Research Of Channel Characteristic And Model Of Power Frequency Communication

Power Frequency Communication System (PFCS) is a new kind of distribution network communication technology. It can transmit information on distribution power line with a special communication theory. This technolodgy is invented by the U.S. scientists, has been applied in the U.S. widely to transfer the residents'electric fee information or water fee information etc. PFCS is now still in the exploration stage. Now in China, several researches has been studying in PFCS, but they all placed an extra emphasis on the research of equipments, ignored the theory study of channel and key technology, their PFCS has normal communication effects.Channel is the transmit media of communication signal. The channel of PFCS includes the medium-voltage and low-voltage distribution networks, equipments and varies of loads, has the feature of sperated location and complexity, especially to China diatribution network. Therefore, to improve the PFCS application level in China distribution network, we need to study the channel characteristics, to settle foundation for PFCS researchment.This report based on the PFCS essence-the power system transient phenomenon, analyzes PFCS in power system analysis methed., puts forward the equivalent circuit based on three phase distribution line, then analyzis the channel transmit characteristic, seperates the diatribution network in threen sections-medium-voltage low-voltage distributnion line and distributnion transformer, then solve the characteristic of each section seperately, finnally constitute the three charactristics to get the whole channel characteristic. With this method, we can not only get the whole channel characteristic, but also can get the influence to channel characteristics of every kind of devices in distribution network. Then, this paper proposes that the main PFCS noise and disturbance is the harmonics in distribution netwok, and analyzes the noise and disturbance characteristic.Afyer the above studies, we found the diatributnion network low-frequency band characteristic is suit to tansmit the PFCS signal, it has the features of low loss and phase shift. But in low-frrquency band, there are high-level harmonics in China distribution network, the receive signal is almost oblivion in the noise, and a lot of diaturbances may be mistaken as signal. It is a adds difficult in signal demodulation.At the end, this report proposed several suggestions to PFCS and pointed the direction PFCS reseachment is to enhance the signal feature and improve the signal detection technique, considering the channel characteristic.