Overcurrent detection device

Abstract

Provided is an overcurrent detection device that can quickly detect an overcurrent by using two magnetic detection elements provided around three busbars. 【Solution means】The overcurrent detection device 9 includes an α-phase magnetic detection element and a β-phase magnetic detection element provided around three busbars, an analog conversion circuit 91 having two-component input and three-component output, and an analog detection circuit 92 that detects an overcurrent by comparing the output value of the analog conversion circuit 91 with a predetermined threshold value. When the three-phase current values (I -1 , I v , I w ) and the output values (V α , V β ) of the two magnetic detection elements are associated with a 3x3 two-phase / three-phase conversion matrix "A", and the three-phase / two-phase conversion matrix, which is the inverse matrix thereof, is "A -1 ", the analog conversion circuit 91 is configured such that an equation using the two-phase / three-phase conversion matrix A α , V β ) and the output values (V u , V v , V w ) holds.​​

Description

[Technical Field]

[0001] The present invention relates to an overcurrent detection device. More specifically, it relates to an overcurrent detection device that detects the current of each phase of a three-phase motor based on two magnetic detection elements. [Background technology]

[0002] In recent years, efforts to realize a low-carbon or decarbonized society have become more active, and in the field of vehicles, research and development on electric vehicles is being conducted to reduce CO2 emissions and improve energy efficiency.

[0003] Vector control is widely used as a control method for three-phase AC motors installed in electric vehicles and home appliances (such as air conditioners and washing machines). In vector control, the motor control device generates command signals to the inverter based on feedback control of the d-axis current and q-axis current defined on the dq coordinate system, which is the motor's rotating Cartesian coordinate system. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] International Publication No. 2013 / 058282 [Patent Document 2] Chinese patent application CN202211040361.X [Overview of the project] [Problems that the invention aims to solve]

[0005] Thus, in a motor control device, since feedback control of the current is performed on the dq coordinate system, it is necessary to convert the U-phase current, V-phase current, and W-phase current of the motor detected using a current detection device such as the one shown in Patent Document 1 into d-axis current and q-axis current. More specifically, in a motor control device, the three-phase current (Iu, Iv, Iw) detected by the current detection device is first converted into a two-phase current (Iα, Iβ) defined in a fixed coordinate system by Clarke transformation, and then this two-phase current (Iα, Iβ) is converted into a two-phase current (Id, Iq) defined in the dq coordinate system by Parke transformation using the motor rotation angle θ. In this way, in conventional vector control using the output of a current detection device, it is necessary to perform the operation of converting the three-phase current (Iu, Iv, Iw) to a two-phase current (Id, Iq) in the motor control device.

[0006] Furthermore, Patent Document 2 by the present applicant describes a technique (hereinafter also referred to as "spatial Clark transformation") that attempts to directly obtain two-phase currents (Iα, Iβ) without going through a Clark transformation performed by computer calculations by placing two magnetic detection elements at geometrically determined positions around three phase current lines. This spatial Clark transformation allows for a reduction in the number of magnetic detection elements and a reduction in the computational load on the computer compared to conventional methods.

[0007] Figure 7 shows an example of an overcurrent detection device using two magnetic detection elements as described in Patent Document 2. As shown in Figure 7, the overcurrent detection device, which is a microcontroller, performs AD conversion on the α-phase output value and β-phase output value of the α-phase and β-phase magnetic detection elements to determine the two-phase current (I α ,I β ) from three-phase current (I u ,I v ,I wThe three-phase output value is calculated by performing an inverse conversion operation on the α-phase and β-phase output values, and then the overcurrent is detected by comparing the three-phase output value with a predetermined threshold. However, performing these AD conversion, inverse conversion, and comparison processes on a computer takes time. As a result, a time lag occurs between the occurrence of an overcurrent and its detection by the overcurrent detection device, and there is a risk that the circuit may fail during this time.

