Self-test method and apparatus for AC filter capacitors of auxiliary inverters

Abstract

To provide a self-diagnosis method and apparatus for an AC filter capacitor of an auxiliary inverter.SOLUTION: The method comprises: acquiring equivalent resistance, inductance and capacitance values of each circuit in the auxiliary inverter; based on the equivalent resistance, inductance and capacitance values of each circuit, establishing a system of equations according to circuit conditions; solving the system of equations to obtain the resistance of each phase circuit, the inductance values of inductive elements in each phase circuit, and the capacitance values of capacitive elements in each phase circuit; comparing these values with corresponding reference values; and, if differences between the corresponding reference values and the resistance, the inductance values of the inductive elements and the capacitance values of the capacitive elements in each phase circuit in any phase circuit are all within their corresponding thresholds, then determining that the auxiliary inverter is not degraded, or otherwise determining that the auxiliary inverter is degraded.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] This application relates to the field of auxiliary inverter health self-tests, and more particularly to a method and apparatus for self-testing AC filter capacitors of an auxiliary inverter. [Background technology]

[0002] Auxiliary power supply systems are an essential electrical component of railcars, subways, and light rail vehicles, providing power for air conditioning, lighting, and other equipment. To ensure the reliability of auxiliary inverters in rail transit vehicles, the health of AC filter capacitors must be inspected. This is because, in power electronics reliability studies, the reliability of power devices, inductors, and capacitors is often weak, affecting the reliability of the entire system. Generally, an AC filter capacitor can be considered degraded and expired when its capacitance falls below 95% of its original value. This is often due to continued degradation during long-term operation of auxiliary inverters in rail transit vehicles.

[0003] Current inductor-capacitor monitoring methods involve injecting a low-power sinusoidal AC current into the filter capacitor of an urban rail auxiliary power supply system, obtaining capacitor current and voltage parameters through Fourier transform, and then calculating the capacitance and equivalent resistance. However, offline capacitor monitoring requires the capacitor to be removed from the system, which is inconvenient for practical application. To address the issue of capacitor degradation and failure, a reliability assessment model was established for the filter capacitor of an urban rail auxiliary power supply system under actual operating conditions, capturing the capacitance decrease characteristics over time and analyzing the capacitor's health status. Furthermore, a parameter identification method for an urban rail auxiliary power supply system was designed using the least squares method based on hybrid system modeling. This method is highly accurate, but the overall design process and calculations are complex. A convenient and effective way to self-test the health of the AC filter capacitor of an auxiliary inverter is a problem that needs to be solved in the field. Summary of the Invention [Problem to be solved by the invention]

[0004] The present application provides a method and apparatus for self-testing the AC filter capacitor of an auxiliary inverter, which can conveniently and effectively self-test the health status of the AC filter capacitor of the auxiliary inverter. [Means for solving the problem]

[0005] In one aspect, the present application provides a method for self-testing an AC filter capacitor of an auxiliary inverter, the self-testing method comprising: Obtaining an equivalent resistance, an inductance value, and a capacitance value of each circuit in the auxiliary inverter, the circuit being composed of two-phase circuits in the auxiliary inverter, each phase circuit in the auxiliary inverter including an inductor element and a capacitor element, and different circuits being composed of different two-phase circuits; establishing simultaneous equations based on circuit conditions according to the equivalent resistance, inductance value, and capacitance value of each circuit, and solving the simultaneous equations to obtain the resistance of the circuit for each phase, the inductance value of the inductor element in the circuit for each phase, and the capacitance value of the capacitor element in the circuit for each phase, wherein the circuit conditions include that the equivalent resistance of each circuit is the sum of the equivalent resistances of all the inductor elements and capacitor elements in the two-phase circuits that make up the circuit, the inductance value of each circuit is the sum of the inductance values ​​of the inductor elements in the two-phase circuits that make up the circuit, and the capacitance value of each circuit is the sum of the reciprocals of the capacitance values ​​of the capacitor elements in the two-phase circuits that make up the circuit; comparing the resistance of the circuit for each phase, the inductance value of the inductor element in the circuit for each phase, and the capacitance value of the capacitor element in the circuit for each phase with corresponding reference values, and determining that the auxiliary inverter is not degraded if the differences between the resistance of the circuit for any phase, the inductance value of the inductor element, and the capacitance value of the capacitor element and the corresponding reference values ​​do not all exceed corresponding threshold values, and determining that the auxiliary inverter is degraded if not.

[0006] In another example, obtaining the equivalent resistance of each circuit in the auxiliary inverter comprises: Obtaining the DC input voltage of the auxiliary inverter, the sum of the voltages of the capacitor elements in each circuit, and the maximum current flowing through the inductor element; Calculating the difference between the DC input voltage of the auxiliary inverter and the sum of the voltages of the capacitor elements in each circuit to obtain the voltage of the equivalent resistance of each circuit; and obtaining the ratio of the voltage of the equivalent resistance of each circuit to the maximum current, thereby obtaining the equivalent resistance of each circuit.

[0007] In another example, obtaining the inductance and capacitance values ​​of each circuit in the auxiliary inverter comprises: Obtaining a transfer function of the sum of the voltages of the capacitor elements in each circuit with respect to the DC side input voltage of the auxiliary inverter; comparing the transfer function with a standard second-order system to obtain key parameters of an auxiliary inverter system in which the auxiliary inverter is arranged; and obtaining an inductance value and a capacitance value of each circuit according to the equivalent resistance of each circuit and the main parameters of the auxiliary inverter system in which the auxiliary inverter is arranged.

[0008] In another example, the key parameters of the auxiliary inverter system in which the auxiliary inverter is located include damping ratio, damped natural frequency, undamped natural frequency, overshoot, and time to peak value.

[0009] In another example, the auxiliary inverter is a three-phase three-bridge inverter or a three-phase four-bridge inverter.

[0010] In another aspect, the present application provides an apparatus for self-testing an AC filter capacitor of an auxiliary inverter, the apparatus comprising: an acquisition module used to acquire the equivalent resistance, inductance value, and capacitance value of each circuit in the auxiliary inverter, the circuit being composed of two-phase circuits in the auxiliary inverter, each phase circuit in the auxiliary inverter including an inductor element and a capacitor element, and different circuits being composed of different two-phase circuits; a calculation module used to establish simultaneous equations based on circuit conditions according to the equivalent resistance, inductance value, and capacitance value of each circuit, and to obtain the resistance of each phase circuit, the inductance value of the inductor element in each phase circuit, and the capacitance value of the capacitor element in each phase circuit by solving the simultaneous equations, wherein the circuit conditions include that the equivalent resistance of each circuit is the sum of the equivalent resistances of all inductor elements and capacitor elements in the two-phase circuits that make up the circuit, the inductance value of each circuit is the sum of the inductance values ​​of the inductor elements in the two-phase circuits that make up the circuit, and the capacitance value of each circuit is the sum of the reciprocals of the capacitance values ​​of the capacitor elements in the two-phase circuits that make up the circuit; and a comparison module used to compare the resistance of the circuit of each phase, the inductance value of the inductor element in the circuit of each phase, and the capacitance value of the capacitor element in the circuit of each phase with corresponding reference values, and determine that the auxiliary inverter is not degraded if the differences between the resistance of any of the circuits of any phase, the inductance value of the inductor element, and the capacitance value of the capacitor element and the corresponding reference values ​​do not all exceed corresponding threshold values, or determine that the auxiliary inverter is degraded if not.

