50Hz and 100Hz protection and setting method for high voltage DC power input system

Abstract

The invention relates to a 50Hz and 100Hz protection setting method for a high voltage direct current transmission system. The 50Hz protection setting method includes the following processes: 1) The 50Hz protection input or 100Hz protection input is filtered by a low-pass filter (1) to obtain the 50Hz component or 100Hz protection input; 2) The above 50Hz component or 100Hz protection input and Comparing the fixed value in the comparator (2), in the 50Hz protection setting method, if it is greater than the fixed value, after the delay time T1 starts the current reduction section, the delay time T1 is coordinated with the switching time of the pole control and valve control redundancy; the arrival delay Time T2 starts the DC blocking sequence, and the delay time T2 cooperates with the overstress capability of the converter valve and cooperates with the protection of other converter valves. In the 100Hz protection setting method, the above-mentioned 100Hz component is compared with the fixed value in the comparator (2). If it is greater than the fixed value, the DC blocking sequence is started after a delay T. The components with the greatest stress are matched with the corresponding setting values ​​of the AC system. The invention not only realizes backup protection for converter valve faults and AC system faults, but also avoids system instability problems caused by simultaneous power reduction or blocking of multiple DC circuits in the AC-DC hybrid power grid under the premise of ensuring the safety of the main equipment.

Description

Technical field: [0001] The invention is a 50Hz and 100Hz protection setting method for a high-voltage direct current transmission system, which belongs to the innovative technology of the 50Hz and 100Hz protection setting method for a high-voltage direct current transmission system. Background technique: [0002] HVDC transmission technology is of great significance to the operation and development of the power grid. 50Hz and 100Hz protection are two types of protection for HVDC systems. Their protection functions are in the event of converter trigger pulse faults, converter valve faults, commutation Protect the converter valve in case of phase failure. The setting methods of 50Hz and 100Hz protection in existing HVDC transmission projects at home and abroad are as follows: [0003] 1) Calculate the 50Hz and 100Hz component content in the DC line or the polar neutral bus; [0004] 2) Factors to be considered in the fixed value: background harmonics of the AC and DC system...

AI Technical Summary

Problems solved by technology

[0009] 1) The 50Hz protection and 100Hz setting principles mainly consider the bearing capacity of the converter valve, and do not consider the overstress capacity of other equipment;

[0010] 2) There is no clear difference between the setting principles of 50Hz protection and 100Hz protection. Some high-voltage DC projects use the same action characteristics and delays for 50Hz protection and 100Hz protection.

Therefore, when an asymmetrical fault occurs in the AC system, the fast protection refuses to operate or the circuit breaker fails, the fault removal time will be longer, which may cause multiple DC 100Hz protections to operate and block in the AC-DC parallel operation system, which will have a catastrophic impact on the safety of the power grid.

[0012] Therefore, the existing 100Hz protection setting method does not fully consider the characteristics of the AC-DC parallel operation system, and cannot make full use of the overstress capability of the main equipment of the HVDC transmission system to enhance the stability of the power grid when the AC system fails.

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