[0008] The present invention aims to provide an overcurrent detection device that can quickly detect overcurrents by using two magnetic detection elements provided around three busbars, and thereby contribute to improving energy efficiency. [Means for solving the problem]

[0009] (1) The overcurrent detection device according to the present invention (for example, the overcurrent detection device 9 described later) detects overcurrents in the first phase busbar (for example, the U-phase busbar 6u described later), the second phase busbar (for example, the V-phase busbar 6v described later), and the third phase busbar (for example, the W-phase busbar 6w described later) of a three-phase motor (for example, the motor M described later), and comprises an α-phase magnetic detection element (for example, the α-phase magnetic detection element 8α described later) and a β-phase magnetic detection element provided around the first phase, second phase, and third phase busbars. The system comprises a child (for example, the β-phase magnetic detection element 8β described later), an analog conversion circuit (for example, the analog conversion circuit 91 described later) having two-component input and three-component output, and an analog detection circuit (for example, the analog detection circuit 92 described later) that detects overcurrent by comparing the output value of the analog conversion circuit with a predetermined threshold, wherein the current values ​​of the first phase, second phase, and third busbar are "I1", "I2", and "I3", respectively, and the output values ​​of the α-phase and β-phase magnetic detection elements are "V α " and "V β” and assuming that the sum of the three-phase currents flowing through the first phase, second phase, and third bus bar is zero, and the two-phase / three-phase conversion matrix of 3 rows and 3 columns is “A”, the α-phase and β-phase magnetic detection elements are arranged such that the following formula (1-1) holds with respect to the first phase, second phase, and third phase bus bars. When the output values of the α-phase and β-phase magnetic detection elements are respectively the first input component and the second input component of the analog conversion circuit, the first output component, second output component, and third output component of the analog conversion circuit are respectively “V1”, “V2”, and “V3”, and the inverse matrix of the two-phase / three-phase conversion matrix is “A -1 ”, when taking “”, the analog conversion circuit is configured such that the following formula (1-2) holds.

Equation

[0010] (2) In this case, the analog conversion circuit is preferably configured by combining a plurality of resistance elements (for example, resistance elements 91a to 91i described later) and a plurality of operational amplifiers (for example, operational amplifiers 91j and 91k described later).

[0011] (3) In this case, the analog detection circuit includes a first comparator (for example, first comparator 921) that compares the first output component of the analog conversion circuit with a predetermined first threshold value (for example, first voltage threshold value V u_ref ), a second comparator (for example, second comparator 922) that compares the second output component of the analog conversion circuit with a predetermined second threshold value (for example, second voltage threshold value V v_ref ), and a third comparator (for example, third comparator 923) that compares the third output component of the analog conversion circuit with a predetermined third threshold value (for example, third voltage threshold value V w_ref ). It is preferable to include

[0012] (4) In this case, the two-phase / three-phase conversion matrix A and its inverse matrix A -1 are preferably represented by the following formulas (2-`1) and (2-2) respectively.

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[0013] (1) The overcurrent detection device according to the present invention comprises α-phase and β-phase magnetic detection elements provided around three busbars, an analog conversion circuit having two-component input and three-component output, and an analog detection circuit that detects overcurrent by comparing the output values ​​of the three components of the analog conversion circuit with a predetermined threshold. Herein, in the present invention, the current values ​​of the three busbars (I1, I2, I3) and the output values ​​of the α-phase and β-phase magnetic detection elements (V α ,V β Two magnetic detection elements are arranged such that the above equation (1-1) holds true between them, using a 3x3 two-phase / three-phase transformation matrix A, and further, the inverse matrix A of the two-phase / three-phase transformation matrix A is used between the input and output of the analog conversion circuit. -1 (Below, the three-phase / two-phase transformation matrix A -1 The analog conversion circuit is configured such that the above equation (1-2) using (also known as) holds true. In this way, the present invention allows for faster detection of overcurrent than in the case shown in Figure 7 above, by performing three-phase / two-phase conversion processing and comparison processing using an analog circuit without using a computer.

[0014] By the way, when detecting overcurrent without using a computer as in the present invention, the three-phase / two-phase transformation matrix A is as described above. -1 One approach to detecting overcurrent is to directly compare the two-phase output values ​​of the α-phase and β-phase magnetic detection elements with a threshold value without undergoing conversion. However, as will be explained later with reference to Figure 5, when detecting overcurrent based on two-phase output values, it is necessary to set a larger threshold value than when detecting overcurrent based on three-phase output values, and as a result, overcurrents that can be detected using three-phase output values ​​may not be detected. In contrast, according to the present invention, by using an analog conversion circuit, it is possible to quickly detect overcurrents of a similar magnitude as when using three-phase output values, thereby contributing to an improvement in energy efficiency.

