Table of Content

20 March 2016, Volume 49 Issue 3

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Energy Interconnection

Concept and Prospect of Global Energy Interconnection

WANG Yimin

2016, 49(3):  1-5.  DOI: 10.11930/j.issn.1004-9649.2016.03.001.05

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The global energy interconnection will be of great importance to implement“the Belt and Road Initiative”, boost energy revolution and ensure national energy security. The author gives an in-depth discussion on the development practice of global UHV, smart grid and clean energy both in China and abroad, and then comes up with the idea of sustainable energy development by speeding up clean replacement and electricity replacement. The feasibility of establishing global energy interconnection is also elaborated. Lastly, key areas of technological innovation for global energy interconnection are pointed out and corresponding comprehensive benefits to the environment, economy and society are described.

Research on the Soft Environment of Arctic Wind Energy Development

ZHANG Fuqiang, TIAN Feng, JIANG Liping, BAI Jianhua, ZHANG Dong, YU Hongyuan, HUA Zhang

2016, 49(3):  6-11.  DOI: 10.11930/j.issn.1004-9649.2016.03.006.06

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In order to meet the global energy demand by pushing clean and green energy, it is of great significance to develop wind power in Arctic and transmit the generated electric power to the load centers across the northern hemisphere continents. Regarding the soft environmental issues of Arctic wind power development within the framework of Global Energy Interconnection, the constraints of Arctic wind development are analyzed from the viewpoints of international laws and international organizations, the investment laws and policies of Arctic countries, environmental protection as well as the rights of Arctic indigenous peoples. Drawing lessons from the energy project in Russia invested by other countries, the China-Russia joint cooperation is recommended for the development of the Arctic wind power and power grid investment. Moreover, some suggestions to boost Arctic wind power development are put forward.

Energy Internet as Strong Support for the Development of Smart City

ZHANG Shixiang, MIAO Ankang

2016, 49(3):  12-17.  DOI: 10.11930/j.issn.1004-9649.2016.03.012.06

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As a new pattern of urban development in the information era, Smart City creates humanized management and services based on the comprehensive perception, broadband internet and intelligent applications. Energy Internet is a new form of energy system generated through the integration of the Internet and new energy technologies. During the process of integration, Energy Internet also provides support for sustainable development of energy and the construction of Smart City. In this paper, the authors expound the development stage and roadmap of Smart City, clarify the close relationship between Energy Internet and Smart City, summarize the applications of Energy Internet in the various fields of Smart City, and finally analyze in details the supporting role of the internet in the development of smart city.

Important fields and Key Technologies of Innovation for Global Energy Interconnection

XIE Guohui, LI Qionghui

2016, 49(3):  18-23.  DOI: 10.11930/j.issn.1004-9649.2016.03.018.06

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It is urgent to accelerate energy power technology innovation for promoting global energy interconnection(GEI). Five important areas are proposed for GEI technology innovation, including large-capacity long-distance transmission, large-power grid safe operation and control, new energy power generation and integration, advanced energy storage, and internet information and communication. An analysis is made on the each area’s key technologies that have important supporting impacts on GEI, and the focus of research, their future development trend and application prospects.

A Review on the Energy Internet

LIU Xiaoming, NIU Xinsheng, WANG Baihuai, LIN Jikeng, ZHANG Jie, WANG Yuan

2016, 49(3):  24-33.  DOI: 10.11930/j.issn.1004-9649.2016.03.024.10

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Energy Internet, an emerging research topic, which can be used to solve the problems of energy depletion and environmental pollution, is drawing the great attention from experts, scholars and the government. In this paper, a comprehensive review of the energy Internet and its prospect is taken at first. The reasons why it’s getting more attention are analyzed and the connotation and characteristics of the energy Internet are elaborated. Then the domestic and foreign research status of the energy Internet are summarized. Analysis from the aspects of the architectural design, control strategies and connotations are performed. At the end, the challenges and issues in the development of the energy Internet are further analyzed. The research on the energy Internet is analyzed and summarized, the direction for further research and development is put forward, which makes certain references to the future energy Internet.

