Electric vehicle charging station – communication technology and network system technology you must know
Last time we learned about (communication mode and network construction requirements of electric vehicle charging station (pile)) go now let’s continue to learn more this time.
- Radio over light (RoF) technology
Electric vehicle charging stations using optical wireless communication technology and Internet of things technology, whether located in cities, suburbs or remote places, are still part of a perfect network system, and users can enjoy many advantages and functions. The openness of wireless networks, together with various global system for mobile communications (GSM) standards, including GPRS, 3G and other technologies, support transparent IP connectivity, which can connect not only to the Internet, but also to any corner of the world. In addition, the wireless network solution of electric vehicle charging station can effectively use the wireless network and will not burden the system. Therefore, mobile phone operators or telecom operators can provide extremely attractive wireless communication solution services and encourage the promotion of relevant technologies.
The wireless communication network of electric vehicle charging station is convenient to set up, and it can be operated almost anywhere in the world. Since the meters have been integrated in the charging station and the measurement data can be obtained at any time through wireless communication, almost only one cable is needed to start the business. Without laying communication cables for each electric vehicle charging station, the connection can be successfully completed by using wireless communication network. Intelligent electric vehicle charging station is like a simple plug and play system, which can be easily set up in any place, such as street, parking lot or garage.
Radio over optical (RoF) technology is considered as an effective solution to realize low-cost and high-speed wireless communication. It realizes the distribution of radio frequency (RF) signals between the central control office and the remote antenna unit through optical fiber link. While simplifying the remote antenna unit, it realizes the centralization of functions, the sharing of devices and equipment and the dynamic allocation of spectrum bandwidth resources in the central office, Greatly reduce the system transmission cost, improve the system transmission performance, spectrum efficiency, coverage area and flexibility, realize the integration of broadband wireless access and optical transmission technology, and fully meet the communication requirements of distribution network side such as electric vehicle charging pile.
The optical wireless communication system is mainly composed of optical wireless switch, optical fiber line and remote node. The optical wireless communication system structure, in which the optical wireless switch is the core equipment of the optical wireless communication system. The optical wireless switch is composed of five parts: multi-purpose signal processor, communication module group, RF signal exchange unit, analog optical transceiver and system software.
The optical wireless switch has a communication interface with the external Ethernet, which can provide the access connection of terminal equipment, and realize the routing exchange of RF signals, electro-optical photoelectric conversion, subcarrier multiplexing and the management of the whole network. The remote node is composed of photoelectric, electro-optic conversion module and RF bidirectional amplifier, and the structure is very simple. Compared with the existing communication mode of electric vehicle charging pile, the optical wireless communication system has the following advantages:
(1) Large coverage of RF signals.
(2) The RF signal source is concentrated in the switch to realize unified control and management, and the system has high security and reliability.
(3) The network capacity is large, and the wireless network adopts wi-fi802 11b / G standard, network bandwidth up to 54Mb / s.
(4) The equipment has the advantages of convenient installation and maintenance, easy expansion and reasonable price.
(5) The optical wireless switch has the function of capacity reconstruction, which can increase the communication capacity of local area without changing the existing hardware equipment.
(6) The communication network platform of electric vehicle charging station based on optical wireless switch belongs to the internal network built by the power grid company and is completely under the management and control of the power grid company, which is convenient for comprehensive business and function expansion, such as providing vehicle management of parking lot, wireless access of users and other value-added services.
(7) The built-in Wi Fi access point (AP) in the optical wireless switch adopts the standard IP network protocol and can be seamlessly connected with network communication equipment such as power transformation and distribution station, which is in line with the development trend of all IP communication network in the future.
