Thermal Power Units Research Articles

The impact of electricity-carbon market coupling on system marginal clearing price and power supply cost.

In this study, we assessed the impacts of the benchmark designs of emissions allowance allocation in China's national carbon emissions trading system with plant-level data and further estimated the marginal clearing price and power supply cost in Guangdong power market under electricity-carbon market coupling with unit commitment and economic dispatch model. We find that the existing allowances benchmark would result in a considerable surplus of allowances at about 222 Mt. But the benchmarking and exemplary levels on the heat rate of power supply would motivate thermal power units to reduce CO2 emissions. Under a tight balance of supply and demand in Guangdong, peaking thermal power plants will become the marginal clearing units and higher clearing prices will add to the revenue of lower cost inframarginal renewable energy power units. However, the combined impact of electricity-carbon market coupling would cause the marginal clearing price fluctuates obviously from 0 to 1159 CNY/MWh. Compared to the baseline scenario with free CO2 allowances allocation, the efficiency of thermal power utilization would decrease by 23%-59% and the net revenue per MWh power supply of coal-fired power units would decrease by 275%-325% under the stress scenario. Our study suggests that setting a more stringent allowances allocation benchmark for carbon price discovery is necessary. As electricity-carbon market coupling changes the role of coal-fired power plants to provide flexibility service and decrease their revenues, it calls for further market designs on proper reimbursement of flexible resources, under which the electricity market can effectively achieve the synergy among accommodating new energy, ensuring resource adequacy, and delivering cost efficiency. In addition, the synergy can be enhanced by formulating a tax program, which can promote renewable energy investment.

Simulation and evaluation of flexible enhancement of thermal power unit coupled with flywheel energy storage array

Under the background of “carbon neutrality” and “carbon peak” concepts, China desires to develop a new power system based on renewable energy sources (RES), which will be the primary energy support in prospective China. Thus, it is imperative to improve the peak shaving capability of power system to address the problem of random fluctuation and intermittency of RES by developing various energy storage systems. An innovative approach to enhance the flexibility of the conventional thermal power unit (TPU) through the utilization of flywheel energy storage array (FESA) is presented, simulated, and evaluated in this paper. Using the relatively practical and specific model of TPU and FESA, modified frequency modulation and automatic generation control (AGC) instruction tracing operation scenario models are constructed. A comprehensive control strategy of FESA and a well-designed operation coordinated control method for TPU with FESA are proposed and applied. The simulation results are distinctively processed and evaluated by the methods in “two documents”, aiming to assess the real-world operation performance of the model proposed in this paper. The comprehensive analysis of the indicators demonstrates that the FESA can improve the flexibility and economy of the units. This research may guide the usage of FESA to improve the operational flexibility of TPU.

Flexibility transformation strategy of thermal power units for typical scenario considering wind and solar consumption based on generalized Benders decomposition algorithm

Flexibility transformation strategy of thermal power units for typical scenario considering wind and solar consumption based on generalized Benders decomposition algorithm

External tie line power fluctuations smoothing strategy of new urban power grid

In a net-zero carbon power grid (NZCPG) with a relatively high proportion of renewable energy sources, significant power fluctuations occur, severely constraining the development of both the NZCPG and the New Urban Power Grid (NUPG). In the NZCPG, the proportion of traditional hydro and thermal power units used to mitigate power fluctuations has decreased. It is necessary to explore the load resources in the NUPG to stabilize the power fluctuation between the NUPG and the NZCPG, and to reduce the operating pressure of the NZCPG. Firstly, this paper proposes a method for developing external tie line schedules based on the load operation band (LOB) to relax the constraints on the schedule for the NZCPG. Secondly, A revised load response aggregation model is proposed to improve the aggregation accuracy under uncertainty factors by online correcting their impact on the load response characteristics. Thirdly, considering the flexible loads in NUPG can only compensate for a part of the power fluctuation, this paper proposes a method to judge the power fluctuation that these loads can offset. Two PFS optimal strategies are proposed among NUPG partitions considering deviation penalty and within each NUPG partition reducing the number of participated load-users. This paper focuses on the PFS in bulk NZCPGs other than in the distribution grids and microgrids. Our work can effectively smooth the power fluctuation within NUPG regulation capability meanwhile reducing the number of participated load-users. Fourthly, a method is proposed to judge the power fluctuation beyond NUPG regulation capacity in NUPG. Using the actual load response capacity, the over-amplitude/time layered smoothing strategy with optimal load is proposed, which can offset the power fluctuation of the bulk NZCPG to the largest extent. Finally, the IEEE-39 system is used to verify the effectiveness of the proposed methods.© 2017 Elsevier Inc. All rights reserved.

