Boost Packed E-Cell: A Compact Multilevel Converter for Power Quality Ancillary Services

Abstract

This paper proposes Boost Packed E-Cell (BPEC) as an affordable Compact Multilevel Converter (CMLC) for the power quality ancillary services. The BPEC is a transformerless bidirectional CMLC topology and can generate symmetrical and asymmetrical multilevel voltage waveforms with 5-to-11-level resolution using only three low-voltage dc capacitors and eight power switches. Thanks to the serial expansion of the two dc capacitors, BPEC has two dc-links, which means two voltage sensors are enough to control three dc capacitors. Despite other CMLCs, BPEC does not need a fault detector and inherently generates a symmetrical 5-level or an asymmetrical 7-level voltage waveform in the event of a fault of the middle switches or their gate drivers. As a case study, a single-phase Compact Active Power Filter (CAPF) is designed in this paper based on the BPEC to compensate for harmonics and reactive power caused by unknown non/linear loads, simultaneously. Finite control set predictive control strategy is also adopted based on the switched model of the power system containing the grid, unknown non/linear loads, and the BPEC to address the grid power quality concerns. The experiments performed by a prototype including the BPEC power board, MicroLabBox, OPAL-RT OP8662, and Chroma 61086 verify the merits of the proposed CAPF in practice.