[0015] (2) In the present invention, by constructing the analog conversion circuit by combining multiple resistors and multiple operational amplifiers, a three-phase / two-phase conversion matrix A can be easily constructed. -1 This allows for the implementation of matrix operations equivalent to the above.

[0016] (3) In the present invention, the analog detection circuit can detect overcurrent for each busbar by comparing the three output components of the analog conversion circuit with three threshold values ​​using three comparators.

[0017] (4) In the present invention, as shown in formulas (2-1) and (2-2) above, the two-phase / three-phase transformation matrix A and the three-phase / two-phase transformation matrix A -1 By configuring this, the output values ​​of the α-phase and β-phase magnetic detection elements are set to two-phase current (I α ,I β It is possible to quickly detect overcurrent while keeping it proportional to the value. [Brief explanation of the drawing]

[0018] [Figure 1] This figure shows the configuration of an electric vehicle equipped with a current detection device and an overcurrent detection device according to one embodiment of the present invention. [Figure 2] This diagram schematically shows the configuration of the sensor unit. [Figure 3] This diagram schematically shows an example of the arrangement of three busbars and an α-phase magnetic detection element on the α-axis element arrangement plane. [Figure 4] This diagram shows the circuit configuration of the overcurrent detection device. [Figure 5] This figure is obtained by plotting the two-phase currents, which are obtained by performing a Clarke transform on a three-phase current whose three-phase sum is zero, on a two-dimensional plane. [Figure 6] This figure shows an example of the circuit and its equivalent circuit shown in Figure 4. [Figure 7] This figure shows an example of an overcurrent detection device using two magnetic detection elements as described in Patent Document 2. [Modes for carrying out the invention]

[0019] Hereinafter, an overcurrent detection device according to one embodiment of the present invention and an electric vehicle equipped with this overcurrent detection device will be described with reference to the drawings.

[0020] Figure 1 shows the configuration of an electric vehicle V equipped with a current detection device 3 and an overcurrent detection device 9 according to this embodiment. The following description will focus on the case where the current detection device 3 and the overcurrent detection device 9 are mounted on an electric vehicle V, but the present invention is not limited to this. The current detection device 3 and the overcurrent detection device 9 can be mounted not only on an electric vehicle V, but also on any device that controls a three-phase motor based on vector control, such as an air conditioner or washing machine.

[0021] The electric vehicle V comprises a three-phase AC motor M (hereinafter simply referred to as "motor M"), drive wheels W connected to the output shaft of the motor M via a power transmission mechanism (not shown), an inverter 1 connecting a battery (not shown) to the motor M, a sensor unit 7 that generates a signal corresponding to the current flowing through the motor M, a resolver 4 that detects the rotational position of the motor M, a motor control device 2 that controls the inverter 1 based on the detection signals from the sensor unit 7 and the resolver 4, and an overcurrent detection device 9 that detects overcurrents in the three busbars of the motor M (U-phase busbar 6u, V-phase busbar 6v, and W-phase busbar 6w).

[0022] Inverter 1 is a pulse-width modulation (PWM) inverter equipped with a bridge circuit formed by bridging multiple switching elements (e.g., IGBTs), and has the function of converting DC power to AC power. Inverter 1 is connected to a battery on its DC input / output side and to the U-phase, V-phase, and W-phase coils of motor M on its AC input / output side, and converts power between the battery and motor M. Inverter 1 drives the switching elements of each phase on / off according to gate drive signals generated at predetermined timings from a gate drive circuit (not shown), thereby converting DC power supplied from the battery to AC power and supplying it to motor M, and converting AC power supplied from motor M to DC power and supplying it to the battery.

[0023] The sensor unit 7 includes an α-phase magnetic detection element 8α and a β-phase magnetic detection element 8β, which are provided around the three busbars 6u, 6v, and 6w that connect the motor M and the inverter 1. These magnetic detection elements 8α and 8β each generate a detection signal corresponding to the component of the magnetic flux density of the magnetic field generated by the current flowing through each busbar 6u, 6v, and 6w along their respective detection axes. Specific examples of the arrangement layout of these α-phase and β-phase magnetic detection elements 8α and 8β and the three busbars 6u, 6v, and 6w will be explained later with reference to Figures 2 and 3, etc.

