Power conversion device having diagnostic function for rotary electric machine, drive device, and diagnostic method for rotary electric machine

Abstract

Provided is a power conversion device capable of diagnosing deterioration and identifying a deteriorated part in a rotary electric machine. A diagnosis device 400 comprises: a plurality of semiconductor elements 201-206 that switch the current of a DC power source 10 supplied to a plurality of windings 310-330 of a rotary electric machine 30 accommodated in a metal housing 340, and are accommodated in a metal housing 240 connected to the metal housing 340; an operation control unit 401 that controls the semiconductor elements 201-206; a midpoint potential / current detector 232 that, when a midpoint 223 between two capacitors 221, 222 connected in parallel to the DC power source 10 is connected to the metal housing 240, detects the potential or current at the midpoint 223; a storage unit 404 that stores the initial value of the potential or current at the midpoint 223; and a comparison and judgment unit 403 that compares the stored initial value of the potential or current at the midpoint 223 and the potential or current at the midpoint 223 detected when the operation control unit 401 switches the semiconductor elements 201-206, and that judges the deterioration of the rotary electric machine 30.

Description

Power conversion device having a diagnostic function for a rotating electrical machine, drive device, and diagnostic method for a rotating electrical machine

[0001] The present invention relates to a power conversion device having a diagnostic function for a rotating electrical machine for detecting deterioration of the rotating electrical machine and further specifying the location of the deterioration, a drive device including the same, and a diagnostic method for the rotating electrical machine.

[0002] Japanese Patent Application Laid-Open No. 2010-197093 discloses a state determination device including an inverter having a non-linear amplification device and an inductive load. The non-linear amplification device amplifies the voltage of a capacitor connected in parallel with a Y capacitor provided inside the inverter, and determines the insulation state of the inductive load using a state determination device that determines whether the amplified voltage is less than or equal to a specified value.

[0003] Japanese Patent Application Laid-Open No. 2010-197093

[0004] In Patent Document 1, a change in the DC component due to a change in the insulation resistance is detected.

[0005] However, as the state of insulation deterioration, not only the insulation resistance but also the component of the stray capacitance (C) changes. For example, when insulating paper is used, the characteristics of the insulating paper exposed to high temperature change, resulting in performance deterioration, or the insulation performance deteriorates due to peeling at the interface between the insulating paper and the stator, or a change in the thickness of the insulating paper.

[0006] Therefore, detecting only the DC component cannot sufficiently detect deterioration, and there is a problem of reaching insulation breakdown.

[0007] Further, since Patent Document 1 does not describe specific detection timing, for example, it is impossible to specify where an abnormality occurs inside the rotating electrical machine or outside the rotating electrical machine.

[0008] The present invention has been made in view of the above problems, and an object thereof is to provide a power conversion device having a diagnostic function for a rotating electrical machine, a drive device including the same, and a diagnostic method for a rotating electrical machine, which can diagnose deterioration of the rotating electrical machine and specify the location of the deterioration.

[0009] To achieve the above object, the present invention is configured as follows.

[0010] A power converter having a diagnostic function for a rotating electric machine, comprising: a plurality of semiconductor elements that switch the current supplied from a DC power supply to a plurality of windings of a rotating electric machine; and an operation control unit that controls the operation of the plurality of semiconductor elements, further comprising: two capacitors connected in parallel between the DC power supply and the plurality of semiconductor elements; a midpoint potential / current detector that detects the potential or current at the midpoints of the two capacitors electrically connected to the plurality of windings; a storage unit that stores an initial value of the potential or current at the midpoint; and a comparison determination unit that compares the initial value of the potential or current at the midpoint stored in the storage unit with the potential or current at the midpoint detected by the operation control unit by switching the operation of the plurality of semiconductor elements, and determines the deterioration of the rotating electric machine.

[0011] Furthermore, in the method for diagnosing a rotating electric machine, the current supplied from a DC power supply to multiple windings of the rotating electric machine is switched by multiple semiconductor elements, the midpoints of two capacitors connected in parallel between the DC power supply and the multiple semiconductor elements are electrically connected to the multiple windings, the potential or current at the midpoint is detected, and the initial value of the potential or current at the midpoint stored in the memory unit is compared with the potential or current at the midpoint detected by switching the operation of the multiple semiconductor elements to determine the deterioration of the rotating electric machine.

[0012] According to the present invention, it is possible to provide a power converter having a diagnostic function for rotating electric machines that can diagnose deterioration of rotating electric machines and identify the location of deterioration, a drive unit equipped therewith, and a method for diagnosing rotating electric machines. According to the present invention, it is possible to identify the location of deterioration in a rotating electric machine and facilitate the identification of the cause of deterioration. Furthermore, by being able to identify the location of deterioration, it is possible to provide a power converter having a diagnostic function for rotating electric machines that has high maintainability, a drive unit equipped therewith, and a method for diagnosing rotating electric machines.

[0013] This is a diagram illustrating a power converter with a diagnostic function according to Example 1. This is a diagram illustrating the operation of a power converter with a diagnostic function according to Example 1. This is a functional block diagram of a power converter with a diagnostic function according to Example 1. This is a flowchart illustrating the deterioration diagnosis of a power converter with a diagnostic function according to Example 1. This is a diagram illustrating a power converter with a diagnostic function according to Example 2. This is a diagram illustrating a power converter with a diagnostic function according to Example 3. This is a diagram illustrating a power converter with a diagnostic function according to Examples 4 and 5. This is a flowchart illustrating the deterioration diagnosis of a power converter with a diagnostic function in Example 8.

