Variable frequency inverter embedded current waveform analysis method, system and medium

Abstract

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

Description

Technical Field

[0001] This application relates to the field of current waveform analysis technology, and in particular to a method, system and medium for embedded current waveform analysis in frequency converters. Background Technology

[0002] With the rapid development of power electronics and motor control technologies, frequency converters have been widely used in industrial automation, new energy power generation, electric vehicles, and home appliances. As a core component for regulating motor operation, the accurate acquisition and analysis of current signals during the operation of a frequency converter directly determines its control performance and system stability.

[0003] Currently, most existing current signal acquisition schemes use fixed-gain amplifiers or single programmable gain amplifiers for adjustment. While fixed-gain amplifiers are simple in structure and have low noise, they cannot adapt to situations with a large dynamic range of input signals, and are prone to problems such as insufficient amplification of weak signals or overload distortion of strong signals. Single programmable gain amplifiers offer some flexibility, but due to their poor input noise characteristics, they often introduce significant noise when processing weak signals, leading to a decrease in the signal-to-noise ratio.

[0004] In summary, existing technologies suffer from technical problems due to the simple amplifier structure and lack of a dynamic adaptive adjustment mechanism for signal quality. This results in insufficient signal-to-noise ratio under weak signals and easy overload distortion under strong signals, further affecting the sampling accuracy of analog-to-digital converters and the reliability of current waveform analysis. Summary of the Invention

[0005] The purpose of this application is to provide a method, system, and medium for embedded current waveform analysis in frequency converters, in order to solve the technical problems in the prior art, which are that due to the simple amplifier structure and lack of dynamic adaptive adjustment mechanism for signal quality, sufficient signal-to-noise ratio cannot be guaranteed under weak signals, and overload distortion is prone to occur under strong signals, which further affects the sampling accuracy of analog-to-digital converters and the reliability of current waveform analysis.

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

[0007] In a first aspect, this application provides an embedded current waveform analysis method for frequency converters, implemented through an embedded current waveform analysis system for frequency converters. The method includes: acquiring a 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; 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; evaluating the signal quality of the original output voltage signal; dynamically allocating the required total gain to the instrumentation amplifier and the programmable gain amplifier based on a preset coordination rule; amplifying the original output voltage signal before passing it through the analog-to-digital converter to obtain current waveform data for current anomaly analysis; wherein the preset coordination rule includes: when the signal quality is lower than a first threshold, preferentially increasing the gain share of the instrumentation amplifier; when the signal quality is higher than a second threshold, preferentially increasing the gain share of the programmable gain amplifier.

[0008] Preferably, the inverter embedded current waveform analysis method further includes: the sampling resistor is located between the emitter of each lower bridge arm IGBT and the negative terminal of the DC bus in the current path; the input terminal of the programmable gain amplifier is connected to the output terminal of the instrumentation amplifier, and the gain of the instrumentation amplifier and the programmable gain amplifier are digitally controlled by a microcontroller; the input terminal of the analog-to-digital converter is connected to the output terminal of the programmable gain amplifier, and the output terminal is connected to the microcontroller.

[0009] Preferably, the inverter embedded current waveform analysis method further includes: fixing the gain of the programmable gain amplifier according to an optimal fixed value; calculating the required instrumentation amplifier gain, specifically the ratio of the required total gain to the fixed gain value of the programmable gain amplifier; and performing a gain share increase of the instrumentation amplifier according to the required instrumentation amplifier gain.

[0010] Preferably, the inverter embedded current waveform analysis method further includes: fixing the gain of the instrumentation amplifier according to the optimal safety value; calculating 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; determining whether the required gain of the programmable gain amplifier exceeds the maximum allowable gain; if not, increasing the gain share of the programmable gain amplifier according to the required gain; if so, increasing the gain share of the programmable gain amplifier according to the maximum allowable gain of the programmable gain amplifier, and simultaneously recalculating the fixed gain value of the instrumentation amplifier according to the maximum allowable gain of the programmable gain amplifier for control.

