1. Allahabad-211007, Uttar Pradesh
M. Tech Thesis On
POWER SYSTEM STABILITY ENHANCEMENT BY SIMULTANEOUS AC-DC POWER TRANSMISSION
Submitted By:
ABHISHEK CHATURVEDI
ID No. : 11MTEEEPS019
Advisor:
Er. Vinay Kumar Tripathi
(Asst. Professor)
Department of Electrical and Electronics Engineering
Shepherd School of Engineering and Technology
Sam Higginbottom Institute of Agriculture, Technology and Sciences
(Deemed-To-Be-University)
Allahabad , Uttar Pradesh

2. INTRODUCTION

3. The concept of simultaneous ac-dc power transmission
The concept of simultaneous ac-dc power transmission.Long extra high voltage (EHV) ac lines cannot be loaded to their thermal limits due to this instability occurs in the power system
It is possible to load these lines very close to their thermal limits.
The conductors are allowed to carry usual ac along dc superimposed on it.

4. The advantage of parallel ac-dc transmission for improvement of transient stability and dynamic stability and damp out oscillations have been established.
Simulation study is carried out in MATLAB software package. The results shows the stability of power system when compared with only ac transmission.

5. OBJECTIVE OF THE THESIS

6. To emphasize the possibility of simultaneous ac-dc transmission with its inherent advantage of power flow control improves stability and damps out oscillations in power system.
To achieve the advantages of parallel ac-dc transmission in some specific applications LV (low voltage) and MV (Medium voltage) system.
How electricity gets to you
Generation: About half of the electricity in India is generated by coal-fired generation plants. Natural gas and renewable generation, including hydroelectric, biomass are also sources of Indian electricity.
Transmission: Once generated, electricity travels across India from generating plants over high-voltage transmission lines to local transformers. The transformers reduce the voltage level making it suitable for local distribution to customers.
Distribution - this is where comes in Electricity travels from the transformers via low-voltage distribution lines, owned by India, to your home or business.

7. METHODS
AND METHODOLOGY

8. Using flexible ac transmission system (FACTS) components .
Very fast control of SCRs in FACTS devices like state VAR system (SVS), controlled series capacitor (CSC), static phase shiftier (SPS) and controlled braking resistors oscillations as well as to control the voltage profile of the line by controlling the total reactive power flow.
The flexible ac transmission system (FACTS) concepts, based on applying state-of-the-art power electronic technology to existing ac transmission system, improve stability to achieve power transmission close to its thermal limit.

9. BASIC BLOCK DIAGRAM

10. Simulation Model

12. Result’s and Discussion

13. Sending end Voltage, receiving end voltage

14. Sending end current, receiving end current

15. Sub system 4, Active & reactive power

16. Combined AC DC Current

17. Ac current to Zig- Zag Transformer

18. Rectifier dc side Voltage

19. Inverter sending, receiving end Voltage

20. FFT analysis of combined ac-dc power transmission

21. TABLE I
COMPUTED RESULTS
Power Angle
AC Current(kA)
DC Current(kA)
AC Power(MW)
DC Power(MW)
Total Power(MW)

22. TABLE II
SIMULATION RESULTS
Power Angle
PS (MW)
Pac (MW)
Pdc (MW)
Pac loss (MW)
Pdc loss (MW)
PR (MW)

23. Benefits of utilizing FACTS devices
The benefits of utilizing FACTS devices in electrical transmission systems
can be summarized as follows
Better utilization of existing transmission system assets
Increased transmission system reliability and availability
Increased dynamic and transient grid stability and reduction of loop flows
Increased quality of supply for sensitive industries
Environmental benefits Better utilization of existing transmission system assets

24. CONCLUSION
A simple scheme of simultaneous EHV ac-dc power transmission through the same transmission line has been presented.
Active and reactive powers associated with ac and dc, conductor voltage level and total power have been obtained for steady state normal operating condition.
Simulation studies are being made for the co-ordinated control and also individually the control of ac and dc power transmitted through the lines.

25. There is substantial gain in the loading capability of the line
The possibility of converting a dual circuit ac line into simultaneous ac-dc power transmission block to improve power transfer as well as to achieve reliability in the power transfer.
The added dc power flow is flawless and is not the cause of any transient instability.

26. REFERENCES

27. [1] N. G. Hingorani, “FACTS—flexible A. C
[1] N. G. Hingorani, “FACTS—flexible A.C. transmission system,” in Proc. Inst. Elect. Eng th. Int. Conf. A.C. D.C. Power Transmission,
[2] Padiyar.’HVDC Power Transmission System.’ Wiley Eastern, New Delhi, 1993)
[3] H. Rahman and B H Khan “Stability Improvement of Power Systemby Simultaneous AC-DC Power Transmission” Electric Power System Research Journal, Elsevier, Paper Editorial ID No. EPSRD , Press Article No. EPSR-2560— Digital Object.