A grid connected dual voltage source inverter with power quality improvement features

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PROJECTS DEVELOPMENT
A GRID-CONNECTED DUAL VOLTAGE SOURCE INVERTER WITH POWER
QUALITY IMPROVEMENT FEATURES
By
A
PROJECT REPORT
Submitted to the Department of electronics &communication Engineering in the
FACULTY OF ENGINEERING & TECHNOLOGY
In partial fulfillment of the requirements for the award of the degree
Of
MASTER OF TECHNOLOGY
IN
ELECTRONICS &COMMUNICATION ENGINEERING
APRIL 2016

CERTIFICATE
Certified that this project report titled “A GRID-CONNECTED DUAL VOLTAGE
SOURCE INVERTER WITH POWER QUALITY IMPROVEMENT FEATURES” is the
bonafide work of Mr. _____________Who carried out the research under my supervision
Certified further, that to the best of my knowledge the work reported herein does not form part of
any other project report or dissertation on the basis of which a degree or award was conferred on
an earlier occasion on this or any other candidate.
Signature of the Guide Signature of the H.O.D
Name Name

DECLARATION
I hereby declare that the project work entitled “A GRID-CONNECTED DUAL VOLTAGE
SOURCE INVERTER WITH POWER QUALITY IMPROVEMENT FEATURES”
Submitted to BHARATHIDASAN UNIVERSITY in partial fulfillment of the requirement for
the award of the Degree of MASTER OF APPLIED ELECTRONICS is a record of original
work done by me the guidance of Prof.A.Vinayagam M.Sc., M.Phil., M.E., to the best of my
knowledge, the work reported here is not a part of any other thesis or work on the basis of which
a degree or award was conferred on an earlier occasion to me or any other candidate.
(Student Name)
(Reg.No)
Place:
Date:

ACKNOWLEDGEMENT
I am extremely glad to present my project “A GRID-CONNECTED DUAL VOLTAGE
SOURCE INVERTER WITH POWER QUALITY IMPROVEMENT FEATURES” which
is a part of my curriculum of third semester Master of Science in Computer science. I take this
opportunity to express my sincere gratitude to those who helped me in bringing out this project
work.
I would like to express my Director,Dr. K. ANANDAN, M.A.(Eco.), M.Ed., M.Phil.,(Edn.),
PGDCA., CGT., M.A.(Psy.)of who had given me an opportunity to undertake this project.
I am highly indebted to Co-OrdinatorProf. Muniappan Department of Physics and thank from
my deep heart for her valuable comments I received through my project.
I wish to express my deep sense of gratitude to my guide
Prof. A.Vinayagam M.Sc., M.Phil., M.E., for her immense help and encouragement for
successful completion of this project.
I also express my sincere thanks to the all the staff members of Computer science for their kind
advice.
And last, but not the least, I express my deep gratitude to my parents and friends for their
encouragement and support throughout the project.

ABSTRACT:
This paper presents a dual voltage source inverter(DVSI) scheme to enhance the power
quality and reliability ofthe microgrid system. The proposed scheme is comprised of
twoinverters, which enables the microgrid to exchange power generatedby the distributed energy
resources (DERs) and also tocompensate the local unbalanced and nonlinear load.
The controlalgorithms are developed based on instantaneous symmetricalcomponent
theory (ISCT) to operate DVSI in grid sharing andgrid injecting modes. The proposed scheme
has increased reliability,lower bandwidth requirement of the main inverter, lowercost due to
reduction in filter size, and better utilization of microgridpower while using reduced dc-link
voltage rating for themain inverter.
These features make the DVSI scheme a promisingoption for microgrid supplying
sensitive loads. The topology andcontrol algorithm are validated through extensive simulation
andexperimental results.

INTRODUCTION:
A voltage regulation and power flow control scheme for a wind energy system (WES) is
proposed. A distribution static compensator (DSTATCOM) is utilized for voltage regulation and
also for active power injection.
The control scheme maintains the power balance at the grid terminal during the wind
variations using sliding mode control. A multifunctional power electronic converter for the DG
power system is described. This scheme has the capability to inject power generated by WES and
also to perform as a harmonic compensator.
Most of the reported literature in this area discuss the topologies and control algorithms
to provide load compensation capability in the same inverter in addition to their active power
injection.
When a grid-connected inverter is used for active power injection as well as for load
compensation, the inverter capacity that can be utilized for achieving the second objective is
decided by the available instantaneous micro-grid real power.
Considering the case of a grid-connected PV inverter, the available capacity of the
inverter to supply the reactive power becomes less during the maximum solar insolation period.
At the same instant, the reactive power to regulate the PCC voltage is very much needed during
this period.
It indicates that providing multi functionalities in a single inverter degrades either the
real power injection or the load compensation capabilities.

In, a voltage regulation and power flow control scheme for a wind energy system (WES)
is proposed. A distribution static compensator (DSTATCOM) is utilized for voltage regulation
and also for active power injection. The control scheme maintains the power balance at the grid
terminal during the wind variations using sliding mode control.
A multifunctional power electronic converter for the DG power system is described in.
This scheme has the capability to inject power generated by WES and also to perform as a
harmonic compensator.
Most of the reported literature in this area discuss the topologies and control algorithms
to provide load compensation capability in the same inverter in addition to their active power
injection. When a grid-connected inverter is used for active power injection as well as for load
compensation, the inverter capacity that can be utilized for achieving the second objective is
decided by the available instantaneous microgrid real power.
Considering the case of a grid-connected PV inverter, the available capacity of the
inverter to supply the reactive power becomes less during the maximum solar insolation periods
At the same instant, the reactive power to regulate the PCC voltage is very much needed during
this period . It indicates that providing multifunctionalities in a single inverter degrades either the
real power injection or the load compensation capabilities.

