1. IG BASED WINDFARMS USING STATCOM

2. ABSTRACT
With the penetration of renewable energy technologies into the electrical grids, wind energy has become high point of concern for the engineers and researchers for efficient conversion of wind energy into electrical energy and for the stable operation of wind farms with the electrical grid that leads to development of new technologies for wind energy conversion system.
DFIG based variable speed wind energy conversion systems are currently the most widely accepted due to its numerous advantages. To meet the strict criteria of grid codes for the integrated wind farm with the grid has become a major point of concern for engineers and researchers today. Moreover voltage stability is a key factor for the stable operation of grid connected wind farm during fault ride through and grid disturbances.
This project investigates the implementation and comparison of FACTS devices like STATCOM for the voltage stability issue for DFIG-based wind farm connected to a grid and load. The project includes the implementation of FACTS devices as a dynamic voltage restorer at the point of common coupling to maintain stable voltage and thereby protecting DFIG-based wind farm interconnected powers system from isolating during and after the disturbances.
The power system model is simulated in MATLAB / SIMULINK and the results show that the STATCOM is better for the stable operation of wind turbine generator system to remain in service during grid faults.

3. INTRODUCTION
In the last few years, there is a strong trend towards decentralized production and supply, leading to a solution where a growing number of small and medium size producers are connected to energy networks.
But at the same time, the power quality of the generation must be ensured and this means that the electrical parameters of the distribution network have to be maintained within their upper and lower limits.
Therefore, new problems related to the management and operation of energy transfer and distribution and efficient distribution of renewable energy in the grids are actually arising. There is an increasing concern over the environmental impact and sustainability of traditional fossil fuelled power plants

4. . Wind energy is one of the most important and promising renewable energy resources in the world, leading to a growing penetration of the wind energy in electrical system.
As a consequence, the number of small size wind farms used as DG sources located within the distribution system is rapidly increasing in recent years. Installing wind farm in the distribution system can defer the investments for the distribution system expansion, but at the same time, the power quality of the distribution network has to be ensured.
Hence, wind farms are more and more required to take part in the control of electric variables and in particular in reactive power control . The variable-speed wind turbine equipped with Induction generator (IG) is widely used generator in wind farms.
The Induction generator is able to obtain the maximum active power from wind speed and the generated reactive power can be controlled in an independent way. Utilizing IG reactive power control capability, wind farm made up with IG can be used as the continuous reactive power source to support system voltage control without causing any interference in their active power generation process.
Wind farm reactive power control can reduce power losses and improve the voltage profile at the user terminal by providing reactive power compensation in distribution systems

5. BLOCK DIAGRAM

6. The block diagram contains wind farm model, transformer, STATCOM, Controller Model of STATCOM, and the grid lines.
The 20 Megawatts wind model and coupled with the transformer. The STATCOM model are coupled with transformer for the purpose of the real and reactive power compensation.
The STATCOM Model are connected to three phase circuit breaker, when the breaker is in ON period, the real and reactive power will compensate. For that period, the STATCOM performance and can be analyzed.

7. FACTS DEVICES
A flexible alternating current transmission system (FACTS) is a system composed of static equipment used for the AC transmission of electrical energy. It is meant to enhance controllability and increase power transfer capability of the network, voltage regulation, and enhancement of transient stability and mitigation of system oscillations.
Mechanical switching has to be supplemented by rapid response power electronics.

8. FACTS employ high speed Thyristors for switching in or out transmission line components such as capacitors, reactors or phase shifting transformers for desirable performance of systems.
The FACTS technology is not a single high power controller, but rather a collection of controllers, which can be applied individually or in coordination with others to control one or more of system parameters depending on requirements.
Subsequently, devices like thyristor controlled series compensator (TCSC), static compensator (STATCOM), static VAR compensator (SVC), static synchronous series compensator (SSSC), unified power flow controller (UPFC) were proposed and installed under the generic name of flexible AC transmission systems (FACTS) controllers

9. STATCOM
STATCOM or Static Synchronous Compensator is a shunt device, which uses force-commutated power electronics (i.e. GTO, IGBT) to control power flow and improve transient stability on electrical power networks. It is also a member of the so-called Flexible AC Transmission System (FACTS) devices.
The STATCOM basically performs the same function as the static var compensators but with some advantages. The term Static Synchronous Compensator is derived from its capabilities and operating principle, which are similar to those of rotating synchronous compensators (i.e. generators), but with relatively faster operation. 

10. Basic Principle of Operation
In the case of two AC sources, which have the same frequency and are connected through a series reactance, the power flows will be:
Active or Real Power flows from the leading source to the lagging source.
Reactive Power flows from the higher to the lower voltage magnitude source. 
Consequently, the phase angle difference between the sources decides the active power flow, while the voltage magnitude difference between the sources determines the reactive power flow. Based on this principle, a STATCOM can be used to regulate the reactive power flow by changing the output voltage of the voltage-source converter with respect to the system voltage

11. CIRCUIT DIAGRAM

12. SIMULATION
Simulation diagram of wind mill with Statcom.

13. RESULT
Waveform of active and reactive power, generator speed, wind speed and pitch angle

14. CONCLUSION
An appropriately rating FACTS device can provide the necessary reactive power compensation when connected to a weak grid.
Also, a higher rating STATCOM can be used for efficient voltage control and improved reliability in grid connected wind farm but its rating is limited due to economic.
Simulation studies have shown that the additional voltage/var support provided by an external device such as a STATCOM and SVC can significantly improve the wind turbine’s disturbances recovery by more quickly restoring voltage characteristics.
The response of a wind farm to sudden load changes is improved by the use of a STATCOM and SVC in the system.

15. FUTURE SCOPE
The hardware for these proposed controller can be made in future and same can be made in practical system.
The simulated result can be then compared with real system. so that the same system model can be tested for the other type of wind generator like DFIG, permanent magnetic synchronous generator.
The other FACTS devices like SSSC, SVC etc can be tested instead of STATCOM on same model.

16. REFERENCES
farming.html?requestedDomain=in.mathworks.com
176.pdf
_25_07_2016_15_49_53.pdf
0ANALYSIS%20OF%20IG%20BASED%20WIND%20FARM%20WITH%20 STATCOM.pdf