[0014] Embodiments of the present invention will be described below with reference to the figures.

[0015] (Example 1) Figure 1 is a diagram illustrating a power conversion device having a diagnostic function for a rotating electric machine 30 according to Example 1.

[0016] In Figure 1, DC power supplied from a high-voltage DC power supply 10 is converted to three-phase AC power by a power converter 20, and this three-phase AC power is supplied to a rotating electric machine 30 that is driven by it. Here, the DC power supply 10 is a storage battery such as a lithium-ion battery or a power supply directly connected to the power grid.

[0017] The power converter 20 includes a smoothing capacitor 220 for smoothing DC power, a three-phase bridge circuit (U-phase, V-phase, W-phase) composed of six semiconductor elements 201-206, and a control unit 230 equipped with a driver IC 231 for driving and controlling the semiconductor elements 201-206 on and off. The semiconductor elements 201-206 are composed of MOSFETs, each having a drain electrode, a source electrode, and a gate electrode. Here, the MOSFETs may be switching power semiconductor elements made by connecting IGBTs and DIODEs in parallel using Si or SiC, or other semiconductor elements. Although not shown, the control unit 230 and the semiconductor elements 201-206 are connected via multiple signal lines made of metal such as copper. Furthermore, resin-molded busbars are used to connect the smoothing capacitor 220 and the semiconductor elements 201-206. Note that the driver IC 231 may be composed of multiple units.

[0018] The source electrodes of semiconductor elements 201, 202, and 203 are electrically connected to the drain electrodes of semiconductor elements 204, 205, and 206, respectively, and each connection point is connected to a three-phase output wiring. Here, resin-molded busbars are also used for the three-phase output wiring. A current sensor (not shown) is also provided on the three-phase output wiring to detect the current value flowing to the motor. Screws or welding are commonly used for the electrical connections of the busbars. These components constituting the power conversion device 20 are housed inside a second metal housing 240 and fixed with screws (not shown). Here, aluminum is generally used as the material for the second metal housing 240. Furthermore, in order to efficiently transfer the heat generated by semiconductor elements 201-206 to the second metal housing 240, a heat dissipation material (not shown) is placed between the semiconductor elements 201-206 and the second metal housing 240. In addition, the second metal housing 240 is sealed using a metal cover (not shown). Two capacitors, 221 and 222 (described later), are connected in parallel and in series with each other between the smoothing capacitor 220 and the DC power supply 10. The smoothing capacitor 220 and the second metal housing 240 are thermally coupled to ensure that the heat generated by the smoothing capacitor 220 is efficiently transferred to the second metal housing 240. The second metal housing 240 may also be provided with a water channel for cooling.

[0019] The semiconductor elements 201-206 operate by receiving a drive signal output from the driver IC 231 of the control unit 230, and convert the DC power supplied from the high-voltage power supply 10 into three-phase AC power. Here, the driver IC 231 generates a desired drive signal based on a switching signal calculated by a microcontroller (not shown) based on information from other diagnostic devices and sensors.

[0020] A well-known method for microcontroller calculations involves calculating current command values ​​for the d and q axes based on a given target command value, calculating voltage command values ​​for the d and q axes based on the difference between these calculated current command values ​​and the detected current values ​​for the d and q axes, and converting these calculated voltage command values ​​for the d and q axes into U-phase, V-phase, and W-phase voltage command values ​​based on the detected magnetic pole positions. The microcontroller then generates a pulsed modulated wave based on a comparison between the fundamental wave (sine wave) and carrier wave (triangular wave) based on the U-phase, V-phase, and W-phase voltage command values, and outputs this generated modulated wave as a PWM (pulse width modulation) signal to the driver IC 231.

[0021] Furthermore, the control unit 230 has the function of detecting the deterioration state of the power converter 20 based on temperature sensing information from temperature sensors provided on the semiconductor elements 201-206, current sensing information from current sensors, and voltage sensing information from each terminal, and stopping the operation of the driver IC 231 or limiting the output of the power converter 20.

[0022] Y-capacitors 221 and 222 are connected in series between the positive and negative terminal wiring of the power converter 20. Furthermore, the Y-capacitors 221 and 222 are arranged in parallel with the smoothing capacitor 220. Additionally, the midpoint 223 where the Y-capacitors 221 and 222 are electrically connected is electrically connected to the second metal housing 240. Note that EMC (Electromagnetic Compatibility) components such as inductors and capacitors may be placed in the positive or negative terminal wiring before or after the Y-capacitors 221 and 222. A current sensor for measuring DC current may also be provided.

[0023] The other ends of the three-phase output wiring, which is electrically connected to semiconductor elements 201-203 and 204-206, are electrically connected to windings 310, 320, and 330, respectively, provided on the stator of the rotating electric machine 30. Here, at the other ends of the three-phase output wiring and at the locations where the positive and negative terminal wirings are connected to the high-voltage DC power supply 10, there are resin-molded terminal blocks, which are fixed to the first metal housing 340 with screws. Alternatively, the terminal blocks may be connected by removable connectors or by direct welding.

[0024] The rotating electric machine 30 has a rotor (not shown) in addition to a stator, and the stator and rotor are housed in a first metal housing 340. Here, aluminum is generally used as the material for the first metal housing 340. The rotor has permanent magnets on the surface or inside of a laminated steel plate fixed to a shaft (not shown), and the shaft is held rotatably by bearings in the first metal housing 340 or the shaft (not shown). The stator, which has windings 310, 320, and 330, is fixed to the first metal housing 340 by shrink fitting or the like. A water channel may be provided between the first metal housing 340 or between the first metal housing 340 and the stator.

