A detection circuit and an electric energy metering chip and device based on the circuit

Abstract

The present application relates to the technical field of electric energy metering, and discloses a detection circuit and an electric energy metering chip and device based on the circuit. The circuit includes a reference current source, a sampling circuit, an adaptive filtering module, a signal processing module, a disconnection condition detection circuit, and protection measures taken for the conditions. The present application adopts an adaptive filtering module, which greatly reduces the measurement error caused by the change of the reference current source frequency or the interference in the sampling signal, and improves the measurement accuracy of the detection circuit. At the same time, the present application designs a detection circuit for various disconnection conditions in the detection circuit and corresponding disconnection protection measures, thereby increasing the reliability and safety of the metering system operation.

Description

Technical Field

[0001] The present application relates to the technical field of electric energy metering, and in particular to a detection circuit and an electric energy metering chip and device based on the circuit. Background Art

[0002] In the electric energy measurement of smart electric energy meters, the grid current and voltage signals are generally converted into voltage signals that meet the input voltage safety range of ADC (Analog to Digital Converter) through the electric energy meter, sensor and sampling network. The digital signal converted by ADC is then input into the digital processing unit for power calculation and measurement.

[0003] In the power supply system, the accuracy of the electric energy metering device is directly related to the economic interests of both the power supplier and the user. Although the electric energy metering equipment will be calibrated with a standard meter of higher accuracy before leaving the factory to meet the accuracy level specified by the electric energy metering equipment standard, after the electric energy metering equipment is installed on site, it will cause metering errors due to many reasons such as changes in the external environment and aging and failure of components. Whether the electric energy metering equipment will produce metering errors on site, whether measures can be taken to reduce the metering errors, and whether the metering circuit faults can be discovered in time are the key issues of concern to both the power supplier and the user.

[0004] At present, the managers of electricity meters use the method of regular offline spot checks of electricity meter errors during the entire life cycle management process after the electricity meters are connected to the network. They are unable to conduct real-time online monitoring to promptly detect changes in the accuracy of each grid-connected electricity metering device and self-diagnose electricity metering circuit failures, resulting in errors in electricity billing, causing unnecessary trouble and losses to both the electricity supplier and the user. Summary of the invention

[0005] The purpose of the present application is to provide a detection circuit and an electric energy metering chip and device based on the circuit, which greatly reduces the metering error caused by changes in the reference current source frequency or the presence of interference signals in the sampling signal, and improves the metering accuracy and reliability of the metering system.

[0006] In order to solve the above problems, the present application discloses a detection circuit, comprising:

[0007] A reference current source outputting a second frequency AC signal;

[0008] A sampling circuit coupled to the reference current source, the sampling circuit also coupled to a first signal source outputting a first frequency AC signal, and outputting a sampling signal of a mixed signal of the first frequency AC signal and the second frequency AC signal;

[0009] An adaptive filtering module comprises an adaptive filter and a subtractor, wherein the sampling circuit is coupled to an input end of the adaptive filter and a first input end of the subtractor respectively, and an output end of the adaptive filter is coupled to a second input end of the subtractor. The adaptive filter is used to filter the sampled signal to obtain the first frequency AC signal, and the subtractor is used to output the second frequency AC signal after subtracting the sampled signal at the first input end from the first frequency AC signal at the second input end.

[0010] The signal processing module is coupled to the adaptive filtering module and is used to perform signal processing on the second frequency AC signal output by the adaptive filtering module.

[0011] In a preferred example, before using the adaptive filter, it is necessary to calculate and fix the various order parameters of the adaptive filter, and the various order parameters are determined based on the steepest descent method.

[0012] In a preferred example, the order parameters are determined based on the least mean square method. According to an iterative formula for the order parameters of an FIR filter, the mean square expected value of the output of the subtractor is minimized through multiple iterations, thereby obtaining the order parameters of the adaptive filter.

