Power conversion devices and fault diagnosis methods for power conversion devices

Abstract

This invention provides a power conversion device and a fault diagnosis method for the power conversion device. The three-phase / two-phase conversion unit (43) generates a composite vector (ii, i ...) of the three-phase alternating current based on the alternating currents (iu, iiv, iw). αβ The electrical angle calculation unit (44) uses the alternating current (iu) of phase U as a reference to output the composite vector (i). αβ The electric angle of the obtained electric angle is calculated. The quadrant calculation unit (45) determines which quadrant of the pre-divided first to sixth quadrant the electric angle corresponds to, and confirms the composite vector (i). αβ If the specified quadrant has been passed, output the quadrant information. The fault detection unit (47) determines whether the composite vector (i) has passed. αβ Whether it rotates from the first quadrant to the sixth quadrant, if there is a quadrant that has not been passed, it is considered a fault state. Based on the relationship between the electrical angle and the fault location, the fault location of the switching element is determined, and the fault information is output to the PWM signal generation unit (42).

Description

Technical Field

[0001] This invention relates to a power conversion device and a method for diagnosing faults in a power conversion device. Background Technology

[0002] Hybrid and electric vehicles are equipped with power conversion devices to drive the electric motor. These devices convert the direct current supplied by the battery into alternating current by activating switching elements within the inverter circuit, and then use this converted alternating current to drive the electric motor.

[0003] In recent years, in order to meet functional safety specifications for automobiles, it is necessary to detect faults in power conversion devices and transition to a safe state after fault detection. Patent Document 1 discloses the following technology: when the d-axis current Id or q-axis current Iq is detected to be at zero, the fault location in the inverter is determined based on the rotation angle θ of the motor detected by the rotation angle sensor.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2011-50214 Summary of the Invention

[0007] The problem that the invention aims to solve

[0008] In the technology described in Patent Document 1, there is a possibility that the current may be falsely detected when it is near zero.

[0009] Methods for solving problems

[0010] The power conversion device of the present invention comprises: an inverter circuit consisting of switching elements that converts direct current into alternating current; a current detection unit that detects the three-phase output current of the inverter circuit; and a control unit that, when the electrical angle of the composite vector calculated based on the three-phase output current detected by the current detection unit is not within a predetermined range, determines that an open-circuit fault has occurred in the switching element of the inverter circuit in the phase corresponding to the predetermined range.

[0011] The fault diagnosis method of the power conversion device of the present invention performs the following processing: detecting the three-phase output current of an inverter circuit composed of switching elements that converts DC current into AC current; if the electrical angle of the composite vector calculated based on the detected three-phase output current is not included in a specified range, determining that an open-circuit fault has occurred in the switching element of the inverter circuit in the phase corresponding to the specified range.

[0012] Invention Effects

[0013] According to the present invention, faults in switching elements can be detected with high precision regardless of the magnitude of the output current of each phase. Attached Figure Description

[0014] Figure 1 This is a circuit diagram of the power conversion device in the first embodiment.

[0015] Figure 2 This is the circuit structure diagram of the inverter circuit.

[0016] Figure 3 It is a graph representing the AC currents iu, iv, and iw detected by the current detection unit.

[0017] Figure 4 It represents the composite vector i when an open-circuit fault occurs in the upper arm circuit of phase U. αβ A diagram of the rotation trajectory.

[0018] Figure 5 This describes the fault location of the switching element and the composite vector i. αβ A table of relationships.

[0019] Figure 6 It is a diagram representing the six quadrants of the composite vector in the αβ axis coordinate space.

[0020] Figure 7 This is a diagram showing the fault detection judgment table in the first embodiment.

[0021] Figure 8 This is a flowchart illustrating the operation of the control unit in the first embodiment.

[0022] Figure 9 This is a circuit diagram of the power conversion device in the second embodiment.

[0023] Figure 10 This is a diagram showing the timing of acquiring the three-phase current values ​​in the αβ axis coordinate space in the second embodiment.

[0024] Figure 11 This is a flowchart illustrating the operation of the control unit in the second embodiment.

[0025] Figure 12 This is a circuit diagram of the power conversion device in the third embodiment.

[0026] Figure 13 It is the composite vector in the αβ axis coordinate space, and is a diagram representing the situation where an open circuit fault has occurred in the upper arm circuit of phase U.

[0027] Figure 14 This is a diagram showing the fault detection judgment table in the third embodiment.

[0028] Figure 15 This is a flowchart illustrating the operation of the control unit in the third embodiment.

[0029] Figure 16 This is a diagram representing the quadrants of the composite vector in the αβ axis coordinate space in Variation Example 1.

[0030] Figure 17 This is a diagram showing the fault detection judgment table in Modified Example 1.

[0031] Figure 18 This is a diagram representing the quadrants of the composite vector in the αβ axis coordinate space in variation example 2.

[0032] Figure 19 This is a diagram showing the fault detection judgment table in Modified Example 2.

[0033] Figure 20 This is a diagram representing the quadrants of the composite vector in the αβ axis coordinate space in variation example 3.

[0034] Figure 21 This is a diagram showing the fault detection judgment table in Variation Example 3. Detailed Implementation

[0035] [First Implementation Method]

[0036] Figure 1 This is a circuit diagram of the power conversion device 100 of this embodiment.

[0037] The power conversion device 100 converts the DC power obtained from the DC power supply 10 into AC power to drive the motor 20.

[0038] The electric motor 20 is a three-phase motor with three internal windings. The power conversion device 100 detects the fault described below and notifies the higher-level control device of the fault information.

[0039] The power conversion device 100 includes a control unit 40, a drive circuit 50, an inverter circuit 60, and a current detection unit 70. The control unit 40 includes a duty cycle calculation unit 41, a PWM signal generation unit 42, a three-phase / two-phase conversion unit 43, an electrical angle calculation unit 44, a quadrant calculation unit 45, a memory 46, and a fault detection unit 47.

[0040] The current detection unit 70 uses current sensors and the like to measure the alternating current flowing to each phase (U phase, V phase, W phase) of the motor 20. Specifically, it measures the alternating current iu flowing through the U phase, the alternating current iv flowing through the V phase, and the alternating current iw flowing through the W phase, and outputs the results to the three-phase / two-phase conversion unit 43. In this way, the current detection unit 70 detects the output current of each phase of the inverter circuit 60.

[0041] The control unit 40 communicates with an electronic control device (not shown) located outside the power conversion device 100, receives the target torque of the motor 20 from the external electronic control device, and inputs it into the duty cycle calculation unit 41.

[0042] The duty cycle calculation unit 41 uses the target torque, etc., to calculate the target current value that should flow to the motor 20. This target current value is expressed, for example, as a d-axis target current value and a q-axis target current value. Furthermore, based on the target current value and the AC currents iu, iv, and iw detected by the current detection unit 70, the duty cycle calculation unit 41 calculates the duty cycle values ​​of the U-phase, V-phase, and W-phase, and outputs them to the PWM signal generation unit 42.

