Table of Content

05 September 2020, Volume 53 Issue 9

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The Crux of Scientific Development of Wind and PV Power Lies in Overall Planning and Coordination

WU Baoying, SHAO Chong, HUANG Yu, PAN Xudong

2020, 53(9):  1-7.  DOI: 10.11930/j.issn.1004-9649.202005116

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Large amounts of fossil fuel consumption and carbon emissions are the main causes for environmental pollution and climate change. Accelerated devleloping renewable ernergy, reducing reliance on fossil enery, building a clean, low-carbon and efficient energy system is the key to solve environmental pollution and climate change problem and achieve sustainable energy development. In recent years, China has kept its energy saving and emission reduction commitments by developing hydro, wind and PV power, which has already ranked first in the world. Meanwhile, wind and PV power development also has exposed problems such as irrational and insufficient utilization due to uncoordinated development. Focusing on scientific development of wind and PV power in China, this paper analyzes the benefits and impacts of wind and PV power development, and puts forward some reasonable development ideas and policy suggestions from the perspective of energy strategy, planning, management and technology, which can be used as a reference for the high-quality development of wind and PV power.

Coordination Functions of Electricity Price Providing Locational Signals under the Circumstance of Electricity Spot Market

ZHANG Lizi, CONG Ye, TAO Wenbin, ZHENG Fukang, CHEN Zhengfei

2020, 53(9):  9-18,46.  DOI: 10.11930/j.issn.1004-9649.201911112

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The paper investigates the locational signals of the electricity prices and the pricing mechanisms which can provide locational signals, and analyzes the functions of locational signals of electricity prices under the circumstance of electricity spot market. Based on simulation of electricity spot market, the paper quantitatively analyzes the coordination functions of location marginal pricing (LMP) mechanism and zonal transmission pricing mechanism in realizing their pricing role as public utilities under different network structures and system congestion conditions. According to the actual conditions of a provincial power grid in China, a case study was carried out to verify the analysis results through transmission price calculation and electricity spot market simulation. Suggestions are provided for selection of electricity pricing mechanism under the circumstance of electricity spot market in China.

Day-Ahead Market Energy-Reserve Joint Clearing Model Considering Real-Time Market Balancing Cost under Participation of Wind Power Generation

WANG Zhicheng, WANG Xiuli, WANG Shuai

2020, 53(9):  19-27.  DOI: 10.11930/j.issn.1004-9649.202005128

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The uncertainty of wind power generation has posed a challenge to day-ahead electricity market clearing. A novel day-ahead energy-reserve joint clearing model considering the participation of wind power is proposed in this paper. The multi-scenario technique is adopted to describe the uncertainty of wind power output, which is the base of clearing model calculation. The proposed model can mitigate the operation pressure of the real-time market and ensure the stability of system by introducing the reserve clearing cost and the balancing cost of the real-time market. At the same time, the model considers the penalty cost of wind curtailment and load loss to ensure the full utilization of wind power resources and the stability of power system. A case study of an improved IEEE30 system shows that the proposed model can fully utilize wind power resources, effectively reduce the cost of power generation in day-ahead market, as well as reduce the risk of wind curtailment and load loss, and it may have good practical application prospect for the power system with high permeability of wind power generation.

Design of South China (Starting from Guangdong Province) Power Reserve Market

ZHANG Qiaoyu, ZHANG Lan, XIAO Yunpeng, DAI Xiaojuan, LAI Xiaowen

2020, 53(9):  28-37.  DOI: 10.11930/j.issn.1004-9649.201911111

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At present, power reserve in South China region is still managed according to the "two rules", and some irrationalities exit in the design of reserve varieties, price mechanism, settlement mechanism and allocation of reserve resources. It is thus urgently needed to build a power reserve market of South China (Starting from Guangdong Province), and perfect the South China regional electric power market system. On the basis of analyzing the reserve market mechanism abroad and the existing problems of reserve management in the South China region, a power reserve market mechanism applicable to the South China regional power market development is proposed, and a reserve market clearing model is established. The reserve market clearing results under different modes are analyzed through numerical examples, which shows that, under the reserve market modes of offering quantity and price or only offering quantity, the opportunity costs are included in the clearing price, and can compensate the opportunity cost of the tender reserve capacity. The joint optimization mechanism of reserve and electric energy market can insure the income of the units participating in the reserve market is not lower than those only participating in electric energy, which will actively stimulate units to participate in reserve market.