[0025] Furthermore, although not shown in the diagram, mechanical devices such as a reduction gear and a speed increaser are connected to the other end of the shaft of the rotating electric machine 30, and the driving force is obtained using the mechanical energy converted by the rotating electric machine 30.

[0026] A stray capacitance exists between the windings 310-330 on the stator of the rotating electric machine 30 and the ground potential, i.e., the first metal housing 340. When the semiconductor elements 201-206 of the power converter 20 are switched on and off, a charge / discharge current is generated through this stray capacitance. This charge / discharge current is generally called a common-mode current. If the common-mode current leaks outside the power converter 20, it becomes noise and adversely affects the external system. Therefore, the common-mode current is recovered to the midpoint 223 of the Y capacitors 221 and 222 via the second metal housing 240 of the power converter 20, which is electrically connected to the first metal housing 340. Here, one method of electrically connecting the second metal housing 240 and the first metal housing 340 is to directly connect and fix the first metal housing 340 and the second metal housing 240 with screws or the like, a method known as a mechatronic integrated structure. Other methods include using shielded cables for the three-phase output wiring, connecting one end of the shielded cable to the second metal housing 240 and the other end to the first metal housing 340, but in any case, it is desirable to reduce the impedance between the housings.

[0027] When the insulation of the windings 310-330 of the rotating electric machine 30 is normal, a charge / discharge current corresponding to the magnitude of the aforementioned stray capacitance is recovered from the first metal housing 340 through the second metal housing 240 and to the power converter 20 via the midpoint 223. Here, the charge / discharge current is supplied by the voltage change (dV / dt) generated by the switching of the semiconductor elements 201-206, and the magnitude of the voltage depends on the high-voltage power supply 10. The charge / discharge current is an oscillating AC waveform determined by the impedance of the windings 310-330 and the values ​​of parasitic impedance and stray capacitance present in the second metal housing 240 and the first metal housing 340.

[0028] If the insulation of any phase of winding 310-330 deteriorates, the stray capacitance also changes. For example, if the insulating paper provided on the stator of the rotating electric machine 30 is exposed to a high-temperature environment for a long time, the electrical properties of the insulating paper itself may change, delamination may occur between the insulating paper and the stator, or the thickness of the insulating paper may change. These changes lead to changes in stray capacitance, i.e., changes in insulation properties, and the value of the charge and discharge current also changes compared to when the insulation is normal.

[0029] Next, the operating conditions of the power converter 20 for detecting deterioration of the rotating electric machine 30 will be explained using Figure 2. Generally, the power converter 20 outputs a three-phase AC sine wave in order to smoothly control the rotating electric machine 30 which is composed of three phases. However, because the three-phase AC sine wave is symmetrical, even if insulation deterioration of the windings 310-330 occurs and a change in charge / discharge current is detected, it is difficult to pinpoint where in the rotating electric machine 30 the deterioration occurred.

[0030] The driving conditions for the power converter 20 shown in Figure 2 indicate that semiconductor elements 201, 205, and 206 enclosed by the dotted circle are in the ON state, while the other semiconductor elements 202, 203, and 204 are in the OFF state. Since the negative electrode semiconductors 205 and 206 are in the ON state, the motor windings 320 and 330 on the power converter 20 side are at the negative electrode potential, i.e., the ground potential. On the other hand, since semiconductor element 201 is in the ON state, the motor winding 310 on the power converter 20 side is at the potential of the high-voltage power supply 10. Here, if the voltage of the high-voltage power supply 10 is E, the potential of the motor neutral point is at a potential of E / 2.

[0031] Under the driving conditions shown in Figure 2, the motor winding 310 is subjected to the same potential as the high-voltage DC power supply 10, while motor windings 320 and 330 are subjected to half that voltage. Depending on the time change of the voltage applied to each winding, a charging current flows from the stray capacitance present in each winding. The charge / discharge current that flows in the initial state, such as during product manufacturing or shipping, will differ from the charge / discharge current that flows from the stray capacitance that has changed due to insulation degradation as described above after the product has been in operation for a long period of time.

[0032] By comparing these current values, or the voltage values ​​that change along with the current values, the magnitude of insulation degradation can be determined. Here, if the magnitude and speed of the voltage change applied to windings 310-330 are the same as in the initial state, not only the magnitude of the current amplitude but also the frequency of the charge and discharge current will change.

[0033] The power converter 20 is equipped with a midpoint potential detector (also called a midpoint potential / current detector) 232 for detecting changes in charge / discharge current or similarly changing voltage. The midpoint potential detector 232 may use a voltmeter if it is possible to measure the potential of the midpoint of the Y capacitor.

[0034] Since changes in charge and discharge current may contain noise components, it is advisable to repeatedly switch the semiconductor element on and off and capture the characteristics of the changes using frequency analysis or other methods.

[0035] Furthermore, by changing the on / off combination of the positive and negative semiconductors, for example, by turning on semiconductor elements 202, 204, and 206 and turning off the others, the voltage applied to the motor windings 310-330 can be changed. By driving the power converter 20 with this combination and extracting the change in charge / discharge current values, it becomes possible to identify where degradation is occurring in the windings 310-330.

[0036] For example, if insulation degradation occurs in the winding 310 and the stray capacitance changes, a voltage E is applied when the semiconductor element 201 is ON, whereas when the semiconductor element 204 is ON in a different operating mode, the applied voltage decreases. As a result, the magnitude and frequency of the charge and discharge current flowing from the parasitic capacitance change. In this case, the change in charge and discharge current is larger and the frequency is higher when the semiconductor element 201 is ON.

