1 Impact of PEV as Load and Electric Storage on Distribution Operations
1.1 Brief Description
The objectives of this use case are to demonstrate that the distribution monitoring and controlling functions a) take into account the nearreal time behavior of the PEV as loads and as Electric Storage and b) have the needed input information for the close look-ahead times
reflecting the behavior of the PEV as loads and as Electric Storage.
The scope of the use case covers the collection of real-time information from large concentrations of connected PEV, from selected AMI
sites, and from aggregated PEV load and storage models dependent on observable inputs (e.g., time of day and week, etc.). These object
models will need to be developed based on processing data collected from PEV interfaces and AMI. These models will be updated with new
information collected from the mentioned sources. Therefore, a PEV Analysis System will need to be developed within the utility IT
systems. This system will need to be accessible by DMS and by the Aggregators. The information about the behavior of PEV as load and as
Electric Storage combined with the information about regular loads, loads with DR and DER will be used by DMS functions for
monitoring and controlling the operations of distribution and immediate transmission systems. The scope of the monitoring functions will
include the following analyses: loading of distribution elements, voltage deviations and voltage imbalances, load transfer capabilities, loss
components, dynamic voltage limits at the distribution and transmission buses, dispatchable real and reactive loads due to voltage and var
control, DR, DER, PEV, and ES, and aggregated load characteristics at the buses of the transmission EMS models. It will also include
monitoring the current reliability of the distribution system by running distribution contingency analysis periodically and by event. The
controlling functions will include Service Restoration, Voltage, Var, and Watt Control, and Feeder Reconfiguration.
The rationales of this use case are based on the fact that the PEV loads are different from other load by its mobility, more dynamic load
patterns, and the ability to be used as energy storage.
1.2 Narrative
The major advanced DMS functions to be used by distribution operations are as follows:
•
Distribution Operation Model and Analysis (DOMA)
•
Distribution Contingency Analysis (DCA)
•
Fault Location, Isolation, and Service Restoration (FLIR)
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•
Voltage, Var, and Watt Control (VVWC)
•
Feeder Reconfiguration (FR)
1.2.1 DOMA function
DOMA application is based on a real-time unbalanced distribution power flow for dynamically changing distribution operating conditions,
including demand response, electric storage, eclectic vehicles, and distributed generation. It analyzes the results of the power flow simulations,
checking the adequacy of loading, voltages, and current and voltage imbalances. The model is kept up-to-date by real-time updates of topology,
facilities parameters, load patterns and allocation (including PEV loads), and relevant components of the transmission system. In the look-ahead
mode, the application checks whether the scheduled or requested demand response, including PEV storage capabilities, may create adverse
operating conditions in distribution. Based on this assessment, the schedule or request for load and DER management may be altered or recalled.
The function runs periodically, by event, and on demand. The periodicity of the runs is in the range of 3-15 minutes.
The by event runs should start within one minute and be completed in one minute. The function consists of the
following sub-functions:
1.2.1.1 Modeling transmission/sub-transmission system immediately adjacent to distribution circuits
This sub-function provides topology and electrical characteristics of those substation transformers and transmission/sub-transmission
portions of the system, where loading and voltage levels significantly depend on the operating conditions of the particular portion of
the distribution system. The model also includes substation transformers and transmission/sub-transmission lines with load and
voltage limits that should be respected by the application. The transmission related information exchange is accomplished over the
EMS – DMS interface.
1.2.1.2 Modeling distribution circuit connectivity
This sub-function provides a topological model of distribution circuits, starting from the distribution side of the substation transformer
and ending at the equivalent load center on the secondary of each distribution transformer. A topological consistency check is
performed every time connectivity changes. The model input comes from SCADA/EMS, Distribution SCADA, from field crews, from
DISCO operator, from AM/FM/GIS, from outage detections by AMI, WMS, and OMS databases, and engineers.
