Electric quantity metering method and device for adaptive transformation ratio adjustment

Abstract

The invention discloses a self-adaptive transformation ratio adjustment electric quantity metering method and device, the device comprises a high-voltage metering device and a control center, and the high-voltage metering device is composed of a voltage transformer, a current transformer and an electric energy meter. The core innovation point is that the current transformer is provided with a plurality of secondary windings, each winding is respectively connected with a relay with a multi-gang switch contact, the output end of the relay is connected with the electric energy meter, and the relay and the control center realize linkage control. The control center drives a multi-gang switch contact of the relay to be automatically switched to a secondary winding adaptive to the current load by monitoring the current state of the load in real time; factors such as temperature, humidity and the year of a home-entry power grid are introduced to correct a current measured value, and the accuracy of electric quantity metering is improved. Meanwhile, the control center records transformation ratio switching data in real time, reliable support is provided for time-of-use electricity price execution, demand side response and electric quantity tracing, and the intelligence and refinement level of electric power metering is remarkably improved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of electric power measurement and control, and particularly relates to an electric quantity measurement method and device with adaptive variable ratio adjustment. BACKGROUND

[0002] The current high-voltage measurement device for trade settlement generally consists of a voltage transformer, a current transformer and an electric energy meter. The current and voltage on the primary side of the user are respectively converted into secondary current and voltage with smaller values by the current transformer and the voltage transformer, and then are connected to the electric energy meter for electric energy measurement.

[0003] According to the DL / T448-2016 Electric Energy Measurement Device Technical Management Regulation, when the load current is less than 10% of the rated current of the measured meter (5% for S-grade electric energy meter) or less than 20% of the nominal current of the standard instrument, or the power factor is less than 0.5, the electric energy meter is not suitable for load error measurement after actual detection. In actual operation, the user load is fluctuant, the transformer ratio and the specification parameters of the electric energy meter are fixed, and in the current economic downturn situation, many users will be in a low-load operation state for a long time. The secondary current connected to the electric energy meter is far less than 10% of the rated current of the electric energy meter. There is a problem that the electric energy meter cannot directly display the electric quantity value. Frequent replacement of the electric energy meter and the transformer will greatly increase the operation and maintenance cost, and may involve power outage operation, which will affect the power supply reliability. SUMMARY

[0004] The purpose of the present application is to provide an electric quantity measurement method and device with adaptive variable ratio adjustment. The present application selects a current transformer with multiple secondary windings, uses a relay to control the connection of the secondary windings to the electric energy meter, and realizes automatic switching of the variable ratio when the secondary current of the electric energy meter is low. The variable ratio is switched according to the monitoring of the secondary current, and the relatively large current on the secondary side is sent to the electric energy meter during low-load operation. The automatic variable ratio gear switching realizes accurate measurement of the electric energy meter. The present application also introduces temperature, humidity, and the new and old age of the household power grid to adjust the current and voltage data, and further improves the accuracy of the electric energy meter measurement.

[0005] The technical application of the present application is as follows:

[0006] An electric quantity measurement method with adaptive variable ratio adjustment comprises an electric energy meter, a current transformer and a relay. The current transformer has multiple secondary windings to form multiple variable ratio gears, and the multiple secondary windings are connected to the relay. The relay controls the connection of different secondary windings to the electric energy meter. The current on the primary side of the user is converted into secondary current with smaller values by the current transformer, and then is connected to the electric energy meter for electric energy measurement. The measurement accuracy of the electric energy meter is improved, and the electric energy meter can realize accurate measurement under the condition of too small or too large primary current.

[0007] Comprising the following steps:

[0008] S1: Data acquisition

[0009] Real-time monitoring of voltage and current signals of the power meter connected to the power distribution network, setting a high sampling frequency, not less than 1 kHz, collecting environmental parameters such as temperature and humidity, providing data support for subsequent error correction;

[0010] S2: Data processing

[0011] Filtering the collected voltage and current data to remove noise interference;

[0012] S3: Error correction

[0013] Considering the influence of temperature, humidity, and household power grid age on voltage and current, correcting the voltage and current;

[0014] S4: Ratio adjustment judgment

[0015] Set current threshold and fluctuation range, based on the collected real-time current data, make judgment on the ratio adjustment of the power meter ratio gear; when the real-time current is continuously lower than the preset lower threshold and the fluctuation amplitude is small, switch to a smaller ratio gear;

[0016] When the real-time current is continuously higher than the preset upper threshold, switch to a larger ratio gear. In the judgment process, introduce a time delay mechanism to avoid misjudgment due to instantaneous current fluctuation. The delay time is usually set to 5-10 seconds;

[0017] Determine the ratio gear switching rule, execute the ratio gear switching, determine the switching constraints and protection conditions, and update the threshold based on the new gear rated current after the ratio switching;

[0018] S5: Ratio adjustment execution

[0019] Switch different ratio gears of different secondary windings through relays. After the ratio switching is completed, seamlessly connect to the new ratio gear for metering. The entire switching process does not exceed 100 ms, avoiding metering interruption;

[0020] S6: Real-time metering

[0021] Combine the corrected voltage and current data to calculate real-time power and energy. Active power is calculated according to the formula , where U is the corrected voltage effective value, I is the corrected current effective value after ratio adjustment, is the power factor; by integrating the active power, the real-time energy is obtained.