[0013] In a preferred example, it also includes an analog-to-digital converter coupled to the sampling circuit, and the analog-to-digital converter is coupled to the adaptive filtering module.

[0014] In a preferred example, it also includes a first detection module coupled to the two input ends of the analog-to-digital converter, the first detection module is coupled to the signal processing module, and the first detector is used to detect whether there is an abnormal AC signal in the signals of the first input end and the second input end of the analog-to-digital converter.

[0015] In a preferred embodiment, it also includes:

[0016] An RC filter having an input end coupled to the sampling circuit, and an output end of the RC filter coupled to an input end of the analog-to-digital converter;

[0017] A first impedance element is coupled to both ends of the sampling circuit.

[0018] In a preferred embodiment, it also includes:

[0019] A second detection module, wherein the input end is coupled to the reference current source, and the output end is coupled to the signal processing module, for detecting whether an open circuit fault occurs in the reference current source, and feeding back to the signal processing module;

[0020] A second impedance element has one end coupled to the reference current source and the other end coupled to ground.

[0021] In a preferred example, the sampling circuit uses manganese copper or current transformer for sampling.

[0022] The present application also discloses an electric energy metering chip, which includes the detection circuit as described above.

[0023] The present application also discloses an electric energy metering device, which includes the electric energy metering chip described above.

[0024] In the implementation manner of the present application, the detection circuit includes a reference current source, a sampling circuit, an adaptive filtering module, a signal processing module, a disconnection condition detection circuit, and protection measures taken for the condition. The advantages of this circuit are as follows:

[0025] 1. Adaptive filtering module composed of adaptive filter and subtractor:

[0026] (1) Before the adaptive filter is used, it is necessary to calculate and fix the order parameters of the adaptive filter, and the order parameters are determined based on the steepest descent method. Furthermore, the order parameters are determined based on the least mean square method. According to an iterative formula for the order parameters of the FIR filter, the mean square expected value of the output of the subtractor is minimized through multiple iterations, thereby obtaining the order parameters of the adaptive filter;

[0027] (2) The adaptive filter includes an FIR filter with adjustable order. When the target signal is turned off and there is only an AC signal, the adaptive filtering algorithm is used to calculate the order parameters of the FIR filter, so that the output of the subtractor is zero and the order parameters of the filter are fixed. When the target signal is turned on and there is only an AC signal (all sampled signals pass through at this time), after the signal passes through the adaptive filter with fixed order parameters, the subtractor subtracts "all sampled signals" and "sampled signals except the target signal" to accurately obtain the target signal.

[0028] (3) When the target signal or the sampled signal is interfered by an external signal or changes itself, the adaptive filtering algorithm can recalculate the optimal parameters of the adaptive filter to obtain an accurate target signal;

[0029] Because this adaptive filtering module physically separates the reference current source by filtering out other signals, it will not respond to the frequency of the reference current source before and after separation, so the change of the frequency of the reference current source will not cause measurement errors; and if there is an interference signal in the sampling signal, the adaptive filtering module can recalculate the optimal parameters of the adaptive filter to make this interference signal within the filtering range of the adaptive filter, so that the obtained frequency f1 of the reference current source will not be affected.

[0030] Moreover, the use of the above-mentioned adaptive filtering module greatly reduces the measurement error of the detection circuit caused by the change of the reference current source frequency or the existence of interference signals in the sampling signal, and improves the measurement accuracy and reliability of the detection circuit.

[0031] 2. Connect RC filter at both ends of the sampling circuit:

[0032] Both ends of the sampling circuit are connected to the RC filter so that the sampling signal passes through the RC filter before being input into the adaptive filter. The RC filter adopts a differential structure, which can effectively suppress common-mode interference in the signal and greatly reduce the measurement error of the detection circuit caused by signal interference.

[0033] 3. Detection of disconnection conditions and emergency protection measures:

[0034] "Reference current source break detection and protection measures", "sampling line break detection and protection measures" and "live line break detection and protection measures" are introduced respectively. Detection circuits and protection circuits are designed for the break conditions, which greatly increase the reliability and safety of the metering system operation in which the detection circuit is located.

