Microgrid Components Research Articles

Optimal design for a hybrid microgrid-hydrogen storage facility in Saudi Arabia

BackgroundSustainable development requires access to affordable, reliable, and efficient energy to lift billions of people out of poverty and improve their standard of living. The development of new and renewable forms of energy that emit less CO2 may not materialize quickly enough or at a price point that allows people to attain the standard of living they desire and deserve. As a result, a parallel path to sustainability must be developed that uses both renewable and clean carbon-based methods. Hybrid microgrids are promoted to solve various electrical and energy-related issues that incorporate renewable energy sources such as photovoltaics, wind, diesel generation, or a combination of these sources. Utilizing microgrids in electric power generation has several benefits including clean energy, increased grid stability, and reduced congestion. Despite these advantages, microgrids are not frequently deployed because of economic concerns. To address these financial concerns, it is necessary to explore the ideal configuration of microgrids based on the quantity, quality, and availability of sustainable energy sources used to install the microgrid and the optimal design of microgrid components. These considerations are reflected in net present value and levelized energy cost.MethodsHOMER was used to simulate numerous system configurations and select the most feasible solution according to the net present value, levelizied cost of energy and hydrogen, operating cost, and renewable fraction. HOMER performed a repeated algorithm process to determine the most feasible system configuration and parameters with the least economic costs and highest benefits to achieve a practically feasible system configuration.ResultsThis article aimed to construct a cost-effective microgrid system for Saudi Arabia's Yanbu city using five configurations using excess energy to generate hydrogen. The obtained results indicate that the optimal configuration for the specified area is a hybrid photovoltaic/wind/battery/generator/fuel cell/hydrogen electrolyzer microgrid with a net present value and levelized energy cost of $10.6 billion and $0.15/kWh.ConclusionWith solar photovoltaic and wind generation costs declining, building electrolyzers in locations with excellent renewable resource conditions, such as Saudi Arabia, could become a low-cost hydrogen supply option, even when accounting for the transmission and distribution costs of transporting hydrogen from renewable resource locations to end-users. The optimum configuration can generate up to 32,132 tons of hydrogen per year (tH2/year), and 380,824 tons per year of CO2 emissions can be avoided.

A two-level power management strategy in a DC-coupled hybrid microgrid powered by fuel cell and energy storage systems with model predictive controlled interface converter

This paper intends to present a DC-coupled hybrid microgrid, including proton exchange membrane fuel cell (PEMFC), battery bank, and supercapacitor, which is suitable for applications such as distributed power generation and the power system of vessels. In the proposed configuration, the PEMFC serves as the main energy source, and supercapacitor and battery bank are as energy storage systems. A comprehensive model of the 6 kW PEMFC, including the dynamic model along with the electrical model, is presented. Three DC-DC converters, consisting of an inter-leaved boost with voltage multiplier converter (IBVM) connected to the fuel cell and two bi-directional converters connected to the storage devices are employed. Additionally, an AC-DC converter is utilized to ensure stable AC voltage supply, proper power flow, and DC-link voltage control. Moreover, this paper provides a two-level power management strategy (PMS) to control and optimally distribute power between the components of the hybrid microgrid. The proposed strategy is divided into device-level and system-level controls. At the device-level control, a decentral-ized model predictive control strategy (MPC) without using any proportional-integral-derivative (PID) controllers is proposed to control the different modules of the hybrid microgrid. Also, at the system-level control, a rule-based strategy is developed to optimally distribute power between power sources and ensure stable operation under different operation modes. The simulation results in Matlab/Simulink environment are given to verify the effectiveness of the PEMFC model, the chosen converters, the proposed control methods, and the proposed hybrid microgrid.

