promises and challenges of utility scale pv grid integration … · 2009-02-04 · promises and...
TRANSCRIPT
Promises and Challenges of
Utility Scale PV Grid Integration
- lessons from Lana’i
Leo F. Casey, Satcon
Robert F. Johnson, SunPower
Bob Reedy, FSEC
1.13.2009
Outline
• Leo Casey, Robert Johnson, Bob Reedy- Introduction to
Presenters and Organizations
• Robert Johnson- Lana’i PV Power Plant Project Overview
• Leo Casey- Lana’i Grid Stability Challenges
• Robert Johnson- Communications & Controls
Implementation
• Bob Reedy – Integration with SEGIS Plans
The Lana’i Grid and its Stability
Challenges for Renewables
Recloser
(36)
(34)
(35)
(32)
(31)
(19)
(300)
(3)
450
kVAR
RECL 4022
RECL 4023
RECL 4021
(33)
(30)
(310)
(14)
(13)
(12)
1222 SW (NO)
(100)
RECL 1226 RECL 1227
(16) (15)
RECL 1228
RECL 1225
SW (NO) (11)
1229 SW
(102)
(103)
(101)
(77)
(7)
(71)
(9)
(5)
(4)
(6)
(61)
(8)
(1)
(999)City #1
City #2
Hotel Ckt
G~
=== V
Z
Z
G~
G~
G~
G~
G~
G~
G~
G~
Future CHP
R
WELL2
WELL1
Intertie Breaker
V1 V2 V3 Battery
1223 SW
1221 SW
1212 SW1208 SW1210 SW
MANELE
MANELSUB
4023
4022
4021
E1B
KOELE_LD
KOELETAP
HARBOR12
WELL4
MAUNB33
WELL5
WELL3
WELLB30
WELL9MAUNALEI
WELL
E6
E1
LALASUB
E13
PPTSF
KAUMALA
KOELE
HARBOR
PPTAP
LALATAP
LSRBT1LSRPV3LSRPV2LSRPV1
LANAI6LANAI5LANAI4LANAI3LANAI2
HOTEL
LANAI1
L8_D-8L7_D-7
LSRPV
LANAI A
• Two 2.2MW diesel Generating Stations
• Six 1MW diesel Locomotive ‘standby’ generators
• Nominal 4MW load
• Expensive power(fuel), great solar resource
• “diesel” grid
Lana’i PV Plant Impact Overview
• 1.5MW Solar Farm
• 12 SatCon, GEN I, 135kW Inverters
• 12 independent tracking solar arrays
• 10% of Lana’i annual power demand
• 30% Supply during peak solar hours (4MW)
• BUT potentially destabilizing AND limits of
Lana’I grid are extremely wide so non-UL1741
non IEEE1547 inverter required, and under
Utility Control
LSR Point
of Common
Coupling
Lanai Generators
R
Hotel
Intertie Breaker
DC
AC
DC
AC
DC
AC
DC
AC
DC
AC
DC
AC
DC
AC
DC
AC
DC
AC
DC
AC
DC
AC
DC
AC
DC
AC
DC
AC
DC
AC
DC
AC
DC
AC
DC
AC
DC
AC
DC
AC
DC
AC
DC
AC
DC
AC
DC
AC
DC
AC
DC
AC
DC
AC
DC
AC
DC
AC
DC
AC
DC
AC
DC
AC
DC
AC
DC
AC
DC
AC
DC
AC
DC
AC
DC
AC
DC
AC
DC
AC
DC
AC
DC
AC
DC
AC
DC
AC
DC
AC
DC
AC
DC
AC
DC
AC
DC
AC
DC
AC
Battery
135 kVA per
Inverter Rating
Recloser
Anticipated PV Output and effect on System Load for July
0
1,000
2,000
3,000
4,000
5,000
6,000
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
Hour of the Day
Kilo
wat
ts
Lanai System Load Net System Load w/PV PV Output
Anticipated PV Output and effect on System Load for January
0
500
1,000
1,500
2,000
2,500
3,000
3,500
4,000
4,500
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
Hour of the Day
Kilo
watts
Lanai System Load Net System Load w/PV PV Output
Players / Rules of Engagement
MECO – Maui Electric Company
– Utility Company: Buying power from Solar Farm
Lanai Sustainability Research, LLC.
