With the increasing connection of renewable energy power plants (REPPs), there are some problems that power frequency distance protection criterion cannot identify grid faults. Therefore, this paper focuses on the extraction algorithm of power frequency and protection criteria in the device, and analyzes the adaptability of distance protection algorithms from different manufacturers with high proportion of renewable energy power plants. Regarding the power frequency extraction algorithm, the aperiodic component characteristics of the shortcircuit current provided by different renewable energy power plants were explored. The error of Fourier algorithm caused by the influence of harmonic was further derived. For the protection criteria, the adaptability of directional circle, polygon, phase comparison, and power frequency variation distance protection was compared and analyzed, and the distance protection criteria that can be well applied to high proportion of renewable energy power plants were clarified.

Distributed energy storage technology can change the temporal and spatial distribution of energy and can improve the flexibility of the distribution network to integrate the distributed renewable energy. Under the traditional mode, the cost of energy storage is high, and the utilization rate of energy storage resources is low. Cloud energy storage is a new business model that can respond to the demand for distributed energy storage. Under the cloud mode, the virtual energy storage configuration model is built by considering the factors that affect the demand for virtual energy storage, such as load, the output of renewable energy, timeofuse electricity price, and cost. A community with 14 typical users is selected as a case to verify the validity of the model established above. Case analysis shows that, under the cloud mode, the virtual capacity and power demand of energy storage for users are 18.2% and 7.1% lower, the annual cost is 4.12% lower, and the utilization rate of energy storage is 8.12% higher than it under the traditional mode. Therefore, the cloud mode of energy storage has a good prospect in the application.

This study addresses the scenario of bamboo waste pyrolysis and the resource utilization of its pyrolysis products, employing a methodology grounded in life cycle assessment and sensitivity analysis. It establishes a comprehensive life cycle carbon emission inventory and calculation approach. The primary sources of carbon emissions and reductions within the pyrolysis system are identified, and the sensitivity of carbon reduction capacity to various parameters is assessed. Results indicate that the carbon emissions from pyrolyzing 1 ton of bamboo waste amount to 838.684 kg, resulting in an annual reduction of 38.3 million t of carbon emissions and an annual electricity generation of 2.1×10¹⁰ kW·h in China. The predominant contributors to carbon emissions in the system are the combustion for power generation of biooil and syngas (34.8%), while carbon reduction is primarily driven by the application of bamboo charcoal to soil (34.0%). The system's carbon reduction capacity exhibits high sensitivity to bamboo waste proportion, annual harvest volume, and pyrolysis product yield, with sensitivity coefficients of 1.297,1.000, and 0.702. Notably, the soil carbon sequestration effect resulting from bamboo charcoal application presents significant carbon reduction potential, estimated at 13 million t annually for an 8.9% bamboo charcoal application rate. This study concludes that bamboo waste pyrolysis holds substantial carbon reduction potential, providing a novel avenue for China to leverage bamboo waste for renewable energy production and effectively mitigate climate change towards achieving "dualcarbon goals".

The characteristics of zero moment of inertia of modular multilevel converter, it can not support the frequency fluctuation of AC power grid, so that the overall inertia of AC/DC hybrid system decreases, affecting the dynamic performance and stability of the system. Therefore, an improved powervoltage droop control combined with a virtual synchronous machine technology of coordinated control strategy, in the case of de voltage stability of ac power grid frequency adjustment, at the same time, reasonable allocation of power between the converter, in the case of without communication system to establish effective energy management system. In order to verify the feasibility and effectiveness of the proposed control strategy, a comparative test was conducted with the traditional double closedloop control. The results show that the proposed control strategy effectively solves the dynamic performance and stability problems of the system caused by low inertia and under damping.

In freezing and icing environment, the field tests of 2 MW wind turbine blades by aerothermal antiicing/deicing method is carried out to verify the antiicing/deicing effect and energy consumption. Firstly, this paper analyzes the complex process of blade surface icing and then its icing distribution on the surface of NACA64618 airfoil is simulated. Secondly, the blade active aerothermal antiicing/deicing system for 2 MW wind turbine is constructed in the field demonstration project. Finally, three tests are finished with the help of the panoramic infrared thermal imaging detection, including the static deicing test, static antiicing test and production test with antiicing, and then evaluate blade antiicing/deicing effect and heating energy consumption. The test results show that the blade surface begins to melt and fall off after continuous heating for 2 hours when the ice thickness is 30 mm and the heating control temperature is 50 °C, and the heating energy consumption power is less than 50 kW, which can provide a reference for the design of engineering application system of aerothermal antiicing and deicing of wind turbine blade.

