Island Power Supply Research Articles

Maritime law enforcement concerning offshore energy platforms: Navigating international law constraints and challenges

Offshore energy platforms (OEPs) serve as a crucial frontier in utilizing renewable energy sources to meet energy demands, powering essential maritime operations such as remote island power supply, offshore oil and gas exploration, seawater desalination, and marine renewable energy harvesting. However, the development of OEPs raises significant legal concerns for maritime law enforcement. Employing a policy analysis approach, this research delves into the multifaceted challenges faced by the current international legal framework in regulating enforcement activities pertaining to OEPs. These challenges encompass ambiguity in OEP legal status, difficulties in balancing safety measures with diverse maritime interests, obstacles in environmental assessment and enforcement, and heightened enforcement challenges in areas beyond national jurisdiction. The study explores potential strategies for resolution and collaboration on an international scale. Through this investigation, the study aims to provide valuable insights to promote greater clarity and coherence in maritime law enforcement practices concerning OEPs, thereby enhancing safety, security, and environmental sustainability for OEP operations in maritime environments globally.

Optimal Scheduling of Island Microgrids with Seawater Pumped Storage Plants for Multi‐Energy Complementarity

The rapid development of new energy sources, such as offshore wind power and photovoltaic power, has provided a new solution to the problem of power supply for islands far from the mainland. Wave energy is a kind of renewable energy originated from the ocean, but the existing island power supply programs seldom consider this favorable natural condition. In addition, seawater variable‐speed pumped storage is a new idea to consume offshore wind power and improve the reliability of coastal and island power systems. In view of the stochastic and intermittent nature of new energy sources, this paper adopts seawater variable‐speed pumped storage power plants as energy storage equipment, and put forward an island power supply scheme with wind power, photovoltaic power generation, wave power generation, pumped storage power plants and diesel generator sets as a multifunctional complementary isolated grid. Firstly, wave energy generators, wind farms, photovoltaic farms, pumped storage power stations and diesel generator sets are modeled separately. Then, considering their respective operating conditions, constraints and load requirements, the optimal scheduling of island microgrids with multi‐energy complementarity is constructed. Finally, based on the improved particle swarm optimization algorithm, the model is solved. According to the wind power photovoltaic and wave power output curves of several typical scenarios in an island far away from the mainland, the cost and benefit of different schemes are compared to verify the effectiveness of the optimal scheduling in this paper. © 2024 Institute of Electrical Engineers of Japan and Wiley Periodicals LLC.

Optimal configuration of distributed energy storage considering intending island recovery in faulty distribution networks

With the rapid development of distributed generation, represented by photovoltaic power, the access of a large number of distributed generation poses threats to the security and reliable operation of islanded distribution networks. However, relying on the distributed energy storage system can stabilize the island power supply, which can effectively improve the reliability of the island distribution network. To this end, under the premise of knowing photovoltaic output and load forecast curve, this paper proposes a distributed energy storage optimization configuration method in the active islanding operation mode of multi-source distribution network, which satisfies the “N-1″ safety criterion. First, this paper establishes an optimization configuration model for distributed energy storage with multiple objectives, including minimizing the load shedding in the non-fault loss of power zone, the initial investment cost of distributed energy storage, the node voltage deviation and the system frequency offset. Then, aiming at the islanded power flow calculation process mentioned above, an improved trust region algorithm is proposed, and integrating this method with the harmony search algorithm and ”N-1″ safety criterion solves the model. Finally, the IEEE 33-node distribution system is used to test the performance of the proposed algorithm. The results show that the proposed improved trust region algorithm has the advantages of fast convergence speed and short time-consumption compared with the traditional trust region algorithm. And the proposed optimization configuration scheme for distributed energy storage can satisfy the “N-1″ safety criterion of the distribution network under different fault scenarios.

Multi-scenario planning of pelagic island microgrid with generalized energy storage under the influence of typhoon

Stand-alone microgrid system consist of hybrid wind/photovoltaic/energy storage is one of the effective approaches to solve the problem for future pelagic island power supply. Also, the frequent typhoons have brought serious impact to the pelagic island microgrids. In this context, a multi-scenario planning model for pelagic island microgrid with generalized energy storage (GES) is proposed to address the issues of high-impact, low-probability typhoon events and insufficient flexibility in low-impact, high-probability situations. Given the impact of typhoons, the planning scenarios of island microgrids are divided into regular, typhoon and typhoon early warning scenarios. Meanwhile, the selection method for each type of scenario is given. In addition, this paper establishes the unified GES model which includes power to gas-gas storage-micro gas turbine (P2G-GS-MT), transferable loads, reducible loads, and electric energy storage. The proposed methodology has been validated on an enhanced microgrid, resulting in a cost reduction of 11.9% compared to traditional method. The results demonstrate that this approach reduces the planning capacity of equipment, cost reduction, and ensure uninterrupted power supply to important loads even during typhoon conditions.

