A method for reducing dynamic measurement error of smart meter

Abstract

The application provides a method for reducing dynamic measurement error of a smart electric energy meter s (n) an input PGA gain feedback control unit, which can calculate PGA module gain amplification multiple k of a next period after passing through a sampling point analysis algorithm module and a current gain control algorithm module i , and feeds back k i to the PGA module of the current sampling unit, so as to improve sampling precision of the ADC module in the current sampling unit.

Description

Technical Field

[0001] This invention relates to the field of dynamic error measurement of smart energy meters, and specifically to a method for reducing dynamic measurement errors of smart energy meters. Background Technology

[0002] With the increasing introduction of dynamic loads into the smart grid, such as electric arc furnaces in steelmaking, rolling mills, medium-frequency induction heating furnaces, and high-speed rail electric locomotives, the amplitude of the current signal of the electrical load fluctuates widely, and the load power exhibits frequent and random dynamic changes. Current smart meters are primarily designed for steady-state current, and dynamic measurement errors are unavoidable when measuring dynamically fluctuating current loads.

[0003] Figure 1 This is a block diagram of an existing electricity meter metering module system, including a signal voltage / current sampling unit, a power measurement unit, and an energy measurement unit, where the PGA is a programmable gain amplifier. Under actual dynamic load conditions of the power grid, the amplitude of the current signal varies greatly. To reduce metering errors caused by different input signal ranges, the PGA's internal algorithm typically incorporates gain feedback control in the current sampling unit to switch to the appropriate PGA range. However, existing technologies usually control the PGA gain using the effective value of the current; that is, the effective value of the currently sampled current is calculated, and if it exceeds the current range, feedback is sent to the PGA unit for gain switching, thus completing the range switching. Measuring the effective value of the current typically requires at least one power frequency cycle. Furthermore, periodic interference in the power grid signal can easily cause large variations in the current signal amplitude. Considering all these factors, existing technologies typically lag the PGA gain switching time by more than two cycles. This may result in a mismatch between the PGA gain and the current current signal amplitude, leading to measurement errors. For example, selecting a large gain factor for a high-current signal might cause the signal under test to exceed the measurement range of the ADC (Analog-to-Digital Converter), while selecting a small gain factor for a low-current signal might result in insufficient PGA gain, causing the ADC to deviate from its optimal sampling range. Both signals exceeding the ADC's measurement range and the ADC deviating from its optimal sampling range will introduce significant measurement errors into the ADC sampling of the energy meter. Summary of the Invention

[0004] To address the sampling errors caused by the large-scale dynamic changes in the sampling amplitude of the ADC in current smart energy meters, this invention proposes a method to reduce the dynamic measurement error of smart energy meters. This method, based on sampling point analysis, can greatly improve the sampling accuracy of the ADC for dynamic current loads, while also reducing range switching errors.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A method for reducing dynamic measurement errors in smart energy meters includes a voltage sampling unit, a current sampling unit, an active power measurement unit, a PGA (Programmable Gain Amplifier) ​​gain feedback control unit, and an energy measurement unit. The current sampling unit includes a PGA module and an ADC (Analog-to-Digital Converter) module, and the PGA gain feedback control unit includes a sampling point analysis algorithm module. The analog voltage signal u... s (t) is converted into a digital signal u after passing through the voltage sampling unit. s (n), analog current signal i s (s) is converted into a digital signal i after passing through the PGA module and ADC module in the current sampling unit. s (n), digital signal u s (n) and i s (n) The active power signal p can be obtained through the active power measurement unit. o (n), active power signal p o (n) The energy signal e can be obtained by the accumulation and calculation of the energy measurement unit. o (n); where the digital signal i s (n) The PGA module gain amplification factor k is also calculated by the sampling point analysis algorithm module in the PGA gain feedback control unit. i and k i Feedback input is sent to the PGA module in the current sampling unit;

[0007] in,

[0008]

[0009]

[0010] Among them, I m (t) represents the amplitude of the current signal as a function of time, and f0 is the fundamental frequency of the power grid (usually 50Hz). I represents the phase value of the current signal (usually a fixed value), t represents time, and I represents the phase value of the current signal. m (n) represents the amplitude of the current signal that varies with the sampling point, F s Here, n is the sampling frequency of the ADC module, and n is a natural number.

