阅读说明：本技术 一种应用于电能表检定装置标准表的频率测量方法 (Frequency measurement method applied to standard meter of electric energy meter calibrating device ) 是由 范建华 付刚 朱建国 叶恒 于 2020-11-10 设计创作，主要内容包括：本发明公开了一种应用于电能表检定装置标准表的频率测量方法,通过对功率源输入电压的采样,对电压采样数据进行数字直流滤波处理,缓存多级采样滤波数据,根据过零条件判断过零点,使用计数器对两个过零点间进行重复计数,以及结合两个零点两侧采样滤波数据估计过零点位置,进行频率计算。本发明使得电能表检定装置标准表的频率测量无需硬件过零检测电路,节省硬件成本；同时可靠的过零判断机制以及简便的计算方法,提高了电能表检定装置标准表的频率测量精度。(The invention discloses a frequency measurement method applied to a standard meter of an electric energy meter calibrating device, which comprises the steps of sampling input voltage of a power source, carrying out digital direct-current filtering processing on voltage sampling data, caching multi-level sampling filtering data, judging zero crossing points according to zero crossing conditions, repeatedly counting two zero crossing points by using a counter, estimating the positions of the zero crossing points by combining the sampling filtering data on two sides of the two zero points, and carrying out frequency calculation. According to the invention, the frequency measurement of the standard meter of the electric energy meter calibrating device does not need a hardware zero-crossing detection circuit, so that the hardware cost is saved; meanwhile, the frequency measurement precision of the standard meter of the electric energy meter calibrating device is improved by a reliable zero-crossing judgment mechanism and a simple and convenient calculation method.)

1. A frequency measurement method applied to a standard meter of an electric energy meter calibrating device is characterized by comprising the following steps:

step 1: the power source outputs sine wave voltage to access a standard table;

step 2: the standard table program frequency is F, the standard table controls the A/D converter according to the sampling rate F_sSampling the power source voltage;

and step 3: filtering the voltage sampling data by digital direct current filtering;

and 4, step 4: carrying out 2 i-level cache on the filtered voltage sampling data, and every time N appears in the sampled and filtered data₁,N₂,…N_2i-1,N_2iWhen the sampling filtering data N is output, the zero-crossing signal is output, and the sampling filtering data N is output at the same time_i、N_i+1；

And 5: counting by the counter, simultaneously detecting whether a zero-crossing signal exists, if no, continuing counting by the counter, and counting the counter value N when the zero-crossing signal is detected_zcAnd sampling the filtered data N_i、N_i+1Step 6 is transmitted, meanwhile, the counter is reset, step 5 is repeated, and sampling filtering data are continuously output;

step 6: according to the current counter value N_zcSampled filtered data N_i、N_i+1Sampled filtered data N from the previous time_j、N_j+1(with N)_j、N_j+1Indicated for discrimination, initially 0), the power source input waveform frequency f is calculated, and the frequency measurement of the current standard table is completed.

2. The method for measuring the frequency of the standard meter of the electric energy meter calibrating device according to claim 1, wherein the filtered data N is sampled in the step 4₁,N₂,…N_2i-1,N_2iSatisfies the following conditions: n is a radical of₁,N₂,…N_i<0，N_i+1,N_i+2,…N_2i≥0。

3. The method for measuring the frequency of the standard meter of the electric energy meter calibrating device according to claim 1, wherein the step 6Sampling the filtered data N_i、N_i+1Satisfies the following conditions: n is a radical of_i<0，N_i+1≥0。

4. The method as claimed in claim 1, wherein the power source input waveform frequency in step 6 is:

Technical Field

The invention particularly relates to the technical field of frequency measurement, in particular to a frequency measurement method applied to a standard meter of an electric energy meter calibrating device.

Background

The frequency is an important index for representing the operating characteristics of a power system, plays a critical role in the fields of power quality monitoring, power system protection and the like, and the specific 50Hz periodic sine wave is also used for electricity consumption of residents in China. Meanwhile, in the working process of the standard meter of the electric energy meter calibrating device, strict requirements are placed on the measurement of the power consumption frequency, and the waveform frequency output by the power source needs to be measured in real time.

Common frequency measurement generally comprises hardware zero-crossing period counting, software zero-crossing period counting and Fourier transform difference value calculating methods, but the hardware zero-crossing period counting method needs to use a hardware zero-crossing circuit, occupies hardware resources and has higher cost; the precision of software zero-crossing period counting is low; the fourier transform difference calculation method is complex in calculation mode.

Disclosure of Invention

In order to overcome the defects and shortcomings of the prior art, the invention provides the frequency measuring method applied to the standard meter of the electric energy meter calibrating device, which can simply, quickly and accurately measure the frequency of the standard meter in the electric energy meter calibrating device, does not occupy hardware resources and saves the cost.