[0011] In another example, the acquisition module is specifically used to acquire the DC input voltage of the auxiliary inverter, the sum of the voltages of the capacitor elements in each circuit, and the maximum current flowing through the inductor elements; The acquisition module is specifically further used for calculating the difference between the DC input voltage of the auxiliary inverter and the sum of the voltages of the capacitor elements in each circuit, to obtain the voltage of the equivalent resistance of each circuit; The acquisition module is further specifically used to calculate the ratio of the voltage of the equivalent resistance of each circuit to the maximum current, and obtain the equivalent resistance of each circuit.

[0012] In another example, the acquisition module is further specifically used for acquiring a transfer function of a sum of voltages of capacitor elements in each circuit relative to a DC side input voltage of the auxiliary inverter; The acquisition module is further specifically used for comparing the transfer function with a standard second-order system to obtain key parameters of an auxiliary inverter system in which the auxiliary inverter is arranged; The acquisition module is further specifically used for obtaining the inductance value and capacitance value of each circuit according to the equivalent resistance of each circuit and the main parameters of the auxiliary inverter system in which the auxiliary inverter is arranged.

[0013] In another aspect, the present application provides an electronic device including a processor and a memory communicatively coupled to the processor, the memory stores computer-executable instructions; The processor executes computer-executable instructions stored in the memory to implement the self-test method described above.

[0014] In another aspect, the present application provides a computer-readable storage medium having computer-executable instructions stored thereon, the computer-executable instructions being used to implement the above-described self-test method when executed by a processor. [Effects of the Invention]

[0015] The present application provides a method and apparatus for self-testing AC filter capacitors of an auxiliary inverter, which includes obtaining an equivalent resistance, inductance value, and capacitance value of each circuit in the auxiliary inverter, establishing simultaneous equations according to the equivalent resistance, inductance value, and capacitance value of each circuit based on circuit conditions, and solving the simultaneous equations to obtain the resistance of each phase circuit, the inductance value of the inductor element in each phase circuit, and the capacitance value of the capacitor element in each phase circuit, wherein the circuit conditions include that the equivalent resistance of each circuit is the sum of the equivalent resistances of all inductor elements and capacitor elements in the two-phase circuits that make up the circuit, and the inductance value of each circuit is The capacitance value of each circuit is the sum of the inductance values ​​of the inductor elements in the two-phase circuits that make up the circuit, and the capacitance value of each circuit is the sum of the reciprocals of the capacitance values ​​of the capacitor elements in the two-phase circuits that make up the circuit. The resistance of each phase circuit, the inductance value of the inductor elements in the circuit of each phase, and the capacitance value of the capacitor elements in the circuit of each phase are compared with corresponding reference values, and if the differences between the resistance of any phase circuit, the inductance value of the inductor element, and the capacitance value of the capacitor element and the corresponding reference values ​​do not all exceed the corresponding threshold value, it is determined that the auxiliary inverter is not degraded, and if not, it is determined that the auxiliary inverter is degraded. According to the method of the present application, by turning on different circuits in the auxiliary inverter, a DC step response is injected into the auxiliary inverter system, and step response signals of the filter inductor current and the filter capacitor voltage are obtained by sampling. The waveforms are compared with those of a standard second-order system, and parameters such as the undamped natural frequency, damping ratio, overshoot, and peak value time of the system are calculated, thereby inversely estimating the equivalent resistance, inductance value, and capacitance value of each circuit. The resistance of each phase circuit, the inductance value of the inductor element, and the capacitance value of the capacitor element that make up the circuit are determined, and the resistance of each phase circuit, the inductance value of the inductor element, and the capacitance value of the capacitor element are compared with reference values ​​to determine the power consumption level of each element and determine whether it has deteriorated.Furthermore, the method provided by the present application does not require the removal of components, is applicable to the operation of auxiliary inverters for rail transit vehicles, has low program complexity, low calculation volume, simple operation, lower performance requirements for the controller, and high measurement accuracy, and can implement self-testing of the health status of AC filter capacitors in a convenient and effective manner. [Brief explanation of the drawings]

[0016] The accompanying drawings are incorporated in and constitute a part of this specification to illustrate embodiments consistent with the present application and together with the description serve to explain the principles of the present application. [Figure 1] 1 is a schematic diagram of an application scene of the example shown in the present application; [Figure 2] 1 is a flowchart of a self-test method for an AC filter capacitor of one auxiliary inverter provided in Example 1 of the present application; [Figure 3] FIG. 2 is a schematic topology diagram of an auxiliary inverter structure according to the example presented in the present application. [Figure 4] This circuit is shown using the a-phase and b-phase circuits as an example. [Figure 5] 1 is a flowchart of another method for self-testing an AC filter capacitor of an auxiliary inverter provided in accordance with a first embodiment of the present invention; [Figure 6] 4 is a schematic diagram of the inductor current and capacitor voltage variations of an exemplary auxiliary inverter AC filter following a step input voltage; FIG. [Figure 7] 1 is a flowchart of another auxiliary inverter AC filter capacitor self-test method provided in accordance with a first embodiment of the present application; [Figure 8] 10 is a simulated waveform of the step response of an exemplary auxiliary inverter filter. [Figure 9] 1 is a structural schematic diagram of a self-test device for AC filter capacitors of an auxiliary inverter provided in Example 2 of the present application; [Figure 10] FIG. 10 is a structural schematic diagram of an electronic device provided in Example 3 of the present application. DETAILED DESCRIPTION OF THE INVENTION

[0017] Specific examples of the present application are illustrated by the accompanying drawings above and will be described in more detail below. These drawings and contextual descriptions are not intended to limit the scope of the concepts of the present application in any way, but rather to explain the concepts of the present application to those skilled in the art by reference to specific examples.

