Flexible ac gearbox system (FACTS) technology has been applied in recent years to improve power quality, reduce harmonic distortion, regulate demand, stabilise voltage, and optimise energy consumption. Power flow management, voltage regulation, reactive power compensation, improving transient and steady state voltage stability, reducing power loss, power conditioning, and quality improvement are further uses.

The definition, metrics, and categorization of electric power quality, along with other topics, are the main topics of this thesis. The measurement, examination, and enhancement of the bus voltage to sustain a sinusoidal waveform at the rated voltage and frequency is known as power quality. The primary factors contributing to disruptions and issues with power quality include unforeseen circumstances, the electric utility, the end-user, and the manufacturer. Power quality events may be categorised using the magnitude-duration plot, which divides the voltage magnitude into three areas and the duration of these events into four regions. 

A decrease in the lifetime of appliances and equipment, an increase or decrease in the fundamental voltage component, additional losses, heating, noise, malfunctions and failures of components, controllers, and loads, resonance and ferro resonance, flicker, harmonic instability, and unwanted torques are some of the main negative effects of poor power quality. Guidelines, recommendations, and standards are the three levels of applicability and validity for documents related to power quality control. 

For harmonic analysis, three methods are employed: iterative processes, frequency-domain modelling, and time-domain simulation. Harmonic voltages are produced throughout the power systems by harmonic current propagation. Numerous methods of mitigating power quality issues have been put forth. In distorted networks, reactive power compensation, enhanced voltage regulation, power factor correction, and a decrease in power/energy loss can be achieved through the appropriate placement and sizing of shunt capacitor banks.