Power conversion device, remote monitoring system for power conversion device, and lifetime estimation method for power conversion device

Abstract

To provide a power conversion device which improves the estimation accuracy of a deterioration degree of a switching element by performing loss arithmetic more accurate than in the prior arts based on a real-time junction temperature, a remote monitoring system and a lifetime estimation method therefor.SOLUTION: A power conversion device comprises: a junction-fin temperature operator capable of operating a temperature between a junction and a fin; and a fin temperature sensor capable of detecting a fin temperature. The junction-fin temperature operator operates a junction temperature from a sum of the temperature between the junction and the fin and the fin temperature, and calls loss characteristics based on a junction temperature at that time from the operated junction temperature, thereby operating a more accurate loss. A temperature is estimated from the operated loss and an overheat characteristic table, and a deterioration degree is subsequently operated.SELECTED DRAWING: Figure 12

Description

[Technical field]

[0001] The present invention relates to a power conversion device, a remote monitoring system for the power conversion device, and a method for estimating a lifetime of the power conversion device. [Background technology]

[0002] Inverters, a type of power conversion device, are widely used in the industrial world as motor drive devices in manufacturing equipment, lifting devices, transport devices, etc. In these various applications, inverters are required to operate stably. If an inverter fails, it will cause a halt in factory production and equipment operation, causing a huge impact.

[0003] Inverters use power semiconductor devices such as IGBTs and diodes to control the flow and interruption of current and perform the desired power conversion. The power semiconductor devices are bonded by wire bonding or soldering to a copper foil pattern formed on an insulating substrate, which electrically connects them to circuits external to the power semiconductor device. The insulating substrate is mounted on a metal base, and the power semiconductor device is cooled via the metal base. A component that incorporates a power semiconductor device in a housing that has a structure for electrical connection to an external circuit and a cooling structure is called a power module.

[0004] When current flows through or is cut off in a power semiconductor device, the power semiconductor device generates heat, and a temperature difference (hereafter referred to as △T) occurs between the junctions of the power semiconductor device (the junctions between the device and wire bonding, and the junctions between the device and copper foil pattern) and the fins (metal base equipped with a cooling structure).When the inverter is stopped, heat generation stops and △T becomes smaller.

[0005] The joints of the above power semiconductor devices are made of materials with different thermal expansion coefficients, so fluctuations in ΔT cause thermal stress at the joints. Repeated fluctuations in ΔT can cause peeling or cracks in the joints, leading to failure. The time it takes to cause such failures varies depending on the degree and frequency of ΔT. The degree and frequency of ΔT vary depending on how the power conversion device is used and the device driven by the power conversion device.

[0006] In addition, the load on the IGBT and the diode also varies depending on the usage of the device. Therefore, in order to prevent such failures, it is necessary to take measures to understand the degree of load on the IGBT and the diode according to the usage of the power conversion device.

[0007] Patent Document 1 is a conventional technique in this technical field. In Patent Document 1, a power conversion device equipped with a switching element is used, and the loss of the switching element is calculated from the current flowing through the switching element and a loss data table. The temperature change of the switching element (junction) is calculated from the calculated temperature change and transient thermal resistance characteristics. The degree of deterioration of the switching element is estimated from the relationship between the calculated temperature change and the number of power cycles lifespan. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] WO2021-106175 Summary of the Invention [Problem to be solved by the invention]

[0009] In Patent Document 1, a certain loss data table is used to calculate the loss of the switching element. However, the degree of damage to the switching element varies greatly depending on the junction temperature of the switching element.

