1. A NON-LINEAR CONTROL ALGORITHM FOR IMPROVING PERFORMANCE OF WIND GENERATOR USING DOUBLY-FED INDUCTION GENERATOR INSTITUTE OF ELECTRICAL POWER ENGINEERING Chair Electric Drives and Basics of Electrical Power Engineering M.Sc. Phung, Ngoc Lan Athens, Feb/Mar.2006

2. A non-linear control algorithm for improving performance of wind generator using doubly-fed induction generator Page 2 Introduction  Conventional control of doubly fed induction machine (DFIM) in wind generator  Based on the continuous or discreet model of DFIM  Decoupling in active- and reactive power (P&Q) control  A voltage dip – what happened ?  A new control scheme !  Decoupling of P&Q is guaranted  Better performance in dynamical operation mode  Non-linear control of DFIM with Exact-Linearization  Current model of DFIM is able to be exactly linearized !  A new current controller is with only P-Type controllers  The complete control structure is simple.  Decoupling is guaranteed - „Direct-Decoupling“

3. A non-linear control algorithm for improving performance of wind generator using doubly-fed induction generator Page 3 Contents 1.DFIM – Model and its characters. 2.Conventional control of DFIM in wind generator 3.„Exact-Linearization“ – Concept and implementation with DFIM 4.Control structure with „Direct-Decoupling“ 5.Conclusion and prospects

4. A non-linear control algorithm for improving performance of wind generator using doubly-fed induction generator Page 4 Contents 1.DFIM – Model and its characters. 2.Conventional control of DFIM in wind generator 3.„Exact-Linearization“ – Concept and implementation with DFIM 4.Control structure with „Direct-Decoupling“ 5.Conclusion and prospects

5. A non-linear control algorithm for improving performance of wind generator using doubly-fed induction generator Page 5 Control system of DFIM in wind generator PM Powermodule; S Switch; L Inductor Microcontroller 3~ PM 3~ S DFIM n PM Transformer L Udc Us Un Ir Is

6. A non-linear control algorithm for improving performance of wind generator using doubly-fed induction generator Page 6 Demonstration of voltage-, flux- and current vector in d-q coordinator

7. A non-linear control algorithm for improving performance of wind generator using doubly-fed induction generator Page 7 Electrical model of DFIM in d-q coordinator

8. A non-linear control algorithm for improving performance of wind generator using doubly-fed induction generator Page 8 Electrical model of DFIM in state-space - Rotor angular speed: Input variable of the model - Model of DFIM in state-space shows a bilinear system

9. A non-linear control algorithm for improving performance of wind generator using doubly-fed induction generator Page 9 Contents 1.DFIM – Model and its characters. 2.Conventional control of DFIM in wind generator 3.„Exact-Linearization“ – Concept and implemetation with DFIM 4.Control structure with „Direct-Decoupling“ 5.Conclusion and prospects

10. A non-linear control algorithm for improving performance of wind generator using doubly-fed induction generator Page 10 Control variables of the active- and reactive power The active power P and reactive power Q will be separately controlled through i rd and i rq

11. A non-linear control algorithm for improving performance of wind generator using doubly-fed induction generator Page 11 A control structure of DFIM in wind generator

12. A non-linear control algorithm for improving performance of wind generator using doubly-fed induction generator Page 12 Contents 1.DFIM – Model and its characters. 2.Conventional control of DFIM in wind generator 3.„Exact-Linearization“ – Concept and implementation with DFIM 4.Control structure with „Direct-Decoupling“ 5.Conclusion and prospects

13. A non-linear control algorithm for improving performance of wind generator using doubly-fed induction generator Page 13 Why do we apply „Exact-Linearization“ ? The nonlinear characters of DFIM Exact linearization guarantees not only the linearity between inputs and outputs but also the decoupling between each pair of input and output variable in the new model ---> ‚noninteracting‘ Performance of system in dynamical operation mode should be improved With the success of exact-linearization, different methods to design controllers for the new linear model could be applied.

