Unit power factor multipulse bridgeless rectifiers using half-controlled DC-DC converters

• Grant number: 15/15872-9
• Support Opportunities: Regular Research Grants
• Start date: February 01, 2016
• End date: July 31, 2018
• Field of knowledge: Engineering - Electrical Engineering - Power Systems
• Principal Investigator: Falcondes José Mendes de Seixas
• Grantee: Falcondes José Mendes de Seixas
• Host Institution: Faculdade de Engenharia (FEIS). Universidade Estadual Paulista (UNESP). Campus de Ilha Solteira. Ilha Solteira , SP, Brazil
• Associated researchers: Angelo César de Lourenço ; Claudiner Mendes de Seixas ; João Carlos Pelicer Junior ; Luciano de Souza da Costa e Silva ; SAULO CRNKOWISE GARCIA

Abstract

It will be seen active, passive and hybrid three phase AC/DC topologies, aiming to harmonic contents reduction in the power grid. Firstly, the focus will be the isolated multipulse converters based on Y, Delta, zigzag and polygon connections, besides those non-isolated ones, based on transformers and autotransformers connections. Both converter types, because of their topology, promise power grid harmonic contents reduction, leading to power factor increase with low voltage ripple on the load.Emphasis will be given on high voltage DC-DC converters when operating with AC-DC multipulse converters, aiming to produce low harmonic distortion on the grid, regulated DC output, simple switches command and control and, depending of the topology, high or low frequency isolation. The first idea is to work with DC-DC topologies, based on classic Boost arrangements that operate as current source. Next step, main efforts will be made to incorporate the passive (diodes) and active switches (IGBTs) of the Boost converters into diode bridges. This technique is known as Bridgeless, i.e. there is not a rectifier stage (with only diodes) followed by a DC-DC stage. It has the main advantage to reduce losses and improve current distribution on the semiconductors. In the case of three-phase diode bridges, the Bridgeless technique is beginning to appear in recent technical literature, named as Half-controlled. However, nothing is heard about using Bridgeless or Half-controlled in multipulse three-phase systems.This project looks for better exploring the approach of converters which can result on new combined topologies from different transformers and autotransformers connections and several DC-DC converters which support the technique to be incorporated on the diode bridges (Bridgeless or Half-controlled). This Project may also open a promising research line to bring contributing for this important issue.Preliminary simulation analysis performed by the research group, has shown surprising results, i.e. if each rectifier operates in Discontinuous (or Critical) conduction mode, there is a kind of interleaving of the currents, thereby ensuring a continuous conduction mode into the grid and in the transformer windings. Besides the advantages of interleaving, this operation mode as voltage follower avoids the use of current sensors and control loop, which are the main difficulties of the systems used for power factor correction. Another great advantage is IGBTs command circuits simplicity, assembled on the same voltage reference, do not needing any synchronism or lag with three-phase systems. The command is sent during the entire time for all IGBTs, respecting only the adjustment of the duty cycle.All the theoretical study, the mathematical analysis and comparative results will be followed by digital simulation with specific mathematical programs for numerical and graphical results. As a practical application, the goal is to look for simple and robust topologies, which permits good voltage regulation output and low harmonic content on the power grid. In many applications, those solutions are used to equip or replace three-phase existing rectifiers (retrofit), specially in ASD - Adjustable Speed Drives. Another major promising area is in rectifier systems for aircraft, called MEA - More Electric Aircraft. (AU)