A variable switching frequency algorithm to improve the total efficiency of single-phase grid-connected inverters

The selection of an optimal switching frequency of pulse width modulation (PWM) for single-phase inverters is one of the most effective ways to improve the inverters´ efficiency. However, the lower switching frequency results in the higher harmonic voltage and current. For grid- connected inverters, the harmonic current distortion is significantly affected by the switching frequency. Therefore, the choice of switching frequency is usually considered as a tradeoff between lowering the total demand distortion (TDD) of output current and reducing the switching losses. In this paper, a variable switching frequency algorithm that changes the carrier frequency of a modified space vector pulse width modulation (SVPWM) control in real time based on different operating conditions is developed to improve the overall efficiency of the inverter while meeting a TDD requirement specified in IEEE Standard 1547. The performance of the proposed algorithm is verified by both Matlab-based simulation and experiments conducted on a 12kw single-phase inverter.