Table of Content

05 June 2019, Volume 52 Issue 6

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Energy Efficiency Optimal Dispatch for Terminal Energy Internet

LONG Tao, BIE Zhaohong

2019, 52(6):  2-10.  DOI: 10.11930/j.issn.1004-9649.201904005

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Efficient and clean supply of energy is a top priority for China's development. In order to improve the energy utilization efficiency and renewable energy accommodation, an energy efficiency optimal dispatch model is proposed for terminal energy internet. In view of the multi-energy flow characteristics of terminal energy internet, a new indicator named energy utilization exergy-efficiency is proposed for terminal energy internet, which introduces the concept of exergy and considers the impact of the grid connection and renewable energy access. A corresponding model of energy efficiency optimal dispatch is thus established. The rationality and superiority of the proposed indicator and model are verified by case study. The results show that, energy utilization exergy-efficiency can more accurately reflect the efficient use of energy by terminal energy internet; energy efficiency optimal dispatch can promote energy cascade utilization, energy-saving and emission-reduction, and there is consistency between the results of the proposed dispatch and economic dispatch. So the energy efficiency optimal dispatch can help guide the development of outsourcing electricity prices for terminal energy internet in the incremental distribution network area.

Active Distribution Network Planning Model and Benders Solution Strategy Considering Multi-energy Complementation

HUANG He, GAO Song, ZHU Lei, HAN Jun, LIU Pengxiang, WU Zhi, GU Wei

2019, 52(6):  11-18.  DOI: 10.11930/j.issn.1004-9649.201903084

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An active distribution network planning model and a solution strategy is proposed in this paper considering the multi-energy complementation. With consideration of the uncertainties and complementary characteristics of various renewable energy sources, typical scenarios are generated using the density-based clustering method, and an active distribution network planning model is build based on second order cone programming with the optimal cost-benefit of the distribution network as objective function. Considering that the distribution network planning in multi-energy complementary environment is a mixed integer nonlinear programming problem with a large number of scenarios, an efficient solution strategy is provided for the planning model based on the modern Benders decomposition algorithm under the framework of Branch-and-cut solution. In the end, the IEEE-24 node test system is used for case study, and the result has verified the validity of the planning model and the efficiency of the solution strategy.

Multi-Objective Optimal Dispatch of District Integrated Energy System Considering Resilience

QI Shixiong, WANG Xiuli, SHAO Chengcheng, WANG Zhidong, ZHU Chengzhi

2019, 52(6):  19-26.  DOI: 10.11930/j.issn.1004-9649.201903117

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Given the background of energy internet development, the district integrated energy system has become an efficient and clean terminal energy consumption carrier. Based on the electricity-gas-heat multi-energy coupling system framework, this paper analyzes the operating economy of district integrated energy system with consideration of the threat of potential natural disasters. Aimed at the contradiction between the resilience of district integrated energy system to disasters and its operating economy, a multi-objective optimization scheduling method is proposed. Then, the increase of operating costs caused by the improvement of resilience to potential natural disasters and the overall economic performance of system are coordinated by the multi-objective weighted fuzzy programming method. Finally, the feasibility of the proposed multi-objective optimization scheduling method is verified by a case study. The result shows that the resilience of district integrated energy system to natural disasters can be enhanced effectively at the expense of certain operating economy.

Study on the Connotation and Path of China’s High-Quality Energy Development

DAI Hongcai, ZHANG Yunzhou, LI Suxiu, ZHANG Ning

2019, 52(6):  27-36.  DOI: 10.11930/j.issn.1004-9649.201902175

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As an important industry supporting economic development and affecting the ecological environment, the high-quality development of the energy industry is crucial to the high-quality development of China's economy. Since the concept of high-quality energy development was put forward, relevant researches have not been commonly conducted until now. It is urgent to research the connotation and paths of high-quality energy development. A model system is firstly constructed for the analysis of medium- and long-term energy outlook in China, highlighting the characteristics of the power system and its impacts on energy transition. Secondly, two scenarios are set for China’s medium- and long-term energy development. Thirdly, the connotation of China's energy high-quality development is analyzed and the main indicators are proposed. Finally, under the two scenarios, China's medium- and long-term energy development path is forecasted, and comparative analysis is carried out based on the main evaluation indicators of energy high-quality development.

