• Journal of Power Electronics
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• v.10 no.4
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• pp.428-433
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• 2010

This paper proposes a harmonics reduction technique for the input currents of three phase PWM converters. The quality of the phase angle information on the utility voltage connected to the PWM converters affects their control performance. Under a distorted utility voltage, the extracted phase angle based on the synchronous reference frame PLL method is distorted. This causes large harmonics in the input currents of a PWM converter. In this paper, a harmonics reduction method that makes the input currents in the PWM converter sinusoidal even under distorted utility conditions is proposed. By the proposed method, without additional hardware, the THD (Total Harmonic Distortion) of the input currents can be readily limited to below 5% which is the harmonic current requirements of IEEE std. 519. Its validity is verified by simulations and experimental results.

• Proceedings of the KIEE Conference
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• 1993.07b
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• pp.853-855
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• 1993

In this paper, a further improved system obtaining very low distorted waveforms of input ac currents of three phase rectifier circuit is proposed. The proposed system consists of an uncomplicated 24 pulse diode bridge rectifier that is transformerless, by adding only switching circuit which consists of two switchs to conventional system. Also to optimum the effectiveness or the harmonic reduction, the optimum turn ratio of an autotransformer and the optimum switching control angle are decided by computer simulation. And then, the voltage waveform obtained has a total harmonic distortion of 8.1%, and the predominant harmonics 23th and 25th. This paper describes operation principle, analysis of the waveforms of input voltage and current. The theoretial results are verified through simulation.

• Transactions on Electrical and Electronic Materials
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• v.18 no.3
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• pp.129-135
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• 2017

This paper introduces a design and a simulation of a hybrid active power filter (HAPF) for harmonics reduction given an ideal supply source. The synchronous reference frame method has been used here to identify the reference currents. The proposed HAPF uses a new artificial- intelligence technique called Particle Swarm Optimization (PSO) for tuning the parameters of a proportional and integral controller called PI-PSO. The PI-PSO controller is used to archive optimality for the DC-link voltage of the HAPF-inverter. The hysteresis non-linear current control method is used in this approach to compare the extracted reference and the actual currents in order to generate the pulse gate required for the HAPF. Results obtained by simulations with Matlab/Simuling show that the proposed approach is very flexible and effective for eliminating harmonic currents generated by the non-linear load with the HAPF based PSO tuning.

• Journal of Power Electronics
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• v.19 no.1
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• pp.265-277
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• 2019

The application of shunt active power filters (S-APFs) is considered to be the most popular approach for harmonic compensation due to its high simplicity, ease of installation and efficient control. Its functionality mainly depends upon the rapidness and precision of its internally built control algorithms. A S-APF is generally operated in the current controlled mode (CCM) with the detection of harmonic load current. Its operation may not be appropriate for the distributed power generation system (DPGS) due to the wide dispersion of nonlinear loads. Despite the fact that the voltage detection based resistive-APF (R-APF) appears to be more appropriate for use in the DPGS, the R-APF experiences poor performance in terms of mitigating harmonics and parameter tuning. Therefore, this paper introduces a direct harmonic voltage detection based control approach for the S-APF that does not need a remote harmonic load current since it only requires a local point of common coupling (PCC) voltage for the detection of harmonics. The complete design procedure of the proposed control approach is presented. In addition, experimental results are given in detail to validate the performance and superiority of the proposed method over the conventional R-APF control. Thus, the outcomes of this study approve the predominance of the discussed strategy.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.11
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• pp.1560-1565
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• 2013

This paper proposes the control method for compensating for unbalanced grid current and reducing a total harmonic distortion (THD) of the grid current at the three-phase grid-connected inverter systems under unbalancd and distorted grid voltage conditions. The THD of the grid current caused by grid voltage harmonics is derived by considering the phase delay and magnitude attenuation due to the hardware low-pass filter (LPF). The Cauchy-Schwarz inequality theory is used in order to search more easily for a minimum point of THD. Both the gain and angle of a compensation voltage at the minimum point of THD of the grid current are derived. The negative-sequence components in the three-phase unbalanced grid voltage are cancelled in order to achieve the balanced grid current. The simulation and experimental results show the validity of the proposed control methods.

