Electric Power

Planning Mechanism and Incentive Strategies of European Offshore Wind Power and Their Enlightenment

MA Jinlong, SUN Yong, YE Xueshun

2022, 55(4): 1-11,92. DOI: 10.11930/j.issn.1004-9649.202110034

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China has rich offshore wind energy resources, and the development of its offshore wind power is in the key stage from coastal zones to pelagic zones, from shallow water to deep water, and from start-up to large-scale development. Europe is the pioneer of the offshore wind power industry and the world’s largest market in this regard, which has accumulated rich experience in offshore wind power development and can provide an important reference for the development of China’s offshore wind power. Therefore, three major European offshore wind power countries, i.e., the United Kingdom, Denmark, and Germany, are taken as examples for analysis in this paper. First, the planning mechanism and its advantages and disadvantages are comparatively analyzed from the aspects of the major responsible parties of planning and their responsibility as well as the planning process. Then, the typical incentive strategies adopted by Europe to promote the development of offshore wind power are analyzed, and the characteristics and implementation experience of different incentive strategies are studied according to the specific situation of the three countries. Finally, considering the European experience and China’s national conditions, some suggestions concerning planning mechanisms and incentive strategies are put forward to promote the development of China’s offshore wind power.

An Intrusion Tolerance Assessment Method for Cyber-Physical Power System

YAO Pengchao, YAN Bingjing, Hao Weijie, YANG Qiang

2022, 55(4): 13-22. DOI: 10.11930/j.issn.1004-9649.202111141

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With the increasing integration of information and communication technology, the cyber-physical power system (CPPS) is facing not only uncertainties from the physical world but also threat from cyberspace. It is urgently needed for a method to assess the defensive capability of CPPS against cyber attacks. An assessment method is proposed for intrusion tolerance and optimal defense resource allocation of CPPS based on mean failure time and reliability. Firstly, a semi-Markov chain attack model is established for the advanced persistent threat (APT) to analyze the penetration process of attacks from cyber level to CPPS. Besides, a stochastic game model is adopted to dynamically describe the interaction process between attackers and defenders in CPPS, subsequently predicting the optimal strategy of attackers under Nash equilibrium, and determining the optimal defense strategy against malicious attacks. Finally, the effectiveness of the intrusion tolerance assessment method is verified through a CPPS security testbed, which shows that the intrusion tolerance capability has a significant role in the secure operation of the CPPS.

Joint Service Caching and Computing Offloading Strategies for Electrical Equipment Intelligent IoT Platform

SUN Yi, CHANG Shaonan, CHEN Kai, CUI Qiang, SHEN Weijie

2022, 55(4): 23-32,43. DOI: 10.11930/j.issn.1004-9649.202110035

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Mass data constitutes a challenge to the electrical equipment intelligent industrial Internet of Things (EIP), and it is urgently needed for edge computing to assist the real-time processing of data. Current works mainly focus on the application of edge computing in Industrial Internet of Things(IIoT), while the impact of service caching strategy on edge computing is not paid enough attention. Aiming to solve above problem, a joint service caching and task offloading strategy for EIP was proposed. In order to solve the revenue conflict between service providers and equipment suppliers, we investigated and proved the existence of a two-stage Stackelberg game and the Nash equilibrium(NE). Further more, we proposed a generalized Benders decomposition algorithm combined with particle swarm optimization to solve the mixed integer programming efficiently. The simulation results show that the proposed strategy can effectively improve the task processing efficiency, reduce the computing cost of suppliers, and improve the service revenue of the service providers.

A Method for Mining GOOSE Protocol Parsing Vulnerabilities Based on Fuzzing

LIU Linbin, MIAO Quanqiang, LI June

2022, 55(4): 33-43. DOI: 10.11930/j.issn.1004-9649.202109105

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The existing fuzzing methods for industrial control protocol do not consider the characteristics of the embedded terminal systems, and have few research on the industrial control protocol without TCP/IP. Firstly, a fuzzing-based method for mining generic object-oriented substation event (GOOSE) protocol parsing vulnerabilities is proposed: the mutation mode is used to generate test cases, and three mutation strategies are presented based on GOOSE message field type, abstract syntax notation one (ASN.1) encoding mode and bit reversal; two terminal abnormalities monitoring methods are proposed based on GOOSE heartbeat message and system operation information. Then, the implementation system architecture and test process of the proposed method are designed. Two undisclosed GOOSE protocol parsing vulnerabilities are discovered in testing the embedded terminals of a manufacturer in a smart substation laboratory environment, which verifies the effectiveness of the proposed method. Finally, recommendations for preventing malformed message attacks are put forward based on such vulnerabilities.

