Arabian Journal for Science and Engineering

, Volume 42, Issue 12, pp 5071–5081 | Cite as

Intelligent Distributed Control Techniques for Effective Current Sharing and Voltage Regulation in DC Distributed Systems

Research Article - Electrical Engineering
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Abstract

The droop control method is a basic technique for parallel operation of source converters. The cable line resistance of source converters is one of the causes for circulating current, degradation of load sharing, and poor voltage regulation in DC microgrid application. The control objective of microgrid is to minimize trade-off between bus voltage regulation and effective current sharing. The distributed control technique based on droop control is superior among other control technique in terms of expandability and reliability. This paper presents a distributed control technique which not only helps an effective solution for parallel operation of source converters, but also facilitates availability of maximum power to the load. The droop resistance of distributed controller is adjusted by using a fuzzy inference system in order to reduce the bus voltage degradation. This proposed scheme offers simplicity and robust control over the existing distributed control scheme. The performance of the DC microgrid which consists of three source converters with different cable line resistances and common load is verified in the MATLAB/Simulink environment.

Keywords

Droop control Fuzzy inference system Hysteresis current control DC microgrid 

List of Symbols

\(d_i\)

Duty cycle

DEU

Distributed energy units

FIS

Fuzzy inference system

LN

Large negative

LP

Large positive

MN

Medium negative

MP

Medium positive

m

mth source converter

i

Suffix of ith source converter

\(i_{\mathrm{o},i}\)

Output current

\(i_{\mathrm{o},i}^\mathrm{rated} \)

Rated output current of source converter

\(I_{\mathrm{ref},i}^\mathrm{pu} \)

Reference current in per unit

\(I_i^\mathrm{rated} \)

Rated input current of source converter

\(\Delta i_{12} \)

Current difference between converters 1 and 2

\(\Delta i_{12}^{\prime } \)

\(\Delta i_{12} \) for higher values of \(r_{\mathrm{d},i} \)

\(\Delta i_{12}^{{\prime }{\prime }} \)

\(\Delta i_{12} \) by the adjusted value of \(r_{\mathrm{d},i} \)

\(\Delta i\)_\(_{{i-j}}\)

Current difference between ith and jth converter

\(I_{\mathrm{ref},i}\)

Reference current

\(I_{\mathrm{ref}}\)

Average reference current

\(I_{\mathrm{s},i}\)

Source input current in steady state

\(\Delta I\)

Hysteresis current band

N

Number of parallel source converters

\(P_{\mathrm{ref},i}\)

Reference power

\(P_{\mathrm{rated},i}\)

Rated power

\(r_{\mathrm{d,o}} \)

Constant droop resistance value

\(r_{\mathrm{d},i} \)

Droop resistance

\(r_\mathrm{d} \)

Equal droop resistance value

\(r_{\mathrm{d},i}^{\prime } \)

Higher droop resistance value

\(r_{\mathrm{d},i}^{{\prime }{\prime }} \)

Adjusted droop resistance value

\(\Delta r_{\mathrm{d},i} \)

Incremental droop resistance

\(R_{\mathrm{c},i}\)

Cable line resistance

\(R_\mathrm{L}\)

Load resistance

\(R_\mathrm{c}\)

Equal cable line resistance

SN

Small negative

SP

Small positive

\(T_{i}\)

Integral time constant

\(V^{*}_{\mathrm{o},i}\)

Local output voltage reference

\(V^{*}_{\mathrm{o}}\)

Bus voltage reference

\(\Delta V_{\mathrm{max}}\)

Maximum DC bus voltage regulation

\(\Delta V_\mathrm{o}\)

Bus voltage regulation

\(\Delta V'_\mathrm{o}\)

\(\Delta V_{\mathrm{o}}\) by the higher value of \(r_{\mathrm{d},i} \)

\(V_{\mathrm{o},i}\)

Output voltage

\(V_{\mathrm{s},i}\)

Source voltage

\(V_\mathrm{o}\)

DC bus voltage

\(\delta V_{\mathrm{o},i}\)

Reference offset voltage

\(w_{\mathrm{Lpf},i}\)

Low-pass filter cutting frequency

\(Z_{\mathrm{c},i}\)

Impedance of cable line

ZO

Zero

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Copyright information

© King Fahd University of Petroleum & Minerals 2017

Authors and Affiliations

  1. 1.National Institute of TechnologyKurukshetraIndia

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