Different Distributed Energy Resources Research Articles

Integrated Passive Anti-Islanding Protection in Micro Grid

In last two decades due to major interest amongst power system engineers and policy makers penetration of different distributed energy resources (DREs) into power distribution network are significantly increased. Integration of DREs with conventional power grid is a complex issue and will impose some challenges against power engineers. The major challenge is protection of micro grid, which is based on how your protection strategies distinguish islanding and non islanding conditions correctly and timely. Methods used for have strengths and limitations in the areas like speed, accuracy, power quality and Non detection islanding zone. The prime motive of this research is to presents an efficient new integrated anti-islanding protection strategy using passive parameters. The proposed algorithm having a novel islanding detection technique, which discriminate the islanding events from the non islanding events of similar signature accurately with minimum non detection zone and minimum impact on power quality. The proposed strategy is the combination of different conventional and latest passive relays based on single and multiple parameters. Integration of different relays made in such a strategic way that it combines the strengths and benefits of each method and minimizes their limitations. The presented algorithm tested under MATLAB/SIMULINK environment in different network conditions. Finally, the efficiency of the algorithm has checked by testing it on standard microgrid structure. The results received from simulation confirmed that algorithm is detecting islanding conditions reliably and efficiently, followed by generation of trip/block signal correctly.

Design of an intelligent hybrid diagnosis scheme for cyber-physical PV systems at the microgrid level

With focusing on solar photovoltaic (PV) systems operating at microgrid (MG) level, this study investigates the impacts of different physical faults and cyberattacks as well as designing an intelligent faults/attacks detection and diagnosis system. The ability to quickly identify and diagnose faults/attacks enables local controllers and energy management system to accommodate or mitigate the negative effects of physical faults or cyberattacks in a MG. This allows the MG to carry on operating without experiencing any significant interruptions. In this regard, the current paper investigates a hybrid AC/DC MG made up of different distributed energy resources (DER), including solar PV arrays, wind turbines, and battery energy storage systems. An intelligent hybrid diagnosis (IHD) scheme is introduced for online monitoring and diagnosing the data to reflect the real-time status of the PV system operating at the MG level. This hybrid system uses three parallel units, including a “fuzzy inference system (i.e., a rule-based unit)”, a “power spectrum estimator (i.e., a signal-based unit)”, and an “adaptive neuro-fuzzy inference system (i.e., a model-based unit)”. A realistic MG benchmark model with a wide range of operating conditions and dynamic electrical loads in the presence of potential MG disturbances is used to demonstrate the high performance and resilience of the proposed IHD scheme under various types of faults/attacks scenarios.

AGGREGATION PRICE MODELS FOR MICROGRIDS WITH DISTRIBUTED ENERGY RESOURCES

The development of Microgrid states the problem of choosing the optimal technologies for its composition.This paper is to present cost based demand-side management methods for the Microgrids with DistributedGeneration sources to optimize their operation. While implementing variable pricing models the aggregatorshould take into account characteristics of different Distributed Energy Resources (DER) (diesel engines, gasturbines, fuel cells, solar panels, small hydropower plants and wind turbines) and LCOE for each type of DER tostimulate each local electricity market participant separately. The system Microgrid using three diesel generatorsand the option of replacing one generator with a solar electric and wind generator installation was considered.

IoT-Based Mobile Energy Storage Operation in Multi-MG Power Distribution Systems to Enhance System Resiliency

Multi-microgrids have gained interest in academics and industry in recent years. Multi-microgrid (MG) allows the integration of different distributed energy resources (DERs), including intermittent renewables and controllable local generators, and provides a more flexible, reliable, and efficient power grid. This research formulates and proposes a solution for finding optimal location and operation of mobile energy storage (MES) in multi-MG power distribution systems (PDS) with different resources during extreme events to maximize system resiliency. For this purpose, a multi-stage event-based system resiliency index is defined and the impact of the Internet of things (IoT) application in MES operation in multi-MG systems is investigated. Moreover, the demand and price uncertainty impact on multi-MG operational performance indices is presented. This research uses a popular PG & E 69-bus multi-MG power distribution network for simulation and case studies. A new hybrid PSO-TS optimization algorithm is constructed for the simulations to better understand the contributions of MES units and different DERs and IoT on the operational aspects of a multi-MG system. The results obtained from the simulations illustrate that optimal operation of MES and other energy resources, along with the corresponding energy sharing strategies, significantly improves the distribution system operational performance.

