Integrated higher‐order pulse‐width modulation filter–transformer structure for single‐phase static compensator

A power filter is necessary to connect the output of a power converter to the grid so as to reduce the harmonic distortion introduced in the line current and voltage by the power converter. Many a times, a transformer is also present before the point of common coupling. Magnetic components often constitute a significant part of the overall weight, size and cost of the grid interface scheme. So, a compact inexpensive design is desirable. A higher‐order LCL‐filter and a transformer are increasingly being considered for grid interconnection of the power converter. This study proposes a design method based on a three‐winding transformer, that generates an integrated structure that behaves as an LCL‐filter, with both the filter inductances and the transformer that are merged into a single electromagnetic component. The parameters of the transformer are derived analytically. It is shown that along with a filter capacitor, the transformer parameters provide the filtering action of an LCL‐filter. A single‐phase full‐bridge power converter is operated as a static compensator for performance evaluation of the integrated filter transformer. A resonant integrator‐based single‐phase phase locked loop and stationary frame AC current controller are employed for grid frequency synchronisation and line current control, respectively.