Defining CPS Challenges in a Sustainable Electricity Grid

AUTHORS:Jay Taneja, Randy Katz, and David Culler

Computer Science DivisionUniversity of California, Berkeley

Presenting by:Phanindar Reddy Tati

Abstract Introduction The California Electricity Grid Towards A Sustainable Grid Opportunities for Cyber Physical Systems Conclusion

Contents:

Cyber-Physical Systems (CPS) are characterized as complex distributed systems exhibiting substantial uncertainty due to interactions with the physical world. Today’s electric grids are often described as CPS because a portfolio of distributed supplies must be dispatched in real-time to match uncontrolled, uncertain demand while adhering to constraints imposed by the intervening transmission and distribution network. With the increased control complexity required by deep penetration of fluctuating renewable supplies, the grid becomes more profoundly a CPS and needs to be addressed as a system. In this evolving CPS, a large fraction of supply is under-actuated, a substantial portion of demand needs to become dispatchable, interactions among distributed elements are no longer unidirectional, and operating requirements of elements are more dynamic. To more sharply define these CPS challenges, we obtain a yearlong, detailed measurement of the real-time blend of supplies on the primary California grid dispatched to meet current demand and then scale the solar and wind assets, preserving uncontrolled weather effects, to a level of penetration associated with California’s 2050 GHG targets. In this representation of a future sustainable grid, we assess the impact of demand shaping, storage, and agility on the reconstituted supply portfolio, characterize resulting duration curves and ramping, and investigate the distributed control and management regime. We articulate new operational and market opportunities and challenges that may materialize from intermittent periods of abundance and scarcity in the overall energy network. We find that in a sustainable grid, lulls in renewable production during winter are more critical than peaks in demand during summer, capacity for load shifting and energy storage are more valuable as renewables penetration increases, and that grid balancing requires integrated management of supply and demand resources.

Abstract:

How Electricity Grid is a CPS? As renewable resources increases, Grid gets more complex Interaction among distributed elements are no longer

unidirectional System needs to be more dynamic To discuss more sharply in real time, California Electricity

Grid considered In this paper, Authors discusses about

Sustainable Grid Impact of demand shaping, storage Investigated Distributed control and Management New operational and Market opportunities, Challenges

Continued…

• ABSTRACT

A portfolio of electric power generation resources must be managed dynamically to meet an uncontrolled time-varying demand

Primary control loop is managed by an operator to avoid iterative unit commitment problem; based on a prediction of load, generation capacity

Matching of generation to load is refined through hour-ahead and 5-minute ahead markets based on recently observed demand

Generators to manage mismatches Utilizing Information Technology- ‘SMART METERS’

Introduction:

• ABSTRACT • INTRODUCTION

Smart Meters Monitors loads Delivery of signal to trigger response from demand Checks power quality at intermediate points

Continued…

Information PlanesPhysical Planes

Classic Grid• ABSTRACT

• INTRODUCTION

Integration of large amounts of renewable resources makes the Electricity Grid more challenging

To achieve deep penetration of renewable resources

Zero-Emissions Load Balancing

Continued…

model

LOAD-FOLLOWING-SUPPLY

SUPPLY-FOLLOWING LOAD

• ABSTRACT • INTRODUCTION

PROBLEM: Maintaining the dynamic match between supply and demand in a grid with a deep penetration of Renewables

Methods: Pervasive monitoring, modeling Mitigation employing a rich information plane Distributed intelligence

Basis for this Study: Data released by California Independent System Operator (CA ISO)

Authors performed a scaling study if much larger array of renewable assets were deployed

Continued…

• ABSTRACT • INTRODUCTION

Authors answering a question

What would the grid be like with a deep penetration of renewables today?

Not considering changes in Demand Dynamics are not universal but Methodology is similar

Continued…

• ABSTRACT • INTRODUCTION

CA ISO: Independent, non-profit corporation that monitors, controls

electric power Has 25,865 mile network Released hourly supply data for it’s 10 different types of

generation sources

The California Electricity Grid

• INTRODUCTION • THE CALIFORNIA ELECTRICITY GRID

Here, Overall demand is defined as the sum of these generation sources.

Electricity demand varies on multiple timescales: Daily: Peaks in late afternoon Weekly: Weekends 9.6% less than week days Seasonally: Winter 15.8% less than summer

CHALLENGE: Matching highly-variable electricity demand with a portfolio of generation resources

33% of power should be produced from Renewable resources by 2020 (wind, solar, geothermal, biomass, biogas, hydroelectric)

Continued…

• INTRODUCTION • THE CALIFORNIA ELECTRICITY GRID

Temporal Variations:

Nuclear resources- Stable base load Hydroelectric- More power in summer Thermal- To meet day-to-day variations

Continued…

• INTRODUCTION • THE CALIFORNIA ELECTRICITY GRID

Continued…

Solar and Wind Power in California:

Solar -403MW Wind -2.8GW Day Time- More Solar power Night- More Wind power Combination could do better Unpredictable resources

• INTRODUCTION • THE CALIFORNIA ELECTRICITY GRID

Scaling Methodology: To model a sustainable grid of scale CA ISO with a large fraction of renewable energy

Scale solar and wind each by constant factor Reduce imports, thermal power until demand equals generation Energy produced beyond present-day energy is Excess

Assumptions: Proportional scaling of wind and solar hourly through yearly Estimated solar based on distribution of length of the day Geographic diversity of both wind and solar is similar in future

Authors selected 60% renewables threshold

Towards A Sustainable Grid:

• THE CALIFORNIA ELECTRICITY GRID • TOWARDS A SUSTAINABLE GRID

Continued…

• THE CALIFORNIA ELECTRICITY GRID • TOWARDS A SUSTAINABLE GRID

Characterization of a grid with 60% renewables

Summer, Excess power Exported or used to enable new energy-agile practices

Winter, less power Still has to meet day-to-day demand

Continued…

• THE CALIFORNIA ELECTRICITY GRID • TOWARDS A SUSTAINABLE GRID

A grid with deep renewables as predicted in the sustainable grid, presents a family of CPS challenges and opportunities

Cooperative portfolio Management:

Opportunities for Cyber Physical Systems

• THE CALIFORNIA ELECTRICITY GRID • TOWARDS A SUSTAINABLE GRID

Continued…

Loads-Following Supply

Operators controls supply to match the demand

Existing grids works on this

Supply-Following Loads:

Shifts the part of burden of maintaining the match onto demand

From periods of deficit to excess

Shifts to thermal at points of deficit

• THE CALIFORNIA ELECTRICITY GRID • TOWARDS A SUSTAINABLE GRID

Use of Storage: 128GW storage/ worldwide 99.9% hydroelectric (Stores water)

Allows shaping of supply rather than demand and is substitutable for any type of power generation

Continued…

• THE CALIFORNIA ELECTRICITY GRID • TOWARDS A SUSTAINABLE GRID

Load curtailment and Energy Efficiency:

From Summer to Winter, Operator targets the critical hours (where power generation is costly)

Reduction of energy consumption at any hour of the day becomes more valuable

More energy-efficient demand improves performance Energy-storage is more valuable

Continued…

• THE CALIFORNIA ELECTRICITY GRID • TOWARDS A SUSTAINABLE GRID

Modern electric grids are CPS Build a model of what the grid would look like with

sufficient sources to provide 60% of the electricity consumed

Introduced Supply-following loads Discussed energy storage, demand curtailment This study is preliminary step These CPS efforts will move us a step closer to the

sustainable grid design As resources are being consumed rapidly, sustainable grid

is necessary

Conclusion:

• TOWARDS A SUSTAINABLE GRID• CONCLUSION