Improved power computation method for droop-controlled single-phase VSIs in standalone microgrid considering non-linear loads

Abstract

Computation of active and reactive powers is a crucial step in droop-controlled single-phase voltage source inverters (VSIs) in standalone microgrid since the performance and stability of the power-sharing strategy are strongly influenced by its speed and accuracy, especially in the case of non-linear loads. Here, an improved performance of power-sharing among single-phase droop-controlled VSIs in an islanded microgrid, considering DC component and nonlinear loads is presented. To achieve this goal, an enhanced power-sharing control scheme including a Multiple Enhanced Second-Order Generalized Integrator Frequency-Locked Loop (MESOGI-FLL) for power calculation is proposed. As a result, the proposed power computation technique provides high rejection capability of DC component and current harmonics, hence, perfect estimation of the fundamental component of the inverter output current and its 90◦ phase-shifted component. This strategy makes the power calculation method-based control scheme immune to disturbance effects of the DC component and the high current harmonics. Detailed analysis, mathematical modelling of MESOGI, as well as a comparison with recent methods, are also provided. Simulation and experimental tests were carried out and the obtained results have shown the effectiveness and robustness of the proposed power-sharing controller even under nonlinear load operating conditions.