JP7306093B2 - Capacitance measuring device, deterioration diagnosis device, deterioration diagnosis method and capacitance measurement program - Google Patents

Description

The present invention relates to a capacitance measurement device, a deterioration diagnosis device, a capacitance measurement method, a deterioration diagnosis method, and a capacitance measurement program.

A capacitance measuring device for measuring the capacitance of a capacitor is known in the prior art. For example, Patent Literature 1 discloses an apparatus equipped with a measuring device for measuring characteristic values such as capacitance of a capacitor. The device stores the characteristic values of the capacitor measured by the measuring instrument in a database.

Japanese Patent Application Laid-Open No. 2004-37258 (published on February 5, 2004)

Patent Document 1 does not disclose details of a method for measuring the capacitance of a capacitor. Therefore, the device disclosed in Patent Document 1 has room for further improvement regarding the method of measuring the capacitance of the capacitor. An object of one embodiment of the present invention is to easily calculate the capacitance of a capacitor.

In order to solve the above problems, a capacitance measuring device according to an aspect of the present invention provides an input for inputting a voltage measurement value of a voltage applied to a capacitor and a current measurement value of a current flowing through the capacitor. a voltage change rate measuring unit for measuring a first voltage change rate of the voltage applied to the capacitor at a predetermined time from the voltage measurement input by the input unit; With reference to the voltage measurement value and the current measurement value, at least from the voltage measurement value and the current measurement value at the predetermined time and the first voltage change rate measured by the voltage change rate measurement unit and a calculation unit that calculates the capacitance of the capacitor.

According to the above configuration, the capacitance of the capacitor can be easily calculated using the voltage measurement value, current measurement value, and voltage change rate of the capacitor. Therefore, a capacitance measuring device for measuring the capacitance of a capacitor can be realized at low cost.

The voltage change rate measurement unit measures the first voltage change rate at two points of time as the predetermined points of time, and the calculation unit measures the voltage measurement value and the current measurement value at the two points of time, The capacitance of the capacitor may be calculated from the first voltage change rate at the two points in time measured by the voltage change rate measuring unit. According to the above configuration, the capacitance of the capacitor can be easily calculated by referring to each value for calculating the capacitance of the capacitor at two points in time.

The time period between the two points in time may be less than or equal to a predetermined time period. According to the above configuration, for example, the period between two points in time is set to be less than or equal to the predetermined period so that the change in each value for calculating the capacitance of the capacitor is small at the two points in time. Thereby, the accuracy of calculation of the capacitance of the capacitor can be improved.

The capacitance measuring device further includes a current change rate measuring unit that measures a current change rate of the current flowing through the capacitor at the predetermined time from the current measurement value input by the input unit, and the voltage change The rate measurement unit further measures a second voltage change rate that is a value obtained by differentiating the first voltage change rate, and the calculation unit measures the voltage measurement value and the current measurement value at the predetermined point in time, and the In addition to the first voltage change rate measured by the voltage change rate measuring section, the second voltage change rate measured by the voltage change rate measuring section and the current change rate measuring section The capacitance of the capacitor may be calculated from the rate of current change.

According to the above configuration, the capacitance of the capacitor is calculated using the second voltage change rate, which is a value obtained by differentiating the first voltage change rate. For example, when obtaining the second voltage change rate by approximation, more information is used than when obtaining the first voltage change rate. Therefore, by calculating the capacitance of the capacitor using the second voltage change rate, it is possible to improve the accuracy of calculating the capacitance of the capacitor.

In order to solve the above-described problems, a degradation diagnosis device according to an aspect of the present invention includes an input unit for inputting a voltage measurement value of a voltage applied to a capacitor and a current measurement value of a current flowing through the capacitor. a voltage change rate measurement unit for measuring a voltage change rate of the voltage applied to the capacitor at a predetermined time from the voltage measurement value input by the input unit; and the voltage measurement value input by the input unit. and the current measurement value, and based on at least the voltage measurement value and the current measurement value at the predetermined time and the voltage change rate measured by the voltage change rate measuring unit, the capacitance of the capacitor and a calculation unit for calculating the admittance of the leakage current, the amount of decrease in the capacitance of the capacitor from the initial value calculated by the calculation unit, and the admittance of the leakage current of the capacitor calculated by the calculation unit an amount of increase from the initial value; and a result output unit for outputting the result of deterioration diagnosis of the capacitor.

