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This paper addresses the challenges encountered by grid-connected photovoltaic (PV) systems, including the stochastic behavior of the system, harmonic distortion, and variations in grid impedance. To this end, an in-depth technical and pedagogical analysis of three linear multivariable current control strategies is performed: proportional-integral (PI), proportional-resonant (PR), and deadbeat (DB). The study contributes to theoretical formulations, detailed system modeling, and controller tuning procedures, promoting a comprehensive understanding of their structures and performance. The strategies are investigated and compared in both the rotating (dq) and stationary (αβ) reference frames, offering a broad perspective on system behavior under various operating conditions. Additionally, an in-depth analysis of the PR controller is presented, highlighting its potential to regulate both positive- and negative-sequence components. This enables the development of more effective and robust tuning methodologies for steady-state and dynamic scenarios. The evaluation is conducted under three main conditions: steady-state operation, transient response to input power variations, and robustness analysis in the presence of grid parameter changes. The study examines the impact of each controller on the total harmonic distortion (THD) of the injected current, as well as on system stability margins and dynamic performance. Practical aspects that are often overlooked are also addressed, such as the modeling of the inverter and photovoltaic generator, the implementation of space vector pulse-width modulation (SVPWM), and the influence of the output LC filter capacitor. The control structures under analysis are validated through numerical simulations performed in MatLab® software (R2021b) using dedicated computational routines, enabling the identification of strategies that enhance performance and ensure compliance of grid-connected photovoltaic systems.

The central inverter topology presents some advantages such as simplicity, low cost and high conversion efficiency, being the first option for interfacing photovoltaic mini-generation, whose shading and panel orientation studies are evaluated in the project planning phase. When it uses only one power converter, its control structures must ensure synchronization with the grid, tracking the maximum power generation point, appropriate power quality indices, and control of the active and reactive power injected into the grid. This work develops and contributes to mathematical models, the principles of formation of control structures, the decoupling process of the control loops, the treatment of nonlinearities, and the tuning of the controllers of a single-stage photovoltaic system that is integrated into the electrical grid through a three-phase voltage source inverter. Using the parameters and configurations of an actual inverter installed at the power plant CRESP (Reference Center for Solar Energy of Petrolina), mathematical modeling, implementation, and computational simulations were conducted in the time domain using MatLab® software (R2021b). The results of the currents injected into the grid, voltages, active powers, and power factor at the connection point with the grid are presented, analyzed, and compared with real measurement data during one day of operation.

One of the main concerns in designing control structures for Voltage Source Inverters (VSI) is ensuring the generation of sinusoidal currents that comply with international power quality standards. In this context, the present study investigates the evaluation of multivariable control techniques characterized by their Deadbeat nature, within coordinates dq . One of these techniques incorporates a virtual emulation of the current loop filter behavior. The application of these controllers is demonstrated in the context of a three-phase VSI connected to the electrical grid. These controllers not only show their effectiveness in decoupling control loops but also have greater stability without the presence of phase delays. With a specific emphasis on developing and fine-tuning multivariable Deadbeat controllers using dq coordinates, the study leverages three distinct models to analyze the stability and evaluate the performance of the control strategy. The synthesis of system models and consequently of controllers was made possible by the α β and dq coordinate conversion method, developed in this study. This tool holds significant potential not only in synthesis but also in system analysis. The simulated solar setup uses a 5.1 kW photovoltaic system with second-generation modules. It includes an internal current loop, an external energy loop, and a multi-level VSI controlled by Space Vector Pulse Width Modulation (SVPWM). This complex combination of elements serves as the context for the tested control strategies, undergoing thorough testing and evaluation.

Usually, the secondary voltage of a Coupling Capacitor Voltage Transformer (CCVT) is not a perfect replica of its primary voltage. In this study, the steps to design a hardware capable of performing the correction of the CCVT secondary voltage is presented. The device is basically a recursive digital filter whose parameters are obtained from the CCVT frequency response. The evaluation of the device is made by connecting it to the Real Time Digital Simulator (\\( RTDS ^TM\\)) and carrying out real time simulations for two case studies: harmonic distortion and short-circuit in a 230 kV system. It is shown that the hardware device brings the CCVT secondary voltage waveform close to the primary voltage signal.