Electric power system

Abstract

To detect a U-phase, a V-phase or a W-phase current sensor being abnormal.SOLUTION: An electric power system comprises: a U-phase, a V-phase and a W-phase current sensor which detect a U-phase, a V-phase and a W-phase current of a motor; a neutral-point current sensor which detects a current at a neutral point; and a controller which performs current control over the U phase, V phase and W phase so that differences between current commands of the U phase, V phase and W phase based upon a current command at the neutral point and detection values of the U-phase, V-phase and W-phase current sensors are canceled in external charging for supplying electric power from an external power supply to the motor and at least some of one or more batteries through voltage conversion of an inverter. The controller determines whether or not at least one of the U-phase, V-hase and W-phase current sensors becomes abnormal by comparing respective conversion values, obtained by converting a detection value of the neutral-point current sensor into current values of the U phase, V phase and W phase, with the respective detection values of the U-phase, V-phase and W-phase current sensors in the external charging.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to power systems. [Background technology]

[0002] A power system has been proposed that includes a motor with a three-phase coil, a three-phase inverter connected to the motor, and a battery connected to the inverter (see, for example, Patent Document 1). In this power system, power supplied from a charging facility to the neutral point of the motor is boosted by the motor and inverter and then supplied to the battery. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-175363 Summary of the Invention [Problem to be solved by the invention]

[0004] In the above-described power system, if a voltage is boosted in each phase of the motor and inverter despite an abnormality in one of the U-, V-, or W-phase current sensors that detects the current in the U-, V-, or W-phase of the motor, the voltage will not be boosted (current regulation) appropriately in the phase corresponding to the current sensor with the abnormality, causing a circulating current to flow through the motor and inverter, which could cause them to overheat. The power system disclosed herein primarily aims to detect an abnormality in the U-, V-, and W-phase current sensors. [Means for solving the problem]

[0005] The power system of the present disclosure employs the following means to achieve the above-mentioned primary object: The power system of the present disclosure is a power system including a motor having a three-phase coil, a three-phase inverter connected to the motor, and one or more batteries connected to the inverter, and includes U-phase, V-phase, and W-phase current sensors that detect currents in the U-phase, V-phase, and W-phase of the motor, a neutral point current sensor that detects a current at the neutral point, and a neutral point current sensor that detects a current at the neutral point during external charging in which power from an external power source is supplied to at least a part of the one or more batteries with voltage conversion by the motor and the inverter. and a control device that controls the currents of the U, V, and W phases so that differences between current commands for the U, V, and W phases based on a current command and the detection values ​​of the U, V, and W phase current sensors are canceled out, and the control device determines whether an abnormality has occurred in at least one of the U, V, and W phase current sensors by comparing converted values ​​obtained by converting the detection value of the neutral point current sensor to current values ​​for the U, V, and W phases with the detection values ​​of the U, V, and W phase current sensors during the external charging.

[0006] In the power system of the present disclosure, during external charging, the detected value of the neutral point current sensor is converted into U-phase, V-phase, and W-phase current values, and the converted values ​​are compared with the detected values ​​of the U-phase, V-phase, and W-phase current sensors to determine whether an abnormality has occurred in at least one of the U-phase, V-phase, and W-phase current sensors. In this way, an abnormality in the U-phase, V-phase, and W-phase current sensors can be detected. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a schematic configuration diagram of a power system 20 according to an embodiment of the present disclosure. [Figure 2] 10 is a flowchart illustrating an example of a processing routine. [Figure 3] FIG. 10 is a schematic configuration diagram of a power system 20 according to a modified example. DETAILED DESCRIPTION OF THE INVENTION

[0008] A mode (embodiment) for carrying out the present disclosure will be described with reference to the drawings. Fig. 1 is a schematic configuration diagram of a power system 20 according to an embodiment of the present disclosure. As shown in the figure, the power system 20 according to the embodiment includes a motor 22, an inverter 24, a capacitor 25, a battery 26, a connector 40, a relay R, and an electronic control unit 50. The power system 20 is used in electric vehicles and hybrid vehicles.

[0009] The motor 22 is configured as a three-phase AC motor having a rotor with a permanent magnet embedded in the rotor core and a stator with three-phase (U-phase, V-phase, and W-phase) coils wound around the stator core. The inverter 24 includes six transistors T11 to T16 and six diodes D11 to D13 connected in parallel to the six transistors T11 to T16, respectively. The transistors T11 to T16 are arranged in pairs, two at a time, on the source side and two at the sink side with respect to a positive line 30p and a negative line 30n to which a battery 26 is connected. The connection points of two transistors in each pair of the transistors T11 to T16 are connected to the U-phase, V-phase, and W-phase coils of the motor 22, respectively. The capacitor 25 is connected to the positive line 30p and the negative line 30n. The battery 26 is configured as, for example, a lithium-ion secondary battery or a nickel-metal hydride secondary battery, and is connected to the inverter 24 via the positive line 30p and the negative line 30n.

