Mitigating low frequency ripple in multiply micro sources inverter system with waveform control method

DC power systems comprising single-phase DC/AC inverters draw low-frequency AC ripple currents at twice the output frequency from the DC input. Such a 100/120 Hz ripple current may create instability in the DC clean energy system, lowers its efficiency, and shortens the lifetime of the DC source. This paper presents a general waveform control method that can mitigate such a low-frequency ripple current being drawn from the multiply micro sources in micro grid while it delivers AC power to the load regardless of the number of inverters connected in series at the AC side.With the application of waveform control, the double frequency pulsation power can be confined to the AC side (between the capacitors and the AC load), while the average DC output power is supplied by the multiply micro sources. Theoretical analysis and results are provided to explain the operation and showcase the performance of the approach. Results validate that the proposed solution can achieve significant mitigation of the pulsation power as well as high quality output voltage without the need for extra hardware.