PROPORTIONAL CONTROLLER BASED GRID CONNECTED WIND SYSTEMS

1. PROPORTIONAL CONTROLLER BASED GRID CONNECTED WIND SYSTEMS By B.SIVAPRASAD K.P.REGHU V.MINISH EEE, SXCCE Under the guidance of Mr. D.R.BINU BEN JOSE SENIOR LECTURER, EEE DEPT, SXCCE

2. ABSTRACT • This project presents the simulation of a closed loop scheme for interfacing wind driven Permanent Magnet (PM) alternator with utility grid through a line commutated inverter. • A proportional controller can be used in conjunction with certain block sets from MATLAB/SIMULINK for generating appropriate firing pulses for the SCRs in the inverter. • The control objective is to extract maximum power from the wind energy system and to transfer this power to the utility. This is achieved by controlling the firing angle delay of the inverter. • The complete closed loop scheme will be modeled and simulated in MATLAB/ SIMULINK environment and the simulation results will be presented • It has the advantage of having permanent gear ratio (PGR) which avoids unnecessary wear and tear of gear tooth instead of variable gear ratio (VGR) where frequent maintenance and replacement of gear is required. • The alternator output will normally be of variable voltage and variable frequency (VVVF). Thepower at VVVF will be converted to DC and interfaced with the grid using line commutated inverter. • This project also investigates the harmonics of the line current and the use of passive filter for the minimization of grid current harmonics.

3. INTRODUCTION • In our project we use permanent magnet alternator whose output is a variable voltage variable frequency, which is first rectified using a diode bridge and the DC power is then transferred to the utility at its own voltage and frequency using a line commutated inverter. • This project investigates a simple maximum power point tracking system for variable speed wind turbines. • The control uses a closed loop circuit which will fire the thyristors at the maximum power operating point. • The closed loop system is developed using a simple proportional controller, which convert the power delivered to the grid into corresponding firing angle using which the inverter is fired. • With increase in the speed, the PM generator output will increase, the corresponding firing angle decreases and thereby the power delivered to the grid increases.

4. Block schematic diagram of the closed loop scheme

5. CLOSED LOOP SCHEME • Directly interfacing the wind energy system to the utility gives rise to problems of voltage fluctuations, flickering and generation of sub-harmonics/harmonics associated with the pulsating torque. • Since, the reactive power consumed by a controlled rectifier is a function of the firing delay angle, there is a limit on the maximum value of the firing delay angle. • This constraint will limit the operating speed range of the wind driven permanent magnet alternator, since, once the firing delay angle reaches its upper limit there is no control on the dc link voltage. • Hence, the input voltage to the rectifier has to be restricted by limiting the maximum speed of the wind turbine mechanically. This will prevent complete utilization of available wind energy. • The problems are overcome by using an uncontrolled diode bridge rectifier and a line commutated inverter.

6. MAXIMUM POWER TRACKING CONTROLLER • The control objective is to track and extract maximum power from the WES and to transfer this power to the utility grid. • To achieve this maximum power tracking controller is implemented using a proportional controller. • The power transferred over the DC link can be related to the maximum power output (Pmax) of the WES by the conversion efficiency of the generator and the rectifier. • The maximum power output of the WES is a function of the wind velocity (Vw) and the tip speed ratio λ. • The maximum power output of the permanent magnet alternator at different (Vw) is computed.

7. OPEN LOOP SIMULATION OF A GRID CONNECTED PM ALTERNATOR DRIVEN BY WIND TURBINE

8. REAL AND REACTIVE POWER OF OPEN LOOP SCHEME REAL POWER REACTIVE POWER

9. RECTIFIER OUTPUTOF OPEN LOOP SCHEME

10. GRID VOLTAGE AND CURRENT OF OPEN LOOP SCHEME

12. CLOSED LOOP SIMULATION OF A GRID CONNECTED PM ALTERNATOR DRIVEN BY WIND TURBINE

13. FILTER CIRCUIT

14. SIMULATION OF MULTIPLIER AND SIGNAL CONDITIONING CIRCUIT

15. REAL AND REACTIVE POWER OF THE CLOSED LOOP SCHEMEWITHOUT FILTER WITH FILTER

16. GRID VOLTAGE AND CURRENT OF CLOSED LOOP SCHEMEWITHOUT FILTER

17. GRID VOLTAGE AND CURRENT OF CLOSED LOOP SCHEMEWITH FILTER

18. RMS GRID CURRENT WITH FILTER WITHOUT FILTER

19. RECTIFIER OUTPUTOF CLOSED LOOP SCHEME

20. AVERAGE POWER OUTPUT OF RECTIFIER

21. HARMONIC CURRENT WAVEFORMS WITH FILTER

22. FIRING PULSE VARIATION OF PULSE GENERATOR

23. VARIATION OF FIRING ANGLE OF PULSE GENERATOR

24. REAL POWER VS TURBINE TORQUE

25. CONCLUSION • PM Alternator is used so wind energy available can be utilized to the maximum level. • Maximum power tracking is possible for all particular wind speed by using Proportional Controller. • With increase in the speed, the PM generator output will increase, the corresponding firing angle decreases and thereby the power delivered to the grid increases. • Passive filter is used for the minimization of grid current harmonics.

26. REFERENCES • R.M.Hilloowala ,A.M. Sharaf, ‘A Utility Interactive Wind Energy Conversion scheme with an Asynchronous DC link using a Supplementary Control loop’, IEEE Transactions on Energy Conversion,Vol.9,No.3,September 1994. • Salman K. Salman and Anita L.J. Teo ‘Windmill Modeling Consideration and Factors Influencing the Stability of a Grid- Connected Wind Power-Based Embedded Generator’, IEEE Transactions On Power Systems, Vol. 18, No. 2, May 2003. • D.Watson, J.Arrilaga and T.Densen “Controlled dc power supply from wind driven self excited induction machines”, IEEE proc. Vol.126, No.12, pp. 1246-48,1979. • G.L.Johnson, “Wind Energy Systems”, Prentice Hall Inc., Englewood Cliffs, NewJercy,1985.

27. THANK YOU