize the installed capacities of the systems, aiming at reducing the conventional energy consumption and the life cycle costs. With a complete database, the integration and optimization methodology are finally applied to a typical building located in Fukuoka City in Japan. It is shown by the computer simulation that the methodology which we propose can help to reduce considerable quantity of residential energy consumption and expense.