[0011] Preferably, the inverter embedded current waveform analysis method further includes: when the signal quality is higher than a first threshold and lower than a second threshold, maintaining the current gain setting unchanged, or performing a balanced distribution of the instrumentation amplifier and the programmable gain amplifier.

[0012] Preferably, the inverter-embedded current waveform analysis method further includes: acquiring a signal during the idle period of the motor controller where the inverter is located, calculating the standard deviation as an estimated reference value for the noise amplitude, calculating the amplitude of the original output voltage signal, and comparing it with the estimated reference value to output 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; and 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 inverter embedded current waveform analysis method further includes: monitoring the current gain level status of the programmable gain amplifier; if the current gain level is already at its settable minimum 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.

[0014] Preferably, the inverter embedded current waveform analysis method further includes: 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 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 started to extract the effective signal.

[0015] Secondly, this application also provides an inverter-embedded current waveform analysis system for performing the inverter-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 inverter, including at least a sampling resistor, a cascaded instrumentation 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; and an anomaly analysis module for evaluating the signal quality of the original output voltage signal, dynamically allocating the required total gain to the instrumentation amplifier and the programmable gain amplifier based on a preset coordination rule, amplifying the original output voltage signal and then passing it through the analog-to-digital converter to obtain current waveform data for current anomaly analysis; wherein the preset coordination rule includes: a first threshold judgment module for preferentially increasing the gain share of the instrumentation amplifier when the signal quality is lower than a first threshold; and 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] Thirdly, a computer-readable storage medium storing a computer program that, when executed, implements the steps of the inverter embedded current waveform analysis method described in any one of the first aspects above.

[0017] The technical solution provided in this application has at least the following technical effects or advantages: by achieving the technical goal of coordinated gain allocation between the instrumentation amplifier and the programmable gain amplifier and adaptive adjustment based on real-time signal quality, it achieves the technical effects of ensuring high-quality acquisition of current signals, improving the accuracy of waveform anomaly analysis and system stability within the full dynamic range.

[0018] The above description is merely an overview of the technical solution of this application. To enable a clearer understanding of the technical means of this application and to facilitate its implementation according to the description, and to make the above and other objects, features, and advantages of this application more apparent, specific embodiments of this application are described below. It should be understood that the content described in this section is not intended to identify key or important features of the embodiments of this application, nor is it intended to limit the scope of this application. Other features of this application will become readily apparent through the following description. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are merely exemplary. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0020] Figure 1 This is a flowchart illustrating the embedded current waveform analysis method for frequency converters in this application.

[0021] Figure 2 This is a schematic diagram of the structure of the inverter embedded current waveform analysis system of this application.

[0022] Figure labeling: Sampling circuit acquisition module 1, total gain calculation module 2, anomaly analysis module 3, first threshold judgment module 4, second threshold judgment module 5. Detailed Implementation

[0023] This application provides an embedded current waveform analysis method, system, and medium for frequency converters, solving the technical problems in existing technologies where the single amplifier structure and lack of dynamic adaptive adjustment mechanism for signal quality lead to insufficient signal-to-noise ratio under weak signals and easy overload distortion under strong signals, further affecting the sampling accuracy of analog-to-digital converters and the reliability of current waveform analysis. It achieves the technical goal of coordinated gain allocation between instrumentation amplifiers and programmable gain amplifiers and adaptive adjustment based on real-time signal quality, thus ensuring high-quality current signal acquisition across the entire dynamic range, improving the accuracy of waveform anomaly analysis, and enhancing system stability.

[0024] The technical solutions of this application will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. It should be understood that this application is not limited to the exemplary embodiments described herein. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application. It should also be noted that, for ease of description, only the parts related to this application are shown in the accompanying drawings, not all of them.

[0025] Example 1, please refer to the appendix. Figure 1 This application provides a method for embedded current waveform analysis in frequency converters, which is applied to a system for embedded current waveform analysis in frequency converters. The method specifically includes the following steps:

[0026] 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.

