Operation Of Proposed Strategy Research Articles

An Economic Performance Improving and Analysis for Offshore Wind Farm-Based Islanded Green Hydrogen System

When offshore wind farms are connected to a hydrogen plant with dedicated transmission lines, for example, high-voltage direct current, the fluctuation of wind speed will influence the efficiency of the alkaline electrolyzer and deteriorate the techno-economic performance. To overcome this issue, firstly, an additional heating process is adopted to achieve insulation for the alkaline solution when power generated by wind farms is below the alkaline electrolyzer minimum power threshold, while the alkaline electrolyzer overload feature is used to generate hydrogen when wind power is at its peak. Then, a simplified piecewise model-based alkaline electrolyzer techno-economic analysis model is proposed. The improved economic performance of the islanded green hydrogen system with the proposed operation strategy is verified based on the wind speed data set simulation generated by the Weibull distribution. Lastly, the sensitivity of the total return on investment to wind speed parameters was investigated, and an islanded green hydrogen system capacity allocation based on the proposed analysis model was conducted. The simulation result shows the total energy utilization increased from 62.0768% to 72.5419%, and the return on investment increased from 5.1303%/month to 5.9581%/month when the proposed control strategy is adopted.

Day-ahead dispatch with carbon trading for multi-regulation participation and emission reduction considering multi-type energy storage

In this work, a day-ahead dispatch optimization model with energy-type, power-type, and composite-type energy storage systems (ESSs) is established to participate in multiple frequency control ancillary services (FCASs), in wind-energy-integrated power systems. This model is designed to better handle the operational uncertainties of wind energy, mitigate operational risks and reduce carbon emissions. Leveraging the complementary features of different types of ESSs, the proposed operation strategies of regulation units can respond to multiple FCASs and achieve the optimal task allocation among different types of resources. Various uncertainty handling approaches are adopted to better cope with the randomness of step disturbances and wind power fluctuations. Furthermore, a new environmental factor is devised in the dispatch objective and the time-of-use carbon-price carbon emission trading (ToU-CET) and ladder-type CET (LT-CET) models are developed. They can incorporate dynamic carbon prices and leverage mechanisms to reduce carbon emissions during daily operations. The effectiveness of the proposed model is verified by case studies, and the decisions can help save energy and reduce carbon emissions in modern power systems with wind power generators with high security and reliability.

Dual-drive coordinated operation strategy for internet data centers by exploiting spatiotemporal flexibility

With the rapid expansion of computational infrastructure, the electricity consumption of geographically dispersed Internet Data Centers (IDCs) has imposed a substantial influence on the power grid. Geographically distributed IDCs, which present a versatile electricity demand with significant operational flexibility, hold potential for mitigating cost issues and balancing regional supply and load demand. To exploit this flexibility, this paper has developed a dual-drive coordinated operational strategy, which integrates locational electricity prices and unit carbon emission costs based on the dynamic carbon emission intensity (DCEI) of various regions as interaction signals to improve coordination effectiveness. The upper-level determines the consumption behaviour of IDCs, the lower-level provides feedback on dual-drive signals factoring in IDCs' involvement in grid operation, whilst an iterative algorithm is suggested to solve the bi-level model. Case studies based on real-world datasets demonstrate that the proposed operation strategy can achieve arbitrage through multi-regional carbon-electricity markets, significantly reduce operating costs, and support the rapid development of IDCs. Additionally, this strategy facilitates optimal matching of power load in IDCs with renewable energy sources, thereby mitigating imbalances in regional renewable energy supply and demand.

