v&r pom-transient stability (ts) tool update

V&R POM-Transient Stability (TS) Tool Update

Marianna Vaiman, V&R Energy

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WECC JSIS MeetingNovember 19, 2020

Copyright © 1997-2020 V&R Energy Systems Research, Inc. All rights reserved.

Agenda

Copyright © 1997-2020 V&R Energy Systems Research, Inc. All rights reserved. 2

1. V&R Updates

2. POM-Transient Stability


1. V&R Updates

Recent Deployments


SDGE – ROSE VSA (Voltage Stability Analysis)– Uses CAISO CIM15XML model

– Based on Peak-ROSE VSA with enhancements per SDGE requirements

– Runs in real-time every time a Periodic File is received from CAISO at SDGE and works in off-line mode

– Under testing at SDGE

ATO (Automated Topology Optimizer) Tool for Real-Time Operations Support at SPP – Automatically identifies system reconfiguration measures to mitigate voltage

and thermal violations that could not be mitigated using other measures

– System reconfiguration measure is switching out lines and transformers

D-PMU ROSE (Distribution PMU ROSE)– Real-time PMU-based distribution system analysis, including bad data

detection, observability analysis, optimal PMU placement, DLSE, event detection (uses machine learning)

– FLISR, Volt VAR Optimization, DER Dispatch

Speeding Up Calculations


POM Suite/ROSE 2020

– AC contingency analysis on 8000-bus case (after topology processing)

– 5,758,474 processed contingencies within one simulation run

– 49,228 critical contingencies found (e.g., contingencies resulting in one of the constraints being violated)

– Execution time: 02:46:51.6440713 (~0.00174 sec/contingency) or about 34.5k contingencies per minute

A new version to be released in 2021 – POM Core

– About 5 time faster than POM Suite/ROSE 2020

Massive Analysis


Observing a trend across the utilities and ISOs to run massive N-1-1 and N-2 contingency analysis with automated remedial actions:

– Largest list seen so far is over 20mln contingencies in one simulation

– No screening – straight forward AC contingency analysis using full Newton method

– Integrated with automatic identification of remedial actions

Contingency screening

– Working with several users (MISO, ERCOT, and others) on various screening approaches to reduce contingency lists while considering both voltage and thermal constraints

High Performance Adaptive Deep Reinforcement Learning (DRL)based Real Time Emergency Control to Enhance

Power Grid Resilience in Stochastic Environments

ARPA-E project with PNNL, V&R Energy, Google and PacifiCorp

Developing a DRL-based and analytical based hybrid emergency control method for transient stability preservation

V&R Energy’s role: analytical approaches for generator tripping, load shedding and intentional islanding and incorporation of the hybrid approach into ROSE platform

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2. POM – Transient Stability

Modes of POM-TS OperationBasicTS Mode

AutomaticTS Mode

Script Mode


Fast Fault Screening (FFS)

Critical Clearing Time (CCT)

Potential Cascading Modes – TS (PCMTS)

OPtimal Mitigation Measures – TS (OPMTS)

Reads library of dynamic models in Siemens PTI’s PSS/E and GE’s PSLF formats

Easy inclusion of user-defined models through POM scripting

No compiling required

Fast Fault ScreeningFast Fault Screening (FFS) capability of POM-TS:

– Determines the most severe faults

– Takes approximately 1 minute to determine 25 most severe faults in the system

The Ranking Index (RI) provides a very fast approximation of the fault severity:

– Does not require running time-domain simulations (simulates for 0.1 sec)

– CCT value can also be automatically calculated as benchmark

The severity of the fault is classified in the following order:

– Faults leading to voltage instability

– Faults leading to loss of generation

– Faults with the smallest critical time

FFS is used in System planning (TPL-001-4) and Operations


M. Y. Vaiman, M. M. Vaiman, A. Gaikwad, “Fast Fault Screening Methodology for Transient Stability Analysis of Bulk Power Systems”, 2013 IEEE PES GM, GM1737.

