A Conservative Power Theory-based PLL-less Control Strategy and Performance Evaluation for Single-phase PV Grid-tied Inverter

A PLL-less control strategy for single-phase PV grid-tied inverter is proposed in this paper with the "self-synchronization" nature of the emerging conservative power theory. Dedicated PLLs which are normally used in traditional grid-tied renewable energy systems are eliminated, thus leading to a simple control structure as well as preventing the possible adverse effects brought by the PLLs in weak-grid conditions. Power feedforward and proportional DC voltage control are introduced to enhance the dynamic performance and stabilize the DC voltage, respectively. The performances of the CPT-based method and two other typical methods are further compared from different aspects, an evaluation mechanism is applied to comprehensively compare and evaluate these three methods based on the simulation results. The results demonstrate that the proposed method can use two controllers without PLL to achieve the best control performance and synchronization.