Control Strategies of the Doubly Fed Induction Machine for Wind Energy Generation Applications

Transcription

1 Control Strategies of the Doubly Fed Induction Machine for Wind Energy Generation Applications AUTHORS Dr. Gonzalo Abad, The University of Mondragon, SPAIN. Dr. Miguel Ángel Rodríguez, Ingeteam Transmission & Distribution S.A., SPAIN. Dr. Grzegorz Iwanski, Warsaw University of Technology, POLAND. SCOPE AND BENEFITS Over the last few years, there has been a strong penetration of energy resources into the power supply network. Wind energy generation has played and still is expected that will play a very important role in this area for the coming years. Doubly Fed Induction Machine (DFIM) based wind turbines have arisen as one of the leader technologies for wind turbine manufacturers, demonstrating that it is a cost effective, efficient and reliable solution. However, recent grid codes are increasing restrictions to wind turbines in general, imposing newer and challenging performances especially during grid faults. Due to this fact, there is still a lot of work to do to adapt the technology of the wind turbines, to these faulty scenario new requirements, again in an efficient and reliable manner. Consequently, this tutorial will be particularly focus on the control of the DFIM based wind turbines. A survey of the most relevant control strategies used for this machine will be carried out, together with a description of different models, estimators and specific issues of this machine, when it operates under the wind energy generation application. The control strategies analyzed range from standard solutions used by wind turbine manufacturers, to the last developments to address faulty network situations, including the standalone wind energy generation system analysis. Technical details are analyzed, such as, block diagrams, analytical developments, advantages and disadvantages, simulation and experimental performances, etc. Finally, a special attention is paid to the future trends and tendencies of this DFIM based wind turbines. EPE guidelines for tutorials 1

2 CONTENTS Monday, September 7th - Tutorial day (Location to be defined) 08:00-09:30 Registration for Tutorials 09:30-11:00 Tutorials Part 1 The first part of the tutorial is divided into two different sections. Firstly, an introduction to the variable speed wind turbines based the DFIM is given accompanied by a survey of solutions of wind turbine manufacturers. In addition, an overview of different applications where this machine is used is also provided. In the second section, the modeling of the DFIM is studied, covering different models, mainly oriented to design control strategies as well as validate performances of the machine. Detailed model differential equations are provided, together with the most representative characteristic curves. Further on, several observer and estimator structures are presented, comparing their advantages and disadvantages, in order to account a reliable estimation of immeasurable magnitudes such as, torque, fluxes, synchronization angles, etc. 1.- Applications of the Doubly Fed Induction Machine (DFIM) Variable Speed Wind Energy Systems Doubly Fed Induction Machine based wind energy generation system Industrial solutions. Wind turbine manufacturers Applications with prime movers different from wind: water turbines, diesel and biogas engines, etc. 2.- Mathematical model of the DFIM Dynamic Modeling and steady-state analysis of the DFIM Dynamic Modeling of the DFIM considering the Iron Loss Dynamic Modeling of the DFIM based on symmetrical components analysis Estimator, PLLs and observer structures for the DFIM. 11:00-11:30 Coffee break :00 Tutorials Part 2 Part 2 deals with control solutions for the DFIM. Firstly, particular attention is paid to the start-up of the DFIM, considering that most of wind turbines are supplied by a reduced power VSC. Hence, solutions utilized to synchronize with the grid, calibrate the zero position of the rotor flux, etc. will be described. Then, a wide range of control solutions are studied and compared, taking into account the basic control principles employed by most of the manufacturer as well as, newer control structures oriented to improve the performances of high power wind turbines. 3.- Control strategies for grid connected DFIM based wind turbines Synchronization with the grid and start-up of the DFIM Field Oriented Control (FOC) and tuning procedures of the regulators Classic direct torque control (DTC) and direct power control (DPC) Predictive direct torque control (PDTC) and direct power control (PDPC) PDTC and PDPC based on multilevel voltage source converters (VSC). EPE guidelines for tutorials 2

