Download Hybrid Reactive Power Compensators

Dynamic Reactive Power Control
for Wind Power Plants
Techwindgrid ’09 Grid Integration Seminar
Madrid 20/21 April 2009
Ernst Camm Charles Edwards
Ken Mattern Stephen Williams
©2009
www.sandc.com
Presentation Outline
• Introduction to S&C Electric Company
• Introduction to Dynamic Reactive Power Control for
Wind Power Plants
• Inverter
Inverter--based Dynamic Compensators
• Hybrid Reactive Power Compensators
• Power Factor Control Using Hybrid Reactive Power
Compensators
• Harmonic Resonance And Harmonic Current Injection
by WTGs
• Summary
Introduction to S&C Electric Company
• Established in 1911
• Employee
Employee--owned company
• Headquarters in Chicago, IL
USA
• 2,100 employees worldwide
• Leading provider of products
and services for electric
power switching, protection,
automation, power quality
solutions, and engineering
services
Introduction to S&C Electric Company
• Manufacturing & engineering
facilities in USA
–
–
–
–
Chicago, IL
Franklin, WI
Orlando, FL
Alameda, CA
• S&C subsidiaries
–
–
–
–
–
S&C Electric Canada Ltd
S&C Mexicana, S. de R.L. de C.V.
S&C Electric do Brasil Ltda
S&C Electric (Suzhou) Co., Ltd
S&C Electric Europe Ltd
Introduction to Dynamic Reactive Power
Control for Wind Power Plants
• Grid code reactive power
requirements for wind power
plants
– Vary power factor to meet
system operating
conditions
– Control voltage
• Incentives for reactive power
production/consumption
– Bonus/penalty payments
during different demand
periods
Power Factor
Inducti
ve
Capacit
ive
<0.95
0.95 to <0.96
0.96 to <0.97
0.97 to <0.98
0.98 to <1.0
1.0
0.98 to <1.0
0.97 to <0.98
0.96 to <0.97
0.95 to <0.96
<0.95
Bonus/Penalty by
demand period
[% of reference tariff]
Peak
(Punta)
Flat
(Llano)
Valley
(Valle)
-4
-3
-2
-1
0
0
0
2
4
6
8
-4
0
0
0
2
4
2
0
0
0
-4
8
6
4
2
0
0
0
-1
-2
-3
-4
Inverter--based Dynamic Compensators
Inverter
• Voltage source inverter using PWM
techniques to synthesize a voltage
either greater than or less than the
bus where the inverters are
connected
• Commercial inverterinverter-based dynamic
compensators are available in
modules of ±1.25 MVAR at 480 V
• Short
Short--term capabilities of 3.3 MVAR
per module (i.e. 264% of the
continuous rating) for up to 3
seconds
• Capability to swing from full inductive
to full capacitive output, or vice
versa, in about 2 milliseconds
Inverter--based Dynamic Compensators
Inverter
• Two modules can be connected to
a single 2.5 MVA, 0.48/33 kV stepstepup transformer for connection to a
33 kV (or other medium voltage)
collector substation
• Larger dynamic compensators are
comprised of multiple ±2.5 MVAR
units with stepstep-up transformers
• A single ±1.25 MVAR module can
be connected via its own stepstep-up
transformer if the total MVAR rating
requires an odd number of inverters
Hybrid Reactive Power Compensators
• Consist of an inverter
inverter--based
dynamic compensator and one or
more mediummedium-voltage mechanically
mechanically-switched shunt capacitor banks and
reactors
• Dynamic compensator can control
up to six switched shunt devices
(SSDs)
– Can be configured to control
either voltage, reactive power, or
power factor
• Dynamic compensator is typically
sized such that the largest capacitor
or reactor bank does not exceed
about 70 to 75% of the rated total
dynamic range
Hybrid Reactive Power Compensators
• Installation for 48 MW wind
power plant
– ±6.25 MVAR dynamic
compensator
– two 8 MVAR, 33 kV shunt
capacitor banks
– one 8 MVAR shunt reactor
• Provides reactive power in the
range of 0.95 leading
(inductive) to 0.95 lagging
(capacitive) power factor at
the 33 kV POC
Power Factor Control Using Hybrid
Reactive Power Compensators
100
WPP MW
80
60
MW, MVAR
• Hybrid reactive power
compensators can be used to
dynamically control the power
factor at the POC with response
times dictated by intentional delays
associated with the switching of
SSDs
• Local collector bus voltage and
current sensing and “slow”
feedback of voltage and current at
the POC through SCADA allows
compensator to dynamically control
the power factor at a remote POC
using a line drop compensation
algorithm
40
INVERTER MVAR
WPP NET MVAR
20
0
-20
0
1
2
3
4
5
6
Hours
7
8
9
10
11
Harmonic Resonance And Harmonic
Current Injection by WTGs
• Application review must include review of potential
harmonic resonance conditions
– Harmonic resonance analysis
– Harmonic distortion analysis based on representative
“ambient” harmonic levels
• In cases where WTGs with power factor correction
capacitors are involved, careful attention must also be
paid to any potential resonance conditions caused by
the WTG capacitors
Harmonic Resonance And Harmonic
Current Injection by WTGs
100
10
|Z|
• If resonance conditions with high
local impedances at characteristic
harmonic frequencies (i.e. 5th, 7th,
11th, 13th, etc. harmonics) are
identified
– Capacitor banks in the hybrid
reactive compensation system
can be converted to harmonic
filter banks
• If resonance conditions due to
WTGs with power factor correction
capacitors
– Damped C
C--type filter commonly
used to lower local impedance
of the wind power plant over a
wide range of frequencies
1
0.1
Low Output
High Output
Damped
0.01
0
1
2
3
4
5
6
7
8
Harmonic number (n)
9
10
11
12
13
14
Harmonic Resonance And Harmonic
Current Injection by WTGs
• If utilizing WTGs with DFIG or full
full-converter WTGs with appreciable
levels of harmonic current injection
– Sometimes necessary to apply
a highhigh-pass filter to prevent
some of the harmonic currents
from flowing into the system
causing high levels of harmonic
voltage and current distortion
– If hybrid compensator is
applied, one or more of the
capacitor banks can be
converted to highhigh-pass filters
Reactor
L
Resistor
R
Capacitor
C
Summary
• Hybrid reactive power compensation systems provide an
economical means of meeting typical grid code
requirements for power factor and voltage control
• The application and associated wind power plant and
power system parameters must be carefully reviewed to
– Optimize the design of the hybrid reactive power
compensator
– Identify any potential resonance conditions that may
be caused by WTG power factor correction
capacitors or collector substation capacitors applied
in the hybrid compensator