Distributed Authentication of Power Grid Safety and Stability Control Terminals Based on DHT and Blockchain

LAI Yening, FENG Ke, YU Tongwei, WANG Wang, TANG Guanjun

2022, 55(4): 44-53. DOI: 10.11930/j.issn.1004-9649.202109102

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The power grid safety and stability control system has limited terminal resources and high requirement for real time response, and existing authentication schemes can hardly satisfy the requirements of the system for safety, real-time ability and storage efficiency. By combining the distributed Hash table (DHT) technology with the blockchain technology, a blockchain distributed storage optimization method is firstly proposed based on DHT of Skip Graph structure. And then a distributed authentication scheme of power grid safety and stability control terminals is designed based on DHT and blockchain technology, and the process and key algorithms for terminal registration, network access and authentication are given. The safety and spatial-temporal complexity of the proposed scheme are analyzed. The authentication scheme is systematically implemented, and experiments are performed on its average authentication latency and average terminal storage cost, which has verified the feasibility of the proposed scheme and its advantages in spatial-temporal efficiency. The proposed scheme improves the communication safety between terminals of the power grid safety and stability control system without affecting the communication efficiency, thus ensuring the safe and stable operation of power grid.

A Design Method of Hybrid MMC Full-bridge Submodule Proportion Applied to DC Traction Power Supply System for Urban Rail Transit

XI Yanna, LI Xiaotong, LI Ziming, WEI Yingdong, LI Xiaoqian, WANG Fangmin, LI Wei, LI Weirui

2022, 55(4): 54-62. DOI: 10.11930/j.issn.1004-9649.202011100

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The characteristic of urban rail DC traction power supply system is low voltage and large current. The capacity of a converter fails to meet the demand, limited by the current capacity of the switching device. Hybrid modular multilevel converter (MMC) is composed of full-bridge submodule and half-bridge submodule. It can be used in systems with modulation ratio greater than one. Utilizing the negative level output capability of the full-bridge submodule, the increase of the AC voltage or the reduction of the DC voltage can be achieved. This article is aimed at the hybrid MMC that can be applied in the DC traction power supply system and proposes a design method for the proportion of full-bridge submodule. This method meets the needs of high modulation ratio steady state operation and DC fault clearing capability. A 1 500 V subway system is selected as an example and three sets of parameters are also selected. The simulation model was built in PSCAD software to verify the correctness of the design method.

Generation-Storage Cooperative Optimization Control Method for Distribution Network Based on HSA-PSO Algorithm

DANG Bin, ZOU Qiqun, ZHANG Bin, FU Dong, YOU Mengkai, LE Jian

2022, 55(4): 63-69. DOI: 10.11930/j.issn.1004-9649.202101025

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Currently voltage control and network loss caused by the integration of high-penetration of distributed generations are usually tackled out by means of reactive power compensation. However, there are fewer control methods that take into account distributed generations and energy storage systems. Based on the cooperation control of distributed generations and energy storage systems, this paper establishes a multi-objective optimal control model of the distribution network with the goals of minimizing voltage deviation, minimizing network power loss and maximizing the consumption of distributed generation. Combining harmony search algorithm and particle swarm optimization algorithm effectively, a harmony search-particle swarm optimal algorithm(HSA-PSO) is proposed to solve the established model. The simulation example verifies the effectiveness of the optimization control method.

Dispatching Architecture and Planning Method of Future Distribution Network

ZHAO Yinan, SONG Bin, QIAN Zhenyu, LI Shunxin

2022, 55(4): 70-77. DOI: 10.11930/j.issn.1004-9649.202106020

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With the development of Internet of Things（IoT）technology, the large-scale access of smart terminal equipment is the general trend. At the same time, a large number of distributed generation access also has an impact on the distribution network architecture. This paper first studies the distributed architecture of distribution network in the future and puts for-ward the idea of distribution network which can transform between centralized form and distributed form. The evaluation and division method of coupling units are given. Then, the method of flexibility modeling is studied and applied to distribution network planning. Finally, an example is given to test the assumption.

