• Proceedings of the KIPE Conference
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• 2002.11a
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• pp.129-132
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• 2002

In this paper, a PWM Buck-Boost AC-AC converter for improvement of power quality of custom power is presented. The PWM Buck-Boost AC-AC converter is modelled by using circuit DQ transformation whereby the both static and dynamic characteristics are analyzed completely. Finally, the converter system is implemented with the design criteria and the experimental results show the validity of modelling and analysis.

• Proceedings of the KIEE Conference
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• 1993.07b
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• pp.767-769
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• 1993

A multilevel PWM voltage source inverter, especially five-level one, is introduced to obtain a static var compensator(SVC) as a large scale power, source. In this paper, the three phase SVC is modeled using circuit DQ transformation and completely analyzed. Finally, through the experimental results from 5-kVA SVC, the validity of the analyses and the feasibility of the SVC system are shown for high power applications.

• Journal of international Conference on Electrical Machines and Systems
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• v.2 no.3
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• pp.330-335
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• 2013

This paper performs two kinds of Field-Oriented Control (FOC) for dual three phase permanent magnet synchronous motor (DTP-PMSM).The first is based on vector space decomposition to study the effect of current harmonics on electromechanical energy conversion. And the second presents the coupling relations between two sets of windings using two d-q transformation. And then this paper has deeply studied the differences between these two strategies, the different effect on the control of harmonic current and the reason for these differences. MATLAB-based Simulation studies of a 3KW DTP-PMSM are carried out to verify the analysis of differences between the two FOC strategies.

• Journal of international Conference on Electrical Machines and Systems
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• v.3 no.4
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• pp.433-445
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• 2014

Single phase voltage source converter (VSC) is an important power electronic converter (PEC), including single-phase voltage source inverter (VSI), single-phase voltage source rectifier (VSR), single-phase active power filter (APF) and single-phase grid-connection inverter (GCI). As the fundamental part of large scale PECs, single-phase VSC has a wide range of applications. In the paper, as first, on the basis of the concept of the discontinuous pulse-width modulation (DPWM) for three-phase VSC, a new DPWM of single-phase VSR is presented by means of zero-sequence component injection. Then, the transformation from stationary frame (abc) to rotating frame (dq) is designed after reconstructing the other orthogonal current by means of one order all-pass filter. Finally, the presented DPWM based single-phase VSR is established analyzed and simulated by means of MATLAB/SIMULINK. In addition, the DPWMs presented by D. Grahame Holmes and Thomas Lipo are discussed and simulated in brief. Obviously, the presented DPWM can also be used for single-phase VSI, GCI and APF. The simulation results show the validation of the above modulation algorithm, and the DPWM based single-phase VSR has reduced power loss and increased efficiency.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.4
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• pp.576-585
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• 2016

The current control methods of Y-connected 7 Phase BLDC motor are sine wave current control and square wave control. The sine wave current control method needs dq axis transformation of $7{\times}7$ matrix for current control and very complex. Also this method is not suitable for multi Phase BLDC motor of trapezoidal back emf wave. Therefore, in Y connected multi phase BLDC motor, the square wave current control methods are required. Generally, in the 3Phase BLDC system, Average current control method is used for current control. The average current is obtained that the summation of absolute value of each phase current magnitude is divided by the number of conduction phase. However, if average current control method is applied to multi-phase system, there is a problem that each phase currents are different. This problem affects unbalance of each phase torque and fluctuation of total torque. This paper proposed each phase current control method of Y connected 7Phase BLDC system. Proposed method is used for PI controller of each phase for each phase current control. This method can perfect square wave current control. Also, configuration of the method is easier than DQ axis transformation. Proposed method is verified through simulation and experiments.

