Power conversion apparatus and remote monitoring system

Abstract

To provide a power conversion apparatus and a remote monitoring system in which the life of a power semiconductor device can be computed with high precision.SOLUTION: A power conversion apparatus performs desired power conversion while controlling a current to flow or be interrupted in an inverter having a power semiconductor device, and includes a motor controller that controls the inverter by calculating a gate signal on the basis of a current value detected by a current sensor, a speed command, and a carrier frequency, a temperature history computer that computes a temperature history by estimating loss in the power semiconductor device, a temperature history storage device that saves a computation result of the temperature history, and a damage computer that computes a damage to the power semiconductor device from the temperature history read out from the temperature history storage device.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a power conversion apparatus including a power semiconductor device. [Background technology]

[0002] Power conversion devices, such as general-purpose inverters, are widely used in industry as motor drive devices for manufacturing equipment, elevators, transport equipment, etc. In these various applications, general-purpose inverters are required to operate stably. If a general-purpose inverter were to stop functioning, it would cause a halt in factory production and equipment operation, resulting in a significant impact.

[0003] General-purpose 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 joined by wire bonding or soldering to copper foil patterns formed on an insulating substrate, which electrically connects them to external circuits. The insulating substrate is mounted on a metal base, and the power semiconductor devices are cooled via the metal base. A component that incorporates a power semiconductor device in a housing that has a structure for electrical connection to external circuits and a cooling structure is called a power module.

[0004] When current flows through or is cut off in a power semiconductor device, the device generates heat, creating a temperature difference (hereafter referred to as ΔT) between the junction and the fin (a metal base with a cooling structure). When the inverter is shut down, heat generation ceases and ΔT decreases. The junctions (wire bonding and junctions with copper foil patterns) of the power semiconductor devices generally use materials with different thermal expansion coefficients, so fluctuations in ΔT impose thermal stress on the junctions. Repeated fluctuations in ΔT can cause peeling or cracks in the junctions, leading to failure. The time it takes for such failures to occur depends on the magnitude and frequency of ΔT. The magnitude and frequency of ΔT vary depending on how the power conversion system is used and the devices it drives. Furthermore, the load on the IGBTs and diodes varies depending on the system's operating conditions. Therefore, to prevent such failures, measures are needed to understand the load on the IGBTs and diodes according to the system's operating conditions.

[0005] Prior art in this technical field is disclosed in Patent Document 1. Patent Document 1 proposes an electric motor control device in which a temperature change estimation unit estimates a temperature change in a semiconductor element based on an output current signal calculated from a current flowing through the semiconductor element of a switching circuit, an operating frequency signal, and a carrier frequency signal, and calculates a temperature change amplitude, a thermal stress calculation unit converts power cycle curve data stored in a power cycle curve data storage unit into the number of power cycles corresponding to the temperature change amplitude and calculates a thermal stress signal, and a lifespan estimation unit estimates the lifespan of the semiconductor element based on the thermal stress signal and outputs the lifespan estimation result signal to a display unit. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] International Publication No. 2004 / 082114 Summary of the Invention [Problem to be solved by the invention]

[0007] In Patent Document 1, calculations are performed simultaneously by the temperature change estimator, the thermal stress calculator, and the lifespan estimator. This configuration places a heavy load on the calculator that performs these calculations, making it difficult to perform highly accurate calculations. Furthermore, while the specification exemplifies a method for calculating the heat generation amount of a semiconductor element as a function of the output current I using equation (1), there is a problem in that the effective currents flowing through the power transistor and diode differ depending on whether the power is running or regenerating, making it difficult to accurately calculate the respective losses. [Means for solving the problem]

[0008] One example of the present invention is a power conversion device that controls the flow and interruption of current using an inverter having a power semiconductor device to perform desired power conversion, and includes a motor controller that calculates a gate signal based on a current value detected by a current sensor, a speed command, and a carrier frequency to control the inverter, a temperature history calculator that estimates losses in the power semiconductor device and calculates a temperature history, a temperature history storage device that stores the results of the temperature history calculation, and a damage calculator that calculates damage to the power semiconductor device from the temperature history read from the temperature history storage device. [Effects of the Invention]

