Three-phase system and distributed control method thereof

A three-phase system, comprising:

• three-phase circuit, each phase circuit of the three-phase circuit including at least one power conversion cell;
• and
• at least three phase controllers for controlling each phase circuit, respectively,
• wherein each of the phase controllers generates active power signal (XA, XB and XC) reflecting active power of the corresponding phase circuit according to voltage signal reflecting the corresponding phase circuit, respectively;
• each of the phase controllers also receives active power signals reflecting active powers of other two phase circuits, and generate zero-sequence component according to the active power signals (XA, XB and XC) reflecting active power of each phase circuit and phase signals (YA, YB and YC) reflecting current phase or voltage phase of each phase circuits, wherein,
• the zero-sequence component=(XA×YA+XB×YB+XC×YC)×K0, where K0 is a proportional coefficient;
• each of the phase controllers further regulates bridge arm voltage of each power conversion cell in the corresponding phase circuit according to the zero-sequence component correspondingly.

A distributed control method of a three-phase system, wherein the three-phase system comprises:

• three-phase circuits, each phase circuit of the three-phase circuit including at least one power conversion cell;
• and
• at least three phase controllers for controlling each phase circuit, respectively, each of the phase controllers including a communication interface through which the at least three phase controllers are in communications connection with each other;
• wherein the distributed control method comprises:
• when loads at DC sides of the three-phase system are unbalanced,
• generating, by each of the phase controllers, active power signal (XA, XB, XC) reflecting active power of the corresponding phase circuit according to voltage signal of the corresponding phase circuit, respectively;
• receiving, by each of the phase controllers, active power signals reflecting active powers of other two phase circuits, and generating zero-sequence components according to the active power signals (XA, XB and XC) reflecting active powers of each phase circuits and phase signals (YA, YB and YC) reflecting current phases or voltage phases of each phase circuits, wherein,
• the zero-sequence components=(XA×YA+XB×YB+XC×YC)×K0, where K0 is a proportional coefficient;
• regulating, by each of the phase controllers, bridge arm voltages of the respective power conversion cells in the corresponding phase circuit according to the zero-sequence components correspondingly.