Modeling Processes of Emergence and Growth of Fractal Structures and Chamber Defects of Thermal Power Units

The paper considers modeling the emergence and growth of possible fractal structures and defects on the inner surface of the chambers of thermal power units, which allow control and regulation of the development of such stochastic dynamic processes. We are talking about the use of modeling procedures for the given analysis, which are quite universal in the framework of certain approaches. A general qualitative consideration of the modeling of processes such as the deposition of materials on a solid surface of various complex configurations, and the occurrence of its fracturing and defects of fractal types, is given. In the first part, we consider an analogy between the processes of the emergence and growth of fractal structures and chamber defects with laser processes of controlled deposition of substances on the surface of a solid body and the growth of its fracturing. A number of models have been developed for the emergence and growth of fractal inhomogeneities of various types and configurations on a solid surface with identification of the possibility of their preliminary monitoring at the initial stage of their appearance. At the same time, both various surfaces in the form of coatings and the formation of fracturing and cluster zones of inhomogeneities and defects have been analyzed. The emphasis in the course of research has been made both on the analysis of their regulated structure, and also on the dynamics of the growth of fracturing and cluster zones of heterogeneities and defects in a certain direction. At the initial stage, the indicated process of formation of fractures and cluster zones of inhomogeneities and defects in space was monitored with different scaling: nano- and microscales. This study has been carried out within the framework of an analogy under the following conditions: firstly, given control over the cha-racteristics of similar objects in the corresponding laser experiment; secondly, the presence of a real possibility of ensuring their formation on the inner surfaces of the chambers in contact with the working substance; thirdly, the possibility of such structures influencing on the efficiency of various types of thermal power units in the context of achieving the desired direction and/or undesirability of changing the indicators and characteristics of units taking into account the laws of technical thermodynamics.

Coal consumption prediction in thermal power units: A feature construction and selection method

Coal consumption prediction in thermal power units: A feature construction and selection method

Peaking Capacity Market Design and its Demand Evaluation Method

In order to achieve the major strategic goal of carbon peaking by 2030 and carbon neutralization by 2060, a new power system with new energy should be built to create a clean, low-carbon, safe and efficient energy system, and further promote the construction of the power market. It is necessary to build a peaking capacity market to ensure the safe and stable operation of the power grid. In the paper, a peaking capacity market mechanism is designed to encourage thermal power units to strengthen equipment transformation, operation and maintenance, and reduce the unscheduled shutdown of thermal power units. Key processes of the market including market demand evaluation, bidding, clearing, settlement are introduced. Based on the market operation, the power generation capacity of thermal power resources is expected to be fully enhanced during peaking periods of power system to ensure the system-wise capacity adequacy.

Artificial Intelligence Assisted Energy Optimization and Control Method for Microgrids

<p>As the future direction of power development, microgrids are particularly important for rational and efficient energy management. This article establishes an optimization model with multiple uncertainties as parameters for the microgrid energy system, with the objective function of minimizing operating costs. Then, an improved harmony algorithm was used to solve for the optimal solution of the model parameters. Finally, a microgrid system consisting of wind and thermal power units established in a certain area of Hebei Province was used for solution analysis. After experimental verification, the proposed method in this paper achieved significant improvements in both operational cost reduction and microgrid efficiency.</p> <p> </p>

Performance study of thermal-nuclear co-generation system based on exergy and thermal economy analysis

The thermal-nuclear co-generation system realizes the effective complementarity of power generating efficiency and pollutant emission reduction while simultaneously reducing the consumption of fossil fuels and pollutant emissions. First, four potential combined thermal-nuclear power generation schemes are proposed in this research. The performance of each scheme is examined, and the system is compared and examined based on two indicators: nuclear energy share and nuclear energy generation efficiency. For the chosen ideal combination scheme, exergy analysis and a thermo-economic structural theory analysis are carried out. The examination of the assembly for the Direct heating scheme, which the study's findings indicated was the optimum option, revealed that the combined unit could achieve 38.14% assembly efficiency, which is 2.29% greater than that of the nuclear unit alone. The feasibility of combining thermal and nuclear power is demonstrated by the study of the influence of the key parameters on the cost per unit of assembly and the calculation that the co-generation system's economic efficiency is higher than that of nuclear or thermal power units built separately in terms of fuel economy.

