Hybrid PFM and SPWM Control Scheme for DCM Single-Leg-Integrated Boost Inverter

Under the conventional pulsewidth modulation + sinusoidal pulsewidth modulation (SPWM) hybrid control, the discontinuous conduction mode single-leg-integrated boost (SLIB) inverter confronts an overmodulation problem under a wide change in load, leading to the distorted output waveform. One approach to address this issue is to keep the boost leg duty cycle constant and regulate load power. However, it is not suitable for standalone or photovoltaic grid-connected power systems. Therefore, a pulse frequency modulation (PFM) + SPWM hybrid control scheme is proposed to overcome the shortcomings in this article. Under the proposed scheme, the boost leg of the inverter works in PFM, whereas the other leg works in SPWM. Since the dc-link voltage is controlled by frequency, instead of load power or duty cycle, the inverter can avoid overmodulation for a wide load range and be applied on occasions where the load power is nonadjustable, which is more practical in comparison with the counterpart. The feasibility of the proposed hybrid control is verified by experiment through a 500-W prototype.