Embedded current waveform analysis method and system for frequency converter and medium

Abstract

The invention provides a frequency converter embedded current waveform analysis method and system and a medium, and relates to the technical field of current waveform analysis, and the method comprises the steps: obtaining a sampling circuit configured in a current path of a frequency converter; calculating the required total gain based on the original output voltage signal of the sampling resistor and the required input voltage of the analog-to-digital converter; the signal quality of the original output voltage signal is evaluated, the required total gain is dynamically distributed to an instrument amplifier and a programmable gain amplifier, the original output voltage signal is amplified and then passes through an analog-to-digital converter, and current waveform data is obtained for current anomaly analysis; when the signal quality is lower than a first threshold value, the gain share of the instrument amplifier is increased preferentially; when the signal quality is higher than a second threshold, the gain share of the programmable gain amplifier is increased preferentially. According to the invention, the technical problem of low accuracy of current waveform analysis in the prior art can be solved, and the technical effect of improving the accuracy of waveform analysis is achieved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of current waveform analysis, and particularly relates to a frequency converter embedded current waveform analysis method, system and medium. BACKGROUND

[0002] With the rapid development of power electronics technology and motor control technology, frequency converters have been widely used in industrial automation, new energy power generation, electric vehicles and household appliances. As the core component of regulating the running state of the motor, the accurate collection and analysis of the current signal in the working process of the frequency converter directly determines the control performance and system stability.

[0003] At present, the existing current signal collection scheme mostly uses fixed gain amplifiers or single programmable gain amplifiers for adjustment. Although the fixed gain amplifier has simple structure and low noise, it cannot adapt to the case where the input signal has a large dynamic range, and is prone to problems such as insufficient amplification of weak signals or overload distortion of strong signals. The single programmable gain amplifier has a certain flexibility, but due to its poor input noise characteristics, it often introduces large noise when processing weak signals, resulting in a decrease in signal-to-noise ratio.

[0004] In summary, the existing technology has the technical problem that due to the single structure of the amplifier and the lack of dynamic adaptive adjustment mechanism for signal quality, it is difficult to ensure sufficient signal-to-noise ratio in weak signals, and it is prone to overload distortion in strong signals, further affecting the sampling accuracy of the analog-to-digital converter and the reliability of the current waveform analysis. SUMMARY

[0005] The purpose of the present application is to provide a frequency converter embedded current waveform analysis method, system and medium, which solves the technical problem in the prior art that due to the single structure of the amplifier and the lack of dynamic adaptive adjustment mechanism for signal quality, it is difficult to ensure sufficient signal-to-noise ratio in weak signals, and it is prone to overload distortion in strong signals, further affecting the sampling accuracy of the analog-to-digital converter and the reliability of the current waveform analysis.

[0006] In view of the above problems, the present application provides a frequency converter embedded current waveform analysis method, system and medium.

[0007] In a first aspect, the application provides a method for analyzing current waveform in a frequency converter, which is implemented by a system for analyzing current waveform in a frequency converter, and comprises the following steps: obtaining a sampling circuit configured in a current path of the frequency converter, which at least comprises a sampling resistor, a cascade instrument amplifier and programmable gain amplifier, and an analog-to-digital converter; calculating a required total gain based on an original output voltage signal of the sampling resistor and a required input voltage of the analog-to-digital converter; evaluating a signal quality of the original output voltage signal, and dynamically allocating the required total gain to the instrument amplifier and the programmable gain amplifier based on a preset coordination rule, so as to amplify the original output voltage signal and then convert it by the analog-to-digital converter to obtain current waveform data for current abnormality analysis; wherein the preset coordination rule comprises: when the signal quality is lower than a first threshold, preferentially increasing a gain share of the instrument amplifier; and when the signal quality is higher than a second threshold, preferentially increasing a gain share of the programmable gain amplifier.

[0008] Preferably, the method further comprises: the sampling resistor is located between an emitter of each lower bridge arm IGBT and a negative terminal of a DC bus; an input end of the programmable gain amplifier is connected to an output end of the instrument amplifier, and the gains of the instrument amplifier and the programmable gain amplifier are controlled by a microcontroller; an input end of the analog-to-digital converter is connected to an output end of the programmable gain amplifier, and an output end is connected to the microcontroller.

[0009] Preferably, the method further comprises: gain fixing of the programmable gain amplifier is performed according to an optimal fixed value; required instrument amplifier gain is calculated, specifically a ratio of the required total gain to the gain fixed value of the programmable gain amplifier; and gain share increase of the instrument amplifier is performed according to the required instrument amplifier gain.

[0010] Preferably, the method further comprises: gain fixing of the instrument amplifier is performed according to an optimal safety value; required programmable gain amplifier gain is calculated, specifically a ratio of the required total gain to the gain fixed value of the instrument amplifier; it is judged whether the required programmable gain amplifier gain exceeds an allowed maximum gain; if not, gain share increase of the programmable gain amplifier is performed according to the required programmable gain amplifier gain; if yes, gain share increase of the programmable gain amplifier is performed according to the allowed maximum gain of the programmable gain amplifier, and the gain fixed value of the instrument amplifier is recalculated and controlled according to the allowed maximum gain of the programmable gain amplifier.