Global Energy Demand Prospect Based on CO2 Emission Reduction Target in 2050

ZHU Fagen, SHAN Baoguo, MA Ding, LIU Xiaocong, LI Jiangtao

2016, 49(3):  34-38.  DOI: 10.11930/j.issn.1004-9649.2016.03.034.05

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Forecasting long-term energy demand and proposing corresponding sustainable energy development strategies has been a hot research area for a long time. Based on the combined“bottom-up” and“top-down” thinking, a global energy demand analysis model is established in this paper by employing simulation methods including time series, trend extrapolation, econometrics and energy system (equilibrium) analysis. By designing a 2 ℃ scenario in which CO2 emission from energy sector is reduced by 50% in 2050, the proposed model analyses the world energy demand in 2050. The key findings under 2 ℃ scenario are as follows: i) Asia Pacific, particularly India, will become an important engine for global energy demand growth, while the global energy demand will reach the ceiling in 2045; ii) the structure of primary energy demand will be dominated by non-fossil energy and the non-hydro renewable energy will be the main driver for the transformation; iii) electricity will play a dominant role in the change of final energy consumption structure and it will take the place of petroleum to take up the largest share in final energy.

Opportunities and Challenges for Intelligent Power Utilization from Mobile Internet

HUO Molin, ZHU Fagen, SHAN Baoguo

2016, 49(3):  39-45.  DOI: 10.11930/j.issn.1004-9649.2016.03.039.07

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Mobile Internet has characteristics such as open sharing, portable, real name identity and geographic positioning. It is changing every industry including intelligent power utilization. It changes user behavior and experience requirements, and enhances interactions between users and enterprise. It also promotes mobile, real-time, interactive, personalized power utilization. This paper analyzes opportunities and challenges of mobile Internet on smart power utilization from the perspectives including user behavior, marketing, business model, industry ecology, industry competition. Suggestions for enterprises to develop effective development strategy and business measures are recommended to promote rapid development of smart power utilization.

Research on Russian Far East Siberia Power Supply System Based on Global Energy Internet Patterns

WEI Xiaoxia, ZHANG Jinfang, HUANG Han

2016, 49(3):  46-50.  DOI: 10.11930/j.issn.1004-9649.2016.03.046.05

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This paper focuses on the Russian Far East Siberia hydro, coal, oil and gas resources reserves situation andsums up the coal, oil and gas, hydropower development conditions and development potential. With the security, economy, cleanness and efficiency of the energy in consideration, the energy supply pattern is given and the energy supply pattern system model is built. Based on the Internet global energy patterns and the north hemisphere energy interconnection assumption, and the resource data of the Russian Far East Siberia as well the empirical analysis of the energy supply system is performed. The model has a good reference value for the global development and delivery of the clean energy.

Power System

Research on Measures to Ensure Power System Security and Stability in Power Grid Construction

QIN Qin, ZHOU Qinyong, GUO Qiang, QIN Xiaohui

2016, 49(3):  51-58.  DOI: 10.11930/j.issn.1004-9649.2016.03.051.08

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During the 13th Five-year period (2016-2020) of power grid planning, China will witness a rapid development in construction of UHV projects. At the same time, the eastern and central regions will still be the center of power load, and the large energy bases will further move to the west and north. Grid construction will face new challenges in power security and stability due to abovementioned situation. Based on the experience and lessons in power security and stability of existing grid, this paper analyzes the potential security and stability problems brought by future grid development. Measures are proposed to ensure the security and stability of power system with full consideration of the coordination relationship between power base and load center, UHV and 500 kV, AC and DC.

Feasibility Research on Line Circuit Breaker Without Closing Resistor of Suzhou-Shanghai UHV Transmission Project

LI Zhenqiang, WANG Hongchao, HE Huiwen, HE Ying

2016, 49(3):  59-64.  DOI: 10.11930/j.issn.1004-9649.2016.03.059.06

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To save the project investment and improve the reliability of the breakers, the feasibility of the AC UHV line-breaker without closing resistor is analyzed, and the criteria of canceling UHV line-breaker closing resistor are put forward. It is pointed out through analysis that the difficulty of canceling UHV line-breaker closing resistor is bigger than that in the 500 kV project, but it is still possible. The simulation model is built by EMTP program to calculate, the closing and single phase reclosing overvoltage, the time to crest and the line flashover rate of the Suzhou-Shanghai UHV line-breaker without closing resistor. Based on the calculation results and the criteria, it is suggested that the closing resistor be installed in the line-breakers at Suzhou side , but not at Shanghai side.

