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High-performance unified power quality
conditioner using command generator
tracker-based direct adaptive control
strategy
Abstract:
This study proposes a command generator tracker-based direct adaptive control
technique (CGT-DAC) in a three-phase three-wire unified power quality
conditioner (UPQC). This proposed CGT-DAC improves the PQ issues
such as current and voltage harmonics, sag/swell and voltage unbalance in the
power system distribution network. CGT is a model reference control law for a
linear time-invariant system with known coefficients and is formulated
for the generation of reference signals for both shunt and series inverter.
Furthermore, CGT can adaptively regulate the DC-link capacitor voltage without
utilising additional controller. Moreover, DAC is designed to track a linear
reference model to reduce the tracking error between model reference output and
measured signal to be controlled. Therefore, the proposed CGT-DAC approach
provides more robustness, flexibility and adaptability in all operating
conditions of the power system over a conventional proportional–integral (PI)
controller. This proposed control strategy of UPQC is validated through
MATLAB/SIMULINK followed by the experimental system of real timehardware-in the loop-based OPAL-RT system and adequate results are reported
after a comparative assessment with the conventional PI-controller.
Existing system:
 Development of electronics, electrical devices and appliances has become
more and more sophisticated. Similarly, they demand uninterrupted and
conditioned power. Hence, with ever changing power scenario, power
quality (PQ) assurance to the end user is one of the important concerns.
 To overcome PQ issues, several PQ mitigation equipment are installed in
power distribution network. However, the conventional PQ mitigation
equipment are inadequate to eliminate PQ problems such as current and
voltage harmonics, voltage sag/swell and voltage unbalances associated with
the power distribution network.
 Therefore, unified PQ conditioner (UPQC) is one of the modern and very
promising power conditioning devices. The UPQC is constructed using
shunt and series inverter connected back to back through a common DC-link
capacitor.
 Recently, significant attention has been paid to the control circuit designs of
the UPQC, with the objective to obtain reliable control algorithms and fast
response so that the UPQC can simultaneously compensate most of the PQ
problems in the distribution system.
Proposed system:
 Control law for UPQC is designed through the appropriate adaptive gains,
which are selected from the states of the CGT, and tracking error. Therefore,
asymptotic tracking is achieved by keeping the difference between the true
UPQC output and CGT output nearly zero.
 Thus, the states of the UPQC maintain in desired trajectories in all operating
conditions of the power system. These control inputs are applied to the
triangular carrier pulse-width modulator controller for generation of required
switching pulse for shunt and series inverter of UPQC.
 The performance of the proposed approach is validated through
MATLAB/SIMULINK followed by the real-time experimental studies
utilising hardware-in-the-loop (HIL) system OPAL-RT simulator (OP5600)
with Xilinx SPARTAN-3(3xc3s5000) OP5142 field programmable gate
array (FPGA) processor for user interconnection.
 For analysing current and voltage tracking performance of UPQC, a
comparative assessment has been performed between proposed approach
and conventional PI-controller.
Circuit diagram:
Reference:
1 Ketzer, M.B., Brandão Jacobina, C.: ‘Multivariable load current sensorless
controller for universal active power filter’, IET Power Electron., 2014, 7, (7),
pp. 1777–1786
2 Khadkikar, V.: ‘Fixed and variable power angle control methods for unified
power
quality conditioner: operation, control and impact assessment on shunt and series
inverter kVA loadings’, IET Power Electron., 2013, 6, (7), pp. 1299–1307
3 Khadkikar, V., Chandra, A., Barry, A.O., et al.: ‘Power quality enhancement
utilising single-phase unified power quality conditioner: digital signal
processor-based experimental validation’, IET Power Electron., 2011, 4, (3),
pp. 323–331
4 Modesto, R.A., Oliveira da Silva, S.A., Albano de Oliveira Júnior, A.: ‘Power
quality improvement using a dual unified power quality conditioner/
uninterruptible power supply in three-phase four-wire systems’, IET Power
Electron., 2015, 8, (9), pp. 1595–1605