Degradation prediction device and degradation prediction program for power conversion equipment

Abstract

A degradation inference device and degradation inference program product for a power conversion device capable of inferring degradation of switching elements without the need for special sensors are provided. The degradation inference device (30) includes: an arithmetic unit (31) that calculates the change in the characteristics of the inverter's IGBTs based on a voltage command that is a target voltage of the power conversion device and the output voltage value of the power conversion device; a determination unit (32) that determines whether the change in the characteristics calculated by the arithmetic unit (31) has changed by more than a threshold compared to the initial state; and a reporting unit (33) that reports a warning when the determination unit (32) determines that the change in the characteristics has changed by more than a threshold. The arithmetic unit (31) includes a polarity determination unit (31f) formed by an upper arm and a lower arm that determines the polarity based on the output current from the power conversion device, and a switching unit (31g) that switches the change in characteristics based on the polarity determination unit (31f); a pair of determination units (32) are provided for determining the change in characteristics after switching by the switching unit (31g).

Description

Technical Field

[0001] This invention relates to a degradation inference apparatus and degradation inference program product for inferring the degradation of switching elements used in power conversion devices such as inverters or converters. Background Technology

[0002] In power conversion devices such as motor drive inverters or power transmission converters, power is controlled by controlling the switching width of the switching elements used for power conversion. These switching elements are fundamental components of the power conversion device; if they fail, the devices receiving power from the power conversion device will stop, or the entire system will shut down, causing significant disruption.

[0003] To prevent malfunctions, some systems replace the semiconductor switching elements used in power conversion devices that have exceeded their service life with new ones. However, this not only increases maintenance costs but also leads to a shortage of maintenance personnel. Therefore, there is a need for a mechanism that can detect signs of malfunctions and issue alarms before the semiconductor switching elements in power conversion fail.

[0004] Regarding techniques for detecting signs of malfunctions in advance, techniques such as those described in Patent Document 1 are known. The power conversion device described in Patent Document 1 includes: a leakage current detection mechanism for detecting the gate leakage current of a semiconductor switching element for power conversion; and an element abnormality detection mechanism that, based on the leakage current at the start of use of the device, outputs an element abnormality detection signal indicating a sign of abnormality when the magnitude of the leakage current changes by a certain value or more.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent Application Publication No. 2003-70231 Summary of the Invention

[0008] The problem that the invention aims to solve

[0009] However, the power conversion device described in Patent Document 1, as a leakage current detection mechanism between the gate and emitter of a semiconductor switching element, is newly provided with a VGE detection circuit for detecting the gate voltage applied between the interconnection point between the gate resistor and the gate of the semiconductor switching element and the emitter of the semiconductor switching element.

[0010] In power conversion devices, even if there are mechanisms for measuring input voltage or current, output voltage or current, etc., for conversion control, they typically lack mechanisms for measuring and feeding back the characteristics of the switching elements. Therefore, in the power conversion device described in Patent Document 1, it is necessary to install new, special sensors in the switching elements.

[0011] To measure the leakage current between the gate and emitter, there is a simple method of connecting a resistor and measuring the voltage. However, if current flows through the gate control signal, the conditions for conduction and de-conduction will change. Therefore, only a special measuring mechanism such as a clamping galvanometer can be used.

[0012] Therefore, the purpose of this invention is to provide a degradation inference device and degradation inference program product for a power conversion device that can infer the degradation of switching elements without the need for special sensors.

[0013] Methods used to solve problems

[0014] The degradation inference device for a power conversion device of the present invention is characterized by comprising: an arithmetic unit that calculates the change in the characteristic of a switching element for power conversion in the power conversion device based on a voltage command that is a target output voltage of the power conversion device and the output voltage value of the power conversion device; a determination unit that determines whether the change in the characteristic calculated by the arithmetic unit has changed by a threshold or more compared to an initial state; and a reporting unit that reports a warning when the determination unit determines that the change in the characteristic has changed by a threshold or more; the arithmetic unit comprises: a polarity determination unit that determines the polarity of a current based on an output current from the power conversion device, wherein the power conversion device is formed by an upper arm and a lower arm formed by the switching element; and a switching mechanism that switches the change in the characteristic based on a switching signal from the polarity determination unit; a pair of determination units are provided for determining the change in the characteristic after switching by the switching mechanism.

[0015] Furthermore, the degradation inference program product of the power conversion device of the present invention is characterized by including a degradation inference program that enables a computer to function as the following mechanism: an arithmetic mechanism that calculates the change in the characteristic of the switching element for power conversion in the power conversion device based on a voltage command that is a target output voltage of the power conversion device and the output voltage value of the power conversion device; a determination mechanism that determines whether the change in the characteristic calculated by the arithmetic mechanism has changed by a threshold or more compared to the initial state; and a reporting mechanism that reports a warning when the determination mechanism determines that the change in the characteristic has changed by a threshold or more; the arithmetic mechanism includes: a polarity determination mechanism that determines the polarity of the current based on the output current from the power conversion device, wherein the power conversion device is formed by an upper arm and a lower arm formed by the switching element; and a switching mechanism that switches the change in the characteristic based on a switching signal from the polarity determination mechanism; a pair of determination mechanisms are provided for determining the change in the characteristic after switching by the switching mechanism.

[0016] According to the present invention, the calculation mechanism calculates the change in the characteristics of the switching element based on the voltage command to the power conversion device and the output voltage value of the power conversion device. A determination mechanism then determines whether the change in the characteristics exceeds a threshold value. When the determination mechanism determines that the change in the characteristics exceeds the threshold value, a reporting mechanism issues a warning. Since the voltage command to the power conversion device, the output voltage value of the power conversion device, and the output current can be obtained from the DC voltage measurement mechanism, output voltage measurement mechanism, and output current measurement mechanism provided by the inverter, no special sensors are required.

