Predictive Control in Matrix Converters

1. Predictive Control in Matrix Converters Marco Esteban Rivera Abarca e-mail: marcoesteban@gmail.com Universidad Técnica Federico Santa María Department of Electronics Engineering Valparaíso, Chile. Marie Curie ECON2 Summer School University of Nottingham, England July 9-11, 2008

2. Outline Introduction Power Circuit and Basic Concepts Control Strategy: Predictive Direct Torque Control (PDTC) Models used to Obtain Predictions 4.1 Matrix Converter 4.2 Induction Machine 4.3 Input Filter Results Improvements Future Work Conclusion Outline Introduction Power Circuit Control Strategy: PDTC Models Results Improvements Future Work Conclusion Ready for the next

3. Introduction • Matrix Converter is a single-stage power converter and represents an alternative to back-to-back converters in cases where size and the absence of large capacitors or inductances are relevant issues. • Model Predictive Control has been used in applications related to power converters, generally with modulation techniques. In this work is presented a control strategy to control input PF, torque and flux on an IM, based on Predictive Control: Outline Introduction Power Circuit Control Strategy: PDTC Models Results Improvements Future Work Conclusion • without linear controllers • without hysteresis • without modulators (PWM) Ready for the next

4. Power Circuit and Basic Concepts Matrix Converter Outline Introduction Power Circuit Control Strategy: PDTC Models Results Improvements Future Work Conclusion Input Filter Bidirectional Switch Load : Induction Machine Ready for the next

5. Control Strategy: Predictive Direct Torque Control (PDTC) An intuitive approach Time (k+1) Outline Introduction Power Circuit Control Strategy: PDTC Models Results Improvements Future Work Conclusion Time (k+1) Time (k+1) Time (k+1) Time (k+1) Time (k+1) Time (k+1) Power Supply Time (k+1) Matrix Converter Switching State (k) Switching State (k+1) Digital Controller Induction Machine Ready for the next

6. The reactive input power is also predicted for each state. 2 The switching state that minimizes g is selected to be applied during the next sampling interval. A quality function g is evaluated for each prediction. 5 4 The torque reference is generated by a PI controller. 3 Predictions of Flux and Torque are computed for each of the 27 switching states by means of a model. Measurements are acquired. 1 2 Control Strategy: Predictive Direct Torque Control (PDTC) Block diagram of the Predictive strategy Outline Introduction Power Circuit Control Strategy: PDTC Models Results Improvements Future Work Conclusion Ready for the next

7. Objectives related to the load: Minimize the error on the electric torque and flux magnitude. Objectives related to input variables: Controllable input Power Factor (most cases unity PF, no reactive power). The versatility of the method allows to include other objectives simply by adding terms to the quality function. Control Strategy: Predictive Torque Control (PTC) Quality Function g : The Evaluation Criterion Must reflect the desired objectives, in order to determine the best state. Outline Introduction Power Circuit Control Strategy: PDTC Models Results Improvements Future Work Conclusion Considering both objectives (adding): Ready for the next

8. Models Matrix Converter Outline Introduction Power Circuit Control Strategy: PDTC Models Results Improvements Future Work Conclusion Induction Machine Input Filter Ready for the next

9. Models Matrix Converter Outline Introduction Power Circuit Control Strategy: PDTC Models Results Improvements Future Work Conclusion Induction Machine Input Filter Ready for the next

10. Quality Function: B=0 No PF or reactive input power control. B=146·10-6 Controlled PF/reactive input power. Low ripple and fast dynamic response. B=0 No PF or reactive input power control. B=146·10-6 Controlled PF or reactive input power. Sinusoidal output currents, smooth freq. transition. Practically identical output variables High distortion in the input current. THD=68.5% Low distortion in the input current. THD=4.7%. PF=1. Simulation Results Parameters Outline Introduction Power Circuit Control Strategy: PDTC Models Results Improvements Future Work Conclusion Ready for the next

11. Improvements How to reduce the processing time? Outline Introduction Power Circuit Control Strategy: PDTC Models Results Improvements Future Work Conclusion What happens when I don´t have a correct model of the load? Perfect Prediction? Ready for the next

12. Improvements • Improve the code of the algorithm. Outline Introduction Power Circuit Control Strategy: PDTC Models Results Improvements Future Work Conclusion • Other techniques of predictive control like DMC and GPC. High computational cost. • Improve the predictive models: - Kalman Filter to flux estimator. - Load parameters estimation using LS and RLS methods. - Correction of Input Currents: Study Input Filter. - Correction of Input Currents: AC Supply Unbalanced. Ready for the next

13. Improvements Kalman Filter in flux estimator Outline Introduction Power Circuit Control Strategy: PDTC Models Results Improvements Future Work Conclusion Stator Flux [Wb] Rotor Flux [Wb]

14. Improvements Load parameters estimation using LS and RLS methods Outline Introduction Power Circuit Control Strategy: PDTC Models Results Improvements Future Work Conclusion Load Parameters Real & Estimated Signal

15. Improvements Correction of Input Currents: Study Input Filter Outline Introduction Power Circuit Control Strategy: PDTC Models Results Improvements Future Work Conclusion

16. Improvements Correction of Input Currents in presence of unbalances Outline Introduction Power Circuit Control Strategy: PDTC Models Results Improvements Future Work Conclusion • Minimization negative sequence of input currents. • To generate a reference of input currents.

17. Future Work Outline Introduction Power Circuit Control Strategy: PDTC Models Results Improvements Future Work Conclusion • Experimental Implementation Predictive DTC. • Experimental Implementation of Improvements studied in UCC. • Publications of results respective. • Experimental Strategy using an Indirect Matrix Converter.

18. Conclusion • Simple and effective control for a matrix converter based induction motor drive. • Controls together input and output variables (PF and motor). • Discrete-time switching - semiconductors switch only at predefined and equidistant instants (No PWM). • This discrete approach match with the discrete nature of the matrix converter’sswitching states and digital control platforms. • The versatility of the method allows to include additional objectives. The topic is still open for research. Outline Introduction Power Circuit Control Strategy: PDTC Models Results Improvements Future Work Conclusion

19. I appreciate your attention Marco Rivera e-mail: marcoesteban@gmail.com

20. Selection of the Weighting Factors Outline Introduction Power Circuit Control Strategy: PTC Models Results Benefits? Conclusion PF Control Extra Ready for the next

21. Reactive Power A Torque Error A Flux Error Always B=1 1 High value Low value A Selection of the Weighting Factors Outline Introduction Power Circuit Control Strategy: PTC Models Results Benefits? Conclusion Extra Ready for the next