According to the above configuration, for each of a wide variety of capacitors, deterioration diagnosis of the capacitor can be easily performed without constructing a database for diagnosing the characteristics of the capacitor and the deterioration of the capacitor, which serve as criteria for diagnosis. Therefore, compared with the case of constructing the database, it is possible to realize a deterioration diagnosis device for diagnosing deterioration of capacitors at a low cost.

The result output unit may further output a life prediction result of the capacitor from the amount of decrease and the amount of increase. According to the above configuration, it is possible to confirm the result of life prediction of the capacitor in addition to the result of deterioration diagnosis of the capacitor.

In order to solve the above problems, a capacitance measurement method according to an aspect of the present invention includes a voltage measurement step of measuring a voltage applied to a capacitor as a voltage measurement value; a voltage change rate measurement step of measuring a voltage change rate of the voltage applied to the capacitor at a predetermined time from the voltage measurement value measured in the voltage measurement step; and the voltage With reference to the voltage measurement value and the current measurement value measured in the measuring step and the current measurement step, respectively, at least the voltage measurement value and the current measurement value at the predetermined time and the voltage change rate measurement and a calculating step of calculating the capacitance of the capacitor from the voltage change rate measured in the step.

In order to solve the above problems, a deterioration diagnosis method according to an aspect of the present invention includes a voltage measurement step of measuring a voltage applied to a capacitor as a voltage measurement value, and a current flowing through the capacitor as a current measurement value. a voltage change rate measuring step of measuring a voltage change rate of the voltage applied to the capacitor at a predetermined time from the voltage measurement value measured in the voltage measuring step; and the voltage measuring step and the voltage measurement value and the current measurement value measured in each of the current measurement steps, and at least the voltage measurement value and the current measurement value at the predetermined point in time, and the voltage change rate measurement step a calculation step of calculating the capacitance of the capacitor and the admittance of the leakage current from the voltage change rate measured by the method; and an amount of decrease from the initial value in the capacitance of the capacitor calculated in the calculation step and a result outputting step of outputting the result of deterioration diagnosis of the capacitor from the amount of increase from the initial value of the admittance of the leakage current of the capacitor calculated in the calculating step.

In order to solve the above problems, a capacitance measurement program according to an aspect of the present invention is a capacitance measurement program for causing a computer to function as the capacitance measurement device, comprising: the input unit, the It may be for causing a computer to function as the voltage change rate measuring unit and the calculating unit.

According to one aspect of the present invention, the capacitance of a capacitor can be easily calculated.

1 is a block diagram showing the configuration of a vehicle equipped with a capacitance measuring device according to Embodiment 1 of the present invention; FIG. FIG. 2 is a diagram showing an equivalent circuit for a capacitor provided in the power conversion device included in the vehicle shown in FIG. 1; 4 is a graph showing measurement results of voltage and current of a capacitor in an experimental example relating to the processing of the calculation unit of the capacitance measuring device provided in the vehicle shown in FIG. 1; 7 is a graph showing calculation results of the capacitance of a capacitor and the admittance of leakage current in an experimental example regarding the processing of the calculation unit. FIG. 5 is a graph obtained by changing the horizontal axis from time to electric field in the graph shown in FIG. 4 . BRIEF DESCRIPTION OF THE DRAWINGS It is a block diagram which shows the structure of a product inspection apparatus provided with the capacitance measuring device which concerns on Embodiment 1 of this invention. FIG. 2 is a block diagram showing the configuration of a vehicle equipped with a capacitance measuring device according to Embodiment 2 of the present invention; FIG.

[Embodiment 1]
(Configuration of capacitance measuring device 10)
A configuration of the capacitance measuring device 10 will be described with reference to FIG. FIG. 1 is a block diagram showing the configuration of a vehicle V1 equipped with a capacitance measuring device 10 according to Embodiment 1 of the present invention. A vehicle V1 such as a HEV (Hybrid Electric Vehicle) or an EV (Electric Vehicle) includes a power converter E1 as shown in FIG.

The power conversion device E1 is a device that performs power conversion between direct current and alternating current. The power conversion device E1 includes a deterioration diagnosis device 1, a capacitor 2, a voltmeter 3, an ammeter 4, and a storage unit 5. A deterioration diagnosis device 1 is connected to a capacitor 2 , a voltmeter 3 , an ammeter 4 and a storage unit 5 . A capacitor 2 is connected in parallel with a voltmeter 3 and in series with an ammeter 4 . Note that the voltmeter 3 and the ammeter 4 may be located outside the power converter E1 and provided in the vehicle V1.