[0022] Further, the S1 step includes:

[0023] Based on the power system measurement accuracy requirements, set the sampling frequency of voltage and current signal, synchronous acquisition of three-phase voltage (u a , u β , u c ) and three-phase current (i a , i β , i c ) instantaneous value, using synchronous sampling technology to ensure the phase difference measurement error of voltage and current signal ≤0.1°;

[0024] Environmental parameter acquisition deployment: install temperature and humidity sensor near the electric energy meter, collect environmental temperature T and relative humidity H at the frequency of 10Hz, transmit data to central processing unit through RS485 bus, provide basic data for subsequent temperature drift error correction.

[0025] Further, the S2 step comprises:

[0026] S21: Anti-aliasing filter processing: the collected voltage and current signals are first passed through a second-order Butterworth low-pass filter with a cutoff frequency of 500Hz to suppress high-frequency noise interference; the filter transfer function is:

[0027] G(s) = 1 / [(s / (2π×500)) 2 +1.414×(s / (2π×500))+1]

[0028] Where s is the Laplace operator;

[0029] S22: Sliding window mean filtering: the filtered instantaneous value is smoothed by a sliding window with length N = 20, and the voltage and current smoothed value at time t is calculated:

[0030] u a(t) =(1 / N)×∑ k＝t-19 t u a(k)

[0031] i a(t) =(1 / N)×∑ k＝t-19 t i a(k)

[0032] (In the formula, u a(k) , i a(k) are the A-phase voltage and current instantaneous value of the kth sampling point.

[0033] Further, the S3 step comprises:

[0034] S31: Temperature drift correction function: establish a temperature correction model for current measurement value, and the correction formula is:

[0035] I c orr=I m eas×[1+α×(T-25)+β×(T-25) 2 ]

[0036] where I m eas is the original measured current effective value,

[0037] α=0.001-0.002 / ℃, β=0.00001-0.000015 / ℃2 are temperature coefficients, T is the ambient temperature, and 25℃ is set as the reference temperature;

[0038] S32: Humidity influence correction: when the relative humidity H>85%, introduce the humidity correction coefficient K H =1+0.001×(H-85), correct the voltage measurement value:

[0039] U c orr=U m eas×K H

[0040] U m eas is the original measured voltage effective value, and the influence of insulation resistance change on voltage measurement in a high humidity environment is eliminated through the correction;

[0041] S33: Influence correction of new and old household power grid: when the household power grid age>10 years, introduce the age correction model, and the correction formula is:

[0042] The corrected actual current effective value I actual The calculation formula is as follows:

[0043] I actual =I c orr×[1+α×(Y-10)+β×(Y-10) 2 ]

[0044] Where:

[0045] I c orr is the drift correction current value, Y is the actual service age of the household power grid, and when Y≤10, the correction coefficient is 1, and no correction is needed;

[0046] α is a linear correction coefficient, with a value range of 0.002-0.005, reflecting the linear influence of power grid aging on current measurement, and is obtained by fitting the measured data of power grids of different ages;

[0047] β is a quadratic correction coefficient, with a value range of 0.0001-0.0003, representing the nonlinear influence of the increasing degree of power grid aging on current measurement, and is also determined by fitting the measured data.

[0048] Further, the S4 step comprises:

[0049] S41: Current threshold calculation model:

[0050] Based on the rated current of the current ratio gear, set the upper and lower threshold values, set the rated primary current corresponding to the current ratio gear as I rated,current , the measurement interval is 30%-70% of the rated current, and the threshold calculation formula is:

[0051] Lower threshold value: I low = I rated,current × 0.3

[0052] Upper threshold value: I high = I rated,current × 0.7

[0053] S42: Fluctuation amplitude determination parameter:

[0054] Define the fluctuation coefficient C V to measure the stability of the current, set the fluctuation threshold C V,th = 0.1, i.e. the fluctuation amplitude is ≤10%, and the calculation formula is:

[0055] Where, σ I is the standard deviation of the current effective value in t minutes, μ I is the average value of the current effective value in t minutes, and is calculated by:

[0056]

[0057] n is the current effective value of n periods in t minutes;

[0058] S43: Time delay parameter setting: set the ratio adjustment delay time t delay = 5-10 seconds, which is used to filter transient fluctuations and avoid misjudgment;

[0059] S44: Ratio gear switching rule: preset ratio gear sequence K = [K1, K2, K3,...], K1, K2, K3,.. indicate different ratio gears, and the switching logic is:

[0060] If the real-time current is continuously lower than the preset lower threshold value and the fluctuation amplitude is small, the current gear K i is switched to K i-1 , and it is required to ensure that i>1, i.e. there is a smaller gear;

[0061] If the real-time current is continuously higher than the preset upper threshold value, the current gear K i is switched to K i+1 , and it is required to ensure that i

[0062] S45: Switching constraint and protection: Set minimum switching interval t min Avoid frequent switching. If t min has been switched, even if the condition is met, it is delayed to the interval after execution, the constraint formula is: Allow switch = (t now -t last ) ≥ t min

[0063] Where t now is the current time, t last is the last switching time;

[0064] S46: Threshold dynamic update: After the variable ratio switching, immediately update the threshold based on the new gear rated current:

[0065] I low,new = I rated,new × 0.3, I high,new = I rated,new × 0.7

[0066] And upload the new variable ratio parameters to the central processing unit, and update the local cached gear information synchronously.

[0067] Further, the S5 step includes:

[0068] Switch the variable ratio gear by driving the relay through the control algorithm:

[0069] S51: Relay drive signal generation:

[0070] PID control algorithm is used to generate relay drive signal to ensure the accuracy and stability of relay action;

[0071] The calculation formula of control quantity u(t) is:

[0072]

[0073] Where, e(t) = K new -K current is the variable ratio gear deviation, K p , K i , K d are the proportional, integral and differential coefficients respectively;

[0074] S52: Relay switching control:

[0075] According to the generated drive signal, control the relay action to realize the switching of the variable ratio gear from K current to K new ;

[0076] In the switching process, the state of the relay is monitored in real time to ensure that the switching action is completed within a specified time; a switching time threshold t is set max If the switching time exceeds the threshold t max , a fault alarm signal is sent out

[0077] S53: ratio switching completion detection

[0078] The position state of the relay is detected by a sensor, and when it is confirmed that the ratio switching is completed, a switching completion signal is sent out to trigger the metering system to switch to the new ratio gear K new .

[0079] Furthermore, the S5 step further comprises

[0080] S54: electric quantity metering formula switching

[0081] Before the ratio switching, the electric quantity metering formula is

[0082]

[0083] After the switching is completed, the electric quantity metering formula is seamlessly switched to

[0084]

[0085] Where (t1) is the moment when the ratio switching is completed.

[0086] An electric quantity metering device with adaptive ratio adjustment, comprising a high-voltage metering device composed of a voltage transformer, a current transformer and an electric energy meter, and a control center, characterized in that the current transformer has a plurality of secondary windings, the plurality of secondary windings are respectively connected to relays, the relays are provided with multi-union switch contacts capable of being respectively connected to different windings, the relay output connection end is connected to the electric energy meter, and the relay is connected to the control center.

[0087] An electric quantity metering device with adaptive ratio adjustment, characterized in that the electric energy meter is integrated with a data acquisition communication module and a 485 interface, communication is performed through the 485 interface of the electric energy meter, and the electric energy meter is connected to the control center.

[0088] Advantages of the present application:

[0089] 1. High-precision metering in the full load range, especially optimization of deep valley small load scenarios

[0090] The traditional current transformer has the contradiction of "easy saturation under large load and insufficient sensitivity under small load" due to the fixed ratio: when the load current is extremely low in the deep valley period (such as night residential power or industrial low valley production, the current may be less than 5% of the rated current), the output current of the secondary winding with fixed ratio is too small, which is easily disturbed by noise, resulting in a significant increase in the metering error of the electric energy meter (even more than ±2%).

[0091] The multiple secondary windings of the current transformer correspond to different variable ratio specifications, and the control center can select the winding that adapts to the current load through relay switching:

[0092] When the deep valley small current is switched to the large variable ratio winding, the small primary current is converted into a larger secondary current, the sampling sensitivity of the electric energy meter is improved, and the error is controlled within ±0.2%;

[0093] When the high peak large current is switched to the small variable ratio winding, the secondary current is prevented from being too large to cause the electric energy meter to be overloaded or the current transformer core to be saturated, and the measurement linearity under large load is ensured.

[0094] 2. Adaptive dynamic adjustment without manual intervention

[0095] The traditional variable ratio adjustment of the transformer needs to manually replace the winding or the transformer during power failure, which is complicated and affects the continuity of power supply, and is difficult to cope with dynamic changes in load.

[0096] The application realizes automatic switching of the variable ratio through the linkage of the multi-connection switch contact of the relay and the control center:

[0097] The control center collects the current data of the electric energy meter in real time (or directly collects the secondary side current of the current transformer), and decides the switching time through a preset algorithm (such as current threshold judgment);

[0098] The multi-connection switch contact of the relay quickly responds to the control instruction (switching time ≤100ms), and the winding switching can be completed without power failure, avoiding measurement interruption.