A Time-Domain Analysis Model for Modular-Multilevel-Based Grid-Forming Converters in Isolated Power Supply

The modular multilevel based grid-forming converter (MMGC) is considered to be a viable solution in isolated island power supply. However, the existing analysis model cannot meet the requirement of its performance evaluation and circuit parameters design. This paper proposes a high-accurate time-domain steady-state analysis model for MMGC, where the coupled relationships among the load, the MMGC, and the dc-side system can be fully reflected; the amplitudes and phase angles of electrical quantities, including their harmonic components, can be directly calculated. Then, the influence of <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LC</i> filters on submodule capacitor are studied. The study found that the submodule capacitance is highly correlated to the filter capacitance and almost uncorrelated to the filter inductance. It is also found that the filter capacitance selection should consider the load characteristic; a larger filter capacitance is required in the inductive load supply scenario. Finally, the studies are verified by both simulation and experiment.

Robust control strategy of VSC-HVDC systems based on feedback linearization and disturbance compensation method

The Voltage Source Converter based High Voltage Direct Current (VSC-HVDC) technology has become the development direction of new energy grid-connected, DC power transmission and island power supply technology in the future due to its superior characteristics. The effective and reliable control method is important to realize the stable operation of VSC-HVDC system during disturbances. However, the common adopted control scheme for VSC-HVDC system lacks of superior dynamic response when system suffers external disturbances. Although some relatively new control methods have been continuously proposed and applied to the VSC-HVDC system, such as no-beat control, fuzzy control, sliding mode control and repetitive control, etc., they usually depend on detailed and exact system model. This paper focuses on the feedback linearization and disturbance compensation methods in VSC-HVDC system. Firstly, the mathematical model of VSC-HVDC system in dq coordinate system with modeling errors and external disturbances is derived. Secondly, in order to improve the dynamic response and robustness of the control, the feedback linearization and disturbance compensation method is used and designed to realize the decoupling control of the VSC-HVDC system. Finally, the VSC-HVDC system with conventional control and the proposed control is compared and analyzed on the PSCAD/EMTDC simulation platform. The results show that the proposed controller based on feedback linearization and disturbance compensation principle has better dynamic performance and higher robustness of regulation performance.

Multilayered Helical Spherical Triboelectric Nanogenerator with Charge Shuttling for Water Wave Energy Harvesting.

As an important part of natural resources, islands support the marine economy and build a blue barrier for marine ecological civilization. However, the power supply on these islands is difficult, limiting the development of marine internet of things (IoTs). In order to break the status quo, this work applies triboelectric nanogenerators (TENGs) to island power supply and ecological monitoring. A spherical TENG with two multilayered helical units is designed to harvest water wave energy, in which the space utilization rate reaches 92.5%. Then a charge shuttling mechanism is developed to improve the electrical output. The output current and power of a single TENG without power management reach 200.3µA and 16.2mW respectively, corresponding to a peak power density of 23.2W m-3 . Moreover, a scheme of the power managed TENG is proposed for realizing large-scale wave energy harvesting. The TENG is demonstrated to successfully power a water quality detector, a Bluetooth thermo-hygrometer, and an intelligent wireless alarm system for remote environmental monitoring. This work not only proposes a new type of TENG for water wave energy harvesting with improved performance, but also provides a new strategy for intelligent ocean IoTs, which even contributes to the carbon neutralization.

