Key technologies and applications involved in smart grid
Technical Overview of Smart Grid
Smart grid is to achieve energy substitution and compatible utilization. It needs to integrate the data in the system on the basis of creating an open system and establishing a shared information model to optimize the operation and management of the grid. It mainly uses the terminal sensor to form an instantaneously connected network interaction between users, users and grid companies, so as to realize real-time (real-time), high-speed (high-speed), and two-way (two-way) data reading. The overall efficiency of the power grid. It can use sensors to perform real-time monitoring and data integration on the operation status of key equipment such as power generation, transmission, distribution, and power supply. When it meets the peak period of power supply, it can dispatch in different regions in time to balance the power supply gap. In order to achieve optimal management of the operation of the entire power system; at the same time, smart meters can also be used as Internet routers to promote the power sector to communicate, run broadband services or broadcast television signals based on its end users.
From June 27 to 28, 2009, the first Smart Grid Research Forum was held in Tianjin University. The forum arranged a total of 14 academic reports, and discussed the construction and development of China's smart grid from multiple perspectives such as the basic concept, technical composition, and equipment requirements of the smart grid. Academician Yu Yixin's report from Tianjin University is "the driving force, technical composition and implementation route of smart grid". The report pointed out that the safe and stable operation of the system, demand-side management, and distributed power are the driving forces behind the construction of smart grids. Smart grid is a comprehensive application of communications, advanced sensors, distributed computing and other technologies to improve the safety, reliability and efficiency of transmission and distribution networks.
Academician Cheng Shijie of Huazhong University of Science and Technology pointed out in the report "Energy Storage Technology and Its Application in Smart Grid" that in the power system with a large proportion of renewable energy power generation, the application of energy storage technology is to solve how to ensure that the system is normal A feasible way to run this puzzle. It also proposes the basic requirements of smart grids for energy storage systems, that is, large enough energy storage capacity, fast enough power response speed, large enough exchange power, high enough energy storage efficiency, small enough discharge cycle, long enough Long service life and small enough operating costs.
Professor Wang Chengshan, Dean of the School of Electrical and Automation Engineering, Tianjin University, gave a report on "Distributed Power, Microgrid, and Intelligent Distribution System". The key technologies, applications, and existence of distributed power, microgrid, and intelligent distribution system The problem was introduced, and the relationship between the three was analyzed. Professor Xu Bingyin of Shandong University of Technology, “Distribution Automation Technology in Intelligent Distribution Networksâ€, Canadian BC Hydropower Company Luan Wenpeng ’s “Advanced Measurement Systemâ€, State Grid Demand Side Management Center Chen Jianghua ’s “Demand Side Management Practice in China "Achievements and Prospects" and "Smart Grid-Vision, Technology and Application" by Liu Qianjin of ABB Company have analyzed and discussed the technical characteristics, implementation methods and development prospects of the smart grid from different angles.
2 Key technologies of smart grid
China's digital power grid construction covers all aspects of power generation, dispatch, transmission and distribution, power distribution and users, including: information platform, dispatch automation system, stability control system, flexible AC transmission, substation automation system, microcomputer relay protection, distribution network Automated system, electricity management collection system, etc. In fact, the current digital power grid construction in China can be regarded as the prototype of the smart grid.
2.1 Reference measurement technology
Parameter measurement technology is a basic component of smart grid. Advanced parameter measurement technology obtains data and converts it into data information for use in all aspects of smart grid. They assess the health of the power grid equipment and the integrity of the power grid, perform meter readings, eliminate electricity cost estimates, and prevent electricity theft, alleviate grid congestion, and communicate with users.
In the future, the smart grid will eliminate all electromagnetic meters and their reading systems, and replace them with smart solid-state meters that allow power companies to communicate with users in both directions. The smart meter based on the microprocessor will have more functions. In addition to measuring the use of electricity and electricity charges at different times of the day, it also stores the peak electricity price signals and electricity rates issued by the electricity company, and informs users of what to implement Rate policy. More advanced features include the user's own preparation of schedules based on the tariff policy, and automatic control of the user's internal power usage strategy.
