Commutation failure prevention and control method for direct-current transmission system under grid fault

A DC transmission system, preventive control technology, applied in the direction of power transmission AC network, etc., can solve the problem that the improvement effect of commutation margin cannot be fully exerted, and achieve the effect of improving immunity

Active Publication Date: 2019-09-06
CHONGQING UNIV
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  • Abstract
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Problems solved by technology

Since the relationship between the commutation voltage drop and the trigger angle adjustment requirement is not taken into account, the improvement effect of CFPREV on the commutation margin cannot be fully exerted by fixed gain or fixed output.

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  • Commutation failure prevention and control method for direct-current transmission system under grid fault
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  • Commutation failure prevention and control method for direct-current transmission system under grid fault

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Embodiment Construction

[0036] The present invention will be further described in detail below in conjunction with the accompanying drawings.

[0037] like figure 1 , image 3 and Figure 4 As shown, the present invention discloses a method for preventing and controlling commutation failure of a direct current transmission system under a power grid fault, which includes the following steps:

[0038] Step 1: Start timing from the voltage zero-crossing time, measure the voltage zero-crossing time to the time t′ of the trigger angle pulse action, measure the time t″ from the voltage zero-crossing time to the corresponding valve shut-off time, and determine the commutation within the voltage half-wave The time interval corresponding to the angle ω is the angular velocity;

[0039] Step 2: When the AC system fails and the voltage of the DC commutation bus drops, record the occurrence time t f ;

[0040] Step 3: If t f not in , determine that the AC fault occurs before the commutation process, ca...

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Abstract

The invention discloses a commutation failure prevention and control method for a direct-current transmission system under a grid fault. The method comprises the following steps: based on LCC-HVDC commutation failure mechanism analysis, an LCC-HVDC critical commutation voltage calculation formula under a symmetrical short circuit fault of an alternating-current power grid of a receiving end is derived by considering the influence of dynamic change of a direct current and a fault moment in a commutation process; and meanwhile, by considering the influence of a drop amplitude of an alternating-current voltage on a commutation margin, a calculation method of a trigger angle adjustment amount is provided, and further a CFPREV improvement strategy of LCC-HVDC is provided. According to the method, the problem that a starting voltage and the trigger angle adjusting amount of existing CFPREV are mainly based on engineering experience values is solved, so that the initial commutation failure immunocompetence can be improved; and the method has a great significance for safe and stable operation of the alternating-current/direct-current power grid.

Description

technical field [0001] The invention relates to the field of power system protection and control, in particular to a method for preventing and controlling phase commutation failure of a direct current transmission system under a grid fault. Background technique [0002] High-voltage direct current transmission (LCC-HVDC) based on grid-commutated converters has been widely used in large-capacity, long-distance transmission and regional grid interconnection due to its advantages of large transmission capacity, low loss and allowing non-synchronous networking. Since the LCC-HVDC converter station uses the thyristor without self-shutdown capability as the converter element, the failure of the AC power grid at the receiving end can easily cause the commutation failure of the inverter station. Commutation failure not only causes a short-term surge of DC current and impact on the converter valve, but also causes a large sag of DC transmission power. If a single commutation failure ...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H02J3/36
CPCH02J3/36Y02E60/60
Inventor 欧阳金鑫龙晓轩张真庞茗予肖超
Owner CHONGQING UNIV
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