Voltage Modulation and Current Control of Boost Inverters for Stand-Alone or Grid-Tied Operation

Boost inverters can step up dc voltage and carry out dc-to-ac conversion by means of a differential output across two boost converters. Although the differential output is beneficial to reject the common-mode noise, the inconsistency in circuit parameters between the two converters may cause an inevitable dc component in ac current. In addition, since the voltage gain of the boost converter is in nonlinear correlation with the duty ratio, the control bandwidth required for input state and output state would disparate and make the control design difficult. To overcome the nonlinearity of the boost inverter, a passivity-based voltage modulator was presented to take the place of the modulator derived from the ideal voltage gain. While the input state (inductor current) is stabilized by the proposed modulator according to the desired output voltage and ac current, the remaining problem is the control of the dc-biased sinusoidal output voltage to meet the required ac current. The integration of a dc-component compensator, a proportional-resonant controller, and a voltage drop compensator were presented for achieving ac current regulation with a satisfactory response. To further refine the power efficiency of the boost inverter, the lower limit of the dc bias of the converter output voltage was considered. Experimental results show the effectiveness of the proposed approaches.