The New Active Output Filter for Variable Speed Constant Frequency Aerospace Applications
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A concept called “Active Output Filter” (AOF) for performing output filtering in switching converter is proposed. The methodology is based on voltage harmonic injection via a combination of H Bridge and minimized LC filter to cancel out the odd harmonics from a 400Hz square wave 3 phase inverter to achieve a pure sinusoidal output with modulation index of 1.27. Investigation reveals that AOF allows a substantial size reduction and gives competitive efficiency, as compared to passive inductor capacitor filter. Moreover, the main square wave inverter has a capability to regulate the output voltage depending on the Load requirements providing a wide range of modulation index. The operation principle of the concept is demonstrated for Variable Speed Constant Frequency (VSCF) high power aircraft application. The exploration lays a foundation for further investigation into the use of AOF concept for other power electronic converter systems.
SubjectActive Output Filter
Size reduction, Three phase
modulation index of 1.27
LOW THD, harmonic voltage injection, self balancing capacitors
Alhuwaishel, Fahad (2015). The New Active Output Filter for Variable Speed Constant Frequency Aerospace Applications. Master's thesis, Texas A & M University. Available electronically from