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Abstract: This paper delves into the core technologies of the smart grid, focusing primarily on measurement, communication, information management, scheduling, power electronics, and distributed energy integration. Drawing from the U.S. smart grid research and application examples, it summarizes and reviews the functions achieved by smart grid technology.
1. Overview of the Smart Grid
The smart grid is designed to achieve energy transformation and compatible utilization. It aims to integrate system data and optimize grid operations by creating an open system and establishing a shared information model. Through real-time, high-speed, two-way data collection via terminal sensors, it creates an instant connection between users, businesses, and grid companies, enhancing the overall efficiency of the grid. Sensors can monitor and integrate operational data for critical equipment such as generators, transmission lines, substations, and power supply systems in real-time. During peak power supply periods, it can promptly dispatch resources to balance supply gaps, optimizing the entire power system's operation. Additionally, smart meters can serve as Internet routers, enabling power companies to offer broadband services or broadcast TV signals directly to end users.
At the first Smart Grid Research Forum held at Tianjin University on June 27-28, 2009, 14 academic reports were presented, covering the construction and development of smart grids in China from basic concepts, technical components, and equipment requirements. Academician Yu Xinxin of Tianjin University emphasized in his report, "Driving Forces, Technical Composition, and Implementation Routes of Smart Grids," that ensuring the safe and stable operation of the system, managing user demands, and integrating distributed power sources are key drivers for smart grid development. The smart grid integrates advanced communication, sensor, and distributed computing technologies to enhance the security, reliability, and efficiency of the transmission and distribution network.
In his report on "Energy Storage Technology and Its Application in Smart Grids," Academician Cheng Shijie of Huazhong University of Science and Technology highlighted that in power systems with significant renewable energy generation, energy storage technology plays a crucial role in ensuring the system operates normally. Essential requirements for energy storage systems include sufficient capacity, rapid response, high efficiency, long service life, and minimal operational costs.
Professor Wang Chengshan from Tianjin University delivered a report titled "Distributed Power, Microgrids, and Intelligent Distribution Systems," introducing key technologies, applications, and challenges of distributed power, microgrids, and intelligent distribution systems while analyzing their interconnections. Other experts like Professor Xu Bingzhen from Shandong University of Technology and Qi Wenpeng from British Columbia Hydropower Company explored technical characteristics, implementation methods, and development prospects of smart grids from different angles.
2. Key Technologies of the Smart Grid
China’s digital power grid construction spans power generation, dispatching, transmission, distribution, and user links, including information platforms, dispatch automation systems, stability control systems, flexible AC transmission, substation automation systems, microcomputer relay protection, automated distribution systems, and power management acquisition systems. These efforts represent the prototype of the smart grid.
2.1 Advanced Measurement Technology
Parametric measurement technology is a foundational component of the smart grid. Advanced measurement techniques gather data and convert it into actionable information for various smart grid applications. They assess the health of grid equipment and the integrity of the grid, manage metering, eliminate electricity bill estimates, prevent theft, alleviate grid congestion, and engage in user communication.
Future smart grids will replace all electromagnetic meters and their reading systems with solid-state smart meters capable of two-way communication between power companies and users. These microprocessor-based smart meters will offer enhanced functionality, including real-time electricity usage tracking, billing at different times of the day, peak power price signals, and customizable rate schedules that automatically adjust user power consumption.
For power companies, parametric measurement technology provides additional data support to system operators and planners, offering insights into power factors, power quality, phase relationships, equipment health, meter damage, and failure locations. New software systems will aggregate, store, analyze, and process this data for broader utility use within the power company.
Future digital protection will be embedded in computer agents, significantly improving reliability. A computer agent is an autonomous, adaptive software module that interacts with other systems. The wide-area monitoring system, protection, and control solutions will integrate digital protection, advanced communication technologies, and computer agents. In this integrated distributed protection system, elements can adaptively communicate with each other, providing flexibility and adaptability that enhance reliability. Even if some systems fail, others with computer agents can still protect the system.
2.2 Smart Grid Communication Technology
Building a high-speed, two-way, real-time, integrated communication system is the foundation for realizing a smart grid. Without such a communication system, no characteristic of a smart grid can be realized. Since data acquisition, protection, and control of the smart grid depend on such a communication system, constructing it is the first step towards a smart grid. The communication system should extend deeply into the grid, reaching thousands of households, thus forming two closely connected networks—the grid and the communication network. Only then can the goals and main features of the smart grid be realized. The high-speed, two-way, real-time, integrated communication system transforms the smart grid into a vast, dynamic, real-time information and power exchange interaction infrastructure. When such a communication system is completed, it improves the reliability of power supply, increases asset utilization, enriches the power market, and enhances resistance to grid attacks, thereby increasing the value of the grid.