[0035] A large number of technical features are recorded in the specification of this application, which are distributed in various technical solutions. If all possible combinations of technical features of this application (i.e., technical solutions) are to be listed, the specification will be too long. In order to avoid this problem, the various technical features disclosed in the above-mentioned invention content of this application, the various technical features disclosed in the various embodiments and examples below, and the various technical features disclosed in the accompanying drawings can be freely combined with each other to form various new technical solutions (these technical solutions are all deemed to have been recorded in this specification), unless the combination of such technical features is technically infeasible. For example, in one example, feature A+B+C is disclosed, and in another example, feature A+B+D+E is disclosed, and features C and D are equivalent technical means that play the same role. Technically, only one can be used, and it is impossible to use them at the same time. Feature E can be combined with feature C technically. Then, the solution of A+B+C+D should not be deemed to have been recorded because it is technically infeasible, and the solution of A+B+C+E should be deemed to have been recorded. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 is a circuit block diagram of a detection circuit according to the first embodiment of the present application

[0037] Figure 2 (a) is a block diagram of the principle of the adaptive filtering module according to the first embodiment of the present application

[0038] Figure 2(b) is a principle block diagram of the adaptive filtering module in the training state according to the first embodiment of the present application

[0039] Figure 2 (c) is a principle block diagram of the adaptive filtering module in the working state according to the first embodiment of the present application.

[0040] Figure 3 This is a principle block diagram of an adaptive filtering module according to the present application.

[0041] Figure 4 This is a block diagram of the parameter fixing algorithm of a FIR transverse filter according to the present application.

[0042] Figure 5 is an embodiment of the RC filter according to the present application

[0043] Figure 6 A typical current detection device with current self-calibration function according to the present application

[0044] Figure 7 An embodiment of a current detection device with current self-calibration function according to the present application DETAILED DESCRIPTION

[0045] In the following description, many technical details are provided to help readers better understand the present application. However, those skilled in the art can understand that the technical solution claimed in the present application can be implemented even without these technical details and various changes and modifications based on the following embodiments.

[0046] Description of some concepts:

[0047] Creep: When the electric energy meter is in operation or calibration, it is often the case that the dial continues to rotate when only voltage is applied and the load current is zero. This phenomenon is called voltage creep, or simply creep.

[0048] Steepest descent method: Also known as the gradient method, it is the oldest analytical method. Other analytical methods are either its deformation or inspired by it, so it is the basis of optimization methods. The steepest descent method is an important analytical method for the unconstrained nonlinear programming problem minf(x) of n-variable functions. Studying the principle of the steepest descent method and its algorithm implementation is of great significance to us.

[0049] Least Mean Square Algorithm: Least Mean Square Algorithm, referred to as LMS algorithm, is an improved algorithm of the steepest descent algorithm. It is an optimized extension of the Wiener filter theory after applying the rapid descent method. The algorithm does not require the statistical characteristics of the input signal and the expected signal to be known. The weight coefficient of the "current moment" is obtained by adding a proportional term of the negative mean square error gradient to the weight coefficient of the "previous moment". It has the characteristics of low computational complexity, good convergence in an environment where the signal is a stationary signal, unbiased convergence of its expected value to the Wiener solution, and stability when the algorithm is implemented using finite precision, making the LMS algorithm the most stable and widely used algorithm in the adaptive algorithm.

[0050] In order to make the objectives, technical solutions and advantages of the present application more clear, the implementation methods of the present application will be further described in detail below with reference to the accompanying drawings.