– Owner of Solar Farm: Selling Power
&
SunPower, PV System Designer, Integrator
Satcon, Grid Connected Inverter manufacturer (Bob Reedy –
FSEC, SEGIS partner)
Serra, SCADA Interface, SunPower Sub-Contractor
Lanai PV Interconnect Requirements Study, June 25, 2008, KEMA Inc.MECO-LSR Power Purchase Contract, “Power Purchase Contract for As-
Available Energy, August 8th, 2008”
1) Remote control of Real Power, also termed curtailment
2) Remote control of Power Factor, within a fairly narrow range
3) Grid disturbance ride-thru capability
4) Ramp rate limits and control (dP/dt)
Over 500 systems on 4 continents
Over 400 MW installed
Largest solar projects in North America
Worldwide footprint World record solar cell efficiency = MORE POWER
Established and Proven. Technology
Leaders.
Publicly traded (NASDAQ) and partnerships
with top-tier financiers
4,000 Employees: All we do is solar Over 85 patents and over 20 years of R&D
Over a quarter century of experience
Energy efficiency expertise
SunPower Provides Solar
Wherever You Need It
ResidentialCommercial Power Plants
Largest Residential Install
Base in North America
Largest Commercial
Install Base in North
America
Largest Solar PV Power
Plants in North America
Number 1 Number 1Number 1
Satcon - Grid Connected Electronics
Grid Energy +Grid Support + Utility Scale
• Founded 1985
• Public 1992 (SATC)
• 275 employees
• 115 patents
The New Value Equation
2010 +2000 2005
Utility ReadyLarge Scale Grid
Integrated AdoptionCommercial
ReadyEarly Majority
Ov
era
ll P
V O
utp
ut
Visionary
ReadyEarly Adopters
Today
Florida Solar Energy Center
Research, Applications,
Education, Training,
Testing
Solar Energy Division
Building Efficiency
Division
Advanced Fuels for
Energy Division
Creating Energy Independence Since 1975
A Research Institute of the University of Central Florida
Lana’i PV Power Plant – Project Overview
Manele
Hotel
PV Plant
Miko Power
Plant
Lana’i City
& Koehle
Lodge
1.2MW AC
Lana’i PV Power Plant – Project Overview
PV Array
Inverters
1-4
PV Array
Inverters
5-8
PV Array
Inverters 9-
12
Inverters 9-
12
Inverters 5-
9
Inverters 1-
415kV Switchgear
Overhead
Lines to
Miko Basin
Power Plant
Overhead
Lines to
Manele Bay
Hotel
Lana’i PV Power Plant – Single Line
• Single Line
Provisions
for energy
storage
system
MECO Control Requirements
• The PPA signed between LSR and MECO stipulates several site control features:
– Curtailment Control
• Utility provides set point in fairly continuous increments between 0-1200kW
• Plant response should be rapid without violating ramp-rates limits
• Utility receives status indicating achievement of set point
– Power Factor Control
• Utility provides set point between 0.95 lagging to 0.98 leading
• Utility receives status indicating achievement of set point
• The PV Plant produces and consumes reactive power at utility command
– Ramp-Rate Limiting
• Plant output fluctuations need to be limited to 6kW/s during beginning/end of
day and startup and shutdown periods
• Plant output fluctuations needed to be limited to 40-60 kW/s at other times
Design – PV Site Controller - Architecture
Grid Operators on Maui control power
output and power factor set points from
their Areva HMI
Data is transmitted Ethernet over a
microwave uplink
Redundant control is available at Lanai
Control Center if communication fails
with Maui. Set points are passed
through to data gateway at PV siteData is transmitted via DNP3 protocol
over fiber to the onsite data gateway
Data Gateway (Orion 5r) acts as both
master and slave device. It translates
set points from DNP3 to modbus and
receives set points from PV Site
Controller
Data is transmitted via modbus over
RS232 and RS485 to PV Site Controller
PV Site controller maps set
points, status points and
process values between Utility
SCADA and site devicesCommunication to inverters and
other devices is via modbus TCP
over fiber and copper
Status Data, Process Values & Control Algorithm
• In addition to setting power output and
power factor, the grid operator requires data
on status and real-time process values to
evaluate plant operation
• Status Data
– Inverter on/off
– Last commanded global curtailment and
power factor set points
– Last commanded individual inverter
curtailment and power factor set points
– Intertie breaker status open/closed
• Process Variables
– Real-time power output and power factor at
point of interconnection
– Individual inverter real and reactive power
output
– Available generation capacity based on real-
time calculation using irradiance, wind speed
and temperature data
Change In Curtailment
Set Point From Orion 5r?
Write Inverter
Curtailment Set
Points to All
Inverter
Write All Inverter
Power Factor Set
Points to Inverter
Read Curtailment
Process Value
From Meters
Read Power
Factor Process
Value From
Meters
Read MET Data
From SunPower
DAS
Change In Power Factor
Set Point From Orion 5r?