V. Kolluri, S. Mandal, M. Y. Vaiman, M. M. Vaiman, S. Lee, and P. Hirsch, "Fast Fault Screening Approach to Assessing Transient Stability in Entergy's Power System", IEEE Proceedings, 2007, pp:1 - 6.

Comparing Cases in Terms of Transient Stability Limitations

Planning cases, EMS cases

Case with the highest RI is the most vulnerable


Critical Clearing Time (CCT)

Automates critical clearing time computations:

– Eliminates manual time-consuming cut-and-try critical clearing time calculations;

– Utilizes time-domain simulation to compute critical clearing time under different fault conditions.

CCT Scenarios:

– Bus Fault Scenario

– Transformer Fault Scenario

– Branch Fault Scenario


CCT ActivitiesBranch Fault– Calculates CCT depending on fault type:

either bus fault, or fault on transmission line and transformer:

Checked for Line and Transformer faults;

Unchecked for Bus faults.

Max Generation– Calculates CCT while either leaving generators at their current (base case)

output prior to performing CCT computation, or bringing generators to their maximum output prior to performing CCT computation:

Checked if generators are brought to their maximum output;

Unchecked if generators are at their current real power output.


CCT Output

File cct.csv:

– Branch(es) opened as a part of the fault scenario;

– Critical clearing time;

– Generators at Risk (e.g. units which become unstable)


Cascading from Transient Stability Perspective


An event is classified as a cascading outage if one of the following conditions are met:– Sharp drop in transient

voltages in a large part of the network,

– Sharp drop in frequency followed by system separation,

– Islands are formed as a result of protection operation, with

significant amount of load/generation within the island,

– Disconnection of large amount of generation,

– Disconnection of large amount of load.

Time-Domain Simulation during Cascading Analysis


At time specified in the Time of initiating event, s an initiating event occurs (a three-phase fault is applied):

If time after last tripping exceeds the value listed in the field Time after last event, s simulation of this event stops:

– During a cascading event, elements are being tripped

– Tripped elements may be lines, transformers, loads, and generators

Critical Cascade Criteria


Computation stops if at least one of the Critical Cascade criterion is met:

– Islanding

– Interface limit violation

– MW load loss

– MW generation loss

– Cascade propagation

Critical Tripping Criteria


Tripping occurs during a cascading event if at least one of the tripping criteria is met:

– Line tripping threshold

– Transformer tripping threshold

– Load tripping threshold

– Generator tripping thresholds

Element Tripping and Delays


When one of the tripping criteria satisfies, the corresponding element is being tripped.

Tripping occurs only if a criterion continues to be met during time interval specified in Relay Delay section.

In this case, the element will be tripped after time listed in Relay Delay section elapsed.

Modeling Relay Operation in PCMTS


Four types of relays considered during the analysis:

– Distance relays;

– Overcurrent relays;

– Undervoltage relays;

– Underfequency relays.

Relay operation is modeled using delays listed in the Relay Delays section

It is assumed that the above relays are installed on all lines, transformers, loads, and generators

Additional Checks


Generator Angle Deviation

– Checks maximum change in the rotor angle deviation

– If this option is enabled, PCMTS computes the difference between maximum and minimum generator rotor angles, and determines the maximum difference

Steady-state stability

– After time-domain computation is completed, all elements tripped as a result of a cascading chain, are tripped using steady-state (e.g., load flow) computation

PCMTS Results at SPP


Classification of Cascading Outcome


Identifying possible outcomes of cascading:

– Based on determination and comparison of damping parameters

Outcome

Number

Outcome Type

1 Decreasing amplitude oscillations

2 Increasing amplitude oscillations

3 Oscillations with decreasing frequency

4 Oscillations with increasing frequency

5 Monotonously increasing frequency

6 Monotonously decreasing frequency

Thank you!


v&r pom-transient stability (ts) tool update

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