[0027] Specifically, a sampling circuit is configured in the current path of the frequency converter to capture the current signal flowing through the power devices. The sampling circuit includes at least a sampling resistor, a cascaded instrumentation amplifier and a programmable gain amplifier, and an analog-to-digital converter (ADC). The sampling resistor is a small resistor placed in the current path; the voltage drop generated when current flows through it reflects the current magnitude. The cascaded instrumentation amplifier is an amplifier used to amplify weak differential signals, featuring high input impedance and high common-mode rejection ratio, enabling it to extract effective voltage signals even in environments with strong interference. The programmable gain amplifier is an amplifier whose amplification factor can be digitally controlled by a microcontroller, flexibly adjusting the gain according to different operating conditions to ensure the signal remains within a reasonable range. The ADC is responsible for converting the continuous voltage signal into a discrete digital signal that can be recognized by digital circuits.

[0028] 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.

[0029] Specifically, the original output voltage signal of the sampling resistor refers to the voltage difference generated by Ohm's law when current flows through the sampling resistor. This voltage difference is extremely weak, and if directly fed into an analog-to-digital converter (ADC), it may be too weak to be accurately distinguished. The required input voltage of the ADC refers to the voltage amplitude required for the ADC to operate within its optimal range. Therefore, the required total gain is calculated by the ratio of the expected full-scale input of the ADC to the original output voltage signal, representing the proportional relationship between the voltage amplitude required by the ADC at full-scale input and the original output voltage provided by the sampling resistor. The expected full-scale input of the ADC refers to the maximum input voltage range within which the ADC can operate stably, while the original output voltage signal is the initial voltage generated by current flowing through the sampling resistor.

[0030] 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.

[0031] Specifically, evaluating the signal quality of the original output voltage signal refers to analyzing the voltage signal obtained from the sampling resistor, such as by using the amplitude-to-noise ratio or spectral analysis to determine the clarity and reliability of the voltage signal. Higher signal quality means the signal is easier to amplify and utilize, while lower signal quality means it is easily masked by noise. Based on preset coordination rules, the required total gain is dynamically allocated to the instrumentation amplifier and the programmable gain amplifier. The working ratio of the two amplifiers is determined according to a pre-set division of labor principle. For example, when the signal quality is poor, more gain is allocated to the instrumentation amplifier to improve the front-end signal fidelity, while 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 operating conditions.

[0032] Amplifying the original output voltage signal before passing it through an analog-to-digital converter (ADC) means that the signal is first processed by two stages of amplifiers, amplifying the weak millivolt-level signal to the volt level, before being sent to the ADC for digitization. The signal must be amplified to fill its effective range; otherwise, the resolution will be poor. This results in current waveform data for current anomaly analysis. The digital signal output from the ADC is used as a curve of current changing over time. Algorithms then detect anomalies, such as sudden changes in current, excessive fluctuations, or frequency deviations, to determine if a system fault exists.

[0033] The preset coordination rules include: when the signal quality is lower than a first threshold, prioritizing the increase of the gain share of the instrumentation amplifier; when the signal quality is higher than a second threshold, prioritizing the increase of the gain share of the programmable gain amplifier.

[0034] Specifically, the pre-defined coordination rules refer to the pre-defined control logic used to guide different amplifiers on how to allocate gain when facing different signal qualities. This ensures that the signal can be fully amplified while maintaining stability and low distortion, thereby improving the reliability of the overall signal processing.

[0035] When the signal quality falls below the first threshold, it indicates that the input signal is too weak and may be close to noise levels. In this case, relying primarily on a programmable gain amplifier for amplification can easily amplify the noise as well, leading to a deterioration in the signal-to-noise ratio. Therefore, it is advisable to prioritize increasing the gain share of the instrumentation amplifier, as its input stage noise is lower, allowing it to boost weak signals to a suitable level early on, making it easier for subsequent processing stages to distinguish between the effective signal and background noise.