[0043] When a fault information is output from the fault detection unit 47, the PWM signal generation unit 42 controls the PWM signal to prevent the motor 20 from being driven. The state in which the motor 20 is not driven can be exemplified by, for example, the state in which all six switching elements in the inverter circuit 60 are disconnected (referred to as the freewheel state in this embodiment). Other examples include the state in which three switching elements of the upper arm circuit are turned on and three switching elements of the lower arm circuit are turned off (referred to as the upper arm active short-circuit state in this embodiment), and conversely, the state in which three switching elements of the upper arm circuit are turned off and three switching elements of the lower arm circuit are turned on (referred to as the lower arm active short-circuit state in this embodiment).

[0044] The drive circuit 50 receives the PWM signal output by the PWM signal generation unit 42 and outputs the drive signal used to switch the switching elements on / off to the inverter circuit 60.

[0045] The inverter circuit 60 internally includes a smoothing capacitor and six switching elements. During power operation, it converts the DC power obtained from the DC power supply 10 into AC power to drive the motor 20. Additionally, during regeneration, it converts the power from the motor 20 into DC power to charge the DC power supply 10.

[0046] The three-phase / two-phase conversion unit 43 generates the composite vector i of the three-phase AC currents based on the AC currents iu, iv, and iw. αβ .

[0047] The electrical angle calculation unit 44 uses the alternating current iu of phase U as a reference and outputs the composite vector i. αβ The vector angle (hereinafter referred to as the electrical angle).

[0048] Quadrant calculation unit 45 determines which quadrant from the first to the sixth quadrant the acquired electrical angle corresponds to, thereby confirming the composite vector i. αβ The quadrant it passes through is identified, and the information for that quadrant is output.

[0049] The decision table, which will be described later, is stored in memory 46.

[0050] Fault detection unit 47 determines the composite vector i αβ It checks whether the electrical angle has rotated one full revolution from the first quadrant to the sixth quadrant. Then, if there is a quadrant that has not been passed, it is considered a fault state. Referring to the judgment table in the memory 46, the fault location of the switching element is determined according to the relationship between the electrical angle and the fault location, and the fault information is output to the upper control device and the PWM signal generation unit 42.

[0051] Details of the three-phase / two-phase conversion unit 43, electrical angle calculation unit 44, quadrant calculation unit 45, memory 46, and fault detection unit 47 will be described later.

[0052] Furthermore, the various structures within the control unit 40 are hardware-independent and can also be controlled by the CPU and, as described later... Figure 8 The flowchart shown illustrates the program that implements the functions of each structure. When each structure within the control unit 40 is implemented using a CPU and a program, the number of hardware components is reduced, resulting in lower costs. On the other hand, when each structure is constructed using hardware independent of the control unit 40, the processing load on the control unit 40 is reduced, enabling faster diagnostic processing.

[0053] Figure 2 This is the circuit structure diagram of inverter circuit 60.

[0054] The inverter circuit 60 has series circuits for the upper and lower arms of phases U, V, and W. The series circuit 61 for the upper and lower arms of phase U consists of the upper arm switching element Tuu and the upper arm diode Duu, and the lower arm switching element Tul and the lower arm diode Dul. The series circuit 62 for the upper and lower arms of phase V consists of the upper arm switching element Tvu and the upper arm diode Dvu, and the lower arm switching element Tvl and the lower arm diode Dvl. The series circuit 63 for the upper and lower arms of phase W consists of the upper arm switching element Twu and the upper arm diode Dwu, and the lower arm switching element Twl and the lower arm diode Dwl.

[0055] The upper arm circuit 64 includes a U-phase upper arm switching element Tuu and a U-phase upper arm diode Duu, a V-phase upper arm switching element Tvu and a V-phase upper arm diode Dvu, and a W-phase upper arm switching element Twu and a W-phase upper arm diode Dwu. The lower arm circuit 65 includes a U-phase lower arm switching element Tul and a U-phase lower arm diode Dul, a V-phase lower arm switching element Tvl and a V-phase lower arm diode Dvl, and a W-phase lower arm switching element Twl and a W-phase lower arm diode Dwl. The switching elements are, for example, power MOSFETs (Metal Oxide Semiconductor Field Effect Transistors) or IGBTs (Insulated Gate Bipolar Transistors).

[0056] The smoothing capacitor 66 smooths the current generated by the switching elements, suppressing pulsations in the DC current supplied from the DC power supply 10 to the inverter circuit 60. This smoothing capacitor 66 may be, for example, an electrolytic capacitor or a film capacitor.

[0057] Figure 3 It is a graph representing the AC currents iu, iv, and iw detected by the current detection unit 70.

[0058] exist Figure 3 In the diagram, the horizontal axis represents time, and the vertical axis represents the current value (amperes). The AC current iu of phase U is represented by a solid line, the AC current iv of phase V is represented by a long dashed line, and the AC current iw of phase W is represented by a short dashed line. Then, in Figure 3 In the figure, it indicates that a fault occurred in the upper arm circuit of phase U at time t.

[0059] like Figure 3 Before time t, under normal conditions of each switching element of inverter circuit 60, the AC waveforms of the AC currents iu, iv, and iw are depicted with their phases offset by 120°. At time t, if an open-circuit fault occurs in the upper arm switching element Tuu of phase U, the upper half of the AC current iu of phase U is missing because the current that should flow through the switching element Tuu becomes blocked.

[0060] Figure 4 It represents the composite vector i when an open-circuit fault occurs in the upper arm circuit of phase U. αβ The diagram shows the rotation trajectory. The composite vector i when an open-circuit fault occurs in the upper arm circuit of phase U. αβ The rotation trajectory is as follows Figure 4 As shown by the solid line, the left side is a semicircle. On the other hand, in the absence of a fault, as... Figure 4 As shown by the dashed line, it becomes a circle.

[0061] The three-phase / two-phase conversion unit 43 calculates the composite vector i of the three-phase currents iu, iv, and iw, with the positive direction of the U-phase current iu (here referring to the direction from the inverter circuit 60 to the motor 20) set to 0°. αβ This operation is usually called a three-phase / two-phase conversion, and the result is represented on the αβ axis. Let the positive direction of the current iu in phase U be the α axis, and the axis orthogonal to the α axis be the β axis.

[0062] Under normal conditions, the resultant vector i of the three-phase currents αβ It rotates in a manner that depicts a circle. However, if an open-circuit fault occurs in the upper arm circuit of phase U, the synthesized vector i... αβ Since it does not produce the right-side component of the circle, the rotational trajectory becomes a semicircle on the left side.

[0063] The composite vector i generated by the three-phase / two-phase conversion unit 43 αβ The following explanation is provided. Based on the U-phase current iu, the three-phase AC currents iu, iv, and iw are expressed by the following equations (1) to (3).

[0064] [Formula 1]

[0065] i u =A u e jθ (1)

[0066] [Formula 2]

[0067]

[0068] [Formula 3]

[0069]

[0070] Here, Au, Av, and Aw are the absolute values ​​of the AC currents of phase U, phase V, and phase W, respectively.

[0071] According to Euler's formula, for example, the U phase can be decomposed into the following equation (4).

[0072] [Formula 4]

[0073] i u =A u (cosθ+jsinθ) (4)

[0074] In addition, the vector transformation matrix of the U-phase reference is represented by the following equation (5).

[0075] [Formula 5]

[0076]

[0077] Therefore, regarding the three-phase current, the two-phase components i on the αβ axis can be obtained through the following conversion equation (6). α i β .

