Phase synchronization of autonomous AC grid system with passivity-based control

This paper discusses a ring-coupled buck-type inverter system to harness energy from direct current (DC) sources of electricity. The DC-DC buck converter circuit is modified with an H-bridge to convert the DC input voltage to a usable alternating current (AC) output voltage. Passivity-based control (PBC) with port-controlled Hamiltonian modelling (PCHM) is a method where the system is controlled by considering not only the energy properties of the system but also the inherent physical structure. PBC is applied to achieve stabilization of the AC output voltage to a desired amplitude and frequency. Unsynchronized output voltages in terms of phase angle or frequency can cause detrimental effects on the system. Phase-locked loop (PLL) is employed in the ring structure to maintain synchronization of the AC output voltage of all inverter units in the ring-coupled system.