Analysis of wireless communication technology in smart grid

I. Overview of





Smart Grid is designed to ensure the safety and stability of power system. It is combined with the safety and stability control system of power system and dispatching automation system, which is called the three pillars of power system safe and stable operation. China's smart grid after several 10 years of construction, has begun to take shape, through the satellite, microwave, carrier, optical cable and other means of communication to build the interchange communication network. With the development of wireless communication technology, the characteristics of wireless communication system have changed greatly. In view of the fact that wireless communication network is not dependent on the grid, and has strong ability to resist natural disasters, and has the advantages of large bandwidth, far transmission distance, and not line-of-sight transmission, it is very suitable to make up for the defects of single and incomplete coverage of the current communication mode. The following is a brief introduction to the application of wireless communication system features and advantages and disadvantages, and analysis of its application in the power system prospects.





second, wireless technology introduction





(i) The concept of wireless communication technology





at present, wireless communication and its application has become one of the most active research fields of information science and technology nowadays. It is generally composed of wireless base station, wireless terminal and application Management Server.





(ii) the development of wireless communication technology





Wireless communication technology according to the transmission distance can be divided into the following four kinds of technology, namely, based on IEEE802.15 wireless domain network (WPAN), IEEE802.11 based wireless local area network (WLAN), IEEE802.16 based wireless metropolitan area Network (WMAN) and Wireless wide area network (WWAN) based on IEEE802.20.





in general, the long-distance wireless access technology representatives are: GSM, GPRS, 3G, short-range wireless access technology representatives include: WLAN, UWB and so on. According to the mobility can be divided into mobile access and fixed access. Fixed wireless access technology mainly include: 3.5GHz wireless Access (MMDS), Local multicast distribution service (LMDS), 802.16d, mobile wireless access technology mainly includes: based on 802.15 Wpan, WLAN based on 802.11, WiMAX based on 802.16e , based on the 802.20 Wwan. According to the bandwidth, it can be divided into narrowband wireless access and broadband wireless access. The broadband wireless access technology representatives have 3G, LMDS, WiMAX, narrowband Wireless access Technology representative of the first generation and the second generation of cellular mobile communication systems.





1. Mainstream wireless communication technology





from the trend of technology development, it can be seen that the wireless communication technology with Ofdm+mimo as its core will become the main direction of the future development of wireless communication. At present, the wireless communication technology based on this technology mainly includes: B3G, WiMAX, Wi-Fi, wmn and so on 4 kinds of technology.





2. Other Wireless communication technology





In addition to the above-mentioned mainstream wireless communication technology, the existing wireless communication technology also includes: IrDA, Bluetooth, RFID, UWB, trunking communication and other short-range communication technology and LMDS, MMDS, point-to-point microwave, satellite communications and other long-distance communication technology.





(1) irda:infrared Data Association, is point-to-point data transmission protocol, communication distance between 0-1m, the fastest transmission speed up to 16Mbps, communication medium for the wavelength of about 900 nm near infrared.





(2) Bluetooth:bluetooth works in the global Open 2.4GHzISM band, using hopping frequency spectrum expansion technology, communication medium for 2.402GHz to 2.480GHz of electromagnetic waves.





(3) Rfid:radio Frequency identification, that is, radio frequency identification, commonly known as electronic tags. It is a non-contact automatic identification technology, through the radio frequency signal automatically identify the target object and obtain the relevant data. RFID consists of three basic elements of label, reader and Antenna.





(4) Uwb:ultra wideband, or Ultra wideband technology. UWB communication is also known as carrier-free baseband communication, almost full digital communication system, the need for RF and microwave devices are few, so can reduce the complexity of the system and reduce costs.





three, wireless technology advantage and disadvantage analysis





(i) WLAN technical analysis





Wi-Fi technology and products have been quite mature, but also high-volume production. The technology is suitable for wireless LAN, as the extension of wired network, for special location broadband applications, although Wi-Fi technology is widely used, but it still has a certain security risks, Wi-Fi is the use of radio frequency (RF) technology, through the air to send and receive data. Because wireless networks use radio waves to transmit data signals, they are very vulnerable to attacks from outside, and hackers can easily steal data within the airwaves and even enter an unprotected intranet.





(ii) WiMAX technology analysis





WiMAX is an advanced technology, the introduction of relatively late, there is a small frequency of reusability, low utilization, but due to the recent completion of standardization, the large-scale extension of the technology will need to test the practice. From the perspective of application, the technology can meet the requirements of the Internet in a large range, covering can include outdoor and indoor, can carry out large area of signal coverage, even if only a few base stations can achieve the entire city coverage. WiMAX because of its advanced technology and ultra far transmission distance, has been favored by the industry, is the future of mobile technology development direction, and provide excellent last kilometer network access services.





(iii) WMN Technical analysis





WMN is a technology that is being studied, which is constantly being integrated into different aspects of the technology, and does not have a mature product line to support large-scale applications of the technology. From the perspective of application, WMN this new network not only has a wide application space in wireless broadband access, in other aspects such as the combination of data, Image Acquisition module can monitor or data acquisition, and widely used in environmental detection, industry, transportation and other fields. With the continuous upgrading of other technologies, WMN better with the integration, complementarity, so as to avoid weaknesses, play their respective advantages.





(iv) 3G technical analysis





3G introduced the standard in 1996 and completed the completion of the standard in 2000, including the upper level agreement. 3G network deployment has a considerable practical experience, there is a complete set of network theory, including the network of link budget, communication model budget and computer simulation. From the commercial perspective, at present, 3G in some areas have been large-scale commercial applications, such as many European countries, Japan, South Korea have built a 3G network. 3G technology has entered a practical stage, and many countries and regions are building or will be building 3G networks.