Communication Constraints for Distributed Secondary Control of Heterogeneous Microgrids: A Survey

Heterogeneous microgrids provide a promising solution for accommodating different distributed energy resources (DERs) and enhancing the system performance in terms of reliability, resilience, flexibility, and energy efficiency. With the penetration of microgrids, the cyber-enabled distributed control techniques are playing an increasingly important role in microgrids for coordinating a multitude of heterogeneous and spatially distributed DERs. To identify the influence of communication constraints on the reliability and stability operation of heterogeneous microgrids, this survey presents a comprehensive review and comparison of cyber-enabled distributed control techniques for microgrid's secondary control layer. Local controls of an unavailable state signal are calculated in a distributed and cooperative matter according to merely invoked cyber messages. Then, the recent developments in the communication constraints of distributed controlled microgrids are discussed. Specifically, the communication constraints (e.g., time-varying network topology, communication delay, noise disturbance, limited communication bandwidth, uncertainties of communication links, and cyber attacks) on the operation of the distributed controllers and the possible challenges are presented and compared. Finally, a short discussion section is contained to summarize the existing research and suggest some interesting research directions along with several open issues that are critical to further exploring the promising research area.

An online tripping index to improve microgrid dynamic stability based on estimating critical boundary area

This paper presents an online index for adaptive protection of microgrids concerning the low inertia concept. A three-step approach is developed to consider two offline and online environments, and the proposed scheme is designed. In Step - 1 , a comprehensive study of the microgrid dynamical model is investigated through two different distributed energy resources (DERs), including generator-based and inverter-based resources. In this step, based on the low-inertia concept, a dynamical model of an adaptive protection scheme is proposed through a set of non-model-based indexes. In Step-2 , considering online evaluations of produced indexes, two different equations are provided in the form activation point and triggering point which the corresponding adaptive protective zones are provided. In this step, considering different operational and topological points of microgrid, the protective abilities of proposed indexes are validated and reorganized. Finally Step-3 concentrates on the ability of the proposed defensive scheme in real-time operating mode. In this step, considering different fault scenarios, the accuracy estimation and fast detection of the developed protection scheme are investigated, and the microgrid dynamic security is evaluated. Results present the effectuality of the proposed scheme to fast and secure detection of unstable scenarios using adaptive non-model-based signals concerning different system structures.

Solutions to Increase PV Hosting Capacity and Provision of Services from Flexible Energy Resources

Future smart grids will be more dynamic with many variabilities related to generation, inertia, and topology changes. Therefore, more flexibility in form of several active and reactive power related technical services from different distributed energy resources (DER) will be needed for local (distribution network) and whole system (transmission network) needs. However, traditional distribution network operation and control principles are limiting the Photovoltaic (PV) hosting capacity of LV networks and the DER capability to provide system-wide technical services in certain situations. New active and adaptive control principles are needed in order to overcome these limitations. This paper studies and proposes solutions for adaptive settings and management schemes to increase PV hosting capacity and improve provision of frequency support related services by flexible energy resources. The studies show that unwanted interactions between different DER units and their control functions can be avoided with the proposed adaptive control methods. Simultaneously, also better distribution network PV hosting capacity and flexibility services provision from DER units even during very low load situations can be achieved.

