By Markus Staeblien, General Manager of Smart Grid Business Unit, Texas Instruments
Each country and utility has its own reasons, strategy and understanding for a smart grid; therefore, different technologies are required to meet their needs. These technologies would not exist without a semiconductor solution — analog components that attach to the line to condition the signals and digital components for analyzing, measuring, calculating and communicating data over a smart grid.
Measuring energy is a key functionality and finds its place in various portions of the grid such as generation, distribution and consumption of energy inside or outside of a building. Energy measurement during generation and distribution is much more complex than at consumption.
The efficiency and quality of energy generation and distribution relies completely on the ability of the systems to measure key components with high accuracy. Key parameters that quantify the quality of power are variations in voltage levels (HV, MV), transients, surges, harmonic content, protections, etc.
The electronics that are needed to capture and maintain quality are comparatively more expensive and intelligent with self-healing capabilities. Voltage and current are analog signals, with the power being an instantaneous product of the two. A challenge faced by most engineers is choosing the right type of sensors and converting the analog waveforms accurately for processing with digital computers.
The measuring devices in high-end meters now rely on the frequency-domain analysis, in addition to time-domain parameters calling for high-end digital signal processors (DSPs), and generally reside in substations and power plants. If the quality of service is maintained, the focus shifts to the transmission, where emphasis is given to loss minimization, continuity of service and intelligent load management.
Once the power is available for consumption in buildings, the meters are less complex and form two sets of metering spaces called utility metering and sub-metering. Depending on the load that needs to be serviced and the region’s grid structure, the energy is available as 3-phase or 1-phase.
Meters measuring energy outside are utility meters and inside are sub-meters. Utility meters always involve billing by monetary means, whereas sub-meters rarely involve money. Irrespective of the meter type, the measuring parameters include voltage, current, power factor, active/reactive power and energies, and the ability to track time-stamped usage.
The expected accuracy of utility meters is much more stringent (usually within 0.5 percent to 0.1 percent error) than sub-meters (within 1 percent to 2 percent). Sub-meters have forayed into the metering market in plugs, power strips, power supply equipment, appliances, circuit breakers, and more. Texas Instruments has a large and growing portfolio of metrology chips that support the different measurement technologies, 1-3 phases and accuracies.
Without communication, the energy usage of appliances such as HVAC systems, dryers, heaters and plug-in electric vehicles is unknown to utilities and energy customers.
Communication enables the consumer and utility to gather information in real-time and allows utilities to ease energy usage within the capacity of their power grid. This also permits data to be consolidated within residences, multi-dwelling structures or industrial facilities. Wireless connectivity technologies such as Wi-Fi (IEEE 802.11) and ZigBee (IEEE 802.15.4) RF mesh networking have become popular alternatives in the past several years.
These operate in the 2.4GHz ISM band and at 900MHz. There are other technologies, such as wireless M-Bus, that operate at frequencies around 170MHz. There is currently wide deployment of RF mesh technology in smart meters, especially in urban areas where residences are closely spaced.
Wireline communication for smart grid applications uses power line communication (PLC) technology to exchange data over existing power lines. To achieve cost effectiveness without using repeaters, transmission distances on outdoor power lines should be at least 2km, and reliable transmission through distribution transformers outside residences is sometimes necessary.
Communication between 10Kbps and 100Kbps is necessary for demand response applications and meeting latency requirements of applications such as PEVs.
The PLC technology that best meets global broad application needs and cost effectiveness is narrowband OFDM (orthogonal frequency division multiplexing), which has become very popular over the past decade. Digital HDTV, 4G LTE cellular, WiMAX and Wi-Fi are examples of networks that use OFDM to achieve robustness, cost-effectiveness, and scalability.
TI is testing smart grid technologies around the world and understands the unique requirements within each country, offering chipsets and a technology roadmap that enable rapid smart grid deployments.