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Double-fed fan crowbar adaptive cut-out control method for preventing repeated switching of crowbar

A control method and technology of doubly-fed wind turbines, applied in the auxiliary control strategy of rotor-side converters, and in the field of doubly-fed wind turbine crowbar adaptive cut-off control, can solve the safety hazards of wind turbines, DFIG electromagnetic torque impact, and increase system reactive power Power and other issues to achieve the effect of reducing safety impact, improving transient stability, and avoiding re-investment

Active Publication Date: 2017-11-24
TIANJIN UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0005] 1. When the fault is more serious, the crowbar will switch repeatedly, which increases the reactive power of the system absorbed by DFIG, which is not conducive to the recovery of system voltage, and at the same time will reduce the service life of power electronic switching devices, and bring DFIG The impact of electromagnetic torque will cause harm to the safety of the fan;
[0006] 2. When the fault is relatively minor, the delayed removal of the crowbar makes the input time of the crowbar too long, which increases the system reactive power that DFIG needs to absorb during the crowbar input period, which is not conducive to the low voltage ride-through performance of DFIG

Method used

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  • Double-fed fan crowbar adaptive cut-out control method for preventing repeated switching of crowbar
  • Double-fed fan crowbar adaptive cut-out control method for preventing repeated switching of crowbar
  • Double-fed fan crowbar adaptive cut-out control method for preventing repeated switching of crowbar

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Effect test

Embodiment 1

[0039] An embodiment of the present invention provides a DFIG crowbar adaptive cutting control method to prevent repeated switching of the crowbar, see figure 1 with figure 2 , the method includes the following steps:

[0040] 101: Through real-time calculation, assume the maximum value of the rotor current that will appear when the crowbar is cut off at the current moment;

[0041] 102: If the maximum value of the rotor current is less than the action threshold of the crowbar, cut off the crowbar;

[0042] In actual implementation, this step removes the crowbar as early as possible on the premise that the crowbar will not be switched repeatedly, so as to reduce the reactive power absorbed from the system when DFIG operates as an asynchronous machine, and reduce the impact on the safety of the fan and its control device.

[0043] 103: Obtain the auxiliary control strategy of the rotor-side converter that matches with the crowbar removal, and formulate the reference value of...

Embodiment 2

[0046] The scheme in embodiment 1 is further introduced below in combination with specific calculation formulas, see the following description for details:

[0047] In the embodiment of the present invention, a crowbar protection circuit is added on the rotor side of DFIG, and its switching state is controlled by IGBT. The control signals are respectively the rotor current and the maximum value that will be generated by cutting off the crowbar rotor current calculated according to formula (2) at the current moment; At the same time, corresponding auxiliary control is performed on the rotor side converter of DFIG. figure 1 Shown is the DFIG structure diagram of the protection scheme, which includes the following contents:

[0048] 201: Calculation of the possible maximum value of the rotor current after the crowbar is cut off;

[0049] Taking the time when the crowbar is cut off as zero time, the expression of the rotor current after the crowbar is cut off is:

[0050]

[...

Embodiment 3

[0077] Combine below Figure 3-Figure 5(d) The scheme in embodiment 1 and 2 is carried out feasibility verification, see the following description for details:

[0078] A stand-alone infinite system with DFIG wind farm such as image 3 As shown, the wind farm consists of six 1.5MW (unit) DFIGs. Assume that a three-phase short circuit occurs at the grid-connected point of the fan at 0.05s, and the voltage drop depths are 60% and 80% respectively. The fault is removed at 0.25s, and the fault lasts for 200ms. The crowbar resistance is 0.1Ω. The traditional control strategy of the crowbar circuit and the action value of the rotor current in this method are both I r_th = 2(pu). In addition, the crowbar traditional control method returns the value I r _ re =1.5(pu), the delay is cut off by 1 synchronous period.

[0079] From Figure 4(a) and Figure 4(d), it can be observed that when the voltage drop depth at the grid-connected point is 60%, when the traditional crowbar control ...

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Abstract

The invention discloses a double-fed fan crowbar adaptive cut-out control method for preventing repeated switching of a crowbar. The method comprises the following steps of: when an amplitude of a rotor current exceeds an operating value of a crowbar at the side of the rotor, placing the crowbar and simultaneously, locking a converter at the side of the rotor; if the rotor current is smaller than the operating value of the crowbar, calculating a rotor current maximum value which is to be generated when assuming that the crowbar is cut out at a current moment, and when the rotor current maximum value is smaller than the operating value of the crowbar, cutting out the crowbar and recovering working of the converter at the side of the rotor; and in a fault period, setting a q-axis component of the rotor current according to a preferred output reactive power of a double-fed wind driven generator, and enabling reference values of d-axis and q-axis components of the rotor current to meet constraint conditions. According to the double-fed fan crowbar adaptive cut-out control method disclosed by the invention, the crowbar is guaranteed to be cut out as soon as possible in the premise that the crowbar cannot be placed, so that placing time of the crowbar is shortened and effects that a slave system absorbs the reactive power a little and safety influence on a fan and a control device thereof is reduced are achieved.

Description

technical field [0001] The invention relates to the field of low-voltage ride-through of wind farms, in particular to a crowbar adaptive cutting control method for double-fed wind turbines to prevent repeated crowbar switching, and a rotor-side converter auxiliary control strategy coordinated with crowbar cutting. Background technique [0002] Doubly-fed wind generator (DFIG), as one of the current mainstream wind turbines, has the characteristics of small converter capacity, independent decoupling control of active power and reactive power, and its capacity in the grid has increased rapidly year by year. When the power grid failure causes the voltage drop at the grid-connected point, if all the wind turbines in the large-capacity wind farm are disconnected from the grid, it will have an adverse effect on the safe operation of the power system and cause power imbalance in the grid. Therefore, it is required to have a certain low voltage ride through (LVRT) capability. At pr...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H02J3/16H02P9/10H02P21/28H02P101/15
CPCH02J3/16H02P9/10H02P21/28H02P2101/15Y02E40/30
Inventor 姜惠兰薛静玮陈娟
Owner TIANJIN UNIV
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