[0078] [Formula 6]

[0079]

[0080] In this embodiment, the following situation is considered: based on the location of the switching element that becomes an open-circuit fault, vector i is synthesized. αβ The generated results are different.

[0081] Figure 5 This describes the fault location of the switching element and the composite vector i. αβ A table of relationships.

[0082] like Figure 5 As shown, in the case of a fault in the upper arm circuit of phase U, the synthesized vector i αβ When the left side becomes a semicircle, and a fault occurs in the upper arm circuit of phase V, the synthesized vector i αβ In the case of a semicircle on the lower right side, and a fault in the upper arm circuit of phase W, the synthesized vector i αβ It forms a semicircle on the upper right side.

[0083] Additionally, in the event of a fault in the lower arm circuit of phase U, the synthesized vector i αβ When the right side becomes a semicircle, and a fault occurs in the lower arm circuit of phase V, the synthesized vector i αβ In the case of a semicircle on the upper left side, and a fault in the lower arm circuit of phase W, the synthesized vector i αβ It forms a semicircle on the lower left side.

[0084] Therefore, due to the synthesis vector i αβ The missing portion varies depending on the location of the fault, so the αβ axis plane is divided into 6 quadrants. This is achieved by detecting the missing quadrant and synthesizing the vector i. αβ The angle of advance can help determine the faulty phase of the switching element and whether it is the upper arm circuit or the lower arm circuit.

[0085] Next, the calculation of the electrical angle in the electrical angle calculation unit 44 will be explained. This is based on converting the three-phase alternating currents iu, iv, and iw into two-phase components i on the αβ axis. α i β The result is obtained by calculating the composite vector i using the following formula (7). αβ The electrical angle θ on the αβ axis αβ .

[0086] [Formula 7]

[0087]

[0088] As an example of the implementation method of this electrical angle calculation, the current value with a width corresponding to the installation accuracy is used to calculate i. α i β and electrical angle θ αβ The relationship diagram is stored in the arithmetic unit and memory, and the output electrical angle θ is... αβ If all switching elements of inverter circuit 60 are functioning normally, then the electrical angle θ αβ Rotate around the intersection of the α-axis and β-axis.

[0089] Figure 6 It is a diagram representing the six quadrants of the composite vector in the αβ axis coordinate space.

[0090] like Figure 6 As shown, the quadrant calculation unit 45 divides the coordinate space into quadrants predetermined in the αβ axis coordinate space. For example, it divides the space into quadrants 1 to 6 by (1) the β axis, (2) a straight line tilted at 60° relative to the β axis, and (3) a straight line tilted at 120° relative to the β axis. Then, with this division, each quadrant has an angle range of 60°. The quadrant calculation unit 45 calculates which quadrant the acquired electrical angle corresponds to and confirms the composite vector i. αβ Whether the vehicle has passed through each of the defined quadrants, and output the quadrant information.

[0091] Figure 7 This is a diagram showing the fault detection judgment table in this embodiment.

[0092] Figure 7 The decision table shown is pre-stored in memory 46. For example... Figure 7 As shown, the judgment angle range and fault location are stored corresponding to the judgment regions in the first to sixth quadrants. Figure 7 In the judgment table shown, ○ indicates a quadrant that has passed, and × indicates a quadrant that has not passed at the fault location.

[0093] The center of the judgment angle range in the first quadrant is 0 degrees, the minimum is 330 degrees, and the maximum is 30 degrees. Then, the × mark indicates that when the fault location is the upper arm circuit of phase U, the lower arm circuit of phase V, or the lower arm circuit of phase W, the synthesized vector i is... αβ It does not pass through the first quadrant.

[0094] The judgment angle range in the second quadrant is centered at 60 degrees, with a minimum of 30 degrees and a maximum of 90 degrees. Then, an × symbol is used to indicate the composite vector i when the fault location is the upper arm circuit of phase U, the upper arm circuit of phase V, or the lower arm circuit of phase W. αβ It does not pass through the second quadrant.

[0095] The judgment angle range in the third quadrant is centered at 120 degrees, with a minimum of 90 degrees and a maximum of 150 degrees. Then, an × symbol is used to indicate the composite vector i when the fault location is the lower arm circuit of phase U, the upper arm circuit of phase V, or the lower arm circuit of phase W. αβ It does not pass through the third quadrant.

[0096] The judgment angle range in the fourth quadrant is centered at 180 degrees, with a minimum of 150 degrees and a maximum of 210 degrees. Then, an × symbol is used to indicate the composite vector i when the fault location is the lower arm circuit of phase U, the upper arm circuit of phase V, or the upper arm circuit of phase W. αβ It does not pass through the fourth quadrant.

[0097] The angular range for the fifth quadrant is centered at 240 degrees, with a minimum of 210 degrees and a maximum of 270 degrees. Then, an × symbol is used to indicate the composite vector i when the fault location is the lower arm circuit of phase U, the lower arm circuit of phase V, or the upper arm circuit of phase W. αβ It does not pass through the fifth quadrant.

[0098] The judgment angle range in the sixth quadrant has a center of 300 degrees, a minimum of 270 degrees, and a maximum of 330 degrees. Then, an × symbol is used to indicate the composite vector i when the fault location is the upper arm circuit of phase U, the lower arm circuit of phase V, or the upper arm circuit of phase W. αβ It does not pass through the sixth quadrant.

[0099] The fault detection unit 47 determines whether the composite vector has rotated one electrical angle from the first quadrant to the sixth quadrant. Then, based on the quadrant information from the quadrant calculation unit 45, if there is a quadrant that has not been passed, it is considered a fault state. The fault location is determined according to the determination table in the memory 46, and the fault information is output.

[0100] Figure 8 This is a flowchart showing the operation of the control unit 40.

[0101] exist Figure 8 In step S101, it is determined whether the maximum motor speed Nmax [rpm] is less than 60 / 6ts. Here, ts is the sampling time for acquiring the current value. If the maximum motor speed Nmax [rpm] does not meet the condition shown in step S101, since the motor 20 is rotating too fast, the process proceeds to step S102, where the upper control device is notified that the fault diagnosis is invalid.

[0102] The sampling time for acquiring the current value in the current detection unit 70 is roughly determined by the performance of the ADC (analog-to-digital converter) provided by the arithmetic unit (microcomputer) of the control unit 40. The case with the fewest sampling times during one revolution of the electrical angle is when the motor speed is the highest.

[0103] For example, when the sampling time ts[sec] of the ADC is 100[us], only 6 points of motor speed N[rpm] can be obtained as shown in the following formula (8).

[0104] [Formula 8]

[0105]

[0106] The sampling time ts and the maximum motor speed Nmax [rpm] are stored in a memory (not shown) within the control unit 40, thereby confirming whether the detection of the current detection unit 70 and the control unit 40 is a valid installation condition.

[0107] When the maximum motor speed Nmax [rpm] satisfies the conditions shown in step S101, the motor speed 20 can achieve at least 6 points of rotation per electrical angle. That is, the current detection unit 70 and the control unit 40 perform current detection with a sampling period of at least 6 points during one cycle of the fundamental component of the output current. In other words, the current detection unit 70 and the control unit 40 perform current detection with a sampling frequency of at least 6 times the frequency of the output current. If the conditions shown in step S101 are met, proceed to step S103.

