Comparison of series hybrid active power filters based on experimental tests

Current harmonics are the one of the problems associated with the power networks. They are caused by non-linear loads including e.g. saturated transformers, arc furnaces and equipment including semiconductor switches. Because of current harmonics, voltage harmonics are produced. The presence of voltage harmonics in the power network is harmful, because additional losses are caused and in the worst case malfunctioning of the network components may occur. Because of these harmful effects, national and international standards have been created to limit current harmonics. The current harmonics can be reduced by using current filters, which can be divided into passive power filters, active power filters and hybrid power filters. In this paper, a comparison of three series hybrid active power filters is presented. After a short introduction to the topic the operating principles of the main circuits and control systems of these filters are presented. The rest of the paper presents the experimental tests, where the current filtering performance of each filter is tested. Tests are performed for each filter topology in the same operation conditions using filter prototypes. The performance of the filters is tested in cases where harmonics producing loads are 5 kVA three-phase diode rectifiers with RL- and RC-loads. The current filtering performance of the series hybrid active power filters presented is compared based on the presented test results