Method and system for adaptive single-phase reclosing of wind farm ac transmission lines

A single-phase adaptive reclosing method for the AC transmission line of a wind farm, where no parallel reactor is installed on either side of the AC transmission line, is characterized by the following steps:

• Step1:
• Sample the fault phase voltage using a signal acquisition device;
• Step2:
• Subject the obtained fault phase voltage to short-time Fourier transform to extract the fundamental frequency voltage component amplitude Uf(k);
• Step3:
• Subject the obtained fundamental frequency voltage component amplitude of the fault phase to differential amplification processing to obtain Ud(k);
• Step4:
• Set a maximum discrimination time limit and construct a fault nature identification criterion;
• Step5:
• Perform fault nature identification, if identified as a permanent fault, lock out the reclosing device;
• if identified as a transient fault, proceed to Step 6;
• Step6:
• Calculate the fault disappearance time td, determine the reclosing time tc through the fault disappearance time, and perform reclosing at time tc.
• Step 4 is specifically as follows:
• Step4.1:
• Set a maximum discrimination time limit tmax;
• Step4.2:
• Construct a fault nature identification criterion:
• if within a certain time window Udi(m)>ε, ε being a set threshold, it is judged as a transient fault, otherwise it is judged as a permanent fault.
• Step 6 is specifically as follows:
• Step6.1:
• According to the sliding times i of the sampling time window Ts2 obtained in
• Step4.2 and the mutation sampling point m, the time td of fault disappearance is calculated.
• t
• d
• =
• m
• ·
• T
• c
• +
• i
• +
• t
• o
• +
• 3
• ⁢
• 0
• where Tc is the interval between two adjacent sampling points, and is calculated as follows:
• T
• c
• =
• 1
• f
• s
• where fs is the signal sampling frequency;
• Step6.2:
• Use the obtained fault disappearance time td, combined with the arc channel insulation recovery time t to determine the reclosing time te, and output the closing signal.
• t
• c
• =
• t
• d
• +
• t

The method of claim 1, characterized in that Step 1 specifically includes:

• Step1.1:
• Install a voltage signal acquisition device on the wind farm side of the transmission line;
• Step1.2:
• After a single-phase grounding fault occurs in the wind farm transmission line, use the signal acquisition device to sample the voltage of the fault phase.

The method of claim 1, characterized in that Step 2 specifically includes:

• Step2.1:
• Define a sliding time window Ts1 with a sampling window length and a sliding factor both equal to 20 ms;
• Step2.2:
• Perform short-time Fourier transform on the sampled fault phase voltage within each sliding time window Ts1 to extract the amplitude of the fundamental frequency voltage component Uf(k).

The method of claim 1, characterized in that Step 3 specifically includes:

• Step3.1:
• Define a sliding time window Ts2 with a sampling window length of a and a sliding factor of b;
• Step3.2:
• Perform j times differential amplification processing on the fundamental frequency voltage component amplitude Uf(k) within each sliding time window Ts2:
• U
• di
• (
• k
• )
• =
• [
• U
• fi
• (
• k
• +
• 1
• )
• -
• U
• fi
• (
• k
• )
• ]
• j
• ,
• k
• =
• 1
• ,
• 2
• ,
• …
• ,
• N
• where i represents the i-th sliding time window Ts2, and N represents the number of sampling points contained in a sampling time window.

A system for implementing the single-phase adaptive reclosing method for the AC transmission line of a wind farm as described in claim 1, characterized by comprising:

• A signal acquisition module, used to obtain voltage data of the fault phase at the protection installation on the wind farm side after a fault occurs;
• A numerical calculation module, used to perform short-time Fourier transform on the obtained fault phase voltage data, extract the fundamental frequency amplitude voltage component amplitude, and perform differential amplification processing;
• A fault judgment module, used to construct a fault nature identification criterion, combine a sliding time window to determine the fault nature within the maximum discrimination time limit, and output the determination result;
• A closing control module, used to receive the output signal from the fault judgment module and control the circuit breaker to take corresponding actions.

The system of claim 7, characterized in that the signal acquisition module specifically includes:

• A data acquisition unit:
• used to collect analog voltage quantities of the fault phase at the protection installation on the wind farm side;
• An analog-to-digital conversion unit:
• used to convert the obtained voltage analog quantity into a digital quantity.

The system of claim 7, characterized in that the fault judgment module specifically includes:

• A time limit setting unit:
• used to set the maximum discrimination time limit and determine the sampling window length;
• A fault discrimination unit:
• used to construct a fault nature identification criterion, combine a sliding time window to determine the fault nature within the maximum discrimination time limit, if judged as a permanent fault, output a lockout signal;
• if judged as a transient fault, output a closing signal.

The system of claim 7, characterized in that the closing control module specifically includes:

• A lockout control unit:
• used to receive the circuit breaker lockout signal and control the circuit breaker not to act;
• A closing control unit:
• used to receive the circuit breaker closing signal, after a fixed deionization time, control the circuit breaker to reclose.