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PhD defence by Xin Zhao on Grid Support by Power Converters in Microgrids

Time

17.02.2017 kl. 13.00 - 16.00

Description

Xin Zhao, Department of Energy Technology, will defend the thesis "Grid Support by Power Converters in Microgrids".

TITLE

Grid Support by Power Converters in Microgrids

PHD DEFENDANT

Xin Zhao

SUPERVISOR

Professor Josep Guerrero

MODERATOR

Associate Professor Sanjay Chaudhary 

OPPONENTS

Associate Professor Dezso Sera, Dept. of Energy Technology, Aalborg University Esbjerg (Chairman)
Professor Li Ran, Warwick University, UK
Professor George Weiss, Tel Aviv University, Israel

ABSTRACT

Due to the exhaustive exploitation of fossil energy, increasing attention has been drawn from both industrial and academic field for seeking alternative energy. Consequently, renewable energy, such as solar energy, and wind energy, becomes an attractive solution in the past decades. Normally, such kind of renewable energy sources (RESs) are integrated to form a small-scale power system, the well-known MG, via power electronic interfacing (PEI) converters to deliver electricity to the power grid and support various local electrical loads in an efficient and reliable way. However, concerning the booming increasing capacity of MGs, these small-scale power grids are rapidly becoming of increasing importance in view of grid support functions, such as low-voltage ride-through (LVRT), and harmonic compensation capability. Thus, this Ph.D. project has the objective of embedding the MGs with LVRT and harmonic compensation capability through properly controlling the PEI converters.

Focusing on LVRT strategies, a negative sequence droop control based LVRT strategy, which consists of a primary voltage/current loop and a secondary LVRT control loop, is proposed in the Ph.D. project for voltage-controlled converters. The proposed LVRT control strategy can contribute to maintain the connection between MGs and the power grid during voltage sags. Moreover, by injecting positive/negative sequence power into the grid, the load side voltage can be recovered back to the nominal value. In this way, potential damages to the electrical loads can be avoided. In addition, dynamic consensus algorithm (DCA) based current sharing scheme is proposed to equally allocate positive/negative sequence currents among the converters with high reliability in a distributed way.

Moreover, a voltage harmonic suppression strategy is proposed for current-controlled converters. Compared with conventional harmonic compensation strategies, the proposed scheme has the advantages of: 1) it achieves seamless integration of the voltage harmonic control loop and the fundamental current control loop, 2) high harmonic compensation performance can be achieved by only sensing locally measurable signals, 3) it offers the possibility of harmonic current sharing between multiple parallel converters.

It can be concluded that power electronic converters are playing a more active role than ever before concerning LVRT and harmonic mitigation capability. Robust, simple control should be paid specific attention while establish such kind of systems. With the help of basic communication network, the proposed control can be integrated into single power electronic module controller. Consequently, the whole system complexity is reduced in a large scale.

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PhD defence by Xin Zhao on Grid Support by Power Converters in Microgrids

ALL ARE WELCOME. THE DEFENCE WILL BE IN ENGLISH.

AFTER THE DEFENCE THERE WILL BE AN INFORMAL RECEPTION AT PONTOPPIDANSTRAEDE 111 IN TNE COFFEE ROOM.

 

Host

Department of Energy Technology

Address

Pontoppidanstræde 111, auditorium

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