Characteristics of Windage Yaw in UHV Insulator Strings under Fluctuating Wind

MIN Xuan, WEN Zhike, ZENG Yunfei, FU Jing

2016, 49(3):  65-71.  DOI: 10.11930/j.issn.1004-9649.2016.03.065.07

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Comparing with low voltage lines, insulator strings are longer and geographic span is greater in UHV lines, hence dynamic characteristics of insulator strings windage yaw is more prominent. A numerical model of 4 spans insulator strings-conductor is established. Simulation study of windage yaw characteristics in UHV insulator strings under fluctuating wind with speed time history is performed by changing wind speed, vertical loads, conductor types and single/double insulator strings. The results show that fluctuating response coefficient β of UHV insulator strings is between 1.1~1.2 under different conditions. With constant wind speed, insulator strings windage yaw angle decrease as conductor cross section increase. Double composite insulators and disc insulators can be simplified as corresponding single type when calculating windage yaw angle of UHV insulator strings.

Research of Live Working Gap Discharging Characteristics on UHV Steel Tubular Tower Transmission Lines

TANG Pan, LEI Xinglie, LIU Kai, LIU Ting, XIAO Bin, PENG Yong, SU Ziming, WU Tian

2016, 49(3):  72-75.  DOI: 10.11930/j.issn.1004-9649.2016.03.072.04

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Along with construction and development of UHV transmission project, steel tubular towers have been widely used. In order to ensure live working safety on UHV steel tubular tower, electric field distribution around UHV steel tubular tower and angle-steel tower are simulated. The impulse discharging characteristics of various typical live working conditions through 1∶1 steel tubular tower model test are analyzed and safety distance for live working under various conditions are obtained. Difference of impulse discharging characteristics between steel tubular tower and angle-steel tower is analyzed by impulse discharging test. The research result can provide technical support for live working on UHV steel tubular tower transmission lines.

Smart Grid

Switch Configuration Optimization Based on Self-healing Requirement of Distribution Network

YUAN Yue, WANG Shouxiang, JIANG Ling, ZHOU Jianhua, SUN Rong

2016, 49(3):  76-82.  DOI: 10.11930/j.issn.1004-9649.2016.03.076.07

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Self-healing is the most important characteristics of the smart distribution system. Through switch configuration optimization, the distribution network can not only satisfy the requirement of reliability and economy, but also have good self-healing property. In order to reflect the requirement of self-healing, the paper proposes the self-healing evaluation indicators and the blocked algorithm of load self-healing rate for the smart distribution system in terms of self-healing time, customer and load. The outage interruption cost is added to the objective function of the traditional switch configuration optimization, and the minimum healing rate is added to the constraints. An improved binary particle swarm optimization algorithm is proposed through adjustment of the inertia coefficient and learning factors to realize the switch configuration optimization of the distribution network that is adaptable to the self-healing requirement. A case study has proved the model’s rationality and the proposed method’s effectiveness.

Life Cycle Cost Estimation of Smart Substation Based on Blind Number Theory

LIU Yang, SU Haoyi

2016, 49(3):  83-87.  DOI: 10.11930/j.issn.1004-9649.2016.03.083.05

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In order to solve the problems of uncertain factors existing in the process of life cycle cost estimation of smart substation, a blind number theory-based mathematical model is established for life cycle cost estimation of smart substation on the basis of an analysis of the cost characteristics of smart substations. With consideration of the time value of the capital, the breakdown structure and calculation method of the life cycle cost is analyzed with the blind number theory for both the gas-insulated switchgear smart substation and air-insulated switchgear smart substation. A smart substation is taken for case study and the results show that the proposed model is able to calculate the possible range and corresponding confidence of the life cycle cost of smart substations. Compared with the traditional deterministic analysis methods, the novel method is more scientific and rational in calculation results, and can provide the decision-making support for the cost optimization of smart substation project.

Security Isolation Strategies Based on Virtual Connections Cut Set for Relay Protection in Smart Substation

CHEN Qiaoping, CHEN Zhiguang, HUANG Yong, SU Zhongyang

2016, 49(3):  88-93.  DOI: 10.11930/j.issn.1004-9649.2016.03.088.06

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To improve reliability of relay protection system isolation in smart substation, an automatic security isolation strategies generation method based on virtual connection cut set is proposed. This paper first analyzes the necessity of security isolation of relay protection system in smart substation. Then the proposed model is constructed including equipment and associated information models, virtual connection cut set model and relational model between branch and soft strips. Finally, the 110 kV side relay protection system of a 110 kV substation is taken as an example to analyze proposed method. Security isolation strategy analysis results show the effectiveness of proposed method.

