Flying the electric grid through wind and Sun

Transcription

1 Flying the electric grid through wind and Sun Prabir Barooah Mechanical and Aerospace Engineering, University of Florida with help from Prof. Sean Meyn, He Hao, Yashen Lin, Tim Middelkoop, and

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3 Happy Halloween

4 Outline Part 1: the power grid today Part 2: great things are happening, but... Part 3: overcoming hurdles to a sustainable future Part 4: parting comments

5 Flying the power grid smoothly U.S. power grid supply and demand must be balanced at every instant throughout the grid U.S 2003 blackout India 2012 blackout if not,

6 Flying the power grid smoothly is a control problem Demand + Σ Error Control C Gas Turbine Coal Batteries Water Pump Disturbances from nature Power Grid H Power HVAC Actuation Baseline Generation Control of the grid spatially distributed (many locations) temporally distributed (many time scales, from microseconds to years) mix of automated and human decision making, balancing authorities, ISOs (independent system operators) economics, policy, technology Balancing authorities, 2007

7 Balancing currently achieved by > feedforward : scheduling and dispatching generation to match predicted load > feedback : regulation and... Power (GW) Day-ahead forecast Hourly schedule Power (GW) Hour ahead forecast Total dispatch Residual Load following Time (h) Time (h)

8 (Frequency) regulation: valuable ancillary service Power (GW) Realized load Total dispatch Regulation Time (h) Regulation: maintains supply- demand balance in seconds - minutes time scale Traditionally: provided by fast- ramping generators (not coal, not nuclear), gas turbine, hydro Grid operator computes regulation reference (filtered ACE)

9 Outline Part 1: the power grid today Part 2: great things are happening, but... Part 3: overcoming hurdles to a sustainable future Part 4: parting comments

10 Renewable energy sources: Sun and wind Potential for tremendous societal benefit : 33% energy from solar and wind will reduce carbon emissions by ~30%, and save ~7 billion $ per year (NREL western wind and solar integration study, phase 2, Sept. 2013) Potential for headache: (Germany, U.S. Pacific Northwest) not controllable, (i) Volatile (time varying), (ii) Unpredictable

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12 More renewable energy => need more ancillary service Regulation requirement Load- following requirement Hellman, Resources and transmission planning to achieve a 33% RPS in CAISO..., 2010 How to obtain the additional ancillary service inexpensively? Traditional coal, gas- turbine, generators? Giant batteries? Flywheels?

13 Outline Part 1: the power grid today Part 2: great things are happening, but... Part 3: overcoming hurdles to a sustainable future Part 4: parting comments

14 A paradigm shift will help solve this problem Now: control generation to meet demand Future: tune demand to meet generation Enabling resource: flexible loads Residential flexible loads (A/Cs, refrigerators,..) Commercial flexible load (HVAC,..) Deferrable loads (pool pumps,...)

15 A paradigm shift will help solve this problem Now: control generation to meet demand Future: tune demand to meet generation Enabling resource: flexible loads Residential flexible loads (A/Cs, refrigerators,..) Commercial flexible load (HVAC,..) Deferrable loads (pool pumps,...) Constraint: capacity and bandwidth of loads (time scale of flexibility) Need: control techniques to tune loads to provide ancillary service, without causing inconvenience to consumers the loads serve

16 A paradigm shift will help solve this problem Now: control generation to meet demand Future: tune demand to meet generation Enabling resource: flexible loads Residential flexible loads (A/Cs, refrigerators,..) Commercial flexible load (HVAC,..) Deferrable loads (pool pumps,...) Constraint: capacity and bandwidth of loads (time scale of flexibility) Need: control techniques to tune loads to provide ancillary service, without causing inconvenience to consumers the loads serve clarification: zero energy ancillary service

17 #1 Source of flexible loads: buildings HVAC systems in commercial buildings: approx 20% of national electricity consumption (U.S.) Large thermal inertia, so small and fast variation in air flow has little effect on indoor climate Buildings with VAV (variable air volume) systems are particularly well suited for load tuning

18 VAV (Variable air volume) HVAC systems chiller

19 Case study #1: obtain high frequency ancillary service, in [1/(5 min) 1/(8 sec)] Existing building control Regulation Signal r Fan Controller Regulation Controller + fan speed command u r Fan fan speed v p b+r Desired air flow Building + climate controller Air flow

20 Case study #1: obtain high frequency ancillary service, in [1/(5 min) 1/(8 sec)] Grid operator Regulation Signal BP filter r Fan Controller Regulation Controller + fan speed command u r Fan fan speed v p b+r Desired air flow Building + climate controller Air flow Band pass filter to ensure the climate control unit doesn t fight the regulation command

