Islanded Mode Research Articles

Optimal Dispatching of Smart Hybrid Energy Systems for Addressing a Low-Carbon Community

A smart hybrid energy system (SHES) is presented using a combination of battery, PV systems, and gas/diesel engines. The economic/environmental dispatch optimization algorithm (EEDOA) is employed to minimize the total operating cost or total CO2 emission. In the face of the uncertainty of renewable power generation, the constraints for loss-of-load probability (LOLP) and the operating reserve for the rechargeable battery are taken into account for compensating the imbalance between load demand and power supplies. The grid-connected and islanded modes of SHES are demonstrated to address a low-carbon community. For forecasting load demand, PV power, and locational-based marginal pricing (LBMP), the proper forecast model, such as long short-term memory (LSTM) or extreme gradient boosting (XGBoost), is implemented to improve the EEDOA. A few comparisons show that (i) the grid-connected mode of SHES is superior to the islanded-connected mode of SHES due to lower total operating cost and less total CO2-eq emissions, and (ii) the forecast-assisted EEDOA could effectively reduce total operating cost and total CO2-eq emissions of both modes of SHES as compared to no forecast-assisted EEDOA.

Control strategy of multiple interlinking converters for low-voltage hybrid microgrid based on adaptive droop

Distributed generation supply efficiency can be fully realized with the use of a microgrid as a power interface and an efficient operation control technique. The key component of an AC/DC hybrid microgrid is the interlinking converter, which enables flexible power interactions between AC and DC subgrids. This paper proposes an adaptive droop control strategy for multiple ICs in the hybrid microgrid. This control strategy can not only reduce unnecessary power flow between subgrids, but it can also compensate for droop in AC and DC bus voltages. With the proposed control strategy, the problem of inaccurate power distribution and existing circulation caused by the line impedance or capacity difference of ICs can be solved. Taking the island mode of a low-voltage hybrid microgrid as an example, the impact of line impedance on IC transmission power is examined in this paper. As a starting requirement for ICs, the AC/DC bus voltage and the subgrid’s load state are combined. Dead zones are settled to reduce unnecessary power flow. The adaptive droop coefficient is made up of both voltage regulation and power regulation. Voltage regulation maintains the supplied side of the microgrid in its rated state, while power regulation solves issues with power distribution and circulation brought on by line impedance. The adaptive droop link enhances the accuracy of inter-IC power distribution and inter-subgrid power coordination. We verified the validity of the proposed strategy using MATLAB and a hardware-in-the-loop (HIL) experimental platform.

Study of coordinated control strategy for hybrid AC–DC microgrid in islanding mode

As a kind of generation and distribution system with autonomous control, AC–DC hybrid microgrid plays a pivotal role in the transformation and development of modern power grids. To address the problems of microgrid system instability that occur in islanding mode, the study proposes a coordinated control strategy for hybrid AC/DC microgrid in islanding mode. First, the bidirectional AC/DC interconnection converter is modelled and parametrically designed; second, the control strategy of the interconnection converter in islanding mode is raised, including both active power control with double-loop control and seamless switching of operation modes with pre-synchronous control, and in the end, the effectiveness of the strategy is examined. The data display that under this strategy, the real and reactive power output gaps between the micro sources in the hybrid microgrid do not exceed 0.01 kW and 0.03 kVAR, respectively, and the current during islanding switching is more stable up to 32 A. This shows that the strategy effectively improves the shortcomings of the traditional regulation method, realizes the accurate distribution of real and reactive power, improves the power sharing between DC and AC subgrids, strengthens the stability and reliability of the hybrid microgrid, and helps to promote the technological progress of the hybrid microgrid and escorts the efficient and green development of the smart grid.

