JP2018031633A - Power conversion unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power conversion unit which can correct a voltage measured by a voltage measuring circuit with a simple configuration.SOLUTION: A power conversion unit 100 includes: a power converter 1 equipped in a vehicle; a capacitor 2 connected between a high voltage line 11 and a ground line 12 of a main circuit 10 of the power converter 1; a voltage measuring circuit 4 for measuring a voltage between the high voltage line 11 and the ground line 12; and a calculating unit 9 for controlling the power converter 1, using an output value of the voltage measuring circuit 4. The calculating unit 9 calculates a gain Gof a voltage measuring circuit 4 from an output value sampled at predetermined sampling intervals while the capacitor 2 charged at a predetermined voltage is discharged and the time change amount of the output value.SELECTED DRAWING: Figure 1

Description

  The present invention relates to, for example, a power conversion unit that converts AC voltage or DC voltage of a high-output circuit in the field of power electronics, and more specifically, the gain and time of a power conversion device mounted in the power conversion unit. The present invention relates to a power conversion unit having a function of correcting constant individual variations and changes over time.

  In power converters such as in-vehicle chargers, AC / DC converters, DC / DC converters, and inverters, it is necessary to monitor the voltage between input terminals or between output terminals with a voltage measurement circuit in order to control these devices. There is. In a conventional in-vehicle voltage monitoring device, when a high voltage battery is to be observed, the output voltage of the high voltage battery is once set to a desired voltage level by resistance voltage division, and then to about 0 to 5 V with an insulation amplifier and an amplifier circuit. The amplified signal is input to the A / D port of the microcomputer, and overvoltage detection and discharge detection are performed under the control of the microcomputer. Here, since the input voltage of the isolation amplifier is usually about 300 mV, when monitoring the voltage of a high voltage battery whose voltage range is 0 to 1000 V, the voltage output from the high voltage battery is about 1000 minutes. It must be divided to about 1. On the other hand, highly accurate detection performance is required for the voltage measurement circuit because of the necessity of overvoltage detection for improving efficiency by improving controllability and protecting the product.

Therefore, as a voltage measuring device using an A / D conversion circuit, a reference voltage generation circuit for generating a plurality of reference voltages is provided, and a reference voltage applied to the input terminal and a voltage at the output terminal corresponding thereto are input to the input terminal. There is one that approximately obtains a function of the output terminal and calculates a voltage of the output terminal corresponding to the voltage to be measured by this function (for example, Patent Document 1).
In addition, for a voltage measuring device that measures an input voltage input to an inverter device capable of converting DC power of a DC power source into AC power, a low voltage detection circuit is controlled from a high voltage battery side by controlling a system main relay (SMR) or the like. By correcting the error of each detection circuit based on the detection value of each detection circuit when the applied voltage applied to the high-voltage detection circuit is changed, it is possible to correct errors that occur over time without adding a reference voltage circuit There was a voltage measuring apparatus (for example, patent document 2).

JP 51-84279 A JP 2014-219239 A

However, in the voltage measuring device of Patent Document 1, the number of parts increases due to the addition of the reference voltage generation circuit, the configuration becomes complicated, and the manufacturing cost increases.
Further, in the method of Patent Document 2, the detection value of the battery voltage detection circuit provided separately from the pressure detection circuit and the high voltage detection circuit is used in order to prevent deterioration of measurement accuracy in the correction of the gain error. This cannot be applied to an AC / DC converter or a DC / DC converter that cannot make full use of a plurality of detection circuits.

  The present invention has been made to solve the above-described problems, and provides a power conversion unit capable of correcting a voltage measured by a voltage measurement circuit with a simple configuration.

  A power conversion unit of the present invention includes a power conversion device mounted on a vehicle, a capacitor connected between a high-voltage line and a ground line of a main circuit provided with the power conversion device, and between the high-voltage line and the ground line. A power conversion unit comprising a voltage measurement circuit for measuring a voltage and an arithmetic device for controlling the power converter using an output value of the voltage measurement circuit, the arithmetic device being charged to a predetermined voltage During the discharge of the capacitor, the gain of the voltage measurement circuit is calculated from the output value sampled at a predetermined sampling interval and the time variation of the output value, and the gain of the voltage measurement circuit is corrected. .

