CN-121863391-B - Method and device for controlling network-structured flexible direct current converter station based on coupling virtual impedance

Abstract

The invention discloses a method and a device for controlling a grid-structured flexible direct current converter station based on coupling virtual impedance, wherein the method comprises the steps of obtaining three-phase current and three-phase voltage of an alternating current side of the converter station; the method comprises the steps of obtaining a converter station control voltage according to a three-phase voltage, filtering a dq-axis fundamental frequency component of the three-phase current according to a pre-selection filter to obtain a dq-axis oscillation component, obtaining a dq-axis direct compensation voltage according to the dq-axis oscillation component and a first control coefficient, carrying out decoupling control according to the dq-axis oscillation component, a second control coefficient and a third control coefficient, then carrying out integral control to obtain the dq-axis decoupling compensation voltage, adding the dq-axis direct compensation voltage and the dq-axis decoupling compensation voltage to obtain a dq-axis damping remodelling compensation voltage, and modulating and controlling after the converter station control voltage and the dq-axis damping remodelling compensation voltage are overlapped.

Inventors

• LI YUNFENG
• WANG YIZHI
• SUN YANYING
• ZHANG YUHANG
• LIN JUNJIE
• DU ZHENYU
• ZHOU XIAO
• ZHANG YU

Assignees

• 长沙理工大学
• 中国电力科学研究院有限公司

Dates

Publication Date

20260512

Application Date

20260316

Claims (4)

1. 1. The control method of the grid-structured soft direct current converter station based on the coupling virtual impedance is characterized by comprising the following steps of: The method comprises the steps of obtaining three-phase current and three-phase voltage of an alternating-current side of a converter station, obtaining control voltage of the converter station according to the three-phase voltage, filtering a dq axis fundamental frequency component of the three-phase current according to a pre-selection filter, and obtaining a dq axis oscillation component; The dq axis decoupling compensation voltage is obtained by performing decoupling control according to the dq axis oscillation component, the second control coefficient and the third control coefficient and then performing integral control; Adding the dq-axis direct compensation voltage and the dq-axis decoupling compensation voltage to obtain a dq-axis damping remodeling compensation voltage; obtaining a converter station control voltage from the three-phase voltage includes: The dq axis component of the three-phase voltage is subjected to difference with a reference value and then passes through an integral controller, so that the dq axis control quantity is obtained; adding the dq axis control quantity and a fixed value feedforward to obtain the dq axis converter station control voltage And : ; Wherein, the Is a Laplacian operator; The integral link coefficient; And D-axis components of three-phase voltages respectively And q-axis component of three-phase voltage A kind of electronic device A threshold value; And Respectively is And A kind of electronic device A domain reference value; Is a rated voltage value; Adding the dq-axis direct compensation voltage and the dq-axis decoupling compensation voltage to obtain a dq-axis damping remodeling compensation voltage, including the dq-axis damping remodeling compensation voltage And Expressed as: ; Wherein, K1 is a first control coefficient, K2 is a second control coefficient, K3 is a third control coefficient; And Is the dq-axis oscillation component; The modulating and controlling after superposing the convertor station control voltage and the dq axis damping remodelling compensation voltage comprises the following steps: Superposing the control voltage of the converter station and the dq axis damping remodelling compensation voltage to obtain the virtual potential of the flexible direct current converter station: ; And modulating according to the virtual potential to realize the control of the grid-structured flexible direct current converter station.
2. 2. The method of claim 1, wherein deriving the dq-axis direct compensation voltage from the dq-axis oscillation component and the first control coefficient comprises: The dq-axis oscillation component is set And Multiplying the first control coefficient K1 to obtain dq axis direct compensation voltage And The first control coefficient K1 is a preset direct control coefficient; And Expressed as: 。
3. 3. The method for controlling a grid-formed flexible direct current converter station based on coupling virtual impedance according to claim 2, wherein performing integral control after performing decoupling control according to the dq-axis oscillation component, the second control coefficient and the third control coefficient, obtaining a dq-axis decoupling compensation voltage comprises: Decoupling control is carried out according to the dq axis oscillation component, the second control coefficient K2 and the third control coefficient K3, and the dq axis decoupling compensation voltage is obtained through integral control And The second control coefficient K2 and the third control coefficient K3 are preset decoupling control coefficients; And Expressed as: 。
4. 4. A grid-built soft-direct converter station control device based on a coupled virtual impedance, characterized in that the device is adapted to implement the method of any of claims 1 to 3.