[0017] Furthermore, since the switching mechanism can switch a pair of integrators based on the polarity of the current determined by the polarity determination mechanism, it can calculate the changes in the characteristics of the upper and lower arms. Therefore, the signs of malfunctions in the upper and lower arms can be inferred from the pair of determination mechanisms.

[0018] The aforementioned determination mechanism can store the change in characteristic corresponding to the output voltage value of the aforementioned power conversion device and set it as an initial state, and determine the aforementioned threshold based on this initial state. In this way, the threshold for the change in characteristic corresponding to the output current can be determined, so the degradation of the switching element can be accurately inferred.

[0019] The aforementioned arithmetic mechanism may include: a subtraction mechanism that calculates the difference between the voltage command and the output voltage value; and an integration mechanism that outputs the integral value of the difference obtained by integrating the difference calculated by the subtraction mechanism to the determination mechanism. By integrating the difference between the voltage command calculated by the subtraction mechanism and the output voltage value by the integration mechanism, small fluctuations in the voltage value can be ignored, and since the difference is accumulated, the signs of degradation can be amplified.

[0020] The aforementioned integrator can output the integral value obtained by definite integral over a specified interval as the difference integral value. By calculating the difference integral value from the definite integral over the interval, divergent integral values ​​can be suppressed.

[0021] The aforementioned arithmetic mechanism may include: a first averaging mechanism that calculates the average value of the input voltage value input to the power conversion device at each time interval synchronized with the carrier signal; a multiplication mechanism that multiplies the average value of the input voltage value from the first averaging mechanism by a modulation factor to calculate the voltage command and outputs it to the subtraction mechanism; and a second averaging mechanism that calculates the average value of the output voltage value of the power conversion device at each time interval synchronized with the carrier signal and outputs it to the subtraction mechanism. By averaging the input voltage value by the first averaging mechanism and averaging the output voltage value by the second averaging mechanism, the operator can monitor the operating status of the power conversion device by observing the waveform during maintenance and other situations.

[0022] Invention Effects

[0023] This invention can infer the degradation of switching elements without the need for special sensors. Attached Figure Description

[0024] Figure 1 This is a diagram illustrating an example of a power conversion device.

[0025] Figure 2 This is a diagram illustrating a degradation inference apparatus according to Embodiment 1 of the present invention.

[0026] Figure 3 (a) is a diagram showing an example of the waveforms of the average value of the U-phase voltage command from the multiplication mechanism and the average value of the output voltage from the second averaging mechanism when the polarity of the output current is positive. Figure 3 (b) is a diagram showing an example of the waveforms of the average value of the U-phase voltage command from the multiplication mechanism and the average value of the output voltage from the second averaging mechanism when the polarity of the output current is negative.

[0027] Figure 4 This is a diagram illustrating an example of the waveform of the integral value from the integrator when a three-phase AC motor is driven by an inverter. Figure 4 (a) is a diagram showing an example of the waveform of the output from one of the integrators when the polarity of the output current is positive, with the upper and lower arms in their initial state and the delays of the upper and lower arms being equal. Figure 4 (b) is Figure 4 The delayed state of (a) is a diagram representing an example of the waveform of the output from the integrator when the polarity of the output current is negative.

[0028] Figure 5This is a diagram illustrating an example of the waveform of the integral value from the integrator when a three-phase AC motor is driven by an inverter. Figure 5 (a) shows a state where the upper arm's disconnection delay increases and the lower arm's delay remains unchanged from its initial state. It is an example of the waveform of the output from one of the integrators when the polarity of the output current is positive. Figure 5 (b) is Figure 5 The delayed state of (a) is a diagram representing an example of the waveform of the output from the integrator when the polarity of the output current is negative.

[0029] Figure 6 This is a diagram illustrating an example of the waveform of the integral value from the integrator when a three-phase AC motor is driven by an inverter. Figure 6 (a) shows a state where the upper arm's delay remains at its initial state and the lower arm's disconnection delay increases. It is an example of the waveform of the output from one of the integrators when the polarity of the output current is positive. Figure 6 (b) is Figure 6 The delayed state of (a) is a diagram representing an example of the waveform of the output from the integrator when the polarity of the output current is negative.

[0030] Figure 7 This is a diagram illustrating an example of the waveform when a three-phase AC motor is driven by an inverter, and the differential integral value from the integrator is integrated over an interval. Figure 7 (a) is a diagram showing an example of the waveform of the output from one of the integrators when the polarity of the output current is positive, with the upper and lower arms in their initial state and the delays of the upper and lower arms being equal. Figure 7 (b) is Figure 7 The delayed state of (a) is a diagram representing an example of the waveform of the output from the integrator when the polarity of the output current is negative.

[0031] Figure 8 This is a diagram illustrating an example of the waveform when a three-phase AC motor is driven by an inverter, and the differential integral value from the integrator is integrated over an interval. Figure 8 (a) shows a state where the upper arm's disconnection delay increases and the lower arm's delay remains at the initial state. It is an example of the waveform of the output from one of the integrators when the polarity of the output current is positive. Figure 8 (b) is Figure 8 The delayed state of (a) is a diagram representing an example of the waveform of the output from the integrator when the polarity of the output current is negative.

[0032] Figure 9 This is a diagram illustrating an example of the waveform when a three-phase AC motor is driven by an inverter, and the differential integral value from the integrator is integrated over an interval. Figure 9 (a) shows a state where the upper arm's delay remains at its initial state and the lower arm's disconnection delay increases. It is an example of the waveform of the output from one of the integrators when the polarity of the output current is positive. Figure 9 (b) is Figure 9 The delayed state of (a) is a diagram representing an example of the waveform of the output from the integrator when the polarity of the output current is negative.