For power companies, parameter measurement technology provides more data support for power system operators and planners, including power factor, power quality, phase relationship (WAMS), equipment health and capacity, meter damage, and faults Data such as positioning, transformer and line loads, temperature of key components, power outage confirmation, power consumption and prediction. The new software system will collect, store, analyze, and process this data for use in other businesses of the power company.
Future digital protection will be embedded in computer agents, greatly improving reliability. The computer agent is an autonomous and interactive adaptive software module. The wide area monitoring system, protection and control scheme will integrate digital protection, advanced communication technology and computer agent programs. In such an integrated and distributed protection system, the protection elements can communicate with each other adaptively. Such flexibility and adaptability greatly improve reliability, because even if some systems fail, others have computer agent programs. The protection elements of the system can still protect the system.
2.2 Smart grid communication technology
The establishment of a high-speed, two-way, real-time, integrated communication system is the basis for implementing a smart grid. Without such a communication system, any feature of a smart grid cannot be realized. Because the data acquisition, protection and control of the smart grid all require the support of such a communication system, the establishment of such a communication system is the first step towards a smart grid. At the same time, the communication system needs to penetrate into thousands of households like the power grid, thus forming two closely connected networks—the power grid and the communication network. Only in this way can the goals and main features of the smart grid be achieved. The high-speed, two-way, real-time, integrated communication system makes the smart grid a dynamic, real-time information and power exchange and interaction large-scale infrastructure. When such a communication system is completed, it can improve the power supply reliability and asset utilization of the power grid, prosper the power market, resist attacks from the power grid, and thereby increase the value of the power grid.
The communication technology applicable to the smart grid needs to have the following characteristics: First, it has bidirectional, real-time, and reliable characteristics. In theory, it should be a special power communication network isolated from the public network for security reasons. Second, it is technologically advanced and able to carry the existing business of the smart grid and its future expansion. Third, it is best to have independent intellectual property rights, and have the ability to customize development and business upgrade for power smart grid business.
As a direct company engaged in the construction and operation of the backbone information and communication network of State Grid Corporation of China, State Grid Information and Communication Co., Ltd. attaches great importance to the construction of smart grids, actively carries out relevant preliminary research work, and focuses on promoting information and communication technology (ICT) Product research and development, carrying out research on a new generation of power information and communication (ICT) network model, and accelerating the development of information and communication industrialization.
The power customer information collection system for power customers is an important part of the smart grid. ICT actively participates in research related to the information and communication profession and submits a special technical report on communication to the State Grid Corporation of China. At the same time, actively promote the industrialization process, and further improve the power information collection master station software platform, the collector based on power line broadband communication technology and other products.
Smart grid customer service is an important part of the smart grid's power consumption, and it is an important means to achieve real-time interactive response between the grid and customers, enhance the grid's comprehensive service capabilities, meet interactive marketing needs, and improve service levels. ICT has set up smart grid customer service pilots in Beijing Lianxiangyuan Community and No. 95 Fucheng Road, respectively. Among them, the pilot project of No. 95 Fucheng Road features fiber home entry and set-top boxes and televisions as display means to realize a series of special services such as three-meter copying and querying, property, distribution, and network value-added, reflecting good interaction. Sexual and intelligent features.
2.3 Information Management System
The information management system in the smart grid should mainly include five functions such as collection and processing, analysis, integration, display, and information security. (1) Information collection and processing. It mainly includes detailed real-time data acquisition system, distributed data acquisition and processing services, dynamic sharing of intelligent electronic device (IED) resources, large-capacity high-speed access, redundancy and accurate data synchronization. (2) Information analysis. Conducting business analysis on the collected, processed, and integrated information is an important auxiliary tool for developing grid-related business. Vertically, it includes "Generation-Transmission-Distribution-Demand Side" four-level industrial chain business analysis and "Country-large area-provincial-prefecture" four-level grid information analysis. Horizontally includes business module analysis such as power generation planning, power outage management, asset management, maintenance management, production optimization, risk management, market operation, load management, customer relationship management, financial management, and human resource management. (3) Information integration. The information system of the smart grid should realize industrial chain information integration and power grid information integration in the vertical direction, and horizontally realize the information integration of the internal business of power grid enterprises at all levels. (4) Information display. To provide personalized visual interfaces for various types of users, it is necessary to reasonably use video and audio technologies such as flat display, three-dimensional animation, voice recognition, touch screen, and geographic information system (GIS). (5) Information security. The smart grid must clarify the degree of confidentiality and authority of various stakeholders, and protect their data and economic interests. Therefore, we must study technologies such as network survival, active real-time protection, secure storage, network virus prevention, malicious attack prevention, network trust system, and new passwords under complex large systems.
