N.V.N. Anusha, Sri. M. Gopichand Naik, D. Deepak Chowdary
Abstract: In modern distribution systems the proliferation of non-linear loads results in a deterioration of the quality of voltage waveforms at the load end. Therefore, power-conditioning equipment is becoming more important for electric utilities and their customers. With the rapid development of semiconductor devices in power and control circuits, a new generation of equipment for power quality, the active power filters, has been developed. Implementation of multilevel inverter for active power filter in High Voltage system eliminates use of bulky and high cost transformer. The control of an active filter comprises two major parts the reference current computation and the current control. In this paper three fundamental methods of generating the reference current (i) PQ theory (ii) PLL Method (iii) Fuzzy Method are presented.In this paper comparison of control strategies using multilevel inverter based shunt active power filter is presented. This paper presents the modeling of cascaded type multi level inverter based active power filter for different control methods are presented. PQ method is used to obtain the fundamental mains by reference current generation. A PLL is used to obtain fundamental mains voltage and used to calculate average load power. A fuzzy controller is used to obtain fundamental mains voltage and to determine the THD. Carrier phase shifted pulse width modulation scheme is implemented to generate switching signals which reduces the individual device switching frequency. This system is modeled in MATLAB / SIMULINK environment. Simulation circuit is analyzed and results are compared for different control methods.
Keywords: Multilevel inverter, Active Power filters APF, Carrier phase shifted-Pulse width modulation, Total harmonic distortion THD Phase locked loop PLL