Sistema de condicionamento de potência com correntes senoidais na rede de alimentação

Abstract

Power Conditioning Systems (PCS) may impact the system power quality due to the current harmonic distortion and also increase the potential of harmonic resonances due to the use of capacitive elements in their front-end filters included to deal with this distortion. In this context, the True Unity Power Factor (TUPF) converter is proposed as an alternative to perform the necessary bidirectional power flow with high efficiency, use of conventional topologies and transformers and without capacitive filter elements. The objective of this work is to propose modulation and closed-loop control techniques which promote the effective working of the proposed technology for this application, although without being restrict to it. Furthermore, this work also aims a deep analysis of working aspects of the composing parts of this technology. Therefore, the main contributions to the scientific and technological advance are: to propose and physically implement voltage and current control techniques capable of working along with the selective harmonic elimination PWM for TUPF converters in parallel, series-connected or independent dc links. Here a new real-time filtering technique for highly distorted currents was also implemented. Then the bidirectional power flow capability and constant current / constant voltage operation modes needed for battery applications are analyzed. Additional contributions are the analysis of losses, harmonics cancellation in transformers, voltage harmonics at the converters and capabilities for reactive power support. These contributions are extended to the three level neutral point clamped topology. The work develops through a theoretical analysis of the working of such technology added of computational calculation when convenient. It is described the design of the closed-loop current and voltage controls, including their variants, as well as their interaction with the selective harmonic elimination PWM. First, the results are evaluated in computational simulations. Then, the control implemented through microprocessors, FPGA and adequate electronic circuits is tested in a hardware-in-the-loop system. Finally, the concept is tested in a low scale prototype (30 kVA). The presented simulation and experimental results show the dynamic and steady-state working capability of the TUPF converter supplying practically sinusoidal currents in several applications and operation modes.