Current control device and current control method for permanent magnet synchronous motor

Abstract

A current control device (10) for a permanent magnet synchronous motor (20) outputs current to the permanent magnet synchronous motor, and comprises a plurality of current controllers (10_1, ... ,10_m) that are respectively provided for a plurality of phases (20_1, ... ,20_m) of windings of the permanent magnet synchronous motor provided with the windings of the plurality of phases, that supply current to the windings, and that are connected in parallel to each other. The current control device (10) performs control such that a component, which offsets a reverse phase current generated when an output of one current controller among the plurality of current controllers has been blocked, is superimposed on a current controller for which an output has not been blocked among the plurality of current controllers.

Description

[Technical Field]

[0001] The present application relates to a current control device and a current control method for a permanent magnet synchronous motor. [Background technology]

[0002] Permanent magnet synchronous motors used in industrial and automotive applications have a low failure rate for the motor itself that outputs torque, but the failure rate of the inverter that drives the motor tends to be high. For this reason, a system has been proposed in which the inverter is duplicated so that even if one inverter fails, the other inverter continues to drive the motor (see, for example, Patent Document 1).

[0003] Patent Document 1 discloses that the assist motor that constitutes the electric power steering device is a permanent magnet synchronous motor with two systems of windings, each with three phases. In a system that has a permanent magnet synchronous motor with such three-phase, two-system windings and a current control device (inverter), if the current control device of one system fails, an open / close switch is provided between the permanent magnet synchronous motor and the current control device to cut off the short-circuit current circulating in the failed current control device or the current that causes unstable behavior. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-201199 Summary of the Invention [Problem to be solved by the invention]

[0005] However, with the configuration disclosed in Patent Document 1, when the connection between the current control device and the permanent magnet synchronous motor of the faulty system is cut off and the current supply is interrupted, the power supplied to the permanent magnet synchronous motor is halved, and therefore the torque output is also halved.In addition, the magnetic flux balance of the permanent magnet synchronous motor, which was maintained in balance by the three-phase two system, is lost, and there is a possibility that primary or secondary low-order torque pulsations (hereinafter referred to as torque ripples) that do not occur under normal conditions will occur.

[0006] The present application discloses a technique for solving the above-mentioned problems, and aims to provide a current control device and current control method for a permanent magnet synchronous motor that multiplexes current control devices and can suppress torque reduction and reduce torque ripple even when the connection between the current control device of one of the systems and the permanent magnet synchronous motor is cut off. [Means for solving the problem]

[0007] The current control device for a permanent magnet synchronous motor disclosed in the present application comprises: A current control device for controlling a permanent magnet synchronous motor having multiple phase windings, a current controller provided for each phase of the winding and configured to output a current to be passed through the winding; and a control unit that controls the plurality of current controllers, the plurality of current controllers are connected in parallel with each other; The control unit calculates the negative-phase current from the current of each phase using the symmetric coordinate method, and performs control to superimpose a component that offsets the negative-phase current that occurs when the current output from one of the multiple current controllers is interrupted on the other current controllers. [Effects of the Invention]

