• Journal of Power Electronics
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• 제15권2호
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• pp.327-337
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• 2015

This study discusses the design of a parallel-operated DC-DC single-ended primary-inductor converter (SEPIC) for low-voltage application and current sharing with a constant output voltage. A coupled inductor is used for parallel-connected SEPIC topology. Generally, two separate inductors require different ripple currents, but a coupled inductor has the advantage of using the same ripple current. Furthermore, tightly coupled inductors require only half of the ripple current that separate inductors use. In this proposed work, tightly coupled inductors are used. These produce an output that is more efficient than that from separate inductors. Two SEPICs are also connected in parallel using the coupled inductors with a single common controller. An analog control circuit is designed to generate pulse width modulation (PWM) signals and to fulfill the closed-loop control function. A stable output current-sharing strategy is proposed in this system. An experimental setup is developed for a 18.5 V, 60 W parallel SEPIC (PSEPIC) converter, and the results are verified. Results indicate that the PSEPIC provides good response for the variation of input voltage and sudden change in load.

• Journal of Power Electronics
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• 제12권1호
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• pp.83-87
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• 2012

Input-series-output-parallel (ISOP) modular converters consisting of multiple modular DC/DC converters can enable low voltage rating switches for use in high voltage input applications. In this paper, an input voltage sharing control strategy for input-series-output-parallel (ISOP) full-bridge (FB) DC/DC converters is proposed. By sensing the difference in the input current of two modules, the system can achieve input voltage sharing for DC-DC modules. The effectiveness of the proposed control strategy is verified by simulation and experimental results obtained with a 200w-50kHz prototype.

• 전력전자학회논문지
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• 제18권4호
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• pp.387-396
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• 2013

This paper investigates the droop control of parallel inverters for an islanded mode of microgrid. Frequency and voltage droop control is one of power control and load demand sharing methods. However, although the active power is properly shared, the reactive power sharing is inaccurate with conventional method due to the unequal line impedances and the power coupling of active - reactive power. In order to solve this problem, an improved droop method with virtual inductor concept and a voltage and current controller properly designed have been considered and analyzed through the PSiM simulation. The performance of improved droop method is analyzed in not only low-voltage line but also medium voltage line.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제49권4호
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• pp.282-290
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• 2000

In this paper, the charge control with the input voltage feedback is proposed for the input series-output series-output parallel connected converter configuration for the high speed train power system application. This control scheme accomplishes the output current sharing for the output-parallel connected modules as well as the input voltage sharing for the input series connected modules for all operating conditions including the transients. It also offers the robustness for the input voltage sharing control according to the component value mismatches among the modules. And this configuration enables the usage of MOSFET for a high voltage system allowing a higher switching frequency for lighter system weight and smaller size. The performance of the proposed scheme is verified through the experimental results.

• Journal of Power Electronics
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• 제13권3호
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• pp.479-486
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• 2013

This paper presents a control strategy for distributed systems, which can be used in islanded microgrids. The control strategy is based on the droop method, which uses locally measured feedback to achieve load current sharing. Instead of the traditional droop method, an improved one is implemented. A virtual inductor in the synchronous frame for three-phase inverters is proposed to deal with the coupling of the frequency and the amplitude related to the active and reactive power. Compared with the traditional virtual inductor, the proposed virtual inductor is not affected by high frequency noises because it avoids differential calculations. A model is given for the distributed generation system, which is beneficial for the design of the droop coefficients and the value of the virtual inductor. The effectiveness of the proposed control strategy is verified by simulation and experiment results.