Evaluation Method for Optimal Operation Mode of Integrated Energy Supply System Based on Load Ratio

LIU Xingyue, TANG Lin, YU Na

2019, 52(6):  37-44,53.  DOI: 10.11930/j.issn.1004-9649.201903014

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The integrated energy supply system can provide loads for cooling, heating and power for users at the same time, and there are two operation modes: CCHP operation and separation production. Firstly, based on the life cycle theory, a comprehensive evaluation index system is constructed including greenhouse gas treatment cost in the energy life cycle and system operation cost. By comparing the performance between separation production and CCHP in terms of comprehensive evaluation index under the modes of CCHP-FHL and CCHP-FEL, an evaluation method of the optimal operation mode is obtained based on the load of cooling, heating and power. Finally, the evaluation method is applied in an example system to evaluate the performance of CCHP-FHL and CCHP-FEL modes under separation production and CCHP operation in 3 types of typical days in winter, spring & autumn, and summer respectively. It can be concluded that the optimal operation mode is no longer a single operation mode, but a mixed operation mode determined by the proportion of cooling, heating and power loads. It is verified that the evaluation method can be used to evaluate and optimize the integrated energy supply system conveniently and effectively.

Coordinated Dispatch Method of Heat and Power Systems Considering Peaking Ancillary Services

LIN Chenhui, WU Wenchuan, WANG Bin, SUN Yong

2019, 52(6):  45-53.  DOI: 10.11930/j.issn.1004-9649.201904071

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China's northern regions are rich in wind resources, but the wind curtailment becomes a critical problem during the heating season due to the output characteristics of combined heat and power units. The central heating system covers a large area, and has a huge pipeline volume and a strong heat storage capacity and thermal inertia. If the central heating system can be dispatched reasonably, the peak regulation of the power system can be significantly improved, and the wind power consumption can be promoted. In order to improve the peak regulation capacity of power grids, the peaking ancillary service market has been launched in various areas in China to stimulate renovation and flexibility of the thermal power units and to expand their output regions. This paper makes a study of the coordinated dispatch method of heat and power systems considering peaking ancillary services, and constructs heating system models to characterize their dynamic characteristics, in which the ancillary services are considered in the objective function. Simulation tests are conducted through a provincial-level system, which demonstrate the rationality of the proposed model, The economic benefits of the model are calculated in promoting wind power consumption.

Optimization Model of Multi-period Time of Use Strategy Considering Multiple Assessment Indices

WANG Lei, YANG Hejun, MA Yinghao, ZHANG Dabo

2019, 52(6):  54-59.  DOI: 10.11930/j.issn.1004-9649.201903074

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Time of use (TOU) strategy is one of the main measures of demand side management (DSM) in power system at present, which can effectively reduce load fluctuation and realize peak load shifting. Reasonable selection of peak-valley time of use or peak-flat-valley time of use strategy is conducive to improving power system reliability and customer satisfaction. Therefore, a customer response model is proposed based on price elasticity matrix to quantitatively calculate the customer comprehensive satisfaction. The peak load, peak-valley difference and comprehensive customer satisfaction are calculated respectively according to corresponding models, and a multi-index model is constructed for assessment of peak-valley or peak-flat-valley TOU price. The objective function of TOU electricity price optimization problem is established using the aforementioned indices. The correctness and effectiveness of the proposed method are verified through simulating three types of customers.

