Large Amount Of Renewable Energy Research Articles

Dynamic simulation of gas turbines via feature similarity-based transfer learning

Since gas turbine plays a key role in electricity power generating, the requirements on the safety and reliability of this classical thermal system are becoming gradually strict. With a large amount of renewable energy being integrated into the power grid, the request of deep peak load regulation for satisfying the varying demand of users and maintaining the stability of the whole power grid leads to more unstable working conditions of gas turbines. The startup, shutdown, and load fluctuation are dominating the operating condition of gas turbines. Hence simulating and analyzing the dynamic behavior of the engines under such instable working conditions are important in improving their design, operation, and maintenance. However, conventional dynamic simulation methods based on the physic differential equations is unable to tackle the uncertainty and noise when faced with variant real-world operations. Although data-driven simulating methods, to some extent, can mitigate the problem, it is impossible to perform simulations with insufficient data. To tackle the issue, a novel transfer learning framework is proposed to transfer the knowledge from the physics equation domain to the real-world application domain to compensate for the lack of data. A strong dynamic operating data set with steep slope signals is created based on physics equations and then a feature similarity-based learning model with an encoder and a decoder is built and trained to achieve feature adaptive knowledge transferring. The simulation accuracy is significantly increased by 24.6% and the predicting error reduced by 63.6% compared with the baseline model. Moreover, compared with the other classical transfer learning modes, the method proposed has the best simulating performance on field testing data set. Furthermore, the effect study on the hyper parameters indicates that the method proposed is able to adaptively balance the weight of learning knowledge from the physical theory domain or from the real-world operation domain.

Application of random matrix model in multiple abnormal sources detection and location based on PMU monitoring data in distribution network

With the conversion of the global power economy and energy structure, access to a large amount of renewable energy has led to a decrease in power system inertia. The slight abnormal disturbance in the distribution network may have a significant impact on social and economic development. Aim at enhancing power stability and system resiliency; this study focuses on the detection and location of multiple abnormal sources in the distribution network. Most traditional methods use models relying on precise line parameters, subject to poor adaptability to the distribution network with a large number of nodes, and rapidly changing topology. Therefore, this study proposes a novel random matrix model, driven by monitoring data from phasor measurement units distributed on the overhead transmission lines. In this model, linear shrinkage (LS) theory, and Marchenko–Pastur law are combined for noise reduction to ensure the dynamic character and anti-noise ability. Moreover, data dimensions and sample points may be at the same level in an extensive scale network. The LS and standard condition number rule (SCN) are used for estimating the number of abnormal sources. Finally, the effectiveness of this paper's model is verified in PSCAD. The results indicate that the method has specific dynamic performance and anti-noise ability.

Unbalanced responsibility division considering renewable energy integration

A reasonable division of the unbalanced contribution is the premise of responsibility division and mitigation. As a large amount of renewable energy integrates into the power system, the disturbance of the system increases and the system impedance is no longer much smaller than the load impedance. The traditional unbalanced responsibility division method is difficult to calculate accurately. This study proposes a new method for calculating unbalanced contribution, which can effectively avoid the limitations of traditional methods. The robust independent component analysis is used to estimate the equivalent source signal. The sparse component analysis method is used to construct the screening criterion to screen the equivalent source signals to obtain estimated signals that are more in line with the real source signals. Then the equivalent negative sequence impedance of upstream and downstream is calculated, and the unbalanced responsibility is divided. This method is still effective when the system impedance is not much different from the load impedance. At the same time, the calculation accuracy is high and the anti-interference ability is strong. Simulation and field test verify the correctness and effectiveness of the proposed method.