Hybrid power-heat microgrid solution using hydrogen as an energy vector for residential houses in Spain. A case study

In order to favor a transition to a renewable energy economy, it is necessary to study the possible permeation of renewable energy sources not only in the electric grid or industrial scale, but also in the small householding scale. One of the most interesting technologies available for this purpose is solar energy, since it is a mature technology that can be easily installed in every rooftop. Thus, a techno-economic assessment was carried out to evaluate the installation of a solar-based power-heat hybrid microgrid considering the use of hydrogen as an energy vector in a typical residential house in Spain. Lead-acid batteries plus the photovoltaic and solar thermal energy installation are complemented with a hydrogen system composed of an electrolyzer, two metal hydride bottles, and a fuel cell. A simulation tool has been generated using experimental models developed and validated with real equipment for each one of the electric microgrid component. Three operating modes were tested making use of this tool to better manage the energy consumed/produced and optimize the economic output of the facility. The results show that setting up a hydrogen-based microgrid in a residential house is unviable today, mainly due to the high cost of hydrogen generation and consumption equipment. If only solar energy is considered, the microgrid inversion (12.500 €) is recovered in ten years. On the other hand, selling the electricity output has almost no repercussions considering current electrical rates in Spain. Finally, while using an optimization algorithm to manage energy use, battery life-spam, and economic benefit slightly increase. However, this profit may not be enough to justify the use of a more complex control system. The results of this research will help users, renewable energy companies, investigators, and policymakers to better understand the different factors influencing the spread of renewable smart grids in households and propose solutions to address these.

Defense Installation Energy Resilience for Changing Operational Requirements

We propose a methodology to determine the impact of different potential mission scenarios upon energy resilience for mission-critical loads attached to a military base’s microgrid infrastructure. The proposed methodology applies to any installation with changing operational states that has energy-resilience requirements. The proposed methodology may be used by energy managers to account for potential mission scenarios that a base may be part of, followed by assessing the microgrid energy resilience to supply the critical loads for said mission scenarios, especially where the external grid power may be unavailable and/or damage to microgrid components may be present. In the event a microgrid design is unable to provide sufficient electrical energy, distributed energy resources and energy storage systems including renewable energy resources may be added to improve energy resilience. A case study is conducted on a fictitious representative military base, microgrid design, and changing mission demands to demonstrate the application of the proposed methodology. This article contributes a methodology for energy managers to evaluate energy resilience using microgrids by accounting for potential mission scenarios, their energy requirements, resulting energy preparedness, and recommendations for improvement, as necessary.

A Techno-Economic Analysis of Energy Storage Components of Microgrids for Improving Energy Management Strategies

Microgrids are essential elements of the energy transition because they allow optimal use of renewable energy sources (photovoltaic panels, wind turbines) and storage devices (batteries, supercapacitors) by connecting them to consumption poles (e.g., buildings, charging stations of electric vehicles). Lithium-ion batteries and supercapacitors are the main electrical storage devices usually used by microgrids for energy and power transient management. In the present paper, microgrid simulations have been performed. Electrothermal and aging models of storage components are presented. Strategies and scenarios for the batteries are presented either based on the state of charge limitation or hybrid association with supercapacitors. The contribution of this study is to provide a management strategy which considers the aging of storage systems in the real-time management of the microgrid in order to extend their life, while minimizing installation costs. The first approach for a techno-economic study provided in that study enables us to improve the strategies by optimizing the use of the battery. The results obtained in this paper demonstrate the key role of the techno-economic approach and knowledge of the aging processes of storage devices in improving the energy management and global feedback costs of microgrids. The simulation results show that battery life can be improved by 2.2 years. The improvement in battery life leads to a reduction in the total cost of the installation by reducing the cost of the batteries.

Control and operation of a ship AC/DC microgrid under transient propulsion and manoeuvring load conditions

Moving towards more electric ships with sustainable designs can help in reducing the carbon footprint of the global transportation systems. Ship networks can be based on AC/DC microgrids with resilient structures to accommodate different types of power-generation and energy storage systems for supporting the dynamic loads of the vessel’s propulsion and bow-thruster units. This paper presents a shipboard AC/DC microgrid with a super-capacitor (SC) system to support the ship’s power system and to enhance its operational reliability under severe/transient loading scenarios, mainly arising from abrupt changes in the propulsion and bow-thruster power. A control system with SC voltage re-balancing mechanism is proposed for stabilizing the DC-bus voltage via bi-directionally power-controlled DC-DC converters utilizing the non-linear hyperbolic functions. The mechanism concurrently generates steady, slow-changing diesel-driven power through the microgrid voltage source converters to re-balance the SC voltage. The power system, including the diesel-generators, the microgrid components and the propulsion/thruster units, has been simulated in detail using the physical modelling-tools in the Matlab-Simulink® software, and run under harsh loading scenarios. The results demonstrated the effectiveness of the proposed control system with the microgrid structure and compared favourably with those obtained using other methods reported in the literature.