Robust Economic Dispatch Model of Interconnected Microgrid Considering Tie Line Power Stability

KANG Kai, DENG Shaoping, ZHANG Chao, ZHANG Yunlong, WU Xiong, WANG Zhao

2019, 52(6):  60-67.  DOI: 10.11930/j.issn.1004-9649.201903086

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Low energy utilization efficiency and serious environmental pollution problems have promoted dramatic development of distributed microgrids all over the world. A microgrid is a controllable entity which can be viewed as an equivalent fixed load with sequence and periodicity from the perspective of the grid when its tie line power can be periodically stable. However, the tie line power stability can be risky due to the uncertainty of renewable energy in microgrid. To address this challenge, this paper proposes a robust economic dispatch model of the interconnected microgrid considering tie line power stability, where the power delivered from/to the grid can always be maintained at a stable level by coordinating other dispatchable distributed generators and battery energy storage system. Additionally, this model can reduce the risk from the uncertainty of renewable energy. The column-and-constraint generation method is used to solve the robust model. Simulation on a modified IEEE 33-bus distribution system indicates that the proposed model is effective to give a robust equivalent load profile of the interconnected microgrid.

Master-Slave Game Based on Economic Optimization Method of Multi-Microgrid System

TONG Xin, HU Cungang, RUI Tao

2019, 52(6):  68-76.  DOI: 10.11930/j.issn.1004-9649.201903077

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With the deepening reform of the electricity market on the sale side, it is of great significance to study the economic optimization of multi-microgrid (MMG) system. This paper proposes a master-slave game based economic optimization method of MMG system, which consists of day-ahead optimization stage and real-time optimization stage. In the day-ahead optimization stage, the microgrid operator (MGO) optimizes the schedule of the energy storage units based on the day-ahead forecast information and grid price information; In the real-time optimization stage, the system operator (SO) solves the internal optimal price by constructing master-slave game model based on the real-time forecast information, encourages MGO to participate in energy trading in MMG system, and improves energy sharing between microgrids. The results of case studies show that the two-stage economic optimization method proposed in this paper can effectively improve the benefits of MGO and SO, and reduce the peak-to-average load ratio of MMG system.

Key Problems and Prospects of Integrated Energy System for Green Ecological Townships

HE Wei, CHEN Bo, ZENG Wei, WANG Dan, HE Guixiong, WEI Wei, GUO Li, LEI Yang

2019, 52(6):  77-86,93.  DOI: 10.11930/j.issn.1004-9649.201903083

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As an important part of economic and social development, townships have their own unique characteristics in natural resource, energy utilization characteristics and energy infrastructure conditions compared with cities. Based on an analysis of the characteristics and existing problems of green ecological townships with a consideration of the township’s clean-energy resource and their energy demand for the cooling, heating and electricity, and in order to realize the multi-energy complementarity of electricity, gas and heat and the interactive optimization of source, network and load, this paper discusses the key problems of the integrated energy system for the green ecological townships from the aspects of multi-energy coordinated planning, operation optimization and comprehensive evaluation, and makes a prediction for the future development direction of the township’s integrated energy system.

Research Status and Technical Route of Regional Integrated Energy System Simulation Platform

ZENG Ming, LIU Yingxin, WANG Xing, DONG Houqi, ZHANG Zhigang, HUO Xianxu

2019, 52(6):  87-93.  DOI: 10.11930/j.issn.1004-9649.201902064

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Regional integrated energy system is an important development direction of China's energy system transformation. The simulation of regional integrated energy system can provide scientific simulation test and theoretical support for its planning, operation optimization and operation strategy formulation. With the development of the "Internet +" smart energy demonstration project and the multi-energy complementary integration demonstration project, initial progress has been made in the construction and development of the regional integrated energy system in China. At the same time, abundant research results have been achieved in the field of regional integrated energy system simulation both at home and abroad, but there are still many problems, such as incomplete optimization objectives and planning boundary, etc. In this paper, the basic content, research status and existing problems of the regional integrated energy system simulation platform are systematically analyzed. On this basis, the technical route and realization ideas of the integrated energy system simulation are discussed comprehensively, with a view to providing a reference for the in-depth study of the integrated energy system simulation.

Development of Distributed Energy Microgrid System in U.S.

