| Synchronous Generators (SG) have been in forefront of centralized power generation for a long time. The frequency in the power system including large Synchronous Generators is governed by the rotational frequency which is subject to prime mover power. Synchronous Generators preserve kinetic energy in their huge rotors. This kinetic energy is inserted to the power system on the occurrence of fault or disturbance to sustain the energy balance. The massive rotating masses of synchronous generators also provides large inertia which counteracts abrupt variation in frequency and augments the stability of power system. Renewable energy sources (RES) e.g. photovoltaic cell and wind turbines are on the rapid rise in recent years to solve energy crisis and environmental problems. But incorporation of RES in power systems leads to complication of power system administration and protection which limits the penetration of RES in power system. RES and Distributed Generators (DGs) are interfaced with the power grid with power electronic inverters which results in lack of inertia in the system. The concept of microgrid was proposed to enable the addition of DG units in the power system. A microgrid consists of a combination of DG units, energy storage systems and loads which diminishes the complication for the power system operator and increases power quality and reliability for regional consumers. Nevertheless, inverter-interfaced DG units with conservative control procedures are still not able to deliver adequate inertia to support the frequency of the grid.
The principles of basic VSG control are discussed in this work and existing topology of virtual inertia emulation is reviewed. The various control techniques virtual inertia concept is discussed in literature survey. The optimal placement and optimal amount of virtual inertia is also discussed. The advantage of incorporating VSG system in a model is established by comparing it with a system without VSG. Alternating inertia concept in an offline manner using fuzzy logic controller is compared with VSG control with fixed parameters of swing equation establishing the benefit of alternating inertia in the system. SAIC concept is discussed which adapts the value of inertia constant according to disturbance in real-time. A comparison between SAIC, offline alternating virtual inertia and VSG with fixed parameters is done which establishes the supremacy of SAIC on other two techniques. SAIDC technique which involves the control method which adapts the value of inertia constant as well as damping coefficient according to disturbances in the system is also discussed and have been proved to be most prominent among all four techniques by its comparison with SAIC, offline alternating virtual inertia control and VSG control with fixed value of swing equation parameters. Model Predictive Controller (MPC) is discussed in this work and is utilized for the emulation of virtual inertia. The various case studies have been done with MPC such as switching of non-linear load and SLG fault. MPC controller is compared with Proportional-integral (PI) controller in these case studies and it is established that MPC provides better control than PI controller. The basic concepts and control methods introduced in this work may participate in the expansion of microgrids and amalgamation of power electronic inverter-based DGs in power grid. With improved inertial microgrid regulator approaches a “greener” and “smarter” distribution network consisting of prominent infiltration of DGs and RES units. There are still numerous concerns and trials for the successful operation of VSGs in microgrids. For the betterment of control techniques, the VSG’s parameters of swing equation utilized in microgrids may be optimized by employing modern control theories. The operation of VSG control technique in a microgrid using MPC under a fault condition is also discussed and analysed.
1805266003 Deeksha Singh