Topology Derivation and Mission Profile Based Modeling of Bridgeless PFC Converters

Active power factor correction (PFC) converters are typically used as the
front-end in the power electronic equipment to avoid the distorted AC input
current, which may cause noises, overheat, component malfunctions, etc. The
commonly used single-phase PFC converter consists of a diode bridge and
a DC-DC converter cell. However, there are always two conducting diodes
in the diode bridge that results in considerable conduction losses. Therefore,
in order to minimize the conduction losses, PFC converters without the
diode bridges, namely the bridgeless PFC converters, are gaining popularity
in recent decades.
Numerous bridgeless PFC topologies with different configurations targeting
on various power levels and applications are proposed to replace their
conventional topology counterparts. However, only several references cover
the topic that why this bridgeless configuration can work and how bridgeless
topologies can be derived. Thus, the first contribution of this thesis is to
demonstrate the bridgeless topology derivation methods, which essentially
arranges two converter cells in the input-parallel output-parallel (IPOP) and
input-parallel output-series (IPOS) to obtain the topologies. This approach
not only enables the systematical derivations of the dual-converter cell-based
bridgeless topologies, but also offer the bridgeless topology categories according
to the IPOP and IPOS cell configurations. Moreover, four possible research
aspects are given among this topology topic. As an example, the dualcell
bridgeless topology simplification guidelines are presented to derive the
same converter cell-based bridgeless family and explain why some of the
family members have simpler structures. Besides, by comparing the topologies,
the converter performance differences between the simplified bridgeless
topologies and their original IPOP and IPOS topologies are summarized.
On the other hand, given that various bridgeless topologies are available,
the second major goal of this thesis is to conduct a comparative study based
on modeling and a consistent design procedure. Moreover, for the sake of
simplicity and consistency, components from the same product series are
considered in the database. Besides, this design procedure selects the key
components according to the calculated junction/hot-spot temperatures or the winding factor for the inductor cores, which are derived by the iteration loop based on the built component models. The obtained topology benchmarking results are in terms of volume, cost, and power loss. Case study 1 demonstrates how to build this design procedure step by step and case study 2 shows how to use the benchmarking results with a specific mission profile to estimate the bridgeless topology material cost payback period compared with the conventional topology. Moreover, based on the benchmarking results in case study 2, the IPOS boost topology with high efficiency and the unique DC split output structure is chosen for further study, along with the conventional boost topology. Combining the base transceiver station (BTS) load mission profile, a simplified mixed conduction mode (SMCM) control for the IPOS boost topology
is proposed to mainly improve the power factor (PF) and input current total
harmonic distortion (THDi) in the light loads. Furthermore, the power loss
model results also show the slightly increased efficiency in light loads. The
control effectiveness and the improved performance are verified by the experiment test. Furthermore, given the typical BTS mission profiles in a rural
area, the state-of-the-art mission profile-based reliability analysis method is
employed. Then, the accumulated failure of the IPOS boost PFC converter
under the average current (AVC) control and the SMCM control, along with
the conventional boost PFC converter under the AVC control are estimated.
The analysis results indicate that given 20 years of operation, the SMCM controlled IPOS boost PFC converter has the accumulated failure 0.24 %, mildly
lower than the AVC controlled IPOS boost PFC converter (0.27%) and considerably lower than the AVC controlled conventional boost PFC converter
(2.06%). Hence, the SMCM controlled IPOS boost PFC converter is a promising
candidate for telecom BTS in the rural area.
The research outcomes are verified by simulations and experiments. The
contributions have been summarized in three journal papers and three conference papers.

Funding: CSC Scholarship (China)