[0010] In other words, the method of Patent Document 1 has a problem in that the accuracy of the calculated loss, as well as the subsequent calculation accuracy of the temperature and the degree of degradation, is low due to the difference between the on-site junction temperature and the loss data table. [Means for solving the problem]

[0011] Therefore, the present invention is provided with a junction-fin temperature calculator capable of calculating the junction-fin temperature, and a fin temperature sensor capable of detecting the fin temperature. The junction temperature is calculated from the sum of the junction-fin temperature and the fin temperature. From the calculated junction temperature, loss characteristics based on the junction temperature at that time are retrieved, and more accurate loss is calculated. The temperature is estimated from the calculated loss and a transient thermal characteristic table, and then the degree of deterioration is calculated. Effect of the Invention

[0012] The power conversion device according to the present invention performs loss calculations with higher accuracy than conventional methods based on real-time junction temperature, thereby improving the accuracy of estimating the degree of degradation. [Brief description of the drawings]

[0013] [Figure 1] 1 is a configuration diagram of a power conversion device according to an embodiment of the present invention. [Diagram 2] 1 is a circuit diagram of an inverter in an embodiment of a power conversion device of the present invention. [Diagram 3] FIG. 2 is a perspective view of a power module of a power conversion device according to an embodiment of the present invention. [Figure 4] 1 is a cross-sectional view of a power module of a power conversion device according to an embodiment of the present invention. [Diagram 5] FIG. 4 is a diagram showing the collector-emitter voltage-collector current characteristics of an IGBT of a power conversion device according to an embodiment of the present invention. [Figure 6] FIG. 4 is a diagram showing the single-pulse switching loss-collector current characteristics of the IGBT of the power conversion device according to the embodiment of the present invention. [Figure 7]FIG. 4 is a diagram showing forward voltage-forward current characteristics of a diode of a power conversion device according to an embodiment of the present invention. [Figure 8] FIG. 4 is a diagram showing the single pulse recovery loss-forward current characteristics of the IGBT of the power conversion device according to the embodiment of the present invention. [Figure 9] FIG. 2 is a diagram showing thermal impedance-time characteristics of an IGBT of a power conversion device according to an embodiment of the present invention. [Figure 10] FIG. 4 is a diagram showing thermal impedance-time characteristics of a diode of a power conversion device according to an embodiment of the present invention. [Figure 11] FIG. 11 is a diagram showing the relationship between a junction temperature threshold and an electrical characteristic table in an embodiment of the present invention. [Figure 12] 4 is a flowchart showing a process in a temperature history calculator in the embodiment of the present invention. [Figure 13] 4 is an example of an electrical characteristics table according to an embodiment of the present invention. [Figure 14] 11A and 11B are diagrams illustrating outputs of life calculation results in the embodiment of the power conversion device of the present invention. [Figure 15] FIG. 4 is a diagram showing the life cycle-Tjc characteristics of the power semiconductor element of the power conversion device in the embodiment of the present invention. [Figure 16] 1 is an example of a remote monitoring system using a power conversion device of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0015] 1 is a configuration diagram of a power conversion device according to an embodiment of the present invention. A power conversion device 100 according to the embodiment of the present invention includes a main circuit 200, a life estimation device 300, and an interface device 400.

[0016] The main circuit 200 is composed of a diode rectifier 201 that rectifies the AC power sent from the AC power source 101, a smoothing capacitor 202, IGBTs 203 (a, b, c, d, e, f) which are power semiconductor switching elements, and an inverter 205 equipped with diodes 204 (a, b, c, d, e, f) connected in inverse parallel to the IGBTs.

[0017] 2 is a circuit diagram of an inverter in an embodiment of the power conversion device of the present invention. In this embodiment, the inverter 205 is a three-phase two-level inverter. The inverter 205 is controlled by a motor control unit 206. Specifically, the motor control unit 206 calculates a gate signal at a set carrier frequency f_C based on a current value detected by a current sensor 207(a, b) and a speed command.

[0018] The calculated gate signal is amplified by the gate driver 208 and input as a gate voltage to the IGBTs 203 (a, b, c, d, e, f). The ratio of the carrier period to the gate on-period is called on-duty D. This outputs a voltage so that the motor 102 operates at the commanded speed. In both the IGBTs 203 and diodes 204, the junction temperature rises due to Joule loss when on, switching loss when switching current off, and recovery loss, and the junction temperature drops when off.

[0019] Fig. 3 is a perspective view of a power module of a power conversion device in an embodiment of the present invention. A perspective view of a power module 220 incorporating an IGBT 203 and a diode 204 is shown in Fig. 4, and a cross-sectional view taken along line A-A' in Fig. 3 is shown. In Fig. 3, a plurality of power semiconductor elements 222 such as the IGBT 203 and the diode 204, and a temperature sensor 223 are arranged on a surface inside a housing 221 (only one semiconductor element is shown in Figs. 3 and 4).