Emergency Dispatch Approach for Power Systems with Hybrid Energy Considering Thermal Power Unit Ramping

Future power systems will face more extreme operating condition scenarios, and system emergency dispatch will face more severe challenges. The use of distributed control is a well-designed way to handle this. It enables multi-energy complementation by means of autonomous communication, which greatly improves the flexibility of the grid. First, in the context of global energy conservation and emission reduction, this paper adopts the energy usage method of “renewable energy is the main source of energy, supplemented by thermal power and energy storage” to reduce the system abandoned wind (light) rate while supplementing the energy storage capacity. Second, a consensus algorithm is added to the system while considering the coordination between thermal units and energy storage. An “interface” for autonomous communication between thermal units and energy storage is created using the incremental cost of each agent. To address the recurring issue of power imbalance during emergency dispatch of the system, the consensus algorithm is enhanced so that the communication interval varies with the unit rate. This is based on the climbing characteristics of each thermal power unit. Finally, the effectiveness of the proposed method is verified in an IEEE-30 bus system.

Frequency Control Strategy of Energy Storage and Thermal Power Unit Considering Cost and Performance

Considering differentiated frequency regulation(FR) characteristics between energy storages and thermal power units, a frequency control strategy considering cost and performance is proposed to realize the complementary advantages of them. A joint objective of minimizing total cost and minimizing the penalty for failure of energy storage to track a given signal is proposed. The technical characteristics of FR resources, such as power and creep rate, are adopted as constraints. The comparison results demonstrate that the suggested approach improves the FR regional grid’s performance and reduces the regulation cost.

Research on optimization of power dispatching under the constraint of deviation electricity

In the medium- and long-term electricity market, uncertain power output, and power load will lead to the deviation between the actual generation and the signed medium- and long-term contract electricity. In order to reduce the system deviation balance cost and ensure the balance of power supply and demand, it is necessary to find a suitable dispatch method. First, a monthly electricity decomposition model of thermal power units is proposed in this paper. After that, we propose a power dispatching model under the constraint of deviated electricity quantity to minimize the cost of electricity deviation. The simulation results of numerical examples show that the proposed dispatching model and method can effectively reduce the monthly contract power deviation and the balance cost.

Multi-objective solution of optimal power flow based on TD3 deep reinforcement learning algorithm

With the increasing proportion of renewable energy generator units in power grid, the research on how to coordinate and control the optimal power flow (OPF) problem of traditional power generation and renewable energy power generation is gradually being paid attention to. In this paper, considering the line constraints and generator set constraints, an OPF problem including thermal power units and renewable energy units is established, and multiple solution objectives are set. The goals include line safety, renewable energy output, unit generation capability and unit operating costs. As an off-policy learning strategy, TD3 reinforcement learning method outperforms other reinforcement learning methods in learning strategies which include dual critic networks, actor network delayed update, replay buffer sampling and target policy smoothing regularization. As a result, for this multi-objective solution problem, we adopt the TD3 reinforcement learning solution method and verify the effects through an example. It reveals in the experiments that TD3 learning method can achieve better results through algorithm comparison and line disconnection analysis. Algorithm analysis shows TD3 method can achieve faster convergence while the disconnection analysis shows the robustness of the proposed method. Through this solution method, a reasonable generator set output arrangement can be obtained. At the same time, in the case of using different weight coefficients, it will have different effects on the control strategy.