[0108] In step S103, the current detection unit 70 acquires the AC currents iu, iv, and iw of each phase.

[0109] In the next step S104, the three-phase / two-phase conversion unit 43 acquires the composite vector i on the αβ axis. αβ .

[0110] In the next step S105, the electrical angle calculation unit 44 calculates the composite vector i based on the alternating current iu of phase U. αβ The electrical angle is then calculated. In step S106, the quadrant calculation unit 45 outputs quadrant information, which indicates which quadrant among the pre-divided first to sixth quadrants the acquired electrical angle corresponds to.

[0111] In step S107, it is determined whether i is 6 or higher. i is the quadrant number obtained.

[0112] If i is not above 6, it means that the sixth quadrant has not been obtained, and proceed to step S108.

[0113] In step S108, it is determined whether the quadrant has progressed from the last time. If the quadrant has not progressed, the processing ends, and the next sampling time t is reached. s Execution begins from step S101. Figure 8 The process is as shown. In step S108, if the quadrant advances from the last start, then in step S109, 1 is added to i and the process ends.

[0114] In step S107, if it is determined that the sixth quadrant has been obtained, proceed to step S110. In step S110, the fault detection unit 47 determines whether the quadrant information output in step S106 covers all quadrants, i.e., whether all quadrants have been passed. If not all quadrants have been passed, proceed to step S111.

[0115] In step S111, the fault detection unit 47 considers the fault state as a fault state, determines the fault location by referring to the judgment table in the memory 46 and the quadrants that were not passed, and outputs the fault information to the upper control device and the PWM signal generation unit 42.

[0116] In step S112, it is determined whether there is an open-circuit fault in the lower arm circuit. If there is an open-circuit fault in the lower arm circuit, in step S113, the PWM signal generation unit 42 generates and outputs a PWM signal indicating a three-phase short-circuit state in the upper arm. As a result, the inverter circuit 60 enters an active short-circuit state in the upper arm.

[0117] On the other hand, in step S112, if there is an open-circuit fault in the upper arm circuit, in step S114, the PWM signal generation unit 42 generates and outputs a PWM signal indicating a three-phase short-circuit state in the lower arm. Thus, the inverter circuit 60 becomes an active short-circuit state in the lower arm.

[0118] After processing in steps S113 and S114, the process ends. Figure 8 The processing shown.

[0119] In step S110, if the fault detection unit 47 determines that the inverter circuit 60 is normal if the quadrant information output in step S106 has passed all quadrants, it proceeds to step S115. In step S115, the acquired quadrant number i is returned to zero. Then, in step S116, the PWM signal generation unit 42 generates a PWM signal corresponding to the duty cycle value of each phase. Then, after a predetermined time, the process is repeated. Figure 8 The following steps are processed: S101 and below.

[0120] Therefore, to determine whether a switching element is faulty, it is necessary to represent all quadrants on the αβ axis coordinate system, from the first to the sixth quadrant. This requires a complete electrical angle rotation to obtain at least six sampling points, and the sampling time corresponding to this situation must be determined for acquiring the three-phase current values. In other words, it is not simply a matter of acquiring six samples at a specific location on the αβ axis coordinate system, but rather acquiring information from all six quadrants. Therefore, the three-phase current values ​​are acquired at a sampling frequency at least six times the electrical angle frequency.

[0121] According to this embodiment, since fault detection is performed using electrical angle, it is independent of the amplitude accuracy of the three-phase AC current value. By using only the current value of the three-phase AC current, faults in switching elements can be detected with high accuracy.

[0122] Furthermore, when the αβ axis plane is divided into 6 quadrants, fault detection is performed using quadrant confirmation information. Therefore, if 6 electrical angles are obtained for each revolution of the motor, the AC current value of several cycles can be obtained within one revolution of the motor to detect the fault.

[0123] In addition, for fault detection, in order to obtain higher reliability, it is not possible to determine whether it is normal or faulty based on the result of one electrical rotation, but based on the results of multiple rotations.

[0124] Furthermore, the case where the electrical angle is left-handed rotation has been explained, but the same method can be applied even when the flow direction of the three-phase current is right-handed, such as during regeneration.

[0125] Furthermore, this embodiment does not require a rotary sensor such as a rotary transformer, but only uses the value of a current detection unit 70 such as a current sensor. Therefore, the type of motor can be applied regardless of whether it is a synchronous machine or an induction machine.

[0126] [Second Implementation]

[0127] Figure 9 This is a circuit diagram of the power conversion device 200 in this embodiment.

[0128] to and Figure 1 The same parts of the power conversion device 100 in the first embodiment shown are given the same reference numerals, and their descriptions are omitted.

[0129] In addition to the duty cycle calculation unit 41, PWM signal generation unit 42, three-phase / two-phase conversion unit 43, electrical angle calculation unit 44, quadrant calculation unit 45, memory 46, and fault detection unit 47, the control unit 40' also has a synthetic vector rotation direction calculation unit 81, a motor speed calculation unit 82, and a required speed calculation unit 83.

[0130] The composite vector rotation direction calculation unit 81 obtains the target torque of the motor 20 from the electronic control device (not shown) located outside the power conversion device 200, calculates the rotation direction of the composite vector based on the target torque, and outputs it to the fault detection unit 47.

[0131] The motor speed calculation unit 82 calculates the motor speed N based on the three-phase AC currents iu, iv, and iw, and outputs the result to the required speed calculation unit 83.

[0132] The required speed calculation unit 83 pre-stores the motor speed N, the sampling time Ts of the current sensor, and the correspondence table of the required electrical angle speeds for all quadrants. Based on the motor speed N obtained from the calculation result of the motor speed calculation unit 82, it refers to the correspondence table and outputs the corresponding electrical angle speed Nr.

[0133] Furthermore, the various structures within the control unit 40' are hardware-independent and can also be controlled by the CPU and, as described later, by [other mechanisms]. Figure 11 The flowchart shown illustrates the program that implements the functions of each structure. When each structure within the control unit 40' is implemented using a CPU and a program, the reduced number of hardware components results in lower costs. Furthermore, when each structure is constructed with hardware independent of the control unit 40', the processing load on the control unit 40' is reduced, enabling faster diagnostic processing.

[0134] In this embodiment, the three-phase current value is acquired when the motor 20 rotates more than one revolution, and the fault of the switching element in the inverter circuit 60 is detected using the quadrant pass information of more than one revolution.

[0135] Depending on the timing of the three-phase current acquisition and the rotational speed of the motor 20, it is sometimes impossible to obtain the electrical angle of the composite vector that passes through all quadrants within one electrical angle rotation. For example, under the condition of acquiring data every 103° of electrical angle, the motor 20 rotates approximately 2 times to pass through all 6 quadrants.

[0136] Figure 10 It is a diagram showing the timing of obtaining the three-phase current values ​​in the αβ axis coordinate space.

[0137] Figure 10 The × symbol indicates the timing of three-phase current value acquisition, and the numbers indicate the acquisition order. Figure 10 In the process, data is acquired every 103° of electrical angle to obtain quadrant information for approximately 2 weeks of the motor 20 in 6 quadrants.

