Method and device for controlling transient energy transfer during DC fault in flexible DC transmission system

Abstract

The present invention belongs to the field of power system protection and control, and discloses a method and device for controlling the timing of transient energy transfer during a DC fault in a flexible DC transmission system. The method comprises: upon receiving a DC fault signal from the flexible DC transmission system, increasing the d-axis current loop proportional coefficient of the sending-end converter to obtain a target d-axis voltage reference value; increasing the AC q-axis current reference value of the sending-end converter to limit the AC q-axis output voltage to obtain a target q-axis voltage reference value; adding DC active damping control when the AC d-axis current of the sending-end converter decays to zero; calculating a target DC active damping limit value based on the target d-axis voltage reference value and the target q-axis voltage reference value; designing the DC active damping value based on fault ride-through requirements; and maintaining the DC control link until the DC fault current decays to zero. The method of the present invention can reduce energy accumulation in the sending-end converter, accelerate the speed of transient energy transfer during faults, and suppress the voltage stress of the capacitors of the sending-end converter submodules.

Claims

1. A method for controlling transient energy transfer during DC faults in a flexible DC transmission system, characterized in that: include: S1: When receiving the DC fault signal of the flexible DC transmission system, increase the sending end converter d The axis current loop PI controller proportional coefficient is obtained d Shaft voltage reference value; S2: When receiving the DC fault signal of the flexible DC transmission system, increase the AC current of the sending end converter q The shaft current reference value limits the AC current of the sending-end converter. q Shaft output voltage, get the target q Shaft voltage reference value; S3: Continue to execute S1-S2 until the sending end converter AC d The shaft current decays to zero; S4: When the sending end converter AC d When the shaft current decays to zero, DC active damping control is added to the control link of the sending-end converter; S5: According to the target d Shaft voltage reference and target q The shaft voltage reference value is used to calculate the target limit value of the DC active damping control link; S6: Taking the target amplitude limit value as the target negative level of the sending-end converter bridge arm, designing a target DC active damping value according to the fault ride-through requirement to obtain a DC active damping output voltage; S7: Continue to execute S4-S6 until the DC fault current decays to zero; When a DC fault signal of the flexible DC transmission system is received, the AC current of the sending-end converter is increased. q The shaft current reference value limits the AC current of the sending-end converter. q Shaft output voltage, get the target q Shaft voltage reference values, including: When receiving a DC fault signal from the flexible DC transmission system, increase the AC current of the sending-end converter. q The shaft current reference value is based on the AC current of the sending end converter. q Shaft current reference value and AC q The difference between the actual values ​​of the shaft current is taken as q The axis current loop PI controller input value is q The shaft current loop PI controller calculates the AC current of the sending-end converter q Shaft output voltage; Limit the AC power supply of the sending-end converter q Shaft output voltage, controls the AC converter at the sending end d The shaft current decays rapidly, according to the target of the sending-end converter d Shaft voltage reference and AC q Shaft output voltage, q The shaft output voltage is limited to obtain the target value of the sending end converter q Shaft voltage reference value.

2. The method according to claim 1, characterized in that When a DC fault signal is received from the flexible DC transmission system, the sending end converter is increased. d The axis current loop PI controller proportional coefficient is obtained d Shaft voltage reference values, including: When a DC fault signal is received from the flexible DC transmission system, the sending end converter is increased. d The proportional coefficient of the shaft current loop PI controller is based on the AC d Shaft current reference value and AC d The difference between the actual values ​​of the shaft current is taken as d The axis current loop PI controller input value is d The shaft current loop PI controller calculates the target of the sending-end converter d Shaft voltage reference value.

3. The method according to claim 1, characterized in that According to the stated goal d Shaft voltage reference and target q The shaft voltage reference value is used to calculate the target limit value of the DC active damping control link, including: According to the stated goal d Shaft voltage reference and target q The shaft voltage reference value is calculated to obtain the sending end converter abc Amplitude of the three-phase AC voltage reference value; According to the amplitude and the bridge arm output voltage range, a target amplitude limit value of the DC active damping control link is calculated.

4. The method according to claim 1, wherein The target amplitude limit value is used as the target negative level of the sending-end converter bridge arm, and the target DC active damping value is designed according to the fault ride-through requirement to obtain the DC active damping output voltage, including: Taking the target amplitude limit value as the target negative level of the sending-end converter bridge arm, the target DC active damping value is designed according to the fault ride-through requirement; The actual value of the DC fault current, the reference value of the DC fault current and the target DC active damping value are used as inputs of the DC active damping link to obtain a DC active damping output voltage.

5. A timing control device for transient energy transfer during DC fault in a flexible DC transmission system, characterized in that: include: comminicate d Axis control module, used to increase the sending end converter when receiving a DC fault signal from the flexible DC transmission system d The axis current loop PI controller proportional coefficient is obtained d Shaft voltage reference value; comminicate q Axis control module, used to increase the AC current of the sending end converter when receiving a DC fault signal of the flexible DC transmission system q The shaft current reference value limits the AC current of the sending-end converter. q Shaft output voltage, get the target q Shaft voltage reference value; AC transient energy transfer control module, used to continuously execute AC d Axis Control Module - AC q Axis control module, until the sending end converter AC d The shaft current decays to zero; The DC damping input control module is used to control the DC damping input when the AC d When the shaft current decays to zero, DC active damping control is added to the control link of the sending-end converter; The DC output limit control module is used to control the d Shaft voltage reference and target q The shaft voltage reference value is used to calculate the target limit value of the DC active damping control link; An active damping output control module is configured to design a target DC active damping value based on the target amplitude limit value as the target negative level of the sending-end converter bridge arm and the fault ride-through requirement to obtain a DC active damping output voltage; A DC transient energy transfer control module is used to continuously execute the DC damping input control module-active damping output control module until the DC fault current decays to zero; When a DC fault signal of the flexible DC transmission system is received, the AC current of the sending-end converter is increased. q The shaft current reference value limits the AC current of the sending-end converter. q Shaft output voltage, get the target q Shaft voltage reference values, including: When receiving a DC fault signal from the flexible DC transmission system, increase the AC current of the sending-end converter. q The shaft current reference value is based on the AC current of the sending end converter. q Shaft current reference value and AC q The difference between the actual values ​​of the shaft current is taken as q The axis current loop PI controller input value is q The shaft current loop PI controller calculates the AC current of the sending-end converter q Shaft output voltage; Limit the AC power supply of the sending-end converter q Shaft output voltage, controls the AC converter at the sending end d The shaft current decays rapidly, according to the target of the sending-end converter d Shaft voltage reference and AC q Shaft output voltage, q The shaft output voltage is limited to obtain the target value of the sending end converter q Shaft voltage reference value.

6. An electronic device, characterized in that: include: one or more processors; a memory for storing one or more programs; When the one or more programs are executed by the one or more processors, the one or more processors implement the method according to any one of claims 1 to 4.

7. A computer-readable storage medium having computer instructions stored thereon, characterized in that: When the instruction is executed by a processor, the steps of the method according to any one of claims 1 to 4 are implemented.

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