Governments and power companies across the world have recognized that the traditional grid, which has not significantly changed in 100 years, must be replaced by more efficient, flexible and intelligent energy-distribution networks, called smart grid. These are digitally monitored, self-healing energy systems that deliver electricity or gas from generation sources, including distributed renewable sources, to points of consumption. They optimize power delivery and facilitate two-way communication across the grid, enabling end-user energy management, minimizing power disruptions and transporting only the required amount of power. The result is lower cost to the utility and customer, more reliable power, and reduced carbon emissions.
Power lines reach all units that require “power” from a direct connection to a plug. Hence, power lines are a cheap communication medium always available to interconnect units without adding unnecessary and expensive cables or radio frequency systems.
A narrowband communication over power lines is sufficient for simple information exchange such as measure, command to actuators, check system, and so on, and allows a wide number of applications both in outdoor and indoor environments. For example, utilities can use the outdoor network for remote street lighting control and monitoring or for Automatic Meter Reading (AMR) and Management (AMM), simultaneously providing many client services like power consumption control and tariff selection. In the home, the indoor electrical grid can be used to connect home appliances realizing home or building automation, security and safety systems, temperature and lighting fixtures control. To make this possible, a Power Line Modem (PLM) is necessary. Like ordinary modems, a modem suitable for use over power lines is able to convert a binary data stream into a sequence of signals with predefined characteristics (frequencies, levels) and vice versa converts them back into the binary data stream, completing the modulation / demodulation process. They must be able to convey the modulated signals over the power line and detect arriving signals, which comprises the transmission/receiving process.
As mentioned briefly above, one of the first applications was the Automatic Meter Reader, or AMR. Traditional electromechanical meters are based on a technology that is unsuitable for further significant development. Electronic meters offer many significant advantages for the utility companies and consumers, including lower costs for manufacturing, calibration and maintenance, greater accuracy and, most important, the ability to provide the consumer with detailed information based on their own real consumption and the electricity supplier with punctual service quality data.
The AMR evolution is the smart meter, a key building block of the smart grid. The benefits of the Smart Meter to both the electric utility and customers are concrete: consumers can more accurately monitor and control their consumption (for example, by using appliances such as washing machines, dishwashers or electric showers at times when the cost is lowest) and energy providers can generate and distribute power more efficiently.
The emerging smart grid is essentially an intelligent and digital electricity network and is being used to define the next generation of distribution networks for electricity. Using their home networks, consumers will be able to communicate with the smart grid, through their electricity meters, offering smarter power management for utility companies and consumers alike.
Within the smart grid, there are three major market sections – grid infrastructure (i.e., concentrators), utility meters, and home/building management – each with varying application requirements.
Micro-inverters used in harvesting energy from solar and other alternative energy sources use power line modems to communicate to the smart grid. Below is a block diagram of an up-to-date solar harvesting system.
New standards were developed to meet the market requirements, like:
• S-FSK modulation up to 2.4 Kbit/s bit rate, IEC 61334-5-1 protocol
• The Meters & More specification. B- FSK and multi-mode n-PSK modulations
• Very robust OFDM modulation PRIME protocol. PRIME (PoweRline Intelligent Metering Evolution) is a Physical and Mac layer standard definition based on up-to-date technologies, in order to guarantee that future market requirements are met and that utilities’ investments are future proof. PRIME is open, looking for different vendors’ equipment interoperability, as a way to push for the growth of a new market so that, at the end of the day, all players (utilities, industry, customers, etc) will benefit from this approach. PRIME is based on OFDM multiplexing in CENELEC-A band.
Smart grids are intelligent networks for the distribution of energy. Home automation, smart metering and renewable sources are among the key building blocks for smart grids that we are addressing. Smart meters provide detailed information and real-time data to enable consumers to manage the power consumption in their homes, encouraging them to run washing machines in low usage times, for instance. Smart grids are the emerging intelligent networks for the distribution of energy.
Home automation, smart metering and renewable sources are among the key building blocks for the smart Grids.
In the context of the smart grid, the smart meter is the hub between the Home Area Network (HAN), and the outdoor smart grid, connected to the electric utility.
The picture below illustrates this key role of the smart meter:
The new HomePlug wideband PLC arena provides the key advantage of the ‘no-new-wire’ approach to users. High-speed home networks can be created by using the power sockets and wiring infrastructure that already exist in the home.
HomePlug is also an industry-wide alliance (www.homeplug.org
) whose sponsors include STMicroelectronics. The Alliance's mission is to enable and promote rapid availability, adoption and implementation of cost effective, interoperable and standards-based home powerline networks and products. The HomePlug technologies are fully compliant to the IEEE1901 standard for broadband-over-powerline networks (Medium Access Control and Physical Layer Specifications) and offer a complete ecosystem of interoperable technologies ensuring the forward migration path to Gigabit-class service.
There are two major variants within HomePlug standard, and they are interoperable:
• HomePlug GP (Green PHY), which targets ‘smart Grid’ and smart-energy applications
• HomePlug AV (Audio/Video), which is the consumer standard, aimed primarily at home networking.
Recently, the HomePlug Alliance received a letter from the Coordination Office Charging Interface, Carmeq GmbH, representing five German automakers stating that these OEMs had selected PLC IEEE1901 Profile Green PHY (HomePlug GP) as the communication technology between plug-in electric cars and charging stations. GM, Ford and Toyota followed by adopting HomeplugGP shortly after, making HomepluGP the de facto
standard for EV charging.
In the future, Electric Vehicle to Grid (V2G) Communication will allow utilities and consumers to manage the process of charging plug-in electric vehicles, providing the much needed ability to control the amount of energy consumed from the power grid during peak hours. The emerging V2G standards will provide a common communication technology for the physical & data link layer.
The new IEEE P1901.2 low frequency (less than 500 kHz) narrowband power line communications standard is designed to provide the new benchmark of performance and reliability while offering interoperability with the existing "PRIME" and "G3-PLC" OFDM technologies.
The new P1905.1 defines an abstraction layer for multiple home networking technologies. It integrates P1901 with other home networking technologies. The abstraction layer provides a common data and control Service Access Point to the heterogeneous home networking technologies described in the following specifications: IEEE 1901, IEEE 802.11, IEEE 802.3 and MoCA 1.1.
From the early usage of power line communication, in Automatic Meter Reading (AMR), to replace the technician from the utility company, reading power meters in person, with an automated process, the industry has come a long way.
Today, power line communication is used in micro-inverters for solar or other new alternative energy power sources, electric vehicle charging, concentrators, smart meters, thermostats, home automation and factory automation, street lights control etc.
The evolution from smart metering to a smart grid today is a key milestone. Many groups and industry consortia are working on the definition of a common communication protocol for smart grid services, like: OPEN meter project, Meters and More Association and PRIME Alliance (created by large European utilities such as Enel/Endesa and Iberdrola to promote and maintain field proven and widely deployed PLC technologies), IEEE P1901.2 (the new emerging working group inside IEEE dedicated to narrowband PLC) and HomePlug Alliance, the leading group in broadband power line communication.
About the author:
Ivan Gatchev received a Degree in Electrical Engineering from the University of Ottawa, Ottawa, Ontario, Canada in 1987. He joined STMicroelectronics in 1999, and has been working in Product Marketing for Dedicated Products and later in ST’s Analog, Power and MEMS organization. Before joining ST, he worked as a Field Applications Engineer in the Semiconductor Industry for several years and earlier in his career in the RF & Microwave industry in various roles. He is now focused on industrial application-specific products. Ivan is based in Santa Clara, CA, USA, in the heart of Silicon Valley.