Part-load thermal efficiency enhancement in gas turbine combined cycles by exhaust gas recirculation

Gas turbine power plants are popular for offshore power generation due to high power density and their reliability. However, growing usage of renewable energies put gas turbines in a load following backup operation. These power plants suffer part-load efficiency losses when operating at less than full capacity, resulting in higher carbon dioxide (CO2) emission from natural gas combined cycles or higher consumption of carbon-free fuels in decarbonized gas turbines. In this article, a solution is proposed for enhancement of power plant part-load thermal efficiency based on exhaust gas recirculation in the gas turbine cycle. Recirculating exhaust gas into the gas turbine have been studied by several researchers and engineers due to its benefit for carbon-free combustion and carbon capture mechanisms. The proposed operation strategy is evaluated for single-spool and two-spool gas turbines operating jointly with a steam bottoming cycle harvesting the waste heat for further power production. In the suggested strategy, eliminating the necessity to cool down the recirculated gas resulted in less equipment footprint for the power plant which makes it more favorable for offshore applications. An in-house design and simulation tool is developed for evaluating gas turbines with modern gas recirculating systems and a flexibility in operation with carbon-free fuel mixtures. The enhancement in efficiency boost, emission reduction, and fuel consumption is quantified demonstrating the improvements with the proposed solution.

Life cycle optimization framework of charging–swapping integrated energy supply systems for multi-type vehicles

The energy supply infrastructure is an important guarantee for vehicle electrification. Its economy, service capability and grid friendliness are critical factors drawing wide attention. To reduce the cost of energy storage devices that alleviate the high-power grid impact from fast charging station, this study proposes a novel energy supply system configuration that integrates fast charging for passenger vehicles and battery swapping for heavy trucks, and discharges the large-capacity swapping batteries to support fast charging. The influences of station configurations, including in-station batteries, charging and swapping equipment on the system economy, service quality, and grid capacity demand are revealed through system modeling and analysis. The impact of the charging time on battery degradation during operation is also explored. Moreover, a life cycle optimization framework for the charging–swapping integrated system is formulated, together with the complementary control strategy that realizes bidirectional energy coupling of fast charging and battery swapping loads. In this framework, the battery swapping service model is established to quantify the service quality; the electrochemical mechanism model is used to evaluate the battery degradation during charging and discharging processes; and the life cycle cost model is established by integrating the investment and operation costs of the energy supply system. On this basis, the design and control variables are collaboratively optimized towards the maximal life cycle benefits. Based on the actual load characteristics of charging and swapping stations, a comparative study is performed for the proposed operation scheme and the general service quality-prioritized scheme. The obtained results show that the maximum station power is reduced by more than 0.6 MW, and the total life cycle cost of the energy supply system is reduced by over 1 million RMB under the proposed scheme, verifying its notable effect of life cycle economy improvement.

A Novel-Driven Scheme Regarding to Current Dynamics Enhancement for Switched Reluctance Motor System

Aiming at lowering the cost and enhancing the current dynamics for switched reluctance motor (SRM) system, a novel driven scheme is proposed by combing the self-boost voltage converter (SBVC) and chopping limit active regulation (CLAR) current control strategy. First, the working modes of SBVC are analyzed during the one-phase and two-phase operation situations. And the DC-link voltage pump-up mechanism and capacitor parameters selection method are developed. Then, the CLAR current control strategy is performed to adjust the excitation voltage and demagnetization voltage and then shape the current waveform. Owing to the proposed current profile generation technique, the excitation time and demagnetization time can be actively adjusted to enhance the current dynamics under different mission profiles. Compared to the existing current dynamics enhancement strategy, the proposed operation strategy achieves the lower cost, better current tracking performance, lower torque ripple and wider speed range. Simulations and experiments are performed on a four-phase 8/6 SRM to verify the validity of the proposed operation strategy in different mission profiles.