Supplying the energy of islands with geopolitical positions using distributed generations to increase energy security

The islands usually face challenges in their energy supply due to their specific location. On islands that are distant from the land, power is typically provided by diesel generators. Therefore, oil tankers must regularly refuel the island in order to supply the necessary fuel for diesel generators. As a result, if the fueling procedure is not completed for whatever reason, the island will not receive the necessary energy, which will result in an unavoidable loss of load. Due to their strategic location, some of these islands are used as military islands to protect the nations and waterways. Given the vital role that these military islands play for nations, a delay in supplying the island with energy can seriously harm security, the economy, and other factors. Transferring fuel to these islands is typically difficult, and in some cases impossible, under certain circumstances, such as war. Therefore, reducing the island's reliance on fossil fuels as much as feasible is vital to ensure the energy security of these specific islands. Diesel generators provide electricity to Larak Island, which is situated in the Strait of Hormuz. Larak Island serves as a military island due to its geopolitical location, hence it is crucial to consistently provide Larak with electricity. Therefore, in this paper, a combination of distributed generations and system storage is used to supply the Larak island. The photovoltaic, wind and tidal plants are considered the main power plants, and fuel cells with electrolyzers and hydrogen tanks have also been used as storage systems. In addition, the diesel generator is considered the system backup. The considered objective functions to design and manage Larak island's power supply system are reducing diesel generators fuel consumption, reducing electricity cost, and reducing electricity outages and lost power generation of renewable resources.

Defining the Number of Mobile Robotic Systems Needed for Reconfiguration of Modular Manufacturing Systems via Simulation

The European vision of the Factory of the Future is based on increasing competition and sustainability by transformation from cost orientation to high-adding value with technical and organisational innovations. One of the expected outcomes is an increase in modularisation, i.e., the reconfigurability of the technical system in manufacturing conditions. Modular manufacturing systems (MMS), will consist of modular platforms (MP) that are capable of rapid rebuilding, and reconfiguration performed by adding or removing a module by Mobile Robotic Systems (MRS). In the conditions of MMS, to make the most efficient use of reconfiguration MRS capacities, it is necessary to know the optimal ratio of these MRS to the number of modular platforms (MP) used in MMS, which does not exist today. This ratio will help industrial companies that are deploying MMS-based solutions to plan the number of MRSs needed to reconfigure deployed systems. As a method of determining this optimal ratio, an experimental approach via simulation was chosen, using data from custom MRS and MP prototypes with testing different layouts of modular platforms with the view of warehouse layout, manufacturing island, manufacturing island power supply, and MRS. Based on the results, it can be determined that the MP-MRS limit ratio is 2:1, where the further increase in MRS has only a minimal impact on the reconfiguration period. With the reduction of MP transferred to one MRS, there is a gradual decrease in the time required for reconfiguration. When the ratio of 1:1 is attained, the time required for reconfiguration lowers, but not as dramatically as in bigger ratios.

A robust restoration decision-making strategy for unbalanced distribution networks considering the uncertainty of photovoltage generators

The intermittent and stochastic power injections of the penetration of photovoltaic (PV) generators make the processing of fault restoration in the distribution network need to consider more uncertainties. A new scheme of robust fault restoration methods, aiming to maximize the recovery of outage power, is proposed for unbalanced distribution networks utilizing affine numbers to describe the uncertainty of PV outputs. Besides, the safe operation of the network is taken into account as its constraint condition. This restoration method is presented in two subsequent steps. The first step is the restoration of the island power outage, with the objective to reasonably isolate the power outage area containing the black-start PV to achieve island power supply recovery. Then the second step is to maximize the use of the remaining capacity of the main network and restore the power outage to ensure the power supply of the entire network. To solve the mathematical restoration model accurately, the piecewise linear approximation method based on the best isometric idea is introduced to relax the original objective function into a linear solvable form. An efficient decomposition algorithm, named column-and-constraints generation (C&CG), is used to solve the model, which can further improve the computational efficiency of the algorithm. Numerical tests on different test systems demonstrate that the proposed robust restoration methodology yields obvious advantages in resisting system uncertainties by contrast with the existing deterministic restoration methods.

Clustering analysis of typical scenarios of island power supply system by using cohesive hierarchical clustering based K-Means clustering method

Scenario analysis plays an important role in the planning and operation of the island power supply system. In this paper, a cohesive hierarchical clustering based K-means clustering method is proposed and used for clustering analysis of typical scenarios of island power supply systems. At first, the source and load characteristics of a typical island power supply system are analyzed. Then, three characteristic indexes to distinguish island types are proposed which can achieve the feature extraction of typical scenarios of island power supply systems. On this basis, the cohesive hierarchical clustering based K-means clustering method is proposed for the clustering analysis of typical scenarios of the island power supply system. A case study is made to verify the effectiveness of the proposed method. The case study results indicate that the proposed method can effectively classify different islands into several types, and the features of the typical scenarios of each type of island are analyzed.