Quantifying the impact of inverter-based distributed energy resource modeling on calculated fault current flow in microgrids

Microgrid fault calculations are crucially important for setting the relay protection in both modes of operation – grid-connected and islanded. To obtain accurate results for this class of analysis, distributed energy resources within the microgrid must be accurately modeled. As most of distributed energy resources within the emerging microgrids are inverter-based, their precise models are of a significant importance. Thus, the aim of this research is to quantify the impact of the model accuracy on short circuit calculation results as well as quantifying the differences in the results obtained by models that are in a complete accordance with various Grid Code requirements, and simplified models proposed in the most commonly used International Standard for fault calculations – IEC 60909. To accomplish this goal, in this paper, various shares of inverter-based distributed energy resources’ penetration in the total generation power of a microgrid – from 50% to 90%, are thoroughly analyzed, and the differences between the results obtained by using standardized models relative to more accurate modeling that considers Grid Code requirements are presented. The obtained results suggest when the share of inverter-based resources in the total generation power of a microgrid is considerable, especially in the islanded operational mode, simplified models from the IEC 60909 standard become unreliable. According to these observations, we lay out cases in which the simplified and standardized models for inverter-based distributed energy resources are reliable to use. Additionally, we provide recommendations on improvement of the standardized models in critical cases of microgrids with high penetration of these resources, that operate in the islanded mode.

ANALYSIS OF REGULATORY DOCUMENTATION AND TECHNICAL REQUIREMENTS REGARDING THE FUNCTIONING OF THE NETWORK IN "ISLAND MODE"

The article examines main issues regarding the admissibility and conditions of operation of microgrids in the so-called " islanding mode" (IM), namely: identification of the appearance of an IM, regulatory and legal aspects of admissibility, and technical requirements for its implementation. Main methods and approaches to the issue of identification of IM, concepts of "planned" and "unwanted" IM are analyzed, possible advantages and consequences of the operation of a part of the distribution network in the IM are considered. An analysis and comparison of the legal framework regarding the possibility of IM usage in the countries of the European Union and Ukraine was carried out. Changes to the national legislation regarding the harmonization of regulatory documentation of Ukraine and the European Union, which were caused by Ukraine's desire to integrate its energy system into the European Network of Transmission System Operators for Electricity (ENTSO-E), are presented. The normative and legal documentation of both national and international use, regarding the norms of integration into the distribution networks of sources of distributed generation and their functioning in the IM, is presented and reviewed. Issues related to the technical support of the operation of the IM in the distribution network, subject to compliance with the relevant requirements for power supply quality indicators, are considered. Additionally, analysis of the advantages that distribution networks and consumers have with the possibility of using IM was carried out and the problems that may arise in the event of incorrect planning, identification and technical implementation of the isolated operation of a part of the network with local energy sources were identified. Information has been collected and presented regarding the maximum limits to the frequency and voltage in the distribution network, which are permissible for short-term deviations of these indicators depending on the standard that regulates the operation of the corresponding distribution networks. The importance of taking into account all the previously mentioned aspects of the operation of distribution networks in the IM is summarized, and conclusions are drawn regarding the feasibility of ensuring the possibility of the operation of networks in the specified mode in Ukraine

Battery Energy Management System Using Edge-Driven Fuzzy Logic

Building energy management systems (BEMSs), dedicated to sustainable buildings, may have additional duties, such as hosting efficient energy management systems (EMSs) algorithms. This duty can become crucial when operating renewable energy sources (RES) and eventual electric energy storage systems (ESSs). Sophisticated EMS approaches that aim to manage RES and ESSs in real time may need high computing capabilities that BEMSs typically cannot provide. This article addresses and validates a fuzzy logic-based EMS for the optimal management of photovoltaic (PV) systems with lead-acid ESSs using an edge computing technology. The proposed method is tested on a real smart grid prototype in comparison with a classical rule-based EMS for different weather conditions. The goal is to investigate the efficacy of islanding the building local network as a control command, along with ESS power control. The results show the implementation feasibility and performance of the fuzzy algorithm in the optimal management of ESSs in both operation modes: grid-connected and islanded modes.

Evaluation of a hybrid power system based on renewable and energy storage for reliable rural electrification

Microgrids system consisting of single or multiple energy resources and storage is used to provide electricity to remote rural areas. Subsequently, they can be worked in both grid-connected and islanded modes. Microgrids can provide stable energy solutions to areas where grid extension is either costly or not feasible. The system's long-term economic stability and sustainability must be considered throughout the microgrid's design. Renewable energy sources have a variety of objectives and possible restrictions. The current plan suggests a rural microgrid with integrated solar, diesel, and battery systems. The proposed microgrid for the rural area of Uttarakhand (India) is given a techno-economic and feasibility analysis. For the hilly region of India, a standalone microgrid is created to handle the home peak load of 13kW. Moth flam optimization (MFO) is utilized to optimize the proposed energy framework, and the results are compared with those of a genetic algorithm (GA) and particle swarm optimization (PSO). The optimal hybrid system's net current and energy costs are calculated to be $58372.00, with the cost of energy per unit being $0.14/kWh. Sensitivity analysis and robustness viability have been performed for the configuration. The finding suggested that the energy framework using MFO is 18% and 16% less expensive than GA and PSO, respectively. This research adds new direction to critical sustainable development among developed countries.