Communication technologies suitable for the smart grid need to possess the following characteristics: First, they must be two-way, real-time, and reliable. For security reasons, they should be isolated from the public network, forming a dedicated power communication network. Second, they must be technologically advanced and capable of supporting existing smart grid services while allowing future expansion. Third, they should ideally have independent intellectual property rights, enabling customized development and business upgrades specific to the power smart grid.
As a subsidiary of the State Grid Corporation responsible for building and managing backbone information communication networks, State Grid Information and Communication Co., Ltd. places great emphasis on smart grid construction. It actively conducts preliminary research and promotes the development of hardware and software related to information and communication technologies (ICT). It studies new models for next-generation power information communication (ICT) networks and accelerates the industrialization of information communication.
The electricity customer electricity information collection system is an essential part of the smart grid. ICT actively participates in research related to information and communication professions and submits communication technical reports to the State Grid Corporation. It also actively promotes industrialization efforts, further improving the software platform for the power information collection main station and the collector based on power line broadband communication technology.
Smart grid customer service is a vital component of the smart grid power link. It is an important means to achieve real-time interactive responses between the grid and customers, enhancing the comprehensive service capabilities of the grid, meeting interactive marketing needs, and improving service levels. ICT has established smart grid customer service pilots in Beijing Lianxiangyuan Community and 95 Chengcheng Road. The pilot project at No. 95 Fucheng Road emphasizes fiber-to-the-home features, using set-top boxes and TVs as display tools to offer specialized services like three-table copying and inquiries, property management, distribution, and network value-added services, reflecting interactive and intelligent features.
2.3 Information Management System
The information management system in the smart grid should primarily include five functions: acquisition and processing, analysis, integration, display, and information security. (1) Information acquisition and processing. This includes detailed real-time data acquisition systems, distributed data acquisition and processing services, dynamic sharing of intelligent electronic device (IED) resources, high-capacity high-speed access, redundant backup, and accurate data timing. (2) Information analysis. Analyzing collected, processed, and integrated information is an important aid to the development of grid-related services. Vertically, it involves four-stage industrial chain business analysis ("generation - transmission - distribution - demand side") and four-level grid information analysis ("national - regional - provincial - prefectural"). Horizontally, it includes power generation planning, outage management, asset management, maintenance management, production optimization, risk management, market operations, load management, customer relationship management, financial management, human resource management, and other business module analyses. (3) Information integration. The smart grid information system should achieve information integration along the industrial chain and vertically across grid information, as well as horizontally integrate internal business of grid enterprises at all levels. (4) Information display. Providing personalized visual interfaces for various users requires the reasonable use of video and audio technologies such as flat displays, 3D animations, speech recognition, touch screens, and geographic information systems (GIS). (5) Information security. The smart grid must define the confidentiality and authority of each stakeholder and protect its data and economic interests. Therefore, it is necessary to study technologies such as network survivability, active real-time protection, secure storage, network virus prevention, malicious attack prevention, network trust systems, and new encryption algorithms under complex large systems.
2.4 Intelligent Scheduling Technology
Intelligent scheduling is a crucial link in the construction of the smart grid. The smart grid dispatching technical support system is the core of intelligent scheduling research and construction. It provides the technical basis for comprehensively improving the dispatching system's ability to control large power grids, optimize resource allocation, deepen risk prevention capabilities, and make scientific decisions. It enhances management capabilities, flexible and efficient regulatory capabilities, and fair and friendly market deployment capabilities.
The existing dispatching automation system faces many problems, including non-automated processes, disorganized information, insecure control processes, lack of centralized control methods, and difficulty in decision-making. To adapt to the construction and operation management requirements of large power grids, ultra-high voltage grids, and smart grids, and to realize scientific decision-making of dispatching services, efficient management of power grid operations, and rapid responses to power grid incidents, it is necessary to analyze and study intelligent scheduling.
To accelerate the preparation of the overall design and application function specifications of the smart grid dispatching technical support system, the State Grid Electric Power Research Institute was entrusted by the State Power Dispatching Center to undertake the overall design of the smart grid dispatching technical support system. From July 6th to 18th, 2009, under the leadership of the National Dispatching Center, the State Grid Electric Power Research Institute successfully completed the overall design of the smart grid dispatching technical support system and discussed the definition of the smart grid dispatching technical support system functional specification system. This provided guidance for the rapid and orderly construction of the smart grid dispatching technical support system. Members of the State Grid Electric Power Research Institute participated in the overall design of the basic platform of the smart grid dispatching technical support system and the four major applications and successfully completed the functional flow and overall design of the dispatching plan application, safety check application, and dispatch management application.
2.5 Advanced Power Electronics Technology
Power electronics technology is a modern technology that uses power electronic devices to transform and control electrical energy. Its energy-saving effect can reach 10% to 40%, reducing the size of electromechanical equipment and achieving the best working efficiency. Currently, semiconductor power components are developing towards higher voltages and larger capacities. In the power electronics industry, flexible AC transmission technology represented by SVC, new ultra-high voltage transmission technology represented by high-voltage direct current transmission, and electric power represented by high-voltage frequency conversion transmission technology, synchronous breaking technology represented by intelligent switches, and user power technology represented by static var generators and dynamic voltage restorers have emerged.