[0020] 4 is a cross-sectional view of a power module of a power converter according to an embodiment of the present invention. A power semiconductor element 222, solder 224 under the chip, copper foil 225, insulating substrate 226, solder 227 under the substrate, and metal base 228 are laminated in this order, and the solder 224 under the chip and the solder 227 under the substrate are bonded to adjacent layers. The other side of the semiconductor element is bonded with a metal wire 229.

[0021] Since the power semiconductor element 222 is joined with materials having different thermal expansion coefficients, stress is applied to the joint when the temperature of the power semiconductor element rises and falls. The resistance to this stress is called the power cycle resistance, and is indicated by the number of usable cycles for a given temperature amplitude, called the life cycle.

[0022] Therefore, if the temperature history of a semiconductor element is known, it is possible to estimate the lifetime.

[0023] The on-duty depends on an arbitrary modulation method, but is determined, for example, by the ratio of DC voltage vd to motor voltage vo (vo / vd).

[0024]

number

[0025]

number

[0026]

number

[0027] Here, rq and vq are the slope and intercept of a linear approximation curve of the collector-emitter voltage-collector current characteristics of an IGBT as shown in FIG.

[0028] The collector-emitter voltage-collector current characteristics of an IGBT are temperature dependent. Figure 5 shows characteristics 331 at low temperature, its approximation curve 332, characteristics 331' at high temperature, and approximation curve 332' at high temperature. In this example, the slope rq' of approximation curve 332' at high temperature is smaller than the slope rq at low temperature. The intercept vq' of approximation curve 332' at high temperature is larger than the slope vq at low temperature. FIG. 6 is a diagram showing the single-pulse switching loss vs. collector current characteristics of the IGBT of the power conversion device in the embodiment of the present invention.

[0029] aq and bq are the slope and intercept of the linear approximation curve of the switching loss vs. collector current characteristics per single pulse of the IGBT when the DC voltage is vdb, as shown in Figure 6.

[0030] The switching loss per pulse vs. collector current characteristic has temperature dependency. Figure 6 shows a characteristic 338 at low temperature, its linear approximation curve 337, a characteristic 338' at high temperature, and a linear approximation curve 337' at high temperature. In this example, the slope aq' of the approximation curve 338' at high temperature is smaller than the slope aq at low temperature. The intercept bq' of the approximation curve 332' at high temperature is larger than the slope vq at low temperature.

[0031] FIG. 7 is a diagram showing forward voltage-forward current characteristics of a diode of a power conversion device in an embodiment of the present invention.

[0032] rd and vd are the slope and intercept of a linear approximation curve 342 of the forward voltage-forward current characteristic 341 of the diode shown in FIG.

[0033] The forward voltage-forward current characteristic of a diode has temperature dependency. Fig. 7 shows a characteristic 341 at low temperature, its linear approximation curve 342, a characteristic 341' at high temperature, and a linear approximation curve 342' at high temperature. In this example, the slope rd' of the linear approximation curve 342' at high temperature is smaller than the slope rd at low temperature. The intercept vd' of the linear approximation curve 342' at high temperature is larger than the slope vd at low temperature.

[0034] FIG. 8 is a diagram showing the single pulse recovery loss vs. forward current characteristics of the IGBT of the power conversion device in the embodiment of the present invention.

[0035] ad and bd are the slope and intercept of a linear approximation curve 347 of the diode recovery loss per single pulse vs. forward current characteristic 346 when the DC voltage is Vdb, as shown in FIG.

[0036] The recovery loss per pulse vs. forward current characteristic has temperature dependency. Fig. 8 shows a characteristic 346 at low temperature, its linear approximation curve 347, a characteristic 346' at high temperature, and a linear approximation curve 347' at high temperature. In this example, the slope ad' of the linear approximation curve 347' at high temperature is smaller than the slope ad at low temperature. The intercept bd' of the linear approximation curve 347' at high temperature is larger than the slope bd at low temperature.

