Mode identification method for voltage dropping root-mean-square value and dropping frequency estimation

Abstract

The invention discloses an identification method for voltage dip root-mean-square value and dip frequency estimation. The identification method is characterized by comprising steps of establishing whole grid node voltage dip mode databases of various fault types, constructing a monitored node voltage dip mode, performing identification and classification on voltage dip types and choosing the corresponding whole grid voltage dip mode database according to a short circuit fault type, performing estimation on the voltage dip root-mean-square value of the whole grid nodes, and obtaining a voltage dip frequency estimation value under each voltage dip threshold through statistics. The mode identification method is simple in an estimation principle and an implementation process, high in mode identification accuracy and short in calculation time.

Description

technical field [0001] The invention belongs to the technical field of voltage drop estimation of power system power quality, in particular to a pattern recognition method for voltage drop root mean square value and drop frequency estimation. Background technique [0002] The wide application of computer technology, automation technology, power electronics technology and microelectronics technology in the power supply network has put forward higher requirements for the power quality of the power supply network, especially for short-term power quality disturbances such as Voltage Dip. Voltage sag has become the most concerned and concerned power quality issue among current power users, society and academia. [0003] Estimating the root mean square value of the voltage drop of the bus node and the frequency of the voltage drop within a specific time when a short-circuit fault occurs in the power grid is a prerequisite for solving the problem of voltage drop. Voltage drop is de...

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Problems solved by technology

[0019] 2) The number of faults occurring on the lines in the system can only be an integer greater than or equal to 0

[0031] The above three estimation methods of voltage drop have the following disadvantages and problems: (1) The actual measurement statistical method requires a long monitoring time, a large number of monitoring points, and huge time and economic costs; (2) The random estimation method is limited by the element Uncertain factors such as device failure rate, and it is only applicable to the estimation of long-term scale, but cannot accurately give the estimation results of the frequency of voltage dips in a specific period; (3) The state estimation equation of the state estimation method is highly underdetermined, and has There are multiple feasible solutions, and it is not clear which solution is the optimal solution closest to the actual situation in the physical sense

(4) The existing state estimation equation and its constraint conditions are complex, and the equation needs to be reconstructed according to different voltage drop thresholds, and the application of linear programming to solve the problem takes a lot of time

(5) The existing state estimation method can only judge whether a node has a voltage drop, but cannot give the specific root mean square value of the voltage drop, and has lost a lot of important voltage drop information

However, it is limited by uncertain factors such as the failure rate of components, and it is impossible to give the estimation results of the frequency of voltage dips in a specific time period

Although the existing state estimation method can give the estimated value of the frequency of node voltage dips within a specific period of time, the mathematical principles and models are relatively complex, and it is difficult to solve highly underdetermined equations. It is necessary to rebuild the state equation for calculation under different voltage dip thresholds. And only the frequency of voltage dips can be obtained, and important voltage dip information such as the root mean square value of the node voltage is lost

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