Joint Optimal Energy Management and Voyage Scheduling for Economic and Resilient Operation of All-Electric Ships Considering Safe Return

Marine power systems are isolated from external grids, making them more vulnerable than land-based power systems. When ships are sailing on the ocean, complicated maritime environment and electrical component failure pose a crucial challenge to a safe and resilient shipboard power system. Different from fixed terrestrial microgrids, all-electric ships (AES) are mobile transportation vessels, complying with the navigation regulation of safe return to port. Thus, the economic and resilient operation needs to be considered from both energy and transportation aspects. In this regard, this study proposes a two-stage coordinated optimization framework for an AES, taking into account the impact of navigation. In the first stage, the normal operation mode follows the pre-voyage plan, which jointly optimizes voyage and energy management to reduce the whole voyage operation costs and greenhouse gas emissions simultaneously. In the second stage, a resilience-oriented optimization is developed to defend against emergencies by rescheduling navigation speed and generation. Furthermore, resistance during the whole AES navigation is also considered. Numerical results demonstrate the necessity of resistance impact on the voyage and the efficiency of the proposed operation scheme in economic and resilient operation for AESs.

Forecast-based charging strategy to prolong the lifetime of lithium-ion batteries in standalone PV battery systems in Sub-Saharan Africa

Standalone PV battery systems have great potential to power the one billion people worldwide who lack access to electricity. Due to remoteness and poverty, durable and cheap systems are required for a broad range of applications. However, today’s PV battery systems do not yet fully meet this requirement. Especially batteries still prove to be a hindrance, as they represent the most expensive and fastest-aging component in a PV battery system. This work aims to address this by prolonging battery life. For this purpose, a forecast-based charging strategy was developed. As lithium-ion batteries age slower in a low state-of-charge, the goal of the operation strategy is to only charge the battery as much as needed. The impact of the proposed charging strategy is examined in a case study using one year of historical data of 14 standalone systems in Nigeria. It was found that the proposed operation strategy could reduce the average battery state-of-charge by around 20% without causing power outages for the mini-grids. This would significantly extend the life of the battery and ultimately lead to a more durable and cheaper operation of standalone PV battery systems.

Fast and Accurate Weight Updating Strategy for Resistive Random-Access Memory (RRAM)-Based Neural Networks

The mathematical relationships between the operating voltages and the conductance of resistance random-access memory (RRAM) are found based on the statistical measurements of the 1-transistor 1-RRAM (1T1R) array. According to the corresponding relationships, a one-shot operation scheme without verification after programming is proposed for weight updating of RRAM-based neural networks. The proposed operation scheme enables parallel column-by-column SET and row-by-row RESET, which achieves fast and accurate conductance modulation in the 1T1R array. By utilizing the one-shot scheme for weight updating of the deep-Q network, the training efficiency improves 40 times compared with the incremental step pulse programming (ISPP) scheme.

Part-load performance analysis of a dual-recuperated gas turbine combined cycle system

To undertake peak shaving tasks, gas turbine combined cycle (GTCC) units often deviate from the design operating point. In order to improve the off-design performance of GTCCs, a dual-recuperated gas turbine combined cycle (DRGTCC) system based on partial recuperation and compressor inlet air heating is proposed in this paper. The operating characteristics of the novel system using the proposed operation strategy are investigated, and the effects of pressure drop in recuperators and ambient temperature on system performance are discussed. The results indicate that, compared with the GTCC system, the DRGTCC system has higher turbine inlet temperature (TIT) and turbine expansion ratio at the same power output, and the performance has been improved especially at lower power outputs. When the inlet temperature of the compressor is increased from 0 °C to 45 °C, the air mass flowrate can be regulated between 46.0% and 100% of the design value. The combined cycle efficiency of the DRGTCC system is improved by 2.55 percentage points at 45.5% design combined cycle load. Moreover, the sensitivity analysis shows that the system performance decreases with the increase of the pressure drop in recuperators, and the ambient temperature affects the load regulation range and efficiency.