[0010] Connector 40 is configured to be connectable to a connector of a charging stand provided at home, at a charging stand, or the like, and is connected to the neutral point of motor 22 via positive line 42p and relay R, and to negative line 30n via negative line 42n. A capacitor 43 is connected to positive line 42p and negative line 42n. Relay R connects and disconnects the neutral point of motor 22 to positive line 42p by turning on and off. When relay R is on, a three-phase boost converter is formed by motor 22 and inverter 24 between positive line 42p and negative line 42n and positive line 30p and negative line 30n. Specifically, a U-phase boost converter is formed by the U-phase coil of motor 22 and transistors T11 and T14, a V-phase boost converter is formed by the V-phase coil of motor 22 and transistors T12 and T15, and a W-phase boost converter is formed by the W-phase coil of motor 22 and transistors T13 and T16.

[0011] The electronic control unit 60 includes a microcomputer. The electronic control unit 60 receives inputs of the rotational position θm of the rotor of the motor 22 from the rotational position sensor 22a, currents Iu, Iv, and Iw of the U-phase, V-phase, and W-phase of the motor 22 from current sensors 22u, 22v, and 22w, the voltage Vb of the battery 26 from the voltage sensor 26v, the current Ib of the battery 26 from the current sensor 26i, and the current In flowing to the neutral point of the motor 22 from the current sensor 42a. The electronic control unit 60 outputs control signals to the transistors T11 to T16 of the inverter 24 and to the relay R. The electronic control unit 60 calculates the state of charge (SOC) of the battery 26 based on the integrated value of the current Ib of the battery 26. The electronic control unit 60 is capable of communicating with a charging stand.

[0012] In the power system 20 of the embodiment, when external charging is performed to charge the battery 26 using power from a charging stand, the inverter 24 is controlled so that the power supplied from the charging stand to the neutral point of the motor 22 is boosted by the three-phase boost converter (motor 22 and inverter 24) and then supplied to the battery 26. Basically, the electronic control unit 50 sets a current command In* for the neutral point of the motor 22 based on the power storage rate SOC of the battery 26 and transmits the set current to the charging stand, and causes the current of the current command In* to flow from the charging stand to the neutral point of the motor 22. Next, one-third of the current command In* is set as the current commands Iu*, Iv*, Iw* for the U, V, and W phases, and duty commands Du*, Dv*, Dw* for the U, V, and W phases are set by current feedback control so that the differences between the current commands Iu*, Iv*, Iw* for the U, V, and W phases and the currents Iu, Iv, Iw for the U, V, and W phases are canceled out. Then, the duty commands Du*, Dv*, Dw* for the U, V, and W phases are used to control the switching of transistors T11 to T16 of inverter 24.

[0013] Next, the operation of the power system 20 according to the embodiment, particularly the diagnosis of an abnormality of the current sensors 22u, 22v, and 22w during external charging, will be described. Fig. 2 is a flowchart showing an example of a processing routine repeatedly executed by the electronic control unit 50 during external charging when an abnormality has not been determined (detected) in any of the current sensors 22u, 22v, and 22w. When this routine is executed, the electronic control unit 50 determines whether the absolute value of the value (In / 3 - Iu) obtained by subtracting the U-phase current Iu from the current sensor 22u from one-third of the neutral point current In of the motor 22 from the current sensor 42a is greater than a threshold value ΔIref (step S100). If it is determined that the absolute value of the value (In / 3 - Iu) is greater than the threshold value ΔIref, the electronic control unit 50 determines (detects) an abnormality in the current sensor 22u (step S110) and terminates this routine. In this case, the U-phase current Iu used in the above-described current feedback control can be obtained by subtracting the V-phase and W-phase currents Iv and Iw from the current sensors 22v and 22w from the neutral point current In of the motor 22, instead of the detection value of the current sensor 22u. This can prevent a situation in which an appropriate voltage increase (current adjustment) is not performed in the U-phase, causing a circulating current to flow through the motor 22 and the inverter 24, resulting in overheating.