2.4 Intelligent scheduling technology
Smart dispatch is an important link in the construction of smart grids, and the smart grid dispatching technical support system is the core of smart dispatch research and construction. It is a comprehensive improvement of the dispatching system's ability to control the large power grid and optimize the allocation of resources, deep risk defense capabilities, and scientific decision-making. The technical foundation of management ability, flexible and efficient regulation ability and fair and friendly market deployment ability.
Existing dispatch automation systems are faced with many problems, including non-automation, messy information, unsafe control processes, lack of centralized control methods, and difficulty in accident decision-making. In order to meet the requirements of the construction and operation management of large power grids, UHVs and smart grids, to achieve scientific decision-making of dispatching operations, efficient management of power grid operations, and rapid response to power grid abnormalities and accidents, intelligent dispatch must be analyzed and studied.
In order to speed up the overall design of smart grid dispatching technical support system and the preparation of application function specifications, State Grid Electric Power Research Institute was entrusted by the National Power Dispatching Center to undertake the overall design work of smart grid dispatching technical support system. From July 6 to 18, 2009, under the leadership of the National Survey Center, the working group of the State Grid Electric Power Research Institute successfully completed the overall design of the smart grid dispatching technical support system, and discussed and determined the functional specification system of the smart grid dispatching technical support system. Provide guidance for the rapid and orderly construction of intelligent smart grid dispatching technology support systems. The members of the working group of the State Grid Electric Power Academy participated in the overall design of the basic platform of the smart grid dispatching technology support system and the four major applications, and undertaken and successfully completed the functional processes and overall design of the dispatch planning application, safety check application and dispatch management application.
2.5 Advanced Power Electronics Technology
Power electronic technology is a modern technology that uses power electronic devices to transform and control electrical energy. The energy saving effect can reach 10% to 40%, which can reduce the size of electromechanical equipment and achieve the best working efficiency. At present, semiconductor power components are developing towards high voltage and large capacity. The power electronics industry has developed flexible AC transmission technology represented by SVC, new ultra-high voltage transmission technology represented by HVDC transmission, and electrical equipment represented by high-frequency frequency conversion. Transmission technology, synchronous breaking technology represented by intelligent switches, and user power technology represented by static reactive power generators and dynamic voltage restorers.
Flexible AC transmission technology is one of the key technologies for large-scale grid connection of new energy and clean energy. It combines power electronics technology with modern control technology and continuously reduces power transmission losses through continuous adjustment and control of power system parameters. Improve the transmission capacity of transmission lines and ensure the stability of the power system.
HVDC transmission technology has unique advantages for long-distance transmission and HVDC transmission. Among them, the light DC transmission system uses GTO, IGBT and other switchable devices to form the converter, making the medium-sized DC transmission project also competitive at short transmission distances. In addition, the converter, which can be turned off, can also be used to supply power to isolated small systems such as offshore oil platforms and islands. In the future, it can also be used in urban power distribution systems to connect distributed power sources such as fuel cells and photovoltaic power generation. Light DC transmission system is more helpful to solve the problem of clean energy grid stability.
The biggest advantage of high-voltage frequency conversion technology is that the power saving rate is generally up to about 30%, but the disadvantage is that the cost is high, and high-order harmonics are generated to pollute the power grid. Synchronous breaking (intelligent switching) technology is to complete the opening or closing of the circuit at the specified phase of voltage or current. At present, most high-voltage switches are mechanical switches, which have a long breaking time and great dispersion, making it difficult to achieve accurate phasing. The fundamental way to achieve synchronous breaking is to replace mechanical switches with electronic switches.