[0009] According to the present invention, the lifetime of a power semiconductor device can be calculated with high accuracy. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a configuration diagram of a power conversion device according to a first embodiment. [Figure 2] 1 is a circuit diagram of an inverter of a power conversion device according to a first embodiment. [Figure 3] FIG. 2 is a perspective view of a power module of the power conversion device according to the first embodiment. [Figure 4] 1 is a cross-sectional view of a power module of a power conversion device according to a first embodiment. [Figure 5] 3 is a diagram showing a time transition of a DC voltage of the power conversion device in the first embodiment. FIG. [Figure 6] 4 is a diagram showing the collector-emitter voltage-collector current characteristics of the IGBT of the power conversion device in the first embodiment. FIG. [Figure 7] 4 is a diagram showing the single-pulse switching loss-collector current characteristics of the IGBT of the power conversion device in Example 1. FIG. [Figure 8] 4 is a diagram showing forward voltage-forward current characteristics of a diode of the power conversion device in the first embodiment. FIG. [Figure 9] 4 is a diagram showing the single pulse recovery loss vs. forward current characteristics of the IGBT of the power conversion device in the first embodiment. FIG. [Figure 10] FIG. 3 is a diagram showing the thermal impedance-time characteristics of the IGBT of the power conversion device according to the first embodiment. [Figure 11] FIG. 4 is a diagram showing thermal impedance-time characteristics of a diode of the power conversion device in the first embodiment. [Figure 12] 5 is a diagram showing an example of a calculation result of the temperature history of the power conversion device in the first embodiment. FIG. [Figure 13] FIG. 4 is a diagram showing a reversal point of the temperature history of the power conversion device in the first embodiment. [Figure 14] FIG. 3 is a diagram showing the life cycle-Tjc characteristics of the power semiconductor elements of the power conversion device in Example 1. [Figure 15] 10 is a diagram illustrating a method for comparing a life calculation result of the power conversion device with a reference value in the first embodiment. FIG. [Figure 16] 10 is a diagram showing a life display of a life calculation result of the power conversion device in the first embodiment. FIG. [Figure 17] 10 is a diagram showing a display of a notification of a life calculation result of the power conversion device in the first embodiment. FIG. [Figure 18] FIG. 10 is a configuration diagram of a remote monitoring system having a power conversion device according to a second embodiment. [Figure 19] FIG. 10 is a conceptual diagram of a remote monitoring system in which a plurality of power electronics devices are connected to a monitoring device via a communication network in a second embodiment. [Figure 20] FIG. 10 is a configuration diagram of a power conversion device according to a third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. [Example]

[0012] 1 is a configuration diagram of a power conversion device in this embodiment. In FIG. 1, a power conversion device 100 includes a main circuit 200, a lifespan estimation device 300, and an interface device 400.

[0013] First, the main circuit 200 will be described. The main circuit 200 is configured with an inverter 205 including a diode rectifier 201 that rectifies AC power sent from the AC power supply 101, a smoothing capacitor 202, an IGBT 203 that is a power semiconductor switching element, and a diode 204 connected in anti-parallel to the IGBT 203. In this embodiment, the inverter 205 will be described as a three-phase two-level inverter shown in FIG. 2.

[0014] The inverter 205 is controlled by a motor controller 206. Specifically, the motor controller 206 calculates a gate signal using the current value detected by current sensors 207a and 207b, a speed command, and a set carrier frequency fc. The calculated gate signal is amplified by a gate driver 208 and input as a gate voltage to the IGBTs 203 (a, b, c, d, e, and f). The ratio of the gate on period to the carrier cycle is called the on-duty D. This outputs a voltage so that the motor 102 operates at the commanded speed. In both the IGBT 203 and the diode 204, the junction temperature rises due to Joule loss when they are on, switching loss when they are switched off, and recovery loss, and the junction temperature drops when they are off.