[0037] In this way, by switching the on and off states of the semiconductor elements 201-206, it becomes possible to identify the deteriorated parts of the rotating electric machine 30. In addition to directly detecting the potential, an amplifier may be used as the detector 232 for the midpoint potential of the Y capacitors 221 and 222, such as the method described in Patent Document 1.

[0038] Figure 3 is a functional block diagram of the degradation diagnosis device 400 according to Embodiment 1. In Figure 3, the degradation diagnosis device 400 includes an operation control unit 401, a comparison and determination unit 403, and a storage unit 404. The comparison and determination unit 403 compares the value of the neutral point potential or current of the midpoint 223 measured by the midpoint potential / current detector 232 with the initial value stored in the storage unit 404, and outputs the determination result to the operation control unit 401. The operation control unit 401 sets the driving conditions (described later) of the power converter 20 and controls the measurement operation of the midpoint potential / current detector 232. The operation control unit 401 also displays the degradation determination result from the comparison and determination unit 403 on the display unit 350.

[0039] Figure 4 is a flowchart of the degradation diagnosis of the degradation diagnosis device 400 according to Example 1. In the degradation diagnosis of the rotating electric machine 30 by the degradation diagnosis device 400, the degradation diagnosis is performed using the change in the midpoint voltage or current of the Y capacitors 221 and 222, which is obtained when the rotating electric machine 30 is not rotating.

[0040] In step S1 of Figure 4, the operation control unit 401 sets a drive condition 1 indicating the on / off state of semiconductor elements 201 to 206 to the power converter 20. Drive condition 1 is the state when semiconductor elements 201, 205, and 206 are on, and semiconductor elements 202, 203, and 204 are off.

[0041] Next, in step S2, the operation control unit 401 causes the midpoint potential / current detector 232 to measure (detect) the potential or current of the Y capacitor midpoint 223. Then, in step S3, the comparison determination unit 403 compares the measured potential or current of the Y capacitor midpoint 223 with the initial state potential or current stored in the storage unit 404 to determine whether or not it has deteriorated and where the deterioration is located. If it has deteriorated, in step S10, the operation control unit 401 causes the display unit 350 to display that it has deteriorated and the location of the deterioration (such as any of the U-phase winding 310, V-phase winding 320, or W-phase winding 330).

[0042] In step S3, if the comparison determination unit 403 determines that there is no deterioration, the process proceeds to step S4, and the operation control unit 401 sets drive condition 2 indicating the on / off states of the semiconductor elements 201 to 206 in the power conversion device 20. Drive condition 2 is a state where the semiconductor elements 202, 204, and 206 are on and the semiconductor elements 201, 203, and 205 are off.

[0043] Then, the process proceeds to step S5, and the operation control unit 401 causes the midpoint potential / current detector 232 to measure (detect) the potential or current of the Y-capacitor midpoint 223. Then, in step S6, similar to step S3, the comparison determination unit 403 compares the measured potential or current of the Y-capacitor midpoint 223 with the potential or current in the initial state stored in the storage unit 404, and determines whether there is deterioration and the location of deterioration. If there is deterioration, in step S10, the operation control unit 401 causes the display 350 to display that there is deterioration and the location of deterioration (such as any one of the U-phase winding 310, V-phase winding 320, and W-phase winding 330).

[0044] In step S6, if the comparison determination unit 403 determines that there is no deterioration, the process proceeds to step S7, and the operation control unit 401 sets drive condition 3 indicating the on / off states of the semiconductor elements 201 to 206 in the power conversion device 20. Drive condition 3 is a state where the semiconductor elements 203, 204, and 205 are on and the semiconductor elements 201, 202, and 206 are off.

[0045] Then, the process proceeds to step S8, and the operation control unit 401 causes the midpoint potential / current detector 232 to measure (detect) the potential or current of the Y-capacitor midpoint 223. Then, in step S9, similar to steps S3 and S6, the comparison determination unit 403 compares the measured potential or current of the Y-capacitor midpoint 223 with the potential or current in the initial state stored in the storage unit 404, and determines whether there is deterioration and the location of deterioration. If there is deterioration, in step S10, the operation control unit 401 causes the display 350 to display that there is deterioration and the location of deterioration (report of deterioration and location of deterioration).

[0046] In step S9, when the comparison determination unit 403 determines that there is no deterioration, the process ends. When the comparison determination unit 403 determines that there is no deterioration, the display 350 can display that the U-phase winding 310, the V-phase winding 320, and the W-phase winding 330 are not deteriorated.

[0047] Here, in the illustrated example, the deterioration diagnosis device 400 is provided outside the power conversion device 20. The power conversion device 20 and the deterioration diagnosis device 400 are electrically connected by wiring or the like. When the deterioration diagnosis device 400 determines deterioration, it is also possible to send a stop signal to the power conversion device 20. Alternatively, it is also possible to report the deterioration state to a higher-level system or a maintenance provider and propose the maintenance timing of the rotating electrical machine 30.

[0048] Note that the deterioration diagnosis device 400 may be arranged inside the power conversion device 20.

[0049] According to the first embodiment of the present invention, it is possible to provide a power conversion device having a diagnosis function of the rotating electrical machine 30, a drive device, and a diagnosis method of the rotating electrical machine, which can diagnose the deterioration of the rotating electrical machine 30 and specify the deteriorated location.

