IRJET- Microgrid Control Techniques

International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056
Volume: 05 Issue: 06 | June-2018 www.irjet.net p-ISSN: 2395-0072
© 2018, IRJET | Impact Factor value: 7.211 | ISO 9001:2008 Certified Journal | Page 2167
MICROGRID CONTROL TECHNIQUES
G Nisha
1 Department of Electrical Engineering, Research Scholar, Vellore Institute of Technology,
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Abstract - A microgrid is one of the improving concepts and
creates the power grid works as smarter. Control techniquein
Microgrid working and operation is a key element for
application and research. The paper establishes the detail
about the Microgrid development through the control
techniques for present scenario. Here the process is classified
into two different research areas. There are control strategy
and hardware design. And, also master-slave control method
and Peers-to-Peers methods are explained in this paper.
Key Words: Islanded, Distributed Generation, Microgrid,
Grid Connected, Master-slave control, Peers-to-Peers.
1. INTRODUCTION
The large RPM implementation of the world economy is a
need for developing the electrical power withlargequalityis
more. Consider the Large-scale generation; themainportion
is Distribution Network. The Distribution Network is an
important part for present grid development scenario.
Though, main grid or mega grid connection is notstrongalso
it generates the difficult for the distribution network. It
creates the security and lossissues. Also, it makesnumerous
severe problem in network. Depend on this research few
popular accidents happen in past decades. Most of the
researchers focus on the improvement of the network and
grid protection and control in DG (Distributed Generation),
also makes the effective answer to creating the grid is
dynamic. In generally DS is eco-friendly. For this, if low loss
generation technique gives it should help the public grid. In
this case not easy to construct the DG with the public grid in
parallel connection. Many of the RES containsno inertia and
low inertia which creates Distribution Generation linked to
the public grid; it will make the oscillation in voltage and
power. For these issues solved by new Microgrid principle.
The MG principle considersas a cluster of load connectionas
well as micro-sources works a one controllable system. It
will give both of the power and thermal through the local
region. In this paper control is one of the keys. Many
research people concentrate the micro-grid control for
operating modes, two modes are available. There are
connected mode and islanded mode. The analysis base on
the control strategies for the development of control
strategies and power electronics device & drives.
2. ANALYSIS ON POWER ELECTRONICS DEVICE AND
DRIVES
Various of the synchronous machine and most of the DS
linked MG through the Electronic power devices. As a result,
the improvement of the power electronic devices is nearly
connected to the control strategiespresent in the Microgrid.
One of the interface devices is Inverter. It classified into two
types. That is, half bridge and full-bridge. Most of the
researchers suggest full-bridge inverter and also the
research using a full-bridge inverter.
The Full bridge inverter must bring numerous harmonic
distortion compares to the half-bridge inverter. In a
microgrid, half-bridge inverter construction is very
complicated. Since, it needslarge DC capacitor.Thecapacitor
range comes approximately around 46000µF. If need to
reduce the capacity range means, use novel half-bridge
inverter will be introduced.
Then the Power Electronic Transformer (PET) introduces
the fresh way for MG control. The PET is utilised at a Point of
Common Coupling. It has three significant benefits. The
advantages are 1. Good Controllability, 2. Power flow could
be control in bidirectional, and 3. Frequency isolation.
2.1. CONTROL METHOD: GRID-CONNECTED MODE
In this method, the MG act in parallel with public grid. It is
used to their power exchange. The public grid will regulate
the frequency of the MG if the MG has to monitor the output
of real and reactive power. Another one of the control isP-Q.
The P-Q control could straight regulate the output power. It
is a common use of grid-connected mode. Control variable
get Phase angle to current and current will be decoupled at
the axis of dq by using the Park transformation. The
transformation is simple.
Fig-1: Grid Connected Mode
2.2. CONTROL METHOD: ISLANDED MODE
In this mode, the Microgrid is disconnected from the public
grid. It works as independently. Master-slave and Droop

