1. Maulana Azad National Institute
of Technology, Bhopal
Department of Energy

2. MICROGRID AND ITS CONTROL
Ph D Seminar-I
by
Mrs. ANULA KHARE
Scholar NO. 083113201
under guidance of
DR. SAROJ RANGNEKAR

3. Outline
• Concept and architecture of micro
grid
• Modes of operation
• Control strategy
• Literature review
• References

4. INTRODUCTION
WHAT IS A MICROGRID ?

5. Conceptual Micro grid

6. BASIC ARCHITECTURE OF
MICRO GRID
• Group of radial feeders
• Point of coupling(pcc)
• Micro Grid central
controller (MGCC)
• Power electronic-interface-
e.g. rectifier,Inverters.
• Micro sources
• storage
• Critical and non critical
loads

7. Power Electronics Interfaced
Micro source
–

8. Storage
• It is very much a key to unlock the doors of
renewable energy.
• Needed because of inherent intermittency
of supply from renewable sources.
• Needed to ensure secure and continuous
supply during off grid and on grid
condition.

9. TYPES OF STORAGE
• Electrochemical energy storage –
Battery and super capacitors.
• Super conducting magnetic storage.
• Kinetic energy (inertia) storage.
• Thermal storage.

10. ADVANTAGES OF
MICROGRID
• Energy efficiency
• Minimization of overall energy
consumption
• Improved environmental impact
• Improvement of energy system reliability
• Network benefits
• Cost efficient electricity infrastructure
replacement

11. POWER OUTPUT CONTROL
OF MICRO SOURCES
• Resembles with electrical power
system – speed governors and voltage
regulators replaced by a central
supervisory controller
• To keep real and reactive power output
constant : P-Q control

12. MODE OF OPERATION
• Single master operation (SMO).
• Multi master operation (MMO).
• Grid connected operation
• Stand alone or Islanded mode of
operation.

13. SMO
• Most of the micro sources connected
to the network with a P-Q control type
and a single VSI inverter is associated
with the storage device- the master
which provides frequency reference.

14. MMO
• There are several inverters operating
as VSI with a predefined
frequency/active power and
voltage/reactive power droop. Other P-
Q controlled inverters may also co-
exist.

15. GRID CONNECTED
• Micro grid(MG) connected parallel to main
grid – to either draw or supply power to
grid.
• Should not actively regulate voltage at
PCC.
• Harmonics and DC current injected to grid
should be below required levels.
• Should satisfy all of its load requirements
and contractual obligations with grid.

16. ISLANDED OPERATION
• Disconnected from main grid due to abnormal
conditions in grid or due to planned switching.
• Problem of voltage and frequency management.
• Problem of balance between supply and demand
• Problem of power quality management
• Micro source issues
• Communication among MG components.
• For multi customer system have to be well
organized concerning contractual issues.

17. Cooperation Of Micro Source And Storage
Device During Islanding Operation
. Pure droop control.
• Inverter mode control.
• Primary energy source control.
• Autonomous control.
• Reverse droop control.
• Multi agent based PQ control.

18. PURE DROOP CONTROL

19. Micro source controller for
inverter modes control.

20. Primary Energy Source Control

21. Reverse droop control

22. Autonomous Control

23. Comparison of above
strategies
• Inverter mode ,primary energy source and multi
agent based control approaches guarantee that
voltage and frequency will not vary much from
nominal value hence suitable to drive quality
sensitive loads
• Pure droop reverse droop and autonomous control
are suitable for loads which can tolerate
fluctuations
• Choice also depend on micro source,ownership
and storage

24. Literature Review
(1) S. Chakraborty, Manoja D. Weiss and Simoes, “Distributed Intelligent Energy
Management System for a Single Phase , High frequency AC micro grid”, IEEE
transaction on industrial electronics, vol. 54, no.1,Feb.2007
In this paper a single phase high frequency
micro grid is shown as a solution for better
utilization of micro grid. 1-Φ 500 Hz buses are
used to combine renewable sources with loads and
grid.Proposed system utilizes an active filter called
unified power quality conditioner .Also a unified
power flow conditioner is used to control the power
flow from/to grid.