Yes
Yes
No
No
Begin
Write Inverter
Curtailment Set
Points From
Inverters to PLC
Status Register
Write Inverter
Power Factor Set
Points From
Inverters to PLC
Status Register
SUNPOWER DAS
(CR1000 w/NL115 )
Modicon
PV Site Controller
Orion 5r RTU(MECO Comm Link )
Inverter Inverter
Inverter Inverter
Switch
VerisMeter
Inverter Inverter
Inverter Inverter
Switch
VerisMeter
Inverter Inverter
Inverter Inverter
Switch
VerisMeter
Primary Switch
Modbus TCP
Over Fiber Modbus TCP
Over Fiber
Modbus TCP
Over Fiber
Modbus RTU
Over RS -232
Modbus TCP
Over Cat 5
Modbus TCP
Over Cat 5
Modbus TCP Over Cat 5 to Switch
Cellular Router
(Digi ConnectPort )
Modbus TCP Over Cat 5 to Switch
Modbus TCP Over Cat 5 to Switch
ATT 3G Connection via
Static IP
Modbus RTU
Over RS-485
Modbus RTU
Over RS -485
Orion as Master
Modbus TCP
Over Cat 5
Modbus TCP
Over Cat 5
Digi Serial to TCP/IP
Gateway
Bitronics
M871 Meter
DNP
Orion as
Slave
Modbus RTU
Over RS - 485
Control System – Communication Network
Interfacing with the Utility SCADA
MECO’s HMI interface with intertie breaker and
recloser**Screen shots provided by Dwight Weiding of MECO
Interfacing with the Utility SCADA
MECO’s HMI interface with Lanai PV
Plant* *Screen shots provided by Dwight Weiding of MECO
Interfacing with the Utility SCADA
MECO’s HMI interface with Lanai PV
Plant
MECO’s HMI interface with Lanai
Grid**Screen shots provided by Dwight Weiding of MECO
PV Site Controller – Control Details & Challenges
– Curtailment is measured at point of interconnection, but control is achieved at the inverters
• Must account for variable transformer losses & maintenance scenarios where inverters are offline
• Suggests a closed loop control approach, but fairly complicated to implement, primarily due to latency
issues
• Open loop control requires several scale factors dependent on plant configuration
– Power Factor also measured at point of interconnection
• Must account for discrepancy in measured PF versus commanded PF
• Difficulty developing HMI for this feature. Actual implementation uses discrete set points, e.g. 0.95, 0.96,
0.97 lagging and 0.98, 0.99 leading, etc.
– One big challenge is communication latency
• This latency can occur at the inverter, which requires time to process command and then act
• Another source of latency is created by the communication network itself and the protocol employed
– Managing the broad range of device types, protocols, communication mediums and
scaling factors makes for a complex system.
Performance Data – Set Points with Ramp Rates
Performance Data – Power Factor Control
Future Developments
• These control features are new to PV plants and there is muchdevelopment work to be done, and many opportunities:
• Optimization of control techniques
• Normalization of Utility HMIs
• Integration with storage
• Ancillary services like voltage support
• Open loop versus closed loop control
• Remote Restart & Reclosing
• Parallels to Smart Grid
Power Limit (Curtailment) & Power Factor Control
• Power Limit involves disabling MPPT routine (“quasi” slew rate
possible within Inverter)
• The full range for the power factor command is from 0.71 leading to
0.71 lagging, plus status flag
• Power factor control is realized by keeping real current and reactive
current at a fixed ratio determined by the commanded power factor
Power Factor Control
Communication of power factor
set point
Modbus TCP
Power factor range 0.98 Leading to 0.95
Lagging
Power factor increment size 0.005
Power Factor response time <5s
Power Limit Control
Communication of power-limit set point Modbus TCP
Power-limit range 0-135 kW
Power-limit increment size 32.96 W
(135/4096)
Ramp-rate limit 6 kW/s
Response time <5s
Curtailment Power Factor Control Testing -
Results
•Implemented
•Tested in Certification Lab
•Verified at PV-Lana’i
Ride-Through
• Traditional Inverters (IEEE1547 & UL1741) operate in narrow range
of voltage and frequency and are required by statute to disconnect
immediately in the presence of fairly minor deviations.
• The intent here is to operate over a much wider range, and to
tolerate fairly rapid dynamics.
• Inverter must operate safely, for extended periods, over the wide
voltage and frequency extremes being considered.
