Motor controller

Abstract

To solve the problem of a risk that stable power supply is unavailable since a voltage value of each phase suddenly changes and causes bus voltage to change and electromagnetic noise to occur with switching of a switching stationary phase when two-phase modulation system is applied to a motor controller.SOLUTION: A correction amount is applied to a duty for driving an inverter so that a sudden change of bus voltage caused by switching of a stationary phase for fixing switching of a switching element is suppressed.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to an electric motor control device. [Background technology]

[0002] Common motor control devices and motor drive systems that convert the form of power output include an AC / DC (Alternate Current / Direct Current) converter that converts AC power to DC power, an inverter that converts DC power to AC power, etc. These motor control devices and motor drive systems often include semiconductor switching elements.

[0003] The motor control device and motor drive system are comprised of a DC power supply, an inverter circuit consisting of a capacitor and multiple semiconductor switches and connected to the DC power supply, and an AC motor connected to the inverter circuit as a load. In particular, the power supply for the drive system of an electric vehicle is often a system with a lithium-ion battery or a boost converter via a lithium-ion battery.

[0004] An inverter circuit converts DC power from a DC power source into AC power by turning multiple semiconductor switches on and off at a predetermined switching frequency, and adjusts the torque and rotation speed of the AC motor (load). Depending on the operating conditions, the AC motor can also function as a generator, charging the DC power source with regenerative power generated by the generator. Efficient permanent magnet three-phase synchronous motors are often used as AC motors in electric vehicles.

[0005] In a drive system using a three-phase synchronous motor, the inverter circuit is configured by connecting three sets of series circuits, each of which has an upper-stage switching element and a lower-stage switching element connected in series, in parallel with a DC power supply, and the midpoint of each of the three sets of series circuits is connected to the input of the U-phase, V-phase, and W-phase of the three-phase synchronous motor, respectively.

[0006] Furthermore, by sequentially turning on and off the switching elements provided for each phase of the inverter circuit, AC power with a phase difference of 120 degrees is supplied to each phase of the three-phase synchronous motor, thereby driving the three-phase synchronous motor. Hereinafter, unless otherwise specified, the term "motor" refers to a three-phase synchronous motor. The operating principles of the inverter circuit are well known, so a detailed explanation will be omitted here.

[0007] Inverters like the one above drive electric motors by supplying bus voltage from an external source. The typical control method for three-phase inverters is three-phase modulation, but to reduce switching losses and improve voltage utilization, two-phase modulation is also available, in which one of the three phases is fixed. Two-phase modulation is a modulation method in which one phase of the three-phase inverter is fixed as a switching phase, by repeating a state in which the upper arm is on and the lower arm is off for each of the u, v, and w phases, or vice versa. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Publication No. 2023-81503 Summary of the Invention [Problem to be solved by the invention]

[0009] In such motor control devices, the bus voltage fluctuates due to the operation of the semiconductor switches that make up the inverter. To suppress the bus voltage fluctuations, the capacitance of the voltage smoothing capacitor, which is a suppression element, may be increased. In this case, the size and weight of the entire drive system increase, and costs also increase. Furthermore, when using two-phase modulation, the voltage value of each phase changes abruptly as the fixed phase is switched, which causes the bus voltage to change suddenly and generates electromagnetic noise, which can lead to the power supply being unable to provide a stable power supply.

[0010] To address this issue, there is a method for suppressing the sudden change in bus voltage when the fixed phase is switched by using three-phase modulation before and after switching the fixed phase of the two-phase modulation.

[0011] For example, as described in Patent Document 1, when an inverter is driven by two-phase modulation, command values ​​for three-phase modulation are calculated at the same time. When the fixed phase of two-phase modulation is switched, there is a method of giving three-phase modulation command values ​​to all phases for a certain section to drive the inverter by three-phase modulation.

[0012] However, the technique disclosed in Patent Document 1 includes a three-phase modulation period, which increases switching loss in the correction period compared to driving using two-phase modulation.

[0013] The present disclosure has been made to solve the above-mentioned problems, and can provide a motor control device that can reduce switching loss and suppress abrupt changes in bus voltage. [Means for solving the problem]

[0014] The electric motor control device of the present disclosure includes: This inverter converts DC power from a DC bus into AC power consisting of multiple phases and supplies the converted power to an AC motor, a power conversion circuit including a plurality of switching elements, which converts DC power into the plurality of phases of AC power by turning on and off the switching elements; a switching control means for controlling the on / off of a plurality of switching elements; Equipped with The switching control means includes an output command calculation unit that modulates a switching element of at least one of the multiple phases by fixing it to on or off for a predetermined period of one cycle and outputs a duty that sequentially switches the fixed phase; an output command correction amount calculation unit that calculates a correction amount for correcting a duty to suppress fluctuations in a bus voltage of a DC bus when a fixed phase is switched to a non-fixed phase; an output command correction unit that calculates a corrected duty for each phase based on the output of the output command calculation unit and the output of the output command correction amount calculation unit; The present invention is characterized by having the following. [Effects of the Invention]