Loss Analytic Calculation and Error Analysis for HVDC Converter

LI Biaojun, XIANG Quanzhou, YAO Chuantao, YU Qiong

2022, 55(4): 78-84. DOI: 10.11930/j.issn.1004-9649.202108111

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The loss of modular multilevel converter (MMC) HVDC converter valve is not only an important performance and economic evaluation index of the system, but also the direct basis for the selection of converter valve power devices, junction temperature evaluation and cooling system design. The main converter valve loss are the conduction loss and switching loss of power devices such as IGBT and Diode, accounting for more than 90%. At present, there are a large number of research results on the loss calculation and optimization methods of MMC HVDC converter valve. Based on the existing analytical calculation methods, this paper obtains the general loss calculation expression covering the system working conditions and device characteristics through further accurate derivation. The influence factors associated with loss and their weights are extracted, which provides a basis for targeted loss optimization. Considering that the nearest level control strategy is adopted for the converter valve in practical engineering, the error sources of the analytical calculation method are analyzed, and a feasible and high precision loss calculation method based on waveform data of project site is proposed.

Sample-Control-Device of Smart Substation

LI Xiaobo, YU Yang, YAO Hao, XI Wei, CAI Tiantian

2022, 55(4): 85-92. DOI: 10.11930/j.issn.1004-9649.202108009

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At present, smart substations adopt process-level equipment of "intelligent terminals and merging units". In this way, the merging unit cannot meet the basic requirement of "the damage of a single component inside the device cannot cause the protection to malfunction". In the process layer, messages between equipment are mostly in one-frame mode. Once the message is abnormal, it will often cause the protection to malfunction. In order to improve the reliability of relay protection, a new generation device architecture with complete dual is proposed. Key technologies such as voltage seamless selection technology, time-delay measurable switching technology, process layer networking and Lagrange interpolation are proposed.

Key Technology of Automatic Analysis of Fault Area Wave Recording of Power System

YE Yuanbo, CHENG Xiaoping, ZHANG Zhaoyun, LIU Hongjun, WANG Wei, SHAO Qingzhu

2022, 55(4): 93-99. DOI: 10.11930/j.issn.1004-9649.202105168

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In this paper, an automatic analysis method of power system fault recording is proposed and developed. It is an important part of relay protection real-time evaluation system based on wide area information. Through the use of automatic analysis system, the efficiency and quality of power system fault recording analysis are greatly improved, and the labor cost is greatly reduced, which greatly reduces the time of fault analysis and improves the quality of fault analysis. The system has been trial run in a power dispatching center. The operation results show that the scheme has good feasibility and effectively improves the maintenance efficiency of operation and maintenance personnel.

A Field Calibration Method for UHF Partial Discharge On-line Monitoring System Based on Cross-check Algorithm

LI Nan, LI Songyuan, SHANG Xuejun, GUO Bowen, LI Lin, ZU Guoqiang, HOU Kai

2022, 55(4): 100-107. DOI: 10.11930/j.issn.1004-9649.202110058

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Partial discharge (PD) on-line monitoring device plays an important role in comprehensive perception and intelligent diagnosis of equipment conditions. Affected by the operational environment, manufacturing technology and other factors, the on-line PD sensors are deteriorated in performance with the increase of their service time, the sensors’ calibration is thus imperative. An optimized field calibration method is proposed for the internal ultrahigh frequency partial discharge (UHF-PD) sensors of on-line PD monitoring system. Firstly, the influencing factors on the field calibration of the UHF-PD on-line monitoring system are analyzed from three aspects including sensors’ working features, installation location and signal transmission attenuation properties. Then, a novel cross-check method is proposed based on the traditional GIGRE method. Through horizontal comparison between different phases and mirror comparison between input/output signals, the effects of absolute-value check on the accuracy of sensor’s calibration is significantly decreased, thus improving the overall calibration efficiency. Finally, the proposed method was applied in a 500 kV substation for field calibration of the UHF-PD on-line monitoring system, and identified three typical defects, including the degraded sensors’ sensitivity, unreasonable sensors arrangement and faulted acquisition board. The results verified the effectiveness and feasibility of the proposed method.

