Electric power conversion system, controller and control method

Abstract

To reach the target lifetime of a semiconductor device.SOLUTION: An electric power conversion system comprises semiconductor elements QU-QZ for power conversion and a controller 50 that determines the operating temperature limit at which the life of the semiconductor elements reaches the target life and limits the output of an electric power conversion system 101 so that the operating temperature of the semiconductor elements does not exceed the operating temperature limit.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to a power conversion device, a control device, and a control method. [Background technology]

[0002] A known control device includes a remaining life estimation means for estimating the remaining life of a power switching element used in a power converter based on power cycles, and a diagnosis result output means for outputting a signal instructing replacement of the power switching element before the life estimated by the remaining life estimation means is reached. This control device also includes a load pattern storage means for storing a load pattern of the power converter and calculating a moving average of the load pattern over a predetermined period, a replacement time setting means for estimating the time when the power switching element will fail using a future load pattern as the moving average and setting the replacement time, and an output limit setting means for outputting a command to limit the output of the power converter based on information from the replacement time setting means. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-67690 Summary of the Invention [Problem to be solved by the invention]

[0004] However, with conventional techniques, even if the output of the power conversion device is limited, it may be difficult to extend the life of the semiconductor element to the target life.

[0005] An object of the present disclosure is to extend the life of a semiconductor element to a target life. [Means for solving the problem]

[0006] The present disclosure provides, as one means for solving the problem, a semiconductor element for power conversion; The present invention provides a power conversion device comprising: a control device that determines an operating temperature limit value at which the life of the semiconductor element reaches a target life, and that limits the output of the power conversion device so that the operating temperature of the semiconductor element does not exceed the operating temperature limit value.

[0007] The present disclosure provides another means for solving the problem, Provided is a control device that includes a control circuit that determines an operating temperature limit value at which the life of a semiconductor element used in a power conversion device will reach a target life, and the control circuit limits the output of the power conversion device so that the operating temperature of the semiconductor element does not exceed the operating temperature limit value.

[0008] The present disclosure provides another means for solving the problem, A control method is provided for determining an operating temperature limit value at which the life of a semiconductor element used in a power conversion device reaches a target life, and for limiting the output of the power conversion device so that the operating temperature of the semiconductor element satisfies the operating temperature limit value. [Effects of the Invention]

[0009] According to the present disclosure, the life of a semiconductor element can be made to reach a target life. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 10 is a diagram showing an example of a change in junction temperature of a semiconductor element. [Figure 2] 10 is a diagram illustrating an example of the relationship between the amount of change in junction temperature of a semiconductor element and the number of power cycles for its life. [Figure 3] 1 is a diagram illustrating an example of a configuration of a power conversion device according to a first embodiment. [Figure 4] FIG. 10 is a diagram illustrating an example of a process for determining a first operating temperature limit value. [Figure 5] FIG. 10 is a diagram illustrating an example of a process for determining a second operating temperature limit value. [Figure 6] FIG. 10 is a diagram illustrating an example of a process for outputting a failure forecast. [Figure 7] FIG. 10 is a diagram showing an example of the configuration of a control device that limits output using a first operating temperature limit value. [Figure 8] FIG. 10 is a diagram illustrating an example of the configuration of a torque limit value generator. [Figure 9] FIG. 10 is a diagram illustrating an example of the configuration of a temperature limit value generator that calculates a first operating temperature limit value. [Figure 10] FIG. 10 is a diagram illustrating an example of the configuration of a degradation degree calculator. [Figure 11] FIG. 10 is a diagram illustrating an example of the configuration of a temperature limit value generator that calculates a second operating temperature limit value. [Figure 12] FIG. 10 is a diagram showing an example of the configuration of a control device that limits output using a second operating temperature limit value. [Figure 13] FIG. 4 is a diagram for explaining a first method for generating a trigger signal. [Figure 14] FIG. 10 is a diagram for explaining a second method for generating a trigger signal. [Figure 15] FIG. 2 is a diagram illustrating an example of the configuration of a control device that outputs a failure forecast. DETAILED DESCRIPTION OF THE INVENTION

[0011] The following describes the embodiments.

[0012] <About power cycle life> FIG. 1 is a diagram showing an example of changes in the junction temperature of a semiconductor element. In FIG. 1, the horizontal axis represents time t, and the vertical axis represents the junction temperature Tj of the semiconductor element. When the junction temperature Tj of a semiconductor element, such as a power semiconductor device, changes as shown in FIG. 1, the semiconductor element is subjected to thermal stress due to differences in the thermal expansion coefficients of the materials that make up the semiconductor element. When this thermal stress is repeated, the semiconductor element experiences fatigue and deterioration until it reaches the end of its life. Because the fatigue and deterioration of a semiconductor element largely depend on the range of fluctuations in the rise and fall of the junction temperature Tj, the life of a semiconductor element varies depending on operating and environmental conditions. The life due to thermal stress is called the power cycle life (power cycle tolerance).

[0013] 1 illustrates one power cycle in which the junction temperature Tj changes to a peak value Tj(max) by a change width ΔTj, where the time width T corresponds to the length of one power cycle.

[0014] 2 is a diagram illustrating the relationship between the amount of change in junction temperature of a semiconductor element and the number of power cycles over its life. The horizontal axis represents the change in junction temperature ΔTj, and the vertical axis represents the number of power cycles over its life Ntbl. The number of power cycles over its life Ntbl represents the number of power cycles over which the semiconductor element reaches the end of its power cycle life.