• Proceedings of the KIPE Conference
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• 2001.10a
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• pp.556-560
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• 2001

In this paper, a soft-switching discontinuous mode (DCM) power factor corrected (PFC) converter is analyzed by applying the double Fourier series expansion. It is found that the fundamental component and higher-order harmonics included in the input current waveform are obtained by the Fourier series expansion of the mean value of the inductor current. From the theoretical analysis, a new method removing the distortion of the input current waveform is proposed. In spite of an open loop system, the proposed method makes a great improvement of the total harmonic distortion even if the ratio of output voltage to input voltage is very low.

• Proceedings of the KIPE Conference
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• 2007.11a
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• pp.130-132
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• 2007

Recently, regulation for THD(Total Harmonic Distortion) such as IEC 61000-3-2, IEEE 519 is being reinforced about a product which directly connects to AC line in order to prevent distortion of common power source in electronic equipment and electrical machinery. In order to satisfy these regulations, conventional circuits were used two-stage structure attached power factor correction circuit at ahead of converter but this method complicate the circuit and then a number of element increases thereupon the cost of production rises. In this paper, we propose a high efficiency single-stage 300W PFC flyback converter, that improved power factor and efficiency than conventional two-stage power module.

• Journal of Power Electronics
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• v.18 no.2
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• pp.323-331
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• 2018

Buck power factor correction (PFC) converters, compared with conventional boost PFC converters, exhibit high efficiency performance in the entire range of universal line voltage. This feature has gotten more attention for eliminating the zero crossing dead angle of buck PFC rectifiers. Furthermore, bridgeless structures for the reduction of conduction losses have been proposed. The aim of this paper is to introduce a single-phase buck rectifier that simultaneously has unity power factor (PF) and bridgeless structure while operating in the continuous conduction mode (CCM). For this purpose, two auxiliary flyback converters without any active switches are applied to a bridgeless buck rectifier to eliminate the zero crossing dead angle and achieve unity power factor, low total harmonic distortion (THD) and high efficiency. The operation and design considerations of the proposed rectifier are verified on a 150W, 48V prototype using a conventional peak-current-mode control. The measurement results show that the proposed rectifier has nearly unity power factor, THD less than 7% and high efficiency.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.12 no.5
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• pp.527-534
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• 1987

Two phase voltage controlled oscillation was realized by using the Electronic analog simulation of nonlinear simultaneous 2st order equation in terms of vibration and it's usefullness was sustined. Sinde it is complex and expensive to implement the circuits actually which composits and multiplicate the two phase signal squared respectively, this paper is obtained the simplificotion and switching circuit. The circuit introducced in this paper had propotionality of frequency to control input voltage, rapid response time, and little phase error, also this circuit operated with very low THD(Total Harmonic Distortion) and constant amplitude at higher than 10 :1 of frequency ratio.

• Journal of Electrical Engineering and Technology
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• v.12 no.1
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• pp.78-90
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• 2017

This paper presents the design of closed loop controllers operating a single-phase AC-DC three-level converter for improving power quality at AC mains. Closed loop inhibits outer voltage controller and inner current controller. Simulations of three level converter with three different voltage and current controller combinations such as PI-Hysteresis, Fuzzy-Hysteresis and Fuzzy tuned PI-Hysteresis are carried out in MATLAB/Simulink. Performance parameters such as input power factor and source current total harmonic distortion (THD) are considered for comparison of the three controller combinations. The fuzzy-tuned PI voltage controller with hysteresis current controller combination provides a better result, with a source-current THD of 0.93% and unity power factor without any source side filter for the three level converter. For load variations of 25% to 100%, a THD of less than 5% is obtained with a maximum value of only 1.67%. Finally, the fuzzy-tuned PI voltage with hysteresis controller combination is implemented in a Xilinx Spartan-6 XC6SLX25 FPGA board for experimental validation of power quality enhancement. A prototype 100 W, 0-24-48 V as output converter is considered for the testing of controller performance. A source-current THD of 1.351% is obtained in the experimental study with a power factor near unity. For load variations of 25% to 100%, the THD is found to be less than 5%, with a maximum value of only 2.698% in the experimental setup which matches with the simulation results.