• Proceedings of the KIEE Conference
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• 1996.07a
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• pp.262-264
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• 1996

This paper presents a new dual loop control using novel vector phase locked loop(VP-PLL) for a high power static var compensator(SVC) with three-level GTO voltage source inverter(VSI). Through circuit DQ-transformation, a simple dq-axis equivalent circuit is obtained. From this, DC analysis is carried out to obtain maximum controllable phase angle ${\alpha}_{max}$ per unit current between the three phase source and the switching function of inverter, and AC open-loop transfer function is given. Because ${\alpha}_{max}$ becomes small in high power SVC, this paper proposes VP-PLL for more accurate $\alpha$-control. As a result, the overall control loop has dual loop structure, which consists of inner VP-PLL for synchronizing the phase angle with source and outer Q-loop for compensating reactive power of load. Finally, the validity of the proposed control method is verified through the experimental results.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.1051_1052
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• 2009

This paper deals with operational characteristic analysis of a single-phase PCS (Power Conditioning System) for PV (Photovoltaic) power generation system with AF (Active Filter) function. The theory of dq transformation has been applied to the control strategy of a single-phase PV power generation system to implement the AF function. Application of the virtual two-phase using phase-shift makes it possible to use the dq theory for the single-phase PV power generation system. The authors are sure that the proposed system is a very useful to compensate harmonics caused by nonlinear loads in a single-phase utility system. In this paper, not only a theoretical aspect of the single-phase PV-AF system is discussed, but also the DSP (Digital Signal Processor) based experiment results are presented to demonstrate the effectiveness of the single-phase PV-AF system.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.29 no.12
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• pp.83-87
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• 2015

This paper presents a simple notch filter, which is so suitable for three-phase unbalanced and distorted power line. In the d-q synchronous transformation, three-phase unbalanced and distorted voltages generate lots of ripple voltages on d-q axes. The ripples make disturbances on controllers such as PLL of phase tracking. Unbalanced state makes ripple of double the frequency of power line. Odd harmonics 5th and 7th on the line make even 4th and 6th ripples on d-q axes due to the rotating reference frame, respectively. Cascaded two comb filters, delay lines 1/4T and 1/8T, are adopted for the ripple rejection. The filter rejects harmonics 2nd, 4th, 6th, 10th and so on. They are very effective to remove the ripples of both unbalance and distortion. The filter, implemented by two FIFOs on an experimental system, is adopted on a PLL controller of power line phase tracking. Through the simulation and experimental results, performance of the proposed comb filter has been validated.

• Journal of IKEEE
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• v.24 no.4
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• pp.954-960
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• 2020

This paper proposes a speed variable proportional resonant current control method for a single-phase permanent magnet synchronous motor(PMSM). Due to the electromagnetic characteristics of a single-phase PMSM, negative and zero torques are generated in the part corresponding to the phase difference between the stator current and the back electromotive force. In addition, overcurrent limitation is required because of the low stator resistance and inductance in sensorless operation. When using the vector control for current control of single-phase PMSM under these conditions, processes of coordinate transformation, inverse coordinate transformation, and generation of virtual dq-axis components are required. However, the proposed variable speed proportional resonant current control method does not need the coordinate transformation used for AC motors. In this paper, we have confirmed stable maneuverability by using variable proportional resonant current control algorithm, and proposed sensorless control based on a mathematical model of a single-phase PMSM without a position sensor when reaching a constant speed. The usefulness of the current control method was verified through several experiments.

• Proceedings of the KIPE Conference
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• 2001.10a
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• pp.576-580
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• 2001

This paper presents a casca multilevel PWM rectifier without the isolation transformers for energy build-up at each inverter modules; The features and advantages of the proposed PWM rectifier can be summarized as follows; 1) It realizes the high power high voltage AC/DC power conversion, 2) It uses no transformer which is bulky and heavy, 3) It has hybrid structure so that switching devices can be effectively utilized, 4) It produces high quality AC current even in high power high voltage applications, 5) The input power factor remains unity by simple modulation index control. The multilevel rectifier is analyzed by using the circuit DQ transformation whereby the characteristics and control equations are obtained. Finally, it will be shown that the system simulation reveals the validity of analyses