[0033] Figure 10 This diagram illustrates how the output voltage of a power conversion device can be set from the phase voltage to the line-to-line voltage. Detailed Implementation

[0034] (Implementation Method 1)

[0035] The accompanying drawings illustrate a degradation inference device for a power conversion device according to Embodiment 1 of the present invention.

[0036] In this embodiment 1, the power conversion device is as follows: Figure 1 The inverter 10 is shown. First, the structure of the inverter 10 will be described.

[0037] The inverter 10 of this embodiment 1 is a device that outputs three-phase AC from DC. For example... Figure 1 As shown, a three-phase AC motor M is connected to the inverter 10.

[0038] Inverter 10 has first arms 11 to third arms 13, with upper arms 111, 121, 131 and lower arms 112, 122, 132 connected in series.

[0039] Upper arms 111-131 are connected to the positive power line P via first wiring 141a-141c. Lower arms 112-132 are connected to the negative power line N via second wiring 142a-142c. Upper arms 111-131 and lower arms 112-132 are connected via third wiring 143a-143c.

[0040] The upper arms 111-131 and the lower arms 112-132 are composed of switching elements and return-current diodes. The switching elements are formed of semiconductor devices. For example, bipolar transistors, MOSFETs (metal-oxide-semiconductor field-effect transistors), and IGBTs (Insulated Gate Bipolar Transistors) can be used as switching elements. In this embodiment 1, IGBTs, which can carry large currents and have fast switching speeds, are used as switching elements.

[0041] The inverter 10 has a control mechanism that controls the switches of the upper arms 111-131 and the lower arms 112-132 via PWM (Pulse Width Modulation).

[0042] The control mechanism includes: a voltage command mechanism 15, which commands the output of phases U to W as the target voltage; a modulation factor calculation mechanism 16, which outputs a modulation factor signal based on the voltage command from the voltage command mechanism 15 and the input voltage value represented by the input voltage value signal; an oscillation mechanism 17, which outputs a carrier signal; a comparison mechanism 18, which compares the modulation factor signal with a triangular wave signal and outputs a switching signal (gate signal); and a reversing mechanism 19, which reverses the switching signal output to the upper arms 111 to 131 for the lower arms 112 to 132.

[0043] The voltage command mechanism 15 includes a U-phase voltage command mechanism 151 for the U-phase, a V-phase voltage command mechanism 152 for the V-phase, and a W-phase voltage command mechanism 153 for the W-phase.

[0044] The U-phase voltage command, V-phase voltage command, and W-phase voltage command are output from the U-phase voltage command mechanism 151, the V-phase voltage command mechanism 152, and the W-phase voltage command mechanism 153.

[0045] The modulation factor calculation unit 16 is a divider that divides the voltage command from the voltage command unit 15 by the input voltage value represented by the input voltage value signal measured by the DC voltage measurement unit (described later) and outputs the modulation factor. The modulation factor can be set to -1.0 to 1.0.

[0046] The modulation factor calculation mechanism 16 includes a U-phase modulation factor calculation mechanism 161 for the U-phase, a V-phase modulation factor calculation mechanism 162 for the V-phase, and a W-phase modulation factor calculation mechanism 163 for the W-phase.

[0047] Voltage commands (U-phase voltage command, V-phase voltage command, and W-phase voltage command) are output to the comparison mechanism 18 from the U-phase modulation factor calculation mechanism 161, the V-phase modulation factor calculation mechanism 162, and the W-phase modulation factor calculation mechanism 163, and the modulation factor is output through the U-phase modulation factor signal, the V-phase modulation factor signal, and the W-phase modulation factor signal.

[0048] The oscillation mechanism 17 outputs a triangular wave signal as a carrier signal.

[0049] The comparison mechanism 18 includes a U-phase comparison mechanism 181 for the U-phase, a V-phase comparison mechanism 182 for the V-phase, and a W-phase comparison mechanism 183 for the W-phase.

[0050] The reversing mechanism 19 includes a U-phase reversing mechanism 191 for the U phase, a V-phase reversing mechanism 192 for the V phase, and a W-phase reversing mechanism 193 for the W phase.

[0051] In addition, the inverter 10 includes: a DC voltage measuring mechanism 21 for measuring the input voltage value; a voltage divider 22 for obtaining a reference potential for the output voltage (U-phase voltage, V-phase voltage, W-phase voltage) from the connection point of resistors 22a and 22b connected in series between the positive power line P and the negative power line N; an output voltage measuring mechanism 23 for measuring the output voltage of the inverter 10; and an output current measuring mechanism 24 for measuring the output current of the inverter 10.

[0052] Figure 1 The DC voltage measuring mechanism 21 shown outputs the input voltage value as the input voltage value signal.

[0053] The resistors 22a and 22b of the voltage divider 22 are set to the same resistance value so that the median voltage of the input voltage becomes the reference potential.

[0054] The output voltage measuring mechanism 23 measures the output voltage of each phase. The output voltage measuring mechanism 23 includes a U-phase output voltage measuring mechanism 231 for the U-phase, a V-phase output voltage measuring mechanism 232 for the V-phase, and a W-phase output voltage measuring mechanism 233 for the W-phase.

[0055] The output voltage values ​​are output from the U-phase output voltage measuring mechanism 231, the V-phase output voltage measuring mechanism 232, and the W-phase output voltage measuring mechanism 233 via the U-phase output voltage value signal, the V-phase output voltage value signal, and the W-phase output voltage value signal.

