The quality of electrical power plays vital role inthe utility systems and industry. The quality of the power tendsto have a direct economic impact on consumers and suppliers.Growing consumer demands lead to power quality issues.Many consumers may experience severe technical andeconomic impacts due to power quality problems such asvoltage sag, swell, harmonics and voltage interruptions. In thispaper the main focus is on UPQC, which is a combination ofseries and shunt active power filters. The series APF alleviatesvoltage based distortions, while shunt APF mitigates currentbased distortions. UPQC alleviates the voltage and currentbased distortions concurrently as well as independently. UPQCimproves power quality by compensating both harmonics andload current which thereby makes source current and loadvoltage sinusoidal at the required voltage level. The modelingof series APF, shunt APF and the UPQC has been carried outusing MATLAB/Simulink.