[0008] According to the present disclosure, when a fault occurs, only the current of the current controller of the faulty phase is cut off, and current is no longer supplied to only the winding of the phase connected to the faulty current controller, so the torque reduction rate is 1 / m, where m is the number of phases, and it is possible to suppress the reduction in torque output as the number of phases increases.In addition, by generating and superimposing a current that offsets the negative-phase current caused by a fault, it is possible to suppress low-order torque ripple caused by the negative-phase current. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a schematic diagram showing the configuration of a permanent magnet synchronous motor system including a current control device and a permanent magnet synchronous motor according to an embodiment of the present invention; [Figure 2] FIG. 2 is a schematic diagram showing the configuration of a permanent magnet synchronous motor system of Comparative Example 1 according to the present embodiment. [Figure 3] FIG. 10 is a schematic diagram showing the configuration of a permanent magnet synchronous motor system of Comparative Example 2 according to the present embodiment. [Figure 4] 10 is a diagram showing waveforms of currents of each phase flowing in the permanent magnet synchronous motor system of Comparative Example 1. FIG. [Figure 5] 10A and 10B are diagrams showing torque ripples in a permanent magnet synchronous motor system of Comparative Example 1 during normal operation and during a fault. [Figure 6] 10 is a diagram showing waveforms of currents of each phase flowing in the permanent magnet synchronous motor system of Comparative Example 2. FIG. [Figure 7] 10 is a diagram showing torque ripples when a fault occurs in the current control device of the permanent magnet synchronous motor according to the present embodiment. FIG. [Figure 8] 3A and 3B are diagrams showing waveforms of currents of each phase flowing in the permanent magnet synchronous motor system according to the present embodiment. [Figure 9] 10 is a diagram showing waveforms of zero-phase, positive-phase, and negative-phase currents flowing in a current control device of a permanent magnet synchronous motor of Comparative Example 1. FIG. [Figure 10] 3A and 3B are diagrams showing waveforms of zero-phase, positive-phase, and negative-phase currents that flow when a fault occurs in the permanent magnet synchronous motor system according to the present embodiment. [Figure 11]FIG. 2 is a diagram showing an example of a phasor representation of a current flowing in the permanent magnet synchronous motor system according to the present embodiment. [Figure 12] FIG. 10 is a diagram showing an example of a phasor display of a current that flows when a fault occurs in the permanent magnet synchronous motor system according to the present embodiment. [Figure 13] 10 is a diagram showing torque ripples when a fault occurs in the current control device of the permanent magnet synchronous motor according to the present embodiment. FIG. [Figure 14] 4 is a flowchart for explaining a current control method for a permanent magnet synchronous motor according to the present embodiment. [Figure 15] 1 is a diagram showing the relationship between the number of poles p and the number of windings w for maximizing torque in a permanent magnet synchronous motor according to the present embodiment. FIG. [Figure 16] FIG. 1 is a diagram showing an example of a suitable combination of the number of poles p, the number of windings w, and the number of phases m in a permanent magnet synchronous motor according to the present embodiment. [Figure 17] 1 is a hardware configuration diagram of a control unit included in a current control device for a permanent magnet synchronous motor according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0010] This embodiment will be described with reference to the drawings. In each drawing, the same reference numerals indicate the same or corresponding parts. The current control device and current control method for a permanent magnet synchronous motor according to this embodiment are suitable for industrial and automotive permanent magnet synchronous motors.

[0011] Embodiment 1 Hereinafter, a current control device for a permanent magnet synchronous motor according to this embodiment will be described with reference to the drawings. FIG. 1 is a diagram showing the configuration of a permanent magnet synchronous motor system including a permanent magnet synchronous motor and its current control device according to this embodiment. In FIG. 1, a current control device 10 is composed of m (m is an odd number equal to or greater than 3) current controllers 10_1, 10_2, 10_3, 10_4, . . . , 10_m, and the current controllers 10_1, 10_2, 10_3, 10_4, . . . , 10_m are connected in parallel. Each current converter is, for example, an inverter with switching elements configured in a full bridge, as shown in the figure. The switching elements may be, for example, MOSFETs (Metal-Oxide-Semiconductor Field-Effect Transistors), IGBTs (Insulated Gate Bipolar Transistors), or the like.

[0012] Permanent magnet synchronous motor 20 has m-phase windings 20_1, 20_2, 20_3, 20_4, . . . , 20_m. One-phase current controller 10_1 is connected to one-phase winding 20_1, and two-phase current controller 10_2 is connected to two-phase winding 20_2. That is, one current controller is individually connected to one phase winding. Here, the number of windings constituting permanent magnet synchronous motor 20 is not necessarily m, but may be more than m. For example, when the number of poles p=4 and the number of turns k=5, the number of windings k=the number of phases m. However, when p=8 and k=10, which is double the configuration of p=4 and k=5, the number of windings k≠the number of phases m. In this case, the two windings per phase are connected in series or in parallel.

[0013] Motor relays 40_1, 40_2, 40_3, 40_4, 40_m may be arranged between windings 20_1, 20_2, 20_3, 20_4, 20_m and current controllers 10_1, 10_2, 10_3, 10_4, 10_m. The motor relays 40_1, 40_2, 40_3, 40_4, 40_m have a function of cutting off current supply to permanent magnet synchronous motor 20 when a fault occurs in the respective phases.

