Essential Reliability Services Engineering the Changing Grid

Transcription

1 Essential Reliability Services Engineering the Changing Grid Robert W. Cummings Senior Director Engineering and Reliability Initiatives i-pcgrid March 39, 2016

2 Change is Coming Characteristics and behavior of the system are changing Rapid penetration of new types of loads Rapid penetration of new types of electronically-coupled resources Retirement/displacement of conventional generation Reduced inertia Variable resources We MUST engineer the changes to maintain reliability 2

3 Changing Load Load composition changing Electric vehicle charging LED lighting Variable speed drive motors Distributed Energy Resources Inverter-based resources o Roof-top solar panels o Micro turbines o Small wind turbines Load becoming schizophrenic Load models no longer adequate for simulations 3

4 Changing Resources Changing Dispatch Mix High penetration of renewables variable resources Minimum generation levels on conventional units Ramping needs increase for load following Retirement of large fossil-fired generation plants Loss of dynamic reactive support for voltage control Possible reduced system inertia Lower levels of synchronizing torque Changing System Inertia Trade-offs between inertia and Primary Frequency Response 4

5 Cautionary Tales Inadvertent creation of new reliability hazards Very large DC transmission projects New largest single hazards Series-compensated transmission lines Sub-synchronous resonance Sub-synchronous controls interaction Inverter-based resources Digital controls on conventional generation System controls SVCs, Statcoms, DC converter stations, 5

6 Potential Interaction Examples Potential response to combination of voltage and frequency perturbations associated with complex system disturbances High-quality supply loads that are Voltage/Frequency-sensitive Experience of 600 to 900 MW load loss due to transfers to backup supplies during faults Locational injection impact on transmission elements and interfaces Response masquerading as a power swings protection system concerns 6

7 ERS Fundamentals Building blocks of physical capabilities Accentuated by resource changes Not all MWs are equal Some partly covered through ancillary services Accommodate local/regional needs Resource Adequacy Essential Reliability Services Reliability 7

8 Essential Reliability Measures Synchronous Inertial Response Interconnection level Initial Frequency deviation following largest contingency Synchronous Inertial Response Balancing Authority level Ramping capability Voltage performance Overall system reactive performance 8

9 2015 LTRA #3: Reliability Trends and Emerging Issues Reliability Finding #3: Operators and planners face uncertainty with increased levels of distributed energy resources and new technologies Distributed energy resources (DERs) are contributing to changing characteristics and control strategies in grid operations. 25 GW 20 GW Actual and Projected Cumulative Distributed PV Installed Capacity in U.S. Since 2010 NERC is establishing a Task Force focused on examination of reliability impacts of large amounts of DER on the BPS. 15 GW 10 GW 5 GW 0 GW Actual Projected Non-Residential Distributed PV Residential Distributed PV 9

10 The Control Shift Distribution 10% Variability absorbed by load variability Operational characteristics do not permeate to BPS Bulk-Power System Supports system inertia and recovery modes Dispatchable based on demand Centralized to System Operator 90% 10

11 The Control Shift Distribution Bulk-Power System 30% Disturbances permeate to BPS (common-mode) Dynamic and fast demand response Potential for over-generation More rigorous generator control and dispatchability Increased reliance on BPS generation Additional equipment to control local voltages 70% 11

12 The Control Shift Distribution 50% Bulk-Power System Integrated Power System Supports electricity services Provider of long-haul power transfers Reliability backbone DERs must act as a system resource Storage, curtailment, coordination, grid support, and control Operator or aggregator function may be needed 50% 12

13 ERSTF Report Recommendations All new resources should have the capability to support voltage and frequency Monitoring of the ERS measures, investigation of trends, and use of recommended industry practices will serve as an early warning indicator to reliability concerns if issues are not addressed with suitable planning and engineering practices. Further examination by NERC of the forecasting, visibility, and participation of DERs as an active part of the electric grid is needed. 13

14 CAISO Load Balancing Concerns 14

15 CAISO Net Load Pattern Changes 15

16 Risk to Reliability Changing Resource Mix Potential for lower inertia with retirement of coal and oil-fired synchronous generators Higher penetration of renewables with potentially lower frequency response No assurance of adequate inertia or frequency response capability for some resource dispatch scenarios Trade-offs between inertia and Primary Frequency Response Conservative approach All resources should have frequency responsive capability to assure that frequency response is available for any resource dispatch. 16

17 Governor/Load Response (MW) Frequency (Hz) Frequency Response Basics A Pre Event Frequency NERC Frequency Response = Generation Loss (MW) Frequency Point A -Frequency Point B C c Frequency Nadir: Generation and Load Response equals the generation loss Slope of the dark green line illustrates the System Inertia (Generation and Load). The slope is ΔP/(D+2H) B Settling Frequency: Primary Response is almost all deployed Governor Response Load Response Frequency Time (Seconds)

18 Frequency Response Control Continuum Inertial Response Primary Control (Gen. Response) Milliseconds Seconds to 1-2 minutes Spinning Reserves Secondary Control (AGC) Recovery of Reserves Minutes Minutes to Hours Non-Spinning Reserves 18

19 Kinetic energy, MWs Monitor Trends in Frequency Synchronous inertia is declining x ERCOT Historic Kinetic Energy Boxplots ( ) 19

20 Importance of System Inertia in ERCOT 60.0 Hz 59.4 Hz Bus frequency (Hz) Generation Trip: 2,750 MW Case 1---: Net Load = 65 GW, SI = 372 Case 2---: Net Load = 35 GW, SI = 236 Case 3---: Net Load = 17 GW, SI = Hz Time (sec) Inertia (GW-second): 1 > 2 > 3

21 Trade-off between Inertia and Primary Frequency Response 60.0 Hz Bus frequency (Hz) Generation Trip: 2,750 MW Case 1---: Net Load = 65 GW, PFR=1,300MW Case 2---: Net Load = 35 GW, PFR=2,500MW Case 3---: Net Load = 17 GW, PFR=4,700MW Hz Time (sec) Primary Frequency Response (MW): 3 > 2 > 1 21

22 BAL Standard Focus Areas of Frequency Response Does not guarantee performance for each event, measured by median performance Provides consistent methods for measuring Frequency Response and determining the Frequency Bias Settings Asynchronous Resources Modifying RS/OC Guideline to include desired operating characteristics for all resources Coordinating with IEEE on Standard 1547 for DER Not currently required to have the capability to provide FR Planning Frequency Response studies in the planning horizon 22

23 Summary Characteristics and behavior of the system are changing Rapid penetration of new types of loads Rapid penetration of new types of electronically-coupled resources Current simulation tools are lacking necessary models for new technologies Controls interaction could cause instability Essential Reliability Services must be maintained Frequency response Voltage control and reactive support Dispatchable resources for load following We MUST engineer the change to maintain reliability 23

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