• 전기전자학회논문지
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• 제26권1호
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• pp.1-9
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• 2022

전력시스템의 신뢰성을 보장하며 분산전원의 수용성을 높이기 위해 IEEE 1547과 같은 표준을 개정하여 분산전원의 계통 연계기준을 강화하고 있다. 본 논문은 이러한 표준을 준수하는 IEEE 1547-2018 기반의 스마트 인버터 기능의 제어 알고리즘을 제안하고, 스마트 인버터 기술의 검증을 위해 구축한 Power HILS 기반의 테스트 플랫폼을 소개한다. 스마트 인버터 기능 중 Volt-var 제어와 Frequency-watt 제어 알고리즘은 상호운용성 표준을 준수하도록 해당 기능의 curve를 상위로부터 설정할 수 있도록 하며, 각 기능의 Enable 신호 시점을 상위 지령에 따라 제어할 수 있도록 하였다. 표준에 따라 Power HILS 테스트 플랫폼을 통해 Volt-var 제어와 Frequency-watt 제어에 대한 형식시험을 수행하였고, 명시된 표준 형식시험을 전부 만족함을 측정 결과를 통해 검증하였다.

• 전기전자학회논문지
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• 제27권4호
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• pp.657-667
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• 2023

배전계통에 연계되는 분산전원의 수가 증가함에 따라 계통 내 과전압 문제를 일으키지 않고 접속될 수 있는 한계접속용량인 photovoltaic(PV) hosting capacity(HC)를 추정하는 것이 매우 중요해졌다. 이에 본 연구에서는 접속점의 전압을 유지하는 제어를 수행하면서 향상된 hosting capacity를 추정하기 위한 방안을 제안하고 있다. 제안된 방안은 two-stage optimization framework로 구성되며 Stage 1에서 IEEE Std 1547-2018 가이드라인을 이용한 Volt-Var(VV) 및 Volt-Watt(VW) 제어 PV hosting capacity 추정을 수행한다. Stage 2에서는 VV 및 VW의 파라미터를 개선하는 절차를 거쳐 향상된 PV HC 값을 다시 도출해낸다. 제안한 방식의 성능 검증을 위해 IEEE 37-버스 시스템이 OpenDSS를 사용해 테스트되었으며 결과에서 제안된 방식의 적용을 통해 PV hosting capacity가 증가함을 확인하였다.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2018년도 전력전자학술대회
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• pp.144-146
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• 2018

In order to meet the harmonics standards such as IEEE 519 and P1547 the output quality of a grid connected inverter should satisfy a certain level of Total Harmonic Distortion (THD) value. However, the output quality of an inverter gets degraded due to the grid voltage harmonics, the dead time effects and the nonlinearity of the switches, which all contributes to a higher THD value of the output. In order to meet the required THD value for the inverter output under the distorted grid condition the use of harmonic controller is essential. In this paper a novel feedforward harmonic compensation method is proposed in order to effectively eliminate the low order harmonics in the inverter current to the grid. In the proposed method, unlike the conventional harmonic control methods, the hamonic components are directly compensated by the feedforward terms generated by the PR controller with the grid current in the stationary frame. The proposed method is simple in implementation but powerful in eliminating the harmonics from the output. The effectiveness of proposed method is verified through the PSIM simulation and the experiments with a 5kW single phase grid connected inverter.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2018년도 추계학술대회
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• pp.104-106
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• 2018

The harmonics and the DC offset in the grid can cause serious synchronization problems for grid connected inverters (GCIs) which leads not able to satisfy the IEEE 519 and p1547 standards in terms of phase and frequency variations. In order to guarantee the smooth and reliable synchronization of GCIs with the grid, Phase Locked Loop (PLL) is the crucial element. Typically, the performance of the PLL is assessed to limit the grid disturbances e.g. grid harmonics, DC Offset and voltage sag etc. To ensure the quality of GCI, the PLL should be precise in estimating the grid amplitude, frequency and phase. Therefore, in this paper a novel Robust PLL technique called Digital Lock-in Amplifier (DLA) PLL is proposed. The proposed PLL estimate the frequency variations and phase errors accurately even in the highly distorted grid voltage conditions like grid voltage harmonics, DC offsets and grid voltage sag. To verify the performance of proposed method, it is compared with other six conventional used PLLs (CCF PLL, SOGI PLL, SOGI LPF PLL, APF PLL, dqDSC PLL, MAF PLL). The comparison is done by simulations on MATLAB Simulink. Finally, the experimental results are verified with Single Phase GCI Prototype.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2018년도 추계학술대회
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• pp.95-97
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• 2018

The power quality of Single Phase Grid-Connected Inverters (GCIs) has received much attention with the increasing number of Distributed Generation (DG) systems. However, the performance of single phase GCIs get degraded due to several factors such as the grid voltage harmonics, the dead time effect, and the turn ON/OFF of the switches, which causes the harmonics at the output of GCIs. Therefore, it is not easy to satisfy the harmonic standards such as IEEE 519 and P1547 without the help of harmonic compensator. To meet the harmonic standards a certain kind of harmonic controller needs to be added to the current control loop to effectively mitigate the low order harmonics. In this paper, the harmonic compensation is performed using a novel robust harmonic compensation method based on Digital Lock-in Amplifier (DLA). In the proposed technique, DLAs are used to extract the amplitude and phase information of the harmonics from the output current and compensate it by using a simple PI controller in the feedforward manner. In order to show the superior performance of the proposed harmonic compensation technique, it is compared with those of conventional harmonic compensation methods in terms of the effectiveness of harmonic elimination, complexity, and implementation. The validity of the proposed harmonic compensation techniques for the single phase GCIs is verified through the experimental results with a 5kW single phase GCI. Index Terms -Single Phase Grid Connected Inverter (SPGCI), Harmonic Compensation Method, Total Harmonic Distortion (THD) and Harmonic Standard.