Mechanism Design and Trial Operation Analysis of Shandong Power Spot Market

WANG Yong, YOU Daning, FANG Guanghua, ZHANG Guoqiang, WANG Jin, KUANG Honghui

2020, 53(9):  38-46.  DOI: 10.11930/j.issn.1004-9649.202004242

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In order to summarize the trial operation experience of the first batch of pilot areas for power spot market construction, and promote the construction of power spot market in China, the market mechanism of Shandong power spot market is introduced, and the existing problems and some feasible solutions are studied based on an analysis of its trial operation situation. The operation features of Shandong power grid, such as the high penetration of clean energy, have dictated that the centralized power spot market mode may be more suitable for Shandong. Shandong power spot market consists of two timing markets, i.e., a day-ahead market and a real-time market, and an intra-day unit commitment, which is used as a cohesive mechanism. During the trial operation period, the overall operation of Shandong power grid is stable, and the power spot market clearing price changes with the relations between power market supply and demand. However, there are still some problems that need to be solved, including the market monitoring ability, the peak shifting compensation mechanism, and the prevention and control measures of users' trading risks. The research results show that the Shandong power spot market has basically met the conditions for continuous operation, but the improvement of market mechanism still needs to be continuously strengthened.

Unbalanced Funds Analysis under the Background of Coexistence of Planning and Market

ZHAO Zhenyu, GU Weizhen, CHEN Yuguo, LI Xiufeng, JIANG Yan, GAO Daochun, DUAN Ruiqin, WU Yang

2020, 53(9):  47-54.  DOI: 10.11930/j.issn.1004-9649.202001057

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In the process of electric power system reform in China, the coexistence of planning and market may not change in the short term. With electricity market expanding, the decoupling operation mode of planning and market is unsustainable. While the issue of unbalanced funds is more prominent when planning and market are coupled. A study is made on the unbalanced funds against the background of coupling pattern. The paper splits the calculation formula of unbalanced funds into various parts whose sources are relatively clear, and hereby proposes allocation schemes. Meanwhile, suggestions are provided on managing market congestion surplus according to the theoretical amount and the proportion of market power consumption to the total. Case studies have verified the adaptability of the proposed method to the coupling pattern.

Key Issues of Zhejiang Electricity Spot Market

HU Zhaoyang, FENG Donghan, TENG Xiaobi, ZENG Jiani

2020, 53(9):  55-59,70.  DOI: 10.11930/j.issn.1004-9649.202005158

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As a representative provincial market, Zhejiang spot electricity market has encountered some challenges in its construction and operation. Firstly, the characteristics of Zhejiang spot electricity market are analyzed. Secondly, the factors influencing the calculation accuracy of local marginal price are studied and discussed, and the corresponding improvement measures are proposed. Finally, from the views of market design and operation mechanism, some technical suggestions on construction of provincial markets are made based on the operation experiences of grid, in order to promote the stable and orderly development of provincial spot electricity markets.

Excessive Consumption Trading System for the Accommodation of Renewable Energies Based on Blockchain

ZHANG Xian, XIE Kai, ZHANG Shengnan, PANG Bo, TANG Honghai

2020, 53(9):  60-70.  DOI: 10.11930/j.issn.1004-9649.202002085

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In order to accelerate the construction of a clean, low-carbon, safe and efficient energy system, and promote the development and utilization of renewable energy, the responsible weights for renewable energy accommodation of provincial regions are set to establish and enhance the consumption of renewable energy. Excessive consumption trading, as an important supplementary method to guarantee market entities to complete their own accommodation responsibilities, is significant to promote accommodation of renewalbe energy . This article introduces the connotation and necessity of the excessive consumption trading, elaborates the framework of the excessive consumption trading market including generation and distribution of the excessive consumption, transaction organization of the excess consumption, the connection between the green certificate transaction and excessive consumption trading, and the corresponding settlement and accounting method. Moreover, a renewable energy accommodation responsibility weighting system based on blockchain is deployed to support the sufficient consumption of renewable energy to achieve by participating in market transactions. Finally, from the aspects of rule-making, distribution principles, and data sharing, we put forward suggestions for the development of renewable energy accommodation in China.