[0015] FIG. 3 shows a perspective view of a power module 220 incorporating an IGBT 203 and a diode 204, and FIG. 4 shows a cross-sectional view taken along line AA' in FIG.

[0016] In FIG. 3, a plurality of power semiconductor elements 222 such as IGBT 203 and diode 204, and a temperature sensor 223 are arranged on the surface inside a housing 221 (only one semiconductor element is shown in FIGS. 3 and 4).

[0017] 4, power module 220 is formed by laminating power semiconductor element 222, under-chip solder 224, copper foil 225, insulating substrate 226, under-substrate solder 227, and metal base 228 in this order, with under-chip solder 224 and under-substrate solder 227 joining adjacent layers. The other side of the semiconductor element surface is joined with metal wire 229.

[0018] Because the power semiconductor element 222 is bonded with materials having different thermal expansion coefficients, stress is applied to the bonded portion when the temperature of the power semiconductor element rises and falls. The ability to withstand this stress is called power cycle capability, and is expressed as the number of usable cycles for a given temperature amplitude, called the life cycle. Therefore, if the temperature history of a semiconductor element is known, it is possible to estimate its lifespan.

[0019] Next, the lifetime estimation device 300 will be described. In Fig. 1, the lifetime estimation device 300 in this embodiment is triggered by a calculation command A, and a temperature history calculator 301 estimates the losses of the semiconductor elements of the IGBT and the diode from the carrier frequency fc and on-duty D obtained from the motor controller 206, the DC voltage Vd detected by the voltage sensor 209, the current I detected by the current sensor 207, a thermal characteristic table 303 of the IGBT and the diode, and an electrical characteristic table 302. This will be described in detail below.

[0020] First, as shown in Fig. 5, for example, it is determined that the DC voltage 321 is below the reference voltage 322 and that the DC voltage is above the reference voltage and is therefore regenerative. Alternatively, the motor power factor is estimated from control information held by the motor controller, and powering or regeneration is determined. Then, when the current is in the positive direction, the loss Pq of the IGBT in the upper arm is calculated, for example, by the following formula (1) during powering, and by the following formula (2) during regeneration.

[0021]

number

[0022]

number

[0023] Here, rq and vq are the slope and intercept of a linear approximation curve 332 of the IGBT collector-emitter voltage-collector current characteristics 331 shown in Fig. 6. Also, aq and bq are the slope and intercept of a linear approximation curve 337 of the IGBT switching loss per pulse-collector current characteristics 336 when the DC voltage is vdb shown in Fig. 7. In Fig. 1, these variables are stored in the electrical characteristics table 302.

[0024] Furthermore, the loss Pd of the diode in the lower arm is calculated when the current is in the positive direction, for example, during powering, using the following equation (3), and during regeneration, using the following equation (4).

[0025]

number

[0026]

number

[0027] Here, rd and vd are the slope and intercept of a linear approximation curve 342 of the diode forward voltage-forward current characteristics 341 shown in Fig. 8. Also, ad and bd are the slope and intercept of a linear approximation curve 347 of the diode recovery loss per single pulse-forward current characteristics 346 when the DC voltage is vdb, shown in Fig. 9. In Fig. 1, these variables are stored in the electrical characteristics table 302.

[0028] Next, the temperature history of each semiconductor element, the IGBT and the diode, is calculated. This will be explained in detail below.

[0029] First, the temperature difference ΔTq between the junction and fin of the IGBT is calculated, for example, by the following equation (5).

[0030]

number

[0031] Here, τthq and rthq are variables of an approximation curve 352 of the thermal impedance-time characteristic 351 of the IGBT shown in Fig. 10. In Fig. 1, these variables are stored in the thermal characteristic table 303.

[0032] TIFF2025188283000007.tif11153The calculation of loss Pq and △Tq are performed at an arbitrarily settable period of △t, and the i-th △Tq is △Tq[i]. In Figure 1, the calculation result of △Tq[i] is sent to and saved in the temperature history storage device 304. When calculating equation (5), △Tq[i-1] is read from the temperature history storage device 304.

