Comparative analysis of real time reference generation techniques for four-wire shunt active power filters

This paper presents a comparison of three different techniques used for the generation of the current reference signal in shunt active power filters. The three different techniques are evaluated and compared in terms of compensation performance under steady state and transient operating conditions, implementations requirements, and compensation in four wire power distribution systems, with unbalanced single phase nonlinear loads. The three techniques analyzed are the instantaneous reactive power theory (PQ theory), the synchronous reference frame theory (SRF) and peak detection method (PDM). The technical evaluation is done by considering the robustness for the operation with unbalanced and distorted supply voltages, unbalanced load currents, control signals conditioning and processing delays introduced by the implementation with a DSP. The comparison is based on theoretical analysis and simulated results obtained with Matlab. The principal conclusion is that the compensation performance of the different techniques is similar under ideal conditions, but under the presence of unbalanced and voltage distortion, the compensation performance is quite different, and not all the reference methods allows full compensation. The synchronous reference frame algorithm presents the best performance for different operating conditions.