[0015] As can be seen from the characteristic curve (power cycle life curve) shown in Figure 2, the number of power cycles Ntbl in the life span is heavily dependent on the variation ΔTj of the junction temperature Tj. The larger the variation ΔTj, the smaller the number of power cycles Ntbl in the life span. In other words, the larger the variation ΔTj, the shorter the life span of the semiconductor element. When comparing at the same variation ΔTj, the higher the junction temperature Tj, the shorter the life span of the semiconductor element tends to be.

[0016] On the other hand, in the case of semiconductor elements used in a power conversion device, the main cause of temperature rise in the semiconductor elements is loss in the semiconductor elements. Therefore, if the output current of the power conversion device is reduced, the temperature rise in the semiconductor elements that pass that output current can be suppressed. When the power conversion device is used as a motor drive device, the torque generated by the motor can be reduced (torque limiting) by reducing the output current from the power conversion device to the motor. Therefore, limiting the torque by limiting the output current suppresses temperature rise in the semiconductor elements, thereby extending the life of the semiconductor elements.

[0017] The technology disclosed herein limits the output of a power conversion device, thereby allowing the lifespan of semiconductor elements used to generate that output to reach a target lifespan.

[0018] <Power conversion device according to the first embodiment> Fig. 3 is a diagram showing an example of the configuration of a power conversion device according to the first embodiment. The power conversion device 101 shown in Fig. 3 converts input power from a power supply into AC power for driving a motor M. The power conversion device 101 shown in Fig. 3 is used as a motor drive device for driving the motor M.

[0019] The motor M is an electric motor having multiple coils. For example, the motor M is a three-phase electric motor having a U-phase coil, a V-phase coil, and a W-phase coil. The motor M may be a motor equipped with a speed / position sensor (a sensor-equipped motor) or a motor not equipped with a speed / position sensor (a sensorless motor). The motor M is an example of a load to which power is supplied from a power conversion device.

[0020] The speed / position sensor detects the angular frequency ω1 of the rotor of the motor M and the angular position (magnetic pole position θm) of the magnet of the rotor of the motor M, and outputs the detected values ​​of the angular frequency ω1 and the magnetic pole position θm to the control device 50. The control device 50 may detect the magnetic pole position θm by integrating the angular frequency ω1 detected by the speed / position sensor. If a speed / position sensor is not used, the control device 50 may estimate the magnetic pole position θm of the motor M using an observer. For example, the control device 50 estimates the magnetic pole position θm of the motor M using an observer based on the two-phase or three-phase phase currents detected by the current sensor 30 and the output voltage command value of the inverter circuit 20 calculated by the control device 50 or the phase voltage detection value obtained from the phase voltage detection circuit.

[0021] The power conversion device 101 includes a DC power supply 10, an inverter circuit 20, a current sensor 30, a plurality of temperature sensors 40u, 40v, 40w, 40x, 40y, and 40z, and a control device 50. In the following description, the plurality of temperature sensors 40u, 40v, 40w, 40x, 40y, and 40z may be collectively referred to as a plurality of temperature sensors 40. Alternatively, one of the plurality of temperature sensors 40u, 40v, 40w, 40x, 40y, and 40z may be referred to as a temperature sensor 40.

[0022] The power conversion device 101 includes a main circuit including a DC power supply 10 and an inverter circuit 20. The DC power supply 10 supplies DC power to the inverter circuit 20. The DC power supply 10 may include a converter that converts externally supplied AC or DC into DC, or a rectifier circuit that converts externally supplied AC into DC. The DC power supply 10 may include a DC link connecting the converter or rectifier circuit to the inverter circuit 20.

[0023] The inverter circuit 20 inversely converts the DC input from the DC power supply 10 into AC and supplies the converted AC to the motor M. The inverter circuit 20 has a plurality of semiconductor elements Q_U, Q_V, Q_W, Q_X, Q_Y, and Q_Z. The semiconductor elements Q_U, Q_V, Q_W, Q_X, Q_Y, and Q_Z are switching elements that are turned on or off in accordance with corresponding gate drive signals Gu, Gv, Gw, Gx, Gy, and Gz supplied from a gate driver (not shown).

[0024] In the following description, the multiple semiconductor elements Q_U, Q_V, Q_W, Q_X, Q_Y, and Q_Z may be collectively referred to as multiple semiconductor elements Q. Alternatively, one semiconductor element among the multiple semiconductor elements Q_U, Q_V, Q_W, Q_X, Q_Y, and Q_Z may be referred to as semiconductor element Q.

[0025] The inverter circuit 20 is a power conversion circuit that converts input direct current into alternating current by switching on and off a plurality of semiconductor elements Q. The inverter circuit 20 supplies an alternating current drive current (a three-phase drive current in the case of a three-phase motor M) to the motor M, thereby rotating the rotor of the motor M.

[0026] The semiconductor elements Q are semiconductor elements for power conversion. For example, each of the semiconductor elements Q includes a transistor and a diode connected in antiparallel to the transistor. Specific examples of the transistor include power semiconductors such as an IGBT (Insulated Gate Bipolar Transistor) and a MOSFET (Metal Oxide Semiconductor Field Effect Transistor). The diode may be a parasitic diode.

[0027] The current sensor 30 detects the output current from the inverter circuit 20 of the power conversion device 101 to the motor M. In this example, the current sensor 30 detects the current values ​​of the U, V, and W phase currents flowing through the motor M and outputs phase current detection values ​​iu, iv, and iw representing the detected current values ​​to the control device 50. In the case of a three-phase motor M, the current sensor 30 may detect the current flowing in each of the three-phase output lines, or may detect the current flowing in each of two of the three-phase output lines. The control device 50 may calculate the phase current detection value for the remaining phase from the phase current detection values ​​for two phases based on the relationship iu+iv+iw=0. The current sensor 30 may also detect current using another known detection method.