[0011] Preferably, the method further comprises: when the signal quality is higher than the first threshold and lower than the second threshold, the current gain setting is kept unchanged, or balanced allocation of the instrument amplifier and the programmable gain amplifier is performed.

[0012] Preferably, the variable frequency drive embedded current waveform analysis method further comprises: collecting a segment of signal in the idle period of the motor controller where the variable frequency drive is located, calculating the standard deviation as an estimated reference value of the noise amplitude, calculating the amplitude of the original output voltage signal, comparing the estimated reference value, and outputting the first dimension signal quality of the original output voltage signal; performing FFT on the original output voltage signal, observing the difference between the fundamental component and the base noise, and outputting the second dimension signal quality of the original output voltage signal; weighting the first dimension signal quality and the second dimension signal quality to generate the signal quality of the original output voltage signal.

[0013] Preferably, the variable frequency drive embedded current waveform analysis method further comprises: monitoring the current gain position state of the programmable gain amplifier, if the current gain position has been at the minimum gain position settable, and the digital sampling value of the analog-to-digital converter reaches the saturation threshold, the microcontroller sends the first protection instruction to reduce the gain of the instrument amplifier according to the preset protection mechanism.

[0014] Preferably, the variable frequency drive embedded current waveform analysis method further comprises: if the programmable gain amplifier has been adjusted to the maximum gain, but the signal quality is still lower than the preset weak signal threshold, the microcontroller detects whether there is room for improvement in the gain of the instrument amplifier, if there is, the gain of the instrument amplifier is improved according to the improvement space, if there is not, the digital average filtering algorithm is started to extract the effective signal.

[0015] In a second aspect, the application also provides a variable frequency drive embedded current waveform analysis system for executing the variable frequency drive embedded current waveform analysis method as described in the first aspect, comprising: a sampling circuit acquisition module for acquiring a sampling circuit configured in the current path of the variable frequency drive, at least including a sampling resistor, a cascaded instrument amplifier and a programmable gain amplifier, and an analog-to-digital converter; a total gain calculation module for calculating the required total gain based on the original output voltage signal of the sampling resistor and the required input voltage of the analog-to-digital converter; an abnormality analysis module for evaluating the signal quality of the original output voltage signal, dynamically allocating the required total gain to the instrument amplifier and the programmable gain amplifier based on a preset coordination rule, amplifying the original output voltage signal and then passing through the analog-to-digital converter to obtain current waveform data for current abnormality analysis; wherein the preset coordination rule comprises: a first threshold judgment module for preferentially increasing the gain share of the instrument amplifier when the signal quality is lower than a first threshold; a second threshold judgment module for preferentially increasing the gain share of the programmable gain amplifier when the signal quality is higher than a second threshold.

[0016] In a third aspect, a computer readable storage medium having stored thereon a computer program which, when executed, implements the steps of the variable frequency converter embedded current waveform analysis method of any one of the first aspect.

[0017] The technical solutions provided in the present application have at least the following technical effects or advantages: by achieving the technical goal of cooperative gain distribution of the instrument amplifier and the programmable gain amplifier and adaptive adjustment based on real-time signal quality, the technical effect of ensuring high-quality acquisition of current signals in a full dynamic range, improving waveform abnormality analysis accuracy, and improving system stability is achieved.

[0018] The above description is only a summary of the technical solutions of the present application. In order to more clearly understand the technical means of the present application, the following detailed description can be implemented according to the content of the specification, and in order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the following specific embodiments of the present application are described. It should be understood that the content described in this section is not intended to identify the key or important features of the embodiments of the present application, nor is it intended to limit the scope of the present application. Other features of the present application will become apparent from the following description. BRIEF DESCRIPTION OF DRAWINGS

[0019] In order to more clearly illustrate the technical solutions in the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description are only exemplary, and for those skilled in the art, other drawings can be obtained without creative labor on the basis of the provided drawings.

[0020] Figure 1 The flowchart of the variable frequency converter embedded current waveform analysis method of the present application.

[0021] Figure 2 The structure diagram of the variable frequency converter embedded current waveform analysis system of the present application.

[0022] Legend: sampling circuit acquisition module 1, total gain calculation module 2, abnormality analysis module 3, first threshold judgment module 4, second threshold judgment module 5. DETAILED DESCRIPTION

[0023] The application provides a frequency converter embedded current waveform analysis method, system and medium, solves the technical problem that in the prior art, due to the single structure of an amplifier and the lack of a dynamic self-adaptive adjustment mechanism for signal quality, it is impossible to guarantee sufficient signal-to-noise ratio in weak signals, and overload distortion is prone to occur in strong signals, further affecting the sampling accuracy of an analog-to-digital converter and the reliability of current waveform analysis. The technical goal of achieving the cooperative gain distribution of an instrument amplifier and a programmable gain amplifier and self-adaptive adjustment based on real-time signal quality is achieved, and the technical effect of guaranteeing high-quality acquisition of current signals in a full dynamic range, improving waveform abnormality analysis accuracy and system stability is achieved.