3 13:00-14:00 Lunch break 14:00-15:30 Tutorials Part 3 Part 3 deals with the issues related to the standalone operation mode of DFIM. Firstly, the difference in the features and topologies of grid connected and autonomous DFIM are presented and methods of initial excitation are discussed. Next, the dependence of the stator voltage on the rotor current is analyzed and basics of linear control for standalone DFIM are presented. The sensorless control method of the output voltage vector providing fixed output amplitude and frequency is presented then, considering the cases with linear, nonlinear and unbalanced load supply. Discussion on the different rotor current controllers in the inner control loop is done. In the last section the transient states during grid connection and disconnection are presented and the methods of surgeless synchronization and uninterruptible supply after the loss of main are shown. 4.- Standalone DFIM based generation systems Topologies of standalone DFIM based generation systems Initial excitation problems in case of island power systems Three and four wire standalone systems Advantages of DFIM for different primary movers Hybrid standalone power systems equipped with DFIM based turbines Mathematical model of standalone DFIM generation system with output filter Basic equations relations between stator voltage and rotor current Selection of the filtering capacitors Sensorless control method of fixed frequency, variable speed, standalone DFIM based generation system PLL synchronization for determination of the rotor current frequency Rotor current controllers Symmetrical components based voltage asymmetry correction Controlled grid connection transients Synchronization by superior PLL structure Detection of the mains outage and uninterruptible load supply. 15:30-16:00 Coffee break 16:00-17:30 Tutorials Part 4 The last part of the tutorial is also divided into two sections. The first section, is oriented to present and analyze the latest control solutions, for the DFIM under faulty operation conditions of the grid. These control solutions are specially designed to meet the latest and most restrictive grid code requirements for wind turbines. Hence, different control strategies are deeply analyzed in order to address the difficulties provoked by an unbalanced grid voltage situation and a grid polluted by harmonics. Further on, the voltage ride trough analysis of DFIM based wind turbines is carried out. This study will cover the limits of this kind of wind turbines to handle with voltage dips without any special protection, as well as, a wide EPE guidelines for tutorials 3

4 analysis of different protections (active-passive crowbars, rotor-dc bus crowbars, varistors, etc.) and the subsequent control actions to address strong faulty conditions. Finally, in the second section, the new trends and tendencies of DFIM are presented. Novel configurations and supplying topologies for this machine are studied remarking the benefits and applications areas, as well as highlighting the most attractive aspects of these new configurations. 5.- Control of DFIM based wind energy generation system, under distorted grid voltage operation conditions Unbalanced voltage grid operation conditions Control based on DTC and DPC control strategies Control based on FOC Grid under presence of voltage harmonics Grid distorted under voltage dips. Voltage Ride Through analysis Control methods based on Crowbar protection Control method based on DTC without Crowbar protection. 6.- New supplying topologies for DFIM based wind energy generation systems Special configurations of DFIM Future trends on DFIM. 15:00-19:00 Possibility for registration for the EPE2009 in the lobby WHO SHOULD ATTEND - Researchers on the fields: Power electronics, control strategies for drives, control strategies for doubly fed induction machine, wind energy generation, high power drives, etc. - People related to the application: energy generation with wind turbines: Electric and electronic engineers, decision-makers and development people engineers, system operators, wind turbine manufacturers, etc. Technical Level: Advanced EPE guidelines for tutorials 4

5 ABOUT THE INSTRUCTORS Gonzalo Abad was born in Bergara in Spain, on October 11, He received a degree in Electrical Engineering from the University of Mondragon, Spain, in 2000, the M.Sc. degree in Advanced Control from the University of Manchester, U.K., in 2001 and the Ph.D. degree in Electrical engineering from the University of Mondragon, Spain, in He joined the Electronics Department of the University of Mondragon, in 2001 and is currently an Associate Professor. He teaches courses in power electronics, power converters, control and robotics. His main research interests include renewable energies, power conversion and motor drives. He has published several papers in the areas of wind power generation, multilevel power converters and direct torque control of AC drives. He has participated in different industrial projects related to these fields. Electronics and Informatics Department. The University of Mondragon. Loramendi 4, Aptdo Mondragon - Gipuzkoa - Spain Tlf Fax [email protected] Miguel Angel Rodríguez Vidal was born in San Sebastian, Spain, in August He received his M. Sc degree in electrical engineering from the Swiss Federal Institute of Technology Lausanne (Switzerland) in 1992 and the Ph.D. degree in industrial engineering from the University of Zaragoza in From 1992 to 2008, he worked as Associate Professor in the Electronics Department of the University of Mondragon and participated in different research projects in the field of wind energy systems, lift drives, and railway traction. In September 2008 he joined Ingeteam Transmission and Distribution as Senior Engineer. His research interests include electrical machines modeling and control, in particular, for single - and doubly-fed asynchronous machines, and voltage source inverter control for FACTs applications. Ingeteam Transmission & Distribution S.A. C/ Usausuaga, 7 Pol. Artunduaga Basauri (Bizkaia) Spain Tel Fax [email protected] EPE guidelines for tutorials 5

6 Grzegorz Iwanski was born in Kielce, Poland in He received MSc degree in robotics and PhD degree in electrical engineering from Warsaw University of Technology (WUT) in 2003 and 2005 respectively. Since January 2006 to December 2008 he was a research worker in Electrical Drive Division of Warsaw University of Technology. He was involved in international project within 6FP EU and investigated the high temperature current sensors dedicated to high density automotive power electronics converters. Currently he is a lecturer in Institute of Control and Industrial Electronics WUT. He teaches courses on power electronics and drives and power conversion systems. His research interests is variable and adjustable speed power generation with permanent magnet and doubly fed induction generators, automotive power electronics and drives and current measurement systems for power electronics. He is author of 30 conference and journal papers. Institute of Control and Industrial Electronics Warsaw University of Technology 75, Koszykowa St., Warsaw, Poland Tel Fax [email protected] EPE guidelines for tutorials 6