Method and system for optimizing metering front end of intelligent electric meter

Abstract

The invention discloses a method and a system for optimizing a metering front end of an intelligent electric meter. The method comprises the following steps of: setting an anti-aliasing network with a near-linear phase at the front end of a metering channel and synchronously sampling; determining a range switching window based on zero crossing or a preset voltage change rate, executing automatic range switching in the window, and performing overlapping sampling and digital splicing on samples before and after switching; determining a rectification conduction empty window based on the rectification conduction prediction, suspending sampling in the empty window, and compensating a missing sample; injecting a reference signal into the channel at the calibration injection window, obtaining a correction coefficient according to response, and performing online correction; the three types of windows are not overlapped and are uniformly scheduled by a synchronous time sequence; and completing power and energy calculation according to the corrected voltage and current sequence. The system comprises an anti-aliasing network unit, a range control unit, a rectification conduction detection unit, an air window door control unit, an injection and online correction unit, a time sequence synchronization unit, a metering calculation unit and the like. According to the invention, low-distortion, wide-range and consistent metering output can be realized in practical application.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of power electronics, and particularly relates to a smart meter measurement front-end optimization method and system. BACKGROUND

[0002] The measurement front-end of a smart meter is usually composed of a voltage channel and a current channel. The voltage channel enters an anti-aliasing network and an analog-to-digital converter after being divided and buffered. The current channel is sampled by a shunt, a transformer and a Hall device, enters the analog-to-digital converter after being pre-amplified and anti-aliased. The digital side calculates active power, reactive power, apparent power and related harmonic indicators based on the synchronous sampling results. With the increase of distributed power sources, nonlinear loads and low power factor conditions, the measurement front-end needs to maintain amplitude and phase accuracy in a very wide dynamic range, while suppressing the influence of power supply rectification, switching noise, surges and temperature drift on the measurement link.

[0003] Existing solutions mostly use fixed or simple stepped range configurations and conventional anti-aliasing networks, and correct the front-end errors through offline calibration. In engineering applications, the following problems are prone to occur: range switching mostly occurs at any time, and the introduction of steps and phase mutations at the switching moment leads to power and energy calculation jumps; the phase response of the conventional anti-aliasing network is nonlinear, and the device error of the superposition channel causes voltage and current phase mismatch, which is amplified in low power factor and harmonic scenarios; the rectification conduction and ripple of the small power supply in the meter are coupled to the measurement chain in common-mode or differential-mode paths, and the key sampling time is disturbed; offline calibration is difficult to track long-term drift caused by temperature and aging; sampling, range switching and calibration operations lack unified timing arrangement, and are prone to mutual interference.

[0004] Therefore, it is necessary to propose a systematic optimization scheme for the measurement front-end to improve the accuracy, stability and maintainability of measurement in complex power consumption environments. SUMMARY

[0005] Embodiments of the present application provide a smart meter measurement front-end optimization method and system to address the measurement accuracy and robustness problems in complex power consumption environments.

[0006] To solve the above technical problems, embodiments of the present application disclose the following technical solutions: on the one hand, an intelligent electric meter front-end optimization method is provided, comprising: setting a near-linear-phase anti-aliasing network at the front end of a voltage channel and a current channel, and synchronously sampling the anti-aliased voltage signal and current signal; determining a range switching window based on zero-crossing or a preset voltage change rate, performing automatic range switching within the range switching window, and performing overlapping sampling and digital splicing before and after switching to avoid steps; determining a rectification conduction empty window based on rectification conduction prediction of the meter front end, pausing meter sampling within the rectification conduction empty window, and compensating for missing sampling; injecting a reference signal into the voltage channel and / or the current channel within a calibration injection window, obtaining a correction coefficient according to the response of the reference signal, and performing online correction on the meter channel according to the correction coefficient; performing metering calculation according to the corrected voltage signal and current signal to obtain a metering result; wherein the range switching window, the rectification conduction empty window and the calibration injection window are mutually non-overlapping and are scheduled by a synchronous time sequence.

[0007] Further, the anti-aliasing network is a near-linear-phase passive network, which adopts a T-type or equivalent structure, the phase response within the measurement bandwidth is kept approximately linear, and the cutoff frequency of the network is set to a range higher than the fundamental wave of the power frequency and lower than the Nyquist frequency of the analog-to-digital conversion sampling, so as to reduce aliasing and phase distortion.

