Inverter Loss Reduction Method of Air Conditioners With Adjustable DC-Link Voltage Control and Six-Step Operation

This paper proposes a control method for a two stage power conversion system of a residential air conditioner drivetrain to enhance power density and reduce the hardware cost of the converters. In hardware design, the heatsink is determined based on the rated operating point, where the maximum loss occurs. When the motor operates at its rated operating point, the converter loss can be minimized using six-step operation. Compared to the existing six-step operation methods to reduce switching device losses, the proposed control method utilizes the DC-link voltage and the phase angle of the voltage vector as 2 degrees of freedom for control, which enables independent control of the dq-axis current, thus enabling optimal operation such as maximum torque per ampere. However, in the low-speed operation region, where efficiency is critical for the energy efficiency grade, linear modulation shou…