This paper presents a review of the power and torque coefficients of various wind generation systems, which involve the real characteristics of the wind turbine as a function of the generated power. The coefficients are described by mathematical functions that depend on the trip speed ratio and blade pitch angle of the wind turbines. These mathematical functions are based on polynomial, sinusoidal, and exponential equations. Once the mathematical functions have been described, an analysis of the grouped coefficients according to their function is performed with the purpose of considering the variations in the trip speed ratio for all the coefficients based on sinusoidal and exponential functions, and with the variations in the blade pitch angle. This analysis allows us to determine the different coefficients of power and torque used in wind generation systems, with the objective of developing algorithms for searching for the point of maximum power generated and for the active control of wind turbines with variations in the blade pitch angle.

Unavoidably, the controlsystem of any permanent magnet synchronous motor (PMSM) is subjected to perturbations, e.g., motor nonidealities and inverter nonlinearities. To reject these perturbations, a new super-twisting (ST) control variant, called speed adaptive super-twisting (S-AST) control, is proposed in this paper. In the S-AST control, a proportional-integral (PI) and a ST controllers are merged using an adaptive law that is based on the motor speed measurement. This is done to reduce the chattering problems that the standard ST control presents. In addition, a mathematical design for the S-AST control is proposed, where the relationship between the chattering amplitude, the switching frequency and the system perturbations is shown. The main contribution in this paper is the application of the S-AST controller to reduce the total harmonic distortion (THDi) of the PMSM currents. By comparing the S-AST control against PI control, the THDi is reduced from 9.9% to 1.27%, in simulation, and the THDi is reduced from 22.79% to 1.56%, experimentally. These results demonstrate how the S-AST control is an excellent alternative to improve the waveform of the PMSM currents.

In this work, methods are implemented to improve two aspects of energy quality in a wind generation system. First, the harmonic reduction is achieved by applying a linear control technique in the Grid Side Converter; and second, the power factor of the wind generation system using a Doubly Fed Induction Generator (DFIG) is adjusted by injecting reactive power. The reduction of the harmonic content is performed with a digital resonant controller, which tracks the periodic signals corresponding to the current harmonics of the Grid Side Converter (GSC), which is part of a “back to back” converter in a wind generation system. This technique allows implementing a current controller of the GSC with a high level of rejection of current harmonics, of frequencies with orders (1 + 6k) and (1 − 6k) (where k is an integer), when executed in the synchronous reference frame (dq). The purpose of this work is to inject currents to the grid with very low harmonic distortion and provide a method for tuning the resonant controller for a simple L filter; also, the GSC is used to generate reactive power. These two improvements achieve a unity power factor, and this is necessary to comply with the new codes where a leading power factor helps regulate the grid voltage.

This paper presents enhancements of a predictive direct torque control for synchronous reluctance machines down to zero speed. The proposed control scheme is used when high- performance torque control is desired with the advantages of constant switching frequency and relative long sampling time. To get that, the control algorithm calculates one step in advance the switching instants of two possible active voltage space phasors that build the demanding torque. Next, the trajectory of the stator flux is predicted with these two pre-selected voltage space phasors and the optimum of them, which leads to the best trajectory of the stator flux at the end of the cycle, will be applied to the machine. At very low speeds a second active voltage space phasor is used to counteract the drop of the stator flux. In this paper it is shown, how the switching instant of this second voltage space phasor can be successfully predetermined before the switching instants of the other two voltage space phasors for torque and flux control as well as the criteria for its appropriate selection. The proposed algorithm has been implemented by using a digital signal processor (DSP) and a field programmable gate array (FPGA) embedded in the same board. Experimental results at very low and zero speed using a commercially available machine verify the effectiveness of the enhanced control scheme.

The penetration of renewable energies in the context of distributed generation represents challenges such as maintaining the reliability and stability of the system and considering the random behavior proper of generation and consumption. In this context, microgrids make it possible to manage effectively the generation and consumption of this energy, incorporating, electronic power converters, energy storage systems, and hierarchical control schemes. This paper presents the modeling, design, and application of controllers for a photovoltaic inverter operating in island mode. For this application, the photovoltaic inverter regulates the inverter output voltage via two control configurations implemented to follow the voltage reference imposed by the scheme droop. The first control scheme is configured with a two-degrees-of-freedom controller plus a repetitive controller. In this configuration, the repetitive controller is implemented in the direct loop. The second scheme is configured with an integral proportional controller—proportional controller plus a resonant controller. This configuration is formed by an integral proportional control in the direct loop plus a resonant controller and a proportional controller in the feedback loop. Both control configurations are implemented to improve the inverter disturbance rejection capability when it feeds both linear and non-linear local loads. In addition, these configurations allow the parallel connection of inverters with good performance, using a droop scheme that allows the parallel connection of converters. The tests are carried out by means of simulations using PSIMTM, which shows that, with the implemented controllers, the total harmonic distortion of the inverter output is below 5%, as recommended by the IEEE 519-1992 standard.

This paper presents a comprehensive comparative study between Proportional–Integral (PI) and Linear Quadratic Regulator (LQR) control strategies applied to a Permanent Magnet Synchronous Machine (PMSM) in an electric vehicle traction system. The main contribution lies in establishing a fair basis for comparison by designing both controllers under equivalent closed-loop dynamic conditions—specifically, with similar closed-loop bandwidths and step responses—to isolate the effect of the control strategy itself. The study evaluates key performance aspects such as disturbance rejection, energy efficiency, and sensitivity functions, as well as practical considerations including tuning complexity, implementation effort, and debugging feasibility. Simulation and experimental validation under the US06 driving cycle confirm that the LQR controller achieves superior robustness and energy performance compared to the PI controller, although the PI controller retains advantages in simplicity and ease of implementation. Although LQR is an advanced optimal method, its direct comparison with the industry-standard PI is justified to assess whether the additional design complexity translates into practical benefits for electric traction applications. This work provides a structured, experimentally validated approach for controller benchmarking, offering valuable insight into the trade-offs between classical and optimal control strategies.