Controlled Impedance-Admittance-Torque Nonlinear Modeling and Analysis of Modern Power Systems

Modern power systems are continuously transformed into decentralized ones where distributed generation (DG) plays a key role. Almost all the different distributed energy resources (DERs) are connected in geographically dispersed places through controlled power electronic interfaces in a manner that essentially affects the dynamic performance and control of the whole power system. Simultaneously, rotating machines in power production or absorption, dominate the system response and stability. In this new frame, this paper proposes a novel generalized dynamic representation and full scale modeling of a modern power system based on the well-known impedance-admittance (IA) network model for the electricity grid, substantially extended to include in detail both the power converter devices by considering the controlled power electronic dynamics and the electrical machines by inserting their full electromechanical dynamics. This formulation results in a holistic nonlinear dynamic description, defined here as controlled impedance-admittance-torque (CIAT) model of the whole system which features common structural characteristics. The model is deployed in state space, involves all the controlled inputs in DG, namely the duty-ratio signals of each power converter interface, all the other external inputs affecting the system, namely all the known or unknown voltage, current, and torque inputs. As shown in the paper, the proposed CIAT model retains its fundamental properties for any DG and network topology, standard or varying. This enables the compression of the accurate analytic power system dynamic description into a matrix-based generic nonlinear model that can be easily used for analysis studies of such large-scale systems. Taking into account the nonlinear nature of the CIAT matrix-based model and the persistent action of the external inputs, Lyapunov methods deployed on recently established input to state stability (ISS) notions are systematically applied for the system analysis. Hence, the traditionally used small-signal model-based analysis that suffers from the intermittent and continuously changing operation of DERs is completely substituted by the proposed formulation. A modern power system example with different DERs involved is analyzed by this way and is extensively simulated to verify the validity of the proposed method.

Hybrid PSO-TS Based Distribution System Expansion Planning for System Performance Improvement Considering Energy Management

Energy management (EM) has become very attractive in smart grid era for both industry and academia. EM in a power distribution system (PDS) can reduce the system losses, operational costs and emissions, and increases system’s reliability, voltage stability and efficiency. This article expands the PDS using different distributed energy resources (DERs) and observes their impacts on EM success, operational costs, system losses, and emissions. Moreover, the impacts of integrating reactive sources (RSs), energy storage systems (ESSs), and electric vehicles (EVs) on the system’s operational performance is investigated. An index is defined to measure the energy management success rate (EMSR) and several case studies are created for investigating variety of system expansion options individually and collectively. Furthermore, a new reliability index, namely reliability index success rate (RISR), is defined and sensitivity analysis are presented to investigate the DERs impacts on system’s voltage controllability and the defined reliability index. A new hybrid PSO-TS optimization algorithm is developed, and the well-known PG&E 69-bus distribution network is selected for the simulations. Several case studies presented in the paper provide a clear understanding of the impacts of integrating different resources on the EM as well as other operational aspects of a PDS. The results reveal that the system expansion using DERs with different capacities along with EM strategies could have significant impacts on PDS performance depending on the DERs types’ and capacities. Due to their availability and low operational costs, gas turbine further improves the performance indices comparing to the renewables that have uncertain availability and to diesel generators with their high operational costs.

Optimal Planning and Operational Management of Open-Market Community Microgrids

In this article, a new business model comprising multiple stakeholders is proposed to develop a frame for future flexible retail energy market in community microgrids. The microgrid comprises multiple and different distributed energy resources (DERs) such as renewable generation units, battery energy storage systems (BESSs), and micro diesel engines (MDE), to minimize daily operational costs of the system. To solve the defined complex optimization model, some operational strategies are proposed and then genetic algorithm is adopted to determine the hourly optimal power dispatch. The case study shows that the proposed model minimizes the daily operating cost of the community system effectively.

