New-Tech Magazine Europe | Dec 2015 Digital edition

Figure 4: STMicroelectronics power supply reference design for smart-metering applications.

Figure 3: Schematic for IEC 61850 Gateway illustrates requirement for multiple-voltage regulators. (Courtesy of Texas Instruments)

The IEC 61850 Gateway forms a key part of this communication system and again TI has stepped in with chips designed to make the power supply for these products easier to develop. The gateway will likely require multiple power-management chips to deal with multiple AC and DC inputs. Figure 3 shows a schematic with a selection of voltage converters including a 24/48VDC input/5 VDC output switching regulator, a 230VAC input/5 VDC output switching regulator and 5VDC input/multiple DC output low-drop-out linear regulator (LDO). Another option for gateway power is a power management IC (PMIC) such as the TI TPS69510. The PMIC can accept 5 V Li-ion battery power and provides three step-down (“buck”) converters, one boost converter, and eight LDOs, and is designed to support the specific power requirements of OMAP-based applications. The eight general-purpose LDOs power the OMAP-based processors, power to other devices in the system, and power to DDR memory supplies in applications requiring these memories. Managing consumption Consumers become familiar with the concept of smart grids when utility maintenance crews arrive at their home to replace antiquated meters with intelligent units. According

AC and DC inputs (24 to 250VDC or 88 to 276VAC) and provides a 15V, 800mA (12 W) output from a 100 by 100 mm form factor (making the power supply suitable for protection relays that have to be housed in compact housings). The power supply uses a two-stage converter topology comprising a DC- to-DC step-up (“boost”) regulator designed around a TI TPS40120 current-mode controller which forms the input to a quasi-resonant flyback converter designed around a UCC28740 pulse-width-modulation (PWM) controller. The output of the flyback converter forms the 15 V, 0.8 A output from the power supply. Enabling interoperability In conventional electricity distribution grids, infrastructure is operated in isolation and without gathering any information about grid performance or the cause of faults. Full implementation of a smart grid requires these “dumb” devices to be replaced with Intelligent Electronic Devices (IED). In addition to performing essential electrical tasks such as transforming voltages, redirecting energy flows, and isolating sections of the grid in the event of faults, IEDs constantly monitor voltages, currents, power quality, and

other parameters that can affect grid performance. This information is passed between IEDs (such that they can be automatically activated to correct abnormal grid operation) and back to operators (who can then quickly respond to peaks and troughs in demand or outages) via dedicated communication channels. These communication channels provide rapid and reliable transmission of information and rely on wired- and wireless-technology and Internet, Ethernet, industry standard, and proprietary protocols. The electricity distribution industry is working hard to adopt a communications standard to enable interoperability between the disparate elements of an electricity grid. The favored standard is IEC 61850, which is already established for communications in electrical substations. IEC 61850 is now being extended beyond the substation to the Intelligent Electronic Devices (IED) that make up smart grids. IEC 61850’s strength is its ability to rapidly exchange data yet preserve the original meaning of the information. As such, the standard promises to markedly enhance communication between, and coordination of, smart- grid infrastructure.

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