[0024] In the following, the technical solutions in the application will be described clearly and completely with reference to the drawings. Obviously, the described embodiments are only a part of the embodiments of the application, rather than all the embodiments of the application. It should be understood that the application is not limited by the example embodiments described herein. Based on the embodiments of the application, all other embodiments obtained by a person of ordinary skill in the art without creative work fall within the scope of protection of the application. In addition, it should be noted that, for the convenience of description, only parts related to the application are shown in the drawings, rather than all.

[0025] Embodiment one, please refer to the accompanying Figure 1 The application provides a frequency converter embedded current waveform analysis method, applied to a frequency converter embedded current waveform analysis system, and specifically includes the following steps: A sampling circuit configured in a current path of a frequency converter is acquired, and at least includes a sampling resistor, a cascaded instrument amplifier and programmable gain amplifier, and an analog-to-digital converter.

[0026] Specifically, in the current path of the frequency converter, a sampling circuit is configured to capture the current signal flowing through the power device. The sampling circuit at least includes a sampling resistor, a cascaded instrument amplifier and programmable gain amplifier, and an analog-to-digital converter. The sampling resistor refers to a small resistance resistor placed in the current path, which reflects the current size through the voltage drop generated when the current flows. The cascaded instrument amplifier is an amplifier used for amplifying weak differential signals, which has high input impedance and high common-mode rejection ratio, and can extract effective voltage signals in the presence of strong interference. The programmable gain amplifier is an amplifier whose amplification factor can be digitally controlled by a microcontroller, which flexibly adjusts the gain according to different working conditions, so as to ensure that the signal always remains in a reasonable range. The analog-to-digital converter is responsible for converting continuous voltage signals into discrete digital signals that can be recognized by digital circuits.

[0027] Based on the original output voltage signal of the sampling resistor and the required input voltage of the analog-to-digital converter, the required total gain is calculated.

[0028] Specifically, the original output voltage signal of the sampling resistor refers to the voltage difference generated by the current passing through the sampling resistor due to Ohm's law, which is very weak. If it is directly sent to the analog-to-digital converter, it may be too weak to be accurately distinguished. The required input voltage of the analog-to-digital converter refers to the voltage amplitude required for the analog-to-digital converter to work in the best range. Therefore, the required total gain is calculated by the ratio of the desired full-scale input of the analog-to-digital converter to the original output voltage signal, which represents the proportional relationship between the voltage amplitude required by the analog-to-digital converter at full-scale input and the original output voltage provided by the sampling resistor. The desired full-scale input of the analog-to-digital converter refers to the maximum input voltage range in which the analog-to-digital converter can work stably, and the original output voltage signal is the initial voltage generated by the current passing through the sampling resistor.

[0029] The signal quality of the original output voltage signal is evaluated, and the required total gain is dynamically allocated to the instrumentation amplifier and the programmable gain amplifier based on a preset cooperative rule. After amplifying the original output voltage signal, the current waveform data is obtained through the analog-to-digital converter for current anomaly analysis.

[0030] Specifically, evaluating the signal quality of the original output voltage signal refers to analyzing the voltage signal obtained from the sampling resistor, such as judging the clarity and reliability of the voltage signal through the ratio of amplitude to noise or frequency spectrum analysis. The higher the signal quality, the easier the signal is to be amplified and utilized, and the lower the signal quality, the easier it is to be covered by noise. Based on the preset cooperative rule, the required total gain is dynamically allocated to the instrumentation amplifier and the programmable gain amplifier, and the working proportion of the two amplifiers is determined according to the pre-set division principle. For example, when the signal quality is poor, more gain is preferentially allocated to the instrumentation amplifier to improve the front-end signal fidelity, and when the signal quality is good, more gain is allocated to the programmable gain amplifier to enhance the flexibility of the back-end, thereby ensuring that the signal is reasonably amplified under different working conditions.

[0031] After amplifying the original output voltage signal, the current waveform data is obtained through the analog-to-digital converter for current anomaly analysis, which means that the signal is first processed by two-stage amplifiers to amplify the weak millivolt-level signal to the volt-level, and then sent to the analog-to-digital converter for digitization. Among them, the signal must be amplified to occupy its effective range, otherwise the resolution is poor. Then, the digital signal output by the analog-to-digital converter is taken as the curve data of the current change over time, and then the abnormal situation is detected through algorithm, such as whether the current appears mutation, fluctuation is too large or frequency deviation, so as to judge whether the system has a fault.

[0032] The preset cooperative rule includes: when the signal quality is lower than a first threshold, preferentially increasing the gain share of the instrumentation amplifier; and when the signal quality is higher than a second threshold, preferentially increasing the gain share of the programmable gain amplifier.

[0033] Specifically, the preset cooperation rule refers to a control logic defined in advance, which is used to guide different amplifiers to allocate gain when facing different signal qualities, so as to ensure that the signal can be sufficiently amplified and maintain stability and low distortion, thereby improving the reliability of overall signal processing.