[0015] The motor control device disclosed herein can provide a motor drive system that is always driven using two-phase modulation, thereby reducing switching loss and suppressing sudden changes in bus voltage, resulting in high efficiency and achieving compactness and low cost by reducing the capacitor capacity. [Brief explanation of the drawings]

[0016] [Figure 1] 1 is a block diagram showing a configuration of an electric motor control device according to a first embodiment. [Figure 2] 2 is a block diagram showing an example of the configuration of an output command calculation unit of the electric motor control device according to the first embodiment. FIG. [Figure 3] 5 is a diagram showing an example of an output from an output command calculation unit of the electric motor control device according to the first embodiment. FIG. [Figure 4] FIG. 3 is a diagram illustrating a fixed switching state of the motor control device according to the first embodiment. [Figure 5] 2 is a block diagram showing an example of the configuration of an output command correction amount calculation unit of the electric motor control device according to the first embodiment. FIG. [Figure 6] FIG. 4 is a diagram showing an example of a result of calculation of an output command correction amount of the electric motor control device according to the first embodiment. [Figure 7] 5 is a diagram illustrating an example of the operation of an output command correction amount calculation unit of the electric motor control device according to the first embodiment. FIG. [Figure 8] 5 is a diagram illustrating an example of the operation of an output command correction amount calculation unit of the electric motor control device according to the first embodiment. FIG. [Figure 9] 5 is a diagram illustrating an example of the operation of an output command correction amount calculation unit of the electric motor control device according to the first embodiment. FIG. [Figure 10] 2 is a block diagram showing an example of the configuration of an output command corrector of the electric motor control device according to the first embodiment. FIG. [Figure 11] 5 is a diagram showing an example of a calculation result of an output command corrector of the electric motor control device according to the first embodiment. FIG. [Figure 12] 5 is a diagram illustrating the magnitude of a duty after correction to which a correction amount of an output command corrector in the electric motor control device according to the first embodiment has been added. FIG. [Figure 13] 5 is a diagram illustrating the magnitude of a duty after correction to which a correction amount of an output command corrector in the electric motor control device according to the first embodiment has been added. FIG. [Figure 14] 5 is a diagram illustrating the effect when a correction amount with an opposite sign is given to the output command correction amount calculation unit of the electric motor control device according to the first embodiment. FIG. [Figure 15] 2 is a diagram illustrating an example of a hardware configuration of a switching control means of the electric motor control device according to the first embodiment. FIG. [Figure 16] 2 is a diagram illustrating an example of a hardware configuration of a switching control means of the electric motor control device according to the first embodiment. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0017] Hereinafter, preferred embodiments of the electric motor control device and electric motor drive system according to the present invention will be described with reference to the drawings. In each drawing, the same or corresponding parts will be denoted by the same reference numerals.

[0018] Generally, electric motors, also called motors, convert electric power into driving force for power running, but they can also convert driving force back into electric power for regenerative operation with the same structure. Similarly, electric generators, also called generators, convert driving force into electric power for regenerative operation, but they can also convert electric power back into driving force for power running with the same structure. In other words, electric motors and generators have basically the same structure, and both are capable of power running and regenerative operation. Therefore, in this specification, a rotating electric machine that functions as both an electric motor and a generator will simply be referred to as an electric motor.

[0019] Embodiment 1 First, the configuration and operation of an electric motor control device 1 according to an embodiment will be described with reference to FIG. The motor control device 1 is connected to a DC power source 90 by DC buses 21a and 21b via a power switch 70, and driving power or regenerative power is exchanged with the DC power source 90. The motor control device 1 is also connected to a motor 10 by an AC bus 2, and driving power or regenerative power is exchanged with the motor 10.

[0020] The electric motor 10 is also provided with a rotation speed detection unit (rotation angle sensor) 60 that detects the rotation speed from the rotation angle of the rotor. The electric motor 10 is capable of rotating and regenerating rotational energy as electrical energy, and is, for example, a three-phase brushless electric motor such as a permanent magnet three-phase AC synchronous electric motor.

[0021] The motor control device 1 is also composed of an inverter circuit 20 and switching control means 40. The inverter circuit 20 is composed of a capacitor 22 connected between DC buses 21a and 21b on the power supply input side, voltage detection means 23 that detects the voltage between the DC buses 21a and 21b of the inverter circuit 20, and a plurality of switching elements 31, 32, 33, 34, 35, and 36, and is equipped with a power conversion circuit 30 that performs DC-AC power conversion, a current detection unit 24 that detects the current flowing through the AC bus 2 of the motor 10, and switching control means 40.