[0024] The motor control device 2 is a computer that generates a drive signal for the gate drive circuit of the inverter 1 and inputs it to the gate drive circuit by performing vector control based on detection signals from two magnetic detection elements 8α and 8β and the resolver 4.

[0025] The motor control device 2 includes an AD conversion unit 21, a current value acquisition unit 22, a dq conversion unit 23, and a duty cycle calculation unit 24 as modules related to the execution of the vector control described above.

[0026] The AD conversion unit 21 performs AD conversion on the detection signals of the α-phase and β-phase magnetic detection elements 8α and 8β, thereby converting the output values ​​(V) of these α-phase and β-phase magnetic detection elements 8α and 8β. α ,V β ) obtain.

[0027] The current value acquisition unit 22 acquires the output values ​​(V) of the α-phase and β-phase magnetic detection elements 8α and 8β obtained by the AD conversion unit 21. α ,V β Based on this, the α-phase current value I, which corresponds to the two-phase current obtained by performing a Clarke transform on the three-phase current (Iu, Iv, Iw) as shown in equation (3-1) below, is α and β-phase current value I β In this embodiment, the current value acquisition unit 22 acquires the output values ​​(V) of the α-phase and β-phase magnetic detection elements 8α and 8β as shown in the following formula (3-2). α ,V β) are used directly as the α-phase and β-phase current values ​​(I α ,I β The present invention will explain how to obtain the value as (V). α ,V β ) with a predetermined α-phase gain G α and β-phase gain G β The result of multiplying by the α-phase current value I α and β-phase current value I β It may also be obtained as follows. In this case, these α-phase and β-phase gains (G α ,G β The values ​​of ) are the α-phase and β-phase current values ​​(I α ,I β The amplitudes of the two are set to be equal. Therefore, in this embodiment, the current detection device 3 for detecting the current flowing through the three-phase busbars 6u, 6v, and 6w of the motor M is composed of two magnetic detection elements 8α and 8β, an AD conversion unit 21, and a current value acquisition unit 22.

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[0028] The dq conversion unit 23 converts the current value (I) obtained by the current value acquisition unit 22. α ,I β The d-axis current Id and q-axis current Iq are calculated by performing known calculations using the detection signals of resolver 4.

[0029] The duty cycle calculation unit 24 acquires the d-axis current command Idc and q-axis current command Iqc according to the driving force requested by the driver, and generates a drive signal for the gate drive circuit of the inverter 1 to realize the driving force requested by the driver by performing feedback control based on the deviation of these current values ​​(Idc-Id, Iqc-Iq), and inputs it to the gate drive circuit. Furthermore, when the duty cycle calculation unit 24 receives a protection signal transmitted from the overcurrent detection device 9 described later, in other words, when the overcurrent detection device 9 detects an overcurrent in the busbars 6u, 6v, and 6w, it performs a predetermined protection process to protect the inverter 1 and motor M from overcurrent.

[0030] Figure 2 is a schematic diagram showing the configuration of the sensor unit 7. The sensor unit 7 comprises an α-phase magnetic detection element 8α and a β-phase magnetic detection element 8β arranged around three busbars 6u, 6v, and 6w, and a substrate 80 on which these magnetic detection elements 8α and 8β are fixed. That is, the two magnetic detection elements 8α and 8β are arranged around the three busbars 6u, 6v, and 6w in an integrated state by the substrate 80. As shown in Figure 2, the following description will explain the case in which the detection center of the α-phase magnetic detection element 8α is placed in a virtual α-phase element arrangement plane Pα that is orthogonal to the three busbars 6u, 6v, and 6w, and the detection center of the β-phase magnetic detection element 8β is placed in a virtual β-phase element arrangement plane Pβ that is orthogonal to the three busbars 6u, 6v, and 6w and different from the α-phase element arrangement plane Pα, but the present invention is not limited to this. The α-phase element arrangement plane Pα and the β-phase element arrangement plane Pβ may be a common virtual plane. In other words, the detection centers of the α-phase magnetic detection element 8α and the β-phase magnetic detection element 8β may be located within a common element arrangement plane that is orthogonal to the three busbars 6u, 6v, and 6w.

