Turning power distribution feeders into microgrids: challenges & opportunities Andrea Mammoli Mechanical Engineering University of New Mexico !

a"prototype"of"a"future"distribu/on"feeder

NEDO microgrid

450 kW total

islanding switch

Commercial facility

300 kW PV 4MWh thermal store

ABQ studios 4MWh ice storage

Educational facility

2MWh thermal solar HVAC

Prosperity 500 kW PV

1MWh / 250 kW E 0.25 MWh / 500 kW P

Cogenra 1 MW CPV

2.5MWh kW ORC

Piller 21 MJ flywheel

1 MW C/T

Residential 300 houses

1 MW peak load DR / scheduling

Studio14 @ Mesa del Sol

our goal: to turn the entire feeder into a microgrid

what"the"u/lity"sees

Studio14

Tramway11

Sewer14

quack!

Problems"and"possible"(microgrid)"solu/ons

• Naturally!increasing!PV!penetra2on!at!the!distribu2on!level!

•  EVs!and!residen2al!ba9eries!• Higher!cooling!loads!• Need!for!higher!resilience!in!the!face!of!extreme!events!

• Mismatch!between!regulatory!framework!and!technology!

•  Lots!of!poten2al!for!control!at!the!commercial!and!residen2al!level!from!pervasive!IT!

• Decreasing!cost!of!ba9ery!storage!

• Growth!of!aggrega2on!service!providers!

•  Exis2ng!infrastructure!can!be!modified!at!moderate!cost!

A"tradi/onal"microgrid

•  240!kW!recip!genset!•  80!kW!phosphoric!acid!fuel!cell!•  50!kW!PV!array!•  160!kWh!ba9ery!storage!•  Heat!recovery!•  Cold!thermal!storage!•  Electric!&!absorp2on!chillers!• MicroQEMS!for!districtQlevel!energy!management!

•  BEMS!to!manage!systems!inside!microgrid!in!response!to!EMS!

U/lity=scale"distributed"PV"with"ba?ery

PV field (500 kW)power and energybatteries(1 MWh total)

PV inverterDAS

battery inverter

PNM-DOE PV + battery project•  Ba9eries!with!ultracapacitors!smooth!PV!intermi9ency!by!injec2ng!kW!

•  Storage!ba9eries!used!for!mul2ple!purposes!including!peak!shaving,!arbitrage!and!firming,!via!MPC!control!

!!

Less"conven/onal"resources:"HVAC"fans

PV!power!

bandpass!filter!of!PV!

fan!speed!

fan!current!net!power!

HVAC!fans!can!be!used!to!absorb!the!intermi9ent!part!of!nearby!PV!genera2on!with!li9le!if!any!effect!on!thermal!comfort!or!energy!consump2on!

More"op/ons"for"load"control

1000 residential units - afternoon peak dominated by cooling - can we put TCLs to good use?

20 large commercial units - based on UNM building data - cooling load could be shifted by active thermal storage

hidden"treasure:"TCLs"as"storage

!  In!New!Mexico,!A/C!loads!are!responsible!for!47%!of!peak!load!(Itron!Q!2006)!

!  Lots!of!other!TCLs!–!refrigerators,!water!heaters,!clothes!dryers!

!  increasingly,!these!devices!can!talk!to!the!world!–!think!Google!!

!  Can!these!do!more!that!“conven2onal”!DR?!

Two"hours"in"the"life"of"a"thermostat

TCLs"in"undisturbed"state

How"an"aggregate"of"TCLs"can"track"a"signal

Opera/onal"desirables

•  DayQahead!scheduling!•  ReQscheduling!when!be9er!informa2on!is!available!• maintaining!power!balance!in!real!2me!•  avoiding!voltage!fluctua2ons!•  automated!islanding!based!on!voltage!or!frequency!• maintain!power!quality!in!islanded!mode!•  synchroniza2on!and!reconnec2on!•  protec2on!/!safety!•  ancillary!services:!frequency!regula2on,!volt/VAR!support,!spinning!reserve,!demand!response,!black!start!support!

•  economic!benefits!to!service!area!

Scheduling"via"SoJware=as=a=Service

Example"of"an"op/mized"schedule

solar!chiller!operates!at!night!when!possible!cold!storage!charging!from!electric!chiller!always!offQpeak!no!storage!on!weekends!

Reac/ng"to"changing"circumstances

!  DayQahead!schedules!are!based!on!forecasts.!

!  When!reality!deviates!from!the!forecast,!adjustments!must!be!made.!

!  At!any!given!2me,!the!op2mal!use!of!resources!should!s2ll!be!sought.!

!  Model!Predic2ve!Control!is!applied!here!to!op2mize!based!on!current!condi2ons,!with!forecasts!made!on!a!shorter!2me!horizon.!

Minimize"cost"˄"func/on Subject"to"constraints" ˅

First"we"decompose"frequency"bands

We!can!associate!resources!with!slow!response!to!low!frequency!band,!ones!with!moderately!fast!response!to!medium!frequencies,!and!so!on,!cascading.!

Then"we"solve"the"MPC"for"each"band

As!expected,!cheap!resources!make!up!the!bulk!of!the!service,!while!the!others!come!on!line!as!needed.!!Individual!resources!can!consist!of!selfQcontained!physical!systems,!or!aggrega2ons!of!many,!and!can!be!more!or!less!localized.!!!

What"we"have"learned

!  Distribu2on!feeders!are!excellent!candidates!for!microgrifica)on+!  Some!DERs!are!s2ll!quite!expensive!–!a!0.5MW!microgrid!can!cost!several!$M!

–!on!the!order!of!approximately!$10/W.!O&M!can!also!be!problema2c!!  There!are!many!challenges!that!need!to!be!met!–!especially!in!islanded!mode,!

due!to!the!smaller!number!of!dispatchable!resources!–!so!control!is!key!!  There!are!opportuni2es!hiding!in!plain!sight!–!for!example,!control!of!TCLs!

provides!us!with!an!inexpensive!“ba9ery”!!  A!framework!to!integrate!the!design!and!control!of!the!feeder!microgrid!is!

star2ng!to!materialize!

Credits !  Ma9!Robinson!–!MS!UNM!ME!!  Leila!Ghanbari!–!MS!UNM!ECE!!  Feng!Cheng!–!PhD!UNM!ECE!!  Nicholas!Heine!–!PhD!UNM!ME!!  Yasser!Yasaei!–!PhD!UNM!ECE!

!  Birk!Jones!–!PhD!UNM!ME!

!  Alessandro!Pensini!–!PhD!DTU!