EPE Association: EPE 2007 - Subtopic 07-1 - LS: Optimal control, robust control, non-linear control

EPE 2007 - Subtopic 07-1 - LS: Optimal control, robust control, non-linear control
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 2007 - Conference > EPE 2007 - Topic 07: 'Application of control methods to electrical systems' > EPE 2007 - Subtopic 07-1 - LS: Optimal control, robust control, non-linear control

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   Potentials for Reducing the Power Requirement of Magnetic Suspension Systems by implementing a Linear Quadratic Gaussian Controller
By SCHUHMANN Thomas; FLEISCHER Erik; HOFMANN Wilfried [View]
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Abstract: Magnetic bearings provide an energy-saving and resource-sparing possibility for supporting rotors running at high speed. This paper studies the potential of reducing the energy demand of magnetic levitation systems. Practical investigations show that this is obtainable by combining an optimal state estimator with an optimal state space controller. This configuration is known as Linear Quadratic Gaussian (LQG) regulator. In a sequential way, all the steps required for implementing this control strategy are depicted, starting with describing and modelling of the system which is a fully magnetically levitated blower in this case. Subsequently, the realization of the system state estimator is delineated. Both hints for carrying out the discretization of the continuous time model and a simple approach for choosing the variance matrices of the estimator are given. Special attention is paid to the design of the state feedback controller. The influence of the weighting matrix elements on the controller performance is investigated as well as an integrative extension of the regulator which ensures good reference response behaviour. Finally, measurements concerning the energy consumption of the levitation system are presented. The results show that both in static and dynamic case the implementation of the LQG regulator yields reduced control energy effort, compared to a system controlled by a conventional PID controller. It is noteworthy that, simultaneously to the enhancement of energy efficiency, implementing the LQG controller improves the dynamic properties of the levitation system, e.g. transient time and overshoot.

   Design of robust PID controllers for PMSM drive with uncertain load parameters
By SOUSA Marcus; FADEL Maurice; CAUX Stephane; LIMA Antonio [View]
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Abstract: Permanent magnet synchronous motor (PMSM) drive systems coupled to elastic loads may exhibit instability and poor performance under mechanical uncertainties. Two techniques for tuning the speed controller of a PMSM drive system are proposed and compared in this paper. The first technique is based on the frequency domain and the other exploits evolutionary programming concepts like genetic algorithm. Complexity of both tuning techniques, simulation and experimental results are discussed for PMSM drive system fed with current regulated PWM voltage source inverter.

   Analysis of stability for networks including converters
By STROBL Bernhard [View]
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Abstract: Stability is a very important property of control loop systems. For Linear Time Invariant (LTI) systems the Nyquist criterion is well known. In systems with converters, signals with different frequencies are related, these systems are not LTI. To describe them, the theory for Linear Time Periodic (LTP) systems can be used: The transfer function of the LTI systems is extended to the transfer matrix of LTP systems; the Nyquist criterion can also be extended for these systems using the eigenloci of the transfer matrix. Regarding Exponentially Modulated Periodic (EMP) signals as stationary solutions for LTI or LTP systems, an alternative approach is presented: The Nyquist criterion can be derivated using the relation between the Nyquist plot and the conformal map of the transfer function for LTI systems. With this, a transfer function of the open loop is defined also for LTP systems. As will be shown the Nyquist criterion can be applied to this transfer function for LTP systems.

EPE 2007 - Subtopic 07-1 - LS: Optimal control, robust control, non-linear control
You are here: EPE Documents > 01 - EPE & EPE ECCE Conference Proceedings > EPE 2007 - Conference > EPE 2007 - Topic 07: 'Application of control methods to electrical systems' > EPE 2007 - Subtopic 07-1 - LS: Optimal control, robust control, non-linear control
	[return to parent folder]

	Potentials for Reducing the Power Requirement of Magnetic Suspension Systems by implementing a Linear Quadratic Gaussian Controller By SCHUHMANN Thomas; FLEISCHER Erik; HOFMANN Wilfried	[View] [Download]
Abstract: Magnetic bearings provide an energy-saving and resource-sparing possibility for supporting rotors running at high speed. This paper studies the potential of reducing the energy demand of magnetic levitation systems. Practical investigations show that this is obtainable by combining an optimal state estimator with an optimal state space controller. This configuration is known as Linear Quadratic Gaussian (LQG) regulator. In a sequential way, all the steps required for implementing this control strategy are depicted, starting with describing and modelling of the system which is a fully magnetically levitated blower in this case. Subsequently, the realization of the system state estimator is delineated. Both hints for carrying out the discretization of the continuous time model and a simple approach for choosing the variance matrices of the estimator are given. Special attention is paid to the design of the state feedback controller. The influence of the weighting matrix elements on the controller performance is investigated as well as an integrative extension of the regulator which ensures good reference response behaviour. Finally, measurements concerning the energy consumption of the levitation system are presented. The results show that both in static and dynamic case the implementation of the LQG regulator yields reduced control energy effort, compared to a system controlled by a conventional PID controller. It is noteworthy that, simultaneously to the enhancement of energy efficiency, implementing the LQG controller improves the dynamic properties of the levitation system, e.g. transient time and overshoot.

	Design of robust PID controllers for PMSM drive with uncertain load parameters By SOUSA Marcus; FADEL Maurice; CAUX Stephane; LIMA Antonio	[View] [Download]
Abstract: Permanent magnet synchronous motor (PMSM) drive systems coupled to elastic loads may exhibit instability and poor performance under mechanical uncertainties. Two techniques for tuning the speed controller of a PMSM drive system are proposed and compared in this paper. The first technique is based on the frequency domain and the other exploits evolutionary programming concepts like genetic algorithm. Complexity of both tuning techniques, simulation and experimental results are discussed for PMSM drive system fed with current regulated PWM voltage source inverter.

	Analysis of stability for networks including converters By STROBL Bernhard	[View] [Download]
Abstract: Stability is a very important property of control loop systems. For Linear Time Invariant (LTI) systems the Nyquist criterion is well known. In systems with converters, signals with different frequencies are related, these systems are not LTI. To describe them, the theory for Linear Time Periodic (LTP) systems can be used: The transfer function of the LTI systems is extended to the transfer matrix of LTP systems; the Nyquist criterion can also be extended for these systems using the eigenloci of the transfer matrix. Regarding Exponentially Modulated Periodic (EMP) signals as stationary solutions for LTI or LTP systems, an alternative approach is presented: The Nyquist criterion can be derivated using the relation between the Nyquist plot and the conformal map of the transfer function for LTI systems. With this, a transfer function of the open loop is defined also for LTP systems. As will be shown the Nyquist criterion can be applied to this transfer function for LTP systems.