M.Sc. Phung, Ngoc Lan Athens, Feb/Mar.2006

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

2. 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“ Introduction A non-linear control algorithm for improving performance of wind generator using doubly-fed induction generator

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

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

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

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

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

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 A non-linear control algorithm for improving performance of wind generator using doubly-fed induction generator

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

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

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

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

13. Why do we apply „Exact-Linearization“ ? • The nonlinear characters of DFIM • Performance of system in dynamical operation mode should be improved • 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‘ • With the success of exact-linearization, different methods to design controllers for the new linear model could be applied. A non-linear control algorithm for improving performance of wind generator using doubly-fed induction generator

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

15. Notice • 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 „Exact-Linearization“ – the concept (2) • With a coordinator transformation • And with a state feedback controller • The new linear system will be A non-linear control algorithm for improving performance of wind generator using doubly-fed induction generator

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

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

18. „Exact-Linearization“ – Implementation with DFIM (2) • Notice • 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 • In the new state-space, system will be: • In detail: A non-linear control algorithm for improving performance of wind generator using doubly-fed induction generator

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

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

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

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

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

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

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

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

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

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