This paper discusses control strategies for improving power quality in grid-connected variable speed wind energy conversion systems (WECS) utilizing doubly fed induction generators (DFIG). It highlights the challenges posed by harmonic distortion and power quality issues associated with renewable energy sources and presents solutions such as active harmonic filters and battery energy storage systems. The findings emphasize the importance of optimizing control techniques to enhance reliability and stability in renewable energy grid systems.

1. A Paper Presentation
on
Control Strategies for Improvement of Power Quality in Grid
Connected Variable Speed WECS with DFIG - An Overview
Paper ID-192
4th International Conference Intelligent Circuits &
Systems (ICICS-2022) 8-9th April 2022, LPU-Jalandhar
*Pradeep Singh,
**Dr. Krishan Arora,
***Dr. Umesh C. Rathore.
*Research Scholar, LPU-Jalandhar,
** Associate Professor, LPU-Jalandhar,
*** Professor, Govt. Hydro Engg.
College-Bandla, Bilaspur, HP
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2. POWER SCENARIO IN INDIA……
10%
8%
3%
14%
2%
56%
7%
POWER SCENARIO AS ON 31/12/2022
Wind Solar Bio Power Hydro Nuclear Coal Gas
• Coal (56 %)
• Hydro (14 %)
• Wind (10 %)
• Solar (8 %)
• Gas (7 %)
• Bio-Power (3 %)
• Nuclear (2 %)
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2

3. POWER SCENARIO EXPECTED BY 2039-2040
32%
3%
9%
1%
2%
17%
36%
POWER SCENARIO EXPECTED BY 2039-
2040
Coal Gas Hydro Bio Power Nuclear Wind Solar
• Coal (32 %)
• Hydro (9 %)
• Wind (17 %)
• Solar (36 %)
• Gas (3 %)
• Bio-Power (1 %)
• Nuclear (2 %)
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4. INTRODUCTION
Renewable Energy Sources like Wind, Solar etc. are alternatives for fossil fuels.
However, Intermittent Characteristics of RE sources like wind shall fluctuate
the power output of the wind turbine generator (WTG).
When the large scale WTG is connected to the grid, PQ problem arises.
Wind Loading conditions disrupt the Power Quality (PQ) & Fundamental
Frequency components also the reason for interruption of PQ.
Active Harmonic Filters (AHFs), Passive Harmonic Filters (PHFs) and Energy
Storage Systems improves the grid regulation by smoothening the power
output from the WTG to meet the load and peak demand thereby increase the
reliability of the RE grid connected system.
This paper focuses on control strategies for PQ & different loading conditions.
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5. TYPES OF WIND GENERATORS
SCIG - Type-I Wind Generator.
WRIG - Type-II Wind Generator.
Type-I and Type-II used only for Fixed Wind Speed Conditions and we
have the problems of sag, swell and transients.
DFIG - Type-III Wind Generator.
Full Converter- Type-IV Wind Generator.
Type-III and Type-IV used for variable wind speed conditions and we
experience the problems of harmonics in the grid side.
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6. POWER QUALITY PROBLEMS
 Voltage Sag (Dip)
 Voltage Spikes
 Voltage Swell
 Harmonic Distortion
 Voltage Fluctuations
 Noise
 Voltage Imbalance
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7. POWER QUALITY SOLUTIONS
 Filters
 Isolation Transformers
 Voltage Regulators
 Dynamic Voltage Restorer (DVR)
 Uninterruptable Power Supply (UPS)
 Unified Power Quality Conditioner (UPQC)
 Static VAR Compensator (SVC)
 Thyristor Based Static Switch (TBSS)
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8. HARMONIC MITIGATION TECHNIQUES
Passive Harmonic Filters.
Active Harmonic Filters.
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9. 6/29/2024 9
Active Power
Filters
Lattice Structure
Standard Switched
Hybrid Filters
Shunt Active Filter +
Series Active Filter
Voltage Structure
UPQC
Series Active
Filters
Shunt Active
Filters
Shunt Active Filter +
Series Passive Filter
Series Active Filter +
Shunt Active Filter
Capacitor Inverted
Series Active Filter +
Shunt Passive Filter
Current Fed
Inverter
Voltage Fed
Inverter
CLASSIFICATION OF ACTIVE HARMONIC FILTERS (AHFS)

10. TYPES OF ENERGY STORAGE SYSTEM (ESS)
 Mechanical Energy Storage System
 Electrochemical Energy Storage System
 Thermal Energy Storage System
 Electrical Energy Storage System
 Hydrogen Based Storage System
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11. BATTERY ENERGY STORAGE SYSTEM
To store the excess energy from the renewable energy when demand
is low and this energy in the high demand time.
Enabling the fast response characteristics to variations between
demand and supply.
Provides active and reactive power support to the system when the
power from renewable energy sources fluctuates.
In the grid connected mode, it provides reactive power support for
stabilizing the system voltages.
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12. APPLICATIONS OF BESS
Peak Shaving.
VAR Support.
Oscillation Damping.
Power Quality.
Voltage Support.
Long Term Load Leveling.
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13. BASIC MATLAB MODEL FOR A WINDMILL
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14. WAVEFORMS OF BASIC MODEL FOR WECS……
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14
Output Power with the change in wind speed

15. ……WAVEFORMS OF BASIC MODEL FOR WECS
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Rotor Speed with the change in wind speed Grid Voltage due to Voltage Dips

16. ……WAVEFORMS OF BASIC MODEL FOR WECS
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Grid Voltage due to Voltage Dips Bus Voltage due to Voltage Dips

17. ……WAVEFORMS OF BASIC MODEL FOR WECS
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Torque Variation with the change in wind speed

18. CONCLUSION
The most effective way to solve harmonic problems is to use an active harmonic
filter in that Hybrid Filters.
Another way to remove the PQ issues by using the BESS (Battery Energy Storage
System).
One wat to control the switching time by using a different optimization
techniques
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19. 6/29/2024 19
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