IEEE PES T&D Conference & Exposition 2022 - 100

balance and render part of the grid non-compliant. One costeffective
solution is passive filtering. However, this can be restrictive
in size, be inefficient, and has the added risk of resonance
during a transient event if the system changes over time, causing
a shift in its resonance frequencies to adversely interact with
the filters. Another solution is active filtering. This can detect and
eliminate harmonics as well as provide limited voltage regulation
and reactive power compensation in a shunt configuration, but
typically at a slower rate than other power electronics-based solutions.
Active filtering solutions also can be quite costly depending
on the configuration. Typical active filtering for harmonics occurs
at the 480V/690V range, primarily for industrial customers, but
filtering at distribution level voltages may be the next logical step
as more harmonic content will come from generation sources as
opposed to loads as DGPV becomes more prevalent.
Application of Power Quality
Compensator
Mitsubishi Electric's power quality compensator is a power
electronics-based, two- or four-quadrant control product for
electric distribution market customers requiring improved
voltage stability and autonomous real or reactive power
control. The compensator has features not typically associated
with D-STATCOMs, such as real power capability
for voltage sag and outage support, active harmonic mitigation
features, power factor control, frequency regulation,
and more. It addresses common power quality issues seen at
distribution level feeders typically associated with 5kV to
35kV voltages. The power quality compensator is designed
to be paralleled to provide reactive power support between
1 to 32MVar and address various power quality issues on
the distribution grid. The compensator is a response to distributed
energy resource penetration on the distribution grid
and market segments not traditionally targeted by centralized
transmission level solutions. It is a customized solution
to meet utility and industrial power quality requirements. A
2MVA compensator is shown in Figure 2.
The power quality compensator includes a compact,
advanced power converter to control and regulate bi-directional
power flow and an advanced IEC 61131-based application-level
controller capable of interfacing with a utility's
supervisory control and data acquisition system and feedback
devices. It has been primarily deployed at the point
of common coupling (PCC) at utility-scale solar plants to
support voltage regulation, harmonics, and flicker complications
due to PV generation.
Voltage Control
As the compensator's primary control feature, automatic voltage
regulation (AVR) is a dedicated control mode to regulate
voltage at the PCC. Using local or remote voltage measurements
(or estimations) from the feeder, the power quality compensator
sources (capacitive) or absorbs reactive (inductive)
power onto the grid to regulate voltage to a given setpoint based
on customer setting. The AVR can be parameterized with zero
or slow action within a programmable dead-band. The deadband
is important for allowing user reactive power commands
and letting other controllers, such as flicker mitigation, operate
as required with minimal or no interference from AVR. The
dead-band also allows the compensator to perform voltage
regulation in parallel with other voltage-regulating devices on
the feeder network. In addition to minimizing the current draw,
factors that determine dead-band selection include:
✔ coordination with other devices on the feeder from the
point of view of reducing operations,
✔ the amount of operating zone needed for flicker mitigation,
and
✔ the ability to command a reactive power reference from
an outer loop controller for operational considerations.
Dedicated Flicker Control and
Implementation Overview
Visible flicker is caused by voltage fluctuation components
in the frequency range < 20 Hz and is most perceptible for
fluctuations around 8 Hz in commercial
incandescent
MV
Bus
CB1
Tx1
2 MVA
MV/480 V
and
dimConverter
1
1 MVA
figure 2. Skidded 2MVA power quality compensator.
100
ieee power & energy magazine
Converter 2
1 MVA
2 MVA VVC Solutions System
mable LED lamps as also seen
in the Mitsubishi laboratory. The
measured feeder voltage is processed
through a band-pass filter
to reject DC due to the steady-state
voltage and limit the action of the
flicker control to high-frequency
components. The control path typically
can add phase adjustments
and rate-of-change computation to
improve its action. Power quality
compensator output current or kVA
proportional to these processed
measurements is used to mitigate
the voltage fluctuation and visible
flicker. When available, a current
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IEEE PES T&D Conference & Exposition 2022

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