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Looped-chain-based active current sharing strategy in DC microgrids

Li D., Liu Y., Gu Y., Qi H.

Archives of Electrical Engineering

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2017

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Vol. 66, nr 3

559--569

EN

The integration of renewable energy sources in modern electric grids have drawn increasing attention nowadays. In order to effectively manage large-scale renewable energy sources and achieve flexible and efficient operation, the concept of microgrids have been proposed. Considering the nature of DC outputs in many distributed energy resources (DERs), DC microgrids have been extensively studied in the past years. Among the operational issues in DC microgrids, current sharing issues have become an important topic since it is highly relevant to the operation of DC microgrids. By adopting a proper design of current sharing strategy in DC microgrids, the current rating violations in each interface converter can be successfully avoided. In this paper, a looped-chainbased active current sharing strategy is proposed to realize high accuracy current sharing in DC microgrids. In particular, the output current is shared between the neighboring interface converters. Hence, following a clockwise or counter-clockwise order, a loopedchain- based control diagram can be established to share the reference value of the output current. A final status in the whole DC microgrid is that the output current of every interface converter is equalized. Hence, the desired current sharing objective can be satisfied. A MATLAB simulation model is established to verify the proposed loopedchain- based active current sharing strategy in DC microgrids.

2

Decentralized Fuzzy PID Excitation controller Combined with Turbine Regulating for Voltage Stability in Power Systems

Gao H, Hu X., Wang B., Qi H.

Przegląd Elektrotechniczny

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2012

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R. 88, nr 10a

284-288

EN

This study deals with the design of a decentralized fuzzy proportional–integral–derivative (PID) excitation controller combined with turbine regulating to enhance the voltage stability in power systems after start-up or sudden disturbances. Based on the turbine regulating, we design the fuzzy PID (FPID) excitation controller combined with turbine regulating (FPID-TR). Simulation results show the effectiveness of the proposed controller for stabilizing the voltage in power systems.

PL

W artykule opisano sterownik PID wzbudzenia połączony z regulacją turbiny zastosowany w celu poprawy stabilności systemu energetycznego przy nagłych zakłóceniach. Sterownik wykorzystuje logikę rozmytą. (Sterownik PID wzbudzenia połączony z regulacją turbiny w celu poprawy stabilności systemu energetycznego)

3

A Novel Single-Phase Transformerless Inverter for Grid-Connected Photovoltaic Systems

San G., Qi H., Guo H.

Przegląd Elektrotechniczny

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2012

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R. 88, nr 12a

251-254

EN

Eliminating the leakage current is one of the most important issues for transformerless inverters in grid-connected photovoltaic system applications, where the technical challenge is how to keep the system common-mode voltage constant to reduce the leakage current. A novel singlephase three-level topology for transformerless photovoltaic systems is presented in this paper. Compared with the conventional H-bridge topology, it only needs two additional asymmetrically distributed switches, and the system common-mode voltage can be kept constant with a simple modulation scheme. Test results verify the theoretical analysis and the feasibility of the proposed topology.

PL

W artykule przedstawiono nową trójpoziomową topologię jednofazowego przekształtnika w beztransformatorowym układzie pracującym z panelami fotowoltaicznymi. System pozwala na utrzymanie stałego napięcia common-mode, poprzez wykorzystanie dodatkowych łączników oraz prostego algorytmu modulacji.