• 전력전자학회논문지
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• 제18권1호
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• pp.10-17
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• 2013

In this paper, a new active damping method of LCL filter without capacitor voltage sensors is proposed for 3 phase PWM Inverter. Normally, L filter or LCL filter is used as an output filter of grid connected PWM inverter. An LCL filter has more excellent performance than L filter to reduce harmonic current, so the small inductance value can be used. However, the resonance problem in LCL filter is happen due to the zero impedance by the addition of LC branch. To solve the resonance problem, the various active damping method has been proposed so far. Generally, the virtual resistor active damping methods is required to additional hardware sensors for measurement of capacitor voltage and current. In this paper, the new active damping method is proposed without any capacitor voltage or current sensors. In the proposed method, the resonance component of the capacitor voltage of LCL filter can be observed by a simple MRAS(Model Reference Adaptive System) observer without additional hardware sensors, and this component is suppressed by feedforward compensation. The validity of the proposed method is proven by simulation and experiment on the 3-phase PWM inverter system.

• 한국산업융합학회 논문집
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• 제17권3호
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• pp.103-112
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• 2014

BY the Transformers and reactors, the input electrical energy is converted into magnetic energy. At the end through the magnetic energy was passed at the output parameter. Specially At the flyback transformer or a reactor airgap were designed to contain more magnetic energy. But that work is very difficult for the optimal design. It is that Contradictions are between the length of the Air-gap, Winding inductance, DC bias. As to e Several conflicting conditions in order to determine the optimum Air-gap has a lot of experience and trial & error is necessary. The approach proposed in this paper, the auxiliary winding on the core attached to part of primary core, that by applying a DC voltage has a dramatic effect like Core with designed Air-gap. This inventiveness and advantage is to regulate arbitrarily the Saturation Flux Quantity by the input signal to secondary winding. Accordingly obtained the biggest effect is that increasing limits of the saturation current destined by the material and shape of the conventional core. In other words, that can decreas the size of the transformer and reactor, While maintaining the current saturation capacity. This paper, prove its effect as using the local flux saturation in transformers and reactors for research by the computer program using the finite element method (FEM) simulation, followed by actual experiment to verify

• 한국전자파학회논문지
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• 제9권5호
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• pp.648-658
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• 1998

본 논문에서는 PCB (printed circuit board) 접지면에 셜치된 캡(gap)이 불요전자파 방사에 미치는 영향을 정 량적으로 해석하였다. 본 연구의 해석법으로 복잡한 구조체의 전자기적 특성을 해석하는데 주파수영역 전자파 수치해석 방법들과 비교하여 여러 가지 장점올 가지는 시간영역 해석법인 FDTD(finite difference time dom main) 방법올 사용하였다. 해석 구조체는 일반적으로 생산되는 PCB와 유사한 크기를 선정하였으며 소자충은 전압원과 마이크로스트립만이 폰재하는 단순화된 구조이다. PCB 접지변에 설치된 캡에 의해 생기는 인덕턴스 의 크기와 입출력 케이블올 통한 불요전자파 방사량을 FCC 및 CISPR 규정치와 함께 제시하였으며 갱의 크기 에 따라 방사되는 불요전자파의 세기가 크게 변화되는 것을 관찰할 수 있다. 본 논문의 해석결과는 실제 PCB 셜 계에 있어서 잘봇된 캡의 설치로 인한 불요전자파 방사를 막는데 유용하게 사용될 수 있으리라 생각된다.

• 전기학회논문지
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• 제65권12호
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• pp.2109-2112
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• 2016

The rate of rise of the fault current in DC grids is very high compared to AC grids because of the low line impedance of DC lines. In AC grids the arc of the circuit breaker under current interruption is extinguished by the zero current crossing which is provided naturally by the system. In DC grids the zero current crossing must be provided by the circuit breaker itself. Unlike AC girds, the magnetic energy of DC grids is stored in the system inductance. The DC circuit breaker must dissipate the stored energy. In addition the DC breaker must withstand the residual overvoltage after the current interruption. The main contents of this paper are to ${\cdot}$ Explain the theoretical background for the design of DC circuit breaker. ${\cdot}$ Develop the simulation model in PSIM of the real scaled DC circuit breaker for 1,800V DC railway. ${\cdot}$ Suggest design guidelines for the DC circuit breaker based on the experimental work, simulations and design process.

• 전력전자학회논문지
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• 제16권3호
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• pp.250-257
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• 2011

본 논문은 병렬 삼상 부스트 컨버터에서 Interleaved PWM에 의해 발생하는 고 주파수 순환전류를 효과적으로 저감시키기 위해서, AC 입력단에 연결되는 삼상 결합 인덕터의 특성을 분석하였다. 제시된 삼상 결합 인덕터 분석은 삼상 결합 인덕터의 구조와 전압 방정식의 해석을 통하여 이루어졌다. 그리고 이것을 바탕으로 기존의 저 주파수 평균화 모델에 삼상 결합 인덕터를 추가하여, 고 주파수 순환전류와 저 주파수 순환전류를 동시에 저감시킬 수 있는 새로운 형태의 평균화 모델을 제안하였다. 새로운 평균화 모델의 영상성분을 이용하면, 삼상 결합 인덕터와 라인 인덕터의 순환전류에 대한 총 인덕턴스를 각각 구해 비교 할 수 있다. 시뮬레이션과 실험결과를 토대로 병렬 삼상 부스트 컨버터에서 사용되는 삼상 결합 인덕터의 유용성을 검증하였다.