A Model Predictive Control-Based Decision-Making Strategy for Residential Microgrids

This work presents the development of a decision-making strategy for fulfilling the power and heat demands of small residential neighborhoods. The decision on the optimal operation of a microgrid is based on the model predictive control (MPC) rolling horizon. In the design of the residential microgrid, the new approach different technologies, such as photovoltaic (PV) arrays, micro-combined heat and power (micro-CHP) units, conventional boilers and heat and electricity storage tanks are considered. Moreover, electricity transfer between the microgrid components and the national grid are possible. The MPC problem is formulated as a mixed integer linear programming (MILP) model. The proposed novel approach is applied to two case studies: one without electricity storage, and one integrated microgrid with electricity storage. The results show the benefits of considering the integrated microgrid, as well as the advantage of including electricity storage.

Thermal analysis and optimization of stand-alone microgrids with metal hydride based hydrogen storage

Stand-alone microgrids, also known as remote area power supply systems, are crucial towards providing electricity access to off-the-grid locations/buildings and for communities trying to become 100% dependent on renewables. Design and development of efficient energy storage system remains a key challenge for the stand-alone microgrid technology. Metal hydride based hydrogen-energy storage system, offering long term energy storage at near ambient conditions and additional benefits of thermal and green hydrogen output, have attracted researchers and industrialists worldwide. In this work, LaNi5 (Lanthanum Penta-nickel) based hydrogen-energy storage system for stand-alone microgrid application is studied. An optimization study is performed to find the optimal sizes of hybrid (solar + wind) and wind microgrid components for the requirements of typical Indian village/UK community of 50 households located at various geographical locations, having diverse solar and wind resources availability. The study ensures that the microgrid satisfies the required electric load but is not over-designed, which is achieved by limiting the two performance parameters i.e., unmet load fraction and excess electricity fraction, below 10%. The optimization study is done based on an hourly analysis for a year using the simulation software HOMER. A thermal analysis is carried out to quantify the additional benefit of thermal output from the energy storage system. Comparisons between the performance and thermal output of optimized hybrid and wind microgrids are carried out for the selected locations. Also, green hydrogen produced for energy storage and available for use at the end of the year is quantified. Upon comparing hybrid (solar PV + wind turbine) and wind energy based microgrids, it is observed that hydrogen storage requirement decreases by up to 97% while using hybrid energy source depending on the location. Besides serving electrical load, the microgrid delivers thermal outputs of about 1kWh and 5kWh for Indian and UK locations respectively.

Operational Resilience of Nuclear-Renewable Integrated-Energy Microgrids

The increasing prevalence and severity of wildfires, severe storms, and cyberattacks is driving the introduction of numerous microgrids to improve resilience locally. While distributed energy resources (DERs), such as small-scale wind and solar photovoltaics with storage, will be major components in future microgrids, today, the majority of microgrids are backed up with fossil-fuel-based generators. Small modular reactors (SMRs) can form synergistic mix with DERs due to their ability to provide baseload and flexible power. The heat produced by SMRs can also fulfill the heating needs of microgrid consumers. This paper discusses an operational scheme based on distributed control of flexible power assets to strengthen the operational resilience of SMR-DER integrated-energy microgrids. A framework is developed to assess the operational resilience of SMR-DER microgrids in terms of system adaptive real-power capacity quantified as a response area metric (RAM). Month-long simulation results are shown with a microgrid developed in a modified Institute of Electrical and Electronics Engineers (IEEE)-30 bus system. The RAM values calculated along the operational simulation reflect the system resilience in real time and can be used to supervise the microgrid operation and reactor’s autonomous control.

