DC converter valve state detection method based on temporal features of converter terminal currents

Patent metadata

Field	Value
Publication number	US-11959976-B2
Application number	US-202117761729-A
Country	US
Kind code	B2
Filing date	Jan 15, 2021
Priority date	Jan 21, 2020
Publication date	Apr 16, 2024
Grant date	Apr 16, 2024

Abstract

The present invention discloses a DC converter valve state detection method based on temporal features of converter terminal currents, including the following steps: collecting three-phase AC currents on a converter valve-side of a DC transmission system; defining a current when the currents of two commutating valves are equal as a base value, greater than the base value as a valve conducting current, and less than the base value as a valve blocking current; constructing a valve conducting state by a relative relationship among amplitudes of the three-phase AC currents, and calculating a time interval of each valve conducting state; comparing time intervals of 6 valve conducting states with a time interval of a valve conducting state in normal operation, and determining whether the 6 valve states are normal according to the result of comparison and locating all abnormal valves. The present invention can reliably detect valve states and locate abnormal valves through sequence detection. This method can be applied to actual fault phase judgment and commutation failure judgment, providing a good support for accurate judgment of DC control and protection.

First claim

What is claimed is:

1. A DC converter valve state detection method based on temporal features of converter terminal currents, comprising the following steps:
S1. defining a HVDC transmission converter valve model, comprising a valve VT 1 , a valve VT 2 , a valve VT 3 , a valve VT 4 , a valve VT 5 , and a valve VT 6 , wherein the valve VT 1 and the valve VT 4 are connected in series to form a first branch, the valve VT 3 and the valve VT 6 are connected in series to form a second branch, the valve VT 5 and the valve VT 2 are connected in series to form a third branch, and the first, second, and third branches are connected in parallel, and wherein a connecting point between the valve VT 1 and the valve VT 4 in the first branch is defined as an a-phase measuring point of three-phase AC currents, a connecting point between the valve VT 3 and the valve VT 6 in the second branch is defined as a b-phase measuring point of the three-phase AC currents, a connecting point between the valve VT 5 and the valve VT 2 in the third branch is defined as a c-phase measuring point of the three-phase AC currents, and three-phase AC currents i a , i b and i c on a converter valve-side of a DC transmission system are collected, where i a , i b and i c represent an a-phase, a b-phase, and a c-phase of the three-phase AC currents respectively;
S2. defining a current when the currents of two commutating valves are equal as a base value, greater than the base value as a valve conducting current, and less than the base value as a valve blocking current;
S3. defining sequence detection as follows: a valve current relative relationship is constructed by a ratio of the valve conducting current to the valve current base value, a duty cycle of the valve current relative relationship being greater than a threshold is defined as a valve conducting state, and the valve conducting state is integrated within one cycle to construct a valve conduction time interval; and
S4. according to the steps S2 and S3, comparing time intervals of valve conducting states of the valve VT 1 , the valve VT 2 , the valve VT 3 , the valve VT 4 , the valve VT 5 , and the valve VT 6 with a time interval of a valve conducting state in normal operation, and determining whether the valve state is normal and locating an abnormal valve according to a result of comparison.

2. The DC converter valve state detection method based on temporal features of converter terminal currents according to claim 1 , wherein the step S2 comprises:
S21. obtaining valve currents i VT1 , i VT2 , i VT3 , i VT4 , i VT5 and i VT6 of the valve VT 1 , the valve VT 2 , the valve VT 3 , the valve VT 4 , the valve VT 5 , and the valve VT 6 by calculating absolute values of the three-phase AC currents i a , i b and i c according to the following formula:

{

i

VT
⁢
1

=

❘
"\[LeftBracketingBar]"

i
a

❘
"\[RightBracketingBar]"

;

i
a

<
0

i

VT
⁢
2

=

❘
"\[LeftBracketingBar]"

i
c

❘
"\[RightBracketingBar]"

;

i
c

>
0

i

VT
⁢
3

=

❘
"\[LeftBracketingBar]"

i
b

❘
"\[RightBracketingBar]"

;

i
b

<
0

i

VT
⁢
4

=

❘
"\[LeftBracketingBar]"

i
a

❘

Assignees

• Univ South China Tech

Inventors

• Li Xiaohua
• Yin Shanshan
• Li Jiewen

Classifications

• G01R31/56 Primary

  Testing of electric apparatus (testing of transformers G01R31/62; testing of connections G01R31/66) · CPC title

• H02J3/36

  Arrangements for transfer of electric power between AC networks via high-voltage DC [HVDC] links; Arrangements for transfer of electric power between generators and networks via HVDC links · CPC title

• G01R31/00 Primary

  Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere ({measuring superconductive properties G01R33/1238;} testing line transmission systems H04B3/46; testing or measuring semiconductors or solid state devices during manufacture {H10P74/00}) · CPC title

• G01R31/42 Primary

  AC power supplies · CPC title

• Y02E60/60

  Arrangements for transfer of electric power between AC networks or generators via a high voltage DC link [HVCD] · CPC title