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

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.

1. Homann M., Schumacher W. High bandwidth phase voltage and phase current control loop of a permanent magnet synchronous motor based on delta sigma bitstreams. Proc. of the 2016 18th European Conference on Power Electronics and Applications (EPE’16 ECCE Europe), 2016, pp. 1–10. https://doi.org/10.1109/EPE.2016.7695308

2. Hirota A., Saha S., Mun S.-P., Nakaoka M. An advanced simple configuration delta-sigma modulation three-phase inverter implementing space voltage vector approach. Proc. of the 2007 IEEE Power Electronics Specialists Conference, 2007, pp. 453–457. https:// doi.org/10.1109/PESC.2007.4342030

3. Jarzebowicz L. Impact of low switching-to-fundamental frequency ratio on predictive current control of PMSM: A simulation study. Proc. of the 2018 25th International Workshop on Electric Drives: Optimization in Control of Electric Drives (IWED), 2018, pp. 1–5. https://doi.org/10.1109/IWED.2018.8321400

4. Li C., Vankayalapati B., Akin B. Latency compensation of SD-ADC for high performance motor control and diagnosis. Proc. of the IEEE 13th International Symposium on Diagnostics for Electrical Machines, Power Electronics and Drives (SDEMPED), 2021, pp. 289–294. https://doi.org/10.1109/SDEMPED51010.2021.9605522

5. Anuchin D., Surnin D., Lashkevich M. Accuracy analysis of shunt current sensing by means of delta-sigma modulation in electric drives. Proc. of the 2018 17th International Ural Conference on AC Electric Drives (ACED), 2018, pp. 1–5. https://doi.org/10.1109/ACED.2018.8341706

6. Zhuo Y.-C., Hsu C.-J., Qiu Z.-H., Lai Y.-S. Bandwidth boost method of current control for servo motor drives with current observer. Proc. of the 2021 IEEE International Future Energy Electronics Conference (IFEEC), 2021, pp. 1–6. https://doi.org/10.1109/IFEEC53238.2021.9661769

7. Anuchin A. Lashkevich M., Shpak D., Aliamkin D., Zharkov A., Briz F. Current control of ac drives using shunt current sensors and deltasigma modulation. Proc. of the IECON 2018 — 44th Annual Conference of the IEEE Industrial Electronics Society, 2018, pp. 445–449. https://doi.org/10.1109/IECON.2018.8591705

8. Anuchin A., Kozachenko V. Current loop dead-beat control with the digital PI-controller. Proc. of the 2014 16th European Conference on Power Electronics and Applications, 2014, pp. 1–8. https://doi.org/10.1109/EPE.2014.6910795

9. Ohta K., Kanazawal Y., Akatuka H., Hori S., Doki S., Tadano H., Shiozaki K. Variable switching frequency control for efficiency improvement of motor drive system by using GaN three phase inverter. Proc. of the 2020 IEEE International Conference on Industrial Technology (ICIT), 2020, pp. 119–123. https://doi.org/10.1109/ICIT45562.2020.9067266

10. Lu J., Hou R., Di Maso P., Styles J. A GaN/Si hybrid T-Type Threelevel configuration for electric vehicle traction inverter. Proc. of the 2018 IEEE 6th Workshop on Wide Bandgap Power Devices and Applications (WiPDA), 2018, pp. 77–81. https://doi.org/10.1109/WiPDA.2018.8569194

11. Shang S., Yang M., Xu D. Design and research of servo drive system based on GaN power device. Proc. of the 2018 21st International Conference on Electrical Machines and Systems (ICEMS), 2018, pp. 1313–1317. https://doi.org/10.23919/ICEMS.2018.8549260

12. Kurniawan A.W., Firmansyah E., Wijaya F.D. Experiment result of high frequency switching SiC mosfet gate driver. Proc. of the 2022 14th International Conference on Information Technology and Electrical Engineering (ICITEE), 2022, pp. 54–57. https://doi.org/10.1109/ICITEE56407.2022.9954115

13. Spang M., Hofstoetter N. Evaluation of current measurement accuracy for a power module with integrated shunt resistors. Proc. of the PCIM Europe 2017; International Exhibition and Conference for Power Electronics, Intelligent Motion, Renewable Energy and Energy Management, 2017, pp. 1–8.

14. AMC1305x Small High-Precision Reinforced Isolated Delta-Sigma Modulators Datasheet Texas Instruments, 2017.

15. Schreier R. Second and Higher-Order Delta-Sigma Modulators. MEAD, March 2008.