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1.2.1.3 Modeling distribution nodal loads
This sub-function provides characteristics of real and reactive load connected to secondary side of distribution transformer or to
primary distribution circuit in case of primary meter customers. These characteristics shall be sufficient to estimate kW and kvars at a
distribution node at any given time and day and include the load shapes and load-to-voltage sensitivities (for real and reactive power)
of various load categories, as well as financial attributes. In real-time mode, the nodal loads are balanced with real-time measurements
obtained from corresponding primary circuits. A validity check is applied to real-time measurements. The load model input comes
from Distribution SCADA , from CIS and Behavior Databases for DR, PEV, and ES, supported by AMI, customer EMS, and
contractual agreements and linked with AM/FM/GIS, as well as from selected Smart Meters, from aggregators, and from weather
forecast systems. The PEV load models shall include the current loads, the availability and capacity of PEV as Electric Storage, the
contractual conditions of the electric storage use (capacity, duration, cost, etc.), and the estimates of short-term load forecast, for lookahead functions.
1.2.1.4 Modeling distributed energy resources.
This sub-function provides characteristics of real and reactive load generated by DER, connected to secondary side of distribution
transformer or to primary distribution circuits. These characteristics shall be sufficient to estimate the generated kW and kvars at a
distribution node at any given time and day and shall include the generation schedules for short-term look-ahead timeframes and
corresponding financial attributes. They also shall include capability curves. In real-time mode, the nodal generations are balanced
with real-time measurements obtained from corresponding primary circuits. A validity check is applied to real-time measurements.
The DER model input comes from Distribution SCADA, from CIS and Behavior Databases for DER, supported by AMI and linked
with AM/FM/GIS, from selected Smart Meters, from aggregators, from contractual agreements, and from weather forecast systems.
1.2.1.5 Modeling distribution circuit facilities
This sub-function models the following distribution circuit facilities for 60 Hz and higher frequency simulations:
1. Overhead and underground line segments
2. Switching devices
3. Substation and distribution transformers, including step-down/up transformers
4. Station, feeder, and LV capacitors and their controllers
5. Feeder series reactors
6. Voltage regulators (single- and three-phase) and their controllers
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7. LTC’s and their controllers
8. Distribution generators (synchronous and converter-based)
9. Power Electronic Devices
All facilities should be modeled with sufficient details to support the required accuracy of Distribution Operation Modeling and
Analysis application.
1.2.1.6 Distribution power flow
The sub-function models the unbalanced power flow including the impact of automatically controlled devices (i.e., LTCs, capacitor
controllers, voltage regulators) and Real Time Pricing (RTP), solves radial and meshed networks with multiple supply busses (DER,
Electric Storage).
1.2.1.7 Evaluation of transfer capacity
This sub-function estimates the available bi-directional transfer capacity for each designated tie switch. The determined transfer
capacity is such that the loading of a tie switch does not lead to any voltage or current violations along the interconnected feeders. The
transfer capacity analysis shall take into account the availability and cost of DER, DR, PEV, ES and Volt/Var control.
1.2.1.8 Power quality analysis
This sub-function performs the power quality analysis by:
1.
2.
3.
4.
5.
Comparing (actual) measured and calculated voltages against the limits
Determining the portion of time the voltage or imbalance are outside the limits
Determining the amount of energy consumed during various voltage deviations and imbalance
Recording the time when voltage violations occur
Summarizing and analyzing voltage quality parameters retrieved from AMI devices.
The power quality parameters will significantly change with the change of the amount and location of PEV loads and will also depend
on the use of this load – as load or as electric storage.
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The sub-function provides the ability to estimate the expected voltage quality parameters during the planned changes in connectivity
and reactive power compensation.
1.2.1.9 Loss analysis
This sub-function bases its analysis on technical losses (e.g., I2R, core, dielectric) calculated for different elements of the distribution
system (e.g., per feeder or substation transformer). For the defined area, these losses are accumulated for a given time interval (month,
quarter, year, etc.). They are further compared with the difference between the energy input (based on measurements) into the defined
area and the total of relevant billed kWh (obtained from CIS and AMI), normalized to the same time interval. The result of the
comparison is an estimate of commercial losses (e.g., metering errors and theft).
1.2.1.10
Estimates of voltage drop in the secondaries.
Based on the voltages measured by AMI devices and loads aggregated at the secondary buses of the distribution transformers, the
application will derive dependencies of the voltage drop between the bus and the customer terminals. These dependencies will be used
as an attribute of the object model of the LV equivalent in the DMS computing applications. The voltage drops in the secondaries will
significantly depend on the amount and location of the PEV loads.