[0022] The capacitor 22 has the function of suppressing voltage ripples on the DC buses 21a and 21b, the function of reducing the power supply impedance of the inverter circuit 20 to improve the AC current driving capability of the inverter circuit 20, and the function of absorbing surge voltages.

[0023] The voltage detection means 23 has a function of detecting the voltage between the DC buses 21 a and 21 b. In addition, the voltage detection means 23 may, for example, divide the voltage between the DC buses 21 a and 21 b using a voltage dividing resistor to a voltage that can be read by the switching control means 40, and output DC bus voltage information to the switching control means 40.

[0024] The current detection unit 24 detects the motor current flowing through the AC bus 2, converts the current into a voltage, and outputs motor current information to the switching control means 40. As an example, the current may be detected by a shunt resistor. Alternatively, a current sensor using a Hall element may be used.

[0025] The power conversion circuit 30 is configured, for example, by an inverter circuit in which six switching elements are full-bridge connected. That is, switching elements 31, 32, 33, 34, 35, and 36 are connected in series to each other to form arms, which are connected in parallel to the DC power supply 90. The midpoints of the switching elements 31 and 32 are connected to a U-phase input of the electric motor 10, the midpoints of the switching elements 33 and 34 are connected to a V-phase input of the electric motor 10, and the midpoints of the switching elements 35 and 36 are connected to a W-phase input of the electric motor 10. Here, the switching elements 31, 33, and 35 connected to the positive side of the DC power supply 90, i.e., the DC bus 21a, are referred to as upper arm switching elements (or upper arms), and the switching elements 32, 34, and 36 connected to the negative side of the DC power supply 90, i.e., the DC bus 21b, are referred to as lower arm switching elements (or lower arms).

[0026] As the switching element, for example, a metal oxide semiconductor field effect transistor (MOSFET) is generally used, but in addition to this, an insulated gate bipolar transistor (IGBT) is also used. Each MOSFET of the switching element is provided with a free wheel diode (FWD) in parallel, with the forward direction being the direction from the negative side to the positive side of the DC power supply 90, i.e., the direction from the lower side to the upper side.

[0027] The rotation angle sensor 60 detects the rotation angle of the rotor of the electric motor 10 by, for example, a resolver or an encoder. The rotation angle of the rotor detected by the rotation angle sensor 60 is input to the switching control means 40. The rotation angle of the rotor is used by the switching control means 40 as the rotation speed.

[0028] The switching control means 40 is responsible for controlling the entire motor control device 1, and includes a current detection means 41, an output command calculation unit 42, an output command correction amount calculation unit 43, an output command correction unit 44, and a switching control signal generation unit 45.

[0029] Based on the output result of the current detection unit 24, the current detection means 41 performs a three-phase / dq conversion using the current information iu, iv, iw flowing through the motor and the angle θ of the motor detected by the rotation angle sensor 60, and outputs the d-axis current id and the q-axis current iq.

[0030] The output command calculation unit 42 calculates the duties of each of the u-phase, v-phase, and w-phase. FIG. 2 is a block diagram showing an example of the configuration of the output command calculation unit 42. As shown in FIG. 2, a d-axis current command value and a q-axis current command value provided by a higher-level control unit and a d-axis current detection value and a q-axis current detection value calculated by the current detection means 41 are input to a d-axis current control unit 421 and a q-axis current control unit 422, which output a d-axis voltage command and a q-axis voltage command. A two-phase to three-phase conversion unit 423 calculates voltage command values ​​for each of the u-phase, v-phase, and w-phase based on these outputs and the motor angle, which is motor position information detected by the rotation angle sensor 60. A duty conversion unit 424 calculates the duty of each phase based on the calculated voltage command values ​​for each phase and the bus voltage value detected by the voltage detection means 23. For example, the u-phase duty can be calculated as follows: u-phase duty = u-phase voltage command / (bus voltage / 2) The v-phase duty and w-phase duty can be calculated in the same way.

[0031] FIG. 3 shows the results of calculation of the duty of each phase in the two-phase modulation method by the output command calculation unit 42. In FIG. 3, the horizontal axis represents time and the vertical axis represents the duties of the u, v, and w phases. The dotted lines in FIG. 3 indicate the timing of switching each fixed switching phase. FIG. 4 also shows an explanation of fixed switching states A to F. FIG. 4 shows the fixed switching phase and the states of the upper and lower arms. FIGS. 3 and 4 illustrate an example in which the switching phase switches sequentially by 60 degrees over one 360-degree cycle. When using the two-phase modulation method as shown in FIG. 3, a duty is generated so that a certain phase sequentially switches between fixed switching states in which the upper arm is on (ON) and the lower arm is off (OFF), or the upper arm is off and the lower arm is on. That is, a two-phase modulation duty is generated by calculation in which the lower arm switching element of the phase with the smallest duty is turned on to fix the switching, or the upper arm switching element of the phase with the largest duty is turned on to fix the switching.

