Self-diagnosis method and apparatus for ac filter capacitor of auxiliary inverter

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] The present application relates to the field of auxiliary inverter health self-test, and in particular to a method and apparatus for self-testing an auxiliary inverter AC filter capacitor. [Background technology]

[0002] The auxiliary power supply system is an essential main electrical part of rail vehicles, subways and light rail vehicles, which needs to supply power to ensure the air conditioning, lighting and other facilities of the train. In order to ensure the reliability of the auxiliary inverter of the rail transit vehicle, it is necessary to inspect the health of the AC filter capacitor, because in the reliability study of power electronics, the reliability of the power device, inductor and capacitor device is weak and related to the reliability of the whole system. Generally speaking, the AC filter capacitor can be considered as degraded and expired when the capacitance value is lower than 95% of its initial capacitance value, which is often caused by the continuous degradation in the long-term operation of the auxiliary inverter of the rail transit vehicle.

[0003] At present, the inductor capacitor monitoring method is to inject a small-power sine wave AC current into the filter capacitor of the urban railway auxiliary power supply system, obtain the capacitor current and voltage parameters by Fourier transform, and calculate the capacitance value and equivalent resistance. However, the offline capacitor monitoring technology requires the capacitor to be removed from the system, which is inconvenient for practical application. Regarding the problem of capacitor degradation and failure, a reliability evaluation model is established under actual operating conditions for the filter capacitor of the urban railway auxiliary power supply system, to obtain the characteristic that the capacitance decreases with time, and to analyze the health state of the capacitor. In addition, based on the modeling of the hybrid system, a parameter identification method for the urban railway auxiliary power supply system is designed using the least squares method, which has high accuracy but the overall design process and calculation are complicated. How to conveniently and effectively self-test the health state of the AC filter capacitor of the auxiliary inverter is a problem to be solved in this field. Summary of the Invention [Problem to be solved by the invention]

[0004] The present application provides a method and apparatus for self-testing an 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 method comprising: Obtaining an equivalent resistance, and 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 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, 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 the capacitor elements in the two-phase circuits that constitute 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 constitute 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 constitute 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 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 ​​all do not exceed corresponding threshold values, determining that the auxiliary inverter is not degraded, and if not, determining that the auxiliary inverter is degraded.

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

[0007] In another example, obtaining the inductance and capacitance values ​​of each circuit in the auxiliary inverter includes: Obtaining a transfer function of a sum of voltages of capacitor elements in each circuit with respect to a DC 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; obtaining an inductance value and a capacitance value of each circuit according to an equivalent resistance of each circuit and the main parameters of the auxiliary inverter system in which the auxiliary inverter is disposed.

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

[0009] In another embodiment, 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 for acquiring 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 includes an inductor element and a capacitor element, and different circuits are composed of different two-phase circuits; a calculation module used for 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 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 the inductor elements and the capacitor elements in the two-phase circuits constituting the circuit, the inductance value of each circuit is the sum of the inductance values ​​of the inductor elements in the two-phase circuits constituting 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 constituting the circuit; a comparison module for 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 ​​all do not exceed corresponding threshold values, and determining that the auxiliary inverter is degraded if not.

[0011] In another example, the acquisition module is specifically used for acquiring 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; The acquisition module is specifically further used for obtaining 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 obtaining the voltage of the equivalent resistance of each circuit; The acquisition module is further specifically used for obtaining a ratio between the voltage of the equivalent resistance of each circuit and the maximum current, and obtaining 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 the voltages of the capacitor elements in each circuit relative to the DC input voltage of the auxiliary inverter; The acquisition module is further specifically used for comparing the transfer function with a standard secondary system to obtain key parameters of an auxiliary inverter system in which the auxiliary inverter is disposed; The acquisition module is specifically further used for obtaining an inductance value and a capacitance value of each circuit according to an equivalent resistance of each circuit and main parameters of an auxiliary inverter system in which the auxiliary inverter is disposed.

