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Smart Grid evolution from power line components to electric cars

By Steve Ohr, Consultant, Semiconductor Industry Analyst

The Goal of Smart Grid deployments do not just decentralize the distribution of power generating stations, but also increases the communications intelligence that enables greater levels of power monitoring and control, recognizing electric vehicles as energy sources — as well as energy consumers — in the distribution.

 

Western nations of the world are extraordinarily fortunate in the ability obtain electricity 24 hours per day, seven days per week — at very little cost. The units of electric power consumption (kilo-watt hours, kWh) are becoming highly commoditized, if not entirely free. At 12-to-13 cents, residential consumers can afford to buy kWh in bulk. (See https://www.eia.gov/outlooks/steo/ for energy prices.) But the ready availability of electricity should not be taken for granted: The advent of the Smart Grid actually forces us to make decisions as to what lives on the Smart Grid, and what makes a good citizen of that community.

Smart Grids can be visualized as the offspring of two marching armies: Ever more efficient power transmission technologies, and long-reach communications. On one march, you’ll see work on energy generation components — 650 V MOSFETs, 1,800 V switches and diodes, and newer work on large-scale energy storage technology. On the second march, you’ll see improved communications technologies — more Supervisory Control And Data Acquisition (SCADA) networks and access points, and IEC61850 electrical subsystem protocols.

 

What makes a grid “smart?”

It is in fact the two-way communication between the utility companies and their customers — supported by sensing in the power transmission path — that makes the grid intelligent. Like the Internet itself, the Smart Grid is made up of computer access points with bidirectional on- and off-ramps.

A check list for Smart Grid reflects the requirements managing a Smart City. Demand for services and commodities (e.g., electricity, natural gas, gasoline, water, waste. treatment, transportation).

It is the communications capability that enables granular monitoring of Smart Grid components, and swift response to network fault conditions

 

 

Because of their potential impact on real service providers, Smart Grid infrastructure providers like RAD, Schneider Electric, Siemens, Cisco, and IBM, to name a few, would add talking points (like analytic data services). ABB’s focus on smart cities, for example, streamlines energy monitoring and usage for residential and business customers.

These vendors would add additional march lines to the definition of “Smart:” These include “automation,” the ability for computing machinery to sense and control remotely without human intervention. The companies see a convergence of operational technology (OT), where computers control manufacturing machinery, or autonomous vehicles with information technology (IT), where data is produced for external analysis and consumption.

SECURITY becomes a major concern for Smart Grid contractors and service providers, and — even before the invasion of the Wanna Cry ransomware attacks — it heads the list of care-abouts among electric utility companies compiled by RAD. RAD provides global telecom access products. Its substation vendor survey indicated the utilities’ intent to implement SCADA-compliant monitoring and control.

The implementation of SCADA secure networks is supported by U.S. government white papers. The benefits associated with the Smart Grid stem from its granular structure. A power fault can disrupt electrical service, but if the fault occurs in the Smart Grid network, the granular structure allows that fault to be isolated, and the extent of the damage to be minimized.

Smart Grids will also manage peak demand scenarios, and smooth the integration of renewable energy systems (e.g., solar and wind) The convergence of IT and OT affects banking, communications, traffic management, and security. A smarter grid will add resiliency to the electric power system and making it better prepared to address real-world emergencies such as severe storms, earthquakes, brush fires and terrorist attacks.

 

Weighing the contribution of electric vehicles

Ideally, the Smart Grid should facilitate the attachment of energy sources as well as energy consumers. These would include solar energy sources or wind farms, as well as plug-in electric vehicles (PEVs).

The main feature of PEVs is not their zero-to-sixty acceleration, but their fossil fuel economy. Their batteries are typically charged by electricity produced by power plants burning fossil fuels. The charging typically takes place in a residential facility, at night to implement off-peak power consumption.

The energy transfer efficiency from the grid to the PEVs’ wheels is about 59%–62%. Conventional gasoline-powered vehicles have a 17%–21% conversion efficiency.