Lightning Risk Assessment of 10 kV Distribution Line Based on TOPSIS Algorithm Improved by Weighted Mahalanobis Distance

DU Yan, XIE Congzhen, LI Yancheng, XIE Xinhao, LUAN Le, LUO Simin

2022, 55(4): 108-116. DOI: 10.11930/j.issn.1004-9649.202107085

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The insulation of overhead line in 10 kV distribution network is unsatisfied and lightning tripping accidents occur frequently in thunderstorm weather. Due to the complexity of large-scale line model construction, it is difficult to realize the risk assessment at the grid level based on physical model, such as lightning tripping rate. Besides, due to the lack of monitoring devices in the distribution network, the data quality is undesirable, which seriously affects the calculation accuracy of the model. In this paper, a lightning risk assessment method for 10 kV distribution network was proposed. Based on multi-dimensional data such as line operation, and meteorological environment information, the lightning assessment for large-scale distribution network lines was carried out under the condition of low quality data. Setting the geographical grid as evaluation unit, this paper extracted ten lightning-strike risk indexes from three dimensions, including meteorological, corridor environment, and characteristic parameters of line. Then TOPSIS algorithm improved by weighted Mahalanobis distance was used to build the lightning risk assessment system of 10 kV distribution network, and the risk was scaled. Finally, risk assessment results were verified by historical trip statistics in Guangzhou 10 kV distribution network, and the effectiveness of the assessment method was proved.

The Minimum Effective Insulation Length of Insulating Tools for Live Working on ±1100 kV Grounding Electrode Lines

LEI Xinglie, CHENG Dengfeng, CAO Songyuan, PENG Yong, XIA Lingzhi

2022, 55(4): 117-122. DOI: 10.11930/j.issn.1004-9649.202106065

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The minimum effective length of insulating tools is an important parameter to ensure the safety of live working personnels, but there are no such provisions or references for live working on grounding electrode lines in existing standards or researches. In order to ensure the safety of live working on the grounding electrode lines, simulation is carried out on a ±1 100 kV grounding electrode line to obtain the maximum over-voltage and its waveform characteristics. AC, DC, and standard operating impulse discharge tests are conducted on typical insulating tools for live working, and the influence of test layout, types of insulating tools, and applying voltage types on the discharge voltage are analyzed. The results show that the DC discharge voltage is the lowest in the case of short insulating tools. Finally, based on the test results, fitting formula are proposed respectively for determing the AC, DC, and standard switching impulse discharge characteristics for short insulating tools. In addition, the minimum effective insulation length of insulating tools are proposed for live working on ±1 100 kV grounding electrode lines.

Error Evaluation Method for Parameter Check of Electromechanical Transient Model of HVDC Transmission Control System

LIU Tao, WU Guoyang, DAI Hanyang, SU Zhida, SONG Xinli, XIAO Xiong, HAO Jie

2022, 55(4): 123-131. DOI: 10.11930/j.issn.1004-9649.202103099

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At present, the electromechanical transient model and parameters are generally used for simulation analysis of the LCC-HVDC transmission system with the power grid commutation converter as the core, but there is no practical error evaluation method for checking the parameters. Aiming at the electromechanical transient model and key parameters of the DC transmission control system, this paper proposes an error evaluation method for independent calculation of divided intervals and overall verification of configuration weights, based on the similarity method and analytic hierarchy process idea for power system simulation credibility evaluation, and a reasonable error evaluation standard is also given. Firstly the time series of the HVDC transmission system simulation and experiment are divided into multiple intervals, and the analytic hierarchy process (AHP) method is used to configure the weight coefficients for each interval. And then the error index of each interval and the overall error index are calculated. The validity of the error evaluation method is verified with test data of actual DC projects. The proposed method can evaluate the simulation accuracy and overall simulation effect of each stage of the entire time series, and can provide a technical support for the parameter verification of the electromechanical transient model of the DC transmission control system.