A film capacitor, for example, is preferably used as the capacitor 2 . A film capacitor is constructed by evaporating a metal onto a plastic film and winding the film. Film capacitors are characterized by being able to handle high voltages, having good high-frequency characteristics, and having little dielectric loss, compared to ceramic capacitors and electrolytic capacitors.

Therefore, film capacitors are widely used in electronic applications, vehicle applications, and industrial applications. Thus, by using a film capacitor as the capacitor 2 of the power conversion device E1 provided in the vehicle V1, it is possible to handle high voltage, improve high frequency characteristics, and reduce dielectric loss.

The voltmeter 3 measures the voltage applied to the capacitor 2 as a voltage measurement value (voltage measurement step). The voltmeter 3 provides the deterioration diagnosis device 1 with the voltage measurement value obtained by the measurement. The ammeter 4 measures the current flowing through the capacitor 2 as a current measurement value (current measurement step). The ammeter 4 provides the deterioration diagnosis device 1 with the current measurement value obtained by the measurement.

The deterioration diagnosis device 1 is a device that diagnoses deterioration of the capacitor 2 . When installed in the vehicle V1, the deterioration diagnosis device 1 diagnoses the deterioration of the capacitor 2 while the vehicle V1 is in operation. Note that the deterioration diagnosis device 1 may be provided in an industrial machine other than the vehicle V1. The deterioration diagnostic device 1 includes a capacitance measuring device 10 and a result output section 140 . A capacitance measuring device 10 is a device that measures the capacitance of the capacitor 2 . The capacitance measuring device 10 includes an input section 110 , a voltage change rate measuring section 120 and a calculating section 130 .

The input unit 110 inputs the voltage measurement value provided to the deterioration diagnosis device 1 from the voltmeter 3 and the current measurement value provided to the deterioration diagnosis device 1 from the ammeter 4 . In other words, the input unit 110 inputs a voltage measurement value of the voltage applied to the capacitor 2 and a current measurement value of the current flowing through the capacitor 2 . The input unit 110 stores the input voltage measurement value and current measurement value in the storage unit 5 .

The voltage change rate measurement unit 120 measures a first voltage change rate (voltage change rate) of the voltage applied to the capacitor 2 at a predetermined time from the voltage measurement value input by the input unit 110 (voltage change rate measurement). process). The first voltage change rate is, for example, a value obtained by first-order differentiation of the voltage applied to the capacitor 2 at a predetermined time. At this time, voltage change rate measurement unit 120 refers to the voltage measurement value stored in storage unit 5 . Voltage change rate measurement unit 120 stores the measured first voltage change rate in storage unit 5 . The predetermined point in time is appropriately determined by the user who uses the deterioration diagnosis device 1 . Details of the predetermined time will be described later.

The calculation unit 130 refers to the voltage measurement value and current measurement value input by the input unit 110 . Further, the calculation unit 130 calculates the capacitance and leakage current admittance of the capacitor 2 from the voltage measurement value and the current measurement value at the predetermined time and the first voltage change rate measured by the voltage change rate measurement unit 120. Calculate At this time, the calculation unit 130 refers to the voltage measurement value, current measurement value, and first voltage change rate stored in the storage unit 5 . The calculating unit 130 stores the calculated capacitance of the capacitor 2 and the calculated admittance of the leakage current in the storage unit 5 .

Note that in the second embodiment described later, the calculation unit 130A calculates the second voltage change rate, the current change rate, in addition to the voltage measurement value and the current measurement value at the predetermined time and the first voltage change rate. , the capacitance of the capacitor 2 and the admittance of the leakage current are calculated.

Therefore, the calculation unit according to one aspect of the present invention calculates the value of the capacitor 2 from at least the voltage measurement value and the current measurement value at the predetermined time and the first voltage change rate measured by the voltage change rate measurement unit 120. Calculate the admittance of the capacitance and leakage current (calculation step). According to the above configuration, the capacitance of the capacitor 2 can be easily calculated using the voltage measurement value, the current measurement value and the first voltage change rate of the capacitor 2 . Therefore, the capacitance measuring device 10 for measuring the capacitance of the capacitor 2 can be realized at low cost.

