CN115166340B - A method for processing sampling data of a subway DC protection device - Google Patents

Abstract

The invention provides a method for processing sampling data of a subway direct-current protection device, which comprises the following steps of: step 1: calculating the number of sampling data of an average value according to the pulse width output by the rectifier unit: step 2: calculating the average value of the N sampling data; and step 3: the average value of the current values is used as a reference current value to calculate di/dt. The invention calculates the average value of all sampling data of each pulse wave, and calculates the current change rate by using the average value, thereby not only keeping the intrinsic characteristic of the current corresponding to the sampling moment, but also solving the interference of periodic pulsation on the current change rate calculation and avoiding unreasonable resetting of the protection function.

Description

A method for processing sampling data of a subway DC protection device

technical field

The invention belongs to the technical field of subway DC protection, and in particular relates to a method for processing sampling data of a subway DC protection device.

Background technique

10V，4-20mA或0-150MV。上述连续的模拟量输入至直流保护装置内，经过滤波、采样并存储到对应的存储器内，方能用于后续的数字信号处理，进行保护计算。其中的采样，一般都是采用等间隔采样的方式。连续模拟量经等间隔采样后，各离散的采样数据成为直流保护装置后续计算的基础数据。The DC protection device configured in the subway DC traction system converts high voltage and high current into low voltage and low current analog quantities that can be processed by electronic devices through shunts and isolation amplifiers before data collection, such as

10V, 4-20mA or 0-150MV. The above-mentioned continuous analog quantities are input into the DC protection device, filtered, sampled and stored in the corresponding memory before being used for subsequent digital signal processing and protection calculation. Sampling among them generally adopts the method of sampling at equal intervals. After the continuous analog quantity is sampled at equal intervals, each discrete sampling data becomes the basic data for the subsequent calculation of the DC protection device.

When the DC protection device samples at equal intervals, the smaller the sampling period T is, the higher the sampling quality is, and the more accurate the description of the continuous analog quantity is. When the sampling period tends to be infinitely small, the discrete sampling points tend to form a continuous analog curve. However, reducing the sampling period T without limit not only increases the unnecessary calculation burden of the DC protection device, but also causes problems when the DC protection device calculates the current change rate di/dt.

。采样周期T小于脉波宽度，则地铁直流保护装置的采样数据具有周期性脉动。As we all know, the DC voltage output by the rectifier has periodic pulsating characteristics. When the sampling period T is less than the width of the rectified pulse wave, the sampled data of the DC protection device also has a corresponding periodic pulsation. In order to more accurately retain the original characteristics of the analog current, improve the accuracy of fault recording, improve the efficiency of event recording, and facilitate the analysis of the accident process, etc., combined with the current technical level, the sampling period of the current DC protection device is generally 0.1 milliseconds, that is, every 10 points are sampled in milliseconds. The subway generally uses two sets of 12-pulse rectifier units to run in parallel to form an equivalent 24-pulse rectifier, which rectifies 35kV or 33kV 50Hz (that is, the period is 20 milliseconds) AC power into 1500V DC power. Therefore, there are 24 pulses in a 20 millisecond power frequency period, and the corresponding pulse width is

. If the sampling period T is less than the pulse width, the sampling data of the subway DC protection device has periodic pulsation.

I时，由于保护逻辑计算只与保护启动时刻和终止时刻的采样数据有关，中间时刻的周期性脉动采样数据不会对保护逻辑造成任何影响。The sampling accuracy will not affect the calculation of most of the parameters of the subway DC protection device, such as the calculation of the current variation

When I, because the protection logic calculation is only related to the sampling data at the protection starting time and termination time, the periodic pulsating sampling data at the intermediate time will not have any impact on the protection logic.

When the subway DC protection device calculates the current change rate di/dt, the protection logic calculation needs to use all the sampling data from the start time to the end time, and the sampling accuracy will have a great impact on the calculation. If the sampling data is directly used, the calculated di/dt value does not conform to the overall change trend, and it also has periodic pulsation.

I+di/dt保护中的重要参数，目的在于区分牵引负荷电流的正常波动与短路故障电流的快速提升。The physical definition of the current change rate di/dt is the ratio of the current change to the time taken, which is a measure of the current change speed and is the measure of the DC protection device.

The important parameter in I+di/dt protection is to distinguish the normal fluctuation of the traction load current from the rapid increase of the short-circuit fault current.

，其中，

：保护启动后的任意时刻；T：直流保护装置采样间隔；

：保护启动后任意时刻对应的采样电流值；

的下一个采样周期对应的采样电流值；di/dt：每个采样点计算出的电流变化率。

,in,

: any time after the protection starts; T: sampling interval of the DC protection device;

: The corresponding sampling current value at any time after the protection starts;

The sampling current value corresponding to the next sampling period; di/dt: the current change rate calculated at each sampling point.