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

[0015] The present application provides a method and apparatus for self-testing 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; 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 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 the inductor elements and the capacitor elements in the two-phase circuits constituting 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 constitute 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 constitute the circuit. The resistance of the circuit for each phase, the inductance value of the inductor elements in the circuit for each phase, and the capacitance value of the capacitor elements in the circuit for each phase are compared with corresponding reference values, and 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 ​​all do not 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 a standard secondary system, and parameters such as the undamped natural frequency, damping ratio, overshoot, and peak value time of the system are calculated to inversely estimate the equivalent resistance, inductance value, and capacitance value of each circuit. The resistance of the circuit of each phase, the inductance value of the inductor element, and the capacitance value of the capacitor element are determined. The resistance of the circuit of each phase, the inductance value of the inductor element, and the capacitance value of the capacitor element are compared with reference values ​​to know the consumption level of each element and determine whether it has deteriorated.In addition, the method provided by the present application does not require removal of components, is applicable to the operation of auxiliary inverters of 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-test of the health status of AC filter capacitors in a convenient and effective manner. [Brief description of the drawings]

[0016] The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments consistent with the present application and are used together with the specification to explain the principles of the present application. [Figure 1] FIG. 2 is a schematic diagram of an application scene of the example presented in the present application; [Diagram 2] 4 is a flowchart of a self-test method for an AC filter capacitor of one auxiliary inverter provided by Example 1 of the present application; [Diagram 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 phase a and phase b circuits as examples. [Diagram 5] 4 is a flowchart of a self-test method for an AC filter capacitor of another auxiliary inverter provided in accordance with Example 1 of the present application; [Figure 6] 4 is a schematic diagram of the variation of inductor current and capacitor voltage of an exemplary auxiliary inverter AC filter following a step input voltage; [Figure 7] 4 is a flowchart of a self-test method for an AC filter capacitor of another auxiliary inverter provided in accordance with Example 1 of the present application. [Figure 8] 4 is a simulation waveform of a step response of an exemplary auxiliary inverter filter. [Figure 9] FIG. 11 is a structural schematic diagram of a self-test device for an AC filter capacitor of an auxiliary inverter provided in accordance with Example 2 of the present application; [Figure 10] FIG. 11 is a structural schematic diagram of an electronic device provided in Example 3 of the present application. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] Specific examples of the present application are illustrated by the attached 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] Exemplary embodiments are described in detail herein, examples of which are illustrated in the accompanying drawings. When the following description refers to the accompanying drawings, the same numerals in different accompanying drawings represent the same or similar elements, unless otherwise specified. The embodiments described in the following exemplary embodiments 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 automatic driving, and FIG. 1 is a schematic diagram of the application scenario of the example shown in this application. The auxiliary power supply system is an essential main electrical part of rail vehicles, subways, and light rail vehicles, and needs to supply power to ensure the air conditioning, lighting and other facilities of the train. In order to ensure the reliability of the auxiliary inverter of the rail transit vehicle, it is necessary to inspect the health of the AC filter capacitor. This is because in the reliability study of power electronics, the power device, inductor and capacitor device are weak and are related to the reliability of the whole system. Generally, the AC filter capacitor can be considered to be degraded and expired when the capacitance value is lower than 95% of its initial capacitance value. This is often caused by the continuous degradation in the long-term operation of the auxiliary inverter of the rail transit vehicle.

[0020] At present, the inductor capacitor monitoring method is to inject a small-power sine wave AC current into the filter capacitor of the urban railway auxiliary power supply system, obtain the capacitor current and voltage parameters by Fourier transform, and calculate the capacitance value and equivalent resistance. However, the offline capacitor monitoring technology requires the capacitor to be removed from the system, which is inconvenient for practical application. Regarding the problem of capacitor degradation and failure, a reliability evaluation model is established under actual operating conditions for the filter capacitor of the urban railway auxiliary power supply system, to obtain the characteristic that the capacitance decreases with time, and to analyze the health state of the capacitor. In addition, based on the modeling of the hybrid system, a parameter identification method for the urban railway auxiliary power supply system is designed using the least squares method, which has high accuracy but the overall design process and calculation are complicated. How to conveniently and effectively self-test the health state of the AC filter capacitor of the auxiliary inverter is a problem to be solved in this field.

