Comparison of control strategies for multilevel inverter based active power filter used in high voltage systems

In this paper comparison of control strategies used for multilevel inverter based shunt active power filter is presented. Recently use of high voltage nonlinear load is considerably increased in industry and elimination of harmonics in HV system has become an important aspect. Implementation of multilevel inverter (MLI) for active power filter (APF) in HV system eliminates use of bulky and high cost transformer. The two methods for reference signal generation are simulated and performance is compared. In case of distorted supply voltage p-q theory gives unsatisfactory results while average power method successfully eliminates harmonics even the supply voltage is distorted. A PLL based unit vector template is used to obtain fundamental mains voltage and used to calculate average load power. Carrier phase shifted pulse width modulation (CPSPWM) scheme is implemented to generate switching signals which reduces the individual device switching frequency. Simulated results prove the effective elimination of harmonics with multilevel inverter in high voltage system.