Implementation of Variable Hysteresis Band Current Control Technique in a Shipâ€™s Doubly-Fed Induction Machine System
Dr. John Ch. Dermentzoglou and Dr John M. Prousalidis
Topics of this Paper (which will be published shortly) To Investigate the possibility of successful integration of a
Doubly-Fed Induction Machine into a Ship’s Electric System for accommodating the need of an emergency unit for both propulsion or power production purposes, by implementing another form of Vector Control the “Variable Hysteresis Current Control Technique” This effort is the “last” Control Technique investigated and presented within “Defkalion Research Program” concerning the Possibility of integrating DFIM in a Ship’s System as Shaft Machines for both Propulsion or Power Production Purposes.
Topics of this Research (which will be published shortly) For the above mentioned technical issues , there was undertaken a tremendous effort in order the system under study, to resemble closely to a practical one. For example in the Software used, the integrals used were replaced by passbandFilters, the current sensors were modeled also by taking into account commercial types e.t.c.
System Under Investigation
What is Vector Control In general the Vector Control of a DFIM is being accomplished by controlling suitably the two PWM converters with Back-toBack Connection as shown in Fig. 2. ďƒ˜ Stator Converter regulates the intermediate dc voltage in order to be kept constant, regardless of power direction. It provides separate regulation of the stator active and reactive power by treating independently the two components of stator currents in d-q axis. ďƒ˜ Rotor Converter regulates the amount of power flown in order to achieve speed regulation.
What is Vector Control
Rotor Converter Control
Stator Converter Control
Principle of Hysteresis Band Current Control
Principle of Hysteresis Band Current Control If Ia<(Ia*-HB) upper switch of the leg a (phase a) of the
Bridge is “OFF” and lower switch is “ON” (SA=1) If Ia>(Ia*+HB) upper switch of the leg a (phase a) of the Bridge is “ON” and lower switch is “OFF” (SA=0) The narrowest band demanded, results in higher switching frequencies which in turn result in high EMI, and high switching losses. The shape of the waveform of the current per phase is modulated by its rate of change, the dc-link voltage and its inductance.
Principle of Variable Hysteresis Band Current Control ďƒ˜ In order to keep the switching frequency constant and in
acceptable values a Variable Hysteresis Band method is being adopted, having the following form in the general case:
Î”HB=f(current slop, L,Vdc-link) (1) The above derives by combining the two following equations
Principle of Variable Hysteresis Band Current Control
1st simulation results The first simulation results of the system’s behavior were rather disappointing . Many oscillations ore instability regions were observed. To overcome such a set-back two options were considered. TheVHBCC to be accompanied by a fuzzy system The rotor side converter to be modified as follows in order the system to be linearized arround several operational points.
Modification of the rotor-side converter
System Linearization & PID controller
System Linearization & PID controller U(t): Input vector (ΔIq) Γ(t):Disturbance vector (ΔIqref,ΔT) Y(t):Output vector (Δω)
Conclusions-Future Work Implementation of a complete mathematical model
describing full mechanical system ( propeller, bearings) in order to study the interactions within the whole electromechanical system. Laboratory implementation assisted by microcontroller assistance (already embarked on) Implementation of other controllers than PI, e.g. Fuzzy, Neural etc.
ACKNOWLEDGMENT THE WORK PRESENTED IN THIS PAPER HAS BEEN DEVELOPED WITHIN THE FRAMEWORK OF THE THALES-DEFKALION PROJECT. THIS RESEARCH HAS BEEN CO-FINANCED BY THE EUROPEAN UNION (EUROPEAN SOCIAL FUND – ESF) AND GREEK NATIONAL FUNDS THROUGH THE OPERATIONAL PROGRAM "EDUCATION AND LIFELONG LEARNING" OF THE NATIONAL STRATEGIC REFERENCE FRAMEWORK (NSRF) - RESEARCH FUNDING PROGRAM: THALES: REINFORCEMENT OF THE INTERDISCIPLINARY AND/OR INTERINSTITUTIONAL RESEARCH AND INNOVATION.
Implementation of Variable Hysteresis Band
Current Control Technique in a Ship’s Doubly-Fed Induction Machine System
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