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 singlephase 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.

Design and analysis of virtual impedance control scheme based on MESOGI for improving harmonic sharing of nonlinear loads

“…The MESOGI can provide an accurate estimation of the quadrature fundamental and harmonic components free from DC offset even for highly distorted current 33 . Also, according to (5), the implemented virtual impedance takes into consideration these components for obtaining its output.…”