[0011] The working steps of the sampling point analysis algorithm module are as follows:

[0012] (1) First, based on the current sampling frequency Fs and the fundamental frequency f0, the amplitude of the current signal is calculated to be I. M The number of sampling points corresponding to integer multiples: N2, N4, N8, N 16 Where N2 represents the amplitude of the actual current signal as I. MThe number of sampling points with amplitude limitation is twice that of the actual current signal, N4 represents the number of sampling points when the actual current signal amplitude is I. M The number of sampling points with amplitude limitation is 4 times that of the actual current signal amplitude I. M The number of sampling points with amplitude limitation is 8 times that of the time limit, N 16 This indicates that when the actual current signal amplitude is I M The number of sampling points with a time-limited amplitude that is 16 times the maximum; among which, I M This represents the maximum value of the current range of the ADC module.

[0013] (2) During the actual sampling process, the number of sampling points within the current fundamental period T0 of the power grid that equal the current maximum range I of the ADC module is calculated by accumulating the data. M and with N C express;

[0014] (3) Comparative analysis, when N2≤N C When <N4, it proves that the amplitude of the actual current signal is the maximum value I of the current range of the ADC module. M The gain amplification factor k of the PGA module is 2-4 times that of the PGA module. i The value should be reduced by a factor of 4 to ensure that the actual current signal amplitude is within the optimal sampling range of the ADC; when N4 ≤ N C When <N8, it proves that the actual current signal amplitude is I. M The gain amplification factor k of the PGA module is 4-8 times that of the PGA module. i The value should be reduced by a factor of 8 to ensure that the actual current signal amplitude is within the optimal sampling range of the ADC; when N8 ≤ N C <N 16 At that time, it was proven that the amplitude of the actual current signal was I. M The gain amplification factor k of the PGA module is 8-16 times that of the PGA module. i It should be reduced by a factor of 16 to ensure that the actual current signal amplitude is within the optimal sampling range of the ADC;

[0015] (4) The gain amplification factor k of the PGA module obtained in step (3) is used to calculate the gain amplification factor k of the PGA module. i Feedback is sent to the PGA module.

[0016] The technical solution of the present invention can achieve the following technical effects:

[0017] The method for reducing dynamic measurement error of smart energy meters provided by this invention is based on sampling point analysis to determine that the actual current signal amplitude is within the optimal sampling range of the ADC, which greatly improves the sampling accuracy of the ADC for dynamic current loads, improves the measurement accuracy of smart energy meters, and can reduce range switching errors, and has good application prospects. Attached Figure Description

[0018] Figure 1Here is a system block diagram of an existing electricity meter metering module;

[0019] Figure 2 To improve the system block diagram of the electricity meter metering module;

[0020] Figure 3 Schematic diagram showing current signal amplitude exceeding ADC range;

[0021] Figures 4-7 A schematic diagram showing a current signal amplitude exceeding an integer multiple of the ADC range.

[0022] Figure 8 A schematic diagram illustrating the effect of applying the sampling point analysis algorithm of this invention. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the described embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0024] Figure 2 The improved energy meter metering module system block diagram of this invention includes a voltage sampling unit, a current sampling unit, an active power measurement unit, a PGA (Programmable Gain Amplifier) ​​gain feedback control unit, and an energy measurement unit. The current sampling unit includes a PGA module and an ADC (Analog-to-Digital Converter) module, and the PGA gain feedback control unit includes a sampling point analysis algorithm module. The analog voltage signal u from the voltage sensor... s (t) is converted into a digital signal u after passing through the voltage sampling unit. s (n), the analog current signal i from the current sensor. s (t) is converted into a digital signal i after passing through the PGA module and ADC module in the current sampling unit. s (n), digital signal u s (n) and i s (n) The active power signal p can be obtained through the active power measurement unit. o (n), active power signal p o (n) The energy signal e can be obtained by the accumulation and calculation of the energy measurement unit. o (n); where the digital signal i s (n) is further processed by the sampling point analysis algorithm module in the PGA gain feedback control unit to obtain the new PGA module gain amplification factor k. i and k iFeedback is input to the PGA module in the current sampling unit.

[0025] In this invention, in order to improve the sampling accuracy of the ADC module in the current sampling unit, the digital signal i is... s (n) Inputting the PGA gain feedback control unit, the new PGA module gain amplification factor k can be calculated after passing through the sampling point analysis algorithm module. i and k i Feedback is sent to the PGA module of the current sampling unit. The following is a detailed explanation of the working steps of the sampling point analysis algorithm module.

