Driving device for wound-field rotary electric machine

Abstract

To achieve control of low loss when increasing a current to flow in a rotor coil, and reduce system loss that may increase when decreasing the current to flow in the rotor coil.SOLUTION: A driving device for a wound-field rotary electric machine is disclosed comprising a first switching element between one end of a rotor coil and a high potential side line of a power supply, a second switching element between the other end of the rotor coil and a low potential side line of the power supply, and a control unit. When decreasing a current to flow in the rotor coil, the control unit drives the rotary electric machine in a first mode for switching the states of both the first switching element and second switching element between an on state and an off state, and when increasing the current to flow in the rotor coil, drives the rotary electric machine in a second mode for switching the state of one of the first switching element and second switching element between the on state and the off state while maintaining the state of the other in the on state.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a drive device for a wound field type rotating electric machine. [Background technology]

[0002] Regarding a wound-field type rotating electric machine arranged around the crankshaft of an internal combustion engine, a technique is known in which, when supplying current to a rotor winding, a first switching element electrically connected between a power source and a brush is PWM-controlled (Pulse Width Modulation), while a second switching element electrically connected between the brush and ground is controlled to be in a constantly on state. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2017-055533 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the above-described conventional techniques, when the current flowing through the rotor winding is reduced, the rate at which the current is reduced tends to be slow, which may result in increased system loss.

[0005] Therefore, in one aspect, the present disclosure aims to reduce system losses that may increase when the current flowing through the rotor winding is reduced, while achieving low-loss control when the current flowing through the rotor winding is increased. [Means for solving the problem]

[0006] According to one aspect, there is provided a drive device for a wound field type rotating electric machine that drives a wound field type rotating electric machine in which a rotor winding is wound around a rotor core, the drive device comprising: a first switching element electrically connected between one end of the rotor winding and a high potential side line of a power supply; a second switching element electrically connected between the other end of the rotor winding and a low potential side line of the power supply; a control device for controlling the first switching element and the second switching element, The control device drives the first switching element and the second switching element in a first mode in which the states of both the first switching element and the second switching element are switched between on and off when the current flowing through the rotor winding is reduced, and drives the first switching element and the second switching element in a second mode in which one of the first switching element and the second switching element is maintained in an on state while the other is switched between on and off when the current flowing through the rotor winding is increased. Effect of the Invention

[0007] In one aspect, the present disclosure makes it possible to achieve low-loss control when increasing the current flowing through the rotor winding, while reducing system losses that may increase when reducing the current flowing through the rotor winding. [Brief description of the drawings]

[0008] [Figure 1] 1 is a configuration diagram showing a vehicle drive system including a drive device for a rotating electric machine according to an embodiment of the present invention; [Diagram 2] 2 is a schematic cross-sectional view showing a part of a cross section of a rotating electric machine; [Diagram 3] FIG. 2 is a diagram illustrating an example of various functions implemented by a microcomputer according to the present embodiment. [Figure 4] 4 is a flowchart showing an example of processing related to each function shown in FIG. 3 and executed by a microcomputer. [Diagram 5] 11A to 11C are diagrams illustrating examples of various waveforms when switching from a single arm drive mode to a double arm drive mode. [Figure 6] 6 is an explanatory diagram of a current (rotor winding current) flowing through a rotor winding in a specific period in FIG. 5. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Each embodiment will be described in detail below with reference to the accompanying drawings. Note that the dimensional ratios in the drawings are merely examples and are not intended to be limiting, and shapes and the like in the drawings may be partially exaggerated for the sake of explanation.

[0010] Fig. 1 is a configuration diagram showing a vehicle drive system 1 including a drive device 5 for a rotating electric machine according to this embodiment. Fig. 2 is a schematic cross-sectional view showing a part of a cross section of a rotating electric machine 3.

[0011] The vehicle drive system 1 has a dual power supply configuration including a low-voltage battery 2A and a high-voltage battery 2B, and includes a rotating electric machine 3 and a drive device 5.

[0012] The low-voltage battery 2A is, for example, a lead battery, and has a rated voltage of, for example, 12V.

