Controlling a modular converter in two stages

Patent metadata

Field	Value
Publication number	US-9590530-B2
Application number	US-201514629674-A
Country	US
Kind code	B2
Filing date	Feb 24, 2015
Priority date	Aug 28, 2012
Publication date	Mar 7, 2017
Grant date	Mar 7, 2017

Abstract

A modular converter having a plurality of converter modules for converting an input voltage into an output voltage to be supplied to a load by receiving a control input reference vector, a control input vector and a control input parameter vector; determining a control output reference vector from the control input reference vector, the control input vector and the control input parameter vector in a first control stage; and controlling the converter modules by generating switching signals based on the control output reference vector in a further control stage.

First claim

The invention claimed is:

1. A method for controlling a modular converter, the modular converter including a plurality of converter modules configured for converting an input voltage into an output voltage to be supplied to a load, the method comprising:
receiving a control input reference vector, a control input vector and a control input parameter vector;
determining a control output reference vector from the control input reference vector, the control input vector and the control input parameter vector in a first control stage; and
controlling the converter modules by generating switching signals based on the control output reference vector in a further control stage;
wherein the control output reference vector is determined by:
predicting at least one future state of the modular converter with a prediction model of the modular converter, wherein the prediction model is adapted for calculating the future state of the modular converter based on an actual state of the modular converter, a state of the modular converter having current values and/or voltage values of the modular converter;
enhancing the at least one future state with respect to an objective function by minimizing the objective function with respect to a dynamical evolution in time of the prediction model, wherein the objective function is based on a cost value associated with switching costs of the converter modules, the objective function penalizes differences between the control input reference vector at a time step and a predicted evolution of the control input vector at the time step, and the objective function minimizes a change in evolution of the control output reference vector; and
determining the control output reference vector from the future state.

2. The method of claim 1 , wherein the modular converter controlled by the method is a modular multi-level converter wherein each converter module of the modular multi-level converter includes two power connectors, at least two power semiconductors and a capacitor, wherein the power connectors are short-circuited in a first switching state of the power semiconductors and are connected to the capacitor in a second switching state of the power semiconductors.

3. The method of claim 2 , comprising:
determining a voltage vector from the control output reference vector in a second control stage with a modulator; and
controlling the converter modules by generating switching signals from the voltage vector in a third control stage.

4. The method of claim 3 ,
wherein the control input reference vector is a current reference vector, the control input vector is an actual current vector and the control input parameter vector is an actual voltage vector; and/or
wherein the control output reference vector is a voltage reference vector.

5. The method of claim 4 ,
wherein a sequence of future states is predicted for a plurality of time steps in the future; and
wherein the control output reference vector is determined from a next future state associated with a next time step.

6. The method of claim 5 ,
wherein the prediction model is based on linear equations relating voltages and/or currents at a time step with voltages and/or currents at a next time step.

7. The method of claim 1 , comprising:
determining a voltage vector from the control output reference vector in a second control stage with a modulator; and
controlling the converter modules by generating switching signals from the voltage vector in a third control stage.

8. The method of claim 1 ,
wherein the control input reference vector is a current reference vector, the control input vector is an actual current vector and the control input parameter vector is an actual voltage vector; and/or
wherein the control output reference vector is a voltage reference vector.

9. The method of claim 1 ,
wherein a sequence of future states is predicted for a plurality of time steps in the future; and
wherein the control output reference vector is determined from a next future state associated with a next time step.

10. The method of claim 1 ,
wherein the prediction model is based on linear equations relating voltages and/or currents at a time step with voltages and/or currents at a next time step.

11. The method of claim 1 ,
wherein the prediction model includes a model of the converter modules and/or a model of the load.

12. The method of claim 1 , comprising:
compensating a time delay caused by the determining of the control output reference vector by predicting currents at a next time step using actual voltages and/or currents.

13. The method of claim 1 ,
wherein the objective function is based on a vector norm.

14. The method of claim 1 ,
wherein the objective function is based on a quadratic and/or linear norm.

15. The method of claim 1 , comprising:
controlling the converter modules by generating switching signals from a rounded control output reference vector.

16. The method of claim 1 , comprising:
detecting a converter module with a fault;
short-circuiting the detected converter module; and
removing the short-circuited converter module from the prediction model.

17. A controller for controlling a modular converter, wherein the controller is configured for performing the steps of:
predicting at least one future state of the modular converter with a prediction model of the modular converter, wherein the prediction model is adapted for calculating the future state of the modular converter based on an actual state of the converter, a state of the modular converter having current values and/or voltage values of the modular converter;
enhancing the at least one future state with respect to an objective function by minimizing the objective function with respect to a dynamical evolution in time of the prediction model, wherein the objective is based on a cost value associated with switching costs of converter modules of the modular converter, the objective function penalizes differences between the control input reference vector at a time step and a predicted evolution of the control input vector at the time step, and the objective function minimizes a change in evolution of the control output reference vector; and
determining a control output reference vector from the future state.

18. A modular converter for supplying a load with electrical voltages, the modular converter comprising:
a plurality of converter modules having semiconductor switches and a capacitor;
a first controller according to claim 17 for generating a control output reference vector; and
a further controller for generating switching signals for the converter modules based on the control output reference vector.

19. The modular converter of claim 18 ,
wherein the modular converter is a modular multi-level converter.

Assignees

• Abb Technology Ag
• Abb Schweiz Ag

Inventors

• Geyer Tobias

Classifications

• H02M7/483 Primary

  Converters with outputs that each can have more than two voltages levels · CPC title

• H02H7/1227

  responsive to abnormalities in the output circuit, e.g. short circuit · CPC title

• H02M7/537 Primary

  using semiconductor devices only, e.g. single switched pulse inverters · CPC title

• H02M2007/4835

  Electricity · mapped topic

• H02M2001/0003

  Electricity · mapped topic