  According to the present invention, since the gain of the voltage measurement circuit is calculated from the output value of the voltage measurement circuit and the amount of change over time when the capacitor charged to a predetermined voltage is discharged, the voltage measurement circuit has a simple configuration. The gain can be acquired and corrected, and the voltage measured by the voltage measurement circuit can be accurately corrected.

It is a figure which shows the basic composition of the power conversion unit in Embodiment 1 of this invention. In Embodiment 1 of this invention, it is a figure which shows the time change of the observation voltage linearly approximated. It is a flowchart which shows the calculation process of the gain of the voltage measurement circuit which concerns on Embodiment 1 of this invention, and the time constant of a main circuit. It is a flowchart which shows operation | movement of the power conversion unit in Embodiment 2 of this invention.

Embodiment 1 FIG.
Embodiment 1 of the present invention will be described below with reference to FIGS. 1 is a diagram showing a basic configuration of a power conversion unit according to Embodiment 1 of the present invention. The power conversion unit 100 converts the input power received from the positive input terminal P and the negative input terminal N into desired power by the power conversion device 1 provided in the main circuit 10, and outputs the high voltage side output terminal Vout and the ground side output terminal. The battery is supplied to a battery, a motor or the like (not shown) connected to the LGND. In the main circuit 10 of the power conversion unit 100, a filter or a voltage smoothing capacitor 2 and a discharge resistor 3 are connected in parallel between the high voltage line 11 and the ground line 12 on the input side of the power conversion device 1.

  The high voltage line 11 is connected to the positive input terminal P on the input side of the power conversion device 1 and is connected to the high voltage side output terminal Vout on the output side. The ground line 12 is connected to the negative input terminal N on the input side of the power conversion device 1 and is connected to the ground side output terminal LGND on the output side. The combined capacity between the high voltage line 11 and the ground line 12 is 0.1 μF to several thousand F. The time constant τ of the main circuit 10 is determined from the resistance values of the discharge resistor 3 and the voltage measuring circuit 4 and has a predesigned value. However, the actual time constant τ is designed due to individual variations and changes over time. Value may be different. Although it is not usually considered that the order of the time constant τ changes due to individual variations or changes over time, the actual time constant τ is corrected each time when considering the discharge characteristics of the charge charged in the capacitor 2. There is a need.

  The power conversion device 1 is, for example, an AC / DC converter, a DC / DC converter, or an inverter mounted on a hybrid vehicle or a plug-in hybrid vehicle. Although not shown, wide gaps such as MOSFET, IGBT, SiC, GaN, etc. It consists of switching elements, diodes, and inductors made of semiconductors.

The voltage measurement circuit 4 is a circuit for detecting the observation target voltage within a desired dynamic range range at the A / D terminal of the arithmetic device 9, and is connected in parallel with the power conversion device 1. The voltage measurement circuit 4 insulates a high voltage side such as a Li-ion battery mounted on a plug-in hybrid vehicle or a hybrid vehicle and a low voltage side such as a lead battery, and amplifies the input voltage to a desired voltage signal. Insulation amplifier 6, voltage dividing resistor 5 that divides the observation target voltage into the input voltage range of insulation amplifier 6, intermediate amplifier 7 that amplifies or attenuates the voltage signal amplified by insulation amplifier 6 to a desired signal level, and intermediate amplifier 7 Is provided with a filter 12 for removing noise from the voltage signal that has passed through. The voltage signal that has passed through the filter 12 is output to the arithmetic unit 9 as the observed voltage V _μAD . In the present embodiment, the observation target voltage is the input voltage V _in of the power conversion unit 100, that is, the voltage between the positive input terminal P and the negative input terminal N, which is between the high voltage line 11 and the ground line 12. Is equal to the voltage of
Further, the Oyobi offset _{V offset} gain _{G sens} voltage measurement circuit 4, since the variation due to individual variation or change over time, when correcting the actual input voltage _{V in} from the observed voltage V _MyuAD the actual gain It is necessary to acquire G _sens and offset V _offset and correct them.

