The extensive use of renewable energy sources (RESs) in energy sectors plays a vital role in meeting the present energy demand. The widespread utilization of allocated resources leads to multiple usages of converters for synchronization with the power grid, introducing poor power quality. The integration of distributed energy resources produces uncertainties which are reflected in the distribution system. The major power quality problems such as voltage sag/swell, voltage unbalancing, poor power factor, harmonics distortion (THD), and power transients appear during the transition of micro-grids (MGs). In this research, a single micro-grid is designed with PVs, wind generators, and fuel cells as distributed energy resources (DERs). A nonlinear auto regressive exogenous input neural network (NARX-NN) controller has been investigated in this micro-grid in order to maintain the above power quality issues within the specific standard range (IEEE/IEC standards). The performance of the NARX-NN controller is compared with PID and fuzzy-PID controllers. The single micro-grid is extended to design a three-phase large-scale realistic micro-grid structure to test the feasibility of the proposed controller. The realistic micro-grid is verified through addition of line-impedance, communication delay, demand response, and off-nominal situations. The proposed controller is also validated by simulating different test scenarios using MATLAB/Simulink and TMS320-based processor-in-loop (PIL) for real-time implementation.

Nowadays the increasing complexity and dimensionality of modern power systems have given rise to low frequency electromechanical oscillations (LFOs). These oscillations pose a major threat to the stability of power system and cause unnecessary limitations to its smooth operation. For the fast damping of system and successful mitigation of oscillations, Flexible AC Transmission System (FACTS) devices are utilized. Static Synchronous Compensator (STATCOM) is one such versatile shunt connected FACTS device that controls the bus voltage influencing the power flow and enhancing the transient stability of the system very fast because no moving parts are involved. However the PID controller of STATCOM is a linear controller that cannot respond effectively to non linear power system. Hence taking non linearities into account, the PID controller of STATCOM is tuned dynamically with a very robust and powerful meta heuristic optimization technique called harmony search inspired from improvisation process of jazz musician. It is a relatively recent technique that is considered superior because of its easy execution and reduced modifiable parameters. However it also has some noticeable defects like less convergence speed and premature convergence. To overcome the shortcomings of HS, a Modified Harmony Search (M-HS) is proposed in this paper to obtain much better transient as well as dynamic stability results. To justify and validate the effectiveness of M-HS optimized PID in reducing oscillations it is compared and contrasted with HS optimized PID and conventional PID of STATCOM using MATLAB/SIMULINK environment. Furthermore the THD calculation in each case is carried out. The results depict the efficacy and potential of M-HS techniques over HS and conventional PID controller in damping out oscillations and restoring system stability.