[0037] Next, calculate the temperature of the IGBT and the diode from the loss obtained above and the thermal characteristics of the IGBT and the diode.

[0038]

number

[0039]

number

[0040] 9 is a diagram showing the thermal impedance-time characteristics of the IGBT of the power conversion device according to the embodiment of the present invention. τthq and rthq are variables when the thermal impedance-time characteristics of the IGBT are approximated by Equation 11.

[0041] 10 is a diagram showing the thermal impedance-time characteristics of the diode of the power conversion device in the embodiment of the present invention. τthd and rthd are variables when the thermal impedance-time characteristics of the IGBT are approximated by Formula 11.

[0042]

number

[0043]

number

[0044]

number

[0045] The temperature of the heat sink is acquired by using a temperature sensor and input to a temperature calculator. The temperature sensor may be, for example, built into the power module and installed in the heat sink near the power module. For example, a thermocouple, a thermistor, or the like may be used as the temperature sensor.

[0046] Next, based on the above-described calculation result of the junction temperature, the variables used in the calculation of Equation 2 and Equation 3 are reset.

[0047] 11 is a diagram showing the relationship between the junction temperature threshold and the electrical characteristic table in an embodiment of the present invention. A temperature region is determined in which the junction temperature 361 is divided into thresholds 3621 and 3622. In section 3631, the junction temperature is determined to be equal to or lower than the threshold 3621. In section 3632, the junction temperature is determined to be equal to or higher than the threshold 3621 and equal to or lower than the threshold 3622.

[0048] In section 3633, the junction temperature is determined to be equal to or higher than threshold 3622. The thresholds may be set within a typical operating range of a power semiconductor, for example, threshold 3621 may be set to 50° C., and threshold 3622 may be set to 100° C. Here, an example of two types of thresholds has been described, but the number of thresholds may be one or more. Based on the above determination, the electrical characteristics table 302 shown for each temperature range in FIG. 13 is referenced, and a set of variables rq, vq, aq, bq, rd, vd, ad, and bd for the temperature range to which the junction temperature belongs is selected.

[0049] For example, in the electrical characteristics table, in the collector-emitter voltage-collector current characteristic of an IGBT shown in FIG. 5, in the low junction temperature region 361, it resembles characteristic 331, but as the junction temperature 361 increases, it resembles characteristic 331', and therefore the slope rq (rq') and intercept vq (vq') of the linear approximation curve of the collector-emitter voltage-collector current characteristic also generally have different characteristics.

[0050] Next, the temperatures of the IGBT and the diode are calculated again using the formulas 2, 3, 4, and 5 based on the electrical characteristics table 302 corresponding to the junction temperature 361.

[0051] As shown in Figure 12, the above flow first estimates the junction temperature, measures the fin temperature, calculates the junction temperature, selects the variable value corresponding to the junction temperature from the electrical characteristics table, and calculates the temperatures of the IGBT and diode, as shown in Figure 13.

[0052] Here, the method of estimating the junction temperature 361 is illustrated as being calculated from the sum of the junction temperature and the heat sink temperature, but a temperature sensor may be provided to measure the junction temperature. The junction temperature can also be estimated by referring to variables that are correlated with the ambient temperature, the load factor of the inverter, operation time, etc.

[0053] There may be one or more thresholds 3621, 3622 dividing the temperature regions. When there are two or more thresholds, the intervals between the thresholds may be equal or unequal. In addition, the values ​​in the electrical characteristics table and the temperature ranges may be arbitrarily set from the outside via an appropriate interface such as the display 402 shown in FIG. 14.

[0054] This example shows that 36% of the power semiconductor element's lifespan remains during normal operation.

[0055] The above procedure is repeated until the tasks essential for maintaining the functionality of the power converter, such as the inverter's PWM calculations, are completed and the microcontroller has spare processing capacity. This state is called the standby state shown in Figure 12, and in this state the system moves on to the next flow, which is degradation evaluation.

[0056] Since the temperature change is stored for a certain period of time, the frequency of occurrence of temperature fluctuations is counted using a counting method such as the rainflow method. From this result, the damage d[1] of the entire temperature history is calculated using, for example, Equation 8.