[0018] Illustrative examples are described in detail herein, examples of which are illustrated in the accompanying drawings. When the following description refers to the accompanying drawings, like numerals in different accompanying drawings represent the same or similar elements unless otherwise specified. The embodiments described in the following illustrative examples do not represent all embodiments consistent with the present application. Rather, they are merely examples of apparatus and methods consistent with certain aspects of the present application, as detailed in the appended claims.

[0019] The specific application scenario of this application is the field of autonomous driving. Figure 1 is a schematic diagram of an example application scenario shown in this application. Auxiliary power supply systems are essential electrical components of rail vehicles, subways, and light rail vehicles, and require power to ensure train air conditioning, lighting, and other equipment. To ensure the reliability of auxiliary inverters in rail transit vehicles, the health of AC filter capacitors must be inspected. This is because, in power electronics reliability studies, the weaknesses of power devices, inductors, and capacitors affect the reliability of the entire system. Generally, an AC filter capacitor can be considered degraded and ineffective when its capacitance falls below 95% of its initial capacitance value. This is often due to continued degradation during long-term operation of auxiliary inverters in rail transit vehicles.

[0020] Current inductor-capacitor monitoring methods involve injecting a low-power sinusoidal AC current into the filter capacitor of an urban rail auxiliary power supply system, obtaining capacitor current and voltage parameters through Fourier transform, and then calculating the capacitance and equivalent resistance. However, offline capacitor monitoring requires the capacitor to be removed from the system, which is inconvenient for practical application. To address the issue of capacitor degradation and failure, a reliability assessment model was established for the filter capacitor of an urban rail auxiliary power supply system under actual operating conditions, capturing the capacitance decrease characteristics over time and analyzing the capacitor's health status. Furthermore, a parameter identification method for an urban rail auxiliary power supply system was designed using the least squares method based on hybrid system modeling. This method is highly accurate, but the overall design process and calculations are complex. A convenient and effective way to self-test the health of the AC filter capacitor of an auxiliary inverter is a problem that needs to be solved in the field.

[0021] The present application obtains the equivalent resistance, inductance value, and capacitance value of each circuit in the auxiliary inverter, establishes simultaneous equations based on the equivalent resistance, inductance value, and capacitance value of each circuit and circuit conditions, and solves the simultaneous equations to obtain the resistance of each phase circuit, the inductance value of the inductor element in each phase circuit, and the capacitance value of the capacitor element in each phase circuit. The circuit conditions include that the equivalent resistance of each circuit is the sum of the equivalent resistances of all inductor elements and capacitor elements in the two-phase circuits that make up the circuit. The inductance value of each circuit is the sum of the inductance values ​​of the inductor elements in the two-phase circuits that make up the circuit. The capacitance value of each circuit is the sum of the reciprocals of the capacitance values ​​of the capacitor elements in the two-phase circuits that make up that circuit, and the resistance of the circuit for each phase, the inductance value of the inductor element in the circuit for each phase, and the capacitance value of the capacitor element in the circuit for each phase are compared with corresponding reference values, and if the differences between the resistance of any of the circuits for any phase, the inductance value of the inductor element, and the capacitance value of the capacitor element and the corresponding reference values ​​do not all exceed corresponding threshold values, it is determined that the auxiliary inverter is not degraded, or if not, it is determined that the auxiliary inverter is degraded. According to the method of the present application, by turning on different circuits in the auxiliary inverter, a DC step response is injected into the auxiliary inverter system, and step response signals of the filter inductor current and the filter capacitor voltage are obtained by sampling. The waveforms are compared with those of a standard second-order system to calculate parameters such as the system's undamped natural frequency, damping ratio, overshoot, and peak value time, thereby inversely estimating the equivalent resistance, inductance value, and capacitance value of each circuit. The resistance of each phase circuit, the inductance value of the inductor element, and the capacitance value of the capacitor element that make up the circuit are determined, and the resistance of each phase circuit, the inductance value of the inductor element, and the capacitance value of the capacitor element are compared with reference values ​​to determine the power consumption of each element and determine whether it has deteriorated.Furthermore, the method provided by the present application does not require the removal of components, is applicable to the operation of auxiliary inverters for rail transit vehicles, has low program complexity, low calculation volume, simple operation, lower performance requirements for the controller, and high measurement accuracy, and can implement self-testing of the health status of AC filter capacitors in a convenient and effective manner.

[0022] The brief explanations of terms used in this application are intended only to facilitate understanding of the following embodiments, and are not intended to limit the scope of the present application. Unless otherwise specified, these terms should be understood in their ordinary and customary sense.

[0023] The technical solutions of the present application and the technical solutions of the present application will be described in detail below using specific examples. Some of the following specific examples may be combined with each other, and the same or similar concepts or processes may not be described in some examples. In the description of the present application, unless otherwise expressly defined and limited, each term should be understood as having a broad meaning in the art. Hereinafter, the embodiments of the present application will be described with reference to the drawings.

[0024] Example 1 FIG. 2 is a flowchart of a self-test method for an AC filter capacitor of one auxiliary inverter provided by the first embodiment of the present application. As shown in FIG. 2, the method includes steps 201 to 203. In step 201, the equivalent resistance, inductance value and capacitance value of each circuit in the auxiliary inverter are obtained, and the circuit is composed of two-phase circuits in the auxiliary inverter, and each phase circuit in the auxiliary inverter includes an inductor element and a capacitor element, and different circuits are composed of different two-phase circuits. In step 202, a simultaneous equation is established based on the circuit conditions according to the equivalent resistance, inductance value, and capacitance value of each circuit, and the resistance of each phase circuit, the inductance value of the inductor element in each phase circuit, and the capacitance value of the capacitor element in each phase circuit are obtained by solving the simultaneous equation, wherein the circuit conditions include that the equivalent resistance of each circuit is the sum of the equivalent resistances of all inductor elements and capacitor elements in the two-phase circuits that make up the circuit, the inductance value of each circuit is the sum of the inductance values ​​of the inductor elements in the two-phase circuits that make up the circuit, and the capacitance value of each circuit is the sum of the reciprocals of the capacitance values ​​of the capacitor elements in the two-phase circuits that make up the circuit. In step 203, the resistance of the circuit for each phase, the inductance value of the inductor element in the circuit for each phase, and the capacitance value of the capacitor element in the circuit for each phase are compared with corresponding reference values, and if the differences between the resistance of any of the circuits for any phase, the inductance value of the inductor element, and the capacitance value of the capacitor element and the corresponding reference values ​​do not all exceed the corresponding threshold values, it is determined that the auxiliary inverter is not degraded; otherwise, it is determined that the auxiliary inverter is degraded.