[0036] When the signal quality exceeds the second threshold, it indicates that the signal itself is already clear, with a large amplitude and relatively small noise impact. Continuing to rely on the instrumentation amplifier for amplification at this point may lead to excessive output or even saturation, causing distortion. Therefore, it is advisable to prioritize increasing the gain share of the programmable gain amplifier. This avoids overloading the instrumentation amplifier and allows for precise control of the final signal amplitude using the programmable gain amplifier's flexible adjustment capabilities, ensuring it perfectly matches the input range of the analog-to-digital converter.

[0037] Furthermore, this application also includes: the sampling resistor is located between the emitter of each lower bridge arm IGBT and the negative terminal of the DC bus in the current path; the input terminal of the programmable gain amplifier is connected to the output terminal of the instrumentation amplifier, and the gain of the instrumentation amplifier and the programmable gain amplifier is digitally controlled by the microcontroller; the input terminal of the analog-to-digital converter is connected to the output terminal of the programmable gain amplifier, and the output terminal is connected to the microcontroller.

[0038] Specifically, the lower IGBT is an insulated-gate bipolar transistor used in power electronic conversion. In inverter circuits, they are used in pairs, with the upper and lower arms connected to the positive and negative terminals of the DC power supply, respectively. The emitter is the electrode of the IGBT. A sampling resistor is located between the emitter of each lower IGBT and the negative terminal of the DC bus in the current path. Current flows through the sampling resistor and is then connected to the negative terminal of the DC bus, thus forming a voltage signal as the current flows through the sampling resistor, facilitating the acquisition of current information by subsequent circuits.

[0039] The input of the programmable gain amplifier is connected to the output of the instrumentation amplifier. That is, the voltage signal formed by the sampling resistor is initially amplified by the instrumentation amplifier to ensure that the small voltage difference can be separated from the noise, and then passed to the programmable gain amplifier for further amplification.

[0040] The gain of the instrumentation amplifier and the programmable gain amplifier is digitally controlled by a microcontroller. A microcontroller is a chip with computing and logic processing capabilities. It can dynamically adjust the gain level of the instrumentation amplifier and the programmable gain amplifier through digital signals according to the required amplification factor calculated by the algorithm. This ensures that the voltage signal is neither drowned out by noise nor distorted due to excessive amplification during the amplification process.

[0041] The input of the analog-to-digital converter (ADC) is connected to the output of the programmable gain amplifier (PGA). This means the voltage signal, after two stages of amplification, is fed into the ADC for digitization. The output of the ADC is connected to a microcontroller. The microcontroller receives the final digital signal, performs waveform analysis, and adjusts the gains of the instrumentation amplifier and the PGA based on the analysis results or real-time status, achieving closed-loop control.

[0042] Furthermore, this application also includes: fixing the gain of the programmable gain amplifier according to an optimal fixed value; calculating the required instrumentation amplifier gain, specifically the ratio of the required total gain to the fixed gain value of the programmable gain amplifier; and performing a gain share increase of the instrumentation amplifier according to the required instrumentation amplifier gain.

[0043] Specifically, the gain of the programmable gain amplifier is fixed at an optimal value, meaning the amplifier's gain is locked at a value with optimal noise performance. This optimal noise performance value is determined using the gain vs. noise curve in the chip's datasheet. The optimal fixed value is an intermediate value that balances signal amplification and noise suppression capabilities; for example, 16x provides the lowest noise. This results in stable and clean amplification in most cases, while avoiding distortion or jitter caused by frequent adjustments.

[0044] Calculating the required instrumentation amplifier gain means, given a fixed gain for the programmable gain amplifier, working backward from the total amplification required by the system to determine the amount of gain the instrumentation amplifier needs to provide. Specifically, this is done by dividing the required total gain by the fixed gain value of the programmable gain amplifier.

[0045] Based on the required instrumentation amplifier gain, the gain ratio of the instrumentation amplifier is increased. The amplification factor of the instrumentation amplifier is adjusted by the microcontroller to achieve the calculated ratio, thereby ensuring that the signal at the front end is enhanced as much as possible under low noise conditions and improving the overall signal-to-noise ratio. Table 1 shows the instrumentation amplifier gain record under fixed values ​​of the programmable gain amplifier.