[0050] Further, according to the first embodiment of the present invention, since it is possible to specify the deteriorated location inside the rotating electrical machine 30, the workability during maintenance can be significantly improved.

[0051] In addition, since only the deteriorated location needs to be repaired or replaced, there is also an economic merit. Furthermore, the ability to specify the deteriorated location is extremely important for elucidating the cause of deterioration, and it is possible to supply a power conversion device, a drive device, and a diagnosis method of the rotating electrical machine having a more reliable diagnosis function of the rotating electrical machine 30.

[0052] (Second Embodiment) The second embodiment of the present invention will be described with reference to FIG. 5.

[0053] In Example 2, the power converter 20 is set to a two-phase energized state. For example, the current Iu flowing through the U phase and the current Iv flowing through the V phase are set to be the same, and the current Iw flowing through the W phase is set to 0A. The power converter 20 is driven by switching the phase through which no current flows, and the changes in charge and discharge current values ​​under each driving condition are compared.

[0054] The operation control to set the power converter 20 to a two-phase energized state and the operation to compare the changes in charge / discharge current values ​​are performed by the operation control unit 401 shown in Figure 3. The degradation diagnosis flow of the diagnostic device can be applied to the degradation diagnosis flowchart shown in Figure 4 when the two-phase energized state is set.

[0055] In Embodiment 2 of the present invention, the same effects as in Embodiment 1 can be obtained. That is, the voltage value applied to the motor windings 310-330 can be determined, the charge and discharge currents from the stray capacitance can be compared, and as a result, the occurrence and location of deterioration of the rotating electric machine 30 can be identified.

[0056] Furthermore, in this embodiment 2, deterioration detection can be achieved by synchronizing the detection timing while the drive current is supplied to the rotating electric machine, and inspection can be performed even while the electric drive system is in operation. As a result, it becomes possible to detect deterioration of the electric drive system more safely.

[0057] (Example 3) Example 3 of the present invention will be explained using Figure 6.

[0058] In the third embodiment, the current sensor 250 is positioned at the midpoint 223 between the Y capacitors 221 and 222. The other configurations are the same as those shown in Figure 1.

[0059] Commonly used current sensors 250 include magnetic detection methods that combine magnetic detection elements such as Hall elements with magnetic materials, and resistance detection methods that use resistors such as shunt resistors. The current sensor 250 is located in the second metal housing 240 or where the Y capacitors 221 and 222 are mounted. Possible locations where the Y capacitors 221 and 222 are mounted include printed circuit boards and busbars.

[0060] The current value detected by the current sensor 250 is transmitted to the midpoint potential / current detector 232. The current sensor 250 and the midpoint potential / current detector 232 are electrically connected by wiring made of copper or similar material.

[0061] The degradation diagnosis flow in Example 3 is the same as the degradation diagnosis flow in Example 1 (Figure 4).

[0062] In Example 3 of the present invention, the same effects as in Example 1 can be obtained.

[0063] Furthermore, in Embodiment 3, the presence or absence of a malfunction in the rotating electric machine 30 and the location of the malfunction are detected based on the current value detected by the current sensor 250. This makes it possible to detect the presence or absence of a malfunction in the rotating electric machine 30 and the location of the malfunction with high accuracy.

[0064] Furthermore, the detection of the presence or absence of a malfunction in the rotating electric machine 30 and the location of the malfunction, as shown in Example 3, can also be applied to Example 2.

[0065] (Example 4) Example 4 of the present invention will be described with reference to Figure 7.

[0066] In Example 4, the rotating electric machine 30 is equipped with multiple sets of windings ((310, 320, 330), (310b, 320b, 330b)). In the example shown in Figure 7, two sets of windings are shown as multiple sets. Also, the same number of power converters 20 and 20b are arranged as the number of sets of windings. The degradation diagnostic device 400 and the display unit 350 are used in common with the two power converters 20 and 20b, and their configuration and operation are the same as in Example 1, so a detailed explanation is omitted.

[0067] In a configuration like that of Example 4, if the operation for detecting the deterioration state described above is performed separately by the power converter 20 and the power converter 20b, it becomes possible to identify the deteriorated parts of the rotating electric machine 30, which is equipped with multiple sets of windings ((310, 320, 330), (310b, 320b, 330b)).

[0068] Therefore, in Example 4, it is possible to provide a power converter, a drive unit, and a method for diagnosing a rotating electric machine that have the same maintainability-friendly diagnostic function as in Example 1, for multiple power converters 20, 20b.

[0069] In addition, in Example 4, it is also possible to diagnose and identify deteriorated parts of the rotating electric machine 30 by repeatedly switching the positive electrode semiconductor elements 201-203 and 201b-203b on and off. By repeatedly switching the positive electrode semiconductor elements 201-203 and 201b-203b on and off in this way, the accuracy of, for example, frequency analysis can be improved.

[0070] (Example 5) Example 5 of the present invention will be described with reference to Figure 7.

[0071] In contrast to Embodiment 1, the example shown in Figure 7 includes a second power converter 20b housed in a second metal casing 240b, in addition to the first power converter 20. The second power converter 20b is connected to a high-voltage DC power supply (DC power supply) 10, similar to the first power converter 20. Note that the control unit 230b may be mounted on the same circuit board as the control unit 230.

[0072] Furthermore, the rotating electric machine 30 has a first set of windings 310, 320, and 330, and a second set of windings 310b, 320b, and 330b. The second set of windings 310b, 320b, and 330b are wound around the same stator as the first set of windings 310, 320, and 330, but are electrically independent of each other. The second set of windings 310b, 320b, and 330b are housed in a first metal housing 340.