[0014] Further, a power supply 30 is connected to each of the current controllers 10_1, 10_2, 10_3, 10_4, . . . , 10_m. In Fig. 1, the power supply 30 is a DC power supply, but this may also be an AC power supply. If the power supply 30 is an AC power supply, a circuit for converting AC to DC, such as a converter, is required between the power supply 30 and each of the current controllers 10_1, 10_2, 10_3, 10_4, . . . , 10_m. Switches 50_1, 50_2, 50_3, 50_4, ···, 50_m are arranged between each of the current controllers 10_1, 10_2, 10_3, 10_4, ···, 10_m and the power supply 30 as a cutoff mechanism in case of some kind of failure in each of the current controllers 10_1, 10_2, 10_3, 10_4, ···, 10_m or to prevent a backflow of current to the power supply 30. Here, each of the current controllers 10_1, 10_2, 10_3, 10_4, ···, 10_m has a control unit 101 such as a microcomputer that issues commands. The control unit 101 may be provided for each current controller, or one control unit may collectively control all the current controllers as shown in the figure. The control unit also has a function of detecting a failure in each phase.

[0015] The operation and effects of the current control device according to this embodiment will be described below in comparison with a comparative example. First, the configuration of the comparative example will be described. synchronization In the diagram of the motor system, this is referred to as Comparative Example 1. As shown in FIG. 2, in the permanent magnet synchronous motor system of Comparative Example 1, current control of three phases in one system is performed by one current controller 10A_1, 10A_2. The two current controllers 10A_1, 10A_2 are connected in parallel to a power supply 30A via switches 50A_1, 50A_2. synchronization The motor 20A is a permanent magnet motor with two three-phase systems. synchronizationThe motor includes a first winding system having a one-phase winding 20A_1_1, a two-phase winding 20A_1_2, and a three-phase winding 20A_1_3, and a second winding system having a one-phase winding 20A_2_1, a two-phase winding 20A_2_2, and a three-phase winding 20A_2_3. A current controller 10A_1 is connected to the first winding system via a motor relay 40A_1, and a current controller 10A_2 is connected to the second winding system via a motor relay 40A_2.

[0016] FIG. 3 shows a comparison example of a permanent magnet current control device according to the present embodiment. synchronization This is a diagram of a motor system, which is referred to as Comparative Example 2. This comparative example is a five-phase example. Permanent magnets in Comparative Example 2 synchronization The motor 20B has m-phase (m=5) windings 20B_1, 20B_2, 20B_3, 20B_4, and 20B_5, similar to the present embodiment. Here, the five-phase windings 20B_1, 20B_2, 20B_3, 20B_4, and 20B_5 are individually connected to the current controller 10B via motor relays 40B_1, 40B_2, 40B_3, 40B_4, and 40B_5. However, the five-phase windings 20B_1, 20B_2, 20B_3, 20B_4, and 20B_5 are not connected to individual current controllers, but are connected to a single current controller 10B, and the windings of each phase are connected at the neutral point of the current controller 10B. In addition, the current controller 10B is connected to a power source 30B via a switch 50B. Although this comparative example shows an example of five phases, the same applies to an m-phase motor.

[0017] First, a comparison between the permanent magnet synchronous motor system according to the present embodiment and a permanent magnet synchronous motor system of Comparative Example 1 will be described. Permanent magnet of comparative example 1 synchronization In a motor system, if one winding connected to one current controller fails, or if one element constituting a current controller fails, the current controller on the side where the failure occurred may be shut down. In this case, one of the two current controllers will stop, and the power supplied to permanent magnet synchronous motor 20A will be halved. Therefore, when power is P, angular speed is ω, and torque is T, ignoring losses, the relationship between power P, angular speed ω, and torque T is as follows: P=ωT Therefore, if the power P is halved, the torque T is also halved.

[0018] In contrast, in the permanent magnet synchronous motor system according to this embodiment, the windings of each phase are individually connected to m current controllers, meaning that each phase is independent. Therefore, even if a failure occurs in a winding or current controller of each phase, the current to the failed winding is cut off by stopping only the failed current controller or by turning off either the motor relay or the power switch. Therefore, since one phase is cut off, if the total number of phases is m, the torque reduction is about 1 / m, making it possible to suppress torque reduction more effectively than in the permanent magnet synchronous motor system of Comparative Example 1.

