Rapid power calculation method suitable for electric energy meter and use and acquisition terminal, electric energy meter and use and acquisition terminal

Abstract

The invention discloses a rapid power calculation method suitable for an electric energy meter and an acquisition terminal, the electric energy meter and the acquisition terminal, and relates to the technical field of electric power measurement. According to the method, voltage and current signals are sampled, direct-current components are removed, and harmonic interference is suppressed through band-pass filtering; estimating the frequency of the power grid in real time by using zero-cross detection and linear interpolation; processing the filtered voltage and current signals by adopting a delay cancellation model based on a rotation matrix, and eliminating a negative frequency component to generate a corresponding orthogonal vector; and synchronously calculating active power and reactive power through algebraic operation according to the orthogonal vector. According to the method, establishment time delay introduced by a traditional low-pass filter is avoided, rapid tracking of a power value can be achieved when the load power is subjected to step change, electric energy metering deviation in the transient process is effectively reduced, and meanwhile calculation accuracy and robustness under the power grid frequency fluctuation working condition are improved through a frequency self-adaption mechanism.

Description

Technical Field

[0001] This invention relates to the field of electricity metering, specifically to a rapid power calculation method applicable to electricity meters and data collection terminals, and also to electricity meters and data collection terminals based on this method. Background Technology

[0002] As key metering devices for trade settlement and energy efficiency management, electricity meters and data collection terminals have the core task of accurately measuring and accumulating electricity consumption. The accuracy of electricity metering fundamentally depends on the ability to accurately calculate active and reactive power; therefore, the speed and accuracy of power measurement have become important indicators for evaluating electricity meters and data collection terminals.

[0003] Currently, the commonly used power calculation method in the industry is a digital implementation based on instantaneous power theory. This method first performs a dot product operation on the sampled voltage and current values ​​to obtain the instantaneous power value at each sampling moment. Then, a low-pass filter with an extremely low cutoff frequency is used to process these instantaneous power signals, extracting the DC component, which corresponds to the effective value of active power. Similarly, in reactive power calculation, a 90° phase shift is typically applied to the voltage or current signal, followed by the same dot product and filtering operations.

[0004] While the aforementioned methods achieve good metering results under stable load conditions, they exhibit significant limitations in applications with rapidly changing or drastic load fluctuations. To ensure sufficient filtering effectiveness in steady-state conditions to suppress power frequency fluctuations and noise, the bandwidth of the low-pass filter must be designed to be very narrow (typically only a few hertz). This results in a large filter settling time constant. When the load power undergoes a step change, such as the sudden start-up or shutdown of high-power equipment or the introduction of impulsive loads, the power value calculated by traditional methods takes hundreds of milliseconds or even longer to gradually track the true value. This response lag introduces significant energy metering deviations near load switching points, leading to under- or over-metering of electricity, making it difficult to meet the high-precision, rapid-response metering requirements of smart grids in complex power consumption environments such as dynamic loads and intermittent renewable energy access. Summary of the Invention

[0005] This invention proposes a fast power calculation method, a power meter, and a power acquisition terminal applicable to electricity meters and user acquisition terminals. Its purpose is to improve the power calculation speed and achieve rapid power estimation when the load fluctuates.

[0006] The technical solution of this invention is as follows:

[0007] A rapid power calculation method applicable to electricity meters and data acquisition terminals is proposed. This method continuously samples voltage and current signals, stores the sampled data in a buffer, and processes the data according to the following steps at regular intervals:

[0008] Step 1: Remove the DC component from the voltage sampling signal and the current sampling signal;

[0009] Step 2: Input the AC data sequences of the voltage channel and the current channel into the bandpass filter to filter out harmonic signal interference and obtain the filtered data sequences of the voltage channel and the current channel;

[0010] Step 3: Estimate the current frequency based on the filtered data sequence of the voltage channel;

[0011] Step 4: Use the delay cancellation method to obtain the orthogonal vectors of the voltage channel and the current channel. The orthogonal vectors contain a set of in-phase and quadrature components that are mutually orthogonal signals.

[0012] Step 5: Calculate the active power and reactive power at the corresponding time based on the orthogonal vectors of the voltage channel and the current channel.

