Coordinated control method and device for series voltage source converter valve group

A coordinated control device for series voltage source converter valve groups, wherein the series voltage source converter valve groups refer to N voltage source converter valve groups connected in series, N is the total number of voltage source converter valve groups connected in series, the N voltage source converter valve groups can be configured at a DC voltage control end of a DC electrode or configured at active power control end of the DC electrode of a DC power transmission system, characterized in that the device comprising:

• a discrimination unit, an acquisition and distribution unit, a DC voltage control unit and an active power control unit, wherein:
• the discrimination unit is configured for determining whether the end where the series voltage source converter valve groups are located is a DC voltage control end based on the operating status of the DC electrode;
• the acquisition and distribution unit is configured for obtaining a total DC voltage reference value Udcref at the DC voltage control end, a total DC voltage reference value at the active power control end, a total active power reference value Pref, a DC voltage measured value UdV-i at the DC voltage control end, a DC voltage measured value at the active power control end for each voltage source converter valve group based on the operating status of the DC electrode, and allocating the total DC voltage reference value Udcref at the DC voltage control end, a total DC voltage reference value at the active power control end and the total active power reference value Pref according to the total number N of voltage source converter valve groups in series, and obtaining a DC voltage reference value UdVref-i at the DC voltage control end, a DC voltage reference value at the active power control end for said each voltage source converter valve group and the active power reference value PVref-i for said each voltage source converter valve group after evenly allocating the total DC voltage reference value at the active power control end;
• the DC voltage control unit is configured for controlling the DC voltage of said each voltage source converter valve group at the DC voltage control end of the DC electrode based on the DC voltage reference value UdVref-i at the DC voltage control end for said each voltage source converter valve group and the DC voltage measured value UdV-i for said each voltage source converter valve group of the series voltage source converter valve groups at the DC voltage control end of the DC electrode, and realizing the control for the DC voltage of the DC electrode and the DC voltage balance for said each voltage source converter valve group;
• the active power control unit is configured for controlling the active power of said each voltage source converter valve group at based on an active power reference value PVref-i of said each voltage source converter valve group at the active power control end and an active power compensation amount ΔPV-i of the valve group for said each voltage source converter valve group at the active power control end in the series voltage source converter valve groups at the active power control end of the DC electrode, and realizing the control for the active power of the DC electrode and the DC voltage balance for each voltage source converter valve group at the active power control end of the DC electrode;
• the DC voltage control unit comprising the following subunits:
• a calculation subunit of DC voltage reference value of the voltage source converter valve group for DC voltage control, configured for obtaining a total DC voltage reference value Udcref at the end where the series voltage source converter valve groups are located according to a DC voltage control target of the DC electrode, allocating the total DC voltage reference value according to the total number N of voltage source converter valve groups in series by evenly dividing the total DC voltage reference value among the N voltage source converter valve groups, and obtaining a DC voltage reference value UdVref-i of each voltage source converter valve group for the N voltage source converter valve groups in operating after evenly allocating the total DC voltage reference value, where
• U
• dVref
• -
• i
• =
• U
• dcref
• N
• ,
• i∈(1, . . . , N);
• a receiving subunit of the DC voltage measured value of the voltage source converter valve group for DC voltage control, configured for obtaining a DC voltage measured value UdV-i of each voltage source converter valve group for the series voltage source converter valve groups;
• a calculation subunit of DC bias of the voltage source converter valve group for DC voltage control, configured for using ½ of the DC voltage reference value UdVref-i of each voltage source converter valve group for the series voltage source converter valve groups in operating as a bridge arm voltage DC bias of said each voltage source converter valve group;
• a control subunit of the voltage source converter valve group for DC voltage control, configured for calculating a difference between the DC voltage reference value UdVref-i of each voltage source converter valve group and the DC voltage measured value UdV-i of each voltage source converter valve group for the series voltage source converter valve groups in operating, and inputting the difference into a DC voltage control outer loop of said each voltage source converter valve group, so as to perform closed-loop control of a DC voltage of said each voltage source converter valve group,
• the active power control unit including the following subunits:
• a calculation subunit of active power reference value of the voltage source converter valve group for active power control, configured for obtaining a total active power reference value Pref at the active power control end where the series voltage source converter valve groups are located according to an active power control target of the DC electrode, allocating the total active power reference value according to the total number N of voltage source converter valve groups in series by evenly dividing the total active power reference value among the N voltage source converter valve groups, and obtaining an active power reference value PVref-i of each voltage source converter valve group for the voltage source converter valve groups in operating after evenly allocating the total active power reference value, where
• P
• Vref
• -
• i
• =
• P
• ref
• N
• ,
• i∈(1, . . . , N);
• a calculation subunit of the DC voltage reference value of the voltage source converter valve group for active power control, configured for obtaining a total DC voltage reference value at the active power control end where the series voltage source converter valve groups are located, allocating the total DC voltage reference value at the active power control end according to the total number N of voltage source converter valve groups in series by evenly dividing the total DC voltage reference value at the active power control end among the N voltage source converter valve groups, and obtaining a DC voltage reference value at the active power control end of each voltage source converter valve group for the N voltage source converter valve groups in operating after evenly allocating the total DC voltage reference value at the active power control end;
• a receiving subunit of the DC voltage measured value of the voltage source converter valve group for active power control, configured for obtaining a DC voltage measured value at the active power control end of each voltage source converter valve group for the series voltage source converter valve groups in operating;
• a calculation subunit of DC bias of the voltage source converter valve group for active power control, configured for using ½ of the DC voltage reference value at the active power control end of said each voltage source converter valve group for the series voltage source converter valve groups in operating as a bridge arm voltage DC bias of said each voltage source converter valve group at the active power control end;
• a control subunit of the voltage source converter valve group for active power control, configured for obtaining an active power compensation amount ΔPV-i of the valve group which has voltage-equalization effect for said each voltage source converter valve group at the active power control end for the series voltage source converter valve groups in operating, and adding the active power compensation amount ΔPV-i of said each voltage source converter valve group at the active power control end and the active power reference value PVref-i of said each voltage source converter valve group at the active power control end to obtain a value, and inputting the value into an active power control outer loop of the valve group so as to control the active power of said each voltage source converter valve group at the active power control end.