The optimal control of wave energy converter clusters helps to make full use of wave resources, for which a wave power cluster optimization method based on a hybrid particle swarm algorithm is proposed. Directdriven wave power generators are taken as the research object to explore the mathematical model for the shortterm scale of the steady state of power generation clusters. Wave dynamic pressure, radiation influence among devices and shading effect among devices are considered in order to simulate more accurately the actual effect of deploying a certain density of wave energy devices. With wave cluster power maximization as the optimization objective, a hybrid particle swarm algorithm is proposed to solve the optimal parameters of the power generation cluster taking into account the motion of the power generation devices and the energy constraints of the sea area.Crossover and mutation operations are added to the traditional algorithm to cope with the problem of multipeakability in the solution space of the complex equations. The results of the algorithms verify the effectiveness of the cluster optimization method with good solution quality.They also show that the larger the size of the wave power generation cluster, the more complex the radiative influence between the devices and the more obvious the shading effect.

To ensure the economy of power operation in parks and increase the proportion of clean electric energy, an optimization model of lowcarbon power operation in parks based on green power and voluntary emission reduction transactions is proposed. This model comprehensively considers the purchase cost of green power and thermal power, the cost of photovoltaic power generation, and the income from voluntary emission reductions. The objective function is to minimize the total operating cost, and green electricity, thermal power generation and photovoltaic power generation are optimized with combination of random probability constraints in three stages: mediumand longterm, dayahead and realtime. Based on the data of an enterprise park in Nanjing, the analysis results show that under the reasonable price of voluntary emission, the optimization model can slightly reduce the total operating cost of the park, and significantly improve the use ratio of clean electric energy and the park's ability to cope with disturbances. In addition, the impacts of the voluntary emission reduction price and confidence value on the optimization results are analyzed.

In this paper, considering the soil stratification and groundwater seepage, combined with the measured data, the fluid temperature inside the buried pipe and the thermophysical parameters of different layered soils are obtained through the calculation of the outer wall temperature of the buried pipe, so as to establish the heat transfer model of the buried pipe stratified according to the equivalent physical properties of the soil. The experimental results show that the strati–fied heat transfer model is closer to the measured value than the conventional homogeneous model, and the error is smaller; The average absolute error between the simulated outlet water temperature and the measured value is 0.21 °C, and the average absolute error between the simulated inlet and outlet heat transfer temperature difference and the measured value is 0.14 °C based on the equivalent physical properties of soil stratification, which has a high accuracy and can provide a basis for engineering design and serve as the basis for the subsequent optimization study of the buried pipe heat transfer.

The joint participation of energy storage stations and wind farms in the black start of a system can reduce load outage time and accelerate system recovery. This paper focuses on a large energy storage power station and wind farm combined power generation system and proposes a coordinated control strategy for black start considering the restoration capability of energy storage power stations. The wind farm employs a maximum power tracking control method, while the energy storage power station adopts the V/f control method to jointly form a black start power source. Soft energization is employed for the energy storage power station and critical load restoration are performed before the wind turbines are connected to enhance the stability of restored system. An estimation method for the recovery amount of load is introduced, considering the recovery capability of energy storage stations. Based on the auxiliary load demand of the thermal power plant and wind power prediction, the state of charge of the energy storage power station during the black start process is predicted. Then, considering the power and state of charge constraints of the energy storage power station, the amount of critical load to be restored is determined. Transient simulations are carried out in PSCAD/EMTDC to verify the effectiveness of the proposed strategy.

Renewablerich remote areas are facing problems such as high cost of external energy supply, low reliability of internal green micropower, high fuel transportation cost and environmental pollution caused by diesel generators as backup power sources, which is not meeting the needs of low carbonization. To solve those problems, this paper propses a design of microenergy network based on hydrogen energy storage in an offgrid hydrogen storage energy supply scenario. The framework for a hydrogenbased zerocarbon microenergy network on account of the spatial and temporal distribution characteristics of renewable energy in remote areas is presented. Furthermore, the paper proposes the resource endowment and operation constraints of the hydrogen based micro energy network, formulates operation strategies for energy surplus and shortage periods and carries out the case simulation. Simulation results of a village in Yunnan Province prove the feasibility of the proposed microenergy network and its operation strategies, which effectively eliminates the influence of unstable regional green micropower output and seasonal shortage on the reliability of the power supply system and reduces regional thermal load burden. Furthermore, it helps decarbonize the regional energy system. Research results provide a reference for energy consumption improvement and carbon reduction in renewablerich areas such as remote areas and islands.