EXISTING SYSTEM:
The scheme ensures that unity power factor (UPF) is achieved at the load terminal during
nominal operation, which is not possible in the traditional method. Also, the compensator injects
lower currents and, therefore, reduces losses in the feeder and voltage source inverter.
Further, a saving in the rating of DSTATCOM is achieved which increases its capacity to
mitigate voltage sag. Nearly UPF is maintained, while regulating voltage at the load terminal,
during load change. The state-space model of DSTATCOM is incorporated with the deadbeat
predictive controller for fast load voltage regulation during voltage disturbances.
With these features, this scheme allows DSTATCOM to tackle power-quality issues by
providing power factor correction, harmonic elimination, load balancing, and voltage regulation
based on the load requirement. It uses a three-phase, four-wire, two-level, neutral-point-clamped
VSI. This structure allows independent control to each leg of the VSI.

PROPOSED SYSTEM:
This paper demonstrates a dual voltage source inverter (DVSI) scheme, in which the
power generated by the Microgrid is injected as real power by the main voltage source inverter
(MVSI) and the reactive, harmonic, and unbalanced load compensation is performed by auxiliary
voltage source inverter (AVSI). In the DVSI scheme, as total load power is supplied by two
inverters, power losses across the semiconductor switches of each inverter are reduced.
This increases its reliability as compared to a single inverter with multifunctional
capabilities. Also, smaller size modular inverters can operate at high switching frequencies with
a reduced size of interfacing inductor, the filter cost gets reduced.
Moreover, as the main inverter is supplying real power, the inverter has to track the
fundamental positive sequence of current. This reduces the bandwidth requirement of the main
inverter. The inverters in the proposed scheme use two separate dc links. Since the auxiliary
inverter is supplying zero sequence of load current, a three phase three-leg inverter topology with
a single dc storage capacitor can be used for the main inverter.
This in turn reduces the dc-link voltage requirement of the main inverter. Thus, the use of
two separate inverters in the proposed DVSI scheme provides increased reliability, better
utilization of microgrid power, reduced dc grid voltage rating, less bandwidth requirement of the
main inverter, and reduced filter size. Control algorithms are developed by instantaneous
symmetrical component theory (ISCT) to operate DVSI in grid-connected mode, while
considering nonstiff grid voltage.

ADVANTAGES:
 Inject real power to the grid.

BLOCK DIAGRAM:

TOOLS AND SOFTWARE USED:
 MPLAB – microcontroller programming.
 ORCAD – circuit layout.
 MATLAB/Simulink – Simulation

APPLICATIONS:
 Distributed generation (DG).

CONCLUSION:
A DVSI scheme is proposed for microgrid systems withenhanced power quality. Control
algorithms are developed togenerate reference currents for DVSI using ISCT. The
proposedscheme has the capability to exchange power from distributedgenerators (DGs) and also
to compensate the local unbalancedand nonlinear load.
The performance of the proposed schemehas been validated through simulation and
experimental studies.As compared to a single inverter with multifunctionalcapabilities, a DVSI
has many advantages such as, increasedreliability, lower cost due to the reduction in filter size,
andmore utilization of inverter capacity to inject real power fromDGs to microgrid. Moreover,
the use of three-phase, threewiretopology for the main inverter reduces the dc-link
voltagerequirement. Thus, a DVSI scheme is a suitable interfacingoption for microgrid supplying
sensitive loads.

REFERENCES:
[1] A. Kahrobaeian and Y.-R. Mohamed, “Interactive distributed generationinterface for flexible
micro-grid operation in smart distribution systems,”IEEE Trans. Sustain. Energy, vol. 3, no. 2,
pp. 295–305, Apr. 2012.
[2] N. R. Tummuru, M. K. Mishra, and S. Srinivas, “Multifunctional VSCcontrolled microgrid
using instantaneous symmetrical components theory,”IEEE Trans. Sustain. Energy, vol. 5, no. 1,
pp. 313–322, Jan.2014.
[3] Y. Zhang, N. Gatsis, and G. Giannakis, “Robust energy managementfor microgrids with
high-penetration renewables,” IEEE Trans. Sustain.Energy, vol. 4, no. 4, pp. 944–953, Oct.
2013.
[4] R. Majumder, A. Ghosh, G. Ledwich, and F. Zare, “Load sharingand power quality enhanced
operation of a distributed microgrid,” IETRenewable Power Gener., vol. 3, no. 2, pp. 109–119,
Jun. 2009.
[5] J. Guerrero, P. C. Loh, T.-L. Lee, and M. Chandorkar, “Advanced controlarchitectures for
intelligent microgrids—Part II: Power quality, energystorage, and ac/dc microgrids,” IEEE
Trans. Ind. Electron., vol. 60, no. 4,pp. 1263–1270, Dec. 2013.

A grid connected dual voltage source inverter with power quality improvement features

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A grid connected dual voltage source inverter with power quality improvement features