• 전력전자학회논문지
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• 제15권4호
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• pp.296-308
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• 2010

본 논문은 영구자석형 동기발전기를 이용한 풍력발전 시스템의 3병렬 운전과 계통연계 기술을 제안한다. 영구자석형 풍력발전 시스템에서 back-to-back 컨버터는 발전기와 계통에 직접 연결되므로 시스템 정격에 준하는 전력 반도체 소자와 필터가 요구된다. 본 논문은 시스템의 전력변환부를 3병렬로 연결하고 병렬 운전에 의해 발생할 수 있는 순환 전류는 적절한 내부 인덕터 선정으로 해결한다. 낮은 스위칭 주파수로 운전되는 대용량 풍력발전 시스템의 THD 규정을 만족시키기 위해 최적 설계된 LCL필터를 사용하고 LCL필터에 의해 발생할 수 있는 공진 문제는 전력이론을 통한 능동 댐핑 기법을 통하여 추가적인 손실 없이 보상한다. 또한 계통 왜곡 및 불평형 시 발생할 수 있는 전력 품질의 문제는 추가적인 보상 알고리즘을 적용하여 향상시킨다. 시뮬레이션 및 실험을 통하여 병렬 운전 시스템과 알고리즘의 타당성을 검증한다.

• 전력전자학회논문지
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• 제6권5호
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• pp.416-422
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• 2001

BLDC (Brushless DC) 전동기는 선형적인 토크 대 전류, 속도 대 전압특성을 갖고 있으며 기계적 전기적인 잡음이 없고, 가감속 제어가 용이하며, 토크 대 관성의 비가 매우 높아 소형으로 높은 출력을 낼 수 있다는 장점을 가지고 있다. 그러나 전기자 전류의 전환 (Commutation)시 고정자 권선의 인덕턴스 성분과 역기전력으로 인해 발생되는 전류리플은 BLDC 전동기의 구동시 발생되는 토크리플의 중요한 원인이 되어, 고정밀 서보계통에 대한 응용에 큰 장애가 되고 있다. 본 논문에서는 퓨리에 시리즈계수를 사용한 새로운 전류제어 알고리즘을 개발하여 상전류 전환시 발생하는 전류리플을 최소화함으로서 토크리플을 현저히 감소 시켰으며, BLDC 전동기의 구동을 위해 널리 사용되고 있는 UNIPOLAR PWM 방식과 시뮬레이션 및 실험을 통해 비교함으로써, 새로운 알고리즘의 효용성을 입증하고자 한다.

• 전기학회논문지
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• 제66권2호
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• pp.328-338
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• 2017

In this paper, a zero torque control scheme adopting current sharing function (CSF) used in integrated Switched Reluctance Motor (SRM) drive with DC battery charger is proposed. The proposed control scheme is able to achieve the keeping position (KP), zero torque (ZT) and power factor correction (PFC) at the same time with a simple novel current sharing function algorithm. The proposed CSF makes the proper reference for each phase windings of SRM to satisfy the total charging current of the battery with zero torque output to hold still position with power factor correction, and the copper loss minimization during of battery charging is also achieved during this process. Based on these, CSFs can be used without any recalculation of the optimal current at every sampling time. In this proposed integrated battery charger system, the cost effective, volume and weight reduction and power enlargement is realized by function multiplexing of the motor winding and asymmetric SR converter. By using the phase winding as large inductors for charging process, and taking the asymmetric SR converter as an interleaved converter with boost mode operation, the EV can be charged effectively and successfully with minimum integral system. In this integral system, there is a position sliding mode controller used to overcome any uncertainty such as mutual inductance or DC offset current sensor. Power factor correction and voltage adaption are obtained with three-phase buck type converter (or current source rectifier) that is cascaded with conventional SRM, one for wide input and output voltage range. The practicability is validated by the simulation and experimental results by using a laboratory 3-hp SRM setup based on TI TMS320F28335 platform.

• 전력전자학회논문지
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• 제19권1호
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• pp.64-70
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• 2014

In this paper, the new LLCL filter is proposed for grid connected three-phase PWM inverter for passive damping. LLCL filter inserts a small inductor in the branch of the capacitor of the traditional LCL filter to compose a series resonant circuit to reduce the switching-frequency component on grid current. Using LLCL filter, the switching-frequency current ripple components can be attenuated much better than the LCL filter, leading to a decrease in the total inductance. However, the resonance phenomena caused by zero impedance from the addition of LC branch in LLCL filter can be a big problem. Resonance phenomena of LLCL filter can be a source of grid system instability, so proper damping methods are required. However, it is difficult to apply a passive damping method in the conventional LLCL filter, because the damping resistor increase impedance of the LC branch. Therefore, switching frequency component of grid current can not much attenuated by low Q of LC series resonance effect. In this paper, a new LLCL filter is proposed to overcome the conventional LLCL filter with passive damping. The validity of the proposed method is proven by simulation and experimental result.

• Journal of Power Electronics
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• 제18권1호
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• pp.234-250
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• 2018

This paper presents a new load sharing control for use between paralleled three-phase inverters in an islanded microgrid based on the online line impedance estimation by the use of a Kalman filter. In this study, the mismatch of power sharing when the line impedance changes due to temperature, frequency, significant differences in line parameters and the requirements of the Plug-and-Play mode for inverters connected to a microgrid has been solved. In addition, this paper also presents a new droop control method working with the line impedance that is different from the traditional droop algorithm when the line impedance is assumed to be pure resistance or pure inductance. In this paper, the line impedance estimation for parallel inverters uses the minimum square method combined with a Kalman filter. In addition, the secondary control loops are designed to restore the voltage amplitude and frequency of a microgrid by using a combined nominal value SOGI-PLL with a generalized integral block and phase lock loop to monitor the exact voltage magnitude and frequency phase at the PCC. A control model has been simulated in Matlab/Simulink with three voltage source inverters connected in parallel for different ratios of power sharing. The simulation results demonstrate the accuracy of the proposed control method.