Optimized power flow management based on Harris Hawks optimization for an islanded DC microgrid

Abstract This article presents an energy management system (EMS) in a DC microgrid (MG) operating in an islanded mode to control the power flow in the distribution network. The microgrid system considered in this research consists of distributed generation sources like a solar photovoltaic system, a fuel cell energy system, and an energy storage system controlled by an optimized energy management system. As the distributed energy sources used are primarily renewable, unpredictable weather conditions may cause irregular energy generation. These variations impact the power flow in the DC bus, making it challenging to maintain a supply and demand balance. Therefore, an intelligent energy management system using the Harris Hawks Optimization (HHO) is implemented to enhance the microgrid’s performance and efficiency. The HHO algorithm is based on the hunting nature of the Harris Hawks, and the EMS is developed to maintain the optimal power flow and to handle the constraints. The performance of the presented system is analyzed with the particle swarm optimization (PSO) based Proportional Integral (PI) controller in different operating scenarios to validate the effectiveness of the DC microgrid system.

Sliding mode control for pulsed load power supply converters in DC shipboard microgrids

Pulsed power load (PPL) is a special load type in shipboard microgrids (SMGs), which consists of the generation module, energy storage system, and various types of loads. Having a reliable power supply to shipboard loads is a challenge as the SMG operates in islanded mode in most cases. Particularly, the PPLs require high transient power transfer with fast dynamics and strong robustness. Conventional solution to supply for the PPL is based on proportional-integral (PI) control, which can be used by linearizing the system around the equilibrium operation point. However, for a pulsed power supply (PPS) system, the load demand drastically changes in a short time, usually in millisecond level, making the operating point changes when the pulsed power is triggered or terminated. To supply the PPL with fast dynamics and robustness, an improved PPS control method is presented in this paper. By adopting a nonlinear sliding mode control (SMC) method, fast voltage regulation and robust pulse power tracking can be achieved. In the PPS, the PPL power demand is divided into two terms: one is the average power that is supplied by the SMG and the other is the fast pulsed power that is supplied by the storage capacitor. The size and cost of the storage capacitor are reduced as it is intentionally driven to a deep discharge. The PPS system configuration and coordination principle, SMC controllers, and sizing of passive elements in the PPS are analyzed in detail. The effectiveness of the presented PPS is verified by simulation results.

Utility Interactive Renewable Microgrid with Backup Power Functionality

This paper deals with three-phase wind-solar-photovoltaic microgrid (WPV-MG), which is capable of performing in grid-tied and island modes of operation under steady state and in DSTATCOM (Distribution Static Compensator) mode, utility-interactive and disconnecting modes under dynamic state. This microgrid (MG) uses a single VSI (Voltage Source Inverter) with reduced power converters and switches. At the DC bus of VSI, a battery bank is used to provide load leveling either at less renewable generation or at light loads. The control of VSI is also able to maintain power balance among various units and provides PQ (Power Quality) improvement in the MG under local nonlinear loads. During no renewable power generation, it works as a DSTATCOM to improve PQ and provides power factor correction and reduces voltage harmonics in PCC (Common Coupling Point) under local linear/nonlinear loads. During abnormal grid conditions, it provides power backup to local consumers under island operation. For this three-phase WPV-MG, a laboratory prototype is developed and its performance under different operations is validated through test results.