[0057]

number

[0058] 15 is a diagram showing the life cycle-Tjc characteristics of the power semiconductor element of the power conversion device in the embodiment of the present invention, where alx and blx are coefficients of the life cycle characteristic curve that represents the relationship between temperature amplitude and life.

[0059] This calculation result d[1] is sent to the cumulative damage calculation unit 307 shown in Fig. 1 and added to the cumulative damage d[0] read from the past cumulative damage storage device 308. That is, the new cumulative damage d[0] is calculated using Equation 9.

[0060]

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[0061]

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[0062] 12 is a flow chart showing the process in the temperature history calculator in the embodiment of the present invention. First, it is determined whether the inverter has started operating (S2). Once operation is confirmed, the switching frequency and on-duty are obtained from the motor control unit (S3).

[0063] In addition to this information, losses are estimated based on the output current and DC voltage obtained from the sensor (S4), the parameters in the electrical characteristics table, and formulas 2 and 3 (S5). Next, the temperature difference between the junction and case is estimated (S7) from the estimated losses and the thermal characteristics table, and formulas 4 and 5 (S6). Next, the junction temperature is calculated from the temperature difference between the junction and case, the heat sink temperature, and formulas 6 and 7 (S8).

[0064] The obtained junction temperature is compared to see if it is within the temperature range of the electrical characteristics table (S9).

[0065] If the temperature is not within the temperature range, the electrical characteristics table within the temperature range is referenced and the parameters are reselected. After the parameters in the electrical characteristics table converge to within the range of the estimated junction temperature, the temperature amplitude is calculated based on Equation 4 and Equation 5 (S10) and stored in the temperature history storage device (S11).

[0066] If the temperature is not within the range and the computing device has spare processing capacity (S12), the degree of damage to the power semiconductor (Formula 8) (S13), the degree of cumulative damage (Formula 9) (S14), and the remaining life of the power semiconductor (Formula 10) (S15) are estimated from the temperature history.

[0067] Next, a remote monitoring system for the power conversion device 100 will be described with reference to Fig. 1 and Fig. 16. The power conversion device 100 includes a communication device 501 and a monitoring device 503 that monitors a plurality of inverters via a communication network 502.

[0068] 16 shows an example of a remote monitoring system using the power conversion device of the present invention. The temperature history calculator 301 sends the temperature history calculation result and the alarm determination result to the communication device 501. The communication device 501 sends this information to the monitoring device 503 via the communication network 502.

[0069] Each of the power electronics devices 100 is connected to a communication network 502 via a communication device provided therein. A monitoring device 503 is also connected to the communication network 502 and monitors the multiple power electronics devices 100.

[0070] The monitoring device 503 periodically receives the identifier and remaining life of the inverter from each power conversion device 100 in association with each other, and when the remaining life becomes shorter than a predetermined remaining life, outputs the identifier and remaining life of the inverter in association with each other to the output device.

[0071] At this time, the contact information associated with the manager of the inverter may also be output.

[0072] With the above configuration, the monitoring device 503 can monitor a plurality of power conversion devices 100. Furthermore, by equipping the monitoring device 503 with a display device such as a more detailed display than the display 402 and a high-performance arithmetic device, integrated management and analysis can be performed, such as comparing the operating conditions of a plurality of power conversion devices 100 and detecting abnormal operation.

[0073] For example, the daily operating status can be managed even from a location far from the power conversion equipment, such as an office, making management operations more efficient. Furthermore, by accumulating data, the information required for formulating maintenance and operation plans can be updated on an ongoing basis. In addition, when an abnormality occurs, the operating status can be shared objectively with related departments, reducing downtime. [Explanation of symbols]