[0019] Furthermore, even if all current controllers are not shut down, the current imbalance that occurs when a fault occurs usually causes low-order torque pulsation (hereinafter referred to as torque ripple) in the torque waveform output by the permanent magnet synchronous motor.

[0020] FIG. 4 shows the current waveforms of each phase of each system in a normal state in the permanent magnet synchronous motor system of Comparative Example 1 shown in FIG. 2, and the current waveforms of each phase when a fault occurs in one-phase winding 20A_1_1 (indicated as phase 1-1 in the figure) of the first system winding. No change is observed in the current waveforms of the second system windings in which no fault occurs, but changes occur in the current waveforms of each phase in the first system windings. The motor relay 40A_1 connected to the one-phase winding 20A_1_1 of the first system winding in which the fault occurs cuts off the winding 20A_1_1. As a result, no current flows through the winding 20A_1_1. However, because the windings connected to each current controller are connected at the neutral point, in the first system where a fault has occurred, the phase of the current flowing through the other unfaulted phase windings 20A_1_2 and 20A_1_3 (referred to as phase 1-2 and phase 1-3 in the figure, respectively) changes from 120° to 180° in an attempt to maintain current balance. Figure 5 shows the change in torque in Comparative Example 1. As shown in Figure 5, the torque waveform, which normally has a minute torque ripple that repeats six pulsations per electrical cycle as shown by the solid line, changes to a large torque ripple waveform that repeats two pulsations per electrical cycle as shown by the dashed line.

[0021] Next, a comparison between the permanent magnet synchronous motor system according to the present embodiment and a permanent magnet synchronous motor system of Comparative Example 2 will be described. 6 shows the current waveforms of each phase in a normal state and when a fault occurs in one-phase winding 20B_1 (denoted as "phase 1" in the figure) in the permanent magnet synchronous motor system of Comparative Example 2 shown in FIG. 3. When a fault occurs in one-phase winding 20B_1, motor relay 40B_1 cuts off winding 20B_1. As a result, the phases of the remaining normal phase windings shift from 72° to 90° to maintain current balance.

[0022] Figure 7 shows changes in torque in the permanent magnet synchronous motor systems according to Comparative Example 2 and the present embodiment. The solid line in Figure 7 represents normal operation, the dashed-dotted line represents the torque waveform assuming a fault in Comparative Example 2, and the dashed line represents the torque waveform assuming a single-phase fault in the present embodiment. During normal operation, as shown by the solid line, a minute torque ripple repeats 10 times per cycle, whereas during a fault, a large torque ripple repeats 2 times per cycle, as shown by the dashed-dotted and dashed lines.

[0023] FIG. 8 is a diagram showing current waveforms flowing through each phase in the permanent magnet synchronous motor system according to the present embodiment shown in FIG. 1. FIG. 8 compares a normal state with a state in which a fault occurs in one phase winding 20_1 or an element of the power controller, causing motor relay 40_1 to be disconnected and current to the faulty phase to be cut off. Even if one phase fails, the phases are not connected at the neutral point, so the current phase does not change in an attempt to balance the currents. That is, because each phase is independently connected to the current controller, it is possible to independently control the phase of each phase. Therefore, unlike the current phase during a fault in Comparative Example 2 in FIG. 6, the phase does not change. Therefore, as can be seen from the comparison of the present embodiment shown by the dashed line in FIG. 7 with Comparative Example 2 shown by the dashed line during a fault, the present embodiment can suppress a decrease in torque output.

[0024] A method for suppressing torque ripple in the permanent magnet synchronous motor system according to the present embodiment described above will now be described.

[0025] The symmetric coordinate method is a method for calculating the occurrence of accidents and faults, such as wire breaks and short circuits, in circuits including motors. This method defines zero-sequence, positive-sequence, and negative-sequence. For example, for the three-phase circuit of the permanent magnet synchronous motor system shown in Figure 2 (Comparative Example 2), Figure 9 shows the currents flowing through the stator when a balanced three-phase AC current is applied as shown in Figure 4 under normal conditions and when a fault occurs as shown in Figure 4. As shown in Figure 9, under normal conditions, only the positive-sequence current has a value, and the zero-sequence current and negative-sequence current are zero. In contrast, when a fault occurs as shown in Figure 4, a negative-sequence current occurs. This negative-sequence current causes torque halving and torque ripple to increase. However, this negative-sequence current cannot be adjusted in Comparative Example 2, where multiple phases are connected to a single current controller and the windings share a neutral point.