Resilience-Oriented Optimization of Source-Grid-Load Flexible Resources in Distribution Systems: Review and Prospect

YU Zhuofei, LIU Fei, LIU Ruihuan, LIN Chaofan, WU Di, SUN Houtao, CHEN Chen, BIE Zhaohong

2022, 55(4): 132-144. DOI: 10.11930/j.issn.1004-9649.202102084

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The safe operation of power systems is seriously challenged by increasingly extreme natural disasters and malicious attacks. The technology of resilient distribution systems can significantly improve the capabilities of distribution systems in resisting and responding to extreme events and efficiently restoring loads. Meanwhile, with the development of smart grid technology, distribution systems have access to various flexible resources, which can improve the reliability and economy of distribution systems in normal conditions, while the potential for resilience enhancement has not yet been fully uncovered. Therefore, this paper presents a systematic review of the resilience-oriented optimization of flexible resources in distribution systems. The categories and modeling methods of flexible resources on source-grid-load sides, as well as their applications in resilient distribution systems, are reviewed and discussed in detail. Moreover, the research trends in resilience enhancement of distribution systems by using the source-grid-load flexible resources are concluded, which can provide constructive guidance for the future development of distribution systems in China.

Annual Operation Mode Study of Integrated Energy System Considering Seasonal Natural Gas Storage

LIU Hechuan, ZHOU Xiaoxin, YANG Xiaoyu, LI Yalou, LI Xiong

2022, 55(4): 145-155. DOI: 10.11930/j.issn.1004-9649.202103031

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For the evaluation of the adequacy and security of energy supply in the integrated energy system with increasing electricity and gas coupling, it is necessary to simulate its annual operation mode. A multiple time scale simulation method for annual energy production of the integrated energy system is proposed to optimize the annual operation mode of the electricity and gas coupling system. Seasonal fluctuation factors such as natural gas storage are also considered in this method. The proposed method is validated in a designed system with increasing consumption of natural gas due to clean energy heating, and the impact of large-scale seasonal natural gas storage on the annual operation mode of the integrated energy system is analyzed. Furthermore, the influence of the increasing installed capacity of the combined cooling, heating, and power (CCHP, also known as tri-generation) unit on the coupling system is presented. The results indicate that the CCHP unit can reduce the working intensity of the seasonal natural gas storage unit, namely, the reduction of operation time and storage capacity. The main reason for this effect is that the refrigeration mode of CCHP is more efficient than that of electric refrigeration, which curtails the consumption of natural gas.

Micro-grid Hierarchical Energy Trading Strategy Based on Double Blockchain Storage

YU Yunjun, YANG Shengbao, MIN Weidong, YU Guanghua, WEI Bolu

2022, 55(4): 156-165. DOI: 10.11930/j.issn.1004-9649.202012097

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In micro-grid electric energy transaction, the traditional method is to store the internal data of electric energy transaction model through single chain block chain technology, but the original model needs large storage space. In order to save the storage resources of micro-grid trading system, this paper uses the method of physical block chain and transaction block chain double chain storage structure to store the data of micro-grid electric energy trading model. It effectively solves the stored in single chain storage is effectively solved and the storage cost of data is saved. In the electric energy trading strategy of micro-grid, two-way auction mechanism is used to trade electric energy, and supply-demand balance is used to trade electric energy. Considering the difference of different types of distributed power supply and load in micro-grid. This paper uses game theory method to analyze the power bidding strategy of micro-grid, under the condition of satisfying the balance of supply and demand. The distributed power supply and load of micro-grid are optimized according to their profit maximization. Finally, the effectiveness of the trading strategy is verified by an experimental example of micro-grid.

Transient Voltage-Reactive Power Modeling of Offshore Wind Power Collection and Transmission System with AC Cables and Characteristic Analysis

