Converter cell comprising an energy converter in parallel to a clamp inductor
A converter cell includes a first terminal; a second terminal; a plurality of switching elements provided with respective gate units; an energy storage element; an clamp inductor provided to restrict a rate of change of current from the energy storage element to the switching elements; and a first energy converter provided in parallel to the clamp inductor. The first energy converter is provided to power the gate units by utilising energy from the clamp inductor when the converter cell changes state to be in a short circuit state.
1. A modular multilevel converter cell comprising:
a first terminal;
a second terminal;
a plurality of switching elements provided with respective gate units;
an energy storage element;
a clamp inductor in a serial connection with the energy storage element,
wherein the energy storage element is provided in parallel, via said clamp inductor, across a first leg of two switching elements, thereby the clamp inductor is configured to restrict a rate of change of current from the energy storage element to the switching elements; and
a first energy converter in the form of a DC, direct current, to DC converter provided in parallel to the clamp inductor, the first energy converter being configured to power the gate units by utilising energy from the clamp inductor when the converter cell changes state to be in a short circuit state.
2. The converter cell according to claim 1 , the converter cell further comprises a second energy converter, the second energy converter being a DC to DC converter configured to power the gate units using energy from the energy storage element when the first energy converter provides insufficient power for powering the gate units.
3. The converter cell according to claim 1 , wherein each switching element is an integrated gate-commutated thyristor, IGCT.
4. The converter cell according to claim 1 , wherein a component string is provided in parallel with the clamp inductor, the component string comprising a diode and a converter capacitor, wherein the first energy converter is provided in parallel to the converter capacitor.
5. The converter cell according to claim 1 , wherein the converter cell is a four quadrant converter.
6. The converter cell according to claim 1 , wherein the converter cell is a two quadrant converter.
7. A multilevel AC/DC, alternating current/DC, converter comprising a plurality of converter cells according to claim 1 .
8. The converter cell according to claim 2 , wherein the second energy converter is a bidirectional DC to DC converter.
9. The converter cell according to claim 2 , wherein the second energy converter is a buck converter.
10. The converter cell according to claim 2 , wherein each switching element is an integrated gate-commutated thyristor, IGCT.
11. The converter cell according to claim 2 , wherein a component string is provided in parallel with the clamp inductor, the component string comprising a diode and a converter capacitor, wherein the first energy converter is provided in parallel to the converter capacitor.
12. The converter cell according to claim 2 , wherein the converter cell is a four quadrant converter.
13. The converter cell according to claim 3 , wherein a component string is provided in parallel with the clamp inductor, the component string comprising a diode and a converter capacitor, wherein the first energy converter is provided in parallel to the converter capacitor.
14. The converter cell according to claim 4 , the converter cell further comprises a second energy converter, the second energy converter being a DC to DC converter configured to power the gate units using energy from the energy storage element when the first energy converter provides insufficient power for powering the gate units, and wherein the second energy converter is provided in parallel to the serial connection of the energy storage element and the clamp inductor.
15. The converter cell according to claim 5 , wherein the converter cell is a full bridge cell.
16. The converter cell according to claim 6 , wherein the converter cell is a half bridge cell.
17. The converter cell according to claim 8 , wherein each switching element is an integrated gate-commutated thyristor, IGCT.
18. The converter cell according to claim 8 , wherein a component string is provided in parallel with the clamp inductor, the component string comprising a diode and a converter capacitor, wherein the first energy converter is provided in parallel to the converter capacitor.
19. The converter cell according to claim 9 , wherein each switching element is an integrated gate-commutated thyristor, IGCT.
20. The converter cell according to claim 9 , wherein a component string is provided in parallel with the clamp inductor, the component string comprising a diode and a converter capacitor, wherein the first energy converter is provided in parallel to the converter capacitor.