Stability analysis on WECC Systems with Wind Penetration and Composite Load Model Hyungdon Joo and Melissa Yuan Mentor Yidan Lu Professor Kevin Tomsovic

Stability analysis on WECC Systems with Wind Penetration and Composite Load Model

Hyungdon Joo and Melissa YuanMentor Yidan Lu

Professor Kevin TomsovicYoung Scholars Program

Young Scholars Presentation17 July 2014

Knoxville, Tennessee

Overview

• Topic and Purpose of Research

• Introduction• What is the WECC?• Generic wind model for Type 3 WTG• Composite Load Model• Contingencies/NERC/WECC Standards

• Methodology of Research TSAT stability analysis

• Results Contingency simulation for case studies

• Conclusions and Summary

• Future Work

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Topic and Purpose of Research

Topic:

•Analyzing the stability of WECC network given integration of wind power•Specific attention given to Pacific DC intertie

•Application of new composite load model in the study of grid stability

•Analyzing the combined effect of wind integration and motor penetration on system stability.

Purpose:

•To update the operating limit of the Pacific DC Intertie with new generation and load patterns.

More economic in improving existing components than building new components

•To observe the influence of wind turbine and motor loadDampingTransmission fault clearing

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What is the WECC?

• Western Electricity Coordinating Council (WECC) Canada: Alberta and British Columbia United States:

Washington, Oregon, California, Idaho,

Nevada, Utah, Arizona, Colorado, Wyoming,

Montana, South Dakota, New Mexico, Texas Mexico: northern area, Baja California

• Pacific Intertie (3 AC line and 1 DC line) Path 65(DC) Path 66 (AC) 3.1GW of DC and 3 GW of AC Oregon Los Angeles

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Generic Wind Model for Type 3 WTG

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Blade Pitch Limited by Integrators

Aerodynamic Model Shaft Dynamics Model

• Four separate models Pitch control Model

Calculates optimal blade pitch from shaft speed and power input Pitch Control and Compensator are Non-windup Integrators

Turbine Model Simplified modeling of turbine aerodynamics and

shaft dynamics Calculates shaft speed given blade pitch

Generic Wind Model for Type 3 WTG (cont’d)

• Generator Model No Mechanical-state variables (in Turbine Model) Calculates power injected into network in response

to power commands from Converter control model

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Power Commands from Coverter

Power Injected into network

Type 3 WTG Generator Model

Generic Wind Model for Type 3 WTG (cont’d)

• Converter Control Model Controls Real and Reactive Power output Reactive power control

Faster due to power electronic converter Three control modes Reactive Power Command output

Active (torque) power control Slower due to physical components Anti-windup limits on power Real Power Command output

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3.Constant Reactive Power

2.Constant Power Factor Angle

1.Plant-side Voltage Regulation

Realistic Limits on Power

Power Outputs

Composite Load Model

• 60% of load is represented by 3-phase and 1-phase motors and 30% by constant power load, 10% represented by frequency depended load.

• Bus 150, 3118MW of load consists of 20% 1-phase motor and 80% constant power load

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Composite Load Model (cont’d)

• Distribution Equivalent Data Transformer tap control and substation

feeders

• Equivalent load modeled at High voltage transmission bus

• Additions to Conventional model – bulk-power delivery transformer, a feeder equivalent, and end use loads at different types

• More realistic for Transient Stability Studies

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Introduction to Contingencies

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Category Contingencies System Limits or Impacts

Initial Event(s) and Contingency Element(s)

Elements Out of Service

Thermal Limits

Voltage Limits

System Stable

Loss of Demand or Curtailed Firm Transfers

Cascading Outages c

A-No Contingencies

All Facilities in Service

None Normal Rating a

Normal Rating a

Yes No No

B- Event resulting in the loss of a single element

SLG or 3 phase fault with normal clearing or loss an element without fault

Single A/R A/R Yes Nob No

Single pole block with normal clearing

Single A/R A/R Yes Nob No

a) Normal Rating (A/R) refers to the applicable normal and emergency facility thermal rating

b) Planned or controlled interruption may occur in certain areas without impacting the overall security of the interconnected transmission systems.

Methodology of Research

• Conversion of PSSE wind model data to TSAT data format

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TSAT Stability Analysis

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• Case I is control with no wind penetration or composite load

• Doubly-Fed Induction Generator (DFIG) Model is used for 11 wind turbines in Case II and Case IV.

• Composite Load Model with representation of compressor stalling applied in Case III and Case IV.

Case Number Bus Number Wind Penetration Load Model

Case I 181 bus 0% Constant Power

Case II 197 bus 12% ( NW and CA) Constant Power

Case III 181 bus 0% Composite Load Model

Case IV 197 bus 12% (NW and CA) Composite Load Model

TSAT Stability Analysis

• Pacific HVDC is represented by constant load in NW and injection in CA.

• 247 non-fault AC contingencies are analyzed in 20 seconds of transient period and 5 seconds of post-transient period.

• 8 critical contingencies around pacific intertie are identified post transient voltage check.

