Pulsing Method for an Inverter with a Bi-Directional Switch Setting for Reduced Switching Frequency

Abstract

In this paper a modulation strategy for an active rectifier is discussed with respect to the description of the modulation function. The rectifier is equipped with bi-directional switches to allow full control of the energy flow. This modulation strategy is based on a carrier signal whilst the switching frequency remains variable within a certain range. The switching frequency is dependent on the input value of the inverter output voltage. This modulation strategy allows easy set-up of the output voltage in the full range of positive and negative rectified input voltage. This also allows the direct connection of an energy storage system with a varying voltage as for example a battery system. Due to a variable number of switching pulses this modulation scheme allows a reduction in switching processes depending on the working point, while the underlying switching frequency remains constant based on the underlying PWM signal. This paper focuses on the simplification of the modulation tables and fast Fourier transformations of the different voltage stages in order to evaluate the high frequency impact of the modulation scheme.