• Journal of Power Electronics
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• v.17 no.5
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• pp.1256-1267
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• 2017

A fault tolerant structure and its corresponding control strategy for electromagnetic stirring power supplies are proposed in this paper. The topology structure of the electromagnetic stirring power supply contains two-stages. The fore-stage is the PWM rectifier. The back-stage is the fault tolerant inverter, which is a two-phase three-bridge orthogonal inverter circuit while operating normally. When the power switch devices in the inverter are faulty, the structure of the inverter is reconfigured. The two-phase half bridge inverter circuit is constructed with the remaining power switch devices and DC-link capacitors to keep the system operating after cutting the faulty power switch devices from the system. The corresponding control strategy is proposed to let the system work under both normal and fault conditions. The reliability of the system is improved and the requirement of the electromagnetic stirring process is met. Finally, simulation and experimental results verify the feasibility of the proposed fault tolerant structure and corresponding control strategy.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.187-189
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• 2007

In this paper, the cascade 3-phase IHMCL inverter using two low frequency transformers is proposed. The proposed inverter is constructed by connecting a 3-phase IHCML inverter. the cascade 3-phase IHCML inverter has several advantages. One advantage is that only one input power source is required because of using transformers to isolate. Another advantage is that the switching frequency of the high power switches is almost fundamental frequency of reference and the other the switching frequency of the low power switches is higher. It can be known that cascade 3 phase IHCML inverter has the excellent efficiency and the outstanding electric quality. lastly, we tested the 5kW cascade 3-phase IHCML inverter to clarify the proposed electric circuit and reasonableness of control signal for the proposed inverter.

• Journal of Electrical Engineering and Technology
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• v.8 no.2
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• pp.295-303
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• 2013

This paper reports an investigation of pulse width modulation (PWM) techniques for two-phase brushless DC (BLDC) motors fed by a two-phase eight-switch inverter in a fan application. The three-phase BLDC motor is widely applied in industry; however, a lower-cost two-phase BLDC motor and drive circuit has been greatly in demand in recent years. In this paper, we introduce a mathematical model of the two-phase BLDC motor with sinusoidal back electromotive forces (EMFs) based on traditional three-phase BLDC motors. To simplify the drive algorithm and speed up its application, we analyze the principle of block commutation for a two-phase BLDC motor drive in the 180-electrical-degree conduction mode, and we further propose five PWM schemes to improve the commutation performance of the two-phase BLDC drive. The effectiveness of the proposed PWM methods is verified through experiments.

• The Transactions of the Korean Institute of Power Electronics
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• v.12 no.4
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• pp.310-317
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• 2007

In this paper, the system equation for the balanced two-phase induction motor is derived and the characteristics for speed control is also analyzed in the region of constant torque and constant power. The modified vector control theory is applied to two-phase motor drive system. The speed of two-phase motor drive can be controlled precisely by the modified indirect vector control theory. The modified vector control theory is simpler comparing to the conventional vector control because of the simpler axis transformation. The computer simulations and the experimental results presented to confirm the vector control for two-phase inverter fed two phase induction motor system.

• Journal of Power Electronics
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• v.17 no.5
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• pp.1173-1185
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• 2017

In this paper, a new single phase multilevel inverter topology with a single DC source is presented. The proposed topology is developed based on the concepts of the L-Z source inverter and the switched capacitor multilevel inverter. The input voltage to the proposed inverter is boosted by two steps: the first step by an impedance network and the second step by switched capacitor units. Compared to other existing topologies, the presented topology can produce a higher boosted multilevel output voltage while using a smaller number of components. In addition, it provides more flexibility to control boosting factor, size, cost and complexity of the inverter. The proposed inverter possesses all the advantages of the L-Z source inverter and the switched capacitor multilevel inverter like controlling the start-up inrush current and capacitor voltage balancing using a simple switching strategy. The operating principle and general expression for the different parameters of the proposed topology are presented in detail. A phase disposition pulse width modulation strategy has been developed to switch the inverter. The effectiveness of the topology is verified by extensive simulation and experimental studies on a 7-level inverter structure.

• Journal of Power Electronics
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• v.13 no.2
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• pp.223-231
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• 2013

A modular three-phase multilevel inverter especially suitable for electrical drive applications has been previously presented. This topology is based on series connection of power cells in which each cell comprised of two inverter legs in series. In this paper, in order to generate the maximum number of voltage levels with reduced number of switches, three algorithms are proposed for determination of the magnitudes of dc voltage sources. In addition, a new hybrid multilevel inverter is proposed that is composed of series connection of the previously presented multilevel inverter and some H-bridges. The proposed topology has been compared with some other presented multilevel inverters. The performance of the proposed multilevel inverter has been verified by simulation and experimental results of a single-phase 39-level multilevel inverter.

• Journal of Power Electronics
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• v.16 no.4
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• pp.1504-1512
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• 2016

This paper presents a new single-phase asymmetrical cascaded multilevel DC-link inverter. The proposed inverter comprises two stages. The main stage of the inverter consists of multiple similar cells, each of which is a half-bridge inverter consisting of two switches and a single DC source. All cells are connected in a cascaded manner with a fixed neutral point. The DC source values are not made equal to increase the performance of the inverter. The second circuit is a folded cascaded H-bridge circuit operating at a line frequency. One of the main advantages of this proposed topology is that it is a modular type and can thus be extended to high stages without changing the configuration of the main stage circuit. Two control schemes, namely, low switching with selective harmonic elimination and sinusoidal pulse width modulation, are employed to validate the proposed topology. The detailed approach of each control scheme and switching pulses are discussed in detail. A 150W prototype of the proposed system is implemented in the laboratory to verify the validity of the proposed topology.

• Proceedings of the KIPE Conference
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• 2007.07a
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• pp.193-195
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• 2007

This paper proposed a novel current measurement method for two-phase half-bridge inverter using single current sensor. The proposed method measures DC link input current and a phase current simultaneously and reconstructs each phase currents by simple calculation according to voltage vector. The commutation modes of two-phase half-bridge inverter is analized. The current sampling and reconstructing method is also presented. The proposed method is verified through simulation and experimental results on two-phase induction motor drive system.

• Proceedings of the KIEE Conference
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• 1990.11a
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• pp.267-271
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• 1990

This paper describes a 3-Phase Quasi-Resonant DC Link Inverter (3-phase QRI), which has two operating modes, ie. inverting mode and rectifying mode. First the 3-Phase QRI is simplified and the resonant circuit is analyzed in comparison with two resonant DC-to-DC converters. This analysis shows that the maximum voltage of resonant capacitor is limited to twice the input voltage irrespective of operating modes. A new simple control method in rectifying mode is suggested, which does not require any other element in power circuit. The characteristic of 3-Phase Quasi Resonant Inverter has been verified by simulation using the proposed control method.

• Journal of Power Electronics
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• v.11 no.3
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• pp.285-293
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• 2011

This paper proposes two SRM driving systems using a variable dc-link voltage controlled by a single-phase inverter. Two SRM converter topologies of a half bridge type and a full bridge type are proposed according to the power circuits of an inverter. The phase current can be controlled by means of a PWM controller at the inverter, and the turn-on/off angle at the phase switches can be controlled by a position sensor at the converter in the drive system. The inverter acts as a peak-current limiter if the transient current exceeds its maximum value. SRMs using the proposed topologies maintain high efficiency due to energy regeneration after the turn-off of power switches. The operational modes of the proposed topologies are verified by simulation and experimental results.