[0021] The present application obtains an equivalent resistance, an inductance value, and a capacitance value of each circuit in the auxiliary inverter, establishes simultaneous equations based on circuit conditions according to the equivalent resistance, inductance value, and capacitance value of each circuit, and obtains 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. The circuit conditions include that the equivalent resistance of each circuit is the sum of the equivalent resistances of all the inductor elements and the capacitor elements in the two-phase circuits that constitute 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 constitute 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 constitute the circuit, and 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 are compared with corresponding reference values, and if the differences between the resistance of any of the circuits of the 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. According to the method of the present application, by turning on different circuits in the auxiliary inverter, a DC step response can be injected into the auxiliary inverter system and sampled to obtain step response signals of the filter inductor current and the filter capacitor voltage. The waveform is compared with a standard secondary system to calculate parameters such as the undamped natural frequency, damping ratio, overshoot, and peak value time of the system, thereby inversely estimating the equivalent resistance, inductance value, and capacitance value of each circuit. The resistance of the circuit of each phase, the inductance value of the inductor element, and the capacitance value of the capacitor element that constitutes the circuit can be determined. The resistance of the circuit of each phase, the inductance value of the inductor element, and the capacitance value of the capacitor element can be compared with reference values ​​to know the consumption level of each element and determine whether it has deteriorated.In addition, the method provided by the present application does not require removal of components, is applicable to the operation of auxiliary inverters of 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-test of the health status of AC filter capacitors in a convenient and effective manner.

[0022] In addition, the brief explanation of terms in this application is intended only to facilitate understanding of the embodiments described below, and is not intended to limit the embodiments of this application. Unless otherwise specified, these terms should be understood in their ordinary and customary sense.

[0023] The technical solution of the present application and the technical solution of the present application are described in detail below using specific examples. Some specific examples below may be combined with each other, and the same or similar concept or process may not be described in some examples. In the description of the present application, unless otherwise expressly specified 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, an equivalent resistance, an inductance value and a capacitance value of each circuit in the auxiliary inverter are obtained, the circuit is composed of two-phase circuits in the auxiliary inverter, 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, according to the equivalent resistance, inductance value, and capacitance value of each circuit, a simultaneous equation is established based on circuit conditions, 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 constitute 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 constitute 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 constitute the circuit. In step 203, the resistance of the circuits 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 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 the corresponding threshold values, it is determined that the auxiliary inverter is not degraded, and if not, 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 the 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 by 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 side of the three-phase three-bridge inverter and the three-phase four-bridge inverter is represented by a DC constant voltage source Vdc and is output through a filter, and the filter includes three-phase filter inductors and filter capacitors of a, b, and c, the equivalent resistance of the filter inductor is Rf, the inductance value is represented as Lf, the equivalent resistance of the filter capacitor is Rc, and the capacitance value is represented as 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 a fourth bridge compared with the three-phase three-bridge.

[0027] As for the auxiliary inverter, each phase circuit includes an inductor element and a capacitor element, and is configured as one circuit that makes any two of the phase circuits conductive. Figure 4 shows a circuit shown by taking a-phase and b-phase circuits as an example. As shown in Figure 4, the upper tube of the a-phase and the lower tube of the b-phase of the auxiliary inverter of the rail transit vehicle are made conductive to obtain the equivalent resistance, inductance value, and capacitance value of the circuit. At this time, the equivalent resistance of the circuit includes the sum of the resistance of the inductor element and the capacitor element in the a-phase circuit and the resistance of the inductor element and the capacitor element in the b-phase circuit, and is expressed as Rca + Rfa + Rcb + Rfb, where 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 value of the circuit may be expressed as La + Lb, where La is the inductance of the inductor element 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 the a-phase and b-phase circuits being conductive, the a-phase and c-phase circuits are conductive to form another circuit, and the equivalent resistance Rca+Rfa+Rcc+Rfc, inductance value La+Lc, and capacitance value Cac of the circuit composed of the a-phase and c-phase circuits are obtained. Similarly, the b-phase and c-phase circuits are conductive to obtain the equivalent resistance Rcb+Rfb+Rcc+Rfc, inductance value Lb+Lc, and capacitance value Cbc of the circuit composed of the b-phase and c-phase circuits. The equivalent resistances of the three circuits are connected in series to obtain the resistance of the circuit of each phase, and the resistance of the circuit of each phase is the sum of the resistance of the inductor element and the resistance of the capacitor element of the circuit of this phase. 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 the circuit for each phase are obtained by calculating the capacitance values ​​of the three circuits simultaneously. The capacitance value of the circuit for phase a is Ca. The capacitance value of the circuit for phase b is Cb, and the capacitance value of the circuit for phase c is Cc.