[0138] Figure 11 This is a flowchart illustrating the operation of the control unit 40' in the second embodiment.

[0139] exist Figure 11In step S201, the motor speed calculation unit 82 calculates the motor speed N based on the three-phase AC currents iu, iv, and iw. In the next step S202, the required speed calculation unit 83 determines the required electrical angle speed Nr for all quadrants based on the speed N and the current sampling time Ts. The required speed calculation unit 83 prepares, for example, a correspondence table of motor speed N, current sensor sampling time Ts, and required electrical angle speed Nr for all quadrants, and outputs the corresponding electrical angle speed Nr based on the motor speed N obtained from the calculation result of the motor speed calculation unit 82, referring to the correspondence table.

[0140] In addition, Figure 11 In step S203, the current detection unit 70 acquires the AC currents iu, iv, and iw of each phase. In the next step S204, the three-phase / two-phase conversion unit 43 acquires the composite vector i on the αβ axis. αβ In the next step S205, the electrical angle calculation unit 44 calculates the composite vector i based on the alternating current iu of phase U. αβ The electrical angle is then calculated. In step S206, the quadrant calculation unit 45 outputs quadrant information, which indicates which quadrant among the pre-divided first to sixth quadrants the acquired electrical angle corresponds to.

[0141] Moreover, in Figure 11 In step S207, the synthetic vector rotation direction calculation unit 81 obtains the target torque of the motor 20 from the external electronic control device. Then, in step S208, the synthetic vector rotation direction calculation unit 81 calculates the rotation direction of the synthetic vector based on the target torque and outputs it to the fault detection unit 47.

[0142] In step S209, the fault detection unit 47 determines whether the synthesized vector is rotated to the left.

[0143] If the rotation is to the left, proceed to step S210; if the rotation is to the right, proceed to step S211. In steps S210 and S211, the obtained angle is represented as (θ). αβ ) n The previously obtained angle is represented as (θ) αβ ) n-1 .

[0144] In step S210, it is determined whether the angle of the synthesized vector satisfies the condition of equation (9) with the α axis as the reference.

[0145] [Formula 9]

[0146] 180°≤(θ αβ ) n-1 <360°and0°≥(9 αβ ) n<180° (9)

[0147] In step S211, it is determined whether the angle of the synthesized vector satisfies the condition of equation (10) with respect to the α axis.

[0148] [Formula 10]

[0149] 0°≤(θ αβ ) n-1 <180° and 180° ≤ (θ) αβ ) n <360° (10)

[0150] If the conditions are met in steps S210 and S211, proceed to step S212; otherwise, terminate the process. In step S212, increment i by 1. Then, in the next step S213, determine whether i is greater than the electrical angular rotational speed Nr.

[0151] For example, in the case where the resultant vector is a left turn, in step S210, since the resultant vector has moved from the negative side (right side) of the α axis to the positive side (left side), it can be said that it has passed the 0° point. Therefore, in step S212, the counter i is added, and in step S213, it is confirmed whether the required rotational speed Nr has been obtained. In the case where the resultant vector is a right turn, in step S211, since the resultant vector has moved from the positive side (left side) of the α axis to the negative side (right side), it can be said that it has passed the 0° point. Therefore, in step S212, the counter i is added, and in step S213, it is confirmed whether the required rotational speed Nr has been obtained.

[0152] In step S213, if it is determined that i is greater than the electrical angular rotational speed Nr, it means the synthesized vector has passed through all quadrants, and the process proceeds to step S214. If it is not determined that i is greater than the electrical angular rotational speed Nr in step S213, the process ends, and after a predetermined time, it is repeated. Figure 11 The processing shown.

[0153] In step S214, the fault detection unit 47 determines whether the quadrant information output in step S206 covers all quadrants, i.e., whether all quadrants have been passed. If not all quadrants have been passed, the process proceeds to step S215.

[0154] In step S215, the fault detection unit 47 considers the fault state as faulty, determines the fault location by referring to the decision table and the quadrants that were not passed, which are pre-stored in the memory 46, and outputs the fault information to the upper-level control device and the PWM signal generation unit 42. Furthermore, the decision table and... Figure 7 The fault detection judgment table shown in the first embodiment is the same.

[0155] In step S216, it is determined whether there is an open-circuit fault in the lower arm circuit. If there is an open-circuit fault in the lower arm circuit in step S216, in step S217, the PWM signal generation unit 42 generates and outputs a PWM signal indicating a three-phase short-circuit state in the upper arm. Thus, the inverter circuit 60 enters an active short-circuit state in the upper arm. Alternatively, in step S217, all six switching elements in the inverter circuit 60 are disconnected, entering a freewheel state.

[0156] On the other hand, in the case of an open-circuit fault in the upper arm circuit, in step S218, the PWM signal generation unit 42 generates and outputs a PWM signal that results in a three-phase short-circuit state in the lower arm. Thus, the inverter circuit 60 becomes an active short-circuit state in the lower arm. Alternatively, in step S218, all six switching elements within the inverter circuit 60 are disconnected, resulting in a freewheel state.

[0157] After the processing in steps S217 and S218, the process ends. Figure 11 The processing shown.

[0158] In step S214, if the fault detection unit 47 determines that the quadrant information output in step S206 has passed all quadrants, the inverter circuit 60 is normal, and proceeds to step S219. In step S219, the counter i returns to zero. Then, in step S220, the PWM signal generation unit 42 generates a PWM signal corresponding to the duty cycle value of each phase. Then, after a predetermined time, the process is repeated. Figure 11 The processing shown.

[0159] According to this embodiment, since fault detection is performed using electrical angle, it is independent of the amplitude accuracy of the three-phase AC current value, and faults in switching elements can be detected with high accuracy using only the current value of the three-phase AC current.

[0160] Furthermore, based on the relationship between the timing of acquiring the three-phase current value and the rotational speed of the motor 20, even if the electrical angle of the composite vector that passes through all quadrants within one revolution of the electrical angle cannot be acquired, according to this embodiment, the fault of the switching element can be detected even if it passes through all quadrants within multiple revolutions of the electrical angle.

[0161] [Third Implementation Method]

[0162] Figure 12 This is a circuit diagram of the power conversion device 300 in this embodiment.

[0163] to and Figure 1In the first embodiment shown, the same parts of the power conversion device 100 are given the same symbols, and their descriptions are omitted. In the third embodiment, the fault location is determined based on the position of the missing quadrant, but in this embodiment, the quadrant at which the fault begins to be missing is determined in advance, thus identifying the fault location earlier.

[0164] In addition to the duty cycle calculation unit 41, PWM signal generation unit 42, three-phase / two-phase conversion unit 43, electrical angle calculation unit 44, quadrant calculation unit 45, memory 46, and fault detection unit 47, the control unit 40 also has a synthetic vector rotation direction calculation unit 81, a delay unit 84, and a prediction quadrant determination unit 85.

[0165] The composite vector rotation direction calculation unit 81 obtains the target torque of the motor 20 from an electronic control device (not shown) located outside the power conversion device 300, calculates the rotation direction of the composite vector based on the target torque, and outputs it to the prediction quadrant determination unit 85.

[0166] The delay unit 84 delays the quadrant information from the quadrant calculation unit 45 by one sample and transmits it to the prediction quadrant determination unit 85.

