Power Electronics Inverter with a Modified Sigma-Delta Modulator and an Output Stage Based on GaN E-HEMTs

Abstract

The chapter presents a conception of a power electronics inverter based on a modified sigma-delta modulator (SDM) being used in the inverter’s control block. The proposed modulator includes a comparator with dynamic hysteresis instead of a latched comparator, which is typically used in single-bit SDMs. Thanks to this feature, the resolution of the SDM output bit stream is, theoretically, unlimited. As a result, the value of the THD of an inverter output voltage (current) is much lower than that of a typical SDM solution. This benefit is not offset by an increase in the system’s complexity. Moreover, the control system is simpler than in the case of a conventional inverter. Due to the very high frequency of an SDM output bit stream, in a power stage of the inverter, the gallium-nitride (GaN)-based E-HEMTs (Enhancement mode High Speed Mobility Transistors) are implemented. However, in the case of a lower value of an inverter output power, an Si-based device is still the proper choice. In the chapter, the inverter control circuit basics, the results of simulation experiments and a possible practical arrangement of this one as a voltage-controlled voltage source (VCVS) are presented.