25. …
Continued
Both unified power quality conditioner and
unified power flow conditioner consist of
series and shunt active filters that use
instantaneous ‘p-q’ theory to calculate
compensating voltage and current, which
then are synthesized using pulse width
modulation in voltage source inverter(VSI).

26. Optimization of Operating Cost
• A distributed integrated energy management
system (DIEMS) has been implemented for
optimization of operating cost. A neural
network is incorporated in DIEMS.
• Function of DIEMS is to generate set points
for the sources and storage in such a way that
economically optimized
power dispatch will be maintained to
fulfill certain load demands.

27. Salient features of HFAC
. Advantages-easy filtering of
harmonics,improved luminous
efficiency,increased flexibility and reliability of
storage,reduction in size of passive circuit
components .
• Power transmission and distribution- two
significant factors affect the suitability of
transmission is increased voltage drop and
Power loss along the line.
• Applications of HFAC-military, aircraft
industry,iron steel industry,light and air
conditioning.

28. (2)Hannu Laaksonen and Kimmo Kauhaniemi, “Voltage and Current THD
in micro grid With Different DG Unit and Load Configurations”, CIRED
Seminar on Smart Grids for Distribution, Paper No. 0057 , 2008
This paper studies the voltage and current total
harmonic distortion (THD) before and after
islanding in the micro grid with different micro
grid configurations.
• Causes – caused by nonlinear devices. System
impedance at each harmonic frequency
determines impact of nonlinear load on voltage
distortion, higher order harmonics caused by
converters may resonate with system impedance.

29. continued
• Standards -Various organizations on national and
international level have made standards both for
individual and total harmonic distortion of voltage,
for distributed generator units more tight limits are
defined.
• When the micro grid transfers from normal
operation to islanded operation, micro grid is
more sensitive to disturbances, therefore the
effect of different filter types, sizes and switching
frequencies must be carefully examined.

30. Solutions suggested—
(1) L-C-L filters should be used
(2) Amount of thyristor connected rectifier
loads directly connected to micro grid should
be low (15-20% of total load)
(3) IGBT based converters must be preferred
(4) SVM should be preferred over PWM
(5) Use of negative sequence filtering in
control system of converters is beneficial

31. References
[1] John Baker, “New technology and possible advances in
energy storage,” Energy Policy 36, 4368-4373, 2008.
[2] Peter J. Hall,Euan J. Bain,” Energy-storage technologies
and electricity generation,” Energy Policy 36, 4352-
4355,2008.
[3] M. Uzunoglu, O.C. Onar and M.S. Alam,”modelling
control and simulation of a PV/FC/UC based hybrid power
generation system for stand alone applications”,Renewable
energy,doi:10.1016/j.renene,2008.
[4] J. Pecas Lopes, etal,”Defining Control Strategies for Micro
Grids islanded operation,” IEEE Trans. On Power Systems,
vol.21,PP 616924, 2006

32. continued
[5] J. Pecas Lopes, etal,”Micro Grid Black start and
Islanded Operation,” 15th Power Systems
Computation Conference, Belgium,2005.
[6]H. Laaksonen, P. Saari and R.Komulainen,”Voltage
and Frequency Control of Inverter Based Weak LV
Network Micro grid,”International Conference on
Future Power Systems, 2005..
[7] J. Oyarzabal, etal,”Agent-based Micro Grid
Management System,”International Conference on
Future Power Systems, 2005

33. ...continue
d
[8] D. Georgakis, etal,”Operation of a Prototype Micro
Grid System Based on Micro sources Equipped with
Fast-acting Power Electronics Interfaces,” 35th annual
IEEE Power Electronics Specialists Conference,
Vol.4,2521-2526, 2004.
[9] P. Chiradeja and R. Ram Kumar, “An approach to
quantify the technical benefits of distributed
generation,”IEEE trans on Energy Conversion, Vol. 19,
No. 4, 764-773, December 2004.
[10] Ph. Strauss and A. Engler,”AC coupled pv hybrid
systems and micro grid state of art and future trends,”
third world conference on photovoltaic energy
conversion,Japan, May 2003.

34. THANK YOU