In recent years,there has been an increased emphasis on the quality of power delivered tofactories, commercial establishments, and residences. This is due in part tothe prevalence of harmonic-creating systems in use. Such harmonic generatingequipment contributes to the harmonic burden the system must accommodate. Inaddition, utility switching and fault clearing produce disturbances that affectthe quality of delivered power. One of the biggest problems in power qualityaspects is the harmonics content in the electrical system. Generally, harmonicsmay be divided into two types: voltage harmonics and current harmonics. Currentharmonics is usually generated by harmonics contained in voltage supply anddepends on the type of load such as resistive load, capacitive load, andinductive load.
Both harmonics can be generated by either the source or theload side 1, 2. Harmonicsgenerated by load are caused by nonlinear operation of devices, including powerconverters, arc-furnaces, gas discharge lighting devices, etc. Load harmonicscan cause the overheating of the magnetic cores of transformer and motors. Onthe other hand, source harmonics are mainly generated by power supply withnon-sinusoidal voltage waveform.
Voltage and current source harmonics implypower losses, electromagnetic interference and pulsating torque in AC motordrives 3. Much of the equipment in usetoday is susceptible to damage or service interruption during poorpower-quality events. Everyone with a computer has experienced a computershutdown and reboot with a loss of work resulting. Often this is caused by poorpower quality on the power line.
Poor power quality also affects the efficiencyand operation of electric devices and other equipment in factories and offices. IEEE has donesignificant work on the definition, detection, and mitigation of power qualityevents. IEEE Standard 1100 (IEEE 1999) defines power quality as the concept ofpowering and grounding sensitive electronic equipment in a manner suitable forthe equipment. Electrical equipment susceptible to power quality or moreappropriately to lack of power quality would fall within a seemingly boundlessdomain. All electrical devices are prone to failure or malfunction when exposedto one or more power quality problems.
The electrical device might be anelectric motor, a transformer, a generator, a computer, a printer,communication equipment, or a household appliance. All of these devices andothers react adversely to power quality issues, depending on the severity ofproblems 4.
