MODULATION METHOD FOR CONTROLLING AT LEAST TWO PARALLEL-CONNECTED, MULTI-PHASE POWER CONVERTERS

1 . A modulation method for controlling at least two parallel-connected, multi-phase power converters, wherein the method comprises

generating synchronized switching sequences for the power converters on the basis of a common modulation reference, wherein each synchronized switching sequence comprises a first half sequence followed by a second half sequence, and wherein,

for at least one of the power converters, the first half sequence is a rising-edge half sequence and the second half sequence is a falling-edge half sequence, and

for at least one other of the power converters, the first half sequence is a falling-edge half sequence and the second half sequence is a rising-edge half sequence.

2 . A modulation method according to claim 1 , wherein initializations of the synchronized switching sequences of at least two power converters have a first time interval between them, and the method comprises

updating the value of the modulation reference at the start of or at intermediate times of each synchronized switching sequence of each power converter.

3 . A modulation method according to claim 1 , wherein the generating of synchronized switching sequences comprises

running a first periodical counter and a second periodical counter, wherein the period of the first counter and the second counter is the length of the synchronized switching sequence, and the first and second counters have a phase shift between each other, and,

for each power converter,

determining switching instant values on the basis of the common modulation reference

generating the first half sequences on the basis of a comparison between the first counter and the switching instant values, and

generating the second half sequences on the basis of a comparison between the second counter and the switching instant values.

4 . A modulation method according to claim 1 , wherein the method comprises

updating the value of the modulation reference for each half sequence in or at intermediate times within a switching sequence.

5 . An arrangement for controlling at least two parallel-connected, multi-phase power converters, wherein the arrangement comprises

a modulator system for generating switching sequences of the power converters on the basis of a common modulation reference, wherein each synchronized switching sequence comprises a first half sequence followed by a second half sequence, and wherein,

for the synchronized switching sequences of at least one of the power converters, the first half sequence is a rising-edge half sequence and the second half sequence is a falling-edge half sequence, and,

for the synchronized switching sequences of at least one other of the power converters, the first half sequence is a falling-edge half sequence and the second half sequence is a rising-edge half sequence.

6 . An arrangement according to claim 5 , wherein the modulator system is configured to

generate synchronized switching sequences of at least two power converters such that the synchronized switching sequences are initialized at a first time interval, and

update the value of the modulation reference at the start of or at intermediate times of each synchronized switching sequence of each power converter.

7 . An arrangement according to claim 5 , wherein the modulator system comprises

a first periodical counter and a second periodical counter, wherein the period of the first counter and the second counter is the length of the synchronized switching sequence, and the first and second counters have a phase shift between each other, and,

for each power converter,

means for determining switching instant values on the basis of the common modulation reference

means for generating the first half sequences on the basis of a comparison between the first counter and the switching instant values and the second half sequences on the basis of a comparison between the second counter and the switching instant values.

8 . A modulation method according to claim 2 , wherein the generating of synchronized switching sequences comprises

running a first periodical counter and a second periodical counter, wherein the period of the first counter and the second counter is the length of the synchronized switching sequence, and the first and second counters have a phase shift between each other, and,

for each power converter,

determining switching instant values on the basis of the common modulation reference

generating the first half sequences on the basis of a comparison between the first counter and the switching instant values, and

generating the second half sequences on the basis of a comparison between the second counter and the switching instant values.

9 . A modulation method according to claim 2 , wherein the method comprises

updating the value of the modulation reference for each half sequence in or at intermediate times within a switching sequence.

10 . A modulation method according to claim 3 , wherein the method comprises

updating the value of the modulation reference for each half sequence in or at intermediate times within a switching sequence.

11 . An arrangement according to claim 6 , wherein the modulator system comprises

a first periodical counter and a second periodical counter, wherein the period of the first counter and the second counter is the length of the synchronized switching sequence, and the first and second counters have a phase shift between each other, and,

for each power converter,

means for determining switching instant values on the basis of the common modulation reference

means for generating the first half sequences on the basis of a comparison between the first counter and the switching instant values and the second half sequences on the basis of a comparison between the second counter and the switching instant values.