Model predictive pulse pattern control based on optimizing a sequence of averaged switch positions

Patent metadata

Field	Value
Publication number	US-12119737-B2
Application number	US-202017767793-A
Country	US
Kind code	B2
Filing date	Sep 29, 2020
Priority date	Oct 11, 2019
Publication date	Oct 15, 2024
Grant date	Oct 15, 2024

Abstract

A method for controlling an electrical converter system is provided herein. The method includes determining a switching signal and a reference trajectory of at least one electrical quantity of the electrical converter system over a horizon of future sampling instants; generating a sequence of averaged switch positions from the switching signal over the horizon; determining a sequence of optimized averaged switch positions with optimized averaged switch positions by optimizing a cost function based on the sequence of averaged switch positions; determining an optimized switching signal for the current sampling interval by moving switching transitions in the switching signal, such that the average of the switching signal with the modified switching transitions equals the optimized averaged switch position; and applying at least the next switching transition of the optimized switching signal for the current sampling interval to the electrical converter system.

First claim

The invention claimed is:

1. A method for controlling an electrical converter system, the method comprising:
determining a switching signal and a reference trajectory of at least one electrical quantity of the electrical converter system over a horizon of future sampling instants, wherein the switching signal and the reference trajectory are determined from a table of optimized pulse patterns, and wherein the switching signal comprises switching transitions between output levels of an electrical converter of the electrical converter system and the reference trajectory indicates a desired future trajectory of the at least one electrical quantity of the converter system;
generating a sequence of averaged switch positions from the switching signal over the horizon, wherein the switching signal is divided into sampling intervals, wherein the sequence of averaged switch positions comprises an averaged switch position per sampling interval, and wherein the averaged switch position is determined by averaging the switching signal defined by the switching instants and output levels in the sampling interval;
determining a sequence of optimized averaged switch positions by optimizing a cost function based on the sequence of averaged switch positions, wherein the cost function comprises an error term with a difference of the reference trajectory and a predicted trajectory, wherein the cost function additionally comprises a term with a difference of the averaged switch positions and the optimized averaged switch positions, and wherein the predicted trajectory is determined over the horizon from a model of the converter system, into which a sequence of modified averaged switch positions and measurements of the converter system are input;
determining an optimized switching signal for a current sampling interval by moving switching transitions in the switching signal, such that in the current sampling interval the average of the switching signal with the modified switching transitions equals the optimized averaged switch position; and
applying at least the next switching transition of the optimized switching signal for the current sampling interval to the electrical converter system.

2. The method of claim 1 ,
wherein sampling intervals without switching transitions are discarded from the sequence of averaged switch positions, and wherein the averaged switch positions are solely optimized in the sampling intervals comprising switching transitions.

3. The method of claim 1 ,
wherein the sequence of optimized averaged switch positions is determined by solving a quadratic program into which the averaged switch positions, the reference trajectory, and the predicted trajectory are input.

4. The method of claim 1 ,
wherein the sequence of optimized averaged switch positions is determined by optimizing the cost function subject to constraints; and
wherein the averaged switch positions are constrained, such that the modified switching transitions stay within the respective sampling interval.

5. The method of claim 1 ,
wherein the sequence of optimized averaged switch positions is determined by optimizing the cost function subject to constraints; and
wherein the averaged switch positions are constrained, such that the modified switching transitions stay in the original order.

6. The method of claim 1 ,
wherein the reference trajectory has a converter contribution, which is determined from the optimized pulse patterns;
wherein the reference trajectory has a grid contribution, which is determined from an estimated sinusoidal grid voltage; and
wherein the reference trajectory is the sum of the converter contribution and the grid contribution.

7. The method of claim 1 ,
wherein the converter contribution to the reference trajectory is determined at support points with a different spacing as the controller sampling instants, and values of the reference trajectory at the sampling instants are determined by interpolation.

8. The method of claim 1 ,
wherein the optimized pulse patterns and a converter contribution of the reference trajectory are determined offline and stored in a lookup table.

9. The method of claim 1 ,
wherein the modified switching transitions of the optimized switching signal are determined by solving a linear program with a further cost function, which minimizes the differences of the unmodified switching transitions and the respective modified switching transitions.

10. A computer for controlling an electrical converter system, the computer comprising at least one processor, the at least one processor programmed to:
determine a switching signal and a reference trajectory of at least one electrical quantity of the electrical converter system over a horizon of future sampling instants, wherein the switching signal and the reference trajectory are determined from a table of optimized pulse patterns, and wherein the switching signal comprises switching transitions between output levels of an electrical converter of the electrical converter system and the reference trajectory indicates a desired future trajectory of the at least one electrical quantity of the converter system;
generate a sequence of averaged switch positions from the switching signal over the horizon, wherein the switching signal is divided into sampling intervals, wherein the sequence of averaged switch positions comprises an averaged switch position per sampling interval, and wherein the averaged switch position is determined by averaging the switching signal defined by the switching instants and output levels in the sampling interval;
determine a sequence of optimized averaged switch positions by optimizing a cost function based on the sequence of averaged switch positions, wherein the cost function comprises an error term with a difference of the reference trajectory and a predicted trajectory, wherein the cost function additionally comprises a term with a difference of the averaged switch positions and the optimized averaged switch positions, and wherein the predicted trajectory is determined over the horizon from a model of the converter system, into which a sequence of modified averaged switch positions and measurements of the converter system are input;
determine an optimized switching signal for a current sampling interval by moving switching transitions in the switching signal, such that in the current sampling interval the average of the switching signal with the modified switching transitions equals the optimized averaged switch position; and
apply at least the next switching transition of the optimized switching signal for the current sampling interval to the electrical converter system.

11. A non-transitory computer-readable medium, in which a computer program according to claim 10 is stored.

12. A controller for an electrical converter system, the controller programmed to:
determine a switching signal and a reference trajectory of at least one electrical quantity of an electrical converter system over a horizon of future sampling instants, wherein the switching signal and the reference trajectory are determined from a table of optimized pulse patterns, and wherein the switching signal comprises switching transitions between output levels of an electrical converter of the electrical converter system and the reference trajectory indicates a desired future trajectory of the at least one electrical quantity of the converter system;
generate a sequence of averaged switch positions from the switching signal over the horizon, wherein the switching signal is divided into sampling intervals, wherein the sequence of averaged switch positions comprises an averaged switch position per sampling inter

Assignees

• Abb Schweiz Ag

Inventors

• Geyer Tobias
• Birth Annika

Classifications

• H02M7/525

  with automatic control of output waveform or frequency (H02M7/517 - H02M7/523 take precedence) · CPC title

• H02M7/483

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

• H02M1/0025

  Arrangements for modifying reference values, feedback values or error values in the control loop of a converter · CPC title

• H02M7/53876

  based on synthesising a desired voltage vector via the selection of appropriate fundamental voltage vectors, and corresponding dwelling times · CPC title

• H02M1/0012 Primary

  Control circuits using digital or numerical techniques (in DC/DC converters H02M3/157, H02M3/33515; in DC-AC converters H02M7/53873) · CPC title