• The nominal voltage “V” referenced in the requirements is 12.47 kV
at the point of grid interconnect, and 60Hz is the nominal frequency
‘f’ referenced in the table below.
• Implemented, tested (Cert Lab), tested in Microgrid, simulations,
observations
Required Ride-Through Capabilities
Grid
Frequenc
y
Inverter Response
65 Hz < f Inverters must disconnect after
160 milliseconds
62 Hz f
65 Hz
Inverters may disconnect after 2
seconds
61 Hz f
< 62 Hz
Inverters may disconnect after 6
seconds
57 Hz f
< 61 Hz
Inverters will stay online
55 Hz f
< 57 Hz
Inverters will stay online through
this extended ride-through
range55 Hz > f Inverters may initiate
disconnection from the grid
within 160 milliseconds
Grid Voltage Inverter Response
1.20 pu < V Inverters shall stay online for more
than 160 milliseconds
1.10 pu V
1.20 pu
Inverters shall stay online for at
more than 3 seconds
0.90 pu V
< 1.10 pu
Inverters shall remain online
0.70 pu V
< 0.90 pu
Inverters shall stay online for more
than 2 seconds
0.05 pu V
< 0.70 pu
Inverters shall stay online for more
than 600 milliseconds
0.05 pu > V Inverters may initiate disconnection
from the grid
•Verified quasi statically
•Verified dynamically in MicroGrid
Transient Ride-Through Performance - Simulation
• The PV inverter equipment was supplied as UL1741 compliant, but the required ride-through
capability for this project is a dramatic departure from UL standard practice,
• Grid Voltage Monitor. Anti-islanding protection has been disabled, and the ac line voltage
monitoring function has been re-designed to accommodate the specified voltage and frequency
deviations without initiating an inverter shut-down.
• Inverter Control and Self-Protection. The transient response of the inverter controls has been
evaluated to make sure that transient grid voltage deviations will not cause inverter over-current to
occur.
• A detected over-current would result in an immediate trip for inverter self-protection. This
investigation was based on a computer simulation of the power circuit, including a detailed model
of the inverter control system. the phase-locked loop (PLL) algorithm was replaced with an
alternative algorithm that is considered more suitable for dynamic tracking during voltage
disturbances.
• For this project, computer simulation was used to model equipment performance for a number of
fault conditions at the PV station MV bus. These cases are illustrated in the following charts
• The results indicate that the inverter current will not reach the over-current trip threshold for the two
unbalanced faults shown in Figs. 2 and 3. In the third case (balanced three-phase to ground fault),
shown in Fig. 4, the inverter current peak immediately following the onset of the fault is close to the
trip level and indicates that there is a slight possibility of an over-current trip under extreme
conditions. We have moved the trip points up accordingly. Automatic restart is another possibility.
Ride-Through Simulation Results - Model
Simulation Results (1)
Simulated A-phase to ground fault at the Lanai PV station MV bus.
Simulation Results (2)
Simulated A-phase to B-phase to ground fault at the Lanai PV station MV bus.
Simulation Results (3)
Simulated 3-phase to ground fault at the Lanai PV station MV bus
34
FSEC Team SEGISGoal: “Walk Like a Duck”
=PV in Aggregate, Behaving Like
Conventional Utility Generation--
& Then Some
35
FSEC Team SEGIS: Innovations
Utility Control of Islanding
Maintain DG when needed most
Utility Control of Inverter VAR Generation
Use of DG asset in a new way
Shared Inverter Designs for Complex Sites
Cul-de-Sac Plant, Linear PV Farm, Weird Roofs
36
FSEC Team SEGIS:Critical Features
Enhanced island protection
Utility control of online/offline status
PV generation ride-through of grid disturbances
Fast & Dispatchable VAR Support
Peak-shifting & anytime-emergency peak
generation with energy storage & BEMS
37
FSEC Team SEGIS:Enhanced Features
Stabilization of Mini/Micro Grids (Island Mode)
Harmonic Cancellation
Deliberate Phase Unbalance
Prognostics and Diagnostics
Real-time phase balance of feeder circuits
Enhanced transient response (H Constant)
Oscillation Damping
Spinning & Ready Reserve
38
The Really BIG ISLAND:
Eastern Interconnect-- “the World’s Biggest Machine”
925,000,000 hp - 2,000,000 sq mi -- 3600rpm
39
Frequency ExcursionsSouthern Control Area Frequency
8-14-03
59.000
59.200
59.400
59.600
59.800
60.000
60.200
60.400
60.600
60.800
61.000
3:10:00 PM 3:11:00 PM 3:12:00 PM 3:13:00 PM 3:14:00 PM 3:15:00 PM 3:16:00 PM 3:17:00 PM 3:18:00 PM 3:19:00 PM 3:20:00 PM
Fre
qu
en
cy
, H
z.