[0013] As a further improvement to the rapid power calculation method applicable to electricity meters and data collection terminals, the specific process of step 1 is as follows:

[0014] Step 1-1: Calculate the number of sampling points per cycle based on the sampling frequency;

[0015] Let the frequency of the sampled signal be... The sampling frequency is Then the number of sampling points per wave is:

[0016] ;

[0017] During calculation, if an estimated frequency has already been obtained in step 3, the latest estimated value will be used as the mean. ,otherwise Take the preset initial value;

[0018] Steps 1-2: For the sampled voltage and current data, calculate the corresponding DC components by accumulating integer multiples of the frequency.

[0019] Steps 1-3: Subtract the DC component of the corresponding channel from each sampling point of voltage and current to obtain the AC data sequence of the voltage and current channels:

[0020] ;

[0021] ;

[0022] in, and The first Voltage and current sample values ​​at each moment, and These are the DC components of voltage and current, respectively. and The first The AC component value is obtained by subtracting the corresponding DC component from the voltage and current sample values ​​at each moment. The AC data sequence that constitutes the voltage channel. The AC data sequence that constitutes the current channel.

[0023] As a further improvement to the rapid power calculation method applicable to electricity meters and user terminals, the calculation method for steps 1-2 is as follows:

[0024] ;

[0025] ;

[0026] in, This represents the calculated DC component of the current channel. Indicates the current channel's first... The sampled value at each moment. This indicates the number of points that need to be accumulated to calculate the DC component. This represents the cumulative integer number of cycles. This indicates the floor function.

[0027] As a further improvement to the rapid power calculation method applicable to electricity meters and user terminals, the specific process of step 3 is as follows:

[0028] Step 3-1: Perform zero-crossing judgment on the filtered data sequence of the voltage channel: Compare each value with 0 in turn. If the value at a certain moment is less than 0 and the next value is greater than or equal to 0, then record the index number corresponding to that moment in the filtered data sequence as Index1, and the value as... The next value is denoted as ;Will and Save to cache Cache1:

[0029] ;

[0030] Step 3-2: Following the method in Step 3-1, continue to find the next zero-crossing position, and use the same method to save the two values ​​near the zero-crossing point to cache Cache2;

[0031] Let Index2 be the index number of the first point at the next zero-crossing position in the filtered data sequence. Then let... =Index2-Index1, and simultaneously record the two values ​​in cache2 as... and Then we have:

[0032] ;

[0033] Step 3-3: Based on the values ​​stored in Cache1 and Cache2, use linear interpolation to calculate the precise location of the zero-crossing point;

[0034] Steps 3-4: Estimate the frequency based on the precise positions of two adjacent zero-crossing points to obtain the frequency estimate:

[0035] ;

[0036] in, Sampling frequency, This is the zero-crossing position corresponding to Cache1. This is the zero-crossing position corresponding to Cache2.

[0037] As a further improvement to the rapid power calculation method applicable to electricity meters and user terminals, in step 3-3: a rectangular coordinate system is established with the difference between the index number and Index1 of the filtered data sequence as the horizontal axis and the value as the vertical axis. and Draw a straight line from the two corresponding points, and let the expression of the line be:

[0038] ;

[0039] available:

[0040] ;

[0041] The intersection point of the straight line and the x-axis is:

[0042] ;

[0043] Similarly, past and Draw a straight line from the two corresponding points. The intersection point of this line with the x-axis is:

[0044] .

[0045] As a further improvement to the rapid power calculation method applicable to electricity meters and user terminals, the specific process of step 4 is as follows:

[0046] Step 4-1: Establish a single-phase delay cancellation model according to the following formula:

[0047] ;

[0048] in, express Input signal at time, express Output signal at time, Let be a rotation matrix. The rotation angle is used to adjust the phase of the delayed signal in order to cancel out negative frequency components. Indicates the input signal delay. , where is the period of the signal. This is an estimate of the frequency. Take the integer part;

[0049] Step 4-2: Convert each element in the filtered data sequence of the voltage channel and current channel obtained in Step 2 into vector form, and then input the obtained vector as the input signal into the delay cancellation model in Step 4-1 to obtain the corresponding output signal, which is in vector form.