[0008] Further, the automatic range switching comprises: pre-activating the input switch of the target range channel and keeping the current range channel continuously sampling at the beginning of the range switching; after the target range channel is stabilized, the output switch of the current range channel is disconnected and the output switch of the target range channel is connected to form a transition zone, which is all or a sub-interval of the range switching window; weighted splicing or minimum error splicing is performed on the current range samples before switching and the target range samples after switching in the transition zone, so that the output waveform is continuous in amplitude and phase, thereby avoiding steps.

[0009] Further, the rectification link of the meter front end adopts a full-wave rectification branch composed of a plurality of low-junction-capacitance small-signal diodes, which is used to reduce the capacitive coupling of the rectification switching process to the meter channel; the determination of the rectification conduction empty window comprises: determining the half-cycle starting point based on grid zero-crossing detection, establishing a conduction period estimation model combining the conduction threshold of the small-signal diode and the rising / falling slope of the energy storage capacitor voltage, or identifying the conduction interval by detecting the rising edge / falling edge of the conduction current of the rectification branch or the peak-valley time of the ripple voltage of the energy storage capacitor; a gate signal corresponding to the start and end time of the conduction interval is generated according to the conduction interval, which is used to control the meter sampling to be paused within the conduction interval and to be restored outside the conduction interval.

[0010] Further, the injection amplitude of the reference signal is not higher than one percent of the rated amplitude of the measurement signal, and the frequency selection avoids the main frequency point and its integer multiples of the measurement calculation; the online correction includes: calculating the gain ratio and phase difference of the injected channel output relative to the reference signal, respectively obtaining the amplitude correction coefficient and the phase correction coefficient, and triggering the update when the temperature change exceeds the temperature preset threshold or the load working condition change exceeds the load preset threshold.

[0011] Further, the synchronous timing schedule arranges the start and end time of the range switching window, the rectifier conduction empty window and the calibration injection window in each power grid cycle according to the power grid frequency estimation, ensures that the three types of windows do not overlap each other, and the range switching window is preferentially placed near the voltage zero-crossing or in the interval where the voltage change rate is lower than the preset voltage change rate, and a minimum time safety interval is set between the calibration injection window and the rectifier conduction empty window to avoid mutual interference.

[0012] Further, the compensation for the missing samples includes: in the effective sampling interval before and after the rectifier conduction empty window, the missing samples are recovered by interpolation or fitting extrapolation according to the time and amplitude relationship of the adjacent samples, and the compensated continuous sequence is used in the measurement calculation.

[0013] Further, the current channel adopts a four-terminal sampling structure to reduce the error introduced by the wiring voltage drop, and the temperature coefficient of the shunt is compensated in the measurement calculation combined with the temperature measurement to reduce the linear error under the condition of large current and temperature rise.

[0014] Further, the measurement calculation includes calculating active power, reactive power, apparent power and power factor based on the synchronous sampling of voltage and current signals, and completing energy accumulation and power index output after applying the correction coefficients.

[0015] On the other hand, an intelligent electric meter measurement front-end optimization system is provided, which includes: a near-linear phase anti-aliasing network configured in the front end of the voltage channel and the current channel; a range control unit for implementing range switching and performing overlapping sampling and digital splicing in the zero-crossing or the interval where the voltage change rate is lower than the preset voltage change rate; a rectifier conduction detection and empty window gating unit for electrical connection with a rectifier branch composed of a low junction capacitance small signal diode array, identifying the conduction interval based on the conduction current or energy storage capacitor end ripple voltage of the rectifier branch, and outputting a gating signal corresponding to the interval to suspend sampling and trigger missing sample compensation; an injection and online correction unit for injecting a reference signal in a calibration injection window and calculating amplitude and phase correction coefficients; a synchronous timing unit for scheduling a range switching window, a rectifier conduction empty window and a calibration injection window in each power grid cycle; a measurement calculation unit for calculating and outputting measurement results.