(Details of Processing by Calculation Unit 130)
In the calculation process of the capacitance of the capacitor 2 and the admittance of the leakage current in the calculation unit 130, the equivalent circuit shown in FIG. 2 is considered for the capacitor 2 that is the target of deterioration diagnosis. FIG. 2 is a diagram showing an equivalent circuit for the capacitor 2 provided in the power converter E1 provided in the vehicle V1 shown in FIG. As shown in FIG. 2, let us consider a case where a current I flows from the outside of the capacitor 2 to the capacitor 2 .

In this case, the current I will be the current measured by the ammeter 4 . Also, a leakage current I2 is generated in the capacitor 2 . A current obtained by subtracting the leakage current I2 from the current I is defined as a current I1. That is, the current I is equal to the sum of the currents I1 and I2. Here, let C be the capacitance of the capacitor 2 and Y be the admittance of the leakage current I2 of the capacitor 2 . The admittance Y is the parallel admittance with the capacitor 2, and is the admittance of the leakage current I2.

In addition, the two predetermined time points are a time point (t−a seconds) after a second from a certain time point (t seconds) and a time point (t+a seconds) after a second from a certain time point (t seconds). Consider the case of time points. In this case, the calculator 130 calculates the capacitance C and the admittance Y of the capacitor 2 by measuring the voltage V(ta), the current I(ta) and A first voltage change rate dV(ta)/dt is used.

Further, the calculator 130 uses the measured voltage value V(t+a), the measured current value I(t+a), and the first voltage change rate dV(t+a)/dt at t+a seconds. At this time, the voltage change rate measuring unit 120 measures the first voltage change rates dV(ta)/dt and dV(t+a)/dt at the two time points as the predetermined time points. When the calculator 130 uses these values, simultaneous equations of the following equations (1) and (2) are obtained from the equivalent circuit shown in FIG.

Consider the above system of equations as a second-order linear system of equations, and consider the voltage measurements and the first rate of voltage change at the two points in time as coefficients of the system of equations. Also consider the current measurements at the two points in time as known variables, and the capacitance and addance of capacitor 2 as unknown variables. As a result, the following formula (3) is obtained.

When the simultaneous equations are constructed in this way, as shown in the following equation (4), the calculation unit 130 calculates the electrostatic capacity of the capacitor 2 at a certain point in time (t seconds) by a simple 2-row, 2-column inverse matrix calculation. Capacitance C and admittance Y can be calculated. That is, the calculation unit 130 performs calculation processing of formulas (1) to (4) to calculate the capacitance C and the admittance Y of the capacitor 2 at a certain point in time (t seconds).

In this way, the calculation unit 130 calculates the capacitor 2 from the voltage measurement value and the current measurement value at the two time points and the first voltage change rate at the two time points measured by the voltage change rate measurement unit 120. , and the admittance Y of the leakage current I2 is calculated. According to the above configuration, by referring to the respective values for calculating the capacitance C of the capacitor 2 and the admittance Y of the leakage current I2 at the two points in time, the capacitance C of the capacitor 2 and the leakage current I2 can be easily calculated.

Moreover, it is preferable that the period (2a seconds) between the time point (t−a seconds) and the time point (t+a seconds) is less than or equal to the predetermined period. In other words, the period between the two points in time is preferably equal to or shorter than the predetermined period. According to the above configuration, for example, between the two points in time, the change in each value for calculating the capacitance C of the capacitor 2 and the admittance Y of the leakage current I2 is small. A period is set to a predetermined period or less. Thereby, the accuracy of calculation of the capacitance C of the capacitor 2 and the admittance Y of the leakage current I2 can be improved.

The result output unit 140 refers to the capacitance C of the capacitor 2 and the admittance Y of the leakage current I2 calculated by the calculation unit 130 from the storage unit 5 . The result output unit 140 outputs the deterioration diagnosis result of the capacitor 2 based on the amount of decrease in the capacitance C of the capacitor 2 from the initial value and the amount of increase in the admittance Y of the leakage current I2 of the capacitor 2 from the initial value. (result output step).

According to the above configuration, for each of a wide variety of capacitors 2, deterioration diagnosis of the capacitor 2 can be easily performed without constructing a database for diagnosing the characteristics of the capacitor 2 and the deterioration of the capacitor 2, which serve as diagnostic criteria. be able to. Therefore, the deterioration diagnosis device 1 for diagnosing the deterioration of the capacitor 2 can be realized at a low cost compared to the case of constructing the database.

