Four-quadrant modulation technique to extend modulation index range for multilevel selective harmonic elimination / compensation

1. A four-quadrant modulation method comprising:

determining the phase of a grid, wherein determining the phase of the grid comprises determining phase information of the grid;

determining switching angles O r and O f , wherein (a) O r is a rising switching angle, (b) O f is a falling switching angle, and (c) O r and O f are within the whole four-quadrant [0, 2π];

detecting switching angles O r and O f with undesired states and transforming them into practical states and leaving remaining switching angles O r and O f unchanged; and

after detecting switching angles O r and O f and transforming them, inputting the transformed switching angles O r and O f and the phase information into a logic circuit to generate driving signals.

2. The four-quadrant modulation method according to claim 1 , wherein determining switching angles θ r and θ f comprises determining switching angles θ r and θ f without any limitations on a range of θ r .

3. The four-quadrant modulation method according to claim 2 , wherein determining switching angles θ r and θ f comprises determining switching angles θ r and θ f without any limitations on a range of θ f .

4. The four-quadrant modulation method according to claim 3 , wherein the switching angles θ r and θ f with undesired states are transformed to practical states by assigning new switching angles θ r ′ and θ f ′ , wherein θ r ′=−π+θ r and θ f ′=π+θ r ′.

5. The four-quadrant modulation method according to claim 1 , wherein the method is applied to a DC/AC inverter, an AC to DC rectifier, or a device with an AC/DC/AC topology.

6. The four-quadrant modulation method according to claim 5 , wherein the switching angles θ r and θ f with undesired states are transformed to practical states by assigning new switching angles θ r ′ and θ r ′ , wherein θ r ′=π+θ r and θ f ′=−π+θ r ′.

7. The four-quadrant modulation method according to claim 1 , wherein the method is applied to a neutral point clamped (NPC) topology, a flying capacitor (FLC) topology, a cascaded H-bridge (CHB) topology, a modular multilevel topology, a modular multilevel converter, or a multi-module converter.

8. The four-quadrant modulation method according to claim 7 , wherein the switching angles θ r and θ f with undesired states are transformed to practical states by assigning new switching angles θ r ′ and θ r ′, wherein θ r ′=π+θ f and θ f ′=−π+θ r ′.

9. The four-quadrant modulation method according to claim 1 , wherein the method is applied to a multilevel selective harmonic elimination (SHE), a multilevel selective harmonic elimination and compensation (SHC), a selective harmonic mitigation (SHM), or a selective harmonic optimization (SHO).

10. The four-quadrant modulation method according to claim 9 , wherein the switching angles θ r and θ f with undesired states are transformed to practical states by assigning new switching angles θ r ′ and θ r ′, wherein θ r ′=π+θ f and θ f ′=−π+θ r ′.

11. The four-quadrant modulation method according to claim 1 , wherein determining the phase of the grid comprising using a phase locked loop to determine the phase of the grid.

12. The four-quadrant modulation method according to claim 1 , wherein the switching angles θ r and θ f with undesired states are transformed to practical states by assigning new switching angles θ r ′ and θ f ′, wherein θ r ′=−π+θ r and θ f ′=π+θ r ′.

13. A four-quadrant modulation method, comprising:

providing a 3-cell 7-level cascaded multilevel inverter;

determining a phase of a grid of the inverter, wherein determining the phase of the grid of the inverter comprises determining phase information of the grid;

determining switching angles O r and O f , wherein (a) O r is a rising switching angle, (b) Of is a falling switching angle, and (c) O r and O f are within the whole four-quadrant [0, 2π];

detecting switching angles O r and O f with undesired states and transforming them into practical states and leaving remaining switching angles O r and O f unchanged; and

after detecting switching angles O r and O f and transforming them, inputting the transformed switching angles O r and O f and the phase information into a logic circuit to generate driving signals.

14. The four-quadrant modulation method according to claim 13 , wherein determining switching angles θ r and θ f comprises determining switching angles θ r and θ f without any limitations on a range of θ r and without any limitations on a range of θ f .

15. The four-quadrant modulation method according to claim 13 , wherein the method is applied to a DC/AC inverter, an AC to DC rectifier, or a device with an AC/DC/AC topology.

16. The four-quadrant modulation method according to claim 13 , wherein the method is applied to a neutral point clamped (NPC) topology, a flying capacitor (FLC) topology, a cascaded H-bridge (CHB) topology, a modular multilevel topology, a modular multilevel converter, or a multi-module converter.

17. The four-quadrant modulation method according to claim 13 , wherein the method is applied to a multilevel selective harmonic elimination (SHE), a multilevel selective harmonic elimination and compensation (SHC), a selective harmonic mitigation (SHM), or a selective harmonic optimization (SHO).

18. The four-quadrant modulation method according to claim 13 , wherein determining the phase of the grid comprising using a phase locked loop to determine the phase of the grid.

19. The four-quadrant modulation method according to claim 13 , wherein the switching angles θ r and θ f with undesired states are transformed to practical states by assigning new switching angles θ r ′ and θ f ′, wherein θ r ′=−π+θ f and θ f ′=π+θ r ′.

20. The four-quadrant modulation method according to claim 13 , wherein the inverter comprises six switching states.