Carrier reconstruction method for eliminating DC and low-frequency circulating currents in multi-parallel converters

A carrier reconstruction method for eliminating DC and low-frequency circulating currents in multi-parallel converters, wherein for n parallel converters, the carrier reconstruction is performed by alternately setting complementary initial phase angles of carriers to achieve carrier balance and symmetry within two periods;

• wherein the carrier initial phase angles for the n parallel converters are set as follows:
• a carrier initial phase angle for a first converter is θ1, while taking the first converter as a reference, a carrier phase shift between every two adjacent converters is 2π/n;
• taking a carrier of the first converter as the reference, a carrier phase shift of a second converter is Δθ2=2π/n, a carrier initial phase angle of the second converter is θ2=θ1+2π/n;
• taking the carrier of the first converter as the reference, a carrier phase shift of a k-th converter is Δθk=2π(k−1)/n, a carrier initial phase angle of the k-th converter is θk=θ1+2π(k−1)/n;
• taking the carrier of the first converter as the reference, a carrier phase shift of a n-th converter is Δθn=2π(n−1)/n, a carrier initial phase angle of the n-th converter is θn=θ1+2π(n−1)/n;
• when θ1=0° or π, the k-th converter has the carrier initial phase angle θk, and a corresponding p-th converter has a carrier initial phase angle θp that satisfies θp=2π−θk;
• wherein n is a positive integer greater than 1, and when n is even, the first converter and a (n/2+1)-th converter do not need carrier reconstruction, while the remaining n−2 converters need carrier reconstruction;
• and when n is odd, the first converter does not need carrier reconstruction, while the remaining n−1 converters need carrier reconstruction;
• wherein the carrier reconstruction comprises:
• when the carrier initial phase angle of the k-th converter and the carrier initial phase angle of the p-th converter satisfy θp+θk=2π:
• for the k-th converter, with two-switching-period repetition adopted, wherein the carrier initial phase angle for a first switching period is θk, and selecting carrier initial phase angle for a second switching period is θp, setting the carrier initial phase angles alternately to achieve carrier balance and symmetry within two periods;
• for the p-th converter, with two-switching-period repetition adopted, wherein the carrier initial phase angle for the first switching period is θp, and the carrier initial phase angle for the second switching period is θk, setting the carrier initial phase angles alternately to achieve carrier balance and symmetry within two periods.