FENG Wei, LU Hongyou, Chris Marnay, ZHANG Ning, GUO Zun

2019, 52(6):  94-103.  DOI: 10.11930/j.issn.1004-9649.201904056

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This paper provides definitions of distributed energy microgrid system. Firstly, it reviews U.S. past ten years’ experience on developing microgrid demonstration projects and policies from federal government to local cities and utility companies. Then, it compares key simulation software developed through U.S. microgrid research. Finally, this paper introduces different business models of distributed energy microgrid construction often adopted in the U.S. market. The goal of this research is to review U.S. distributed energy microgrid research and provide useful experience to China on comprehensive energy-internet demonstration.

Ultra-Short-Term Optimal Scheduling of Power System Orienting to Flexible Resources Configuration

HUANG Qihang, MA Xue, BAI Zuoxia, TAO Xin, WANG Xiuli

2019, 52(6):  104-110,120.  DOI: 10.11930/j.issn.1004-9649.201903026

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The integration of large-scale new energy sources has led to an increase in the volatility of the power system, resulting in more serious peak regulation and ramp problems. This paper studies how to consider the use of flexible resources in ultra-short-term optimal scheduling to meet the requirements of peak regulation and ramp orienting to flexible resource configuration. Firstly, this paper proposes a flexible resource operation model and a power system optimization scheduling model in the ultra-short-term period to calculate the vacancies of peak regulation and ramp in power system. Secondly, in order to consider the numbers of flexible resources that need to be added when the power system is short of flexibility, a flexible resource configuration model is proposed, and an ultra-short-term scheduling process orienting to flexible resource configuration is given. Finally, through case studies based on the actual data of a province, the simulation analyses of the ultra-short-term optimal scheduling with and without adding the flexible resources are carried out, and the validity of the proposed method is proved.

Real-Time Economic Optimization Method for Microgrid Considering Energy Storage Charge and Discharge Benefits

LING Chanhui, ZHENG Changbao, HU Cungang, RUI Tao

2019, 52(6):  111-120.  DOI: 10.11930/j.issn.1004-9649.201903073

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Aiming at the economic dispatching problem of island, this peper proposed an optimal scheduling model considering the enery storage charge and discharge eddiciency, which fully considers the cost of energy acquisition in the past period and the operation benefit in the future period, so as to determine the mode of energy storage unit participating in the economic optimization of microgrid in the current period. On this basis, each agent in the microgrid can maximize its own operating efficiency through exchanging expected transaction power and electricity price with its neighboring agents. In this model, the alternating direction multiplier method is used to solve the optimal transaction volume and price between agents. Finally, under three different weather scenarios, the operation results of distributed economic optimal dispatch of islanded microgrid are analyzed, and the validity of the proposed model and solution method is verified.

Simulation of the Power Frequency Electric Field in the AC Filter Area of the HVDC Converter Station

WANG Yanzhao, ZHOU Bing, ZHANG Yemao, XIE Huichun, LIU Zhenhuan

2019, 52(6):  121-127.  DOI: 10.11930/j.issn.1004-9649.201808059

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With the increasing of the public’s attention on the electromagnetic environment, it is necessary to predict and evaluate precisely the level of the electromagnetic environment at the design stage for high voltage direct current (HVDC) converter station. Different 3D simulation models of 1 000 kV AC side region are established according to the design scheme of the AC side converter area of ±1 100 kV Guquan converter station. By using the finite element analysis software, the power frequency electric field at the patrol channel around the AC filter field is analyzed on the basis of the different models. In addition, the influence of the height and the phase spacing of the bus-bar are also analyzed. The calculation results show that the capacitor bank in the AC filter area contributes relatively little to the power frequency electric field at the patrol channel around the AC filter area, but the tube above the patrol channel contributes relatively large. Therefore, the model of the capacitor tower can be simplified to reduce the calculation consumption. Based on the simplified simulation model, it is found that the power frequency electric field on the patrol channel decreases with the increase of the height of the bus-bar, and it also decreases with the decrease of the phase spacing. For the Changji converter station, the maximum value of the power frequency field on the inspection channel in the 1 000 kV AC area is 11.8 kV/m when the height of the bus-bar is 16.5 m and the spacing distance is 14.2 m. This value satisfies the requirements of engineering design. In order to verify the accuracy of the calculation method, the same method is used to simulate the power frequency electric field in the 500 kV AC field of Tongli converter station, and the simulation results agree well with the test results.

