• Proceedings of the KIPE Conference
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• 2017.07a
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• pp.451-452
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• 2017

본 논문에서는 3상 PWM 전압형 컨버터의 LCL필터 설계기법을 제안한다. 3상 전압형 컨버터는 스위칭으로 인한 고조파를 함유하고 있기 때문에, 입력측 고조파 감소를 위한 수동필터가 필수적이며, 용량, 입력역률, 입출력 조건 등 여러 가지 파라미터를 필요하기 때문에 설계하는 데에 어려운 단점이 있다. 이에 본 논문에서는 LCL필터의 최적 설계기준을 제안하며, 이에 대한 유효성을 입증하기 위해 PSIM 시뮬레이션을 통해 검증한다.

• Proceedings of the KIPE Conference
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• 2012.07a
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• pp.209-210
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• 2012

NPC 인버터는 높은 효율과 우수한 출력 THD로 계통연계 시스템에 많이 채용되고 있다. 이때 LCL필터는 계통연계 기준을 만족하면서 가격과 부피측면을 고려하여 인덕턴스와 캐패시턴스는 가능한 작게 설계하는 것이 중요하다. 본 논문에서는 계통연계형 NPC 인버터에서 PWM기법을 고려하여 계통전류의 고조파 기준을 만족하면서 설계자가 독립부하 전압리플, 인덕터 부피, 무효전류량, 시스템 대역폭에 가중치를 적용할 수 있는 LCL필터 최적설계 방법을 제안한다.

• Proceedings of the KIPE Conference
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• 2010.11a
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• pp.38-39
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• 2010

태양광 및 풍력발전에서 계통연계 인버터의 LCL필터설계 시계통에 주입되는 전류의 고조파 저감만을 고려하였으나 연료전지 발전과 같이 독립부하가 존재하는 경우, 이 같은 설계 기법을 적용 시 독립부하의 전압은 일정한 품질을 보장할 수 없다. 본 논문에서는 계통에 주입되는 전류 품질 뿐만 아니라 독립부하의 전압 품질도 고려한 LCL필터 설계방법을 제안한다.

• Journal of Power Electronics
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• v.15 no.5
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• pp.1338-1347
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• 2015

DC injection is a critical issue in transformerless grid-connected inverters. DC injection control based on virtual capacitor has the advantages of low cost, low loss, high accuracy and easy implementation. In this paper, the principle of DC injection control based on virtual capacitor was analyzed. In addition, the applicable conditions, working process, steady state error and advantages were also discussed in detail. The design of the control parameters based on virtual capacitor was proposed in a grid-connected inverter with LCL filter. The robustness of the control parameters was also discussed. Simulation and experimental results verify the validity of the analysis and demonstrate that this research has a certain value in engineering applications.

• Journal of Power Electronics
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• v.14 no.6
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• pp.1322-1333
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• 2014

To track the sinusoidal current under stationary frame and suppress the effects of low-order grid harmonics, the multi-resonant quasi-proportional plus resonant (PR) controller has been extensively used for digitally controlled LCL-type pulse-width modulation (PWM) converters with capacitor-current-feedback active damping. However, designing the controller is difficult because of its high order and large number of parameters. Moreover, the computation and PWM delays of the digitally controlled system significantly affect damping performance. In this study, the delay effect is analyzed by using the Nyquist diagrams and the system stability constraint condition can be obtained based on the Nyquist stability criterion. Moreover, impact analysis of the control parameters on the current loop performance, that is, steady-state error and stability margin, identifies that different control parameters play different decisive roles in current loop performance. Based on the analysis, a simplified controller design method based on the system specifications is proposed. Following the method, two design examples are given, and the experimental results verify the practicability and feasibility of the proposed design method.