1.2.1.11
Fault analysis
This sub-function calculates a bolted three-phase, line-to-line-to-ground and line-to-ground fault currents for each protection zone
associated with feeder circuit breakers and field reclosers. The minimum fault current is compared with protection settings while the
maximum fault current is compared with interrupting ratings of breakers and reclosers. If the requirements are not met, the message is
generated for the operator. The fault currents will change with the change of the amount and location of the electric storage.
1.2.1.12
Evaluation of operating conditions
This sub-function determines the difference between the existing substation bus voltage and the substation bus voltages limits. The
sub-function also estimates the available dispatchable real and reactive load obtainable via volt/var control, DER, DR, PEV, and ES.
Operator or other applications can use this information for selective load reduction. The sub-function provides aggregated at the
transmission buses operational parameters to be used in transmission operation models. These characteristics include: aggregated at
the buses load-to-voltage dependencies, remedial action schemes parameters, DER protection behavior, etc.
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1.2.2 Contingency Analysis
When there is a significant penetration of PEV with or without storage capabilities, the results of the contingency analysis may differ
depending on the amount and location of the connected PEV. On the other hand, for some contingencies, utilizing the capabilities of
PEV as electric storage in the supply (discharging) mode may reduce the number and/or duration of customer interruptions. The
application performs an N-m contingency analysis in the relevant portion of distribution. The function runs in the following manners:
1. Periodically
2. By event (topology change, load change, availability of control change)
3. Study mode, in which the conditions are defined and the application is started by the user.
The application informs the operator on the status of real-time distribution system reliability and prepares a list of decisions for load
restoration and the need in enabling the supply of electric storage.
1.2.3 Fault Isolation and Service Restoration
This sub-function running in near-real time may perform in two modes of operations:
1. Closed-loop mode, in which the sub-function is initiated by the Fault location sub-function. It generates a switching order
(i.e., sequence) for the remotely controlled switching devices to isolate the faulted section, and restore service to the nonfaulted sections. The solution may include enabling the available PEV as electric storage (as well as DER, DR, and other
ES) to support supply of loads connected to healthy sections of the feeder and avoid overloads of backup feeders. It may
also include the use of PEV storage capacity to temporarily supply a number of customers until a slower backup source
comes into service. The decision to use PEVs as a source of supply will be made based on the actual connectivity of PEV,
on the contractual conditions of their use, and on their current behavioral models. The commands for execution of the
switching order should be delivered over near real-time communications.
2. Advisory mode, in which the sub-function is initiated by the Fault location sub-function. It generates a switching order for
remotely- and manually-controlled switching devices to isolate the faulted section and for remotely- and manuallycontrolled switching devices and DR, DER ES, and PEV storage devices to restore service to the non-faulted sections. The
switching order is presented to operator for approval and execution
When work is completed, the sub-function is instructed to generate a switching order for restoration of the normal configuration. The
generated switching orders are based on considering the availability of remotely controlled switching devices, feeder paralleling,
creation of islands supported by distributed energy resources, and on cold-load pickup currents. The cold-load pickup may
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significantly depend on the behavior of the PEV loads during the repair time. Charging of some of the PEV used as electric storage
may be delayed to reduce the cold-load pickup current.
1.2.4 Voltage, Var, and Watt Control (VVWC) with DR, DER, PEV, and ES
The application calculates the optimal settings of voltage controller of LTCs, voltage regulators, Distributed Energy Resources, power
electronic devices, capacitor statuses, and may enable PEV electric storage means for optimizing the operations following current
objectives. The application takes into account operational constraints if both distribution and transmission operations, and, if so opted,
it takes into account real-time energy prices, when the objective is cost minimization. The optimization of voltage and var control is a
complex task, which requires a large amount if input data and a sophisticated algorithm. The task will become much more complex
and effective with significant penetration of DER, DR, PEV, ES, and power electronics.
The optimization is based on searching the best combination of controllable variables applied to the power flow simulations. The
power flow simulation with the best combination shall result in the optimal solution for the selected objective, respecting all imposed
operational constraints. Because of the complex inter-relationships between the controllable variables, loads and power flows, a
comprehensive operation model shall be used as a background of the VVWC application. This application is based on a real-time
unbalanced distribution power flow for dynamically changing distribution operating conditions, including loads depending on voltage,
demand response, electric storage, eclectic vehicles, distributed generation activities, and reactions of locally controlled distributed
intelligence schemes. The model is kept up-to-date by real-time updates of topology, facilities parameters, load patterns, and relevant
components of the transmission system.