Fault Location of Distribution Network by Applying Matrix Algorithm Based on Graph Theory

HU Funian, SUN Shoujuan

2016, 49(3):  94-98.  DOI: 10.11930/j.issn.1004-9649.2016.03.094.05

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Based on an analysis of the existing weakness of fault location algorithm for distribution network, an improved fault location algorithm based on graph theory is proposed in this paper. Firstly a network topology matrix is produced according to the distribution network. When a fault occurs, the fault information matrix can be generated from the fault signal uploaded from FTU through GPRS. Then a fault judgement matrix is obtained by adding the two matrixes above, and the fault section can be located according to the failure criterion. The proposed algorithm can not only locate a single fault of the distribution network with single power source, but also make a quick judgement of the multiple faults and the feeder end fault of the distribution network with multiple power sources. Furthermore, the algorithm is also applicable to the incomplete fault information from FTU. The simulation results show that the proposed algorithm is concise and practical with low computation cost, and can satisfy the requirements of modern distribution network automation.

Analysis on the SOE Error and Relevant Experimental Methods

YU Gaowang, WANG Zhenhua, WANG Li, ZHANG Yanchao, Bi Daqiang

2016, 49(3):  99-103.  DOI: 10.11930/j.issn.1004-9649.2016.03.099.05

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Development of smart substation gives rise to the high requirements on telesignal and SOE resolution of measurement & control devices. A deep analysis is made on the abnormal phenomenon occurring in the process of testing telesignal and SOE resolution of measurement & control devices. Duo to the limit of the telesignal’s time tag that the smallest unit is in millisecond level, the requirement that the measure & control device’s telesignal and SOE resolution be less than 1ms cannot be totally satisfied in theory. During testing the damped oscillation wave of EMC，the causes for the telesignal and SOE resolution error is theoretically proved by simulation, that is: a decaying DC component with the initial value of 220 V is coupled into the circuit of the telesignal 2 after the telesignal 1 acts, which results in the telesignal 2’s action in advance. Finally, according to the characteristics of damping oscillatory wave experiment, a decoupling scheme is proposed, which can avoid the interaction between the telesignal circuits by changing the testing wiring that the telesignal 1 and signal 2 are plugged into different power circuits respectively.

Intelligent Substation Load Distribution Technology

HU Bin, WANG Xuyang, HOU Jia

2016, 49(3):  104-109.  DOI: 10.11930/j.issn.1004-9649.2016.03.104.06

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It is highly significant for supporting smart grid development to carry out research on smart substation load distribution technology and scheme. Based on the reactive power optimization and network reconfiguration, a mathematical model is established for smart substation load distribution, and a combination of guide search method and virtual flow method is developed for minimizing active power loss. Taking a full consideration of the change of distribution network and operation mode after integration of distributed energy resources, a smart substation load distribution system scheme has been developed by applying scenario analysis methodology based on power output characteristics. Correspondingly the smart substation load automatic distribution algorithm is optimized in order to adjust load distribution according to distributed energy output. It has been verified that this scheme can guarantee the correct entrance and exit of reactive power compensation devices and the correct opening and closing of section switches and connective switches, and it can improve the speed and reliability of power grid analysis and control with line active power loss reduced.

Research on Policy System and Development Priorities of Smart Grid in Japan

HU Bo, ZHOU Yicheng, YANG Fang, BAI Cuifen, HE Bo

2016, 49(3):  110-114.  DOI: 10.11930/j.issn.1004-9649.2016.03.110.05

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After the“3·11” earthquake, the development strategies of smart grid in Japan have been optimized and improved. The paper attempts to summarize the published policies and planning of smart grid in Japan, and depicts the profile of smart grid in Japanese eyes from the perspective of definition, function and development priority. Moreover, an analysis is made on the technology progress, standard development and pilot project construction in such key fields as renewable energy generation, energy storage battery and smart home.