[0028] The obtained resistance of the circuit for each phase, the capacitance of the capacitor element, and the inductance of the inductor element are compared with reference values, and if any difference between the resistance of the circuit for each phase, the capacitance of the capacitor element, and the inductance of the inductor element and the reference value does 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 auxiliary inverter AC filter capacitor self-test method provided by Example 1 of the present application. As shown in FIG. 5, in step 201, obtaining an 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] Referring to the example shown in the scene, a DC step response is injected into the auxiliary inverter system, and U0 is the step input voltage. Figure 6 is a schematic diagram of the change of the inductor current and capacitor voltage of the illustrated auxiliary inverter AC filter according to the step input voltage. ipeak is the peak value of the inductor current, and uc is the capacitor voltage at the time of the peak value of the inductor current. Taking a and b phases as an example, the upper tube of the a phase and the lower tube of the b phase of the auxiliary inverter of the rail transit vehicle are turned on, and when the input voltage on the DC side is U0, the peak value ipeaka of the inductor current of the a phase filter in the step response system is measured. The peak value ipeakb of the inductor current of the b phase filter is the same as the peak value ipeaka of the inductor current of the a phase filter, which is the current of the circuit. At this time, since the inductor current is at its maximum value, the inductor voltage is partially set to 0, and the difference between the input voltage on the DC side 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 by dividing the voltage of Rca+Rfa+Rcb+Rfb by the current ipeaka in the circuit, we get the value of Rca+Rfa+Rcb+Rfb, which gives the equivalent resistance of the circuit.

[0031] Optionally, Fig. 7 is a flowchart of another auxiliary inverter AC filter capacitor self-test method provided by embodiment 1 of the present application. As shown in Fig. 7, in step 201, obtaining an inductance value and a 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 input voltage on the DC side of the auxiliary inverter is obtained. In step 702, the transfer function is compared with a standard second order system to obtain key parameters of the auxiliary inversion system in which the auxiliary inverter is placed. In step 703, obtain 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 located.

[0032] With reference to the example shown in the scene, the equivalent relational expression of the capacitor voltage of the circuit is calculated by using Kirchhoff's law formula for the conductive circuit, and the transfer function of the capacitor voltage for the step input of the DC side is obtained through Laplace transformation, and the transfer function is compared 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 judging the health state of the AC capacitor. Optionally, the main parameters of the auxiliary inverter system in which the auxiliary inverter is disposed include damping ratio, damped natural frequency, undamped natural frequency, overshoot and peak value time. The following formula is the expression of the standard second-order system shown as an example.

[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 formula illustrates the mathematical relationship between the five main parameters:

[0035]

number

[0036] Taking phase a and phase b as an example, the maximum value of the sum of the capacitor voltages in the phase a and b circuits of the auxiliary inverter of the rail transit vehicle is measured, and in the steady state, the sum of the capacitor voltages of phase a and b is equal to the amplitude of the DC input voltage, so the maximum value is measured and compared with the DC input Vdc to obtain the overshoot σ% of the filter capacitor voltage, and the damping ratio ζ can be inversely estimated. The time from the conduction of the switching element to the time 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 according to the damping ratio ζ. The inductance value of the phase a and b circuits is obtained according to the obtained values ​​of the main parameters, and the capacitance value of the circuit is estimated according to ωn. Based on the method of this example, the inductance value and capacitance value of each circuit can be obtained.

