A Modified Virtual Synchronous Generator for Multi-Converter Islanded Microgrid under Diverse Load Conditions

The growing penetration of Distributed Generators (DGs) results in a reduction of grid inertia. Low inertia poses significant challenges, particularly in the islanded mode of operation. To address this issue, one promising solution is to emulate the physical inertia of a synchronous generator in the power electronics control of the inverter. Among the various schemes proposed in the literature, a virtual synchronous generator (VSG) is well known. A VSG control provides inertia support by implementing the rotor dynamics of a synchronous machine in power electronics control. In VSGs, the average power obtained from the low pass filter (LPF) is used as feedback for the virtual torque equation. The cutoff frequency of the LPF limits bandwidth and decelerates dynamic response. To overcome this limitation, a compensator-based VSG has been proposed in this paper, which gives more flexibility in tuning the bandwidth of the controller. This reduces the tuning effort of controller gains in voltage and current control and improves small signal stability. Apart from the compensator, an additional damping loop is also included to suppress oscillations during disturbances. The small signal model (SSM) of the VSG was derived and incorporated into the microgrid model. The developed model was validated through eigenvalue analysis, time domain, and real-time simulations along with controller hardware in loop (CHIL) implementation. VSG-operated microgrid small signal stability was analyzed by feeding different types of loads like passive load, active load, and dynamic induction motor load. The effectiveness of VSG was established by comparing its performance with conventional droop control. The proposed VSG was found to outperform the conventional droop control in the presence of rectifier interfaced active load and constant power load.