Description

Method and device for controlling network-structured flexible direct current converter station based on coupling virtual impedance Technical Field The invention relates to the field of power electronics, in particular to a method and a device for controlling a grid-structured soft direct current converter station based on coupling virtual impedance. Background In recent years, power systems are forming a trend for high-proportion new energy sources and high-proportion power electronic devices. The current converter commonly used in engineering is usually a grid-following type control framework, and as the grid-following type current converter is accessed into a power grid in a large scale, the local area power grid becomes weak, and the occurrence probability of broadband oscillation is increased due to interaction between the grid-following type current converter and a weak power grid. The grid-structured control converter eliminates the interaction influence between the weak power grid and the phase-locked loop because the traditional phase-locked loop is not needed to realize synchronization, is suitable for application scenes of the weak power grid and the island power grid, but still faces the oscillation problem similar to that of the grid-structured converter. The inner loop control of the network construction control technology mainly comprises a voltage-current double closed loop structure and a voltage-single closed loop structure based on space vectors, wherein the voltage-current double closed loop structure provides effective damping due to the fact that the proportional loop of a current loop PI controller is energy-saving, the oscillation risk is mainly concentrated in a medium-high frequency band (more than 200 Hz), and the impedance characteristic of a low frequency band is good. In contrast, on the one hand, the control object of the voltage single closed loop structure is an alternating voltage which changes relatively slowly, so that the bandwidth of the controller is narrower, the damping is provided to be weaker, and near power frequency oscillation with lower association degree with a control strategy is easy to occur. On the other hand, due to the dynamic switching characteristics of a plurality of sub-modules in each phase of bridge arm, the internal dynamics and circulation suppression of the MMC (modular multilevel converter ) make the MMC more complex than the VSC (voltage source converter, two-level voltage source converter), and due to the delay effect, high-frequency oscillation is unavoidable. Therefore, a new technical solution is needed to solve the technical problem of how to improve the impedance characteristics of the network-structured MMC soft dc converter station in a wide frequency range based on voltage single closed-loop control. Disclosure of Invention The invention provides a method and a device for controlling a network-structured soft direct current converter station based on coupling virtual impedance, which are used for solving the technical problem of how to improve the impedance characteristic of the network-structured MMC soft direct current converter station in a wide frequency range based on voltage single closed-loop control. In order to achieve the above object, the present invention provides a control method of a grid-structured soft direct current converter station based on coupling virtual impedance, comprising: the method comprises the steps of obtaining three-phase current and three-phase voltage of an alternating-current side of a converter station, obtaining control voltage of the converter station according to the three-phase voltage, filtering a dq-axis fundamental frequency component of the three-phase current according to a pre-selection filter, and obtaining a dq-axis oscillation component; The dq axis decoupling compensation voltage is obtained by performing decoupling control according to the dq axis oscillation component, the second control coefficient and the third control coefficient and then performing integral control; And adding the dq-axis direct compensation voltage and the dq-axis decoupling compensation voltage to obtain the dq-axis damping remodelling compensation voltage, and modulating and controlling after superposing the control voltage of the converter station and the dq-axis damping remodelling compensation voltage. Preferably, deriving the converter station control voltage from the three-phase voltage comprises: the dq axis component of the three-phase voltage is differenced with the reference value and then passes through an integral controller to obtain the dq axis control quantity; the dq axis control quantity is added with the fixed value feedforward to obtain the dq axis converter station control voltage And: ; Wherein, the Is a Laplacian operator; The integral link coefficient; And D-axis components of three-phase voltages respectivelyAnd q-axis component of three-phase voltageA kind of electronic deviceA threshol