• Journal of international Conference on Electrical Machines and Systems
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• v.2 no.2
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• pp.190-196
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• 2013

It presents a unification of buck-boost and flyback converter for driving a cascaded H-bridge multilevel inverter with a single independent DC voltage source. Cascaded H-bridge multilevel inverter is useful to make many output voltage levels for sinusoidal waveform by combining two or more H-bridge modules. However, each H-bridge module needs an independent DC voltage source to generate multi levels in an output voltage. This topological characteristic brings a demerit of increasing the number of independent DC voltage sources when it needs to increase the number of output voltage levels. To solve this problem, we propose a converter combining a buck-boost converter with a flyback converter. The proposed converter provides independent DC voltage sources at back-end two H-bridge modules. After analyzing theoretical operation of the circuit topology, the validity of the proposed approach is verified by computer-aided simulations using PSIM and experiments.

• Journal of Power Electronics
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• v.15 no.1
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• pp.10-17
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• 2015

A quasi-constant on-time controlled buck front end in combined discontinuous conduction mode and boundary conduction mode is proposed to improve power factor (PF).When instantaneous AC input voltage is lower than the output bus voltage per period, the buck converter turns into buck-boost converter with the addition of a level comparator to compare input voltage and output voltage. The gate drive voltage is provided by an additional oscillator during distortion time to eliminate the cross-over distortion of the input current. This high PF comes from the avoidance of the input current distortion, thereby enabling energy to be delivered constantly. This paper presents a series analysis of controlling techniques and efficiency, PF, and total harmonic distortion. A comparison in terms of efficiency and PF between the proposed converter and a previous work is performed. The specifications of the converter include the following: input AC voltage is from 90V to 264V, output DC voltage is 80V, and output power is 94W.This converter can achieve PF of 98.74% and efficiency of 97.21% in 220V AC input voltage process.

• Journal of Power Electronics
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• v.19 no.2
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• pp.380-393
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• 2019

Traditional boost converters have difficulty realizing high efficiency and high voltage gain conversion due to 1) extremely large duty cycles, 2) high voltage and current stresses on devices, and 3) low conversion efficiency. Therefore, a function decoupling high voltage gain DC/DC converter composed of a DC transformer (DCX) and an auxiliary converter is proposed. The role of DCX is to realize fixed gain conversion with high efficiency, whereas the role of the auxiliary converter is to regulate the output voltage. In this study, different forms of combined high voltage gain converters are compared and analyzed, and a structure is selected for the function decoupling high voltage gain converter. Then, topologies and control strategies for the DCX and auxiliary converter are discussed. On the basis of the discussion, an optimal design method for circuit parameters is proposed, and design procedures for the DCX are described in detail. Finally, a 400 W experimental prototype based on the proposed optimal design method is built to verify the accuracy of the theoretical analysis. The measured maximum conversion efficiency at rated power is 95.56%.

• The Transactions of the Korean Institute of Power Electronics
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• v.27 no.5
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• pp.391-396
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• 2022

In this study, a new voltage-balancing dual-active bridge converter that integrates a DAB converter with a voltage balancer is proposed for a bipolar DC distribution system. The proposed converter is configured to connect two loads to the transformer secondary center tap of the DAB converter, and no additional components are added. The proposed converter has the same operation as the conventional DAB converter, and it makes both output voltages similar. Moreover, the imbalanced current offset between the two loads is bypassed only on the secondary side of the transformer. Consequently, the proposed converter integrates a voltage balancer without any additional components, and no additional loss occurs in the corresponding components. Thus, high efficiency and high power density can be achieved. The feasibility of the proposed converter is verified using 3 kW prototypes under 380 V input and 190/190 V output conditions.

• Journal of Electrical Engineering and Technology
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• v.12 no.1
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• pp.189-197
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• 2017

This paper elaborates two novel proposed topologies (type-I and type-II) of the high step-up DC-DC converter using switched inductor and voltage multiplier cell. The advantages of these proposed topologies are the less voltage stress on semiconductor devices, low device count, high power conversion efficiency, high switch utilization factor and high diode utilization factor. We analyze the Type-II topologies operating principle and mathematical analysis in detail in continuous conduction mode. High-intensity discharge lamp for the automotive application can use the derived topologies. The proposed converters give better performance when compared to the existing types. Also, it is found that the proposed type-II converter has relatively higher voltage gain compared to the type-I converter. A 40 W, 12 V input voltage and 72 V output voltage has developed for the type-II converter and the performances are validated.

