4/11/2018

Dr. Maya Prica, Assistant ProfessorCase Western Reserve UniversityCleveland, OH

mxp438@case.edu

FERC – Technical Conference

Panel 5

Incorporating DERs in Modeling, Planning and Operations Studies

Transformation of the nation’s electric grid creates both challenges and opportunities

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CentralizedDispatchableGeneration

Predictable Load

Capacity Available

Distributed Intermittent Generation

Variable Net-Load and Customer Intervention

Capacity Constrained

Source: Dr. Sonja Glavaski, “NODES: Controlling the Grid Edge,” https://arpa-e.energy.gov/sites/default/files/Glavaski_FastPitch.pdf

Modeling DERs A model is a mathematical representation of a physical system

A model should only be detailed enough to provide needed information and answers to questions and not so detailed that the computation time is excessive

Main drivers for model development are voltage related or protection related issues

Type of models:o Economic o Steady-stateo Dynamic o Transient

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Modeling accuracy

The mathematical modeling DERs that include electrical features like harmonics, volt/freq ride through, dynamic response, etc. is mature and commercially available

Most of the time, the models have missing or unknown parameters that cause modeling inaccuracy

Software vendors are adding new models as new methodologies become available

Developed models need to be approved by utilities Aggregated models are mostly based on 3-phase balanced

representation of distribution circuits, for example, PVs may be connected by phase but their aggregated model for analysis assumes 3-phase balanced operation

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Most utilities are using commercially available modeling software packages Transmission modeling

o PTI-PSS-E (Siemens)o PSLF (GE Energy Consulting)o CYME (EATON)o PROMOD (ABB)

Distribution modeling o CYME (EATON) o Synergi (DNV GL)o MilSoft (Utility Solutions)o SINCAL (Siemens)o ASPEN (ASPEN)o DEW/ISM (Electrical Distribution Design)o OpenDSS (EPRI) – Open source, adopted by some commercial vendors

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The evolution load models

Static models – algebraic equation known as ZIP load model

CLOD – developed to simulate some dynamic behaviors of aggregated loads

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Source: https://ccaps.umn.edu/documents/CPE-Conferences/MIPSYCON-Papers/2017/CaseStudyonAggregateLoadModelinginTransientStabilityStudies.pdf

Evolution of load models (cont.)

CMLD – comprehensive dynamic model

Adaptation of the CLMD model to incorporate DER (under development)

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Source: https://ccaps.umn.edu/documents/CPE-Conferences/MIPSYCON-Papers/2017/CaseStudyonAggregateLoadModelinginTransientStabilityStudies.pdf

Modeling the interaction between T&D

There is no common methodology for analyzing the interaction between T&D systems

There is some research being done and several efforts to develop methodologies

T&D interaction modeling needs to be an “add on” rather than a replacement of existing systems

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T&D Interaction:1. Bundled 2. Iterative

Per phase model, balanced system 3-phase model, unbalanced system

1. Bundled, both systems are analyzed simultaneously as 3-phase, unbalanced2. Iterative, two step process, T&D are analyzed separately

Integrated T&D with PSS®SINCAL

Power utilities are able to analyze the impacts and benefits of DERs on their distribution system that could lead to issues on the transmission system

PSS®SINCAL can simulate:o Thermal loading of network equipmento Load and Generation Profileo Load Flowo Voltage Limitso Voltage Fluctuationso Reverse Power Flowo Protection Assessmento Short-circuit Assessment

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Source: https://www.siemens.com/content/dam/webassetpool/mam/tag-siemens-com/smdb/energy-management/services-power-transmission-power-distribution-smart-grid/consulting-and-planning/power-systems-simulation-software/pss-sincal-assets/10-psssincal-dertd-datasheet-intl-version.pdf

Integrated T&D with PSS®SINCAL and CYME SCE - DER modeling efforts Couple the distribution circuit model (e.g. CYME) to the load

at a certain bus in the bulk system and solve the coupled T&D system

10Sources: https://www.wecc.biz/Administrative/SCE%20DER%20Studies.pdf

New paradigm requires new models

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Enabling DERs to participate in the market without coordination with the distribution system operator may compromise distribution system reliability and power quality

Static Load flow analysis will not be sufficient; there will be a need to conduct load and generation profile simulation and to look at the entire system

Industry does not have the ability to study multiple resources aggregated across multiple circuits responding to an ISO/RTO signal

New paradigm: resources respond to an ISO/RTO signal that is different than a local reliability challenge of a distribution system.

More granular modeling of DERs at the edge of the network is needed

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Challenges:o System model sizeo Integrating DER control models

into the existing system modelso DER value - RTO/ISO price signals

are based on the transmission nodes. All resources below a transmission node receive the same value which does not consider the true value to the distribution system

New models that can capture control, coordination of DERs and their true value are needed

Communication and security

Detailed models of DERs at the bulk power system level would not provide better DERs visibility

Visibility of DERs may be achieved by adding real-time telemetry

Visibility and situational awareness of the system may be achieved by adding SCADA across distribution systems (presently only 1-2 percent of distribution system equipment has real-time telemetry)

Concern: reliable communication and cyber security Concern: security of modeling details and collected data –

physical security of data and models

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Evolving industry requires evolving models

IEEE 1547 is a system of options Each utility may have different options and settings

requirements Some settings will come from the bulk power system, some

will come from the distribution system IEEE 1547 will require the power industry to evolve New models will be needed for utilities to better understand

different options and their impact on system operation These models will evolve as industry evolves

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CWRU activities

CWRU is supporting utilities in developing and testing new models and tools

CWRU has worked on utility projects, both system studies and demonstration projects with EPRI and the US DOE:o SHINES – PV-energy storage model development and system control o Distributed energy storage for frequency regulation – methodology

development and impact studyo Energy storage/wind integrationo Grid demonstration project

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Summary Software vendors are adding new models as new

methodologies become available New models and tools are needed:

o Industry does not have the ability to study multiple resources aggregated across multiple circuits responding to an ISO/RTO signal

o Methodologies for DER impact studies needs to be developedo More granular modeling of DERs at the edge of the network is needed

Evolving industry requires evolving models Cyber, models and data security is a concern Economic value of DERs needs to be revisit

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