[0051] The first embodiment of the present application relates to a detection circuit, the circuit block diagram of which is as follows Figure 1 As shown, the detection circuit includes: (1) a reference current source that outputs a second frequency AC signal; (2) a sampling circuit coupled to the reference current source, the sampling circuit is also coupled to a first signal source that outputs a first frequency AC signal, and the sampling circuit outputs a sampling signal that is a mixed signal of the first frequency AC signal and the second frequency AC signal; (3) an adaptive filtering module, including an adaptive filter and a subtractor, the sampling circuit is coupled to the input end of the adaptive filter and the first input end of the subtractor respectively, the output end of the adaptive filter is coupled to the second input end of the subtractor, the adaptive filter is used to filter the sampling signal to obtain the first frequency AC signal, and the subtractor is used to subtract the sampling signal at the first input end from the first frequency AC signal at the second input end and then output the second frequency AC signal; (4) a signal processing module, the signal processing module is coupled to the adaptive filtering module, and the signal processing module is used to perform signal processing on the second frequency AC signal output by the adaptive filtering module.

[0052] Alternatively, if Figure 2 As shown, the adaptive filtering module includes an adaptive filter and a subtractor. Before the adaptive filter is used, it is necessary to calculate and fix the parameters of each order of the adaptive filter.

[0053] Alternatively, if Figure 2 As shown, the adaptive filtering module includes two working states: a training state and a working state; wherein the training state is used to calculate and fix the parameters of the adaptive filtering.

[0054] Specifically, taking the first signal source as the power grid as an example, when the adaptive filtering module is in the training state, the connection mode of the adaptive filtering module is as follows: Figure 2As shown in (b), the target signal is turned off, and only the 50Hz power grid signal is added to the input signal. By training the adaptive filter, the output end of the adaptive filter module is made zero; after completing the above training, the adaptive filter module can work normally (i.e., it is in working state), and its connection method is as follows: Figure 2 As shown in (c), the input signal is a mixed signal of the target signal and the 50HZ power grid signal. This mixed signal is filtered out by an adaptive filter to remove other signals and only retains the signal related to the 50Hz power grid, and then output to the second input end of the subtractor. Finally, the mixed signal at the first input end of the subtractor is subtracted from the signal at the second input end to obtain the target signal.

[0055] Optionally, the training state of the adaptive filter can be controlled by setting a switch at the target signal output terminal.

[0056] Optionally, each order parameter of the adaptive filter is determined based on the steepest descent method.

[0057] Optionally, each order parameter of the adaptive filter is determined based on a least mean square method.

[0058] Alternatively, if Figure 3 As shown, this adaptive filter is an order-adjustable FIR filter. According to the iterative formula of each order parameter, the mean square expected value of the output of the subtractor in the adaptive filtering module can be minimized through multiple iterations, thereby obtaining each order parameter of the adaptive filter.

[0059] An implementation method for fixing the parameters of each order of the adaptive filter of the present application is: after the adaptive filtering module (including the subtractor and the adaptive filter) is connected to the sampling circuit and the reference current source, the reference current source is turned off and only an AC signal is present. The AC signal passes through the adaptive filter to make the output of the subtractor zero, and then according to the iterative formula of each order parameter, the mean square expected value of the output of the subtractor is minimized through multiple iterations to obtain the optimal parameters, and then the parameters of each order of the filter are fixed.

[0060] An embodiment of the adaptive filter of the present application is a FIR transversal filter. Figure 4 For this purpose, the internal structure of the FIR transversal filter is as follows:

[0061] Weight sequence: h(k) = [h1(k),h2(k),…,h M (k)] T (1)

[0062] Regression vector: x(k) = [x(k), x(k-1), …, x(k-M+1)] T (2)

[0063] According to equations (1) and (2), the output of the FIR transversal filter is:

[0064]

[0065] It should be understood that the iterative formulas of the various order parameters described in this application are set according to the situation and through the algorithm module.

[0066] Optionally, the present application determines the magnitude of the measurement error of the detection circuit by using a signal processing module to analyze the change in information (such as amplitude, phase, etc.) of a target signal (such as a second frequency signal output by a reference current source) relative to a preset calibration value.

[0067] Optionally, in the present application, when the sampling signal is interfered by an external signal or changes itself, the adaptive filtering module recalculates the parameters of each order of the adaptive filter through "training", thereby obtaining an accurate target signal.