Wind characteristics of Tamil Nadu coast towards development of microgrid - A case study for simulation of small scale hybrid wind and solar energy system

Wind's intermittent nature poses a considerable challenge for an effective microgrid design, particularly in “Island mode.” The objective of this research is to investigate the wind characteristics of a coastal location in Tamil Nadu, India, with a special emphasis on wind consistency, to establish a successful microgrid at the site. The research was based on wind data acquired from an 80 m high meteorological mast established in Manamelkudi, Pudukkottai District, Tamil Nadu, India, from January to December 2017. Based on the analysis, it is observed that, while being within the moderate wind potential regime, the region has a substantially stable wind pattern when compared to the in-land windy places. According to the assessment, the site is expected to effectively complement solar generation, with 74% of its wind generation occurring between 06:00 p.m. and 06:00 a.m. Considering the consistency of wind and the complementary nature of solar generation, the Manamelkudi location is considered to have promising potential for the development of microgrid systems using wind and solar hybrid power. The investigation demonstrated that the geography of the site plays a critical role in the consistent wind pattern of the Manamelkudi site.

Reliability-Based Optimal Integrated Microgrid Scheduling in Distribution Systems

This paper proposes a reliability-based optimal scheduling model of integrated microgrids. The proposed model is capable of delivering optimal scheduling of each individual microgrid and aggregated system. In addition, it is compatible with both grid-connected and islanded operation modes. The developed problem formulation of the proposed model takes into account the reliability indices SAIDI, SAIFI, and CAIDI to evaluate the reliability of the integrated system. Numerical simulations on a modified IEEE-33 bus test system, involving four integrated microgrids, were performed to investigate the advantages and the robustness of the developed model. Furthermore, the impact of merging Battery Energy Storage Systems (BESSs) on the optimization outcome is examined, which demonstrates its significant effectiveness in improving the power systems' reliability.

Islanding Detection System for Grid Connected Photovoltaic System under Different Fault Condition Using Intelligent Detection Method (IDM)

A distributed power generating system can run in an off-grid or off grid mode and can be powered by either sustainable or nonrenewable energy sources. The widespread use of renewable energy sources, like grid-connected solar systems, presents distribution networks with additional technological difficulties, such as accidental islanding. Utility employees who are islanding may not be aware that a circuit is still energized, which might be harmful. On islanding detection in gird-connected PV systems, several proposed solutions were considered. In order to examine their current limits, this study aims to develop an islanding detection system for grid connected solar systems under various fault conditions using intelligent detection method (IDM). To use and monitor the many grid-connected PV system characteristics in this context, numerous sensors and controllers were proposed. The controller will carry out the islanding detection based on the sensor data’s categorization of defect. The circuit breaker will do the islanding, and an intelligent technique has been proposed to identify the islanding condition under different fault condition. For real-time realization, a 1 kW grid-connected solar system had been used, and an artificial neural network (ANN) was employed as a smart approach to identify the islanding mode under various fault conditions.

Performance analysis on parallel operation of multimode droop controller doubly fed induction generator based wind energy conversion system with Other wind unit, solar units, loads and facts device

Due to their numerous advantages, wind turbines with changeable speed power production systems are increasingly being used. This study proposes the architecture and specifications of an induction turbine-generating wind system, as well as a PI controller-based DC voltage link regulator and optimal torque control system. The suggested control technique as stated in this paper allows the system to function in grid-linked mode as well as the islanded mode and also in parallel with other power generation units, loads, FACTS devices, etc. This paper involves the analysis of different test cases in grid-connected mode as well as an islanded mode with a PV generation unit, passive loads, induction motor loads, and other wind energy generation systems. The paper also includes an analysis of the response of the system with the switching on and off of the other units. MATLAB 2013a thereby validates the system findings and analysis.

Modeling and Simulation of a Large-Scale Wind Power Plant Considering Grid Code Requirements

The load demand to a power grid, as well as the interest in clean and low-cost energy resources, has led to the high integration of wind power plants into power system grids. There are grid code standards that are set for the design and integration of these wind power plants. These codes often look at the design operation of the wind power plant in islanded mode, where possible analysis of the most sensitive power system quantities such as voltage, frequency, reactive power, etc. is carried out. Therefore, in this study, attention was paid to the application of these codes to keep the design and integration of wind power plants well standardized as much as possible. The purpose of this paper is to review and discuss the literature and theory about the design of wind turbine generators and model and simulate a large-scale wind power plant. The modeling was successfully carried out on RSCAD, and the results obtained show that the wind power plant can be further used for other studies such as voltage stability improvement in power grids.