[0032] The output command correction amount calculation unit 43 detects or estimates the timing of switching the fixed phase, and calculates the duty correction amount of the output command. Fig. 5 is a block diagram showing an example of the configuration of the output command correction amount calculation unit 43. For example, the output command correction amount calculation unit 43 can calculate the phase of each phase voltage from the motor rotation angle detected by the rotation angle sensor 60, and determine the timing of switching the fixed phase.

[0033] The output command correction amount calculation unit 43 calculates the optimum duty correction amount by simulation or actual measurement at the operating point corresponding to each speed and torque output so as to minimize the bus voltage fluctuation after switching the switching fixed phase, or calculates the duty correction amount by one or a combination of the bus voltage, inverter modulation factor, switching frequency, and motor inductance value. The duty correction amount has the following relationship with each parameter: (A) The higher the bus voltage, the larger the duty correction amount. (a) The higher the modulation rate of the inverter circuit, the larger the duty correction amount is. (c) The lower the switching frequency, the larger the duty correction amount. (d) The lower the motor inductance value, the larger the duty correction amount is set.

[0034] The output command correction amount calculation unit 43 performs correction while maintaining the operation of two-phase modulation during the period from immediately after switching of the switching fixed phase to immediately before switching of the next switching fixed phase, so it operates with the same number of switching operations as in two-phase modulation. Therefore, the number of switching operations is smaller and the switching loss is smaller than in the conventional method described in Patent Document 1, in which the switching fixed phase is changed to three-phase modulation before and after switching.

[0035] The output command correction amount calculation unit 43 corrects the duty of at least one phase other than the fixed switching phase by applying a duty correction amount. For example, in the case of a three-phase inverter, when the u phase corresponds to the fixed switching phase, the correction is performed by one of the following methods (1) to (3). (1) The duty of the v phase is corrected by applying a duty correction amount. (2) The duty of the w phase is corrected by applying a duty correction amount. (3) The duty of the v-phase and w-phase is simultaneously corrected by applying a duty correction amount.

[0036] Here, if (1) or (2) is used, the difference in duty from conventional two-phase modulation is small due to the correction, making it possible to output an output similar to that of conventional two-phase modulation, and there is little risk of current ripple and torque ripple occurring without having to worry about output fluctuations. Furthermore, when (3) is used, the amount of correction per phase is smaller than when (1) and (2) are used. Therefore, when the duty is high and the modulation rate is close to 1, the correction does not cause overmodulation, and the bus voltage can be suppressed more effectively.

[0037] For example, in the following case, even if the modulation rate is high, the bus voltage can be suppressed without the risk of overmodulation by correcting it using the method shown in (3). (1) The duty of the v phase is corrected by applying a duty correction amount k. (2) The duty of the w phase is corrected by applying a duty correction amount k. (3) The duty of the v-phase and w-phase is simultaneously corrected by applying a duty correction amount k / 2 to each of them.

[0038] The output command correction amount calculation unit 43 corrects the duty by applying a fixed duty correction amount for a fixed period of time, and then gradually brings the duty correction amount closer to 0, thereby preventing the current ripple, voltage ripple, and torque ripple from increasing even if the duty changes due to a sudden change in the voltage command value.

[0039] The output command correction amount calculation unit 43 applies a correction amount to the duty within a certain electrical angle to suppress sudden fluctuations in the bus voltage, and then applies a correction amount with the opposite sign to the original correction amount. By applying a correction amount with the opposite sign in this way, it is possible to cancel out the current offset that occurs during the correction process. The effect of canceling out the current offset will be described later.

[0040] An example of the result of the correction amount calculation by the output command correction amount calculation unit 43 is shown in Fig. 6. Fig. 6 shows an example of the switch state of each fixed switching phase, the magnitude of the duty correction amount, and the correction phase. The above-mentioned duty correction amount k is a value selected from the results of simulations when the fluctuation of the bus voltage is the smallest.

[0041] An example of the operation of the output command correction amount calculation unit 43 is shown in Fig. 7 and Fig. 8. Fig. 7 shows the change in the duty correction amount when changing from state A to state B shown in Fig. 6, and Fig. 8 shows the change in the duty correction amount when changing from state B to state C shown in Fig. 6. In Fig. 7 and Fig. 8, the horizontal axis shows time and the vertical axis shows the magnitude of the duty correction amount.