[0013] The high-voltage battery 2B is, for example, a lithium-ion battery, and has a rated voltage significantly higher than that of the low-voltage battery 2A, for example, a rated voltage of 40 V or more. In this embodiment, as an example, the rated voltage of the high-voltage battery 2B is 300 V or more. The high-voltage battery 2B may be in the form of a fuel cell or the like.

[0014] The rotating electric machine 3 is of a wound field type and includes a rotor 310 having a rotor winding 316 wound around a rotor core 312. As shown in Fig. 2, the rotor core 312 has teeth 3122 protruding radially outward, and a conductor wire forming the rotor winding 316 is wound around the teeth 3122. A stator 320 is provided radially outward of the rotor 310. The stator winding 322 is wound around the teeth 3210 of the stator core 321, as shown in Fig. 2.

[0015] The driving device 5 includes a microcomputer 50 (hereinafter referred to as “microcomputer 50”) and an electric circuit section 60.

[0016] The microcomputer 50 may be realized as, for example, an ECU (Electronic Control Unit). The microcomputer 50 is connected to various electronic components (other ECUs and sensors) in the vehicle via a network 6 such as a CAN (Controller Area Network).

[0017] The microcomputer 50 receives various commands such as control commands from a higher-level ECU (not shown) via the network 6. Based on the control commands, the microcomputer 50 controls the rotating electric machine 3 via the electric circuit unit 60. The microcomputer 50 operates based on power from the low-voltage battery 2A.

[0018] The electric circuit section 60 includes a smoothing capacitor 62 , a power conversion circuit section 63 , and a power supply circuit section 64 .

[0019] The smoothing capacitor 62 is provided between the high potential side line 20 and the low potential side line 22 of the high voltage battery 2B. Both ends of the smoothing capacitor 62 may be connected to a resistor R0 for passive discharge.

[0020] The power conversion circuit unit 63 is in the form of an inverter, and forms, for example, a three-phase bridge circuit. The power conversion circuit unit 63 is connected between the high potential side line 20 and the low potential side line 22 in a manner that the power conversion circuit unit 63 is in parallel with the smoothing capacitor 62. The power conversion circuit unit 63 includes switching elements SW3 of a high potential side arm and switching elements SW4 of a low potential side arm.

[0021] The power supply circuit section 64 includes a bridge circuit section 641 and a drive circuit section 642 .

[0022] The bridge circuit section 641 is connected in parallel with the smoothing capacitor 62 and the resistor R0 for passive discharge between the high potential side line 20 and the low potential side line 22. The bridge circuit section 641 includes a pair of switching elements SW1, SW2 and a pair of diodes D1, D2.

[0023] The switching element SW1 is connected in series to the diode D1 in such a manner that the switching element SW1 is connected to the cathode on the high potential side of the diode D1. One end of the rotor winding 316 is connected between the switching element SW1 and the diode D1. The switching element SW2 is connected in series to the diode D2 in such a manner that the switching element SW2 is connected to the anode on the low potential side of the diode D2. The other end of the rotor winding 316 is connected between the switching element SW2 and the diode D2. Hereinafter, for the sake of distinction, the switching element SW1 and the configuration related thereto of the pair of switching elements SW1, SW2 may be referred to as the "high potential side", and the switching element SW2 and the configuration related thereto may be referred to as the "low potential side".

[0024] The pair of switching elements SW1, SW2 are switched between on and off states via the drive circuit unit 642. The pair of switching elements SW1, SW2 change the state of current flow to the rotor winding 316 under the control of the drive circuit unit 642. The switching elements SW1, SW2 are, for example, insulated gate bipolar transistors (IGBTs), but may be of other types such as metal oxide semiconductor field-effect transistors (MOSFETs).

[0025] The drive circuit section 642 drives the gate of the high potential side switching element SW1 based on a control signal from the microcomputer 50, and drives the gate of the low potential side switching element SW2 based on a control signal from the microcomputer 50.

[0026] Next, the characteristic configuration of this embodiment will be described with reference to FIG.

[0027] FIG. 3 is a diagram illustrating an example of various functions implemented by the microcomputer 50 of the present embodiment.

[0028] The microcomputer 50 includes an inverter control unit 500 and a rotor winding energization control unit 510 .