Stability Analysis of Microgrid with Load Shedding Scheme using RTDS

A microgrid system was simulated using the powerful RTDS simulator, the modelling was done on the RSCAD software, and the microgrid comprised of a diesel generator, a photovoltaic (PV) system and a Doubly-Fed Induction Generator (DFIG) wind turbine system as DERs. The paper comprises the study on stability analysis of the microgrid in grid-connected and islanded modes of operation, along with a successful load shedding scheme which was implemented based on the loads distinguished as low priority and high priority loads in order to keep the system balanced during faults.

Optimized PV Fed Zeta Converter Integrated with MPPT Algorithm for Islanding Mode Operation

One of the sustainable energy sources available everywhere is solar energy. Solar energy may be transformed into electrical energy using photovoltaic cells; it can also be utilized in various applications like domestic, agricultural, industries and traffic lights. The power produced from solar energy is at a minimum level. Hence, the tracking maximum power point and converters are employed to step up the power from solar. Most of the research works utilized the Maximum Power Point Tracking (MPPT) with modified methods of perturb and observe and Swarm intelligence algorithms. The converters like buck boost converter, cuk and cuk-sepic converter are utilized to step up the voltage and it suffers from the harmonic distortion. Hence, in this, the Hybrid GA based PSO used for MPPT and the Zeta converter used for reducing the harmonics and maintaining the quality of power in the output side. The total operation was performed in Island mode and it was realized in MATLAB Simulink under Windows 10 environment. Then, the performance is evaluated for MPPT and total harmonic distortion.

Optimal Model Predictive Control for Virtual Inertia Control of Autonomous Microgrids

For the time being, renewable energy source (RES) penetration has significantly increased in power networks, particularly in microgrids. The overall system inertia is dramatically decreased by replacing traditional synchronous machines with RES. This negatively affects the microgrid dynamics under uncertainties, lowering the microgrid frequency stability, specifically in the islanded mode of operation. Therefore, this work aims to enhance the islanded microgrid frequency resilience using the virtual inertia frequency control concept. Additionally, optimal model predictive control (MPC) is employed in the virtual inertial control model. The optimum design of the MPC is attained using an optimization algorithm, the African Vultures Optimization Algorithm (AVOA). To certify the efficacy of the proposed controller, the AVOA-based MPC is compared with a conventional proportional–integral (PI) controller that is optimally designed using various optimization techniques. The actual data of RES is utilized, and a random load power pattern is applied to achieve practical simulation outcomes. Additionally, the microgrid paradigm contains battery energy storage (BES) units for enhancing the islanded microgrid transient stability. The simulation findings show the effectiveness of AVOA-based MPC in improving the microgrid frequency resilience. Furthermore, the results secure the role of BES in improving transient responses in the time domain simulations. The simulation outcomes are obtained using MATLAB software.

Multi-objective optimization strategy of islanding microgrid based on improved NSGA-II algorithm

Aiming at the microgrid system with distributed energy sources such as wind, diesel generator, and fuel cell and flexible load in islanding mode, the optimal dispatching model is established to consider the optimal load and reduce the economic cost. This study adopts the improved NSGA-II algorithm, which can improve the optimization efficiency and get the optimal solution better. The simulation analysis of the microgrid in the islanded mode is carried out within a cycle of 24 h. The results of the model show that this strategy can effectively optimize the load curve and reduce the current cost of supply.

Inter-connected AC/DC HMGS power management with 3-phase and 1-phase ILC

In AC/DC hybrid micro grid system (HMGS) power converters are always tested for is performance in distribution, its ability to provide accurate power sharing, transient stability and load dynamics. The existing control methods either complex or limited to achieve optimal power flow. This paper proposes a modified decentralized droop control scheme for interlinking converter (ILC) connected to interconnected AC and DC grids. A three coordinated model is proposed where AC frequency, ILC power and DC voltage are corresponding axis. The power sharing through the ILC is dependent on the AC frequency droop and DC voltage droop which occurs due to overloading. The control scheme is designed for single and three phases ILC. The obtained results are compared with double loop control method which shows less frequency deviations, accurate power sharing. The ILC performs autonomously and transfer power bidirectional under islanded mode. The simulation is carried in MATLAB/Simulink.