Based on a large six cylinder intake port injection ignition M100 methanol engine, the effects of injection timing on engine performance at 1100 r/min and 100% load were studied using a combination of bench tests and CFD fluid simulation software CONVERGE. In this paper, five different injection timings (449, 439, 429, 419, 409°CA ATDC) are set for simulation calculations. A comprehensive comparison of the simulation results shows that in terms of combustion, the forward movement of the injection timing can effectively improve the combustion quality of the engine. As the injection timing advances, the peak combustion pressure, cumulative heat release, and peak temperature in the cylinder gradually increase, and the phases corresponding to CA10, CA50 and CA90 gradually move forward. The combustion duration gradually decreases, the quality of the incylinder mixture gradually increases, and the ignition speed gradually accelerates. In terms of emissions, the forward shift of fuel injection timing can effectively improve the engine's CO, HC and SOOT emissions, but the NOx emissions have increased.

A dual closedloop control strategy based on a combination of linear auto disturbance rejection and proportional integral control is proposed to address the resonance phenomenon of multiple inverters connected to the grid caused by the coupling effect between grid impedances. Firstly, based on the topology of multiple inverters, a mathematical model of the grid connected system with multiple inverters is established, and the mechanism of resonance generation is analyzed; Then, an equivalent circuit model of a multi inverter grid connected system is established, and the thirdorder system is processed in stages. The secondorder system adopts secondorder auto disturbance rejection, and the firstorder system adopts proportional integral control, forming a dual closedloop control strategy; Furthermore, the Lyapunov stability function is established to prove the stability of the closedloop control system; Finally, establish a digital simulation model of the parallel inverter system, and compare the simulation results of PI, 3rd order auto disturbance rejection, and improved linear auto disturbance rejection simultaneously; The results show that the proposed dual closedloop control strategy not only has excellent resonance suppression ability, but also can achieve better stability of the system.

In the islanded DC microgrid, the energy storage converters play the role of grid forming. The random characteristics of distributed generation and electric loads lead to the fluctuation of DC microgrid bus voltage, affecting system safety and power supply reliability. In this paper, to suppress the fluctuations and improve the transient response of bus voltage, a perturbation suppression strategy based on state feedback is designed, when the droop control strategy is adopted to form the grid. In this paper, the influencing factors of the transient response of the bus voltage are first analyzed, and the feedforward compensation method is proposed, which can realize the decoupling of the voltage loop and the current loop. Then, the equivalent simplification of the control system is completed without affecting the transient characteristics, and the application of the disturbance observer is achieved. The power disturbance is fed forward to the voltage loop by means of a disturbance observer, and disturbance suppression based on state feedback is realized. Finally, experimental results are given to verify the effectiveness of the proposed control strategy.

As wind power generation technology matures and wind power penetration continues to increase, the equivalent inertia and frequency modulation reserve capacity in power systems decrease, leading to an increased frequency modulation burden on the grid. To address the issue of insufficient inertia and frequency response capability of wind turbines due to the decoupling of rotor speed and grid frequency, this paper proposes a comprehensive control strategy for wind turbines based on fuzzy logic control. By embedding a fuzzy logic controller into the wind turbine control system, frequency modulation parameters are dynamically adjusted. On this basis, considering the operational characteristics of wind turbines at different wind speeds, the wind speed is zoned, and a comprehensive control strategy is developed to adapt to the speedpower characteristics of turbines within each zone. This improves the frequency response capability of wind turbines in medium and high wind speed zones.

Wind resource analysis is crucial for the establishment of a wind farm, and the acquisition of wind measurement data is an important prerequisite for wind resource analysis. The layout scheme of the wind tower directly affects the accuracy of wind measurement data. Taking a wind farm under complex terrain as an example, based on computational fluid dynamics method, Meteodyn WT software is used to simulate the wind resources of the wind farm, and by comparing and analyzing the wind tower wind speed and annual power generation of the wind farm from different numbers and locations under the layout scheme of wind towers, the results show that the range represented by wind towers in complex terrain is extremely small, and when selecting representative wind towers, it is necessary to divide different terrains, and it is recommended to use the multitower comprehensive method. Wind towers in special terrain cannot be used as a representative choice for the entire wind farm, but when there is occlusion or crossterrain, a separate wind tower needs to be set up at this location to reduce errors. The research results can provide a reference for the site selection and number of wind towers under complex terrain in the future, so as to improve the accuracy and rationality of wind resource analysis.