Capacity optimization of hybrid energy storage system for flexible islanded microgrid based on real-time price-based demand response

The islanded microgrid (IMG) is universally accepted as an important method to solve the island power supply problem. The optimal capacity of the hybrid energy storage system (HESS) is necessary to improve safety, reliability, and economic efficiency in an IMG. To improve the IMG ability to deal with uncertainty, this paper proposed a flexible islanded microgrid (FIMG) model with real-time price (RTP)-based demand response (DR). Through RTP to guide users’ electricity consumption behaviors more in line with renewable energy sources (RES) output law, the capacity allocation of the HESS was optimized and the system had sufficient flexibility in each scheduling period. In this paper, two decision variables of the HESS, the number of lead-acid batteries and supercapacitors, were determined based on the objective of comprehensive operating cost (COC) and flexibility insufficiency rate (FIR) minimization. Firstly, the non-dominated sorting genetic algorithm II (NSGA-II) was devoted to obtaining the Pareto set that satisfies the FIMG day-ahead scheduling. Then, both the loss of produced power probability (LPPP) and the loss of power supply probability (LPSP) corresponding to each Pareto solution were gotten based on the real-time dispatch strategy. Finally, taking COC, FIR, LPPP, and LPSP as evaluation indicators, the improved Technique for Order Preference by Similarity to an Ideal Solution (TOPSIS) was applied to select the optimal solution from the Pareto set. In the case study, a FIMG on an island in Guangdong province was analyzed and discussed. By studying typical days in winter and summer of the FIMG, the superiority of the proposed model and methods was verified.

Research on Voltage Sharing Optimal Control Strategy of Modular Multilevel Converter Based on Computer

With the environmental protection requirements of smart grid in China, the power electronic technology has been developed rapidly, which greatly promotes the development of FACTS and HVDC. Based on the development requirements of facts and HVDC in China, modular multilevel converter (hereinafter referred to as MMC) has become the core component of high voltage converter, which has many advantages, such as modular design, high output waveform quality, active power troubleshooting control, high reliability, etc. MMC is a new type of voltage source converter, which is suitable for many occasions, such as new energy grid connection, island power supply, large city power supply, etc. With the continuous increase of voltage level in China, the requirements of MMC for power supply companies are gradually improved. At present, computer simulation analysis has been applied to the research of MMC, which can help designers to optimize the scheme better. Therefore, this paper analyzes the equalization control of MMC capacitor voltage (hereinafter referred to as CV). Through computer simulation and analysis of control parameters, the voltage sharing optimal control (hereinafter referred to as VSOC) of MMC is carried out, which solves the current flexible DC transmission system.

Optimal Sizing of an Island Hybrid Microgrid Based on Improved Multi-Objective Grey Wolf Optimizer

The hybrid renewable energy system is a promising and significant technology for clean and sustainable island power supply. Among the abundant ocean energy sources, tidal current energy appears to be very valuable due to its excellent predictability and stability, particularly compared with the intermittent wind and solar energy. In this paper, an island hybrid energy microgrid composed of photovoltaic, wind, tidal current, battery and diesel is constructed according to the actual energy sources. A sizing optimization method based on improved multi-objective grey wolf optimizer (IMOGWO) is presented to optimize the hybrid energy system. The proposed method is applied to determine the optimal system size, which is a multi-objective problem including the minimization of annualized cost of system (CACS) and deficiency of power supply probability (DPSP). MATLAB software is utilized to program and simulate the hybrid energy system. Optimization results confirm that IMOGWO is feasible to optimally size the system, and the energy management strategy effectively matches the requirements of system operation. Furthermore, comparison of hybrid systems with and without tidal current turbines is undertaken to confirm that the utilization of tidal current turbines can contribute to enhancing system reliability and reducing system investment, especially in areas with abundant tidal energy sources.

Optimal Scheduling of Island Microgrid with Seawater-Pumped Storage Station and Renewable Energy

The rapid development of renewable energy, represented by wind and photovoltaic, provides a new solution for island power supplies. However, due to the intermittent and random nature of renewable energy, a microgrid needs energy-storage components to stabilize its power supply when coupled with them. The emergence of seawater-pumped storage stations provides a new method to offset the shortage of island power supply. In this study, an optimal scheduling of island microgrid is proposed, which uses seawater-pumped storage station as the energy storage equipment to cooperate with wind, photovoltaic and diesel generator. First, a mathematic formulation of seawater-pumped storage station with renewable energy is presented. Then, to reach the goal of economic dispatch, an optimal scheduling model of island microgrid is established with the consideration of both respective operation constraints and island load requirements. Finally, the effectiveness of the proposed model is verified by an island microgrid over two typical seasons. The simulation results show that the proposed framework not only increases the usage of renewable energy, but also improves the operational reliability and economy of island microgrids.