[0074] 100 Power conversion device, 101 AC power supply, 102 Motor, 200 Main circuit, 201 Diode rectifier, 202 Smoothing capacitor, 203 (a, b, c, d, e, f) IGBT, 204 (a, b, c, d, e, f) Diode, 205 Inverter, 206 Motor control unit, 207 (a, b) Current sensor, 208 Gate driver 220 power module, 221 housing, 222 power semiconductor element, 223 temperature sensor, 224 solder under chip, 225 copper foil, 226 insulating substrate, 227 solder under substrate, 228 metal base, 229 metal wire, 300 life estimation device, 301 temperature history calculator, 302 electrical characteristic table, 303 thermal characteristic table, 304 temperature history storage device, 305 damage calculation unit, 306 withstand characteristic table, 307 cumulative damage calculation unit, 308 cumulative damage storage device, 309 life estimation device, 321 DC voltage, 322 reference voltage, 336 switching loss-collector current characteristic, 337 linear approximation curve, 341 diode forward voltage-forward current characteristic, 342 linear approximation curve, 346 recovery loss-forward current characteristic, 347 linear approximation curve, 351 Thermal impedance-time characteristics of IGBT, 356 Thermal impedance-time characteristics of diode, 361 Junction temperature, 362 Life cycle-Tjc characteristic curve, 400 Interface device, 401 Alarm determination device, 402 Display device, 421 Life estimation result, 422 Reference value, 501 Communication device, 502 Communication network, 503 Monitoring device

Claims

1. an inverter including a temperature sensor for supplying power for driving a motor; and a main circuit including a motor control unit for controlling the motor; a damage calculation unit that calculates the degree of damage to the element based on the drive period of the inverter received from the motor control unit and history information of temperature changes obtained from the temperature sensor; a life estimation device including a life estimation unit that calculates a remaining life of an element based on a degree of damage obtained from the damage calculation unit; A power conversion device comprising an interface device that outputs the remaining life calculated by a life estimation unit.

2. 2. The power conversion device according to claim 1, A power conversion device in which a temperature sensor is installed on the heat sink of the inverter, and a damage calculation unit converts the temperature change of the heat sink obtained from the temperature sensor into the temperature change of the junction of the element, thereby determining the degree of damage to the element.

3. 2. The power conversion device according to claim 1, The life estimation device is a power conversion device that has a temperature history calculation unit that calculates the cumulative number of temperature changes from the inverter drive cycle, calculates the rising temperature from a temperature sensor, and calculates history information of temperature changes from the cumulative number of temperature changes and the rising temperature, and a damage calculation unit that calculates the degree of damage to the elements from the history information of temperature changes calculated by the temperature history calculation unit.

4. 2. The power conversion device according to claim 1, The life estimation device is equipped with a cumulative damage calculation unit that calculates the cumulative damage of the element from the degree of damage to the element obtained from the damage calculation unit, and the life estimation unit calculates the remaining life of the element from the cumulative damage of the element calculated by the cumulative damage calculation unit.

5. The power conversion device according to claim 3, The life estimation device is provided with a thermal characteristics table that stores the correspondence between the temperature of the heat sink of the inverter and the temperature of the element, and the temperature history calculation unit refers to the thermal characteristics table to obtain history information of temperature changes of the element.

6. The main circuit supplies power to drive the motor, the temperature sensor attached to the inverter outputs the inverter temperature, and the motor control unit outputs the inverter drive cycle. A damage calculation unit included in the life estimation device calculates the degree of damage to the element based on the inverter drive cycle received from the motor control unit and history information of temperature changes obtained from the temperature sensor, A life estimation unit calculates the remaining life of the element based on the degree of damage obtained from the damage calculation unit, A method for estimating a remaining life of a power conversion device, in which an interface device outputs a remaining life calculated by a life estimation unit.

7. an inverter including a temperature sensor for supplying power for driving a motor; and a main circuit including a motor control unit for controlling the motor; a damage calculation unit that calculates the degree of damage to the element based on the drive period of the inverter received from the motor control unit and history information of temperature changes obtained from the temperature sensor; a life estimation device including a life estimation unit that calculates a remaining life of an element based on a degree of damage obtained from the damage calculation unit; a plurality of power conversion devices each having an interface device that outputs the remaining lifespan calculated by the lifespan estimation unit and a monitoring device are connected via a network; A remote monitoring system for a power conversion device, in which a monitoring device receives information on the remaining life of an inverter sent from the power conversion device, and outputs the received information on the remaining life of the inverter in association with an identifier of the inverter.

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