• Proceedings of the KIEE Conference
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• 2000.11b
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• pp.361-364
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• 2000

In this study, the system which can make the generator's output voltage more stable by using the inverter in terms of PWM method, is designed It is one of the method reducing velocity of the wind in the process of the wind power generation. Thus, in this system, it is necessary to use a excellent current control inverter. So pulse with modulation method with a high-speed switching element is introduced to control the output current. And also, in order to get a fast response when the standard current generated by the vector control algorithm is supplied with the generator, the output control system with the fast response character and the best current control character is suggested. In this way, the result from the introduction of the control system is that a response character to the changable velocity of the wind is excellent, causing the remarkable reduction of the percentage of the harmonic and the outstanding stability of the variation of the output voltage.

• Journal of Power Electronics
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• v.15 no.2
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• pp.378-388
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• 2015

This paper proposes a pulse width modulation (PWM)-based sliding mode controller (SMC) for a full-bridge DC-DC converter that can eliminate static output voltage error. Hysteretic SMC in DC-DC converter does not have a fixed switching frequency, and applying hysteretic SMC to full-bridge converters is difficult. Fixed-frequency SMC, which is also called PWM-based SMC, based on equivalent control overcomes these shortcomings. However, the controller order reduction in equivalent control in PWM-based SMC causes static output voltage error. To resolve this issue, an integral item is added to the PWM-based SMC. Sliding mode coefficients are designed by applying a standard second-order system to the sliding mode surface. The effect of adding an integral item on the controller is analyzed, and an integral coefficient design method is proposed. Experiment results on a three-level full-bridge DC-DC converter verify the control scheme and design method proposed in this paper.

• Journal of Power Electronics
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• v.15 no.2
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• pp.309-318
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• 2015

This study proposes a dual-output single-stage bridgeless single-ended primary-inductor converter (DOSSBS) that can completely remove the front-end full-bridge alternating current-direct current rectifier to accomplish power factor correction for universal line input. Without the need for bridge diodes, the proposed converter has the advantages of low component count and simple structure, and can thus significantly reduce power loss. DOSSBS has two uncommon output ports to provide different voltage levels to loads, instead of using two separate power factor correctors or multi-stage configurations in a single stage. Therefore, this proposed converter is cost-effective and compact. A magnetically coupled inductor is introduced in DOSSBS to replace two separate inductors to decrease volume and cost. Energy stored in the leakage inductance of the coupled inductor can be completely recycled. In each line cycle, the two active switches in DOSSBS are operated in either high-frequency pulse-width modulation pattern or low-frequency rectifying mode for switching loss reduction. A prototype for dealing with an $85-265V_{rms}$ universal line is designed, analyzed, and built. Practical measurements demonstrate the feasibility and functionality of the proposed converter.

• The Transactions of the Korean Institute of Power Electronics
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• v.17 no.5
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• pp.409-415
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• 2012

This paper presents a new software-based on-line dead-time compensation technique for a single-phase grid-connected photovoltaic (PV) inverter system. To prevent a short circuit in the inverter arms, a switching delay time must be inserted in the pulse width modulation (PWM) signals. This causes the dead-time effect, which degrades the system performance around zero-crossing point of the output current. To reduce the dead-time effect around the zero-crossing point of grid current, a harmonic mitigation of grid current is used as an additional part of the synchronous frame current control scheme. This additional task mitigates the harmonic components caused by the dead-time from the grid current. Simulation and experimental results are shown to verify the effectiveness of the proposed dead-time compensation method in the single-phase grid-connected inverter system.

• Journal of Power Electronics
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• v.18 no.1
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• pp.34-44
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• 2018

This paper presents a pulse-width adjustment (PWA) strategy for a novel bidirectional DC-DC boost converter to improve the performance of the dynamic inductor current response. This novel converter consists of three main components: a full-bridge converter (FBC), a high-frequency isolated transformer with large leakage inductance, and a three-level voltage-doubler rectifier (VDR). A number of scholars have analyzed the principles, such as the soft-switching performance and high-efficiency characteristic, of this converter based on pulse-width modulation plus phase-shift (PPS) control. It turns out that this converter is suitable for energy storage applications and exhibits good performance. However, the dynamic inductor current response processes of control variable adjustment is not analyzed in this converter. In fact, dc component may occur in the inductor current during its dynamic response process, which can influence the stability and reliability of the converter system. The dynamic responses under different operating modes of a conventional feedforward control are discussed in this paper. And a PWA strategy is proposed to enhance the dynamic inductor current response performance of the converter. This paper gives a detailed design and implementation of the PWA strategy. The proposed strategy is verified through a series of simulation and experimental results.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.1632-1633
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• 2007

