Common-mode voltage suppression method and system for quasi-z-source simplified three-level inverter

A common-mode voltage suppression method for a quasi-Z-source simplified three-level inverter, comprising:

• judging a sector where a reference voltage vector is located according to a magnitude and a phase angle of the reference voltage vector;
• selecting two large vectors and two small vectors with low common-mode voltage magnitudes as basic voltage vectors according to the sector where the reference voltage vector is located;
• writing a volt-second balance equation according to the selected basic voltage vectors, and calculating, in combination with an introduced distribution factor of duty cycles of small vectors, initial values of distribution factors of a duty cycle of each basic voltage vector and duty cycles of small vectors;
• designing a neutral-point voltage balance controller so as to obtain a corrected value of the distribution factor of the duty cycles of the small vectors;
• and
• utilizing the corrected value of the distribution factor of the duty cycles of the small vectors and the initial values and combining with a set neutral-point voltage balance control threshold to update the distribution factor of duty cycles of the small vectors so as to update the duty cycle of each basic voltage vector;
• and
• inserting shoot-through states into the small vectors, designing a corresponding switching sequence, converting the switching sequence into a driving signal of a power switch, and controlling an operation of the quasi-Z-source simplified three-level inverter;
• wherein a process of calculating an initial value of a distribution factor of the duty cycles of the small vectors comprises:
• calculating a minimum and maximum values of the distribution factor of the duty cycles of the small vectors according to a degree of modulation, the phase angle of the reference voltage vector and a shoot-through duty cycle;
• and when the reference voltage vector is located in sector 1, the minimum and maximum values of the distribution factor of the duty cycles of the small vectors are respectively:
• φ
• min
• =
• max
• ⁢
• {
• 0
• ,
• d
• ST
• 2
• -
• 2
• ⁢
• m
• ·
• sin
• ⁡
• (
• π
• 3
• +
• θ
• )
• ,
• 1
• -
• 3
• ·
• m
• ·
• sin
• ⁡
• (
• π
• 6
• +
• θ
• )
• 1
• -
• m
• ·
• sin
• ⁡
• (
• π
• 3
• +
• θ
• )
• }
• ⁢
• φ
• max
• =
• min
• ⁢
• {
• 1
• ,
• 1
• -
• d
• ST
• 2
• -
• 2
• ⁢
• m
• ·
• sin
• ⁡
• (
• π
• 3
• +
• θ
• )
• ,
• m
• ·
• sin
• ⁡
• (
• π
• 3
• -
• θ
• )
• 1
• -
• m
• ·
• sin
• ⁡
• (
• π
• 3
• +
• θ
• )
• }
• wherein m, θ, and dST are the degree of modulation, the phase angle of the reference voltage vector and the shoot-through duty cycle, respectively;
• and
• obtaining the initial value of the distribution factor of the duty cycles of the small vectors according to duty cycles of the two large vectors according to an arithmetic mean value of the minimum value and the maximum value of the distribution factor of the duty cycles of small vectors.