Diagnosis of Electrical Corrosion Fault in Wind Turbine Generator Bearing Based on Vibration Signal Analysis

JIANG Rui, TENG Wei, LIU Xiaobo, TANG Shiyao, LIU Yibing

2019, 52(6):  128-133.  DOI: 10.11930/j.issn.1004-9649.201903023

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The electrical corrosion is a normal fault mode of generator bearing in wind turbine. Besides, electrical corrosion fault has ripped effect on bearing surface and excite relative weaker impulse response than local fault, which makes it difficult to extract fault features. Based on the characteristics of vibration signal due to the electrical corrosion, the minimum entropy deconvolution (MED) is used as the pre-processing method to enhance impulse fault feature in vibration signals. Then, the envelope spectrum is used to identify bearing fault feature to improve the diagnosis effect. In this paper, the basic principle and implementation process of MED is introduced. Furthermore, the proposed method is used to diagnosis the electrical corrosion fault of a real case of bearing in a wind turbine generator. Vibration signal measured on the generator bearing box is processed with MED and envelope spectrum. And diagnosis of electrical corrosion faults is realized. The results confirm validity of the application effect of minimum entropy deconvolution method.

Influence of Conductivity Defects of Composite Insulators on Live-Line Working Approach Distance

LEI Xinglie, LI Yuze, PENG Yong, FANG Yuqun, QIAN Liqun

2019, 52(6):  134-139.  DOI: 10.11930/j.issn.1004-9649.201811005

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The composite insulators are likely to have such defects as aging, damage and mandrel carbonization after a long-term operation, which could cause safety problem for its' live-line maintenance. In this paper, taking the I-series composite insulators of a 500 kV transmission line as an example, the discharge characteristics of the composite insulators under different conductivity defects are obtained through impulse discharge tests, and the location and size limitation requirements of the conductivity defects are determined through the insulation coordination method of live-line working. The testing results show that when the conductivity defect exists at the high-voltage end, the impulse discharge voltage of the gap is lower, which has a greater impact on the safety of live-line working; In order to ensure the safety of live-line working, when the conductivity defect exists at the high-voltage end of composite insulator, the maximum allowable length of conductivity defect is 0.7 m; when the conductivity defect exists in the middle of composite insulator, the discharge voltage is the lowest when defect exists at the position about 1/4 of the length of the insulator away from the high-voltage end, and the maximum allowable length of conductivity defect is 0.9 m. The location and size limitation requirements of the conductivity defects of composite insulators determined in this paper can provide a technical support for the safety of live-line overhaul working of composite insulators on transmission lines and guide the safety detection of composite insulators before live-line working.

Research on Blockchain Application in Electricity Charge Settlement of Distributed Generation

YE Ming, WANG Gang, ZHOU Zhen, YANG Fang

2019, 52(6):  140-146.  DOI: 10.11930/j.issn.1004-9649.201902201

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Distributed generation (DG) directly supplies power to users nearby, is conducive to improving energy efficiency and expanding the scale of renewable energy utilization. In this paper, based on the application scenario of distributed generation microgrid settlement business, a heterogeneous distributed generation settlement system is constructed by introducing blockchain and smart contract technology. The abstraction, generation and distribution method of smart contract, automatic execution method of settlement contract, cross-checking method of tariff data and convergence consensus method of transaction records are designed concretely. Finally, the system deployment and implementation suggestions are proposed based on specific application scenarios, in order to provide a new solution for improving the efficiency of settlement in distributed generation microgrid.

