the role of utility-scale pv plants in grid stability and reliability

8/10/2019 The Role of Utility-Scale PV Plants in Grid Stability and Reliability

1/60


2/60

Key Messages

PV power plant is a cost-effective energy res

Well designed Grid Friendly PV plant activstabilizes grid and enhances its reliability

PV variability can be managed with existinginfrastructure through forecasting and site diwith minimum impact


3/60

First Solar Utility Scale PV Plant LeaderOver 3GW Completed or In Development (10MW AC 550MW AC Plants)


4/60

Utility Scale PV Power Plant Overview

PV ModuleArrays Inverters

Transformers

Combiner

BoxesPhotovoltaicCombiningSwitchgear

34.5kV (AC) Typical

300 to690V (AC)

1000V (DC)Substation

Gen Tie-line Pow69 to 525kV (AC)


5/60

PV Module

PV ModuleArrays

1000V (DC)


6/60

Combiner Box

Combiner

Boxes

1000V (DC)

Aggregates DC wiring from m(80KW-160KW)

Provides single dc output to i


7/60

1000V (DC)

Inverters

300 to690V (AC)

Utility Scale Solar Plant Inverters

Converts DC power to AC (l

Grid Management Functions

Reactive Power, etc.) UL1741 and IEEE1547 com


8/60

Transformer

Increases low AC voltage to m

AC voltage for Collection SysTransformers

34.5kV (AC) Typical

300 to690V (AC)


9/60

Power Conversion Station (PCS) Inverter & Step-up Transform


10/60

Photovoltaic Combining Switchgear (PVCS)

PhotovoltaicCombiningSwitchgear

34.5kV (AC) Typical

Aggregates AC power from mtransformers (up to 40MW)


11/60

Substation and Generator Tie-line

Substation

Gen Tie-line Pow69 to 525kV (AC)

Provides plant controls, disconnects, andstep up transformer

Delivers electricity to the grid


12/60

TOPAZ SOLAR

Largest utility scale solar plant in


13/60

AGUA CALIEN

Reliable bulk power generation utilizing advanced plant controls and forecas


14/60

COPPER MOUN

Co-located with existing gas combined cycle pow


15/60

GREENOUGH

Displacing the energy requirements of a desalinatio


16/60

Nakorn Ratchasima, Thailand 7


17/60

PHALODI

Providing energy security to India and displacing 1 million tons


18/60

DEWA SOLAR


19/60

PV Plant Variability Agua Caliente July 2013


20/60

Grid Integration and Plant Control Systems


21/60


22/60

Source: U.S. Department of Energy. "Benefits of Using Mobile Transformers and Mobile Substations for Rapidly Restoring Electric Service: A Report to the United State"

Conventional C

Generationtop down p

high voltage

voltage line

Typical Convention Generation, Transmission and Distribution System

PowerFlow

PowerFlow


23/60


As load cha

generators respond ins

change its o

Bulk electr

not commo

What happens when load changes? . Generator has to change output

LoadIncrease100kWGenerationIncrease

100kW


24/60


In Practice Aggregated load matters

LoadIncrease100kW

LoadDecrease

500kW

GeneratorDecrease

400kW What really

the changesaggregated

individual l

M lti l G t d C t l A


25/60

Source: Bernd Engel, SMA

Multiple Generators and Control Areas

In grid of reasonable size, multiple genera

are present and are scheduled for dailyoperation

Total Generation = Aggregated Load + L

a Control Area

Must maintain regulating and contingency

reserves to meet control performance andreliability standards

Multiple Loads

Multiple Generators

D il L d F i d G Di h


26/60

Time of Day

0 6 12 18 24

Daily Load Forecasting and Generator Dispatch

Day AheadForecast

Load

Econom

use load

commit

day ahe

G id O D l i h V i bili & U i


27/60

Time of Day

0 6 12 18 24

Grid Operators Deal with Variability & Uncertainty

Day AheadForecast

Load

Use load forecast a

uncertainty in load

generation throughand dispatch opera

ActualLoad

Load Following and Regulation Reserves


28/60

Load Following and Regulation Reserves

Regulation = Actual Load Real-time Forecast LoadLoad Following = Real-time Forecast Load Hourly Schedule