This paper presents a new method of designing digital controller based on closed-loop identification of a pulse width modulation (PWM) converter system. We consider the control system structure which is composed of both current control loop and voltage control loop. The current controller can be designed independently of voltage loop. Whereas voltage controller can not do easily due to the PWM switching component which is nonlinear in nature. Furthermore, the control objective of inner loop is to track the sine wave of 60 Hz, but the outer loop shall maintain the constant DC voltage irrespective to load change. To systematically design outer loop controller, we propose a method finding linear approximate model of the nonlinear inner loop part including current controller by closed loop identification. Based on the identified model, we show that a simple digital voltage controller can be directly designed and it has good performance.

• Journal of Power Electronics
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• v.17 no.4
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• pp.1117-1126
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• 2017

The main contribution of this paper is the use of sensorless active diodes to generate the gate signals for a three-phase boost-rectifier with a self-powered control scheme. The sensorless operation is achieved making use of the gate control signals generated by the active diode schemes on each of the switching devices using a pulse width half-controlled boost rectifier modulation technique (PWM-HCBR). The proposed scheme synchronizes the gate control signals with a three phase voltage supply. Autonomous operation is obtained making use of the output DC bus to feed the control circuitry, the active diodes and the driver circuitry. The three-phase boost-rectifier is supplied by a three-phase permanent magnet electric generator powered by a solar concentrator dish with variable voltage and variable frequency conditions. Experimental results report an efficiency of up to 94.6% for 25 W and an input of 3.6 V peak per phase with 450.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2014.05a
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• pp.391-394
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• 2014

In this paper, we introduce a method of determining the absolute position of the rotor for the vector control of Hall sensor type multi-pole BLDC motor using the DSP(TMS320F28335), and implement an algorithm to complement the problems of the conventional method. The switching method of the inverter for providing desired sinusoidal current to each phase of a motor, we adopt Space-Vector pulse width modulation method. In order to increase the speed range, Field-Weakness control method are used. In order to verify the proposed algorithm, we compare the value of Iqe, Ide and phase currents with the values before compensated.

• Journal of Power Electronics
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• v.19 no.1
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• pp.119-133
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• 2019

Although the dual modulation wave method can solve the low-frequency neutral point potential (NPP) fluctuation problem for three-level neutral point clamped converters, it also increases the switching frequency and limits the zero-sequence voltage. That makes it harmful when dealing with the NPP drift problem if the converter suffers from a long dead time or asymmetric loads. By introducing two degrees of freedom (2-DOF), an NPP control based on a search optimization method can demonstrate its ability to cope with the above mentioned two types of NPP problems. However, the amount of calculations for obtaining an optimal 2-DOF is so large that the method cannot be applied to certain industrial applications with an inexpensive digital signal processor. In this paper, a novel optimal 2-DOF-based NPP control is proposed. The relationships between the NPP and the 2-DOF are analyzed and a method for directly determining the optimal 2-DOF is also discussed. Using a direct calculation method, the amount of calculations is significantly reduced. In addition, the proposed method is able to maintain the strongest control ability for the two types of NPP problems. Finally, some experimental results are given to confirm the validity and feasibility of the proposed method.

• The Transactions of the Korean Institute of Power Electronics
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• v.26 no.2
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• pp.141-149
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• 2021

In the field of electric vehicles and AGVs, wireless power transfer (WPT) charging systems have been developed recently because of its convenience, reliability, and positive environmental impact due to cable and cord elimination. In this study, we propose a WPT charging system using a single stage AC-DC converter that can be reduced in size and weight and thus can ensure convenience. The proposed single-stage AC-DC converter can control a wide output voltage (36-54 VDC) within coupling ranges by using the variable link voltage applied to the WPT resonant circuit through phase-shifted modulation at a fixed switching frequency. Moreover, the input power factor and total harmonic distortion can be improved by using the proposed converter. A 1 kW prototype that can operate with an air gap range of 40-50 mm is fabricated and validated through experimental results and analysis.