Research Projects

Increased use of inverter-based renewable energy sources (IBRES) is now required due to the scarcity of conventional energy sources and the growing demand for fuels. The majority of IBRS are made to function as current sources and follow grid voltage. The term grid-following inverter (GFLI) refers to these IBRES. The growing use of IBRS raises a number of problems regarding power system stability. The idea of grid-forming inverter (GFMI) is gaining attraction in both academics and industry as a remedy. Providing frequency regulation and dispatchability during frequency stability is the primary distinction between synchronous generators and IBRES. Virtual synchronous generator (VSG) is one of the grid-forming solution. In order to provide frequency regulation, voltage regulation, and active and reactive power control similar to conventional synchronous generators, the idea of a VSG is introduced. VSG control emulates inertia and damping characteristics in the inverter, such as an SG. In addition, the active power-frequency and reactive power-voltage droop control of VSG regulate the active and reactive power according to frequency and voltage variations. So, VSG addresses the stability problems by offering adequate virtual inertia in inverter-based renewable energy sources. In addition, it lowers maximum frequency excursion and rate of change of frequency (RoCoF). The availability of energy storage makes using a battery energy storage system as a VSG more common. However, the real challenge comes with the integration of renewable energy sources with intermittent natures, such as solar and wind, with the grid. As the number of renewable energy sources increases to provide the power needed to meet the load requirement, parallel operation of multiple VSGs becomes necessary. The parallel operation of VSGs presents several challenges that can impact system stability and performance. These issues occur from the complexities of load sharing, frequency response, and control strategies required to maintain synchronization among multiple VSGs. Synchronization of the multiple VSGs is very important for stable operation during transients (like load changes or faults). Hence, a proper synchronization control algorithm is required. Also, multiple VSGs may oscillate in frequency and voltage due to lack of coordination, especially during load transients or faults. Conventional VSG control may not work with nonlinear loads. So, the VSG control needs to be modified. Also, during grid transients, parallel-connected VSGs may behave unpredictably, such as with high current flow. In this proposed work, an attempt will be made to seamlessly operate multiple VSGs in parallel in islanded microgrids as well as in grid-connected mode. Parallel operation of VSGs can be realized using the droop characteristics. Harmonic compensation is added in the VSG control for the parallel operation of VSGs with non-linear loads. Also, a current limiter is used to limit current.

IBRES, GFLI, GFMI, VSG, RoCoF.