The Coordination Method and Its Characteristics of Two-Level Electricity Market

LI Xiaogang, YANG Libing, WU Min, LIU Yansong, ZOU Bin, SHAO Ping

2020, 53(9):  71-80,116.  DOI: 10.11930/j.issn.1004-9649.202003217

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The coordination method for provincial market and inter-provincial market is the core for two-level market operation, which includes coordination for two-level market congestion management and coordination for two-level market clearing. Two two-level market coordination methods, including the market splitting method and the inter-provincial flow-based market coupling method are introduced, and their characteristics are discussed with specific cases. The market splitting method calculates the power flow through the power transfer factors, and gradually increases the congested lines in the system as the constraint condition for the market clearing model. Through multiple iterations, the method can achieve the market effect with the same nodal price for the one-level market. The flow-based market coupling method calculates, under the condition that the net export of each province is known, the power flow of the tie lines between provinces through the regional power transfer factor, and achieves the inter-provincial market clearing with consideration of the tie line power flow constraint. The flow-based coupling method can directly obtain inter-provincial market results through the declared provincial net export curves without multiple iterations. The market splitting method is suitable for the case that the provincial market for each province is well constructed, while the flow-based coupling method is suitable for the case that provincial market for each province is different in market perfection.

Trans-provincial Transmission Pricing Mechanism Based on Point Rate

CHEN Zheng, LENG Yuan, GU Weide, JIN Dongya, JING Zhaoxia, XIE Wenjin

2020, 53(9):  81-89.  DOI: 10.11930/j.issn.1004-9649.202003022

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Reasonable trans-provincial transmission pricing is the premise for achieving fair competition between trans-provincial electricity trading, and optimizing resources in a larger scope. Aiming at the problems of trans-provincial transmission pricing, a point rate based trans-provincial transmission pricing method is proposed from the perspective of cost allocation and transmission price structure. The method calculates the used degree of trans-provincial tie lines by each provincial power grid through analyzing the electrical source flow, and allocates the trans-provincial transmission costs according to the used degree, consequently realizing the rationality of cost sharing. At the same time, from the perspective of price structure, determining reasonable trans-provincial transmission prices will make the trans-provincial transmission costs not hinder the inter-provincial transactions, which is conducive to the optimization of resources in a large region. The validity of the proposed method is verified by an IEEE-14 node example.

A Fast Power Market Clearing Method Based on Active Constraints Identification by Deep Learning

WU Yunliang, ZHANG Jianxin, LI Bao, LI Peng, LI Zhiyong, ZHOU Xin, YANG Yan, LAI Xiaowen

2020, 53(9):  90-97,207.  DOI: 10.11930/j.issn.1004-9649.202005028

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The day-ahead power market clearing needs to solve the security-constrained economic dispatch (SCED) problem. Although the SCED problem is a linear programming (LP) model, the model size is too large to be effectively solved because the massive security constraints in the N–1 scenarios need to be considered. Therefore, this paper proposes a fast clearing method for day-ahead power market based on the deep neural network. Firstly, a computation framework for SCED model based on deep neural network is designed, and embeds deep learning technology into the existing day-ahead power market clearing framework, which can effectively improve the solving speed of the SCED model without compromising precision. Secondly, a deep learning strategy is proposed for identification of active constraint sets, which can provide technical support for deep neural networks to effectively identify the active constraints of SCED from two aspects: feature vector design and efficient processing of the results of deep neural network. Finally, the effectiveness of the proposed method is verified in the IEEE 30 standard test system with renewable energy sources. The deep neural network is used to pre-identify the active constraints of the SCED model, which is beneficial to reduce the complexity of the model and improve the calculation efficiency of market clearing.