Control are the important control strategies using in this
method.
Fig -2: Islanded Mode
A. Peers-to-Peers Control
In this control method is applicable for synchronous
machine. It is used to obtain the power transferring in
between the number of parallel sources not connecting any
of the communication lines. Also, the conventional droop
method used for poor voltage regulation.
In this method four parameters are present.
There is P/f, Q/V.
Where,
P - The active power
Q - The reactive power
f - The frequency
V - The output voltage.
These four parameters present in the conventional droop
method process. Since the frequency modulation value
current within the MG limitation. Particularly, when thegrid
consists of the frequency sensitive loads.WhileusingtheP/V
process frequency droop could be exchanged at output
impedance (R).
In this above figure, Vdc is Voltage in DC, Vgis RMS value of
voltage in AC. In parallel control, multiple sources are
connected. In that case, load sharing is important and
essential. For this cause using large droop control method.
But this method is weak to analyze the system stability and
dynamic characteristics. In this state space analyzing the
Eigen value for the system. When the Eigen value is larger, it
will go for RHP as well as the system said to unstable. The
method of root locus will examine the result.[6]
When working stability problem, development by modeling
the additional loop containing the 3-lag portion. [19-20].
These lag and lead will neglect the large frequency
oscillation.
The equation will be written as,
Where, m and n indicating the Q/V, P/f droop slope relation.
f* indicating the Reference Voltage
V* indicating the Reference Voltage
ɸ indicating the phase angle
In this method, the P controller is exchanged into the PID
controller. [20] [3] the output result will display the two
developments. It could raise the dynamic characteristics by
using the pole placement method. It could be utilised to
regulate the quality control. To add an extra loop for these
methods. It will raise the difficulty of the system. For this
system, U/I multi droop control method will be introduced.
It is applicable for P/f droop control. It is called as Variable
Droop method.
The development could protect the generation of
Distribution Generation goes to the upper limit and
concurrently raise the output of the high Distribution
Generation. The disadvantage of this type ispowersharingis
less. Also, less efficient in the additional loop, so the slope is
minimal.
Another side the inner issue for this controller is oscillation,
additional noise (harmonics), intermittence, and the
difference between the output impedance and effect of
system stability. If develop the load sharingefficiencymeans,
have to introduced the H∞ Control Method. If adding this
compensation, the outer loop it will improve the control
accuracy as well as the efficiency of the Distribution
Generation. For harmonicsreduction processintroducedthe
Robust Control Method Process.
B. Master-Slave Method
Inter-unit communication need for Master-Slave Method.
When showing the CS architecture, master-slave method is
one of the hierarchical control methods. The main unit
collects the data from the various controller of a slave also
pass the control sign again back to the process. In high scale
MG, this control method is more useful for every section.
The Mater-Slave Control Method majorly classified intotwo.
There are Decentralized and Centralized. MGCC implements
the centralised control. It worksbrain fortheentirenetwork.
Here, none of the particular commander unit present in this.
When MG work individually from the maingrid(publicgrid),
any one of the groups should be Turn ON within the master
unit. The application of the master unit is performing like a
public grid to modify another unit generation amplitudeand
frequency.

Fig-3: Mater-Slave Control Method
3. CENTRAL CONTROL METHOD
Micro-Grid Control Center is key element to develop the
control strategy in central. The principle should be
applicable for Micro-Grid Control Center lies through the
essential part of the analysis. Therefore, obtaining the index
consisting of the financial, stability, eco-friendly and many
researchers analysed the many various control types. It
should be classified into three techniques. The techniques
are Fuzzy Control, Optimal Control, and Neural Network.
Smart Grid one of the important for economical operation.
Discuss the performance and characteristicsoftheeconomic
working principle, estimation loss, as well as advantages
present in the environment. These analyses used to
construct the objective function. When considering the
situation as well as economic benefits the object function
obtains the highest profit. Likewise, theMGoperatesusefully
in environmentally friendly and economical too.
4. P- GRADING CONTROL METHOD
Here much analysis’s applied the concept of the control
strategy. Compared to the upgrading method and central
control approach could eliminate the more cost in Micro-
Grid Control Center unit. It is also removing the difficulty in
communication. Depend on theupgradingapproachneedthe
unit of upgraded to contain large capacity.Therefore,ithelps
another units (i.e.) Power and Frequency. The requirement
controls the MG flexibility working as well as the operation
of the MG.
5. CONCLUSION
Microgrid control research Islanded mode is important part
of the analysis. For this mode, obtain the droop control, not
including any of the communication. The disadvantageofthe
droop control method is very apparent. And it could not
solve load sharing and voltage regulation attheequalperiod.
In future research goes under the solve those type of
problem in this method. The MG operation control analysis
focuses the control strategiespresent in the MG side.Mostof
the researchers concentrating through thepublicgridisvery
low. The stability examination focus penetration of the MG
particularly numerous MG penetration requirement focus.
To main grid, MG neither source nor load. It is very flexible.
Also, create the examination challenges. Determination of
Load utilised to analysis the stability present in the
conventional grid. It might be a methodology toenhance the
examination aswell asmonitor the publicgridpartwhenMG
enters to the Public Grid.
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