[0068] Optionally, the detection circuit involved in the present application also includes an analog-to-digital converter coupled to the sampling circuit, the analog-to-digital converter is coupled to the input end of the adaptive filtering module, and the analog-to-digital converter performs analog-to-digital conversion on the sampling signal output by the sampling circuit.

[0069] Optionally, the detection circuit involved in the present application also includes a first detection module coupled to the two input ends of the analog-to-digital converter, the first detection module is coupled to the signal processing module, and the first detector is used to detect whether there is an abnormal AC signal (such as an interference signal) in the signal of the first input end and the second input end of the analog-to-digital converter.

[0070] Optionally, the first detection module further includes a detector and a detection algorithm. In order to prevent misjudgment due to the presence of interference signals at the first input terminal and the second input terminal of the analog-to-digital converter, the detection algorithm can reliably detect abnormal AC signals at the first input terminal and the second input terminal of the analog-to-digital converter to determine whether the live wire of this detection circuit is actually disconnected, and feed it back to the signal processing module for processing, or the signal processing module transmits the determination result to the meter maintenance personnel through external communication.

[0071] Optionally, the detection circuit involved in the present application also includes an RC filter whose input end is coupled to the sampling circuit, and the output end of the RC filter is coupled to the input end of the analog-to-digital converter. This RC filter can effectively suppress common-mode interference in the signal, thereby improving the measurement accuracy of the detection circuit.

[0072] An embodiment of the RC filter in the present application is composed of a resistor R1, a capacitor C1, a resistor R2, and a capacitor C2, such as Figure 5 As shown, the use of symmetrical differential form can effectively suppress common-mode interference in the signal.

[0073] Optionally, the detection circuit involved in the present application also includes a first impedance element coupled to both ends of the sampling circuit. This first impedance element can block the signal when the sampling line of the detection circuit is disconnected or falls off, thereby preventing serious metering distortion and over-metering of electricity bills.

[0074] Optionally, the detection circuit involved in the present application also includes a second detection module and a second impedance element; the input end of the second detection module is coupled to the reference current source, and the output end is coupled to the signal processing module. The second detection module monitors the output voltage of the reference current source at all times to detect whether the reference current source has an open circuit fault, and feeds back to the signal processing module; one end of the second impedance element is coupled to the reference current source, and the other end is coupled to the ground. The first impedance element provides a freewheeling loop when the reference current source has an open circuit fault, thereby playing a protective role.

[0075] It is important for those skilled in the art to understand that since the current self-calibration theory is based on the fact that the reference current source is constant, once the reference current source is open-circuited, the system will believe that the sampling resistor involved in the sampling circuit has changed to a very small value, thereby calibrating the first signal source (such as the power grid) to a very large value. In terms of meter measurement, the most intuitive result is that the meter will be overcharged, causing losses to the user. In addition, an open current source will cause uncontrollable damage to the system.

[0076] Optionally, the impedance element involved in the present application may be a resistor, a capacitor or an inductor.

[0077] Optionally, the sampling circuit in the detection circuit involved in the present application uses manganese copper or current transformer for sampling.

[0078] The functions of the signal processing module in the present application are diverse and expandable. Optionally, the signal processing module is used to calculate the current signal of the detection circuit; optionally, the signal processing module is used to compare the change of the reference current source output signal (such as amplitude) relative to the preset calibration value to determine the size of the measurement error of the detection circuit, and then re-fix the parameters of each order of the adaptive filter; optionally, the signal processing module is used to receive and process disconnection conditions; optionally, the signal processing module communicates with the outside.

[0079] The second embodiment of the present application relates to an electric energy metering chip, which includes the detection circuit involved in the first embodiment of the present application and has the beneficial effects of the detection circuit.