The energy transfer efficiency from the grid to the PEVs’ wheels is about 59% – 62%. Conventional gasoline-powered vehicles, in comparison, have a 17% – 21% conversion efficiency. Surplus battery energy, not consumed by the vehicle, can be sold back to the Grid.

 

 

But the impact of electric vehicle charging on the Grid is not insubstantial, charged at home, presumably at off-peak hours, PEVs will nonetheless make significant demands on the Smart Grid infrastructure — up to 30 kW for an all-electric Nissan Leaf (or 32 kW for a Tesla Sedan) — per 100 miles of driving. (See, How much does it cost to charge an electric car?)

In the future, PEVs and charging stations may play an important part in balancing the energy on the grid by serving as distributed sources of stored energy (like flow batteries), a concept called “vehicle to grid.” Grid management can inject the energy accumulated this way back onto the Grid to bolster peak requirements, or avoid brownouts or rolling blackouts. They could also help integrate variable power sources into the grid, including wind and solar power. Financial incentives may be available for PEV owners, that allow their car batteries packs to be used this way — as much as one Euro per kWh, speculates Dr. Martin Schulz, Principle in Applications Engineering for Infineon Technologies, and a frequent contributor to the literature on Smart Grids

 

The first march: Enabling a charging infrastructure for PEVs

One of the key factors for consumer acceptance of PEVs will be the availability of charging stations. Currently, a small number of companies (some supported by the U.S. Department of Energy) are deploying charging stations in cities throughout the United States.

There are market scenarios, Martin Schulz foresees in which the consumption of energy is commoditized, if not entirely free, accounted for the same way as kilobytes passed by your mobile phone. But with PEVs gaining market penetration, this “free refueling” is likely to come to an end, and charging station owners will be seeking convenient ways to charge electric car owners for their “fill-ups.” It is likely that charging stations would accept credit cards to pay for the charge.

Infineon, has arguably the largest portfolio of semiconductor components supporting the construction of Smart Grids. The list of semiconductor company power management device makers includes NXP, STMicroelectronics, ON Semiconductor, and Texas Instruments. Most of these companies’ Smart Grid components focus on Smart Meters and Power of LAN Communications (PLC) controllers. Power Integrations is also in the market, aggressively pursuing high-voltage gate drivers for inverters.

Infineon’s product line includes high-current/high-voltage power semiconductors and modules for interfacing a wide variety of inverters. Infineon makes a variety of power modules and semiconductors designed to serve charging station inverters. The 600 and 650 V 3-Level NPC-1 portfolio from 30 A to 300 A.

There are several different topologies widely used. For photo voltaic solar cells, the inverters can accommodate serial strings or parallel cells with higher current outputs. Infineon products supporting Smart Grid deployments include 650 V CoolMOS-Series FETs, parallelized for ultra-low on-resistance RDSON. Thermal Interface Material (TIM), a heat-transmissive material, designed to significantly streamline thermal dissipation between semiconductor devices and their heat sinks. Silicon carbide semiconductors, with fast recovery diodes, can reduce dynamic losses by as much as 80%. These products, Schulz reminds, offer the possibility of increasing the switching frequency of inverters and power supplies. In addition to incremental improvements in efficiency, higher switching frequencies enable smaller filter components, including transformers, and a smaller cooling requirement.

The almost universal focus on increased efficiency has diminishing returns, says Dr. Schulz. What is the savings of 99% efficiency vs. 98%, he asks. The extra 1% efficiency may not justify the cost, he suggests — unless you’re calculating the cost of running an electric bus fleet.

“Where the Smart Grid charges 10,000 electric car batteries,” Dr. Schultz says, “You make a number of component tradeoffs, just to elevate energy transfer by 1%. You parallel MOSFETs to reduce on-resistance (RDSON) and increase output current – but higher current modules cost more, and designers of the Smart Grid may opt for toward greater product life, which is now edging toward 15 years or more.” Where markets are cost driven they’ll use discrete solutions of separate diodes and transistors (SiC and/or CoolMOS ) in designs up to 10 kW — rather than more integrated modules.

 

 

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