[0029] The inverter control unit 500 controls the on / off state of each of the switching elements SW3, SW4 of the power conversion circuit unit 63 via the gate driver circuit 52, thereby controlling the energization of the stator windings 322. At this time, the inverter control unit 500 may calculate a control target value based on a control command (e.g., a required torque value) from a higher-level ECU (not shown), and control the energization of the stator windings 322 so that the control target value is realized.

[0030] The rotor winding energization control unit 510 controls the energization state of the rotor winding 316 of the rotating electric machine 3 via the drive circuit unit 642. At this time, the inverter control unit 500 may calculate a control target value (e.g., a target current value) based on a control command (e.g., a required torque value) from a higher-level ECU (not shown), and control energization of the rotor winding 316 so that the control target value is realized.

[0031] In this embodiment, the rotor winding energization control unit 510 includes a determination information acquisition unit 512, a switching condition determination unit 514, a both-arm drive control unit 516, and a one-arm drive control unit 518, as shown in FIG.

[0032] The determination information acquisition unit 512 acquires determination information used in a switching condition determination process by the switching condition determination unit 514, which will be described later. The determination information to be acquired is determined according to the switching condition determination process, and some examples will be described later.

[0033] The switching condition determination unit 514 executes a switching condition determination process for determining whether a switching condition is satisfied. The switching condition is a condition for switching between a both-arm drive mode (an example of a first mode) in which the both-arm drive control unit 516 operates and a one-arm drive mode (an example of a second mode) in which the one-arm drive control unit 518 operates, and is specified in advance.

[0034] In this embodiment, the switching conditions are basically defined in advance so that the one-arm drive mode is formed when the current flowing through the rotor winding 316 is increased, and the two-arm drive mode is formed when the current flowing through the rotor winding 316 is decreased. Note that the switching conditions may function in such a manner that such a basic relationship is impaired under exceptional circumstances. Such exceptional circumstances are optional and may not exist, and will not be specifically mentioned below.

[0035] The success or failure of the switching condition may be determined based on control information related to the magnitude of the current flowing through the rotor winding 316 so that the one-arm drive mode is formed when the current flowing through the rotor winding 316 is increased, and the two-arm drive mode is formed when the current flowing through the rotor winding 316 is decreased. In this case, the success or failure of the switching condition can be easily determined based on various types of control information that are easily obtained.

[0036] For example, the switching condition from the one-arm drive mode to the two-arm drive mode may be determined based on a current command (e.g., a target duty) for the rotor winding 316. In this case, the switching condition may be satisfied when the current command in the current cycle is lower than that in the previous cycle. In this case, the determination information to be acquired includes a current command for the rotor winding 316. Alternatively, the switching condition may be determined based on a detection value (an output value of a current sensor or a value after filtering thereof) of a current flowing through the rotor winding 316. In this case, the switching condition may be satisfied when the detection value of the current in the current cycle is lower than that in the previous detection cycle. In this case, the determination information to be acquired includes a detection value of a current flowing through the rotor winding 316. Alternatively, the switching condition may be satisfied when the current command is lower than the detection value of the current by a threshold value or more. Alternatively, the switching condition from the one-arm drive mode to the two-arm drive mode may be determined based on a current command for the stator winding 322. In this case, the switching condition may be satisfied when the current command in the current cycle is lower than that in the previous cycle. Similarly, the switching condition may be determined based on a detection value (the output value of the current sensor or its filtered value) of the current flowing through the stator winding 322. In this case, the switching condition may be satisfied when the detection value of the current in the current detection period is lower than that in the previous detection period.

[0037] Also, the switching condition from the both-arm drive mode to the one-arm drive mode may be determined based on a current command for the rotor winding 316. In this case, the switching condition may be satisfied when the current command for the current cycle increases compared to the previous cycle. Alternatively, the switching condition may be determined based on a detection value of the current flowing through the rotor winding 316 (the output value of the current sensor or its filtered value). In this case, the switching condition may be satisfied when the detection value of the current flowing through the rotor winding 316 increases compared to the previous detection cycle. Alternatively, the switching condition may be satisfied when the current command exceeds the detection value of the current by a threshold value or more. Alternatively, the switching condition from the both-arm drive mode to the one-arm drive mode may be determined based on a current command for the stator winding 322. In this case, the switching condition may be satisfied when the current command for the current cycle increases compared to the previous cycle. Similarly, the switching condition may be determined based on a detection value of the current flowing through the stator winding 322 (the output value of the current sensor or its filtered value). In this case, the switching condition may be satisfied when the detection value of the current flowing through the stator winding 322 increases compared to the previous detection cycle.