[0050] Suppose that the filtered data sequence of the current channel is in the th... The element corresponding to each time point is Its vector form is as follows: , This represents the matrix transpose operation; the vector is expressed as the input signal. Then the corresponding delayed cancellation output signal is:

[0051] ;

[0052] The voltage channel and current channel are processed separately using the above method. The filtered data sequences of the voltage channel and current channel are then processed separately. The output signals at each time point are denoted as follows: and That is, the orthogonal vectors of the voltage channel and the current channel at the corresponding moment.

[0053] As a further improvement to the aforementioned rapid power calculation method applicable to electricity meters and data collection terminals, and The value can be:

[0054] .

[0055] As a further improvement to the aforementioned rapid power calculation method applicable to electricity meters and user terminals: in step 5, using , Representing vectors respectively The values ​​of position 0 and position 1; , Representing vectors respectively The values ​​at positions 0 and 1;

[0056] Calculate the number according to the following formula. Active power at a given moment and reactive power :

[0057] .

[0058] The present invention also discloses an energy meter, including a processor and a memory, wherein a program stored in the memory is configured to be executed by the processor to implement the above-described fast power calculation method.

[0059] The present invention also discloses a terminal for data acquisition, including a processor and a memory, wherein a program stored in the memory is configured to be executed by the processor to implement the above-described fast power calculation method.

[0060] Compared with the prior art, the present invention has the following beneficial effects:

[0061] 1. This invention introduces a signal orthogonal decomposition method based on a time-delay signal cancellation model, replacing the traditional method of extracting DC components using a low-pass filter in power calculation. This fundamentally solves the power response lag problem caused by long filter settling times. The method uses a rotation matrix to adjust the phase of the time-delay signal to eliminate negative frequency components, thereby directly extracting a set of orthogonal components from the voltage and current signals. Based on these orthogonal components, the RMS values ​​of active and reactive power can be calculated synchronously within a single sampling point through simple algebraic operations. The entire calculation process involves only one time-delayed addition and one multiplication-addition operation, resulting in high computational efficiency. This allows for rapid tracking of power values ​​when the load undergoes a step change, significantly reducing energy metering errors during load switching.

[0062] 2. This invention performs real-time frequency estimation, which is fed back to the DC component removal and orthogonal decomposition stage to form a closed-loop regulation. This not only improves the accuracy of power calculation under frequency variation conditions, but also enhances the system's robustness to grid frequency fluctuations. Detailed Implementation

[0063] The technical solution of the present invention will be described in detail below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0064] Example 1

[0065] A rapid power calculation method applicable to electricity meters and data acquisition terminals is proposed. This method continuously samples voltage and current signals, stores the sampled data in a buffer, and processes the data according to the following steps at regular intervals:

[0066] Step 1: Remove the DC component from the voltage sampling signal and the current sampling signal.

[0067] According to the Nyquist sampling theorem, the sampling frequency should be greater than twice the highest cutoff frequency of the signal. Empirically, the sampling frequency is preferably more than 10 times the signal frequency. For a 50Hz power frequency signal, the sampling frequency can be set to 6.4kHz or 12.8kHz.

[0068] The specific steps are as follows:

[0069] Step 1-1: Calculate the number of sampling points per cycle based on the sampling frequency.

[0070] Assume the frequency of the sampled signal is The sampling frequency is Then the number of sampling points per wave is:

[0071] .

[0072] Due to the initial signal frequency Unknown, generally based on prior knowledge Assign an initial value. In this example, The initial value can be set to 50Hz. During calculation, if an estimated frequency value has already been obtained, the latest estimate should be used as the initial value. ,otherwise Take a preset initial value. In subsequent steps, the frequency will be... Through continuous updates and adjustments, it eventually tends towards a steady-state value.

[0073] Steps 1-2: For the sampled voltage and current data, calculate the corresponding DC components by accumulating the data using integer multiples of the frequency. The specific process is as follows:

[0074] ;

[0075] ;

[0076] in, This represents the calculated DC component. Indicates the first The sampled value at each moment. This indicates the number of points that need to be accumulated to calculate the DC component. This represents the cumulative integer number of cycles. This indicates the floor function.

[0077] Steps 1-3: Subtract the DC component of the corresponding channel from each sampling point of voltage and current to obtain the AC data sequence of voltage and current channels.