[0167] The quadrant prediction determination unit 85 outputs the predicted quadrant information to the fault detection unit 47 based on the quadrant information obtained by the delay unit 84 before sampling and the rotation direction of the synthesized vector.

[0168] Furthermore, the various structures within the control unit 40” are hardware-independent and can also be controlled by the CPU and, as described later, by [other mechanisms]. Figure 15 The flowchart shown illustrates the program that implements the functions of each structure. When each structure within the control unit 40” is implemented using a CPU and a program, the number of hardware components is reduced, resulting in lower costs. On the other hand, when each structure is constructed using hardware independent of the control unit 40”, the processing load on the control unit 40” is reduced, enabling faster diagnostic processing.

[0169] Figure 13 It is the composite vector in the αβ axis coordinate space, and is a diagram representing the situation where an open circuit fault has occurred in the upper arm circuit of phase U.

[0170] exist Figure 13 The diagram depicts the leftward rotation of the composite vector. In the case of an open-circuit fault in the upper arm circuit of phase U, the rotation trajectory of the composite vector changes as follows: Figure 13 The semicircle shown by the solid line. That is, the position of the quadrant that initially lacked the sixth quadrant.

[0171] Figure 14 This is a diagram showing the fault detection judgment table in this embodiment.

[0172] exist Figure 14 The decision table shown indicates the case where the composite vector is rotated to the left; this decision table is pre-stored in memory 46. For example... Figure 14 As shown, the decision angle range and the order of missing faults are stored corresponding to the decision regions of the first to sixth quadrants.

[0173] like Figure 14 As shown, when a fault occurs in the upper arm circuit of phase U, the fault time deficiency sequence is in the order of quadrant 6, quadrant 1, and quadrant 2. When a fault occurs in the lower arm circuit of phase U, the fault time deficiency sequence is in the order of quadrant 3, quadrant 4, and quadrant 5. When a fault occurs in the upper arm circuit of phase V, the fault time deficiency sequence is in the order of quadrant 2, quadrant 3, and quadrant 4. When a fault occurs in the lower arm circuit of phase V, the fault time deficiency sequence is in the order of quadrant 5, quadrant 6, and quadrant 1. When a fault occurs in the upper arm circuit of phase W, the fault time deficiency sequence is in the order of quadrant 4, quadrant 5, and quadrant 6. When a fault occurs in the lower arm circuit of phase W, the fault time deficiency sequence is in the order of quadrant 1, quadrant 2, and quadrant 3.

[0174] Figure 15 This is a flowchart illustrating the operation of the control unit 40 in the third embodiment.

[0175] exist Figure 15 In step S301, it is determined whether the maximum motor speed Nmax [rpm] is less than 60 / 6t. s Furthermore, the processing in steps S301 to S306 is the same as that described in the first embodiment. Figure 8 The processes in steps S101 to S106 are the same, so this explanation is brief.

[0176] If the conditions shown in step S301 are not met, since the speed of motor 20 is too fast, the process proceeds to step S302, whereby the upper control device is notified that the fault diagnosis is invalid.

[0177] In step S303, the current detection unit 70 acquires the AC currents iu, iv, and iw of each phase.

[0178] In the next step S304, the three-phase / two-phase conversion unit 43 acquires the composite vector i on the αβ axis. αβ .

[0179] In step S305, the electrical angle calculation unit 44 calculates the composite vector i based on the alternating current iu of phase U. αβ The electrical angle is then calculated. In step S306, the quadrant calculation unit 45 outputs quadrant information, which indicates which quadrant among the pre-divided first to sixth quadrants the acquired electrical angle corresponds to.

[0180] In step S307, quadrant information from quadrant calculation unit 45 is input to delay unit 84 and delayed by one sample.

[0181] In step S308, the synthetic vector rotation direction calculation unit 81 obtains the target torque of the motor 20. Then, in step S309, the synthetic vector rotation direction calculation unit 81 calculates the rotation direction of the synthetic vector based on the target torque and outputs it to the prediction quadrant determination unit 85.

[0182] Next, in step S310, the prediction quadrant determination unit 85 determines the prediction quadrant information based on the rotation direction of the synthesized vector and the quadrant information delayed by the delay unit 84, and outputs it to the fault detection unit 47. Figure 13 In the example where the upper arm circuit of the left-rotating, U-phase synthesized vector has an open-circuit fault, if the current time point is the sampling time point of the fifth quadrant, the information of the sixth quadrant is output to the fault detection unit 47 as the predicted quadrant information.

[0183] In step S311, the fault detection unit 47 compares the predicted quadrant information obtained from the predicted quadrant determination unit 85 with the current quadrant information. In step S312, the fault detection unit 47 determines whether the predicted quadrant information and the current quadrant information are consistent. Figure 13 In the example, the sixth quadrant passed at the current time point is missing. In step S312, it is determined that the sixth quadrant is inconsistent with the predicted quadrant information (the next quadrant to be passed after the previously passed fifth quadrant), and the process proceeds to step S313.

[0184] In step S313, the fault detection unit 47 considers the fault state as faulty, determines the fault location by referring to the fault time deficiency sequence in the determination table in the memory 46, and outputs the fault information to the upper-level control device and PWM signal generation unit 42. Figure 14 In the example, if the fault is in the sixth quadrant, the first missing sequence is the upper arm circuit of phase U, which is an open circuit fault, then the location of the fault is determined.

[0185] In step S314, it is determined whether there is an open-circuit fault in the lower arm circuit. If there is an open-circuit fault in the lower arm circuit, in step S315, the PWM signal generation unit 42 generates and outputs a PWM signal indicating a three-phase short-circuit state in the upper arm. As a result, the inverter circuit 60 enters an active short-circuit state in the upper arm.

[0186] On the other hand, in step S314, if there is an open-circuit fault in the upper arm circuit, in step S316, the PWM signal generation unit 42 generates and outputs a PWM signal indicating a three-phase short-circuit state in the lower arm. Thus, the inverter circuit 60 becomes an active short-circuit state in the lower arm.

[0187] After processing in steps S315 and S316, the process ends. Figure 15 The processing shown.

[0188] In step S312, if the fault detection unit 47 determines that the predicted quadrant information and the current quadrant information are consistent, and there are no missing quadrants in the previously passed quadrants and the currently passed quadrants, and the inverter circuit 60 is normal, then proceed to step S317. In step S317, the PWM signal generation unit 42 generates a PWM signal corresponding to the duty cycle value of each phase. Then, after a predetermined time, the process is repeated. Figure 15 The processing shown.

[0189] Furthermore, while quadrant information can be delayed by one sample and compared with quadrant information one sample ago, it is also possible to delay quadrant information by two samples and compare it with quadrant information two samples ago. Thus, even if the quadrant information one sample ago is in a transitional and blurred state, the missing quadrant can be reliably captured by using the quadrant information two samples ago.

[0190] According to this embodiment, since fault detection is performed using electrical angle, it is independent of the amplitude accuracy of the three-phase AC current value, and faults in switching elements can be detected with high accuracy using only the current value of the three-phase AC current.

[0191] Furthermore, according to this embodiment, the fault location can be determined in advance without waiting for the electrical angle of the synthesized vector to rotate one full revolution.

