Modulação por largura de pulso para conversor current-fed dual active bridge operando em modo de condução descontínua para carregadores de bateria

Abstract

With the significant growth of renewable energy sources and the need for an efficient and interconnected energy structure, distributed generation has been developing and allowing the user to stop being just the final consumer. One of the alternatives to produce energy is microgeneration by solar photovoltaic sources. In this type of generation, energy is generated intermittently, and a potential solution is battery energy storage systems. Low voltage energy storage systems have standards of 12 V / 24 V / 48 V. Whereas the DC bus used for the interface with the grid has a high voltage between 350 V and 450 V. Thus, to perform the interface between batteries and DC bus it is essential to use high voltage conversion ratio bidirectional DC-DC converters that provide a controllable charging and discharging process and provide an output voltage within specifications. Among the topologies of converters, isolated full-bridge current (CF-DAB) converters have advantages such as isolation, high voltage conversion ratio, and low current ripple on the low voltage side. However, current-fed topologies may have transformer and semiconductor overvoltages due to the dispersion inductance of the transformer that is in series with the inductor on the low voltage side. One solution to avoid this problem is to disable the semiconductors on the low voltage side with ZCS. In this way, this work proposes an asymmetric PWM modulation strategy applied to the CF-DAB converter operating in discontinuous conduction mode (DCM). In this modulation strategy, there is no necessity to add inductance in series with the transformer’s dispersion inductance to adjust the power processed by the converter. That improves the converter efficiency. The DCM operation ensures soft switching of the semiconductors over a wide range of operating, without incorporating other devices, such as auxiliary inductors or auxiliary circuits for active clamping. A design methodology for third-order filters is proposed to meet the requirements of battery chargers’ standards. The operation of the converter and the design methodology is presented. Next, the converter design and simulations for 500 Ware presented. Finally, the experimental results of the implemented prototype are shown, such as waveforms and curves efficiency.