Analysis of Smart Grid User Side Communication Network and Technical Challenges

ZHOU Jing, HU Ziwei, SUN Yuanyuan, MA Qi

2016, 49(3):  115-118.  DOI: 10.11930/j.issn.1004-9649.2016.03.115.04

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In order to realize smart grid function, a high-speed, two-way, real-time and integrated communication system is required to make smart grid a large-scale, dynamic, real-time information and power exchange infrastructure. It discusses the opportunities and challenges in the development of smart grid, intelligent measurement in communication technology, network security and standardization. The key issues in interoperability implementation, scalable network solutions establishment and existing network technology application to intelligent measurement are also discussed. At last, the state of art of international smart grid communication standardization is introduced, which provides reference value to communication network architecture and solution of China’s smart grid.

New Energy

Study on Pricing Policies of Renewable Power Under the Market-Oriented Reform

LI Yang

2016, 49(3):  119-122.  DOI: 10.11930/j.issn.1004-9649.2016.03.119.04

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Renewable power has been developing very quickly since 2006 in China. The pricing policy plays a significant role in the process. This paper reviews the policy framework of pricing and cost sharing for renewable power, analyzes the problems and barriers of the existing pricing policies, such as lack of dynamic regulation, shortage of capital, mismatch of rights and responsibility. The State government is carrying out the reform in the electric power system. Pricing policies for renewable power must be innovated to adapt the situation. Several policy recommendations are given in the paper to promote the healthy and sustainable development of renewable power.

Optimal Dispatch of DC Distribution Network with Distributed Energy Resources

LIANG Haifeng, LIN Jialin, LI Peng

2016, 49(3):  123-127.  DOI: 10.11930/j.issn.1004-9649.2016.03.123.05

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DC distribution network has great advantage in promoting the absorption of distributed renewable energy sources and solving the development bottleneck of the traditional AC distribution network. Based on the existing research of DC distribution network, this paper discusses the DC distribution network integrated with various distributed energy resources(DER) in terms of network building mode and system structure, and specially studies the optimal dispatch method for DC distribution network integrated with various DERs. The operating strategies of the grid-connected units and multi-period optimal dispatch strategy are designed, and a multi-objective optimal dispatch mathematical model is built with consideration of the operating cost, environmental benefit and system loss. A case study shows that the proposed method is effective in enhancing the optimal operation of DC distribution network integrated with various DERs and improving the network’s operation indicators.

Capacity Ratio of Energy Storage over Intermittent DG and Practical Estimating Method

YANG Fenyan, CHEN Xiaoke, HUANG Jiajian, LI Lanfang, ZHANG Zequn, XIAO Jun, Dong Lei,ZOU Guangyu

2016, 49(3):  128-133.  DOI: 10.11930/j.issn.1004-9649.2016.03.128.06

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With an increased penetration of distributed generation (DG) in the distribution network, the impact of DG's intermittency and volatility becomes more significant. Energy storage system (ESS) is a key solution for the problem associated with intermittent DG. However, research to date has not been able to establish the capacity relationship between energy storage and DG. This paper examines the ratio between ESS and DG based on the spectral analysis method, and proposes a practical estimating method. First, the principles and algorithm for optimizing ESS capacity are introduced. In addition, the spectral analysis method is used to optimize EES capacity based on actual operation data of intermittent DG. The relationships are analyzed between the maximum fluctuation and the ESS rated capacity, as well as the rated capacity and the rated energy of EES. As rated capacity is often available for DG projects, additional analysis is undertaken to assess the relationship between rated capacity and the maximum fluctuation, which can then be used to determine the relationship between ESS capacity and DG rated capacity. Based on this approach, the optimal size for capacity and energy can be approximated for EES with a simple manual calculation instead of complex energy storage optimization. Finally, we compare the algorithm of ESS capacity optimization with the practical method using a case study. The results indicate the practical method is simple and effective.

Case Study and Mechanism Analysis of Sub-Synchronous Resonance in Wind Power Plants

LIU Hui, LI Yunhong, LI Yu, XIE Xiaorong

2016, 49(3):  134-140.  DOI: 10.11930/j.issn.1004-9649.2016.03.134.07

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Large-scale Doubly-fed induction generator-based wind power plants connected to the series-compensated transmission system are facing the risk of sub-synchronous resonance(SSR). A regional grid recently suffered from a spate of SSR failures. The incidents have seriously affected the safe and stable operation of the power grid. The SSR phenomenon characteristics of the wind power in the region are summarized from the aspects of precondition, spectral characteristics, damping ratio and performance of different kinds of wind turbines. Based on the analysis, simulations in PSCAD/EMTDC are used to demonstrate a typical SSR. Through the eigenvalue analysis, the mechanism of the wind power SSR phenomenon is defined as the DFIG control-involved induction generator effect.

