Development Of The Master Station Device In TWACS Based On The Distributed Structure

TWACS(Two Way Automatic Communication System) is a kind of communication system based on the power distribution network, which appeared in the United States in the 1990s. TWACS transmits information through producing distortion on voltage and current waveform at the voltage zero-crossing moment. It can pass the transformer to realize long distance transmission by a simple and effective way, and is very suitable for low speed channel transmission mode. It has the advantages with low cost, long transmission distance, strong anti-jamming capability, convenient maintenance, etc.Currently TWACS in our country is mainly used for long-distance meter reading in individual transformer area, etc. Due to the application scope is very small, present main parts of traditional master station equipments are using Industrial Personal Computer for collocating A/D acquisition card. Inbound demodulation is through the accumulation and calculation for current sample value. The inbound demodulation performance of master station mode is poorer, and with the shortcoming of slow speed, low efficiency and high failure rate. So it is difficult to adapt to the situation when transformer is with large number, multiple lines at the same time having inbound signals and the power grid structure is complex, etc., so it needs to be improved.According to this phenomenon, the paper analyzes the TWACS principle and system composition, studies and realizes TWACS master station equipments based on distributed structure. For the distributed structure master station equipments according to the basic function of TWACS master station, the master station equipments will be divided into management unit, multiple inbound signal demodulation unit, outbound signal modulation unit. Management unit will be through the communication protocol to achieve parallel receiving and management of multiple line inbound signal. In the master station, management unit is composed of Information Processing Center and backend software. Inbound demodulation unit consists of MCU,16 A/D converter and voltage, current sensor etc.. Supercomputing of MCU circuit module, inbound demodulation according to the inbound modulation and coding and by time-domain difference and cross-correlation algorithm etc., which has replaced traditional Industrial Personal Computer concentrated demodulation. Outbound signal modulation unit composed by silicon-controlled rectifier control circuit for the modulation and sending of outbound signal. MCU circuitry of the inbound demodulation unit calculates quickly, which provides hardware base for parallel demodulation of multiphase inbound signal.TWACS master station equipments designed according to this method is tested in oilfield network, the operation results show that the distributed structure master station can adapt to the industrial production rugged environment with strong noise, multiple lines and more transformer. The new master station equipments can correctly received concurrent transmission of multiple lines inbound signal, and with high the communication quality. At present, the master station equipments mode and equipments have been used in practical project.