2.6 Distributed Energy Access Technology
The core of the smart grid is to build an intelligent network system with unified access and distributed management of multiple energy sources with intelligent judgment and adaptive adjustment capabilities. It can monitor and collect power grid and user electricity information in real time, and adopt the most economical and Safe transmission and distribution methods deliver electrical energy to end users, achieve optimal configuration and utilization of electrical energy, and improve the reliability of grid operations and energy efficiency.
There are many types of distributed power (DER), including small hydropower, wind power, photovoltaic power, fuel cells and energy storage devices (such as flywheels, supercapacitors, superconducting magnetic energy storage, flow batteries and sodium-sulfur batteries, etc.). Generally speaking, its capacity is from 1kW to 10MW. DER in the distribution network is widely used because it is close to the load center, which reduces the need for grid expansion and improves the reliability of power supply. In particular, distributed renewable energy, which helps reduce the greenhouse effect, has grown rapidly with the strong support of government policies in many countries. At present, in several countries in Northern Europe, DER already has more than 30% of the power generation quota. In the United States, DER currently accounts for only 7% of the total capacity, and this share is expected to reach 25% by 2020.
A large number of distributed power sources are operated on the medium-voltage or low-voltage distribution network, completely changing the characteristics of the unidirectional power flow of the traditional distribution system, requiring the system to use new protection schemes, voltage control and instruments to meet the needs of bidirectional power flow. However, seamless integration of these distributed power sources into the power grid through advanced automation systems and coordinated operation will bring huge benefits. In addition to saving investment in the transmission grid, it can improve the reliability and efficiency of the entire system, provide emergency power and peak load power support to the grid, and other auxiliary service functions, such as reactive power support, power quality improvement, etc .; It also provides great flexibility for system operation. For example, in storms and icy weather, when the large power grid is severely damaged, these distributed power sources can form islands or microgrids to provide emergency power supply to important users such as hospitals, transportation hubs, and broadcast television.
3 Function realization of smart grid
At present, the most mature smart grid research is mainly in the United States. Several states in the United States have begun to design smart grid systems. GE, IBM, Siemens, Google, Intel and other information industry leaders have all invested in smart grid business.
MaiTInSchoenbauer of the US Department of Energy ’s China Office attended the first Smart Grid Research Forum held in Tianjin University in June 2009 and introduced the relevant situation of the US Smart Grid. MarTInSchoenbauer introduced the "US Department of Energy's Smart Grid Business". The US Department of Energy is launching the establishment of a smart grid information sharing exchange platform and information library to fund smart grid technology research and development projects. important content.
Boulder, Colorado, is the first smart grid city in the United States. Every family has arranged smart meters, people can intuitively understand the electricity price at that time, so as to arrange some things, such as washing clothes, ironing clothes, etc., at a time when the electricity price is low. Electricity meters can also help people prefer to use clean energy such as wind power and solar energy. At the same time, the substation can collect the electricity consumption of each household. Once a problem occurs, it can be re-equipped with electricity.
In West Virginia, USA, Allegheny Energy's "SuperCircuitproject" combines advanced monitoring, control, and protection technologies to enhance the reliability and safety of power supply lines. The grid will integrate biodiesel power generation, energy storage, and advanced metering infrastructure (smart meters) and communication networks to quickly predict, identify, and help solve network problems.
Fort Collins, Colorado (U.S.) and utility companies owned by the city support multiple clean energy programs. One of them involves combining nearly 30 kinds of renewable energy such as solar energy and wind energy in five user areas. The plan, together with other distributed power supply systems, supports a zero-energy zone in the city called FortZED.
The University of Hawaii is developing a power distribution management system platform, which uses smart metering as a portal station, which integrates demand response, residential energy-saving automation, distributed power generation optimization management, power distribution system storage and load, and allowable power distribution system. Various control methods coordinated with other systems in the main grid.
Illinois Institute of Technology's "PeRFectPower" project uses advanced technology to build a prototype of a microgrid that can respond to changes in the main grid, enhance the reliability of the grid, and reduce power demand.
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