[0042] As shown in Figures 7 and 8, after the switching fixed phase is switched, the correction amount is changed in Section 1 to suppress fluctuations in the bus voltage. In Section 2, the correction amount is changed so that it has the opposite sign to that of Section 1. Also, after the switching phase is switched, the correction amount is set to 0 in all sections other than Section 1 and Section 2, so that no correction is made. As shown in Figure 7, after the switching phase is switched from State A to State B, the duty correction amount is changed gradually from 0 to k and from k to 0 in Section 1, and then gradually changed from 0 to -k and from -k to 0 in Section 2.

[0043] Furthermore, as shown in Fig. 8, after the switching phase switches from state B to state C, the duty correction amount is gradually changed from 0 to -k and from -k to 0 in section 1, and gradually changed from 0 to k and from k to 0 in section 2. Note that although the diagram shows a stepwise change, this represents the quantization error of digital control, and is not limited to a stepwise change.

[0044] An example of the operation of the output command correction amount calculation unit 43 is shown in Fig. 9. In Fig. 9, the horizontal axis represents time, the vertical axis represents the duty after correction, and the timing of switching each fixed switching phase is indicated by a dotted line in Fig. 9. As shown in Fig. 9, after the fixed switching phase is switched, the correction amount is changed so as to correct phases other than the fixed switching phase so as to suppress fluctuations in the bus voltage, as shown in Fig. 6.

[0045] The output command corrector 44 calculates the corrected duty of each phase by adding the duty correction amount of each phase calculated by the output command correction amount calculator 43 to the duty of each phase calculated by the output command calculator 42. Fig. 10 is a block diagram showing an example of the configuration of the output command corrector 44.

[0046] An example of the calculation results of the output command corrector 44 is shown in Fig. 11. In Fig. 11, the horizontal axis represents time, the vertical axis represents the duty of each phase, and the dotted lines in Fig. 11 indicate the timing of switching each fixed phase. As shown in Fig. 11, after the fixed phase switches, as shown in Fig. 6, a correction amount is applied to all phases other than the fixed phase so as to suppress fluctuations in the bus voltage during periods A to F, and then the correction amount is gradually made to approach zero. Furthermore, after a correction amount is applied for a certain period, a correction amount with an opposite sign is applied.

[0047] The switching control signal generator 45 generates an on / off control signal for controlling the on / off of the plurality of switching elements 31 to 36 that make up the power conversion circuit 30 .

[0048] The switching control signal generating unit 45 generates on / off control signals for each switching element 31 to 36 of the power conversion circuit 30 in accordance with DC bus voltage information from the voltage detecting means 23, rotation angle information (rotation speed) of the electric motor 10 from the rotation angle sensor 60, electric motor current information from the current detecting unit 24, the corrected duty output from the output command correcting unit 44, and the torque command value and current command value of the electric motor 10 input from outside, and outputs the generated on / off control signals to the power conversion circuit 30.

[0049] The switching elements 31 to 36 are each turned on and off by an on / off control signal from the switching control signal generating unit 45, converting DC power into AC power to supply to the electric motor 10, and charging the DC power supply 90 with regenerative power generated when the electric motor 10 is in a regenerative state.

[0050] In short, other control devices, including a vehicle ECU (Electronic Control Unit) not shown, receive the target torque or target current of the electric motor 10 via a CAN (Controller Area Network), and perform current feedback control using DC bus voltage information input from voltage detection means 23, rotation angle information of the electric motor 10 input from rotation angle sensor 60, and electric motor current information input from current detection unit 24, to calculate on / off control signals for each of switching elements 31 to 36 of the power conversion circuit 30 so as to obtain the target torque or target current of the electric motor 10, and output on / off control signals to the power conversion circuit 30. Note that current feedback control is well known, and therefore a detailed description thereof will be omitted here.

[0051] The type of semiconductor used for the switching elements 31 to 36 in the power conversion circuit 30 is not particularly limited, but may be, for example, a wide bandgap semiconductor. Wide bandgap semiconductor elements may be made of, for example, silicon carbide (SiC), gallium nitride (GaN)-based materials, or diamond (C).

[0052] Inverter circuits configured with switching elements formed from such wide bandgap semiconductors are characterized by a high withstand voltage, low loss, and high frequency drive capability compared to conventional inverter circuits configured with switching elements formed from silicon (Si). Hereinafter, inverter circuits configured with switching elements formed from wide bandgap semiconductors will be referred to as wide bandgap inverter circuits, and inverter circuits configured with switching elements formed from silicon (Si) will be referred to as silicon inverter circuits.