[0025] The execution body of this embodiment is a self-test device for an AC filter capacitor of an auxiliary inverter, and the self-test device for an AC filter capacitor of an auxiliary inverter may be implemented by a computer program, such as application software, or may be implemented as a medium on which a related computer program is stored, such as a USB memory or a cloud drive, or may be implemented as a physical device on which a related computer program is integrated or installed, such as a chip.

[0026] Referring to the example shown in the scene, FIG. 3 is a schematic topology diagram of an auxiliary inverter structure according to the example shown in the present application. As shown in FIG. 3, the auxiliary inverter is a three-phase three-bridge inverter or a three-phase four-bridge inverter. In FIG. 3, (a) is a schematic topology diagram of a three-phase three-bridge inverter structure, and (b) is a schematic topology diagram of a three-phase four-bridge inverter structure. The DC sides of the three-phase three-bridge inverter and the three-phase four-bridge inverter are represented by a DC constant voltage source Vdc and output through a filter. The filter includes three-phase filter inductors and filter capacitors (a, b, and c). The equivalent resistance of the filter inductor is Rf, its inductance value is Lf, and the equivalent resistance of the filter capacitor is Rc, its capacitance value is Cf. The filter capacitor is connected in a star connection. The three-phase four-bridge inverter has an increased inductor Ln and equivalent resistance Rn of the fourth bridge compared to the three-phase three-bridge inverter.

[0027] For the auxiliary inverter, each phase circuit includes an inductor and a capacitor, and two of the phases are connected together to form a single circuit. Figure 4 shows an example of a-phase and b-phase circuits. The upper tube of phase a and the lower tube of phase b of the auxiliary inverter for a rail transit vehicle are connected as shown in Figure 4, and the equivalent resistance, inductance, and capacitance of the circuit are obtained. The equivalent resistance of the circuit includes the sum of the resistances of the inductors and capacitors in the a-phase circuit and the b-phase circuit, and is expressed as Rca + Rfa + Rcb + Rfb, where Rca is the resistance of the capacitor in the a-phase circuit. Rfa is the resistance of the inductor in the a-phase circuit, Rcb is the resistance of the capacitor in the b-phase circuit, and Rfb is the resistance of the inductor in the b-phase circuit. The inductance of the circuit can also be expressed as La + Lb, where La is the inductance of the inductor in the a-phase circuit. Lb is the inductance of the inductor element in the b-phase circuit. The capacitance value of the circuit may be expressed as Cab, which is the sum of the reciprocal of the capacitance value Ca of the capacitor element in the a-phase circuit and the reciprocal of the capacitance value Cb of the capacitor element in the b-phase circuit. Similarly to connecting the a-phase and b-phase circuits, connecting the a-phase and c-phase circuits to form another circuit yields the equivalent resistance Rca+Rfa+Rcc+Rfc, inductance La+Lc, and capacitance Cac of the circuit consisting of the a-phase and c-phase circuits. Similarly, connecting the b-phase and c-phase circuits yields the equivalent resistance Rcb+Rfb+Rcc+Rfc, inductance Lb+Lc, and capacitance Cbc of the circuit consisting of the b-phase and c-phase circuits. The equivalent resistances of the three circuits are connected in series to obtain the resistance of each phase circuit, which is the sum of the resistance of the inductor element and the resistance of the capacitor element in that phase circuit. In other words, the resistance of the a-phase circuit is Rca+Rfa, the resistance of the b-phase circuit is Rcb+Rfb, and the resistance of the c-phase circuit is Rcc+Rfc. The inductance values ​​of the three circuits are calculated simultaneously to obtain the inductance value of the inductor element in each phase circuit, and the inductance value of the a-phase circuit is La. The inductance value of the b-phase circuit is Lb, and the inductance value of the c-phase circuit is Lc.The capacitance values ​​of the capacitor elements in each phase circuit are obtained by calculating the capacitance values ​​of the three circuits simultaneously. The capacitance value of the a-phase circuit is Ca, the capacitance value of the b-phase circuit is Cb, and the capacitance value of the c-phase circuit is Cc.

[0028] The obtained resistance of the circuit of each phase, the capacitance of the capacitor element, and the inductance of the inductor element are compared with reference values, and if the differences between the resistance of the circuit of each phase, the capacitance of the capacitor element, and the inductance of the inductor element and the reference values ​​do not exceed a predetermined threshold, it is determined that the auxiliary inverter is not degraded, and the threshold may be in the form of a percentage.

[0029] Optionally, FIG. 5 is a flowchart of another self-test method for an AC filter capacitor of an auxiliary inverter provided by Example 1 of the present application. As shown in FIG. 5, in step 201, obtaining the equivalent resistance of each circuit in the auxiliary inverter includes steps 501 to 503. In step 501, the DC input voltage of the auxiliary inverter, the sum of the voltages of the capacitor elements in each circuit, and the maximum current flowing through the inductor element are obtained. In step 502, the difference between the DC input voltage of the auxiliary inverter and the sum of the voltages of the capacitor elements in each circuit is calculated to obtain the voltage of the equivalent resistance of each circuit. In step 503, the ratio of the voltage of the equivalent resistance of each circuit to the maximum current is calculated to obtain the equivalent resistance of each circuit.

[0030] For example, a DC step response is injected into the auxiliary inverter system, where U0 is the step input voltage. Figure 6 shows a schematic diagram of the inductor current and capacitor voltage of the illustrated auxiliary inverter AC filter as a function of the step input voltage. ipeak is the peak value of the inductor current, and uc is the capacitor voltage at the peak value of the inductor current. Taking phases a and b as an example, the upper tube of phase a and the lower tube of phase b of the auxiliary inverter for a rail transit vehicle are turned on. When the DC input voltage is U0, the peak value ipeaka of the inductor current of the filter for phase a in the step response system is measured. The peak value ipeakb of the inductor current of the filter for phase b is the same as the peak value ipeaka of the inductor current of the filter for phase a, which is the current of the circuit. Since the inductor current is at its maximum value, the inductor voltage is partially zero. The difference between the DC input voltage and the filter capacitor voltage is the voltage of the equivalent resistance of the circuit. In other words, the voltage is Rca+Rfa+Rcb+Rfb, and if you divide the voltage of Rca+Rfa+Rcb+Rfb by the current ipeaka in the circuit, you get the value of Rca+Rfa+Rcb+Rfb, which gives you the equivalent resistance of the circuit.