[0046] Table 1: Gain Records of Instrumentation Amplifiers with Fixed Programmable Gain Amplifier Values

[0047] Original signal (volts) Analog-to-digital converter full-scale input (volts) Total gain required Programmable gain amplifier fixed value Required instrumentation amplifier gain Actual instrumentation amplifier gain 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

[0048] Furthermore, this application also includes: fixing the gain of the instrumentation amplifier according to an optimal safety value;

[0049] 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 gain of the programmable gain amplifier exceeds the maximum allowable gain; if not, increase the gain share of the programmable gain amplifier according to the required gain; if so, increase the gain share of the programmable gain amplifier according to the maximum allowable gain of the programmable gain amplifier, and simultaneously recalculate the fixed gain value of the instrumentation amplifier according to the maximum allowable gain of the programmable gain amplifier for control.

[0050] Specifically, the gain of the instrumentation amplifier is fixed according to the optimal safety value. This locks the amplifier's amplification factor at a safe level that ensures sufficient signal amplification without saturation due to excessively large input signals. For example, if the maximum allowable output voltage of the instrumentation amplifier is 3.3 volts, and the expected input signal may reach 0.66 volts, then selecting a gain of 5 will ensure that the output is within 3.3 volts while maintaining the linear operating range.

[0051] After determining the instrumentation amplifier gain, the required programmable gain amplifier gain is calculated, and the amplification factor of the programmable gain amplifier is derived based on the total gain requirement. Specifically, the required total gain is divided by the fixed gain value of the instrumentation amplifier to obtain the ratio, thereby ensuring that the combination of the two amplifier stages can meet the input requirements of the analog-to-digital converter while maintaining the safety of the preceding stage.

[0052] Determine if the required gain of the programmable gain amplifier exceeds the maximum permissible gain to prevent the programmable gain amplifier from being set beyond its limits and entering the nonlinear region, which would lead to output distortion. If the maximum gain is not exceeded, directly adjust the gain component of the programmable gain amplifier according to the calculated ratio. If the maximum gain is exceeded, set the programmable gain amplifier to the maximum permissible gain, and recalculate the fixed gain value of the instrumentation amplifier so that the combination of the two still meets the overall gain requirement to compensate for the gain difference.

[0053] Furthermore, this application also includes: when the signal quality is higher than a first threshold and lower than a second threshold, maintaining the current gain setting unchanged, or performing a balanced distribution of the instrumentation amplifier and the programmable gain amplifier.

[0054] Specifically, when the signal quality is above the first threshold and below the second threshold, it indicates that the input signal is neither too weak nor has reached ideal clarity, and is in a stable, moderate range. Frequent adjustments to the amplifier gain may cause the system to switch back and forth between different gain levels, introducing additional fluctuations or transient distortion. Therefore, maintaining the existing gain setting ensures system continuity and stability.

[0055] On the other hand, a balanced distribution strategy can also be adopted, that is, in the stable range, the gains of the instrumentation amplifier and the programmable gain amplifier are set to be as close as possible. This can ensure that the instrumentation amplifier does not bear too high amplification pressure alone, and also avoid the programmable gain amplifier from over-amplifying and introducing large noise.

[0056] Furthermore, this application also includes: acquiring a signal during the idle period of the motor controller where the frequency converter is located, calculating the standard deviation as an estimated reference value for the noise amplitude, calculating the amplitude of the original output voltage signal, and comparing it with the estimated reference value to output 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; and weighting the first dimension signal quality and the second dimension signal quality to generate the signal quality of the original output voltage signal.

[0057] Specifically, acquiring a signal during the idle period of the motor controller where the frequency converter is located refers to acquiring the voltage signal in the current path during the gap time when the motor is not executing power conversion or control commands, such as the PWM dead time. This avoids interference from changes in operating conditions and makes it easier to distinguish between signal and noise. The standard deviation is calculated as an estimated reference value for the noise amplitude. The standard deviation is a statistical indicator used to measure the magnitude of signal fluctuation; the larger 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. Ratioing the signal amplitude to the estimated reference value measures the relative strength of the signal to the noise; this ratio serves as the first dimension of signal quality for the original output voltage signal.

