With the development of my country's economy, the development and utilization of energy has become increasingly strained. Since March, many parts of my country have experienced off-season power shortages, and low energy efficiency is one of the important reasons for these shortages. Under these circumstances, improving energy efficiency is urgently needed. Meanwhile, with the continuous development of urban road networks and the increase in the number of streetlights, people's demands for energy conservation and streetlight management are also rising. Adopting advanced technologies to save energy and improving the level of automated control and management of streetlights have become top priorities in the construction of urban lighting systems.
1. Current Status of Street Lighting Management
1) The lighting facilities have poor uniformity in switching on and off, low level of intelligence, lack remote modification of switching on and off times, cannot be modified according to actual conditions, resulting in significant energy waste and increased financial burden.
2) Streetlight equipment is scattered, there are few management personnel, management is difficult, and the equipment operation status cannot be monitored in real time, accurately and comprehensively, and there is a lack of flexible control methods; 3) Manual inspection is labor-intensive, inefficient, costly, wastes manpower, material resources and financial resources, and lacks an effective fault early warning mechanism.
2. Introduction to ZigBee
ZigBee is an emerging short-range, low-complexity, low-power, low-transmission-rate, and low-cost two-way wireless networking communication technology. It is a technology that lies between RFID (Radio Frequency Identification) and Bluetooth.
3GPRS Introduction
GPRS (General Packet Radio Service) is a new bearer service that provides an efficient and low-cost wireless packet data service, particularly suitable for intermittent, bursty, and frequent data transmission. GPRS is always online, offers fast access speeds, and allows users to maintain a connection to the wireless network at any time, significantly improving the efficiency of remote data acquisition.
4. Introduction to PLC
A Programmable Logic Controller (PLC) is an automatic control device with an instruction memory, digital or analog input/output interfaces, capable of performing logic, sequential, timing, and other functions to control machines or production processes. PLCs are characterized by their versatility, ease of use, wide adaptability, high reliability, strong anti-interference capabilities, and simple programming.
5. System Working Principle
Configuration software is used as the host computer control platform, communicating with the field controllers (PLCs) via GPRS. The monitoring center software sends action commands to each field controller via the GPRS network, enabling the field controllers to complete various configuration and data acquisition tasks, and analyzes and processes the data sent by the field controllers. The field controllers receive signals from the individual lamp controllers via ZigBee wireless communication devices, analyze and process them, and send information to the monitoring center through the GPRS communication system, thereby realizing remote wireless control of the streetlights, as shown in Figure 1.
6 System Components
The system consists of three parts: field controllers, individual lamp controllers, and a monitoring center.
6.1 Field Controller
Composed of a PLC independent control module, a GPRS communication module, and a ZigBee wireless communication module, it performs functions such as data acquisition, control output, data communication, and fault alarm. The field controller is connected to the lighting management and monitoring center server via GPRS and to the individual lamp controller via the ZigBee wireless communication module, thereby achieving real-time communication, as shown in Figure 2.
6.2 Single Lamp Controller
Each street light is equipped with a single-lamp controller, consisting of a ZigBee wireless communication module and a microcontroller module that performs power acquisition and remote signaling functions. The ZigBee wireless module has a mesh topology, which provides built-in redundancy for the ZigBee subnet. If a node in the network becomes disconnected and unable to function, its data will be automatically routed to a replacement node to ensure system reliability and stability. The single-lamp controller is the execution part of the control function in the street light monitoring system. It controls the status of the street light and monitors its operating current, voltage, power factor, etc., transmitting these parameters wirelessly to the field controller. Simultaneously, it receives all control commands from the field controller, thus realizing remote control functionality, as shown in Figure 3.
Figure 3. Composition of a single-lamp controller
6.3 Monitoring Center
The monitoring center, consisting of monitoring center software and a GPRS communication module, provides centralized control of the entire lighting system. The monitoring center software enables remote monitoring, data acquisition, database creation, and data analysis. The GPRS communication module scans the power consumption and output status of each street light in real time and can also transmit various valid commands from the monitoring center software to the field controllers. In case of an alarm, a message is sent to the patrol personnel's mobile phone via GSM SMS.
7. Monitoring Center Software Introduction
Configuration software is specialized software used for data acquisition and process control. This system uses KingSCADA as the development tool, which has the advantages of strong adaptability, good openness, easy expansion, economy, and short development cycle. It can make full use of the graphical editing function and provide users with a user-friendly visual interface.
The monitoring center software is the control center of the entire street light monitoring system. It is responsible for remote communication with the monitoring terminals in the control site and for processing the acquired data. Its main functions are as follows:
1) Query Function: The field controller sends parameters such as voltage, current, power, and equipment operating status of a single lamp back to the monitoring center via a wireless channel. The host in the monitoring center analyzes and processes this data and provides it to the management personnel in the form of intuitive reports or charts, providing accurate basis for decision-making.
2) Control function combines manual and automatic control, providing flexible and reliable switch control functions. The switch scheme and switch time in "Set Parameters" are sent to the field controller, so that the field controller can operate according to the specified scheme.
3) The parameter monitoring center can automatically or manually control the switching of all lights, or control any single light to switch on or off. It can also set half-night light or full-night light modes at will, and save the set parameters and requirements.
4) Alarm function: When the field controller actively alarms or detects a fault in the single lamp controller, the monitoring center software will issue an audible and visual alarm signal to remind the staff, and display the location, status and type of the fault alarm on the screen. At the same time, the alarm record will be saved and the field inspection personnel will be notified by SMS.
5) Data statistics and report statistics: Collect data information from parameters and generate reports for easy analysis and research. The reports can be printed.
8. Conclusion
This system, based on the specific requirements of street light control, establishes a user-friendly visual interface and integrates wireless communication technology, automated control technology, and monitoring system networking. It effectively solves problems related to flexibility, real-time performance, reliability, and economy in street light control. It boasts strong anti-interference capabilities, stable communication, and accurate delivery of commands from the host computer to the monitoring terminal. This not only significantly reduces the cost of laying communication cables but also achieves energy conservation.
