Page 54 – Flying Capacitor Multilevel Inverter
Subject: Power Electronics
Level: GATE / PSU / Interview
🔹 1. What is Flying Capacitor Inverter?
Flying Capacitor (FC) Multilevel Inverter uses capacitors instead of clamping diodes to generate intermediate voltage levels.
It is also called Capacitor-Clamped Multilevel Inverter.
🔹 2. Basic 3-Level FC Structure
- 4 switches per phase
- Flying capacitor
- Single DC source
Output Levels: +Vdc/2 0 −Vdc/2
🔹 3. Working Principle
Capacitors are charged to specific voltages and inserted in series with DC source to produce stepped output.
Voltage balancing is achieved by controlling switching sequence.
🔹 4. Number of Capacitors
Number of flying capacitors per phase = (m − 1)(m − 2) / 2
Where m = number of levels Example: For 3-level → (3−1)(3−2)/2 = 1 capacitor🔹 5. Voltage Stress
Switch voltage stress = Vdc / (m − 1)
Same as NPC inverter.🔹 6. Advantages
- No clamping diodes required
- Better redundancy in switching states
- Good for reactive power control
- Reduced voltage stress
🔹 7. Disadvantages
- Large number of capacitors
- Complex voltage balancing
- Higher cost
- Bulky structure
🔹 8. Comparison Insight
- NPC → Many diodes
- CHB → Many isolated DC sources
- FC → Many capacitors
🔥 Exam Important Formulas
✔ Flying Capacitors = (m − 1)(m − 2)/2 ✔ Switch stress = Vdc/(m − 1) ✔ Output levels = m ✔ Complex voltage balancing control
Multilevel Inverter Series – Shaktimatha Learning
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