60.236 Hz. at 3:10:54 PM CDT
Set Point Frequency
Eastern Interconnection Frequency
t0
25 sec of interest
40
Something Really Scary !
Apparent & Approximate
Envelope of the Undamped
Oscillation, before System
Reconfiguration (Islands) Led to
a Damped Oscillation
Effective Breakup of the EI into Islands
(largely due to operation of Zone 3
distance relays)
Eastern Interconnection Frequency
8-14-03
t0
Note:
Frequency of the Oscillation is
about 1/3 Hz. This is the
“Frequency of the Frequency”
Undamped Period Damped Period
41
Southern Control Area
Generator UF coordination curve
54
54.5
55
55.5
56
56.5
57
57.5
58
58.5
59
59.5
60
1 10 100 1000 10000
Time (Cycles)
Fre
qu
en
cy (
Hz)
Trip Point per
IEEE 1547
Trip Point of
Turbines
42
“Anti-Anti” IslandingBack to Basics:
Control Areas Use PermissivePLCC to Maintain GenerationDuring Disturbances
No Freq Push issues withhigh penetration
Certainty with down lines
Provides Control AreaShutdown Capability duringOver Generation events
William of Ockham
b. 1285 Surrey, England
43
Old View – Island BAD
44
New View – Island GOOD
MicroGrids – “ACCESS” & SDS Enable UPS-PQ
3 3
UTILITY GRID
FACILITY LOADS
1000 kW MAX
CRITICAL LOADS
21 kV, 60 Hz
21 kV, 60 Hz
3
480 V, 60 Hz
480
21000
3
3
3
1000 kW
max
500 kW
max
500 kW
max
EXISTING FUEL CELL
EXISTING PV ARRAY
NEW ENERGY STORAGE
FACILITY LOADS
1000 KW MAX
CRITICAL LOADS
UTILITY
GRID
STATIC
DISCONNECT
SWITCH
(SDS)
ISLAND GRID
ENERGY STORAGE UNIT
CONTROLS VOLTAGE AND
FREQUENCY IN ISLAND MODE
•Renewables plus back-up generation plus storage plus SDS
•UPS quality power
Simulated 3-Phase Fault on Utility Grid
2.2 MVA, 0.8 P.F. Constant Load on MicroGrid
ENERGY STORAGE CONVERTER OUTPUT CURRENT
FUEL CELL CONVERTER OUTPUT CURRENT
ISLAND GRID VOLTAGE
ISLANDVOLTAGE
MAINTAINED
GRID CURRENTS THROUGH INTER-TIE
UTILITY GRID (480 V) VOLTAGES (L-N)
FAULT
SDS CLOSED
SDS OPENED
DISCHARGINGCHARGING
CHARGING
FUEL CELL
OUTPUT
MAINTAINED
3 3
UTILITY GRID
FACILITY LOADS1000 kW MAX
CRITICAL LOADS
480 , 60 Hz
480 , 60 Hz
3
480 V, 60 Hz
480
21000
3
3
RENEWABLE
DIESEL GENSETS (TQGs)
NEW ENERGY STORAGE
MICROGRID
LOADS
UTILITY
GRID IF
PRESENT
STATIC
DISCONNECT
SWITCH
(SDS)
TACTICAL MICROGRID
ENERGY STORAGE UNIT
CONTROLS VOLTAGE AND
FREQUENCY IN MICROGRID
G D
Utility Grid Connection optional – Tactical
Micro Grid
Simulated Operation in Island Mode -Load
Suddenly Increased (1.1 to 2.2 MVA, 0.8 P.F.)
ENERGY STORAGE CONVERTER OUTPUT CURRENT
FUEL CELL CONVERTER OUTPUT CURRENT
ISLAND GRID VOLTAGE
ISLAND
VOLTAGEMAINTAINED
GRID CURRENTS THROUGH INTER-TIE
UTILITY GRID (480 V) VOLTAGES (L-N)
FUEL CELL
OUTPUT
MAINTAINED
LOAD SUDDENLY INCREASED
CHARGING
DISCHARGING
Lanai
True “Island” Grid
Palawai Basin - 10 Acre Site
Advanced Inverter Features implemented
under Utility Contrtol
Thank you.
Leo Casey
(617) 897-2435
Contact: Contact:
Robert Johnson
(510) 260-8373
Contact:
Bob Reedy
(321) 638-1470