Lo

Ad

(10

Re

Au

adj

oumi

i f S l G id


29/60

Y

Power Systems PGrid Stability & Reliability

Milliseconds to Minutes Hours to Days

Load Balancing

Key Topics Impact of PV Solar on Power Grid

PV solar

intermittency raisesgrid stability andreliability concerns

PV Variability

increasesoperationalcomplexity

Higher

penetratrequiresgrid flex

V i bl G i I i T i


30/60

Variable Generation Integration Topics

Source: Pacific North West Laboratory, Grid Stability; The Challenges of power grid stability. http://eioc.pnnl.gov/research/gridstability.stm

Grid Stability & Reliability

Msec to Minutes Years

Power Systems Planning & Design

Hours to Days

Load Balancing

Milliseconds to Minutes


CONCERN

Add grid controls to support reand grid security

LEARNING

Solar PV generation doesnot contribute to the reliabilitybulk generation

NERC T k F I t itt t R I t t th G id


31/60

NERC Task Force on Intermittent Resources Impact to the Grid

Voltage, VAR control and/or power factor regu

Fault ride through

Real power control, ramping, and curtailment

Primary frequency regulation

Frequency droop response

Short circuit duty control

Modern solar plants can now contribute to threliability and efficiency of grid operationthe following capabilities:

V lt S t P Fl R l


32/60

P

20 kV

Transformer

0,4 kV Conductor House 1House 2

Last 1La

P

Substation

MV Grid

V o

l t a g e

Voltage Support Power Flow Reversal

A l l o w a

b l e

R a n g eDistance

PV

MaximumLoad

Normal FlowVoltage Drop

High Feed-inLow Load

+ Reactive Power

Reverse Flow withPV Reactive Power

Voltage DropHigh Feed-in

Low Load

Reverse FlowVoltage

Violation

PV With Reactive Power Capability Avoids Costly Network Upgrades

Sourc


33/60

Voltage Regulation


34/60

Voltage Regulation

Utility Scale Active Power Control


35/60

Utility Scale Active Power Control

ReducedPower

Grid Integration and Plant Control System


36/60

Grid Integration and Plant Control System

Real-time ControllersSatellite Imagery

Transformer

Inverters

PV ModuleArrays

CombinerBoxes

Power Conversion Station (PCS) Photovoltaic CombiningSwitchgear (PVCS) Substation

Plant SCADA system

Checks gridrequired set

Sends indivieach invertelosses, and p

Controls quout of the PV

All every 100Short TermForecasting

Set Points

Without a Plant Control System


37/60

Without a Plant Control System

InverterCurtailed

Locally

InverterCurtailedLocally

Benefit of Plant Level Control System


38/60

Benefit of Plant Level Control System


39/60

Proprietary plant controller

Dynamic Power Factor Regulation


40/60

Dynamic Power Factor Regulation

Source: Agua Caliente PV Plant in Yuma, Arizona, USA May 23, 2012. ~212MW on-line.

Command Power Factor

Power Factor SetPoint Changedfrom 0.98 to 1.0

Reaches 90%Steady State Valuein ~ 3.2 seconds

InvertersChangeVAr Output

Plant Curtailment Test


41/60

Power Curtailment at Different Levels

Source: Agua Caliente PV Plant in Yuma, Arizona, USA March 13, 2012. ~90MW on-line.

Set PointReduced

Set PointIncreased

Ramp rates betweenset point changesare controlled

Inverters areTurned Down/OFF to curtail

output

Ramp Rate Controls


42/60

Stopping and Starting One Block (30MW)

Source: Agua Caliente PV Plant in Yuma, Arizona, USA March 13, 2012. ~90MW on-line.