[0028] The plurality of temperature sensors 40 detect the junction temperatures Tj of the corresponding semiconductor elements among the plurality of semiconductor elements Q. The plurality of temperature sensors 40 output temperature detection values ​​Tj_U, Tj_V, Tj_W, Tj_X, Tj_Y, and Tj_Z representing the junction temperatures Tj detected by each of them to the control device 50. The plurality of temperature sensors 40 are, for example, on-chip sensors mounted on the semiconductor chip.

[0029] The control device 50 generates a plurality of control signals for controlling the inverter circuit 20 that drives the motor M, based on the phase current detection values ​​iu, iv, and iw and the temperature detection values ​​Tj_U, Tj_V, Tj_W, Tj_X, Tj_Y, and Tj_Z. A gate driver (not shown) is a circuit that generates a plurality of gate drive signals Gu, Gv, Gw, Gx, Gy, and Gz that drive the gates of a plurality of semiconductor elements Q in the inverter circuit 20 in accordance with the plurality of control signals. The control device 50 may or may not include a gate driver. If the control device 50 does not include a gate driver, it supplies a plurality of control signals to a gate driver included in the main circuit.

[0030] The control device 50 estimates the lifetimes of the semiconductor elements Q using a predetermined estimation method, and performs processing to determine, using a predetermined generation method, an operating temperature limit value Tj_lim at which the estimated lifetime reaches a target lifetime. The control device 50 then performs control to limit the output of the power conversion device 101 so that the operating temperature of the semiconductor elements Q does not exceed the operating temperature limit value Tj_lim.

[0031] <First control method performed by the control device> Next, the first control method performed by the control device 50 will be described.

[0032] FIG. 4 is a diagram illustrating a first control method performed by the control device, and more specifically, a diagram illustrating an example of a process for determining a first operating temperature limit value Tjop(1). In FIG. 4, the horizontal axis represents the operating time of the power conversion device 101. The operating time of the power conversion device 101 may be interpreted as the operating time or energization time of one semiconductor element Q. In FIG. 4, the vertical axis represents the degree of deterioration of one semiconductor element Q.

[0033] In Figure 4, Ya(1): Operation time of the semiconductor element Q from the time when the power conversion device 101 is newly installed (when it is newly operating) to the first timing Yb(1): Estimated lifetime of semiconductor element Q when there is no output limit due to the operating temperature limit value Tj_lim (estimated lifetime of semiconductor element Q predicted at the first timing) Yend: Design life time of semiconductor element Q ε_end: Degree of deterioration of semiconductor element Q's life span εa(1): Degradation degree of semiconductor element Q at the first timing The design life time Yend is an example of a target life of a semiconductor element.

[0034] The control device 50 includes a memory that stores in advance lifespan characteristic data such as a map representing a power cycle life curve (FIG. 2) of the semiconductor element Q or coefficient data for an arithmetic equation. The lifespan characteristic data is stored in the memory at the time of product shipment. The control device 50 observes a power cycle temperature waveform of the junction of the semiconductor element Q based on a temperature detection value obtained by the temperature sensor 40 during actual operation of the power conversion device 101. The control device 50 sequentially calculates a degradation degree that represents a degradation state of the semiconductor element Q according to a predetermined calculation method based on the power cycle temperature waveform observed during actual operation of the power conversion device 101 and the lifespan characteristic data previously stored in the memory.

[0035] The control device 50 performs the following process 1 and process 2 at the first timing.

[0036] [Process 1] The control device 50 uses the operating time Ya(1) from the time of installation to the first timing and the deterioration level εa(1) of the semiconductor element Q at the first timing to estimate (predict) the operating time Yb(1) at which the deterioration level of the semiconductor element Q will reach the life determination deterioration level ε_end.

[0037] [Process 2] The control device 50 calculates the time difference Δ1 between the operating time Yb(1) and the design life time Yend, and if the time difference Δ1 is equal to or greater than a predetermined time, determines the first operating temperature limit value Tjop(1) at which the estimated life of the semiconductor element Q reaches the design life time Yend using a predetermined generation method.

[0038] The control device 50 performs output current limitation (torque limitation) of the power conversion device 101 so that the operating temperature (junction temperature Tj during operation) of the semiconductor element Q does not exceed the first operating temperature limit value Tjop(1) during actual operation of the power conversion device 101 after the first timing.

[0039] In this way, the control device 50 determines the first operating temperature limit value Tjop(1) at which the estimated life of the semiconductor element Q reaches the designed life time Yend, and limits the output of the power conversion device 101 so that the operating temperature of the semiconductor element Q does not exceed the first operating temperature limit value Tjop(1). According to this first control method, the first operating temperature limit value Tjop(1) at which the life of the semiconductor element Q reaches the designed life time Yend is taken into consideration when limiting the output of the power conversion device 101. This improves the life extension effect of the semiconductor element Q by limiting the output, and allows the life of the semiconductor element Q to reach the target life.

[0040] 4, since the operating time Yb(1) is shorter than the design life time Yend, if the deterioration of the semiconductor element Q continues at the same rate as up to the first timing, there is a risk that the semiconductor element Q will fail before reaching the design life time Yend. When the operating time Yb(1) is shorter than the design life time Yend, the control device 50 can extend the life of the semiconductor element Q to or beyond the design life time Yend by limiting the output using the first operating temperature limit value Tjop(1).

