Drive system and method of operation thereof for reducing DC link current ripple
A system and method for operating a drive system coupleable to one or more DC and AC electrical ports is disclosed. The drive system includes a DC link, at least one DC-DC converter, at least one DC-AC converter, a DC link capacitor, and a control system configured to control operation of one or more of the at least one DC-DC converter and the at least one DC-AC converter relative to one another based on operational parameters thereof. In controlling operation of one or more of the at least one DC-DC converter and the at least one DC-AC converter, the control system controls at least one of a switching frequency of the at least one DC-DC converter, a switching frequency of the at least one DC-AC converter, a DC-DC converter carrier signal phase, a DC-AC converter carrier signal phase, and a duty cycle of the at least one DC-DC converter.
1. A drive system comprising:
a direct current (DC) link;
a DC-DC converter coupled to the DC link;
a DC-AC converter coupled to the DC link;
a DC link capacitor coupled to the DC link between the DC-DC converter and the DC-AC converter susceptible to current ripple; and
a control system configured to control operation of the DC-DC converter and the DC-AC converter relative to one another by controlling a duty cycle of the DC-DC converter and at least one of a switching frequency and carrier signal phase of the DC-AC converter such that current components related to the DC-DC converter and the DC-AC converter cancel each other.
2. The drive system of claim 1 , wherein the control system is configured to control operation of the DC-DC converter and the DC-AC converter relative to one another based on operational parameters of the DC-DC converter and the DC-AC converter in order to reduce current ripple across the DC link capacitor.
3. The drive system of claim 2 , wherein the operational parameters of the DC-DC converter comprise at least one of a number of phases, a duty cycle, and a switching frequency.
4. The drive system of claim 2 , wherein the operational parameters of the DC-AC converter comprise at least one of a modulation method, a modulation index, and a switching frequency.
5. The drive system of claim 1 , wherein the control system is configured to control a switching frequency of the DC-DC converter based on a number of phases of the DC-DC converter.
6. The drive system of claim 1 , wherein the control system is configured to control a carrier signal phase of the DC-DC converter or the carrier signal phase of the DC-AC converter based on a duty cycle of the DC-DC converter when the control system is configured to control the carrier signal phase of the DC-DC converter or the carrier signal phase of the DC-AC converter, respectively.
7. The drive system of claim 1 , wherein the control system is configured to control a carrier signal phase of the DC-DC converter or the carrier signal phase of the DC-AC converter based on an interval of a current cycle of one or more AC electrical ports coupled to the DC-AC converter when the control system is configured to control the carrier signal phase of the DC-DC converter or the carrier signal phase of the DC-AC converter, respectively.
8. The drive system of claim 7 , wherein the current cycle comprises six, sixty-degree sectors defined by a difference between a voltage angle and a modulator phase angle.
9. The drive system of claim 8 , wherein the carrier signal phase of the DC-DC converter or the DC-AC converter is shifted by πrad for first, third, and fifth sectors of the current cycle and is shifted by 0 rad for second, fourth, and sixth sectors of the current cycle.
10. The drive system of claim 8 , wherein the carrier signal phase of the DC-DC converter or the DC-AC converter is shifted by π/2 rad for first, third, and fifth sectors of the current cycle and is shifted by 0 rad for second, fourth, and sixth sectors of the current cycle.
11. The drive system of claim 8 , wherein the carrier signal phase of the DC-DC converter or the DC-AC converter is shifted by π/2 rad for second, fourth, and sixth sector of the current cycle and is shifted by 0 rad for first, third, and fifth sectors of the current cycle.
12. The drive system of claim 8 , wherein the carrier signal phase of the DC-DC converter or the DC-AC converter is shifted by π/3 rad for first, third, and fifth sectors of the current cycle and is shifted by 0 rad for second, fourth, and sixth sectors of the current cycle.
