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CN-121983975-A - Seamless fault ride-through method and system for internal potential autonomous synchronous network-structured converter

CN121983975ACN 121983975 ACN121983975 ACN 121983975ACN-121983975-A

Abstract

The invention discloses a seamless fault ride-through method and a system for a network-structured converter with autonomous synchronous internal potential, wherein the method comprises the steps of generating an independent three-phase reference potential instruction by constant voltage amplitude and power frequency angular speed reference; the method comprises the steps of calculating active power input by a current transformer to a power grid through a grid-built second-order swing equation, generating a virtual power angle through the grid-built second-order swing equation, forming an internal potential command through voltage amplitude generated by reactive power droop control at the common connection point, synchronously converting a reference potential command and the internal potential command into a rotating coordinate system, calculating a difference value, converting the voltage difference value into d-axis reference current and q-axis reference current of a current inner ring at an external potential ring through a preset fixed virtual impedance matrix, obtaining d-axis current component and q-axis current component and current closed-loop adjustment through current conversion at the common connection point based on the reference current, generating three-phase voltage, and finally forming a pulse width modulation signal to drive a switching device to control the grid-built current transformer. The invention can complete high-quality, safe and flexible seamless fault ride-through.

Inventors

  • WANG JIANHUA
  • Jin Xiaokuan

Assignees

  • 东南大学

Dates

Publication Date
20260505
Application Date
20251226

Claims (10)

  1. 1. The seamless fault ride-through method of the network-structured converter with autonomous synchronization of internal potential is characterized by comprising the following steps: Generating independent three-phase reference potential command by constant voltage amplitude and power frequency angular speed reference ; Active power input to a power grid by a converter calculated at a public connection point PCC is generated into a virtual power angle through a network construction second-order rocking equation Voltage amplitude generated with reactive power droop control at PCC Forming an internal potential command ; Will be And (3) with Synchronous transition to Respectively calculating the rotation coordinate system as a reference And (3) with The difference between the d-axis and q-axis; Transforming the voltage difference value into d-axis and q-axis reference currents of the current inner loop at the potential outer loop through a preset fixed virtual impedance matrix And ; Based on the reference current, the d-axis current component, the q-axis current component and the current are obtained through current transformation at the PCC, and the closed-loop regulation is carried out to generate three-phase voltage And finally forming a pulse width modulation signal to drive the switching device to control the grid-structured converter.
  2. 2. The method of claim 1, wherein the independent three-phase reference potential command is generated from a constant voltage amplitude and a power frequency angular velocity reference The method comprises the following steps: the expression of the amplitude and phase of each phase voltage is: ; Wherein, the 、 、 Respectively is At the potentials of the A phase, the B phase and the C phase, Is that Is used for the constant voltage amplitude of (a), The constant rotation angular velocity is obtained by integrating the power frequency reference angular velocity.
  3. 3. The method of claim 1, wherein the grid-formed converter transmits three-phase active power to the grid And reactive power By three-phase voltage at PCC And three-phase current And (3) calculating in real time to obtain: ; Wherein, the 、 、 Respectively three-phase voltages at PCC The voltage values of the A phase, the B phase and the C phase, 、 、 Three-phase currents at PCC respectively Current values in phase a, phase B, and phase C.
  4. 4. The method of claim 1, wherein the active power generates a virtual power angle by a net-structured second-order rocking equation The second-order rocking equation of (2) is: ; Wherein, the In order to be an active power command value, And Virtual management and virtual damping which can be set in a net-structured second-order rocking equation are respectively carried out; reactive power droop control to generate voltage amplitude The sagging control is as follows: ; Wherein, the Is a reactive power command value, and the reactive power command value, For a nominal internal potential magnitude, Is a reactive sag coefficient; Generated internal potential command The expression is: ; Wherein, the 、 、 Respectively is Internal potentials in phase A, phase B, and phase C.
  5. 5. The method according to claim 1, characterized in that the following is carried out And (3) with Synchronous transition to Respectively calculating the rotation coordinate system as a reference And (3) with The difference between d axis and q axis is realized by the following transformation matrix: ; ; Wherein, the 、 Respectively is At the same time The d-axis and q-axis components of the rotational coordinate system as references, 、 Respectively is At the same time The d-axis and q-axis components of the rotational coordinate system are referenced.
  6. 6. The method of claim 1, wherein the specific voltage difference and virtual impedance matrix are transformed to: ; Wherein, the And Respectively a preset virtual resistance and virtual inductance value, Is a preset virtual reactance value. And D-axis and q-axis voltage difference expressions, respectively.
  7. 7. The method of claim 1, wherein the d-axis and q-axis current components are transformed from the current at the PCC based on the reference current and current closed loop regulation to generate a three-phase voltage The method comprises the following steps: generating d-axis and q-axis voltage modulation signals by the following control equation And The method comprises the following steps of: ; Wherein, the And Proportional and integral control parameters of the current regulation respectively, For the value of the inductance of the electrical network, And Respectively the power grid voltages are The d-axis and q-axis components of the rotational coordinate system as references, 、 Respectively the current of the power grid is The d-axis and q-axis components of the rotational coordinate system as references, Is a complex frequency variable in the laplace transform; generating three-phase voltages by transforming matrices : ; Wherein, the 、 、 Respectively is Components in phase a, phase B, phase C.
  8. 8. The utility model provides a network constructed converter seamless fault ride through system of internal potential autonomous synchronization which characterized in that includes: A three-phase reference potential generating unit for generating independent three-phase reference potential instruction from constant voltage amplitude and power frequency angular velocity reference ; An internal potential generating unit for generating a virtual power angle by calculating the active power input to the power grid by the converter at the public connection point PCC through a network-structured second-order rocking equation Voltage amplitude generated with reactive power droop control at PCC Forming an internal potential command ; A difference value calculating unit for calculating the difference value And (3) with Synchronous transition to Respectively calculating the rotation coordinate system as a reference And (3) with The difference between the d-axis and q-axis; A reference current calculation unit for transforming the voltage difference value into d-axis and q-axis reference currents of the current inner loop at the potential outer loop through a preset fixed virtual impedance matrix And ; The basic three-term voltage generation unit is used for generating three-phase voltage by performing current transformation on the reference current and the PCC to obtain d-axis and q-axis current components and performing current closed-loop regulation ; PWM modulation unit for converting three-phase voltage The pulse width modulated signal PWM is formed to drive the switching device to control the grid-formed converter.
  9. 9. An electronic device, comprising: A memory for storing a computer program; A processor for executing the computer program to implement the method of any one of claims 1 to 7.
  10. 10. A computer program product comprising computer programs/instructions which, when executed by a processor, implement the method of any of claims 1 to 7.