[0078] ;

[0079] .

[0080] in, and The first Voltage and current sample values ​​at each moment, and These are the DC components of voltage and current, respectively. and The first The AC component value is obtained by subtracting the corresponding DC component from the voltage and current sample values ​​at each moment. The AC data sequence that constitutes the voltage channel. The AC data sequence that constitutes the current channel.

[0081] Step 2: Input the AC data sequences of the voltage channel and the current channel into the bandpass filter to filter out harmonic signal interference and obtain the filtered data sequences of the voltage channel and the current channel.

[0082] Digital filter design is a conventional technique, therefore this step does not provide specific implementation details. Based on engineering experience, a 6th-order Butterworth IIR filter with a passband of 45Hz-55Hz can meet the requirement of -40dB stopband attenuation. It should also be noted that although IIR filters do not satisfy linear phase, the effect of the filter on phase can be canceled out because the voltage and current paths pass through the filter simultaneously.

[0083] The filtered data sequence of the voltage and current channels is the first... The values ​​at each time point are respectively represented as and .

[0084] Step 3: Estimate the current frequency based on the filtered data sequence of the voltage channel.

[0085] Step 3-1: Perform zero-crossing judgment on the filtered data sequence of the voltage channel: Compare each value with 0 in turn. If the value at a certain moment is less than 0 and the next value is greater than or equal to 0, then record the index number corresponding to that moment in the filtered data sequence as Index1, and the value as... The next value is denoted as .Will and Save to cache Cache1.

[0086] Obviously there are:

[0087] .

[0088] Step 3-2: Following the method in Step 3-1, continue to find the next zero-crossing position, and use the same method to save the two values ​​near the zero-crossing point to cache Cache2.

[0089] Let Index2 be the index number of the first point at the next zero-crossing position in the filtered data sequence. Then let... =Index2-Index1, and simultaneously record the two values ​​in cache2 as... and Then we have:

[0090] .

[0091] Step 3-3: Based on the values ​​stored in Cache1 and Cache2, use linear interpolation to calculate the precise location of the zero-crossing point.

[0092] Establish a Cartesian coordinate system with the difference between the filtered data sequence index and Index1 as the x-axis and the value as the y-axis. and Draw a straight line from the two corresponding points, and let the expression of the line be:

[0093] ;

[0094] available:

[0095] ;

[0096] The intersection point of the straight line and the x-axis is:

[0097] ;

[0098] Similarly, past and Draw a straight line from the two corresponding points. The intersection point of this line with the x-axis is:

[0099] .

[0100] Steps 3-4: Estimate the frequency based on the precise positions of two adjacent zero-crossing points to obtain the frequency estimate:

[0101] ;

[0102] in, The sampling frequency.

[0103] Clearly, the method in step 3 allows for one frequency estimation per cycle. In practical engineering applications, multiple averaging methods can be considered to further improve the accuracy of frequency estimation.

[0104] In the next calculation, the estimated frequency will be used as the frequency. Apply it to step 1.

[0105] Step 4: Use the DSC delay cancellation method to obtain the orthogonal vectors of the voltage channel and the current channel. The orthogonal vectors contain a set of in-phase and quadrature components that are mutually orthogonal signals.

[0106] Step 4-1: Establish a single-phase delay cancellation model according to the following formula:

[0107] ;

[0108] in, express Input signal at time, express Output signal at time, Let be a rotation matrix. The rotation angle is used to adjust the phase of the delayed signal in order to cancel out negative frequency components. Indicates the input signal delay. , where is the period of the signal. This is an estimate of the frequency. Take the integer part.

[0109] In this invention, and The value can be:

[0110] .

[0111] Step 4-2: Convert each element in the filtered data sequence of the voltage channel and current channel obtained in Step 2 into vector form, and then input the obtained vector as the input signal into the delay cancellation model in Step 4-1 to obtain the corresponding output signal, which is in vector form.

[0112] Suppose that the filtered data sequence of the current channel is in the th... The element corresponding to each time point is Its vector form is as follows: , This represents the matrix transpose operation. The vector, as the input signal, is expressed as... Then the corresponding delayed cancellation output signal is:

[0113] .