Overview: State-of-the Art Commercial Membranes for Anion Exchange Membrane Water Electrolysis

AbstractOne promising way to store and distribute large amounts of renewable energy is water electrolysis, coupled with transport of hydrogen in the gas grid and storage in tanks and caverns. The intermittent availability of renewal energy makes it difficult to integrate it with established alkaline water electrolysis technology. Proton exchange membrane (PEM) water electrolysis (PEMEC) is promising, but limited by the necessity to use expensive platinum and iridium catalysts. The expected solution is anion exchange membrane (AEM) water electrolysis, which combines the use of cheap and abundant catalyst materials with the advantages of PEM water electrolysis, namely, a low foot print, large operational capacity, and fast response to changing operating conditions. The key component for AEM water electrolysis is a cheap, stable, gas tight and highly hydroxide conductive polymeric AEM. Here, we present target values and technical requirements for AEMs, discuss the chemical structures involved and the related degradation pathways, give an overview over the most prominent and promising commercial AEMs (Fumatech Fumasep® FAA3, Tokuyama A201, Ionomr Aemion™, Dioxide materials Sustainion®, and membranes commercialized by Orion Polymer), and review their properties and performances of water electrolyzers using these membranes.

Bidding strategy of hybrid power plant in day‐ahead market as price maker through robust optimization

Renewable energy such as wind power plays an important role in power generation. Large amount of renewable energy can allow these producers to change the market price and be as a price maker in the market. Thus, we propose an optimal bidding strategy in the day-ahead market for the hybrid power plant that participates as a price maker in the day-ahead market and as a price taker in the balancing market. Hybrid power plant is composed of wind power producer, battery storage and demand response. The uncertainty of day-ahead market price is modeled through Robust Optimization. In case studies, bidding strategy of hybrid power plant as a price maker and price taker configuration is presented. Then, joint operation of hybrid power plant is compared to disjoint operation and the effect of participating in market as coordinated unit on total profit is investigated. Moreover, the changes in profit according to risk level are determined and finally, offering curves are obtained by dividing the confidence bounds of day-ahead market price to some subintervals. The simulation is done based on Nord Pool Market and the results validate hybrid power plant can behave as a price maker in the day-ahead market and the profit of all units increases in joint operation.

Electricity grid decarbonisation or green methanol fuel? A life-cycle modelling and analysis of today′s transportation-power nexus

Methanol from captured CO2 provides a more sustainable alternative to gasoline due to its low carbon footprint, yet it requires a large amount of renewable energy that could be used instead to decarbonise the electricity mix. A techno-economic and environmental analysis of methanol produced from captured CO2 and renewable energy is conducted to shed light on the transportation-power nexus. The investigated scenarios differ in how the carbon-free energy source – electricity from wind – is used to either decarbonise the electricity mix or produce green methanol to displace conventional fossil fuels. The assessment is carried out for six countries that differ in the composition of their electricity mix and gasoline consumption. The results of this holistic assessment show that, at present, decarbonising the electricity grid using renewable energy sources and carbon capture and storage would offer greater environmental benefits, without incurring large changes in direct economic costs, compared to producing methanol from the hydrogenation of captured CO2. Though this insight might change in the future if the carbon intensity of the mix is reduced and green methanol becomes cheaper, it highlights the need to consider the transportation-power nexus in assessing alternative fuels and thereby prevent shifting of emissions from one sector to another over their life cycle.

Evaluation of the peak-shaving capability of the receiving-end power system with multi-infeed UHV

Peak-shaving capability mainly refers to the capability of the power system to maintain the balance between the active output and load balance in real-time. Sufficient peak-shaving capability is one of the important conditions to ensure the security and stability of the power system. The access of multi-infeed ultra-high voltage will largely weaken the peak-shaving capability of the power system and thus increase its peak-shaving pressure. This paper first introduces the characteristics of renewable energy generation such as wind generation and photovoltaic generation since a large amount of renewable energy from the sending-end system through several UHV delivery often increases the peak-shaving pressure of the receiving-end power system. On this basis, it analyses the impact of multi-infeed UHV on peak-shaving of power system. Then, an evaluation method that uses equivalent peaking capacity to measure the peak-shaving capability of the UHV receiving-end power system with multi-infeed UHV is proposed. Finally, Zhejiang Power System is used as an example to evaluate its peak-shaving regulation capability in the typical years and the typical day using the proposed method.

