LYT000A HITACHI control module

LYT000A HITACHI control module

(3) The dispatcher data center is composed of ADSL MODEM, firewall, router, data center server, client and gateway. The data center server receives the data from each heat exchanger station through the ADSL Modem, and carries out the data storage, historical trend analysis, report printing, etc. Some of the data is also sent to the MIS system of the whole factory.

3 System Network

The system is mainly through GPRS DTU and mobile company GPRS network to complete. DTU mainly completes the task of data transmission and forwarding between HOLLiAS-PLC G5 and dispatching center, and is also the working interface with mobile GPRS network. The main parameters are as follows:

(1) With mobile GPRS APN (access node network) mode. There are two main APNs: CMNET and private line access. CMNET uses the public network of China Mobile. The security and data transmission control have some drawbacks compared with the dedicated line access. Therefore, the author chooses the dedicated line access.

(2) Data sending destination, namely the IP address or domain name of the data center server or router.

(3) Interface parameters with HOLLiAS-PLC G5 CP240, including baud rate, stop bit, parity check, data bit and flow control.

(4) DTU configuration of GPRS network quality parameters in different regions.

After the data is sent to the CGSN on the mobile GPRS network by DTU, the mobile GPRS network has a channel interface with the Internet. Therefore, the mobile CGSN server can forward the data to the data center server or router through the Internet. In order to ensure the security of data transmission between mobile network and data center router, the author uses VPN function. This function establishes a VPN GRE tunnel between the router in the data center and the mobile egress gateway server to ensure the security of data transmission between the router and the mobile egress gateway.

The data of each heat exchanger station transmitted by the mobile GPRS network passes through the Internet, is detected by the firewall through the signal demodulation of the ADSL Modem, and then sent to the router VPN after decryption, and then forwards the decrypted data packet to the specified data center server for data reception and processing. At the same time, the data center server is responsible for sending corresponding control command data to each heat exchange station. Each client obtains data from the data center server to complete the monitoring and control, alarm, history curve and other functions of each heat exchange station on their own man-machine interface software.

In addition, in the dispatching center network, the gateway machine is connected with the MIS network of the whole factory, and is responsible for sending various operating parameters of the heat network to the MIS network for the corresponding MIS software of the upper level to complete the data analysis, data mining and other functions, which greatly improves the economy of the heat network operation. Here, OPC is used as the data interface between gateway computer and MIS network data server, which is easy to use and easy to debug and configure.

GPRS Technology

GPRS, short for General Packet Radio Service, is a new bearer service developed on the existing GSM system, aiming to provide data services in the form of packet for GSM users. GPRS

Theoretical bandwidth up to 171.2Kbps, the actual application bandwidth is about 10~70Kbps, in this channel to provide TCP/IP connection, can be used for Internet connection, data transmission and other applications.

GPRS is a new mobile data communication service, which provides a connection between mobile users and data network, and provides high-speed wireless IP to mobile users. GPRS adopts packet switching technology, each user can occupy multiple wireless channels at the same time, the same wireless channel can be shared by multiple users, resources are effectively used, the data transmission rate is as high as 171.2Kbps. Using GPRS technology to achieve data packet sending and receiving, users are always online and charged according to traffic, rapidly reducing the cost of service.

The remote monitoring system of heat network based on GPRS technology has the following characteristics:

The always-on GPRS DTU can be automatically attached to the GPRS network once it is started, and establish a communication link with the data center, and send and receive the data of user data equipment at any time, with high real-time;

GPRS DTU is always online and is charged according to the number of data packets received and sent. There is no charge for the transmission of data traffic.

The transmission speed of GPRS network will reach 160Kbps at the fastest. The rate depends on the network Settings of mobile operators. According to the network situation of China Mobile, stable data transmission of 20~40Kbps can be provided at present.

The GPRS wireless DDN system can build a virtual mobile data communication network covering the whole of China anytime and anywhere through the Internet network, providing access convenience for the majority of small and medium users and saving access investment;

The communication link is maintained by professional operators. As GPRS data service of China Mobile is adopted, the link maintenance is also taken care of by China Mobile, which eliminates the worry of communication link maintenance.

Lightning protection due to the use of China Mobile GPRS data service, so on the premise of not affecting the Internet, GPRS DTU transmission power is very small, the antenna is very short, and no overhead, to overcome the wired transmission and radio transmission easy lightning damage equipment shortcomings.

4 Process control description

In this scheme, the author uses HOLLiAS-PLC G5 to complete the following functions in each heat exchange station: the collection of on-site temperature, pressure, flow and liquid level signals; Control of regulating valves on site; Control and operation monitoring of motor and frequency converter on site. In the heat exchange station, it is easy to complete the human-computer interaction through the touch screen to control the stable operation of various devices. For the control of field regulating valve and various motors, the design of local control, touch screen control, remote control center control three ways.

(1) According to the outdoor meteorological temperature and the average temperature of the water supply and return of the secondary network, adjust the primary network water supply or the electric regulating valve on the return water pipeline, so as to change the flow of the heat exchanger into the primary network and ensure the heat supply of the secondary network.

(2) According to the outdoor meteorological temperature, the temperature of water supply and return of the secondary network, and the pressure of water supply and return, the operating frequency of the circulating water pump is adjusted by the frequency converter, so as to change the operating flow of the secondary network. (This scheme is adopted for the circulating water pump in the current heat exchange station which is controlled by frequency conversion).

(3) According to the deviation between the measured pressure value of the constant pressure point and the set pressure value, the running frequency of the water pump is changed by the frequency converter to ensure the constant pressure of the constant pressure point.

(4) Among them, the outdoor meteorological temperature data adopts the weighted average of the outdoor temperature of each new unit and is processed by the central station before being sent to each revamped unit for automatic control.

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