Microgrids and Resilience: A Review

The occurrence of large-scale disturbances is increasing at an alarming rate throughout the world. As a consequence of this trend, a primary concern of today’s power system is to enhance its resilience against low-probability, high-impact events. In this regard, microgrids, as the smart grid’s building blocks, offer promising approaches toward achieving higher levels of distribution system resilience by accommodating and integrating various distributed energy resources. Accordingly, microgrid-based techniques have been the focus of a growing body of research seeking a more resilient power system. These methods mainly rely on the stand-alone operation of microgrids to supply loads locally in case of extreme events. The objective of this paper is to present an updated comprehensive review of the literature on two main categories of microgrid-based resilience enhancement approaches in distribution systems: 1) optimal microgrid formation and 2) optimal microgrid scheduling and energy management. Distinctive from other review papers, this article systematically surveys the research studies under multiple well-sectionalized features, such as various technologies, techniques, models, constraints, and concepts for each of the above two categories. These features include but are not limited to networked microgrids, demand response programs and electric vehicles scheduling, multi-energy microgrids, dynamic optimization schemes, control schemes, communication resilience, hybrid microgrids, and mobile energy resources. Additionally, a comprehensive introduction to resilience definitions and assessment methods, microgrid components, architectures, and control schemes, as well as, sources of uncertainty is provided.

A bi-cyclic co-optimization method for sizing of electricity-hydrogen hybrid energy storage microgrid

Due to the nonlinear and strong coupling relationships between the sizing parameters of the microgrid components and the operation strategy parameters, this paper proposes a bi-cycle co-optimization method for optimal sizing the microgrid components cost-effectively.

Genetic Algorithm on 2nd Voltage Harmonic Mitigation in Hybrid Microgrids

This work introduces a compensation scheme that uses a genetic algorithm to mitigate the 2^nd voltage harmonic component of hybrid microgrids. The foremost advantage of the proposed scheme, is its capability to effectively compensate the 2^nd harmonic component regardless of the feeder impedance, the location of the equipment and without any need for real-time communications. A graphical representation of the genetic algorithm parameters is also presented, being a handily tool for designing it for any microgrid application and the mathematical analysis of hybrid microgrids under the prospect of harmonic compensation is given. Simulations and experimental tests verify the effectiveness of the proposed method, indicating that its efficiency is maintained at about 90&#x0025;, while the efficiency of the other methods falls below 35&#x0025; when the impedance of the connection line increases at <inline-formula> <tex-math notation="LaTeX">$1+\,\,\text{j}0.16\,\,\Omega _{\mathrm {(\text{@}100 Hz)}}$ </tex-math></inline-formula>. Finally, a comparative analysis is also performed between the proposed method and existing ones.

The optimal design and operation of a hybrid renewable micro-grid with the decoupled liquid air energy storage

This study explores the multiple functions of liquid air energy storage (LAES) in a hybrid renewable micro-grid, which hasn't been covered so far, to decarbonize the distributed energy systems that are increasingly popular. To cope with this, a decoupled off-design LAES model was developed, and integrated into a micro-grid mixed-integer linear programming (MILP) design framework. This methodology enables studying the optimal energy to power ratios of LAES, and the identification of specific value streams of the storage, as well as optimally sizing the micro-grid equipment and LAES units simultaneously, to achieve the balanced economics and environmental benefits. The simulation has led to three major results. Firstly, the optimal charge/discharge power and storage capacity of LAES vary with the services it provides. The optimal charge/discharge energy to power ratio are 8/3 h, 12/6 h and 12/6 h corresponding to the arbitrage, wind stabilization and operating reserve. Secondly, for a micro-grid with ∼50% of wind power, LAES presents the key value in supporting the system operation by providing multiple functions. It is split into six explicit revenue streams that can be stacked up for the first time, including the time shifting (13.2%), renewable firming (11.4%), peak shaving (28%), flexibility (21%) and reserve value (20.4%), as well as the waste heat recovery (6%). Thirdly, in comparison with the mildly reduced LAES capital cost and enlarged electricity price differences, a higher renewable percentage would be a major driving force to increase the attractiveness of LAES in micro-grids. The system design framework can determine the optimal sizes of the micro-grid components and the LAES units. Specifically, the optimal charge/discharge energy to power ratio (27/14 h) and the storage tank size (608 t) of LAES in a micro-grid with 75% wind power are obtained, leading to ∼60% of carbon emission reduction on the 2016 level. The importance of this work lies in it provides the preliminary business model of applying small-scale LAES in hybrid renewable micro-grids, and can promote the optimal deployment of LAES under different scenarios in micro-grids.

