The smart grid is clearly going to combine technologies in creative ways to connect all the devices – modern and legacy, wired and wireless – that need to be on the grid, including a new idea, pulses over power lines.
The industry is zeroing in on Power Line Communication (PLC) technology as one of two primary contenders for standardized home energy management, Advanced Metering Infrastructure (AMI), and new energy distribution systems. But truly mainstream smart grid deployment has been stymied by the lack of technology that can deliver bidirectional communications at ultra-low power and low cost, with a small enough footprint for pervasive in-house "smartplugs" and other monitoring/control devices.
An opportunity that exploits the transient behavior of electrical networks has now emerged to solve these challenges. By using the network’s reaction to load changes, it is possible to generate a high-level low-energy pulse, which, in turn, can be used to create next-generation smart metering solutions capable of transferring and collecting data or controlling equipment remotely over power line (either residential grid or AC power circuit) networks. The pulse is fully compliant with EMC regulations, and because its magnitude can be significantly higher than surrounding noise, it is possible to ensure a very robust communication signal even after propagation.
Previous PLC technologies require carriers to transport data, which means that signal processing is needed to optimize the communications stream along with an analog[
] front end, adding to costs. These technologies also require inductive coupling, which increases power consumption. In contrast, by generating electromagnetic pulses similar to those generated by electrical appliances on the grid’s power line infrastructure, it is possible to transport data and create a significantly less expensive, better performing, low-voltage command and control network (see Figure 1).
This approach cuts costs by eliminating complex signal processing capabilities and minimizes module size since no analog front end is required. It also dramatically reduces power consumption to less than 10 mW, as compared to solutions that need energy through inductive coupling, and shrinks module size to 2.5 cm2, making it possible to embed the technology into a wide range of devices throughout the home.
Smart grid requirements
Utilities and equipment suppliers around the world want to modernize their electrical distribution grids to optimize the use of variable energy sources, establish automation and monitoring capabilities, and leverage real-time transmission between the entities that drive energy conservation. Such modernized smart grids are intended to promote energy independence and combat global warming, among other goals.
Much is expected of a smart grid, including capabilities outlined in the U.S. Department of Energy’s Modern Grid Initiative report. They must be attack-resistant and able to heal themselves. They must provide higher-quality power to cut costs associated with power outages and help deliver consumer incentives to actively participate in grid operations. They also must be able to accommodate all generation and storage options and improve efficiency while enabling electricity markets to flourish.
Three technologies are required to drive these capabilities, including AMI, home command and control, and efficient energy distribution.
The first step: standards
One of the biggest barriers to smart grid adoption is now being resolved, as utilities around the world settle on two primary technologies for future AMI deployment. The first technology, PLC, is now being modified to support specific smart grid needs. Europe and Asia are focusing on PLC technology.
The second technology is wireless and mostly based on the IEEE 802.15.4 protocol. Other geographic regions are using wireless technology (including ZigBee, IEEE 802.15.4, and many proprietary wireless standards across a 440 MHz to 2.4 GHz frequency range) and, on a very limited basis, some wireline technology.
Utilities and manufacturers are also making progress in defining the different communications layers for future standard adoption. For instance, the HomePlug Powerline Alliance and ZigBee Alliance are working on creating a new physical layer called Green Profile for HomePlug (HP-GP).
In addition to these foundational standards, a true smart grid network must address the need to interact with other standards from other industries. This includes heating and air conditioning, commercial buildings, home appliances and automation, and so on. New standards are required across different layers of the communications protocol stack to ensure reliable two-way communication between all of the technologies used by smart meters, in-house Smart Energy products (including gateway solutions), and general distribution solutions deployed by utilities.
At the lower level of the communications protocol stack, most utilities that have already deployed smart meters want at least some level of backward compatibility with the most recently deployed legacy solutions, but only for technologies such as IEEE 802.15.4 (including ZigBee) and PLC. Because PLC technology is used for applications such as IPTV to deliver video content within the house, various products using similar technologies need to coexist. Standards like the P1901 are addressing this coexistence issue by creating mechanisms that will allow multiple PLC solutions to time-share the use of PLC bandwidth.
