Open AccessDissertation
On Control of Back-to-Back Converters and Sensorless Induction Machine Drives
TLDR
In this paper, the authors focus on the design and analysis of the control system structure for back-to-back converter squirrel-cage induction machine drives, where the back electromotive force is used as the basis for sensorless control.Abstract:
This thesis focuses on design and analysis of the control system structure for back-to-back converter squirrel-cage induction machine drives. Particularly, sensorless control of induction machines, meaning vector control without a mechanical shaft sensor, and vector control of pulsewidth-modulated (PWM) rectifiers are considered. The back electromotive force is used as the basis for sensorless control in this thesis. A variant of the classical "voltage model" is adopted for sensorless flux estimation. It is shown that the estimator must be redesigned for the purpose of arbitrarily placement of the closed-loop poles. A thorough stability analysis of the redesigned estimator shows that asymptotical stability can be guaranteed at nominal speeds. The stability at very low frequencies is, however, largely affected by the knowledge of the stator resistance. The presence of a singularity for zero stator frequency is found, which makes it impossible to guarantee stable operation at very low frequencies, except for the case of zero external load torque. The underlying mechanisms behind the two widely acknowledged instability phenomena for sensorless control at low frequencies are revealed. The most critical form of instability is the infamous flux collapse: the flux collapses to approximately zero, giving nearly total loss of torque, and uncontrolled rotation in the direction of the external load torque. The less well-known instability phenomenon frequency lockup is not as critical: the field orientation deteriorates, such that the torque reduces but not vanish, and the stator frequency and rotor speed lock on to constant values close to zero. A control system structure is developed for the PWM rectifier. The previously proposed concept of virtual flux is adopted for grid-voltage synchronization, and three different synchronization algorithms are analyzed. The PWM rectifier is also considered for an active filtering application, for which a vector current control system designed for the deadbeat response is designed. An analysis shows that the resulting deadbeat control system is equivalent to previously proposed Smith predictor structures.read more
Citations
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Journal ArticleDOI
Input-Admittance Calculation and Shaping for Controlled Voltage-Source Converters
TL;DR: In this paper, input-admittance expressions for a voltage-source converter are derived and it is seen how the admittance can be shaped in order to get a positive real part in the desired frequency regions by adjusting the controller parameters.
Journal ArticleDOI
Power-Synchronization Control of Grid-Connected Voltage-Source Converters
TL;DR: In this article, a power-synchronization control method for grid-connected voltage-source converters (VSCs) is proposed, which utilizes the internal synchronization mechanism in ac systems, in principle, similar to the operation of a synchronous machine.
Dissertation
Analysis, Modeling and Control of Doubly-Fed Induction Generators for Wind Turbines
TL;DR: In this paper, the energy efficiency of a variable-speed wind turbine system using a doubly-fed induction generator is compared to other wind turbine generator systems, and the sensitivity of different current controllers with respect to grid disturbances is investigated.
Journal ArticleDOI
Interconnection of Two Very Weak AC Systems by VSC-HVDC Links Using Power-Synchronization Control
TL;DR: In this paper, a voltage-source converter (VSC) based high-voltage dc (HVDC) transmission is investigated for interconnection of two very weak ac systems.
Journal ArticleDOI
Nonlinear Control of a Variable-Speed Wind Turbine Using a Two-Mass Model
TL;DR: In this paper, a nonlinear approach, using a two-mass model and a wind speed estimator, for variable-speed wind turbine (WT) control is presented. But, their performance is weak, as the dynamics aspects of the wind and aeroturbine are not taken into consideration.
References
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Book
Applied Nonlinear Control
TL;DR: Covers in a progressive fashion a number of analysis tools and design techniques directly applicable to nonlinear control problems in high performance systems (in aerospace, robotics and automotive areas).
Book
Computer-Controlled Systems: Theory and Design
TL;DR: This volume focuses on the design of computer-controlled systems, featuring computational tools that can be applied directly and are explained with simple paper-and-pencil calculations.
Journal ArticleDOI
Instantaneous Reactive Power Compensators Comprising Switching Devices without Energy Storage Components
TL;DR: In this paper, a new instantaneous reactive power compensator comprising switching devices is proposed, which requires practically no energy storage components, and is based on the instantaneous value concept for arbitrary voltage and current waveforms.
Book
Robust process control
TL;DR: A state-of-the-art study of computerized control of chemical processes used in industry is presented in this article for chemical engineering and industrial chemistry students involved in learning the micro-macro design of chemical process systems.
Journal ArticleDOI
Current control techniques for three-phase voltage-source PWM converters: a survey
TL;DR: Current control techniques for three-phase voltage-source pulsewidth modulated converters, including bang-bang (hysteresis, delta modulation) controllers and predictive controllers with on-line optimization are reviewed.
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