13. The drive system of claim 8 , wherein the carrier signal phase of the DC-DC converter or the DC-AC converter is shifted by π/3 rad for second, fourth, and sixth sector of the current cycle and is shifted by 0 rad for first, third, and fifth sectors of the current cycle.
14. The drive system of claim 1 , wherein the control system is configured to control a carrier signal phase of the DC-DC converter based on a power factor of one or more AC electrical ports coupled to the DC-AC converter.
15. The drive system of claim 14 , wherein the control system is configured to implement a leading phase shift when the power factor is leading and a lagging phase shift when the power factor is lagging.
16. A method of operating a drive system, the drive system including a DC link capacitor susceptible to current ripple coupled between a DC-DC converter and a DC-AC converter, the method comprising:
controlling operation of the DC-DC converter and the DC-AC converter relative to one another by controlling a duty cycle of the DC-DC converter and at least one of a switching frequency and carrier signal phase of the DC-AC converter such that current components related to the DC-DC converter and the DC-AC converter cancel each other.
17. The method of claim 16 , further comprising controlling operation of the DC-DC converter and the DC-AC converter relative to one another based on operational parameters of the DC-DC converter and the DC-AC converter in order to reduce current ripple across the DC link capacitor.
18. The method of claim 17 , wherein the operational parameters of the DC-DC converter comprise at least one of a number of phases, a duty cycle, and a switching frequency.
19. The method of claim 17 , wherein the operational parameters of the DC-AC converter comprise at least one of a modulation method, a modulation index, and a switching frequency.
20. The method of claim 16 , further comprising controlling a switching frequency of the DC-DC converter based on a number of phases of the DC-DC converter.
21. The method of claim 16 , further comprising controlling a carrier signal phase of the DC-DC converter or the carrier signal phase of the DC-AC converter based on a duty cycle of the DC-DC converter when controlling the carrier signal phase of the DC-DC converter or the carrier signal phase of the DC-AC, respectively.
22. The method of claim 16 , further comprising controlling a carrier signal phase of the DC-DC converter or the carrier signal phase of the DC-AC converter based on an interval of a current cycle of one or more AC electrical ports coupled to the DC-AC converter when controlling the carrier signal phase of the DC-DC converter or the carrier signal phase of the DC-AC, respectively.
23. The method of claim 22 , wherein the current cycle comprises six, sixty-degree sectors defined by a difference between a voltage angle and a modulator phase angle.
24. The method of claim 23 , wherein the carrier signal phase of the DC-DC converter or the DC-AC converter is shifted by π rad for first, third, and fifth sectors of the current cycle and is shifted by 0 rad for second, fourth, and sixth sectors of the current cycle.
25. The method of claim 23 , wherein the carrier signal phase of the DC-DC converter or the DC-AC converter is shifted by π/2 rad for first, third, and fifth sectors of the current cycle and is shifted by 0 rad for second, fourth, and sixth sectors of the current cycle.
26. The method of claim 23 , wherein the carrier signal phase of the DC-DC converter or the DC-AC converter is shifted by π/2 rad for second, fourth, and sixth sector of the current cycle and is shifted by 0 rad for first, third, and fifth sectors of the current cycle.
27. The method of claim 23 , wherein the carrier signal phase of the DC-DC converter or the DC-AC converter is shifted by π/3 rad for first, third, and fifth sectors of the current cycle and is shifted by 0 rad for second, fourth, and sixth sectors of the current cycle.
28. The method of claim 23 , wherein the carrier signal phase of the DC-DC converter or the DC-AC converter is shifted by π/3 rad for second, fourth, and sixth sector of the current cycle and is shifted by 0 rad for first, third, and fifth sectors of the current cycle.
29. The method of claim 16 , further comprising controlling a carrier signal phase of the DC-DC converter based on a power factor of one or more AC electrical ports coupled to the DC-AC converter.
30. The method of claim 29 , further comprising implementing a leading phase shift when the power factor is leading and a lagging phase shift when the power factor is lagging.