[0099] 3. Reliable structure and strong anti-interference ability

[0100] The application adopts the hardware architecture of "multiple secondary windings + relay multi-connection switch", which has higher stability than the complex electronic stepless variable ratio adjustment technology:

[0101] The multiple secondary windings of the current transformer are independently wound, and have good electromagnetic isolation, avoiding signal interference between different windings;

[0102] The multi-connection switch contact of the relay adopts mechanical contacts (or magnetic latching relays), has small contact resistance (≤50mΩ), stable contact during switching, and supports long-term high-frequency operation (mechanical life ≥100,000 times), and meets the long-term operation demand of the power grid;

[0103] 4. Strong compatibility and easy upgrading

[0104] The application is based on the basic architecture of the traditional high-voltage measurement device (voltage transformer, current transformer, electric energy meter) for optimization, and does not overturn the core components of the original measurement system:

[0105] Only add the number of secondary windings to the current transformer, retain the original primary side wiring method, and do not need to modify the high voltage line;

[0106] The relay output is directly connected to the existing electric energy meter, and the electric energy meter does not need to be specially customized (compatible with mainstream communication protocols such as DL / T645);

[0107] The control center can be integrated into the existing power distribution automation system, and data interaction is realized through standard interfaces (RS485, NB-IoT).

[0108] 5、Data continuity and traceability are improved

[0109] During the relay switching process, the control center records the ratio switching time, the current winding specification, the load current value and other data in real time, and synchronously to the electric energy meter and the background system:

[0110] Avoiding the measurement disputes caused by record loss in traditional manual switching;

[0111] The background can accurately analyze the power composition of different load intervals based on the ratio switching record and electric energy data, and provide data support for time-of-use pricing execution and demand side response. BRIEF DESCRIPTION OF DRAWINGS

[0112] Figure 1 The structure diagram of the electric energy meter connected to the secondary winding of the current transformer.

[0113] Figure 2 The circuit principle diagram of the electric energy meter connected to the secondary winding of the current transformer. DETAILED DESCRIPTION

[0114] Example 1

[0115] An adaptive ratio adjustment electric quantity measurement method, comprising the following steps:

[0116] S1: Data acquisition

[0117] Real-time monitoring of voltage and current signals in the power system, setting a high sampling frequency, not less than 1kHz, collecting environmental parameters such as temperature and humidity, providing data support for subsequent error correction;

[0118] s11: Parameter acquisition and frequency setting

[0119] Based on the measurement accuracy requirements of the power system, the sampling frequency of voltage and current signals is set to 1kHz, and three-phase voltage (u a , u β , u c ) and three-phase current (i a , i β , i c) Instantaneous value, using synchronous sampling technology to ensure that the phase difference between voltage and current signal is measured with an error of ≤0.1°;

[0120] Environmental parameter acquisition deployment: Install a temperature and humidity sensor near the metering device to collect environmental temperature T and relative humidity H at a frequency of 10 Hz, and transmit the data to the local processing unit through the RS485 bus to provide basic data for subsequent temperature drift error correction;

[0121] Real-time effective value calculation: Based on the sampling data, the average effective value of three-phase voltage and current is calculated synchronously.

[0122] S2: Data processing

[0123] Filter the collected voltage and current data to remove noise interference;

[0124] S21: Anti-aliasing filter processing: The collected voltage and current raw signals are first passed through a second-order Butterworth low-pass filter with a cutoff frequency of 500 Hz to suppress high-frequency noise interference; The filter transfer function is:

[0125] G(s) = 1 / [(s / (2π×500)) 2 +1.414×(s / (2π×500))+1]

[0126] Where s is the Laplace operator, and through this filter, noise above 500 Hz is attenuated by ≥40 dB;

[0127] S22: Sliding window mean filtering: The filtered instantaneous value is smoothed using a sliding window with a length of N=20 to calculate the voltage and current smoothed value at time t:

[0128] u a(t) =(1 / N)×∑ k＝t-19 t u a(k)

[0129] i a(t) =(1 / N)×∑ k＝t-19 t i a(k)

[0130] Where u a(k) , i a(k) are the A-phase voltage and current instantaneous values at the kth sampling point, and this algorithm reduces the impact of instantaneous pulse interference on data;

[0131] S3: Error correction

[0132] Consider the influence of temperature, humidity, and the age of the household power grid on voltage and current, and correct the voltage and current;

[0133] S31: Temperature drift correction function: a temperature correction model of current measurement value is established, and the correction formula is:

[0134] I c orr=I m eas×[1+α×(T-25)+β×(T-25) 2 ]

[0135] where I m eas is the original measured current effective value, α = 0.002 / ℃, β = 0.00001 / ℃ 2 is the temperature coefficient, T is the ambient temperature (unit: ℃), and 25℃ is the reference temperature;