[0058] Performing an FFT on the original output voltage signal involves converting the time-domain signal to the frequency domain, thereby distinguishing the energy distribution of different frequency components. Observing the difference between the fundamental component and the background noise allows us to determine whether the main signal is sufficiently prominent in the frequency domain. The fundamental component corresponds to the power frequency signal of the motor or its harmonics, while the background noise represents the level of background noise in the spectrum. The larger the difference between the fundamental component and the background noise, the clearer the signal is in the frequency domain. This difference is used as a second dimension of signal quality.

[0059] By weighting the first and second dimensions of signal quality, the evaluation results from both the time and frequency domains are combined to generate a more comprehensive signal quality index. By allocating the influence of both dimensions with different weights, the final weighted result can consider the reliability of both amplitude and spectrum aspects, avoiding misjudgments caused by a single index. The weighting coefficients are customized by those skilled in the art based on the specific circumstances.

[0060] Furthermore, this application also includes: monitoring the current gain level status of the programmable gain amplifier; if the current gain level is already at its settable minimum 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.

[0061] Specifically, the current gain level of the programmable gain amplifier is monitored in real time. The current gain level refers to different gain levels, such as 1x, 2x, 5x, 10x, etc.

[0062] If the current gain level is already at its minimum settable gain level, it means the programmable gain amplifier has been adjusted to the lowest possible amplification factor, indicating that the input signal itself is already strong and does not require excessive amplification. At this point, if the digital sample value of the analog-to-digital converter (ADC) reaches the saturation threshold, it means the voltage amplitude of the input signal is close to or exceeds the maximum value that the ADC can handle. For example, if the ADC's range is 0 to 3.3 volts, and the input signal is close to or exceeds 3.3 volts, the digital scale will stop increasing, meaning the ADC's digital sample value has reached the saturation threshold. In this situation, the microcontroller needs to send a first protection command. The microcontroller is a processing chip with logic and control capabilities that issues commands promptly based on the monitored state. The first protection command reduces the gain of the instrumentation amplifier according to a preset protection mechanism. The instrumentation 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 instrumentation amplifier, the signal can be compressed to a reasonable range, preventing the amplification link from being impacted by excessively strong signals.

[0063] Furthermore, this application also includes: if the programmable gain amplifier has been adjusted to its maximum gain, but the signal quality is still lower than a 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, a digital averaging filter algorithm is started to extract the effective signal.

[0064] Specifically, when the programmable gain amplifier (PGA) is adjusted to its maximum gain, it means that the PGA's amplification factor has been set to the highest level it can provide, and the circuit cannot further increase the amplification capability of the PGA. If the signal quality is still below the preset weak signal threshold even when the PGA is adjusted to its maximum gain, it means that even at the highest amplification factor of the PGA, the amplitude of the input signal is still too small to meet the needs of subsequent analysis. Signal quality is measured by the ratio of amplitude to noise. When the ratio is too low, the signal will be overwhelmed by noise, leading to unreliable detection results.

[0065] The microcontroller detects whether there is room for gain improvement in the instrumentation amplifier, determining if the current gain has reached its allowable upper limit. If there is still room for improvement, the gain is increased accordingly to further amplify the signal. If there is no room for improvement, it means the gain of the instrumentation amplifier has reached its maximum, and the entire analog amplification chain can no longer enhance the signal. In this case, a digital averaging filter algorithm is needed to extract the effective signal. Digital averaging filtering is a signal processing method that reduces the impact of random noise by averaging multiple sampling points over a certain period, thus making the useful signal hidden in the noise clearer. By sampling and averaging multiple times, digital averaging filtering can effectively smooth out noise fluctuations, making the final signal waveform closer to the actual current change.