  The arithmetic unit 9 is a digital IC such as a digital signal processor (DSP), a microcomputer, and the like, and includes a storage unit 9a for storing a calculation result, and a command signal from an external engine control unit (ECU) (not shown) The power conversion apparatus 1 is driven and controlled based on the input voltage calculated from the observation voltage of the voltage measurement circuit 4 so as to realize the output characteristics. The dynamic range at the A / D terminal of the arithmetic unit 9 is 0 to 5 V in the present embodiment, but is not limited to this.

  In the configuration of FIG. 1, there are two voltage dividing resistors 5 and one intermediate amplifier 7, but the number of voltage dividing resistors 5 and intermediate amplifiers 7 is not limited to this, and the voltage to be observed and You may change suitably according to the dynamic range in the A / D terminal of the arithmetic unit 9. Further, the storage unit 9a of the calculation device 9 may be omitted, and the calculation result may be stored in a storage device provided outside.

式（１）より、観測電圧Ｖ_μＡＤ（ｔ）を補正して入力電圧Ｖ_ｉｎ（ｔ）を求めるには、式（２）の計算を行えばよい。

一方、ゲインＧ_ｓｅｎｓ及びオフセットＶ_{ｏｆｆｓｅｔ}は、電圧測定回路４の各部品の個体ばらつきや経時的変化の影響を受け、その値が変動するため、式（２）において未知変数となっている。このため、入力電圧Ｖ_ｉｎ（ｔ）を正確に求めるには、まずゲインＧ_ｓｅｎｓ及びオフセットＶ_{ｏｆｆｓｅｔ}を求める必要がある。そこで、本発明では、コンデンサ２に既知の電圧Ｖ_{ＩＮｍａｘ}を充電し、放電開始時刻ｔ＝０としたときのコンデンサ２の両端電圧の時間変化を利用することでゲインＧ_ｓｅｎｓ及びをオフセットＶ_{ｏｆｆｓｅｔ}求める。まず、コンデンサの２の両端電圧は、入力電圧Ｖ_ｉｎ（ｔ）に等しいので、式（３）が成り立つ。

ここで、時定数τも上述したように個体ばらつきや経時的変化により変動するため、式（３）において時定数τも未知変数として求めなければならない。
次に、式（１）に式（３）を代入すると式（４）が得られる。

式（４）の右辺第１項の指数関数部分は、式（５）に示すようにテイラー展開できるため、時刻ｔが時定数τに比べて十分小さければ式（６）のように線形近似可能である。

式（６）を式（４）に代入して得られる式（７）を時間微分すると式（８）となるため、観測電圧Ｖ_μＡＤ（ｔ）の時間変化量ΔＶ_μＡＤ（ｔ）について式（９）が成り立つ。

式（７）及び式（９）より、下記の連立方程式、式（１０）が成り立つ。

式（１０）の右辺にある行列の逆行列を求めれば、式（１１）、式（１２）に示すようにＧ_ｓｅｎｓ＊Ｖ_{ＩＮｍａｘ}／τ及び、Ｇ_ｓｅｎｓ＊Ｖ_{ＩＮｍａｘ}＋Ｖ_{ｏｆｆｓｅｔ}が求まる。さらに、式（１３）に示すようにゲインＧ_ｓｅｎｓ及び時定数τを求めることができる。

Next, the voltage correction process by the arithmetic unit 9 will be described. With respect to the input voltage V _in (t) and the observation voltage V _μAD (t) of the power conversion unit 100 at time t, the following expression (1) is established. Here, G _sens and V _offset are the gain and offset of the voltage measurement circuit 4.

In order to obtain the input voltage V _in (t) by correcting the observed voltage V _μAD (t) from Equation (1), the calculation of Equation (2) may be performed.

On the other hand, the gain G _sens and the offset V _offset are unknown variables in the equation (2) because their values fluctuate due to the influence of individual variations and changes with time of each component of the voltage measurement circuit 4. For this reason, in order to accurately determine the input voltage V _in (t), it is first necessary to determine the gain G _sens and the offset V _offset . Therefore, in the present invention, the gain G _sens and the offset V _offset are _obtained by charging the capacitor 2 with the known voltage V _INmax and using the time change of the voltage across the capacitor 2 when the discharge start time t = 0. . First, since the voltage across the capacitor 2 is equal to the input voltage V _in (t), equation (3) holds.

