A method for judging DC unipolar ground faults in flexible DC transmission systems
A single-pole grounding fault and power transmission system technology, applied in fault location, measurement of electricity, measurement of electrical variables, etc., can solve the problems of single judgment condition, low reliability, and easy misjudgment, and achieve accurate judgment results and improve accuracy. rate and avoid misjudgment
Active Publication Date: 2018-08-07
STATE GRID CORP OF CHINA +4
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Problems solved by technology
The only judgment condition of this judgment method is the voltage of the positive and negative DC bus bars. The judgment condition is relatively simple, and misjudgment is easy to occur. Although the threshold value meets the voltage judgment conditions, there is no DC unipolar ground fault in fact, resulting in misjudgment
Therefore, the reliability of this discrimination method is low. In order to improve system reliability, protection timeliness, and operation and maintenance efficiency, it is urgent to propose an efficient and universally applicable DC unipolar grounding system for flexible DC transmission systems with modular multilevel converters. Fault identification method
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[0020] The present invention will be further introduced below in conjunction with the accompanying drawings and specific embodiments.
[0021] Such as figure 1 Shown is the flow chart of the method for judging the DC unipolar ground fault of the flexible DC transmission system of the present invention. It can be seen from the figure that the method is to realize the rapid detection of the DC unipolar ground fault through the change of the positive and negative DC bus to ground voltage and ground current. , Accurate identification, the specific process is as follows: first obtain the positive and negative DC bus voltages on the DC side, if the absolute value of one of the voltage values is less than the low-voltage limit and the absolute value of the other voltage is greater than the high-voltage limit, and the duration is satisfied If the condition is greater than the set discrimination time, it can be determined that a single-pole ground fault occurs on the DC bus correspon...
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The invention discloses a method for judging a DC unipolar grounding fault in a flexible DC power transmission system. The ground voltage of positive and negative DC busbars on the DC side is obtained. If the absolute value of one of the voltage values is less than the low-voltage limit value and the absolute value of the other voltage value is is greater than the high-voltage limit and meets the condition that the duration is greater than the set screening time, it can be determined that the DC bus corresponding to the voltage value whose absolute value is less than the low-voltage limit has a unipolar ground fault. The present invention selects the positive and negative DC bus-to-ground voltage as the identification parameter of the DC unipolar ground fault according to the voltage variation characteristics in the development process of the DC unipolar ground fault. improve the accuracy of fault identification and avoid misjudgments caused by other faults. This method can quickly and accurately identify DC unipolar ground faults in flexible HVDC transmission systems with modular multilevel converters.
Description
technical field [0001] The invention belongs to the technical fields of flexible power transmission and distribution of electric power systems, power electronics and user electric power, and in particular relates to a method for judging DC unipolar grounding faults in flexible DC transmission systems of modular multilevel converters. Background technique [0002] With the development of fully-controlled power electronic devices and the application of power electronic technology in power systems, the flexible DC transmission technology based on voltage source converters has been paid more and more attention. Modular multi-level converter is a kind of voltage source converter in the application of flexible direct current transmission system. It is composed of multiple half-bridge sub-modules connected in a certain way. By separately controlling the input of IGBT components of each sub-module The cut-off state makes the AC voltage output by the converter close to a sine wave, r...
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IPC IPC(8): G01R31/02G01R31/08
Inventor 吴金龙行登江王先为杨美娟张浩李道洋
Owner STATE GRID CORP OF CHINA