[0026] In contrast to this, in the current control device according to the present embodiment, the windings of each phase are individually connected to the current controller, so it is possible to adjust the phase independently for each phase. This method will be described below.

[0027] When the zero-phase current is I0, the positive-phase current is Ip, and the negative-phase current is In, the AC currents of each phase are I1, I2, . . ., I m Using this, I0, Ip, and In are as follows: I0=(I1+I2+I3+I4+···+I i +···+I m ) / m ...Equation (1) Ip=(I1+aI2+a2I3+a3I4+···+a m-1 I m ) / m ...Equation (2) In=(I1+a m-1 I2+a m-2 I3+a m-3 I4+... +a m-i I i +···aI m ) / m...Equation (3) Here, a~a m-1 , I1~I m are complex numbers, ai =exp(j2π / m) (j is the imaginary unit) is. That is, for phase i (1≦i≦m), the current amplitude under normal conditions is I, and a current with a current amplitude of I′=I / m and a phase θi=2π / m×(mi) should be superimposed on each phase.

[0028] FIG. 10 shows current waveforms obtained by converting the current in the case where one-phase winding fault shown in FIG. 8 occurs in the permanent magnet synchronous motor system according to this embodiment into zero-phase, positive-phase, and negative-phase waveforms using the symmetric coordinate method. As can be seen from FIG. 10, a negative-phase current is generated. This negative-phase current is generated when the current in I1 becomes zero in the faulty phase, for example, in the case of a fault in one phase. Therefore, in order to make In zero in the above equation (3), the following must be true: (a m-1 I2+a m-2 I3+a m-3 I4+···+a m-i I i + +aI m ) / m=0...Equation (4)

[0029] Figure 11 shows the phasor representation of the AC current of each phase under normal conditions, for example, in a five-phase AC with m=5, and Figure 12 shows the case when one phase has failed. The horizontal axis of the phasor representation is the real number, and the vertical axis is the imaginary number, and the diagram shows the phase of each current. As shown in Figure 11, under normal conditions, the current flowing through each of the phases 2 to 5 is as follows: I2=Icos(ωt‐2π / 5) I3=Icos(ωt‐4π / 5) I4=Icos(ωt‐6π / 5) I5=Icos(ωt-8π / 5)...Equation (5) is. This indicates that under normal circumstances, the amplitude of the current output by each current controller is I, and the phase of the current output by the i-th (1≦i≦m; i is an integer, here m=5) current controller is delayed by 2×π×(i-1) / m.

[0030] In the event of a fault, the negative-sequence current is calculated using the symmetric coordinate method according to equation (4), and a component that offsets the negative-sequence current generated by the fault in phase 1 is superimposed on each of phases 2 to 5. As shown by the dashed vectors in Figure 12, currents I2' to I5' for phases 2 to 5, on which a component that offsets the negative-sequence current generated by the fault in phase 1 is superimposed, are as follows: I2′=Icos(ωt‐2π / 5)+I′cos(ωt‐8π / 5) I3′=Icos(ωt‐4π / 5)+I′cos(ωt‐4π / 5) I4′=Icos(ωt‐6π / 5)+I′cos(ωt‐6π / 5) I5′=Icos(ωt‐8π / 5)+I′cos(ωt‐2π / 5) ...Equation (6) Here, I′=I / 5.

[0031] The torque waveforms when currents I2' to I5' are applied are shown in Fig. 13. As shown in Fig. 13, torque pulsation is significantly reduced by superimposing a component that cancels out the negative-sequence current. This is because it is now possible to suppress the low-order torque ripple waveforms generated by the negative-sequence current.