[0114] The voltage channel and current channel are processed separately using the above method. The filtered data sequences of the voltage channel and current channel are then processed separately. The output signals at each time point are denoted as follows: and That is, the orthogonal vectors of the voltage channel and the current channel at the corresponding moment.

[0115] The principle behind the delay-cancellation model in this step, which yields the orthogonal components of a signal, is as follows: According to Euler's formula, a real signal can be decomposed into the sum of a positive frequency and a negative frequency. In this embodiment of the invention, a 50Hz power frequency signal can be decomposed into two frequencies, +50Hz and -50Hz. This is achieved by adjusting the rotation angle in the delay-cancellation model. This can eliminate the -50Hz signal, while the retained positive frequency components (+50Hz) are decomposed into two dimensions of the output vector, forming a pair of orthogonal signals.

[0116] Step 5: Calculate the active power and reactive power at the corresponding time based on the orthogonal vectors of the voltage channel and the current channel.

[0117] by , Representing vectors respectively The values ​​of position 0 and position 1; , Representing vectors respectively The values ​​at positions 0 and 1.

[0118] Calculate the number according to the following formula. Active power at a given moment and reactive power :

[0119] ;

[0120] because , The signals are orthogonal to each other. , Since they are orthogonal signals, based on the sum-to-product relationship of trigonometric functions, the relevant time... The variables are canceled out during the sum-to-product process, therefore the final result is... and The desired RMS signal.

[0121] Since the power calculation process of this invention only involves one signal delay addition step and one data multiplication and addition step, it avoids the digital filter step in conventional engineering methods for power calculation. Therefore, power estimation can be achieved quickly when the load fluctuates.

[0122] Example 2

[0123] This embodiment discloses an energy meter, including a processor and a memory. A program stored in the memory is configured to be executed by the processor, and when executed, it implements the fast power calculation method described in Embodiment 1. This energy meter uses the fast power calculation method.

[0124] Example 3

[0125] This embodiment discloses a data acquisition terminal, including a processor and a memory. A program stored in the memory is configured to be executed by the processor, and when executed, it implements the fast power calculation method described in Embodiment 1. This is the fast power calculation method used by the energy meter.

[0126] It should be noted that, as will be apparent to those skilled in the art, the present invention is not limited to the details of the exemplary embodiments described above, and that the present invention can be implemented in other specific forms without departing from the spirit or essential characteristics thereof. The scope of the present invention is defined by the claims rather than the foregoing description.

Claims

1. A fast power calculation method suitable for electric energy meters and end-use terminals, characterized in that: The method continuously samples voltage and current signals, stores the sampling data in a cache, and processes the sampling data every interval according to the following steps: Step 1: remove the DC components in the voltage sampling signal and the current sampling signal; Step 2: input the AC data sequences of the voltage channel and the current channel into a band-pass filter to filter out harmonic signal interference and obtain the filtered data sequences of the voltage channel and the current channel; Step 3: estimate the current frequency according to the filtered data sequence of the voltage channel; Step 4: obtain the orthogonal vector of the voltage channel and the orthogonal vector of the current channel using the delay cancellation method, which contains a set of in-phase components and quadrature components that are orthogonal to each other; Step 5: calculate the active power and reactive power at the corresponding time according to the orthogonal vector of the voltage channel and the orthogonal vector of the current channel.

2. The method for fast power calculation suitable for electric energy meter and using sampling terminal according to claim 1, characterized in that, The specific process of step 1 is as follows: Step 1-1: calculate the number of sampling points per cycle according to the sampling frequency; Let the frequency of the sampling signal be , and the sampling frequency be , then the number of sampling points per cycle is: ； In the calculation, if the estimate of the frequency has been obtained in the previously performed step 3, the latest estimate is taken as , otherwise the preset initial value is taken. Step 1-2: calculate the corresponding DC component by accumulating an integer multiple of the cycle for the voltage and current sampling data, respectively; Step 1-3: subtract the DC component of the corresponding channel from each sampling point of the voltage and current to obtain the AC data sequence of the voltage channel and the current channel: ； ； in, and The first Voltage and current sample values ​​at each moment, and These are the DC components of voltage and current, respectively. and The first The AC component value is obtained by subtracting the corresponding DC component from the voltage and current sample values ​​at each moment. The AC data sequence that constitutes the voltage channel. The AC data sequence that constitutes the current path.