14. A non-linear control algorithm for improving performance of wind generator using doubly-fed induction generator Page 14 „Exact-Linearization“ – the concept (1) Given a nonlinear MIMO-System with m inputs and m outputs then it is able to transfer the system in another state-space, where the linearity between the inputs and outputs is guaranted. Matrix L is invertible when the following conditions are satisfied: Sum of elements of vector of relative degree Number of state variables Relative degree j-th

15. A non-linear control algorithm for improving performance of wind generator using doubly-fed induction generator Page 15 „Exact-Linearization“ – the concept (2) With a coordinator transformationAnd with a state feedback controller The new linear system will be A coordinator transformation Requirements of knowing the feedback of state variables The linearity between inputs and outputs is effective in the whole new state-space Notice

16. A non-linear control algorithm for improving performance of wind generator using doubly-fed induction generator Page 16 „Exact-Linearization“ – Implementation with DFIM Considering three equations of DFIM with, then

17. A non-linear control algorithm for improving performance of wind generator using doubly-fed induction generator Page 17 „Exact-Linearization“ – Implementation with DFIM (1) The model in state-space will be in form of with By having Sum of elements of vector of relative degree: Relative degree j-th Matrix L is invertible Exact-linearization of the considering system can be implemented with the state feedback controller:

18. A non-linear control algorithm for improving performance of wind generator using doubly-fed induction generator Page 18 „Exact-Linearization“ – Implementation with DFIM (2) In the new state-space, system will be: In detail: The linearity between inputs and outputs. Decoupling between each channel – defined as ‚direct-decoupling‘ The transfer function of the new system consists of only Integration elements The coordinator transformation have only algebraic operations Notice

19. A non-linear control algorithm for improving performance of wind generator using doubly-fed induction generator Page 19 Contents 1.DFIM – Model and its characters. 2.Conventional control of DFIM in wind generator 3.„Exact-Linearization“ – Concept and implementation with DFIM 4.Control structure with „Direct-Decoupling“ 5.Conclusion and prospects

20. A non-linear control algorithm for improving performance of wind generator using doubly-fed induction generator Page 20 v Structure of the new linear model

21. A non-linear control algorithm for improving performance of wind generator using doubly-fed induction generator Page 21 Control system of DFIM in wind generator with direct-decoupling

22. A non-linear control algorithm for improving performance of wind generator using doubly-fed induction generator Page 22 Circuit diagram with Plecs

23. A non-linear control algorithm for improving performance of wind generator using doubly-fed induction generator Page 23 Performance of linearized model and current controller Performance of w1, y1 (ird) and w2, y2 (irq) ird irq w1 w2 Performance of current controller ird* & ird irq* & irq

24. A non-linear control algorithm for improving performance of wind generator using doubly-fed induction generator Page 24 Simulation: Grid voltage and electrical torque Grid voltage ~50% ~75% 100% Torque – Linear Control Torque – Nonlinear Control

25. A non-linear control algorithm for improving performance of wind generator using doubly-fed induction generator Page 25 Simulation: Active and reactive power P – Linear Control P – Nonlinear Control Q – Linear Control Q – Nonlinear Control

26. A non-linear control algorithm for improving performance of wind generator using doubly-fed induction generator Page 26 Simulation: Rotor current ird – Linear Control ird – Nonlinear Control irq – Linear Control irq – Nonlinear Control

27. A non-linear control algorithm for improving performance of wind generator using doubly-fed induction generator Page 27 Conclusion and perspectives Control system of DFIM with exact-linearization: practical and easy to implement. The simulation with Matlab/Simulink/Plesc shows good results, the complete control system is being verified on experiment rig Performance of system is improved with the static ‚ direct-decoupling ‘ current controller Advanced methods can be used in design process of controllers

28. A non-linear control algorithm for improving performance of wind generator using doubly-fed induction generator Page 28 Thank you for your attention !