Further, the result output unit 140 predicts the service life of the capacitor 2 based on the amount of decrease in the capacitance C of the capacitor 2 from the initial value and the amount of increase in the admittance Y of the leakage current I2 of the capacitor 2 from the initial value. may also be output. According to the above configuration, in addition to the result of the deterioration diagnosis of the capacitor 2, the result of life prediction of the capacitor 2 can be confirmed. In addition to this, it is possible to easily predict the life of the capacitor 2 without building a database for predicting the life of the capacitor 2 .

The initial value of the capacitance C of the capacitor 2 is determined as the rated value of the capacitor 2 . Also, the initial value of the admittance Y of the capacitor 2 is determined by the rated value of the leakage current I2 of the capacitor 2 . Therefore, even if the capacitor 2 is of various types, the initial values of the capacitance C and admittance Y of the capacitor 2 are determined by the rated values. Therefore, deterioration diagnosis and lifetime prediction of the capacitor 2 can be easily performed from the amount of decrease in the capacitance C from the initial value and the amount of increase in the admittance Y from the initial value.

Note that the result output unit 140 calculates the capacitance C of the capacitor 2 based on the ratio of the amount of decrease from the initial value in the capacitance C of the capacitor 2 and the ratio of the amount of increase in the admittance Y of the leak current I2 of the capacitor 2 from the initial value. The result of degradation diagnosis and the result of life prediction may be output. The ratio of the amount of decrease from the initial value in the capacitance C is the ratio occupied by the amount of decrease when the initial value is 100%. The ratio of the amount of increase in admittance Y from the initial value is the ratio occupied by the amount of increase when the initial value is 100%.

If the ratio of the amount of decrease in the capacitance C from the initial value is greater than or equal to the first predetermined value and the ratio of the amount of increase in the admittance Y from the initial value is greater than or equal to the second predetermined value, the result output unit 140 , the deterioration diagnosis result may be output assuming that the capacitor 2 is deteriorated. The result output unit 140 may sequentially output the deterioration diagnosis result and the life prediction result of the capacitor 2 during operation of the vehicle V1.

(Experimental example)
Next, experimental examples regarding the processing of the calculation unit 130 will be described with reference to FIGS. 3 to 5. FIG. In this experimental example, a high voltage DC power supply was used to apply a high voltage to the capacitor, and the voltage and current of the capacitor were measured. The capacitor to be evaluated is a film capacitor obtained by winding a polypropylene film having an electrode area of 1 m ² and a thickness of 4 μm with aluminum deposited thereon. Voltage and current were measured with a logger, and capacitance and admittance were calculated from the measured data using spreadsheet software such as a spreadsheet.

FIG. 3 is a graph showing measurement results of the voltage and current of the capacitor 2 in an experimental example regarding the processing of the calculator 130 of the capacitance measuring device 10 provided in the vehicle V1 shown in FIG. In FIG. 3, the horizontal axis is time [seconds], the left vertical axis is voltage [V], and the right vertical axis is current [A]. Also, VN indicates voltage and IN indicates current.

FIG. 4 is a graph showing calculation results of the capacitance C of the capacitor 2 and the admittance Y of the leakage current I2 in an experimental example regarding the processing of the calculation unit 130. As shown in FIG. Specifically, the graph G1 is a graph showing the calculation results of the capacitance C of the capacitor 2, and the graph G2 is a graph showing the calculation results of the admittance Y of the leakage current I2 of the capacitor 2. FIG.

In graph G1, the horizontal axis is time [seconds] and the vertical axis is capacitance [F]. In graph G2, the horizontal axis is time [seconds] and the vertical axis is admittance [S]. The graph G1 and the graph G2 are graphs created by calculation using the formulas (1) to (4) described above.

FIG. 5 is a graph obtained by changing the horizontal axis from time to electric field in the graph shown in FIG. Specifically, graph G3 is a graph obtained by changing the horizontal axis from time to electric field from graph G1, and graph G4 is a graph obtained by changing the horizontal axis from time to electric field from graph G2. In the graph G3, the horizontal axis is the electric field [V/μm] and the vertical axis is the capacitance [F]. In the graph G4, the horizontal axis is the electric field [V/μm] and the vertical axis is the admittance [S].

