Induction motors (IM) have been a fundamental part of industrial applications for over a century and the number of their applications continues to expand. A significant amount of the world’s total energy expense is consumed by this kind of motor. Hence, it is very important to increase the energy efficiency of these machines. Due to its good performance, field-oriented control (FOC) is the most common strategy to control IM. FOC requires references for stator current and rotor magnetic fluxes. For velocity regulation, a velocity reference is used instead of a stator current reference. However, at motor start-up or when a change of torque is required, it would be convenient for these references to be variable in order to reduce energy consumption. In this work, it is shown that this is indeed the case, and a technique to find optimal time-variable references for stator currents and magnetic rotor fluxes to reduce energy consumption is proposed. It is shown that, depending on the mechanical load, an energy reduction of 20–45% can be achieved.

The use of several different sources to feed a load jointly is convenient in many applications, in particular those where two or more renewable energy sources are employed. These applications include energy harvesting, hybrid vehicles, and off-grid systems. A multi-input converter able to admit sources of different characteristics and select the output power of each source is necessary in such applications. Several topologies of multi-input converters have been proposed to this aim; however, most of them are controlled by simple strategies based on a small signal model of multi-input converters. In this work, a low cost high gain step-up multi-input converter is analyzed. A nonlinear model is derived. Using this model, a detailed design procedure is proposed. A 500 W converter prototype was constructed to confirm that the model predicted the real behavior of the converter. Using the nonlinear model, indirect voltage control of basic converters was extended to the multi-input converter. The obtained controller had a fast performance, and it was robust under load and input voltage variations. With the obtained model, the proposed design procedure, and the controller, a converter that was initially proposed for photovoltaic applications was enabled to be used in a broader range of applications. The herein exposed ideas for modeling, the design procedure, and control could be also applied to other multi-input converters.

Translating a control law to code so that it can be executed in real time by a microcontroller is time-consuming and requires knowledge in diverse areas. There are powerful tools like Matlab and DSpace, that can ease the process, however, these tools are expensive and hide the way the translation is actually made. These two factors greatly diminish the use of these tools in education and small business. This paper presents SystDynam, a high-level language designed for describing static and dynamical systems and hence, controllers. The language was purposely created to be easy to process in order to obtain a C code by using free software tools. Therefore, a senior student or a control engineer with a short training in language processors can understand how the translation is made. The necessary code for translation is described here and is freely available. Having the controller described by C code, it can be compiled to be executed as the main task in a real-time operating systems, thereby obtaining the real-time controller. The complete process can also be used for emulating dynamical systems, thereby enabling the use of hardware in the loop simulations and low-cost rapid prototyping and providing an auxiliary tool for teaching some engineering courses.