[0031] Figure 3 schematically shows an example of the arrangement of three busbars 6u, 6v, and 6w and an α-phase magnetic detection element 8α on the α-phase element arrangement surface Pα. In Figure 3, the three busbars 6u, 6v, and 6w are arranged linearly at equal intervals in the order of V-phase busbar 6v, U-phase busbar 6u, and W-phase busbar 6w on the α-phase element arrangement surface Pα, but the present invention is not limited to this.

[0032] Here, the output value V of the α-phase magnetic detection element 8α is shown. α This is the magnetic sensitivity coefficient (k) for each busbar 6u, 6v, 6w of the α-phase magnetic detection element 8α. αu ,k αv ,k αw Using ), it is expressed by the following equation (4-1). These magnetic sensitivity coefficients (k αu ,k αv ,k αw ) are values ​​determined by the relative position of the α-phase magnetic detection element 8α with respect to the three busbars 6u, 6v, and 6w, and the orientation of the detection axis. More specifically, for example, the magnetic sensitivity coefficient k of the α-phase magnetic detection element 8α with respect to the W-phase busbar 6w. αw It is defined by the following equation (4-2) according to Ampère's law. In the following equation (4-2), μ is the permeability. Also, in the following equation (4-2), θ wα is the angle between the magnetic field vector of the W-phase busbar 6w and the detection axis Oα of the α-phase magnetic detection element 8α, and (x α ,z α ) is the coordinate value of the α-phase magnetic detection element 8α on the α-phase element arrangement plane Pα, and (x w ,z w ) is the coordinate value of the W-phase busbar 6w on the α-phase element arrangement plane. Note that other magnetic sensitivity coefficients (k αu ,k αw ) is also defined based on Ampere's law, similar to equation (4-2) below, so a detailed explanation is omitted. As described above, the magnetic sensitivity coefficient (k αu ,k αv ,k αw The position of the α-phase magnetic detection element 8α relative to the three busbars 6u, 6v, and 6w, and the orientation of the detection axis are determined accordingly.

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[0033] Although not shown in the diagram, the output value V of the β-phase magnetic detection element 8β is also shown. β This is the magnetic sensitivity coefficient (k) for each busbar 6u, 6v, 6w of the β-phase magnetic detection element 8β. βu ,k βv ,k βwUsing ), it is expressed by the following equation (5). These magnetic sensitivity coefficients (k βu ,k βv ,k βw ) is a value determined by the relative position of the β-phase magnetic detection element 8β with respect to the three busbars 6u, 6v, and 6w, and the orientation of the detection axis, and is the magnetic sensitivity coefficient k determined by the above equation (4-2). αw Similarly, it is determined based on the coordinate values ​​of the β-phase magnetic detection element 8β and each busbar 6u, 6v, 6w on the β-element arrangement surface Pβ, as well as the orientation of the detection axis of the β-phase magnetic detection element 8β.

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[0034] In this embodiment, the above magnetic sensitivity coefficient (k αu ,k αv ,k αw ) and (k βu ,k βv ,k βw The following describes the case where the α-phase magnetic detection element 8α and the β-phase magnetic detection element 8β are arranged for the three busbars 6u, 6v, and 6w such that the following equation (6) holds for ). As a result, the output value of the α-phase magnetic detection element 8α and the β-phase magnetic detection element 8β (V α ,V β ) is expressed as shown in the above equations (3-1) and (3-2), as a three-phase current (I u ,I v ,I w The two-phase current (I) obtained by performing a Clark transform on ) α ,I β It can be made proportional to ).

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[0035] In the following, we assume that the three-phase sum of the currents flowing through busbars 6u, 6v, and 6w is 0, and the three-phase current (I u ,I v ,I w ) and the output values ​​(V) of the magnetic detection elements 8α and 8β α ,V βBetween them, a 3×3 matrix A defined by the following formula (7-1) is called a "two-phase / three-phase conversion matrix". Therefore, when the magnetic detection elements 8α and 8β are arranged with respect to the bus bars 6u, 6v, and 6w so that the above formula (6) holds, each component of the two-phase / three-phase conversion matrix A is represented by the following formula (7-2).