[0031] Optionally, Fig. 7 is a flowchart of another method for self-testing an AC filter capacitor of an auxiliary inverter provided in Example 1 of the present application. As shown in Fig. 7, in step 201, obtaining the inductance value and capacitance value of each circuit in the auxiliary inverter includes steps 701 to 703. In step 701, a transfer function of the sum of the voltages of the capacitor elements in each circuit with respect to the DC input voltage of the auxiliary inverter is obtained. In step 702, the transfer function is compared with a standard second order system to obtain the key parameters of the auxiliary inverter system in which the auxiliary inverter is placed. In step 703, obtain the inductance and capacitance values ​​of each circuit according to the equivalent resistance of each circuit and the main parameters of the auxiliary inverter system in which the auxiliary inverter is located.

[0032] For example, Kirchhoff's law is used to calculate the equivalent relationship of the capacitor voltage of a conductive circuit, and a Laplace transform is performed to obtain the transfer function of the capacitor voltage relative to a step input on the DC side. The transfer function is compared with a standard second-order system to obtain the main parameters of the auxiliary inverter, thereby calculating the parameters of the AC filter of the auxiliary inverter and determining the health status of the AC capacitor. Optionally, the main parameters of the auxiliary inverter system in which the auxiliary inverter is installed include the damping ratio, damped natural frequency, undamped natural frequency, overshoot, and peak value time. The following formula is an example of a standard second-order system:

[0033]

number

[0034] where ωn is the undamped natural frequency, ζ is the damping ratio, ωd is the damped natural frequency, tp is the time to peak value, and σ% is the overshoot. The following equation is an example of the mathematical relationship between the five main parameters:

[0035]

number

[0036] Taking phases a and b as an example, the maximum sum of the capacitor voltages in the phase a and b circuits of a rail transit vehicle's auxiliary inverter is measured. Since the sum of the phase a and b capacitor voltages is equal to the amplitude of the DC input voltage at steady state, measuring this maximum value and comparing it with the DC input voltage Vdc yields the filter capacitor voltage overshoot σ% and allows for inverse estimation of the damping ratio ζ. The peak value time tp is the time from when the switching element turns on until the filter capacitor voltage reaches its peak value. At this point, the damped natural frequency ωd of the phase a and b circuit is calculated, and the undamped natural frequency ωn can be calculated based on the damping ratio ζ. The inductance value of the phase a and b circuit is obtained based on the obtained key parameter values, and the capacitance value of the circuit is estimated based on ωn. Using this method, the inductance and capacitance values ​​of each circuit can be obtained.

[0037] For example, the reference values ​​for the resistance of each phase in the circuit, the capacitance of the capacitor elements, and the inductance of the inductor elements are U0 = 100V, La = Lb = Lc = Ln = 150uH, Ca = Cb = Cc = 1200uF, and Rca + Rfa = Rcb + Rfb = Rcc + Rfc = 0.2Ω. Figure 8 shows simulated waveforms of the step response of the exemplary auxiliary inverter filter. (a) shows the simulated waveform of the step response of the exemplary three-phase three-bridge inverter filter, and (b) shows the simulated waveform of the step response of the exemplary three-phase four-bridge inverter filter. The input voltage U0 is maintained at 100V. At 0.1s, the upper tube of phase a and the lower tube of phase c are turned on, generating a step input. The waveform of the sum of the voltages of capacitors Ca and Cc is a typical underdamped oscillation waveform of a second-order system. The final voltage remains stable at 100V, and the inductor currents iLa and iLc also exhibit the oscillation pattern of a standard underdamped second-order system. The final voltage remains stable at 0A. At 0.15s, when the lower tube of phase a and the lower tube of phase c are energized, the capacitor voltage discharges to 0V. At 0.2s, when the upper tube of phase a and the lower tube of phase b are energized, a step input is generated, and the waveform of the sum of the voltages of capacitors Ca and Cb exhibits the oscillation pattern of a standard underdamped second-order system. The final voltage remains stable at 100V, and the inductor currents iLa and iLb also exhibit the oscillation pattern of a standard underdamped second-order system. The final voltage remains stable at 0A. At 0.25s, when the lower tube of phase a and the lower tube of phase b are energized, the capacitor voltage discharges to 0V. When the upper loop of phase b and the lower loop of phase c are turned on at 0.3 s, a step input occurs, and the waveform of the sum of the voltages of capacitors Cb and Cc takes the form of a standard underdamped oscillation of a second-order system. The final voltage remains stable at 100 V, and the inductor currents iLb and iLc also take the form of a standard underdamped oscillation of a second-order system, with the final current remaining stable at 0 A. When the lower loop of phase b and the lower loop of phase c are turned on at 0.35 s, the capacitor voltage discharges to 0 V. Table 1 shows the simulated step response of the example three-phase four-bridge inverter system.

[0038] [Table 1]

[0039] By back-estimating based on the simulation results, we can obtain that Rca + Rfa = 0.20208Ω, Rcb + Rfb = 0.20208Ω, Rcc + Rfc = 0.19867Ω, La = 151.617uH, Lb = 151.617uH, Lc = 149.059uH, Ca = 1187.89uF, Cb = 1187.89uF, Cc = 1208.27uF. These basically match the actual parameters of the circuit, with an error of about 1%.

[0040] Actual design examples have proven that the self-test method for the AC filter capacitor of the auxiliary inverter provided by the present application can be applied to the topology structures of a three-phase three-bridge inverter and a three-phase four-bridge inverter, and the errors between the calculated results of the system equivalent resistance, filter inductance, and filter capacitance values ​​and the actual parameters are all small.

[0041] In this embodiment, the equivalent resistance, inductance, and capacitance of each circuit in the auxiliary inverter are obtained, and simultaneous equations are established based on the equivalent resistance, inductance, and capacitance of each circuit, based on circuit conditions. The simultaneous equations are then solved to obtain the resistance of each phase circuit, the inductance of the inductor element in each phase circuit, and the capacitance of the capacitor element in each phase circuit. The circuit conditions include the equivalent resistance of each circuit being the sum of the equivalent resistances of all inductor elements and capacitor elements in the two-phase circuits that make up the circuit. The inductance of each circuit is the sum of the inductance values ​​of the inductor elements in the two-phase circuits that make up the circuit. The capacitance value of each circuit is the sum of the reciprocals of the capacitance values ​​of the capacitor elements in the two-phase circuits that make up the circuit. The resistance of each phase circuit, the inductance value of the inductor element in each phase circuit, and the capacitance value of the capacitor element in each phase circuit are compared with corresponding reference values. If the differences between the resistance of any phase circuit, the inductance value of the inductor element, and the capacitance value of the capacitor element and the corresponding reference value do not all exceed corresponding thresholds, it is determined that the auxiliary inverter is not degraded. Otherwise, it is determined that the auxiliary inverter is degraded. Based on the method provided by this embodiment, a DC step response can be injected into the auxiliary inverter system by turning on different circuits in the auxiliary inverter, and step response signals of the filter inductor current and the filter capacitor voltage can be obtained by sampling. By comparing the waveform with a standard second-order system and calculating parameters such as the system's undamped natural frequency, damping ratio, overshoot, and peak value time, the equivalent resistance, inductance value, and capacitance value of each circuit can be inversely estimated, and the resistance of the circuit for each phase, as well as the inductance value of the inductor element and the capacitance value of the capacitor element, can be determined.The resistance of the circuit for each phase, as well as the inductance value of the inductor element and the capacitance value of the capacitor element can be compared with reference values ​​to determine the level of consumption of each element and determine whether it has deteriorated.Furthermore, the method provided by this embodiment does not require the removal of components, is applicable to the operation of auxiliary inverters for rail transit vehicles, has low program complexity and calculation volume, is simple to operate, has lower performance requirements for the controller, and has high measurement accuracy, and can conveniently and effectively implement self-testing of the health status of AC filter capacitors.