Tuning the electronic, optical and structural properties of GaS/C2N van der Waals heterostructure for photovoltaic application: first-principle calculations

Due to the increased energy demand, a large amount of renewable energy is required to sustain the lives of people. The visible light semiconductors for photovoltaic cells with optical properties and a tunable bandgap have been studied to bring the solution to energy crises. Two-dimensional (2D) semiconductors including gallium sulphide (GaS) and carbon nitride (C2N) monolayers as a photovoltaic material were investigated by designing GaS/C2N van der Waals (vdWs) heterostructure. In this study, density functional theory (DFT) was employed to study the structural, photovoltaic applications, electronic and optical properties of GaS/C2N vdWs heterostructure. In comparison with the counterparts of GaS and C2N monolayers, the GaS/C2N vdWs heterostructure showed a lower desirable direct bandgap of 1.251 eV and the projected density of states shows a type-I band alignment. The work function of the heterostructure is much lesser than the GaS monolayer and C2N layer, which signifies that less energy will be needed for electrons to transfer from the ground state. The charge density transfer shows charge redistribution from GaS to C2N. The power conversion efficiency (η) of GaS/C2N heterostructure is calculated to be 17.8%. Based on the results, the 2D GaS/C2N heterostructure is predicted to be effective material in developing a high-performance photovoltaic device for future use.

Bi-Level Optimal Allocation of Flexible Resources for Distribution Network Considering Different Energy Storage Operation Strategies in Electricity Market

Due to the random volatility, a large amount of renewable energy will bring challenges to the security and stability of distribution network. Comprehensive consideration of system economics, security and flexibility has become the focus of research on distribution network optimization planning under the new situation. For the flexible resource allocation problem of distribution network, this paper analyzes the supply and demand relationship of the flexibility of the distribution network, and establishes a bi-level operation-planning joint optimization model for flexible resources. In the operational layer, we not only introduce the insufficient flexibility rate as the evaluation index of system flexibility, but also introduce the network loss, the abandoned wind and solar energy in the economic penalty, aiming at optimizing the annual operating cost of the system. In the planning layer, we evaluate the system security by introducing the comprehensive security index of the system, aiming at optimizing the annual comprehensive cost of the system. In addition, this paper also considers the third-party companies' investment in energy storage system in the electricity market, and further analyses the impact of energy storage operation strategies under different investors on flexible resource allocation. In this paper, the particle swarm optimization algorithm is used to solve the bi-level allocation model. Finally, the IEEE 33-bus test system is used for verification and analysis of the case. The results verify the validity and rationality of the proposed bi-level allocation model.

An Open-Source Protection IED for Research and Education in Multiterminal HVDC Grids

The integration of large amounts of renewable energy will require multiterminal high-voltage direct-current (MTDC) grids to reliably transport the energy over long distances. However, before building an MTDC grid, a functional protection system design is needed. Realistic and industrial studies are required to validate the functionality of such a system. In addition, further academic research as well as education in the field are needed. This paper presents an open-source, low-cost protection intelligent electronic device (IED) prototype for use in a laboratory environment. In particular, the IED design, its fastest measured performance, example results for different fault scenarios, and an assessment of its use in education are shown. The open-source IED is useful to accelerate industrial and academic research, as well as to enable education in protection for MTDC grids.

Mathematical Modeling of Evaporator in Reheat Recovery Drum Boiler

The reheat recovery boiler is widely-used energy conservation equipment aiming to take advantage of the exit flue of gas turbine in combined cycle. Due to large amount of renewable energy getting access to grid, a more flexible and agile operation mode of reheat recovery boiler is in great need, and parameter distribution is arousing great attention of researchers. In present paper, a mathematical model of downcomer-riser-drum is established based on conversation equations. Four typical working condition of heat recovery boiler are studied, and detailed information is demonstrated.