Community Solar Operation Strategy for Smart Energy Communities Considering Resource Fairness

This study proposes a community solar operation strategy for smart energy communities (SECs), which comprise members of an energy consumption group, to minimize the electricity bill of its members. When sharing resources within a group, resource distribution is a critical problem, and fairness in resource sharing is the main constraint for operation. The proposed community solar operation is formulated as a mixed-integer liner problem that can be optimally solved using centralized control and future time information. However, obtaining information of a future time is not causal. By decomposing the problem into individual problems that are solved by each member at each decision time, the proposed strategy operates the community solar in a distributed manner with partial information. The simulation results using the real dataset recorded in Korea show that the use of the proposed operation strategy results in a fair distribution of electricity bill savings with a marginal benefit reduction of 10% compared to the optimal operation that requires a centralized control and information on the future time. Moreover, a discussion on the tradeoff between the benefits of electricity bill savings and guarantee of fairness is provided. Based on the results, this study can serve as a reference for the design of community solar operations for SECs.

Weather-based operation strategy for a dynamically compartmentalized double-skin façade system

This study proposed a weather-based operation strategy for a dynamically compartmentalized double-skin façade (DSF) system. The system features two separate air cavities, each of which serves as an inlet or an outlet. The cavities are placed at different levels to facilitate the buoyancy-driven ventilation and the preheating effect. To enhance the performance, the compartmentalized DSF needs to be operated in active cooling (AC), passive cooling (PC), and hybrid heating (HH) modes based on the outdoor condition. Therefore, this study proposed the appropriate operation strategy for the system and evaluated the influence of the strategy on building's thermal performance. Various mode-control thresholds for switching between AC–PC and between PC–HH modes were examined. A validated building simulation model was used to evaluate the operation strategy through a case study, and the results were discussed on the basis of the two types of performance indicators (PIs): the cooling and heating energy use intensity (for AC and HH modes) and hot and cold discomfort hours (for PC and HH modes). A lower AC–PC threshold increases the cooling energy while decreasing the hot discomfort. The influence of a PC–HH threshold on discomfort hours is not linear and vary by modes; therefore, PIs in each mode should be prioritized to determine the optimal threshold. The case study indicated that the DSF with the proposed operation strategy saved 28% cooling energy and 98% heating energy in comparison to a single-skin façade system. Significant hot discomfort may occur in the HH mode, emphasizing the importance of adaptive operations.

A new operation strategy based on unequal ad-/desorption time for a two-bed adsorption refrigeration system

Adsorption refrigeration is one of green cooling technologies while it uses natural refrigerant and can be driven by renewable energy or waste heat. However, its wide application is restricted by the disadvantages of low efficiency and large size. To improve the performance, this paper proposes a new operation strategy based on unequal ad-/desorption time for a two-bed adsorption refrigeration system. The detailed configuration and working processes of this proposed system are described. Then, a mathematical model is developed to investigate the performance of proposed operation strategy. Through the analysis on the simulation results, the effects of desorption and preheating/-cooling time on thermal/electrical coefficient of performance (TCOP/ECOP) and specific cooling power (SCP) are revealed. TCOP and SCP intersection point is located at around 570 s desorption time. SCP reaches the peak value of 203 W kg−1 at 20 s preheating/-cooling time. The system adopting the new operation strategy can achieve a TCOP of 0.610, an ECOP of 29.23 and a SCP of 203 W kg−1. When compared to the traditional operation strategy, the COP is improved by 53% but the ECOP and SCP is slightly promoted. This work can provide a feasible guideline for applying new operation strategy on practical systems.

Comprehensive assessment and performance enhancement of compressed air energy storage: thermodynamic effect of ambient temperature

In an adiabatic compressed air energy storage system, the significance of ambient temperature variation to determine the components’ off-design operation and system performance was not clear yet. In this paper, a dynamic model of the concerned system considering off-design operation of components and real fluid behavior was established. Design and off-design performance of components and system, as well as the relationship between each component, were investigated under various ambient temperatures. The link between ambient temperature variation and system capacity was elucidated. Results showed that as ambient temperature declined, the total compression ratio of compressor unit increased, whereas the storage pressure of air chamber first increased, then reached a plateau. Compared to design condition, 4.83% higher turbine power and 7.53% higher round trip efficiency were obtained at higher ambient temperatures. At lower ambient temperatures, system efficiency was reduced by up to 4.85%, but output work remained practically unchanged. To improve the off-design performance at lower ambient temperatures, a control strategy of thermal energy storage was proposed. The round trip efficiency and output work were improved by 7.7%–11.3% and 5.3%–7.2% with the proposed operation strategy, which were 5.9%–7.0% and 4.5%–4.8% higher than those under design condition.