Here, since the time constant τ also varies due to individual variations and changes over time as described above, the time constant τ must also be obtained as an unknown variable in Equation (3).
Next, when Expression (3) is substituted into Expression (1), Expression (4) is obtained.

Since the exponential function part of the first term on the right side of equation (4) can be Taylor-expanded as shown in equation (5), linear approximation is possible as in equation (6) if time t is sufficiently smaller than time constant τ. It is.

When the equation (7) obtained by substituting the equation (6) into the equation (4) is time-differentiated, the equation (8) is obtained. _Therefore , the time variation ΔV _μAD (t) of the observed voltage V _μAD (t) 9) holds.

From the equations (7) and (9), the following simultaneous equations, the equation (10), are established.

If the inverse matrix of the matrix on the right side of Equation (10) is obtained, G _sens * V _INmax / τ and G _sens * V _INmax + V _offset are obtained as shown in Equations (11) and (12). Furthermore, the gain G _sens and the time constant τ can be obtained as shown in Expression (13).

ただし、実際の観測では、主回路１０の始動時で、高電圧のメインコンタクタなどにより高圧バッテリラインと主回路１０が接点開放状態（コンデンサ２に充電が行われる前）や電力完全停止時など、コンデンサ２に電圧が印加されていないときの観測電圧Ｖ_μＡＤをオフセットＶ_{ｏｆｆｓｅｔ}とする。 As for the offset V _offset , the voltage after the capacitor 2 is sufficiently discharged, that is, the observed voltage V _μAD (∞) when t = ∞ as shown in the equation (14) is obtained from the equation (4). .

However, in actual observation, when the main circuit 10 is started, the high voltage battery line and the main circuit 10 are in contact open state (before the capacitor 2 is charged) or when the power is completely stopped by a high voltage main contactor, etc. An observation voltage V _μAD when no voltage is applied to the capacitor 2 is _defined as an offset V _offset .

式（１５）及び式（１６）において、Δｔはサンプリング間隔であり、Δｔ＝ｔ_ｎ−ｔ_ｎ−１である。また、時間変化量ΔＶ_μＡＤ（ｔ_ｎ）は、ΔＶ_μＡＤ（ｔ_ｎ）＝Ｖ_μＡＤ（ｔ_ｎ）―ＶμＡＤ（ｔ_ｎ−１）である。Ｇ_ｓｅｎｓ（ｎ）、τ（ｎ）は、それぞれｔ＝ｔ_ｎにおける観測電圧Ｖ_μＡＤ（ｔ_ｎ）及びその変化量ΔＶ_μＡＤ（ｔ_ｎ）から計算される電圧測定回路４のゲイン及び主回路１０の時定数である。 As described above, the time constant τ of the main circuit 10 and the gain G _{sens of the} voltage measurement circuit 4 _can be obtained and corrected from the observed voltage V _μAD (t) and the time variation ΔV _μAD (t) at each time. it can. In this embodiment, as shown in FIG. 2, the observation voltage sampling time is T, the sampling time is tn (n = 0, 1, 2,... N), and the observation voltage V _μAD (t) and The amount of change ΔV _μAD (t) is sampled, and the gain G _sens and time constant τ are calculated. Note that t ₀ = 0 and t _N = T. In this case, Expression (12) and Expression (13) can be rewritten as Expression (15) and Expression (16) below.

In Expression (15) and Expression (16), Δt is a sampling interval, and Δt = t _n −t _n−1 . The time change amount ΔV _μAD (t _n ) is ΔV _μAD (t _n ) = V _μAD (t _n ) −V μAD (t _n−1 ). G _sens (n) and τ (n) are the gain of the voltage measuring circuit 4 and the main circuit 10 calculated from the observed voltage V _μAD (t _n ) and its variation ΔV _μAD (t _n ) at t = t _n , respectively. Is the time constant of.