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[0036] Returning to FIG. 1, the overcurrent detection device 9 detects the overcurrents in the three bus bars 6u, 6v, and 6w based on the output values (V α , V β ) of the two magnetic detection elements 8α and 8β. As will be described below, since the overcurrent detection function of the overcurrent detection device 9 is realized by combining the analog conversion circuit 91, which is an analog circuit, and the analog detection circuit 92, the overcurrent can be detected more quickly than when the overcurrent detection function is realized by computer software as shown in FIG. 7.

[0037] FIG. 4 is a diagram showing the circuit configuration of the overcurrent detection device 9. As shown in FIG. 4, the overcurrent detection device 9 includes an analog conversion circuit 91 having two-component input and three-component output, and an analog detection circuit 92 that detects an overcurrent by comparing the output value of the analog conversion circuit 91 with a predetermined threshold value.

[0038] The output values (V α , V β ) of the two magnetic detection elements 8α and 8β are input to the analog conversion circuit 91. The analog conversion circuit 91 combines a plurality of resistance elements 91a to 91i and a plurality of operational amplifiers 91j and 91k so that the following formula (8-1) holds between the two input components (V α , V β ) and the three output components (V u , V v , V w ). In the following formula (8-1), "A -1" is a 3x3 matrix and is the inverse of the two-phase / three-phase transformation matrix A defined by equation (7-1) above, and hereafter the three-phase / two-phase transformation matrix A -1 Also known as (8-1), by configuring the analog conversion circuit 91 such that the following equation (8-1) holds true, the three output components (V) of the analog conversion circuit 91 are obtained. u ,V v ,V w ) is the three-phase current (I) flowing through the busbars 6u, 6v, 6w. u ,I v ,I w ) can be made proportional to this. Here, if we define each component of the two-phase / three-phase transformation matrix A as shown in equation (7-2) above, then the three-phase / two-phase transformation matrix A -1 Each component is represented by the following formula (8-2).

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[0039] In the circuit configuration shown in Figure 4, the first output component V of the analog conversion circuit 91 u and two input components (V α ,V β The following equation (9-1) holds between ) and the second output component V of the analog conversion circuit 91. v and two input components (V α ,V β The following equation (9-2) holds between ) and the third output component V of the analog conversion circuit 91. w and two input components (V α ,V βThe following equation (9-3) holds between ) and ). In the following equations (9-1) to (9-3), “R1” is the resistance value of resistor element 91a, “R2” is the resistance value of resistor element 91b, “R3” is the resistance value of resistor element 91c, “R4” is the resistance value of resistor element 91d, “R5” is the resistance value of resistor element 91e, “R6” is the resistance value of resistor element 91f, “R7” is the resistance value of resistor element 91g, “R8” is the resistance value of resistor element 91h, and “R9” is the resistance value of resistor element 91i. Therefore, by adjusting the resistance values ​​of each resistor element 91a to 91i, the three-phase / two-phase conversion matrix A shown in equation (8-2) above can be obtained with the circuit configuration shown in Figure 4. -1 This can be achieved.

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[0040] The analog detection circuit 92 detects the first output component V of the analog conversion circuit 91. u and a predetermined first voltage threshold V u_ref The first comparator 921 compares the two, and the second output component V of the analog conversion circuit 91. v and a predetermined second voltage threshold V v_ref The second comparator 922 compares this with the third output component V of the analog conversion circuit 91. w and a predetermined third voltage threshold V w_ref This is an analog circuit composed of a third comparator 923 that compares with and .

[0041] The first comparator 921 has a U-phase current value I as described above. u The first output component V is proportional to u The first voltage threshold V u_ref If it is greater than the value, a protection signal is generated indicating that an overcurrent has flowed through the U-phase busbar 6u and output to the motor control device 2. The second comparator 922, as described above, uses the V-phase current value I v The second output component V is proportional to v The second voltage threshold V v_refIf it is greater than the value, a protection signal is generated indicating that an overcurrent has flowed through the V-phase busbar 6V and output to the motor control device 2. The third comparator 923, as described above, uses the W-phase current value I w The third output component V is proportional to w The third voltage threshold V w_ref If the value is greater, a protection signal indicating that an overcurrent has flowed through the W-phase busbar 6w is generated and output to the motor control device 2.