This paper investigates the effect of surface temperature on the efficiency of photovoltaic cells under high concentrating power, and investigates the coupled fin heat pipe heat sink in concentrating photovoltaic cell systems. Study the effect of the number of fins, distribution and fluid flow on the cell efficiency and surface uniformity of the heat pipe radiator under water cooling and air cooling, and compare it with ordinary radiators. The results show that the minimum temperature of the battery surface with the heat pipe radiator occupies less area, the uniformity is significantly improved, and the battery efficiency is improved; under the working condition of 0.64 m/s flow rate, the fin spacing is 1.5 mm, and the fin thickness is 0.4 mm, the overall performance of the battery is the best, the surface temperature is 314 K, the temperature difference is less than 1 K, the uniformity is best, then the electrical efficiency is 31.25%, and the thermal efficiency is 66.03%.

Based on a highpressure common rail diesel engine, a methanol injection system is installed at the intake manifold. A twostage direct injection (preinjection + main injection) of coaltoFischerTropsch (FT) diesel is installed in the cylinder. A twostage injection FT diesel/methanol (F/M) dualfuel engine test stand is built to explore the effect of different methanol substitution rates on engine emission performance at 2 000 r/min and loads of 25%, 50%, 75% and 100%. Simultaneously, the theoretical basis for realizing the FT diesel/methanol reactivity controlled compression ignition (RCCI) mode is explored. The results indicates that the fuel economy of the F/M dualfuel engine is better at medium and high loads. The emissions of HC, CO, Soot, methanol and formaldehyde increase in the F/M dualfuel combustion mode compared with the singlefuel compressionignition mode. These emissions increase with the augmentationmethanol substitution rate and decrease with an increase in load. In contrast, the emissions of CO2, NOx and NO decrease with an increase in methanol substitution rate but increase with an increase in load. The emissions of NO2 increase with both the rise in methanol substitution rate and load. The test results show that simply adding a methanol injection system to the intake manifold cannot achieve an efficient and lowemission RCCI combustion mode, and its fuel injection strategy needs to be calibrated.

In cold regions, offshore wind turbine structures are susceptible to complex environmental loads, which can lead to vibrationrelated safety concerns. Taking a 6.45 MW offshore monopile wind turbine structure as an example, the vibration response of the structure under the combined action of wind and ice loads is analyzed and compared before and after the implementation of the MTMD (Multiple Tuned Mass Damper) system. The results indicate that the wind and ice loads induce severe vibration responses in the wind turbine tower, with the maximum displacement response occurring at the top of the tower and the maximum acceleration response near the amplitude point of the second mode of vibration. In addition to the first two natural frequencies, the wind and ice loads also excite higherorder responses in the tower structure. By employing an MTMD system that controls the first and second mode frequencies, the displacement, acceleration, and overturning moment responses of the tower structure can be effectively controlled, resulting in significant vibration reduction. However, it should be noted that the TMD (Tuned Mass Damper) device exhibits frequency sensitivity and cannot effectively mitigate vibration responses induced by higherorder frequencies of the structure.

In response to stability issues caused by the dynamic response of wind turbines, in order to study the numerical response of the wind turbine under different wind speeds, a threedimensional structural model of the wind turbine is established based on SolidWorks, the blade root and tip particles are extracted, and the stress and displacement trends under different wind speeds are analyzed by using the finite element analysis method. The wind speed attenuation in the pendulum direction and the brandishing direction of the wind turbine is studied and the shear stress distribution of the flow field near the blade surface is discussed. The results show that the stress and displacement of blade tip and blade root have certain regularity under different wind speeds. When the natural wind passes through the wind turbine, the wind energy is effectively captured, and then shows regular attenuation. This study provides reference value for the dynamic parameters of wind turbine operation and improves the stability of wind turbine operation.

At this stage, the power generation performance of photovoltaic power plant is usually evaluated by performance ratio (PR). In the field test of short term, the PR of whole photovoltaic system will be affected by the temperature, leading to an obvious deviation of PR, which causes interference for the power generation evaluation of plant. Based on the system PR correction calculation method in IEC 617241 2016 standard, this paper analyzes and studies the modules temperature calculation method and temperature correction calculation method. Through the comparative analysis of examples, the system PR temperature correction method with higher accuracy is summarized and given, which brings convenience for the rapid system measurement and calculation, and increases the reliability and accuracy of the system PR evaluation. The analysis results show that the method of weighted average temperature of the module which considers the temperature and irradiation weight is more accurate than the method of module average temperature correction; the system PR can be evaluated much more accurately by the method that is corrected to the annual weighted average temperature of the module.