[0073] The added second power converter 20b has the same configuration as the first power converter 20, and its three-phase output wiring is electrically connected to the second set of windings 310b, 320b, and 330b of the rotating electric machine 30, respectively. The rotating electric machine 30 in this configuration is sometimes called a double-winding machine.

[0074] Thus, Embodiment 5 is a system in which one rotating electric machine 30 is driven by two power converters 20 and 20b. The purpose of this is varied, including adding a power converter 20b to enable larger size and higher efficiency of the power converter 20 when the rotating electric machine 30 outputs a larger torque than in Embodiment 1, and improving the continuity of operation when one system deteriorates. Furthermore, the power converter 20b may be housed outside the second metal housing 240 as long as it is electrically independent.

[0075] The driving conditions for the semiconductor switching elements 201-206 in Example 5 will be described. All positive-side semiconductor switching elements 201-203 in the first power converter 20 are set to the ON state, and all negative-side semiconductor switching elements 204-206 are set to the OFF state.

[0076] On the other hand, the positive electrode semiconductors 201b-203b in the second power converter 20b are all turned off, and the negative electrode semiconductors 204b-206b are all turned on, so that the rotating electric machine 30 does not rotate. Under these operating conditions, the windings 310-330 of the rotating electric machine 30 have the voltage E of the high-voltage DC power supply 10 applied to them. Meanwhile, the windings 310b-330b of the rotating electric machine 30 are at the same potential as ground potential.

[0077] Here, between windings 310-330 and 310b-330b, which are arranged on a single common stator housed in the metal casing 340, there is a stray capacitance between the windings. When the above driving conditions are selected, a charge / discharge current flows between windings 310-330 and 310b-330b, corresponding to the stray capacitance between the windings.

[0078] This charging and discharging current can be detected by a voltage sensor or current sensor provided in the power converters 20 and 20b. For example, the current sensor 250 provided in the three-phase output wiring of the power converter 20 described above can be used. Alternatively, a new detection sensor may be added to the power converter 20 or the rotating electric machine 30. By comparing the magnitude of the current value or voltage or the resonant frequency detected under the above operating conditions with the initial state of the rotating electric machine 30, such as when it is shipped, and the state after the product has been in operation for a long period of time, it is possible to detect insulation degradation between the windings using the degradation diagnostic device 400.

[0079] In Example 5, deterioration between windings 310-330 and 310b-330b of a double-winding rotating electric machine, which could not be detected by conventional technology, can be detected. As a result, not only is new deterioration detected, but the integrity can be restored by repairing or replacing only the deteriorated parts, thus providing a power converter, drive unit, and method for diagnosing a rotating electric machine that have excellent maintainability and cost-effectiveness.

[0080] Furthermore, the rotating electric machine 30 has windings of three or more phases, and the number of sets of semiconductor elements is the same as the number of phases. It is also possible to determine the deterioration of the windings by switching between two combinations of windings of three or more phases.

[0081] (Example 6) Example 6 of the present invention will now be described.

[0082] In Example 5, there were two sets of windings 310-330, 310b-330b and power converters 20, 20b.

[0083] In Example 6, the rotating electric machine 30 is equipped with three or more sets of windings and the same number of power converters as the sets of windings. In this case, the on / off combinations of the semiconductor elements 201-206 and 201b-206b of the power converters 20 and 20b for detecting degradation in Example 5 are applied to Example 6 and carried out according to the number of combinations of windings. For example, if there are three sets of windings, A (windings 310-330), B (windings 310b-330b), and C (windings 310b-330b), the first combination will be A and B, the second combination will be A and C, and the third combination will be B and C. For each combination, the on / off status of the semiconductor elements is set and a diagnosis is performed.

[0084] The diagnostic device 400 in Example 6 has the same configuration as in Examples 1 to 5.

[0085] By configuring the device as in Example 6, even when the rotating electric machine 30 has three or more sets of windings and the same number of power conversion devices as the sets of windings, it is possible to identify which winding set is experiencing deterioration, thereby providing a power conversion device, drive device, and method for diagnosing a rotating electric machine that have a diagnostic function for rotating electric machines that is superior in terms of maintainability and cost-effectiveness.

[0086] (Example 7) The charge / discharge current I in Examples 1 to 6 described above can be derived from the relationship between the time change (dV / dt) of the voltage applied to the windings of the rotating electric machine 30 and the stray capacitance C. Specifically, I = C(dV / dt). In order to improve the detection performance, the charge current I should be increased, and to do so, it is possible to increase (dV / dt). Since (dV / dt) is due to the switching speed of the semiconductor elements 201-206 and 201b-206b, (dV / dt) can be increased by increasing the switching speed of the semiconductor elements 201-206 and 201b-206b.

[0087] Therefore, in Embodiment 7, under the driving conditions for degradation detection described above, the operation control unit 401 controls the power converters 20 and 20b to make the switching speed of the semiconductor elements 201 to 206 and 201b to 206b during degradation diagnosis faster than the switching speed of the semiconductor elements 201 to 206 and 201b to 206b during degradation diagnosis under the driving conditions in which the rotating electric machine 30 applies torque to an external load (not shown) (normal driving conditions other than when the rotating electric machine 30 is being diagnosed for degradation), thereby improving the degradation detection performance.

[0088] Specific methods for increasing the switching speed of semiconductor elements 201-206 and 201b-206b include reducing the gate resistance value between the driver IC and the gate terminal, and using the slew rate adjustment function built into the driver IC.

