A Novel Four-Wire Offgrid DFIG-BES Wind Microgrid for Remote Areas With Neutral Current Compensation For Reduced Transformer Failure

Community and residential loads connected to low voltage AC distribution networks require a neutral point connection. Neutral point forms return path for single-phase loads. Presence of neutral wire reduces effect of unbalanced loading of one phase to get reflected on other load phases. It helps during fault conditions to minimize effect of circulating current by providing low impedance path. However, in case of harmonically polluted load currents, rating of neutral conductor increases, leading to additional losses and unwanted heating effecting other components of network. Wind energy conversion systems (WECS) use transformer for connection to AC network to reduce requirement of higher rating and size of DC link capacitor. Neutral current and harmonic currents of load are processed through the transformer, which leads to additional heating of transformer ands which is detrimental for connected loads. Such conditions can lead to failure of WECS operation and damage transformer and connected sensitive loads due to flow of circulating currents. Hence, this work presents design and control of a novel four wire topology of a WECS comprising of a doubly fed induction generator (DFIG) and a battery energy storage (BES). A grid forming converter (GFC) is deployed to provide independent compensation for load neutral and harmonic currents without affecting the WECS transformer, reducing its failure and heating rate. WECS converters are controlled to improve power quality of stator current and point of common coupling (PCC) voltage as per the IEEE 519-2022 std. Simulation results present MPPT operation of WECS with neutral and harmonic compensation even during dynamic conditions.