A method of identifying data by considering the excitation characteristics is proposed to solve the problem that it is difficult to select suitable samples from the historical operation data to identify the turbine work model. Firstly, Fisher’s information matrix condition number is applied to extract the excitation characteristics of the historical operating data, which together with the trend characteristics and the correlation between parameters constitute the set of feature variables. Secondly, by using the feature variables as inputs and the identification results generated based on the standard turbine work model as outputs, the Random Forest classification algorithm is used to generate a classification rule model for the identification data to realize the online selection of identification data. Finally, the accuracy of the model classification results and the identification effect of the selected data are verified. The result proves that the accuracy of the classification rule model is 97.561%, which can accurately select the sample segments containing sufficient incentives in the historical operation data, and the identification results of the turbine work model are in high consistency with that of the the standard model.

Aiming at the case of large frequency fluctuation in natural gas unit black start project, combining with the gas black start system and the waveform diagram during static frequency convertor (SFC) startup, the failure phenomenon is described in detail and the specific cause of the failure is analyzed. On the basis of considering the slow response speed of diesel generator unit, a super capacitor-assisted black start frequency modulation (FM) strategy is proposed. The SFC power is divided into base power and frequency fluctuation power, among which the base power is borne by the diesel generator unit to ensure stable operation of the system, and the frequency fluctuation power is quickly responded by the supercapacitor to suppress the frequency fluctuation effectively. Through the black start experiment of a 4F gas unit, the strategy not only effectively reduces the frequency fluctuation during the black start process, but also avoids the overcurrent fault during ramp-up and load-change phase, thus the reliability and safety of black start of the gas unit is improved.

In order to enhance the wind power consumption rate, achieve the goal of energy and power carbon peak and carbon neutral, with the goal of the lowest comprehensive cost of the power system, a new energy power system low carbon economic optimization method is proposed to establish the source and load side of the planning model. Firstly, on the source side of thermal power units, low-carbon transformation is performed, and a solution memory and flue gas bypass system is set up to make the unit become a liquid storage carbon capture unit, and dispatchable resources of photovoltaic power plant (concentrating solar power, CSP) and storage battery is introduced to coordinated with wind power. Then, on the load side, the price and incentive-type demand response resources are used for peak shaving and valley filling, and adjusting the users’ power consumption behaviors and power consumption. Finally, four cases are verified, and the results show that, the decarbonization of the power system from both the source and load sides can help promote wind power consumption, increase the share of renewable energy generation, enhance the low-carbon performance of the system, and save costs.

The requirements of over limit evaluation and measuring points layout of vibration/swing in hydropower units in industry standards and national standards are compared. The layout of vibration/swing measurement points on the project site is also described. It is found that the standards related to evaluation and the ones related to measuring points arrangement are inconsistent or unclear with the engineering site, such as vibration evaluation boundary conditions, evaluation criteria, evaluation working conditions and measuring points arrangement. Analysis shows that all the differences between the standards appear in vibration evaluation and measuring points arrangement for fixed parts, and the provisions on radial vibration (swing) of the unit shafting are relatively unified. Inconsistencies in all standards are not conducive to broad-spectrum application, and are prone to ambiguity and disagreement. The phenomenon that the evaluation standard is inconsistent with the measuring points standard, is not conducive to on-site comprehensive vibration evaluation of large or giant units. All the standard evaluation criteria lack the consideration of weight coefficient of amplitude exceeding the limit and cumulative duration, which is not conducive to the development of vibration fault and condition based maintenance, and data accumulation in the new role of hydropower units. The conclusion is expected to provide analytical help and reference for the practitioners of vibration standard compilation, installation and acceptance, operation management and scientific research and test of hydropower units.

Based on a typical 600 MW coal-fired cogeneration unit, novel systems with integrated steam jet and external steam cooler are proposed. In novel system I, the waste heat from exhaust steam is recovered through a steam jet, in which reheat steam is chosen as the working fluid. In novel system II, an external steam cooler is used to reduce the superheat of the mixed steam and the heat load of the boiler. Based on EBSILON professional modeling, the system is analyzed considering the peak shaving performance and thermodynamic performance under the maximum heating condition (extracted steam for heating: 800 t/h) and variable conditions. Moreover, the effects of mixed steam pressure and heat exchanger end difference on the system performance are also investigated. The results show that, under the maximum heating condition, compared with those of the reference system, the heating capacities of the novel system I and II increase by 21.59 and 14.47 percentage points, and the power generation efficiencies are increase by 2.48 and 2.78 percentage points, respectively. With the heating load of 300 MW, the power load regulation ratios of the novel system I and II improve by 6.00 and 3.91 percentage points compared with the reference system, and the lower limits of generation reduce by 84.75 MW and 74.32 MW. The gross efficiency of the novel system I and II improve by 3.02 and 2.65 percentage points, respectively, when the mixing steam pressure is increased from 50 kPa to 85 kPa. With the upper temperature difference increasing from 1 ℃ to 9 ℃, the gross efficiencies of the novel system I and II decrease by 1.67 and 1.51 percentage points, respectively. The result can provide technical references for expanding heating capacity and deep peaking of coal-fired cogeneration systems.