Optimal Operation Strategy for Wind–Hydrogen–Water Power Grids Facing Offshore Wind Power Accommodation

In this study, we utilize the advantages of offshore wind power resources in coastal areas to make up for the shortage of freshwater. At the same time, freshwater can be used as raw material to supply hydrogen energy. An operation strategy considering power and water input for an electrolyzer is proposed and an electrolyzer variable efficiency model under optimal operation mode is also proposed. Considering both energy benefits and operation and maintenance costs, this paper sets up the wind–hydrogen–water power grid system optimal operation model. Simulation analysis is carried out from the aspects of economy, accommodation, uncertainty of impacts of the reservoir capacity, water satisfaction, and so on. The results show that the accommodation rate reaches 98.2% when considering the proposed operation strategy. The average daily operating cost of the system reaches USD 3.9 × 104, and the strategy and model have good economic benefits and practical significance.

Fast and stable operation approach of ship solid oxide fuel cell-gas turbine hybrid system under uncertain factors

This work focuses on investigating the adaptability of solid oxide fuel cell-gas turbine (SOFC-GT) hybrid system for ship application under uncertain factors. The effect of rapids, wind and waves on the performance of ship SOFC-GT is analyzed. In addition, a novel control system combining fuzzy logic theory, temperature feedforward and coordination factor on-line adjustment is proposed to address the problem of load disturbances caused by uncertain factors. The results show that the proposed operation strategy can shorten the thermal response time inside fuel cell stacks by almost 49.97%, meanwhile, reducing the maximum temperature changing rate at the electrochemically active tri-layer cell composed of anode, electrolyte, and cathode (PEN structure) by around 17.86%. Moreover, the reasonable matching between air flow and fuel flow is an essential prerequisite to ensure the safe and efficient operation of ship SOFC-GT. While the SOFC-GT is working at full load, the results indicate that the fuel to air ratio cannot exceed 2.56✕10−2 g/g. Finally, an application scenario of the 5000-ton river-to-sea cargo ship sails from Nanjing Port to Yangshan Port (Eastern China) is conducted to analyze the operation characteristics of ship SOFC-GT under uncertain factors. Two set of 1000 kW SOFC-GT systems with the electrical efficiency of 64.66% is designed for the target ship, the results conclude that the operation strategy of each SOFC-GT system supports 50% load is beneficial in reducing the power tracking time and SOFC temperature overshoot. The average electrical efficiency of 61.45% and 61.04% are achieved in winter and summer typical days respectively in the whole voyage.

Research on Optimal Scheduling of VPP Based on Latin Hypercube Sampling and K-Means Clustering

Based on the classical scenario set, the VPP economic dispatch model is proposed taking into account the uncertainty factors of distributed power sources. The basic model of the VPP is first analyzed, followed by the proposed operation strategy of the VPP based on the basic model, while considering the impact of the time-of-use electricity price on the economics of the VPP. Latin hypercube sampling combined with K-means clustering is used to generate the classical scene set; at the same time, the model is solved using an algorithm that incorporates a genetic mechanism in an improved particle swarm algorithm (PSO). Finally, according to the established model, a calculation example is used to verify. The design is based on two scenarios of the classic scene set and general scene. The optimization configuration results are compared and analyzed. It is confirmed that the VPP optimization configuration under the classic scene set can improve the net income of the VPP.