[0041] <Second control method performed by the control device> Next, a description will be given of a second control method performed by the control device 50. The second control method can be combined with the first control method.

[0042] FIG. 5 is a diagram for explaining a second control method performed by the control device, and more specifically, a diagram for explaining an example of a process for determining the second operating temperature limit value Tjop(2). In FIG. 5, the horizontal axis represents the operating time of the power conversion device 101. The operating time of the power conversion device 101 may be interpreted as the operating time or energization time of one semiconductor element Q. In FIG. 5, the vertical axis represents the degree of deterioration of one semiconductor element Q.

[0043] In Figure 5, Ya(1): Operation time of the semiconductor element Q from the time when the power conversion device 101 is newly installed (when it is newly operating) to the first timing Ya(2): Operation time of the semiconductor element Q from the time when the power conversion device 101 is newly installed (when it is newly operating) to the second timing Yb(2): Estimated lifetime of semiconductor element Q when output limitation due to the first operating temperature limit value Tjop(1) continues after the second timing (estimated lifetime of semiconductor element Q predicted at the second timing) Yend: Design life time of semiconductor element Q ε_end: Degree of deterioration of semiconductor element Q's life span εa(1): Degradation degree of semiconductor element Q at the first timing εa(2): Degradation degree of semiconductor element Q at the second timing The design life time Yend is an example of a target life of a semiconductor element.

[0044] The control device 50 performs the following process 1', process 2', and process 3 at a second timing (for example, timing A or timing B below) after the first timing.

[0045] [Timing A] When the moving average value of the operating temperature of semiconductor element Q up to the second timing has changed by more than a predetermined value compared to the moving average value of the operating temperature of semiconductor element Q up to the first timing when the process to obtain the first operating temperature limit value Tjop(1) was performed.

[0046] [Timing B] When the number of power cycles per unit time of semiconductor element Q up to the second timing has changed by more than a predetermined value compared to the number of power cycles per unit time of semiconductor element Q up to the first timing when the process to determine the first operating temperature limit value Tjop(1) was performed.

[0047] [Process 1'] The control device 50 uses the operating time Ya(2) from the time of installation to the second timing and the deterioration level εa(2) of the semiconductor element Q at the second timing to estimate (predict) the operating time Yb(2) at which the deterioration level of the semiconductor element Q will reach the life determination deterioration level ε_end.

[0048] [Process 2'] The control device 50 calculates the time difference Δ2 between the operating time Yb(2) and the design life time Yend, and if the time difference Δ2 is equal to or greater than a predetermined time, determines the second operating temperature limit value Tjop(2) at which the estimated life of the semiconductor element Q reaches the design life time Yend using a predetermined generation method.

[0049] [Process 3] The control device 50 updates the operating temperature limit value Tj_lim from the first operating temperature limit value Tjop(1) to the second operating temperature limit value Tjop(2) during the actual operation of the power conversion device 101 after the second timing.

[0050] The control device 50 sequentially updates the operating temperature limit value Tj_lim by repeatedly performing process 1', process 2', and process 3 each time the conditions of timing A or timing B are satisfied. During actual operation of the power conversion device 101 from the second timing onwards, the control device 50 limits the output current (torque) of the power conversion device 101 so that the operating temperature (junction temperature Tj during operation) of the semiconductor element Q does not exceed the updated operating temperature limit value Tj_lim.

[0051] In this way, the control device 50 performs processing to determine the operating temperature limit value Tj_lim at multiple times and limits the output of the power conversion device 101 so that the operating temperature of the semiconductor element Q does not exceed the updated operating temperature limit value Tj_lim. According to this second control method, the operating temperature limit value Tj_lim is updated at appropriate times, making it possible to prevent the output limit imposed by the operating temperature limit value Tj_lim from being excessively relaxed or tightened.

[0052] 5, since the operating time Yb(2) is longer than the design life time Yend, if the output limitation by the first operating temperature limit value Tjop(1) continues after the second timing, the life of the semiconductor element Q will be longer than the design life time Yend. However, there is a risk that the output limitation is excessive. When the operating time Yb(2) is longer than the design life time Yend, the control device 50 applies output limitation by the second operating temperature limit value Tjop(2), thereby extending the life of the semiconductor element Q to or beyond the design life time Yend and mitigating excessive output limitation.

[0053] The moving average value used to determine timing A is the moving average value for a predetermined period before timing A. The number of power cycles per unit time used to determine timing B is the number of power cycles per unit time before timing B. The moving average value for a predetermined period or the number of power cycles per unit time is an example of a value that represents a change in the operating temperature of a semiconductor element.

[0054] <Third control method performed by the control device> Next, a description will be given of a third control method performed by the control device 50. The third control method can be combined with either or both of the first control method and the second control method.

[0055] Fig. 6 is a diagram for explaining a third control method performed by the control device, and more specifically, a diagram for explaining an example of a process for outputting a failure forecast. In Fig. 6, the horizontal axis represents the operating time of the power conversion device 101. The operating time of the power conversion device 101 may be interpreted as the operating time or energizing time of one semiconductor element Q. In Fig. 6, the vertical axis represents the degree of deterioration of one semiconductor element Q.