[0034] When the signal quality is lower than the first threshold, it means that the input signal is too weak and may be close to the noise level. At this time, if the programmable gain amplifier is mainly relied on for amplification, the noise will be amplified together, resulting in the deterioration of the signal-to-noise ratio. Therefore, the gain share of the instrument amplifier can be preferentially increased, because the input stage noise of the instrument amplifier is lower, which can enhance the weak signal to an appropriate amplitude at an early stage, so that the subsequent processing can more easily distinguish the effective signal from the background noise.

[0035] When the signal quality is higher than the second threshold, it means that the signal itself is already clear, with a large amplitude and relatively small noise influence. At this time, if the instrument amplifier continues to be relied on for amplification, its output may be too large and even enter a saturation state, causing distortion. Therefore, the gain share of the programmable gain amplifier can be preferentially increased, thereby avoiding overloading of the instrument amplifier, and also utilizing the flexible adjustment capability of the programmable gain amplifier to finely control the final signal amplitude to be exactly adapted to the input range of the analog-to-digital converter.

[0036] Further, the application also includes: the sampling resistor is located between the emitter of each lower bridge arm IGBT in the current path and the negative end of the DC bus; the input end of the programmable gain amplifier is connected to the output end of the instrument amplifier, and the gains of the instrument amplifier and the programmable gain amplifier are digitally controlled by the microcontroller; the input end of the analog-to-digital converter is connected to the output end of the programmable gain amplifier, and the output end is connected to the microcontroller.

[0037] Specifically, the lower bridge arm IGBT is an insulated gate bipolar transistor used for power electronic conversion, which is used in pairs in the inverter circuit, and the upper bridge arm and the lower bridge arm are respectively connected to the positive end and the negative end of the DC power supply. The emitter is an electrode of the IGBT. The sampling resistor is located between the emitter of each lower bridge arm IGBT in the current path and the negative end of the DC bus. The current passes through the sampling resistor and is connected to the negative end of the DC bus, and then the current forms a voltage signal when flowing through the sampling resistor, which is convenient for the subsequent circuit to collect current information.

[0038] The input end of the programmable gain amplifier is connected to the output end of the instrument amplifier, that is, the voltage signal formed by the sampling resistor is preliminarily amplified by the instrument amplifier to ensure that the small voltage difference can be separated from the noise and then transmitted to the programmable gain amplifier for further amplification.

[0039] The gain of the instrument amplifier and the programmable gain amplifier is digitally controlled by a microcontroller. The microcontroller is a chip with computing and logical processing capabilities. It can calculate the required amplification factor according to the algorithm, and dynamically adjust the gain range of the instrument amplifier and the programmable gain amplifier through digital signals, so as to ensure that the voltage signal will not be submerged in noise or distorted due to excessive amplification during the amplification process.

[0040] The input end of the analog-to-digital converter is connected to the output end of the programmable gain amplifier, that is, the voltage signal after two-stage amplification will be sent to the analog-to-digital converter for digital processing. The output end of the analog-to-digital converter is connected to the microcontroller, which can receive the final digital signal for waveform analysis, and also adjust the gain of the instrument amplifier and the programmable gain amplifier according to the analysis results or real-time state, realizing closed-loop control.

[0041] Further, the application also includes: fixing the gain of the programmable gain amplifier according to an optimal fixed value; calculating the required instrument amplifier gain, specifically the ratio of the required total gain to the gain fixed value of the programmable gain amplifier; and performing gain share promotion of the instrument amplifier according to the required instrument amplifier gain.

[0042] Specifically, the gain of the programmable gain amplifier is fixed according to an optimal fixed value, that is, the amplification factor of the programmable gain amplifier is locked at a value with the best noise performance. The value with the best noise performance is determined by the gain and noise relationship curve in the chip data manual Gain vs. Noise. The optimal fixed value is an intermediate value that takes into account both signal amplification capability and noise suppression capability, for example, 16 times when the noise is lowest. Further, in most cases, stable and clean amplification effect is obtained, while distortion or jitter caused by frequent adjustment is avoided.

[0043] Calculating the required instrument amplifier gain means that in the case where the factor of the programmable gain amplifier has been determined, the required total amplification factor of the system is used to back-calculate how many times of gain the instrument amplifier needs to provide. Specifically, the required total gain is divided by the gain fixed value of the programmable gain amplifier to obtain a ratio.

[0044] According to the required instrument amplifier gain, the gain share promotion of the instrument amplifier is performed. The amplification factor range of the instrument amplifier is adjusted by the microcontroller, so that the instrument amplifier reaches the calculated ratio, and further ensures that the signal at the front end is enhanced as much as possible in a low-noise state, improving the overall signal-to-noise ratio. Table 1 is the instrument amplifier gain record under the fixed value of the programmable gain amplifier.

[0045] Table 1: Instrument amplifier gain record under the fixed value of the programmable gain amplifier Raw signal (volts) ADC full scale input (volts) Total gain required Programmable gain amplifier fixed value Instrument amplifier gain required Instrument amplifier gain actual 0.02 2.0 100 16 6.25 6 0.05 2.0 40 16 2.5 3 0.01 2.0 200 16 12.5 13 0.08 2.0 25 16 1.56 2 0.005 2.0 400 16 25 25 Further, the application also includes: fixing the gain of the instrumentation amplifier according to the optimal safety value; calculating the required programmable gain amplifier gain, specifically the ratio of the required total gain and the fixed value of the gain of the instrumentation amplifier; judging whether the required programmable gain amplifier gain exceeds the allowed maximum gain; if not, performing the gain share promotion of the programmable gain amplifier according to the required programmable gain amplifier gain; if yes, performing the gain share promotion of the programmable gain amplifier according to the allowed maximum gain of the programmable gain amplifier, and simultaneously recalculating the fixed value of the gain of the instrumentation amplifier according to the allowed maximum gain of the programmable gain amplifier for control.

