Patent ID: 11933835
Assignee: CHINA UNIVERSITY OF PETROLEUM (EAST CHINA)
Field: Measurement (Instruments)
Classification: CPC G  Y | IPC G

Claim 1:
2. A fault location method for two-level VSC type photovoltaic connected flexible DC distribution network, wherein the fault location method for two-level VSC-type photovoltaic connected flexible DC distribution network comprising:
recognizing a section where a fault lie from a direction of positive current of DC feeders during a fault period; establishing a distance measuring model for bipolar short circuit covering interactions and responses of systems according to equivalent circuits of transient periods during the fault period; and realizing fault location by finding a distance to fault with electric parameters and information of the fault, wherein the fault location method of two-level VSC-type photovoltaic connected bidirectional flexible DC distribution network comprising the following steps:
(Step 1), assuming a T point is an intersection between a DC feeder of at least one at least one photovoltaic sub-system and a DC feeder of at least one At least one AC sub-system, judging the section where the fault occurs according to the direction of the positive current of the DC feeders at the T point during the fault period;
(Step 2), establishing a distance measurement model for the bipolar short circuit fault covering the interactions and responses between the systems by the equivalent circuits of transient periods during bipolar short circuit of the two-level VSC type flexible DC distribution network; and
(Step 3), determining a length of a sampling window according to boundary conditions of the transient periods of the fault, calculating the distance to the fault based on electric parameters and information of the fault at sampling times; calculating average values of the distance to the fault obtained at the sampling points and realizing accurate location of the bipolar short circuit fault,
wherein in the step 2, after occurrence of the fault, turning off immediately IGBTs of the convertors of the sub-systems, analyzing coupling relationships of each of the subsystems at a fault point during the fault period according to conduction and feeding conditions of internal diodes in two-level VSCs and photovoltaic DC/DC, determining boundary conditions and the equivalent circuits of the transient stages during the bipolar short circuit fault; building a corresponding fault mode equation based on Kirchhoff's laws; expressing elements in the fault mode equation that change along with the distance to the fault and transitional resistance and establishing a bipolar short circuit fault distance measurement mode equation containing the distance to the fault and the transitional resistance.