CN-122000899-A - Fault ride-through method and system for grid-structured converter suitable for symmetrical faults

CN122000899ACN 122000899 ACN122000899 ACN 122000899ACN-122000899-A

Abstract

The invention discloses a method and a system for fault ride-through of a grid-connected converter applicable to symmetrical faults, and belongs to the technical field of fault ride-through of grid-connected converters. The invention replaces the function of active synchronization control converter power angle during fault by reactive synchronization, and uses the reactive power demand derived according to the power grid operation rule as the reactive power target of the grid-constructed converter during fault crossing, thereby realizing stable tracking of the reactive power actual value and the reference value during fault. In addition, the invention also provides a strategy for recovering the power angle compensation aiming at the transient overvoltage problem of the designed reactive synchronous control strategy of the grid-connected converter during the fault clearing period, so that the transient overvoltage phenomenon during the recovery period is restrained, and the grid-connected converter can be smoothly transited back to the normal running state.

Inventors

CHEN XIA
TANG ZHAOLONG
LIAO QIANCHAO
HUANG ZHENBIN
YANG HUI
CHEN YIN
WEN JINYU

Assignees

华中科技大学

Dates

Publication Date: 20260508
Application Date: 20260409

Claims (9)

1. The grid-constructed converter fault ride-through method suitable for the symmetrical faults is characterized by comprising the following control operations during faults when the symmetrical faults occur in an external power grid: Obtaining reactive power reference value of current moment grid-constructed converter meeting power grid operation criterion Wherein, the method comprises the steps of, The actual capacity of the networking converter at the current moment is obtained; The port voltage per unit value of the networking converter at the current moment; Switching the grid-formed converter to a reactive power synchronous mode so as to take a reactive power reference value And (3) carrying out reactive power synchronous control on the grid-connected converter for a control target.
2. The method of claim 1, wherein the actual capacity of the grid-connected converter The method comprises the following steps: Wherein, the The current limiting value of the grid-structured current transformer; Is the actual value of the port voltage of the network converter.
3. The method for fault ride-through of a grid-connected converter according to claim 1, wherein the control expression of the reactive power synchronization mode is: Wherein, the The reactive synchronization coefficient is preset; reactive power for the grid-formed converter; the angular speed of the virtual synchronous machine relative to an external power grid in the grid-structured converter is represented by t.
4. The method for fault ride-through of a grid converter according to any one of claims 1 to 3, further comprising switching the grid converter to an active power synchronous mode after the grid symmetry fault is cleared, so as to perform active power synchronous control on the grid converter: inputting the difference value between the active power reference value and the active power actual value of the current time networking converter into a virtual synchronous machine to obtain the virtual angular velocity of the current time networking converter Further calculating to obtain a virtual power angle ; At the virtual power angle Upper superimposed power angle compensation quantity Obtaining the phase angle reference value of the current time networking converter And adjusting the phase angle of the current time networking converter to the phase angle reference value Wherein, the method comprises the steps of, Is a power angle compensation coefficient; The power angle of the grid-structured converter in the normal working state is set; and controlling the power angle of the grid-structured converter after operation adjustment during the fault period when the external power grid has symmetrical faults.
5. The method for fault ride-through of a grid-connected inverter of claim 4, wherein the control expression of the virtual synchronous machine is: Wherein, the Virtual inertia of the virtual synchronous machine; angular velocity of the virtual synchronous machine relative to an external power grid; t represents time; The active power reference value is the active power reference value of the network-structured converter; the actual active power of the grid-constructed converter; rated angular velocity for an external grid system; is the virtual damping of the virtual synchronous machine.
6. A grid-tied converter system comprising a grid-tied converter and a controller for performing the fault ride-through method of any one of claims 1-5.
7. An electronic device comprising a memory and a processor, the memory storing a computer program, the processor executing the computer program to perform the fault ride-through method of any one of claims 1-5.
8. A computer readable storage medium, characterized in that the computer readable storage medium comprises a stored computer program, wherein the computer program, when run by a processor, controls a device in which the storage medium is located to perform the fault ride-through method according to any one of claims 1-5.
9. A computer program product comprising computer programs/instructions which when executed by a processor implement the fault ride-through method of any one of claims 1 to 5.

