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Coordinated fault ride-through method for large-scale offshore wind power transmission via flexible DC

A technology of offshore wind power and flexible direct current, applied in wind power generation, single grid parallel feeding arrangement, etc., can solve the problems of ineffective realization of large-scale offshore wind power coordinated fault ride-through, and achieve coordinated fault ride-through, size reduction, and improved dynamics The effect of recovery properties

Active Publication Date: 2020-08-04
HARBIN INST OF TECH
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0006] The purpose of the present invention is to solve the problem that existing methods cannot effectively realize the coordinated fault ride-through of large-scale offshore wind power through flexible direct current transmission

Method used

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  • Coordinated fault ride-through method for large-scale offshore wind power transmission via flexible DC
  • Coordinated fault ride-through method for large-scale offshore wind power transmission via flexible DC
  • Coordinated fault ride-through method for large-scale offshore wind power transmission via flexible DC

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Experimental program
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Effect test

specific Embodiment approach 1

[0050] Specific implementation mode 1: The coordinated fault ride-through method for large-scale offshore wind power transmission through flexible direct current described in this implementation mode, the method is:

[0051] During the fault period, the sending-end system cooperates with the voltage-active current reduction control of the wind turbine through the segmental step-down control (PVDC) to reduce the step-down depth of the grid-connected point of the wind farm;

[0052] After the fault is cleared, the sending end system realizes the adaptive restoration of the MMC-HVDC DC voltage and the output active power of the wind farm through the adaptive boost control (AVRC) and the voltage-active current rise control of the wind turbine.

[0053] Depend on figure 2 , image 3 , Image 6 shown, t 1 A three-phase short-circuit fault occurs in the power grid at any time, and GSMMC detects the AC voltage V of the GSMMC grid-connected point g drops to its action threshold ...

specific Embodiment approach 2

[0057] Embodiment 2: This embodiment differs from Embodiment 1 in that: the step-down voltage reduction control improves the voltage reduction rate and load shedding efficiency by combining the forced voltage reduction control and the droop control.

[0058] PVDC cooperates with the voltage-active current reduction control (VDACR) of wind turbines to reduce the maximum step-down depth of the wind farm, prevent the frequency instability of the sending end system, and suppress the The DC voltage overshoot improves the safety of the DC system operation, and the V w Reduce ΔV w , to compensate for the adverse effects of system control response delay. . The adaptive voltage boosting scheme (AVRC) cooperates with the voltage-active current rise control (VDACI) of the wind turbine to realize the adaptive recovery of the DC voltage and wind power, improve the dynamic recovery characteristics of the DC voltage, and realize the DC system from the FRT mode to the steady state. The smo...

specific Embodiment approach 3

[0059] Specific implementation mode three: the difference between this implementation mode and specific implementation mode two is: if Figure 7 As shown, the specific process of the forced step-down control is:

[0060] like Figure 8 and 9 As shown, after the step-down control starts, (that is, t 2 time ), regardless of the severity of the fault and the steady-state power level of the wind farm, the grid-connected voltage of the wind farm (WFMMC) immediately decreases by ΔV w , ΔV w called the transient voltage drop, given by Figure 10 It can be seen that ΔV w The expression is:

[0061]

[0062] In the formula, and are the DC voltage thresholds corresponding to the start and exit of step-down control, K FRT is the proportional coefficient of step-down control;

[0063] Proportional coefficient K of step-down control FRT The expression is:

[0064]

[0065] is the grid-connected voltage of the wind farm during normal operation of the system; is the...

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Abstract

The invention discloses a cooperative fault ride-through method for flexible direct-current transmission of large-scale offshore wind power, belongs to the technical field of new energy alternating-current and direct-current grid connection control, and solves the problem that an existing method cannot effectively realize cooperative fault ride-through for the flexible direct-current transmissionof the large-scale offshore wind power. After a power grid has a fault, the wind power can be rapidly reduced, so that a direct-current voltage is guaranteed not to exceed a limit; the phenomena of synchronization instability and direct-current overvoltage of wind power plants are eliminated, so that the running safety of a direct-current system is improved; the active power at the two ends of thedirect-current system can be effectively coordinated after the fault is cleared, so that the dynamic recovery characteristic of the direct-current voltage is improved; and the cooperative fault ride-through for the flexible direct-current transmission of the large-scale offshore wind power is effectively realized. In addition, the size of an MMC-HVDC submodule capacitor is reduced to 80% of the original size, so that the equipment investment is further reduced, and the economic benefit is improved. The method can be applied to the technical field of the new energy alternating-current and direct-current grid connection control.

Description

technical field [0001] The invention belongs to the technical field of new energy AC and DC grid-connected control, and specifically relates to a coordinated fault ride-through method for sending large-scale offshore wind power through flexible DC. Background technique [0002] In recent years, the development and utilization of wind power has achieved rapid development, and the transmission and grid connection of large-scale wind power has become an important research topic. Modular multilevel converter-based flexible direct current transmission (MMC-HVDC) technology has the advantages of high modularity, good waveform quality, and small footprint, and is an effective way for large-scale wind power grid integration. At the same time, the fault ride-through (FRT) capability of HVDC converter stations has a significant impact on the robustness, safety and reliability of grid operation. Therefore, it is necessary to study the FRT control method of the flexible direct current ...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): H02J3/38
CPCY02E10/76
Inventor 李卫星朱蒙晁璞璞牟晓明
Owner HARBIN INST OF TECH
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