[0046] Specifically, the gain of the instrumentation amplifier is fixed according to the optimal safety value, and the amplification multiple of the instrumentation amplifier is locked at a safety value that can ensure sufficient amplification of the signal and will not be saturated due to an excessively large input signal. For example, if the maximum allowed output voltage of the instrumentation amplifier is 3.3 volts, and the expected input signal may reach 0.66 volts, selecting a gain of 5 times can ensure that the output is within 3.3 volts while maintaining the linear operating region.

[0047] After determining the gain of the instrumentation amplifier, the required programmable gain amplifier gain is calculated, and the amplification multiple of the programmable gain amplifier is calculated according to the total gain requirement. Specifically, the required total gain is divided by the fixed value of the gain of the instrumentation amplifier to obtain a ratio, thereby ensuring that the combination of the two-stage amplifier can meet the input requirements of the analog-to-digital converter while maintaining the safety of the previous stage.

[0048] It is judged whether the required programmable gain amplifier gain exceeds the allowed maximum gain, to prevent the programmable gain amplifier from being set outside its limit and entering the nonlinear region, thereby causing output distortion. If the maximum gain is not exceeded, the gain share promotion of the programmable gain amplifier is directly adjusted according to the calculated ratio. If the maximum gain is exceeded, the programmable gain amplifier is set to the allowed maximum gain, and the fixed value of the gain of the instrumentation amplifier is recalculated so that the combination of the two can still meet the total gain requirement to make up for the gain difference.

[0049] Further, the application also includes: when the signal quality is higher than the first threshold value and lower than the second threshold value, keeping the current gain setting unchanged, or performing equal distribution of the instrumentation amplifier and the programmable gain amplifier.

[0050] Specifically, when the signal quality is higher than the first threshold value and lower than the second threshold value, it indicates that the input signal is neither too weak nor reaches a very ideal clarity, and is in a stable interval at a medium level. If the gain of the amplifier is frequently adjusted, it may cause the system to switch back and forth between different gears, thereby introducing additional fluctuations or transient distortion, so the existing gain setting can be kept unchanged to ensure the continuity and stability of the system.

[0051] On the other hand, an equal distribution strategy can also be adopted, that is, in the stable interval, the gains of the instrumentation amplifier and the programmable gain amplifier are set as close values as possible, so as to ensure that the instrumentation amplifier will not bear too high amplification pressure alone, and to avoid excessive amplification of the programmable gain amplifier to introduce larger noise.

[0052] Further, the application also includes: collecting a signal in an idle period of the motor controller where the frequency converter is located, calculating a standard deviation as an estimated reference value of the noise amplitude, calculating the amplitude of the original output voltage signal, and outputting the first dimension signal quality of the original output voltage signal by comparing the amplitude with the estimated reference value; performing FFT on the original output voltage signal, observing the difference between the fundamental component and the background noise, and outputting the second dimension signal quality of the original output voltage signal; and weighting the first dimension signal quality and the second dimension signal quality to generate the signal quality of the original output voltage signal.

[0053] Specifically, collecting a signal in an idle period of the motor controller where the frequency converter is located refers to collecting the voltage signal on the current path in the gap time when the motor does not perform power conversion or control instructions, such as the PWM dead time, so as to avoid the interference caused by working condition changes and more easily distinguish the signal and the noise. Calculating a standard deviation as an estimated reference value of the noise amplitude, the standard deviation is a statistical index used to measure the size of signal fluctuation, and the greater the fluctuation, the stronger the noise. Calculating the amplitude of the original output voltage signal is a measurement of the peak range of the signal in the time domain. Comparing the signal amplitude with the estimated reference value can measure the strength of the signal relative to the noise, and the ratio is taken as the first dimension signal quality of the original output voltage signal.

[0054] Performing FFT on the original output voltage signal refers to performing fast Fourier transform on the original output voltage signal, converting the time domain signal to the frequency domain, and thus distinguishing the energy distribution of different frequency components. Observing the difference between the fundamental component and the background noise can determine whether the main signal is prominent enough in the frequency domain. The fundamental component corresponds to the power frequency signal or its harmonics of the motor operation, and the background noise represents the background noise level in the frequency spectrum. The greater the difference between the fundamental component and the background noise, the clearer the signal in the frequency domain. The difference is taken as the second dimension signal quality.

[0055] Weighting the first dimension signal quality and the second dimension signal quality combines the evaluation results in the time domain and the frequency domain to generate a more comprehensive signal quality index. By allocating the influence of the two according to different weights, the final weighted result can take into account the reliability of the amplitude and the frequency spectrum, avoiding misjudgment caused by a single index. The weighting coefficient is obtained by being self-defined by a person skilled in the art according to the actual situation.