Demand Response Mechanism in Singapore Electricity Market and Its Enlightenment to China's Power Market Construction

ZHANG Lan, ZHANG Jingwei, XIAO Yunpeng, JING Zhaoxia, CHEN Baike, GUAN Yuheng, LUO Gang, BAI Yang

2020, 53(9):  98-106.  DOI: 10.11930/j.issn.1004-9649.202003060

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The demand response mechanism is of great significance for easing the current contradiction between power supply and demand in China and improving the utilization rate of energy resources. Singapore has a relatively mature demand response mechanism in electricity market. Firstly, the paper introduces the reform process of Singapore's electricity market and its operating mechanism at the present stage, with emphasis on the demand response mechanism under Singapore's spot market. Besides, the paper analyzes the settlement mechanism, and summarizes the characteristics and implementation effects of Singapore's demand response mechanism. And then, an IEEE-30 node example is used to analyze the implementation effects of demand response under different market scenarios. Finally, based on the current operating mechanism of China's spot market, some inspirations and ideas are put forward for China to construct the demand response mechanism of the spot market in the near future.

Optimal Time-of-Use Price Strategy With Selecting Customer's Range Based on Cost

HUANG Jianping, CHEN Haoyong, ZHONG Jiayu, CHEN Wutao, DUAN Shengzhi, ZHENG Xiaodong

2020, 53(9):  107-116.  DOI: 10.11930/j.issn.1004-9649.202003059

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The traditional time-of-use price policy ignores the user’s willingness. And the modeling of users’ response behavior does not consider the cost for users’ adjustment of electricity consumption, and the range of users cannot be selected theoretically. Therefore, this paper proposes an optimal time-of-use price strategy for selecting user's range based on cost. The relationship between the extra cost generated by the user's adjustment of electricity consumption behavior and the saved electricity consumption cost is analyzed. Then a model for electricity price and electricity response behavior under the time-of-use electricity price mechanism is derived. When the user's production cost after changing the electricity consumption behavior is higher than the price before the time-of-use price is implemented, the user's willingness to participate in the time-of-use price policy is evaluated as zero, and the user is not included for implementation of the time-of-use electricity price. The simulation and experimental results show that compared with the traditional time-of-use electricity price model that does not select the customer's range, the proposed model can reflect the adjusting process of user’s electricity consumption behavior, and can scientifically select the use’s range to participate in the time-of-use electricity price policy, and can achieve the best total benefits for the power grid and users.

Relationship Between Thermal Aging and Insulation Properties of XLPE

ZHAO Lihua, YANG Lan, LI Weiwei, WU Weiqing, REN Junwen

2020, 53(9):  118-124.  DOI: 10.11930/j.issn.1004-9649.202003216

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In order to study the crossed-linked polyethylene (XLPE) insulation material in thermal decomposition activation energy, electrical and mechanical properties changing with thermal aging degree, accelerated thermal aging tests were carried out at 110 ℃ on XLPE insulation material for AC cables. The thermal decomposition behavior of XLPE at 20~600 ℃ was studied by thermogravimtric analyzer (TGA) test. The electrical properties of the aged XLPE samples were studied by AC breakdown testing, broadband dielectric spectrum testing and volume resistivity testing; and the mechanical properties of the aged XLPE samples were studied by tensile test. The results show that the crosslinking structure and crystalline state of XLPE are destroyed by thermal aging, and the activation energy of XLPE tends to decrease. Due to the rapid oxidation reaction, the XLPE molecular chain breaks and the cross-linking structure weakens, resulting in serious deterioration of XLPE insulation materials. The activation energy, breakdown strength, volume resistivity, elastic modulus and elongation at break tend to decrease with the increase of aging time, while the dielectric constant, dielectric loss and conductivity tend to increase.