[0032] As another example, let us consider the case where m=7 phases. Similarly, let us assume that a fault occurs in one phase. In this case, I'=I / 7, and I2' to I7' are as follows: I2′=Icos(ωt‐2π / 7)+I′cos(ωt‐12π / 7) I3′=Icos(ωt‐4π / 7)+I′cos(ωt‐10π / 7) I4′=Icos(ωt‐6π / 7)+I′cos(ωt‐8π / 7) I5′=Icos(ωt‐8π / 7)+I′cos(ωt‐6π / 7) I6′=Icos(ωt‐10π / 7)+I′cos(ωt‐4π / 7) I7′=Icos(ωt‐12π / 7)+I′cos(ωt‐2π / 7) ...Equation (7)

[0033] Therefore, in the case of m=7 phases, the current Ii', which is the current superimposed on the i-phase when one phase fails and which offsets the negative-sequence current, is Ii′=Icos(ωt‐2π(i−1) / 7) +I / 7×cos(ωt‐2π(7−i) / 7) This becomes:

[0034] That is, in the m-phase, the current output by each current controller under normal conditions is Ii=Icos(ωt‐2π(i−1) / m) When a certain phase fails, the current Ii' obtained by superimposing a component that cancels out the negative-phase current on the other phase i by the control unit of this embodiment is expressed as follows: Ii′=Icos(ωt‐2π(i−1) / m) +I / m×cos(ωt‐2π(mi) / m) is.

[0035] Next, a current control method for a permanent magnet synchronous motor according to this embodiment will be described with reference to the flowchart of Fig. 14. In the following, an example will be taken of a case where a fault occurs in one of the multiple phases. First, in step ST101, the control unit 101 detects a fault in any phase of the permanent magnet synchronous motor 20 or in any of the current controllers 10_1, 10_2, 10_3, 10_4, . . . , 10_m. Although not shown in FIG. 1, the fault can be detected by measuring the current with an ammeter installed in the wiring of each phase.

[0036] Next, in step ST102, the control unit 101 cuts off the current output from the current controller of the phase in which the fault has occurred. As described above, when a fault has occurred in the one-phase winding 20_1, the motor relay 40_1 cuts off the connection between the current controller 10_1 and the one-phase winding 20_1. When a fault has occurred in the current controller 10_1 corresponding to the one-phase winding 20_1, the switch 50_1 is turned off to cut off the connection between the power source 30 and the current controller 10_1. This cuts off the current from the current controller 10_1 of the phase in which the fault has occurred.

[0037] Next, in step ST103, the control unit 101 calculates the negative-phase-sequence current generated due to a fault in one phase using the symmetric coordinate method. No negative-phase-sequence current flows under normal conditions.

[0038] Next, in step ST104, the control unit 101 distributes and superimposes the negative-sequence current to the other phases so as to cancel out the negative-sequence current In generated when one phase fails. When the number of phases m=5, the above-mentioned equations (4) and (5) are used to derive equation (6) and calculate the current Ii' of each phase. Note that by preparing a table or the like in advance, steps ST103 and ST104 can be processed without calculation by utilizing the table when one of the phases fails.

[0039] Here, we will explain the number of poles in a permanent magnet synchronous motor. To maximize torque, it is desirable to have just the right amount of magnetic flux generated from the permanent magnets linked together. When the number of poles, or the number of permanent magnets, is p (p is a natural number), the number of windings is w (w is a natural number), the magnetic flux generated by the permanent magnets is φm, and the amount of magnetic flux linking the windings is φw, this can be expressed by the following equation (8). It is desirable for the ratio of φm to φw, φw / φm, to be close to 1, and this can be expressed as follows: φw / φp=sin((p / w)π / 2)...Equation (8)

[0040] FIG. 15 is a diagram showing the relationship between the number of poles p and the number of windings w in the permanent magnet synchronous motor system according to this embodiment, illustrating the above equation (8). In order to maximize torque, it is desirable that the ratio of φm to φw, φw / φm, approaches 1, and when p / w=1, φw / φp becomes 1. However, when p / w=1, that is, when the number of poles p and the number of windings w match, the repulsive and attractive forces between the magnetic field generated by the windings and the permanent magnets become one to one, so no driving force is generated, and generally, when the permanent magnets synchronizationThe motor will not drive. Therefore, p / w=1 is inappropriate. Taking this into consideration, it is desirable that the smallest unit combination of the number of poles p and the number of windings w satisfies w0=p0±1. In other words, when the number of poles of a permanent magnet synchronous motor is p and the number of windings of each phase is w, and when expressed as p=np0 and w=nw0, it is desirable that w0=p0±1 (w0, p0, and n are natural numbers).