The virtual power plant technology provides a new path for userside demand response to enhance the potential of distributed energy consumption and fill the blind area of grid dispatching. In order to guide users to participate in power dispatching, a virtual energy storage model including smart home load and building phasechange energy storage system with combined cooling and heating was constructed based on the incentive demand response power purchase agreement, and the schedulable margin of various resources was quantitatively analyzed; Taking user response characteristics as an indicator, using entropy weight method to evaluate the dynamic response performance of various user loads, setting the dynamic response priority of virtual energy storage participating in dispatching; taking the maximum benefit of virtual power plants as the goal, comprehensively considering resource power purchase costs, electric heating Based on factors such as balance, a terminal virtual power plant optimal scheduling model that integrates distributed power sources and smart community incentive response loads is proposed, and an improved light optimization algorithm is used to solve the model. The results verify the effectiveness of the proposed method.

Aiming at the problem that the decisionmaking process in the existing power grid transmission line ice melting scheme arrangement takes a long time, and there is a risk of operation stability, which leads to the insufficient decisionmaking ability of the power grid to deal with severe ice disasters, a comprehensive energysupported transmission line ice melting optimization strategy under the dynamic constraints of stability risk is proposed. Firstly, an icing growth model is established based on meteorological data, the corresponding relationship between transmission line icing growth and line faults is analyzed, a line outage probability model is established, and the loss degree of line outage is quantified. Secondly, the mechanism of changing the line flow based on integrated energy to slow down the growth of line icing is analyzed, and the icemelting risk constraints of distribution lines based on integrated energy are considered to establish a line icemelting model based on integrated energy. On this basis, an icemelting optimization method for transmission lines with integrated energy support under the dynamic constraints of stability risk is proposed, which is iteratively solved based on the Lagrangian relaxation method. IEEE RTS79 is used to simulate the ice melting example. The results show that the method based on this paper can improve the efficiency of the transmission line ice melting scheme arrangement and ensure the safe and stable operation of the power grid.

This study investigated the pretreatment of rice straw using different soaking solvents (deionized water, nanobubble water, biogas slurry, and nanobubble water coupled with biogas slurry) for 5 days. The study explored the changes in volatile fatty acid content, lignocellulose content, and methane production in different treatments after soaking pretreatment. The results indicated that the treatment of soaking with nanobubble water and the treatment of combing soaking of nanobubble water with biogas slurry both enhanced the pretreatment effectiveness of the rice straw. The treatment of combing soaking of nanobubble water with biogas slurry showed the optimal pretreatment performance, with the volatile fatty acid content reaching 6 470 mg/L. The cellulose degradation rate and hemicellulose degradation rate reached at 12.1% and 23.7% , respectively, and the maximum cumulative methane yield increased by 19.5%.

In order to solve the problem of incomplete utilization of waste heat in traditional solar thermal storage liquid air energy storage systems (LAESS) and further improve the roundtrip efficiency of the system, a liquid air energy storage system (LAESSO) coupled with solar thermal storage and a dual Organic Rankine Cycle on the basis of the LAESS system is developed. The thermodynamic model of the coupled system is established, and the influence of key parameters on system performance is analyzed. The results show that the net output power of subsystems ORC1 and ORC2 is 1 296 kW and 6 695.83 kW under typical operating conditions; the round trip efficiency of the new system can reach 117.63%; the exergy efficiency is 38.97%; and the energy efficiency is 28.88%, which are 12.58%, 2.35%, and 1.21% higher than those of the reference system, respectively. In addition, the system provides domestic hot water at a temperature of 364.15 K to the users, achieving cogeneration efficacy. Sensitivity analysis of key parameters shows that when the liquefaction pressure (compressor outlet pressure) increases from 15 MPa to 18 MPa and the liquefaction temperature (throttle inlet air temperature) rises from 93.15 K to 113.15 K, the air liquefaction rate, roundtrip efficiency, and exergy efficiency decrease with the increase of liquefaction pressure, and the increase of liquefaction pressure and temperature is not conducive to the system performance; however, when the exhaust pressure increases from 5.3 MPa to 7.7 MPa, the roundtrip efficiency and the exergy efficiency increases. The research results can provide some theoretical support for the liquidaircoupled solar system.

In the high wind and photovoltaic power penetration distribution network, under the influence of the control strategy for inverter, the fault current weakfeed characteristic is obvious, the traditional power frequency protection's operation performance is declining, and even cause unwanted operation or refuse operation. In this paper, the fault current characteristics of synchronous generator and inverter interfaced distributed generation power supply are analyzed, and it is found that there is an obvious difference between the fault current vectors on both sides of the distribution network during internal and external faults, and then the correlation coefficient is used to measure the vector correlation and construct the action criteria. Based on 5G communication technology, a new scheme of correlation pilot protection for high wind and photovoltaic power penetration distribution network is proposed. The simulation results show that the proposed protection scheme can identify the short circuit fault of high wind and photovoltaic power penetration distribution network quickly and stably, has a strong ability to withstand noise, and solves the influence of 5G time delay fluctuation on pilot protection.