Voltage Harmonic Control of Z-source Inverter for UPS Applications

This paper presents a control method for obtaining sinusoidal output voltage regardless of the nonlinear and unbalanced loads. Control of the DC boost stage and capacitor voltage is presented. The resonant regulators are used for selective harmonic cancelation of the output AC voltage. The Z-source inverter is able to provide higher AC voltage related to the DC link voltage than in conventional VSI, possessing embedded property of boost converter. This work presents the optimal control of boost factor and capacitor voltage, reducing the voltage transistor stress under desired AC voltage level. Experiment implementation on TMS320F2812 DSP show possibility of accommodating blanking time DSP circuits for controlling shoot-through duty ratio without any additional external logic. Modified space vector modulation gives only two transistor switching per cycle, thus minimizing the switching loses as much as possible.