[0080] When the electric energy metering chip is used, the electric energy metering chip can accurately obtain the target signal through the detection circuit. If the AC signal is interfered by an external signal, the interference can be filtered out by an RC filter with a differential structure connected to the sampling circuit. Or if the target signal or the detection circuit itself changes, the adaptive filtering module used in the detection circuit can recalculate the optimal parameters of the adaptive filter to obtain an accurate target signal. In this way, the measurement error of the electric energy metering chip is greatly reduced.

[0081] The third embodiment of the present application relates to an electric energy metering device, which includes the detection circuit involved in the first embodiment of the present application and has the beneficial effects of the detection circuit.

[0082] Among them, when the electric energy metering device is in use, the electric energy metering device can accurately obtain the target signal through the detection circuit. If the AC signal is interfered by an external signal, the interference can be filtered out by an RC filter with a differential structure connected to the sampling circuit, or if the target signal or itself changes, the adaptive filtering module used in the detection circuit can recalculate the optimal parameters of the adaptive filter to obtain an accurate target signal; in this way, the measurement error of the electric energy metering device is greatly reduced.

[0083] In order to better understand the technical solution of the present application, a specific example is provided below for illustration.

[0084] Figure 6 It is a typical current detection device with current self-calibration function. R0 is the sampling resistor. Assume that the load current on the live wire L is I load , the frequency is f0, the current generated by the reference current source is I ref , the frequency is f1, the reference current source and the live wire L are connected in parallel at both ends of R0. The ADC module collects V 1P / V1 N The voltage of I load and I ref The signal is filtered using a filter bank to separate I load and I ref , thereby achieving I load At the same time, due to the current I generated by the reference signal source ref is fixed, so the I obtained by the filter bank ref The size of the signal can be used to monitor and self-calibrate the sampling circuit parameters.

[0085] In actual applications, the five wires ①, ②, ③, ④, and ⑤ are used to connect the detection and metering module and the sampling module through wires and connection terminals. Taking a single-phase meter as an example, vibration is inevitable during the installation and transportation of the meter, causing the wires to fall off.

[0086] Specific:

[0087] Case 1: The self-calibration principle of the detection circuit is to extract a signal with a frequency of f1 from the output signal of the ADC module to determine whether the external circuit parameters have changed. In practical applications, it is difficult for f1 to remain in an ideal state. If the frequency f1 of the reference current source changes or there is an interference signal, it will affect the final detection result and cause mismeasurement.

[0088] Case 2: If at least one of the wires ② and ③ is broken, the electric meter will not be able to stop, resulting in serious measurement distortion and over-charging of electricity bills.

[0089] Case 3: If at least one of the wires ① and ④ is open-circuited, since the current self-calibration theory is based on the fact that the reference current source is constant, once the reference current source is open-circuited, the system will think that R0 changes to a very small value, thus I load Calibration to a large value will result in excessive metering, causing losses to users. In addition, an open circuit in the current source will cause uncontrollable damage to the system.

[0090] Case 4: If the No. 5 conductor is broken, the effective value will be too large and the electricity bill will be calculated randomly.

[0091] According to the detection circuit involved in the first embodiment of the present application, Figure 6 The current detection device and the problems raised are improved, and the detailed scheme is as follows Figure 7 As shown, the details are as follows:

[0092] For case 1: Add an adaptive filtering module

[0093] The detection circuit is added with an adaptive filtering module, which includes an adaptive filter and a subtractor. The adaptive filter is a FIR transverse filter. Before use, the parameters of each order of the adaptive filter are calculated and fixed.

[0094] Specific calculation and fixing method: The adaptive filtering module (including the subtractor and the adaptive filter) is connected with the sampling circuit R0 and the reference current source I ref After connecting, close I ref And only AC signals (including I load), the AC signal passes through the adaptive filter, making the output of the subtractor zero, and then according to the iterative formula of each order parameter, through multiple iterations, the mean square expected value of the output of the subtractor tends to the minimum to obtain the optimal parameter, and then the various order parameters of the filter are fixed.