The change from time to electric field is done using the relationship between time and electric field. Dividing the voltage in the graph shown in FIG. 3 by the thickness of the polypropylene film (4 μm) results in the electric field in the graph shown in FIG. Thus, the relationship between time and electric field is obtained from the graph shown in FIG. 3 and the thickness of the polypropylene film. The electric field shown in FIG. 5 stresses the capacitor.

The result output unit 140 outputs the deterioration diagnosis result and the life prediction result of the capacitor 2 with reference to the graph as shown in FIG. In other words, the result output unit 140 refers to the relationship between the electric field and the capacitance C of the capacitor 2 and the relationship between the electric field and the admittance Y of the capacitor 2 to obtain the result of deterioration diagnosis and life prediction of the capacitor 2. Print the result.

Capacitance and admittance can be calculated from a simple voltage waveform and current waveform as shown in FIG. be able to.

Here, the predetermined point in time is appropriately determined by the user who uses the deterioration diagnosis device 1, as described above. For example, the user assumes that the stress on the capacitor is an electric field of 450 V/μm. In this case, since the thickness of the polypropylene film is 4 μm, the voltage VN at which the electric field is 450V is 450×4=1800V.

As shown in FIG. 3, it takes 16 seconds for the voltage VN to reach 1800V. Therefore, the user determines a time point (16-a seconds) when the time is a second backward from 16 seconds and a time point (16+a seconds) when the time is a second forward from 16 seconds as the predetermined time points. It should be noted that in Embodiment 2, which will be described later, the user determines the time point of 16 seconds as the predetermined time point.

(Modification)
Next, a modified example of application of the degradation diagnostic device 1 will be described with reference to FIG. FIG. 6 is a block diagram showing the configuration of a product inspection device A1 including the capacitance measuring device 10 according to Embodiment 1 of the present invention. The product inspection device A1 is a device that inspects a vehicle V2 as a product. The product inspection device A1, for example, inspects the performance of the capacitor 2 provided in the power conversion device E2 provided in the vehicle V2.

Vehicle V2 is different from vehicle V1 in that power conversion device E1 is changed to power conversion device E2. The power electronics device E2 differs from the power electronics device E1 in that it does not include the deterioration diagnosis device 1 . The voltmeter 3, the ammeter 4, and the storage unit 5 may be provided in the power converter E2.

The product inspection device A1 includes a deterioration diagnosis device 1, a voltmeter 3, an ammeter 4, and a storage unit 5, as shown in FIG. A capacitor 2 provided in a power conversion device E2 provided in a vehicle V2 is connected to a deterioration diagnosis device 1, a voltmeter 3 and an ammeter 4 provided in a product inspection device A1.

When installed in the product inspection device A1, the deterioration diagnosis device 1 diagnoses the deterioration of the capacitor 2 installed in the vehicle V2 when the product inspection device A1 inspects the vehicle V2. The deterioration diagnosis device 1 may be provided in a product inspection device that inspects other industrial machines other than the vehicle V2. conduct.

That is, the deterioration diagnostic device 1 may be provided in a product inspection device instead of a vehicle as a product. Therefore, the scope of application of the present invention is not limited to the deterioration diagnosis apparatus provided in the vehicle V1 as a product including the capacitor 2, but the deterioration diagnosis apparatus provided in the product inspection apparatus A1 for inspecting the vehicle V2 as a product. It also applies to equipment.

[Embodiment 2]
A second embodiment of the present invention will be described with reference to FIG. For convenience of description, members having the same functions as the members described in the first embodiment are denoted by the same reference numerals, and description thereof will not be repeated. FIG. 7 is a block diagram showing the configuration of a vehicle V3 equipped with a capacitance measuring device 10A according to Embodiment 2 of the present invention.

As shown in FIG. 7, the vehicle V3 differs from the vehicle V1 in that the capacitance measuring device 10 is changed to a capacitance measuring device 10A. As a result, in the vehicle V3, the degradation diagnostic device 1 is changed to the degradation diagnostic device 1A, and the power conversion device E1 is changed to the power conversion device E3, compared with the vehicle V1.

Capacitance measuring device 10A differs from capacitance measuring device 10 in that voltage change rate measuring unit 120 is changed to voltage change rate measuring unit 120A, and calculating unit 130 is changed to calculating unit 130A. and the provision of a current change rate measuring section 150. FIG.