[0038] When the switching condition from the single arm drive mode to the single arm drive mode is satisfied, the both arm drive control unit 516 may operate until the switching condition from the both arm drive mode to the single arm drive mode is satisfied. During operation, the both arm drive control unit 516 realizes both arm drive by turning on / off both switching elements SW1 and SW2 with a duty corresponding to a current command (current command related to the rotor winding 316). At this time, the both arm drive control unit 516 may realize both arm drive in a mode in which the switching elements SW1 and SW2 are simultaneously turned on (and accordingly turned off simultaneously).

[0039] When the condition for switching from the both-arm drive mode to the one-arm drive mode is satisfied, the one-arm drive control unit 518 may operate until the condition for switching from the one-arm drive mode to the both-arm drive mode is satisfied. During operation, the one-arm drive control unit 518 realizes one-arm drive in which only one of the switching elements SW1 and SW2 (in this embodiment, the switching element SW1 on the high potential side) is turned on / off with a duty corresponding to a current command (a current command related to the rotor winding 316).

[0040] Fig. 4 is a flowchart showing an example of processing related to each function shown in Fig. 3 and executed by the microcomputer 50. The processing routine shown in Fig. 4 may be repeatedly executed at predetermined intervals.

[0041] In step S400, the microcomputer 50 acquires information for determination. The information for determination may be as described above.

[0042] In step S402, the microcomputer 50 judges whether or not the switching condition is satisfied based on the judgment information acquired in step S400. For example, if the current drive mode is the single-arm drive mode, it is judged whether or not the switching condition from the single-arm drive mode to the double-arm drive mode is satisfied. Also, if the current drive mode is the double-arm drive mode, it is judged whether or not the switching condition from the double-arm drive mode to the single-arm drive mode is satisfied. If the switching condition is satisfied, the process proceeds to step S406 via step S404. On the other hand, if the switching condition is not satisfied, the process proceeds directly to step S406. In this case, the current drive mode is maintained without change.

[0043] In step S404, the microcomputer 50 switches the current drive mode to the drive mode to be switched to. For example, if the condition for switching from the both-arm drive mode to the one-arm drive mode is met in step S402, the microcomputer 50 switches the current drive mode to the one-arm drive mode to be switched to.

[0044] In step S406, the microcomputer 50 executes drive control according to the current drive mode. For example, when the current drive mode is the both-arm drive mode, the above-mentioned both-arm drive control unit 516 operates.

[0045] Next, the effects of this embodiment will be described with reference to FIGS.

[0046] Fig. 5 is a diagram showing an example of various waveforms when switching from the single-arm drive mode to the double-arm drive mode. Fig. 5 shows, from the top, a carrier signal, an on / off state of the high-potential side switching element SW1 (represented as "upper arm" in Fig. 5), an on / off state of the low-potential side switching element SW2 (represented as "lower arm" in Fig. 5), and a current flowing through the rotor winding 316 (represented as "rotor winding current" in Fig. 5). Fig. 6 is an explanatory diagram of the current flowing through the rotor winding 316 (rotor winding current) during a specific period T in Fig. 5. Fig. 6 shows a schematic dotted line of a control waveform I'o when the single-arm drive mode is continued.

[0047] In the example shown in Fig. 5, the target duty is relatively high until time t1, and the current flowing through the rotor winding 316 increases. Note that the carrier signal in Fig. 5 is a carrier signal for PWM control. In Fig. 5, a waveform 500 that correlates with the target duty is shown for the carrier signal. The level of waveform 500 decreases as the target duty increases, and the period during which the carrier signal exceeds the level of waveform 500 corresponds to the on-period.

[0048] In this case, up until time t1, the single-arm drive mode is realized, and while the high-potential side switching element SW1 is maintained in the on state, only the low-potential side switching element SW2 is switched between on and off states according to the target duty.