[0136] S32: Humidity influence correction: when the relative humidity H > 85%, introduce the humidity correction coefficient K H =

[0137] 1+0.001×(H-85), correct the voltage measurement value:

[0138] U c orr=U m eas×K H

[0139] The influence of insulation resistance change on voltage measurement in high humidity environment is eliminated by this correction;

[0140] S33: Influence correction of the age of household power grid: when the age of household power grid > 10 years, introduce the age correction model, and the correction formula is:

[0141] The corrected actual current effective value (I actual ) is calculated as follows:

[0142] I actual =I c orr×[1+α×(Y-10)+β×(Y-10) 2 ]

[0143] Where:

[0144] I c orr is the temperature drift corrected current value (unit: A), that is, the current value after ratio switching and basic measurement processing;

[0145] Y is the actual service life of household power grid (unit: years), when Y≤10, the correction coefficient is 1, and no correction is needed;

[0146] α is the linear correction coefficient, the value range is 0.002-0.005, reflecting the linear influence of power grid aging on current measurement, which can be obtained by fitting the measured data of power grids with different service life.

[0147] β is the quadratic correction coefficient, the value range is 0.0001-0.0003, which reflects the nonlinear influence of the aging degree of power grid on current measurement, and is also determined by fitting the measured data.

[0148] The correction formula comprehensively considers the cumulative change rule of line resistance with aging time after the service life of the power grid exceeds 10 years by introducing linear and quadratic terms. When the service life of the power grid increases, the correction coefficient gradually increases, positively compensating the measured current to offset the problem of smaller measured value caused by line loss and signal distortion. In actual application, α and β need to be calibrated according to local power grid materials (such as copper cable, aluminum cable), laying environment (such as indoor, outdoor) and other factors to ensure that the corrected current value is closer to the true value.

[0149] S4: ratio adjustment judgment

[0150] Set the current threshold and fluctuation range, based on the collected real-time current data, to make the judgment of the ratio adjustment of the energy meter ratio gear; when the real-time current is continuously lower than the preset lower threshold and the fluctuation amplitude is small, switch to a smaller ratio gear;

[0151] When the real-time current is continuously higher than the preset upper threshold, switch to a larger ratio gear. In the judgment process, a time delay mechanism is introduced to avoid misjudgment caused by instantaneous current fluctuation. The delay time is usually set to 5-10 seconds;

[0152] S41: current threshold calculation model:

[0153] Based on the rated current of the current ratio gear, set the upper and lower threshold values, and set the rated primary current corresponding to the current ratio gear as I rated,current (for example, 500A), the best measurement interval is 30%-70% of the rated current, and the threshold calculation formula is:

[0154] Lower threshold: I low = I rated,current × 0.3

[0155] Upper threshold: I high = I rated,current × 0.7

[0156] For example, when the current ratio rated current is 500A, I low = 150A, I high = 350A;

[0157] S42: fluctuation amplitude judgment parameter:

[0158] Define the fluctuation coefficient C V to measure the stability of the current, and set the fluctuation threshold CV,th = 0.1 (i.e. fluctuation amplitude ≤ 10%), calculated by:

[0159] where σ I is the standard deviation of current RMS value in 1 minute, μ I is the average value of current RMS value in 1 minute, calculated by:

[0160]

[0161] n = 4, i.e. 4 current RMS values in 1 minute, each in 15 seconds.

[0162] S43: Time delay parameter setting:

[0163] Set the delay time t delay = 5-10 seconds (default 8 seconds) for filtering transient fluctuations to avoid misjudgment.

[0164] S44: Ratio gear switching rule:

[0165] Pre-set ratio gear sequence K = [K1, K2, K3,...] (e.g. K1 = 200 / 5, K2 = 300 / 5, K3 = 500 / 5, corresponding to rated currents 200A, 300A, 500A), switching logic is:

[0166] If the real-time current is continuously lower than the pre-set lower threshold and the fluctuation amplitude is small, the current gear K i is switched to K i-1 (must ensure i > 1, i.e. there is a smaller gear).

[0167] If the real-time current is continuously higher than the pre-set upper threshold, the current gear K i is switched to K i+1 (must ensure i < n, i.e. there is a larger gear).

[0168] S45: Switching constraints and protection:

[0169] Set the minimum switching interval t min = 5 minutes to avoid frequent switching. If switching has been performed within 5 minutes, it is delayed to the interval to execute even if the condition is met, the constraint formula is: Allow switch = (t now -t last ) ≥ t min

[0170] where t now is the current time, t last is the last switching time.