[0037] Referring to the example shown in the scene, the reference values ​​of the resistance of the circuit of each phase in the circuit, the capacitance of the capacitor element, and the inductance of the inductor element are U0=100V, La=Lb=Lc=Ln=150uH, Ca=Cb=Cc=1200uF, Rca+Rfa=Rcb+Rfb=Rcc+Rfc=0.2Ω. Figure 8 shows the simulation waveform of the step response of the exemplary auxiliary inverter filter. a shows the simulation waveform of the step response of the exemplary three-phase three-bridge inverter filter, and b shows the simulation waveform of the step response of the exemplary three-phase four-bridge inverter filter. The input voltage U0 is maintained at 100V, and the upper tube of phase a and the lower tube of phase c are turned on at 0.1s, and a step input is generated. The waveform of the sum of the voltages of the capacitors Ca and Cc is in the form of a standard underdamped oscillation of a secondary system. The final voltage is maintained at a stable 100V, the inductor currents iLa and iLb also have the form of a standard underdamped oscillation of a secondary system, and the final voltage is maintained at a stable 0A. When the lower tube of phase a and the lower tube of phase c are turned on at 0.15s, the capacitor voltage is discharged to 0V. When the upper tube of phase a and the lower tube of phase b are turned on at 0.2s, a step input is generated, and the waveform of the sum of the voltages of capacitors Ca and Cb has the form of a standard underdamped oscillation of a secondary system. The final voltage is maintained at a stable 100V, the inductor currents iLa and iLb also have the form of a standard underdamped oscillation of a secondary system, and the final voltage is maintained at a stable 0A. When the lower tube of phase a and the lower tube of phase b are turned on at 0.25s, the capacitor voltage is discharged to 0V. When the upper tube of phase b and the lower tube of phase c are turned on at 0.3s, a step input occurs, and the waveform of the sum of the capacitor Cb and Cc voltages takes the form of a standard underdamped oscillation of a secondary system. The final voltage is kept stable at 100V, and the inductor currents iLb and iLc also take the form of a standard underdamped oscillation of a secondary system, and the final current is kept stable at 0A. When the lower tube of phase b and the lower tube of phase c are turned on at 0.35s, the capacitor voltage is discharged to 0V. Table 1 shows the simulation results of the step response of the example three-phase four-bridge inverter system.

[0038] [Table 1]

[0039] By inverse estimation according to 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. It can be seen that these are basically consistent with the actual parameters of the circuit, with an error of about 1%.

[0040] Through practical design examples, it has been proven that the self-test method for the AC filter capacitor of the auxiliary inverter provided by the present application is applicable to the topology structures of a three-phase three-bridge inverter and a three-phase four-bridge inverter, and the errors between the calculation 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 value, and capacitance value of each circuit in the auxiliary inverter are obtained, and simultaneous equations are 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 equations. The circuit conditions include that the equivalent resistance of each circuit is the sum of the equivalent resistances of all the inductor elements and the capacitor elements in the two-phase circuits that constitute 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 constitute 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 constituting the circuit, and 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 are compared with corresponding reference values, and if the difference between the resistance of any 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 the corresponding threshold value, it is determined that the auxiliary inverter is not deteriorated. Otherwise, it is determined that the auxiliary inverter is deteriorated. According to the method provided by this embodiment, a DC step response can be injected into the auxiliary inverter system by conducting different circuits in the auxiliary inverter, and the 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 secondary 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 that makes up the circuit, 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, the inductance value of the inductor element, and the capacitance value of the capacitor element can be compared with reference values ​​to determine the degree of consumption of each element and whether or not it has deteriorated.In addition, the method provided by the present embodiment does not require dismantling of components, is applicable to the operation of the auxiliary inverter of the rail transit vehicle, has low program complexity, small calculation amount, simple operation, lower performance requirements for the controller, high measurement accuracy, and can implement self-test of the health status of the AC filter capacitor in a convenient and effective manner.

[0042] Example 2 9 is a structural schematic diagram of the self-test device for AC filter capacitor of auxiliary inverter provided by Example 2 of the present application. As shown in FIG. 9, the device includes the following modules: The acquisition module 91 is used for acquiring 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 includes 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 according to the equivalent resistance, inductance value and capacitance value of each circuit based on circuit conditions, and 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. The circuit conditions include that the equivalent resistance of each circuit is the sum of the equivalent resistances of all the inductor elements and the capacitor elements in the two-phase circuits constituting the circuit. The inductance value of each circuit is the sum of the inductance values ​​of the inductor elements in the two-phase circuits constituting 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 constituting the circuit. The comparison module 93 compares 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 the corresponding reference value, and if the 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 the corresponding threshold value, it is used to determine that the auxiliary inverter is not deteriorated, otherwise, it is used to determine that the auxiliary inverter is deteriorated.