Description

Seamless fault ride-through method and system for internal potential autonomous synchronous network-structured converter Technical Field The invention relates to a power electronic grid-connected control technology, in particular to a seamless fault ride-through method and a seamless fault ride-through system for a grid-formed converter with autonomous synchronization of internal potential. Background The network-structured converter is used as a key stabilizing unit of the high-proportion new energy power system at the present stage, and the core task of the network-structured converter comprises the step of simulating the external characteristics of a synchronous generator and automatically establishing and maintaining the voltage and the frequency of a power grid. However, when a serious transient fault such as a symmetrical or asymmetrical voltage amplitude or phase jump occurs in the power grid, the conventional grid-structured control strategy faces serious challenges. The main stream solutions at present have inherent contradictions that one is based on a strategy of voltage source control (such as a classical virtual synchronous machine), in order to maintain voltage support during faults, excessive unbalanced current is injected into fault points, the safety of the converter is endangered, and protection misoperation can be caused, and the other is to switch to a current limited mode during faults by adopting 'network construction-network following' mixed control or introducing a complex positive and negative sequence separation algorithm. Although the method can limit current, the method has the problems of complex mode switching logic, discontinuous transient process, high speed dependence on phase-locked loop and sequence component detection and the like. The inherent delay in sequence component detection (typically 20 ms for one power frequency cycle) can lead to a delay in the initial control response of the fault, causing current surge and oscillation. Disclosure of Invention The invention aims to provide a seamless fault ride-through method for a network-structured converter, which has a simple control structure and is capable of autonomously synchronizing internal potential without complex parameter setting. The technical scheme is that the seamless fault ride-through method of the network-structured converter with autonomous synchronization of internal potential comprises the following steps: Generating independent three-phase reference potential command by constant voltage amplitude and power frequency angular speed reference ; Active power input to a power grid by a converter calculated at a public connection point PCC is generated into a virtual power angle through a network construction second-order rocking equationVoltage amplitude generated with reactive power droop control at PCCForming an internal potential command; Will beAnd (3) withSynchronous transition toRespectively calculating the rotation coordinate system as a referenceAnd (3) withThe difference between the d-axis and q-axis; Transforming the voltage difference value into d-axis and q-axis reference currents of the current inner loop at the potential outer loop through a preset fixed virtual impedance matrix And; Based on the reference current, the d-axis current component, the q-axis current component and the current are obtained through current transformation at the PCC, and the closed-loop regulation is carried out to generate three-phase voltageAnd finally forming a pulse width modulation signal to drive the switching device to control the grid-structured converter. Further, an independent three-phase reference potential command is generated by constant voltage amplitude and power frequency angular speed referenceThe method comprises the following steps: the expression of the amplitude and phase of each phase voltage is: ; Wherein, the 、、Respectively isAt the potentials of the A phase, the B phase and the C phase,Is thatIs used for the constant voltage amplitude of (a),The constant rotation angular velocity is obtained by integrating the power frequency reference angular velocity. Further, three-phase active power transmitted to the power grid by the grid-structured converterAnd reactive powerBy three-phase voltage at PCCAnd three-phase currentAnd (3) calculating in real time to obtain: ; Wherein, the 、、Respectively three-phase voltages at PCCThe voltage values of the A phase, the B phase and the C phase,、、Three-phase currents at PCC respectivelyCurrent values in phase a, phase B, and phase C. Further, the active power generates a virtual power angle through a net-structured second-order rocking equationThe second-order rocking equation of (2) is: ; Wherein, the In order to be an active power command value,AndVirtual management and virtual damping which can be set in a net-structured second-order rocking equation are respectively carried out; reactive power droop control to generate voltage amplitude The sagging con