Note that in order for the linear approximation of Equation (6) to hold, the sampling time t _n needs to be in a range sufficiently smaller than the time constant τ, and therefore the sampling time T needs to be sufficiently smaller than the time constant τ. In this embodiment, since the order of the time constant τ is determined in advance from the design value, it is possible to determine the upper limit of the sampling time T within a range in which linear approximation is established. For example, the sampling time T is set to the time constant. What is necessary is just to make it 1/300 or less of (tau).
Further, since the time variation ΔV _μAD (t _n ) of the observation voltage V _μAD (t _n ) _{needs to be equal} to or higher than the A / D resolution of the arithmetic unit 9, the sampling interval Δt has a lower limit. What is necessary is just to set it as 1/3000 or more of time constant (tau). In this case, the sampling time T is also 1/3000 or more of the time constant τ.

Next, the operation of the present embodiment will be described. FIG. 3 is a flowchart showing a calculation process of the gain of the voltage measurement circuit 4 and the time constant of the main circuit 10 according to the first embodiment. In the present embodiment, processing in an inspection process before product shipment is targeted. First, in step ST01, the output of the voltage measurement circuit 4 in a state where no voltage is applied to the main circuit 10 is acquired as an offset V _{offset by the} arithmetic unit 9 and stored in the storage unit 9a.
Subsequently, in step ST02, a known voltage V _INmax is applied to the input terminal of the main circuit 10 to charge the capacitor 2 with V _INmax .

Thereafter, the charge accumulated in the capacitor 2 is released and discharged in step _{ST03, and} the output of the voltage measuring circuit 4 is sampled by the arithmetic unit 9, and the observation voltage V _μAD (t _{n is calculated} from the output value of the voltage measuring circuit 4. ) And its change amount ΔV _μAD (t _n ) are acquired and stored in the storage unit 9a.
Next, in step ST04, the gain G _sens (n) and the time constant τ (n) are calculated from the above equation (16).
After the calculation in step ST04, the gain G _sens (n) and the time constant τ (n) are stored in the storage unit 9a in step ST05.

In step ST06, the convergence determination of the gain G _sens (n) and the time constant τ (n) is performed. When it determines with having converged, it progresses to step ST07. In step ST07, the convergence values of the gain G _sens (n) and the time constant τ (n) are acquired, the convergence values are stored in the storage unit 9a, and the process is terminated. When it determines with not having converged, it progresses to step ST08.

In step ST08, by comparing the sampling time _{t n} and the sampling time T, the processing flow advances to step ST09 sampling time _{t n} is determined that the sampling end if more sampling time T. In step ST09, the average value of the gain G _sens (n) and the time constant τ (n) is acquired, the average value is stored in the storage unit 9a, and the process ends. When the sampling time t _n is smaller than the sampling time T and it is determined that the sampling is not finished, the process returns to step ST03.

Through the above arithmetic processing, the offset V _offset and gain G _{sens of} the voltage measurement circuit 4 and the time constant τ of the main circuit 10 reflecting the influence of individual variations and changes over time can be acquired. can be corrected to the input voltage _{V in} from the observed voltage V _MyuAD by equation (2).

Incidentally, in the present embodiment is provided a voltage measurement circuit 4 on the input side of the power conversion apparatus 1, seeking an offset _{V offset} and gain _{G sens} voltage measurement circuit 4 from the relationship between the observed voltage V _MyuAD and the input voltage _{V in} However, the voltage measurement circuit 4 only needs to be able to measure the voltage between the high voltage line 11 and the ground line 12 of the main circuit 10, and therefore may be provided on the output side of the power converter 1. In this case, the same effect can be obtained by obtaining the offset V _offset and the gain G _sens of the voltage measurement circuit 4 from the relationship between the output voltage (voltage between Vout and LGND) and the observation voltage V _μAD .

Further, in this embodiment, linear approximation is performed as in Expression (6), but polynomial approximation is performed with the second-order or higher terms of Expression (5) remaining, and the number of simultaneous equations in Expression (10) is calculated. The gain G _sens and the time constant τ may be obtained with higher accuracy. Further, in the equation (10) derived from the linear approximation, since there are two simultaneous equations, the unknown is only the gain Gsens and the time constant τ, and the offset V _offset is obtained by observation. If the equation (10) that remains until the next term is made into three simultaneous equations, the offset Voffset can also be obtained by calculation. Further, even if there are two equations (10), for example, if the time constant τ is known, the calculation may be performed with the gain G _sens and the offset V _offset as unknown.

