Method for damping resonant component of common-mode current of multi-phase power converter
View Patent ↗The present disclosure describes a method and arrangement for damping a resonant component of a common-mode current of a multi-phase power converter comprising an output filter with a virtual ground connection to the power converter. In the method and arrangement, the common-mode current is determined, a feedback signal is formed on the basis of the common-mode current, and the feedback signal is injected into a common mode current reference in order to dampen the resonance frequency component. A delay is added to the feedback signal so that the feedback signal has a sufficient phase margin with respect to a subsequent cycle of the resonance frequency component of the common-mode current.
1. A method for damping a resonant component of a common-mode current of a multi-phase power converter comprising an output filter with a virtual ground connection to the multi-phase power converter, wherein the output filter comprises at least one inductive component and at least one capacitive component that form a resonant circuit along the virtual ground connection, wherein the common-mode current is controlled on a basis of a common-mode current reference, and wherein the method comprises:
determining the common-mode current,
forming, on a basis of the common-mode current, a feedback signal representing a sinusoidal resonance frequency component of the common-mode current, and
injecting the feedback signal into the common-mode current reference to dampen the sinusoidal resonance frequency component,
wherein forming the feedback signal comprises:
filtering the determined common-mode current with a band-pass filter having a pass-band that coincides with a resonance frequency of the resonant circuit in order to determine the sinusoidal resonance frequency component of the common-mode current at the resonance frequency, and
adding a delay to the feedback signal, the delay being such that the determined sinusoidal resonance frequency component has a phase shift of essentially 360° with respect to the common-mode current in order to form a stable control loop.
2. The method according to claim 1 , wherein a value for the delay added to the filtered resonance frequency component is calculated on a basis of at least a switching delay, phase shift characteristics of the output filter, and a delay induced by measurement.
3. The method according to claim 1 , wherein the gain of the feedback signal is determined on a basis of a modulation index of the multi-phase power converter.
4. The method according to claim 1 , wherein the common-mode current is determined from phase currents or measured directly from the virtual ground connection.
5. The method according to claim 1 , wherein the output filter is a LC filter or a LCL filter.
6. The method according to claim 1 , wherein the multi-phase power converter is a grid-connected converter.
7. The method according to claim 1 , wherein the band-pass filter is a second-degree Butterworth filter.
8. An arrangement for damping a resonant component of a common-mode current of a multi-phase power converter comprising an output filter with a virtual ground connection to the multi-phase power converter, wherein the output filter comprises at least one inductive component and at least one capacitive component that form a resonant circuit along the virtual ground connection, wherein the common-mode current is controlled on the basis of a common-mode current reference, wherein the arrangement comprises means configured to carry out a method comprising:
determining the common-mode current;
forming, on a basis of the common-mode current, a feedback signal representing a sinusoidal resonance frequency component of the common-mode current; and
injecting the feedback signal into the common-mode current reference to dampen the sinusoidal resonance frequency component;
wherein forming the feedback signal comprises:
filtering the determined common-mode current with a band-pass filter having a pass-band that coincides with a resonance frequency of the resonant circuit in order to determine the sinusoidal resonance frequency component of the common-mode current at the resonance frequency; and
adding a delay to the feedback signal, the delay being such that the determined sinusoidal resonance frequency component has a phase shift of essentially 360° with respect to the common-mode current in order to form a stable control loop.
9. The method according to claim 2 , wherein a gain of the feedback signal is determined on a basis of a modulation index of the multi-phase power converter.
10. The method according claim 2 , wherein the common-mode current is determined from phase currents or measured directly from the virtual ground connection.
11. The method according claim 3 , wherein the common-mode current is determined from phase currents or measured directly from the virtual ground connection.
12. The method according to claim 2 , wherein the output filter is a LC filter or a LCL filter.
13. The method according to claim 3 , wherein the output filter is a LC filter or a LCL filter.
14. The method according to claim 4 , wherein the output filter is a LC filter or a LCL filter.
15. The method according to claim 2 , wherein the multi-phase power converter is a grid-connected converter.
16. The method according to claim 3 , wherein the multi-phase power converter is a grid-connected converter.
17. The method according to claim 4 , wherein the multi-phase power converter is a grid-connected converter.
18. The method according to claim 2 , wherein the band-pass filter is a second-degree Butterworth filter.
19. The method according to claim 3 , wherein the band-pass filter is a second-degree Butterworth filter.
20. The method according to claim 4 , wherein the band-pass filter is a second-degree Butterworth filter.