Step-Stress Test Method for Electrical Life Model Based on Cumulative Damage Curve and Its Application in XLPE Cable

BIAN Haoran, YANG Lijun, MA Zhipeng, DING Zhiwen, LI Zhongxuan

2020, 53(9):  125-132.  DOI: 10.11930/j.issn.1004-9649.202005062

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The inverse power function electrical life model (IPM) of XLPE represents the long-term voltage endurance characteristics of XLPE cable insulation. The parameters of IPM model including voltage endurance coefficient (VEC) are the important basis for cable insulation design and pre-qualification test voltage selection. The step-stress test has the advantages of short time and high efficiency, and is more suitable for obtaining the electrical life model parameters of cable samples. However, there are no standards for selection of step stress test parameters. At present, it mainly depends on experience and subjective determination, which seriously affects the validity and comparability of test results. In this paper, the “D-t curve” of accumulated damage of solid insulating materials is taken as the main basis to judge the failure mechanism of insulation. The equivalence of step-stress test and constant-stress test under different test parameters is analyzed, and the step-stress test parameters and field test scheme suitable for engineering application are proposed. With this method, a step-stress test is designed for two types of model cables with insulation thickness of 2.8 mm and 3.5 mm respectively, and the parameters of IPM electrical life model for the two types of model cables are obtained, which validates the feasibility of the proposed method.

Heat Transfer Process of HVDC Submarine Cables under Transient Load

LIANG Zhengbo, LI Lijun, PENG Chao, XU Mingzhong, ZHAO Weijia, WANG Lei

2020, 53(9):  133-140.  DOI: 10.11930/j.issn.1004-9649.202003213

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High-voltage direct current (HVDC) XLPE submarine cable is an important carrier for long-distance and large-capacity power transmission. The HVDC submarine cable load affects temperature distribution, while the temperature has an important influence on the conductivity and electric field strength distribution characteristics of HVDC XLPE insulation. Compared to the steady-state load conditions, the heat transfer process of HVDC submarine cables under transient load conditions is more complicated. In order to study the heat transfer process of HVDC submarine cables under transient load, this paper establishes a thermal field finite element model, and simulates the heat transfer process of HVDC submarine cables under the working conditions from zero load to full load and then to zero load. In the meantime, a test platform is set up to conduct contrast studies. The results show that the simulation results are in good agreement with the test ones, and the simulation model is suitable for describing the heat transfer process of HVDC submarine cables under transient load. The conductor temperature heat transfer process can be well fitted through constructing the transient and steady state components of conductor temperature, and the fitting method is helpful for temperature trend prediction and field maintenance of HVDC submarine cables.

Influence of Deformed Corrugated Aluminum Sheath on the Electric Field of Extruded Insulation DC Cable

ZHANG Hongliang, YIN Yi, XIAO Jinyu, HOU Jinming, YAN Zhiyu, XIE Shuhong, HU Ming

2020, 53(9):  141-149.  DOI: 10.11930/j.issn.1004-9649.202004035

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In order to determine the possible damage to the cable insulation structure by deformed corrugated aluminum sheath of HVDC cable and its influence on the electrical performance during operation, thermal expansion test and radial pressure test were conducted on 500 kV DC cable to identify the concave defects on insulation surface caused by the deformation of corrugated aluminum sheath. A finite element model was established to analyze the variation of insulation field intensity distribution with temperature drop, and the field intensity distribution on the defected insulation surface caused by the deformed corrugated aluminum sheath. The finite element simulation results show that the insulation field strength of cable varies with the insulation temperature difference during the load process, and the defects on the insulation surface can further cause the field strength distortion, the extent of which is related to the applied voltage and insulation temperature difference.

Charge Accumulation Characteristics of Nonlinear Conductive SIR Composites under Polarity Reversal Voltage

YANG Zhuoran, DU Boxue, LI Zhonglei, HAN Chong, ZHANG Cheng

2020, 53(9):  150-156,165.  DOI: 10.11930/j.issn.1004-9649.202004114

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The HVDC cable accessory is the weak point of the cable system. In order to study the effect of the nonlinear conductivity on the charge accumulation property of SiR cable accessory insulation under polarity reversal voltage, this paper prepared a SiR composites sample by mixing the SiC particle with the SiR matrix. The three-electrode method and the surface charge measurement system are applied to obtain the conductivity and surface charge properties. The result shows that the crystal lattice vibration in SiC causes the scattering of carriers, resulting in the decrease in conductivity of sample at high temperature. The surface charge properties of SiR composites sample under polarity reversal voltage indicate that the induced electric field between the surface charges and the heteropolar charges increases the conductivity of SiR composites after the polarity reversal of corona voltage, which accelerates the transfer of surface charge into the inside and the neutralization between heteropolar charges, subsequently suppressing the surface charge accumulation.