[0016] The technical solutions have at least the following beneficial effects: by using the near-linear-phase anti-aliasing network at the front end of the voltage channel and the current channel and implementing synchronous sampling, automatic range switching is completed in a zero-crossing or low voltage change rate window, and output continuity is ensured by overlapping sampling and digital splicing; in a predicted rectifier conduction interval, a sampling empty window is set, missing samples are compensated, a reference signal is injected into the channel in a special calibration injection window, and amplitude and phase correction coefficients are calculated in real time, and finally, the three types of windows are non-overlapping scheduled in each power grid cycle with unified synchronous timing; through the cooperative mechanism, on the one hand, the disturbance of range switching and power supply rectification to the key sampling time is significantly reduced, and the output step and phase mutation are eliminated, and on the other hand, the online tracking and correction of the front-end error are realized without affecting the continuity of metering, thereby improving the consistency and stability of active power, reactive power, apparent power and energy metering in a wide dynamic range, low power factor and harmonic-containing scenarios.

[0017] The technical solutions have the following advantages: the near-linear-phase anti-aliasing network significantly reduces phase distortion in the metering bandwidth, reduces the influence of phase mismatch between channels on power calculation; the range switching triggered by the zero-crossing or low voltage change rate window is combined with overlapping sampling and digital splicing to make the amplitude and phase continuous before and after switching, and avoid energy calculation errors caused by range jumps; the sampling empty window in the rectifier conduction interval and the missing sample compensation suppress the transient interference of rectifier switch noise and ripple on the metering chain, and balance the anti-interference and data integrity; the reference injection and online correction realize adaptive tracking of amplitude and phase errors, and reduce long-term deviations caused by temperature and aging drift; the synchronous timing scheduling ensures that the range switching window, the rectifier conduction empty window and the calibration injection window are non-overlapping, avoids the cross-influence between windows, and overall improves the anti-interference ability, precision maintenance ability and engineering implementability of the metering front end. BRIEF DESCRIPTION OF DRAWINGS

[0018] The technical solutions and other beneficial effects of the present application will become apparent from the following detailed description of specific embodiments of the present application, taken in conjunction with the accompanying drawings.

[0019] Figure 1 An exemplary intelligent electric meter metering front end optimization method provided by the present application is shown in the schematic diagram.

[0020] Figure 2 An exemplary intelligent electric meter metering front end optimization system block diagram provided by the present application is shown.

[0021] Figure 3 A range switching window and overlapping sampling schematic diagram provided by the present application is shown. DETAILED DESCRIPTION

[0022] In order to make the purposes, technical solutions and beneficial effects of the present application clearer, the present application is further described in detail below in combination with the drawings and specific embodiments. It should be understood that the specific embodiments described in the specification are only for the purpose of explaining the present application, and are not intended to limit the present application.

[0023] In the description of the present application, it should be noted that the terms "first", "second", etc. in the specification and claims of the present application are used to distinguish similar objects, and do not necessarily describe a specific order or sequence. It should be understood that the labels used in this way can be interchanged under appropriate circumstances, so that the embodiments of the present application can be implemented in an order other than those illustrated or described herein. In addition, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusion, i.e. a process, method, system, product or device that includes a series of steps or units does not necessarily have to be limited to those steps or units clearly listed, but can also include other steps or units that are not clearly listed or inherent to the process, method, system, product or device. "For" in this paper means having the configuration and ability to achieve the function, but does not limit the specific implementation form; "and / or" is used to represent a parallel relationship, which can represent "and", can represent "or", and can also represent any combination of "and / or"; the order of the description of the steps of the method does not constitute a limitation on the actual execution order under the condition that it does not affect the technical logic; the terms "module", "unit", "device" and the like can be realized by hardware, software or a combination of hardware and software, and the deployment position can be inside the same device or distributed between different devices. The terms "install", "connect", "connect" should be understood broadly, for example, it can be a fixed connection, or a detachable connection, or an integral connection; it can be a mechanical connection, it can be directly connected, or indirectly connected through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0024] In the description of the present application, the "smart metering front-end" refers to the analog and interface circuits directly related to voltage and current signal measurement and its supporting synchronous sampling, window scheduling and digital correction logic, excluding the upper-level business functions not directly related to settlement and communication. The "voltage channel" and "current channel" respectively refer to the links that convert the measured grid voltage and current into sampleable electrical signals, usually including voltage division or sensing elements, buffer / amplification and anti-aliasing networks, and work in conjunction with analog-to-digital converters. The "anti-aliasing network" refers to a front-end filter network that suppresses spectral components above the target bandwidth before sampling to reduce aliasing errors, and the "near-linear phase" means that the phase is approximately linear with respect to frequency within the measurement bandwidth, thereby reducing the phase distortion introduced by filtering; the present case can use a T-type or equivalent topology as an implementation, but is not limited thereto. "Synchronous sampling" refers to the simultaneous or equivalent simultaneous acquisition of voltage and current channels under a unified time base, ensuring the timing consistency of power calculation. "Zero-crossing" refers to the instant when the voltage waveform crosses the reference zero level; "voltage rate of change" refers to the rate of voltage change per unit time (dV / dt). "Range" refers to the programmable range of channel gain or voltage division ratio; "automatic range switching" refers to switching between different ranges to extend the dynamic range according to the input amplitude; "overlapping sampling and digital splicing" refers to retaining the effective samples of the old and new ranges within a short time before and after switching, and forming a continuous output in the digital domain through weighting or error minimization; "step" indicates that the output waveform has a step change in amplitude and phase after switching. "Rectifier conduction prediction" refers to the timing estimation of the conduction interval of the rectifier device for the power supply of the metering front-end; "interpolation or fitting extrapolation compensation" refers to restoring the missing samples to form a continuous measurement sequence based on the effective samples before and after the window.