Plant Stop Command

Plant Start Command

Inverters areStarted inSequenceInverters are

Turned Off inSequence;Ramp Ratesare Controlled

Frequency Droop Control


43/60

q y p

Plant Controls Support Frequency Droop

Ability to reduce active power in casegrid is overloaded (i.e., highfrequency)When grid needs more generation(i.e., low frequency) renewable plantcannot increase active power unless plant is already curtailedthen it can increase power

Decrease Active PowerCase of High Frequen

Power Plant Fault Ride-Through Behavior


44/60

PV Plants arsupport bothfrequency r

capability levscale inverte

pra

(Source: SMA)

What Makes a PV Plant Grid Friendly?


45/60

y



46/60

Hours to Days

Load Balancing

g p

Solar Generation is not fu

Adds variability and uncecomplicates daily dispatch

Years

Power Systems Planning & DesignGrid Stability & Reliability

Msec to Minutes Hours to Days

Load Balancing

CONCERN

Integrate forecasting into daily

Improved operating procedurearea, frequent updates, rampin

LEARNING

Net Demand


47/60

Source: SEC Data. 2020 Load and Generation Mix Projected @5.6% annually for illustration purposes only. FS estimate on PV contribution. Actual resource distribution likely to b

Time of Day (Hours)

D a i l y L o a

d

Load (MW)Net Load Curve (MW)

0 12 24

Aggregation Effect Between Plants Reduces Variability


48/60

Single Location

20 Bundled Locations

One-minute Global Irradiance (W/sq.m)

One-minute Global Irradiance (W/sq.m)

Spatial diversity of solar plants reduces aggregated variabilityminimizing grid impact as the number of solar plants increase

Source: Implications of Wide -Area Geographic Diversity for Short- Term Variability of Solar Power; Andrew Mills and Ryan Wiser, Lawrence Berkeley National Lab

Source: H

Impact of Cloud Passage on Plant Output


49/60

As plants become larger high frequency variability redu

NRG/MidAmerican Agua Caliente 290MW ac


50/60

Yum Dat 2,4 39, PPA EPC

First 2008 EPC Projec tSempra El Dorado10MW

North AmericaLargest PV PlantEnbridge Sarnia80 MW

3 . 0 M i l e s

2.0 Miles
http://powerprojects.firstsolar.com/epc2010/AguaCaliente290/Photos/Agua%20Site%20Aerial%20November%202011.jpghttp://powerprojects.firstsolar.com/epc2010/AguaCaliente290/Photos/Agua%20Site%20Aerial%20November%202011.jpghttp://powerprojects.firstsolar.com/epc2010/AguaCaliente290/Photos/Agua%20Site%20Aerial%20November%202011.jpghttp://powerprojects.firstsolar.com/epc2010/AguaCaliente290/Photos/Agua%20Site%20Aerial%20November%202011.jpghttp://powerprojects.firstsolar.com/epc2010/AguaCaliente290/Photos/Agua%20Site%20Aerial%20November%202011.jpghttp://powerprojects.firstsolar.com/epc2010/AguaCaliente290/Photos/Agua%20Site%20Aerial%20November%202011.jpghttp://powerprojects.firstsolar.com/epc2010/AguaCaliente290/Photos/Agua%20Site%20Aerial%20November%202011.jpghttp://powerprojects.firstsolar.com/epc2010/AguaCaliente290/Photos/Agua%20Site%20Aerial%20November%202011.jpghttp://powerprojects.firstsolar.com/epc2010/AguaCaliente290/Photos/Agua%20Site%20Aerial%20November%202011.jpghttp://powerprojects.firstsolar.com/epc2010/AguaCaliente290/Photos/Agua%20Site%20Aerial%20November%202011.jpghttp://powerprojects.firstsolar.com/epc2010/AguaCaliente290/Photos/Agua%20Site%20Aerial%20November%202011.jpghttp://powerprojects.firstsolar.com/epc2010/AguaCaliente290/Photos/Agua%20Site%20Aerial%20November%202011.jpghttp://powerprojects.firstsolar.com/epc2010/AguaCaliente290/Photos/Agua%20Site%20Aerial%20November%202011.jpghttp://powerprojects.firstsolar.com/epc2010/AguaCaliente290/Photos/Agua%20Site%20Aerial%20November%202011.jpghttp://powerprojects.firstsolar.com/epc2010/AguaCaliente290/Photos/Agua%20Site%20Aerial%20November%202011.jpghttp://powerprojects.firstsolar.com/epc2010/AguaCaliente290/Photos/Agua%20Site%20Aerial%20November%202011.jpghttp://powerprojects.firstsolar.com/epc2010/AguaCaliente290/Photos/Agua%20Site%20Aerial%20November%202011.jpghttp://powerprojects.firstsolar.com/epc2010/AguaCaliente290/Photos/Agua%20Site%20Aerial%20November%202011.jpghttp://powerprojects.firstsolar.com/epc2010/AguaCaliente290/Photos/Agua%20Site%20Aerial%20November%202011.jpghttp://powerprojects.firstsolar.com/epc2010/AguaCaliente290/Photos/Agua%20Site%20Aerial%20November%202011.jpghttp://powerprojects.firstsolar.com/epc2010/AguaCaliente290/Photos/Agua%20Site%20Aerial%20November%202011.jpg