[0041] 16 is a diagram showing an example of a suitable combination of the number of poles p, the number of windings w, and the number of phases m of the permanent magnet synchronous motor in the permanent magnet synchronous motor system according to this embodiment. Here, as the number of phases increases, the number of current controllers also increases, and the number of FETs and other components that make up the current controllers also increases. Switching element Considering that a typical permanent magnet synchronous motor has three phase windings connected to one or two current controllers, it is desirable to keep the number of phases to five or less.

[0042] The control unit 101 of the current controller according to this embodiment includes a processor 110 and a storage device 120, as shown in FIG. 17 , which illustrates an example of hardware. The storage device 120 includes a volatile storage device such as a random access memory and a non-volatile auxiliary storage device such as a flash memory, although not shown. Alternatively, a hard disk auxiliary storage device may be used instead of the flash memory. The processor 110 may include a central processing unit (CPU), an application specific integrated circuit (ASIC), an integrated circuit (IC), a field programmable gate array (FPGA), various logic circuits, various signal processing circuits, and the like. Alternatively, a plurality of processors 110, either of the same type or of different types, may be provided, and each process may be shared among them.

[0043] Processor 110 executes a program input from storage device 120. In this case, the program is input from the auxiliary storage device to processor 110 via the volatile storage device. Processor 110 may also output data such as calculation results to the volatile storage device of storage device 120, or may store the data in the auxiliary storage device via the volatile storage device.

[0044] As described above, according to the present embodiment, the current control device 10 controls the permanent magnet synchronous motor 20 having windings of multiple phases, and includes current controllers 10_1, 10_2, ..., 10_m that supply current to the windings of each phase 20_1, 20_2, ..., 20_m, and a control unit 101 that controls the current controllers. The multiple current controllers 10_1, 10_2, ..., 10_m are connected in parallel with each other, and when the current output from any of the multiple current controllers 10_1, 10_2, ..., 10_m is interrupted, the control unit 101 distributes and superimposes a component that offsets the negative-phase current generated by the current controller whose output current is interrupted to the other current controllers whose output current is not interrupted. As a result, if a fault occurs in a winding of one of the multiple phases or in one of the multiple current controllers, even if that current controller is disconnected from the current controllers of other phases that are not faulty, the phase of the current flowing through the current controllers that are not faulty will not change, thereby suppressing the occurrence of large torque ripple.Furthermore, since control is performed to distribute and superimpose a component that offsets the negative-phase current generated by the current controller whose output current is disconnected to the other current controllers whose output current is not interrupted, it is possible to suppress the occurrence of torque ripple caused by the negative-phase current generated by the current controller that is disconnected. Therefore, it is possible to provide a current control device and a current control method for a permanent magnet synchronous motor that can suppress torque reduction and reduce torque ripple.

[0045] In this embodiment, an example has been shown in which each current converter is an inverter in which switching elements are configured as a full bridge, but in this case, the switching elements may be controlled by PWM (Pulse Width Modulation). During on-off control of the switching elements, the current is cut off when the switching elements are turned off, but this does not indicate the occurrence of a fault in the phase. In the faulty phase, the corresponding switches 50_1, 50_2, 50_3, 50_4, . . . , 50_m cause the output current from the current converter to stop flowing continuously.

[0046] Although exemplary embodiments are described herein, the various features, aspects, and functions described in the embodiments are not limited to application to a particular embodiment, but may be applied to the embodiments alone or in various combinations. Therefore, countless variations not illustrated are contemplated within the scope of the technology disclosed in the present specification, including, for example, modifying, adding, or omitting at least one component. [Explanation of symbols]

[0047] 10: Current control device, 10_1, 10_2, 10_3, 10_4,···, 10_m: Current controller, 20: Permanent magnet synchronous motor, 20_1, 20_2, 20_3, 20_4,···, 20_m: Winding, 30: Power supply, 40_1, 40_2, 40_3, 40_4,···, 40_m: Motor relay, 50_1, 50_2, 50_3, 50_4,···, 50_m: Switch, 101: Control unit, 110: Processor, 120: Storage device.