[0056] The output current measuring mechanism 24 measures the output current of each phase. The output current measuring mechanism 24 can use various current sensors. For example, it can use a current transformer (CT), Hall effect sensor, Rogowski coil, or other similar methods. The output current measuring mechanism 24 includes a U-phase output current measuring mechanism 241 for the U-phase, a V-phase output current measuring mechanism 242 for the V-phase, and a W-phase output current measuring mechanism 243 for the W-phase. The output current values ​​are output from the U-phase output current measuring mechanism 241, the V-phase output current measuring mechanism 242, and the W-phase output current measuring mechanism 243 as U-phase output current signals, V-phase output current signals, and W-phase output current signals, respectively.

[0057] Next, based on the accompanying drawings, the structure of the degradation inference device for inferring the degradation of the IGBTs (upper arms 111 to 131 and lower arms 112 to 132 of the first arm 11 to the third arm 13), which are the switching elements of the inverter 10, will be described.

[0058] Figure 2 The degradation inference device 30 shown is a device that enables a computer to execute a degradation inference program.

[0059] In addition, the degradation inference device 30 includes a calculation mechanism 31, a judgment mechanism 32, and a reporting mechanism 33.

[0060] The computing unit 31 is based on Figure 1 The voltage command for the target output voltage of the inverter 10 shown and the delay calculated from the output voltage value of the inverter 10 are examples of the change in the characteristics of the switching elements.

[0061] The arithmetic unit 31 has a U-phase arithmetic unit 311 for the U-phase, a V-phase arithmetic unit 312 for the V-phase, and a W-phase arithmetic unit 313 for the W-phase. The U-phase arithmetic unit 311, the V-phase arithmetic unit 312, and the W-phase arithmetic unit 313 have the same structure.

[0062] Each arithmetic unit 31 has a first averaging unit 31a, a second averaging unit 31b, a multiplication unit 31c, a subtraction unit 31d, an integration unit 31e, a polarity determination unit 31f, and a switching unit 31g for switching.

[0063] The first averaging mechanism 31a averages the input voltage values ​​of the first arm 11 to the third arm 13 during each time interval synchronized with the triangular wave signal (carrier signal) when they are on and off.

[0064] The second averaging mechanism 31b averages the voltage values ​​represented by the output voltage value signals (U-phase output voltage value signal, V-phase output voltage value signal, W-phase output voltage value signal) of the first arm 11 to the third arm 13 during each time interval synchronized with the triangular wave signal (carrier signal) when they are turned on and off.

[0065] The multiplication mechanism 31c multiplies the voltage value from the first averaging mechanism 31a with the modulation factor signals (U-phase modulation factor signal, V-phase modulation factor signal, W-phase modulation factor signal) from the voltage command mechanism 15 (U-phase voltage command mechanism 151, V-phase voltage command mechanism 152, W-phase voltage command mechanism 153).

[0066] The subtraction mechanism 31d subtracts the voltage value from the second averaging mechanism 31b from the voltage value from the multiplication mechanism 31c.

[0067] The integrator 31e is a device that outputs the differential integral value obtained by integrating the voltage value from the subtraction mechanism 31d, and there is a pair of them.

[0068] Polarity determination mechanism 31f determines the polarity based on the output current measurement mechanism 24 from each phase (refer to...). Figure 1 The polarity of the current is determined by the output current signal of the output current signal.

[0069] The switching mechanism 31g switches the signal from the subtraction mechanism 31d to one of the integrators 31e and the integrator 31e of the other party based on the switching signal from the polarity determination mechanism 31f.

[0070] The determination mechanism 32 detects delay anomalies in the upper arms 111-131 and lower arms 112-132 of the first arms 11-33, which are switching elements, by detecting that the voltage value from the calculation mechanism 31 has changed from the initial state by more than a threshold. The threshold can be set to any value corresponding to the various characteristics or individual differences of the switching elements and the load.

[0071] The determination mechanism 32 includes a U-phase determination mechanism 321 for the U-phase, a V-phase determination mechanism 322 for the V-phase, and a W-phase determination mechanism 323 for the W-phase.

[0072] The U-phase determination mechanism 321 for the U-phase, the V-phase determination mechanism 322 for the V-phase, and the W-phase determination mechanism 323 for the W-phase are provided in pairs for each phase to determine the difference integral values ​​of the integrator 31e from one side and the integrator 31e from the other side.

[0073] Reporting agency 33 will notify users, operators, or maintenance personnel of any abnormalities detected by judging agency 32.

[0074] The operation of the degradation inference device 30 of Embodiment 1 of the present invention, configured as described above, will be explained based on the accompanying drawings. Furthermore, the description of Embodiment 1 will be based on the U-phase as an example.

[0075] [Explanation of the operation of inverter 10]

[0076] First of all, Figure 1 The operation of the inverter 10 shown will be explained.

[0077] A voltage command signal is output from the U-phase voltage command mechanism 151. Based on the voltage command specified by the voltage command signal, the U-phase modulation factor calculation mechanism 161 outputs a U-phase modulation factor signal representing the modulation factor.

[0078] The U-phase comparison mechanism 181 compares the voltage of the triangular wave signal from the oscillation mechanism 17 with the U-phase command voltage from the U-phase voltage command mechanism 151 (U-phase modulation factor calculation mechanism 161). During the period when the U-phase voltage command is higher than the triangular wave signal, a PWM signal for turning on the upper arm 111 of the first arm 11 is output. Furthermore, during the period when the U-phase command voltage is lower than the triangular wave signal, the U-phase reversal mechanism 191 outputs a PWM signal for turning on the lower arm 112 of the first arm 11. By repeating this process, the three-phase AC motor M can obtain AC power as a U-phase output.

[0079] [Explanation of the operation of the degradation prediction device 30]

[0080] As a precursor to IGBT (switching element) failure, it can be predicted that the output voltage of inverter 10 will no longer follow its voltage command (the error becomes larger than usual).