[0095] The adaptive filtering module (including the subtractor and the adaptive filter) with fixed parameters of each order is connected to the sampling circuit R0 and the reference current source I ref After connecting, turn on the reference current source I ref And only AC signals (including I ref and I load ), the AC signal is input to the input end of the adaptive filter with fixed parameters and the first input end of the subtractor respectively, and the adaptive filter with fixed parameters filters the AC signal (i.e., filters out I ref ) The obtained AC signal is input to the second input terminal of the subtractor, and the subtractor subtracts the AC signal at the first input terminal from the AC signal at the second input terminal, and the reference current source I is output. ref signal.

[0096] Because this adaptive filter module physically separates the reference current source by filtering out other signals, it will not respond to the frequency of the reference current source before and after separation, so the change of the frequency of the reference current source will not cause measurement errors;

[0097] If there is an interference signal, the adaptive filtering module can recalculate the fixed parameters of the adaptive filter to make the interference signal within the filtering range of the adaptive filter, so that the obtained frequency f1 of the reference current source will not be affected.

[0098] For situation 2: Add detection and protection measures for dropped sampling lines

[0099] like Figure 7 As shown, in Figure 6 R3 and the first detection module are added on the basis of V1P / V1N pins to detect the signal of sampling line ② and ③ to determine whether the wires are disconnected; at the same time, a 1K resistor R3 is connected between sampling lines ② and ③. When the sampling line is disconnected, the 1K jumper resistor can pull the differential signal V 1P -V1 N , thereby preventing voltage creep caused by dropping the sampling line.

[0100] For situation 3: Add reference current source disconnection detection and protection measures

[0101] exist Figure 7 As shown, in Figure 6R4 and the second detection module are added on the basis of . Taking the 5V metering system as an example, under normal working conditions, the IAMS port voltage V1 of the reference current source is basically equal to 0V. When the reference current source is disconnected (at least one of ① or ④ is disconnected), V1 will become a high level of about 5V. At this time, the detection module will send the disconnection condition to the signal processing module; at the same time, once the second detection module detects the disconnection condition of the reference current source, the resistor R4 provides a freewheeling circuit when the reference current source has an open circuit fault, avoiding the occurrence of meter billing failure or system paralysis.

[0102] For situation 4: Added live line detection and protection measures

[0103] like Figure 7 As shown in FIG. 1 , a first detection module is added on the basis of FIG. 1 , and the first detection module is used to detect V 1P / V 1N Check whether there is any abnormal AC signal on the pin; at the same time, to prevent 1P / V 1N The presence of interference signals on the pin may cause misjudgment. The first detection module further includes a detection algorithm module, which reliably detects V 1P / V 1N The abnormal AC signal on the live wire is used to determine whether the live wire is actually disconnected and feed it back to the signal processing module.

[0104] At the same time, when line ⑤ is disconnected, the V 1P / V 1N Connected to the live wire L and forms a loop with the system GND. Therefore, the loop between the neutral wire N and the live wire L is: neutral wire N—> system GND—> metering detection module—> V 1P / V 1N —> Manganese copper signal line 2 / 3 —> Live line L, and the voltage difference between NL will periodically pass through V 1P / V 1N The ESD protection diode of AVCC (the input voltage provided by the power module) is turned on, thus forming V 1P / V 1N Clamping AC voltage on system GND provides protection.

[0105] Further, if Figure 7 As shown, in Figure 6 An RC filter is added on the basis of the RC filter, which is composed of a resistor R1, a capacitor C1, a resistor R2, and a capacitor C2, and adopts a differential structure, which can effectively suppress common-mode interference in the signal, thereby improving the accuracy of the detection circuit measurement.

[0106] It should be noted that in the application documents of this patent, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that the process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "including one" do not exclude the existence of other identical elements in the process, method, article or device including the elements. In the application documents of this patent, if it is mentioned that an action is performed according to an element, it means that the action is performed at least according to the element, which includes two situations: performing the action only according to the element, and performing the action according to the element and other elements. Expressions such as multiple, multiple, and multiple include 2, 2 times, 2 kinds, and more than 2, more than 2 times, and more than 2 kinds.

