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Design of Robust Controllers for Telecom Power Supplies

Idris A. Gadoura

Dissertation for the degree of Doctor of Science in Technology to be presented with due permission of the Department of Automation and Systems Technology for public examination and debate in Auditorium T2 at Helsinki University of Technology on the 11th of October, 2002, at 12 noon.

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Abstract

A Telecom power supply is studied and analyzed from control system viewpoint. It consists of three stages: AC/DC rectifier, a backup battery, and a Telecom load. The AC/DC rectifier stage can be composed of paralleled DC/DC converters preceded by paralleled AC/DC converters. However, paralleled DC/DC converters are only considered in this thesis because they constitute the main dynamics in practice. A system of paralleled DC/DC converters operating in continuous inductor current mode with either voltage mode control or peak current mode control are modeled and analyzed using state-space representation. The H∞ control design is used in order to guarantee the robust stability and robust performance of the system in spite of different uncertainties. Also the H∞ loop-shaping design is used to design robust controllers in the presence of uncertainties. μ-analysis is used to evaluate the robustness of the system. Simulation results are presented to demonstrate the control design procedure and to compare between the two approaches presented.

A Telecom power system can be composed of voltage-loop and current-loop subsystems. The multi-input-multi-output proportional-integral-derivative (PID) controller is first designed achieving robust stability and robust performance of the voltage-loop. Then, the multi-input-multi-output proportional-integral (PI) controller for current-loop is designed to achieve robust stability and robust performance of the overall system. μ-analysis is used to evaluate the robustness of PID and PI controllers. Simulation results are also presented to demonstrate and validate the control design.

The required output characteristic of a Telecom power system contains three modes of operation: constant-voltage, modified constant-power, and constant-current modes. This nonlinear operation can be achieved by using the fuzzy-logic approach. A fuzzy PID-like controller is implemented to achieve the robust output voltage in spite of load disturbances. A fuzzy PI-like controller is implemented to ensure the overload protection reaching the optimal output characteristic of a Telecom power system. Also the internal-model control (IMC) method is applied to basic DC/DC converters: buck, boost, and buck-boost converters. IMC scheme is used to improve the dynamic performance of basic converters by achieving a robust output voltage against line and load disturbances. Simulations show good dynamic performance of the IMC controller.

This thesis consists of an overview and of the following 8 publications:

  1. Gadoura, I., T. Suntio, and K. Zenger. Robust Control Design for Paralleled DC/DC Converters with Current Sharing. Proc. of the 15th IFAC World Congress on Automatic Control, July 21-26, 2002 in Barcelona, Spain, 6p, CD-ROM.
  2. Gadoura, I., T. Suntio, and K. Zenger. Dynamic System Modeling and Analysis for Multiloop Operation of Paralleled DC/DC Converters. Proc. of the Int. Con. on Power Electronics and Intelligent Motion, June 19-21, 2001 in Nuremberg, Germany, pp. 443-448.
  3. Gadoura, I., T. Suntio, and K. Zenger. Model Uncertainty and Robust Control of Paralleled DC/DC Converters. Proc. of the IEE Int. Con. of Power Electronics, Machines, and Drives, April 16-18, 2002 in Bath, UK, pp. 74-79.
  4. Gadoura, I., T. Suntio, and K. Zenger. Practical Robust Control Design for Paralleled DC/DC Converters using H∞ Loop-Shaping Techniques. Proc. of the Int. Con. on Power Electronics and Intelligent motion, May 14-16, 2002 in Nuremberg, Germany, pp. 335-340.
  5. Suntio, T., I. Gadoura, J. Lempinen, and K. Zenger. Practical Design Issues of Multi-loop Controller for a Telecom Rectifier. Proc. of the IEEE Int. Telecommunications Energy Special Conference, May 07-10, 2000 in Dresden, Germany, pp. 197-201.
  6. Gadoura, I., and T. Suntio. Implementation of Optimal Output Characteristic for a Telecom Power Supply: Fuzzy-logic Approach. International Journal of Control and Intelligent Systems, 2002 (in press).
  7. Gadoura, I., T. Suntio, K. Zenger, and P. Vallittu. Internal Model Control for DC/DC Converters. Proc. of the 8th European Con. on Power Electronics and Applications, September 7-9, 1999, Lausanne, Switzerland, 7p, CD-ROM.
  8. Gadoura, I., T. Suntio, and K. Zenger. Improved Stability Properties of Boost and Buck-boost Converters Using IMC-based Controller. Proc. of the Int. Con. on Power Electronics and Intelligent Motion, June 19-21, 2001 in Nuremberg, Germany, pp. 527-532.

Keywords: telecom power supply, H∞ control, PID-control, fuzzy-logic control, internal-model control

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© 2002 Helsinki University of Technology

Last update 2011-05-26