With the growth of installed capacity of renewable energy power generation, coal-fired units need to undertake more peaking tasks. In order to improve the operational flexibility of coal-fired units, a 1 000 MW unit is taken as the research object, and six heat storage configurations and four heat release configurations of molten salt coupling are proposed based on the Ebsilon software, and the thermo-economic indexes of different heat storage and heat release coupling configurations are analyzed comparatively. The results show that, the peak shifting capacity of the system in the heat storage stage is positively correlated with the pressure loss of the heat transfer steam, and the thermal economy of heating the deaerator outlet feedwater in the heat release stage is the best. The heat storage of the electrically heated molten salt has the highest thermal and exergy efficiency, and configuration D-a has the strongest peak shifting capacity, with a peak shifting depth of up to 23.61%, but it has the largest coal consumption rate and exergy loss. Configuration F-d has the best thermal economy, with peak shifting depth, thermal efficiency, fuel efficiency and coal consumption rate of 23.42%, 39.61%, 38.40% and 310.2 g/(kW·h), respectively.

To address the issues of flashback and high NO_x emissions in hydrogen-enriched gas combustion, a swirl-stabilized burner was designed using mild premixed combustion technology, and a feasibility study was conducted for its application in industrial boilers. Using a combination of experimental and numerical simulation methods, the study explored the equivalence ratio adjustment range of the mild premixed burner and the influence of hydrogen blending ratio on flame shape and pollutant emission characteristics. The experimental results showed that the mild premixed burner can achieve a wide hydrogen blending heat ratio adjustment range of 0~100%. The addition of hydrogen promoted a more uniform flame distribution, and the flame height decreased with the increasing hydrogen blending ratio. Additionally, the NO_x mass concentration experienced a rapid increase (for hydrogen blending ratios less than 30%) followed by fluctuations around 60 mg/m³. As the hydrogen blending ratio increased, the critical equivalence ratio for local flashback decreased, narrowing the stable combustion range between the blowout limit and the partial flashback limit. The widest equivalence ratio stable combustion range was achieved at a hydrogen blending ratio of 40%, which was 0.54~1.06.

The dynamic model of lithium-ion batteries has typical nonlinearities and uncertainties, the estimation accuracy of the state of charge (SOC) of the lithium-ion batteries directly affects the effect of the monitoring and controlling in battery management system (BMS). To enhance the estimation accuracy of the SOC of the lithium-ion batteries, an adaptive sliding mode observer, which based on a variable gain for lithium-ion battery SOC estimating model is proposed. By using the robustness of the sliding mode observer and based on the second-order RC equivalent circuit model, an integral term is introduced in conventional sliding mode surface to improve the robustness on sliding mode surface, and a gradient descent rule is adopted to achieve gain adaptation to reduce the chattering of observer and improve prediction accuracy and robustness. Simultaneously, the stability of the proposed method is proved using Lyapunov theory. Finally, the proposed method is validated and compared with the sliding mode observe (SMO) method under dynamic stress test (DST) and Federal urban driving schedule (FUDS) conditions. The proposed method has less chattering in estimation with higher estimation accuracy and good robustness.

Grid-forming energy storage system is expected to solve the problems like insufficient frequency modulation resources and disturbance resistance decline of large-scale new energy-based power grid. However, its active support ability is greatly limited due to its inherent power coupling characteristics, plus power overshoot, oscillation and even instability problems are most likely to occur with parameter variation. To solve this problem, a full-order small signal model for grid-forming energy storage system is developed, its frequency response characteristics are analyzed according to the output power state space model and its characteristic roots. On this basis, by analyzing the sensitivity and participation factors of the state space matrix parameters, the stable boundary of the grid-forming energy storage converter is given, and the influence of key parameters of the grid-forming energy storage converter on its dynamic power coupling, frequency support and other grid related characteristics is clarified. The simulation and semi physical experimental results have verified the correctness and feasibility of the theoretical analysis, providing a basis for the design of grid connected parameters and stable operation of grid-forming energy storage converters.

The technology of grid-forming energy storage can form a voltage source, which can support the stable operation of large power grids. The technology of grid-forming energy storage is an effective means to support the stable operation of high proportion of new energy connected to the grid. Based on this, the operation mechanism of grid-forming energy storage to support the stability of high proportion of new energy connected to the grid is analyzed. According to the principle and characteristics of grid-forming energy storage technology, five commonly used technologies to improve the stability of the grid are compared and. A model building idea of grid-forming energy storage system considering multi-time-varying parameters is proposed. Moreover, the scheme of grid-forming energy storage technology supporting high proportion of new energy grid-connected and the mechanism analysis of massive grid-forming energy storage equipment grid-connected oscillation is proposed. In addition, the system impedance dynamic identification technology based on signal injection is studied, and then the impedance reconstruction technical route of massive grid-forming energy storage equipment grid-connected system is proposed.

