DSM-Saving energy for the future: PLC(power line communication)- key element in the Smart Grid

PLC(power line communication)- key element in the Smart Grid

By Lin Xiqiao

In recent years ,Smart Grid have become one of the hottest concepts in the electrical field ,it is widely consider Smart Grid will become the next power supply network. To meet the requirement of supply the energy reliable and flexible ,the smart grid network need to communicate between each components. There are many options for smart grid communication like Powerline communication (PLC), optical fiber communication and wireless communication. However PLC is widely considered the best choice for offering ‘last mile’ communication for smart grid due to the economic and convenience issues.

Smart grid is an expanded concept of energy system, inside this system, many components are involving like smart meters, sensors, control units etc. . .Besides hardware components, software like energy managing system is the key infrastructure making the Smart grid different with traditional energy supply network.

Powerline communication using the exist power transmission line as communication channel to transmit signal, it bring many advantages to Smart grid operator. However, because PLC communication channel is use the normal electrical transmission line which is cannot provide good channel environment ,unavoidable it has a noisy environment. On the one hands background noise, impulsive noise, narrowband interference and group delays up to several hundred microseconds will result in high frame error.On the other hand high attenuation rate of channel, which normally around 40dB/KM to 100dB/KM especially when signal go through an transformer it will suddenly reduce up to 30dB. Comparing by the good channel environments in the optical fiber which usually around 0.5dB/KM, Narrowband Powerline Communication, its viability for smart grid realization is being questioned.

PLC has a long history, it was experimented during the World War II, and witness a far development during the recent years .Traditional PLC use single carrier modulation such as FSK(frequency shift keying),PSK(phrase shift keying ),the output speed of single carrier communication usually too slow and with low reliability ,therefore cannot meet the requirement of Smart grid communication.

There are two leading OFDM based standard-G3 PLC and PRIME ,both of them attend to use EU A band to transmit signal modulating with DPSK .However due to the modulating domain is different(G3 PLC is t-DPSK and PRIME is f-DPSK),the design and result of those standard will very a lot . OFDM have been use in majority of wide band communication technology, because it can promote the efficiency in the frequency selective channel without channel estimate algorithm . Moreover PLC bandwidth allowance is also significant for standard design. Different bandwidth allowance will affect the performance of standard. For example, the European Standard CENELEC 50065-1 has divided the 3 kHz to 148.5 kHz low-frequency powerline spectrum into four different frequency bands, and PRIME is focus on CENELEC A band,which occupy the frequency range from 42 KHz to88 KHz while the “HomePlug Command and Control” which is design for America can operate up to 400KHz.Because the different range of frequency bandwidth allowance will have an effect on both physical protocols and data link protocols.