Research and Modeling on Noise Characteristics of Photovoltaic Serial Channel

SUN Fengjie, ZHAO Chenkai

2019, 52(6):  147-153.  DOI: 10.11930/j.issn.1004-9649.201807006

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In order to monitor the working state of each PV module, which can be realized by the carrier communication technology that uses the photovoltaic series as media, it is necessary to master the channel noise characteristics of photovoltaic series. In this paper, based on the measured photovoltaic channel noise in a photovoltaic power plant, a particle swarm optimization BP neural network is proposed to model the channel noise in the photovoltaic serial channel. The experimental and simulation results show that the predicted output of the particle swarm optimization BP neural network model have a consistent variation trend with the tested original noise in power spectral density and time domain waveform, which proves the effectiveness of the proposed model. Compared with the wavelet neural network and BP neural network optimized by genetic algorithm, the BP neural network with particle swarm optimization has less RMS error and higher accuracy.

The Coordinated Control Strategy for W-Flame Once-Through Boiler and the Optimization for Its Engineering Application

WANG Xihui, CHEN Houtao, ZHU Xiaoxing, WANG Zhijie, SHENG Kai

2019, 52(6):  154-159,165.  DOI: 10.11930/j.issn.1004-9649.201812040

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A control system of superior coordinated control quality is vital to the secure, stable and economic operation of a power generation unit and even the electric grid. Taking a 620 MW supercritical unit equipped with double inlet and outlet mills and a W-flame once-through boiler as the study object, a coordinated control strategy based on soft sensing of the feed coal quantity and its engineering application effectiveness are presented. The components of each control loop command in the coordinated control system and the mutual coupling relationship are analyzed in details. According to the test results under actual load fluctuations, the control defects are figured out, and the corresponding optimization scheme is conducted. The results after optimization suggest that the controls over the operating parameters such as the unit load, the main steam pressure and the main steam temperature are in steady state with both the dynamic and static control qualities exceeding the standard requirements.

Unit Initial Pressure Optimization Based on Gravity Search Algorithm and LSSVM

HU Jian, LIU Chao

2019, 52(6):  160-165.  DOI: 10.11930/j.issn.1004-9649.201810094

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The main steam pressure is an important parameter that affects the thermal economy of steam turbine. In order to accurately determine the optimal initial pressure of steam turbine during sliding pressure operation, a hybrid method of steam turbine initial pressure optimization based on gravity search algorithm (GSA) and least square support vector machines (LSSVM) is proposed in this paper. Firstly, with the aid of LSSVM the regression forecasting model is established for the heat rate of steam turbine, in which GSA algorithm is developed to find the optimal parameters of LSSVM to improve the regression accuracy and generalization capability for heat rate forecast. Then, based on the established model, the GSA algorithm is re-applied to seek the optimal main steam pressure with respect to the minimum heat consumption rate under each load level. Finally, taking a 600 MW supercritical steam turbine as the research object, the simulation results show that through optimization search the proposed method can be employed to provide a satisfactory initial pressure value for the main steam operation.

Study on the Current Situation and New Evaluation Model of On-line Chemical Instruments in Power Plant

LIU Xiangliang, WANG Ning, PAN Jun, ZHOU Chen, CHEN Jianwei, LI Chen

2019, 52(6):  166-171,178.  DOI: 10.11930/j.issn.1004-9649.201808104

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In order to investigate deeply the application status of on-line chemical instruments in China, onsite dynamic inspection and analysis were performed on 695 chemical instruments of 11 power plants across 9 provinces using YHJ-V inspection device. The error variance diagram was plotted based on the big data from tests, and then both the current situation and existing problems are summarized. It is concluded that the calculation method recommended by DL/T 246—2015《Chemical Supervision Guidelines》is difficult to be implemented to evaluate the measurement accuracy and supervision reliability of on-line chemical instruments. To be more specific, there is no better way to accurately count the number of total hours and hours of normal operations due to lack of technologies to verify the instrumental measurements. Therefore, a new model for evaluating the accuracy of chemical instruments in electric power industry has been proposed in this paper, which can more objectively calibrate the accuracies of the instrumental measurement and quantitatively determine the difference of instrument management and maintenance levels, which is beneficial to motivate the maintenance team in their routine work so as to take full advantages of chemical instruments for supervision purposes.

