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Licensed Unlicensed Requires Authentication Published by De Gruyter February 5, 2016

Mitigation of Power Quality Problems in Grid-Interactive Distributed Generation System

C. N. Bhende, A. Kalam and S. G. Malla

Abstract

Having an inter-tie between low/medium voltage grid and distributed generation (DG), both exposes to power quality (PQ) problems created by each other. This paper addresses various PQ problems arise due to integration of DG with grid. The major PQ problems are due to unbalanced and non-linear load connected at DG, unbalanced voltage variations on transmission line and unbalanced grid voltages which severely affect the performance of the system. To mitigate the above mentioned PQ problems, a novel integrated control of distribution static shunt compensator (DSTATCOM) is presented in this paper. DSTATCOM control helps in reducing the unbalance factor of PCC voltage. It also eliminates harmonics from line currents and makes them balanced. Moreover, DSTATCOM supplies the reactive power required by the load locally and hence, grid need not to supply the reactive power. To show the efficacy of the proposed controller, several operating conditions are considered and verified through simulation using MATLAB/SIMULINK.

APPENDIX

A. Ratings of inverter

For 500 kW DG is considered, hence inverter is designed only based on DG active power (i. e., reactive power supplied by DG=0). Inverter consists of six IGBT devices. The current rating of device is calculated is approximately 750 A.

B. Ratings of DSTATCOM

For 500 kW load, considering that power factor needs to be maintained at 0.9, the VAR rating of DSTATCOM will be 242.2 kVAR. Required reactive power during voltage sag (for no. of cycles=6 and % dip=40) is calculated as 22.6 kVAR [20]. Hence, total rating of DSTATCOM is considered as 297.49 kVAR (242.2 + 55.29).

C. Design of Cds,Lds of DSTATCOM

Dc side capacitor and interfacing inductance of DSTATCOM are given by Ref. [21]

(3)Cds=(2XX/2)nT(1.8Vm)2(1.4Vm)2
(4)Lds=1.6Vm4hfsw

where

  • Vm (value of the source voltage)=2312,

  • X (of the DSTATCOM)=297.49 kVA,

  • n (of cycles considered for voltage sag)=9,

  • T (time period of the each cycle)=20 msec.,

  • h (constant)=16, and

  • fsw (frequency)=1,050 Hz.

From eqs (1) and (2), the values of Cds and Lds are calculated and given as, Cds=1,100 μF, Lds=7.5 mH.

Acknowledgement

This work was supported by INSA, Govt. of India under “Indo-Australia Science and Technology Visiting Fellowship Programme – 2013”.

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Received: 2015-3-4
Revised: 2016-1-13
Accepted: 2016-1-17
Published Online: 2016-2-5
Published in Print: 2016-4-1

©2016 by De Gruyter

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