Modified schemes of control and modulation of neutral-point-clamped inverters of PV installation

The paper describes and compares algorithms of control and pulsewidth modulation (PWM) of three diode-clamped converters of PV system, insuring both minimization of common-mode voltage and symmetry of the output voltage of system. The analyzed installation includes also three strings of solar panels, connected with dc inputs of the corresponding inverters, and outputs of the inverters are connected specifically with the corresponding windings of power transformer. Results of simulation show remarkable improvement of spectra of winding voltage of the system, and this fact insures to decrease copper losses in the inverter-side windings of power transformer.