[0026] In actual power grids, under dynamic load conditions, the amplitude of the dynamic load current at the power user's port varies greatly, while the frequency and phase of the current remain relatively stable. Therefore, the dynamic analog current signal i s (t) can be represented by the following formula (1).

[0027]

[0028] Among them, I m (t) represents the amplitude of the current signal as a function of time, and f0 is the fundamental frequency of the power grid (usually 50Hz). t represents the phase value of the current signal (usually a fixed value), and t represents time.

[0029] Analog signal i s (t) is converted into a digital signal i after sampling by the PGA module and ADC module. s (n), to improve the sampling accuracy of the ADC, small amplitude values ​​i are usually... s The (t) signal is amplified by the PGA module. Digital signal i s (n) can be represented by the following formula (2).

[0030]

[0031] Where, k i The gain factor of the PGA module is typically ×1, ×2, ×4, ×8, ×16, etc.; n is a natural number, I m (n) represents the amplitude of the current signal that varies with the sampling point, F s This refers to the sampling frequency of the ADC module. Because the amplitude of the dynamic analog current signal changes frequently, the current technology's PGA gain switching lags, causing a mismatch between the PGA amplification factor and the current current signal amplitude. This results in situations where the signal exceeds the current range of the ADC module, such as... Figure 3 Where T0 is the fundamental frequency period of the power grid (usually 0.02 seconds), the solid line represents the current signal to be measured that is limited, the dashed line represents the actual current signal waveform, and M is the number of lagging fundamental frequency periods, usually M>2.

[0032] To solve the analog current signal i s (t) The technical problem of the sampled signal exceeding the current range of the ADC module after being amplified by the PGA module is addressed by this invention, which designs a sampling point analysis algorithm module.

[0033] like Figure 4 I M T represents the maximum value of the current range of the ADC module. s This is the sampling period of the ADC module. When the amplitude of the actual current signal is I... M When the amplitude is doubled, the number of sampling points with amplitude limiting is N2, and the amplitude limiting interval is N2T. s ;like Figure 5 When the actual current signal amplitude is I M When the amplitude is 4 times that of the standard, the number of amplitude-limited sampling points is N4, and the amplitude-limiting interval is N4T. s ;like Figure 6 When the actual current signal amplitude is I M When the amplitude is 8 times that of the standard, the number of amplitude-limited sampling points is N8, and the amplitude-limiting interval time is N8T. s ;like Figure 7 When the actual current signal amplitude is I M When the amplitude is 16 times, the number of limited sampling points is N. 16 There are N units, with the amplitude limiting interval being N. 16 T s .

[0034] The working steps of the sampling point analysis algorithm module are as follows:

[0035] (1) First, based on the current sampling frequency Fs and the fundamental frequency f0, the amplitude of the current signal is calculated to be I. M The number of sampling points corresponding to integer multiples: N2, N4, N8, N 16 Where N2 represents the amplitude of the actual current signal as I. M The number of sampling points with amplitude limitation is twice that of the actual current signal, N4 represents the number of sampling points when the actual current signal amplitude is I. M The number of sampling points with amplitude limitation is 4 times that of the actual current signal amplitude I. M The number of sampling points with amplitude limitation is 8 times that of the time limit, N 16 This indicates that when the actual current signal amplitude is I M The number of sampling points with a time limit of 16 times.

[0036] (2) During the actual sampling process, the number of sampling points within the current fundamental period T0 of the power grid that equal the current maximum range I of the ADC module is calculated by accumulating the data. M and with N C express.

[0037] (3) Comparative analysis, when N2≤NC When <N4, it proves that the amplitude of the actual current signal is the maximum value I of the current range of the ADC module. M The gain amplification factor k of the PGA module is 2-4 times that of the PGA module. i The value should be reduced by a factor of 4 to ensure that the actual current signal amplitude is within the optimal sampling range of the ADC; when N4 ≤ N C When <N8, it proves that the actual current signal amplitude is I. M The gain amplification factor k of the PGA module is 4-8 times that of the PGA module. i The value should be reduced by a factor of 8 to ensure that the actual current signal amplitude is within the optimal sampling range of the ADC; when N8 ≤ N C <N 16 At that time, it was proven that the amplitude of the actual current signal was I. M The gain amplification factor k of the PGA module is 8-16 times that of the PGA module. i It should be reduced by a factor of 16 to ensure that the actual current signal amplitude is within the optimal sampling range of the ADC.

