A DC bus capacitance online monitoring device

Abstract

This invention provides an online monitoring device for DC bus capacitors, belonging to the field of capacitor monitoring technology. It includes an AC / DC module for converting AC to DC, a DC / AC module for converting DC to AC, a current transformer module for acquiring current values, a voltage acquisition module for acquiring voltage values, a capacitor module for filtering, a temperature sensor module for measuring the temperature of the capacitor module, an ADC module for converting analog signals to digital signals, and a CPU module for data processing. The ADC and CPU modules operate on an ESR joint degradation model, calculate the capacitor capacitance and equivalent series resistance using a fast Fourier transform, and apply temperature compensation correction using a temperature coefficient. By analyzing the compensated parameters, a precise alarm is triggered when the capacitor capacitance is below 70% of its rated value or the equivalent series resistance exceeds 200% of its initial value. This solution requires no downtime and has an error of less than 5%.

Description

Technical Field

[0001] This utility model belongs to the field of capacitance monitoring technology, specifically relating to an online monitoring device for DC bus capacitance. Background Technology

[0002] The health status monitoring of existing DC bus capacitors (such as filter capacitors in inverter power supplies and UPS power supplies) mainly relies on two methods:

[0003] Regular offline testing: Using equipment such as LCR bridges to measure capacitance and equivalent series resistance requires stopping the machine to remove the capacitor, causing equipment to stop operating, resulting in low efficiency and no real-time warning of sudden failures.

[0004] Single-parameter online estimation: Some methods only infer aging status based on changes in equivalent series resistance, ignoring the impact of temperature fluctuations and load changes on capacitor parameters, resulting in errors exceeding 20%. This type of method has significant drawbacks:

[0005] Static models have poor adaptability: Capacitance parameters change dynamically with temperature and load, and traditional static models cannot be corrected in real time, resulting in a high misjudgment rate.

[0006] Insufficient anti-interference capability: High-frequency switching noise of the power supply can overwhelm the ripple signal, affecting the accuracy of data extraction;

[0007] Lack of comprehensive diagnosis: The correlation between capacitance decay and the increase in equivalent series resistance is not analyzed simultaneously, making it impossible to construct a joint degradation model, resulting in a high risk of missed / false alarms.

[0008] The aforementioned problems make it difficult for existing technologies to meet the real-time and accurate monitoring requirements of capacitor status in high-reliability scenarios such as high-speed rail and data centers. There is an urgent need for a non-intrusive, multi-parameter fusion high-precision online monitoring solution. Utility Model Content

[0009] The purpose of this invention is to provide an online monitoring device for DC bus capacitance, which aims to solve the problems mentioned in the background art.

[0010] A DC bus capacitance online monitoring device, comprising,

[0011] AC / DC module, used to convert AC to DC;

[0012] DC / AC module, used to convert DC to AC;

[0013] Current transformer module, used to obtain current value;

[0014] A voltage acquisition module is used to obtain voltage values;

[0015] Capacitor modules are used for filtering.

[0016] Temperature sensor module, used to measure the temperature of capacitor module;

[0017] An ADC module converts analog signals into digital signals.

[0018] The CPU module is used for data processing;

[0019] The AC / DC module is electrically connected to the DC / AC module, the capacitor module, the AC / DC module, and the DC / AC module are electrically connected, the current transformer module and the capacitor module are signal connected, the voltage acquisition module and the capacitor module are signal connected, the current transformer module, the voltage acquisition module, the temperature sensor module and the ADC module are signal connected, and the ADC module and the CPU module are signal connected.

[0020] Furthermore, the current inductance module is a Hall current sensor, which is connected in series in the bus circuit to measure the ripple current AI.

[0021] Furthermore, the voltage acquisition module acquires the voltage across the bus capacitor module and extracts the ripple voltage AV.

[0022] Furthermore, the temperature sensor module is fixed to the capacitor shell of the capacitor module to collect the surface temperature T.

[0023] Furthermore, the ADC module and CPU module are used to run and calculate the ESR joint degradation model.

[0024] Furthermore, the ADC module performs an FFT transform on AV and AI to extract the amplitude of the fundamental frequency f0. and ;

[0025] Capacitance C: C= ;

[0026] ESR: ESR= By combining the phase difference between voltage and current, the resistive component of ESR is separated.