[0056] In Figure 6, Ya(1): Operation time of the semiconductor element Q from the time when the power conversion device 101 is newly installed (when it is newly operating) to the first timing Yb(1): Estimated lifetime of semiconductor element Q when there is no output limit due to the operating temperature limit value Tj_lim (estimated lifetime of semiconductor element Q predicted at the first timing) Yc(1): Estimated lifetime of semiconductor element Q when output limitation due to operating temperature limit value Tj(min) continues after the first timing (estimated lifetime of semiconductor element Q predicted at the first timing) Yend: Design life time of semiconductor element Q ε_end: Degree of deterioration of semiconductor element Q's life span εa(1): Degradation degree of semiconductor element Q at the first timing The design life time Yend is an example of a target life of a semiconductor element.

[0057] If it is estimated that the lifetime of the semiconductor element Q will not reach the design lifetime Yend even if the operating temperature limit value Tj_lim is lowered to a predetermined lower limit value (operating temperature limit value Tj(min)), the control device 50 determines that the power conversion device 101 will fail before the design lifetime Yend is reached. In this case, the control device 50 outputs a failure forecast. The failure forecast may include an estimated time until failure. The predetermined lower limit value (operating temperature limit value Tj(min)) is the minimum value of the operating temperature limit value Tj_lim that is allowable in terms of the performance of the power conversion device 101.

[0058] In this way, the control device 50 outputs a visual or audible failure forecast when the determined operating temperature limit value is equal to or lower than a predetermined lower limit value (operating temperature limit value Tj(min)). According to this third control method, the user can be aware of the possibility of failure of the power conversion device 101 in advance from the failure forecast, and therefore, can take preventative measures such as replacement or repair before the power conversion device 101 actually fails.

[0059] <Example of the first control method> Next, a detailed example of the first control method will be described.

[0060] 7 is a diagram for explaining an embodiment of the first control method, and more specifically, a diagram showing an example configuration of a control device that limits output using a first operating temperature limit value. The control device 50 has a control circuit 50A shown in FIG. 7. The control circuit 50A realizes torque control by controlling the motor M on the dq axes, which are orthogonal rotation coordinate axes that rotate in synchronization with the rotor of the motor M.

[0061] The d-axis is a real axis extending in the real angle direction (the direction of the magnetic flux generated by the rotor magnet) that represents the actual magnetic pole position θm of the rotor, and the q-axis is a real axis extending in a direction 90° electrical angle ahead of the d-axis. The d-axis and q-axis are sometimes collectively referred to as the dq-axis or d,q-axis. The dq-axis is an axis on a model used in vector control, etc. The rotor magnetic pole position θm is expressed as the angle that the d-axis advances based on the position of the reference coil (e.g., U-phase coil) of the motor M.

[0062] The control circuit 50A includes a current command generator 51, a current coordinate converter 52, a subtractor 53, a current controller 54, a PWM modulator 55, and a gate driver 56.

[0063] The current command generator 51 generates a command value for controlling the current flowing through the motor M by the inverter circuit 20. The current command generator 51 generates a current command value id based on, for example, a torque command value given as an output of a higher-level control unit (not shown). * and the current command value iq * The torque command value can be interpreted as a current command value. Current command value id * represents the command value of the d-axis current flowing in the d-axis direction of the motor M. Current command value iq * represents the command value of the q-axis current flowing in the q-axis direction of the motor M.

[0064] The current coordinate converter 52 converts the three-phase phase current detection values ​​iu, iv, iw into two-phase current detection values ​​(d-axis current detection value id and q-axis current detection value iq) using a three-phase to two-phase conversion, using the detected value or estimated value of the magnetic pole position θm.

[0065] The subtractor 53 calculates the current command value id *and the d-axis current detection value id, and the q-axis current command value iq * The current controller 54 calculates the q-axis current difference Δiq between the d-axis current command value Vd and the q-axis current detection value iq using proportional-integral control or the like so that the d-axis current difference Δid converges to zero. * and generates the q-axis command value Vq so that the q-axis current difference Δiq converges to zero. * Generate.

[0066] The PWM modulator 55 uses the detected or estimated value of the magnetic pole position θm to generate a two-phase voltage command value Vd * ,Vq * is the three-phase voltage command value (U phase voltage command value Vu * ,V-phase voltage command value Vv * , W-phase voltage command value Vw * ) by two-phase to three-phase conversion.

[0067] The PWM modulator 55 generates three-phase voltage command values ​​(U-phase voltage command value Vu * ,V-phase voltage command value Vv * , W-phase voltage command value Vw * ), it generates PWM signals, which are multiple control signals for switching the six upper and lower arms. PWM signals are pulse-width modulated signals. The PWM modulator 55 generates multiple PWM signals using, for example, a carrier comparison method. The shape of the carrier can be a triangular wave, a sawtooth wave, or the like.

[0068] The gate driver 56 is a circuit that generates a plurality of gate drive signals Gu, Gv, Gw, Gx, Gy, and Gz in accordance with a plurality of PWM signals.

[0069] Next, the function of limiting the operating temperature of the semiconductor device will be described. The power conversion device 101 includes a maximum temperature selector 57, a temperature limit value generator 60, a torque limit value generator 58, a limiter 59, a deterioration degree calculator 61, and a table 62.

[0070] The maximum temperature selector 57 extracts the highest detected temperature value Tj_sel from among the plurality of detected temperature values ​​Tj_U, Tj_V, Tj_W, Tj_X, Tj_Y, and Tj_Z.

[0071] The temperature limit generator 60 generates the operating temperature limit Tj_lim based on the deterioration degree ε of the semiconductor element Q by a method to be described later.

