DRIVING OF A PHASE MODULE BRANCH OF A MULTILEVEL CONVERTER

• US 20100060235A1
• Filed: 01/17/2007
• Published: 03/11/2010
• Est. Priority Date: 01/17/2007
• Status: Active Grant

• Current Assignee: Siemens Energy Global GmbH & Co. KG (Siemens AG)
• Original Assignee: Siemens AG
• Inventors: Euler, Ingo, Dorn, Jörg, Lang, Jörg, Würflinger, Klaus, Dommaschk, Mike, Tu, Quoc-Buu
• Granted Patent: US 8,390,259 B2
• Time in Patent Office: Days
• US Class Current: 320/128
• CPC Class Codes: H02M 1/0003 Details of control, feedback or regulation circuits
• CPC Class Codes: H02M 7/483 Converters with outputs that each can have more than two voltages levels
• CPC Class Codes: H02M 7/4835 comprising two or more cells, each including a switchable capacitor, the capacitors having a nominal charge voltage which corresponds to a given fraction of the input voltage, and the capacitors being selectively connected in series to determine the instantaneous output voltage

Abstract

A method for charging and/or discharging energy storage devices is performed in a multilevel converter including at least one phase module branch having a series circuit of submodules each with at least one power semiconductor circuit for connection or disconnection of an energy storage device in a circuit parallel to the power semiconductor circuit and a submodule sensor for detection of an energy storage actual value. An energy change state is obtained and a determination is made as to whether connected energy storage devices in a phase module branch can be charged or discharged. The next energy storage device to be switched in each phase module branch is selected by predetermined logic dependent on an energy change state, through which energy stored in energy storage devices is kept approximately at the same level. A high clock rate is simultaneously avoided for connection and disconnection of the selected energy storage device.

Claims

1-7. -7. (canceled)

8. A method for charging and/or discharging energy storage devices of a multilevel converter including at least one phase module branch with a series circuit of submodules each having at least one power semiconductor circuit for turning on or off an energy storage device connected in parallel with the power semiconductor circuit and a submodule sensor for detecting an energy storage actual value, the method comprising the following steps:

upon obtaining an energy change state, determining if turned-on energy storage devices of a phase module branch can be charged or discharged;

selecting the next energy storage device to be switched in each phase module branch with a predetermined logic in dependence on the energy change state;

forming a sum of all turned-on energy storage actual values to obtain an energy storage summation actual value;

determining a difference between a predetermined phase module branch energy desired value and the energy storage summation actual value to obtain an energy difference value; and

defining a switching instant of the selected energy storage device if a magnitude of the energy difference value or a magnitude of a quantity derived from the energy difference value exceeds a magnitude of a switching threshold value.

9. The method according to claim 8, which further comprises determining the next energy storage device to be switched as that energy storage device having an energy storage actual value being the smallest or largest depending on the energy change state of all the energy storage actual values of the same phase module branch.

10. The method according to claim 8, which further comprises determining the switching threshold value by multiplication of the energy storage actual value of the next energy storage device to be switched by a predetermined factor, and determining the switching instant if the magnitude of the energy difference value is greater than the magnitude of the switching threshold value.

11. The method according to claim 8, which further comprises integrating the energy difference value over time to obtain an energy difference integral value, and defining the switching instant as an instant at which the energy difference integral value exceeds a positive switching threshold value or falls below a negative switching threshold value depending on the energy change state.

12. The method according to claim 8, which further comprises:

determining the energy storage device of a phase module branch having the

largest energy storage actual value to obtain a maximum energy actual value;

determining the energy storage device of a phase module branch having the

smallest energy storage actual value to obtain a minimum energy actual value;

forming a difference between the maximum energy actual value and the minimum energy actual value to form a largest energy deviation actual value;

comparing the largest energy deviation actual value with a largest energy deviation threshold value;

defining an additional switching instant if the largest energy deviation actual value exceeds the largest energy threshold value; and

turning off one energy storage device and turning on another energy storage device at the additional switching instant in dependence on the energy change state.

13. The method according to claim 12, which further comprises:

in the case of an energy change state in which the energy storage devices of a phase module branch can be charged, at the additional switching instant;

turning off the energy storage device having the largest energy storage actual value from among the energy storage devices of a phase module branch, and simultaneously turning on the energy storage device having the smallest energy storage actual value from among the energy storage devices of the same phase module branch.

14. The method according to claim 12, which further comprises:

in the case of an energy change state in which the energy storage devices of a phase module branch can be discharged, at the additional switching instant;

turning off the energy storage device having the smallest energy storage actual value from among the energy storage devices of a phase module branch, and simultaneously turning on the energy storage device having the largest energy storage actual value from among the energy storage devices of the same phase module branch.