IEEE Power & Energy Magazine - July/August 2017 - 48

ieee power & energy magazine

Cross-Layer Connectivity Functions

Layer-Specific Functions or Applications

(VVO) application, the DMS can
make use of its monitoring and
forecasting group functions to
DMS
evaluate the present and foreDMS Applications
casted support capability of a
Volt-VAR Optimization (VVO)
given microgrid. This information
Fault Location, Isolation, and
is used as input to the VVO optiDER Group Functions
Service Restoration (FLISR)
mization engine that determines
Status Monitoring
On-line Power Flow (OLPF)
how to best leverage the support
Output Forecasting
Other Applications
capabilities available from the
Max Real Power Limiting
microgrid to help meet the VVO
objectives. The desired settings
Real Power Dispatch
can be set points or ranges and
Reactive Power Dispatch
relate to the real and/or reactive
Microgrid Controller
Connect/Disconnect
power exchanged at the microgrid
Core Control Functions (IEEE p2030.7)
POI. Once the desired settings
Dispatch of Microgrid Assets
DER Device Functions
have been determined, the DMS
Transition Grid-Tied <> Islanded
sends a corresponding support
Status Monitoring
request to the microgrid controller
Output Forecasting
through use of the maximum reacFixed PF
tive power limiting real power
Volt-VAR
dispatch, and/or reactive power
Volt-Watt
DER Devices
dispatch group functions (see FigOther Functions
Device-Specific Control Functions
ure 6). The microgrid controller
disaggregates this DMS request
into specific set points assigned to
figure 6. A comparison between functions and applications internal to each control
each of the DER assets it manages,
layer and functions enabling connectivity between control layers.
using the dispatch core function.
Finally, the DER device functions
can
be
used
to
communicate
the individual set points to the
can send the other a request for executing a planned transition at a certain time. When agreement is reached between DER assets, and each asset responds by executing its own
the two, the microgrid controller initiates islanding or re- internal control functions accordingly.
connects at the time agreed upon with its two core control functions, transition and dispatch, as defined in IEEE Enterprise-Level Integration
P2030.7. This involves executing a series of internal control Finally, the topology of an integrated system is shown in
steps to bring the voltage, phase, and frequency at the POI Figure 7 with the DMS, DERMS, DERs, and microgrid conwithin certain limits specified by the distribution system. trollers working together along with other management, a
Unplanned islanding is different; it is triggered automati- geographic information system, and an outage management
cally by abnormal conditions at the POI without any prior system. All of these systems integrate at the enterprise level
communication between the microgrid controller and DMS. and also require interface specifications through standards
The distribution system operator may require the microgrid like the Common Information Model. In a system where
controller to report any unplanned islanding events to the microgrids are present, a microgrid controller is used to
DMS to facilitate the execution of contingency actions for manage the DERs within it. The prediction of DER output
the distribution system.
power can be done by either the microgrid controller or the
When grid tied, microgrids have potential to provide grid DMS. A microgrid controller can communicate directly with
support to the distribution system to help maintain grid reli- DERs or through a DERMS to DERs within the microgrid.
ability or rectify abnormal grid conditions. The DMS speci- A microgrid controller can also communicate directly with
fies and coordinates the type and level of support requested the DMS or through a DERMS to the DMS. The architecfrom the grid-tied microgrid. To that end, the standardized ture for integrating a DMS with microgrid controllers and a
DER group functions enable the DMS and microgrid con- DERMS needs to be considered in the context of the specific
troller to exchange information on current and forecasted DMS applications that interact with these systems. Many of
grid conditions as well as the microgrid capacity to pro- these applications will also require interfaces with other
vide support. DER group functions also enable the DMS enterprise-level systems. This becomes part of an overall
to send specific support requests to the microgrid control- systems level specification for the microgrid controller and
ler. For example, when executing its volt-var optimization its required interfaces.
july/august 2017

Table of Contents for the Digital Edition of IEEE Power & Energy Magazine - July/August 2017