| Communication technology plays a very important role in the distribution grid operation monitoring areas. Using power line communication technology to realize the monitoring and controlling of distribution grid have unique advantages, it can make full use the power line to transfer the monitoring and controlling data, no longer to rebuild communication network. But the PLC communication reliability is infected by the serious interference noise and signal attenuation on the power line. In this paper, the key technologies of power line communication, which can improve PLC communication quality, were studied in detail in the theory, and then PLC communication systems which are suitable for China's 10kV distribution gird operation monitoring are designed. The main contents of our research include:1. Noises, attenuations and their infections to PLC communication systems on actual PLC channels are analyzed in detail. Then narrow band orthogonal frequency division multiplex synchronization techniques is proposed as the modulation of 10kV distribution grid PLC communication. The OFDM theory and its characteristics and realization method are analyzed at first, and then special modulation unit based on ARM chip and FPGA chip is designed.2. According to the PLC channel attenuations properties, a new method for channel estimation based on decision feedback of OFDM system is proposed. In this method, the pre channel estimation value is used to equalize the next receiving symbol, so a loop including decision, feedback and channel estimation is formed. This method can trace the change of PLC channel, easy to calculate and design, no pilot symbols are needed and consecutive estimation can be made, which improves transmission efficiency. This method is applied to the power line communication system, which gets a good performance. Another LMS adaptive channel estimation method which can resist the serious random abrupt inference noises and signal attenuations is proposed also in this paper. Through taking measures of channel estimation, receive properties of OFDM system is improved.3. According to the noises characteristics and the effects to PLC communication qualities of actual 10kV distribution grid PLC channel, a channel coding scheme is presented, which is suitable for PLC communication of 10kV distribution grid. By means of the improved BCH coding and the improved random block interleave coding, the bit-error-rate of PLC communication is reduced effectively. It can be corrected 64 bits sequential errors by this channel coding scheme. The channel coding algorithm of software including error-correcting coding and random block interleave coding is accomplished based on ARM microprocessor.4. On the basis of researching of some key technologies of PLC communication, PLC communication system is designed, which suitable for 10kV distribution grid operation monitoring. By means of this communication system, the 10kV distribution grid operation monitoring system is established. The two research achievements of this paper, PLC communication monitoring system and carrier communication intelligent switch, are applied national invention patens.5. On the basis of analyzed the several typical interferences of 10kV distribution grid and their effects to monitoring equipment in detail, the available hardware and software resistive interference measures are taken. By means these measures, the reliability of the monitoring system is improved.6. At last, according to the China's electrical industry standards, DL/T 790 and DL/T 721, the 10kV distribution grid operation monitoring system designed in this paper is tested on actual distribution grid. After one year running on the actual power line, experiments show that the systems possess reliable communication function and accurate monitoring function, and meet the need of 10kV distribution grid operation monitoring.
|
PDF Full Text Request