<p>Traditionally, renewable energy systems employ grid-connected and standalone inverters that demand high efficiency, low harmonic distortion, and reliable operation. However, the conventional high-frequency modulation of the unidirectional integrated Ćuk inverter (UICI) reduces efficiency and increases the switching stress. Therefore, this paper proposes a novel high-frequency modulation technique for the UICI to overcome these limitations, in which only two of the four bridge switches operate at high frequency, while the remaining operate at low frequency, thereby reducing commutation losses and switching stress. The UICI is designed, modeled, and implemented in standalone and grid-connected operations to demonstrate its versatility and performance. The UICI with the proposed modulation is analyzed and evaluated through computational simulations in MATLAB/Simulink, as well as experimental results. The results demonstrate that the proposed modulation improves the system performance by introducing a freewheeling state in the output inductor that enhances the inductor dynamics and improves the static gain. In standalone operation, the UICI supplies a sinusoidal output voltage with 0.6% of total harmonic distortion (THD) for resistive loads and less than 3.8% for nonlinear loads. In contrast, the system injects current into the utility with less than 3% of THD in grid-connection operation. The UICI achieves an efficiency of around 96% using MOSFET with CoolMOS technology and 94% with standard IGBTs. Hence, these results confirm the advantages of the proposed modulation for the UICI in terms of efficiency, system performance, and reduced switching stress.</p>