There is plenty of loose talk about the “smart grid.” To see what impact it will have on electronics designers, it’s helpful to filter the noise and take a look at what’s really there. The U.S. Department of Energy (DOE) has identified seven characteristics of a smart grid:
- It is self-healing from power disturbances.
- It enables active participation by consumers in demand-response programs (load control).
- It operates resiliently against physical or cyber attack.
- It provides quality power for 21st-century needs.
- It accommodates all generation and storage options.
- It enables new products, services, and markets to function.
- It optimizes utility assets and operational efficiency with the use of sensors.
Obviously, all this requires standardized architectures and interfaces to stimulate development and promote interoperability. This goal is what led to the Electric Power Research Institute’s (EPRI) “Report to NIST on the Smart Grid Interoperability Standards Roadmap.”
Well before the EPRI report was released to NIST, the GridWise Alliance—a public/private consortium with the goal of helping integrate electricity infrastructures, processes, devices, information, and markets—developed a comprehensive action plan that identifies the challenges facing the electricity industry. In addition, the GridWise Architecture Council was formed to shape the architecture of an interactive electric system.
Even earlier, EPRI had published their “IntelliGrid” architecture, a comprehensive technical framework for linking communications and the power grid. In part, EPRI proposed an architected approach to integration by deploying equipment in this order: automatic meter reading (AMR) enables energy markets and time of use pricing, utility information uses the AMR infrastructure to manage outages and demand (loads) and remote-controlled distribution devices automate restoration and enable distributed generation.
Meanwhile, the National Energy Technology Laboratory (NETL), a DOE national laboratory, identified the four milestones of a modern grid strategy (MGS) to accelerate smart grid implementation. The first is advanced metering infrastructure (AMI). Initially, AMR technologies were deployed to reduce costs and improve accuracy, but the value of two-way communications led to the evolution of AMR into AMI. It includes smart meters for advanced measurement, an integrated two-way communications infrastructure including control of loads (demand response), an active consumer interface (which may or may not be part of the appliance), and a meter data-management system. This communications infrastructure was critical for the succeeding three milestones.
The second milestone is advanced distribution operations (ADO). To provide the increased information and control needed for a self-healing grid (sensors, distributed intelligence, outage management capability, and distribution automation), ADO uses AMI communications to collect distribution information and improve operations.
Next is advanced transmission operations (ATO). This milestone aims at improving transmission reliability and efficiency, while managing congestion on the transmission system. It deals with substation automation; advanced protection and control; modeling, simulation, and visualization; advanced grid control devices; and materials.
The final milestone is advanced asset management (AAM). The AAM aims to improve the utilization of transmission and distribution assets and more effectively manage their life cycle. AAM requires smart sensors to provide operational and asset condition information to significantly improve asset management.
NUTS AND VOLTS
Achieving all this presents a host of design opportunities. Smart meters will allow time-based pricing and consumption data exchange, network metering with loss and restoration notification, remote on/off, and load limiting/control for “bad pay” or demand-response purposes. They will also support energy pre-payment, power quality monitoring, and tamper and theft protection. Much of this was evident this past December when Analog Devices introduced its ADE7878 poly-phase multifunction energy metering IC for smart meters.
For demand response, communications with other intelligent devices in the home or business via mesh networks is required. Home area networks (HANs) will constitute consumer portals that link smart meters to controllable electrical loads (smart appliances). The HAN’s attributes can include an in-home display that is responsive to price signals based on consumer-entered preferences. It should have set points that limit utility or local control to within consumer-set limits, and should also allow control of loads without continuing consumer involvement while still allowing consumer override capability.
“Smart buildings” provide a HAN parallel that is more fully implemented today. Industrial and building automation networks employ a similar infrastructure for intelligent control of their electrical loads. Most building automation networks consist of a primary and secondary bus that connects high-level controllers (generally specialized for building automation, but may be generic programmable logic controllers) with lower-level controllers, I/O devices, and a user interface.
Meanwhile, smart meters must communicate back upstream to concentrators. This past December, On Semiconductor introduced its AMIS49587, which provides PHY and MAC layers for data communication at up to 2400 bits/s over power lines using power line carrier (PLC) S-FSK IEC61334 modulation in the Comité Européen de Normalisation Électrotechnique (CENELEC) “A” band (60, 66,72,76, 82, 86 kHz).
The concentrators collect data from groups of meters and transmit that data to a central server via a backhaul channel. They are part of an AMI integrated communications infrastructure employing open, bi-directional, encrypted communications. The infrastructure supports interaction between the utility, the consumer or business portal, and any controllable electrical loads on the HAN or building automation network.
Beyond the concentrators, a meter data-management system analyzes information to be fed to other utility systems. It validates the incoming AMI data to ensure that its output to the other utility processes is complete and accurate, despite communication disruptions or customer premises problems.
Various media can provide all or parts of the backhaul. Some choices include:
- Wireline technologies including power line carrier (PLC), broadband over power lines (BPL), copper UTP, and optical fiber.
- Wireless technologies including multiple address system radio, paging networks, spread spectrum radio, WiFi, ZigBee, OSHAN, TDMA, CDMA, and 3G cellular, WiMAX, and VSAT terminals.
- Other technologies such as hybrid fiber coax (HFC), fiber to the premises (FTTP), and fiber to the home (FTTH).
An integrated communications system comprising combinations of the above media is the most likely future scenario. Urban and remote locations will need different mixes of local and backhaul media.
There are further design opportunities in providing security for the smart grid. The major threats are physical or cyber attack, and the reliability threat of electromagnetic compatibility (EMC) problems. Three recent cyber attacks highlight the possibility of remote destruction of assets, remote hijacking of utility control computers for extortion, and failed penetration tests of utility desktop computers. And the recent shutdown of a nuclear power station caused by a consumer digital camera brings the issue of EMC in utility control settings into sharp focus.