[0053] Therefore, in a motor control device using a wide bandgap inverter circuit, the switching speed of the switching elements can be increased compared to a motor control device using a silicon inverter circuit, and output commands can be realized quickly and accurately, thereby effectively realizing the control of this embodiment.

[0054] Furthermore, although the present embodiment has been described using a two-phase modulation system as an example, the same effect can be obtained by the method described above even in a modulation system in which at least one phase of an inverter having three or more phases is a fixed switching phase. Details will not be described in detail as they can be easily inferred by those skilled in the art from the above description.

[0055] <Effects when applying the embodiment> The effect of this embodiment is shown in FIG. 12. In FIG. 12, the horizontal axis indicates time, and the vertical axes of FIGS. 12a to 12c indicate the magnitude of the duty after correction, which is achieved by applying a duty correction amount to each phase. The vertical axes of FIGS. 12d to 12f indicate the on / off states of the gate signals of the upper arm switching elements 31 to 35 before and after correction for each phase. Here, the dotted line indicates the signal without correction, and the solid line indicates the signal with correction. The vertical axis of FIG. 12g indicates the magnitude of the input / output current of capacitor 22 without correction, and FIG. 12h indicates the magnitude of the input / output current of capacitor 22 with correction. Here, when the input / output current of capacitor 22 is positive, current flows through capacitor 22, and charge is accumulated, resulting in an increase in the bus voltage. Conversely, when the input / output current of capacitor 22 is negative, current flows out of capacitor 22, and charge is released, resulting in a decrease in the bus voltage. FIG. 12i shows the bus voltage without correction and with correction, respectively.

[0056] Figure 12 shows the operation when the fixed switching phase switches from state A (upper arm of u phase fixed ON (ON) and lower arm fixed OFF (OFF)) shown in Figure 6 to state B (upper arm of w phase fixed OFF and lower arm fixed ON). Figures 12a to 12c show the corrections shown in Figure 6, that is, the corrections to the duties of the phases other than the fixed switching phase.

[0057] The operating states with and without duty correction applied are explained using FIG. 13, which shows the same content as FIG. 12. The period x to z enclosed by dashed line Q in FIG. 13 will be explained. By performing correction, the ON / OFF timing of the arms of each phase is changed, as shown in FIGS. 12 and 13d to 13f. During period x, the correction is made so that the ON timing of the upper arm of the u phase shown in FIG. 13d is delayed. That is, the capacitor input / output current without correction (FIG. 13g) shown in FIGS. 13g and 13h) has a longer period during which the current is equal to or greater than 0 compared to the capacitor input / output current with correction (FIG. 13h). In other words, by making a correction to lengthen the period during which current is input to capacitor 22, the period during which charge accumulates in capacitor 22 can be lengthened, and therefore, the bus voltage at the end of period x is higher than without correction.

[0058] During period x, the capacitor voltage starts at a high state due to correction, and during period y, correction is made to shorten the positive period of the current in capacitor 22 compared to when no correction is made. In other words, by shortening the discharge period, the bus voltage can be maintained at a higher state than when no correction is made, and undershoot, in which the bus voltage suddenly drops, is suppressed.

[0059] Furthermore, during period z, the correction is made so that the period during which the capacitor current is negative is longer than when no correction is made. In other words, by lengthening the period during which charge is released from the capacitor, the bus voltage can be maintained at a lower level, suppressing overshoot, which is a sudden rise in the bus voltage.

[0060] Figure 14 shows the effect of applying a correction amount with the opposite sign after applying a correction amount within a certain electrical angle to suppress the sudden fluctuations in the bus voltage mentioned above. The horizontal axis of Figure 14 shows time, and the vertical axis shows the duty of each phase and the difference between the u-phase current with correction and the u-phase current without correction (when driven using two-phase modulation). As can be seen from the area surrounded by the dashed line Q in Figure 13, a current offset occurs in the phase current compared to a system that does not apply duty correction amount, but this current offset can be eliminated by applying a correction amount with the opposite sign as explained in Figures 7 and 8. This makes it possible to obtain an output equivalent to that obtained using conventional systems that use only two-phase modulation without applying duty correction amount.

[0061] As described above, in this embodiment, the storage period and release period of the capacitor charge can be appropriately corrected to always drive using two-phase modulation, and undershoot, which is an excessive drop in the bus voltage, and overshoot, which is an excessive rise in the bus voltage, can be suppressed. As a result, bus voltage changes that occur when the switching phase is switched can be suppressed, and a motor drive system that operates stably can be obtained.

[0062] It should be noted that this embodiment is merely an example and is not intended to be limiting in any way. For example, although the DC power supply 90 and the motor control device 1 are directly connected in the above description, a DC / DC converter that steps up or steps down the voltage may be disposed between the DC power supply 90 and the motor control device 1, or the DC power supply may be connected to the AC power supply via a rectifier or an AC / DC converter that converts AC power from the AC power supply into DC power.