[0027] Temperature compensation correction, based on the capacitor manufacturer's aging curve, corrects the C and ESR values;

[0028] The corrected capacity value is C;

[0029] ESR The corrected ESR;

[0030] Where α and β are the temperature coefficients of the capacitor material;

[0031] If C < 70% of the rated value or ESR > 200% of the initial value, an alarm signal is triggered.

[0032] Compared with the prior art, the beneficial effects of this utility model are:

[0033] This system enables online, real-time, and high-precision health monitoring of DC bus capacitor modules. The device directly acquires the capacitor ripple current through a current transformer module using a Hall effect current sensor connected in series with the bus circuit. A voltage acquisition module is connected in parallel across the capacitor module to extract the ripple voltage. A temperature sensor module fixed to the capacitor casing acquires the surface temperature. An ADC module converts the analog signals into digital signals, which are then transmitted to the CPU module. The CPU module runs an ESR joint degradation model, performs a Fast Fourier Transform on the ripple voltage and ripple current to extract the fundamental frequency amplitude, calculates the capacitance and equivalent series resistance, and performs temperature compensation correction on the calculation results based on the capacitor material's temperature coefficient to eliminate the influence of temperature drift. By simultaneously analyzing the decreasing capacitance and increasing equivalent series resistance trends after temperature compensation, and combining this with preset failure thresholds, multi-parameter fusion diagnosis is achieved. A precise alarm is triggered when the capacitance falls below 70% of the rated value or the equivalent series resistance exceeds 200% of the initial value. This solution requires no downtime or circuit modification, and reduces monitoring errors to less than 5% in environments with strong interference. It significantly improves the reliability of equipment such as inverters and uninterruptible power supplies, and avoids system downtime caused by sudden failures. It is especially suitable for predictive maintenance in high-reliability scenarios such as high-speed rail and data centers. Attached Figure Description

[0034] The accompanying drawings are provided to further illustrate the present invention and form part of the specification. They are used together with the embodiments of the present invention to explain the present invention, but do not constitute a limitation thereof. In the drawings:

[0035] Figure 1 This is a schematic diagram of the overall system of this utility model.

[0036] In the diagram: 1. AC / DC module; 2. DC / AC module; 3. Current transformer module; 4. Voltage acquisition module; 5. Capacitor module; 6. Temperature sensor module; 7. ADC module; 8. CPU module. Detailed Implementation

[0037] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0038] In the description of this utility model, it should be noted that the terms "upper," "lower," "inner," "outer," "top / bottom," etc., indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this utility model. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0039] In the description of this utility model, it should be noted that, unless otherwise explicitly specified and limited, the terms "installed," "equipped with," "sleeved / connected," "connected," etc., should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be a connection within two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model based on the specific circumstances.

[0040] Please see Figure 1 The technical solution provided in this embodiment is as follows:

[0041] A DC bus capacitance online monitoring device, comprising,

[0042] AC / DC module 1 is used to convert AC to DC.

[0043] DC / AC module 2 is used to convert DC to AC.

[0044] Current transformer module 3 is used to obtain current values;

[0045] Voltage acquisition module 4 is used to acquire voltage values;

[0046] Capacitor module 5 is used for filtering;

[0047] Temperature sensor module 6 is used to measure the temperature of capacitor module 5;

[0048] ADC module 7 converts analog signals into digital signals;

[0049] CPU module 8 is used for data processing;

[0050] AC / DC module 1 and DC / AC module 2 are electrically connected. Capacitor module 5, AC / DC module 1 and DC / AC module 2 are electrically connected. Current transformer module 3 and capacitor module 5 are signal connected. Voltage acquisition module 4 and capacitor module 5 are signal connected. Current transformer module 3, voltage acquisition module 4, temperature sensor module 6 and ADC module 7 are signal connected. ADC module 7 and CPU module 8 are signal connected.