Performance Analysis of a 300 MW Coal-Fired Power Unit during the Transient Processes for Peak Shaving

A simulation model based on Dymola modelling was developed to investigate the dynamic characteristics of automatic generation control (AGC) for variable-load thermal power units in this study. Specifically, a 300 MW unit from a power plant in northern China was used to verify the model’s validity in steady-state processes and to analyze the behavior of the main thermal parameters under different rates of load changes. The economic performance of the unit under different rates of load changes is also analyzed by combining the economic indexes of “two regulations” in the power grid. Results indicate that as the rate of load changes increases, boiler output, main steam temperature, reheat steam temperature, main steam pressure, and working temperatures of various equipment fluctuate more intensely. Specifically, at a rate of load reduction of 2.0% Pe MW/min, the maximum deviation of the main steam temperature can reach 7.6 °C, with the screen-type superheater experiencing the largest heat exchange. To achieve a balance between safety and economics for the unit, the rate of load raising should not exceed 1.2% Pe MW/min, and the rate of load reduction should not exceed 0.8% Pe MW/min. This paper applies the covariance index and AGC assessment index of the thermal power unit load control system to the established dynamic simulation model to supplement the AGC assessment index in the “two regulations”, and to provide a flexible and reasonable system evaluation result for field operators to refer to, so as to improve the economics of the system on the basis of safety.

Assessing the total factor productivity of China’s thermal power industry using a network DEA approach with cross-efficiency

In the current tough business environment, improving total factor productivity (TFP) is essential to the survival and development of China’s thermal power industry. On the basis of a network production structure, this research uses a Data Envelopment Analysis (DEA) approach with cross-efficiency to measure the overall and two-stage (power generation and pollutant treatment) TFPs of this industry in China’s 30 provinces. Moreover, the Tobit regression method is introduced to recognize the impact factors on TFP changes. Empirical results reveal that: (1) The overall TFP of the eastern region is the highest (0.6269), and the TFP levels of the central and western regions are relatively close (0.5182 and 0.5378, respectively). (2) Generally, the TFP of the power generation stage is higher than that of the pollutant treatment stage. The mean values of the two stages are 0.5765 and 0.3998, respectively. (3) Economic development and fuel prices are positively associated with the TFP level, whereas technological progress is surprisingly negatively associated. (4) Major policy directions recommended include establishing the power auxiliary service market, implementing the flexibility transformation of small and medium thermal power units, reducing the cross-subsidy to household electricity consumption, removing interregional barriers of electricity transmission, reforming the electricity price system to mitigate the rebound effect, and reducing inefficient investment in pollution treatment retrofit of thermal power plants.

Coordinated optimization control strategy of hydropower and thermal power AGC units

With the rapid increase of penetration level of new energy power generation, the construction of auxiliary service market is facing new challenges. The stricter requirements of the power plant unit AGC are proposed by the power system. How to coordinate and control the output of hydropower and thermal power units to increase the use of hydropower while meeting the requirements of AGC regulation is a problem to be solved. Under the condition of interconnection of units in the whole network, an optimal control strategy for joint commissioning of hydropower and thermal power plants that meets the performance conditions of ‘two rules’ is proposed in this paper. The strategy establishes the connection between hydropower and thermal power units. Combined with the output characteristics and economic characteristics of hydropower units and thermal power units, a coordinated optimization control strategy model of hydropower and thermal power AGC units suitable for the ’two rules’ assessment rules is proposed for each objective and constraint condition in the joint scheduling of hydropower and thermal power. The optimal mathematical model with multiple objectives is constructed to realize the distribution of AGC among different types of power plants and units, which can give full play to the regulation ability of hydropower and thermal power. The proposed strategy achieves the efficient use of clean energy and reduces the grid’s overall operating costs to achieve energy conservation and emission reduction. Simulation results verify the superiority of the proposed strategy.

Analysis of VSC-HVDC support capability for power grids with large-scale renewable energy and multi-infeed HVDC links

Henan Power Grid is located in the north of Central China Power Grid. During its energy transition, thermal power units will be decommissioned on a large scale. Therefore, the scale of the new energy grid connection and regional external power will be further greatly increased to match the load growth demand. Under this background, Henan Power Grid plans to introduce the third HVDC (High Voltage Direct Current). Based on the actual data and the current operation status of Henan Power Grid, this paper proposes an analysis strategy about VSC-HVDC (Voltage Source Converter HVDC) to improve the support capability of the receiving power grid with multi-infeed HVDC. In recent years, VSC-HVDC technology has emerged with the strengths of flexible power regulation and strong voltage support. This paper firstly analyzes the VSC-HVDC power transmission characteristics and clarifies the mechanism of the VSC-HVDC power regulation. Then, based on the actual planning of Henan power grid, the influence of two feed-in schemes (LCC-HVDC (Line Commutated Converter HVDC) and VSC-HVDC) on the voltage stability of power grid and the number of subsequent commutation failures of other conventional DC are compared and analyzed under the three-phase short-circuit fault of AC lines near HVDC terminal location by using PSD-BPA simulation software. The results show that the VSC-HVDC scheme can effectively alleviate the voltage fluctuation (duration within 1 s and fluctuation number within 2 times) after the fault and restrain the number of subsequent commutation failures of conventional DC(with 2 times and even none).