SUN Yanxia, FANG Shiwen, LI Zhen

2022, 55(4): 166-174. DOI: 10.11930/j.issn.1004-9649.202101108

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The transient overvoltage at the sending terminal of the offshore wind power collection and transmission system with AC cables threatens the safe and stable operation of the system. To quantitatively analyze the impact of transient voltage on offshore wind turbines and thereby guide the configuration of the voltage-reactive power control system for offshore wind power, we need to develop a transient voltage-reactive power model of the offshore wind power collection and transmission system with AC cables as soon as possible. This paper approaches this problem by analyzing the characteristics of the equivalent network of the transmission system considering AC cables and clarifying the boundary conditions for the equivalent network to demonstrate inductive characteristics or capacitive ones. Then, for the case of the equivalent network displaying capacitive characteristics, we build a mathematical transient voltage-reactive power model of offshore wind power considering AC cables and verify the validity of the mathematical model on the control hardware in the loop (CHIL) based real-time simulation experiment platform. Finally, with the transient voltage-reactive power model of offshore wind power, we quantitatively analyze the influences of AC cable line length and the control bandwidth and damping ratio of the current loop in the wind turbine grid-side converter (GSC) on transient overvoltage at the generator terminal to lay a theoretical foundation for quantitatively assessing the risk of transient overvoltage in the offshore wind power collection and transmission system with AC cables.

Subsynchronous Oscillation Mitigation Strategy Based on First-Order LADRC for Direct-Drive Wind Turbines

CAI Weizheng, GUO Kunli, LIU Luyu, WU Chaojun

2022, 55(4): 175-184. DOI: 10.11930/j.issn.1004-9649.202105038

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Aiming at solving the problem of subsynchronous oscillations (SSOs) induced by direct-drive wind turbines connected to the weak AC power grid, this paper proposes a first-order linear active disturbance rejection control (LADRC) strategy to suppress this phenomenon, thereby improving system stability. Firstly, the grid-connected mathematical model of direct-drive wind turbines is built, and the propagation mechanism of frequency disturbance components of SSOs is analyzed. On this basis, we design the first-order LADRC inner-loop current controller and optimize and tune the parameters, and the analysis indicates that the controller has a strong inhibitory effect on the frequency disturbance components of SSOs. Finally, using PSCAD/EMTDC simulation software, we build an electromagnetic transient simulation model of direct-drive wind turbines controlled by traditional PI and first-order LADRC. The results demonstrate that the proposed method can block the frequency disturbance components of SSOs and effectively suppress SSOs.

Comprehensive Evaluation of User Energy Storage System Configuration Schemes Based on the Improved Triangular Fuzzy VIKOR Method

MA Zhao, ZHAO Huiru, HUO Huijuan, LU Hao

2022, 55(4): 185-191. DOI: 10.11930/j.issn.1004-9649.202107106

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A comprehensive evaluation model based on improved triangular fuzzy VIKOR method is proposed, which is applied to the evaluation of energy storage system configuration schemes in uncertain decision-making environment. Firstly, the evaluation criteria set of user energy storage system configuration scheme is constructed by the grounded theory, and then some key criteria were select based on the grey relation-rough set method to form the evaluation index system. Then a combination weighting method based on the integration of subjective and objective is put forward to improve the weight accuracy. The subjective weight is obtained by the FAHP method, and the objective weight is obtained by the improved CRITIC method. Finally, considering the conflict and fuzziness between different criteria, an improved triangle fuzzy VIKOR method is constructed to evaluate the energy storage configuration schemes. The validity and feasibility of the model are proved by simulation analysis.

Generalized Cost Study of Energy Storage Power Station Based on Equivalent Efficiency Conversion

XIU Xiaoqing, LI Xiangjun, WANG Jiarui, XIE Zhijia, LV Xiangyu

2022, 55(4): 192-202. DOI: 10.11930/j.issn.1004-9649.202009092

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Energy storage is one of the key technologies to improve the security of modern power system with a high proportion of new energy sources. Unfortunately, the cost of energy storage system has restricted its large-scale commercial application so far. Therefore, in view of the generalized cost of different types of energy storage power stations, by taking their efficiency and lifetime into account, the discrepancies of construction and operating characteristics throughout the entire life cycle between each type of energy storage is analyzed. The full life cycle cost model and levelized cost model of energy model are constructed respectively based on the concept of equivalent efficiency conversion. The project construction period and land acquisition costs of energy storage projects which have been put into operation or planning in recent years, such as pumped storage, lithium-ion battery energy storage, lead-carbon battery energy storage, and vanadium redox flow battery energy storage, are analyzed comparatively. By introducing factors such as project construction period and land acquisition cost, the generalized costs of four types of energy storage are evaluated horizontally and vertically. The impact of changes in terms of the number of charge and discharge cycles, charging electricity price, and investment cost of energy storage power stations on the generalized cost are discussed. The research results can provide helpful references for the selection and planning of energy storage systems.