Integrated Control Strategy for Low Voltage Ride Through of DFIG Involved in the Regulation

LI Fengting, ZHANG Qian, HUANG Rong, HE Shi’en

2016, 49(3):  141-147.  DOI: 10.11930/j.issn.1004-9649.2016.03.141.07

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Based on the analysis of the current situation and the weakness of the low voltage ride through technology of the doubly-fed induction generator, an integrated control strategy that the wind turbine is involved in the regulation is proposed, which can adapt to different Voltage Dips. In the proposed control strategy, the crowbar circuit is replaced by DC-Chopper and the dynamic braking resistor; variable power factor reactive power compensation is provided by the grid side converter based on different Voltage Dips to enhance the stability of the wind turbine after fault ride-through. The dynamic reactive power compensation device-based MCR(MSVC) is used to reduce cost. The model is built to testify the correctness and validity of the proposed control method. Simulation results show that the method better adapts to different Voltage Dips, achieving the capability of low voltage ride through, and enhancing the stability of the unit after fault ride-through in the meanwhile.

Wind Farm Power Curve Optimization Based on Actual Operating Data

RAO Risheng, YE Lin, REN Cheng, SONG Xuri, LANG Yansheng, JIN Jingxin

2016, 49(3):  148-153.  DOI: 10.11930/j.issn.1004-9649.2016.03.148.06

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This paper analyzes the statistical relationship between wind farm’s wind speed and power output using actual operating data. It proposes a methodology to optimize the power output curve for a wind farm based on the traditional wind speed partitioning approach. Historical observation data is equally distributed into each wind speed interval. A piecewise least squares linear regression approach is used to determine the best fir between the wind speed and the power output, and to establish the optimal power output curve using actual operating data. The power output curve is further tested with observed data in real time. Case studies indicate that the power output curve optimization method has high accuracy and can better reflect the actual operating characteristic of a wind farm. The methodology contributes to the study of wind farm operational characteristics and wind power integration research.

Research on Voltage Control of a Ultracapacitor in a DC Micro-Grid System with Two-Terminal Supply

FENG Xiao, ZHANG Jiancheng

2016, 49(3):  154-159.  DOI: 10.11930/j.issn.1004-9649.2016.03.154.06

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In order to take full advantages of distributed power production and the technological and economic characteristics of ultracapacitor, this paper presents a DC micro-grid structure with two supply terminals. It describes functions and advantages of ultracapacitor energy storage system in DC a microgrid and selects different control methodologies according to the placement of ultracapacitor energy storage system. The power supply terminal uses voltage segment control and the load side being constant voltage control. A simulation model of DC micro-grid with an ultracapacitor energy storage is built based on MATLAB/simulink platform, and an analysis is carried out to analyze the impact of the location of ultracapacitor energy storage system on the power quality of a DC micro-grid. The simulation results show that the ultracapacitor energy storage system can effectively restrain the voltage fluctuation caused by the changes of light or load.

A Novel Single-Phase PV Generation System with LVRT Capability

LI Chengyao, YANG Yong, ZHU Binbin

2016, 49(3):  160-165.  DOI: 10.11930/j.issn.1004-9649.2016.03.160.06

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Grid-connected photovoltaic(PV) systems with the capability of low-voltage-ride-through(LVRT) have become a future development trend. A novel control strategy for single-phase two-stage grid-connected PV systems is introduced in this paper. DC-link voltage is flexibly controlled by a two-stage system to minimize voltage variation during grid-fault period. At low-voltage- ride-through stage, a constant peak current strategy is used to avoid triggering over-current protection while the sag depth of grid voltage determines the amount of reactive power delivered for grid recovery. A compensator is added in the proposed strategy to minimize the 2nd-order ripple in the reference active current. Simulation results on the whole system shows that the proposed strategy is effective with satisfying steady-state and dynamic performance.

