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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