April 24, 2014

`Smart’ Inverters May Give Solar Reactive Capability

Fearing a potential shortage of reactive power, PJM last week won stakeholder support for an initiative to consider requiring that renewable resources add technology capable of providing grid support.

The Planning Committee meeting gave near unanimous approval to a problem statement and issue charge to explore whether to require renewables such as solar PV to install  enhanced or “smart” inverters that can produce and absorb reactive power in addition to inverting DC power to AC. Reactive power (vars) is required to maintain the voltage to deliver active power (watts) through transmission lines.

With the increasing amount of renewables, which do not provide reactive support, and the retirement of large traditional generators that do, “there’s a need for additional reactive support to avoid voltage problems,” said PJM’s Frank Koza.

“This is not a here-and-now problem for PJM, but something we should look at to see what the cost and benefit is,” he said.

Koza told the committee that running additional conventional generators for reactive support is not cost effective and could cause negative Locational Marginal Prices. Adding static VAR compensators is cost prohibitive. Neither address frequency issues, he said.

smart inverter with reactive power ability (Source: SMA Solar Technology AG)

smart inverter with reactive power ability (Source: SMA Solar Technology AG)

Renewable power generators in Great Britain and Germany are already using smart inverters to improve grid reliability. Smart inverters can allow renewable generators to stay on line despite low voltages and fluctuating frequencies and reduce the “flicker” that can occur with solar generators on days of mixed sun and clouds, Koza said.

One question to be addressed in the inquiry will be whether smart inverters should be installed on existing equipment, or only required on future installations. (Currently installed smart inverters have their reactive capabilities disabled.)

The Planning Committee plans to develop technical standards for inverters along with related Tariff, Operating Agreement and manual changes. Koza said he hoped work could be completed in time for a FERC filing in August.

One Response to `Smart’ Inverters May Give Solar Reactive Capability

  1. […] The committee will be asked to approve a problem statement and issue charge to explore whether to require renewables such as solar PV to install “smart” inverters that can produce and absorb reactive power. With the increased use of renewable generation and retirement of many large traditional generation units, the need for reactive support is becoming increasingly important. (See `Smart’ Inverters May Give Solar Reactive Capability.) […]

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