An Analytical Solution for Maximum Field Strength at the Pre-fabricated Joints of DC XLPE Cables

LIU Ying, ZHAO Mingwei, CHEN Jiawei

2020, 53(9):  157-165.  DOI: 10.11930/j.issn.1004-9649.202004207

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Due to the complex structure and multiple composite interfaces of the cable joints, the DC electric field distribution is usually analyzed by means of a numerical simulation software, which uses the electric-thermal coupling method for iterative calculation, and is time-consuming. In order to evaluate the maximum field strength at the joint for medium and low voltage DC XLPE cables, a simplified analytical solution was presented. Based on the theories of heat transfer and electromagnetics, a simplified model was established for analyzing the thermal field distribution at the cable joint, and an analytical formula was derived for calculating the field strength at the foot of the stress cone, with which only a few necessary parameters are needed to determine the maximum field strength at the joint. In this paper, by taking the prefabricated joints of silicone rubber and ethylene-propylene rubber for the 10 kV and 35 kV XLPE cables as an example, analytical calculations were carried out under different DC voltages and temperature differences between the joint inside and outside, and the analytical results were compared with those from the finite element simulation. The consistence between them verifies the accuracy of the proposed analytical solution and its applicability for the design and evaluation of the medium and low voltage DC cable pre-fabricated joints in practical projects.

Optimized Operation Using Carbon Recycling for Benefit of Virtual Power Plant with Carbon Capture and Gas Thermal Power

ZHOU Renjun, DENG Ziang, XU Jian, ZHU Jiangsheng, WANG Yangzhi

2020, 53(9):  166-171.  DOI: 10.11930/j.issn.1004-9649.201908007

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Aiming at the problem of carbon utilization and economic operation of the new type of carbon capture and Cogeneration gas unit, a virtual power plant converged with wind power and power-to-gas (P2G) was constructed. The emitted CO₂ was captured and transported to P2G as the carbon raw material for power-to-gas, so as to realize carbon recycling in virtual power plants. The optimal operation model of the virtual power plant was established. The goal was to maximize the benefit of the virtual power plant, and the decision variables were CO₂ capture rate, thermoelectric ratio, electric output of the thermal power plant and electric to gas power. The simulation results show that the virtual power plant in this aggregation mode can obtain higher economic benefits, better wind power consumption, and lower carbon emissions. This virtual power plant and its carbon recycling method are an effective way to reduce wind curtailment, reduce emissions, and enhance carbon utilization. It has significant economic and social benefits.

Economic Dispatch of a Virtual Power Plant Considering Demand Response in Electricity Market Environment

LIU Xin, WU Hongbin, WANG Jingjie, LU Junhua

2020, 53(9):  172-180.  DOI: 10.11930/j.issn.1004-9649.202001092

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As an important part of the energy Internet, the virtual power plant plays a vital role in aggregating distributed energy and user-side resources and improving the trading system of electricity market. However, due to the large installed capacity of renewable energy in the virtual power plant and its randomness in output, it is needed for the renewable energy to bear the penalty cost in the electricity market. It is proposed to use the virtual power plant to aggregate distributed energy to provide power services for multiple types of loads. Firstly, a distributed power output uncertainty model is established with Monte Carlo sampling. Then, with consideration of the demand response, a bi-level optimization model is established for the virtual power plant and the user side, which takes the virtual plant's net income as the upper objective function, and takes into account of such factors as market transaction income, electricity sales revenue, and power generation cost. And furthermore, the user's power purchase behavior and response behavior are optimized by taking the user-side purchase cost as the lower objective function. Finally, a case study is conducted and the results have verified that the proposed model can reduce the bidding bias of a virtual power plant in the power market and increase the profit, and effectively reduce the load purchase cost as well.