[0171] S46: Threshold dynamic update:

[0172] Immediately after the ratio switching, update the threshold based on the new gear rated current:

[0173] I low,new = I rated,new x 0.3, I high,new = I rated,new x 0.7

[0174] And upload the new ratio parameter to the central processing unit, update the local cached gear information synchronously;

[0175] S5: Ratio adjustment execution

[0176] Switch different ratio gears through relays, and seamlessly connect to the new ratio gear for metering after the ratio switching is completed. The entire switching process does not exceed 100 ms, avoiding metering interruption;

[0177] Switch the ratio gear through the control algorithm to drive the relay:

[0178] Relay drive signal generation:

[0179] Generate the relay drive signal using the PID control algorithm to ensure the accuracy and stability of the relay action;

[0180] The calculation formula of the control quantity u(t) is:

[0181]

[0182] Where e(t) = K new -K current is the ratio gear deviation, K p , K i , K d are the proportional, integral, and differential coefficients, respectively.

[0183] Relay switching control: according to the generated drive signal, control the relay action to realize the switching of the ratio gear from K current to K new ;

[0184] During the switching process, the state of the relay is monitored in real time to ensure that the switching action is completed within the specified time; set the switching time threshold t max = 100 ms, if the switching time exceeds the threshold, a fault alarm signal is sent;

[0185] Ratio switching completion detection: detect the position state of the relay through the sensor, and send a switching completion signal to trigger the metering system to switch to the new ratio gear K new after confirming that the ratio switching is completed;

[0186] Electricity metering formula switching:

[0187] Before the transformation ratio switching, the electricity metering formula is

[0188]

[0189] After the switching is completed, the electricity metering formula is seamlessly switched to

[0190]

[0191] Where (t1) is the time when the transformation ratio switching is completed;

[0192] S6: Real-time metering

[0193] Combined with the corrected voltage and current data, real-time power and electricity are calculated, and active power is calculated according to the formula , where U is the corrected voltage effective value, I is the current effective value after transformation ratio adjustment and correction, is the power factor;

[0194] By integrating the active power, real-time electricity is obtained, and the integration time interval is set according to the sampling frequency, usually 1 second.

[0195] The transformation ratio range is a pre-set conversion ratio of different ranges in the metering equipment (such as current transformer or electric energy meter), which is used to adapt to different ranges of current input. Its mathematical expression is:

[0196]

[0197] Example: If the transformation ratio range is set to [100:5, 50:5, 20:5], it corresponds to:

[0198] Range 1: 100A (primary side) → 5A (secondary side)

[0199] Range 2: 50A → 5A

[0200] Range 3: 20A → 5A

[0201] The transformation ratio range is the range of the collected current signal.

[0202] First, when the real-time current is continuously lower than the pre-set lower threshold (such as 5% of the rated current) and the fluctuation range is small (such as the fluctuation amplitude is less than 2%), it is preliminarily judged that it needs to be switched to a smaller transformation ratio range; when the real-time current is continuously higher than the pre-set upper threshold (such as 30% of the rated current), it is judged that it needs to be switched to a larger transformation ratio range.

[0203] Example 2

[0204] See Figure 1 , Figure 2 .

[0205] An adaptive variable ratio adjustment electric energy metering device, comprising a high voltage metering device, which is composed of a voltage transformer, a current transformer and an electric energy meter, and a control center, the current transformer has two secondary windings, the two secondary windings have four terminals, terminals 1 and 2 are the in-out terminal of the secondary current of the first path, terminals 3 and 4 are the terminal of the secondary current of the second path, terminals 5 and 6 are the in-out terminal of the electric energy meter, the terminals of the terminal box form a 2-in-1-out structure. A relay is installed between terminals 1 and 2 and terminals 3 and 4 respectively. The relay output terminal is connected to the electric energy meter, and the relay is connected to the control center.

[0206] The electric energy meter is integrated with a data acquisition communication module and a 485 interface, and the communication is carried out through the 485 interface of the electric energy meter, and the electric energy meter is connected to the control center.

[0207] After the primary current passes through the current transformer, two different sizes of currents are generated in the secondary circuits of the two secondary windings respectively.

[0208] The structure of the electric energy meter terminal box is modified. Different terminal is connected in parallel, and the function of the terminal box is modified to make the terminal box intelligent. The control function is increased, and the logic control circuit is added to the terminal box. Assuming that the current connected between terminals 1 and 2 is large current, and the current connected between terminals 3 and 4 is small current. When the current in the 1, 2 circuit is less than a certain value (such as 0.15A, the commonly used electric energy meter model is 1.5(6)A), the relay operates to control, selects the small variable ratio circuit, the relay contact between 1, 2 is closed, and the relay contact between 3, 4 is opened; when the current connected between terminals 3 and 4 is greater than 5A, the relay contact between terminals 1 and 2 is opened, the relay contact between terminals 3 and 4 is closed, and the large variable ratio circuit is selected.

[0209] The local communication function with the ammeter is increased, the acquisition communication module is added to the terminal box, the communication is carried out through the 485 interface of the electric energy meter, the frozen indication of the electric energy meter is acquired and recorded, and the current indication of the electric energy meter is acquired in real time when the relay operates. A simple electric quantity calculation function is added, the recorded electric energy indication is used to calculate the electric quantity according to the switched variable ratio, and the electric quantity recorded by the electric energy meter is compensated.