[0042] Figure 5 shows the three-phase current (I) at which the sum of the three phases is 0. u ,I v ,I w The two-phase current (I) obtained by the Clark transform ) α ,I β This is a figure obtained by plotting the ) on a two-dimensional plane. Figure 5 shows the case where the amplitude of the current in each phase is 600[A], more specifically I u =600sin(θ), I v =600sin(θ+3 / 2π), I w Let's look at the case where =600sin(θ-3 / 2π).

[0043] When the amplitude of the three-phase current is set to 600[A], for example, when detecting overcurrent with a conventional overcurrent detection device as shown in Figure 7, the threshold must be set to a value equivalent to at least 600[A]. On the other hand, the amplitude of the two-phase current obtained by Clarke transformation of such a three-phase current is approximately 900[A] for both the α phase and the β phase, as shown in Figure 5. Therefore, the output values ​​(V) of the two magnetic detection elements 8α and 8β α ,V β When the signal is input to the analog detection circuit 92 without going through the analog conversion circuit 91 shown in Figure 4, the output value V α ,V β The voltage threshold for this needs to be set to a value equivalent to approximately 900[A]. However, I α =I β When =900[A] is converted in reverse to a three-phase current, I u ,I v ,I w This would result in approximately 600-900[A]. This is because even if an overcurrent exceeding 600[A] flows through busbars 6u, 6v, and 6w, the two-phase current Iα ,I β This means that the voltage may not exceed 900[A]. Therefore, without using the analog conversion circuit 91, the two-phase output value (V) of the magnetic detection elements 8α and 8β is used. α ,V β When overcurrent is detected directly based on ), the output value V α ,V β Before the voltage threshold is exceeded, there is a risk that overcurrent may flow through busbars 6u, 6v, and 6w.

[0044] The overcurrent detection device 9 according to this embodiment provides the following effects. (1) The overcurrent detection device 9 comprises α-phase and β-phase magnetic detection elements 8α and 8β provided around three busbars 6u, 6v, and 6w, an analog conversion circuit 91 having two-component input and three-component output, and an analog detection circuit 92 that detects overcurrent by comparing the output values ​​of the three components of the analog conversion circuit 91 with a predetermined threshold. In this embodiment, the current values ​​of the three busbars 6u, 6v, and 6w (I u ,I v ,I w ) and the output values ​​(V) of the α-phase and β-phase magnetic detection elements α ,V β The two magnetic detection elements 8α and 8β are arranged such that the above equation (7-1) is satisfied between them and the input and output of the analog conversion circuit 91, using a 3x3 two-phase / three-phase conversion matrix A. -1 The analog conversion circuit 91 is configured such that the above equation (8-1) is satisfied. In this embodiment, by performing the three-phase / two-phase conversion and comparison processing using an analog circuit without using a computer, overcurrent can be detected more quickly than in the case shown in Figure 7.

[0045] As explained with reference to Figure 5, the two-phase output value (V α ,V β When detecting overcurrent based on the three-phase output value (V u ,V v ,V w When detecting overcurrent based on ), the threshold needs to be set to a larger value than when detecting overcurrent based on ), and as a result, as mentioned above, the three-phase output value (Vu ,V v ,V w ) may not be able to detect overcurrents that can be detected using ). In contrast, according to this embodiment, by using the analog conversion circuit 91, the three-phase output value (V u ,V v ,V w This method allows for the rapid detection of overcurrents comparable to those detected using other methods, thereby contributing to improved energy efficiency.

[0046] (2) In this embodiment, the analog conversion circuit 91 is configured by combining a plurality of resistor elements 91a to 91i and a plurality of operational amplifiers 91j and 91k, thereby enabling a simple configuration of the three-phase / two-phase conversion matrix A -1 This allows for the implementation of matrix operations equivalent to the above.

[0047] (3) In this embodiment, the analog detection circuit 92 uses three comparators 921, 922, and 923 to analyze the three output components (V) of the analog conversion circuit 91. u ,V v ,V w ) and three thresholds (V u_ref ,V v_ref ,V w_ref By comparing this with the current, overcurrent can be detected for each busbar.