Fuzzy Logic-Based Direct Power Control Method for PV Inverter of Grid-Tied AC Microgrid without Phase-Locked Loop

A voltage source inverter (VSI) is the key component of grid-tied AC Microgrid (MG) which requires a fast response, and stable, robust controllers to ensure efficient operation. In this paper, a fuzzy logic controller (FLC)-based direct power control (DPC) method for photovoltaic (PV) VSI was proposed, which was modelled by modulating MG’s point of common coupling (PCC) voltage. This paper also introduces a modified grid synchronization method through the direct power calculation of PCC voltage and current, instead of using a conventional phase-locked loop (PLL) system. FLC is used to minimize the errors between the calculated and reference powers to generate the required control signals for the VSI through sinusoidal pulse width modulation (SPWM). The proposed FLC-based DPC (FLDPC) method has shown better tracking performance with less computational time, compared with the conventional MG power control methods, due to the elimination of PLL and the use of a single power control loop. In addition, due to the use of FLC, the proposed FLDPC exhibited negligible steady-state oscillations in the output power of MG’s PV-VSI. The proposed FLDPC method performance was validated by conducting real-time simulations through real time digital simulator (RTDS). The results have demonstrated that the proposed FLDPC method has a better reference power tracking time of 0.03 s along with reduction in power ripples and less current total harmonic distortion (THD) of 1.59%.

A combined optimization of the sizing and the energy management of an industrial multi-energy microgrid: Application to a harbour area

• Sizing and operation combined optimization is proposed for an industrial microgrid. • Multi-energy microgrid is studied, with electricity and hydrogen as energy vectors. • The proposed objective functions aim to maximize incomes while minimizing expenses. • Ways of valorisation are compared: self-consumption, electricity and hydrogen sale. • The sizing and economical results are sensitive to investment and price assumptions. The current evolution of technical and environmental regulations and the recent development of hydrogen mobility require technological breakthroughs in the industrial areas, such as in harbours. Thus, multi-energy microgrids integrating low-carbon energy sources, electrical and hydrogen loads and storage solutions have to be designed. To improve their economic viability, the microgrid components must be carefully sized and the energy must be distributed in the most cost-effective way at any time. So as to foster the expansion of multi-energy microgrids in industrial areas, we propose in this paper a two-level optimization for the energy management and the sizing, applied to an original multi-energy scenario considering electricity and hydrogen as energy vectors. The designed energy management optimization takes into account an objective of economic profitability and constraints related to the availability of the sources and storage solutions, their reliability and the costs. The sizing optimization aims to propose different solutions allowing the benefits to be maximized and the expenses to be minimized. One of the main contributions of the paper is to compare the possible ways of valorisation of the energy available in an industrial microgrid. The results show that the sale of hydrogen allows income to be increased, in addition to self-consumption and sale to the electrical grid, but the electrolyzer involves high investments costs. Finally, a sensitivity analysis is presented and shows that the investment costs of electrolyzer and battery and the hydrogen selling price are key points in the optimal design.

Optimal Sizing of Battery Energy Storage Systems Considering Cooperative Operation with Microgrid Components

Battery energy storage systems (BESSs) are key components in efficiently managing the electric power supply and demand in microgrids. However, the BESSs have issues in their investment costs and operating lifetime, and thus, the optimal sizing of the BESSs is one of the crucial requirements in design and management of the microgrids. This paper presents a problem framework and its solution method that calculates the optimal size of the BESSs in a microgrid, considering their cooperative operations with the other components. The proposed framework is formulated as a bi-level optimization problem; however, based on the Karush–Kuhn–Tucker approach, it is regarded as a type of operation scheduling problem. As a result, the techniques developed for determining the operation schedule become applicable. In this paper, a combined algorithm of binary particle swarm optimization and quadratic programming is selected as the basis of the solution method. The validity of the authors’ proposal is verified through numerical simulations and discussion of their results.