[0038] (4) The gain amplification factor k of the PGA module obtained in step (3) is used to calculate the gain amplification factor k of the PGA module. i Feedback is sent to the PGA module.

[0039] Figure 3 and Figure 8 The comparison shows that the PGA gain amplification factor switching time after applying this sampling point analysis algorithm is delayed by a maximum of 1 fundamental frequency period T0, while existing technologies usually delay the PGA gain amplification factor switching time by more than 2 fundamental frequency periods T0, which greatly improves the accuracy of power metering.

[0040] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

[0041] In summary, the above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made within the scope of the claims of the present invention should be covered by the present invention.

Claims

1. A method for reducing dynamic measurement errors in smart energy meters, comprising a voltage sampling unit, a current sampling unit, an active power measurement unit, a PGA gain feedback control unit, and an energy measurement unit; wherein the current sampling unit includes a PGA module and an ADC module, and the PGA gain feedback control unit includes a sampling point analysis algorithm module; and an analog voltage signal u s (t) is converted into a digital voltage signal u after passing through the voltage sampling unit. s (n), analog current signal i s (t) is converted into a digital current signal i after passing through the PGA module and ADC module in the current sampling unit. s (n), digital voltage signal u s (n) and digital current signal i s (n) The active power signal p can be obtained through the active power measurement unit. o (n), active power signal p o (n) The energy signal e can be obtained by the accumulation and calculation of the energy measurement unit. o (n); where, Digital current signal i s (n) The PGA module gain amplification factor k is also calculated by the sampling point analysis algorithm module in the PGA gain feedback control unit. i And increase the gain of the PGA module by factor k. i Feedback input is sent to the PGA module in the current sampling unit; in, Among them, I m (t) represents the amplitude of the current signal as a function of time, and f0 is the fundamental frequency of the power grid. I represents the phase value of the current signal, t represents time, and I represents the phase value of the current signal. m (n) represents the amplitude of the current signal that varies with the sampling point, F s Here, n is the sampling frequency of the ADC module, and n is a natural number. The working steps of the sampling point analysis algorithm module are as follows: (1) First, based on the current sampling frequency Fs and the fundamental frequency of the power grid f0, the amplitude of the current signal is calculated to be I. M The number of sampling points corresponding to integer multiples: N2, N4, N8, N 16 Where N2 represents the current signal amplitude as I. M The number of sampling points with amplitude limitation is twice that of the current signal, N4 represents the number of sampling points when the current signal amplitude is I. M The number of sampling points with amplitude limitation is 4 times that of the current signal, N8 represents the number of sampling points when the current signal amplitude is I. M The number of sampling points with amplitude limitation is 8 times that of the time limit, N 16 This indicates that when the amplitude of the current signal is I M The number of sampling points with a time-limited amplitude that is 16 times the maximum; among which, I M This represents the maximum value of the current range of the ADC module. (2) During the sampling process, the number of sampling points equal to the current maximum range I of the ADC module within the current fundamental period T0 of the power grid is calculated cumulatively. M and with N C express; (3) Comparative analysis, when N2≤N C When <N4, it proves that the amplitude of the current signal is I. M The gain amplification factor k of the PGA module is 2-4 times that of the PGA module. i The value should be reduced by a factor of 4 to ensure that the actual current signal amplitude is within the optimal sampling range of the ADC module; when N4 ≤ N C When <N8, it proves that the amplitude of the current signal is I. M The gain amplification factor k of the PGA module is 4-8 times that of the PGA module. i The value should be reduced by a factor of 8 to ensure that the actual current signal amplitude is within the optimal sampling range of the ADC module; when N8 ≤ N C <N 16 At that time, it is proven that the amplitude of the current signal is I. M The gain amplification factor k of the PGA module is 8-16 times that of the PGA module. i It should be reduced by a factor of 16 to ensure that the actual current signal amplitude is within the optimal sampling range of the ADC module; (4) The gain amplification factor k of the PGA module obtained in step (3) is used to calculate the gain amplification factor k of the PGA module. i Feedback is sent to the PGA module.

2. The method for reducing dynamic measurement error of smart energy meters according to claim 1, wherein, f0 is 50Hz.

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