[0081] Therefore, the degradation inference device 30 firstly... Figure 2 As shown, the first averaging mechanism 31a converts half a cycle of the triangular wave signal from the oscillation mechanism 17 into a DC voltage measurement mechanism 21 (see reference 21). Figure 1 The input voltage value represented by the input voltage value signal from the first averaging unit 31a is averaged. Then, the multiplication unit 31c multiplies the average value of the input voltage value from the first averaging unit 31a with the modulation factor represented by the U-phase modulation factor signal from the U-phase voltage command unit 151. The average value of the U-phase voltage command is calculated by the multiplication performed by the multiplication unit 31c.

[0082] Furthermore, the second averaging mechanism 31b, based on the triangular wave signal from the oscillation mechanism 17, measures the output voltage from the U-phase output voltage measurement mechanism 231 (refer to) during half a cycle of the triangular wave signal. Figure 1 The averaged output voltage value represented by the U-phase output voltage signal.

[0083] In this embodiment 1, the first averaging mechanism 31a and the second averaging mechanism 31b are set to half a period of the triangular wave signal, but as long as they are set to a timing synchronized with the triangular wave signal, they can also be set to 1 period.

[0084] exist Figure 3 In (a), the average value of the U-phase voltage command from the multiplication mechanism 31c and the average value of the output voltage value from the second averaging mechanism 31b are represented. In this way, by averaging the U-phase voltage command or averaging the output voltage value, the waveforms of the voltage command and the output voltage value can be easily visualized.

[0085] Next, the delay of the upper arm 111 of the first arm 11, which is a switching element, is calculated by subtracting the average value of the U-phase output voltage value from the second averaging mechanism 31b from the average value of the U-phase voltage command from the multiplication mechanism 31c by the subtraction mechanism 31d.

[0086] Next, the polarity determination mechanism 31f determines the polarity of the current based on the output current represented by the U-phase output current signal, and switches the switching mechanism 31g according to the switching signal.

[0087] Through this switching signal, when the polarity of the output current is positive, the integrator 31e (in) of one side... Figure 2The upper integrator 31e integrates the difference from the subtraction mechanism 31d. Furthermore, when the output current is negative, the other integrator 31e (in...) integrates the difference. Figure 2 The integrator 31e on the lower side integrates the difference from the subtraction mechanism 31d.

[0088] Here, in Figure 3 (a) represents the average value of the U-phase voltage command from the multiplication mechanism 31c and the average value of the output voltage from the second averaging mechanism 31b when the polarity of the output current is positive.

[0089] In addition, Figure 3 (b) represents the average value of the U-phase voltage command from the multiplication mechanism 31c and the average value of the output voltage from the second averaging mechanism 31b when the polarity of the output current is negative.

[0090] Furthermore, in Figure 4 (a) represents the integrator 31e from one side when the disconnection delay of the upper arm 111 and the lower arm 112 is in the initial state (4 μs) (refer to the integrator 31e from one side). Figure 2 The output (change in characteristic) of the integrator 31e on the upper side is shown in the middle.

[0091] Furthermore, in Figure 4 In (b), it is represented as with Figure 4 The integrator 31e from the other side when the delay state of (a) is the same as the delay (refer to the integrator 31e from the other side) Figure 2 The output of the integrator 31e on the lower side is shown in the middle.

[0092] Figure 4 (a) and Figure 4 The waveform shown in (b) is that of a three-phase AC motor M (refer to...). Figure 1 The waveform represents a state with a certain speed and a certain load, and is the waveform that starts to integrate from time 10 seconds, initiated by the integrating mechanism 31e.

[0093] according to Figure 4 (a) and Figure 4 As can also be seen from (b), the outputs from the integrators 31e and 31e rise or fall at a prescribed slope.

[0094] For example, if Figure 1 The upper arms 111-131 and lower arms 112-132 shown have deteriorated and their characteristics have changed, resulting in an increased disconnection delay. Figure 4 (a) and Figure 4The slopes of the waveforms shown in (b) become gentler. At this point, if there is no switching mechanism 31g, and the difference from the subtraction mechanism 31d is integrated by an integration mechanism 31e, it becomes the addition of positive and negative values, which cancel each other out, so no abnormal signs can be detected.

[0095] However, in the degradation inference device 30, it is determined which of the upper arms 111-131 or the lower arms 112-132 has deteriorated based on the direction of the current output from the first arm 11 to the third arm 13.

[0096] For example, as a change in the characteristics of the upper arm 111, let's assume that the disconnection delay increases from 4 μs to 8 μs. Meanwhile, the disconnection delay of the lower arm 112 remains unchanged from its initial state (4 μs delay).

[0097] exist Figure 5 (a) represents the output of the integrator 31e from one side at this time. Furthermore, in Figure 5 (b) represents the output of the integrator 31e from the other side.

[0098] In Figure 5 (a) and Figure 5 In the waveform shown in (b), it is also similar to Figure 4 Similarly, it is a three-phase AC motor M (refer to...) Figure 1 The waveform represents a state with a certain speed and a certain load, and is the waveform that starts to integrate from time 10 seconds, initiated by the integrating mechanism 31e.

[0099] exist Figure 5 In (b), with Figure 4 There was no change compared to (b), but... Figure 5 In (a), it can be seen that the slope of the disconnection delay becomes gentler compared to the initial state.

[0100] Therefore, if the change in characteristics is detected by one of the U-phase determination mechanisms 321 and the difference from the initial state increases, or the change compared to the initial state exceeds a threshold, it can be inferred that the upper arm 111 has deteriorated. Furthermore, one of the U-phase determination mechanisms 321 can notify the reporting mechanism 33 of the first U-phase alarm signal.

