EQ-W Functions and Description

EQ-W Functions and Description
Technical Note
Equalizer-W Functions & Description
Overview
Original Elspec Equalizer systems
supplied into the wind turbine
generator market were only required
to control power factor, reduce startup current and automatically restart/
shut down during loss of supply and/
or turbine shut down.
Since the middle of 2002, control
requirements
have
substantially
changed. Based on new standards
and requirements being imposed
by utilities and grid operators, wind
turbine generators and wind farms
need to offer voltage control, VAr
control and have the ability to ride
through grid faults
Elspec control schemes were refined to
include these feature enhancements,
resulting in today’s Equalizer-W
solution.
Power Factor Control
Power Factor can be set between 0.75
Inductive to 0.70 Capacitive;
kVAr can be set between -32,000 kVAr
to +32,000 kVAr in steps of 10;
Sub control modes:
Average: System maintains the
average power factor to within a
variable hysteresis % of the smallest
capacitor group rating.
Minimum:
System
maintains
a
minimum power factor value to within
a variable hysteresis % of the smallest
capacitor group rating.
Maximum: The target power factor is
not exceeded, for use where a leading
power factor is unacceptable.
Compensation Modes:
Full Load Control:
system.
Stand-alone
Elspec Power Quality Solutions
Load Sharing: Equalizer-W operates in
conjunction with other EQ-W systems,
each sharing equal % of the load.
Cascade: Equalizer-W operates with a
slower, conventional system.
Voltage Control: The Voltage Control
feature offers stepped regulation of
grid voltage within safe limits. It uses
the connection and disconnection of
available
capacitor groups to shift
the power factor toward inductive
or capacitive, depending on utility
under- or over-voltage. This function
is complementary to the standard
Power Factor Control, and only
operates based on utility voltage level
tolerances. These are set during the
commissioning process and can be
automatically initialized outside of
preset or SCADA-defined parameters.
Reactive Power Control: In this mode,
the Equalizer-W system maintains
reactive power levels within either
preset system parameters or variable
parameters defined remotely by the
wind farm SCADA system.
While
operating with this feature, the
Equalizer-W can export reactive power
to the network even when the wind
turbine generator itself is off-line.
Grid Fault Ride-Through Control: The
parameters of this selectable feature
are usually defined by local utility
requirements.
This control mode
utilizes the total power capabilities of
the Equalizer-W system, and functions
Equalizer-W Controller Set-up Screen
based on the minimum reactive
power levels required to supply the
wind turbine generator with sufficient
magnetizing current to remain on-line
during short-term grid faults.
* Note – For this option to function correctly the control
voltage for the Equalizer system should be supplied via
the wind turbine generator UPS system.
Simplified Functional Description
For projects requiring grid fault ridethrough, the Equalizer-W system must
function using all control options.
Operational descriptions of each
Set Point follow. All set points are
variable parameters that are either
set during commissioning or can be
done remotely through the wind farm
SCADA system. The colored line in
Chart 1 represents the grid voltage as
a per-unit percentage value.
In This Document
Read about:
• The history of the development of the Equalizer-W
• The variety of Equalizer-W control modes
• The various Equalizer-W functions
1
www.elspec-ltd.com
Elspec Technical Note
A
120%
B
110%
Set point B - Upper Level Voltage Threshold 2.
.
C
105%
Set point C - Upper Level Voltage Threshold 1.
.
Set point D – PF / VAr Control – Standard Ops.
.
100%
D
95%
90%
Set point E - Lower Level Voltage Threshold 1.
.
Set point F - Lower Level Voltage Threshold 2.
.
E
F
60%
Power factor or VAr
Control Threshold
Set point A - Critical Upper Voltage Limit .
Voltage Control
Thresholds
Set point G - Grid Fault Threshold.
Grid Fault
Threshold
Chart 1
Operational Definitions – SET
POINTS:
Set Point A – Critical Upper Voltage
Limit
The
system
disconnects
all
compensation.
Set Point B – Upper Level Voltage
Control (2)
System exits PF control, initializes
voltage control. The system begins
disconnecting individual capacitor
groups, irrespective of target PF
parameters. This function is variable
from 101% to 130%.
Set Point C – Upper Level Voltage
Control (1)
System exits voltage control and reenters PF control.
Note: Setting set points A and B to the same threshold
disables the function.
Set Point D - PF Control.
The Equalizer-W will operate normally
in PF Control mode between set points
B and F, unless the upper or lower
voltage control mode is operating. If
voltage control mode is on, PF control
will return to normal operation at set
point C or E (depending upon which
voltage control threshold has been
reached).
Set Point E – Lower Level Voltage
Control (1)
System exits voltage control and reenters PF control.
Set Point G – Grid Fault threshold
System enters ‘grid fault’ mode and
connects all available compensation.
Capacitor groups in use at the onset
of the event remain connected. After
a delay of 2/3 network cycle (also a
variable parameter), the Equalizer-W
system is designed to connect all
other available capacitor groups. The
compensation remains connected until
either the voltage returns to the upper
level voltage threshold at which point
voltage control is re-initialized, until
the system receives a disable signal
from the WTG SCADA system.
Set Point F – Lower Level Voltage
Control (2)
System exits PF control and initializes
voltage control. The system begins
connecting individual capacitor groups
irrespective of target PF parameters.
Note: Setting set points F and G to the same threshold
disables this function.
This document contains Elspec proprietary material. The information contained in this document is believed to be reliable and accurate.
International
©2008 Elspec Ltd.
All rights reserved.
SMT-0004-05E
Elspec Ltd.
P.O. Box 3019
4 HaShoham St., Zone 23
Caesarea Industrial Park
38900, Israel
Tel: +972-4-6272-470
Fax: +972-4-6272-465
email: [email protected]
North America
Elspec North America, Inc.
500 West South Street
Freeport, IL 61032
USA
Tel: +1-815-266-4210
Fax: +1-815-266-8910
email: [email protected]
Europe
Elspec Portugal Lda.
Zona Industrial 1a Fase
4900-231 Chafe
Viana do Castelo
Portugal
Tel: +315-258-351-920
Fax: +315-258-351-607
email: [email protected]
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