Cause Analysis and Related Solution of Induced Fan Vibrations in 300 MW Generation Unit Following the Integration of Induced Fans and Booster Fans

XUE Xiang, QIU Yong, MA Xiang, ZHENG Jin, LI Kailun, ZHANG Zhenmin

2019, 52(6):  172-178.  DOI: 10.11930/j.issn.1004-9649.201809121

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The vibration problems of induced fans with two-stage adjustable rotor blades in a 300 MW power generation unit are described in details. By virtue of hot test, disassembly overhaul and onsite vibration test, the causes of vibrations are analyzed. By taking account of the observations during the vibration process, the data testing and the fault diagnosis all together, the culprit of vibration is figured out and corresponding solutions are proposed. Consequently, the root cause of vibration is eliminated fundamentally. The study result can provide reference for the retrofit and secure operation of axial fans with two-stage adjustable rotor blades in coal-fired generating units.

Catalytic Oxidation of Elemental Mercury over CuO-WO₃/TiO₂ in Simulated Coal-fired Flue Gas

CHEN Chuanmin, NIE Guoxin, JIA Wenbo, LIU Songtao, CAO Yue, ZHAO Yi

2019, 52(6):  179-186.  DOI: 10.11930/j.issn.1004-9649.201904117

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Improving the Hg⁰ oxidation activity of the commercial selective catalytic reduction (SCR) catalyst can enhance the mercury removal activity in coal fired flue gas. In this paper, a series of CuO-WO₃/TiO₂ (CuWTi) catalysts were synthesized by step impregnation method for oxidize elemental mercury (Hg⁰) using simulated coal-fired flue gas at 150-350 ℃. The effects of O₂, SO₂ and NO on Hg⁰ oxidation were also investigated and compared with commercial catalyst. The results indicated that the commercial SCR catalyst and the WTi exhibited below 30% rate on Hg⁰ oxidation without HCl in simulated flue gas, while the Cu₂W₈Ti catalyst performed good activity of Hg⁰ oxidation and NO removal. The X-ray photoelectron spectroscopy (XPS) method was used to characterize the catalysts, and the results suggested that the interaction between CuO and WO₃ created abundant chemisorbed oxygen on the catalyst surface, which was beneficial for Hg⁰ oxidation. The Mars-Maessen mechanism was respected in the process of the Hg⁰ oxidation over Cu₂W₈Ti catalyst.

Analysis and Research on SCR System Performance and Resistance Increase of Air Preheater in Ultra-Low Emission Unit

MA Dawei, HE Jun, ZHANG Qiliang, HUANG Qishun, ZHANG Benyao, CHENG Jing, ZHU Shuai

2019, 52(6):  187-192.  DOI: 10.11930/j.issn.1004-9649.201810071

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Some major problems were encountered such as the difficulties to control NO_x emission concentration and ammonia escape concentration as well as the resistance increase of air preheater during the transformation of SCR denitrification system for ultra-low emission. In this paper, an SCR System of 300 MW unit after the ultra-low retrofit was selected for study purpose. The testing results are summarized as follows: (1) The NO_x at the outlet of unit denitrification was unevenly distributed. However, since the ammonia escape concentration limit was severely exceeded and the on-line ammonia escape monitoring meter readings were no longer eligible to represent the right values, NO_x concentration control would become more difficult and the increase of the resistance of the air preheater had been observed. (2) Excessively pursuing the ultra-low NO_x emission concentration may result in the drastic attenuation of the catalyst activities and some main chemical components. Then eventually severe deposition of ammonium bisulfate comes up on its surface. Therefore corresponding improvement plans are proposed. CEMS multi-point sampling transformation at denitrification outlet should be carried out to monitor NO_x concentration after ultra-low emission transformation. Both the ammonia injection optimization adjustment and the catalyst performance testing should be done on a regular basis to improve the effect of SCR denitrification device and the economy of denitrification operation.