Reduce operational costs of thermal power units in power systems using the flexibility of district cooling systems

The high volatility of wind generation causes the thermal power units to start up and shut down frequently because there is a lack of flexibility in the power systems, which poses a challenge to economic operation. With the increase in cooling demand, district cooling systems (DCSs) have received attention in recent years and have been built in many regions, which offer a novel option to alleviate the above problems by utilizing the complementarity between power and cooling systems. In a typical DCS, the cooling source is a key component that generates cooling energy for the entire cooling system. Utilization of the cooling storage capacity of cooling sources in DCSs is an economical and efficient measure for more operational flexibility of power systems. Therefore, this paper proposes a unit commitment model with combined power systems and DCSs to reduce the operational costs of thermal power units and wind curtailment. In this model, an accurate model of a cooling source with an ice storage tank, where the cooling characteristics and energy transmission process are reflected, is built to fully excavate the flexibility potential of DCSs. Finally, numerical simulations are performed to show that the proposed method reduces the operational costs by 15.78% within a scheduling day and makes the wind curtailment close to zero. The results of the above comparison demonstrate that the method can improve the operational economy and encourage wind power integration while assuring an adequate supply of electricity and cooling.

Multi-objective coordinative scheduling of system with wind power considering the regulating characteristics of energy-intensive load

Energy-intensive load (EIL) has excellent regulating potential in the utilization of wind power: it not only offers high flexibility and large power capacity but also features significant price sensitivity. Without considering the production tasks and the regulating characteristic of energy-intensive load, the current scheduling approach is difficult to implement. A novel multi-objective coordinative scheduling approach is proposed in this paper for wind-power utilization considering the regulating models of energy-intensive load to guarantee the benefits of both power system and energy-intensive load, which can greatly improve the willingness of energy-intensive load to participate in scheduling. Firstly, A general model of regulating characteristics for energy-intensive load is given based on production process. Next, based on this modeling, a coordinative scheduling model is established with three layer. Layer A determines the total tasks of load side and generating side with the goal of minimizing the wind curtailment. Layer B and layer C make decomposition optimization to thermal power units and load control units with the goal of minimizing the generation cost and load-adjustable cost, respectively. Finally, a case study to verify the modeling is presented. The study shows that the proposed method can significantly improve the utilization of wind power at lower cost on the basis of ensuring the production requirements and benefits of energy-intensive load.

An Optimization Method of Steam Turbine Load Resilient Adjustment by Characterizing Dynamic Changes in Superheated Steam Energy

Improving the dynamic regulation ability of thermal power units is effective for realizing flexible scheduling in modern power systems. At present, the unit regulation capacity is usually reflected by the load adjustment of the main steam pressure and flow tracking ability, through the calculation of the given and real-time deviation to complete the load, and by pressure adjustment. However, although the calculation involved in this method is easy and the results are intuitive, overshoot and lag can easily occur. The main reason for this is that the process from boiler combustion to turbine works has strong hysteresis and inertia, and the feedback signal of the pressure and flow rate cannot dynamically reflect the change in boiler combustion and steam energy. According to the heat transfer process of the unit, the main steam temperature can directly reflect the energy transfer in the furnace combustion process and then reflect the changing trend of steam energy. Analyzing the changing characteristics of the temperature, pressure, and flow of superheated steam under rapid load regulations makes it possible to calculate the instantaneous energy storage value of the main steam before the regulating valve, and this value was inserted into the coordinate system as a new feedforward signal. Finally, a simulation model was established by using the actual running data of the unit. A simulation experiment under variable working conditions demonstrated that this method could improve the dynamic adjustment of the unit to load and pressure and help the power grid absorb renewable energy.