Mathematical Modelling and Stability Analysis of Linear Controller for Parallel Inverters in AC Microgrid

Abstract

Distributed generation (DGs) and Microgrid are getting more important to prolong renewable energy penetration within the current utility system. Renewable resources, for example, PV, wind, and energy storage systems (ESS) are generally associated through voltage-source inverters to shape a Microgrid. In order to evaluate the reliability and the stability of the power system, the connection between different DG units and the interlinked converter needs accurate and simple modelling. This thesis proposes a statespace mathematical modelling technique and stability analysis of three-phase inverterbased microgrids. As the stability analysis of the MG (both system and its control strategies) is a very serious issue because of the inverters' low-inertia nature, therefore a suitable choice of system and controller parameters are considered as the main objective of this work. The adequate parameters' values validated that the system is stable throughout steady-state and transient situations, and oscillatory modes are well damped. The root loci plots are utilized to examine the operation of the microgrid with reference to deviation in parameters of proposed controller Moreover, for the power - sharing purpose, the inverter-based DG units are connected in parallel to regulate both the active and reactive power based on the droop control concept among each other and to the main grid during the grid-tied mode. At last, the real-time simulations studies are performed in MATLAB to evaluate the performance of the proposed controllers. The various case studies including grid-tied and islanded modes as well as the transition between both modes are simulated.