The subcycle overvoltage condition describes the electrical generation fault mode that is associated with the

inverter-based resource An inverter-based resource (IBR) is a source of electricity that is asynchronously connected to the electrical grid via an electronic power converter ("inverter"). The devices in this category, also known as converter interfaced generation (CIG) a ...

s (IBR, like

solar photovoltaics Photovoltaics (PV) is the conversion of light into electricity using semiconducting materials that exhibit the photovoltaic effect, a phenomenon studied in physics, photochemistry, and electrochemistry. The photovoltaic effect is commercially ...

and

wind turbines A wind turbine is a device that converts the kinetic energy of wind into electrical energy. , hundreds of thousands of large turbines, in installations known as wind farms, were generating over 650 gigawatts of power, with 60 GW added each y ...

) and can cause a massive and instantaneous loss of

electricity generation Electricity generation is the process of generating electric power from sources of primary energy. For electric utility, utilities in the electric power industry, it is the stage prior to its Electricity delivery, delivery (Electric power transm ...

. When the overvoltage condition is detected, the IBR devices self-protect by disconnecting from the grid and can only come back online once the voltage returns to the design limits. In the meantime, a

cascading failure A cascading failure is a failure in a system of interconnection, interconnected parts in which the failure of one or few parts leads to the failure of other parts, growing progressively as a result of positive feedback. This can occur when a singl ...

can be triggered due to lack of generation capacity that remains online. The typical fault scenario is two-stage: # A line-to-ground or line-to-line fault occurs on a transmission line far away from the generator. This condition, if short-lived, is not very unusual. The inverter electronics cannot tolerate the resulting low-voltage condition and enters the " momentary cessation" (MC) mode where the unit stops providing the power but remains connected to the grid; # Once the fault clears, the line voltage might briefly reach very high level, exceeding the 1.3 pu that was required by older design specifications (in 2022, per IEEE 2800-2022, the tolerance was upped to 1.8 pu). Due to the overvoltage, the IBR disconnects ("trips") and can only join the grid once the power line conditions become normal again. The problem was accidentally exacerbated by a requirement to have a

shunt capacitor Two-terminal components and electrical networks can be connected in series or parallel. The resulting electrical network will have two terminals, and itself can participate in a series or parallel topology. Whether a two-terminal "object" is a ...

across the connection terminals of an IBR. This feature was expected to provide the

reactive power In an electric circuit, instantaneous power is the time rate of flow of energy past a given point of the circuit. In alternating current circuits, energy storage elements such as inductors and capacitors may result in periodic reversals of the ...

support to the grid (the typical inverter is designed for a

unity power factor In electrical engineering, the power factor of an AC power system is defined as the ratio of the ''real power'' absorbed by the load to the ''apparent power'' flowing in the circuit. Real power is the average of the instantaneous product of vol ...

), yet after a short remote line fault it increased the overvoltage at the generator connection and contributed to the problem (the later designs followed the IEEE 1547-2018 standard and did not use the shunt capacitors in the MC mode). As a result,

solar Solar may refer to: Astronomy * Of or relating to the Sun ** Solar telescope, a special purpose telescope used to observe the Sun ** A device that utilizes solar energy (e.g. "solar panels") ** Solar calendar, a calendar whose dates indicate t ...

and

wind farm A wind farm, also called a wind park or wind power plant, is a group of wind turbines in the same location used to produce electricity. Wind farms vary in size from a small number of turbines to several hundred wind turbines covering an exten ...

s with older inverter modules had exhibited multiple farm-wide disconnections that were almost-instantaneous (quarter of the AC cycle). For example, in 2017 the Canyon Fire 2 incident took out 900 MW of solar capacity.

References

Sources

* * Electricity economics {{electric-stub