evolution of control for the power grid
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College of Engineering and Architecture
Evolution of Control for the Power Grid
Anjan BoseWashington State UniversityPullman, Washington, USA
University of Seville
Seville, Spain
June 17, 2016
College of Engineering and Architecture
THE INTERCONNECTED GRID
•Economics
Transfer electric energy from areas where it is cheap to where it is expensive. Electricity trading dates back to the beginning
•Reliability
Neighbors can back up each other. The cost of redundancy is shared.
College of Engineering and Architecture
The Past (before 1960s)
• Hard wired metering
• Ink chart recording
• Light and sound alarming
• Hard wired remote switching
• Analog Load Frequency Control (1930s)
• Economic Dispatch (1950s)
• ED was first to go digital
College of Engineering and Architecture
The Present (since 1960s)
• The digital control center (SCADA-AGC)
• The RTU to gather digital data at substation
• Comm. channel from sub to control center (CC)
• The SCADA
The Data Acquisition from RTU to CC
The Supervisory Control signal from CC to RTU
• The screen based operator display
• Automatic Generation Control (AGC)
The digital algorithm for ED
The digital version of LFC
College of Engineering and Architecture
The Present (since 1970s)
• The Energy Management System (EMS)
• State Estimation (SE)
• Static Security Analysis (n-1)
• Dynamic Security Analysis (stability)
Transient, Oscillatory, Voltage
• Optimal Power Flow based analysis
Preventive Action calculation
Corrective Action calculation
College of Engineering and Architecture
Evolution of Control Center Architecture
• Special real time computers for SCADA-AGC
• Mainframe computer back ends for EMS
• Redundant hardware configuration with checkpoint and failover
• Multiple workstation configuration
Back-up is more flexible
• Open architecture initiated
• CIM (Common Information Model) standard
College of Engineering and Architecture
Communication for Power System
Control Center
RTU RTU RTU
Third Party•Analog measurements
•Digital states
Eastern Interconnect Control/Monitoring Center
RC1
Sub1Sub10
0
RCi RC10
Act1-10 Sen1-100
Subk
… …… …
CC1
CCj
CC1
0
……
… …
College of Engineering and Architecture
Phasor Measurement Units
• Measurements at substations are now handled by microprocessors
• Measurements can be sampled at very high rates
• Measurements can be time-stamped by satellite
Measure magnitude and phase angle (PMU)
• PMU output rates: 30-120 per second
• Data rates for control centers will increase by 2-3 magnitudes
College of Engineering and Architecture
Control
Center
Substation 1
Measurement1
Measurement i
Substation
Server 1
L
A
N
Executive Unit1
Executive Unit i
Substation 2
Measurement1
Measurement i
Substation
Server 2
L
A
N
Executive Unit1
Executive Unit i
Substation 3
Measurement1
Measurement i
Substation
Server 3
L
A
N
Executive Unit1
Executive Unit i
SPS 1
Power System
Communication Systems
SPS 2
R
R
R
R
R
R
R
R
Proposed Communications
College of Engineering and Architecture
Advanced Metering Infrastructure
• Smart Meters
Gateway between utility and customer
Communication to utility and home appliances
Time-of-day and real-time rates
• Applications
Optimize energy efficiency and energy cost
Demand response
Can integrate generation (roof PV), storage (EV)
• Microgrids
Pic of one feeder with the new equipment
23
Switched Capacitors
Regulator
Recloser
Francis & Cedar F3, Spokane, WA
College of Engineering and Architecture
DISTRIBUTION MANAGEMENT SYSTEM
• Measurements along the feeder
• Switches, transformer taps, shunt capacitor and inductor controls
• Communications: Radio, Power Line Carrier, Fiber backhaul
• Closer voltage control increases efficiency
• Greater switching ability increases reliability
• Better coordination with outage management
• Sets up for distributed generation, demand response, electric vehicles or local storage
College of Engineering and Architecture
Substation Automation
• Many substations have
Microprocessor based devices (IED)
Data acquisition at faster rates (30-60 Hz)
Digital protection and control systems
Remote setting capabilities
• Data can be time-stamped by satellite
Measure magnitude and phase angle (PMU)
• Local Area Network to control room (LAN)
• New substation applications
College of Engineering and Architecture
Geographic Information System
• GIS is getting more integrated into all aspects of system operations, especially
Distribution management
Outage management
• This has been helpful in other applications like Crew Management, Distribution Planning, etc
College of Engineering and Architecture
Outage Management System
• The computerization of Outage Management has made huge strides
• Requires less people to handle customer calls
• Requires less people to do crew dispatching
• Time savings are significant
College of Engineering and Architecture
Building Automation
• Smart Meters
Gateway between utility and customer
Utility can send price signals or control signals
Change rates (in real time?)
Control appliances (especially heating/cooling)
• Customer Applications
Optimize energy efficiency and energy cost
Demand response
Can integrate generation (roof PV), storage (EV)
• Microgrids
College of Engineering and Architecture
So What Can You Do?
• Transmission grid: Wide Area Monitoring and Control
• Distribution: Integrated Volt-Var Control, Conservation Voltage Reduction, Automatic-Remote Reconfiguration
• Customer: Demand Response, Optimize Cost-Benefits
College of Engineering and Architecture
What Wide-Area Monitoring, Protection and Control are Available?
• Wide-Area Monitoring Systems (WAMS)
First installation of PMUs was called WAMS
Mostly used for post-event studies
• Wide-Area Protection and Control
Wide-area protection is called SPS or SIPS
Experiments with controlling SVC, HVDC, etc.
• Other applications
Oscillation detection
PMU-only State Estimator
College of Engineering and Architecture
Distribution Applications
• Integrated Volt-Var Control (IVVC)
Use remote control of transformer taps and capacitor banks
Minimize losses
• Conservation Voltage Reduction (CVR)
Minimize voltage to reduce load
• Remote control of sectionalizers for reconfiguration around faults
Minimize outage of customers
College of Engineering and Architecture
Customer Applications
• Large customers can play the market
Demand response
Optimize consumption by rescheduling heating-cooling-large equipment
Optimize solar, electric vehicles, other storage
• Smaller customers have less opportunities
Time-of-day or real-time pricing
Neighborhood microgrid
College of Engineering and Architecture
Data Base Issues• At present all applications (XMS) have separate
data bases and cannot exchange data
• All data must be coordinated across the whole system from consumers to generation
• Standards will be key
• Real time data is geographically dispersed and require a distributed data base
• Data has to be moved timely to where it is needed which requires a flexible communication system
• All data bases in the same interconnection will have to be coordinated
College of Engineering and Architecture
INSTITUTIONAL ISSUES
• Reliability standards – need emphasis on best practices rather than compliance
• Transmission planning – who is responsible?
• Operational procedures – e.g. data sharing
• Market rules – often does not take into account operational realities
• Rate regulation – FERC, state PUCs
• Federal or state energy policies
College of Engineering and Architecture
Conclusions
• Smart grid is developing piecemeal – A holistic systems approach is needed
• The systems approach will have to be driven by utilities – the vendors have no interest in doing this
• The technologies – sensors, computers, communications, controllers - are all available, the system vision is not there
• R&D is needed with a clear path towards implementation
• Institutional policies updated to encourage technological solutions to meet goals
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