| Power line carrier(PLC) communication in the frequency bandwidth between 40kHz and 500kHz is a very important facility of the Power System Control Operating & Management. With the rapid development of power system recently in China, especially a lot of nonattended transformer substations are springged up, a mass of voice, image, telecontrol and protection messages need be exchanged among power plants transformer substations and power dispatching center , which put forward higher request for the speed and reliability of the Power Communication. Using new modulation and upgrading existing carrier system is imperative under the situation, for traditional SSB(Single Sideband) carrier can't meet this request.Coded orthogonal frequency division multiplexing(COFDM)modulation technology using in high voltage PLC is put forward in this paper. It is using OFDM as primary modulation, Outer Reed Solomon (RS) code concatenated with inner codes Trellis coded modulation (TCM) as channel coding, and analyzes the advantage of COFDM modulation technology exerting on power line communication. The power line carrier based on COFDM technology processes the original signal with data compression and data coding first of all, then modulates the signal through OFDM technology-it is the most important kernel part of COFDM modulation, and then transmits processed signal on the high voltage power line, last demodulates the signal according to opposite operation at the receive part. It can reach more than l.5Mbps data transmission speed in the available frequency band of existing power line carrier communication system by academic calculate and simulation. Comparing with the traditional power line carrier, it is provided with higher spectral efficiency, higher transmission speed, robustness to channel fading, immunity to intersymbol interference (ISI) and other predominant capability. High speed communication on the high voltage power line can be realized by the new-style COFDM power line carrier. technology upgrade and amelioration to existing power line carrier by COFDM modulation technology just need substitute former SSB module, which makes full use of existing equipment. This method may save a lot of fund. COFDM using in the high voltage PLC is analyzed in detail, and system parameter is presented.The modulation and demodulation of OFDM can be realized by inverse DFT(discrete Fourier transforms) and DFT, using digital signal processor(DSP) to accomplish Fourier calculation is much more convenient than by normal micro controller unit(MCU) Thus, the module design based on 16-bit fixed point DSP-TMS320VC5410 is put forward in this paper. Single DSP can realize most of the system algorithm in one code period, it supplies with high rate of performance andprice .Intellectual property (IP) core technology (RS complier MEGACORE function )of ALTERA company is exerted to this modulation system, which implements complex RS encoding and decoding . Research time is significantly reduced by inducting IP core technology, reliability and holistic performance of this system is exalted obviously at the same time. A lot of complex programmable logic devices(CPLD) using control devices are exerted in this system design. A great deal of logic devices are cut down, and the reliability is upgraded. Software design of this system is put forward at the article's last chapter, and sixty-four-dollar question of the software realization is also illuminated.High speed and reliable communication is a pivotal question that counteracts Power system real-time watch automatization. COFDM using in the PLC which is put forward in this paper can improve communication speed greatly, and reduce BER, reliability is assured also. So the thesis will make beneficial contribution to make better use of existing PLC system...
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