In addition to the first voltage change rate measurement section, voltage change rate measurement section 120A also measures a second voltage change rate that is a value obtained by differentiating the first voltage change rate. The second voltage change rate is, for example, a value obtained by second-order differentiation of the voltage applied to the capacitor 2 at the predetermined time, and a value obtained by first-order differentiation of the first voltage change rate. At this time, voltage change rate measurement unit 120A refers to the first voltage change rate stored in storage unit 5 . Voltage change rate measurement unit 120A stores the measured second voltage change rate in storage unit 5 .

The current change rate measurement unit 150 measures the current change rate of the current flowing through the capacitor 2 at the predetermined time from the current measurement value input by the input unit 110 . The current change rate is, for example, a value obtained by first-order differentiation of the current flowing through the capacitor 2 at the predetermined time. At this time, current change rate measurement section 150 refers to the current measurement value stored in storage section 5 . Current change rate measurement unit 150 stores the measured current change rate in storage unit 5 .

The calculation unit 130A refers to the voltage measurement value and current measurement value input by the input unit 110 . In addition to the voltage measurement value and the current measurement value at the predetermined time and the first voltage change rate measured by the voltage change rate measurement unit 120A, the calculation unit 130A The capacitance of the capacitor 2 and the admittance of the leakage current are calculated from the second voltage change rate thus obtained and the current change rate measured by the current change rate measuring unit 150 .

At this time, the calculation unit 130A refers to the voltage measurement value, current measurement value, first voltage change rate, second voltage change rate, and current change rate stored in the storage unit 5 . The calculation unit 130A stores the calculated capacitance of the capacitor 2 and the calculated admittance of the leakage current in the storage unit 5 .

(Details of Processing of Calculation Unit 130A)
Similar to the calculation process of the calculation part 130, the equivalent circuit shown in FIG. Here, let us consider a case where a given point in time (t seconds) is the predetermined point in time. In this case, the calculator 130A uses the following values to calculate the capacitance C and the admittance Y of the capacitor 2.

Specifically, the calculation unit 130A calculates the voltage measurement value V(t), the current measurement value I(t), the first voltage change rate dV(t)/dt, and the second voltage change rate ^d2V in t seconds. (t)/dt ² and current rate of change dI(t)/dt are used. When the calculator 130A uses these values, simultaneous equations of the following equations (5) and (6) are obtained from the equivalent circuit shown in FIG.

Also, the following equation (7) is obtained from the above equations (5) and (6). Then, the following formula (8) is obtained from the formula (7).

Furthermore, the voltage measurement value, current measurement value, first voltage change rate, second voltage change rate, and current change rate of the capacitor 2 are obtained by AD (Analog-Digital) conversion of the analog signal at a sampling period of Δt seconds. be done. Calculation of these values is done in digital signal processing. Therefore, the process of time differentiation of voltage and current is replaced by the following equations (9) and (10) by applying the finite difference method.

In the above equations (9) and (10), the voltage and current at a time point (t + Δt seconds) advanced by a predetermined minute time (Δt seconds) from a certain time point (t seconds) are Vi and Ii, respectively. Let the voltage and current at time (t seconds) be Vj and Ij, respectively. Also, let Vk be the voltage at a point in time (t−Δt seconds) after a predetermined microscopic time (Δt seconds) from a certain point in time (t seconds).

Thus, the calculator 130A can calculate the capacitance C and the admittance Y of the capacitor 2 at a certain time (t seconds). That is, the calculation unit 130A performs the calculation processing of formulas (5) to (10) to calculate the capacitance C and the admittance Y of the capacitor 2 at a certain point in time (t seconds).

According to the above configuration, the capacitance C of the capacitor 2 and the admittance Y of the leakage current I2 are calculated using the second voltage change rate, which is a value obtained by differentiating the first voltage change rate. For example, when obtaining the second voltage change rate by approximation, more information is used than when obtaining the first voltage change rate. Therefore, by calculating the capacitance and the admittance Y of the capacitor 2 using the second voltage change rate, the accuracy of calculation of the capacitance and the admittance Y of the capacitor 2 can be improved.

[Example of realization by software]
The control blocks of the deterioration diagnosis devices 1 and 1A (especially the input unit 110, the voltage change rate measurement units 120 and 120A, the calculation units 130 and 130A, the result output unit 140 and the current change rate measurement unit 150) are integrated circuits (IC chips). It may be implemented by a logic circuit (hardware) formed in the same manner as above, or may be implemented by software.