[0101] Next, for example, suppose that the disconnection delay of the upper arm 111 remains in its initial state (4 μs delay), while the disconnection delay of the lower arm 112 increases from 4 μs to 8 μs. Figure 6 In (a), the output of the integrator 31e from one side is shown. Furthermore, in Figure 6 (b) represents the output of the integrator 31e from the other side.

[0102] In Figure 6 (a) and Figure 6 In the waveform shown in (b), it is also similar to Figure 4 Similarly, it is a three-phase AC motor M (refer to...) Figure 1 The waveform represents a state with a certain speed and a certain load, and is the waveform that starts to integrate from time 10 seconds, initiated by the integrating mechanism 31e.

[0103] exist Figure 6 In (a), with Figure 4 There is no change compared to (a), but... Figure 6 As can be seen from (b), the slope of the delay becomes gentler compared to the initial state.

[0104] Therefore, if the U-phase determination mechanism 321 detects that the difference from the initial state has increased and the change compared to the initial state has exceeded a threshold, it can be inferred that the lower arm 112 has deteriorated. Furthermore, the U-phase determination mechanism 321 can notify the reporting mechanism 33 of the second U-phase alarm signal.

[0105] Furthermore, when the disconnection delay of both the upper arm 111 and the lower arm 112 increases from 4μs to 8μs, the output voltage of the upper arm 111, which has a positive current, becomes... Figure 5 The waveform represented by (a) shows that the output voltage of the lower arm 112, where the current is negative, becomes... Figure 6 The waveform represented by (b) is .

[0106] Therefore, based on the representation of the normal state Figure 5 (b) and Figure 6 The waveform represented by (a) has changed, so by detecting that the change is above the threshold, the U-phase first alarm signal that can be inferred to be the deterioration of both the upper arm 111 and the lower arm 112 can be notified to the reporting agency 33.

[0107] In addition, through the Figure 2 The integrators 31e and 31e shown integrate the turn-on delay and turn-off delay (difference) from the subtraction mechanism 31d, which can ignore small changes in voltage value. However, by accumulating the difference, the signs of degradation can be amplified.

[0108] Furthermore, by notifying the reporting agency 33 of any abnormalities, the inverter 10 can be notified to users, managers, maintenance personnel, etc. (see reference). Figure 1 (There is a possibility of malfunction.) The notification can be delivered through various methods such as light from lamps, sound from speakers, emails from the Internet, etc.

[0109] As described above, according to the degradation inference device 30 of this embodiment 1, the calculation unit 31 calculates the change in the characteristics of the IGBT based on the voltage command corresponding to the target output voltage of the inverter 10 and the output voltage value from the inverter 10, and the determination unit 32 determines whether the change in the change in the characteristics is above a threshold. When the determination unit 32 determines that it is above the threshold, the reporting unit 33 can report a warning.

[0110] The voltage command, output voltage value and output current of the inverter 10 can be obtained from the DC voltage measurement mechanism 21, output voltage measurement mechanism 23 and output current measurement mechanism 24 of the inverter 10. Therefore, the degradation inference device 30 can infer the degradation of the IGBT as a switching element without the need to install special sensors.

[0111] Furthermore, by switching the integrator 31e when the polarity of the output current is positive and negative and determining them respectively, it is possible to detect which one or both of the upper arm 111 or the lower arm 112 have deteriorated.

[0112] Furthermore, since the U-phase, V-phase and W-phase are respectively equipped with a calculation mechanism 31 and a judgment mechanism 32, the degradation of each phase can be detected.

[0113] In the above description, the detection of the change in characteristic obtained by subtracting the voltage command to inverter 10, which is an example of a power conversion device, from the output voltage value of inverter 10 was described using the increase in disconnection delay as an example. However, as a change in the characteristic of a switching element, the turn-on delay, turn-off delay, turn-on voltage, turn-on resistance, dv / dt (voltage change rate), etc., can be detected.

[0114] In this embodiment 1, the arithmetic unit 31 averages the input voltage value represented by the input voltage value signal by the first averaging unit 31a, and the output voltage value is averaged by the second averaging unit 31b. In this way, it is possible to obtain... Figure 3 (a) and Figure 3 The waveform shown in (b) allows operators to easily grasp the operating status of inverter 10 by observing the waveform during maintenance.

[0115] However, if it is not necessary to obtain Figure 3 (a) and Figure 3 The waveform shown in (b) indicates that the difference can be integrated by the integration mechanism 31e in the later part of the subtraction mechanism 31d, so the first averaging mechanism 31a and the second averaging mechanism 31b can be omitted.

[0116] (Implementation Method 2)

[0117] Next, the degradation inference apparatus of Embodiment 2 of the present invention will be described.

[0118] pass Figure 2 The pair of integrators 31e shown will perform difference integration, so the difference integral value will diverge significantly over time.

[0119] Therefore, in the integration of integrator 31e, a definite integral (interval integral) is performed over a specified interval, and this is denoted as the difference integral. Hereinafter, this will be referred to as the interval integral.

[0120] The interval integral, for example, can be obtained by the following equation (1) when the interval is set to 5 seconds.

[0121]

[0122] Where T is any time, and e(t) is the integral value from the integrator 31e.

[0123] exist Figures 7 to 9 In the middle, it means that the inverter 10 will convert the... Figure 1 The waveform shown is when the three-phase AC motor M is driven, and the differential integral value from the integrator 31e is calculated with a specified interval, for example, 5 seconds.

[0124] Figure 7 (a) and Figure 7 The waveform shown in (b) is the same as the waveform representing the disconnection delay of the upper arm 111 and the disconnection delay of the lower arm 112 in the initial state (4μs). Figure 4 Correspondingly, this indicates the case where the integral of the difference is replaced by an interval integral.

