Research Of Low Voltage Dc Power Distribution Monitoring System

With the rapidly increament of both kinds and quantities of electricity-comsumed equipment in the power supply system in multiple field like commercial electric distribution system,industrial controlling system and military equipments,the fault probability and safety events occurrence also incease in orders of magnitude.In order to ensure the reliability and safety during the operation of the power supply system,we have to design an intelligent monitoring and controlling system which can accurately monitor the operation status.The voltages and currents on lines as well as on equipments,and the input and output status in key equipments should be monitored in real-time,and the fault detection should also be carried out and dealt automatically online.In this paper,a DC power monitoring and controlling system with remote network interface were designed on the basis of ARM processor,MCU,CAN network and Ethernet network.It can be devided into two part: the one is monitoring and controlling unit and the other is the data transfer unit.Firstly,the electric circuits for the DC power monitoring and controlling system was designed.The circuits mainly consists of: voltage measuring circuits,current measuring circuits which fulfil the basic status sampling function of the power line;the supply voltage measuring circuits for the processor which can be used to realize self-checking,indicting and maintanence for the monitoring and controlling system it self;remote communication interfaces like CAN and Ethernet networks which can be used to transfer and share the status monitored remotely.Among those circuits,a new method for detecting the supply voltage of the processor was adopted to reduce the measurement error greatly.Then,the key and difficult problems involved in the software was detailly analyzed and the corresponding improvement method was also realized.A non-operating system software was used in the monitoring and controlling system.The Sequential Message technique was used to optimize the structure of the software and it also solved the data interfere problem when they are transferred between the main code and interrupt code.An operating-system based software structure was used in the data transfer unit.There were two communication ports used in the data transfer unit,one for collecting data from the monitoring units and the other for transferring data to remote unit.The former is based on CAN network,whereas the later is based on Ethernet network.An algorithm to calculate the disconnection time and it solved the detecting problem of disconnection for the inner CAN network.The data transfer is a multi-task problem in the operating system,and a new Watchdog technique was introduced into the software which can monitoring each task.This method can improve monitoring the TCP/IP protocol stack,and it improved the software reliability and the anti-interfere ability of the whole data transfer unit.Finally,the experiments and the Monte-Carlo analysis were carried out to the DC power monitoring and controlling system.It shows that the new method to measure the processor supply voltage has a significant reduction in measurement error over traditional solutions.By comparing the measured data before and after field calibration,the results show that the calibration results of this method are obvious,and the measurement results of the same channel can be more consistent.In addition to cost advantages and good reliability,the system also has a good interface and extendibility.