• The Transactions of the Korean Institute of Power Electronics
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• v.27 no.1
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• pp.1-8
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• 2022

Recently, photovoltaic (PV) systems have been gradually applied in eco-friendly vehicle applications to improve fuel economy. The relevant market is expected to continue to grow because the installation of large-capacity PV systems to other eco-friendly vehicles, such as electric buses and trains, is being considered. However, in a PV system, power imbalance between submodules and low power generation efficiency occur due to factors such as cell aging, contamination, and shading. To resolve this problem, various differential power processing (DPP) converters have been researched and developed. However, conventional DPP converters suffer from large volume and low efficiency. Therefore, to apply DPP converters to eco-friendly vehicles, increasing efficiency and reducing volume and price compared with existing DPP converters is necessary. In this paper, a novel DPP converter with an integrated transformer is proposed and analyzed. The proposed DPP converter uses a single magnetic component by integrating transformers and secondary sides of conventional DPP converters. Therefore, the proposed DPP converter shows high power density and high efficiency, and it is suitable for PV systems in eco-friendly vehicle applications.

• Journal of Power Electronics
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• v.9 no.2
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• pp.320-333
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• 2009

A Photovoltaic (PV) system's power output varies with the change of climate. Frequency deviations, tie line voltage swings are caused by the varying PV power when large PV power from several PV systems is fed in the utility. In this paper, to overcome these problems, a simple coordinated control method for smoothing the variations of combined PV power from multiple PV systems is proposed. Here, output power command is formed in two steps: central and local. Fuzzy control is used to produce the central smoothing output power command considering insolation, variance of insolation and absolute average of frequency deviation. In local step, a simple coordination is kept between the central power command and the local power commands by producing a common tuning factor. Power converters are used to achieve the same output power as local command power employing PI control law for each of the PV generation systems. The proposed method is compared with the method where conventional Maximum Power Point Tracking (MPPT) control is used for each of the PV systems. Simulation results show that the proposed method is effective for smoothing the output power variations and feasible to reduce the frequency deviations of the power utility.

• Journal of the Korean Society of Industry Convergence
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• v.26 no.6_3
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• pp.1269-1278
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• 2023

This paper presents an operational technique that can secure the stability of DC-Grid centering on MG operated based on ESS in multiple MG where three DC-based microgrid(MG) are interconnected. MG1(PV 600kWp, ESS 1.5MWh) has an 830Vdc grid voltage, MG2(PV 300kWp, ESS 1.1MWh) and MG3(PV 100kWp, ESS 500kWh) are DC-based MG with a 750Vdc grid voltage, and MG1 and MG2, 3 are linked by separate DC/DC converters (BTB). In order to keep different grid voltages stable, the power transmission capacity between MG1 and two MG(MG2, MG3) connected with an independent BTB converter was adjusted to secure the overall stability of the system, and this was verified by confirming that the surplus capacity of ESS was maintained in actual operation.

• Journal of Power Electronics
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• v.17 no.4
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• pp.1037-1047
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• 2017

The Differential Power Processing (DPP) converter is a promising multi-module photovoltaic inverter architecture recently proposed for photovoltaic systems. In this paper, a DPP converter architecture, in which each PV-panel has its own DPP converter in shunt, performs distributed maximum power point tracking (DMPPT) control. It maintains a high energy conversion efficiency, even under partial shading conditions. The system architecture only deals with the power differences among the PV panels, which reduces the power capacity of the converters. Therefore, the DPP systems can easily overcome the conventional disadvantages of PCS such as centralized, string, and module integrated converter (MIC) topologies. Among the various types of the DPP systems, the feed-forward method has been selected for both its voltage balancing and power transfer to a modified H-bridge inverter that needs charge balancing of the input capacitors. The modified H-bridge multi-level inverter had some advantages such as a low part count and cost competitiveness when compared to conventional multi-level inverters. Therefore, it is frequently used in photovoltaic (PV) power conditioning system (PCS). However, its simplified switching network draws input current asymmetrically. Therefore, input capacitors in series suffer from a problem due to a charge imbalance. This paper validates the operating principle and feasibility of the proposed topology through the simulation and experimental results. They show that the input-capacitor voltages maintain the voltage balance with the PV MPPT control operating with a 140-W hardware prototype.

• Proceedings of the KIPE Conference
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• 2014.07a
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• pp.37-38
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• 2014

본 논문은 다중 모듈 통합형 태양광 발전 시스템의 발전 단가를 낮추기 위한 MPPT(Maximum Power Point Tracking) 방법에 관한 것이다. 기존의 다중 모듈 통합형 태양광 발전 시스템에서는 각 모듈마다 MPPT 동작을 필요로 하기 때문에 전류센서와 전압센서를 모두 사용하며, 이는 발전 단가를 상승시키는 원인 중 하나가 된다. 본 논문에서는 시스템의 제작비용을 낮추기 위하여 다중 모듈 통합형 태양광 발전 시스템에서 상대적으로 가격이 비싼 전류센서의 사용을 줄여, 여러 개의 모듈에서도 하나의 전류센서만을 사용하는 MPPT 방법을 제안하고 PSIM 시뮬레이션과 실험을 통해 입증하고자 한다.

• Journal of international Conference on Electrical Machines and Systems
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• v.2 no.2
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• pp.225-231
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• 2013

Low voltage ride through capability augmentation of a hybrid micro-grid system is presented in this paper which reflects enhanced reliability in the system. The control scheme involves parallel connected multiple ac-dc bidirectional converters. When the micro-grid system is subjected to a severe voltage dip by any transient fault single power converter may not be able to provide necessary reactive power to overcome the severe voltage dip. This paper discusses the control strategy of additional power converter connected in parallel with main converter to support extra reactive power to withstand the severe voltage dip. During transient fault, when the terminal voltage crosses 90% of its pre-fault value, additional converter comes into operation. With the help of additional power converter, the micro-grid system withstands the severe voltage fulfilling the grid code requirements. This multiple converter scheme provides the micro-grid system the capability of low voltage ride through which makes the system more reliable and stable.