[0072] The torque limit generator 58 compares the detected temperature value Tj_sel extracted by the maximum temperature selector 57 with the operating temperature limit value Tj_lim generated by the temperature limit generator 60. The torque limit generator 58 generates a torque limit value τ_lim that causes the difference between the detected temperature value Tj_sel and the operating temperature limit value Tj_lim to converge to zero. When the detected temperature value Tj_sel is higher than the operating temperature limit value Tj_lim, the limiter 59 limits the upper limit of the torque command value to the torque limit value τ_lim, thereby limiting the torque by the power conversion device 101.

[0073] 8 is a diagram showing an example of the configuration of a torque limit value generator. The torque limit value generator 58 includes a subtractor 58a that calculates the difference between the detected temperature value Tj_sel and the operating temperature limit value Tj_lim, and a PI controller 58b that generates a torque limit value τ_lim by PI control to converge the difference to zero. The PI control may be replaced by PID control. P represents proportional control, I represents integral control, and D represents differential control.

[0074] Next, a method for generating the operating temperature limit value Tj_lim (=first operating temperature limit value Tjop(1)) in the first control method will be described.

[0075] 4, the temperature limit value generator 60 calculates the deterioration degree εa(1) at a first timing in accordance with a calculation method described later after the power conversion device 101 is newly installed. The temperature limit value generator 60 uses the operation time Ya(1) and the deterioration degree εa(1) to obtain a slope k1 representing the deterioration rate of the semiconductor element Q in accordance with Equation 1.

number

number

number

[0076] 9 is a diagram showing an example of the configuration of a temperature limit value generator that calculates the first operating temperature limit value. εa(1): Degradation degree of semiconductor element Q at the first timing ε: Degree of deterioration from the time of installation to the calculation timing of this generator (present) Ya(1): Operating time of semiconductor element Q from the time of installation to the first timing Y: Operating time of semiconductor element Q from the time of installation to the calculation timing (present) of this generator Let's say.

[0077] The temperature limit generator 60 includes a subtractor 60a that calculates the difference between the degradation rate after the operating time Ya(1) and the slope k2, and a PI controller 60b that generates a first operating temperature limit Tjop(1) by PI control, which converges the difference to zero. PI control may be replaced with PID control. P represents proportional control, I represents integral control, and D represents differential control. The first operating temperature limit Tjop(1) is calculated at predetermined time intervals and is dynamically determined. The temperature limit generator 60 substitutes the first operating temperature limit Tjop(1) into the operating temperature limit Tj_lim.

[0078] Next, a method for calculating the deterioration level of a semiconductor element will be described.

[0079] 10 is a diagram showing an example of the configuration of a deterioration degree calculator. A maximum temperature selector 57 extracts the highest detected temperature value Tj_sel from multiple detected temperature values ​​Tj_U, Tj_V, Tj_W, Tj_X, Tj_Y, and Tj_Z and supplies it to a waveform decomposition calculator 63. The waveform decomposition calculator 63 decomposes the temperature waveform for a predetermined sample period into multiple reference waveforms ΔTj1, ΔTj2, ΔTj3, . . . The waveform decomposition calculator 63 counts the number of times each decomposed reference waveform appears during one operating cycle as the actual number of power cycles N1, N2, N3, . . . This method is widely known as the rainflow method, so a detailed description thereof will be omitted.

[0080] The deterioration degree calculator 61 refers to a table 62 that stores power cycle life curves (FIG. 2) based on the decomposed multiple reference waveforms ΔTj1, ΔTj2, ΔTj3, ..., and derives the number of power cycles in the lifetime Ntbl corresponding to each reference waveform. The deterioration degree calculator 61 adds up the value of "(actual number of power cycles since installation) / (number of power cycles in the lifetime)" for each reference waveform for all reference waveforms. This sum corresponds to the deterioration degree ε. The deterioration degree calculator 61 determines that the lifetime has been reached when the deterioration degree ε is 1 or greater. This method is widely known as Miner's rule, so a detailed explanation of it will be omitted.

[0081] The method for calculating the deterioration degree ε is not limited to this method, and any known method may be used.

[0082] <Example of the second control method> Next, a detailed example of the second control method will be described.

[0083] The operating temperature of the semiconductor elements varies depending on the operating environment of the power conversion device 101. The number of power cycles per unit time varies depending on the operating conditions of the power conversion device 101. Due to these changes, the power cycle life may deviate from the previous estimated value over time. For this reason, the temperature limit generator 60 regenerates the operating temperature limit value Tj_lim in response to changes in the operating environment and conditions.

[0084] In FIG. 5, the control device 50 performs the above-described process 1', process 2', and process 3 at a second timing (for example, the above-described timing A or timing B) after the first timing.

[0085] In process 1′, the temperature limit value generator 60 estimates (predicts) the operating time Yb(2) at which the deterioration level of the semiconductor element Q reaches the life determination deterioration level ε_end according to Equation 4.

number

[0086] In process 2', the temperature limit value generator 60 calculates the time difference Δ2 between the operating time Yb(2) and the design life time Yend, and if the time difference Δ2 is equal to or greater than a predetermined time, determines the second operating temperature limit value Tjop(2) at which the estimated life of the semiconductor element Q reaches the design life time Yend.

[0087] The temperature limit value generator 60 uses the operating time Ya(2) and the deterioration degree εa(2) to calculate the slope k3 that indicates the deterioration rate of the semiconductor element Q according to Equation 5.

number

[0088] 11 is a diagram showing an example of the configuration of a temperature limit value generator that calculates the second operating temperature limit value. εa(2): Degradation degree of semiconductor element Q at the second timing ε: Degree of deterioration from the time of installation to the calculation timing of this generator (present) Ya(2): Operating time of semiconductor element Q from the time of installation to the second timing Y: Operating time of semiconductor element Q from the time of installation to the calculation timing (present) of this generator Let's say.

