Distributed solar installations in California and Hawaii were often delayed or even stopped a few years ago due to voltage issues on circuits. But since both states began requiring smart inverters for new distributed solar, that problem has all but disappeared.
That’s because smart inverters can regulate voltage, and are configured to do so in both states. Smart inverters can also provide other grid services, setting the stage for customers to be paid for those services.
Recognizing the benefits, three other states will soon require smart inverters for new distributed solar and storage, and nine more have an open inquiry or docket to consider smart inverters.
Before smart inverters were required in California, each new solar installation on a distribution circuit would “nudge voltage up slightly,” said Brad Heavner of the California Solar & Storage Association. Once a circuit reached a certain level of solar installations “it became a grid issue” often resulting in a PV project delay or stoppage.
Now, not only are new PV systems in California not causing a problem, “they’re correcting any existing grid problems with voltage rise,” Heavner said. “I haven’t heard any complaints about voltage rise in at least a couple of years.”
Echoing his observations was Rocky Mould with the Hawaii Solar Energy Association, who said that voltage issues there once caused interconnection delays of more than a year and “potentially thousands of dollars of upgrade costs.” But now with smart inverters, “to our knowledge, no customer has been required to pay for a utility upgrade in nearly three years.”
While smart inverters in the two states provide voltage control autonomously through the “volt-var” function specified by regulators in each state, Heavner also said he looks forward to the communications-enabled functions of smart inverters.
For example, California has 690 MW of customer-sited energy storage. Heavner said that represents “a huge virtual power plant that can be tapped into at any time.”
Distributed battery storage could be directed to provide energy to the grid either by utility distributed energy resource management (DERM) systems, he said, or through aggregators “like the inverter companies, that are responding to price signals as they manage fleets of batteries.”
Heavner said that one approach using smart inverter capabilities could be opt-in dynamic pricing for customers that are set up to respond to pricing that changes every hour of the year. Another approach could be an emergency response program, whereby the independent system operator CAISO could issue a signal when “supplies are super tight, then everyone can discharge their batteries and get compensated for it.”
Likewise, the Hawaii Solar Energy Association and allied groups, said Mould, want customers who own solar and battery storage to be compensated for providing energy on an emergency response basis.
Mould would also like all customers with smart inverters to be eligible to provide frequency response grid services, and to be compensated for doing so.
Smart inverter adoption
Next year California and Hawaii are expected to adopt the smart inverter standard IEEE 1547-2018. Minnesota, New York, Maryland, and the District of Columbia also plan to adopt the IEEE standard. In nine other states, the utility regulatory body either had an inquiry or an open docket regarding the smart inverter standard, according to the Electric Power Research Institute.
Each state that requires smart inverters for new distributed solar and storage will also consider which autonomous inverter settings should be activated. A new document from the National Renewable Energy Laboratory details the smart inverter settings for voltage control that are available in inverters compliant with IEEE 1547-2018, as well as the different functions of each setting. These voltage control settings are commonly known as volt-var, volt-watt, and watt-var.
Where there are major voltage problems in California, Heavner said that smart inverters can be directed to provide even more voltage support. That could make a big difference in locations where new voltage stabilization equipment otherwise would be required. With smart inverters “everywhere,” Heavner said, the devices could provide voltage support where it’s needed, and quickly.
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The real metric they should use is local voltage which would indicate load, stress both locally and in the grid and react faster and less need for central control. And where the massive numbers of EVs with V2G need price signals as well as home, building generation, storage both battery and
heat/cold. Since so many of these as so low cost, in 10 years will be the majority of grid storage, on-demand generation.
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