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Small-Signal Average Modeling, Simulation and Carrier-Based Linear Control of a Three-Phase Four-Leg Shunt Active Power Filter

Current harmonics caused by nonlinear loads yield major power quality related problems in the utility. Such harmonics are commonly reduced by employing static compensators known as active power filters (APF). APF topologies are of various types, depending on technical and economical requirements; and their performance is intimately related to the applied control algorithm. In this paper, a new constant-frequency linear control scheme is proposed for a shunt three-phase four-leg APF. The APF is used to compensate the current distortion and the reactive power created by a typical industrial load. The elaboration of the control law is based on a small-signal averaged model of the converter, computed in the (d,q,0) synchronous frame. The control scheme consists of multiple-loops PI controllers that ensure voltage regulation at the DC side of the filter, and current wave shaping at the AC side. The control system is implemented numerically using the Matlab/Simulink tool. The performance of the proposed control approach is finally discussed through the obtained simulation results.