Judgment and Simulation Method of Commutation Failure in DC Transmission System Based on Electromechanical Transient

Abstract

The invention discloses a commutation failure judging and simulation method for a direct current transmission system based on an electromechanical transient state. The commutation failure judging method comprises the steps: establishing an alternative current-direct current electrical power system electromechanical transient simulation model of direct current transmission, calculating alternative current three-phase / single-phase short-circuit fault happening in a certain point of an alternating system, comparing and analyzing changes of bus three-phase voltage effective value on a failure instant high-voltage direct current inversion side to judge whether commutation occurs in the direct current system or not, and conducting commutation judgment to each point of the alternating current system, and calculating and confirming an alternating current fault area. The simulation method comprises the step of simulating direct current commutation failure by artificially modifying direct-current power according to the judging results of the direct current commutation failure. According to the commutation failure judging and simulation method for the direct current transmission system based on the electromechanical transient state, an electromechanical transient simulation program in which an electric power system takes the leading application part is adopted, the commutation failure judging and simulation method has strong adaptability and practical applicability and is simple and useful and conserved in the aspect of computational analysis of the interaction effect between the direct current and alternating current, meanwhile the simulation method is effective and feasible, and fulfills engineering application requirements effectively.

Description

technical field [0001] The invention belongs to the technical field of direct current transmission in electric power systems, and in particular relates to a method for judging and simulating commutation failure of a direct current transmission system based on an electromechanical transient state. Background technique [0002] The commutation failure of the DC transmission system is a common phenomenon in the DC system with the thyristor as the commutation element. A characteristic of a thyristor valve is that during its transition from forward conduction to off, the free ions stored inside during the forward conduction phase must be removed / recombined before the valve can establish forward voltage blocking capability. Therefore, the converter of the DC system needs a certain minimum reverse voltage-time region, that is, the thyristor valve is under the action of the reverse voltage for a period of time to achieve deionization / ion recombination. Analyzing from the concept of...

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Problems solved by technology

[0005] (1) The DC model of the electromechanical transient simulation program does not include the simulated DC system converter valve group and its trigger system, and cannot simulate the voltage and current of the converter valve, and cannot simulate the commutation failure process on the inverter side in detail. Can roughly judge whether commutation failure occurs according to the size of the arc extinguishing angle of the inverter

[0006] (2) The DC model of the electromechanical transient simulation program is based on the symmetry of the three-phase AC voltage of the converter bus. When the AC system is asymmetrically faulty, the voltage of the AC bus of the converter station is no longer symmetrical, and the quasi-steady model Simulation results are not strictly accurate during

[0007] (3) The DC model of the electromechanical transient simulation program only considers the fundamental characteristics of the system, and does not simulate the harmonic characteristics of the DC system, nor does it consider various losses of the converter station, and the reactive power calculation value may cause large error

[0008] The above deficiencies lead to electromechanical transient simulation being optimistic about the commutation failure of the DC system. This is mainly manifested in the fact that the DC power of the electromechanical transient simulation results is slightly larger than the actual operating value during the three-phase (single-phase) short-circuit fault in the AC system. Moreover, when the short-circuit fault disappears, the DC power recovery speed of the electromechanical transient simulation results is relatively faster than the actual operating value

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