It also is likely that higher-layer protocols will converge toward the use of the next Internet Protocol (IPv6). Use of IPv6 networks will be the driving factor to build future solutions that will interoperate at higher protocol layers. Integrating the utilities’ preferred technologies, HomePlug and ZigBee, into an IPv6 network can be accomplished by using IEEE 802.15.4 as a Media Access Control (MAC) and Physical Layer (PHY) and by implementing IETF 6LoWPAN as an adaptation layer to send and receive IPv6 packets. The next generation of smart grid silicon will support IPv6 through an IETF 6LoWPAN adaptation layer.
Other challenges must be addressed. For instance, even if a ZigBee product uses IEEE 802.15.4 as MAC and PHY layers, its routing capabilities differ from those in the IETF 6LoWPAN specification. Furthermore, differences in headers used by IETF 6LoWPAN and ZigBee cannot be decoded from one network to another. These incompatibilities between IETF 6LoWPAN and ZigBee networks make it impossible to provide any compatibility over the air between these two solutions. As of today, ZigBee devices cannot support any IP frames in a simple way. Options such as "encapsulation" capabilities or the use of gateway solutions between existing (SE V1.0) and upcoming (SE V2.0) Smart Energy standard devices have been discussed, but none of these alternatives are very attractive when it comes to cost, ease of deployment, and other important factors.
Creating a smartplug foundation
Devices that control and command the home’s energy appliances will be at the heart of mass-market smart grid deployment. As many major energy appliances as possible must be interfaced to smart meters or other Smart Energy gateway equipment in the house. This will enable consumers to efficiently control energy consumption within their homes. To do this, smartplug devices or capabilities need to be installed to control and command all of the energy appliances and must be capable of reliably connecting the in-home environment to the utilities’ dynamic systems control infrastructure (see Figure 2).
The short-term costs of deploying smartplugs must be funded through monthly energy savings. For this to be possible, the enabling technology must have ultra-low power consumption and a direct connection to the power line. Additionally, the technology by its level of integration must enable very small devices so that they can fit inside any electrical element, from power outlets to lamps to appliances. Costs are also important, which requires that a minimal number of external components should be used. Finally, the technology must support very high-performance devices that balance throughput with whole-home coverage, plus the necessary quality of service and security features to ensure a robust networking environment.
One example of an early PLC implementation using electromagnetic pulses for smart grid applications is WPC technology from Watteco (see Figure 3). The technology supports communications between WPC devices on a single- or multi-phase low-voltage (110 V/220 V) electrical wire (50 Hz/60 Hz) at a 10 kbps rate. WPC technology uses the grid’s resonance frequencies to communicate with electromagnetic pulses, eliminating the need for an external oscillator or analog front end. When the WPC device is connected to a 5 V power supply, all smart grid applications are supported in a compact, easy-to-integrate, low-cost, and power-efficient solution.
WPC technology operates by using the generation of electromagnetic pulses due to load switch-on. No carriers are required, so the communication stream can be significantly optimized. The elimination of signal processing and the need for an analog front end cuts costs and reduces size. Finally, since there is no inductive coupling, power consumption is extremely low.
Many converging factors are driving smart grid deployment. Rising energy demand is creating the need for greater efficiency against the backdrop of growing environmental awareness among consumers and government initiatives aimed at pressuring utility companies to deliver Smart Energy solutions. With key standards and a new generation of silicon that leverages the natural phenomenon of electromagnetic pulses to create an economical and reliable low-voltage power line network, the smart grid is poised to enter a major growth phase for development and deployment.
Didier Boivin is CEO of Watteco, where he applies his 25 years of broadband, wireless, and consumer market experience to the challenge of helping usher in the smart grid era. Before joining Watteco, he was marketing vice president for Centillium Communications. Prior to that, he held senior management positions at companies including DSP[] Group, Alcatel Microelectronics, and Rockwell Semiconductor Systems.
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