Effects of Distributed PV Connected to Grid on Distribution Network Constructions in Typical Functional Zones

GONG Xiaoxu, JIN Qiang, WANG Ji, SHI Zinan, MA Weijing

2016, 49(3):  166-171.  DOI: 10.11930/j.issn.1004-9649.2016.03.166.06

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With a large number of distributed photovoltaic devices connected to the grid, electric energy quality, short circuit capacity and power flow of distribution networks are all impacted more or less. Excess photovoltaic power that cannot be consumed locally will be transmitted back to the grid. So the traditional distribution networks are facing new challenges of reconstruction and upgrading. For distributed PV accessing into different functional areas, the issues are becoming more urgent about how to quantitatively analyze the constructions of distribution networks. In this paper, according to the new guideline of absorption capacity of distributed PV, load density and generation power density in typical functional zones are analyzed and comparison research is accomplished. Effects of distributed PV connected to grid on distribution network constructions in typical functional zones is investigated and suggestions of distribution constructions is proposed under different scenarios, which will provide guidance and advice for distribution network reconfiguration for the absorption of more distributed PV power.

A Prediction Method for Distributed Generation Layout Based on Multi-factor Weights Optimization

HUANG Bibin, LI Qionghui, GAO Fei

2016, 49(3):  172-177.  DOI: 10.11930/j.issn.1004-9649.2016.03.172.06

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Distributed generation(DG) is characterized by low investment, flexible installation, strong policy support and easy government approval. The development of distributed generations is impacted less by the government policy and become market-oriented, it is therefore possible to predict the future DG layout. The DG layout needs to consider multiple factors, including the resources conditions, project economy, and power grid conditions. In order to accurately predict the future DG layout for every province and provide guidance for the scientific planning, a prediction method for DG layout is proposed in this paper based on multi-factor weights optimization, in which a variety of factors are considered and the historical data are used to determine the weights of the factors by optimization. The method, being comprehensive in considering influence factors, accurate in determining the factor weights and easy in program coding, can predict DG layout in the target year based on the multiple factors. The case study of PV DG shows that the Central-east China region will be the key area for the DG development.

Evaluation of Impact of Large-Scale Electric Vehicle Loading on Economic Value of Power System

YANG Fang, ZHANG Yibin, HE Bo, BAI Cuifen

2016, 49(3):  178-182.  DOI: 10.11930/j.issn.1004-9649.2016.03.178.05

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The development of electric vehicle makes great contributions to emission reduction and energy saving. The investment of power system infrastructure is increasing in order to accommodate large-scale EV charging load. A comprehensive evaluation framework of the impact of large-scale electric vehicle loading on power system economic value is proposed. Construction, operation and social development phases are analyzed. A set of monetary indices including investment and benefit is proposed, and the impacts of both orderly and disorder charging mode are studied respectively in case study.

Ultra-Short-Term Wind Power Forecasting Based on QPSO-LSSVM

ZHANG Tao, SUN Xiaowei, SHI Suyi, LI Zhenxing

2016, 49(3):  183-187.  DOI: 10.11930/j.issn.1004-9649.2016.03.183.05

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An accurate forecast of wind power is beneficial to the economic and security dispatch of the power grid. To improve the accuracy of ultra-short-term wind power forecasting, this paper applies the quantum particle swarm optimization(QPSO) to optimize the parameters affecting the regression performance of the least squares support vector machine (LSSVM) in the QPSO-LSSVM model. Based on actual application in a wind farm, it is shown that the QPSO-LSSVM forecasting model has smaller errors on a variety of indicators than the BP neural network based model and PSO-LSSVM model. It has high forecasting accuracy and is robustness, and can be an effective ultra-short-term wind power forecasting methodology.

A Scheme of Full DC Power Convergence for Offshore Wind Farms

SUN Guanqun, CAI Hui, CHEN Weimin

2016, 49(3):  188-192.  DOI: 10.11930/j.issn.1004-9649.2016.03.188.05

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HVDC is the preferred transmission mode for offshore wind farms. All DC electric energy convergence without offshore substation is one of developing trend for topology design of offshore wind farms. Based on DC series-parallel topology structure, a DC Hybrid Matrix(DCHM) topology is proposed. The proposed structure has normally open power electronic switch between adjacent units in different branches. During unit downtime due to failure or other factors, the switch can be closed and loads can be transferred to adjacent unit in order to reduce voltage overload. An optimized wind farm layout design is also proposed based on DCHM structure. The simulation results verify the validity of proposed structure. This scheme can also reduce equipment cost and improve electricity generation efficiency.