Further, the calculation of constant τ when the gain _{G sens} and the main circuit 10 of the voltage measurement circuit 4, performs the convergence determination of the gain _{G sens} and the time constant τ separately obtains the convergence value for the gain _{G sens,} when An average value may be acquired for the constant τ, or an average value may be acquired for the gain G _sens and a convergence value may be acquired for the time constant τ.

Further, in the arithmetic processing gain _Gsens and the time constant tau, it has been determined the gain _{G sens} and tau than in ST04 formula (16), _G sens using equation _{(15) (n) * V} INmax / τ (n) And G _sens (n) * V _INmax + V _offset may be calculated and stored, and the gain G _sens and time constant τ may be obtained from the convergence value or the average value thereof.

  According to the first embodiment, the gain of the voltage measuring circuit is calculated from the observed voltage when the capacitor charged to a predetermined voltage is discharged and the amount of change over time. For this reason, the gain of the voltage measurement circuit can be acquired and corrected with a simple configuration, and the voltage measured by the voltage measurement circuit can be accurately corrected.

  In addition, since the function representing the observed voltage is linearly approximated and the simultaneous equations obtained from this approximate expression are solved to calculate the gain of the voltage measurement circuit and the time constant of the main circuit, there is no need for complicated calculations and simple calculations. A microcomputer or the like that can only be used as an arithmetic unit can be applied.

  In addition, the sampling time of the observation voltage is set sufficiently smaller than the time constant of the main circuit, and the gain of the voltage measurement circuit and the time constant of the main circuit are calculated in a short time. The load is small.

  In addition, by using the convergence value or average value of the gain calculated from the observation voltage at each sampling time as the gain of the voltage measurement circuit used to correct the observation voltage, temporary fluctuations in the observation voltage that occur at a specific sampling time are obtained. And the influence of errors can be reduced. For this reason, the observation voltage can be corrected with high accuracy.

Embodiment 2
Next, a second embodiment of the present invention will be described with reference to FIG. In the second embodiment, the power conversion unit 100 is mounted on a vehicle and shows an operation in an actual use environment. Since the configuration of the power conversion unit 100 is the same as that of the first embodiment, the description thereof is omitted. The second embodiment is based on the premise that the correction process in the inspection process described in the first embodiment is completed. That is, the storage unit 9a of the arithmetic device 9 stores the gain _Gsens of the measurement circuit 4 and the time constant τ of the main circuit 10 acquired by the arithmetic processing of the first embodiment as initial parameters.

FIG. 4 is a flowchart showing the operation of the power conversion unit in the second embodiment.
First, in ST11, the output of the voltage measurement circuit 4 when the contactor (not shown) connecting the external power supply line (not shown) and the positive input terminal P of the main circuit 10 is in an open state is acquired as the offset V _offset. And stored in the storage unit 9a. Then, the power converter device 1 is started in a specific operation mode.

In ST12 in which the power conversion device 1 is activated, the arithmetic device 9 corrects the observation voltage by using the offset V _offset acquired in ST11, the gain G _sens stored in the storage unit 9a, and the equation (2). The conversion device 1 is controlled.

After the power converter 1 is stopped in ST13, the time constant τ of the main circuit 10 and the gain G _sens of the voltage measurement circuit 4 are calculated.
First, the voltage V _INmax ^* is applied to the capacitor 2 in ST14. Here, V _INmax ^* is a voltage obtained from a control target voltage value, a voltage value by a command from the outside of the power conversion unit 100, or input voltage information from a control area network (CAN) or the like. _Corresponds to the known voltage V _INmax at.

Next, in ST15, G _{sens of the} voltage measurement circuit 4 and the time constant τ of the main circuit 10 are calculated. The specific calculation is the same as ST03 to ST09 of the calculation process described in the first embodiment, but the calculation is performed by replacing the known voltage V _INmax with V _INmax ^* in the equation, and the voltage measurement circuit 4 G _sens and the time constant τ of the main circuit 10 are acquired.