[0066] In summary, the inverter embedded current waveform analysis method provided in this application has the following technical effects: by achieving the technical goal of coordinated gain allocation of the instrumentation amplifier and the programmable gain amplifier and adaptive adjustment based on real-time signal quality, it achieves the technical effects of ensuring high-quality acquisition of current signals, improving the accuracy of waveform anomaly analysis and system stability across the entire dynamic range.

[0067] Example 2: Based on the same inventive concept as the inverter-embedded current waveform analysis method in the foregoing examples, this application also provides an inverter-embedded current waveform analysis system. Please refer to the appendix. Figure 2The system includes: a sampling circuit acquisition module 1, 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; a total gain calculation module 2, used to calculate 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; and an anomaly analysis module 3, 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 the analog-to-digital converter to obtain current waveform data for current anomaly analysis; wherein the preset coordination rule includes: a first threshold judgment module 4, used to prioritize increasing the gain share of the instrumentation amplifier when the signal quality is lower than the first threshold; and a second threshold judgment module 5, used to prioritize increasing the gain share of the programmable gain amplifier when the signal quality is higher than the second threshold.

[0068] Furthermore, the inverter-embedded current waveform analysis system is also used for: the sampling resistor being located between the emitter of each lower bridge arm IGBT and the negative terminal of the DC bus in the current path; the input terminal of the programmable gain amplifier being connected to the output terminal of the instrumentation amplifier, and the gain of the instrumentation amplifier and the programmable gain amplifier being digitally controlled by the microcontroller; the input terminal of the analog-to-digital converter being connected to the output terminal of the programmable gain amplifier, and the output terminal being connected to the microcontroller.

[0069] Furthermore, the inverter-embedded current waveform analysis system is also used to: fix the gain of the programmable gain amplifier according to the 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; and perform a gain share increase of the instrumentation amplifier according to the required instrumentation amplifier gain.

[0070] Furthermore, the inverter's embedded current waveform analysis system is also used for: fixing the gain of the instrumentation amplifier according to the optimal safety value; calculating 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; determining whether the required gain of the programmable gain amplifier exceeds the maximum allowable gain; if not, increasing the gain share of the programmable gain amplifier according to the required gain; if so, increasing the gain share of the programmable gain amplifier according to the maximum allowable gain of the programmable gain amplifier, and simultaneously recalculating the fixed gain value of the instrumentation amplifier according to the maximum allowable gain of the programmable gain amplifier for control.

[0071] Furthermore, the inverter-embedded current waveform analysis system is also used to: maintain the current gain setting unchanged when the signal quality is higher than the first threshold and lower than the second threshold, or to perform a balanced distribution of the instrumentation amplifier and the programmable gain amplifier.

[0072] Furthermore, the inverter-embedded current waveform analysis system is also used for: acquiring a signal during the idle period of the motor controller where the inverter is located, calculating the standard deviation as an estimated reference value for the noise amplitude, calculating the amplitude of the original output voltage signal, comparing it with 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; and weighting the first dimension signal quality and the second dimension signal quality to generate the signal quality of the original output voltage signal.

[0073] Furthermore, the inverter's embedded current waveform analysis system is also used to: monitor the current gain level status of the programmable gain amplifier; if the current gain level is already at its set minimum 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.

[0074] Furthermore, the inverter-embedded current waveform analysis system is also used to: if the programmable gain amplifier has been adjusted to its maximum gain, but the signal quality is still lower than the preset weak signal threshold, detect whether there is room for improvement in the gain of the instrumentation amplifier through the microcontroller; if there is, increase the gain of the instrumentation amplifier according to the room for improvement; if not, start the digital average filtering algorithm to extract the effective signal.

[0075] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The inverter embedded current waveform analysis method and specific examples in the aforementioned embodiment one are also applicable to the inverter embedded current waveform analysis system of this 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 of this embodiment. Therefore, for the sake of brevity, it will not be described in detail here.