The application, if so opted, shall also issue operational requirements to Demand Response means, to Electric Storage devices, as well
as to Electric Transportation installations in order to optimally achieve its objective. The application shall be able to utilize selected
AMI data directly from the Smart Meters, as well as from the typified object models updated by AMI information (Fig. 1).
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Setpoints
Integrated
Volt/var/Watt
Optimization
Setpoints/Statuses
LTC/VR
VAR
SOURCES
Updates
DR… Triggers
Distribution
Operation Model
DR/DER
PEV/ES
AMI
DR… execution
Critical points
Figure 1. Integration of Volt/Var/Watt Optimization with DR/DER/PEV/ES in Advanced DMS
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1.2.5 Multi-level Feeder Reconfiguration (MFR)
This application recommends an optimal selection of feeder(s) connectivity for different objectives. It supports three modes of
operation:
1. Closed-loop mode, in which the application is initiated by the Fault Location, Isolation and Service Restoration
application, unable to restore service by simple (one-level) load transfer, to determine a switching order for the remotelycontrolled switching devices to restore service to the non-faulted sections by using multi-level load transfers, demand
response, electric storage capabilities, including PEV, and DER devices.
2. Advisory mode, in which the application is initiated by SCADA alarms triggered by overloads of substation transformer,
segments of distribution circuits, or by DOMA detecting an overload, or by operator who would indicate the objective and
the reconfiguration area. In this mode, the application recommends a switching order to the operator. The switching order
may include using multi-level load transfers, demand response, electric storage capabilities, including PEV, and DER
devices.
3. Study mode, in which the application is initiated and the conditions are defined by the user.
The application performs a multi-level feeder reconfiguration to meet one of the following objectives:
a. Optimally restore service to customers utilizing multiple alternative sources. The application meets this objective by
operating as part of Fault Location, Isolation and Service Restoration.
b. Optimally unload an overloaded segment (load balancing). This objective is pursued if the application is triggered by the
overload alarm from SCADA, or from the Distribution Operation Modeling and Analysis, or from Contingency analysis.
These alarms are generated by overloads of substation transformer or segments of distribution circuits, or by operator
demand.
c. Minimize losses
d. Minimize exposure to faults
e. Equalize voltages
The last three objectives are selected by engineer/planner.
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1.3 Actor (Stakeholder) Roles
Describe all the people (their job), systems, databases, organizations, and devices involved in or affected by the Function (e.g. operators, system
administrators, technicians, end users, service personnel, executives, SCADA system, real-time database, RTO, RTU, IED, power system).
Typically, these actors are logically grouped by organization or functional boundaries or just for collaboration purpose of this use case. We need
to identify these groupings and their relevant roles and understand the constituency. The same actor could play different roles in different
Functions, but only one role in one Function. If the same actor (e.g. the same person) does play multiple roles in one Function, list these different
actor-roles as separate rows.
Actor Name
Actor Type (person, device, system
etc.
Actor Description
Energy Market
Clearinghouse
Company/System
Wide-area energy market operation system providing
high-level market signals for ISO/RTO and Utility
Operations
ISO/RTO
Company/System
Wide-area power system control center providing highlevel load management and other signals for Utility
Operations
Utility Operations
Company/System
Distribution, transmission and generation management
system providing operations with
distribution/transmission/generation-related objectives,
constraints, and input data; performing monitoring and,
controlling of the power system operations.
Utility Apps
Systems
DMS, OMS, WMS, GIS, Demand Response
Management System, PEV Analysis System and
Behavioral Model Databases, etc. Controlling DR, DER,
PEV and ES charging/discharging; processing and
storing data on load management programs, contracts,
relevant historic information, creating behavioral models,
collecting, processing, and storing customer-specific
power quality and reliability chractestics, etc.
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Actor Name
Actor Type (person, device, system
etc.
Actor Description
Metering/Billing/
Utility Back
Office
Systems
CIS, AMI System
Aggregator/Energ
y Services
Company
Company
Intermediary entity between Utility and group of
customers
Domain
Customer
Premises with
PEV
Grouping (Community) ,
Group Description
Actor Name
Actor Description
Actor Type (person, device, system
etc.)
