IEEE Power & Energy Magazine - September/October 2019 - 43

✔ Merchant DERs (or independent power producers)

✔

are third-party provider assets directly connected to
transmission, subtransmission, or distribution systems
providing services directly to the grid that require direct control and an information interface with grid operations. This is necessary given the anticipated size
of merchant resources.
DER aggregators refer to grouping customer assets to
provide services to the grid. For aggregated DERs, the
Hawaiian Electric Companies do not believe it is necessary to directly control each resource. Rather, we
expect to establish and secure an operational interface
with each aggregator to share operational instructions
and appropriate information.
The Hawaiian Electric Companies DER/DR programs
indicate where customers participate in the Hawaiian
Electric Companies' efforts. For programs that the Hawaiian Electric Companies manage, direct interface
with and control of those devices may be needed.
New autonomous operation indicates customers with
advanced inverter DERs who choose not to participate
in an aggregator or utility program. Establishing operational standards for DERs, such as IEEE 1547-2018,
will enable autonomous functionality of DER advanced inverters that will not adversely affect the grid.
In 2016, the Hawaiian Electric Companies updated
their interconnection requirements to include portions
of IEEE 1547-2018 and will continue to harmonize the
interconnection requirements with this standard.
Legacy operation refers to pre-2016 inverter DERs
without advanced inverter functionality capabilities
such as the expanded frequency and voltage range
ride-through. Legacy DER systems will not be directly managed but may require additional investment,

especially at the bulk system level, to account for their
impacts as more DERs are integrated into the grid.
In addition to the normal operational controls described
previously, alternative means of controlling the amount
of power being exported to the grid under abnormal circumstances that threaten grid reliability and stability are
needed. One of the current challenges in accommodating
DERs at the system level is that the amount of active power
fed in is not visible to or controllable by the grid operator. In the event of an excess generation event at the bulk
system level or other conditions that endanger the safety
or reliability of the grid, other resources must be adjusted.
Due to physical operating range limitations of central generators, this needed flexibility may not be possible beyond
a certain limit: that is, each island grid has a systemhosting capacity.
When generation and load are not in balance and available controllable generation is at its minimum output, the
system operator will require that DERs be visible and controllable to maintain grid reliability and stability. If supply
and demand cannot be quickly balanced, system frequency
could deviate from normal operating ranges, which, in extreme
circumstances, could result in an island-wide blackout exacerbated by the loss of legacy DERs with inverters that trip
out of service in response to system frequency or voltage
excursions during these events. This is a situation somewhat
unique to island grids such as Hawai'i's.
To address system reliability in the near term while DER
interoperability matures, the Hawaiian Electric Companies
are taking a multipronged approach beyond the normal
operational controls described previously to enable backup
control of DERs.
✔ Advanced second meter for DERs: A separate, second advanced meter is used as a metering point for

HECO Bulk Power
System Operator

HECO Distribution
Operator

DER Aggregators

HECO DER/DR
Programs

New Autonomous Operation

Merchant DER
Grid Connected

Legacy Operation

figure 2. The model for layered DER control. HECO: Hawaiian Electric Companies.
september/october 2019

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IEEE Power & Energy Magazine - September/October 2019

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