[0210] A display unit is added, an LCD screen is added to the terminal box, and the acquired and recorded data and the calculated data are displayed on the LCD screen.

[0211] The LCD screen displays the following contents: the variable ratio 1, 2, the indication and electric quantity of each period, the variable ratio 3, 4, the indication and electric quantity of each period, the monthly compensation electric quantity, and the deep valley electric quantity. If the deep valley electric quantity is measured, the relay operates, the variable ratio changes, and the deep valley electric quantity under each variable ratio is calculated and added up.

Claims

1. A self-adaptive variable ratio adjustment electric energy metering method, comprising an electric energy meter, a current transformer, and a relay, the current transformer having a plurality of different secondary windings to form a plurality of variable ratio gears, the plurality of secondary windings being connected to the relay respectively, and the different secondary windings being connected to the electric energy meter through the relay, and the current at the primary side of a user being converted into a secondary current with a smaller value by the current transformer and connected to the electric energy meter for electric energy metering, characterized in that, Comprise the following steps: S1: data acquisition Real-time monitoring of the voltage and current signal of the power meter access distribution network, set a high sampling frequency, not less than 1 kHz, collect environmental parameters, such as temperature, humidity, for subsequent error correction to provide data support; S2: data processing The collected voltage, current data filtering, remove noise interference; S3: error correction Consider the temperature, humidity, home into the new and old factors of the influence of voltage, current, voltage, current correction; S4: ratio adjustment judgment Set the current threshold and fluctuation range, based on the real-time current data, the ratio of the power meter ratio adjustment of the judgment; When the real-time current is continuously lower than the preset lower threshold and the fluctuation amplitude is small, switch to a smaller ratio; When the real-time current is continuously higher than the preset upper threshold, switch to a larger ratio, in the judgment process, the introduction of time delay mechanism, avoid the instantaneous current fluctuation caused by misjudgment, usually delay time set for 5-10 seconds; Determine the ratio of the switching rules, execute the ratio of the switching, determine the switching constraints and protection conditions, after the ratio of the switching, based on the new rating current update threshold; S5: ratio adjustment execution Through the relay switch different secondary winding of different ratio, when the ratio of the switching is completed, seamless connection to the new ratio for measurement, the whole switching process does not exceed 100 ms, avoid the measurement interruption; S6: real-time measurement The real-time power and power amount are calculated in combination with the corrected voltage and current data, and the active power is calculated according to the formula = U * I * cosφ, wherein U is the corrected voltage effective value, I is the corrected current effective value adjusted by the ratio, and φ is the power factor. The real-time power amount is obtained by performing an integral operation on the active power.

2. The self-adapting variable-ratio adjustment electric power metering method according to claim 1, characterized in that, S1 step includes: Based on the power system measurement accuracy requirements, set the sampling frequency of voltage and current signal, synchronous acquisition of three-phase voltage (u a , u β , u c ) and three-phase current (i a , i β , i c ) instantaneous value, using synchronous sampling technology to ensure the phase difference measurement error of voltage and current signal ≤0.1°; Environmental parameter acquisition deployment: install temperature and humidity sensor near the power meter, collect environmental temperature T and relative humidity H with 10 Hz frequency, transmit data to the central processing unit through RS485 bus, provide basic data for subsequent temperature drift error correction.

3. The method of claim 1, wherein, S2 step includes: S21: anti-aliasing filter processing: the collected voltage, current signal first through the cut-off frequency of 500 Hz second-order Butterworth low-pass filter, suppress high-frequency noise interference; Filter transfer function is: G(s) = 1 / [(s / (2π x 500)) 2 + 1.414 x (s / (2π x 500)) + 1] Where s is the Laplace operator; S22: sliding window mean filter: the instantaneous value after filtering, using the length N = 20 sliding window for smoothing, calculate the voltage, current smooth value at t time: u a(t) = (1 / N) x ∑ k＝t-19 t u a(k) i a(t) = (1 / N) x ∑ k＝t-19 t i a(k) (In the formula, u a(k) , i a(k) are the A-phase voltage and current instantaneous values of the kth sampling point, respectively.