Interactive Multi-energy Complementary Island Microgrid Ecosystem

Reliable and stable island power supply system is an important guarantee for the development of the island. Based on the island connected to the main network by cable, this paper proposes an interactive multi-energy complementary microgrid consisting of new energy generation, electric energy interaction, electric vehicle charging and discharging, home photovoltaic system, power distribution and emergency rescue. The electricity generated by the residents themselves can be used by themselves, and the excess can be sold back to the main network. This system makes full use of the characteristics of electric vehicles energy storage and mobility and participate in grid dispatching, which can improve the popularity of new energy power generation, balance the peaks and valleys of island electricity consumption and reduce the cost of electricity for residents.

Analysis and suppression of DC oscillation caused by DC capacitors in VSC‐based offshore island power supply system

Voltage source converter‐high‐voltage direct current (VSC‐HVDC) is an effective way to ensure the reliable supply of offshore island power. However, it is easily liable to direct current (DC) oscillation or even instability due to the interaction between the rectifier and inverter stations. In order to solve this problem, this paper analyzes the stability of the VSC‐HVDC system caused by DC capacitors based on VSC impedance modeling and impedance stability criterion. Besides, an adaptive virtual impedance control strategy to suppress the DC oscillation is proposed. The impedance models of the VSC in the rectifier and inverter stations are constructed and verified. Then, the influence of the DC capacitors on the system stability is analyzed based on impedance stability criteria. The analysis shows that the decrease of DC capacitors will cause DC oscillation, and the DC virtual impedance is used to damping the oscillation. Finally, this paper presents a simple but effective adaptive fuzzy segmented virtual impedance control strategy to suppress the oscillation. Electromagnetic transient simulation and hardware‐in‐the‐loop (HIL) test results show that the proposed adaptive virtual impedance is more effective and has better robustness than the conventional virtual impedance. © 2018 Institute of Electrical Engineers of Japan. Published by John Wiley &amp; Sons, Inc.

Determination of load-frequency dependence in island power supply

The measurement results of a field test in an isolated network show that the quasi-stationary load-frequency dependence in small isolated grids can be more pronounced than in large interconnected systems. In a droop-based control strategy of the power plants, the load-frequency dependence has an influence on the steady-state operating point. Therefore, a methodology for the determination of frequency-dependent characteristics of loads is presented. In the examined network, another effect occurs which is considered in this study. Transient frequency deviations have a relevant impact on the consumption of reactive power caused by transformers.

Stand-alone island daily power management using a tidal turbine farm and an ocean compressed air energy storage system

Due to the high predictability and the high energy density, marine tidal resource has become an area of increasing interest with various academic and industrial projects around the world. In fact, several Marine Current Turbine (MCT) farm projects with multi-megawatt capacity are planned to be installed in the coming years. In this paper, a MCT farm is supposed to be the main energy supply for a stand-alone island. To compensate the MCT farm power variation relating to the tidal phenomenon, an Ocean Compressed Air Energy Storage (OCAES) system is considered to achieve the island power management. The novelty in this work is that conventional Diesel Generators (DGs) would only serve as a backup supply while the main island power supply will be fulfilled by the proposed hybrid MCT/OCAES system. A simplified OCAES model is built-up in this paper with cycle efficiency about 60.6%. Simulations under different working conditions are carried out to validate the feasibility of the hybrid power system. The obtained results show that the proposed system power management can greatly help to decrease DG fossil fuel consumption and CO2 emission.

Protection of the Island Microgrid Based on Ocean Energy

With the continuous development and utilization of Marine resources, the island’s developments get more and more attention of the state, however, the island's power supply is always a bottleneck restricting the development of its economy. Microgrid as a kind of effective supply and use of distributed generation of power system, provides an effective solution for remote island power supply. There is a big difference in output characteristic from the power system, for the distributed power mostly use power electronic interface, which provides barriers to the protection of microgrid. The paper first introduces the structure and control mode of island microgrid based on wave energy power and currents can power generation, energy storage power, then analyzes the fault characteristics of the microgrid under different control, lastly summarizes the existing two types of microgrid relay protection method: the traditional overcurrent protection method and digital network protection method based on the communication.