This study proposes a voltage balancing scheme for flying capacitors multilevel converters. The strategy is based on the redundancy of switching states. By using analytic expressions, the authors study the balancing properties of each switching state. Then, based on such properties, the authors choose the switching state which drives the capacitor voltages towards their reference values, and simultaneously will ensure the desired voltage level. The method can be particulary attractive for those applications where the typical pulse-width modulation control is not used, as direct torque control, hysteresis control and sliding-modes control. Experimental results demonstrate the effectiveness of the proposed control scheme, in steady and dynamic conditions.

This paper presents a control scheme based on predictive control theory and Petri nets (PNs) formalism to control a flying capacitor multilevel converter. The proposed scheme takes advantage of the benefits offered by the Finite Control Set -Model Predictive Control (FCS-MPC) methodology and the versatility of PNs to regulate the capacitor voltages and output current, simultaneously. The inclusion of PNs allows to simplify the control scheme. A first PN is used to select, from a subset of switching states, the switching state that accomplishes both control objectives. This approach reduces the computational burden if compared with a typical predictive control scheme. Furthermore, a PN based prediction scheme is used to predict the capacitor voltages. This prediction scheme uses only measurements of output voltage and current, which reduces the number of required sensors. This approach allows to implement the internal capacitor voltages control independently if a multi-leg configuration is needed. The scheme is experimentally validated in a 5-level flying capacitor multilevel converter.

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This article presents an evaluation of Prony method and its implementation considerations for motor current signal analysis diagnostics in rotor cage induction motors. The broken rotor bar fault signature in current signals is evaluated using Prony method, where its advantages in comparison with fast Fourier transform are presented. The broken rotor bar fault signature could occur during the life cycle operation of induction motors, so that is why an effective early detection estimation technique of this fault could prevent an insulation failure or heavy damage, leaving the motor out of service. First, an overview of cage winding defects in rotor cage induction motors is presented. Next, Prony method and its considerations for the implementation in current signature analysis are described. Then, the performance of Prony method using numerical simulations is evaluated. Lastly, an assessment of Prony method as a tool for current signal analysis diagnostics is performed using a laboratory test system where real signals of an induction motor with broken rotor bar operated with/without a variable frequency drive are analyzed. The summary results of the estimation (amplitudes and frequencies) are presented in the results and discussion section.

International audienceThis paper deals with a control proposal for serial multicellular choppers. The proposed scheme takes advantage of the continuous and discontinuous chopper operation, and introduces the use of two Petri nets (PNs) to carry out the control action. The first PN generates the needed voltage level to assure the output reference current tracking, while a second PN solves the problem of capacitor voltage balancing, using switching state redundancies. Also, a stability analysis based on a Lyapunov function is used to ensure the convergency of the states under the commutation rule. The main advantage of this approach is the integration of the continuous and discrete dynamics through PNs, which directly drives the converter power semiconductors. Furthermore, this proposal could lay the basis for future studies in the design of converter controllers using the formal analysis tools offered by PNs. Experimental results from four and five-level choppers are used to emphasize the performance and the effectiveness of the proposed control scheme

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