When the sampling period is 0.1 milliseconds, the short-circuit current output by the 24-pulse rectifier unit as shown in Figure 1, and the corresponding feeder di/dt are shown in Figure 2. As shown in Figure 2, the di/dt curve has periodic pulsation that does not conform to the general trend of the current change rate of the corresponding current curve, which is contrary to the purpose of using this parameter in the DC protection device. Especially when the short-circuit current tends to a steady state, the change rate of the short-circuit current is getting smaller and smaller, while its periodic pulsation is more and more obvious. The current change rate di/dt at this stage is just an important judgment of protection reset. According to the data, the periodic pulsation is easy to lead to unreasonable reset after the protection is started, and the protection function cannot be realized.

Contents of the invention

Aiming at the technical problems existing in the prior art, the present invention provides a method for processing sampling data of a subway DC protection device, which calculates the average value of all sampling data of each pulse wave, and uses the average value to calculate the current change rate, that is, retains the sampling data The time corresponds to the intrinsic characteristics of the current, and solves the interference of the periodic pulsation on the calculation of the current change rate, and will not lead to unreasonable restoration of the protection function.

The technical solution adopted in the present invention is: a method for processing sampling data of a subway DC protection device, comprising the following steps:

Step 1: Calculate the number of sampling data for averaging according to the pulse width output by the rectifier unit:

Among them, m is the rectification pulse number of the rectifier unit; T is the sampling interval of the DC protection device, in milliseconds;

N is the number of sampling data to take the average value, and the closest positive integer is selected according to the calculation result;

Step 2: Calculate the average of N sampled data:

为每N个采样时刻构成组别的基准时刻；

为从基准时刻开始的N个采样时刻对应的电流值；

：第n个序列的N个采样时刻对应电流值的平均值；Among them, n is the sequence that forms a group every N sampling moments;

A reference moment for forming a group for every N sampling moments;

is the current value corresponding to N sampling moments starting from the reference moment;

: The average value of the current value corresponding to the N sampling moments of the nth sequence;

Step 3: Use the average value of the current value as the reference current value for di/dt calculation:

为第n+1个序列的N个采样时刻对应电流值的平均值；in,

is the average value of the current value corresponding to the N sampling moments of the n+1th sequence;

di/dt is the current change rate calculated from the average value of the corresponding current values at N sampling moments.

Further, when the rectifier unit outputs multiple pulse widths, the rectification pulse number corresponding to the largest pulse width is selected as the value of m.

Compared with the prior art, the present invention has the beneficial effects that: the present invention uses the average pulse wave method to process the sampled data, and the pulse width is selected from the maximum rectified pulse wave that occurs during the operation of the DC protection device. width. The present invention uniformly averages the currents corresponding to all the sampling moments in each pulsation cycle into one value, that is, retains the intrinsic characteristics of the currents corresponding to the sampling moments, and solves the interference of periodic pulsations on the calculation of the current change rate. Lead to unreasonable restoration of the protection function.

Description of drawings

Fig. 1 is the output short-circuit current diagram of the 24-pulse rectifier unit with a sampling period of 0.1 milliseconds in the prior art;

Fig. 2 is the current rate-of-change diagram obtained by processing the short-circuit current in Fig. 1 in the prior art;

Fig. 3 is the flowchart of the embodiment of the present invention;

Fig. 4 is that the average value of the embodiment of the present invention gets the pulse width of 24 pulse wave rectifications and this method processes the current rate of change figure that short-circuit current obtains in Fig. 1;

Fig. 5 is a diagram of the output short-circuit current of the 12-pulse rectifier unit with a sampling period of 0.1 milliseconds;

Fig. 6 is that the average value of the embodiment of the present invention gets the pulse width of 12 pulse wave rectifications the current rate of change diagram that this method processes the short-circuit current in Fig. 5 and obtains;

Fig. 7 is that the average value of the embodiment of the present invention gets the pulse width of 24 pulse wave rectifications and this method processes the current rate of change figure that the short-circuit current in Fig. 5 obtains;

FIG. 8 is a diagram of the current change rate obtained by processing the short-circuit current in FIG. 5 in the prior art.

detailed description

In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments.

Example 1

Embodiments of the present invention provide a method for processing sampling data of a subway DC protection device, which processes the short-circuit current shown in Figure 1, as shown in Figure 3, which includes the following steps:

Step 1: Calculate the number of sampled data for averaging:

Among them, the AC system in our country adopts 50Hz power frequency, and the corresponding period is 20 milliseconds.

m is the rectification pulse number of the rectification unit, 24 pulse rectification, m=24.

T is the sampling interval of the DC protection device in milliseconds; generally, the sampling period of the DC protection device is 0.1 milliseconds, that is, T=0.1.

N is the number of sampling data to be averaged, and the nearest positive integer is selected according to the calculation result, that is, 8 is taken for N.

Step 2: Calculate the average of 8 sampled data:

为每8个采样时刻构成组别的基准时刻；

为从基准时刻

开始的8个采样时刻对应的电流值；

为第n个序列的8个采样时刻对应电流值的平均值。Among them, n is the sequence that forms a group every 8 sampling moments;

Constitute the reference time of the group for every 8 sampling time;

from the base time

The current value corresponding to the first 8 sampling moments;

is the average value of current values corresponding to the 8 sampling moments of the nth sequence.