Replicate this table for each logic group.
1.4 Information exchanged
Describe any information exchanged, including between which Actors.
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Interface #
Information Object Name
Information Object Description
1
Request for aggregated load
management (congestion
management) in a particular wide
area, price signals.
From ISO/RTO and Utility Operations, may be in a day ahead timeframe, in a hours in
advances, or in a near real time via RTP signal
1
Utility operation data and available
dispatchable load by means of DR,
DER, PEV and ES
From and Utility Operations to ISO/RTO, near real-time and forecasts for look-ahead
studies.
2
Energy and Ancillary Service
Prices
From Energy Market Clearing House, to Aggregator and Utility Operations, , may be
in a day ahead timeframe, in a hours or minutes in advances
2
Bids for ancillary services
From Aggregator and Utility Operations to Energy Market Clearing House
3
Real Time Prices (market-based or
reliability based), Direct triggers
for enabling PEV storage use,
charge interruptions, requests for
near-real time measurements
From Utility Operations to Customer. VVWC and DOMA determine the voltage and
loading critical sites and request near real-time measurement updates. VVWC under
load reduction objective determines in which voltage-critical points load reduction
would significantly increase the voltage and sends a triggering signal to this point for
exercising discharge of PEV electric storage into grid. VVWC then lowers the voltage
and adjusts capacitors to utilize the additional room created by the PEV discharge. The
DCA and FLIR determines in which nodes the electric storage discharge would
improve the restoration results and issue triggering signals to the corresponding sites.
In case of an aggregated request for load reduction, the utility issues triggering
commands to a large number of customers for demand response, electric storage
discharge, and DER starts.
3
Confirmations on execution of
direct controls, requests, and
reaction on RTP, transmission of
requested real-time measurements
From selected customers with BMS to Utility Operations
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4
4
Load and consumption data, Start
and End times for DR, ES, PEV
connection and discharge. Other
measurements.
From customer to Metering Billing. Paeriodic data (every 1-5 min), by event data
From Metering Billing to customer
5
5
6
From ISO/RTO to Market Clearing House
6
From Market Clearing House to ISO/RTO
7
7
8
From Aggregator/Energy Services Company to Customer
8
From Customer to Aggregator/Energy Services Company
9
9
10
10
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11
From Aggregator/Energy Services Company to ISO/RTO
11
From to ISO/RTO to Aggregator/Energy Services Company
12
From Aggregator/Energy Services Company to Metering/Billing
12
From Metering/Billing to Aggregator/Energy Services Company
12
Measurements and other data
collected from customers
From Metering/Billing to Utility Operations for processing in APPS
12
Request for information updates
From Utility Operations to Metering/Billing
13
Exchange with object model
updates, calculation results,
switching orders, etc.
From Application to Application to other utility IT systems
14
From Aggregator to Utility Operations
14
From Utility Operations to Aggregator
15
15
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6
Energy Market Clearinghouse
ISO/RTO
2
1
2
11
14
Utility Operations
3
App
13
App
12
Aggregator/Energy Services Company
12
8
Metering/Billing/
Utility Back Office
4
ESI
Meter
15
5
Sub Meter/
EUMD
Market and/or financial interfaces
Energy information interfaces
Customer EMS (optional)
10
Metering information interfaces
(Premise & Off-Premise)
9
7
7
PEV (as load and electric storage)
Customer Premises
PEV: Plug-in Electric Vehicle
ISO: Independent System Operator
RTO: Regional Transmission Operator
ESI: Energy Services Interface
EMS: Energy Management System (optional)
EUMD: End Use Measurement Device
Figure 2. Use Case Diagram
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Actor ______________ in Domain _______________
Category
Standards
Requirements and notes
8. Policy
7. Business Objectives
6. Business Procedures
5. Business Context
4. Semantic Understanding
information objects standards this actor understands are identified here
3. Syntactic Interoperability
transfer syntax standards are identified here
2. Network Interoperability
Addressing and routing standards here
1. Basic Connectivity
Physical standards here
Shared Meaning of Content
Object modeling
Resource Identification
Universal identifiers
Time Synch & Sequencing
Security and Privacy
Logging & Auditing
Transaction State Management
System Preservation
Quality of Service
Discovery & Configuration
System Evolution & Scalability
Electromechanical
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