This paper proposes a control method for an electrolytic capacitor-less dual inverter for compressors. Single-phase motor drive systems are required to minimize vibrations, maintain a high power factor, and meet the limit for harmonic current emissions. The proposed control method achieves the harmonic reduction of the dq-axis currents, a high power factor, and a low grid current THD under periodic load torque fluctuations. The effectiveness of the proposed method is demonstrated via experimental results, using an open-end winding IPMSM and an electrolytic capacitor-less dual inverter. The proposed method reduced the 100 Hz harmonic components of dq-axis currents up to 98 % under periodic load torque fluctuations compared with an electrolytic capacitor-less single inverter. The results of FFT analysis of the input current show that the power factor and input current THD of the proposed method are equivalent to or superior to those of conventional methods. Therefore, the proposed control method can effectively achieve vibration reduction, a high power factor, and a reduction in the input current THD under periodic load torque fluctuations.
This study proposes a control method for an electrolytic capacitor-less dual-inverter with an aim to reduce the interharmonic currents. Owing to the low-energy buffer of the electrolytic capacitor-less inverter, load fluctuations superimpose harmonic currents on the input current. The proposed control method facilitates output power pulsation control of main inverter, which is a constant frequency regardless of load fluctuations. The experimental results exhibit a reduction in the interharmonic currents at 20 and 80 Hz by 68 and 72 %, respectively. Moreover, the power factor is improved by 11 pt., and total harmonic distortion (THD) of the input current is reduced by 26 pt. under rated load conditions. Therefore, the proposed control method can effectively reduce the interharmonic currents and improve the power factor and THD of the input current.
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