The conventional steam valve predominantly manages power regulation tasks while also addresses limited-scale primary frequency regulation. Condensate throttling can change energy distribution of the unit to a certain extent, and serve as a potential and selectable auxiliary frequency regulation method. To delve deeper into the frequency regulation capability of condensate throttling, the working principle and advantages are dissected, and static and dynamic models of the condensate throttling system are established, the frequency regulation characteristics are analyzed and the frequency modulation boundary conditions are outlined. To comprehensively enhance the dynamic performance of the condensate throttling primary frequency regulation, the system dynamic model is linearized, and then a model-switching fuzzy predictive control strategy is proposed. In this control strategy, fuzzy logic is introduced into the predictive controller algorithm to dynamically adjust control weighting coefficients in real-time, and predictive models are dynamically switched according to operational changes to enhance control quality. Case studies based on actual data from a certain 600 MW unit are conducted, indicating the static and dynamic frequency modulation capabilities of condensate throttling increase with the unit load, which has engineering application value in primary frequency regulation. Compared with the conventional PID and self-tuning fuzzy parameter PID controllers, the proposed control strategy exhibits superior adjustment time and performance metrics under various operating conditions, demonstrating better adaptability to changes in operating conditions.

Ammonia cofiring in coal-fired boilers is one of the promising technical routes for decarbonization of existing coal-fired power plants. However, ammonia cofiring may potentially result in drastic increase of NO_x emissions due to its high nitrogen content. Effective control of NO_x emissions is thus one of the key factors that affect the technical feasibility of ammonia cofiring in coal-fired boilers. The formation of NO_x during ammonia-coal cofiring is affected by the ammonia combustion as well as its interaction with the coal combustion process. There are significant differences in volatile content of different coal types which may strongly affect the NO_x formation characteristics of ammonia cofiring. For this reason, the NO_x formation characteristics of ammonia cofiring with bituminous and lean coals that have distinct volatile contents are investigated by an experimental rig that allows for flexible control of the combustion environment of ammonia. The results show that, the NO_x emissions from bituminous and lean coals show different trends with the increase of ammonia cofiring ratio under different ammonia cofiring modes. Because of the significant differences in volatile matter content between bituminous and lean coals and the consequent differences in the amount of O₂ consumption, the distributions of O₂ concentration in the furnace are substantially different between the two coals. This results in different competition relationships between the NO formation and reduction reactions of ammonia in the furnace, which consequently leads to different NO_x formation and emission characteristics between the two coals.

The W-shaped flame boiler with closed middle storage pulverizing system is designed to burn low volatile lean coal and anthracite. Blending coal with high proportion of bituminous coal is able to improve the adaptability of fuel and the flexibility of the boiler. It is necessary to solve the technical problems such as explosion prevention of the pulverizing system, anti-burning of pulverized coal pipes and prevention of serious slagging in the furnace. Therefore, an inert explosion-proof pulverizing technology, in which low temperature flue gas is used for temperature adjustment, is proposed. This method solves the problem of explosion prevention of coal pulverizing system effectively. By increasing the capacity of cooling air from primary fan to reduce the temperature of hot primary air conveying pulverized coal and the adaptability of the burners to blended bituminous, the safety of the primary air pipes and the burners will be guaranteed. With the optimization of refractory belt arrangement and combustion adjustment, this method not only controls the slagging, but also improves the performance of combustion in the furnace effectively. By these integrated technologies presented above, the goal of co-firing 70% bituminous coal safely and economically in the W-shaped flame boiler with closed ball mill medium storage pulverizing system is achieved.

Solid oxide fuel cell (SOFC) is a promising energy conversion device. It has the advantages of non-pollution, high energy utilization rate, and good fuel adaptability. However, SOFC often needs to be operated under variable load conditions, which leads to the problems of shorten service life and performance degradation. The study of the relationship between the variable load characteristics of SOFC and its operating conditions is helpful to improve the output performance of the stack, extend its service life, and formulate a reasonable control strategy. A 100 W SOFC short stack testing system was developed to experimentally investigate the variable load characteristics of the SOFC stack under multiple operating conditions. The results show that, increasing the operating temperature can reduce the ohmic resistance and total polarization resistance of the fuel cell stack, thereby enhancing the stack’s steady-state output performance and dynamic response performance. Increasing the hydrogen flow rate in the medium to high current range can reduce the concentration polarization resistance, thereby effectively enhancing the stack’s peak output performance and dynamic response performance. Increasing the air flow rate has a smaller effect on the performance improvement of the stack. Under the constant flow utilization strategy, the response voltage immediately falls within the range of ±5% of the final voltage. By varying the load with constant voltage, the response current can smoothly reach a stable value. Compared with the constant flow strategy and constant current load variation method, the stack shows better dynamic response performance under the constant flow utilization strategy and constant voltage load variation method.

In the context of achieving “dual-carbon” goals, power units function as adaptable power sources for integrating new energy sources, posing significant challenges to their power generation flexibility. The dry-wet joint cooling system plays a pivotal role in ensuring the safe and stable operation of power units. Therefore, there is an urgent need to optimize the operational strategy of the dry-wet joint cooling system to enhance its flexibility and economic efficiency. Focusing on the dry-wet joint cooling system of a 660 MW generator set, a multi-layer perceptron (MLP) neural network model has been established to predict the outlet temperature of the cooling water. A mixed integer nonlinear programming (MINLP) model is formulated and linearized based on actual operating condition constraints. By solving the MLP-MINLP optimization model, the optimal operation strategy for variable-frequency fans in each operating condition of dry-wet joint cooling system is determined, successfully reducing its power consumption. The results indicate that, after optimizing the configuration of variable-frequency fans, there is a significant reduction in total power by approximately 11.16%, and implementing different frequency operations for variable-frequency fans can reduce total power by about 3.62%~5.38% in a limited manner. The MLP-MINLP optimization model can achieve precise and low-power operation of dry-wet joint cooling system, offering a viable solution for optimizing dry-wet joint cooling systems.