[0042] Example 2 9 is a structural schematic diagram of the self-test device for AC filter capacitor of auxiliary inverter provided in Example 2 of the present application. As shown in FIG. 9, the device includes the following modules: The acquisition module 91 is used to acquire the equivalent resistance, inductance value and capacitance value of each circuit in the auxiliary inverter, which is composed of two-phase circuits in the auxiliary inverter, each phase circuit in the auxiliary inverter including an inductor element and a capacitor element, and different circuits are composed of different two-phase circuits. The calculation module 92 is used to establish simultaneous equations based on the equivalent resistance, inductance value, and capacitance value of each circuit and circuit conditions, and solve the simultaneous equations to obtain the resistance of each phase circuit, the inductance value of the inductor element in each phase circuit, and the capacitance value of the capacitor element in each phase circuit. The circuit conditions include that the equivalent resistance of each circuit is the sum of the equivalent resistances of all inductor elements and capacitor elements in the two-phase circuits that make up the circuit. The inductance value of each circuit is the sum of the inductance values ​​of the inductor elements in the two-phase circuits that make up the circuit, and the capacitance value of each circuit is the sum of the reciprocals of the capacitance values ​​of the capacitor elements in the two-phase circuits that make up the circuit. The comparison module 93 compares the resistance of each phase circuit, the inductance value of the inductor element in each phase circuit, and the capacitance value of the capacitor element in each phase circuit with corresponding reference values, and determines that the auxiliary inverter is not deteriorated if the differences between the resistance of any phase circuit, the inductance value of the inductor element, and the capacitance value of the capacitor element and the corresponding reference values ​​do not exceed the corresponding threshold values; otherwise, it determines that the auxiliary inverter is deteriorated.

[0043] For example, the acquisition module 91 connects the upper a-phase tube and the lower b-phase tube of the auxiliary inverter of the rail transit vehicle to obtain the equivalent resistance, inductance, and capacitance of the circuit. The equivalent resistance of the circuit includes the sum of the resistances of the inductor and capacitor elements in the a-phase circuit and the inductor and capacitor elements in the b-phase circuit, and is expressed as Rca+Rfa+Rcb+Rfb. Rca is the resistance of the capacitor element in the a-phase circuit, Rfa is the resistance of the inductor element in the a-phase circuit, Rcb is the resistance of the capacitor element in the b-phase circuit, and Rfb is the resistance of the inductor element in the b-phase circuit. The inductance of the circuit can be expressed as La+Lb, where La is the inductance of the inductor element in the a-phase circuit and Lb is the inductance of the inductor element in the b-phase circuit. The capacitance value of the circuit may be expressed as Cab, which is the sum of the reciprocal of the capacitance value Ca of the capacitor element in the a-phase circuit and the reciprocal of the capacitance value Cb of the capacitor element in the b-phase circuit. Similarly to connecting the a-phase and b-phase circuits, the a-phase and c-phase circuits are connected to form another circuit, and the equivalent resistance Rca+Rfa+Rcc+Rfc, inductance La+Lc, and capacitance Cac of the circuit formed by the a-phase and c-phase circuits are obtained. Similarly, the b-phase and c-phase circuits are connected to obtain the equivalent resistance Rcb+Rfb+Rcc+Rfc, inductance Lb+Lc, and capacitance Cbc of the circuit formed by the b-phase and c-phase circuits. The calculation module 92 simultaneously calculates the equivalent resistances of the three circuits to obtain the resistance of each phase circuit, and the resistance of each phase circuit is the sum of the resistance of the inductor element and the resistance of the capacitor element in that phase circuit. In other words, the resistance of the a-phase circuit is Rca+Rfa, the resistance of the b-phase circuit is Rcb+Rfb, and the resistance of the c-phase circuit is Rcc+Rfc. The inductance values ​​of the three circuits are calculated simultaneously to obtain the inductance value of the inductor element in each phase circuit, and the inductance value of the a-phase circuit is La. The inductance value of the b-phase circuit is Lb, and the inductance value of the c-phase circuit is Lc. The capacitance values ​​of the three circuits are calculated simultaneously to obtain the capacitance value of the capacitor element in each phase circuit, and the capacitance value of the a-phase circuit is Ca.The capacitance value of the b-phase circuit is Cb, and the capacitance value of the c-phase circuit is Cc.

[0044] The comparison module 93 compares the resistance of each phase circuit, the capacitance of the capacitor element, and the inductance of the inductor element obtained with a reference value, and determines that the auxiliary inverter is not deteriorated if the difference between the resistance of each phase circuit, the capacitance of the capacitor element, and the inductance of the inductor element and the reference value does not exceed a predetermined threshold value, which may be in the form of a percentage.

[0045] Optionally, the acquisition module 91 is specifically used to acquire the DC input voltage of the auxiliary inverter, the sum of the voltages of the capacitor elements in each circuit, and the maximum current flowing through the inductor elements. The acquisition module 91 is specifically further used to calculate the difference between the DC input voltage of the auxiliary inverter and the sum of the voltages of the capacitor elements in each circuit, and obtain the voltage of the equivalent resistance of each circuit. The obtaining module 91 is further specifically used to obtain the ratio of the voltage of the equivalent resistance of each circuit to the maximum current, and obtain the equivalent resistance of each circuit.