4. The method of claim 1, wherein, S3 step includes: S31: temperature drift correction function: establish the temperature correction model of current measurement value, correction formula is: I c orr = I m eas x [1 + a x (T - 25) + b x (T - 25) 2 ] where I m eas is the original measured current effective value, a = 0.001 - 0.002 / °C, β = 0.00001 - 0.000015 / °C 2 T is the ambient temperature, and 25°C is set as the reference temperature. S32: Humidity influence correction: When the relative humidity H > 85%, introduce a humidity correction coefficient K H = 1 + 0.001 x (H - 85), correct the voltage measurement value: U c orr = U m eas x K H U m eas is the original measured voltage effective value, and the correction eliminates the influence of insulation resistance change under high humidity environment on voltage measurement; S33: influence correction of new and old home power grid: home into the power grid age > 10 years, introduce the age correction model, correction formula is: the modified actual current effective value I actual The calculation formula is as follows: I actual = I c orr x [1 + a x (Y - 10) + b x (Y - 10) 2 ] Where: I c torr is the drift corrected current value, Y is the actual service life of the incoming power grid, when Y≤10, the correction factor is 1, no correction is needed; Alpha is the linear correction coefficient, the value range is 0.002-0.005, reflect the linear influence of power grid aging on current measurement, through the measured data fitting of different age power grid obtained; Beta is the quadratic correction coefficient, the value range is 0.0001-0.0003, embodies the nonlinear influence of power grid aging on current measurement, also through the measured data fitting to determine.

5. The method of claim 1, wherein, S4 step includes: S41: current threshold calculation model: Based on the rated current of the current gear ratio, set the upper and lower threshold values, set the rated primary current corresponding to the current gear ratio as I rated,current , the measurement interval is 30%-70% of the rated current, and the threshold calculation formula is: Lower threshold: I low = I rated,current x 0.3 Upper threshold: I high = I rated,current x 0.7 S42: fluctuation amplitude determination parameters: Definition of the coefficient of fluctuation C V Measuring the current stability, setting the fluctuation threshold C V,th = 0.1, i.e. the fluctuation amplitude ≤ 10%, the calculation formula is: where σ I is the standard deviation of the current effective value over t minutes, μ I is the average value of the current effective value over t minutes, calculated by the following equation: N is the current effective value of n cycles in t minutes; S43: Time delay parameter setting: Set the variable ratio adjustment delay time t delay = 5-10 seconds, for filtering transient fluctuations, to avoid misjudgment; S44: variable ratio gear shift rule: preset variable ratio gear sequence K = [K1, K2, K3,...], K1, K2, K3,.. refer to different variable ratio gears, and the switching logic is: If the real-time current continuously falls below the preset lower threshold and the fluctuation amplitude is small, the current gear K i is switched to K i-1 , it is necessary to ensure that i>1, that is, there is a smaller gear; If the real-time current is continuously higher than the preset upper threshold value, the current gear K i is switched to K i+1 , it is necessary to ensure that i < n, that is, there is a larger gear. S45: Switching constraint and protection: set minimum switching interval t min Avoid frequent switching. If t min has been performed, even if the condition is met, it is delayed until the interval is executed, and the constraint formula is: Allow switch = (t now -t last ) ≥ t min where t now is the current time, t last is the last switch time; S46: threshold dynamic update: immediately update the threshold based on the new gear rated current after variable ratio switching: I low,new = I rated,new x 0.3, I high,new = I rated,new x 0.7 And upload the new variable ratio parameters to the central processing unit, and update the locally cached gear information synchronously.

6. The method of claim 1, wherein, S5 step includes: Switching of variable ratio gears is driven by controlling algorithm to drive the relay: S51: relay drive signal generation: PID control algorithm is adopted to generate the relay drive signal, ensuring the accuracy and stability of the relay action; The calculation formula of the control quantity u(t) is: where e(t) = K new - K current is the gear ratio deviation, K p , K i , K d are the proportional, integral, and derivative coefficients, respectively. S52: relay switching control: According to the generated driving signal, the relay is controlled to act, so as to realize the switching of the variable ratio gear from K current to K new . During the switching process, the state of the relay is monitored in real time to ensure that the switching action is completed within a specified time; a switching time threshold t is set max , and if the switching time exceeds the threshold t max , a fault alarm signal is issued; S53: variable ratio switching completion detection: The position state of the relay is detected by a sensor, and when it is confirmed that the ratio switching is completed, a switching completion signal is sent to trigger the metering system to switch to the new ratio gear K new .

7. The method of claim 1, wherein, S5 step also includes: S54: electric quantity metering formula switching: Before variable ratio switching, the electric quantity metering formula is After switching is completed, the electric quantity metering formula is seamlessly switched to Where (t1) is the variable ratio switching completion time.

8. A deep valley power metering device with adaptive variable ratio adjustment, comprising a high voltage metering device consisting of a voltage transformer, a current transformer and a watt-hour meter, and a control center, characterized in that, The current transformer has a plurality of secondary windings, and the plurality of secondary windings are respectively connected to the relays, the relays are provided with a plurality of switch contacts which can be respectively connected to different windings, the relay output connection end is connected to the electric energy meter, and the relay is connected to the control center.

9. A deep notch power metering device with adaptive variable ratio adjustment as defined in claim 8, wherein, The electric energy meter is integrated with a data acquisition communication module and a 485 interface, communication is performed through the 485 interface of the electric energy meter, and the electric energy meter is connected to the control center.

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