Flexible AC transmission technology is one of the key technologies for large-scale access of new energy and clean energy to the power grid system. It combines power electronics technology with modern control technology to reduce power transmission losses by continuously adjusting and controlling power system parameters. It improves the transmission capacity of transmission lines and ensures the stability level of the power system.
High-voltage direct current transmission technology has unique advantages for long-distance transmission and high-voltage direct current transmission. Among them, the light-duty DC transmission system uses a shut-off device such as GTO and IGBT to form an inverter, making the medium-sized DC transmission project also competitive at short transmission distances. In addition, the inverter can be turned off and 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 access distributed power sources such as fuel cells and photovoltaic power generation. The light-duty DC transmission system is more conducive to solving the problem of clean energy Internet stability.
The greatest advantage of high-voltage frequency conversion technology is that the power-saving rate is generally about 30%, but the disadvantage is high cost and high-order harmonic pollution of the power grid. Synchronous breaking (smart switching) technology completes the opening or closing of a circuit at a specified phase of voltage or current. At present, high-voltage switches are mostly mechanical switches, which have long breaking times and large dispersions, and it is difficult to achieve accurate phasing breaking. The fundamental way to achieve synchronous breaking is to replace the mechanical switch with an electronic switch.
2.6 Distributed Energy Access Technology
The core of the smart grid is to build an intelligent network system with multi-energy integration and distributed management with intelligent judgment and adaptive adjustment capabilities. It can monitor and collect power and information of the power grid and users in real time, adopting the most economical and safest transmission and distribution methods to deliver electricity to end users, achieving optimal allocation and utilization of electricity, improving the reliability and energy utilization efficiency of grid operations.
There are many types of distributed power supplies (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). Generally, their capacity ranges from 1 kW to 10 MW. DER is widely used in the distribution network because it is close to the load center, reducing the need for grid expansion and improving power supply reliability. In particular, distributed renewable energy, which contributes to reducing the greenhouse effect, has grown rapidly with strong support from many national government policies. Currently, in several countries in Northern Europe, DER has a power generation share of more than 30%. In the United States, DER currently accounts for only 7% of total capacity, and it is expected that by 2020 this share will reach 25%.
A large number of distributed power supplies operate on medium or low voltage distribution networks, completely changing the characteristics of the traditional power distribution system, which was unidirectional current flow. This requires the system to use new protection schemes, voltage control, and instrumentation to accommodate bidirectional power flow. However, the seamless integration of these distributed power sources into the grid and coordinated operation through advanced automation systems can 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 snow and ice, when the large power grid is severely damaged, these distributed power sources can form silos or microgrids to provide emergency power to important users such as hospitals, transportation hubs, and broadcast television.
3. Function Realization of the Smart Grid
Currently, smart grid research is mainly mature in the United States. Many states in the United States have begun designing smart grid systems. GE, IBM, Siemens, Google, Intel, and other information industry leaders have all invested in smart grid business.
Martin Schoenbauer of the U.S. Department of Energy’s China Office attended the first Smart Grid Research Forum held at Tianjin University in June 2009 to introduce the relevant situation of the U.S. smart grid. Martin Schoenbauer introduced the U.S. Department of Energy’s smart grid business. The U.S. Department of Energy is launching a smart grid information sharing and exchange platform and information base, funding smart grid technology research and development projects, and pointed out that clean energy and smart grids will be important content of Sino-U.S. energy cooperation.
The city of Boulder, Colorado, is the first smart grid city in the United States. Every household has arranged a smart meter, allowing people to intuitively understand the electricity price at that time, so that some tasks, such as doing laundry and ironing clothes, can be scheduled during periods of lower electricity prices. Electricity meters can also help people prioritize the use of clean energy such as wind and solar power. At the same time, substations can collect electricity usage from each household. If there is a problem, they can quickly re-equip the power.
In West Virginia, Allegheny Energy’s Super Circuit project combines advanced monitoring, control, and protection technologies to enhance the reliability and safety of power lines. The grid integrates biodiesel power generation, energy storage, advanced metering infrastructure (smart meters), and communication networks to quickly anticipate, identify, and help solve network problems.
Fort Collins, Colorado, and the city’s utility companies support numerous clean energy initiatives. One of them involves combining nearly 30 renewable energy sources such as solar and wind energy in five user areas. The program works with other distributed power systems to support a zero-energy zone called FortZED in the city.
The University of Hawaii is developing a power distribution management system platform that uses smart metering as a portal to integrate demand response, residential energy-saving automation, distributed generation optimization management, distribution and storage of power distribution systems, and various control means that allow the electrical system to coordinate with other systems in the main power grid.
The Perfect Power project at the Illinois Institute of Technology uses advanced technology to prototype a microgrid that responds to changes in the main grid, enhances grid reliability, and reduces power demand.
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