Voltage and Frequency Control for DG Inverter in Low Voltage Islanded Microgrid with Improved Virtual Impedance Droop Control Scheme

This paper presents a band pass filter (BPF) based improved virtual impedance droop (IVID) control scheme. The proposed technique brings back the steady state voltage and frequency deviation to its nominal value for three parallel connected DG units in an islanded microgrid. In addition with virtual impedance offers power decoupling in low voltage microgrid system while virtual impedance co-operating with BPF based droop control ensures proper power sharing even there is a voltage deviation in the DGs system. A comprehensive simulation study is carried out in order to check the effectiveness of the proposed scheme compared to the conventional technique. The proposed controller achieves a notable improvement in voltage and frequency control and power sharing. The approach proposed does not rely on data exchange between sources or requires feeder impedance information. In the case of loads located locally or at a distance, sharing is also improved. Even under nonlinear load conditions, changes in power sharing are not affected.