[0043] With reference to the example shown in the scene, the acquisition module 91 makes the upper tube of the a-phase and the lower tube of the b-phase of the auxiliary inverter of the rail transit vehicle conduct, and obtains the equivalent resistance of the circuit, and the inductance value and the capacitance value. At this time, the equivalent resistance of the circuit includes the sum of the resistance of the inductor element and the capacitor element in the a-phase circuit and the resistance of the inductor element and the capacitor element 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 value of the circuit may 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 represented as Cab, and the capacitance value of the circuit 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 the a-phase and b-phase circuits being brought into conduction, the a-phase and c-phase circuits are brought into conduction to form another circuit, and the equivalent resistance Rca+Rfa+Rcc+Rfc, inductance value La+Lc, and capacitance value Cac of the circuit composed of the a-phase and c-phase circuits are obtained. Similarly, the b-phase and c-phase circuits are brought into conduction to obtain the equivalent resistance Rcb+Rfb+Rcc+Rfc, inductance value Lb+Lc, and capacitance value Cbc of the circuit composed of 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 the circuit of each phase, and the resistance of the circuit of each phase is the sum of the resistance of the inductor element and the resistance of the capacitor element of the circuit of this phase. That is, 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 combined 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 combined 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 obtained resistance of the circuit of each phase, the capacitance of the capacitor element, and the inductance of the inductor element with a reference value, and determines that the auxiliary inverter is not degraded if the difference 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 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 for acquiring the input voltage of the DC side 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. The acquisition module 91 is specifically further used for obtaining the difference between the DC side input voltage of the auxiliary inverter and the sum of the voltages of the capacitor elements in each circuit, and obtaining the voltage of the equivalent resistance of each circuit. The acquisition module 91 is further specifically used for obtaining the ratio between the voltage of the equivalent resistance of each circuit and the maximum current, and obtaining the equivalent resistance of each circuit.

[0046] Referring to 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 time of the peak value of the inductor current. Take phases a and b as an example, the upper tube of phase a and the lower tube of phase b of the auxiliary inverter of the rail transit vehicle are turned on, and the peak value ipeaka of the inductor current of the filter of phase a in the step response system is measured when the input voltage on the DC side is U0. The peak value ipeakb of the inductor current of the filter of phase b is the same as the peak value ipeaka of the inductor current of the filter of phase a, which is the current of the circuit. At this time, since the inductor current is at its maximum value, the inductor voltage is partially set to 0, and the difference between the input voltage on the DC side 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 by dividing the voltage Rca+Rfa+Rcb+Rfb by the circuit current ipeaka, we get the value of Rca+Rfa+Rcb+Rfb, which is the equivalent resistance of the circuit.

[0047] Optionally, the acquisition module 91 is further used for specifically acquiring a transfer function of the sum of the voltages of the capacitor elements in each circuit relative to the input voltage of the DC side of the auxiliary inverter. The acquisition module 91 is further specifically used for comparing the transfer function with a standard second-order system to obtain the main parameters of the auxiliary inversion system in which the auxiliary inverter is disposed. 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 disposed.

[0048] With reference to the example shown in the scene, the acquisition module 91 calculates the equivalent relational expression of the capacitor voltage of the circuit by using Kirchhoff's law formula for the conductive circuit, and obtains the transfer function of the capacitor voltage for the step input of the DC side through Laplace transformation, and compares the transfer function with a standard secondary system to obtain the main parameters of the auxiliary inverter system, thereby calculating the parameters of the AC filter of the auxiliary inverter and judging the health status of the AC capacitor. Optionally, the main parameters of the auxiliary inverter system in which the auxiliary inverter is disposed include damping ratio, damped natural frequency, undamped natural frequency, overshoot and peak value time.

[0049] Taking phase a and phase b as an example, the maximum value of the sum of the capacitor voltages in the phase a and b circuits of the auxiliary inverter of the rail transit vehicle is measured, and in the steady state, the sum of the capacitor voltages of phase a and b is equal to the amplitude of the DC input voltage, so the maximum value is measured and compared with the DC input Vdc to obtain the overshoot σ% of the filter capacitor voltage, and the damping ratio ζ can be inversely estimated. The time from the conduction of the switching element to the time 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 according to the damping ratio ζ. The inductance value of the phase a and b circuits is obtained according to the obtained values ​​of the main parameters, and the capacitance value of the circuit is estimated according to ωn. Based on the method of this example, the inductance value and capacitance value of each circuit can be obtained.

