Method for determining fault removal time of flexible direct current power grid under bipolar short circuit

Abstract

The invention discloses a method for determining fault removal time of a flexible direct current power grid under a bipolar short circuit. The method comprises the steps that the voltage and current instantaneous values at the fault initial period can be obtained according to fault instantaneous direct current voltage and the initial value of the line current; the accumulated electric quantity ofthe fault current and the change amount of the electric charges of a capacitor caused by the charging and discharging of a bus voltage are calculated according to the voltage and current instantaneousvalues at the fault initial period; according to the amount of electric charges carried by the capacitor at the steady-state operating point and the electric charge amount of the capacitor at the limit operating point of the system, the maximum change quantity of electric charges carried by the capacitor is calculated during the fault period; according to a principle of equal electric quantity, when the accumulated electric quantity of the fault current is equal to the maximum change amount of the electric charges of the capacitor during the fault period, the fault removal time of the systemunder the bipolar short circuit fault is obtained. According to the method for determining the fault removal time of the flexible direct current power grid under the bipolar short circuit, the operation requirements of the direct current system on the circuit breaker can be reduced, and the transient stability of the system can be enhanced.

Description

technical field

[0001] The invention relates to the technical field of fault analysis and protection of a flexible DC power grid, in particular to a method for determining the fault removal time of a flexible DC power grid under a bipolar short circuit. Background technique

[0002] With the widespread application of distributed energy and constant power loads, the flexible DC grid has become the focus of research and application at home and abroad relying on its advantages. Compared with the AC distribution network, the flexible DC grid has the advantages of simple conversion device and low cost, and there is no need to pay attention to the impact of frequency mutation and power angle swing on power quality. At present, the measures to improve the voltage stability of the flexible DC grid include adding controllers, and analyzing the fault characteristics of the system and quickly and effectively isolating faults. However, the inertia of the flexible DC grid is low. After ...

Images