Background

Power electronic converters enable power transfer from energy sources to energy loads by reconciling their differences in voltages, currents, frequency of operation while facilitating dc-dc, dc-ac and ac-ac conversion. They form an enabling technology for various applications which include renewable energy integration, long distance high-voltage electric power transmission, electrified transportation systems, industrial motor drives, energy storage systems and so on.

The forming elements of these electronic converters are semiconductor switches (such as MOSFETS, IGBTs, thyristors, etc.) and energy storage elements (such as capacitors and inductors). The switches operate at a switching frequency (fSW ) and connect their associated nodes to different voltage and/or current levels. The energy storage devices act as smoothening elements for the switched voltages and/or currents to meet the source and load performance specifications.

In order to realize power converters that go beyond the ratings of the forming elements, the traditional approach is to connect them in series and/or in parallel. An example application of such power converters is high-voltage dc transmission systems which interconnect two ac systems and require high-voltage high-power dc-ac power conversion.

One primary drawback of current MMLC topologies is that the dc capacitors of the modules have to process single-phase ac power requirements, which results in bulky capacitance requirements that are points of failure for equipment, increases the footprint of the MMLC nodes, and decreases the efficiency of the overall converter system.

Technology Overview

The proposed system is designed to give power electronics engineers new tools to improve upon the current state of the art and to make tradeoff decisions among: power efficiency, lifetime of the system (or maintenance lifecycle), and volumetric footprint of the power system.

The proposed Minimal Capacitor Multi-level Converter (M2C2/CC‑MMLC) approach eliminates this requirement by design thereby enabling ultra-dense high voltage power conversion. While the proposed approach may be ideally suitable for medium to high voltage applications, the module structure can be extrapolated to lower and extremely‑low voltages as well.

Benefits

In addition to requiring fewer capacitors for an equivalent result, the M2C2 topology needs less total capacitance for the same per-unit (p.u.) power conversion. This enables the use of film capacitors as compared to electrolytic capacitors which are typically used in MMLC topology due to the greater capacitance requirements. Therefore, designs which incorporate the novel M2C2 design can be expected to have much longer lifespan since film capacitors have a much longer life than the electrolytic capacitors used in current designs.

Unique module design enables high-density medium to high voltage power conversion.
DC-AC multi-level power converter example requires x600 lesser capacitance. Although the total number of switches have increased by x1.5, the VA rating is similar to state-of-the-art.
Elimination of bulky capacitance requirements enables the use of film capacitors with improved lifetime.
The presented dc-ac multi-level topology is only one of the potential applications of the proposed module.

Applications

These topologies are suitable for applications with distributed dc sources (or loads). Here, the dc module capacitors are replaced by dc sources (or loads). As an example, the dc sources (or loads) may be distributed energy storage batteries connected to the three-phase ac grid. With increased penetration of renewable energy sources to the grid, which are intermittent sources by nature, the need of such storage systems will expand.

Opportunity

Collaboration partners (Major power grid hardware manufacturers, micro‑grid equipment engineers, consumer electronics manufacturers).

Licensees interested in assessing the technology for internal prototyping and demonstration.

OEM manufacturers interested in exclusive or field of use licensing.

Patent applications are not yet published, further detailed information available under confidentiality agreement.

Ultra-Dense Modular Multilevel Power Conversion Architecture

Patents

IP Status

Seeking