[0089] Furthermore, the switching speed of the semiconductor elements 201-206 and 201b-206b must not exceed the withstand voltage of the components provided in the power converters 20 and 20b and the rotating electric machine 30.

[0090] Other configurations and operations can be the same as those in any of Examples 1 to 6. Thus, according to Example 7, in addition to obtaining the same effects as in Examples 1 to 6, by changing the switching speed of semiconductor elements 201 to 206 and 201b to 206b in the operating state and degradation detection state of the electric drive system, it is possible to provide a power converter, drive unit, and method for diagnosing a rotating electric machine that have a diagnostic function for a rotating electric machine and can further improve maintainability by changing the switching speed of semiconductor elements 201 to 206 and 201b to 206b.

[0091] (Example 8) One of the malfunctions of the rotating electric machine 30 is the bearing failure mentioned above. This is caused by common-mode current, and when deterioration occurs in the bearing, the magnitude of the common-mode current also changes. Furthermore, the common-mode current that flows when deterioration occurs in the movable parts of the rotating electric machine 30, such as the bearing, differs in magnitude and frequency from the current that flows due to the insulation deterioration of the rotating electric machine 30 as described above.

[0092] Therefore, by comparing the potential or current value at the midpoint 223 of the Y capacitor when the rotating electric machine 30 is rotating at a constant speed with the potential or current value under the driving conditions described in previous embodiments 1 to 7, it is possible to determine whether deterioration has occurred in the movable parts of the rotating electric machine 30.

[0093] Figure 8 is a degradation diagnosis flowchart of the degradation diagnosis device 400 in Example 8. Note that the degradation diagnosis flowchart shown in Figure 8 is for an example that includes power converters 20 and 20b, as shown in Figure 7. However, Example 8 is also applicable to an example that includes only one power converter 20.

[0094] In step S11 of Figure 8, the operation control unit 401 of the degradation diagnostic device 400 controls the semiconductor elements 201 to 206 of the power converter 20 to rotate the rotating electric machine 30 at a constant speed. Next, in step S12, the potential or current of the Y capacitor midpoint 223 is measured by the midpoint potential / current detector 232. Next, in step S13, the degradation diagnostic device 400 compares the initial potential or current of the Y capacitor midpoint 223 of the power converter 20 stored in the memory unit 404 with the potential or current of the Y capacitor midpoint 223 measured in step S12, and determines whether the difference is greater than or equal to a predetermined threshold.

[0095] In step S13, if there is a difference between the potential or current at the midpoint 223 of the Y capacitor of the power converter 20 and the initial value that exceeds a predetermined threshold, the process proceeds to step S17, where the deterioration diagnostic device 400 displays on the display unit 350 that deterioration has occurred and that the deteriorated area is a movable part such as a bearing.

[0096] In step S13, if there is no difference between the potential or current at the midpoint 223 of the Y capacitor of the power converter 20 and the initial value that exceeds a predetermined threshold, the process proceeds to step S14, where the semiconductor elements 201b to 206b of the power converter 20b are controlled to rotate the rotating electric machine 30 at a constant speed. Next, in step S15, the potential at the midpoint 223b of the Y capacitor is measured. Then, in step S16, the degradation diagnostic device 400 compares the initial potential or current at the midpoint 223b of the Y capacitor of the power converter 20b stored in the memory unit 404 with the potential or current at the midpoint 223b of the Y capacitor measured in step S15, and determines whether there is a difference that exceeds a predetermined threshold.

[0097] In step S16, if there is a difference between the potential or current at the midpoint 223b of the Y capacitor of the power converter 20b and the initial value that exceeds a predetermined threshold, the process proceeds to step S17, where the deterioration diagnostic device 400 displays on the display unit 350 that deterioration has occurred and that the deteriorated area is a movable part such as a bearing.

[0098] In step S16, if there is no difference between the potential of the midpoint 223b of the Y capacitor of the power converter 20b and the initial value that exceeds a predetermined threshold, the process is terminated. In this case, the display unit 350 indicates that the movable parts of the rotating electric machine 30 have not deteriorated.

[0099] Example 8 provides a power converter, a drive unit, and a method for diagnosing a rotating electric machine that have a diagnostic function for a rotating electric machine, which can significantly improve deterioration detection and further enhance maintainability.

[0100] Furthermore, according to Example 8, deterioration in the movable parts of the rotating electric machine 30 can be detected, and maintainability can be further improved.

[0101] Furthermore, the electric drive system according to the present invention can be applied to all products using rotating electric machinery, including electric vehicles such as HEVs and BEVs, mobility systems such as railway vehicles and EVTOLs, construction machinery such as dump trucks and excavators, and industrial systems such as belt conveyors used in the steel industry.

[0102] Furthermore, it can be applied to wind turbines and other devices that generate electricity through the rotation of a rotor and are equipped with a power converter.