[0025] In the description of the present application, "Kelvin four-terminal sampling" refers to a four-terminal connection mode in which current leads and voltage sampling leads are respectively arranged at both ends of the shunt, to reduce the influence of lead and solder joint resistance on voltage measurement and improve current measurement accuracy. "Every grid cycle" or "grid cycle" refers to a time interval with the grid fundamental frequency as the period (e.g. one cycle corresponding to 50Hz or 60Hz). "Measurement calculation" and "measurement result" refer to the active power, reactive power, apparent power, power factor and energy accumulation indicators calculated based on the synchronous sampling of voltage and current signals, and the specific criteria can be selected in the embodiments according to standards or implementation.

[0026] The term "vicinity" as used in the present application is used to represent the neighborhood around a reference point, reference time, reference frequency or reference position, and is not required to be exactly coincident with the reference quantity, and is a non-limiting term. Unless otherwise explicitly limited, the range of "vicinity" can be determined by system parameters or control resolution, and can be embodied as a time window, a value range window or a space window. For example, "vicinity of zero crossing" can be understood as a bounded time window centered on the zero crossing time, bounded by a voltage threshold or a voltage rate of change threshold; "vicinity of low voltage rate of change" can be understood as an interval satisfying |dV / dt| lower than a preset threshold; the specific width of "vicinity" can be set by a threshold, a proportion or a number of sampling periods, but is not limited thereto.

[0027] The above terms are subject to the meanings described in this section unless the context conflicts; terms not appearing in this section but belonging to the art are understood according to the commonly accepted meanings in the art.

[0028] In a smart meter, the measurement front end needs to acquire both voltage and current signals and participate in the calculation of active power, reactive power, apparent power and other parameters. However, common problems in engineering sites include: the large range span amplifies the front-end error or the step and phase mutation of the voltage dividing network during switching; the phase distortion of the traditional anti-aliasing network is obvious within the target bandwidth, affecting the power accuracy in low power factor conditions; the rectifier device of the auxiliary power supply in the meter couples common-mode or differential-mode interference to the measurement link during the conduction instant, causing synchronous sampling jitter; and the amplitude and phase errors drift over time due to device temperature drift and aging. The superposition of the above factors makes it difficult for existing solutions to long-term and stable guarantee of measurement accuracy and consistency in light load and heavy load switching, complex power grid environments containing rectification ripple and harmonics.

[0029] Therefore, the present application proposes a smart meter measurement front end optimization method and system, which configures an almost linear phase anti-aliasing network at the front end of the voltage channel and the current channel and implements synchronous sampling, determines the range switching window based on zero crossing or low voltage rate of change, performs automatic range switching within the window, and makes the output continuous by overlapping sampling and digital splicing before and after switching to avoid steps, sets a rectification conduction dead window according to the prediction of the rectification conduction period, suspends key sampling and compensates for missing samples within the dead window, weakens the power supply and measurement coupling, injects a reference signal into the channel during the calibration injection window, extracts the channel response to obtain amplitude and phase correction coefficients, and realizes online correction. The above range switching window, rectification conduction dead window and calibration injection window are scheduled by synchronous timing within each power grid cycle and do not overlap. Through systematic optimization of the measurement front end, the amplitude and phase errors and coupled noise can be significantly reduced in a wide dynamic range and complex harmonic / ripple environment, and the accuracy, stability and traceability of power and energy measurement can be improved.

