MICRO GRID OPERATION AND CONTROL_C.S.P

MICRO GRID OPERATION AND CONTROL
USING SUPER CAPACITORS
Monday, November 6, 2017 1c.Sai prasad

CONTENTS
INTRODUCTION
OVERVIEW OF MICRO GRID
SUPER CAPACITORS
CHARGING AND DISCHARGING MODELS
CONCLUSION
REFERENCES

INTRODUCTION
Monday, November 6, 2017 3
Modern days of Power system grid has some adverse effects due to
integration of Distributed generation with maingrid.
A systematic method used for solving these effects, known as
MICROGRID.
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MICRO GRID
Micro Grids are localized grids
that can disconnect from
traditional grid to operate
autonomously.
 They are liable to operate while
main grid is down.
Fig. 1 Microgrid structure

NEED FOR MICROGRID
 Microgrid could be the answer to Energy crisis
 Transmission Losses gets highly reduced
 Microgrid provide high quality and reliable energy supply to critical
loads

CONVENTIONAL GRID VS MICROGRID
Efficiency of conventional grid is very low as compared to microgrid
Large amount of Energy in the form of heat is wasted in
conventional grid
Power sources in case of microgrid (often referred to as
Microsources) are small and are located in close to load.

OPERATING MODES
Micro Grid operates in 2 modes
1. Islanded mode
2. Grid connected mode
In islanded mode, the microgrid disconnects itself from the main grid
and operates itself
In grid-connected mode, the microgrid is connected to the main grid
and enables bidirectional power flow.

CONTROL methods using super-capacitors
Process of Constant Current Charging Control
Process of Constant Voltage Charging Control
Process of Discharge Control

Constant current charging control:-
Hysteresis compared mode is used
This approach takes the desired output
current wave form as command signal
Width of hysteresis loop determines
the charging performance
If ring width is too large, switching
frequency will be low, tracking error
increases.
If ring width is too low, higher switching
frequencies takes place which may cause
the loss increases fig.2 Block diagram of hysteresis current control

Constant voltage charging control
Triangular wave comparison method is used
Error will go through the triangle
wave comparator to generate PWM
Waveform to control the
switching device
Fig.3 Block diagram of constant voltage charging control
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Discharge control
Direct current control is used
Output go through the
triangle-wave comparator
to generate PWM waveform to
control the switching device
Fig.4 Block diagram of discharge control

What is meant by Super Capacitors?
 Super-capacitor, also known as Ultracapacitor
It has very high capacitance
 A capacitor stores energy by means of a static
charge as opposed to an electrochemical
reaction
Super-capacitors don’t handle excess voltages
If it Handles high voltages, life of super-capacitor
decreases.
Fig.5 super-capacitor

Comparison among capacitor and Super-capacitor
Parameter Capacitor Super-capacitor
Definition Energy is stored in their
electric field
A super-capacitor tends to
differ from ordinary
capacitor due to its very
high capacitance
Energy Density Comparatively low Comparatively very high
cost Comparatively cheap Comparatively expensive
Applications Sub-miniature Multi layer
ceramic chip capacitor
Micro computer, RAM
Charging Time More Less
Advantages Less battery drain
Less damage
Charges in seconds
Simple charging

Why Super-capacitors instead of capacitors?
Because of High Energy Density when compared to capacitor.
 Fast charge and Discharge Characteristics.
Very High Capacitance

SUPER CAPACITORS ENERGY STORAGE SYSTEM
Fig.6Basic Configuration of Super-capacitor Energy Storage system

Boost Buck circuit:-
Fig .7 circuit diagram of Boost-Buck
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Charging Characteristics :-
P1 is in off condition
P2 manages Energy flow
Energy flows from DC bus side to the super capacitors side
Charging model circuit acts as Boost circuit
It uses Constant current charging mode at starting and constant
voltage charging mode at the ending

Discharging characteristics:-
P2 is in off condition
P1 controls Energy flow
Energy flows from super capacitors side to the DC bus side
 Discharging model circuit acts as Buck circuit
Vₒ = D*𝑉𝑑 is the relationship between input voltage and output
voltage

Comparison Between charging and discharging:-
Under Charging Under Discharging
 P1 off  P2 off
 P2 manages energy flow  P1 manages energy flow
 Boost converter  Buck converter
 It uses constant current charging mode
at starting And constant voltage
charging mode at ending
 It uses constant power Discharge
Mode

CONCLUSIONS
• The purpose of super capacitor as energy storage device to reduce
the fluctuations in the bus voltage
• In future, the use of super capacitors energy storage system as
electrical energy will become popular.

REFERENCES
[1] Wu Bingbing, Yin Zhongdong,Xiao Xiangning.“Super-capacitors Energy storage
systems Applied in the Microgrid”. 2010 5th IEEE Conference on Industrial
Electronics and Applications
[2] Robert Lasseter, Abbas Akhil, chris marnay, etc. “Integration of distributed
energy Resources, The certs Microgrid concept”. Shandong:shangdong University.
[3] LU Hongyi, HE Benteng. “Application of the super-capacitor in a
Microgrid”. Automation of Electric Power Systems,2009,33(2):87-91
[4] WANG chengshan, WAND Shouxiang. “study on some key problems Related to
Distributed Generation Systems”. Automation of ElectricPowersystems,2008
[5] Mushtaq N. Ahmed, Mojgan Hojabri, Ali Mahmood Humada, Hamdan Bin
Daniyal,Hatem Fahad Frayyeh.“An Overview of Microgrid control
strategies”. International Journal of Engineering and Advanced Technology
(IJEAT). ISSN: 2249 – 8958, Volume-4 Issue-5, June 2015

MICRO GRID OPERATION AND CONTROL_C.S.P

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