[0125] also, Figure 8 (a) and Figure 8 The waveform shown in (b) is the same as the waveform representing the opening delay of the upper arm 111 increasing from 4 μs to 8 μs, and the opening delay of the lower arm 112 remaining at the initial state (4 μs). Figure 5 (a) and Figure 5 The corresponding term (b) represents the case where the integral of the difference is replaced by the integral of the interval.

[0126] and then, Figure 9 (a) and Figure 9 The waveform shown in (b) is the same as the waveform representing the initial disconnection delay of the upper arm 111 (4 μs) and the waveform representing the disconnection delay of the lower arm 112 increasing from 4 μs to 8 μs. Figure 6 (a) and Figure 6 The corresponding term (b) represents the case where the integral of the difference is replaced by the integral of the interval.

[0127] In this second embodiment, since the integral is over a 5-second interval, therefore... Figures 7-9As shown, it becomes a constant value 5 seconds after the start of the integration (time 10 seconds).

[0128] Regardless of Figures 8 to 9 In any case, it is related to Figures 4 to 6 Similarly, as shown in the waveform, the slope of the waveform becomes flatter as the delay increases. Therefore, by detecting changes above a threshold compared to the initial state, the degradation of the delay characteristics of the switching element can be detected.

[0129] In addition, such as Figures 8 to 9 As shown, by performing interval integration on the difference integral value through the integrator 31e, divergent integral values ​​can be suppressed.

[0130] (Implementation Method 3)

[0131] Next, the degradation inference apparatus of Embodiment 3 of the present invention will be described.

[0132] constitute Figure 1 The delay of the IGBTs in arms 11 to 33 of the inverter 10 shown is obtained from... Figure 2 The differential integral value is calculated using the difference integral value of the pair of integrators 31e shown. However, this differential integral value is affected by the load current. For example, the delay of the IGBTs constituting the first arm 11 to the third arm 13 is different when there is no load and when a specified current flows as the output current.

[0133] Therefore, in the determination mechanism 32, the output voltages from the first arm 11 to the third arm 13 of each phase are input, and the differential integral value representing the delay corresponding to the output voltage is stored as the initial state. The threshold is determined based on this initial state. In this way, the threshold value of the change in the characteristic corresponding to the load current (output current) can be determined, so the degradation of the switching element (IGBT) can be correctly inferred.

[0134] Furthermore, in embodiments 1 to 3, such as Figure 1 As shown, the example described is a two-level inverter 10 formed by the upper arms 111-131 and the lower arms 112-132, but the degradation inference device of the present invention can also be applied to a three-level inverter.

[0135] Furthermore, in the implementation method, such as Figure 1 As shown, the output voltage measuring mechanism 23, which is formed by the U-phase output voltage measuring mechanism 231 for the U-phase, the V-phase output voltage measuring mechanism 232 for the V-phase, and the W-phase output voltage measuring mechanism 233 for the W-phase, measures the output voltage of each phase and outputs it as the U-phase output voltage value signal, the V-phase output voltage value signal, and the W-phase output voltage value signal.

[0136] However, the output voltage is not only the phase voltage, but can also be the line-to-line voltage.

[0137] For example, suppose the output is given to Figure 2 The output voltage of the U-phase operating mechanism 311 shown replaces the U-phase output voltage value signal, such as... Figure 10 As shown, the U-V output voltage value signal can be set from the U-V output voltage measurement mechanism 251. In this case, the signal of "U-phase modulation factor signal - V-phase modulation factor signal" is used as a substitute for the U-phase modulation factor signal of the U-phase calculation mechanism 311.

[0138] Furthermore, assuming the output is given to Figure 2 The output voltage of the V-phase operational mechanism 312 shown replaces the V-phase output voltage value signal, such as... Figure 10 As shown, the output voltage value signal between V and W can be set from the output voltage measurement mechanism 252 between V and W. In this case, the signal of "V-phase modulation factor signal - W-phase modulation factor signal" is used instead of the V-phase modulation factor signal of the V-phase calculation mechanism 312.

[0139] Furthermore, assuming the output is given to Figure 2 The output voltage of the W-phase operating mechanism 313 shown replaces the W-phase output voltage value signal, such as... Figure 10 As shown, the output voltage value signal between W and U can be set from the output voltage measurement mechanism 253 between W and U. In this case, the signal of "W-phase modulation factor signal - U-phase modulation factor signal" is used instead of the W-phase modulation factor signal of the W-phase operation mechanism 313.

[0140] Even if the output voltage measuring mechanism 25 (U-V output voltage measuring mechanism 251, V-W output voltage measuring mechanism 252, W-U output voltage measuring mechanism 253) is configured to measure the line-to-line voltage, it is still possible to measure the output voltage and calculate the delay as an example of the change in the characteristics of the switching element by the arithmetic unit 31.

[0141] Industrial availability

[0142] Since the present invention can infer the deterioration of power conversion devices, it is preferred for power sources that supply power from a simple power source to a basic system.