[0089] The temperature limit generator 60 includes a subtractor 60a that calculates the difference between the degradation rate after the operating time Ya(2) and the slope k3, and a PI controller 60b that generates a second operating temperature limit Tjop(2) by PI control, which converges the difference to zero. PI control may be replaced with PID control. P represents proportional control, I represents integral control, and D represents differential control. The second operating temperature limit Tjop(2) is calculated at predetermined time intervals and is dynamically determined. The temperature limit generator 60 substitutes the second operating temperature limit Tjop(2) for the operating temperature limit Tj_lim.

[0090] 12 is a diagram for explaining an embodiment of the second control method, and more specifically, a diagram showing an example of the configuration of a control device that limits output using a second operating temperature limit value. The control device 50 has the control circuit 50B shown in FIG. 7. The control circuit 50B differs from the control circuit 50A in that it further includes a timing generator 64.

[0091] When the trigger signal γ output from the timing generator 64 is input (second timing), the temperature limit value generator 60 calculates the slope k3 using the above equation 5, generates the second operating temperature limit value Tjop(2), and outputs the second operating temperature limit value Tjop(2) as the operating temperature limit value Tj_lim.

[0092] Next, a method for generating the trigger signal γ by the timing generator 64 will be described.

[0093] Fig. 13 is a diagram for explaining a first method for generating a trigger signal, and more specifically, a diagram for explaining a method for determining timing A (moving average value of operating temperature). Fig. 13 shows the junction temperature Tj during a period when a torque command value equal to or greater than a predetermined torque value τa is input, and the junction temperature Tj during a period when a torque command value less than the predetermined torque value τa is input. The junction temperature Tj on the vertical axis represents the highest temperature detection value Tj_sel among multiple temperature detection values ​​Tj_U, Tj_V, Tj_W, Tj_X, Tj_Y, and Tj_Z.

[0094] Since the semiconductor element Q repeatedly operates and stops, the torque command value is inputted at a predetermined torque value τa or more during the period y period The same period for the nth time from the base time is called y period The reference time may be the timing when the power conversion device 101 is newly installed. The current flowing through the semiconductor element Q is roughly proportional to the torque command value. The torque value τa is selected to be a value that does not significantly increase the junction temperature Tj, and may be set to zero.

[0095] The timing generator 64 calculates the period y using Equation 6. period Calculate the average junction temperature Tj_ave(n).

number

number

[0096] Fig. 14 is a diagram for explaining a second method for generating a trigger signal, and more specifically, a diagram for explaining a method for determining timing B (the number of power cycles per unit time). Fig. 14 shows the junction temperature Tj during the operating period and the junction temperature Tj during the stopped period. The junction temperature Tj on the vertical axis indicates the highest temperature detection value Tj_sel among multiple temperature detection values ​​Tj_U, Tj_V, Tj_W, Tj_X, Tj_Y, and Tj_Z.

[0097] During operation of the power conversion device 101, the motor M is accelerated and decelerated, causing the junction temperature Tj to repeatedly rise and fall. The difference between the peak temperature and bottom temperature of the junction temperature Tj resulting from this repetition is defined as ΔTn (n is an integer equal to or greater than 1). The timing generator 64 integrates the number of times that this ΔTn exceeds a predetermined temperature change range over a predetermined period. The predetermined temperature change range is set to a small temperature change range (e.g., 20°C) on the power cycle life curve (FIG. 2) where the number of power cycles has only a minor effect on the product life. The predetermined period during which the timing generator 64 integrates the number of times that ΔTn exceeds the predetermined temperature change range is set to the period (e.g., one day) during which the power of the power conversion device 101 that drives the motor M is turned on and off.

[0098] The timing generator 64 outputs a trigger signal γ when the above-mentioned integrated number of times at the newly established timing or the timing at which the first control method was implemented differs from the above-mentioned integrated number of times at the current timing by a predetermined value or more.

[0099] <Example of the third control method> Next, a detailed example of the third control method will be described.

[0100] The first control method, the second control method, limits the junction temperature of the semiconductor element, i.e., torque, to satisfy the design life. The third control method is a process to be performed when the minimum torque required for the power conversion device 101 cannot be satisfied as a result of generating the operating temperature limit value Tj_lim.

[0101] 6, when the operating temperature limit value Tj_lim is calculated at the first timing (or the second timing), it is assumed that the calculated operating temperature limit value Tj_lim is equal to or less than a predetermined lower limit value that can generate the minimum torque required of the power conversion device 101. In this case, the temperature limit value generator 60 sets the operating temperature limit value Tj_lim to the predetermined lower limit value (operating temperature limit value Tj(min)).

[0102] Furthermore, the temperature limit generator 60 determines that the lifetime of the semiconductor device Q does not meet the design lifetime Yend. The control device 50 outputs a failure forecast including an estimated time until failure. The control device 50 calculates the estimated time until failure yf using Equation 8.

number

[0103] 15 is a diagram for explaining an embodiment of the third control method, and more specifically, a diagram showing an example of the configuration of a control device that outputs a failure forecast. The control device 50 has a control circuit 50C shown in FIG. 7. The control circuit 50C differs from the control circuit 50B in that it further includes a memory 65 and a failure forecaster 66.