[0030] Figure 1 The present application provides an exemplary smart meter measurement front end optimization method. As shown inFigure 1 As shown, the exemplary metering front-end optimization method provided by the present application comprises the following steps: S1, setting a near-linear-phase anti-aliasing network at the front end of the voltage channel and the current channel, and synchronously sampling the anti-aliased voltage signal and the current signal; S2, determining a range switching window based on zero-crossing or a preset voltage change rate, performing automatic range switching within the range switching window, and performing overlap sampling and digital splicing before and after switching to avoid steps; S3, determining a rectification conduction empty window based on rectification conduction prediction of the metering front end, pausing metering sampling within the rectification conduction empty window, and compensating for missing sampling; S4, injecting a reference signal into the voltage channel and / or the current channel within a calibration injection window, obtaining correction coefficients according to the response of the reference signal, and performing online correction on the metering channel according to the correction coefficients; S5, performing metering calculation according to the corrected voltage signal and the current signal, and obtaining a metering result. In each of the above steps, the range switching window, the rectification conduction empty window, and the calibration injection window are mutually exclusive and are scheduled by a synchronous timing.

[0031] Figure 2 An exemplary intelligent electric meter metering front-end optimization system block diagram is provided for the present application. As shown, Figure 2 The exemplary intelligent electric meter metering front-end optimization system 100 provided by the present application comprises: a near-linear-phase anti-aliasing network 101 configured at the front end of the voltage channel 11 and the current channel 12; a range control unit 102 for implementing range switching and performing overlap sampling and digital splicing in a zero-crossing or voltage change rate lower than a preset voltage change rate interval; a rectification conduction detection and empty window gating unit 103 for electrical connection with a rectification branch 20 composed of a low junction capacitance small signal diode array, identifying a conduction interval based on the conduction current of the rectification branch 20 or the energy storage capacitor end ripple voltage, and outputting a gating signal corresponding to the interval to pause sampling and trigger missing sample compensation; an injection and online correction unit 104 for injecting a reference signal in a calibration injection window and calculating amplitude and phase correction coefficients; a synchronous timing unit 105 for scheduling the range switching window, the rectification conduction empty window, and the calibration injection window within each power grid cycle; a metering calculation unit 106 for calculating and outputting the metering result of the metering channel 10.

[0032] In combination with Figure 1 and Figure 2The detailed process of the exemplary smart metering front-end optimization method provided in the application is as follows. First, in the sampling preparation of the metering channel 10, the front-end of the voltage channel 11 and the current channel 12 introduces a nearly linear phase anti-aliasing network 101, which performs bandwidth constraint and phase shaping on the analog signal entering the analog-to-digital conversion, so that the phase response of the power frequency and its effective band is basically consistent, thereby reducing the amplitude and phase distortion caused by the front-end network. The cutoff frequency of the anti-aliasing network 101 is set to be higher than the fundamental wave of the power frequency and lower than the Nyquist frequency of the analog-to-digital conversion, so as to suppress aliasing while controlling the in-band phase distortion. The voltage and current channels are synchronously sampled under the same sampling clock, and the clock source is managed by the synchronous timing unit 105 to ensure the time alignment of the two channels at each sampling time, providing a consistent time reference for subsequent power synthesis and harmonic analysis.

[0033] The synchronous timing unit 105 establishes a time axis plan based on grid zero-crossing detection or frequency estimation, and triggers the range control unit 102 to open the input branch of the target range channel in the "near zero-crossing" or the interval where the voltage rate of change is lower than the preset voltage rate of change, so that it enters the stable zone in advance. At the same time, the current range channel continues to be sampled, and after the target range stabilizes, the output branch is switched to the target range. Both ranges are collected in the transition zone, and the overlapping samples are weighted and spliced or minimum error spliced on the digital side, so that the waveform before and after switching is continuous in amplitude and phase, fundamentally avoiding the steps and instantaneous phase jumps caused by range switching.

