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The increased penetration of renewable energy sources and the intensification of peak‐valley differences present challenges to peak regulation in the power system. Fulfilling the peak regulation needs of the power system solely through generation‐side resources proves to be challenging. Large‐scale fixed frequency air‐conditioning (FFAC) and inverter air‐conditioning (IAC) are high‐quality flexible load resources. This paper proposes a hierarchical coordinated control strategy of air‐conditioning (AC) loads for peak regulation service. In the first layer of the control strategy, the load aggregator collaborates with multiple AC groups to ensure the completion of peak regulation tasks with specific power‐constrained requirements. In the second layer of the control strategy, the control centre of each group optimizes the temperature adjustment values for each AC load, aiming to reduce incentive costs. Finally, the proposed method is validated through simulations, demonstrating its capability to achieve coordinated control of FFAC and IAC loads under various power‐constrained requirements. Furthermore, the simulation demonstrates the effectiveness of the control strategy in reducing user discomfort and the AC's incentive costs. [ABSTRACT FROM AUTHOR]

Low- and zero-carbon power systems are central to global decarbonization efforts. Costs for renewable energy (RE) and storage have fallen significantly, and advances in technologies and practices have improved the grid flexibility and stability needed to maintain the reliability of high-RE systems. Zero-carbon power systems, in turn, enable deep decarbonization through the electrification of other sectors, including transportation, buildings, and industry. [ABSTRACT FROM AUTHOR]

• Propose a SMPC based voltage regulation scheme to coordinate DG, OLTC, SVR and CBs considering uncertainty of DG outputs. • Use the time-correlated scenario generation method in the proposed SMPC framework. • Consider the single-phase regulation effect of OLTC, DGs and CBs. With the increasing penetration of renewable energy resources, the uncertainty of renewable energy resources output introduces challenges to voltage control in distribution networks (DNs). To solve these problems, this paper proposes a double-time-scale voltage control scheme for unbalanced DNs based on stochastic model predictive control (SMPC) to coordinate multiple voltage control devices. In fast-time-scale control, the active and reactive power outputs of distributed generators (DGs) are optimized to minimize voltage deviation, active power curtailment and reactive power fluctuation. In the slow-time-scale control, optimal tap changes of on-load tap changers (OLTC), step voltage regulators (SVR), and switched capacitor banks (CBs) are calculated to reduce voltage deviation and tap operations. Additionally, in the fast-time-scale control, the SMPC-based scheme adopts a scenario generation approach to represent the uncertainty of DG output. Considering the temporal correlation of the DG output, different prediction scenarios and scenario probabilities are obtained by the empirical cumulative distribution function fitted by the historical measurement data. In this paper, the effectiveness of the proposed double-time-scale voltage control scheme is verified by the unbalanced IEEE123 node system. The case study demonstrates that the proposed voltage scheme can effectively keep the three-phase voltages in unbalanced DN within the secure operation range and achieve better voltage profiles. [ABSTRACT FROM AUTHOR]

The integration of renewable energy sources may result in more severe active power disturbances, and requires more load shedding. The battery energy storage system (BESS) characterized with high flexibility can handle such uncertain disturbances and reduce load shedding amount. This paper proposes a chance-constrained optimal sizing scheme of the BESS to coordinate with the synchronous generator and emergency load shedding (ELS) for frequency stability. First, considering the role of the synchronous generator, BESS, and ELS in frequency stability control, an extended system frequency response model is established to calculate the amount of load shedding, and the required capability of frequency regulation. Then, a multi-objective and chance-constrained mixed integer nonlinear programming (MINLP) model is built for the BESS sizing to minimize investment cost and maximize operation profits, which considers the uncertainties of disturbances. With the utilization of the linear weighted method, max-affine function-based piecewise linearization method and Bernstein approximation, the model is reformulated into a tractable form, which is iteratively solved by the multi-cut Benders decomposition. Case studies were carried out to verify the effectiveness of the proposed scheme, showing superior performance in reducing load shedding amount and improving frequency nadir. • A hierarchical optimization framework for the BESS sizing to coordinate with synchronous generators and ELS. • An estimation method for the required frequency regulation capability of the BESS and the amount of ELS. • A chance-constrained and multi-objective MINLP model for the BESS sizing with coordinated frequency control and uncertain disturbances. • Reformulate the chance-constrained and multi-objective model into a tractable MILP form. [ABSTRACT FROM AUTHOR]

Highlights • Analyze the challenges for weakness analysis based on grid strength assessment in a realistic power grid. • Analyze the impact of power network structure on grid strength. • Propose a method for fast weakness analysis in a realistic power grid. • Verify the method in a realistic power grid. Abstract The increasing penetration of renewable energy resources (RERs) is challenging power grid planning and operation in maintaining grid reliability. Potential power grid reliability and stability issues may arise when large-scale RERs are connected to a weak power grid. These issues may become more significant due to the mutual interactions among RERs that are interconnected electrically close through a power network. Weakness analysis based on grid strength assessment is useful for identifying the potential weak grid issues. However, when taking into account the impact of the interactions among RERs, the weakness analysis becomes computationally challenging. Different combinations of points of interconnections (POIs) of RERs may have different impacts on grid strength at each POI. Due to the combination nature, such weakness analysis may be time-consuming when identifying the weakest combination of POIs from a large number of potential candidates in realistic power grids. To address this concern, the impact of the power network structure on grid strength is analyzed in this paper. It is found that the impact mainly depends on the impedance ratios at POIs. The findings can be summarized as two criteria to develop a recursive method for fast identification of the weakest combination in this paper. The efficacy of the proposed method is demonstrated through case studies on the IEEE 39-bus system and a realistic power grid. [ABSTRACT FROM AUTHOR]

The commercial jet fuels usually contain about 40% aromatics and naphthene. However, conventional technologies on bio-jet fuels production by hydrodeoxygenation of plant oil and biomass gasification/Fischer–Tropsch synthesis can’t produce renewable aromatics. In this paper, the liquid fuels with high aromatics content were produced by aqueous phase catalytic conversion of biomass sugar/polyol over Ni@HZSM-5/MCM-41 catalysts. Liquid fuel yield of 32 wt% with aromatics content of 84.3% was obtained under the conditions of 300 °C, WHSV of 1.25 h −1 , GHSV of 2500 h −1 and 4.0 MPa of hydrogen pressure with mixed polyol (60% sorbitol + 40% xylitol) as feedstocks. The produced bio-aromatics are substituted benzenes, naphthalenes, and aromatic olefins, which is a wonderful crude oil to be used as jet fuels after it was hydrogenated to improve quality (deep deoxygenation/chemical bond saturation). [ABSTRACT FROM AUTHOR]