Control method and apparatus for common-mode modulated wave of single-phase five-level inverter

A control apparatus for a single-phase five-level converter, wherein the apparatus comprises:

• a control unit, configured to obtain a first-phase initial modulated wave of the single-phase five-level converter and a second-phase initial modulated wave of the single-phase five-level converter, wherein both the first-phase initial modulated wave and the second-phase initial modulated wave are sine waves, and a sum of an amplitude of the first-phase initial modulated wave at any moment and an amplitude of the second-phase initial modulated wave at the moment is zero;
• a modulated wave obtaining unit, configured to obtain a first-level modulated wave output by the single-phase five-level converter, a second-level modulated wave output by the single-phase five-level converter, a third-level modulated wave output by the single-phase five-level converter, a fourth-level modulated wave output by the single-phase five-level converter, and a fifth-level modulated wave output by the single-phase five-level converter, wherein a first level is a positive bus level on a direct-current side, a second level is a level between a zero level and the positive bus level on the direct-current side, a third level is the zero level, a fourth level is a level between a negative bus level on the direct-current side and the zero level, and a fifth level is the negative bus level on the direct-current side;
• a common-mode modulated wave calculation unit, configured to calculate, based on the first-level modulated wave, the second-level modulated wave, the third-level modulated wave, the fourth-level modulated wave, the fifth-level modulated wave, the first-phase initial modulated wave, and the second-phase initial modulated wave, to obtain a common-mode modulated wave of the single-phase five-level converter;
• and
• a pulse-width modulated wave calculation unit, configured to calculate, based on the first-phase initial modulated wave, the second-phase initial modulated wave, and the common-mode modulated wave, to obtain a pulse-width modulated wave of the single-phase five-level converter, including adding the first-phase initial modulated wave and the common-mode modulated wave, to obtain a sixth modulated wave, wherein the pulse-width modulated wave comprises the sixth modulation wave and a seventh modulation wave.

A photovoltaic system, comprising:

• a photovoltaic panel;
• a single-phase five-level converter coupled to the photovoltaic panel for energy conversion between a direct-current and an alternating-current;
• a control apparatus coupled to the single-phase five-level converter to control the single-phase five-level converter, wherein the control apparatus comprises:
• a control unit, configured to obtain a first-phase initial modulated wave of the single-phase five-level converter and a second-phase initial modulated wave of the single-phase five-level converter, wherein both the first-phase initial modulated wave and the second-phase initial modulated wave are sine waves, and a sum of an amplitude of the first-phase initial modulated wave at any moment and an amplitude of the second-phase initial modulated wave at the moment is zero;
• a modulated wave obtaining unit, configured to obtain a first-level modulated wave output by the single-phase five-level converter, a second-level modulated wave output by the single-phase five-level converter, a third-level modulated wave output by the single-phase five-level converter, a fourth-level modulated wave output by the single-phase five-level converter, and a fifth-level modulated wave output by the single-phase five-level converter, wherein a first level is a positive bus level on a direct-current side, a second level is a level between a zero level and the positive bus level on the direct-current side, a third level is the zero level, a fourth level is a level between a negative bus level on the direct-current side and the zero level, and a fifth level is the negative bus level on the direct-current side;
• a common-mode modulated wave calculation unit, configured to calculate, based on the first-level modulated wave, the second-level modulated wave, the third-level modulated wave, the fourth-level modulated wave, the fifth-level modulated wave, the first-phase initial modulated wave, and the second-phase initial modulated wave, to obtain a common-mode modulated wave of the single-phase five-level converter;
• and
• a pulse-width modulated wave calculation unit, configured to calculate, based on the first-phase initial modulated wave, the second-phase initial modulated wave, and the common-mode modulated wave, to obtain a pulse-width modulated wave of the single-phase five-level converter, wherein the pulse-width modulated wave comprises a sixth modulation wave and a seventh modulation wave.