[0034] Figure 3 The range switching window and overlapping sampling provided in the application are shown in the schematic diagram. According to the above overlapping sampling process, an exemplary voltage signal curve of the overlapping sampling process is provided, as shown in Figure 3 For the sampling of the voltage signal, three different ranges A, B and C are provided, among which the measurable voltage amplitude of range B is the largest, exceeding v3, the measurable voltage amplitude of range C is the smallest, with a precision of v1, and the measurable voltage amplitude of range A is in the middle, which is v2. When the current range channel corresponds to range A, the range control unit 102 opens the input branch of the target range channel in advance at the t1 point near the zero-crossing point based on the planning of the synchronous timing unit 105, that is, the corresponding Figure 3The start time of the medium range B is t1, while the range channel corresponding to the range A is kept as the effective output of the ADC. When the range channel of the range B is stable, i.e., at the time t2, the output switch of the range channel corresponding to the range A is disconnected, and the output switch of the range channel corresponding to the range B is connected, forming a transition zone [t1, t2]. The samples before and after switching from the range A to the range B in the transition zone are subjected to weighted splicing or minimum error splicing, so that the output waveform is continuous in amplitude and phase, thereby avoiding steps. Similarly, in the overlapping sampling process of switching the range B to the range C, the transition zone is [t3, t4], which is not described here. In this embodiment, the range switching window planned by the synchronous timing unit 105 is determined by zero-crossing detection. In other embodiments, the range switching window can also be determined according to whether the voltage change rate is less than a preset voltage change rate, i.e., a low voltage change rate is required as the range switching criterion. In this embodiment, the range switching window is equivalent to the transition zone; in other embodiments, the range switching window can also include a time margin for stability, and the transition zone is a subinterval for overlapping sampling and splicing. Digital splicing is performed on the two sequences sampled simultaneously in the transition zone. Taking the above transition zone [t1, t2] as an example, let the weight function w[n] monotonically transition from 0 to 1 in [t1, t2] (which can be linear or a Hanning window), and the output y[n] = (1-w[n])·y_old[n]+w[n]·y_new[n], where y_old[n] is the output of the current range channel, and y_new[n] is the output of the target range channel; or the two channels are first subjected to least square fitting for amplitude and phase alignment, and then spliced, thereby ensuring the continuity of the waveform in amplitude and phase before and after switching, avoiding steps and instantaneous phase jumps. In addition, in the current measurement path, in order to reduce the influence of wiring voltage drop on the measurement result, the current channel 12 adopts a Kelvin four-terminal sampling structure to detect the voltage of the shunt, and the measurement lead and the current-carrying lead are separated to reduce the system error caused by the parasitic resistance; at the same time, the working temperature of the shunt is obtained by combining the temperature sensor, and the resistance value is compensated according to the calibrated temperature coefficient, so as to maintain the measurement linearity under the conditions of large current and temperature rise.

[0035] In order to reduce the crosstalk of the measurement link caused by the rectification process of the measurement power supply, the rectification branch 20 is composed of a small-signal diode array with low junction capacitance. The rectification conduction detection and window gating unit 103 identifies the conduction interval in each half cycle by monitoring the rectification branch current or the ripple voltage at the energy storage capacitor end. When no sensing monitoring is configured, the interval boundary can also be obtained by establishing an equivalent conduction model according to the zero-crossing time and the threshold value of the device and the discharge curve of the energy storage capacitor. The identification result is converted into a gating signal, which suspends the key measurement sampling in the conduction interval and restores the sampling outside the interval. In order to avoid the energy deviation caused by the suspended sampling, the digital post-processing link interpolates or extrapolates the missing samples according to the time and amplitude relationship of the effective samples before and after the window, so as to make the sequence participating in the measurement calculation continuous in time and without significant bias in energy.