[0051] In a specific embodiment of this utility model, a current transformer module 3, connected in series with a Hall current sensor in the bus circuit, measures the ripple current flowing through the capacitor module 5 in real time. Simultaneously, a voltage acquisition module 4 acquires the ripple voltage across the capacitor module 5, and a temperature sensor module 6, fixed to the surface of the capacitor module 5, acquires the temperature. The ripple current signal output by the current transformer module 3, the ripple voltage signal output by the voltage acquisition module 4, and the temperature signal output by the temperature sensor module 6 are transmitted to an ADC module 7. The ADC module 7 converts the analog signals into digital signals, which are then input to a CPU module 8. The CPU module 8 performs a fast Fourier transform on the digitized ripple voltage and ripple current signals to extract the peak-to-peak value of the ripple voltage and the peak-to-peak value of the ripple current at the fundamental frequency. Based on the capacitance calculation formula, the peak value of the ripple current is used... The actual capacitance of capacitor module 5 is calculated using peak value, fundamental frequency, and peak-to-peak ripple voltage. The equivalent series resistance of capacitor module 5 is then calculated by separating the resistive components based on the phase difference between ripple voltage and ripple current. Subsequently, CPU module 8 calls a temperature compensation algorithm to correct the calculated original capacitance and equivalent series resistance based on the temperature coefficient of the capacitor material and temperature data collected by a temperature sensor. This results in corrected capacitance and equivalent series resistance values. Finally, CPU module 8 compares the corrected capacitance value with the rated value and the corrected equivalent series resistance value with the initial value. If the capacitance value is lower than 70% of the rated value or the equivalent series resistance value is higher than 200% of the initial value, an alarm signal is triggered, enabling online real-time assessment and fault warning of the capacitor's health status.

[0052] Specifically, current transformer module 3 is a Hall current sensor, which is connected in series in the bus circuit to measure the ripple current AI.

[0053] In a specific embodiment of this utility model, the Hall current sensor measures the bus current non-contactly through the principle of magnetic induction, without the need to cut off or modify the original power circuit, avoiding the extra power consumption and heat generation problems caused by traditional shunt resistors. The design of being directly connected in series with the bus circuit ensures that the current signal is transmitted without attenuation, and has a high response speed to high-frequency ripple current (such as 100Hz–10kHz), significantly improving the accuracy of ripple current measurement.

[0054] Specifically, voltage acquisition module 4 acquires the voltage across the two ends of bus capacitor module 5 and extracts the ripple voltage AV.

[0055] In a specific embodiment of this utility model, the voltage acquisition module 4 is directly connected across the positive and negative terminals of the capacitor module 5 without any additional impedance, thus avoiding voltage attenuation errors caused by line resistance in traditional indirect measurements. To address high-frequency switching noise in the DC bus, the module adopts a high-bandwidth design to ensure complete extraction of ripple voltage, providing a real data basis for subsequent analysis.

[0056] Specifically, the temperature sensor module 6 is fixed to the capacitor housing of the capacitor module 5 to collect the surface temperature T.

[0057] In a specific embodiment of this utility model, the capacitor shell and the internal core are in direct contact through a thermally conductive material. The surface temperature T is strongly correlated with the core temperature (typical thermal resistance <3℃ / W), which can indirectly capture the aging and heating state inside the capacitor and avoid interference from ambient temperature. An electrolytic capacitor temperature rise exceeding 10℃ will accelerate its lifespan decay (Arrhenius's Law). Module 6 provides an over-temperature warning threshold (such as an alarm >85℃) to prevent thermal runaway.

[0058] Specifically, ADC module 7 and CPU module 8 are used to run and calculate the ESR joint degradation model.

[0059] In a specific embodiment of this utility model, the capacitance C and ESR are calculated in real time with an error of <5% through ripple analysis, temperature compensation and multi-parameter fusion algorithm.

[0060] Specifically, ADC module 7 performs FFT transformation on AV and AI to extract the amplitude of the fundamental frequency f0. and ;

[0061] Capacitance C: C= ;

[0062] ESR: ESR= By combining the phase difference between voltage and current, the resistive component of ESR is separated.

[0063] Temperature compensation correction, based on the capacitor manufacturer's aging curve, corrects the C and ESR values;

[0064] The corrected capacity value is C;

[0065] ESR The corrected ESR;

[0066] Where α and β are the temperature coefficients of the capacitor material;

[0067] If C < 70% of the rated value or ESR > 200% of the initial value, an alarm signal is triggered.

[0068] In specific embodiments of this utility model, users can monitor the health status of the bus capacitors in real time during the normal operation of inverters or UPS power supplies, avoiding system downtime caused by sudden failures. This is especially suitable for high-reliability scenarios such as high-speed rail, airports, data centers, and smart manufacturing.

