Due to the increasing penetration of RESs in distribution power systems, maintaining system stability has grown as a major concern in system operation. The DGs used in the microgrid is interconnected to the grid through power electronic converters which do not provide any mechanical inertia due to which the stability issues arise in the grid. So, this research focuses on virtual inertia emulation techniques for grid-forming inverters in islanded microgrids. First of all, a basic droop control strategy for grid forming inverters was designed and implemented in which simple droop equations for voltage and frequency control are used. Large oscillations were observed during switching events in the droop control scheme because of low inertia in the system.To overcome the problem of low inertia, a VSG control was designed and implemented in which incorporation of swing equation parameters ( J and D ) of SG is done to improve the frequency response. Results of VSG control show superior performance than droop control.
In VSG control, the fixed values of the moment of inertia (J) and damping coefficient (D) are considered for frequency response analysis which may not be suitable for different kinds of disturbances that occur at the load end. So, an adaptive VSG control algorithm is designed in which the online monitoring of J and D is done according to the rate of change of angular frequency (dωdt) and angular frequency deviation (∆ω ) observed at the load end. For the transient changes in load, adaptive VSG control exhibits to have lesser frequency deviation and better dynamic response, compared to other schemes. Hence, it is concluded that adaptive VSG control is preferred over other control schemes in the inverter control for future microgrids. The real-time simulation of all control schemes is validated through the TYPHOON HIL-402 device.
For the frequency regulation in an islanded microgrid, the EV is integrated as a flexible load is also presented. A unique EMS is designed to maintain the power balance in an islanded microgrid. At last to check the physical realizability of the designed controller, the PIL validation was also demonstrated for the V-f control scheme.
1900520885001 Anil Kumar Tiwari