Aiming at the problem that the random fluctuation of new energy output in new energy power grid leads to the large demand for system flexibility and the imbalance between supply and demand of flexibility, this paper proposes a robust optimization planning method for electric – hydrogen energy storage in new energy power grid considering flexibility. Firstly, the operation characteristics of electrohydrogen conversion facilities and electrohydrogen energy storage facilities in the new energy grid are analyzed, and the electrohydrogen energy coupling model is established. Secondly, the characteristics of flexibility demand and flexibility supply capacity after the introduction of electrohydrogen energy storage are analyzed, and the flexibility margin index of new energy power grid considering electrohydrogen energy storage is established. Then, with the goal of minimizing the cost, a robust optimization planning model for the distribution of electricityhydrogen energy storage in new energy power grids considering flexibility is established. Finally, through the simulation of IEEE 33 node system, it is verified that the proposed method can determine the configuration capacity of electrohydrogen energy storage in new energy power grid and improve the flexible adjustment ability of new energy power grid system.

Microgrid has problems such as poor dynamic response performance and large overshoot when subjected to external disturbances under traditional droop control. In accordance with the above issues, this paper proposes a control strategy for photovoltaicenergy storage microgrid based on improved virtual oscillator and sliding mode control. The photovoltaic system adopts a twostage structure, and the front stage DCDC converter adopts sliding mode control to enhance the robustness of the microgrid against external interference; The back stage inverter uses a virtual oscillator control with MPPT algorithm to achieve maximum power point tracking control for photovoltaic cells, while improving the dynamic response speed of the microgrid. The energy storage system uses a battery model, and the inverter uses a virtual oscillator control that introduces virtual inertia. Inertia and damping characteristics are introduced into the virtual oscillator control to provide reliable power and frequency support for the microgrid. Finally, based on the Matlab/Simulink platform, a simulation model of the photovoltaicenergy storage microgrid is built. By comparing the simulation results with traditional droop control strategies, the feasibility and effectiveness of the control strategy proposed in this paper are verified.

The heat transfer efficiency of the solar air collector with smooth heat absorption plate is very low. Using artificial roughness on the absorption plate can interrupt the boundary layer and improve the heat transfer efficiency of the system. The improvement is made based on the rectangular artificial roughness, and a twodimensional simulation of the solar air collector with the rightangle hexagonal artificial roughness is performed using ANSYS FLUENT. The influence of artificial roughness spacing on heat transfer efficiency and flow characteristics in the specific Reynolds number range is discussed, and the thermohydraulic performance is evaluated under different working conditions. The governing equations are solved using the finite volume method and the transport equations of the turbulent kinetic energy and the turbulent dissipation rate are solved using the RNG kɛ turbulence model. The result show that the heat transfer characteristic of the system is significantly improved by the addition of the rightangle hexagonal artificial roughness compared to the smooth plate. The rightangle hexagonal artificial roughness with p = 10mm had the maximum THPP of 1.76 at Re=4000, which is 1.6 times the artificial roughness of the rectangle under the same geometric parameters.

A model of cement calciner using forestry biomass as alternative fuel was established based on Aspen Plus. Poplar wood was selected as the representative forestry biomass to replace 40% of the coal fuel, and the effects of gasification temperature, equivalence ratio, and biomass moisture content on the gas production components and calorific value, the outlet temperature of the cement calciner, and NO emission concentration was investigated under the conditions of lowtemperature gasification in a fluidized bed. Then NO emission concentration was taken as the response value, and the central combination test was carried out to establish the response surface and analyzed. The results showed that at a biomass feed rate of 11 000 kg/h, with the gasification temperature increasing from 550 °C to 700 °C, the content of each combustible component in the produced gas firstly decreased and then increased, and the increase in the content of the combustible component had a promotional effect on the generation of NO; at the equivalence ratio of more than 0.15, coke was mostly consumed by the gasification reaction, and the reduction of NO was weakened, which led to the increase in NO emission concentration; the increase in the moisture content of biomass led to the increase in the emission concentration of NO; the increase in the moisture content of biomass leads to a decrease in the content of each combustible component in the produced gas, and the outlet temperature of the cement calciner showed a decreasing trend; there was an interaction between the three factors, and the significance level of the effect of the equivalence ratio on the NO emission concentration was the highest, and the strongest interaction between the gasification temperature and the equivalence ratio was observed; when the gasification temperature was 550 °C, the equivalence ratio was 0.2, and the biomass water content was 12.5%, the NO emission concentration(442.91 mg/m³) was minimized

The significant uncertainty of highproportion wind power can make the scenarios of cascading failures in the power system more numerous and the mechanisms more complex. Identifying the key propagation modes of cascading failures is of great significance for preventing major power outages. This paper first considers factors such as wind power output uncertainty and component failure, establishes a dynamic analysis model for cascading failures. On this basis, failure propagation path data under massive initial scenarios are generated. Besides, an influence correlation diagram describing the sequential propagation process of cascading failures is established. Moreover, a method for identifying key failure propagation modes is proposed in combination with probabilityconsequences to screen highrisk propagation links of cascading failures under highproportion wind power access. Finally, the IEEE 118 node is used to verify the effectiveness of the proposed method in identifying key propagation modes.