[0192] (Variation Example 1)

[0193] Figure 16 This is a diagram representing the quadrants of the composite vector in the αβ axis coordinate space in Variation Example 1.

[0194] Figure 16 The numbers in the diagram represent quadrant numbers. For example... Figure 16 As shown, the coordinate space is divided into quadrants predetermined in the αβ axis coordinate space, for example, by (1) the β axis, (2) a straight line tilted at 60° relative to the β axis, and (3) a straight line tilted at 120° relative to the β axis, dividing the space into quadrants 1 to 6. Then, the quadrants near the boundaries of each quadrant are defined by the number 7. Thus, in order to prevent misidentification of the quadrants through which the composite vector of the rotation passes, the quadrants near the boundaries are designated as other quadrants.

[0195] Figure 17 This is a diagram showing the fault detection judgment table in Modified Example 1.

[0196] like Figure 17As shown, the storage of judgment angle ranges and fault locations corresponds to each judgment region near the boundaries of the first to sixth quadrants. The symbols in the figure represent... Figure 16 The numbers in the diagram. α within the angular range indicates the angular range near the boundary.

[0197] The center of the judgment angle range in the first quadrant is 0 degrees, the minimum is 330+α degrees, and the maximum is 30-α degrees. Then, the × mark indicates that when the fault location is the upper arm circuit of phase U, the lower arm circuit of phase V, or the lower arm circuit of phase W, the synthesized vector i is... αβ It does not pass through the first quadrant.

[0198] The judgment angle range in the second quadrant is centered at 60 degrees, with a minimum of 30+α degrees and a maximum of 90-α degrees. Then, an × symbol is used to indicate the composite vector i when the fault location is the upper arm circuit of phase U, the upper arm circuit of phase V, or the lower arm circuit of phase W. αβ It does not pass through the second quadrant.

[0199] The same applies to the third to sixth quadrants. Figure 17 In the judgment table shown, ○ indicates a quadrant that has passed, and × indicates a quadrant that has not passed at the fault location.

[0200] Near the boundary, we define six regions with minimum to maximum values ​​of 30-α to 30+α, 90-α to 90+α, 150-α to 150+α, 210-α to 210+α, 270-α to 270+α, and 330-α to 330+α.

[0201] The quadrant calculation unit 45 shown in the first to third embodiments outputs information about the first to sixth quadrants and any quadrant near the boundary.

[0202] The fault detection unit 47 shown in the first to third embodiments outputs fault information by referring to a determination table stored in the memory 46, etc. In this case, fault determination is not performed near the boundary.

[0203] (Variation Example 2)

[0204] Figure 18 This is a diagram representing the quadrants of the composite vector in the αβ axis coordinate space in variation example 2.

[0205] Figure 18 The numbers in the diagram represent quadrant numbers. For example... Figure 18As shown, the coordinate space is divided into quadrants predetermined in the αβ axis coordinate space. For example, the first to sixth quadrants are divided by (1) the β axis, (2) a straight line tilted at 60° relative to the β axis, and (3) a straight line tilted at 120° relative to the β axis. Furthermore, the quadrants near the boundaries of each quadrant are defined by numbers 7 to 12. Thus, in order to prevent misidentification of the quadrants through which the composite vector of the rotation passes, the vicinity of the boundaries of the quadrants is designated as other quadrants.

[0206] Figure 19 This is a diagram showing the fault detection judgment table in Modified Example 2.

[0207] like Figure 19 As shown, the storage of judgment angle ranges and fault locations corresponds to each judgment region near the boundaries of the first to sixth quadrants. The symbols in the figure represent... Figure 18 The numbers in the diagram. α within the angular range indicates the angular range near the boundary.

[0208] The center of the judgment angle range in the first quadrant is 0 degrees, the minimum is 330+α degrees, and the maximum is 30-α degrees. Then, the × mark indicates that when the fault location is the upper arm circuit of phase U, the lower arm circuit of phase V, or the lower arm circuit of phase W, the synthesized vector i is... αβ It does not pass through the first quadrant.

[0209] The judgment angle range in the second quadrant is centered at 60 degrees, with a minimum of 30+α degrees and a maximum of 90-α degrees. Then, an × symbol is used to indicate the composite vector i when the fault location is the upper arm circuit of phase U, the upper arm circuit of phase V, or the lower arm circuit of phase W. αβ It does not pass through the second quadrant. The same applies to the third through sixth quadrants. Figure 19 In the judgment table shown, ○ indicates a quadrant that has passed, and × indicates a quadrant that has not passed at the fault location.

[0210] Near the boundary, the regions 7 to 12 are defined as the six regions with the minimum to the maximum values ​​of 30-α to 30+α, 90-α to 90+α, 150-α to 150+α, 210-α to 210+α, 270-α to 270+α, and 330-α to 330+α, respectively.

[0211] exist Figure 19 In the judgment table shown, corresponding to areas 7 to 12 near the boundary, the ○ mark indicates the area that can be passed, the × mark indicates the area that cannot be passed at the fault location, and the - mark indicates the area where no fault judgment is made. For example, the center of area 7 near the boundary is 30 degrees, the minimum is 30-α degrees, and the maximum is 30+α degrees. Then, the × mark indicates that when the fault location is the upper arm circuit of phase U and the lower arm circuit of phase W, the synthesized vector i is... αβThe circuit does not pass through the vicinity of boundary 7. Furthermore, in the vicinity of boundary 7, the upper arm circuit of phase V and the lower arm circuit of phase V are not subject to fault determination.

[0212] The quadrant calculation unit 45 shown in the first to third embodiments outputs quadrant information for the first to sixth quadrants and any quadrant near the boundary.

[0213] The fault detection unit 47 shown in the first to third embodiments outputs fault information by referring to a determination table stored in the memory 46, etc. In this case, for the boundary vicinity 7 to 12, the determination is made by considering the boundary vicinity 7 as the first quadrant or the second quadrant, the boundary vicinity 8 as the second quadrant or the third quadrant, the boundary vicinity 9 as the third quadrant or the fourth quadrant, the boundary vicinity 10 as the fourth quadrant or the fifth quadrant, the boundary vicinity 11 as the fifth quadrant or the sixth quadrant, and the boundary vicinity 12 as the sixth quadrant or the first quadrant.

[0214] (Variation Example 3)

[0215] Figure 20 This is a diagram representing the quadrants of the composite vector in the αβ axis coordinate space in variation example 3.

[0216] Figure 20 The numbers in the diagram represent quadrant numbers. For example... Figure 20 As shown, the αβ axis coordinate space, which is formed by the α axis that is consistent with the current direction of any phase and the β axis that is orthogonal to the α axis, is divided into quadrants predetermined on the αβ axis. For example, the first quadrant to the sixth quadrant are divided by (1) a straight line that is tilted 30° relative to the β axis, (2) a straight line that is tilted 90° relative to the β axis, and (3) a straight line that is tilted 150° relative to the β axis. Figure 20 The dashed lines in the diagram represent the boundaries of the quadrants. This is in contrast to the first embodiment. Figure 6 The quadrant setting shown is tilted 30° to the left.

[0217] Figure 21 This is a diagram showing the fault detection judgment table in Variation Example 3.

