A new virtual-flux-vector based droop control strategy for parallel connected inverters in microgrids

Voltage and frequency droop method is commonly used in microgrids to achieve proper autonomous power sharing without control wire interconnections. This paper proposes a new control strategy for parallel connected inverters in microgrid applications by drooping the flux instead of the inverter output voltage. Firstly, the relation between the inverter flux and the active and reactive powers is mathematically obtained. Secondly, a novel flux droop method is then developed in order to regulate active and reactive powers by drooping the flux amplitude and the phase angle, respectively. In addition, a small-signal model is developed in order to design the main control parameters and study the system dynamics and stability. The proposed control scheme includes a direct flux control (DFC) algorithm, which avoids the use of PI controllers and PWM modulators. The obtained results shows that the proposed flux droop strategy can achieve active and reactive power sharing with much lower frequency deviation and better transient performance than the conventional voltage droop method, thus highlighting the potential use in microgrid applications.