Electric vehicle charging and changing system is a huge power network resource. Its communication system is characterized by many and scattered measured points, wide coverage and short communication distance. With the continuous construction of urban electric vehicle charging and replacement facilities, its network topology requires a flexible and scalable structure. In this regard, on the basis of the current mainstream Wi Fi wireless access technology, integrate the optical wireless network and its transmission technology under different topologies, Wi Fi wireless access technology, RF switching and reconstruction technology and wireless sensing technology to realize the wide-range distribution of Wi Fi RF signals and 2G / 3G / 4G and other wireless signals, and realize the RF switching, distribution and power control of multiple access points at the same time, Thus, the communication and network system of electric vehicle charging pile based on optical wireless technology is established, and related applications are developed on this basis.
- Communication network of electric vehicle charging station (pile)
At present, electric vehicle charging stations use Ethernet as the core management network. Due to the real-time and safety of CAN bus, it has strong advantages in node control. The communication part of charging control is completed by CAN bus. Can bus has the following unique advantages:
(1) Can can work in multi master mode. Any node on the network can send information to other nodes on the network at any time, regardless of master and slave. The communication mode is flexible.
(2) Can can transmit and receive data through point-to-point, point to multipoint and global broadcasting. The communication medium adopts twisted pair, coaxial cable or optical fiber, which can be selected flexibly. The communication distance can be up to 10km / 5KB / s and the communication rate can be up to 1MB / S / 40m. The number of nodes on can depends on the bus driving circuit, which can actually reach 110.
(3) In case of serious error, can node has the function of automatically closing the output and cutting off its connection with the bus, so that other operations on the bus will not be affected. NRZ encoding / decoding mode and bit filling technology are adopted. With simple user interface and convenient programming, it is easy to form a user system.
(4) Can adopts non-destructive arbitration technology. When two nodes transmit information to the network at the same time, the node with low priority actively stops data transmission, while the node with high priority can continue to transmit data unaffected, effectively avoiding bus conflict.
(5) Can adopts a short frame structure, each frame is 8bit, the transmission time is short, and the probability of interference is low. Each frame of information has CRC verification and other error detection measures to ensure a very low error rate of data.
Due to the above advantages, can bus has become the standard charging control network specified in the technical specification of electric vehicle charging system. The management center usually has the functions of Ethernet management data storage, billing, printing and so on, which requires the protocol conversion between the management center computer and can bus to cooperate with the management computer to control the charging pile.
Icanet-200t developed by itek based on application can easily complete the remote control of multi area and multi node charging pile and charging station, and perfectly integrate can bus and Ethernet.
The basic technical characteristics of icanet-200t are as follows:
(1) It adopts 32-bit high-performance microprocessor.
(2) The can interface adopts an open socket for convenient connection.
(3) 10m / 100M self applicable Ethernet interface, 2KV electromagnetic isolation.
(4) Can channel adopts electromagnetic isolation, DC / DC power isolation and 2.5KV electromagnetic isolation.
(5) It also supports can2 0A and can2 0b protocol, conforming to ISO / dis11898 standard.
(6) The terminal resistance of can interface is selected through external dial switch.
(7) The working voltage is 9 ~ 24V DC.
Between icanet-200t Ethernet to can converter, can bus data and Ethernet data can be transmitted to each other. Two can bus interfaces and one Ethernet interface are integrated internally, and TCP / IP protocol stack is provided. Users can easily complete the interconnection between CAN bus network and Ethernet network, establish Ethernet can two-layer network architecture, and greatly expand the application scope of CAN bus network.
Icanet-200t is an industrial product, which can work in the temperature range of – 25 ℃ ~ 75 ℃. It has 10 / 100M adaptive Ethernet interface. The maximum baud rate of can interface is 1MB / s. It has a variety of working modes such as TCP server, TCP client and UDP. It supports two TCP connections or up to “connections”, Ethernet redundancy and can network redundancy.
Icanet-200t single can bus can connect 110 nodes. In other words, one icanet-200t can manage 220 charging piles, and the communication distance can reach 270m at 250kb / s baud rate. If a single can bus network has more than 110 nodes or a distance of more than 270m, it can be expanded through the intelligent can bridge repeater I can bridge (two channels) or icanhub-p4 (four channels). A single I can bridge can expand L10 can bus nodes, and a single I can bridge P4 can expand 330 can bus nodes.
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