A Hierarchical Control Approach for Power Loss Minimization and Optimal Power Flow within a Meshed DC Microgrid

This work considers the DC part of a hybrid AC/DC microgrid with a meshed topology. We address cost minimization, battery scheduling and the power loss minimization within the power distribution network through constrained optimization. The novelty comes from applying differential flatness properties to the microgrid components and formulating the cost and constraints in terms of the associated B-splines parametrization of the flat outputs (the voltages and currents of the system). This allows us to obtain optimal power profiles to minimize the power dissipation and the cost of the electricity purchase from the external grid. These profiles are tracked by a model predictive controller at the higher level, while at a a lower level a controller deals with the operation of the switches within the DC/DC converters. Extensive simulations under nominal and fault-affected scenarios using realistic data validate the proposed approach.

Renewable integrated UAPF fed microgrid system for power quality enhancement and effective power flow management

In this paper, renewable energy integrated universal active power filter (UAPF) is proposed for the microgrid system. Here, renewable energy sources such as solar and wind with the battery storage system are integrated at DC-link of UAPF. In the proposed microgrid system, the centralized microgrid controller (CMC) is implemented for power quality enhancement and effective power flow management. The main objective of the CMC is to achieve effective utilization of RES, seamless power transfer under various operating conditions, reliable and supplying quality power to the load. In CMC, the instantaneous power balance theory (IPBT) is implemented to generate the switching pulses to shunt active power filter (ShAPF) and series active power filter (SeAPF) for power quality enhancement. In addition, the power flow management strategy is integrated into CMC to generate the appropriate reference signals to the various DC-DC converters for efficient power flow management. The system with the proposed control scheme is simulated on MATLAB/Simulink and the same is validated in the experimental setup under various modes such as interconnected, isolated, and floating mode. In real-time hardware setup, a field-programmable gate array is used for parallel processing of microgrid components.

Optimization Method for Operation Schedule of Microgrids Considering Uncertainty in Available Data

Operation scheduling in electric power grids is one of the most practical optimization problems as it sets a target for the efficient management of the electric power supply and demand. Advancement of a method to solve this issue is crucially required, especially in microgrids. This is because the operational capability of microgrids is generally lower than that of conventional bulk power grids, and therefore, it is extremely important to develop an appropriate, coordinated operation schedule of the microgrid components. Although various techniques have been developed to solve the problem, there is no established solution. The authors propose a problem framework and a solution method that finds the optimal operation schedule of the microgrid components considering the uncertainty in the available data. In the authors’ proposal, the objective function of the target problem is formulated as the expected cost of the microgrid’s operations. Since the risk of imbalance in the power supply and demand is evaluated as a part of the objective function, the necessary operational reserve power is automatically calculated. The usefulness of the proposed problem framework and its solution method was verified through numerical simulations and the results are discussed.

Optimal Design of an Isolated Hybrid Microgrid for Enhanced Deployment of Renewable Energy Sources in Saudi Arabia

Hybrid microgrids are presented as a solution to many electrical energetic problems. These microgrids contain some renewable energy sources such as photovoltaic (PV), wind and biomass, or a hybrid of these sources, in addition to storage systems. Using these microgrids in electric power generation has many advantages such as clean energy, stability in supplying power, reduced grid congestion and a new investment field. Despite all these microgrids advantages, they are not widely used due to some economic aspects. These aspects are represented in the net present cost (NPC) and the levelized cost of energy (LCOE). To handle these economic aspects, the proper microgrids configuration according to the quantity, quality and availability of the sustainable source of energy in installing the microgrid as well as the optimal design of the microgrid components should be investigated. The objective of this paper is to design an economic microgrid system for the Yanbu region of Saudi Arabia. This design aims to select the best microgrid configuration while minimizing both NPC and LCOE considering some technical conditions, including loss of power supply probability and availability index. The optimization algorithm used is Giza Pyramids Construction (GPC). To prove the GPC algorithm’s effectiveness in solving the studied optimization problem, artificial electric field and grey wolf optimizer algorithms are used for comparison purposes. The obtained results demonstrate that the best configuration for the selected area is a PV/biomass hybrid microgrid with a minimum NPC and LCOE of $319,219 and $0.208/kWh, respectively.