[0069] Working principle:

[0070] The current transformer module 3, connected in series with a Hall current sensor in the bus circuit, measures the ripple current flowing through the capacitor module 5 in real time. Simultaneously, the voltage acquisition module 4 acquires the ripple voltage across the capacitor module 5, and the temperature sensor module 6, fixed to the surface of the capacitor module 5, acquires the temperature. The ripple current signal output from the current transformer module 3, the ripple voltage signal output from the voltage acquisition module 4, and the temperature signal output from the temperature sensor module 6 are transmitted to the ADC module 7. The ADC module 7 converts the analog signals into digital signals, which are then input to the CPU module 8. The CPU module 8 performs a Fast Fourier Transform on the digitized ripple voltage and current signals to extract the peak-to-peak value of the ripple voltage and the peak-to-peak value of the ripple current at the fundamental frequency. Based on the capacitance calculation formula, the peak-to-peak value of the ripple current and the fundamental frequency are used to... The actual capacitance of capacitor module 5 is calculated by combining the peak-to-peak value of the ripple voltage with the phase difference between the ripple voltage and the ripple current to separate the resistive components and calculate the equivalent series resistance of capacitor module 5. Then, CPU module 8 calls the temperature compensation algorithm to perform temperature compensation correction on the calculated original capacitance and equivalent series resistance based on the temperature coefficient of the capacitor material and the temperature data collected by the temperature sensor, obtaining the corrected capacitance value and the corrected equivalent series resistance value. Finally, CPU module 8 compares the corrected capacitance value with the rated value and the corrected equivalent series resistance value with the initial value. If the capacitance value is lower than 70% of the rated value or the equivalent series resistance value is higher than 200% of the initial value, an alarm signal is triggered to realize online real-time assessment and fault warning of the capacitor's health status.

[0071] Finally, it should be noted that the above description is merely a preferred embodiment of this utility model and is not intended to limit the utility model. Although the utility model has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this utility model should be included within the protection scope of this utility model.

Claims

1. A direct current bus capacitor on-line monitoring device, characterized in that, include, AC / DC module (1) is used to convert AC to DC. DC / AC module (2) is used to convert DC to AC. Current transformer module (3) is used to obtain current value; Voltage acquisition module (4) is used to acquire voltage values; Capacitor module (5) is used for filtering; Temperature sensor module (6) is used to measure the temperature of capacitor module (5); ADC module (7) converts analog signals into digital signals; CPU module (8) is used for data processing; The AC / DC module (1) is electrically connected to the DC / AC module (2), the capacitor module (5), the AC / DC module (1), and the DC / AC module (2) are electrically connected, the current transformer module (3) and the capacitor module (5) are signal connected, the voltage acquisition module (4) and the capacitor module (5) are signal connected, the current transformer module (3), the voltage acquisition module (4), the temperature sensor module (6), and the ADC module (7) are signal connected, and the ADC module (7) and the CPU module (8) are signal connected.

2. The DC bus capacitor on-line monitoring device according to claim 1, characterized in that, The current transformer module (3) is a Hall current sensor, which is connected in series in the bus circuit to measure the ripple current AI.

3. The DC bus capacitor on-line monitoring device according to claim 2, characterized in that, The voltage acquisition module (4) acquires the voltage across the two ends of the bus capacitor module (5) and extracts the ripple voltage AV.

4. The DC bus capacitor on-line monitoring device according to claim 3, characterized in that, The temperature sensor module (6) is fixed to the capacitor shell of the capacitor module (5) and collects the surface temperature T.

5. The DC bus capacitance online monitoring device according to claim 4, characterized in that, The ADC module (7) and CPU module (8) are used to run and calculate the ESR joint degradation model.

6. The DC bus capacitor on-line monitoring device according to claim 5, characterized in that, The ADC module (7) performs FFT transform on AV and AI, extracts the amplitude of fundamental frequency f0 With ; Capacitance C: C= ; ESR: ESR = 0.0001 ohm , the ESR resistance component is separated from the voltage-current phase difference Temperature compensation correction, based on the capacitor manufacturer's aging curve, corrects the C and ESR values; , the corrected capacity value C; ESR , corrected ESR; Where α and β are the temperature coefficients of the capacitor material; If C < 70% of the rated value or ESR > 200% of the initial value, an alarm signal is triggered.

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