[0033] △Tq[0] can be set to any value appropriate for the timing of issuing calculation command A. For example, if it is determined that the inverter stop time is sufficiently longer than τthq, setting Tq[0] to 0 will enable more accurate calculations. Also, setting △t to a small value will increase the accuracy of the temperature history calculation. To achieve a certain level of accuracy, it is preferable to set △t to less than 1 / 10 of the thermal time constant of the power module. On the other hand, setting △t to a large value reduces the amount of temperature history data per unit time, which has the advantage of saving memory capacity and allowing temperature history to be stored for a longer period of time.

[0034] Next, the temperature difference ΔTd between the junction and the fin of the diode is calculated, for example, by equation (6).

[0035]

number

[0036] Here, τthd and rthd are variables of an approximation curve 357 of the thermal impedance-time characteristic 356 of the diode shown in Fig. 11. In Fig. 1, these variables are stored in the thermal characteristic table 303.

[0037] An example of the calculation results of the temperature history of the upper arm IGBT and diode during powering and acceleration operation is shown in Figure 12. From the top to bottom, Figure 12 shows the waveform of the output frequency f0 of the motor controller 206 in Figure 1, followed by the waveforms of △Tq and △Td, which are the calculation results. In this example, △Tq is maximum at the second peak, and △Td is maximum at the third peak. By saving the temperature history, it is possible to detect the temperature peak at which damage is greatest, which is important for highly accurate life prediction.

[0038] Next, we will explain the process of estimating the degree of degradation (damage) using the above temperature history. Note that hereafter, we will not distinguish between IGBTs and diodes. The damage calculator 305 shown in Figure 1 reads the temperature history from the temperature history storage device 304 and extracts the minimum and maximum points of △T as shown in Figure 13 (hereinafter, the minimum and maximum points will be collectively referred to as inversion points). From the array △T' of the extracted inversion points, the number of times that the amplitude R of △T'' occurs 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 (7).

[0039]

number

[0040] Here, R[j] is the j-th R, and n[j] represents the number of occurrences of R[j]. alx and blx are coefficients of an approximation curve 362 of the life cycle-Tjc characteristic curve 361 shown in Fig. 14, and are stored in the tolerance characteristic table 306 in Fig. 1.

[0041] In this embodiment, an example is shown in which coefficients are used for linear approximation of the tolerance characteristic curve, but approximation may be performed using other methods, or the characteristics may be compiled into a table, etc. The process of extracting the reversal points may be performed by the temperature history calculator 301. If this process is performed by the temperature history calculator 301, it is not necessary to store information other than the reversal points, and the amount of storage can be reduced.

[0042] The calculation result d[1] is sent to the cumulative damage calculator 307 shown in Figure 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 (8).

[0043]

number

[0044] d[0] is initially 0, increases as damage accumulates, and when it reaches 1, it is determined that the end of life has arrived.

[0045] This calculation result d[0] is sent to and stored in the cumulative damage storage device 308. Then, d[0] is sent from the cumulative damage storage device 308 to the life estimator 309, which calculates the life L using equation (9).

[0046]

number

[0047] L is initially 100, decreases as damage accumulates, and reaches 0, which is the end of life.

[0048] With the above configuration, the lifetime estimation device 300 can calculate the lifetimes of the IGBT 203 and the diode 204 in accordance with the power cycle.

[0049] The loss estimation and temperature history calculation processes must be performed from instantaneous current and control information while the inverter is operating. Meanwhile, since the temperature history is stored in a storage device, the damage calculations can be performed when the inverter has spare processing capacity. For example, to smooth the calculation load, the process can be performed when the inverter is in standby mode, when no PWM calculations or the like are performed and the load on the calculation device is small. Alternatively, one damage calculation can be performed between multiple temperature calculation processes.

[0050] Next, a description will be given of the interface device 400. In FIG.