[0036] In the time slice not overlapping with the above windows, the synchronous timing unit 105 triggers the injection of a small reference signal coupled to the voltage channel 11 and / or the current channel 12 with the online correction unit 104. The frequency of the reference signal avoids the fundamental frequency and its integer multiples, and the amplitude is controlled to a small proportion of the rated measurement amplitude, on the premise of not affecting normal measurement. The digital side takes the injection signal as the reference to calculate the gain ratio and phase difference of the injected channel relative to the reference, obtaining the online correction coefficients of amplitude and phase; when the temperature or load working condition changes reach the preset load threshold, the coefficients are automatically refreshed to realize adaptive compensation of the long-term drift caused by op-amp misadjustment, device temperature drift and aging. The correction coefficients correct the voltage and current data obtained by synchronous sampling in the digital domain in real time, and together with the fixed phase characteristics of the anti-aliasing network 101 ensure the matching of the phase and amplitude of the two signals.

[0037] When the above three types of windows of range switching, rectifier conduction empty window and calibration injection are arranged without overlap in each power grid cycle through the synchronous timing unit 105, the measurement calculation unit 106 performs power and energy operation on the corrected voltage and current sequence according to the same time base, and outputs active power, reactive power, apparent power, power factor and the required harmonic index. In this process, the front-end anti-aliasing and phase shaping ensure frequency domain consistency, overlapping sampling and digital splicing guarantee waveform continuity across the range, rectifier conduction empty window and missing sample compensation suppress the coupling interference of power supply rectification on measurement, and the online correction of reference injection continuously calibrates the amplitude and phase errors; each unit is driven by the same timing framework, so as to realize low distortion, wide dynamic range and high consistency of the measurement front end under engineering conditions.

[0038] In summary, the intelligent electric meter front-end optimization scheme proposed in the application, by configuring the nearly linear phase anti-aliasing network 101 in front of the voltage channel 11 and the current channel 12 and implementing synchronous sampling, performing automatic range switching with overlapping sampling and digital splicing in the zero-crossing or low voltage change rate interval, setting the rectifier conduction empty window based on the rectifier branch 20 conduction recognition or prediction and compensating for the missing samples, injecting reference signals into the measurement channel in the time slice that does not overlap with the above window to obtain amplitude and phase correction coefficients to realize online correction, and scheduling the range switching window, the rectifier conduction empty window and the calibration injection window by the unified synchronous timing; at the system level, low junction capacitance small signal diode array or equivalent low coupling rectification structure, timing gating and digital compensation are used to realize the collaborative decoupling and error self-correction of the power supply and measurement chain. The scheme can significantly reduce the front-end phase and amplitude distortion and rectification coupling noise under the premise of ensuring consistent source and caliber, avoid range switching steps and instantaneous phase jumps, expand the dynamic range and improve the active power, reactive power, apparent power and energy metering accuracy and stability under low power factor and harmonic working conditions, and balance the robustness and maintainability of engineering implementation.

[0039] The above embodiments provided by the content are only used to help understand the method, system and core idea of the application. Those skilled in the art can make some improvements and modifications to the application without departing from the principles of the application, and these improvements and modifications also belong to the protection scope of the claims of the application.

Claims

1. A smart metering front-end optimization method, characterized by, The application relates to a voltage and current measurement system and a method thereof. A near-linear-phase anti-aliasing network is arranged at the front end of a voltage channel and a current channel, and the anti-aliased voltage signal and the current signal are synchronously sampled; A range switching window is determined based on zero-crossing or preset voltage change rate, automatic range switching is performed in the range switching window, and overlapping sampling and digital splicing are performed before and after switching to avoid steps; A rectification conduction empty window is determined based on rectification conduction prediction of a measurement front end, measurement sampling is suspended in the rectification conduction empty window, and missing sampling is compensated; a reference signal is injected into the voltage channel and / or the current channel in a calibration injection window, correction coefficients are obtained according to responses of the reference signal, and online correction is performed on the measurement channel according to the correction coefficients; measurement calculation is performed according to the corrected voltage signal and the current signal, and a measurement result is obtained; wherein the range switching window, the rectification conduction empty window and the calibration injection window are mutually non-overlapping and are dispatched by synchronous timing.

2. The smart metering front-end optimization method of claim 1, wherein, The anti-aliasing network is a near-linear-phase passive network, adopts a T-shaped or equivalent structure, the phase response in a measurement bandwidth is kept approximately linear, and the cutoff frequency of the network is set to a range higher than a fundamental wave of a power frequency and lower than a sampling Nyquist frequency of an analog-to-digital conversion, so as to reduce aliasing and reduce phase distortion.