Evaluation of Business Mode for Large-Scale Energy Storage Applications Considering Capacity Constraints

KAI Saijiang, TAN Jie, SUN Yiqian, WANG Heng, YUAN Tiejiang

2022, 55(4): 203-213,228. DOI: 10.11930/j.issn.1004-9649.202101131

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Considering the capacity-related constraints of the application value of energy storage, an accurate quantitative evaluation method for the business mode of large-scale energy storage applications is proposed. A double-cascade function is used to characterize the grid’s requirements for flexible adjustment of resource performance and capacity for energy storage, thermal power, etc. Then according to its revenue in power generation, transmission and distribution, electricity charge, and ancillary service income generated by energy storage at the source, grid, and load side respectively, an income function is established for stakeholders including new energy asset owners, grid operators, users, and energy storage asset owners in the “energy storage +” scenario. Based on stakeholders' share, an energy storage cost function is set up according to the energy storage capacity allocated for the corresponding revenue. Taking account of the investment entities such as new energy, power grids, users or third parties, a game model for energy storage investment is constructed with the objective as the maximization of the net income. Finally, according to the actual situation in Gansu Province, the business mode of large-scale promotion of energy storage under different mode scenarios was evaluated, and the sensitivity analysis of key parameters was conducted to demonstrate the effects of various combinations of operation modes on specific source-load regions. Therefore the feasibility of the proposed method is verified.

Study on Off-design Condition Characteristics and Control Strategy of Fluegas Waste Heat and Water Recovery System of Coal-Fired Power Plants

ZHANG Guozhu, ZHANG Juntai, WEN Yu, YANG Kaixuan, LIU Ming, LIU Jiping

2022, 55(4): 214-220. DOI: 10.11930/j.issn.1004-9649.202011075

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A fluegas waste heat and water recovery system for the coal-fired power plant is studied in this paper. Based on the material, energy balance and equivalent heat drop method, the water-saving and coal-saving capacity of the system were calculated. Off-design models of the system were developed, influences of environmental temperature and control strategy on system performance and state parameters were evaluated. Results show that the water-saving potential of the system is 15.34 kg/s under the design condition, and the energy-saving potential is 2.75 g/(kW·h). When the ambient temperature changes, the temperature of some state points of the system will decrease with the ambient temperature. The coal saving of the low-temperature economizer will be reduced to 1.44 g/(kW·h) when the ambient temperature is –20°C. To prevent low-temperature corrosion of the system, the operation strategy was proposed, the fluegas temperature entering the electrostatic precipitator is increased to 90°C, which can ensure the safe operation of the system. However, the coal saving of the low-temperature economizer is lower than that of the unadjusted by 0.2 g/(kW·h).

Water Balance Model and Water-Saving Analysis for Coal-fired Power Plants

LIU Guangjian, YUE Fengzhan, ZHOU Shuo, WANG Lin, GAN Xue

2022, 55(4): 221-228. DOI: 10.11930/j.issn.1004-9649.202103028

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With the increasing shortage of water resources and the continuous increase of thermal power installed capacity, the application of water-saving technology is an essential issue for the sustainable development of the thermal power industry. The water balance model and water flow diagram is proposed based on coal type, meteorological conditions, and power plant performance parameters. From the water flow diagram, the water balance relationship is intuitively reflected between entering and leaving streams. The key processes to reduce system water use were identified. The energy and water-saving effects of flue gas waste heat and water recovery system are quantitatively analyzed. For supercritical power plant burning bituminous coal, about 60% water losses come from cooling tower evaporation and wind blowing, while cooling tower blowdown accounts for 20%. The moisture content in exhaust fluegas accounts for 15%. The critical points of water saving in thermal power plants are cooling systems, wastewater discharge, and moisture recovery from flue gas. This paper presents a waste heat and moisture recovery from flue gas system. The preliminary analysis shows that, for wet-cooled units, the water consumption per MW·h will drop by 19.2% with flue gas moisture recovered by 60%. For air-cooled units, if the flue gas moisture is recovered by 60%, the water withdraw of the power plant will be zero. If the semi-dry or dry desulfurization system is adopted at the same time, the power plant can become the water supplier.

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