The traditional power maintenance adopts the manual manual maintenance management mode, and the intelligent power monitoring system is based on embedded technology, computer technology, communication technology, etc., and realizes the transformation of the power system to the intelligent and automatic management mode.
With the development of contemporary technology, the power maintenance management of a large number of various types of equipment requires a lot of manpower and material resources. The environment in which communication/electric facilities are located is increasingly complex, sparsely populated, inconvenient in transportation, and high in risk. The difficulty and cost of maintenance. This puts higher requirements on the monitoring and management of power supply equipment. The power monitoring system needs to monitor the status of each state in the system, and must also be able to control and manage each power branch. The maintenance manager can remotely perform maintenance such as data query and control, and can conveniently obtain the required information by using a friendly human-machine interface.
The development of digital technology shows the advantages that traditional technology can't match. The signal sampling, processing, control and communication of the entire power monitoring system can be realized by digital technology. The fully digital control technology can effectively reduce the size of the device and reduce the cost of the device, but at the same time greatly improve the reliability, intelligence and user experience of the device. As the module becomes more intelligent, the maintainability of the new power monitoring system has also been improved.
With the development of embedded technology, the use of embedded real-time operating system is an inevitable choice for power monitoring systems. On the one hand, the embedded real-time operating system has good portability and high reliability; on the other hand, because with the continuous improvement of the performance of the power monitoring system, only the traditional single-chip microcomputer can not adapt to the new demand. As the representative of today's embedded technology, ARM not only has all the above advantages, but also has low cost and high cost performance. The system designed in this paper uses the LM3S9B96 chip from the Luminary Cortex-M3 series ARM produced by TI.
1, working principle
Figure 1 shows the power supply monitoring of 8-way electrical equipment as an example. The principle block diagram of the monitoring system is given.
Figure 1 Block diagram of the 8-way power monitoring system
The 8-way equipment draws power from the main power supply, and each power supply branch works in exactly the same way. After the power monitoring system is started, the main chip is in the power-on reset state, and the eight I/O pins of the GPIOF are at a low level. At this time, the electronic control switch remains in the off state, that is, the power supply branch is in the power-off state. When the main chip core and each peripheral are successfully initialized, the output of the 8 I/O pins of the GPIOF is controlled to be high by its internal embedded program. Accordingly, the power supply branches are energized and start normal operation.
The acquisition module includes a current sensor and a voltage dividing circuit. The current sensor can measure the current value flowing through the power supply branch, and the voltage dividing circuit adjusts the voltage value of the power supply branch to the range of the sampling of the main chip ADC, both of which are analog values. . After the detected values ​​are sampled by AD, the current and voltage values ​​of the respective power supply branches can be calculated in the main chip and compared with preset current and voltage thresholds. If it is within the threshold range, it indicates that the power supply branch is working normally, and outside the threshold range, it indicates that the power supply branch has abnormalities such as overcurrent, overvoltage, undervoltage, etc., and the main chip changes the output of the corresponding pin of the GPIOF. Low level to automatically power off the branch. After checking and troubleshooting, the power supply branch can be controlled by the host computer to issue power.
The upper computer communicates with the embedded lower computer through Ethernet. The upper computer can send commands to the lower computer to control the on/off of the specified power supply branch, and can also set the current and voltage threshold values ​​of each power supply branch. At regular intervals, the current, voltage value and various normal/abnormal states of each power supply branch are sent to the upper computer by the lower computer. The working status of each power supply branch can be observed by the upper computer display control software.
2, design and implementation
2.1 core module
The core module uses the LM3S9B96 chip from the Luminary Cortex-M3 series ARM produced by TI. The chip has an operating speed of 80MHz. It integrates a large-capacity 256KB single-cycle flash ROM and 96KB single-cycle SRAM with 16 channels of 10-bit resolution AD sampling. Module, support; L/IP 10/100M adaptive Ethernet module and rich I/O interface.
The LM3S9B96 has 65 I/O interfaces. It is designed to select 8 I/O interfaces of the GPIOF group as control pins. Each power supply branch needs to collect two values ​​of voltage and current. The 16-channel AD sampling module can meet the 8-way power supply branch. The sampling requirements; integrated MAC + PHY peripherals can also achieve Ethernet communication with the host computer; large-capacity built-in storage space provides a suitable platform for complex programs. Based on the above analysis, the LM3S9B96 chip is well suited for this monitoring system and greatly simplifies circuit design.
2.2 control module
The design of each power supply branch control module is shown in Figure 2. According to the current value required by each branch device, select the appropriate relay as the electronic switch, and add optocoupler isolation protection and power supply on/off indicator between the control pin and the relay.
When the main chip GPIOF control pin is low, the LED light is off, the relay 3 pin input is disconnected from the 5 pin output, and the power supply branch is powered off; when the main chip GPIOF control pin is high, the optocoupler output is low. Flat, the LED light is on, the relay 3 pin input and the 5 pin output are turned on, and the power supply branch is energized.
Figure 2 Power supply branch control module design
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