3. The method for fast power calculation suitable for electric energy meter and using sampling terminal according to claim 2, characterized in that, The calculation method of step 1-2 is as follows: ； ； wherein, represents the calculated direct current component of the current channel, represents the sample value of the current channel at the time point, represents the number of points to be accumulated for calculating the direct current component, represents the accumulated integer number of cycles, represents the floor operation.

4. The method for fast power calculation suitable for energy meter and end-use terminal according to claim 1, wherein, The specific process of step 3 is as follows: Step 3-1: Zero-crossing judgment is performed on the filtered data sequence of the voltage channel: each value is compared with 0 in turn, and if a value at a certain moment is less than 0 and the next value is greater than or equal to 0, then the index number corresponding to the moment in the filtered data sequence is recorded as Index1, the value is recorded as , and the next value is recorded as ; and and are saved to the cache Cache1: ； Step 3-2: continue to find the next zero-crossing position using the method in step 3-1, and save the two values near the zero-crossing time to the cache Cache2 using the same method; Let the first point of the next zero-crossing position be Index2 in the filtered data sequence, then let Index2 = Indexl + 1, and let the two values in the cache Cache2 be denoted as and respectively. Then we have: ； Step 3-3: calculate the precise position of the zero-crossing point using linear interpolation based on the values saved in the caches Cache1 and Cache2; Step 3-4: estimate the frequency based on the precise positions of the adjacent two zero-crossing points to obtain the frequency estimate: ； wherein, is a sampling frequency, is a zero-crossing position corresponding to Cache 1, is a zero-crossing position corresponding to Cache 2.

5. The method for fast power calculation suitable for electric energy meter and using sampling terminal according to claim 4, characterized in that, Step 3-3: Establish a rectangular coordinate system with the index number of the filtered data sequence minus Indexl as the abscissa and the value as the ordinate, and pass through the two points and Draw a straight line through the two points, and let the expression of the straight line be ； The straight line intersects the x-axis at: ； The specific process of step 4 is as follows: ； Similarly, over and The straight line corresponding to the two points, the intersection of the x-axis is: 。 6. The method for fast power calculation suitable for energy meter and consumer terminal as claimed in claim 1, wherein, Step 4-1: establish a single-phase delay cancellation model according to the following formula: Step 4-2: convert each element in the filtered data sequence of the voltage channel and the current channel obtained in step 2 into a vector form, and then input the obtained vector as an input signal into the delay cancellation model in step 4-1 to obtain the corresponding output signal, which is in vector form; ； wherein, represents the input signal at time t, represents the output signal at time t, is a rotation matrix, is a rotation angle, used to adjust the phase of the delayed signal to achieve the purpose of canceling the negative frequency component, represents the delay of the input signal, , is the period of the signal, is the estimated value of the frequency, is an integer; A processor and a memory, a program stored in the memory is configured to be executed by the processor, and when executed, it implements the fast power calculation method as claimed in any one of claims 1 to 8. Let the element corresponding to the time instant n in the filtered data sequence of the current channel be denoted as , which in vector form is denotes the matrix transpose operation; the vector as input signal is denoted as , then the output signal of the corresponding cancellation delay is​​ ； The voltage channel and the current channel are processed by the above method, and the output signals corresponding to the first time moment in the filtered data sequences of the voltage channel and the current channel are respectively denoted as and , which are the orthogonal vectors of the voltage channel and the current channel at the corresponding time moment.​ 7. The method for fast power calculation suitable for electric energy meter and using sampling terminal according to claim 6, characterized in that, and the values of which are: 。 8. The method for fast power calculation suitable for energy meter and consumer terminal as claimed in claim 6, wherein: In step 5, the values of position 0, position 1 of vector , are represented by , respectively; the values of position 0, position 1 of vector , are represented by , respectively. The active power and the reactive power at the i-th time instant are calculated according to the following formulas: :​​ 。 9. An electric energy meter, characterized by: A processor and a memory, a program stored in the memory is configured to be executed by the processor, and when executed, it implements the fast power calculation method as claimed in any one of claims 1 to 8.

10. A terminal for use with a system as claimed in claim 9, characterized in that: ​

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