[0051] Fig. 15 is a diagram illustrating a method for comparing the life calculation result of a power conversion device with a reference value in this embodiment. In Fig. 15, an alarm determination unit 401 compares a life estimation result 421 with a reference value 422 that can be set arbitrarily. A period when the life estimation result 421 is equal to or greater than the reference value 422 is called a non-alarm period, and a period when it is less than the reference value 422 is called an alarm period. During the non-alarm period, the life estimation result is sent to the display unit 402 in Fig. 1, and the life is clearly displayed so that it can be seen, for example, as shown in Fig. 16. In Fig. 16, the display unit 402 shows that the remaining life is 36%.

[0052] During the alarm period, a message is displayed so that the user can understand that the value is below the reference value and is different from normal, as shown in Fig. 17. In Fig. 17, when the value falls below the reference value, "EEE" is displayed on the display 402.

[0053] In this way, by making the lifespan and alarms explicit, it is possible to replace the power module before it reaches its lifespan, and it is also possible to extend the life of the power module by taking degeneration measures such as lengthening the acceleration and deceleration time of the inverter, and it is possible to consider preventive measures against sudden failures and prevent sudden failures from occurring.

[0054] As described above, according to this embodiment, the lifespan of the IGBT and the diode can be calculated with high accuracy. Furthermore, by making the lifespan and alarms explicit, it is possible to prevent sudden failures. [Example]

[0055] Fig. 18 is a configuration diagram of a remote monitoring system having a power electronics device according to this embodiment. In Fig. 18, the same components as those in Fig. 1 are denoted by the same reference numerals, and their description will be omitted. The difference between Fig. 18 and Fig. 1 is that, in addition to the components in Fig. 1, the power electronics device 100 includes a communicator 501 and is connected via a communication network 502 to a monitoring device 503 that monitors a plurality of power electronics devices.

[0056] 18, 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.

[0057] Fig. 19 is a conceptual diagram of a remote monitoring system in this embodiment in which a plurality of power electronics devices are connected to a monitoring device via a communication network. In Fig. 19, each power electronics device 100 is connected to a communication network 502 via a communicator 501. A monitoring device 503 is also connected to the communication network 502 and monitors the plurality of power electronics devices 100.

[0058] With the above configuration, the monitoring device 503 can monitor multiple power conversion devices 100. Furthermore, by equipping the monitoring device 503 with a display device such as a detailed display and a high-performance computing device, comprehensive management and analysis can be performed, such as comparing the operating status of multiple power conversion devices 100 and detecting abnormal operation. For example, daily operating status can be managed even from a location far from the power conversion devices, such as an office, thereby improving the efficiency of management work. Furthermore, by accumulating data, information necessary for formulating maintenance plans and operation plans can be updated sequentially. Furthermore, when an abnormality occurs, objective operating status can be shared with related departments, thereby reducing downtime. [Example]

[0059] In this embodiment, a power conversion device using a regenerative converter will be described. Fig. 20 is a configuration diagram of the power conversion device in this embodiment. In Fig. 20, the same components as in Fig. 1 are given the same reference numerals, and their description will be omitted. Fig. 20 differs from Fig. 1 in that it includes a main circuit 600 using a regenerative converter.

[0060] 20, a main circuit 600 includes a regenerative converter 601, instead of the diode rectifier 201 in FIG. 1, which includes an IGBT 203 that is a power semiconductor switching element and a diode 204 connected in anti-parallel to the IGBT. It also includes a regenerative converter controller 606. The regenerative converter 601 can adjust the power factor of the input power by switching the IGBT 203, which has the advantage of being able to suppress fluctuations in DC voltage.

[0061] Although the embodiments have been described above, the present invention is not limited to the above-described embodiments and includes various modifications. For example, the above-described embodiments have been described in detail to clearly explain the present invention, and the present invention is not necessarily limited to those including all of the described configurations. Furthermore, it is possible to add, delete, or replace part of the configuration of each embodiment with other configurations. Furthermore, the above-described configurations and functions may be implemented in part or in whole by software in which a processor interprets and executes a program that realizes each function, or by hardware, for example, by designing an integrated circuit. [Explanation of symbols]