[0143] Label Explanation

[0144] 10 Inverters

[0145] 11 First Arm

[0146] 12 Second Arm

[0147] 13 Third Arm

[0148] 111, 121, 131 Upper arm

[0149] 112, 122, 132 Lower arm

[0150] 141a~141c First wiring

[0151] 142a~142c Second wiring

[0152] 143a~143c 3rd wiring

[0153] 15. Voltage Command Mechanism

[0154] 151 U-phase voltage command mechanism

[0155] 152 V phase voltage command mechanism

[0156] 153 W phase voltage command mechanism

[0157] 16 Modulation factor calculation mechanism

[0158] 161 U-phase modulation factor calculation mechanism

[0159] 162 V-phase modulation factor calculation mechanism

[0160] 163 W-phase modulation factor calculation mechanism

[0161] 17 Oscillating Mechanism

[0162] 18 Comparison agencies

[0163] 181 U-phase comparison mechanism

[0164] 182 V phase comparison mechanism

[0165] 183 W Comparison Mechanism

[0166] 19 Reversing Mechanism

[0167] 191 U Reverse Rotation Mechanism

[0168] 192 V Reverse Mechanism

[0169] 193 W Reverse Rotation Mechanism

[0170] 21 DC Voltage Measurement Mechanism

[0171] 22 voltage divider

[0172] Resistors 22a and 22b

[0173] 23 Output voltage measuring mechanism

[0174] 231 U-phase output voltage measurement mechanism

[0175] 232 V phase output voltage measuring mechanism

[0176] 233 W-phase output voltage measuring mechanism

[0177] 24 Output current measuring mechanism

[0178] 241 U-phase output current measuring mechanism

[0179] 242 V phase output current measuring mechanism

[0180] 243 W-phase output current measuring mechanism

[0181] 25 Output voltage measuring mechanism

[0182] 251 U-V output voltage measuring mechanism

[0183] 252 V-W Output Voltage Measurement Mechanism

[0184] 253 W-U Interval Output Voltage Measurement Mechanism

[0185] 30 Deterioration Inference Device

[0186] 31. Computing mechanism

[0187] 311 U-phase computing mechanism

[0188] 312 V phase operating mechanism

[0189] 313 W phase operation mechanism

[0190] 31a First Averaging Mechanism

[0191] 31b Second Averaging Mechanism

[0192] 31c Multiplication Mechanism

[0193] 31d Subtraction Mechanism

[0194] 31e Points System

[0195] 31f Polarity determination mechanism

[0196] 31g switching mechanism

[0197] 32. Judgment Institution

[0198] 321 U-phase determination mechanism

[0199] 322 V phase determination mechanism

[0200] 323 W phase determination mechanism

[0201] 33 Reporting Organizations

[0202] P Positive side power cord

[0203] N negative power line

[0204] M Three-phase AC motor

Claims

1. A degradation prediction device for a power conversion device, characterized in that, have: The arithmetic unit calculates the change in the characteristics of the switching element for power conversion in the power conversion device based on the voltage command that is the target output voltage of the power conversion device and the output voltage value of the power conversion device. The determination mechanism determines whether the change in the characteristic calculated by the aforementioned calculation mechanism has changed by more than a threshold compared to the initial state; and The reporting body shall issue a warning when the aforementioned assessment body determines that the change in the aforementioned characteristic exceeds the threshold. The aforementioned arithmetic mechanism includes: a subtraction mechanism for calculating the difference between the aforementioned voltage command and the aforementioned output voltage value; A pair of integrators integrate the difference calculated by the subtraction mechanism and output the integral value of the difference to the determination mechanism. A polarity determination mechanism determines the polarity of the current based on the output current from the power conversion device, wherein the power conversion device is formed by an upper arm and a lower arm formed by the switching element; and a switching mechanism switches the signal from the subtraction mechanism to one of the two integration mechanisms, namely the integration mechanism of one of the pair of integration mechanisms, based on the switching signal from the polarity determination mechanism, thereby switching the differential integral value as the change in the characteristic. In order to determine the change in characteristics after switching by the aforementioned switching mechanism, a pair of determination mechanisms are provided.

2. The degradation inference device for a power conversion device as described in claim 1, characterized in that, The aforementioned determination mechanism stores the change in the characteristic corresponding to the output voltage value of the aforementioned power conversion device and sets it as an initial state, and determines the aforementioned threshold based on this initial state.

3. The degradation inference device for a power conversion device as described in claim 1, characterized in that, The aforementioned integrator will output the integral value obtained by the definite integral over the specified interval as the difference integral value.

4. The degradation inference device for a power conversion device as described in claim 1 or 3, characterized in that, The aforementioned computing mechanism possesses: The first averaging mechanism calculates the average value of the input voltage input to the power conversion device according to each time interval synchronized with the carrier signal; The multiplication mechanism calculates the voltage command by multiplying the average value of the input voltage from the first averaging mechanism by the modulation factor and outputs it to the subtraction mechanism; and The second averaging mechanism calculates the average value of the output voltage of the power conversion device according to each time interval synchronized with the carrier signal and outputs it to the subtraction mechanism.

5. A computer program product comprising a degradation prediction program for a power conversion device, characterized in that, This degradation inference procedure enables the computer to function as a mechanism for: The arithmetic unit calculates the change in the characteristics of the switching element for power conversion in the power conversion device based on the voltage command that is the target output voltage of the power conversion device and the output voltage value of the power conversion device. The determination mechanism determines whether the change in the characteristic calculated by the aforementioned calculation mechanism has changed by more than a threshold compared to the initial state; and The reporting body shall issue a warning when the aforementioned assessment body determines that the change in the aforementioned characteristic exceeds the threshold. The aforementioned arithmetic mechanism includes: a subtraction mechanism for calculating the difference between the aforementioned voltage command and the aforementioned output voltage value; A pair of integrators integrate the difference calculated by the subtraction mechanism and output the integral value of the difference to the determination mechanism. A polarity determination mechanism determines the polarity of the current based on the output current from the power conversion device, wherein the power conversion device is formed by an upper arm and a lower arm formed by the switching element; and a switching mechanism switches the signal from the subtraction mechanism to one of the two integration mechanisms, namely the integration mechanism of one of the pair of integration mechanisms, based on the switching signal from the polarity determination mechanism, thereby switching the differential integral value as the change in the characteristic. In order to determine the change in characteristics after switching by the aforementioned switching mechanism, a pair of determination mechanisms are provided.

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