Realizing A Single Source Three-Phase Controllable Voltage Boosting Inverter using Single Switched-Capacitor

Abstract

The majority of the electric vehicles (EVs) today are using voltage source inverters (VSIs) as traction inverters. Due to the inherent buck character of VSI, a dc-dc converter consisting of an inductor is used to boost the voltage before the conventional three-phase bridge inverter. Hence, the system becomes bulkier and involves higher losses. To overcome the drawback, a switched-capacitor (SC) voltage boosting inverter along with its proposed carrier- based modulation strategy are presented in this study. A switched-capacitor unit (SCU) is connected to the conventional three-phase bridge inverter to obtain the increased voltage at the output. Modified sinusoidal pulse width modulation (SPWM) is used to increase the utilization of the DC source and the linear operating range of the inverter. A single carrier signal is used for comparing and switching signal generation. For modulation of the switches of SCU, new reference signals are generated from the traditional three-phase reference signals. Boosting of the inverter can be controlled by manipulating the newly generated reference signals. To yield fractional boosting, the voltage boost is obtained for a fraction of the active state duration, which thereby is resulting in less voltage drop across the capacitor. A number of SCUs can be added to a conventional VSI for The multi-fold voltage augmentation can be realized by adding number of SCUs to a conventional VSI. The value of the switched-capacitor is designed and the simulation is performed using MATLAB/SIMULINK while the experimental verification is done for the passive load. An OPAL-RT 4510 with a digital output board is used to generate the pulses for the MOSFET inverter switches. The proposed work can be used with existing three-phase bridge inverters. The SCVSI can be used for various low to medium voltage applications i.e. electric vehicles, photovoltaics, battery energy storage systems etc.