In order to solve the problems of waste heat utilization, carbon capture and liquid natural gas (LNG) cold energy utilization of solid oxide batteries fueled by methane, a new type of combined cooling, heating and power system was established. The system includes the improved recompression supercritical mixed working fluid Brayton cycle, the transcritical CO₂ heat recovery Rankine cycle and the secondary mixed working fluid organic Rankine cycle. The thermodynamic analysis, equipment exergy analysis, economic cost analysis of the circulation system, and the multi-objective optimization of the system by using the genetic algorithm in MATLAB. The results show that, increasing P1, T16 and the mass fraction of R14 in the second-stage Rankine cycle can improve the network, thermal efficiency, and exergy efficiency of the system, and reduce the average unit cost. P1 is the pressure at inlet the expander in the compressed supercritical mixed working fluid Brayton cycle, T16 is the inlet temperature of the expander in the transcritical CO₂ regenerative Rankine cycle. Under the optimal working conditions, the thermal efficiency, exergy efficiency and average unit cost of the system are 64.70%, 47.85% and 24.20 dollars/GJ.

The two basic structures and working principles of open type heat source towers, as well as the technology of gas-liquid heat and mass exchange inside the tower are introduced. It systematically summarizes the structural components, antifreeze fluids, heat and mass transfer characteristics, and the current research status, with a focus on the research hotspots and major advancements in the development of antifreeze fluids and the heat and mass transfer processes of the open type heat source tower. Although the open type heat source tower technology still has disadvantages such as insufficient safety and environmental protection of antifreeze, corrosiveness and toxicity, unstable regeneration technology, and high energy consumption, it has a large heat exchange intensity, high heat recovery efficiency, simple structure, and low maintenance cost. It has broad application prospects in the field of building heating. In the future, open type heat source tower technology will develop towards a more efficient, stable, safe, environmentally friendly, energy-saving and low-carbon direction, and build a better green and low-carbon heating system.

To improve the accuracy of carbon emission accounting and make the effect of carbon emission reduction more intuitive, it is proposed to associate power plant generation with carbon emission intensity. Firstly, the carbon emission performance of the gas-steam combined cycle unit is calculated based on Aspen Plus. Then, the carbon emission performance is analyzed from the aspects of four influencing factors: unit load, environmental temperature, heat network input and natural gas composition. The results show that, the established Aspen Plus model can simulate the operation of the power plant accurately. Taking the S106FA multi-axis gas-steam combined cycle unit of a power plant as an example, the calculated carbon emission performance is 342.66 g/(kW·h). The carbon emission is calculated by comparing the measured method and the emission factor method. The carbon emission performance accounting is closer to the measured method, and the deviation between the carbon emission performance method and the measured method is 0.20%. The deviation between the measured method and the emission factor method applying the measured low calorific value and the saved and deficient low calorific value are 5.24% and 19.66%, respectively. Unit load has the most obvious effect on carbon emission performance of the combined cycle unit, followed by heat network input, ambient temperature and natural gas composition. To reduce the carbon emission performance of the combined cycle unit, the power plant needs to arrange the peak regulation time and heat network heating reasonably, and using renewable energy as an alternative or supplementary fuel can be considered.

To accommodate grid-connected large-scale renewable power, coal-fired power plants need to undertake more peak shaving and frequency regulation tasks, so it will engage in the processes of deep peak shaving and load cycling for a long time. In this situation, the performance of wet flue gas desulfurization system (WFGD) will degradation and the auxiliary power consumption will increase significantly. To solve this problem, the dynamic model of an ultra-supercritical 660 MW coal-fired power unit and the dynamic model of the WFGD system based on the double-membrane theory are established. The performance of the desulfurization system is simulated when the slurry circulation pumps are switched under different operating conditions during the load cycling processes. It is found that the precise matching of slurry and flue gas during load cycling processes can achieve the minimum power consumption of the desulfurization system while meeting the SO₂ emission standard. Furthermore, when the slurry circulation flowrate changes stepwise during load cycling processes, the prediction model of changes in SO₂ mass concentration at the WFGD system outlet is obtained. An optimization control strategy for the slurry circulation pumps in fixed-frequency mode is proposed, which can achieve the best match between the slurry and flue gas during load cycling processes. Finally, the energy saving potential for the proposed control strategy is analyzed. When the load cycling rates are 1.0%, 1.5% and 2.0% Pe/min, the energy saving potential is 20.12%, 21.52% and 22.82% during loading down processes from 75% THA to 50% THA conditions, and that value will be 10.04%, 9.90% and 8.66% during loading up processes, respectively. The difference in flue gas flowrate during load cycling processes is found as a key factor causing the disparate of energy saving potential during loading down and loading up processes.

Energy storage system assisted thermal power unit frequency regulation is limited by the capacity of storage device, and its output power can not track the command power for a long time. At the same time, lithium battery energy storage technology also exists problems in safety hazards, cycle life limitations, limited enhancement of unit frequency gain gain and other issues. For this reason, the characteristics of high cycle life and high safety of supercapacitor are used to construct the simulation model of hybrid energy storage system assisted coal-fired thermal power unit frequency regulation in Matlab/Simulink platform. Combining with the operating state of thermal power unit and energy storage system, a set of control strategy based on index calculation and fuzzy control synergy is designed to achieve the adaptive adjustment of hybrid energy storage system output under dynamic operating conditions. Simulations show that, the control strategy can effectively extend the service life of lithium batteries and efficiently utilize the residual power of the hybrid energy storage system. Compared with the conventional control strategy of hybrid energy storage system, the proposed control strategy reduces the average daily use time of lithium battery by 60%, improves the comprehensive index of frequency regulation performance by 34%, and increases the average daily revenue by 20 000 yuan, which has high engineering application value.