[0014] If it is determined in step S100 that the absolute value of the value (In / 3-Iu) is equal to or less than the threshold value ΔIref, the process determines whether the absolute value of the value (In / 3-Iv) obtained by subtracting the V-phase current Iv from the current sensor 22v from one-third of the current In at the neutral point of the motor 22 is greater than the threshold value ΔIref (step S120). If it is determined that the absolute value of the value (In / 3-Iv) is greater than the threshold value ΔIref, the process determines (detects) an abnormality in the current sensor 22v (step S130), and terminates the routine. In this case, the value obtained by subtracting the U-phase and W-phase currents Iu and Iw from the current sensors 22u and 22w from the current In at the neutral point of the motor 22 may be used as the V-phase current Iv used for current feedback control, instead of the value detected by the current sensor 22v. This prevents a situation in which the V-phase is not properly boosted, resulting in a circulating current through the motor 22 and the inverter 24, which could cause them to overheat.

[0015] If it is determined in step S120 that the absolute value of the value (In / 3-Iv) is equal to or less than the threshold value ΔIref, the process determines whether the absolute value of the value (In / 3-Iw) obtained by subtracting the W-phase current Iw from the current sensor 22w from one-third of the current In at the neutral point of the motor 22 is greater than the threshold value ΔIref (step S140). If it is determined that the absolute value of the value (In / 3-Iw) is greater than the threshold value ΔIref, the process determines (detects) an abnormality in the current sensor 22w (step S150), and terminates the routine. In this case, the value obtained by subtracting the U-phase and V-phase currents Iu and Iv from the current sensors 22u and 22v from the current In at the neutral point of the motor 22 can be used as the W-phase current Iw used for current feedback control, instead of the value detected by the current sensor 22w. This prevents a situation in which the W-phase is not properly boosted, resulting in a circulating current through the motor 22 and the inverter 24, which can cause them to overheat. If it is determined in step S140 that the absolute value of the value (In / 3-Iw) is greater than the threshold value ΔIref, it is determined that all of the current sensors 22u, 22v, 22w are normal (step S160), and this routine ends.

[0016] In the power system 20 according to the embodiment described above, whether an abnormality has occurred in any of the current sensors 22u, 22v, 22w is determined by comparing the absolute value of the difference obtained by subtracting the U-phase, V-phase, and W-phase currents Iu, Iv, and Iw from the current sensors 22u, 22v, and 22w from one-third of the neutral point current In of the motor 22 from the current sensor 42a with the threshold value ΔIref. In this way, an abnormality in the current sensors 22u, 22v, and 22w can be detected.

[0017] In the above-described embodiment, the current commands Iu*, Iv*, and Iw* for the U, V, and W phases are set to one-third of the current command In*, but this is not limiting. For example, taking into consideration the heat generation characteristics of each phase of the motor 22 and the inverter 24, the current commands Iu*, Iv*, and Iw* may be set to the products of the current command In* and the coefficients k1, k2, and k3 (k1+k2+k3=1). In this case, whether an abnormality has occurred in any of the current sensors 22u, 22v, and 22w may be determined by comparing the absolute value of the product of the current In from the current sensor 42a and the coefficients k1, k2, and k3 minus the currents Iu, Iv, and Iw from the current sensors 22u, 22v, and 22w with the threshold values ​​ΔIrefu, ΔIrefv, and ΔIrefw, respectively.

[0018] In the above-described embodiment, the power system 20 has been described, but the present invention is not limited to this. For example, the configuration of the power system 120 may be that of a modified example shown in Fig. 3. The power system 120 differs from the power system 20 in that the battery 26, the positive line 30p and the negative line 30n, and the connector 40 are replaced with a battery 126, a relay circuit 130, and a connector 140, and in that an inverter 124 and a capacitor 125 are added.

[0019] The inverter 24 is connected to a positive line 131p and a negative line 131n. The connection points of two pairs of transistors T11 to T16 of the inverter 24 are connected to one end of the three-phase (U-phase, V-phase, W-phase) coils of the motor 22. The inverter 124, like the inverter 24, includes six transistors T21 to T26 and six diodes D21 to D26. The transistors T21 to T16 are arranged in pairs, two on the source side and two on the sink side, with respect to a positive line 126p connected to the second parallel line 137 and a negative line 126n connected to the negative line 131n. The connection points of two pairs of transistors T21 to T26 are connected to the other end of the three-phase (U-phase, V-phase, W-phase) coils of the motor 22. The capacitor 125 is connected to the positive line 126p and the negative line 126n.

[0020] The battery 126 includes a first battery 127 and a second battery 128. The first battery 127 and the second battery 128 are configured similarly to the battery 26. The positive terminal of the first battery 127 is connected to a positive line 131p, and the negative terminal of the second battery 128 is connected to a negative line 131n. The negative terminal of the first battery 127 is connected to the positive terminal of the second battery 128 via a series line 135 to which a relay R1 is attached. Therefore, by turning on the relay R1, the first battery 127 and the second battery 128 function as a single battery connected in series.

