To improve timeliness and accuracy of the location of condenser leakage cooling tube and solve the problem that the leakage cooling tube cannot be located online, the optimal route of leakage cooling tube location technology is demonstrated by combining theoretical analysis with experimental research. The results show that the tracer gas leakage detection technology has the characteristics of high positioning efficiency and high positioning accuracy, and is suitable for developing on-line locating technology of condenser leakage cooling tube. Through establishing the relationship model between and among the helium concentration change value, time, and water tank liquid level during the isolation of one half of the condenser for draining water, the height of the condenser leakage cooling tube can be located, so as to determine the condenser leakage tube row.

The cost of underwater assets in offshore wind farms is relatively low compared with the total cost of offshore wind power projects, yet the quality of these assets is vital for safe and stable operation of the offshore wind farms. The quality issues that can arise with wind turbines, underwater steel structures and foundations of offshore substations, and submarine cables during the construction and operation and maintenance phases are analyzed. Based on cases from practical offshore wind power generation projects, the inspection requirements and methods stipulated by relevant standards are evaluated, and comprehensive and effective underwater inspection methods for various types of quality defects are put forward. These methods have been verified in real cases, forming industry standards and specifications, which provides significant technical guidance and reference value for quality control and operational maintenance of underwater assets in offshore wind farms.

Against the cooling problem of engine heat exchangers, the flow and heat transfer characteristics of hydrogen in vertical and U-shaped tubes at supercritical pressures are studied. The influence of pressure and mass flow rate on heat transfer of the pipeline is studied by numerical method, and the heat transfer law is obtained. The heat transfer mechanism of the elbow section is discussed in depth, and the effect of dimensionless force on heat transfer is analyzed. The results show that, the closer the pressure is to the quasi-critical or when the mass flow rate increases, the convective heat transfer coefficient will increase, resulting in heat transfer enhancement. The bend section of the U-shaped tube can enhance heat transfer effectively, reaching a peak near θ=90°. There is a buoyancy effect in the straight pipe section at the inlet, but when the pressure is higher than 2.0 MPa, the buoyancy effect can be ignored after the hydrogen flows through the elbow section due to the influence of density difference. The Dean vortex caused by the secondary flow is the main factor to enhance the heat transfer performance of the elbow section, and the influence on the inlet section is significantly weaker than that on the outlet section.

Against the shortcomings of intermittency and instability of photovoltaic power generation in microgrids, a hybrid energy storage system composed of vanadium redox batteries (VRB) and super capacitors (SC) is utilized to smooth out the power fluctuations in standalone microgrids, thus to improve the power supply reliability of standalone microgrids. Considering the capacity allocation problem of the hybrid energy storage system, a multi-objective hybrid energy storage system capacity optimization model that minimizes the average annual cost of the hybrid energy storage system and the load shortage rate is developed. Aiming at the poor local search ability of the conventional elite non-dominated solution sorting genetic algorithm (NSGA-II) algorithm for solving the multi-objective optimization problem, an NSGA-II algorithm based on the improved elite retention strategy is proposed. By introducing a new fitness function, the algorithm is sorted and reasonably retains the elite individuals, so it improves the optimization effect, thus to enhance the local search ability, continuously approach the Pareto true frontier, and obtain better capacity configuration solutions. Finally, the rationality of the proposed method is verified by arithmetic examples.

Enhancing peak shaving capability of supercritical carbon dioxide (S-CO₂) boiler is the key to realize flexible operation of S-CO₂ coal-fired power plants. Research on dynamic characteristics of S-CO₂ boiler is beneficial to optimize the boiler operation control strategies. A dynamic simulation model of S-CO₂ boiler is established by the principles of thermodynamics and heat transfer based on the boiler of a 5 MW S-CO₂ cycle power unit designed and built by Xi’an Thermal Power Research Institute, and the reliability of the model is validated with operational data from unit. Based on the simulation model, dynamic characteristics of the above S-CO₂ boiler under step disturbance of different boundary conditions, such as fuel flow rate, working fluid flow rate, and working fluid temperature, are analyzed. The results show that, the S-CO₂ boiler has large thermal inertia, stability times of working fluid temperature at the boiler outlet are different under disturbance of different boundary conditions. With the increase of disturbance range of boundary conditions, stability times become longer. With the increase of boiler heat load, the working fluid pressure at the S-CO₂ boiler outlet decreases, and the working fluid flow rate at the S-CO₂ boiler outlet increases instantaneously in the initial stages of a dynamic process.

The proton exchange membrane (PEM) electrolyzer can convert green electricity into hydrogen energy, but the conversion efficiency of PEM electrolyzer is low, the thermal energy in the electrolyzer outlet water is not fully utilized. To fully use the waste heat in the PEM electrolyzer hydrogen production system, integrated systems incorporating a 660 MW coal-fired unit and PEM electrolyzer are proposed in both power generation (PG) and combined heat and power (CHP) scenarios. EBSILON and MATLAB Simulink softwares are applied for modelling, and thermodynamic and economic analysis is conducted. In PG scenario, the electrolyzer outlet water is used to heat the feedwater of coal-fired unit. While for CHP scenario, the electrolyzer outlet water is used to heat the return water from heating supply network along with the extraction steam. The produced oxygen is sent into the boiler for combustion. The results show that, compared with the reference coal-fired unit, in PG scenario, the power output is enhanced by 2.55 MW with an power supply efficiency rise of 0.17%, and the boiler efficiency increases by 0.04%. While in CHP scenario, the power output can be enhanced by 5.83 MW with an efficiency rise of 0.40%. After attributing the net power output increment to the PEM hydrogen production system, the exergy efficiency of the PEM hydrogen production system is 69.74% in PG mode with an increase of 3.44%, and 75.41% in CHP mode with an increase of 9.11%. For these two scenarios, the system exergy efficiencies reach up to 40.20% and 40.18%. Economic analysis shows that, the annual income growth by selling electricity for PG and CHP scenarios are 5 460 000 yuan and 12 460 000 yuan, with the increments of net present value of 61 320 000 yuan and 140 140 000 yuan, respectively. The levelized cost of hydrogen production in the reference system is 42.72 yuan/kg. The levelized cost of hydrogen production in PG and CHP modes in the integrated system is 42.55 yuan/kg and 40.79 yuan/kg, respectively.

