A Novel PLL-less Direct Power Control of VSCs.

Recent efforts introduced in the control design of grid-tied voltage-source converters (VSCs) are based on a PLL-less (phase locked loop-less) approach, widely known as voltage modulated-direct power control (VM-DPC). Hence, the main control goal that is the adequate power regulation independently from the output voltage alignment is implemented by a simplified manner whereas the design suffers from the fact that it does not take into account the whole system dynamics. Instead of this standard method, in this paper, a novel model-based DPC control scheme is proposed. The main novelties of the proposed approach are summarized to the following: i) all the nonlinearities are considered without needing to cancel, through the control law, the cross-coupling terms or the external ac voltage inputs, ii) the design directly provides the duty-ratio components that drive the VSCs by simple PI controllers with the gains not divided by the dc voltage state. Both the aforementioned points are significant since make the control design independent from the system parameters and clearly robust against ac or dc voltage variations. Furthermore, the whole design is handled in detail and is validated for its stability through a rigorous analysis based on advanced nonlinear techniques that can guarantee the desired system performance under various conditions. Finally, the system response is evaluated by conducting a thorough experimental procedure which fully verifies the theoretical and the standard used mean-value simulation results.