In order to achieve the purpose, the invention is realized by the following technical scheme:

a frequency measurement method applied to a standard meter of an electric energy meter calibrating device specifically comprises the following steps:

step 1: the power source outputs sine wave voltage to access a standard table;

step 2: the standard table program frequency is F, the standard table controls the A/D converter according to the sampling rate F_sSampling the power source voltage;

and step 3: filtering the voltage sampling data by digital direct current filtering;

and 4, step 4: carrying out 2 i-level cache on the filtered voltage sampling data, and every time N appears in the sampled and filtered data₁,N₂,…N_2i-1,N_2iWhen outputting the zero-crossing signal, and simultaneously outputting N_i、N_i+1；

And 5: counting by the counter, simultaneously detecting whether a zero-crossing signal exists, if no, continuing counting by the counter, and counting the counter value N when the zero-crossing signal is detected_zcAnd sampling the filtered data N_i、N_i+1Step 6 is transmitted, meanwhile, the counter is reset, step 5 is repeated, and sampling filtering data are continuously output;

step 6: according to the current counter value N_zcSampled filtered data N_i、N_i+1Sampled filtered data N from the previous time_j、N_j+1(with N)_j、N_j+1Indicated for discrimination, initially 0), the power source input waveform frequency f is calculated, and the frequency measurement of the current standard table is completed.

Further, the filtered data N is sampled in the step 4₁,N₂,…N_2i-1,N_2iSatisfies the following conditions: n is a radical of₁,N₂,…N_i<0，N_i+1,N_i+2,…N_2i≥0；

Further, the sampling filtering data N in the step 6_i、N_i+1Satisfies the following conditions: n is a radical of_i<0，N_i+1≥0。

Further, the input waveform frequency of the power source in the step 6 is:

the invention has the beneficial technical effects that:

1. the frequency measurement does not need a hardware zero-crossing detection circuit, so that the hardware cost is saved;

2. the zero crossing point position is accurately estimated, and the frequency measurement precision of the standard meter of the electric energy meter calibrating device is improved;

3. complex operations such as Fourier transform and the like are not needed, and the calculation is simpler and more convenient according to a reliable zero-crossing judgment mechanism and zero-crossing point approximate processing.

Drawings

Fig. 1 is a flow chart of a frequency measurement method applied to a standard meter of an electric energy meter calibration device according to the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and do not limit the invention.

As shown in fig. 1, in particular, it relates to a frequency measurement method applied to a standard meter of an electric energy meter calibrating apparatus, which includes the following steps:

step 1: the power source outputs sine wave voltage to access a standard table.

Step 2: the standard table program frequency is 25MHz, and the standard table controls the A/D converter to sample the power source voltage according to the sampling rate of 100 kHz.

And step 3: digital dc filtering filters the voltage sample data.

In step 3, digital dc filtering is necessary, because of factors such as an a/D converter, unnecessary dc components are introduced into the sampled value, and zero crossing points are inaccurate, so that frequency measurement is inaccurate, and digital dc filtering needs to be added to preprocess the sampled data.

And 4, step 4: carrying out 2 i-level cache on the filtered voltage sampling data, and every time N appears in the sampled and filtered data₁,N₂,…N_2i-1,N_2iWhen outputting the zero-crossing signal, and simultaneously outputting N_i、N_i+1。

Wherein in step 4, setting i to be 4, namely when N is₁,N₂,N₃,N₄<0 and N₅,N₆,N₇,N₈When the voltage is more than or equal to 0, outputting a zero-crossing signal and simultaneously outputting N₅、N₆. The zero crossing point judged by the embodiment is the zero crossing of the waveform from negative to positive, and if the zero crossing from positive to negative needs to be judged, the judgment condition can be reversely processed; the value of i is not limited to 4, and the value of i can be properly selected according to the harmonic component of the waveform to be measured and the condition of judging the stability of the zero crossing point.

And 5: counting by the counter, simultaneously detecting whether a zero-crossing signal exists, if no, continuing counting by the counter, and counting the counter value N when the zero-crossing signal is detected_zcAnd sampling the filtered data N_i、N_i+1Step 6 is transmitted, meanwhile, the counter is reset, step 5 is repeated, and sampling filtering data are continuously output;

wherein in step 5, the frequency of the input waveform of the power source calculated according to the general calculation method isThe maximum error of the frequency compared with the actual power source input waveform isFor this embodiment, the maximum error ε generated by a general method is used for a 50Hz sine wave to be measured₀＝0.05％。

Step 6: according to the current counter value N_zcAnd sampling the filtered data N_i、N_i+1And the previous sampled filtered data N_i、N_i+1(previous application of N_j、N_j+1Indicated for discrimination, initially 0), the power source input waveform frequency f is calculated, and the frequency measurement of the current standard table is completed.

Step 6: according to the current counter value N_zcSampled filtered data N_i、N_i+1Sampled filtered data N from the previous time_j、N_j+1(with N)_j、N_j+1Indicated for discrimination, initially 0), the power source input waveform frequency f is calculated, and the frequency measurement of the current standard table is completed.

In summary, the invention discloses a frequency measurement method applied to a standard meter of an electric energy meter calibrating device, so that a hardware zero-crossing detection circuit is not needed in frequency measurement, and the hardware cost is saved; the zero crossing point position is accurately estimated, and the frequency measurement precision of the standard meter of the electric energy meter calibrating device is improved; complex operations such as Fourier transform and the like are not needed, and the calculation is simpler and more convenient according to a reliable zero-crossing judgment mechanism and zero-crossing point approximate processing.

The above-mentioned embodiments are illustrative of the specific embodiments of the present invention, and are not restrictive, and those skilled in the relevant art can make various changes and modifications to the corresponding equivalent technical solutions without departing from the spirit and scope of the present invention, so that all equivalent technical solutions should be included in the scope of the present invention.