[0048] (4) In this embodiment, as shown in formulas (7-2) and (8-2) above, the two-phase / three-phase transformation matrix A and the three-phase / two-phase transformation matrix A -1 By configuring the α-phase and β-phase magnetic detection elements 8α and 8β, the output values ​​(V α ,V β ) with two-phase current (I α ,I β It is possible to quickly detect overcurrent while keeping it proportional to the value.

[0049] Although one embodiment of the present invention has been described above, the present invention is not limited thereto. Within the scope of the spirit of the present invention, the details of the configuration may be modified as appropriate.

[0050] For example, in the above embodiment, the overcurrent detection device 9 is configured with the circuit shown in Figure 4, but the present invention is not limited thereto. The overcurrent detection device may be replaced with an equivalent circuit having the same input / output characteristics as the overcurrent detection device 9 shown in Figure 4.

[0051] For example, in the above embodiment, as shown in Figure 4, by incorporating two resistor elements 91h and 91i into the analog conversion circuit 91, the first component output V u V is the output value of the α-phase magnetic detection element 8α. α The present invention is not limited to this, although it is set to be 2 / 3 times the original value. For example, as shown in the equivalent circuit of Figure 6, the analog conversion circuit 91A uses the output value V of the α-phase magnetic detection element 8α. α The output of the first component is V as is. u It may also be output as '. In this case, as shown in Figure 6, by setting the first voltage threshold of the analog conversion circuit 91A to 3 / 2 times that of the example shown in Figure 4, the input / output characteristics of the overcurrent detection device 9A can be made equivalent to those of the overcurrent detection device 9 shown in Figure 4. [Explanation of symbols]

[0052] V...vehicle W…Drive wheels M...Motor (three-phase motor) 6u…U-phase busbar (first-phase busbar) 6V...V-phase busbar (second phase busbar) 6w...W-phase busbar (third-phase busbar) 1…Inverter 2…Motor control device 21…AD conversion unit 22...Current value acquisition unit 23...dq conversion section 24... Duty Calculation Unit 3…Current detection device 4…Resolver 7…Sensor unit 8α...α-axis magnetic detection element 8β…β-axis magnetic detection element 9… Overcurrent detection device 91…Analog conversion circuit 92…Analog detection circuit

Claims

1. An overcurrent detection device for detecting overcurrents in the first phase busbar, second phase busbar, and third phase busbar of a three-phase motor, The α-phase magnetic detection element and the β-phase magnetic detection element are provided around the first phase, second phase, and third phase busbars, An analog conversion circuit having two component inputs and three component outputs, The system includes an analog detection circuit that detects overcurrent by comparing the output value of the analog conversion circuit with a predetermined threshold value, The current values ​​of the first phase, second phase, and third busbar are respectively "I １ ", "I ２ "and" I ３ The output values ​​of the α-phase and β-phase magnetic detection elements are set to "V" respectively. α "and "V β Assuming that the three-phase sum of the currents flowing through the first phase, second phase, and third busbar is 0, and that the 3x3 two-phase / three-phase transformation matrix is ​​"A", the α-phase and β-phase magnetic detection elements are arranged with respect to the first phase, second phase, and third phase busbar such that the following equation (1-1) holds true. When the output values of the α-phase and β-phase magnetic detection elements are respectively used as the first input component and the second input component of the analog conversion circuit, the first output component, the second output component, and the third output component of the analog conversion circuit are respectively "V １ ", "V ２ ", and "V ３ ", and when the inverse matrix of the two-phase / three-phase conversion matrix is taken as "A －１ ", the analog conversion circuit is configured such that the following formula (1-2) holds, and the overcurrent detection device is characterized by this. [Math 1]

2. The overcurrent detection device according to claim 1, characterized in that the analog conversion circuit is configured by combining a plurality of resistors and a plurality of operational amplifiers.

3. The overcurrent detection device according to claim 2, characterized in that the analog detection circuit comprises a first comparator that compares a first output component of the analog conversion circuit with a predetermined first threshold, a second comparator that compares a second output component of the analog conversion circuit with a predetermined second threshold, and a third comparator that compares a third output component of the analog conversion circuit with a predetermined third threshold.

4. The two-phase / three-phase transformation matrix A and its inverse matrix A －１ The overcurrent detection device according to any one of claims 1 to 3, characterized in that the following formulas (2-1) and (2-2) are used to represent the current. [Math 2]

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