Internal Optimization Stochastic Model of Virtual Power Plant Participating in Gas and Electricity Market

PENG Yuanyuan, ZHOU Renjun, ZENG Ziqi, FENG Jian, CHENG Yuanlin, FANG Shaofeng

2020, 53(9):  181-188.  DOI: 10.11930/j.issn.1004-9649.201902182

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The virtual power plant (VPP) generally reduces the impact of uncertainties, but due to the conservative nature of its scheduling schemes, it is difficult for a VPP to obtain the highest economic benefits without considering the internal randomness in the process of participating in the electricity and gas market. In order to fully exploit the economic benefits of VPPs, a stochastic optimization scheduling model is proposed for electric-thermal-gas VPPs with consideration of the uncertainty of electricity price and wind-photovoltaic under gas and electricity market. The objective function of the model is the total benefit of VPPs, which is the difference between the sales of electricity, heat and gas and the cost for electricity to gas conversion, carbon capture, carbon emission and fuel. The superquantile method is introduced to convert the total benefit optimal model of VPPs with multiple random variables into a super-quantile random optimization model. For the convenience of calculation, the model is further processed into a discretization calculation model, and is solved with the spatial particle swarm optimization algorithm. The simulation results show that the VPP obtains the optimal benefits through optimizing the sale schemes of electricity and gas, and with consideration of various random variables in the process of participating in gas and electricity market, the VPP has more opportunities to obtain higher economic benefits after avoiding risks.

Identification and Application of the Flow Characteristics of Steam Turbine Valve Based on LSSVM

WANG Zhijie, ZHU Xiaoxing, WANG Xihui, WANG Zhipeng

2020, 53(9):  189-194.  DOI: 10.11930/j.issn.1004-9649.201907156

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The accurate identification of the valve flow characteristic of steam turbine is of great importance for the turbine control. In this paper, a method based on least-squares support vector machine (LSSVM) is proposed to identify the valve flow characteristics of steam turbine. The historical operation data of the unit was screened to obtain the data under stable condition. Then LSSVM was applied to identify the relationship between the main parameter vector, which was composed of the integrated valve position command, main steam pressure, regulating stage pressure, etc., and the calculated actual steam flow of turbine. Finally, on the basis of the established LSSVM model, the working condition of steam turbine valve flow characteristic testing was simulated by changing the values of main parameter vector, so as to identify the steam turbine valve flow characteristics. This method can be implemented without doing any steam turbine valve flow characteristic test, which greatly reduces the workload and avoids the adverse effect of the test method on the operation security and stability of the unit.

Parameter Calculation of Steam Pipeline Based on Hybrid Modeling

CHEN Hongwei, MA Zherui, LV Chunwang, LIU Yuqiang, ZHANG Wei, WANG Ruikun

2020, 53(9):  195-201.  DOI: 10.11930/j.issn.1004-9649.201907190

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This paper proposes a hybrid model combining mechanism modeling and data-driven modeling together for the calculation of parameters of steam pipelines. Based on the mechanism model, this paper establishes a data-driven error prediction model by virtue of the vector machine algorithm to predict the mechanism error caused by the mechanism model calculation, then uses the error prediction result of the model to correct the mechanism model calculation results. In order to verify the validity of the hybrid modeling calculation, through the case studies, the pipe end steam parameters are calculated by using the mechanism model and the steam parameter prediction model based on vector machine algorithm, and then compared with the mixed model calculation results. The results show that the hybrid model has higher calculation accuracy, which can provide reference for the operation optimization of the heating pipeline.

Study on Environmental Benefits of Wet Plume Treatment Project Based on Actual Measurements

ZHANG Zhiqiang, ZHU Fahua, ZOU Siyi, SHI Pengfei, WANG Xiaoling, YOU Qin, YAO Li, YAN Shaoshuai, WANG Xing

