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This article from a discrete-time model and stability analysis is developed using a Lyapunov approach, taking into account the one sample implementation delay present in digital control applications. Experimental results are provided to demonstrate the effectiveness of the proposed approach, where a conventional hysteresis controller is used as a benchmark. Results show that the proposal is able to deliver adequate reference tracking while using significantly lower sampling frequencies. Moreover, when compared to the hysteresis controller, superior tracking is observed at low speeds, while maintaining a similar level of computational complexity. [ABSTRACT FROM AUTHOR]

This paper presents a rotor speed observer for induction-machine drives based on a sliding-mode approach and magnetizing current estimation. The back electromotive force (EMF) is calculated from the stator current and the stator voltage signals. The magnetizing currents are obtained from the back EMF. A theorem which gives the rotor speed estimate in the continuous-time domain is formulated using the magnetizing current estimation. The stability analysis is achieved based on the Lyapunov approach. Moreover, the discrete-time approach of the method is discussed, and a theorem for the discrete-time implementation is proposed. The limits that ensure the system stability for the switching gains and for the observer gain are discussed. This paper shows that the limits for the gains of the discrete-time algorithm are different from the limits for the gains of the continuous-time algorithm. Simulation results are presented to validate the theoretical analysis. In addition, experimental results based on a fixed-point digital signal processor (DSP) platform (DSP TMS320F2812) demonstrate the performance of the proposed scheme. [ABSTRACT FROM PUBLISHER]

This paper presents a discrete-time adaptive current controller for grid-connected pulse width modulation voltage source converters with LCL filter. The main attribute of the proposed current controller is that, in steady state, the damping of the LCL resonance does not depend on the grid characteristic since the adaptive feedback gains ensure a predefined behavior for the closed-loop current control. An overview of model reference adaptive state feedback theory is presented aiming to give the reader the required background for the adaptive current control design. The digital implementation delay is included in the model, and the stability concerning the variation of the grid parameters is analyzed in detail. Furthermore, current distortions due to the grid background voltage are rejected without using the conventional stationary resonant controllers or the synchronous proportional-plus-integral controllers. Simulation and experimental results are presented to validate the analysis and to demonstrate the good performance of the proposed controller for grid-connected converters subjected to large grid impedance variation and grid voltage disturbances. [ABSTRACT FROM PUBLISHER]