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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 article proposes an alternative for robust control of synchronous reluctance motors using linear matrix inequalities to obtain fixed gains that ensure current and speed regulation, under parameter uncertainties and variations. The proposed design procedure is based on a polytopic model, which takes into account: i) uncertainties and variations of the mechanical and electrical parameters of the motor, ii) one step delay from digital implementation of the control law, and iii) internal model based controllers to guarantee reference tracking. Less conservative linear matrix inequalities, relying on slack variables, ensure robust pole location and certify the closed-loop stability for the entire domain of uncertain and time-varying motor parameters, based on parameter-dependent Lyapunov functions. The linear matrix inequalities ensure a fast and systematic computation of the control gains, that are also easy to be implemented, not adding computational complexity when compared, for instance, to usual strategies based on PI controllers. Experimental results for a 2.2 kW commercial motor are provided, validating the proposed procedure, and illustrating good tracking of currents and speed references, with suitable dynamic responses and reduced cross-coupling effects, when compared to sliding mode and PI controllers. [ABSTRACT FROM AUTHOR]

This paper proposes a discrete-time sliding-mode observer (SMO) for equivalent capacitor voltages control in modular multilevel converters, aiming to reduce the communication complexity in applications with several series-connected submodules. The observed voltages of the equivalent capacitors are used in the voltage control loops, resulting in a simpler implementation, which demands low communication effort, since the individual capacitor voltages are not used in the central processor. The proposed SMO was obtained from discrete-time analysis with a stability improvement, differently from discretized observers previously proposed in the literature. A discrete-time methodology is presented to design the observer and ensure the proper operation of the control system. The proposed SMO design methodology in the discrete-time domain enables a simple design of the observer, ensuring transient and steady-state observer performances. Simulation results are presented to demonstrate an example of the proposed methodology, where the observer operates with the control system under distinct conditions. Additionally, experimental results are included to demonstrate the effectiveness of the proposed control system with discrete-time SMO for the equivalent capacitor voltages. [ABSTRACT FROM PUBLISHER]