An enhanced second carrier harmonic cancellation method for multi-source DC electric power systems

Multi-source DC power systems have been widely used in electric transportations, including more-electric aircraft, electric ship and electric vehicles. These systems normally involve in power electronic converters whose switching actions may cause current fluctuation on DC-bus capacitors. Eliminating certain order harmonics can help the system potentially reduce the volume and weight of the capacitor. In this paper, a simplified model to estimate 2nd carrier harmonic of DC current in two-level converters is proposed. In derived model, magnitude of the harmonic is only determined by the DC-bus current and modulation index of the converter. Meanwhile, the phase angle of it is determined by angle of carrier signals. Based on this model, a new harmonic cancellation method is proposed. The method has high robustness and can work under any fundamental frequency and power sharing ratio. Simulation results are presented in this paper to verify the validation of proposed harmonic model and the enhanced cancellation method.