• 전력전자학회논문지
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• 제16권1호
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• pp.50-57
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• 2011

본 논문에서는 마이컴(ATmega-2560) 기반의 디지털 통신 방식을 이용한 새로운 부하분담(Load-sharing) 알고리즘(Algorithm)을 제안한다. 기존의 아날로그 방식과 달리 고속 통신과 디지털 제어를 수행하고 실시간 제어를 위한 시분할 토큰버스 방식을 적용함으로서 효율적인 부하분담 및 리던던시(Redundancy)를 구현하였다. 또한 자동 ID 설정 알고리즘을 적용함으로서 시스템 비용을 낮추었으며, 제어기의 전압 및 전류 적분값을 공유하는 새로운 알고리즘으로 시스템의 속응성을 향상시켰다. 제작된 병렬 시스템은 각 모듈마다 독립된 제어기가 구성되어 있으며, 마스터(Master) 모듈의 지령치에 따라 슬레이브(Slave) 모듈이 부하분담을 수행한다. 본 논문에서는 PSIM을 통한 시뮬레이션과 시작품 제작을 통해 제안된 알고리즘의 타당성을 검증하였다.

• Journal of Power Electronics
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• 제12권1호
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• pp.58-66
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• 2012

SRMs(Switched Reluctance Motors) are much interested in high speed applications due to the mechanical robustness, simple structure and high efficiency. In spite of many advantages of SRMs, a higher torque ripple discourages the adoption of SRMs in a high speed application. This paper presents a simple negative torque of tail current compensation scheme using a modified TSF(Torque Sharing Function) for the high speed SRMs. Because of the short commutation in the high speed region, the negative torque from the tail current makes the high torque ripple. In order to reduce and compensate the negative torque from tail current, the proposed control scheme produces an additional compensating torque with a reference torque in the active phase winding. And the compensating value is dependent on the tail current of the inactive phase winding. Furthermore, the switching signals of the outgoing phase are fully turned off to restrict the extended tail current, and the torque error of the outgoing phase is compensated by the incoming phase. The proposed modified TSF control scheme is verified by the computer simulations with 30,000[rpm] high speed 4/2 SRM. The simulation and experimental results show the effectiveness of the proposed control scheme.

• Journal of Electrical Engineering and Technology
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• 제10권1호
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• pp.118-127
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• 2015

This paper presents an advanced torque ripple minimization method of a switched reluctance motor (SRM) using torque sharing function (TSF). Generally, TSF is applied into the torque control. However, the conventional TSF cannot follow the expected torque well because of the nonlinear characteristics of the SRM. Moreover, the tail current that is generated at a high speed motor drive makes unexpected torque ripples. The proposed method combined TSF with fuzzy logic control (FLC). The advantage of this method is that the torque can be controlled unity at any conditions. In addition, the controller can track the torque under the condition of the wrong TSF. The effectiveness of the proposed algorithm is verified by the simulations and experiments.

• Journal of Power Electronics
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• 제5권2호
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• pp.160-165
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• 2005

In a parallel operation of UPS, there are two types of circulating currents between UPS. One is the low order circulating current with a fundamental frequency caused by the amplitude and phase differences of UPS output voltages, and the other is the harmonic circulating current with PWM switching frequency caused by non-synchronized PWM waveforms among UPS. The elimination of the low order circulating current is essential for optimal load sharing in parallel operations of UPS, which can be accomplished by the phase and magnitude control at each UPS. The harmonic circulating current may cause troubles and deteriorate in performance of the controller for optimal load sharing in parallel operation of UPS. This paper presents a PWM synchronizing method to eliminate the harmonic circulation current in parallel operation of UPS. The effectiveness of the proposed scheme has been investigated and verified through experiments by a 50kVA UPS.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2016년도 전력전자학술대회 논문집
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• pp.363-364
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• 2016

In this paper, a novel bridgeless interleaved power factor correction circuit with single current sensor is proposed. The proposed control strategy requires only one current sensor for the interleaved bridgeless PFC. By sampling the output current, all the boost indictor currents can be calculated and used to control the input current according to the input voltage. The reduced number of current sensors and associated feedback circuits helps reduce the cost of system. The problem caused by the unequal current gain between current sensors inherently does not exist in the proposed topology. Thus, current sharing between converters can be achieved more accurately and the high frequency distortion is decreased. In addition, the proposed technique can be applied to the other kinds of interleaved PFC topologies. Performance of the proposed control strategy is verified by the experimental results with 6.6kW bridgeless interleaved PFC circuit.