This work presents a novel current multilevel (CML) inverter topology, named boost CML inverter, and its application on energy processing of single-phase grid-connected photovoltaic (PV) systems. The structure allows a high power factor operation of a PV system, injecting a quasi-sinusoidal current into the grid, with virtually no displacement in relation to the line voltage at the point of common coupling among the PV system and the loads. The major appeals of using the CML technique are the balanced current sharing among semiconductor switches and the decrease of the current slope in the circuit devices, with a consequent reduction of conducted and radiated electromagnetic interference (EMI). The CML technique also allows adapting or minimizing current waveforms harmonic content. System description, mathematical approach, and design guidelines are presented, providing an overview of the new topology. In order to validate the proposed concepts, experimental measurements, made in a small-scale laboratory prototype, are also presented. The obtained results evidence the feasibility of the application of this new topology on singlephase grid-connected PV systems.

The paper presents the modelling, analysis and design of a pulse width modulation voltage source inverter (PWM-VSI) to be connected between a DC source, which is supplied from a photovoltaic (PV) array and the AC grid. The control algorithm of the PWM-VSI applies the concepts of the instantaneous p-q (real-imaginary) power theory. The objective is to show that, with an adequate control, the converter can transfer the DC energy from PV array and improve the power factor (and the power quality) of the electrical system. Some design considerations are also discussed. A digital simulation and measurements on a small prototype model verified the feasibility of the proposed control method.

This work presents a performance study of a dc microgrid when it is used a voltage droop technique to regulated the grid voltage and to control the load sharing between different sources. A small model of a dc microgrid comprising microsources and loads was implemented in the Simulink/Matlab environment. Some aspects about centralized (master-slave) and descentralized (voltage droop) control strategies as well as the procedures to design the controllers, with and without droop control, are presented and discussed. Simulation results obtained with the digital model of the dc microgrid with three microsources will be presented to validate the effectiveness of the voltage droop strategy, applied to proportional and proportional-integral controllers, to regulate the microgrid voltage.

This study presents the modelling and design steps of a discrete time recursive repetitive controller (RC) to be used in a grid‐connected photovoltaic (PV) system. It is shown that the linear synchronous reference frame proportional‐integral controller, originally designed to control the converter's output currents, may have its effectiveness compromised because of non‐linearities in the system components. A RC is introduced as an alternative to overcome this drawback and improve the system's output currents. The performance of the designed hybrid controller is tested, under both steady‐state and transient operations, for variations on the power generated by a 30 kWp PV power plant. Experimental results obtained from the operation of the PV system connected to a distribution network, without output passive filters, only through a transformer that operates in a non‐linear region are presented. The results are used to evaluate the performance of the proposed compensation method and to validate the designed hybrid controller.

This study presents the design and implementation steps of a digital predictive controller to regulate a low‐inductance, three‐phase, three‐wire permanent magnet brushless DC motor currents. These types of motors are usually driven by multi‐stage converters, switched at high frequencies, or use additional inductances to limit the current ripple. The motor's trapezoidal back electromotive force and rectangular currents waveforms make the design and the tuning process of linear controllers difficult. This task complexity increases when a wide speed range is considered. Digital predictive controllers are easily implemented in digital signal processors (DSPs), being successfully used to regulate currents of different types of power electronic converters. A unipolar pulse width modulation predictive controller is proposed here to regulate the rectangular currents of a brushless DC motor, without the need for any additional filter or converter. Experimental and simulation results using a 5 kW/48 V three‐phase brushless DC (BLDC) motor are presented to demonstrate the feasibility of this proposal. It will be presented a methodology to compensate the conditioning and sampling circuits delays as well as the inverter's semiconductors voltage drop. The control algorithm was implemented in a TMS320F28335 DSP.

This work deals with the design of a digital current control applied to a variable-speed low inductance BLDC motor drive. A robust static full-state feedback control law is determined by means of a convex optimization problem, subject to linear-matrix-inequality constraints. The optimization is used to achieve a fast time response with reduced overshoot under the parametric variations. Results from a 5kW/48V BLDC motor prototype is used to validate the proposed approach with a superior performance when compared to two other control strategies.