Active voltage damping method with negative DC link current feedback in electric and hybrid electric transmissions

Electric and hybrid electric transmissions in traction drive have a limited capacity power source. Since the traction drive operates in the torque source mode, the DC link voltage becomes unstable and goes into oscillatory mode. This leads to the software protection reaction which prevents the traction inverter overvoltage breakdown. The transition boundary to the oscillatory mode is determined by the power and the value of the capacitance installed in the electric transmission DC link. To increase reliability of the traction inverters, large-capacity electrolytic capacitors are replaced with small- capacity film capacitors which makes the system more prone to oscillations. To solve this problem, active damping methods are used allowing changing the engine dynamic characteristics by means of the control system. The software methods with power and torque proportional control are most widely used. Proportional power control is the simplest method in which the traction drive simulates an RL load. The torque proportional control method adjusts the torque reference according to the change in the DC link voltage. This paper proposes a new negative DC link feedback method. In this case, the torque is adjusted dynamically depending on the current consumed by the traction inverter from the electric transmission common DC link. Mathematical modeling methods were used to compare the known and proposed methods of DC link voltage active damping. Mathematical models have been developed in the MATLAB Simulink environment which makes it possible to investigate the damping capacity at various values of the power consumed by the traction inverter. It is shown that the proposed method with negative DC link current feedback demonstrated tuning simplicity. In comparison with proportional power and torque control methods, the proposed option is robust when setting parameters, provides a large damping coefficient over the entire range of traction drive power, and has a short duration of the transient process. The proposed method can be used to suppress DC link voltage oscillations on any type of hybrid electric and all-electric vehicles traction inverters and ensures stable and reliable equipment operation.

1. Sudhoff S.D., Corzine K.A., Glover S.F., Hegner H.J., Robey H.N. DC link stabilized field oriented control of electric propulsion systems // IEEE Transactions on Energy Conversion. 1998. V. 13. N 1. P. 27–33. https://doi.org/10.1109/60.658200

2. Lu D., Wang X., Blaabjerg F. Impedance-based analysis of DC-link voltage dynamics in voltage-source converters // IEEE Transactions on Power Electronics. 2019. V. 34. N 4. P. 3973–3985. https://doi.org/10.1109/TPEL.2018.2856745

3. Zhao S., Chou W. Analytic model of the voltage oscillation in a power conversion system with DC-link capacitors // Proc. of the 2021 IEEE Energy Conversion Congress and Exposition (ECCE). 2021. P. 5554– 5560. https://doi.org/10.1109/ECCE47101.2021.9595713

4. Maheshwari R., Munk-Nielsen S., Henriksen B., Obel P.M., Kragh H. Active damping technique for small DC-link capacitor based drive system // Proc. of the 2010 IEEE International Symposium on Industrial Electronics. 2010. P. 1205–1209. https://doi.org/10.1109/ISIE.2010.5636895

5. Wang D., Lu K., Rasmussen P.O., Mathe L., Feng Y. Analysis of voltage modulation based active damping techniques for small DC-link drive system // Proc. of the 2015 IEEE Energy Conversion Congress and Exposition (ECCE). 2015. P. 2927–2934. https://doi.org/10.1109/ECCE.2015.7310070

6. Zhang Z., Guo H., Liu Y. DC-link voltage constraint strategy for DC power supply film-capacitor drive system based on improved modelpredictive control // IEEE Transactions on Industrial Electronics. 2022. V. 69. N 10. P. 9849–9859. https://doi.org/10.1109/TIE.2022.3150105

7. Khan M.F., Li W., Gao Q. An effective control strategy based on DC-link voltage regulation for an electrolytic capacitor-less IPMSM drive // Proc. of the 21st International Conference on Electrical Machines and Systems (ICEMS). 2018. P. 1246–1251. https://doi.org/10.23919/ICEMS.2018.8549378

8. Céspedes M., Beechner T., Xing L., Sun J. Stabilization of constant-power loads by passive impedance damping // Proc. of the 2010 Twenty-Fifth Annual IEEE Applied Power Electronics Conference and Exposition (APEC). 2010. P. 2174–2180. https://doi.org/10.1109/APEC.2010.5433538

9. Liu J., Zhang Y., Shen W. Suppression of DC-link voltage oscillation method for capacitorless control based on active damping technique // Proc. of the IEEE 9th International Power Electronics and Motion Control Conference (IPEMC2020-ECCE Asia). 2020. P. 3123–3127. https://doi.org/10.1109/IPEMC-ECCEAsia48364.2020.9368217

10. Merai M., Naouar M.W., Slama-Belkhodja I., Monmasson E. An adaptive PI controller design for DC-link voltage control of single-phase grid-connected converters // IEEE Transactions on Industrial Electronics. 2019. V. 66. N 8. P. 6241–6249. https://doi.org/10.1109/TIE.2018.2871796

11. Mora A., Cárdenas R., Urrutia M., Espinoza M., Díaz M. A vector control strategy to eliminate active power oscillations in four-leg grid-connected converters under unbalanced voltages // IEEE Journal of Emerging and Selected Topics in Power Electronics. 2020. V. 8. N 2. P. 1728–1738. https://doi.org/10.1109/JESTPE.2019.2921536

12. Ferdous M.J., Salma U., Kabir S., Sharif S.E. Mitigating the voltage fluctuation of dc capacitor and coupling point using capacitor current control method in DFIG system // Proc. of the 2018 International Conference on Innovation in Engineering and Technology (ICIET). 2018. P. 1–6. https://doi.org/10.1109/CIET.2018.8660879

13. Lee W., Sul S. DC-link voltage stabilization for reduced DC-link capacitor inverter // IEEE Transactions on Industry Applications. 2014. V. 50. N 1. P. 404–414. https://doi.org/10.1109/TIA.2013.2268733

14. Sun W., Ge X., Hu X. A DC-link oscillation suppression strategy in metro traction drive system based on virtural damping resitor // Proc. of the 15 th IEEE Conference on Industrial Electronics and Applications (ICIEA). 2020. P. 1395–1400. https://doi.org/10.1109/ICIEA48937.2020.9248355

15. Zhao N., Wang G., Zhang R., Li B., Bai Y., Xu D. Inductor current feedback active damping method for reduced DC-link capacitance IPMSM drives // IEEE Transactions on Power Electronics. 2019. V. 34. N 5. P. 4558–4568. https://doi.org/10.1109/TPEL.2018.2864247

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