[0103] 10...High-voltage DC power supply, 20, 20b...Power converter, 30...Rotating electric machine, 201-206, 201b-206b...Semiconductor elements (UH, VH, WH, UL, VL, WL), 220...Smoothing capacitor, 221...Y capacitor, 222...Y capacitor, 223...Y capacitor midpoint, 230, 230b...Control unit, 231...Driver IC, 232...Midpoint potential / current detector, 240...Second metal housing, 250...Current sensor, 310, 310b...U-phase winding, 320, 320b...V-phase winding, 330, 330b...W-phase winding, 340...First metal housing, 350...Display unit, 400...Degradation diagnostic device, 401...Operation control unit, 402...Midpoint measurement unit, 403...Comparison and judgment unit, 404...Storage unit

Claims

1. A power converter having a diagnostic function for a rotating electric machine, comprising: a plurality of semiconductor elements that switch the current supplied from a DC power supply to a plurality of windings of a rotating electric machine; and an operation control unit that controls the operation of the plurality of semiconductor elements, the power converter having a diagnostic function for a rotating electric machine, comprising: two capacitors connected in parallel between the DC power supply and the plurality of semiconductor elements; a midpoint potential / current detector that detects the potential or current at the midpoints of the two capacitors that are electrically connected to the plurality of windings; a storage unit that stores an initial value of the potential or current at the midpoints; and a comparison and determination unit that compares the initial value of the potential or current at the midpoints stored in the storage unit with the potential or current at the midpoints detected by the operation control unit by switching the operation of the plurality of semiconductor elements, and determines the deterioration of the rotating electric machine.

2. A power converter having a diagnostic function for a rotating electric machine as described in claim 1, wherein a smoothing capacitor is connected in parallel between the two capacitors and the plurality of semiconductor elements, the plurality of semiconductor elements are arranged on the positive and negative sides of the DC power supply, and the operation control unit turns on one or more of the plurality of semiconductor elements that are not in the same phase on the positive and negative sides, and the rotating electric machine is not rotating, and the comparison determination unit determines the deterioration of the plurality of windings based on the change in the potential or current of the midpoint detected by the midpoint potential / current detector.

3. A power converter having a diagnostic function for a rotating electric machine as described in claim 1, wherein the operation control unit switches the on / off combination of the positive and negative sides of the plurality of semiconductor elements, and the comparison and determination unit determines the deterioration of the plurality of windings.

4. A power converter having a diagnostic function for a rotating electric machine as described in claim 1, wherein the operation control unit energizes two of the three phases of the rotating electric machine, which is driven by three-phase AC power, and keeps the rotating electric machine in a state where it is not rotating, and the comparison and determination unit determines the deterioration of the plurality of windings.

5. A power converter having a diagnostic function for a rotating electric machine as described in claim 4, wherein the operation control unit switches the on / off combination of the positive and negative sides of the plurality of semiconductor elements, and the comparison and determination unit determines the deterioration of the plurality of windings.

6. A power converter having a diagnostic function for a rotating electric machine according to any one of claims 1 to 5, characterized in that a current sensor is located at the midpoint.

7. A power converter having a diagnostic function for a rotating electric machine according to any one of claims 1 to 5, characterized in that it determines the deterioration of the plurality of windings for each of the plurality of rotating electric machines.

8. A power converter having a diagnostic function for a rotating electric machine as described in claim 1, wherein the plurality of semiconductor elements comprises a set of plurality of semiconductor elements, the first plurality of semiconductor elements for switching the current supplied from the DC power supply to a first plurality of windings of the rotating electric machine, and the second plurality of semiconductor elements for switching the current supplied from the DC power supply to a second plurality of windings of the rotating electric machine, wherein the operation control unit turns on the positive electrode semiconductor element of the first plurality of semiconductor elements and turns off the negative electrode semiconductor element, turns off the positive electrode semiconductor element of the second plurality of semiconductor elements and turns on the negative electrode semiconductor element, and without rotating the rotating electric machine, it compares the initial value of the detected midpoint potential or current with the midpoint potential or current detected by the operation control unit by switching the operation of the first plurality of semiconductor elements and the second plurality of semiconductor elements, and determines the deterioration of the plurality of windings.

9. A power converter having a diagnostic function for a rotating electric machine as described in claim 8, wherein the rotating electric machine has windings of three or more phases, the number of sets of semiconductor elements is the same as the number of phases, and the device switches between two combinations of the windings of the three or more phases to determine the deterioration of the windings.

10. A power converter having a diagnostic function for a rotating electric machine as described in claim 1, wherein the operation control unit controls the operation of the plurality of semiconductor elements to rotate the rotating electric machine at a constant speed, the midpoint potential / current detector detects the midpoint potential or current, and the comparison determination unit compares it with the initial value of the midpoint potential or current stored in the storage unit to determine the deterioration of the movable part of the rotating electric machine.

11. A power converter having a diagnostic function for a rotating electric machine according to any one of claims 1 to 5 or 8 to 10, wherein the operation control unit makes the switching speed of the plurality of semiconductor elements faster during degradation diagnosis than the switching speed of the plurality of semiconductor elements under normal driving conditions.

12. A power converter having a diagnostic function for a rotating electric machine according to any one of claims 1 to 5 or 8 to 10, characterized in that it is equipped with a display for displaying the deterioration determination result of the rotating electric machine.

13. A drive device comprising: a power conversion device having a diagnostic function for a rotating electric machine as described in claim 1; the rotating electric machine; a first metal housing housing the plurality of windings; and a second metal housing housing the plurality of semiconductor elements, wherein the first metal housing and the second metal housing are electrically connected.

14. A method for diagnosing a rotating electric machine, characterized by: switching the current supplied from a DC power supply to multiple windings of the rotating electric machine using multiple semiconductor elements; electrically connecting the midpoints of two capacitors connected in parallel between the DC power supply and the multiple semiconductor elements to the multiple windings to detect the potential or current at the midpoint; and comparing the stored initial value of the potential or current at the midpoint with the potential or current at the midpoint detected by switching the operation of the multiple semiconductor elements to determine the deterioration of the rotating electric machine.

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