[0107] All documents mentioned in this application are considered to be included in the disclosure of this application as a whole, so that they can be used as the basis for modification when necessary. In addition, it should be understood that after reading the above disclosure of this application, those skilled in the art can make various changes or modifications to this application, and these equivalent forms also fall within the scope of protection claimed in this application.

Claims

1. A detection circuit, characterized in that: include: A reference current source outputting a second frequency AC signal; A sampling circuit coupled to the reference current source, the sampling circuit also coupled to a first signal source outputting a first frequency AC signal, and outputting a sampling signal of a mixed signal of the first frequency AC signal and the second frequency AC signal; An adaptive filtering module comprises an adaptive filter and a subtractor, wherein the sampling circuit is coupled to the input end of the adaptive filter and the first input end of the subtractor respectively, and the output end of the adaptive filter is coupled to the second input end of the subtractor. Before using the adaptive filter, it is necessary to calculate and fix the various order parameters of the adaptive filter. After the adaptive filtering module is connected to the sampling circuit and the reference current source, the reference current source is turned off and only an AC signal is present. The AC signal passes through the adaptive filter, so that the output of the subtractor is zero. Then, according to the iterative formula of each order parameter, the mean square expected value of the output of the subtractor is minimized through multiple iterations to obtain the optimal parameter. Then, the various order parameters of the adaptive filter are fixed, the reference current source is turned on and only an AC signal is present. The adaptive filter is used to filter the sampled signal to obtain the first frequency AC signal. The subtractor is used to subtract the sampled signal at the first input end from the first frequency AC signal at the second input end and then output the second frequency AC signal. The signal processing module is coupled to the adaptive filtering module and is used to perform signal processing on the second frequency AC signal output by the adaptive filtering module and detect whether the information of the second frequency AC signal changes relative to a preset calibration value to determine the measurement error of the detection circuit.

2. The detection circuit according to claim 1, characterized in that: Before using the adaptive filter, it is necessary to calculate and fix the various order parameters of the adaptive filter, and the various order parameters are determined based on the steepest descent method.

3. The detection circuit according to claim 2, characterized in that: The order parameters are determined based on the least mean square method. According to an iterative formula for the order parameters of an FIR filter, the mean square expected value of the output of the subtractor is minimized through multiple iterations, thereby obtaining the order parameters of the adaptive filter.

4. The detection circuit according to claim 1, characterized in that: It also includes an analog-to-digital converter coupled to the sampling circuit, and the analog-to-digital converter is coupled to the input end of the adaptive filtering module.

5. The detection circuit according to claim 4, characterized in that: It also includes a first detection module coupled to the two input ends of the analog-to-digital converter, the first detection module is coupled to the signal processing module, and the first detector is used to detect whether there is an abnormal AC signal in the signals of the first input end and the second input end of the analog-to-digital converter.

6. The detection circuit according to claim 5, characterized in that: Also includes: an RC filter having an input end coupled to the sampling circuit, wherein an output end of the RC filter is coupled to an input end of the analog-to-digital converter; A first impedance element is coupled to both ends of the sampling circuit.

7. The detection circuit according to claim 6, characterized in that: Also includes: A second detection module, wherein an input end is coupled to the reference current source, and an output end is coupled to the signal processing module, for detecting whether an open circuit fault occurs in the reference current source, and feeding back to the signal processing module; A second impedance element has one end coupled to the reference current source and the other end coupled to ground.

8. The detection circuit according to claim 7, characterized in that: The sampling circuit uses a manganese copper or a current transformer for sampling.

9. An electric energy metering chip, characterized in that: The electric energy metering chip comprises the detection circuit as described in any one of claims 1-8.

10. An electric energy metering device, characterized in that: The electric energy metering device comprises the electric energy metering chip according to claim 9.

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