• The Transactions of the Korean Institute of Power Electronics
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• v.26 no.5
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• pp.325-333
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• 2021

A 3 kW grid-tied PV inverter with Gallium nitride high-electron mobility transistor (GaN HEMT) for domestic commercialization was developed using boost converter and full-bridge inverter with LCL filter topology. Recently, many GaN HEMTs are manufactured as surface mount packages because of their lower parasitic inductance characteristic than standard TO (transistor outline) packages. A surface mount packaged GaN HEMT releases heat through either top or bottom cooling method. IGOT60R070D1 is selected as a key power semiconductor because it has a top cooling method and fairly low thermal resistances from junction to ambient. Its characteristics allow the design of a 3 kW inverter without forced convection, thereby providing great advantages in terms of easy maintenance and high reliability. 1EDF5673K is selected as a gate driver because its driving current and negative voltage output characteristics are highly optimized for IGOT60R070D1. An LCL filter with passive damping resistor is applied to attenuate the switching frequency harmonics to the grid-tied operation. The designed LCL filter parameters are validated with PSIM simulation. A prototype of 3 kW PV inverter with GaN HEMT is constructed to verify the performance of the power conversion system. It achieved high power density of 614 W/L and peak power efficiency of 99% for the boost converter and inverter.

• Proceedings of the KIPE Conference
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• 2011.11a
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• pp.42-43
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• 2011

PV Simulator는 제한된 작업공간에서 태양광발전계통의 주요 설비인 Power Conditioning System (PCS)의 성능을 평가하거나, 제품 출하 전 PCS의 고장유무를 검사하는데 필수적인 장비이다. 최근에 IEC에서 EN50530규정에 따라 PCS의 MPPT평가도 중요하게 되어 동특성이 우수한 PV Simulator가 요구되고 있다. 현재 출시되고 있는 PV Simulator는 대부분 리니어 방식으로서 안정된 출력을 갖지만 효율이 나쁘다는 단점이 있다. 본 논문에서는 효율을 높이기 위한 스위칭 방식 PV Simulator의 전력회로와 출력용 LCL필터를 설계하고 그 특성을 검증한다.

• Proceedings of the KIPE Conference
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• 2013.07a
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• pp.232-233
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• 2013

본 논문에서는 태양광 인버터에서 전력 품질 개선을 위해서 사용되는 LCL 필터의 설계 방법을 제시한다. 제안된 방법은 생산 품질의 질을 향상시키기 위해 산업체에서 사용되고 있는 다구치 방법론을 이용한다. 기존 설계에서 고려되던 출력 전력 품질(THD), 인덕터의 크기뿐만 아니라 태양광 인버터의 손실, 광량 변화로 인한 입력 조건의 변화, 출력 전압의 변화를 고려하여 설계한다. 설계 결과는 설계 목표 기능 변수를 향상시키고 동시에 그 변동량을 최소화할 수 있다.

• Journal of Power Electronics
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• v.15 no.1
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• pp.278-287
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• 2015

This paper proposes a novel voltage distortion approach for output filter design based on the voltage transfer function for both off-grid and grid-connected Pulse Width Modulation (PWM) Inverters. The method explained in detail is compared to conventional methods. A comparative analysis is performed on an example of L and LCL-filter design. Simulation and experimental results for the off-grid and the grid-connected single phase inverter prove our theoretical predictions. It was found that conventional methods define redundant values of the output filter elements. Assumptions and limitations of the proposed approach are also discussed.

• Journal of Power Electronics
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• v.16 no.4
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• pp.1565-1577
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• 2016

For grid-connected LCL-filtered inverters, dual-loop current control with an inner-loop active damping (AD) based on capacitor current feedback is generally used for the sake of current quality. However, existing studies on capacitor current feedback AD with a control delay do not reveal the mathematical relation among the dual-loop stability, capacitor current feedback factor, delay time and LCL parameters. The robustness was not investigated through mathematical derivations. Thus, this paper aims to provide a systematic study of dual-loop current control in a digitally-controlled inverter. At first, the stable region of the inner-loop AD is derived. Then, the dual-loop stability and robustness are analyzed by mathematical derivations when the inner-loop AD is stable and unstable. Robust design principles for the inner-loop AD feedback factor and the outer-loop current controller are derived. Most importantly, ensuring the stability of the inner-loop AD is critical for achieving high robustness against a large grid impedance. Then, several improved approaches are proposed and synthesized. The limitations and benefits of all of the approaches are identified to help engineers apply capacitor current feedback AD in practice.