51/60



52/60

Years



Msec to Minutes Hours to Days

Load Balancing

Years


Variable generation requires gr

CONCERN

Adopt diverse resource portfolincrease flexibility and reduce

LEARNING

Complementing the Power Portfolio


53/60

Solar is a hedge against fuel price volatility

Power System Planning and Design


54/60

LeananGe

Hours of Operation / Year

S

y s

t e m

L o a

d

Base Load

Generation

Mid-Merit

Generation

Peaking

Generation

System Load

Mid-Merit

Generation

Base Load

Generation

Peaking

Generation

Gas GT

Gas CCGT

Coal

Hydro

Variable generation has impact onlow and minimum load conditions

Addition of varaible generation:Net Load Duration Curve becomesmore steep

Solar generationreduces peak load

Requires a generation mix with more operationalflexibility to serve the net load

(SoNet System Load with VG

California 20% Renewables and Growing to 33%


55/60

Operators have managed high penetration. Others can leverage this learniCAISO Testimony in 2010 CPUC LTPP Docket No. R.10-05-006; July 1, 2011; Exhibit 1, slide 5; trajectory scenario

Successfully integrated renewables today

Building toward 33% reenergy

0

5000

10000

15000

20000

25000

2006 (~10%) 2012 (20%) 2020 E (33%)

GWh

Dispatchable RenewablesWindSolar

Typical Load, Solar and Wind Generating Mar


56/60

Source: CAISOMatt BurkhartSDGE, SemprFeb 13,2013Solar Power G

Net Load and Flexible Capacity Needs


57/60

Source: CAISOMatt BurkhartSDGE, SemprFeb 13,2013Solar Power G

Study needed to determine shape of Flexibility Supply Curve and QuantifyFlexibility Supply Curve


58/60

Sources o

LowCost

HighCost

Markets

FlexibleGeneration

TraditionalStorage

Wind/SolarCurtailment

Storage

In Range of1 or 2%

Hydro with DamsPumped Hydro

Gas StorageSimple Cycle GTCombined CycleSome Coal PlantsReal-Time

Hour AheadDay-AheadPrice Responsive LoadAncillary Service

Conclusions


59/60

Modern PV plants can contribute actively to grid streliability

PV variability can be managed without significant i

existing grid infrastructure through site diversity anforecasting

PV power plants offer a cost-effective energy resou

Lessons learned to date on Renewable Integration Large-scale PV has been successfully integrated in

worldwide No reported issues due to often cited barriers: PV v

harmonics, DC current injection, anti-islanding faiprotection coordination

Bulk energy storage has not been necessary for vargeneration integration


60/60

the role of utility-scale pv plants in grid stability and reliability

Documents