Dynamic Virtual Energy Storage System Operation Strategy for Smart Energy Communities

The concept of a virtual energy storage system (VESS) is based on the sharing of a large energy storage system by multiple units; however, the capacity allocation for each unit limits the operation performance of the VESS. This study proposes an operation strategy of a dynamic VESS for smart energy communities. The proposed VESS operation strategy considers the usage-limited constraint rather than the capacity allocation constraint and it guarantees the usage of VESS resources of each participant for an operation period. Therefore, the degrees of freedom for VESS operation can be increased at each operation time. The dynamic VESS operation problem is formulated as a mixed-integer linear problem that could be solved optimally by applying gradient methods and dual decomposition. The dataset of a VESS in Korea is used for simulation. The simulation results demonstrate that, when the proposed operation strategy is used, the cost efficiency achieved is more than twice that achieved when the existing VESS operation strategy is used. Furthermore, the proposed strategy accurately reflects the characteristics of the participants; thus, more units can participate in the VESS operation service. The proposed VESS operation can improve the system performance of the utility grid and increase the net benefit of the participants.

Optimal probabilistic operation of energy hub with various energy converters and electrical storage based on electricity, heat, natural gas, and biomass by proposing innovative uncertainty modeling methods

In recent years, attention to energy hubs (EHs) has increased significantly as active and intelligent elements in multi-energy systems (MESs). This article proposes a stochastic framework for the optimal operation of a new EH structure with various energy converters and electric storage based on electricity, heat, natural gas, and biomass. The proposed framework plays the role of a bidding strategy for a smart element in MESs. For modeling uncertainties in this framework, such as energy market prices, wind speed, and solar radiation, it is necessary to generate random scenarios based on recorded past behaviors or forecasting future trends. The Monte Carlo (MC) and the ARIMA methods have received significant attention in the literature to generate scenarios. Proposing uncertainty modeling methods in this paper, including the MC based on the Kolmogorov-Smirnov test, the ARIMA model based on Akaike Information Criterion, TBATS model, and the LSTM model of deep learning, as another innovation, has been such that efforts are made to make a significant improvement in the generated scenarios. Comparing various proposed uncertainty modeling methods is one of the most contributions. Based on the actual data in Finland, the simulation results demonstrate the effectiveness of the proposed operation strategy and the uncertainty modeling methods. Increasing the accuracy of uncertainty modeling has a significant impact on EH's profit and energy storage behavior and can also reduce the dependence of EHs on incoming energy carriers.

Coordinate control and energy management strategies for a grid-connected hybrid system

This paper explains how to operate a networked hybrid system. A Proton Exchange Membrane Fuel Cell (PEMFC) and a hybrid photovoltaic (PV) array system are taken into account. The hybrid system can run in Feeder Flow Control (FFC) or Unit Capacity Control (UPC) mode. Changes in load demand are adjusted by the main grid because the hybrid source's output is controlled by reference power in UPC mode. Renewable energy is widely used. When light and temperature fluctuate, a PV battery uses Maximum Power Point Tracking (MPPT) to give maximum power to a load. Photovoltaic electricity is uncontrollable because its output varies with the outside and cell temperature. PEMFC should be added to the hybrid system to overcome its limitations. The output of the hybrid source can be controlled by adjusting the output power of the frequency converter. As a result, it is necessary to set a reference value for the output of the hybrid source. In Feeder-Flow Control (FFC) mode, the feeder flow is controlled to remain constant, the hybrid source takes on additional load, and as a result, the feeder reference power needs to be understood. This method reduces load shedding and boosts electricity under high loads. Under light load, the hybrid power supply switches to UPC mode. When the load requirement is near the border of the mode change, UPC or FFC mode is used. Hysteresis eliminates power reference fluctuations. The proposed operation strategy increases system performance, system stability, and mode transitions by consistently operating the PV array at maximum output power and the Photovoltaic–Fuel Cell (PVFC) within its highefficiency range.