The time constant τ of the main circuit 10 is connected to the capacitance of the capacitor 2, the resistance value of the discharge resistor 3, the impedance of the voltage measuring circuit 4, and the subsequent stage of the contactor (not shown) connecting the power circuit (not shown) and the main circuit 10. The time constant τ varies depending on the operation mode of the vehicle. Similarly, the offset V _offset and the gain G _{sens of} the voltage measurement circuit 4 also differ depending on the operation mode. Therefore, when these are stored in the storage unit 9a in ST16, they are associated with the operation mode and stored separately from the initial parameters acquired in the inspection process.

Next, in ST17, the offset V _offset of the voltage measurement circuit 4 stored in association with the operation mode in ST16, the gain G _sens , the time constant τ of the main circuit 10, and the offset of the voltage measurement circuit 4 stored as initial parameters. V _offset , gain G _sens , and time constant τ of main circuit 10 are compared, and when these changes over time are equal to or greater than a predetermined threshold, it is determined that the part has deteriorated over time. Detect as (defect). The threshold value may be different for each operation mode, or may be a common value for all operation modes. Moreover, the determination part (not shown) which performs this determination may be provided inside the arithmetic unit 9, or may be provided outside.

  According to the second embodiment, the offset and gain of the voltage measurement circuit and the time constant of the main circuit are acquired under the actual use environment, and stored in association with the operation mode of the vehicle. In order to measure the change over time by comparing the offset, gain, and time constant associated with the operation mode with the initial parameters, each component of the voltage measurement circuit, arithmetic device, main circuit, and the path connecting these components Aging deterioration can be detected.

  It should be noted that within the scope of the present invention, the embodiments can be freely combined, or the embodiments can be appropriately modified or omitted.

DESCRIPTION OF SYMBOLS 1 Power converter, 2 Capacitor, 4 Voltage measurement circuit, 9 Arithmetic unit, 9a Memory | storage part, 10 Main circuit, 11 High voltage line, 12 Ground line, 100 Power conversion unit

Claims (10)

A power conversion device mounted on a vehicle;
A capacitor connected between a high-voltage line and a ground line of a main circuit provided with the power converter;
A voltage measuring circuit for measuring a voltage between the high-voltage line and the ground line;
A power conversion unit comprising: an arithmetic unit that controls the power conversion device using an output value of the voltage measurement circuit;
The arithmetic unit calculates the gain of the voltage measurement circuit from the output value sampled at a predetermined sampling interval and the time change amount of the output value during discharging of the capacitor charged to a predetermined voltage. And a power conversion unit that corrects the gain.   The power conversion unit according to claim 1, wherein the arithmetic device acquires the output value before the voltage is applied to the capacitor as an offset value of the voltage measurement circuit.   The power conversion unit according to claim 1 or 2, wherein a sampling time of the sampling is shorter than a time constant of the main circuit.   4. The power conversion unit according to claim 3, wherein the calculation device calculates the gain from a linear approximate expression of a time change of the output value. 5.   4. The power conversion unit according to claim 3, wherein the arithmetic device calculates the time constant from a linear approximate expression of a time change of the output value. 5.   6. The power according to claim 1, wherein the calculation device acquires a convergence value of the gain calculated from the sampled output value, and corrects the gain based on the convergence value. Conversion unit.   6. The power according to claim 1, wherein the arithmetic device acquires an average value of the gain calculated from the sampled output value, and corrects the gain based on the average value. Conversion unit.   The power conversion according to any one of claims 1 to 7, wherein the arithmetic device includes a storage unit that stores the calculated gain, and measures a temporal change from an initial value of the gain. unit.   9. The apparatus according to claim 8, further comprising a determination unit that determines that the main circuit or the voltage measurement circuit has deteriorated over time when the temporal variation is equal to or greater than a predetermined value. The power conversion unit described.   The power storage unit according to claim 8 or 9, wherein the storage unit stores the gain in association with an operation mode of the vehicle.

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