A Fixed-Flexible BESS Allocation Scheme for Transmission Networks Considering Uncertainties

Battery energy storage systems (BESSs) can play a key role in mitigating the intermittency and uncertainty associated with adding large amounts of renewable energy to the bulk power system (BPS). Two BESS technologies that have gained prominence in this regard are Lithium-ion (LI) BESS and Vanadium redox flow (VRF) BESS. This paper proposes a fixed-flexible BESS allocation scheme that exploits the complementary characteristics of LI and VRF BESSs to attain optimal techno-economic benefits in a wind-integrated BPS. Studies carried out on relatively large transmission networks demonstrate that benefits such as reduction in system operation cost, wind spillage, voltage fluctuations, and discounted payback period, can be realized by using the proposed scheme.

Development of optimization model for power system operation, outline of model design and verification of output

AbstractOsaka Gas Co., Ltd., jointly with NTT DATA Mathematical Systems Inc., has developed unit‐commitment model for optimizing dispatch of power generation units. Main purpose of this development is to simulate the future world of electric power system in accordance with national energy policy aiming to introduce large amount of renewable energy as well as vitalized cross‐border power exchange via PX market to enhance economically‐efficient power system operation. The model incorporates not only constraints of supply‐demand balance but also constraints of operating reserves, regulation reserves, maximum CO2‐emissions, etc.

Testing Metal–Oxide Varistors for HVDC Breaker Application

There is growing interest in changing the power grid infrastructure. It is increasingly important to transport a large amount of renewable energy over long distances. To minimize losses, meshed dc-grids are needed but require the development of dc circuit breakers. Without it, a meshed grid cannot be operated. Actually different concepts of dc breakers exist. The majority of them include an energy absorbing element. In ac grids, metal-oxide varistors (MOVs) absorb high energies. However, clarification is needed whether commercial available MOVs are able to handle the energy stresses that arise during dc switching operations. To investigate the energy handling capabilities of conventional metal-oxide material, an endurance test setup has been developed. In this setup, MOV specimens are stressed by repetitive impulse current injections while being permanently connected to dc voltage. This study reports on the endurance behavior of MOV submitted to >10 000 impulse energy injections with 60-100 J/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> . Large differences are observed for MOVs from different manufacturers. Temperature and superimposing the impulses by a constant dc voltage are two parameters of less impact. Two types of MOV showed moderate changes of their electrical properties after >10 000 impulses and would be suitable for dc breaker application.

European Union Electricity Markets: Current Practice and Future View

The European Union (EU) aims to develop an integrated electricity market as an efficient instrument to achieve the energy policy targets of security, affordability, and sustainability. Many milestones have already been reached, including the implementation of a European platform for the simultaneous clearing of day-ahead markets, the design of several platforms for coordinating intraday and regional balancing markets, and the enforcement of guidelines for the design of capacity mechanisms (CMs). There are still many challenges ahead for this market: the integration of large amounts of renewable energy, the proliferation of distributed resources, higher consumer engagement, and the sheer scale and complexity of a market serving 500 million citizens. This is a fascinating task that will keep us busy in the coming years.

A high-speed protection scheme for the DC transmission line of a MMC-HVDC grid

High Voltage Direct Current (HVDC) grids based on Voltage-Source Converters (VSC) are flexible and can absorb large amounts of renewable energy. However, since the magnitude of fault current increases quickly, and it cannot be controlled after DC transmission line fault, the DC transmission line protection should operate very fast after the fault event. Otherwise, the DC circuit breakers will not be able to interrupt such a large fault current, which may cause permanent damage to the devices in the converter station. Based on the analysis of the feature of fault-induced travelling waves after DC transmission line fault, this paper proposes single-ended initial travelling wave based protection scheme. Based on the analysis of the feature of lightning disturbance, this paper also proposes fast identification scheme for lighting disturbance, in order to increase the reliability of the protection and maintain the high operation speed at the same time. A protection device prototype has been designed and implemented. Abundant tests have been conducted to verify the performance of the prototype device. The operation time of the protection is less than 1.2ms.

