Arcane technical standards play key role in solar power’s future

Source: Peter Behr, E&E reporter • Posted: Monday, September 29, 2014

For all their environmental bad marks, U.S. coal-fired power plants have been good citizens of the grid, their engineers are quick to say, rapidly and dependably adjusting output to keep power in balance and flowing.

Now, as wind farms and distributed solar power spread, so must sophisticated electronic devices that will have to help take over the essential stabilizing role of retired coal plants.The PJM Interconnection, for example, which operates the high-voltage grid in the Mid-Atlantic and eastern Great Lakes region, expects older coal-fired power plants with a total of at least 26,000 megawatts of capacity to retire in coming years because of environmental regulation. “They have been the mainstay in terms of frequency control,” said PJM Chief Executive Terry Boston, speaking of the iron-clad requirements in synchronized grids to align generators’ output extremely tightly.Their successor will be the “smart” inverter, a device of circuitry and software whose basic job is to convert direct-current power from renewable generation to alternating current.

The smart versions can do much more, smoothing threatening voltage and frequency spasms and giving grid operators more fine-tuned control. And they can manage “reactive” power — the illusive, essential electromagnetic property that is required for energy to flow along power lines.

But if smart inverters are essential to the grid’s future, their timely deployment is anything but certain, Boston and other industry executives say.

That will require changes in the technical standards that specify the performance of these devices, and the issue is whether the deliberate standards development process can keep up with the need for the devices. If not, the high-voltage grid may become more vulnerable to blackouts, according to Boston and a task force of the North American Electric Reliability Corp., the high-voltage grid’s security regulator.

“To keep the electrons moving and the system stable while we are integrating renewable resources, we need to have dynamic voltage control and dynamic reactive power sources,” said Massoud Amin, a professor of electrical and computer engineering at the University of Minnesota and a leading authority on smart grid technology.

“That’s where smart inverters kick in. They enable solving exactly these problems and technical issues,” he added.

“We have the technology. It is investments that have to be made in order to bring them into fruition, actually integrating them into the system, and creating [technical] standards for interconnection,” Amin said in an interview.

Lessons from Germany

Germany, which has drawn as much as half its electricity on weekends from photovoltaic solar units, has had to rush ahead with a $300 million retrofit, replacing basic inverters with smart ones to ensure stability of its grid.

But widespread deployment of smart inverters in the U.S. won’t occur until the industry’s arbiter of technical standards, the Institute of Electrical and Electronics Engineers (IEEE), works out new design specifications that take into account the dramatic changes underway in the grid, Amin and Boston agree.

“The inverter, from a technology perspective, is there, but we don’t have a consistent standard for manufacturing,” Boston said in an interview. “It’s going to take a couple of years probably to make the modifications we need.”

IEEE standards, developed through a highly respected, painstaking consensus process among utilities and equipment vendors, are voluntary but highly influential.

The standard at issue, IEEE 1547 — “Standard for Interconnecting Distributed Resources With Electric Power Systems” — defines specifications for equipment that is connected to the lower-voltage utility distribution networks. Three-quarters of the states have adopted or referenced IEEE 1547 in their utility regulations, and the Energy Policy Act of 2005 also cited it.

If rooftop solar units — distributed energy resources (DER) in regulatory parlance — continue to expand, the current 1547 standard may not adequately protect the high-voltage grid in worst-case scenarios, according to the report by the NERC task force.

In fact, unless mandatory changes are made, the 1547 specifications could actually increase the risks of widespread, cascading power blackouts “over large areas of the interconnected system,” the NERC report says. “Existing interconnection requirements for DERs do not specifically take into account potential effects on bulk [high-voltage transmission] system reliability,” the report continues. Shocks that start in the transmission grid could trip solar installations, sending new shocks back into the grid, it concludes.

The issue has led some industry leaders to call for fast-track changes to the standard.

“The whole concept of speed, how we enable the standards to make this happen, has to change completely from what we’ve been able to do to this point,” industry executive Chris Curtis told an IEEE conference earlier this year.

“The pace of innovation is not going to slow down, so we’ve got to adapt. Anybody who touches these standards bodies needs to understand that, needs to push themselves to have a greater sense of urgency,” added Curtis, then the North American chief executive for Schneider Electric and now a leader with the major electric equipment manufacturers group.

Boston said, “The risk is too great not to do something” to create requirements for frequency and voltage control in the emerging grid environment. “Going through a long period [of standards review] is troubling to me.”

Boston said he means no disrespect to the standards committee. “I do know it is something that has to move.”

IEEE standards leader Dick DeBlasio defends the process. As chief engineer and principal laboratory program manager at the Energy Department’s National Renewable Energy Laboratory, DeBlasio led a fast-track development directed at smart meter security, and he bristles at any inference that the review of 1547 isn’t moving expeditiously.

Last year, he announced plans for a “comprehensive refresh” of 1547, to be completed by 2018, and emphasized in a recent interview that updates have already begun.

Many grid operators “tend to always want more, and those concerns are being looked at by many experts on our [IEEE] working group,” DeBlasio said in an interview, noting the group’s comprehensive industry and government membership.

He added, “We are now conducting a full revision in looking at the interconnection and relative interfaces such as communications.”

He said he agrees on the need to accelerate the standards process, “but there are protocols we must follow.” Those who want to speed the process should come to the IEEE meetings and help speed it up, he said.

Seeking more tolerant inverters

According to the NERC report, 1547 needs to reflect the risk that disturbances on the transmission grid will cause an automatic, simultaneous shutdown of inverters that takes out a potentially large number of solar units. The loss of those DER units could send a new shock wave reverberating back into the transmission grid, FERC said, heightening risks of a chain reaction.

However, smart inverters can be programmed to respond in random ways — some faster, some slower — when voltage or frequency veers outside permitted limits. That would help cushion the impact and prevent a drastic “cliff edge” loss of DER power, experts say.

A standard that provides such tolerance for disturbances “is a required element to prevent cascading outages” following voltage or frequencies spikes, even those that occur during normal system operation, the NERC report said.

The capability is called voltage ride-through and frequency ride-through, or, more colorfully, a “droop” function that delays equipment shutdown, giving conditions more chance to stabilize. German codes now require a “droop” capacity in smart inverters.

“As written initially, in 2003, IEEE 1547 did not permit what we consider low voltage ride-through,” said Ben York, senior project engineer at the Electric Power Research Institute in Knoxville, Tenn.

A recent amendment to 1547 “allows for that flexibility but doesn’t require it,” York said.

“Normally,” Boston said, “when you’re trying to move a standard forward, someone’s technology is ahead. Everyone wants you to adopt their particular design as the standard.”

“Without strong interconnect standards — an international standard — there is no real motivation to have the same design criteria [for] all manufacturers and all installers,” he added. But a patchwork of different standards that apply in some places but not others won’t ensure the necessary deployment of the technology, he said.

At the IEEE conference, Curtis appealed to manufacturers, contractors, distributors, utilities, operators — “all of us that touch this industry” — to come together around the need for new rules. “We, more often than not, work at things separately. We have to coalesce as an industry.”

“Making standards is a thankless job,” Amin said. “Sometimes it takes seven to 10 years.

“When there is an urgency like this, it can be done by having very seasoned, highly regarded, committed people at the helm who are working, integrating feedback, drafting, getting comments, then getting the consensus and making it the new standard,” Amin added.