21 Band pass filter to prevent fight between controllers Magnitude (db) Regulation Command to Fan Speed Regulation Command to Temperature /600 1/8 Frequency (Hz) 10 0 Regulation Signal BP filter r Fan Controller Regulation Controller + fan speed command u r Fan fan speed v p b+r Desired air flow Building + climate controller Air flow

22 Simulation on models calibrated from Pugh Hall data Building thermal and power dynamics: (1) Building thermal dynamics * : (1) (2) (3) Air flow rate: Fan speed dynamics: (2) (4) Fan power: (3) Pugh University of Florida (4)

23 Simulation: excellent tracking with little impact 5 Regulation Actual Estimation Power (kw) Time (h) Temperature ( o C) Time (h)

24 Prelim. experimental results: check BW separation Experiments in AHU 2 of Pugh Hall (serves auditorium - room 170) Fan command (%) 80 Fan command u a On On u b Fan P f Plant Power (KW) Temp ( o F) Fan power P f Room Temperature Time (s)

25 How much can this help? A LOT! Resource 35 kw fan motor Ancillary service potential 5 kw 46,000 sq.ft bldg, 75 kw fan power 11 kw All buildings in the U.S. with VAV HVAC systems 6.6 GW 70% of the regulation capacity needed by the US in 2012, in the high frequency range ( ~1/1 min) Ref: Ancillary Service for the Grid Via Control of Commercial Building HVAC Systems, He Hao, Anupama Kowli, Yashen Lin, Prabir Barooah, Sean Meyn, American Control Conference, June, 2013

26 Case study #2: obtain medium frequency ancillary service, in [1/(60 min) 1/(5 min)] Medium frequency variation in air flow will affect (i) fan power and (ii) chiller power consumption Good : much more ancillary service! Bad : delay, more complex dynamics, lack of direct actuation ability u fan power [τ 1 τ 2 ] chiller u fan air flow rate m m T la T la small P chiller high freq. variation in air flow rate P chiller! d " low freq. variation in air flow rate

27 Medium frequency A.S.: possible, but more sophisticated control algorithm required P r To handle transport delay in chiller: 1. Predict reference command (Kalman filter), 2. delay tolerant controller Band-pass Filter + Scaling m az Indoor Climate Controller T Power (KW) T (F) Real Reference Real Baseline P b P d Kalman Predictor P dp P Smith Predictor Power Model Regulation Controller m ar m ad Fan/Duct/Damper Dynamics m a Tmix Wmix Zone Dynamics Closed-loop Building Dynamics Approx 80 GW of ancillary service in the medium frequency [1/(5 min) - 1/(60 min)] range, with about 1 o F temperature deviation ma (kg/s) Time (h) Real Baseline Ref: Low Frequency Ancillary Services from Commercial Building HVAC Systems, Yashen Lin, Prabir Barooah, Sean Meyn, IEEE Smart Grid Comm, October, 2013, Vancouver, Canada

28 Case study #3: obtain low frequency ancillary service, in [1/(1 hour) flexible loads Residential flexible loads (A/Cs, refrigerators,..) 1/(6 hours)] Commercial flexible load (HVAC,..) Deferrable loads (pool pumps,...) FP&L has 780,000 customers in south Florida enrolled in On- Call demand response programs, where their A/Cs and pool pumps can be remotely controlled Constraint: capacity and bandwidth of loads (time scale of flexibility)

29 Case study #3: obtain low frequency ancillary service, in [1/(1 hour) flexible loads Residential flexible loads (A/Cs, refrigerators,..) 1/(6 hours)] Commercial flexible load (HVAC,..) Deferrable loads (pool pumps,...) FP&L has 780,000 customers in south Florida enrolled in On- Call demand response programs, where their A/Cs and pool pumps can be remotely controlled Constraint: capacity and bandwidth of loads (time scale of flexibility) Decentralized randomized control of pool pumps in FL (low frequency ancillary service) Ancillary service to the grid from deferrable loads: the case for intelligent pool pumps in Florida, Sean Meyn, Prabir Barooah, Ana Busic and Jordan Ehren, IEEE Con. on Decision and Control, Dec 2013, Florence, Italy.

30 Flying the power grid smoothly through wind and Sun by providing additional actuation from tunable loads Demand + Σ Error Control C Gas Turbine Coal Batteries Water Pump Disturbances from nature Power Grid H Power HVAC Actuation Baseline Generation

31 Hierarchical control architecture: respecting capacity+bandwidth limitation of loads grid operator C Grid G C C C flexible manufacturing HVAC, pool pumps, EVs batteries

32 Parting Comments A sustainable energy future with a high renewable energy portfolio requires substantially large amounts of inexpensive ancillary service Tuning of a large number of loads offers a vast and untapped source of inexpensive ancillary service In principle, can be solved through appropriate automation Many, many, many open research questions: 1. technological 2. social- science related 2. economic Financial support from National Science Foundation