[0046] In the example shown in the scene, the acquisition module 91 injects a DC step response into the auxiliary inverter system, where U0 is the step input voltage. ipeak is the peak value of the inductor current, and uc is the capacitor voltage at the peak value of the inductor current. Taking phases a and b as an example, the upper tube of phase a and the lower tube of phase b of the auxiliary inverter for a rail transit vehicle are turned on. When the DC input voltage is U0, the peak value ipeaka of the inductor current of the filter for phase a in the step response system is measured. The peak value ipeakb of the inductor current of the filter for phase b is the same as the peak value ipeaka of the inductor current of the filter for phase a, which is the current of the circuit. Since the inductor current is at its maximum value, the inductor voltage is partially zero. The difference between the DC input voltage and the filter capacitor voltage is the voltage of the equivalent resistance of the circuit. In other words, it is the voltage of Rca+Rfa+Rcb+Rfb, and if you divide the voltage of Rca+Rfa+Rcb+Rfb by the current ipeaka in the circuit, you get the value of Rca+Rfa+Rcb+Rfb, and the equivalent resistance of the circuit is obtained.

[0047] Optionally, the acquisition module 91 is further specifically used for acquiring the transfer function of the sum of the voltages of the capacitor elements in each circuit relative to the DC side input voltage of the auxiliary inverter. The acquisition module 91 is further specifically used to compare the transfer function with a standard second-order system to obtain the main parameters of the auxiliary inverter system in which the auxiliary inverter is arranged. The acquisition module 91 is further specifically used for obtaining the inductance value and capacitance value of each circuit according to the equivalent resistance of each circuit and the main parameters of the auxiliary inverter system in which the auxiliary inverter is arranged.

[0048] Referring to the example shown in the scene, the acquisition module 91 calculates the equivalent relational equation of the capacitor voltage of the circuit using Kirchhoff's law for the conductive circuit, and obtains the transfer function of the capacitor voltage for the step input on the DC side through Laplace transform, and compares the transfer function with a standard second-order system to obtain the main parameters of the auxiliary inverter system, thereby calculating the parameters of the AC filter of the auxiliary inverter and determining the health status of the AC capacitor. Optionally, the main parameters of the auxiliary inverter system in which the auxiliary inverter is installed include the damping ratio, damped natural frequency, undamped natural frequency, overshoot, and peak value time.

[0049] Taking phases a and b as an example, the maximum sum of the capacitor voltages in the phase a and b circuits of a rail transit vehicle's auxiliary inverter is measured. Since the sum of the phase a and b capacitor voltages is equal to the amplitude of the DC input voltage at steady state, measuring this maximum value and comparing it with the DC input voltage Vdc yields the filter capacitor voltage overshoot σ% and allows for inverse estimation of the damping ratio ζ. The time from when the switching elements turn on to when the filter capacitor voltage reaches its peak value is the peak value time tp. At this time, the damped natural frequency ωd of the phase a and b circuits can be calculated, and the undamped natural frequency ωn can be calculated based on the damping ratio ζ. The inductance value of the phase a and b circuits is obtained based on the obtained key parameter values, and the capacitance value of the circuit is estimated based on ωn. Using this method, the inductance and capacitance values ​​of each circuit can be obtained.

[0050] In this embodiment, the acquisition module acquires the equivalent resistance, inductance value, and capacitance value of each circuit in the auxiliary inverter. The calculation module establishes simultaneous equations based on the equivalent resistance, inductance value, and capacitance value of each circuit and circuit conditions, and solves the simultaneous equations to acquire the resistance of each phase circuit, the inductance value of the inductor element in each phase circuit, and the capacitance value of the capacitor element in each phase circuit. The circuit conditions include that the equivalent resistance of each circuit is the sum of the equivalent resistances of all inductor elements and capacitor elements in the two-phase circuits that make up that circuit. The inductance value of each circuit is the sum of the inductance values ​​of the inductor elements in the two-phase circuits that make up that circuit. The capacitance value of each circuit is the sum of the reciprocals of the capacitance values ​​of the capacitor elements in the two-phase circuits that make up that circuit. The comparison module compares the resistance of each phase circuit, the inductance value of the inductor element in each phase circuit, and the capacitance value of the capacitor element in each phase circuit with corresponding reference values, and determines that the auxiliary inverter is not degraded if the differences between the resistance of any phase circuit, the inductance value of the inductor element, and the capacitance value of the capacitor element and the corresponding reference value do not exceed corresponding thresholds. Otherwise, it determines that the auxiliary inverter is degraded. Based on the method provided by this embodiment, a DC step response can be injected into the auxiliary inverter system by turning on different circuits in the auxiliary inverter, and step response signals of the filter inductor current and the filter capacitor voltage can be obtained by sampling. By comparing the waveform with a standard second-order system and calculating parameters such as the system's undamped natural frequency, damping ratio, overshoot, and peak value time, the equivalent resistance, inductance value, and capacitance value of each circuit can be inversely estimated, and the resistance of the circuit for each phase, as well as the inductance value of the inductor element and the capacitance value of the capacitor element, can be determined.The resistance of the circuit for each phase, as well as the inductance value of the inductor element and the capacitance value of the capacitor element can be compared with reference values ​​to determine the level of consumption of each element and determine whether it has deteriorated.Furthermore, the method provided by this embodiment does not require the removal of components, is applicable to the operation of auxiliary inverters for rail transit vehicles, has low program complexity and calculation volume, is simple to operate, has lower performance requirements for the controller, and has high measurement accuracy, and can conveniently and effectively implement self-testing of the health status of AC filter capacitors.

[0051] Example 3 FIG. 10 is a structural schematic diagram of an electronic device provided in Example 3 of the present application. As shown in FIG. 10, the electronic device includes a processor 291. The server further includes a memory 292, and the electronic device further includes a communication interface 293 and a bus 294. The processor 291, the memory 292, and the communication interface 293 can complete communication between them via the bus 294. The communication interface 293 may be used for information transfer. The processor 291 can call the logic instructions in the memory 292 to perform the method of Example 1 above.

[0052] Also, the logic instructions in the memory 292 described above may be stored in a computer-readable storage medium when implemented in the form of a software functional unit and sold or used as a separate product.

[0053] The memory 292, as a computer-readable storage medium, can be used to store software programs and computer-executable programs, such as program instructions / modules corresponding to the methods in the embodiments of the present application. The processor 291 executes the software programs, instructions, and modules stored in the memory 292 to perform functional applications and data processing, i.e., to implement the method of the above-mentioned embodiment 1.

[0054] The memory 292 may include a program storage area and a data storage area. The program storage area may store an operating system and / or an application program required for at least one function. The data storage area may store data generated based on the use of the terminal device. The memory 292 may include a high-speed random access memory or a non-volatile memory.

[0055] An embodiment of the present application provides a non-transitory computer-readable storage medium having computer-executable instructions stored thereon, which, when executed by a processor, are used to implement the method described in the above-described embodiment.

[0056] Other embodiments of the present application will be readily apparent to those skilled in the art from consideration of the specification and practice of the invention(s) herein. This application is intended to cover any modifications, uses, or adaptations of the present application in accordance with the general principles of the present application, including common sense or customary technical means known in the art but not claimed herein. The specification and examples are considered exemplary, with the true scope and spirit of the present application being indicated by the following claims.