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Transient Voltage Transient Frequency

Post-transient Voltage

Minimum 0.75 at load buses or 0.7 at non-load buses

Minimum 0.8 for maximum 20 cycles at load buses

Minimum 0.96 for 500kV bus voltage following disturbance

Minimum 59.6Hz for maximum 6 cycles at load buses

Minimum 0.95 at any bus after critical contingencies

Case I: Base Case

Contingency Simulation on WECC system

without wind penetration nor composite load model

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DSATools Output Analys is 11.0

Powertech Labs Inc .

Copyright © 2014 All rights reserved

TSAT Jun 30, 2014 13:42:39

Buf. Binary Result F ile Scenario Contingency

Bus # Bus Name Buf.Bus v oltage magnitude (pu)

Time (sec)

0.00 4.00 8.00 12.00 16.00 20.00 0.90

0.96

1.02

1.08

1.14

1.20

3 Melissa_1.bin Base Scenario 76 -- 55-62-1

150 PARDEE 230. 3 61 SYLMAR S 230. 3

Case I: Post-transient Voltage Analysis

• Case I Post-transient Voltage Violation after Pacific Intertie Outage

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CaseLimiting Transfer Capacity

Limiting Factor

Limiting Contingency

Minimum Violation

Value

I4695.93MW

Post-transient Voltage dip

Branch outage 111-173

0.949Pu on Bus 172

II4643.99MW

Frequency Drop

Branch outage 66-78

59.230Hz on Bus 65

III4311.07MW

Non-load Voltage Drop on Bus 134


0.6950Pu on Bus 134

IV4643.99MW

Frequency Drop

Branch outage 66-78

59.230Hz on Bus 65

Case II: Wind penetration

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Limiting Factor


Minimum Violation

Value

I 4695.93MWPost-transient Voltage dip


0.949Pu on Bus 172

II 4643.99MWFrequency Drop

Branch outage 66-78

59.230Hz on Bus 65

III 4311.07MWNon-load Voltage Drop on Bus 134


0.6950Pu on Bus 134

IV 4643.99MWFrequency Drop

Branch outage 66-78

59.230Hz on Bus 65

Case III: Motor penetration

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Case III transient Voltage Response at Limiting Transfer Capacity

Case III transient Voltage Violation in response to North California Outage


Limiting FactorLimiting

ContingencyMinimum

Violation Value



0.949Pu on Bus 172

II 4643.99MW Frequency Drop Branch outage 66-7859.230Hz on Bus 65



0.6950Pu on Bus 134

IV 4643.99MW Frequency Drop Branch outage 66-7859.230Hz on Bus 65

Case IV: Wind and motor penetration

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Freq. Response to Northwest Outage in Case II and IV at Limiting Transfer Capcity

Freq. Standard Violation in Response to Northwest Outage in Case II and IV

Fault cleared, frequency above 59.6 Hz

below 59.6Hz more than 6 cycles


Limiting FactorLimiting

ContingencyMinimum

Violation Value



0.949Pu on Bus 172

II 4643.99MW Frequency Drop Branch outage 66-7859.230Hz on Bus 65



0.6950Pu on Bus 134

IV 4643.99MW Frequency Drop Branch outage 66-7859.230Hz on Bus 65

Conclusions and Summary

• One of the three AC branches near the Pacific Intertie, 111-173 was weakest part of WECC in base case.

• Nearby wind turbines weakened the stability of Northwest with a limiting contingency (branch outage 66-78).

• Air conditioning compressor stalling caused low voltage issues in California during transient period.

• Wind Turbines restored transfer capacity reduced by stalling motors by allowing more dynamic VAR around Pacific Intertie.

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Limiting Factor


Minimum Violation

Value

I4695.93MW

Post-transient Voltage dip


0.949Pu on Bus 172

II4643.99MW

Frequency Drop

Branch outage 66-78

59.230Hz on Bus 65

III4311.07MW

Non-load Voltage Drop on Bus 134


0.6950Pu on Bus 134

IV4643.99MW

Frequency Drop

Branch outage 66-78

59.230Hz on Bus 65

Future Work

• Applying dynamic High Voltage DC (HVDC) model in 200-bus WECC system.

• Including monopole DC contingency in N-1 transfer capacity analysis for all test systems.

• Developing wide area control schemes to restore transfer capacity to compensate for compressor stalling of air conditioning units.

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References

• WECC Wind Power Plant Dynamic Modeling Guidelines - August 2010 draft

• Hiskens, Ian A. Dynamics of Type-3 Wind Turbine Generator Models.

• WECC New Load Model – December 2010• WECC/NERC Planning and Operating Criteria. Section XI• 2012 Spring System Operating Limit Study Report

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Acknowledgements

Thank you to Mentor Yidan Lu andProfessor Kevin Tomsovic

Questions?

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Documents

Stability analysis on WECC Systems with Wind Penetration and Composite Load Model Hyungdon Joo and Melissa Yuan Mentor Yidan Lu Professor Kevin Tomsovic