3. The smart metering front-end optimization method of claim 1, wherein, The automatic range switching comprises the following steps: the input switch of a target range channel is turned on in advance and the current range channel is kept sampling at the beginning of the range switching; the output switch of the current range channel is turned off and the output switch of the target range channel is turned on to form a transition zone after the target range channel is stabilized, the transition zone is all or a subinterval of the range switching window; weighted splicing or minimum error splicing is performed on the current range sample before switching and the target range sample after switching in the transition zone, so that the output waveform is continuous in amplitude and phase, thereby avoiding steps.

4. The smart metering front-end optimization method of claim 1, wherein, A full-wave rectification branch composed of a plurality of low-junction-capacitance small-signal diodes is used in the rectification link of the measurement front end, so as to reduce the capacitive coupling of the rectification switching process on the measurement channel; The determination of the rectification conduction empty window comprises the following steps: a half-cycle starting point is determined based on grid zero-crossing detection, a conduction period estimation model is established by combining the conduction threshold of the small-signal diode and the rising / falling slope of the energy storage capacitor voltage, or the conduction interval is identified by detecting the rising edge / falling edge of the conduction current of the rectification branch or the peak-valley time of the ripple voltage of the energy storage capacitor; a gate signal corresponding to the starting and ending time of the conduction interval is generated according to the conduction interval, which is used to control the suspension of measurement sampling in the interval and the resumption of sampling outside the interval.

5. The smart metering front-end optimization method of claim 1, wherein, The injection amplitude of the reference signal is not higher than one percent of the rated amplitude of the measurement signal, and the frequency is selected to avoid the main frequency point and its integer multiples of the measurement calculation; the online correction comprises the following steps: the gain ratio and the phase difference of the injected channel output relative to the reference signal are calculated, the amplitude correction coefficient and the phase correction coefficient are obtained, and the update is triggered when the temperature change exceeds the temperature preset threshold or the load working condition change exceeds the load preset threshold.

6. The smart metering front-end optimization method of claim 1, wherein, The synchronous timing schedule arranges the start and end time of the range switching window, the rectifier conduction empty window and the calibration injection window in each power grid cycle according to the power grid frequency estimation, ensures that the three types of windows do not overlap, and the range switching window is preferentially placed near the voltage zero-crossing or in the interval where the voltage change rate is lower than the preset voltage change rate, and a minimum time safety interval is set between the calibration injection window and the rectifier conduction empty window to avoid mutual interference.

7. The smart metering front-end optimization method of claim 1, wherein, The compensation for the missing sampling includes: in the effective sampling interval before and after the rectifier conduction empty window, the missing samples are recovered by interpolation or fitting extrapolation according to the time and amplitude relationship of adjacent samples, and the compensated continuous sequence is used in the metering calculation.

8. The smart metering front-end optimization method of claim 1, wherein, The current channel adopts a four-terminal sampling structure to reduce the error introduced by the wiring voltage drop, and the temperature coefficient of the shunt is compensated in the metering calculation combined with temperature measurement, so as to reduce the linear error under the condition of large current and temperature rise.

9. The smart metering front-end optimization method of claim 1, wherein, The metering calculation includes calculating active power, reactive power, apparent power and power factor based on the synchronous sampling of voltage and current signals, and completing energy accumulation and power index output after applying the correction coefficient.

10. A smart metering front-end optimization system, comprising: It comprises: a nearly linear phase anti-aliasing network arranged at the front end of the voltage channel and the current channel; a range control unit for implementing range switching and performing overlap sampling and digital splicing at zero-crossing or in the interval where the voltage change rate is lower than the preset voltage change rate; a rectifier conduction detection and empty window gating unit for electrical connection with a rectifier branch composed of a low junction capacitance small signal diode array, identifying the conduction interval based on the conduction current of the rectifier branch or the energy storage capacitor end ripple voltage, and outputting a gating signal corresponding to the interval to suspend sampling and trigger missing sample compensation; an injection and online correction unit for injecting a reference signal in the calibration injection window and calculating amplitude and phase correction coefficients; a synchronous timing unit for scheduling the range switching window, the rectifier conduction empty window and the calibration injection window in each power grid cycle; a metering calculation unit for calculating and outputting metering results.

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