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This paper proposes a novel configuration of a unified power quality conditioner (UPQC) which can be connected to the distribution system without series injection transformers. The operation of the proposed system was analyzed through simulations with PSCAD/EMTDC and experimental works with a scaled hardware model, assuming that the UPQC is connected with the 22.9-kV distribution line. The proposed UPQC has the ultimate capability of improving power quality at the point of installation on power distribution systems. It has flexibility in expanding the operation voltage by increasing the number of H-bridge modules. Index Terms--dynamic voltage restorer (DVR), H-bridge, PSCAD/EMTDC, static synchronous series compensator (SSSC), Static var Compensator (STATCOM), unified power-flow controller (UPFC), unified power-quality conditioner (UPQC).

This paper describes analysis results of a combined operation of the unified power quality conditioner with the distributed generation. The proposed system consists of a series inverter, a shunt inverter, and a distributed generator connected in the dc link through rectifier. The proposed system can compensate voltage sag and swell, voltage interruption, harmonics, and reactive power in both interconnected mode and islanding mode. The performance of proposed system was analyzed using simulations with power system computer aided design/electromagnetic transients dc analysis program, and experimental results with the hardware prototype. The proposed system can improve the power quality at the point of installation on power distribution systems or industrial power systems. Index Terms--Distributed generation (DG), power system computer-aided design/electromagnetic transients dc analysis program (PSCAD/EMTDC), unified power-quality conditioner (UPQC).

This paper describes a resonant fly-back converter with thyristor switches, which can be used for the dc distribution with a PWM voltage-source inverter The proposed converter operates to change high-voltage dc into low-voltage dc with isolation and large converting ratio. The converter has a main thyristor switch and an LC resonant circuit with an auxiliary thyristor switch for commutation in the primary side of the gap transformer The operation of proposed converter was verified through computer simulations with EMTP and experiments with a hardware scaled-model. The proposed converter could be implemented with commercially available components and proven technologies for supplying electricity to the rural or remote customer Keywords: resonant fly-back converter, gap transformer, PWM (pulse width modulation), EMTP (electromagnetic transients program), TACS (transients analysis of control system)

This paper describes a static synchronous compensator using thyristor PWM current source inverter. The proposed system consists of a 3-phase thyristor bridge with commutation circuit, a dc reactor, and ac filter capacitors. The 3-phase thyristor bridge operates as a current- source PWM inverter with assistance of commutation circuit. The system operation was verified in detail through computer simulations with EMTP, and experiments with a scaled hardware model. The proposed system has two advantages of low switching loss and easy expansion of operation voltage through series connection of thyristors. Index Terms--EMTP (electro-magnetic transients program), GTO (gate turn-off thyristor), HVDC (high voltage direct current transmission), IGBT (insulated gate bipolar transistor), PAM (pulse amplitude modulation), PWM (pulse width modulation), STATCOM (STATic synchronous COMpensator), TACS (transient analysis of control systems).

This letter proposes a novel phase-locked loop (PLL) that is composed of adaptive linear combiner and the proportional-integral control. The operational feasibility was confirmed through a theoretical approach, and the performance was verified through simulations and experimental works. The proposed PLL system shows accurate performance under the voltage disturbances, such as sag, harmonics, and phase-angle jump. Index Terms--Adaptive linear combiner (ALC), phase-locked loop (PLL), proportional integral (PI).