[0021] In addition to the positive line 131, the negative line 131n, the series line 135, and the relay R1, the relay circuit 130 has a first parallel line 136 connecting the negative terminal of the first battery 127 and the negative line 131n, a second parallel line 137 connecting the positive terminal of the second battery 128 and the positive line 126p, a relay R2 attached to the first parallel line 136, a relay R3 attached to the second parallel line 137, and a capacitor 138 connected to the negative line 131n and the second parallel line 137 closer to the positive terminal of the second battery 128 than the relay R3. A connector 140 is connected to the positive line 131p and the negative line 131n. Connector 140 is configured to be connectable to a connector of a charging stand, similar to connector 40, and is connected to positive line 131p and negative line 131n, and also to negative line 30n via negative line 42n. Therefore, by turning on relays R2 and R3, the first battery 127 and second battery 128 can be charged in parallel by power supplied from the charging stand to connector 140. First battery 127 is charged by a charging current that flows through connector 140, positive line 131p, first battery 127, first parallel line 136, and connector 140 in this order. By turning on the upper arm (transistors T11 to T13) of the inverter 24 and switching on the transistors T21 to T26 of the inverter 124, the second battery 128 is charged by a charging current that flows in this order through the connector 140, the positive line 131p, the upper arm of the inverter 24, the motor 22, the inverter 124, the second parallel line 137, the second battery 128, the negative line 131n, and the connector 140. At this time, the voltage is boosted by the motor 22 and the inverter 124.

[0022] Electronic control unit 60 receives inputs of rotational position θm of the rotor of motor 22 from rotational position sensor 22a, currents Iu, Iv, Iw of U-phase, V-phase, and W-phase of motor 22 from current sensors 22u, 22v, and 22w, as well as voltage Vb1 of first battery 127 from voltage sensor 127v, voltage Vb2 of second battery 128 from voltage sensor 128v, current Ip of positive electrode line 131p from current sensor 131a, and current In2 of second parallel line 137 from current sensor 137a. Electronic control unit 60 outputs control signals to relays R1, R2, and R3 and control signals to transistors T21 to T26 of inverter 150 in addition to control signals to transistors T11 to T16 of inverter 24.

[0023] In the power system 120 of the modified example, the current In2 on the second parallel line 137 from the current sensor 137a is converted into U-phase, V-phase, and W-phase currents Iu, Iv, and Iw from the current sensors 22u, 22v, and 22w. The absolute value of the difference is then subtracted from each converted value, and the resulting difference is compared with a threshold value ΔIref to determine whether an abnormality has occurred in any of the current sensors 22u, 22v, and 22w. In this manner, an abnormality in the current sensors 22u, 22v, and 22w can be detected.

[0024] In the modified power system 120, the inverter 124, the capacitor 125, the positive line 126p, and the negative line 126n may be omitted, and the second parallel line 137 may be connected to the neutral point of the motor 22.

[0025] The above describes the forms for implementing the present disclosure using embodiments, but the present disclosure is not limited to these embodiments in any way, and it goes without saying that the present disclosure can be implemented in various forms within the scope that does not deviate from the gist of the present disclosure. [Industrial Applicability]

[0026] The present disclosure is applicable to the power system manufacturing industry and the like. [Explanation of symbols]

[0027] 20 power system, 22 motor, 22u,22v,22w,42a current sensor, 24 inverter, 26 battery, 60 electronic control unit.

Claims

[Claim 1] A power system comprising: a motor having a three-phase coil; a three-phase inverter connected to the motor; and one or more batteries connected to the inverter, U-phase, V-phase, and W-phase current sensors for detecting U-phase, V-phase, and W-phase currents of the motor; a neutral point current sensor that detects a current at the neutral point; a control device that controls currents of the U-phase, V-phase, and W-phase so that differences between current commands for the U-phase, V-phase, and W-phase based on a current command at the neutral point and detection values ​​of the U-phase, V-phase, and W-phase current sensors are canceled out during external charging in which electric power from an external power supply is supplied to at least a part of the one or more batteries with voltage conversion by the motor and the inverter; Equipped with the control device, during the external charging, determines whether or not an abnormality has occurred in at least one of the U-phase, V-phase, and W-phase current sensors by comparing each converted value obtained by converting the detection value of the neutral point current sensor into the current value of the U-phase, V-phase, and W-phase with each detection value of the U-phase, V-phase, and W-phase current sensors; Power system.

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