[0076] In Embodiment 3, based on the same inventive concept as the inverter embedded current waveform analysis method in the foregoing embodiments, this application also provides a computer-readable storage medium storing a computer program, which, when executed, implements the steps of the inverter embedded current waveform analysis method described in any one of Embodiment 1 above.

[0077] The above description of the disclosed embodiments enables those skilled in the art to make or use this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not 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.

[0078] Obviously, those skilled in the art can make various modifications and variations to this application without departing from the spirit and scope of this application. Therefore, if such modifications and variations fall within the scope of this application and its equivalents, this application also intends to include such modifications and variations.

Claims

1. A method of current waveform analysis in a frequency converter, characterized in that The application relates to a current abnormality analysis method and device for a variable frequency drive. The application comprises: a sampling circuit arranged in a current path of the variable frequency drive, at least comprising 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 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 through the instrument amplifier and the programmable gain amplifier, and then performing analog-to-digital conversion to obtain current waveform data for current abnormality analysis; wherein the preset cooperative rules comprise: when the signal quality is lower than a first threshold value, preferentially increasing the gain share of the instrument amplifier; when the signal quality is higher than a second threshold value, preferentially increasing the gain share of the programmable gain amplifier; the sampling resistor is arranged between the emitter of each lower bridge arm IGBT and the negative terminal of a DC bus; the input end of the programmable gain amplifier is connected to the output end of the instrument amplifier, the gain of the instrument amplifier and the programmable gain amplifier is digitally controlled through a 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; when the signal quality is lower than the first threshold value, preferentially increasing the gain share of the instrument amplifier, comprising: fixing the gain of the programmable gain amplifier at 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; according to the required instrument amplifier gain, executing the gain share increase of the instrument amplifier; when the signal quality is higher than the second threshold value, preferentially increasing the gain share of the programmable gain amplifier, comprising: fixing the gain of the instrument amplifier at an optimal safety value; calculating the required programmable gain amplifier gain, specifically the ratio of the required total gain to the gain fixed value of the instrument amplifier; judging whether the required programmable gain amplifier gain exceeds the allowed maximum gain; if not, according to the required programmable gain amplifier gain, executing the gain share increase of the programmable gain amplifier; 2. The method of claim 1, wherein the frequency converter embedded current waveform analysis method is characterized by, if yes, according to the allowed maximum gain of the programmable gain amplifier, executing the gain share increase 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. The application comprises:

3. The method of claim 1, wherein the frequency converter embedded current waveform analysis method is characterized by, 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 executing the balanced allocation of the instrument amplifier and the programmable gain amplifier. evaluating the signal quality of the original output voltage signal, comprising: collecting a signal in an idle period of a motor controller where the variable frequency drive is arranged, calculating a standard deviation as an estimated reference value of noise amplitude, calculating the amplitude of the original output voltage signal, and calculating the ratio of the estimated reference value to the amplitude of the original output voltage signal to output 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 a signal quality of the original output voltage signal.

4. The method of claim 1, wherein the frequency converter embedded current waveform analysis method is characterized by, monitoring 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.

5. The inverter-embedded current waveform analysis method according to claim 4, wherein 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 the effective signal.

6. A current waveform analysis system embedded in a frequency converter, characterized in that The steps of the current waveform analysis method embedded in the frequency converter according to any one of claims 1-5 comprise: a sampling circuit acquisition module configured to acquire a sampling circuit arranged in a current path of the frequency converter, the sampling circuit comprising at least a sampling resistor, a cascade of an instrumentation amplifier and a programmable gain amplifier, and an analog-to-digital converter; a total gain calculation module configured to calculate 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 configured to evaluate a 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 convert the original output voltage signal by 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 configured to preferentially increase a gain share of the instrumentation amplifier when the signal quality is lower than a first threshold; a second threshold judgment module configured to preferentially increase a gain share of the programmable gain amplifier when the signal quality is higher than a second threshold.

7. A computer readable storage medium characterized in that, The computer program is stored on the computer readable storage medium and is executed to implement the steps of the current waveform analysis method embedded in the frequency converter according to any one of claims 1-5.

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