Claims

1. A current control device for controlling a permanent magnet synchronous motor having multiple phase windings, a current controller provided for each phase of the winding and configured to output a current to be passed through the winding; and a control unit that controls the plurality of current controllers, the plurality of current controllers are connected in parallel with each other; The control unit calculates a negative-phase current from the currents of each phase by a symmetric coordinate method, and performs control to superimpose a component that cancels out the negative-phase current that is generated when the current output from one of the multiple current controllers is interrupted on the other current controllers.

2. When the number of phases is m (m is an odd number equal to or greater than 3) and the amplitude of the current output by the current controller under normal conditions is I, When the current output from one of the plurality of current controllers is interrupted, 2. The current control device for a permanent magnet synchronous motor according to claim 1, wherein the control unit controls the magnitude of a component that cancels out the negative-phase current superimposed on each of the other current controllers to be I / m.

3. When the number of phases is m (m is an odd number equal to or greater than 3), the current output from the i-th (1≦i≦m; i is an integer) current controller in a normal state has a current phase delay of 2×π×(i−1) / m, The control unit is configured to determine whether a phase θi (1≦θ≦m) of a component that cancels out the negative-phase current superimposed on the i-th current controller among the current controllers that are not cut off from outputting the current is θi=(m-i+1)×2×π / m 3. The current control device for a permanent magnet synchronous motor according to claim 1, wherein the current control is performed so that:

4. 3. The current control device for a permanent magnet synchronous motor according to claim 1, wherein p≠m is satisfied when the number of poles of the permanent magnet synchronous motor is p (p is a natural number) and the number of phases is m (m is an odd number equal to or greater than 3).

5. When the number of poles of the permanent magnet synchronous motor is p (p is a natural number) and the number of windings of each phase is w (w is a natural number), p = np 0 , w=nw 0 , w 0 = p 0 ±1 (p 0 , w 0 , n is a natural number) 3. The current control device for a permanent magnet synchronous motor according to claim 1, wherein:

6. A current control method for a permanent magnet synchronous motor, the method comprising: controlling a plurality of current controllers provided for respective phases of a permanent magnet synchronous motor having windings of multiple phases, supplying current to the windings, and connecting the current controllers in parallel with each other; a fault detection step of detecting a fault for the plurality of phases; interrupting the current output from the current controller of the phase in which a fault has occurred, among the plurality of current controllers; calculating a negative-sequence current generated by a fault using a symmetric coordinate method; and superimposing a component that offsets the negative-phase current generated due to a fault on the current controller of the phase in which no fault occurs, thereby correcting the current to be output.

7. In the step of calculating the corrected current, When the number of phases is m (m is an odd number equal to or greater than 3) and the amplitude of the current output by the current controller under normal conditions is I, 7. The current control method for a permanent magnet synchronous motor according to claim 6, wherein the currents to be output are corrected so that the magnitude of a component that cancels out the negative-phase current superimposed on each of the current controllers becomes I / m.

8. In the step of calculating the corrected current, When the number of phases is m (m is an odd number equal to or greater than 3), the current output from the i-th (1≦i≦m; i is an integer) current controller in a normal state has a current phase delay of 2×π×(i−1) / m, Among the current controllers, the phase θi (1≦θ≦m) of the component that cancels the negative-phase current superimposed on the i-th current controller is θi=(m-i+1)×2×π / m 8. The current control method for a permanent magnet synchronous motor according to claim 6, wherein the current to be output is corrected so that:

9. 8. The current control method for a permanent magnet synchronous motor according to claim 6 or 7, wherein p≠m is satisfied when the number of poles of the permanent magnet synchronous motor is p (p is a natural number) and the number of phases is m (m is an odd number equal to or greater than 3).

10. When the number of poles of the permanent magnet synchronous motor is p (p is a natural number) and the number of windings of each phase is w (w is a natural number), p = np 0 , w=nw 0 , w 0 = p 0 ±1 (p 0 , w 0 , n is a natural number) 8. The current control method for a permanent magnet synchronous motor according to claim 6, wherein:

Images