[0050] The acquisition module of this embodiment acquires the equivalent resistance, inductance value and capacitance value of each circuit in the auxiliary inverter. The calculation module establishes simultaneous equations according to the equivalent resistance, inductance value and capacitance value of each circuit based on circuit conditions, and obtains 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. 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 constituting the circuit. The inductance value of each circuit is the sum of the inductance values ​​of the inductor elements in the two-phase circuits constituting 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 constituting the circuit. The comparison module compares 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 a corresponding reference value, and determines that the auxiliary inverter is not degraded if the 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 all do not exceed the corresponding threshold value. Otherwise, determines that the auxiliary inverter is degraded. According to the method provided by this embodiment, a DC step response can be injected into the auxiliary inverter system by conducting different circuits in the auxiliary inverter, and sampled to obtain the step response signals of the filter inductor current and the filter capacitor voltage. By comparing the waveform with a standard secondary 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 that makes up the circuit, 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, the inductance value of the inductor element, and the capacitance value of the capacitor element can be compared with reference values ​​to determine the degree of consumption of each element and whether or not it has deteriorated.In addition, the method provided by the present embodiment does not require dismantling of components, is applicable to the operation of the auxiliary inverter of the rail transit vehicle, has low program complexity, small calculation amount, simple operation, lower performance requirements for the controller, high measurement accuracy, and can implement self-test of the health status of the AC filter capacitor in a convenient and effective manner.

[0051] Example 3 Figure 10 is a structural schematic diagram of an electronic device provided in Example 3 of the present application. As shown in Figure 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 each other through 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 execute the method of the above Example 1.

[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 execute functional applications and data processing, i.e., to implement the method of the above 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 according to the embodiment described above.

[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 filed 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 to be 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 various modifications and variations are possible without departing from the scope thereof, which is limited only by the appended claims.

Claims

1. 1. A method for self-testing an AC filter capacitor of an auxiliary inverter, comprising: Obtaining an equivalent resistance, and 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 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, 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 the capacitor elements in the two-phase circuits that constitute 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 constitute 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 constitute the circuit; comparing the resistance of the circuit for each phase, the inductance value of an inductor element in the circuit for each phase, and the capacitance value of a 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 Obtaining a DC input voltage of the auxiliary inverter, a sum of voltages of the capacitor elements in each circuit, and a maximum current flowing through an 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 method of claim 1, further comprising: determining a ratio of a voltage across an equivalent resistance of each circuit to said maximum current to obtain an equivalent resistance of each circuit.

3. Obtaining the inductance value and the capacitance value of each circuit in the auxiliary inverter Obtaining a transfer function of a sum of voltages of capacitor elements in each circuit with respect to a DC 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 according to claim 2, further comprising: obtaining an inductance value and a capacitance value of each circuit according to an equivalent resistance of each circuit and main parameters of an auxiliary inverter system in which the auxiliary inverter is arranged.

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 arranged include: damping ratio, damped natural frequency, undamped natural frequency, overshoot, and 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. A self-test device for an AC filter capacitor of an auxiliary inverter, comprising: An acquisition module for acquiring 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 includes an inductor element and a capacitor element, and different circuits are composed of different two-phase circuits; a calculation module used for 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 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 the inductor elements and the capacitor elements in the two-phase circuits constituting the circuit, the inductance value of each circuit is the sum of the inductance values ​​of the inductor elements in the two-phase circuits constituting 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 constituting the circuit; a comparison module for 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 value does not exceed a corresponding threshold value, and determining that the auxiliary inverter is degraded if not.

7. The acquisition module is specifically used for acquiring 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; The acquisition module is specifically further used for obtaining 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 obtaining 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 a ratio between the voltage of an equivalent resistance of each circuit and the maximum current, and obtaining an equivalent resistance of each circuit.

8. The acquisition module is specifically further used for acquiring a transfer function of a sum of the voltages of the capacitor elements in each circuit relative to the DC input voltage of the auxiliary inverter; The acquisition module is further specifically used for comparing the transfer function with a standard secondary system to obtain key parameters of an auxiliary inverter system in which the auxiliary inverter is disposed; 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 an equivalent resistance of each circuit and main parameters of an auxiliary inverter system in which the auxiliary inverter is disposed.

9. An electronic device including a processor and a memory communicatively connected to the processor, the memory storing 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. A computer-readable storage medium having stored thereon computer-executable instructions, the computer-executable instructions being used, when executed by a processor, to implement a self-test method according to any one of claims 1 to 5.

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