[0056] Further, the application also includes: monitoring the current gain position state of the programmable gain amplifier, if the current gain position has been at its settable minimum gain position, and the digital sampling value of the analog-to-digital converter reaches the saturation threshold, the microcontroller sends a first protection instruction to reduce the gain of the instrument amplifier according to the preset protection mechanism.

[0057] Specifically, the gain position of the programmable gain amplifier is detected in real time, that is, the current gain position state of the programmable gain amplifier is monitored. The current gain position state refers to different levels of amplification, such as 1x, 2x, 5x, 10x, etc.

[0058] If the current gain position has been at its settable minimum gain position, it means that the programmable gain amplifier has been adjusted to the lowest possible amplification, indicating that the input signal itself is already strong and does not need to be amplified too much. At this time, if the digital sampling value of the analog-to-digital converter reaches the saturation threshold, it means that the voltage amplitude of the input signal has approached or exceeded the maximum value that the analog-to-digital converter can handle. For example, if the range of the analog-to-digital converter is 0 to 3.3 volts, and the input signal approaches 3.3 volts or even exceeds it, the digital scale will not continue to grow, that is, the digital sampling value of the analog-to-digital converter reaches the saturation threshold. In this case, the microcontroller needs to send a first protection instruction. The microcontroller is a processing chip with logic and control capabilities that can issue instructions in a timely manner based on the monitored state. The content of the first protection instruction is to reduce the gain of the instrument amplifier according to the preset protection mechanism. The instrument amplifier is originally responsible for amplifying weak signals, but when the input signal is too large, if its gain is not reduced, it will enter the nonlinear region, causing signal distortion. Therefore, by reducing the gain of the instrument amplifier, the signal can be compressed to a reasonable range, avoiding the impact of the over-strong signal on the amplification link.

[0059] Further, the application also includes: if the programmable gain amplifier has been adjusted to the maximum gain, but the signal quality is still below the preset weak signal threshold, detecting through the microcontroller whether there is room for improvement in the gain of the instrument amplifier, if there is, improving the gain of the instrument amplifier according to the improvement space, if there is not, starting the digital average filtering algorithm to extract the valid signal.

[0060] Specifically, the programmable gain amplifier is adjusted to the maximum gain, indicating that the amplification factor of the programmable gain amplifier has been set to the highest gear that the programmable gain amplifier can provide, and the circuit has already been unable to increase the amplification capability on the programmable gain amplifier. If the programmable gain amplifier has been adjusted to the maximum gain, and the signal quality is still lower than the preset signal weak threshold, it means that even at the highest amplification factor of the programmable gain amplifier, the amplitude of the input signal is still too small to meet the needs of subsequent analysis. The signal quality is measured by the ratio of amplitude to noise, and when the ratio is too low, the signal will be overwhelmed by noise, resulting in unreliable detection results.

[0061] By detecting whether there is room for the gain of the instrumentation amplifier to be improved through the microcontroller, it is determined whether the current gain of the instrumentation amplifier has reached the allowed upper limit. If there is still room for improvement, the gain of the instrumentation amplifier is increased according to the remaining space to further amplify the signal. If there is no room for improvement, it means that the gain of the instrumentation amplifier has also reached the maximum value, and the entire analog amplification link cannot enhance the signal any more. At this time, the digital average filtering algorithm needs to be started to extract the effective signal. Digital average filtering is a signal processing method that reduces the influence of random noise by taking the average value of multiple sampling points within a certain time, so that the useful signal hidden in the noise is clearer. Digital average filtering can effectively smooth out the fluctuations of noise by multiple sampling and averaging, so that the final signal is closer to the real current change in waveform.

[0062] In summary, the frequency converter embedded current waveform analysis method provided by the present application has the following technical effects: by achieving the technical goal of cooperative gain distribution of the instrumentation amplifier and the programmable gain amplifier and adaptive adjustment based on real-time signal quality, the technical effects of ensuring high-quality acquisition of current signals in the full dynamic range, improving waveform anomaly analysis accuracy, and system stability are achieved.

[0063] Embodiment two, based on the same inventive concept as the frequency converter embedded current waveform analysis method in the foregoing embodiments, the present application also provides a frequency converter embedded current waveform analysis system, please refer to the attached Figure 2The application relates to a current waveform analysis system embedded in a frequency converter, comprising: a sampling circuit acquisition module 1 used for acquiring a sampling circuit arranged in a current path of a frequency converter, at least comprising a sampling resistor, a cascade instrument amplifier and a programmable gain amplifier and an analog-to-digital converter; a total gain calculation module 2 used for calculating a required total gain based on an original output voltage signal of the sampling resistor and a required input voltage of the analog-to-digital converter; an abnormality analysis module 3 used for evaluating the signal quality of the original output voltage signal, dynamically allocating the required total gain to the instrument amplifier and the programmable gain amplifier based on preset cooperative rules, amplifying the original output voltage signal and then inputting the original output voltage signal into the analog-to-digital converter to obtain current waveform data for current abnormality analysis; wherein the preset cooperative rules comprise: a first threshold value judgment module 4 used for preferentially increasing the gain share of the instrument amplifier when the signal quality is lower than a first threshold value; and a second threshold value judgment module 5 used for preferentially increasing the gain share of the programmable gain amplifier when the signal quality is higher than a second threshold value.

