A Novel Dual Switching Frequency Modulation for Z-Source and Quasi Z-Source Inverters
Abstract-Impedance network inverters (INIs) are the best alternatives for voltage-source and current-source inverters. Boosting capability and shoot-through solution of such converters make them excellent solutions for various applications. Nevertheless, hard switching forces the converter to operate in low switching frequency which results in a bulky impedance network. Moreover, the coupling between shoot-through duty cycle and inverter modulation index makes a trade-off between voltage gain and modulation index (output voltage harmonics). This paper presents a novel dual switching frequency modulation to mitigate the switching losses of the converter which results in a more compact impedance network. The proposed method combines a high frequency pulse width modulation(PWM) with a low frequency sinusoidal pulse width modulation(SPWM). Therefore, the switching losses decreases considerably, in respect to the conventional simple boost modulation. In addition, the impedance network design frequency maintains high and the network size decreases obviously. The proposed approach removes the interdependence between the shoot-through duty cycle and the inverter modulation index. A comparison between the proposed method and the conventional simple boost method is performed to show its advantages over the conventional method. Finally, experimental results are presented to validate the performance of the proposed method.
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