The safe and stable operation of submarine oil-filled cables is critical, but the internal dodecylbenzene (DDB) insulating oil is subject to rapid pyrolysis and gas production at localized high temperatures due to thermal faults. Against this issue, the pyrolysis and gas production processes of dodecylbenzene insulating oil are investigated based on reactive molecular dynamics simulations (ReaxFF-MD) and thermogravimetric-infrared spectroscopy (TG-IR) experiments. The pyrolysis simulation results show that, the initial cracking reaction of the dodecylbenzene molecule is mainly the breaking of C—C bond to produce long-chain macromolecules, and then the gradual pyrolysis produces small alkyl radicals and olefinic molecules, and the DDB will eventually be pyrolyzed to the short-chain alkylbenzene molecules with the side chains of ·C₂H₅, ·CH₃ and ·C₃H₇ groups. The main characteristic gases during pyrolysis are C₂H₄, H₂, and CH₄, which are the same as the results of IR experiments, and the main reaction mechanisms for the generation of the characteristic gases are: (i) the breaking of the C—C bond at the β-position, the hydrogenation reaction, and the dehydrogenation reaction; (ii) the attack of -H radicals to the H atoms on other radicals; and (iii) the reaction of the methyl radicals (·CH₃) with the free hydrogen (·H) radicals, respectively. The kinetic results show that the activation energies of the TG experiment and ReaxFF-MD are 86.606 kJ/mol as well as 99.867 kJ/mol, respectively, and the similar activation energies further validate the reasonableness of the simulation results. The study conclusion provides theoretical support for deep understanding of the cracking and gas production mechanism of dodecylbenzene insulating oil.

The continuous penetration of internet technology into industrial control field has given rise to conceptual systems such as Industry 4.0 and Industrial Internet. Consequently, power plants are evolving towards digitization and informatization, with the intelligence and complexity of field-controlled objects increasing steadily. Control functions of conventional distributed control systems (DCS) are gradually becoming inadequate to meet these new demands. To enhance the maturity level of intelligent manufacturing in China, it is essential to strengthen the core computational control functions of DCS. In response, a novel collaborative control platform is proposed based on software-defined principles. This platform decouples the software and hardware of conventional DCS using software-defined concepts, reconstructs the control and configuration functions on the host computer, and designs and develops a dual-redundant computing engine and configuration and debugging tools. Additionally, protection mechanisms are established to ensure the operational security of the platform and the security of third-party data. This platform inherits the conventional configuration and control functions of conventional DCS while additionally supporting the implementation of various advanced intelligent algorithms. In terms of application, it can both enhance the control performance of conventional DCS and serve as an independent product providing high-quality computing services for other control systems. Consequently, it can be widely applied to various process control scenarios, offering users a reliable, efficient, flexible and cost-effective production control solution. Moreover, it provides an optional platform foundation for the future integration of cutting-edge computer technologies such as artificial intelligence and big data into DCS.

Direct discharging of saturated flue gas from coal-fired utility boiler can lead to significant low-grade waste heat loss. The saturated flue gas waste heat recovery and utilization for centralized heating system is constructed, the operating parameters of the heating system in coal-fired power plant are analyzed, and the feasibility that the saturated flue gas waste heat can be used to heat the return water of the heating system is verified. Finally, the economic efficiency of the centralized heating system is investigated for operation with different targets, and the influence characteristics of the operating parameters are revealed for the thermal performance of the centralized heating system. The research results show that, the temperature of flue gas waste heat can be increased by 30~40 ℃ by absorption heat pump. With the 350 MW coal-fired heating unit as an example, the absorption heat pump recovers the saturated flue gas waste heat with 50.23 MW for re-utilization. The economic benefits brought by enhancing the heating capacity are significantly better than those corresponding to the increase in power generation, and the heating capacity of the coal-fired power plant is increased by 13.4%, and the annual heating revenue is increased by 19 752 000~34 423 200 yuan. The research provides technical references for the saturated flue gas waste heat recovery and utilization in coal-fired power plants.

With the increasingly prominent problem of load fluctuations in high proportion renewable energy grids, improving the fast load response ability of large-scaled thermal power units under full operating conditions has become an urgent need to maintain the safe and stable operation of the power system. Therefore, a rapid load change strategy combined with the high-pressure bypass transformation technology under the flexibility demand of supercritical power units is proposed. Firstly, the high-pressure bypass is added to the high-pressure regenerative system to flexibly change the steam extracted amount from turbine, thus to accelerate the energy supply rate of once-through boiler. Secondly, to adapt to the high ramping rate, a load change scheme is designed with the limitations of main steam pressure, temperature and their change rate that boiler can withstand at sliding-pressure operation mode and the decoupling of load-main steam pressure for unit. Finally, test on a 600 MW coal-fired thermal power unit shows that, the unit can successfully achieve a high load ramping rate of 3%Pe/min under full operating conditions. Moreover, the main steam pressure, position of main steam valve and other parameters are maintained stable. In addition, the load regulation ability of the unit with load ramping rate of 5% Pe/min is verified, confirming the effectiveness of the proposed load rapid regulation strategy.