[0049] After time t1, the target duty decreases, and the current flowing through the rotor winding 316 decreases accordingly. Then, between time t1 and time t2, the condition for switching from the single-arm drive mode to the double-arm drive mode is satisfied, and at time t2, the double-arm drive mode is started. Specifically, at time t2, the high-potential side switching element SW1 is turned off, and thereafter, the high-potential side switching element SW1 and the low-potential side switching element SW2 are switched between on and off states according to the target duty. At this time, as shown in FIG. 5, the high-potential side switching element SW1 and the low-potential side switching element SW2 are turned on and off at substantially the same timing.

[0050] Here, in this embodiment, as described above, the switching conditions are defined so that the two-arm drive mode is established when the current flowing through the rotor winding 316 is reduced. In this regard, it is also possible to reduce the current flowing through the rotor winding 316 while maintaining the one-arm drive mode.

[0051] However, when the current flowing through the rotor winding 316 is reduced in the single-arm drive mode, there is a problem in that the current reduction rate is slower than when the current flowing through the rotor winding 316 is reduced in the double-arm drive mode. The current reduction rate represents the amount of reduction in current per unit time when the current flowing through the rotor winding 316 is reduced. Specifically, the current reduction rate v1 in the double-single-arm drive mode can be expressed as follows: v1=di / dt=(-Vi-Io×R-2×VF) / L Here, Vi is the power supply voltage (the voltage of the high-voltage battery 2B, which is equivalent to the voltage across the smoothing capacitor 62), Io is the magnitude of the current flowing through the rotor winding 316, R is the resistance of the rotor winding 316, VF is the voltage across the diodes D1 and D2 (see FIG. 1) of the bridge circuit section 641, and L is the inductance of the rotor winding 316. In contrast, the current decrease rate v2 in the single arm drive mode can be expressed as follows: v2=di / dt=(-Io×R-VF-VCE) / L Here, VCE is the on-voltage of the switching elements SW1 and SW2. In this case, since Vi>>VCE, |v1|>|v2|, and therefore the current decrease speed becomes slow in the single-arm drive mode.

[0052] If the current reduction speed is slow in response to the reduction in the target duty (i.e., if the response is not good), the system loss (loss in the entire drive system) increases. In other words, a current (see ΔI in FIG. 6) that is more than necessary flows through the rotor winding 316, and the system loss increases accordingly.

[0053] In this regard, according to this embodiment, the double-arm drive mode is established when the current flowing through the rotor winding 316 is reduced, making it possible to reduce system loss that can increase when the current flowing through the rotor winding is reduced. On the other hand, according to this embodiment, the single-arm drive mode is established when the current flowing through the rotor winding 316 is increased, making it possible to minimize switching loss when the current flowing through the rotor winding 316 is increased.

[0054] Although each embodiment has been described above in detail, the present invention is not limited to the specific embodiment, and various modifications and changes are possible within the scope of the claims. In addition, it is also possible to combine all or a plurality of the components of the above-described embodiments. [Explanation of symbols]

[0055] 3... rotating electric machine, 312... rotor core, 316... rotor winding, 321... stator core, 5... drive device (drive device for rotating electric machine), 50... microcomputer (control device), SW1... switching element (first switching element), SW2... switching element (second switching element)

Claims

1. A drive device for a winding field type rotating electric machine that drives a winding field type rotating electric machine in which a rotor winding is wound around a rotor core, a first switching element electrically connected between one end of the rotor winding and a high potential side line of a power supply; a second switching element electrically connected between the other end of the rotor winding and a low potential side line of the power supply; a control device for controlling the first switching element and the second switching element, The control device drives the drive device for a wound field type rotating electric machine in a first mode in which the states of both the first switching element and the second switching element are switched between on and off when reducing the current flowing through the rotor winding, and drives the drive device in a second mode in which one of the first switching element and the second switching element is maintained in an on state while the other is switched between an on state and an off state when increasing the current flowing through the rotor winding.

2. 2. The drive device for a wound field type rotating electric machine according to claim 1, wherein the control device determines whether a switching condition between the first mode and the second mode is satisfied based on control information related to a magnitude of a current flowing through the rotor winding.

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