Comparative Analysis of Performance of Cascaded Seven Level Inverter Based Hybrid and Shunt Active Filters in Distribution Systems

Active filtering of electric power has now become amateur technology for harmonic and reactive power compensation in two-wire, Seven-wire and four-wire ac power networks with nonlinear loads to improve power quality. Active Filters (AF) can be classified based on converter type and topology. The converter type can be either CSI or VSI bridge structure. The topology can be shunt, series or a combination of both. Voltage fed PWM inverter as AF is lighter, cheaper and expandable to multilevel version to enhance the performance. Cascade multilevel inverters have been developed for electric utility applications. A cascaded multilevel inverter can generate almost sinusoidal waveform voltage while only switching one time per fundamental cycle, dispense with multi-pulse inverters' transformers used in conventional utility interfaces and static VAR compensators and enables direct parallel or series transformer-less connection to medium- and high-voltage power systems. Cascaded inverter is much more efficient and suitable for utility applications than traditional multi-pulse and pulse width modulation (PWM) inverters. The superiority of this inverter as an active filter is presented in this paper. This paper summarizes the features, feasibility, and control schemes of the cascade inverter for utility applications including utility interface of renewable energy, voltage regulation, VAR compensation, and harmonic filtering in power systems. This paper presents the comparative study of performance of cascaded seven level inverter based hybrid and shunt active filters.