This report details the design and implementation of a switching DC-DC converter for use in the Energy Harvesting From Exercise Machines (EHFEM) project. It uses a four-switch, buck-boost topology to regulate the wide, 5-60 V output of an elliptical machine to 36 V, suitable as input for a microinverter to reclaim the energy for the electrical grid. Successful implementation reduces heat emissions from electrical energy originally wasted as heat, and facilitates a financial and environmental benefit from reduced net energy consumption.

This thesis report details the design and construction of non-isolated DC-DC converters to create a Multiple Input Single Output (MISO) converter for combining multiple renewable energy sources into one single output. This MISO uses the four-switch buck-boost topology to output a single 48V from multiple nominal 24V inputs. The MISO converter implements a modular approach to deliver 1800W output power. Each module in the MISO is rated at 600W and they share the output power equally. Hardware results show that the converter produces 1800W of output power from three sources with 96.4% efficiency. Each module also demonstrates equal sharing feature of the MISO converter.

Fundação de Amparo a Pesquisa do Estado de Minas Gerais / Permanent magnet motors possess high efficiency and can be commercially competitive. The main purpose of this paper is to describe a low cost four-switch brushless dc motor drive with compensated direct current controlled our compensated hysteresis strategy. The description of the mathematical model is used in the computational simulation models to four-switch and six-switch. These results are here compared in an experimental model of drive, where the six-switch PWM drive and hysteresis drive is compared to the four-switch hysteresis compensated drive and not compensated drive. The four-switch drive has the potential to reduce costs by reducing the number of switches in commercial, industrial and residential applications. / Motores a ímãs permanentes possuem alta eficiência e podem ser competitivos comercialmente em aplicações de potência fracionária. O trabalho apresenta uma estratégia de acionamento a quatro chaves para o motor de corrente contínua a ímãs permanentes sem escovas, com uma estratégia a baixo custo por meio do controle direto de corrente, ou controle por histerese compensado. A descrição do modelo matemático é utilizada em modelos de simulação computacionais a quatro e a seis chaves. Estes resultados são aqui comparados em um modelo experimental de acionamento, onde o acionamento a seis chaves por PWM e histerese é comparado à estratégia a quatro chaves por histerese compensado e por histerese não compensado. O acionamento a quatro chaves tem potencial para redução de custos devido à redução do número de chaves e pode ser utilizado em aplicações comerciais, industriais e residenciais. / Mestre em Ciências

This work presents the direct torque control (DTC) techniques, implemented in four- and six-switch inverter, for brushless dc (BLDC) motors with non-sinusoidal back- EMF using two and three-phase conduction modes. First of all, the classical direct torque control of permanent magnet synchronous motor (PMSM) with sinusoidal back-EMF is discussed in detail. Secondly, the proposed two-phase conduction mode for DTC of BLDC motors is introduced in the constant torque region. In this control scheme, only two phases conduct at any instant of time using a six-switch inverter. By properly selecting the inverter voltage space vectors of the two-phase conduction mode from a simple look-up table the desired quasi-square wave current is obtained. Therefore, it is possible to achieve DTC of a BLDC motor drive with faster torque response while the stator flux linkage amplitude is deliberately kept almost constant by ignoring the flux control in the constant torque region. Third, the avarege current controlled boost power factor correction (PFC) method is applied to the previously discussed proposed DTC of BLDC motor drive in the constant torque region. The test results verify that the proposed PFC for DTC of BLDC motor drive improves the power factor from 0.77 to about 0.9997 irrespective of the load. Fourth, the DTC technique for BLDC motor using four-switch inverter in the constant torque region is studied. For effective torque control in two phase conduction mode, a novel switching pattern incorporating the voltage vector look-up table is designed and implemented for four-switch inverter to produce the desired torque characteristics. As a result, it is possible to achieve two-phase conduction DTC of a BLDC motor drive using four-switch inverter with faster torque response due to the fact that the voltage space vectors are directly controlled.. Finally, the position sensorless direct torque and indirect flux control (DTIFC) of BLDC motor with non-sinusoidal back-EMF has been extensively investigated using three-phase conduction scheme with six-switch inverter. In this work, a novel and simple approach to achieve a low-frequency torque ripple-free direct torque control with maximum efficiency based on dq reference frame similar to permanent magnet synchronous motor (PMSM) drives is presented.