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This paper proposed a harmonic suppression scheme that used a DC-DC converter as an active harmonic injector to cancel voltage harmonics on the HVDC bus within a hybrid power generation centre (HPGC). A permanent magnet synchronous generator and a battery are considered to supply power to a common HVDC bus through their dedicated AC-DC and DC-DC converters respectively within the HPGC. We proposed simplified mathematical models of harmonics from the AC-DC and DC-DC converters. Thereafter, an active power sharing scheme between the PMSG and the battery is developed to control the magnitudes of targeted harmonics to be the same. The targeted harmonics on the HVDC bus can thus be cancelled by properly tuning the carrier signal phase angles within AC -DC and DC-DC converters. A closed-loop control scheme has been developed and this scheme is with no extra hardware cost. To demonstrate the effectiveness of the proposed scheme, we selected the first-band harmonic (fc-3f0) as the targeted harmonic component. The harmonic cancellation scheme for this component has been developed and validated using experimental results. It has been demonstrated that the proposed method can achieve over 90% reduction of this specific harmonic component on the HVDC bus within this HPGC using one DC-DC converter.

Harmonics generated from power electronic converters will impose significant power quality challenges to the electric grid onboard future aircraft. In this paper, we propose an innovative modulation scheme that enables using a buck-boost DC-DC converter as a harmonic absorber. To demonstrate the effectiveness of the proposed method, a hybrid power generation system involving a high-speed electrical generator and a high voltage battery is introduced. The electrical generator is connected to a DC bus through an AC-DC converter and the battery to the DC bus with a DC-DC converter. For the studied hybrid power generation system, it is identified that the first carrier frequency side-band harmonic (fc-3f0) from the AC-DC converter is most relevant and is targeted for cancellation. For the control of the DC-DC converter, a new modulation technique, called equal-gate-width (EGW) modulation is proposed. It allows active control of the magnitude and phase angle of some specific harmonic components from a DC-DC converter. By properly tuning the phase angle and amplitude, the controlled harmonics can thus be used to cancel harmonics from other converters on a common DC bus. Without losing generality, the paper focuses on the development of this specific harmonic cancellation scheme and the effectiveness of our proposed methods has been demonstrated using experimental results.

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