[0063] The output command correction unit 44 may also be configured to have a correction table in which the duty correction amount is set to different magnitudes depending on the rotation speed and output operating point of the AC motor, based on calculations by simulation of the amount of sudden voltage fluctuation in the bus voltage or actual measurements.

[0064] Furthermore, in this embodiment, since the duty of each phase is directly corrected, there is a risk of the output changing abruptly. Therefore, in order to prioritize control that suppresses sudden changes in the load or power supply voltage during transient responses, the output torque may be detected or estimated, and correction may not be performed if the torque pulsation is large.

[0065] Furthermore, although the above embodiment has described the characteristics and operation of a motor control device, it may also be applied to a motor drive system including the motor control device 1 and the motor 10, in which case the advantages of the miniaturization of the motor control device 1 and the miniaturization of the motor 10 can be enjoyed simultaneously.

[0066] 15 and 16 illustrate an example of the hardware configuration of the switching control means 40, which includes a current detection means 41, an output command calculation unit 42, an output command correction amount calculation unit 43, an output command correction unit 44, and a switching control signal generation unit 45. The switching control means 40 includes one or more processors 100 and one or more storage devices 200. Although not shown, the storage device 200 includes a volatile storage device such as a random access memory (RAM) and a nonvolatile auxiliary storage device such as a flash memory. Alternatively, a hard disk auxiliary storage device may be used instead of the flash memory. The processor 100 executes the operations of the current detection means 41, the output command calculation unit 42, the output command correction amount calculation unit 43, the output command correction unit 44, and the switching control signal generation unit 45 described above based on a program input from the storage device 200. In this case, the program is input from the auxiliary storage device to the processor 100 via the volatile storage device. The processor 100 may output data, such as calculation results, to the volatile storage device of the storage device 200, or may store the data in the auxiliary storage device via the volatile storage device.

[0067] The current detection means 41, the output command calculation unit 42, the output command correction amount calculation unit 43, the output command correction unit 44 and the switching control signal generation unit 45 may be executed as functions by a program in one processor 100 (FIG. 15), or each configuration may be executed independently or in combination using an independent processor 100 and a storage device 200, and data may be transmitted and received between each processor 100 and the storage device 200 via a transmission / reception circuit 300 (FIG. 16).

[0068] Although the present disclosure describes exemplary embodiments, 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 this specification, including, for example, the modification, addition, or omission of at least one component.

[0069] Various aspects of the present disclosure are summarized below as appendices.

[0070] (Appendix 1) 1. A motor control device that converts DC power from a DC bus into AC power consisting of multiple phases and supplies the converted power to an AC motor, a power conversion circuit including a plurality of switching elements, which converts DC power into the plurality of phases of AC power by turning on and off the switching elements; a switching control means for controlling the on / off of the plurality of switching elements; Equipped with The switching control means includes an output command calculation unit that modulates a switching element of at least one of the multiple phases by fixing it to on or off for a predetermined period of one cycle and outputs a duty that sequentially switches the fixed phase; an output command correction amount calculation unit that calculates a correction amount for correcting the duty in order to suppress fluctuations in a bus voltage of the DC bus when the fixed phase is switched to a non-fixed phase; an output command correction unit that calculates a corrected duty of each phase based on the output of the output command calculation unit and the output of the output command correction amount calculation unit; An electric motor control device comprising: (Appendix 2) An electric motor drive device comprising: a power conversion circuit that generates a three-phase AC output by switching upper arm switching elements and lower arm switching elements of each phase connected to a DC bus; and switching control means that controls switching of the upper arm switching elements and lower arm switching elements of each phase of the power conversion circuit; and the electric motor drive device that provides the three-phase AC output to an AC electric motor, the switching control means includes an output command calculation unit that calculates a duty for generating a phase voltage of each phase, and calculates a duty for two-phase modulation that fixes switching by turning on the lower arm switching element of the phase whose duty is minimum, or fixes switching by turning on the upper arm switching element of the phase whose duty is maximum; an output command correction amount calculation unit that calculates a correction amount for correcting the duty in order to suppress fluctuations in a bus voltage of the DC bus in a predetermined section where a fixed phase for fixing switching is switched; an output command correction unit that calculates a corrected duty of each phase based on the output of the output command calculation unit and the output of the output command correction amount calculation unit; An electric motor control device comprising: (Appendix 3) 3. The motor control device according to claim 1, wherein the duty is corrected only during a predetermined period in which the bus voltage fluctuates after the fixed phase is switched and before the fixed phase is switched again. (Appendix 4) The motor control device according to any one of claims 1 to 3, characterized in that the duty correction is performed by applying a constant correction amount to the duty for a certain period of time after the start of the duty correction, and then gradually bringing the correction amount closer to 0. (Appendix 5) 5. The motor control device according to claim 4, wherein after the correction amount becomes 0, a correction amount with an opposite sign is applied to the duty. (Appendix 6) 4. The motor control device according to claim 1, wherein the duty correction is performed for any or all of the phases other than the fixed phase. (Appendix 7) 7. The motor control device according to claim 1, wherein the output command correction unit has a correction table in which the correction amount is set according to a rotation speed and an output operating point of the AC motor, based on a calculation by simulation of a voltage fluctuation amount of the bus voltage or an actual measurement value. (Appendix 8) 8. The motor control device according to claim 1, wherein the duty is not corrected when torque pulsation of the output torque of the AC motor is greater than a predetermined value. (Appendix 9) 9. The motor control device according to any one of claims 1 to 8, wherein the semiconductor switching elements constituting the power conversion circuit are formed of wide bandgap semiconductors. [Explanation of symbols]