Optimal integration of DERs in coordination with existing VRs in distribution networks

Voltage regulation (VR) and energy loss minimisation have always been major concerns for distribution network (DN) operators, thereby many conventional VR schemes are dedicatedly employed in existing DNs. In this study, optimal integration of different distributed energy resources (DERs) is investigated in coordination with existing VR scheme, i.e. on-load tap-changer. To show the superiority of the proposed DER integration model, optimal allocations of different DERs are determined with and without considering the coordinated effect of existing VR schemes for annual energy loss minimisation under different scenarios. To solve this complex optimisation problem, the improved genetic algorithm (GA) is adopted. A dynamic node priority list (DNPL) is suggested to further improve the performance of GA. To validate the proposed strategy and DNPL, the DER integration problem is solved for benchmark 33-bus and real-life 108-bus Indian radial distribution systems. The simulation results are found to be inspiring when compared with the existing optimisation techniques and DER integration models without considering VR schemes.

Multi-temporal Optimal Power Flow for voltage control in MV networks using Distributed Energy Resources

Large-scale integration of variable Renewable Energy Sources (RES) brings significant challenges to grid operation that require new approaches and tools for distribution system management, particularly concerning voltage control. Therefore, an innovative approach for voltage control at the MV level is presented. It is based on a preventive day-ahead analysis that uses data from load/RES forecasting tools to establish a plan for operation of the different Distributed Energy Resources (DER) for the next day. The approach is formulated as a multi-temporal Optimal Power Flow (OPF) solved by a meta-heuristic, used to tackle complex multi-dimensional problems. The tuning of the meta-heuristic parameters was performed to ensure the robustness of the proposed approach and enhance the performance of the algorithm. It was tested through simulation in a large scale test network with good results.

Hierarchical energy management mechanisms for an electricity market with microgrids

This study addresses a micro-grid electricity market (MGEM) with day-ahead (DA) and real-time market mechanisms integrated. The bidding mechanisms for the market are described in this study, considering the generation cost of different distributed energy resources (DERs), like distributed generator, energy storage system and demand response. Including load and renewable generation forecasting systems and a fuzzy decision supporting system, a hierarchical micro-grid energy management system (MG-EMS) is then proposed to ensure the benefits of involved micro-grid central controller, DER owners and customers. To verify the feasibility of the proposed system, the whole-year historical pricing and load data for New England independent system operator are employed. The numerical results show that the proposed MG-EMS is promising and effective for the operations of MGEM.

Game-theoretic approach to cooperative control of distributed energy resources in islanded microgrid considering voltage and frequency stability

A microgrid (MG) comprises a low-voltage network with several microsources, critical and noncritical loads, and energy storage systems (ESSs). It can operate in the grid-connected or islanded modes. In islanded mode, the voltage and frequency of the MG should be controlled by different distributed energy resources (DERs). This paper focuses on the analysis of frequency stability in an autonomous MG with renewable energy sources. In this paper, colonial competitive algorithms are used to design the DERs controllers in a cooperative manner that these controllers can keep the MG stable. Artificial neural network tool trained by Levenberg---Marquardt algorithm is used to generate controlling signal for every controller to keep the frequency and voltage in a desired range. This paper investigates a new optimal control solution for maintaining the frequency stability in the MG, by using a combination of an ESS and load-shedding procedure. The cooperative game theory is used in this paper to model the interaction among different DERs, ESSs, and loads.

Unified framework for frequency and voltage control of autonomous microgrids

A general and effective framework for the secondary control of islanded microgrids (MGs) including inverter-based distributed generators and conventional generator is proposed in this study. The proposed framework works based on fuzzy potential function method and provides a clear vision for system designer in order to set the cooperation of different distributed energy resources (DERs) in regulating MG variables. Different potential functions are defined for each controllable microsource such that the minimum value of the potential function represents the microsource control target. The set points of DER units are dynamically updated by the optimisation unit located in MG central controller using available communication links. In addition, the small signal stability assessment is used to determine the parameter of the fuzzy potential function to guarantee the system stability. The simulation studies are carried out in the time-domain, using the developed program in MATLAB environment. The results demonstrate the effectiveness and flexibility of the proposed framework in the frequency and voltage control of islanded MGs.