Power Electronics Converter Topologies
Flying Capacitor (FC)

Multilevel converters have emerged in recent years as a very important alternative in the area of high-power medium-voltage energy control. The need for an increase in the power level of industrial applications is especially important in high power applications such as high power AC motor drives, active power filters, and renewable energies.

The term multilevel refers to the three-level topologies and above. The increase in the number of levels in the converter leads to harmonic distortion. Yet, as the number of levels increases so does the control complexity.

The most common multilevel topologies include the Neutral Point Clamped (NPC) converter (in its 3-Level version), the Active Neutral-Point Clamped (in its 3-Level and Multi-level versions), the T-Type, the Multicell topologies such as the Flying Capacitor (FC), the Stacked Multicell Converter (SMC).

Electrical schema

power_electroonics_converter_topologies_flying_capacitor_(3L)

Example of a 3-level Flying Capacitor

Conversion stage

  • DC/DC mono and bi-directional

  • DC/AC mono and bi-directional

Number of levels

  • Typical: 3 to 4
  • Max: 12

Intellectual Property

Initial patent FR2679715 expired

Notes

  • Natural balancing of flying capacitors
  • Extra balance boosters can be added for transients

Typical application and trends

  • Medium voltage drive up to 4.15kVAC
  • UPS up to 690VAC
  • Solar up to 1500VDC
  • Electric Vehicle
  • SMPS
  • Mobile phone

Advantages

  • DC -DC compatible
  • Minimal number of switches
  • Increased apparent switching frequency

Drawbacks

  • Need flying capacitor

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