Description

Fault ride-through method and system for grid-structured converter suitable for symmetrical faults Technical Field The invention belongs to the technical field of network converter fault ride-through, and particularly relates to a network converter fault ride-through method and system suitable for symmetrical faults. Background With the deep transformation of the global energy structure, the installed capacity of new energy power generation represented by wind power and photovoltaic is increasingly improved in the power system. However, the new energy power supply is commonly connected to the power grid by adopting a power electronic converter, so that a modern power system presents the remarkable characteristic of 'high-proportion new energy and high-proportion power electronic equipment'. Under the background, the inertia level of the power system is reduced, the disturbance rejection capability is weakened, and once a short circuit fault occurs, the linkage off-grid accident and even the system breakdown are extremely easy to occur. Aiming at the serious challenge, the Grid-form (Grid-form) converter technology has been developed. Unlike conventional Grid-following (Following) converters, grid-like converters actively simulate the external characteristics of synchronous generators by introducing control algorithms such as virtual synchronous generators (Virtual Synchronous Generator, VSG) and the like, providing necessary frequency and voltage support for weak current networks. When the power grid has symmetrical faults (such as three-phase symmetrical short circuit), the grid-structured converter can maintain the stability of the electric potential in the output of the grid-structured converter, so that the power oscillation and the off-grid risk caused by the voltage dip of the power grid are effectively prevented. However, although the web-formed control is excellent in improving the robustness of the system, it still faces serious control problems in practical engineering applications. Particularly, during the symmetric fault of the power grid, because the amplitude and the phase of the voltage of the power grid are suddenly changed, if the converter continues to execute the conventional constant frequency or constant power control, the output current is extremely easy to overrun or the power angle is unstable. Therefore, how to design a fault ride-through method of a grid-connected transformer suitable for symmetrical faults is a key subject in the current field of grid-connected transformer research. At present, various fault ride-through methods for the grid-connected converters suitable for symmetrical faults have been proposed in academia and industry. For example, there are proposed a self-adaptive fault ride through method for balancing the state of charge of an energy storage system and the grid support requirement by dynamically adjusting the control center of gravity, and there are known methods for fine tuning by using a dynamic internal potential technique in combination with a voltage-reactive sag curve to enhance the voltage stability of the system. In addition, a combined control method combining second-order sliding mode control and voltage self-adaptive regulation is proposed for solving the problem of transient power angle instability, and aims to strictly limit power angle fluctuation during faults and provide stable reactive support. While the above method theoretically provides sufficient reactive power support, the reactive power support provided by the method is not the power grid operation rule when applied to practical engineering, meanwhile, most of the above methods need accurate fault parameter identification or complicated nonlinear controller design, the calculation process of the reactive power reference value is often complicated, and the calculation burden and the implementation difficulty of the system are increased. Disclosure of Invention Aiming at the defects or improvement demands of the prior art, the invention provides a grid-constructed converter fault ride-through method and a grid-constructed converter fault ride-through system suitable for symmetrical faults, which are used for solving the technical problems that the prior art cannot provide enough reactive power which accords with the operation rule of a power grid and has larger calculated amount. In order to achieve the above object, in a first aspect, the present invention provides a fault ride-through method for a grid-connected converter adapted to a symmetrical fault, including: when the external power grid has symmetrical faults, the following control operation during faults is executed: Obtaining reactive power reference value of current moment grid-constructed converter meeting power grid operation criterion Wherein, the method comprises the steps of,The actual capacity of the networking converter at the current moment is obtained; The port voltage per unit value of the networking converter at the