[0057] It should be understood that the present application is not limited to the exact construction described above and illustrated in the accompanying drawings, and that various modifications and variations are possible without departing from the scope thereof, which is limited only by the appended claims.

Claims

1. 1. A self-test method for an AC filter capacitor of an auxiliary inverter, comprising: Obtaining an equivalent resistance, an inductance value, and a capacitance value of each circuit in the auxiliary inverter, the circuit being composed of two-phase circuits in the auxiliary inverter, each phase circuit in the auxiliary inverter including an inductor element and a capacitor element, and different circuits being composed of different two-phase circuits; establishing simultaneous equations based on circuit conditions according to the equivalent resistance, inductance value, and capacitance value of each circuit, and solving the simultaneous equations to obtain the resistance of the circuit for each phase, the inductance value of the inductor element in the circuit for each phase, and the capacitance value of the capacitor element in the circuit for each phase, wherein the circuit conditions include that the equivalent resistance of each circuit is the sum of the equivalent resistances of all the inductor elements and capacitor elements in the two-phase circuits that make up the circuit, the inductance value of each circuit is the sum of the inductance values ​​of the inductor elements in the two-phase circuits that make up the circuit, and the capacitance value of each circuit is the sum of the reciprocals of the capacitance values ​​of the capacitor elements in the two-phase circuits that make up the circuit; comparing the resistance of the circuit for each phase, the inductance value of the inductor element in the circuit for each phase, and the capacitance value of the capacitor element in the circuit for each phase with corresponding reference values, and determining that the auxiliary inverter is not degraded if any difference between the resistance of the circuit for any phase, the inductance value of the inductor element, and the capacitance value of the capacitor element and the corresponding reference values ​​does not exceed a corresponding threshold value, and determining that the auxiliary inverter is degraded if this is not the case.

2. Obtaining an equivalent resistance of each circuit in the auxiliary inverter includes: Obtaining the DC input voltage of the auxiliary inverter, the sum of the voltages of the capacitor elements in each circuit, and the maximum current flowing through the inductor element; Calculating the difference between the DC input voltage of the auxiliary inverter and the sum of the voltages of the capacitor elements in each circuit to obtain the voltage of the equivalent resistance of each circuit; 2. The self-test method according to claim 1, further comprising: determining a ratio of the voltage of an equivalent resistance of each circuit to said maximum current, thereby obtaining an equivalent resistance of each circuit.

3. Obtaining the inductance value and the capacitance value of each circuit in the auxiliary inverter includes: Obtaining a transfer function of the sum of the voltages of the capacitor elements in each circuit with respect to the DC side input voltage of the auxiliary inverter; comparing said transfer function with a standard second-order system to obtain key parameters of an auxiliary inverter system in which said auxiliary inverter is arranged; 3. The self-test method of claim 2, further comprising: obtaining an inductance value and a capacitance value of each circuit according to the equivalent resistance of each circuit and the main parameters of the auxiliary inverter system in which the auxiliary inverter is installed.

4. 4. The self-test method according to claim 3, wherein the main parameters of the auxiliary inverter system in which the auxiliary inverter is installed include a damping ratio, a damped natural frequency, an undamped natural frequency, an overshoot, and a peak value time.

5. 2. The self-test method according to claim 1, wherein the auxiliary inverter is a three-phase three-bridge inverter or a three-phase four-bridge inverter.

6. 1. A self-test device for an AC filter capacitor of an auxiliary inverter, comprising: an acquisition module used to acquire the equivalent resistance, inductance value, and capacitance value of each circuit in the auxiliary inverter, the circuit being composed of two-phase circuits in the auxiliary inverter, each phase circuit in the auxiliary inverter including an inductor element and a capacitor element, and different circuits being composed of different two-phase circuits; a calculation module used to establish simultaneous equations based on circuit conditions according to the equivalent resistance, inductance value, and capacitance value of each circuit, and to obtain the resistance of each phase circuit, the inductance value of the inductor element in each phase circuit, and the capacitance value of the capacitor element in each phase circuit by solving the simultaneous equations, wherein the circuit conditions include that the equivalent resistance of each circuit is the sum of the equivalent resistances of all inductor elements and capacitor elements in the two-phase circuits that make up the circuit, the inductance value of each circuit is the sum of the inductance values ​​of the inductor elements in the two-phase circuits that make up the circuit, and the capacitance value of each circuit is the sum of the reciprocals of the capacitance values ​​of the capacitor elements in the two-phase circuits that make up the circuit; and a comparison module used for comparing the resistance of the circuit of each phase, the inductance value of the inductor element in the circuit of each phase, and the capacitance value of the capacitor element in the circuit of each phase with corresponding reference values, and determining that the auxiliary inverter is not deteriorated if any difference between the resistance of the circuit of any phase, the inductance value of the inductor element, and the capacitance value of the capacitor element and the corresponding reference value does not exceed a corresponding threshold value, or determining that the auxiliary inverter is deteriorated if not.

7. The acquisition module is specifically used to acquire the DC input voltage of the auxiliary inverter, the sum of the voltages of the capacitor elements in each circuit, and the maximum current flowing through the inductor elements; The acquisition module is specifically further used for calculating the difference between the DC input voltage of the auxiliary inverter and the sum of the voltages of the capacitor elements in each circuit, to obtain the voltage of the equivalent resistance of each circuit; 7. The self-test device according to claim 6, wherein the acquisition module is further specifically used for calculating the ratio between the voltage of the equivalent resistance of each circuit and the maximum current, and obtaining the equivalent resistance of each circuit.

8. The acquisition module is specifically further used for acquiring a transfer function of a sum of voltages of capacitor elements in each circuit relative to a DC input voltage of the auxiliary inverter; The acquisition module is further specifically used for comparing the transfer function with a standard second-order system to obtain key parameters of an auxiliary inverter system in which the auxiliary inverter is arranged; 8. The self-test device of claim 7, wherein the acquisition module is further used for obtaining an inductance value and a capacitance value of each circuit according to the equivalent resistance of each circuit and the main parameters of the auxiliary inverter system in which the auxiliary inverter is installed.

9. An electronic device including a processor and a memory communicatively connected to the processor, the memory stores computer-executable instructions; The electronic device, characterized in that the processor executes computer-executable instructions stored in the memory to implement the self-test method according to any one of claims 1 to 5.

10. 6. A computer-readable storage medium having stored thereon computer-executable instructions, the computer-executable instructions being used, when executed by a processor, to implement the self-test method of any one of claims 1 to 5.

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