The role of malachite nanorods for the electrochemical reduction of CO2 to C2 hydrocarbons

The electrochemical reduction of CO2 to higher hydrocarbons is a very challenging process that has high potential for the storage of large amounts of renewable energy with a high gravimetric and volumetric energy density. The distribution of hydrocarbons from the electrocatalytic reduction of CO2 is primarily determined by the interaction of the cathode material with the CO2 in the electrolyte. While the research on the electrochemical CO2 reduction focuses on the cathode metal and surface structure of the metals, recently evidence was found that the metal itself may not be the active species but rather the product formed from the metal and CO2. In this paper, we report about the synthesis, catalytic activity and selectivity of nanostructured metal carbonate, i.e. malachite, as a highly active catalyst for the electrochemical synthesis of C2 hydrocarbons. These first results obtained on Cu2(OH)2CO3 nanorod-structured “trees” show that carbonate, not the pure metal, is the active catalytic species. This new catalyst favors the production of ethylene (C2H4) and ethane (C2H6) with significantly higher Faradaic efficiency than that of the pure Cu surface.

SOUTH PATAGONIA: WIND/HYDROGEN/COAL SYSTEM WITH REDUCED CO2 EMISSIONS

Wind is a significant renewable energy source in Patagonia, which could generate a very large amount of electrical energy. However, it is not possible to put such a large amount of energy on to the grid due to instability issues. Electrolysis could facilitate the storage of such energy in the form of hydrogen, which could be used for peak power production or for vehicles. However, hydrogen storage and distribution are still very expensive. On the other hand, South Patagonia has reserves of coal which exploitation is not easy. One solution could be underground coal gasification. Unfortunately, using coal results in high emissions of carbon dioxide. Hydrogen from wind energy could be the solution to convert coal to methane and to eventually generate electrical power. In this way, a large amount of renewable energy could be introduced to the energy system with a reduction in the emissions of carbon dioxide.

Operations of a microgrid with renewable energy integration and line switching

With the development of new technologies and their integration to the conventional power grid, the smart grid with the capacity of satisfying power demand by large amount of renewable energy is emerging. Microgrid, a small-scale power system with clearly defined electrical boundaries and ability of self-supply, especially by distributed renewable energy, plays a big role in this process. In this paper, we study the operations of a microgrid with solar photovoltaic generators, energy storage system, and power exchanges with main power grid. More specifically, a mixed integer programming model is formulated for decision-making, such as scheduling of generators within the microgrid, islanding operations through line switching and power trades between microgrid and the main grid, charging and discharging operations of storage system, and also line switching within the microgrid, by robust optimization for capturing the uncertainties of solar power generation. To solve the robust optimization formulation, we formulate our model in order to apply the column-and-constraint generation algorithm, and perform numerical experiments on several test cases to validate the proposed model and algorithm.

Empirical Study on Structure Equation Type Load Model Using Actual High Sampling Rate Measurement

Abstract According as a large amount of renewable energy is introduced in the electric power system, voltage stability has been attracting attentions in a complex real system. This paper proposes a new load model based on structural equations in place of the conventional ZIP models. In the proposed model, the reactive power is included in the formula for explaining the active power. On the contrary, the active power is applied in the expression explaining the reactive power. Furthermore, to estimate this structural equation without bias, variables are selected by considering the identification of the explanatory expression using the measured value. In order to model the change of the load due to the change in the voltage and frequency of the power supply system side, the high sampling measurement value are utilized in the numerical experiment for which are executed at a residence and a laboratory.