CN115166340A - A processing method of sampling data of 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 was 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 processing method for sampling data of subway DC protection device

technical field

The invention belongs to the technical field of subway DC protection, in particular 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 acquisition, 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 they can be used for subsequent digital signal processing for protection calculation. Among them, the sampling is generally in the way of equal interval sampling. After the continuous analog quantity is sampled at equal intervals, each discrete sampled 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, the higher the sampling quality, and the more accurate the description of the continuous analog quantity. 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。It is well known that the DC voltage output by the rectifier device has periodic pulsation characteristics. When the sampling period T is smaller than the rectified pulse width, the sampled data after sampling by the DC protection device also has corresponding periodic pulsations. 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, combined with the current technical level, the sampling period of the current DC protection device is generally 0.1 milliseconds, that is, every Sample 10 points in milliseconds. The subway generally uses two sets of 12-pulse rectifier units to run in parallel to form an equivalent 24-pulse rectification, which rectifies 35kV or 33kV 50Hz (that is, the cycle is 20 milliseconds) AC to 1500V DC. Therefore, there are 24 pulses in a 20-millisecond power frequency cycle, and the corresponding pulse width is

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

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 parameters of the subway DC protection device, such as the calculation of the current variation

At I, since the protection logic calculation is only related to the sampling data at the protection start time and end time, the periodic pulsating sampling data at the middle time will not have any influence 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 sampled data from the start time to the end time, and the sampling accuracy will have a great impact on the calculation. If the sampled data is used directly, the di/dt value that is inconsistent with the overall change trend will be calculated, 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 amount to the time used, which is a measure of the current change speed, and is a function of the DC protection device.

An important parameter in I+di/dt protection, the purpose 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 sampling current value corresponding to 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 taking 0.1 millisecond as the sampling period, the short-circuit current shown in Figure 1 is output to the 24-pulse rectifier unit, and the corresponding feeder di/dt is shown in Figure 2. As shown in the di/dt curve in Figure 2, its periodic pulsation does not conform to the general trend of the current change rate of the corresponding current curve, which is contrary to the purpose of the DC protection device using this parameter. Especially when the short-circuit current tends to be steady, the rate of change of the short-circuit current is getting smaller and smaller, and its periodic pulsation becomes more and more obvious. According to the data, the periodic pulsation can easily lead to an unreasonable reset after the protection is started, and the protection function cannot be realized.

SUMMARY OF THE INVENTION

Aiming at the technical problems existing in the prior art, the present invention provides a method for processing sampled data of a subway DC protection device, which calculates the average value of all sampled data of each pulse wave, and uses the average value to calculate the current change rate, that is, the sampling data is retained. 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 an unreasonable return of the protection function.

The technical scheme 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 averaged sampled data 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 sampled data to be averaged, 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 constitutes a group every N sampling moments;

The reference time for each N sampling time constitutes a group;

is the current value corresponding to the N sampling times starting from the reference time;

: the average value of the current values 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 values 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 current values corresponding to the N sampling moments.

Further, when the rectifier unit outputs various pulse widths, the rectified 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 as follows: the present invention adopts the pulse wave average value method to process the sampled data, and the pulse wave 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 sampling moments in each pulsation period into a single value, which not only retains the intrinsic characteristics of the current corresponding to the sampling moments, but also solves the interference of periodic pulsation on the calculation of the current change rate, and does not lead to unreasonable reversion of the protection function.

Description of drawings

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

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

3 is a flowchart of an embodiment of the present invention;

FIG. 4 is a current change rate diagram obtained by processing the short-circuit current in FIG. 1 by the method in which the average value of the embodiment of the present invention takes the pulse width of 24-pulse rectification;

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

FIG. 6 is a current change rate diagram obtained by processing the short-circuit current in FIG. 5 by the method in which the average value of the embodiment of the present invention takes the pulse width of 12-pulse rectification;

FIG. 7 is a current change rate diagram obtained by processing the short-circuit current in FIG. 5 by the method in which the average value of the embodiment of the present invention takes the pulse width of 24-pulse rectification;

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

Detailed ways

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

Example 1

An embodiment of the present invention provides a method for processing sampled data of a subway DC protection device, processing the short-circuit current shown in FIG. 1 , as shown in FIG. 3 , which includes the following steps:

Step 1: Calculate the number of sampled data to be averaged:

Among them, my country's AC system adopts 50Hz power frequency, and the corresponding period is 20 milliseconds.

m is the number of rectifier pulses of the rectifier 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 sampled data to be averaged, and the closest positive integer is selected according to the calculation result, that is, N is 8.

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 constitutes a group every 8 sampling moments;

Be the reference time for each 8 sampling time to form a group;

for the reference time

The current value corresponding to the first 8 sampling moments;

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

为

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

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 times. 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

An embodiment of the present invention provides a method for processing sampling data of a subway DC protection device, as shown in FIG. 3 , which includes the following steps:

Step 1: Calculate the number of sampled data to be averaged:

Among them, my country's AC system adopts 50Hz power frequency, and the corresponding period is 20 milliseconds.

m is the rectifier pulse number of the rectifier unit. Since there is also a single-unit operation mode in the subway traction power supply system, the switching conditions of 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 rectifier 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, N is 17.

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 constitutes a group every 17 sampling moments;

The reference time for each 17 sampling time to form a group;

for the reference time

The current value corresponding to the first 17 sampling moments;

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

为

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

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 current values corresponding to 17 sampling times.

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

FIG. 7 is a graph of the current change rate obtained by performing data processing on the short-circuit current shown in FIG. 5 by using the above-mentioned method with the pulse width of 24-pulse rectification as the average value, that is, m=24. FIG. 8 is a current change rate diagram 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 between Fig. 6 and Fig. 8 that Fig. 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 subway DC protection device, before the protection device calculates the current change rate di/dt, the "pulse average method" can be used to process the sampled data, and the pulse width should be selected from the DC protection device. The maximum rectified pulse width that occurs during operation. The currents corresponding to all sampling moments in each pulsation cycle are uniformly averaged into one value. This method not only retains the intrinsic characteristics of the current corresponding to the sampling moments, but also solves the interference of periodic pulsation on the calculation of the current rate of change. lead to unreasonable reversion of the protection function.

The present invention has been described in detail above through the embodiments, but the contents are only exemplary embodiments of the present invention, and should not be considered to limit the scope of implementation of the present invention. The protection scope of the present invention is defined by the claims. Anyone who utilizes 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 within the spirit and protection scope of the present invention to achieve the above-mentioned technical effects, or to Equivalent changes and improvements made in the scope of the 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 subway DC protection device, is characterized in that: comprise the following steps: Step 1: Calculate the number of averaged sampled data 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 sampled data to be averaged, and the closest positive integer is selected according to the calculation result; Step 2: Calculate the average of N sampled data:

Among them, n is the sequence that constitutes a group every N sampling moments;

The reference time for each N sampling time constitutes a group;

is the current value corresponding to the N sampling times starting from the reference time;

: the average value of the current values 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:

in,

is the average value of the current values corresponding to the N sampling moments of the n+1th sequence; di/dt is the current rate of change. 2. The method for processing the sampling data of the subway DC protection device as claimed in claim 1, characterized in that: when the rectifier unit outputs multiple pulse widths, the rectified pulse number corresponding to the maximum pulse width is selected as the value of m.

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