In the latter case, the deterioration diagnosis devices 1 and 1A are provided with computers that execute instructions of programs, which are software for realizing each function. This computer includes, for example, one or more processors, and a computer-readable recording medium storing the program. In the computer, the processor reads the program from the recording medium and executes it, thereby achieving the object of the present invention. As the processor, for example, a CPU (Central Processing Unit) can be used. As the recording medium, a "non-temporary tangible medium" such as a ROM (Read Only Memory), a tape, a disk, a card, a semiconductor memory, a programmable logic circuit, or the like can be used. Further, a RAM (Random Access Memory) for expanding the program may be further provided. Also, the program may be supplied to the computer via any transmission medium (communication network, broadcast wave, etc.) capable of transmitting the program. Note that one aspect of the present invention can also be implemented in the form of a data signal embedded in a carrier wave in which the program is embodied by electronic transmission.

The present invention is not limited to the above-described embodiments, but can be modified in various ways within the scope of the claims, and can be obtained by appropriately combining technical means disclosed in different embodiments. is also included in the technical scope of the present invention.

1, 1A deterioration diagnosis device 2 capacitor 10, 10A capacitance measurement device 110 input unit 120, 120A voltage change rate measurement unit 130, 130A calculation unit 140 result output unit 150 current change rate measurement unit

Claims (5)

an input for inputting a voltage measurement of the voltage applied to the capacitor and a current measurement of the current flowing through the capacitor;
a voltage change rate measuring unit that measures a first voltage change rate of the voltage applied to the capacitor at a predetermined time from the voltage measurement value input by the input unit;
With reference to the voltage measurement value and the current measurement value input by the input unit, at least the voltage measurement value and the current measurement value at the predetermined time and the voltage change rate measurement unit 1 voltage change rate and a calculation unit that calculates the capacitance of the capacitor from
a current change rate measurement unit that measures the current change rate of the current flowing through the capacitor at the predetermined time from the current measurement value input by the input unit;
The voltage change rate measuring unit further measures a second voltage change rate that is a value obtained by differentiating the first voltage change rate,
The calculation unit
In addition to the voltage measurement value and the current measurement value at the predetermined time and the first voltage change rate measured by the voltage change rate measurement unit,
and calculating the capacitance of the capacitor from the second voltage change rate measured by the voltage change rate measuring unit and the current change rate measured by the current change rate measuring unit. Capacitance measuring device. an input for inputting a voltage measurement of the voltage applied to the capacitor and a current measurement of the current flowing through the capacitor;
a voltage change rate measuring unit that measures a voltage change rate of the voltage applied to the capacitor at a predetermined time from the voltage measurement value input by the input unit;
With reference to the voltage measurement value and the current measurement value input by the input unit, at least the voltage measurement value and the current measurement value at the predetermined time and the voltage measured by the voltage change rate measurement unit a calculation unit that calculates the capacitance of the capacitor and the admittance of the leakage current from the rate of change;
from the amount of decrease from the initial value of the capacitance of the capacitor calculated by the calculation unit and the amount of increase from the initial value of the admittance of the leakage current of the capacitor calculated by the calculation unit, and a result output unit for outputting a deterioration diagnosis result. 3. The deterioration diagnosis apparatus according to claim 2 , wherein said result output unit further outputs a result of life prediction of said capacitor from said decrease amount and said increase amount. a voltage measurement step of measuring the voltage applied to the capacitor as a voltage measurement;
a current measurement step of measuring the current flowing through the capacitor as a current measurement;
a voltage change rate measuring step of measuring a voltage change rate of the voltage applied to the capacitor at a predetermined time from the voltage measurement value measured in the voltage measuring step;
With reference to the voltage measurement value and the current measurement value measured in the voltage measurement step and the current measurement step, respectively, at least the voltage measurement value and the current measurement value at the predetermined time and the voltage change a calculation step of calculating the capacitance and leakage current admittance of the capacitor from the voltage change rate measured in the rate measurement step;
from the amount of decrease from the initial value in the capacitance of the capacitor calculated in the calculating step and the amount of increase from the initial value in the admittance of the leakage current of the capacitor calculated in the calculating step; and a result outputting step of outputting a result of deterioration diagnosis of the capacitor. 2. A capacitance measurement program for causing a computer to function as the capacitance measurement device according to claim 1, wherein the computer functions as the input unit, the voltage change rate measurement unit , the calculation unit , and the current change rate measurement unit. Capacitance measurement program for functioning.

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