为

Similarly, the 8 sampling moments of the n+1th sequence correspond to the average value of the current value

for

Calculate the average value of the current values corresponding to the 8 sampling moments of each sequence.

Step 3: Use the average value of the current value as the reference current value for di/dt calculation:

di/dt is the current change rate calculated from the average value of the corresponding current values at 8 sampling moments. The calculation result is shown in Figure 4, which accurately reflects the current change rate of the output short-circuit current of the 24-pulse rectifier unit.

Example 2

Embodiments of the present invention provide a method for processing sampling data of a subway DC protection device, as shown in Figure 3, which includes the following steps:

Step 1: Calculate the number of sampled data for averaging:

Among them, the AC system in our country adopts 50Hz power frequency, and the corresponding period is 20 milliseconds.

m is the rectification pulse number of the rectification unit. Since there is also a single unit operation mode in the subway traction power supply system, the working condition of switching between 24-pulse rectification and 12-pulse rectification should be considered according to the larger pulse width, that is, the pulse width of the 12-pulse rectification output, m= 12.

T is the sampling interval of the DC protection device in milliseconds; generally, the sampling period of the DC protection device is 0.1 milliseconds, that is, T=0.1.

N is the number of sampled data to be averaged, and the closest positive integer is selected according to the calculation result, that is, 17 is taken for N.

Step 2: Calculate the average of 17 sampled data:

为每17个采样时刻构成组别的基准时刻；

为从基准时刻

开始的17个采样时刻对应的电流值；

为第n个序列的17个采样时刻对应电流值的平均值。Among them, n is the sequence that forms a group every 17 sampling moments;

A reference moment for each of the 17 sampling moments constituting a group;

from the base time

The current value corresponding to the first 17 sampling moments;

is the average value of the current value corresponding to the 17 sampling moments of the nth sequence.

为

Similarly, the 17 sampling moments of the n+1th sequence correspond to the average value of the current value

for

Calculate the average value of the current values corresponding to the 17 sampling moments of each sequence.

Step 3: Use the average value of the current value as the reference current value for di/dt calculation:

di/dt is the current change rate calculated from the average value of the corresponding current values at 17 sampling moments.

This method is used to process the short-circuit current output by the 12-pulse rectifier unit with a sampling period of 0.1 milliseconds as shown in Figure 5, and the calculation results are shown in Figure 6.

Figure 7 is the average value of the pulse width of 24 pulse rectification, that is, m=24, the current change rate diagram obtained by data processing the short-circuit current shown in Figure 5 by the above method. FIG. 8 is a current change rate graph obtained by performing data processing on the short-circuit current shown in FIG. 5 by a conventional method. It can be seen from the comparison of Figure 6-Figure 8 that Figure 6 can better reflect the current change rate of the output short-circuit current of the 12-pulse rectifier unit.

Under the current sampling level of the DC protection device of the subway, before the protection device calculates the current change rate di/dt, the "pulse average value method" can be used to process the sampled data, and the pulse width should be selected from the DC protection device During operation, the maximum rectification pulse width appears. The currents corresponding to all sampling moments in each pulsation period are uniformly averaged into one value. This method not only retains the intrinsic characteristics of the current corresponding to the sampling moment, but also solves the interference of periodic pulsation on the calculation of the current change rate. Lead to unreasonable restoration of the protection function.

The present invention has been described in detail through the above examples, but the content described is only an exemplary embodiment of the present invention, and cannot be considered as limiting the implementation scope of the present invention. The protection scope of the present invention is defined by the claims. Those who utilize the technical solutions described in the present invention, or those skilled in the art, under the inspiration of the technical solutions of the present invention, design similar technical solutions to achieve the above technical effects within the spirit and protection scope of the present invention, or The equivalent changes and improvements made in the scope of application should still belong to the scope of protection covered by the patent of the present invention.

Claims (2)

1. A processing method of sampling data of a subway direct current protection device is characterized by comprising the following steps: the method comprises the following steps:

step 1: calculating the number of sampling data of an average value according to the pulse width output by the rectifier unit:

wherein m is the number of rectified pulses of the rectifier unit, and m =12 or m =24; t is sampling interval of the direct current protection device, the unit is millisecond, and T is smaller than pulse wave width;

n is the number of the sampled data taking the average value, and the nearest positive integer is selected according to the calculation result;

step 2: calculate the average of N sampled data:

wherein N is a sequence forming a group at every N sampling moments;

forming a group of reference moments for every N sampling moments;

the current values corresponding to N sampling moments from the reference moment;

: the average value of the current values corresponding to the N sampling moments of the nth sequence;

and step 3: the average value of the current values was used as a reference current value for di/dt calculation:

wherein,

the average value of the current values corresponding to the N sampling moments of the (N + 1) th sequence is obtained;

di/dt is the rate of change of current.

2. The method for processing the sampling data of the subway direct-current protection device as claimed in claim 1, wherein: and when the rectifier unit outputs various pulse wave widths, selecting the number of the rectifier pulses corresponding to the maximum pulse wave width as the value of m.

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