[0071] 1: motor control device, 2: AC bus, 10: motor, 20: inverter circuit, 21a, 21b: DC bus, 22: capacitor, 23: voltage detection means, 24: current detection unit, 30: power conversion circuit, 31, 32, 33, 34, 35, 36: switching elements, 40: switching control means, 41: current detection means, 42: output command calculation unit, 43: output command correction amount calculation unit, 44: output command correction unit, 45: switching control signal generation unit, 60: rotation angle sensor, 70: power switch, 90: DC power supply, 100: processor, 200: storage device, 300: transmission / reception circuit

Claims

1. 1. A motor control device that converts DC power from a DC bus into AC power consisting of multiple phases and supplies the converted power to an AC motor, a power conversion circuit including a plurality of switching elements, which converts DC power into the plurality of phases of AC power by turning on and off the switching elements; a switching control means for controlling the on / off of the plurality of switching elements; Equipped with the switching control means includes an output command calculation unit that modulates a switching element of at least one of the plurality of phases by fixing it to on or off for a predetermined period of one cycle and outputs a duty that sequentially switches the fixed phase; an output command correction amount calculation unit that calculates a correction amount for correcting the duty in order to suppress fluctuations in a bus voltage of the DC bus when the fixed phase is switched to a non-fixed phase; an output command correction unit that calculates a corrected duty of each phase based on the output of the output command calculation unit and the output of the output command correction amount calculation unit; An electric motor control device comprising:

2. An electric motor drive device comprising: a power conversion circuit that generates a three-phase AC output by switching upper arm switching elements and lower arm switching elements of each phase connected to a DC bus; and switching control means that controls switching of the upper arm switching elements and lower arm switching elements of each phase of the power conversion circuit; and the electric motor drive device that provides the three-phase AC output to an AC electric motor, the switching control means includes an output command calculation unit that calculates a duty for generating a phase voltage of each phase, and calculates a duty for two-phase modulation that fixes switching by turning on the lower arm switching element of the phase in which the duty is minimum, or fixes switching by turning on the upper arm switching element of the phase in which the duty is maximum; an output command correction amount calculation unit that calculates a correction amount for correcting the duty in order to suppress fluctuations in a bus voltage of the DC bus in a predetermined section where a fixed phase for fixing switching is switched; an output command correction unit that calculates a corrected duty of each phase based on the output of the output command calculation unit and the output of the output command correction amount calculation unit; An electric motor control device comprising:

3. 3. The motor control device according to claim 1, wherein the duty is corrected only during a predetermined period in which the bus voltage fluctuates after the fixed phase is switched and before the fixed phase is switched again.

4. 3. The motor control device according to claim 1, wherein the duty correction is performed by applying a constant correction amount to the duty for a certain period of time after the start of the duty correction, and thereafter gradually bringing the correction amount closer to zero.

5. 5. The motor control device according to claim 4, wherein after the correction amount becomes zero, a correction amount with an opposite sign is applied to the duty.

6. 3. The motor control device according to claim 2, wherein the duty correction is performed for any or all of the phases other than the fixed phase.

7. 3. The motor control device according to claim 1, wherein the output command correction unit has a correction table in which the correction amount is set according to a rotation speed and an output operating point of the AC motor based on a calculation by simulation of a voltage fluctuation amount of the bus voltage or an actual measurement value.

8. 3. The motor control device according to claim 1, wherein the duty is not corrected when torque pulsation of the output torque of the AC motor is greater than a predetermined value.

9. 3. The motor control device according to claim 1, wherein the semiconductor switching elements constituting the power conversion circuit are formed of wide bandgap semiconductors.

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