2020, 53(9):  202-207.  DOI: 10.11930/j.issn.1004-9649.202004038

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In order to evaluate the environmental benefits, onsite measurements were retrieved by using the RJ-SO₃-M portable SO₃ analyzer in the wet plume treatment project of a 600 MW power unit in Handan, Hebei Province. The monitoring data of dust, SO₂ and NO_x before and after the wet plume treatment project were continuously collected under the conditions of similar operating load, coal quality and time period of operations. The results show that the flue gas cooling has very limited effects on the removal of SO₃ by FGD and WESP. In addition, there is no correlation between flue gas temperature drop and SO₃ removal efficiency of FGD, WESP and FGD + WESP. The total removal efficiency of SO₃ by FGD + WESP is between 75.6% and 81.9%, with the average of 78.9% under the conditions of the temperature drop by 0 ℃, 2.9 ℃, 3.9 ℃ and 5.8 ℃ respectively. The temperature drop of flue gas in the wet plume treatment project is beneficial to the removal of particulate matter by WESP. For instance, the mass concentration of dust emission has decreased by 0.5 mg/m³, while the concentration of SO₂ and NO_x emission remains almost unchanged. The removal of SO₃ in flue gas mainly depends on FGD and WESP, but has almost nothing to do with whether the flue gas has been cooled down. Therefore cooling down the flue gas temperatures turns out not an effective way to reduce the emission of pollutants.

Study on Mercury Removal Performance of Alkali Adsorbent in Coal-Fired Power Plant

ZHAO Bing, WANG Haigang, HU Dong, CHEN Kunyang, JIN Xuliang, YIN Aiming

2020, 53(9):  208-213.  DOI: 10.11930/j.issn.1004-9649.201912098

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Mercury pollution in coal-fired power plants has received widespread attention. At present, being the most mature technology, the activated carbon injection technology has been implemented for mercury removal in coal-fired power plants. However, activated carbon needs to be further transformed which is accompanied with its relatively high application cost. Therefore, the mercury removal with various types of adsorbent has become a hot research topic both domestically and abroad. In this article, based on the alkaline adsorbent removal system of Unit 7 of Datang Yangcheng Power Plant, the mercury removal effect of dry NaHCO₃ powder is tested and explored using Ontario Hydro Method (OHM). The results show that at the reaction temperature of SCR, NaHCO₃ can convert most of Hg⁰ and a small amount of Hg²⁺ into Hg^P. Furthermore, the Hg^P conversion rate is close to maximum when the injection volume of NaHCO₃ reaches 480 kg/h. This study provides a practical and feasible technical route for mercury removal from coal-fired flue gas.

Smart Grid Control Attack Defense Based on Semantic Analysis in Industrial Control Operation and Maintenance

MA Jianzhong, HU Kaibo, YU Lifeng

2020, 53(9):  214-220.  DOI: 10.11930/j.issn.1004-9649.201904065

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To reduce the threat of control-related attacks on the smart grid, a semantic analysis framework is proposed in supervisory control and data acquisition (SCADA) system, in which the smart grid information and physical industrial control equipment are used to detect and defend against such attacks. Firstly, the control network is monitored to identify the control commands. Also the semantics and updated measurements related to the control commands are extracted from the network so as to evaluate the physical consequences of the commands. Then through the application of the general self-adaptive power flow analysis algorithm, the semantics information is extracted from the control commands to adjust the parameters. Case studies are carried out on the IEEE 24-node, 28-node and 38-node system and a 2 730-node system respectively. The results show that, compared with AC algorithm, the proposed algorithm reduces the detection delay of 24-node and 38-node systems by about 50% and that of 2 730-node systems by 66%. The average fault alarm rate is 0.01%, and the fault dismissal rate is 0.78% at the worst case.

A Short-Term Load Forecasting Method Based on Load Curve Clustering and Elastic Net Analysis

JIN Bingjie, LIN Yong, LUO Shuxin, WEI Bin, ZHOU Shucan

2020, 53(9):  221-228.  DOI: 10.11930/j.issn.1004-9649.201905111

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A short-term load forecasting method based on load characteristics clustering and elastic net analysis is proposed in this paper. By analyzing and clustering the historical load characteristics, the annual days are classified and its clusters are specified, and the lack of pertinence of the types of the day cluster selection is avoided. At the same time, Elastic net analysis is adopted to identify and select the dominant factors for short-term load forecasting. Furthermore, the neural network forecasting model is established on the basis of input variable optimization. Taking the actual load of a city in Guangdong province as an example, the effectiveness of the proposed method in improving the daily load curve forecasting accuracy is verified by comparing with other methods. Results show that the model established is long-term effective, dispensing with repeated training, which is applicable for short-term load forecasting.