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A comparative study of combined cycles for concentrated solar power for efficient power generation using low Global Warming Potential (GWP) fluids to reduce environmental effects
- Author(s): Yunis Khan ; Hakan Caliskan ; Hiki Hong
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p.
3741
–3754
(14)
AbstractA comparative analysis of a combined system comprising organic Rankine cycles (ORC) and supercritical CO2 (sCO2) cycles for concentrated solar power (CSP) applications was performed in the article. Low global warming potential (GWP) fluids were used to investigate strategies for reducing the effects on global warming. In the current study, four different combinations of the sCO2 cycles and ORC, including basic recuperated, pre‐compression, recompression with main compressor intercooling, and partial cooling, were taken into consideration, and their performances with regard to CSP application were compared. The integrated recompression with main compressor intercooling and ORC arrangement was seen to operate thermodynamically more efficient than the other considered configurations. This configuration's highest thermal and exergy efficiencies were discovered to be 51.9% and 55.84%, respectively, and R1243zf was found to be the best‐performing fluid among other considered low GWP fluids to reduce the environmental effects.
Low global warming potential (GWP) fluids were used to investigate strategies for reducing the effects of global warming and performance compared with hydro fluoro carbons (HFC) fluids. Four different combinations of the sCO2 cycle and ORC, including basic recuperated, pre‐compression, recompression with main compressor intercooling, and partial cooling, were all taken into consideration, and their performances with regard to CSP application were compared. It was found that integrated recompression with main compressor intercooling and ORC was thermodynamically best performing configuration over the other considered configurations.image
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Unified AC/DC hybrid admittance modelling and oscillation stability analysis for interlinking voltage source converter system
- Author(s): Hua Xie ; Yigang Zhao ; Xiangyu Wu ; Runni Yu ; Yin Xu ; Suwei Zhai
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p.
3755
–3776
(22)
AbstractThe voltage source converter (VSC) interlinking AC and DC power networks is a core equipment in AC/DC hybrid power systems. To analyze the stability of this system based on the impedance method, it is necessary to establish the hybrid AC/DC admittance model of interlinking VSC. This paper presents a unified and systematic AC/DC hybrid admittance modelling framework which is widely applicable to different control methods of interlinking VSCs. The hybrid admittance models for interlinking VSCs under PQ control, VdcIq control, and Vf control are explicitly formulated, with their elements individually reflecting the dynamics of the AC side, DC side, and the interaction between them. Subsequently, the impedance network model of interlinking VSC systems is formulated based on the hybrid admittance, and furthermore the frequency‐domain modal analysis is performed to analyze the system oscillation stability. Finally, frequency scanning and time‐domain simulation results in MATLAB/Simulink are provided to validate the effectiveness of the modelling and oscillation stability analysis method.
This paper presents a unified AC/DC hybrid admittance modelling method and oscillation stability analysis method for interlinking voltage source converter systems.image
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A SSSC optimal configuration method to enhance available transfer capability considering multi‐wind farm access
- Author(s): Yanbo Chen ; Deshuai Wang ; Jiaqi Li ; Haiwei Fan ; Jinsong Li ; Yadi Luo ; Li Li
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p.
3777
–3792
(16)
AbstractIn the context of electricity market, the heavy load of some inter‐provincial and intra‐provincial lines limits available transfer capability (ATC). As a series compensation device, static synchronous series compensator (SSSC) can reallocate the power flow of adjacent lines. In order to maximize the inter‐regional ATC, a two‐stage optimal SSSC allocation method considering the uncertainty and correlation of multi‐wind farm is proposed. Firstly, the initial wind power scenarios are generated based on latin hypercube sampling (LHS) and reduced by the improved iterative self‐organizing data analysis techniques algorithm (I‐ISODATA). Then, a multi‐objective optimization model is constructed with the maximum expected power flow transfer entropy (PFTE) and minimum expected SSSC investment cost in all typical wind power scenarios, and non‐dominated sorting genetic algorithm‐II (NSGA‐II) method is used to determine the location of SSSC. In addition, based on the reduced wind power scenarios, the ATC calculation model containing SSSC is constructed, and the modern interior point method is used to determine the control parameters and configuration capacity of SSSC. Finally, based on the improved IEEE39 and IEEE118 node systems, case study proves that the proposed model can determine the optimal SSSC configuration scheme and significantly improves the ATC.
In order to maximize the inter‐regional available transfer capability, a two‐stage optimal static synchronous series compensator allocation method considering the uncertainty and correlation of multiple wind farms is proposed. image
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Research on the strengthening and retrofitting methods of existing wind turbine foundations with embedded‐ring
- Author(s): Wenming Wang ; Yahui Gao ; Dapeng Qiu ; Zhen Wang ; Peicheng Nie ; Huichao Ma
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p.
