• Journal of international Conference on Electrical Machines and Systems
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• 제1권3호
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• pp.354-359
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• 2012

A transformerless converter suitable for multiphase drive application is presented in this paper. The topology employs a cascaded H-bridge rectifier as the interface between the grid and multi inverters which drive the multiphase motor. Compared with the conventional structure, the new topology eliminates the input transformer and also has the advantages such as four quadrant operation, simple configuration, low cost, high efficiency, and so on. The control strategies for the grid-side cascade H-bridge rectifier and the motor-side inverter are studied accordingly. Based on the multi-rotational reference frame, modular control scheme is developed to regulate the multiphase drive system. Simulation results show the proper operation of the proposed topology and the corresponding control strategy.

• Journal of international Conference on Electrical Machines and Systems
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• 제1권3호
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• pp.360-365
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• 2012

Cascaded H-Bridge rectifier (CHBR) is a more attractive solution in traction application for its transformerless structure. Because of the currents of different cells are exactly the same one, it is a challenge job to regulate the voltages of cells with only one current controller. In this paper, a PI-based control scheme is presented to deal with the voltages balance issue in CHBR. To satisfy the demand of rectifier such as unity power factor and regulated output DC voltages, the proposed control scheme consists of two parts. One is for shaping the grid current waveform and regulating the sum of DC-link voltages of all the cells; the other one is for balancing DC-link voltages. The latter is more concerned in this paper and is discussed in detail especially. Simulations and experiments are carried on. The results verified the feasibility and effectiveness of the proposed scheme.

• Journal of Electrical Engineering and Technology
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• 제8권2호
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• pp.316-325
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• 2013

Multilevel inverters produce a staircase output voltage from DC voltage sources. Requiring great number of semiconductor switches is main disadvantage of multilevel inverters. The multilevel inverters can be divided in two groups: symmetric and asymmetric converters. The asymmetric multilevel inverters provide a large number of output steps without increasing the number of DC voltage sources and components. In this paper, a novel topology for multilevel converters is proposed using cascaded sub-multilevel Cells. This sub-multilevel converters can produce five levels of voltage. Four algorithms for determining the DC voltage sources magnitudes have been presented. Finally, in order to verify the theoretical issues, simulation is presented.

• Journal of Power Electronics
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• 제14권5호
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• pp.937-945
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• 2014

This paper presents an optimized space vector pulse-width modulation (OSVPWM) technique for a five-level cascaded H-bridge (CHB) inverter. The space vector diagram of the five-level CHB inverter is optimized by resolving it into inner and outer two-level space vector hexagons. Unlike conventional space vector topology, the proposed technique significantly reduces the involved computational time and efforts without compromising the performance of the five-level CHB inverter. A further optimized (FOSVPWM) technique is also presented in this paper, which significantly reduces the complexity and computational efforts. The developed techniques are verified through MATLAB/SIMULINK. Results are compared with sinusoidal pulse-width modulation (SPWM) to prove the validity of the proposed technique. The proposed simulation system is realized by using an XC3S400 field-programmable gate array from Xilinx, Inc. The experiment results are then presented for verification.

• 한국통신학회논문지
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• 제15권3호
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• pp.232-242
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• 1990

외부 평면파에 의해 유기되는 단일 전송선로의 EMI(Electromagnetic Interference) 전류에 관한 Smith의 해석법을 이용하여 연쇄 접속된 전송선로의 부하 EMI전류를 구한다. 동일한 특성 임피던스를 갖는 선로가 연쇄 접속 되었다는 가정하에 수치계산을 하여 Smith의 연구 결과와 비교한 결과 두 결과가 잘 일치함을 확인하였으며, 선로의 폭과 길이가 각각 1/10로 줄어들면 부하 EMI 전류는 약 40dB 정도 감소함을 알 수 있었다.

• 전기학회논문지P
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• 제55권2호
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• pp.94-102
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• 2006

This paper describes experimental analysis of UPQC, which is composed of cascaded H-bridges and single-phase multi-winding transformers. The operational characteristic was analyzed through experimental works with a scaled model, and simulations with PSCAD/EMTDC. The UPQC proposed in this paper can be directly connected to the distribution line without series injection transformers. It has flexibility to expand the operation voltage by increasing the number of H-bridge modules. The analysis results can be utilized to design the actual UPQC system applicable for the actual distribution system.

• Journal of Power Electronics
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• 제16권1호
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• pp.173-181
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• 2016

In this paper, a new technique for harmonic optimization in cascaded H-bridge 7-level inverters is proposed. The suggested strategy is based on minimizing an objective function which simultaneously optimizes the converter utilization and Total Harmonic Distortion (THD). The Switch Utilization Ratio (SUR) is formulized for both the phase and line-line voltages of a 7-level inverter and is considered in the final objective functions. Based upon the SUR formula, utilization ratio enhancement will reduce the value of feeding DC links, which improves the efficiency and lifetime of the circuit components due to lower voltage stresses and losses. In order to achieve more effective solution in different modulation indices, it is assumed that the DC sources can be altered. Experimental validation is presented based on a three-phase 7-level inverter prototype.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2017년도 전력전자학술대회
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• pp.70-71
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• 2017

This paper presents a new cascaded boost multilevel converter topology for distributed generation (DG) systems. Most of DG systems, such as photovoltaic (PV), wind turbine and fuel cells, normally require the complex structure power converters, which makes the system expensive, complex and hard to control. However, the proposed converter topology can generate a much higher output voltage just by using the standard low-voltage switch devices and low voltage DC-sources in a simplified structure, also enhancing the reliability of the switch devices. Simulation and experimental results with a 1.2kW system are presented to validate the proposed topology and control method.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2017년도 전력전자학술대회
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• pp.445-446
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• 2017

In this paper, adaptive prefiltering method is proposed for reduction of dc-link ripple in cascaded NPC/H-bridge system. Under non-linear load such as electric machine or harmonically distorted conditions, dc-link capacitor voltage with harmonics is inevitable result. In terms of reducing dc-link ripple, prefiltering method combined low pass filter with multiple second order generalized integrator is proposed. Proposed prefiltering method effectively reduces harmonics of dc-link ripple and improves characteristic of THD, simulated by using MATLAB R2014a and PSIM 9.1.4.

• Journal of Power Electronics
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• 제17권3호
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• pp.788-797
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• 2017

The power quality of AC electric railways has become an issue worthy of more and more concern. Many active compensators based on power converters have been proposed, but with complex transformers or coupled branches. This paper presents a single-phase cascaded H-bridge multilevel active power filter (APF), which can directly connect to the 27.5-kV power supplies to deal with power quality problems. According to field measured data, the load characteristics are analyzed, and the system configuration and control system are designed based on the load characteristic analysis. Finally, simulation and experimental results verify the effectiveness of the proposed APF system, considering some problems such as the supply voltage fluctuations and transient inrush currents in AC electric railway systems.