(v) LMDS Technical Analysis





local Multi-point distributed service System LMDS is a fixed wideband wireless access technology which provides point-to-point communication, its working frequency is above 20GHZ, it can provide digital duplex voice, data, Internet and video service in a certain range by using millimeter wave transmission. is a very good broadband fixed wireless access solution. In the optimal case, the distance can reach 8 km, but due to rainfall, the distance is usually limited to 1.5 km.




The main principle of
is to modulate the ATM backbone baseband information into RF signals through sector or base station equipment, many client devices in its area of coverage receive and restore RF signals to ATM baseband signals, without the need for each user to be specially paved with fiber or copper Realize data bidirectional symmetric high bandwidth wireless transmission.





(vi) MMDS Technical Analysis




The main disadvantage of
MMDS is that there are blocking problems and the signal quality is susceptible to the change of weather, the available frequency bands are not wide enough, no more than 200MHz. Secondly, the MMDS is very strict to the transmission path. Because the modulation technology used in MMDS is mainly the phase shift keying PSK (including BPSK, DQPSK, QPSK, etc.) and the orthogonal amplitude modulation QAM modulation technology, it is impossible to achieve the non line-of-sight transmission, which is difficult to be popularized in the present complicated urban environment. In addition, MMDS has no uniform international standards, the manufacturers of equipment compatibility problems.





(VII.) cluster communication technology analysis





Digital trunking system has many advantages, its spectrum utilization is greatly improved, which can further improve the user capacity of the cluster system, it improves the ability of the signal to resist the channel fading, and makes the quality of the wireless transmission better. Because of the use of sophisticated digital encryption theory and practical technology, for digital systems, Confidentiality has also improved a lot.





Digital trunking Mobile communication system can provide a number of services, that is, in addition to digital voice signals, but also the transmission of user numbers, image information. Because the network transmits is the unified digital signal, therefore greatly enhances the cluster network the service function.





(eight) point-to-point microwave communication Technology analysis





The advantages of microwave transmission are mainly embodied in the following aspects: first, can reduce the operating costs of operators. Compared with leased circuit, the investment of microwave system can be recovered in only one year. Second, the microwave transmission system is simple and quick to deploy. Compared with traditional means of transmission, the advantage of its rapid deployment can meet the needs of new business development faster. Third, the current microwave products for the future development is guaranteed, for the operators of new business and new requirements can be given a good support. In the future, the microwave transmission system will upgrade to the full IP platform, can fully support the future development of operators.





(ix) Analysis of satellite communication technology





uses satellites to coordinate land communications in areas where the population is not very dense. In these areas, the spread of a wider but less intensive user can be used as a satellite to connect to a fixed cable network access facilities. In the environment that the terrestrial communication network has already constituted the broadband multimedia communication Network, it is a good and practical scheme to build the broadband satellite access system by satellite, and the economy is reliable.





but satellite communications, after all, is the use of satellite as a communication platform, the construction of its ground station, communication channel rental costs need to spend a lot of money, and communication resources for the satellite communications companies, by its bandwidth constraints, so that a large number of data transmission needs to pay a very large price. Therefore, as the daily production, living use is extremely economic, and satellite communications as emergency communications, combat communications, overseas communications, etc. are more suitable.


Four, wireless technology comprehensive comparison





the complementarity of various technologies in the field of wireless communication is becoming more and more obvious. This mainly shows that different access technologies have different coverage, different applicable regions, different technical features and different access rates. 3G can solve wide-area seamless coverage and strong roaming mobility requirements, WLAN can be used to solve the high-speed data access distance, and UWB can achieve close proximity of ultra-high speed wireless access.





first of all, from a standardized point of view, in the technology covered by this report, only WMN technology is not a mature standard system, LMDS, MMDS, trunking Communications have a variety of standards, but there is no uniform international standards, the remaining technology has completed the standardization work, and has conducted a pilot network and commercial network construction.





from the frequency, Wi-Fi technology, WMN are used in the open band, WiMAX technology, 3G technology and other technologies using the authorized band.





From the coverage, Wi-Fi technology, WMN technology belongs to the LAN wireless access technology, covering only 35m-100m; WiMAX technology, 3G Technology, LMDS Technology, MMDS Technology, trunking communications belong to the metropolitan Area Network access technology, coverage in 1km-54km range, and satellite communications, point-to-point microwave is a WAN technology, usually used for communication backbone network construction.





from the transmission rate, point-to-point microwave and satellite communications belong to the main transmission technology, the different conditions rate changes, while the rest of the technology are access technology, only 3G technology access rate is the smallest, only 384k, while the rest of the technology are dozens of m or even the rate of hundred m.





from the modulation technology, including Wi-Fi technology, WiMAX technology, WMN, 3G technology are using the latest modulation technology OFDM, the rest of the technology are not used in OFDM modulation technology.





from the antenna technology, only 3G and WiMAX technology adopted the MIMO technology, while the other technology is not using MIMO technology; from the transmission environment, only WiMAX technology and 3G technology to support the non visual range Transmission, the rest of the technology requires visual range Transmission environment; From the network security and QoS mechanism, WiMAX technology and 3G technology in this respect to do more excellent, perfect, the rest of the larger problems.




Application and prospect of
wireless technology





at present, in the power system communication, still with high transmission rate, high bandwidth, high reliability and other characteristics of optical fiber communication, but with the power grid for disaster emergency, distribution automation, office intelligence and other requirements, wireless communication will be rapidly deployed, not subject to the characteristics of the ground to seek the application in the power system communication. Therefore, wireless communication can become an important supplementary means of power system communication, which provides a very important part for power system to construct integrated communication network.