[0104] The memory 65 pre-stores the design lifetime Yend and the operating temperature limit value Tj(min) at which the minimum torque required of the power conversion device 101 can be generated. When the first operating temperature limit value Tjop(1) calculated by the first control method is lower than the operating temperature limit value Tj(min), the temperature limit value generator 60 sets the operating temperature limit value Tj_lim as the operating temperature limit value Tj(min). Under this condition, the temperature limit value generator 60 calculates an estimated lifetime Yc(1) of the semiconductor element Q when the output limit due to the operating temperature limit value Tj(min) continues after the first timing, as in the first control method, and supplies this to the failure forecaster 66. The failure forecaster 66 calculates an estimated time until failure yf using the above equation 8 and outputs a failure forecast ALM.

[0105] In this way, the power conversion device, the control device, and the control method according to the first embodiment can make the life of the semiconductor element Q reach the target life.

[0106] In the present disclosure, the control circuit, control device, or control unit is an electronic circuit such as a CPU (Central Processing Unit), FPGA (Field Programmable Gate Array), or ASIC (Application Specific Integrated Circuit). The control circuit, control device, or control unit may be a computer having a memory and a processor. The control circuit, control device, or control unit performs the various control operations described in this specification by executing a program such as instruction code stored in the memory, or by being a circuit designed for a specific application.

[0107] Although the embodiments have been described above, they are presented as examples and the present invention is not limited to the above embodiments. The above embodiments can be implemented in various other forms, and various combinations, omissions, substitutions, modifications, etc. can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, and are also included in the scope of the invention and its equivalents as set forth in the claims.

[0108] For example, the semiconductor element is not limited to a power transistor such as an IGBT or a MOSFET, but may be a diode, a thyristor, a gate turn-off thyristor, a triac, or the like.

[0109] The following additional notes are provided regarding the above-described embodiments. (Appendix 1) a semiconductor element for power conversion; a control device that determines an operating temperature condition under which the semiconductor element's life will reach a target life, and limits the output of the power conversion device so that the operating temperature of the semiconductor element satisfies the operating temperature condition. (Appendix 2) A control device comprising: a control circuit for determining an operating temperature condition under which a semiconductor element used in a power conversion device will reach a target lifespan; and the control circuit limits the output of the power conversion device so that the operating temperature of the semiconductor element satisfies the operating temperature condition. (Appendix 3) A control method comprising determining an operating temperature condition under which a semiconductor element used in a power conversion device will reach a target lifespan, and limiting an output of the power conversion device so that the operating temperature of the semiconductor element satisfies the operating temperature condition. [Explanation of symbols]

[0110] 10 DC power supply 20 Inverter circuit 30 Current Sensor 40u, 40v, 40w, 40x, 40y, 40z temperature sensors 50 Control device 50A, 50B, 50C control circuit 101 Power conversion device Q_U, Q_V, Q_W, Q_X, Q_Y, Q_Z semiconductor elements

Claims

1. a semiconductor element for power conversion; a control device that determines an operating temperature limit value at which the life of the semiconductor element reaches a target life, and limits the output of the power conversion device so that the operating temperature of the semiconductor element does not exceed the operating temperature limit value.

2. The power conversion device according to claim 1 , wherein the control device performs a process of determining the operating temperature limit value at a plurality of times and limits the output so that the operating temperature does not exceed the updated operating temperature limit value.

3. 3. The power conversion device according to claim 2, wherein the control device performs the processing when a value representing a change in the operating temperature up to a second timing after the first timing has changed by more than a predetermined value compared to a value representing a change in the operating temperature up to a first timing.

4. The power conversion device according to claim 3 , wherein the value representing the change in the operating temperature is a moving average value of the operating temperature.

5. The power conversion device according to claim 3 , wherein the value representing the change in the operating temperature is the number of power cycles per unit time of the semiconductor device.

6. The power conversion device according to claim 1 , wherein the control device outputs a failure forecast when the determined operating temperature limit value is equal to or lower than a predetermined lower limit value.

7. The power conversion device of claim 6 , wherein the failure forecast includes an estimated time to failure.

8. the control device estimates a deterioration state of the semiconductor element; The power conversion device according to claim 1 , wherein the operating temperature limit value changes depending on the deterioration state.

9. The power conversion device according to any one of claims 1 to 5, wherein the control device determines a target degradation state at which the lifespan reaches the target lifespan, and determines the operating temperature limit value so that the degradation state of the semiconductor element after determining the target degradation state becomes the target degradation state.

10. The control device estimates a deterioration rate of the semiconductor device, The power conversion device according to claim 1 , wherein the operating temperature limit value changes depending on the deterioration rate.

11. 6. The power conversion device according to claim 1, wherein the control device calculates a target deterioration rate at which the lifetime of the semiconductor element reaches the target lifetime, and calculates the operating temperature limit value so that the deterioration rate of the semiconductor element after calculating the target deterioration rate becomes the target deterioration rate.

12. the control device calculates a time difference between the life of the semiconductor element and the target life, The power conversion device according to claim 1 , wherein the operating temperature limit value changes according to the time difference.

13. The power conversion device according to claim 12 , wherein the control device determines the operating temperature limit value when the time difference is equal to or greater than a predetermined time difference.

14. The power conversion device according to claim 1 , wherein the control device determines the operating temperature limit value when the lifetime of the semiconductor element is shorter than the target lifetime.

15. A control device comprising: a control circuit for determining an operating temperature limit value at which a semiconductor element used in a power conversion device will reach a target lifespan; and the control circuit limits an output of the power conversion device so that the operating temperature of the semiconductor element does not exceed the operating temperature limit value.

16. A control method comprising: determining an operating temperature limit value at which a semiconductor element used in a power conversion device will reach a target life; and limiting the output of the power conversion device so that the operating temperature of the semiconductor element satisfies the operating temperature limit value.

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