[0218] Figure 21 The decision table shown is pre-stored in memory 46. For example... Figure 21 As shown, the judgment angle range and fault location are stored corresponding to the judgment areas in the first to sixth quadrants.

[0219] The angular range for the first quadrant is centered at 30 degrees, with a minimum of 0 degrees and a maximum of 60 degrees. Then, an × symbol is used to indicate that when the fault location is the upper arm circuit of phase U or the lower arm circuit of phase W, the synthesized vector i is... αβ It does not pass through the first quadrant.

[0220] The judgment angle range in the second quadrant is centered at 90 degrees, with a minimum of 60 degrees and a maximum of 120 degrees. Then, an × symbol is used to indicate that when the fault location is the upper arm circuit of phase V or the lower arm circuit of phase W, the synthesized vector i... αβ It does not pass through the second quadrant.

[0221] The same applies to the third to sixth quadrants. Figure 21 In the judgment table shown, ○ indicates a quadrant that has passed, and × indicates a quadrant that has not passed at the fault location.

[0222] The fault detection unit 47 determines whether the composite vector has rotated at least one electrical angle from the first quadrant to the sixth quadrant. Then, based on the quadrant information from the quadrant calculation unit 45, if there is a quadrant that has not been passed, it is considered a fault state. The fault location is determined according to the determination table in the memory 46, and fault information is output. For example, if the composite vector has not passed... Figure 20 In the case of the area indicated by the diagonal line (a range of ±60° width centered on the α axis), it is determined to be a fault in the upper arm circuit of phase U.

[0223] According to variation example 3, even in the synthetic vector representation Figure 18 In cases near the boundaries described in the text, ambiguity in fault detection can also be avoided.

[0224] The following effects can be obtained by implementing the methods described above.

[0225] (1) A power conversion device 100, 200, 300, comprising: an inverter circuit 60 composed of switching elements for converting direct current into alternating current; a current detection unit 70 for detecting the three-phase output current of the inverter circuit 60; and a composite vector i calculated based on the three-phase output current detected by the current detection unit 70. αβ If the electrical angle is not within the specified range, the control units 40, 40', and 40' determine that an open-circuit fault has occurred in the switching element of the inverter circuit 60 in the phase corresponding to the specified range. Thus, faults in the switching elements can be detected with high precision regardless of the magnitude of the output current in each phase.

[0226] (2) A fault diagnosis method for power conversion devices 100, 200, and 300, comprising the following steps: detecting the three-phase output current of an inverter circuit 60 composed of switching elements that converts DC current to AC current, and calculating the composite vector i based on the detected three-phase output current. αβ If the electrical angle is not within the specified range, an open-circuit fault is determined in the phase corresponding to the specified range, indicating that the switching element of the inverter circuit 60 has occurred. Therefore, faults in the switching elements can be detected with high precision regardless of the magnitude of the output current in each phase.

[0227] This invention is not limited to the embodiments described above. Other embodiments within the scope of the technical concept of this invention are also included within the scope of this invention, as long as they do not impair the characteristics of this invention. Additionally, it may be a structure that combines the above embodiments and multiple variations.

[0228] Symbol Explanation

[0229] 10…DC power supply, 20…motor, 40, 40', 40”…control unit, 41…duty cycle calculation unit, 42…PWM signal generation unit, 43…three-phase / two-phase conversion unit, 44…electrical angle calculation unit, 45…quadrant calculation unit, 46…memory, 47…fault detection unit, 50…drive circuit, 60…inverter circuit, 70…current detection unit, 81…synthetic vector rotation direction calculation unit, 82…motor speed calculation unit, 83…required speed calculation unit, 84…delay unit, 85…predictive quadrant determination unit, 100, 200, 300…power conversion device.

Claims

1. A power conversion device, characterized in that, have: An inverter circuit, composed of switching elements, converts direct current into alternating current. A current detection unit detects the three-phase output current of the inverter circuit; and The control unit, if the electrical angle of the composite vector calculated based on the three-phase output current detected by the current detection unit is not within a specified range, determines that an open-circuit fault has occurred in the switching element of the inverter circuit in the phase corresponding to the specified range. In the first to sixth quadrants, which are divided in units of 60° electrical angles, the control unit determines the phase of the inverter circuit in which the open-circuit fault occurs by determining which quadrant the composite vector does not pass through.

2. The power conversion device according to claim 1, characterized in that, The control unit includes a decision table that stores the decision angle range and fault location of the electrical angle corresponding to each decision region in the first to sixth quadrants. The control unit refers to the determination table to determine the phase of the inverter circuit with the open-circuit fault.

3. The power conversion device according to claim 1, characterized in that, The control unit includes a PWM signal generation unit, which generates a PWM signal and supplies it to the inverter circuit. In the event of an open-circuit fault, the PWM signal generation unit controls the PWM signal to prevent the motor connected to the inverter circuit from being driven.

4. The power conversion device according to claim 1, characterized in that, The current detection unit performs current detection at a sampling period of at least 6 points during one cycle of the fundamental component of the output current.

5. The power conversion device according to claim 1, characterized in that, The current detection unit performs current detection at a sampling frequency that is at least 6 times the frequency of the output current.

6. The power conversion device according to claim 1, characterized in that, The control unit determines the required electrical angle for confirmation of all quadrants from the first to the sixth quadrant based on the motor speed and the sampling time of the current from the current detection unit, and determines the open circuit fault when the motor rotates to the determined electrical angle.

7. The power conversion device according to claim 1, characterized in that, The control unit determines the open-circuit fault based on the quadrants traversed and the quadrants previously traversed.

8. The power conversion device according to claim 7, characterized in that, The control unit determines the open circuit fault based on the quadrant passed and the previous quadrant passed.

9. The power conversion device according to claim 1, characterized in that, The control unit defines the vicinity of each boundary in the first to sixth quadrants, and does not determine the open-circuit fault if the synthesized vector passes near the boundary.

10. The power conversion device according to claim 1, characterized in that, The control unit divides the αβ axis coordinate space into the first to sixth quadrants by (1) the β axis, (2) a straight line tilted at 60° relative to the β axis, and (3) a straight line tilted at 120° relative to the β axis. The αβ axis coordinate space is composed of an α axis that is consistent with the current direction of any phase and a β axis that is orthogonal to the α axis.

11. The power conversion device according to claim 1, characterized in that, The control unit divides the αβ axis coordinate space into the first to sixth quadrants by (1) a straight line tilted at 30° relative to the β axis, (2) a straight line tilted at 90° relative to the β axis, and (3) a straight line tilted at 150° relative to the β axis. The αβ axis coordinate space is composed of an α axis that is consistent with the current direction of any phase and a β axis that is orthogonal to the α axis.

12. A fault diagnosis method for a power conversion device, characterized in that, Perform the following processing: The three-phase output current of an inverter circuit, which consists of switching elements and converts direct current into alternating current, is detected. If the electrical angle of the composite vector calculated based on the detected three-phase output current does not fall within a specified range, then in the phase corresponding to that specified range, it is determined that an open-circuit fault has occurred in the switching element of the inverter circuit. The open-circuit fault is determined by the following method: In the first to sixth quadrants, which are divided in units of 60° of the electrical angle, the quadrant through which the composite vector does not pass is determined.

Images