[0062] 100: Power conversion device, 101: AC power supply, 102: Motor, 200: Main circuit, 201: Diode rectifier, 202: Smoothing capacitor, 203: IGBT, 204: Diode, 205: Inverter, 206: Motor controller, 207: Current sensor, 208: Gate driver, 220: Power module, 221: Housing, 222: Power semiconductor element, 223: Temperature sensor, 300: Life estimation device, 301: Temperature history calculator, 302: Electrical characteristics Table, 303: Thermal characteristics table, 304: Temperature history storage device, 305: Damage calculator, 306: Withstand characteristics table, 307: Accumulative damage calculator, 308: Accumulative damage storage device, 309: Life estimator, 321: DC voltage, 322: Reference voltage, 400: Interface device, 401: Alarm determination device, 402: Display, 421: Life estimation result, 422: Reference value, 501: Communication device, 502: Communication network, 503: Monitoring device, 601: Regenerative converter

Claims

1. A power conversion device that controls current flow and interruption using an inverter having a power semiconductor device to perform desired power conversion, a motor controller that calculates a gate signal based on the current value detected by the current sensor, a speed command, and a carrier frequency, and controls the inverter; a temperature history calculator that estimates a loss of the power semiconductor device and calculates a temperature history; a temperature history storage device for storing the calculation results of the temperature history; a damage calculator that calculates damage to the power semiconductor device from the temperature history read from the temperature history storage device;

2. The power conversion device according to claim 1, the temperature history calculator estimates a loss in the power semiconductor device from the carrier frequency, the on-duty, the DC voltage, the current, and the electrical characteristics of the power semiconductor device, and calculates a temperature history of the power semiconductor device from the estimated loss and the thermal characteristics of the power semiconductor device.

3. The power conversion device according to claim 1, The temperature history calculator performs processing while the inverter is operating, A power conversion device characterized in that the processing of the damaged computing unit is performed when there is a margin in the processing capacity of the inverter.

4. The power conversion device according to claim 2, The power semiconductor device is an IGBT and a diode, the temperature history calculator calculates the temperature history of each of the IGBT and the diode individually; The power conversion device is characterized in that the damage calculator calculates damage to each of the IGBT and the diode individually.

5. The power conversion device according to claim 2, the temperature history calculator estimates powering and regeneration information of the inverter from the monitoring of the DC voltage; Estimating losses in the power semiconductor device individually during powering and regeneration based on the powering and regeneration information; The power conversion device is characterized in that the temperature history of the power semiconductor device is calculated individually during power generation and during regeneration from the estimated loss and the thermal characteristics of the power semiconductor device.

6. The power conversion device according to claim 2, The temperature history calculator estimates powering and regeneration information of the inverter from the power factor monitoring, Estimating losses in the power semiconductor device individually during powering and regeneration based on the powering and regeneration information; The power conversion device is characterized in that the temperature history of the power semiconductor device is calculated individually during power generation and during regeneration from the estimated loss and the thermal characteristics of the power semiconductor device.

7. The power conversion device according to claim 1, a cumulative damage calculator that accumulates the damage results of the power semiconductor device calculated by the damage calculator; an accumulated damage storage device for storing the accumulated damage results; A power conversion apparatus comprising: a life estimator that estimates a life of the power semiconductor device from the accumulated damage results read from the accumulated damage storage device.

8. The power conversion device according to claim 7, A power conversion device characterized by comprising an alarm determiner that compares the life estimation result from the life estimator with a reference value, and if the life estimation result is equal to or greater than the reference value, displays the life estimation result on a display as a non-alarm period, and if the life estimation result is less than the reference value, displays on a display that the life estimation result is below the reference value and is different from normal times as an alarm period.

9. A remote monitoring system having the power conversion device according to claim 8, the power conversion device includes a communication device and is connected to a monitoring device that monitors the power conversion device via a communication network; A remote monitoring system characterized in that the power conversion device sends the temperature history calculation result of the temperature history calculator and the alarm determination result of the alarm determination device to the communication device, and the communication device sends the temperature history calculation result and the alarm determination result to the monitoring device via the communication network.

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