Using variable-precision feedback to improve operational speed of the current loop in GaN-inverters

Abstract

With the advent of wide band-gap semiconductors like SiC and GaN, the frequency of pulse-width modulation has increased. In modern electric drives, the switching frequency can reach 100 kHz or more. In this case the performance of the drive is limited by the delay in the current feedback measurement. This delay can be changed by using deltasigma modulators. This type of current sensors allows setting the measurement time. However, as the measurement time decreases, the accuracy of the feedback reduces. This paper proposes the algorithm in which the current controller uses variable-precision feedback. When the error between the reference and feedback is large, it uses faster but less accurate current feedback. When the error is small, it uses slower but accurate feedback. Changing the feedback measurement time requires changing the current controller gains. The algorithm was investigated on a virtual servo drive model. To evaluate the performance of the proposed regulator, the results were compared with standard regulators with different settings. It was proved that this approach allows increasing the speed of the current loop without loss in the transient performance. Besides, the algorithm increases the cut-off frequency in comparison with the standard slow and accurate controller.

Keywords

• current loop
• shunt current sensor
• gan
• servo drive
• delta-sigma modulation
• adaptive controller