3793
–3803
(11)
AbstractHigher demand for the load‐bearing ability of supporting foundations is required if its upper wind turbine is substituted by a larger one. Presently, there is a lack of strengthening and retrofitting methods for existing wind turbine foundations. A combined‐connection retrofitting method by adding anchor bolts to the existing wind turbine foundation with embedded‐ring is prompted in this study. Furthermore, a strengthening measure by adding a stiffening beam, expanding the foundation plate, and adding rock bolts to increase the ability to resist basal bending moment is proposed. Finite element analysis is conducted to analyze the effectiveness of the proposed strengthening and retrofitting methods for a 2 MW wind turbine foundation. The result shows that the peak stress of embedded‐ring is decreased by 36% by using the internal combined‐connection, and the peak tensile stress of concrete is reduced by 4.0%. When the external combined‐connection is adopted, the peak stress of the embedded‐ring is reduced by 69.3%, and the peak tensile stress of the concrete is reduced by 26.0%. It illustrates that the external combined‐connection method is more effective to increase the load‐bearing capability of the connection than the internal combined‐connection method. Additionally, the proposed strengthening measure by adding a stiffening beam, expanding the foundation plate, and adding rock bolts is effective to decrease the responses of foundation. The maximum tensile stress of concrete, the maximum compressive stress of concrete, and the maximum stress of the embedded‐ring are reduced by 19.8%, 31.3%, and 22.2%, respectively. To summarize, the proposed strengthening and retrofitting methods are capable of ensuring the safety and stability of higher‐power wind turbine operation.
When upper wind turbine is substituted by the one having higher hour power generation, the height of wind turbine tower and the length of its blade will increase. There are two obstacles to reuse existing embedded‐ring foundation. Firstly, the connection strength between wind turbine tower and its embedded‐ring is not enough to resist increased basal overturning moment. Secondly, the load‐bearing capability of total foundation should be improved. Highlights are as follows:
1. A combined‐connection construction by adding anchor bolts to existing wind turbine foundation with embedded‐ring is prompted in this study.
2. A strengthening measure by adding stiffening beam, expanding foundation plate, and adding rock bolts to increase the ability of resisting basal bending moment is proposed.
3. Finite element analysis is conducted to analyze the effectiveness of the proposed strengthening and retrofitting methods.image
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Optimal combined wake and active power control of large‐scale wind farm considering available power
- Author(s): Weimin Chen ; Pengda Wang ; Sheng Huang ; Lingxiang Huang ; Wenbo Tang ; Qiuwei Wu
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p.
3804
–3819
(16)
AbstractThe high‐order nonlinear complex characteristics of traditional static wake model (SWM) restrict the fast optimization of wake effect. Therefore, this paper introduces a dynamic wake model (DWM) to describe the time‐varying wake characteristics of wind turbines (WTs) with low computational cost. The traditional SWM is linearized to derive the wake wind speed sensitivity coefficients, which represents the sensitivity of wake wind speed deficit with respect to the active power reference. Considering the natural propagation characteristics of wake effect, a wake delay function is added to realize the future wind speed prediction of different locations of the wind farm. And a joint control strategy of wake and active power based on model predictive control (MPC) is proposed to optimize the power contribution of each WT to minimize wake effects, and maximize total available power. Thus, the increased available power is able to satisfy the power demand from Transmission System Operator (TSO) for ancillary services and enhance power support capability. The control performance of the proposed control strategy is evaluated by simulations under constant and varying incoming wind speed.
A dynamic wake model is proposed to describe the time‐varying wake characteristic and reduce computational complexity. And an MPC‐based control scheme is used to achieve maximum available power of wind farm by reducing the wind speed deficit caused by wake effect. The increased available power is able to satisfy the power demand from Transmission System Operator for ancillary services and enhance power support capability.image
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Integration of renewable distributed generators into the distribution system: a review
- Author(s): T. Adefarati and R.C. Bansal
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Artificial neural network-based photovoltaic maximum power point tracking techniques: a survey
- Author(s): Lina M. Elobaid ; Ahmed K. Abdelsalam ; Ezeldin E. Zakzouk
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Improved performance low-cost incremental conductance PV MPPT technique
- Author(s): Nahla E. Zakzouk ; Mohamed A. Elsaharty ; Ahmed K. Abdelsalam ; Ahmed A. Helal ; Barry W. Williams
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Optimal operation of distributed generations in micro-grids under uncertainties in load and renewable power generation using heuristic algorithm
- Author(s): Nima Nikmehr and Sajad Najafi-Ravadanegh
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Solution to short-term frequency response of wind farms by using energy storage systems
- Author(s): Ju Liu ; Jinyu Wen ; Wei Yao ; Yao Long