• Journal of Power Electronics
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• v.10 no.3
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• pp.251-261
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• 2010

The general function of a multilevel converter is to synthesize a desired output voltage from several levels of dc voltages as inputs. In order to increase the steps in the output voltage, a new topology is recommended in [1], which benefits from a series connection of sub-multilevel converters. In the procedure described in this reference, despite all the advantages, it is not possible to produce all the steps (odd and even) in the output. In addition, for producing an output voltage with a constant number of steps, there are different configurations with a different number of components. In this paper, the optimal structures for this topology are investigated for various objectives such as minimum number of switches and dc voltage sources and minimum standing voltage on the switches for producing the maximum output voltage steps. Two new algorithms for determining the dc voltage sources magnitudes have been proposed. Finally, in order to verify the theoretical issues, simulation and experimental results for a 49-level converter with a maximum output voltage of 200V are presented.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.27 no.12
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• pp.101-108
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• 2013

This paper presents A Zero-Voltage-Switching(ZVS) Three-Level DC/DC Converter using Primary Clamping Diodes. The Previous ZVS Three-Level DC/DC converter realizes ZVS for the switches with the use of the leakage inductance(or external resonant inductance) and the output capacitors of the switches, however the rectifier diodes suffer from recovery which results in oscillation and voltage spike. In order to solve this problem, this paper proposes a novel ZVS Three-Level DC/DC converter, which introduces two clamping diodes to the basic Three-Level converter to eliminate the oscillation and clamp the rectified voltage to the reflected input voltage.

• Journal of Power Electronics
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• v.16 no.1
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• pp.74-83
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• 2016

A new family of zero-voltage-transition converters with synchronous rectification is introduced in this study. Soft switching condition for all the converter operating points is provided in the proposed converters. The reverse recovery losses of the rectifier switch body diode are also eliminated. In comparison with the main switch voltage stress, the auxiliary switch voltage stress is reduced significantly. The auxiliary switch does not need the floating gate drive. The auxiliary inductor is coupled with the main converter inductor, and the leakage inductor is used as the resonance inductor. Thus, all inductors of the proposed converter can be implemented on a single core. The other features of the proposed converters include no extra voltage and current stresses on the main converter semiconductor elements. Theoretical analysis for a synchronous buck converter is presented in detail, and the validity of the theoretical analysis is justified with the experimental results of a prototype buck converter with 180 W and 80 V to 30 V.

• Proceedings of the KIPE Conference
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• 2015.07a
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• pp.357-358
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• 2015

This paper provides a comparison of power converter loss and thermal description for voltage source and current source type 5MW-class medium voltage topologies of wind turbines. Neutral-point clamped three-level converter is adopted for voltage source type topology while two-level converter is employed for current source type topology considering the popularity in the industry. In order to match the required voltage level of 4160V with the same switching device of IGCT as in voltage source converter, two active switches are connected in series for the case of current source converter. The loss analysis is confirmed through PLECS simulations. In addition, the loss factors due to di/dt and dv/dt snubber and ac input filter are presented. The comparison result shows that VSC-based wind turbine system has a higher efficiency than that of CSC under the rated operating conditions.

• Journal of Electrical Engineering and Technology
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• v.10 no.6
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• pp.2297-2306
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• 2015

This paper presents the development of a system with a reverse matrix converter (RMC) for permanent magnet synchronous motor (PMSM) drive and its effective control method. The voltage transfer ratio of the general matrix converter is restricted to a maximum value of 0.866, which is not suitable for applications whose source voltages are lower than the load voltages. The proposed RMC topology can step up the voltage without any additional components in the conventional circuit. Its control method is different from traditional matrix converter’s one, thus this paper proposes control schemes of RMC by means of controlling both the generator and motor side currents with properly designed control loop. The converter can have sinusoidal input/output current waveforms in steady state condition as well as a boosted voltage. In this paper, a hardware system with an RMC for a PMSM drive system is described. The performance of the system was investigated through experiments