[0064] Further, the current waveform analysis system embedded in the frequency converter is further used for: arranging the sampling resistor between the emitter of each lower bridge arm IGBT and the negative end of a direct current bus; connecting the input end of the programmable gain amplifier to the output end of the instrument amplifier, and digitally controlling the gains of the instrument amplifier and the programmable gain amplifier through a microcontroller; connecting the input end of the analog-to-digital converter to the output end of the programmable gain amplifier, and connecting the output end to the microcontroller.

[0065] Further, the current waveform analysis system embedded in the frequency converter is further used for: gain fixing the programmable gain amplifier according to an optimal fixed value; calculating a required instrument amplifier gain, specifically a ratio of the required total gain to the gain fixed value of the programmable gain amplifier; and executing gain share increase of the instrument amplifier according to the required instrument amplifier gain.

[0066] Further, the current waveform analysis system embedded in the frequency converter is further used for: gain fixing the instrument amplifier according to an optimal safety value; calculating a required programmable gain amplifier gain, specifically a ratio of the required total gain to the gain fixed value of the instrument amplifier; judging whether the required programmable gain amplifier gain exceeds an allowed maximum gain; if not, executing gain share increase of the programmable gain amplifier according to the required programmable gain amplifier gain; if yes, executing gain share increase of the programmable gain amplifier according to the allowed maximum gain of the programmable gain amplifier, and simultaneously recalculating the gain fixed value of the instrument amplifier according to the allowed maximum gain of the programmable gain amplifier for control.

[0067] Further, the inverter-embedded current waveform analysis system is further configured to: when the signal quality is higher than the first threshold and lower than the second threshold, keep the current gain setting unchanged, or perform equal distribution of the instrumentation amplifier and the programmable gain amplifier.

[0068] Further, the inverter-embedded current waveform analysis system is further configured to: collect a signal in an idle period of a motor controller in which the inverter is located, calculate a standard deviation as an estimated reference value of a noise amplitude, calculate an amplitude of the original output voltage signal, perform a ratio between the estimated reference value and the amplitude of the original output voltage signal, and output a first dimension signal quality of the original output voltage signal; perform an FFT on the original output voltage signal, observe a difference between a fundamental component and a base noise, and output a second dimension signal quality of the original output voltage signal; and weight the first dimension signal quality and the second dimension signal quality to generate a signal quality of the original output voltage signal.

[0069] Further, the inverter-embedded current waveform analysis system is further configured to: monitor a current gain position state of the programmable gain amplifier, if the current gain position has been at a minimum gain position settable by the programmable gain amplifier, and a digital sampling value of the analog-to-digital converter reaches a saturation threshold, the microcontroller sends a first protection instruction to reduce the gain of the instrumentation amplifier according to a preset protection mechanism.

[0070] Further, the inverter-embedded current waveform analysis system is further configured to: if the programmable gain amplifier has been adjusted to the maximum gain, but the signal quality is still lower than a preset weak signal threshold, the microcontroller detects whether there is a gain space for the instrumentation amplifier, if there is, the gain of the instrumentation amplifier is increased according to the gain space, if not, a digital average filtering algorithm is started to extract an effective signal.

[0071] The embodiments in the specification are described in a progressive manner, and each embodiment focuses on the difference from other embodiments. The inverter-embedded current waveform analysis method and specific examples in the foregoing embodiment one are also applicable to the inverter-embedded current waveform analysis system of the present embodiment. Through the foregoing detailed description of the inverter-embedded current waveform analysis method, those skilled in the art can clearly understand the inverter-embedded current waveform analysis system in the present embodiment. Therefore, for the sake of brevity of the specification, the foregoing will not be described in detail.

[0072] In the third embodiment, based on the inverter-embedded current waveform analysis method in the foregoing embodiments, the same inventive concept is provided. The present application also provides a computer readable storage medium, and the computer readable storage medium stores a computer program. The computer program implements the steps of the inverter-embedded current waveform analysis method in any one of the foregoing embodiments when executed.

[0073] The foregoing description of the disclosed embodiments enables a person skilled in the art to make or use the application. Numerous modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein can be applied to other embodiments without the use of the inventive faculty. Therefore, the present application is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

[0074] It will be readily apparent to one skilled in the art that varying substitutions and modifications can be made to the application disclosed herein without departing from the scope and spirit of the application. Accordingly, it is intended that all such alterations and modifications be considered as within the scope of the application.

Claims

1. A current waveform analysis method embedded in a frequency converter, characterized in that, include: The sampling circuit configured in the current path of the frequency converter includes at least a sampling resistor, a cascaded instrumentation amplifier and a programmable gain amplifier, and an analog-to-digital converter. Calculate the required total gain based on the original output voltage signal from the sampling resistor and the required input voltage of the analog-to-digital converter; The signal quality of the original output voltage signal is evaluated, and the required total gain is dynamically allocated to the instrumentation amplifier and the programmable gain amplifier based on a preset coordination rule. The original output voltage signal is amplified and then passed through an analog-to-digital converter to obtain current waveform data for current anomaly analysis. The preset collaboration rules include: When the signal quality is below a first threshold, the gain share of the instrumentation amplifier is increased preferentially. When the signal quality is higher than the second threshold, the gain share of the programmable gain amplifier is preferentially increased.

2. The inverter embedded current waveform analysis method as described in claim 1, characterized in that, The sampling resistor is located between the emitter of each lower arm IGBT and the negative terminal of the DC bus in the current path; The input of the programmable gain amplifier is connected to the output of the instrumentation amplifier, and the gains of the instrumentation amplifier and the programmable gain amplifier are digitally controlled by a microcontroller. The input of the analog-to-digital converter is connected to the output of the programmable gain amplifier, and the output is connected to the microcontroller.

3. The inverter embedded current waveform analysis method as described in claim 1, characterized in that, When the signal quality is below a first threshold, the gain share of the instrumentation amplifier is preferentially increased, including: The gain of the programmable gain amplifier is fixed according to an optimal fixed value; Calculate the required instrumentation amplifier gain, specifically the ratio of the required total gain to the fixed gain value of the programmable gain amplifier; Perform a gain share boost on the instrumentation amplifier based on the required gain.

4. The inverter embedded current waveform analysis method as described in claim 1, characterized in that, When the signal quality is higher than the second threshold, the gain share of the programmable gain amplifier is preferentially increased, including: The gain of the instrumentation amplifier is fixed according to the optimal safety value; Calculate the required gain of the programmable gain amplifier, specifically the ratio of the required total gain to the fixed gain value of the instrumentation amplifier; Determine whether the required programmable gain amplifier gain exceeds the maximum allowable gain; If not, perform a gain fraction increase of the programmable gain amplifier according to the required programmable gain amplifier gain; If so, the gain fraction of the programmable gain amplifier is increased according to the maximum allowable gain of the programmable gain amplifier, and the fixed gain value of the instrumentation amplifier is recalculated and controlled simultaneously according to the maximum allowable gain of the programmable gain amplifier.

5. The inverter embedded current waveform analysis method as described in claim 1, characterized in that, include: When the signal quality is higher than the first threshold and lower than the second threshold, the current gain setting remains unchanged, or a balanced distribution of the instrumentation amplifier and the programmable gain amplifier is performed.

6. The inverter embedded current waveform analysis method as described in claim 1, characterized in that, Evaluating the signal quality of the original output voltage signal includes: During the idle period of the motor controller where the frequency converter is located, a signal is collected, the standard deviation is calculated as an estimated reference value for the noise amplitude, the amplitude of the original output voltage signal is calculated, and the ratio is made with the estimated reference value to output the first dimension of the signal quality of the original output voltage signal. Perform an FFT on the original output voltage signal, observe the difference between the fundamental component and the base noise, and output the second dimension signal quality of the original output voltage signal; The signal quality of the original output voltage signal is generated by weighting the signal quality of the first dimension and the signal quality of the second dimension.

7. The inverter embedded current waveform analysis method as described in claim 1, characterized in that, The microcontroller monitors the current gain level of the programmable gain amplifier. If the current gain level is already at its minimum settable gain level and the digital sampling value of the analog-to-digital converter reaches the saturation threshold, the microcontroller sends a first protection command to reduce the gain of the instrumentation amplifier according to a preset protection mechanism.

8. The inverter embedded current waveform analysis method as described in claim 7, characterized in that, If the programmable gain amplifier has been adjusted to its maximum gain, but the signal quality is still below the preset weak signal threshold, the microcontroller detects whether there is room for improvement in the gain of the instrumentation amplifier. If there is, the gain of the instrumentation amplifier is increased according to the room for improvement. If not, the digital average filtering algorithm is activated to extract the effective signal.

9. A frequency converter embedded current waveform analysis system, characterized in that, The steps for implementing the inverter embedded current waveform analysis method according to any one of claims 1 to 8 include: The sampling circuit acquisition module is used to acquire the sampling circuit configured in the current path of the frequency converter, including at least a sampling resistor, a cascaded instrumentation amplifier and a programmable gain amplifier, and an analog-to-digital converter. The total gain calculation module is used to calculate the required total gain based on the raw output voltage signal from the sampling resistor and the required input voltage of the analog-to-digital converter. The anomaly analysis module is used to evaluate the signal quality of the original output voltage signal, dynamically allocate the required total gain to the instrumentation amplifier and the programmable gain amplifier based on a preset coordination rule, amplify the original output voltage signal and then pass it through an analog-to-digital converter to obtain current waveform data for current anomaly analysis. The preset collaboration rules include: The first threshold judgment module is used to prioritize increasing the gain share of the instrumentation amplifier when the signal quality is lower than the first threshold. The second threshold judgment module is used to preferentially increase the gain share of the programmable gain amplifier when the signal quality is higher than the second threshold.

10. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores a computer program that, when executed, implements the steps of the inverter embedded current waveform analysis method according to any one of claims 1 to 8.

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