Motor drive unit

Abstract

To provide a high-performance motor drive device. [Solution] An embodiment of a motor drive device includes a power conversion device that supplies three-phase AC power to a motor, a current detection unit that detects the motor current of the motor, a voltage detection unit that detects the voltage on the DC input side of the power conversion device, a voltage control unit that issues on / off commands to multiple semiconductor elements of the power conversion device to apply a drive voltage to the motor, multiple phase adjustment units that adjust the phase of the drive voltage, and a phase adjustment selection unit that selects one of the calculation results of the multiple phase adjustment units and outputs the selected calculation result to the voltage control unit, wherein a first phase adjustment unit of the multiple phase adjustment units controls to advance the phase of the drive voltage when the detection value obtained from the voltage detection unit exceeds a threshold, and the phase adjustment selection unit selects the output of the first phase adjustment unit when the detection value exceeds the threshold.

Description

[Technical Field]

[0001] An embodiment of the present invention relates to a motor drive device. [Background technology]

[0002] To improve the efficiency of motor systems, synchronous motors using permanent magnets have become widespread, and various motor control methods have been proposed. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6268052 specification [Patent Document 2] Patent No. 7163223 specification [Patent Document 3] Patent No. 5957704 specification [Patent Document 4] Patent No. 7295717 specification [Patent Document 5] Patent No. 4736815 specification Summary of the Invention [Problem to be solved by the invention]

[0004] A high-performance motor drive device is realized. [Means for solving the problem]

[0005] The motor drive device of this embodiment includes a three-phase synchronous motor, a power conversion device that converts a DC voltage into three-phase AC power of a certain voltage and a certain frequency through the switching operation of a plurality of semiconductor elements and supplies the converted three-phase AC power to the three-phase synchronous motor, a voltage detection unit that detects the voltage on the DC input side of the power conversion device, a voltage control unit that issues on / off commands to the plurality of semiconductor elements to apply a drive voltage of a certain voltage and a certain frequency from the power conversion device to the three-phase synchronous motor, a plurality of phase adjustment units that adjust the phases of the drive voltages, and a phase adjustment selection unit that selects one of the calculation results of the plurality of phase adjustment units and outputs the selected calculation result to the voltage control unit, wherein a first phase adjustment unit of the plurality of phase adjustment units controls to advance the phase of the drive voltage when the voltage detection value obtained from the voltage detection unit exceeds a first threshold, and the phase adjustment selection unit selects the output of the first phase adjustment unit when the voltage detection value exceeds the first threshold. [Brief explanation of the drawings]

[0006] [Figure 1] FIG. 1 is a block diagram showing an example of the configuration of a motor drive device according to a first embodiment. [Figure 2] 4 is a vector diagram showing current phases related to the motor drive device of the first embodiment. [Figure 3] 4 is a vector diagram showing current phases related to the motor drive device of the first embodiment. [Figure 4] FIG. 3 is a diagram showing the relationship between the phase of a motor induced voltage and the phase of a motor current in the motor drive device of the first embodiment. [Figure 5] 4 is a vector diagram showing current phases related to the motor drive device of the first embodiment. [Figure 6] FIG. 4 is a diagram showing the relationship between an index related to the motor drive device and advance angle control according to the first embodiment. [Figure 7] FIG. 2 is a schematic diagram illustrating the influence of regeneration on the motor drive device of the first embodiment. [Figure 8] FIG. 2 is a schematic diagram illustrating regeneration control for the motor drive device according to the first embodiment. [Figure 9] 4 is a flowchart showing an example of the operation of the motor drive device according to the first embodiment. [Figure 10] 4 is a flowchart showing an example of the operation of the motor drive device according to the first embodiment. [Figure 11] 4 is a flowchart showing an example of the operation of the motor drive device according to the first embodiment. [Figure 12] FIG. 10 is a block diagram showing an example of the configuration of a motor drive device according to a second embodiment. [Figure 13] FIG. 10 is a waveform diagram of a direct current related to the motor drive device of the second embodiment. [Figure 14] 10 is a flowchart showing an example of the operation of the motor drive device according to the second embodiment. [Figure 15] FIG. 10 is a diagram for explaining a method for evaluating the gradient of the motor current in the motor drive device according to the second embodiment. [Figure 16] 10 is a flowchart showing an example of the operation of the motor drive device according to the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0007] A motor drive device and a control method for a motor drive device according to an embodiment will be described with reference to Figures 1 to 16. In the following description, elements having the same function and configuration will be given the same reference numerals. Furthermore, in each of the following embodiments, when components (e.g., circuits, wiring, various voltages and signals, etc.) are given reference numerals with distinguishing numbers / letters at the end, and do not need to be distinguished from one another, the reference numerals will be omitted.

[0008] (Embodiment) (1) First embodiment A motor drive device and a control method thereof according to a first embodiment will be described with reference to FIGS.

[0009] (a) Configuration FIG. 1 is a circuit and functional block diagram of a motor drive device according to the first embodiment.

[0010] As shown in FIG. 1, the motor drive device 100 of this embodiment includes an inverter circuit 1, a three-phase synchronous motor (electric motor) 4, a current detection unit 5, a voltage detection unit 6, an overvoltage detection unit 11, a first phase adjustment unit 12, a motor current detection unit 13, a second phase adjustment unit 14, a phase adjustment selection unit 15, a rotational position detection unit 16A, a rotational speed detection unit 16B, an operation command setting unit 17, and a voltage control unit 18.

[0011] The inverter circuit 1 is a power conversion device including a plurality of switching elements SW. Each switching element SW is composed of an insulated gate bipolar transistor (IGBT) 2 and a freewheeling diode 3. The inverter circuit 1 is composed of, for example, a two-level circuit in which the IGBT 2 and the freewheeling diode 3 connected in anti-parallel are connected in a three-phase bridge configuration. However, the inverter circuit 1 may be replaced with a multilevel circuit having three or more levels. The switching elements SW may be composed of field-effect transistors such as MOSFETs.

[0012] The inverter circuit 1 is connected to a DC power supply Vdc. The inverter circuit 1 controls the on / off commands of a plurality of IGBTs 2 to convert a voltage according to the DC power supply Vdc into AC power (AC voltage) of a desired voltage value and frequency. The inverter circuit 1 supplies the converted AC power to a motor 4. As a result, a drive voltage for the motor 4 is applied from the inverter circuit 1 to the motor 4.

[0013] The motor 4 is a device including a three-phase synchronous motor. The motor 4 is driven in response to the supplied AC power (drive voltage). The driving force of the motor 4 is applied to a load 9 connected to the motor 4. The load 9 is, for example, a fan having large inertia. For example, the motor drive device 100 of this embodiment is a drive device for a fan motor.

[0014] The rotational position detection unit 16A is a means for detecting the rotational position of the motor 4. The rotational position detection unit 16A may be configured using a mechanism based on a detection method using hardware sensors such as position sensors and Hall sensors, or a position sensorless detection method that estimates the rotational position by mathematical calculations based on the motor current, etc. For example, the rotational position detection unit 16A detects a signal synchronized with the rotational position of the motor 4. The rotational position of the motor 4 correlates with the phase of the voltage (inverter voltage) supplied from the inverter circuit 1.

[0015] The rotation speed detection unit 16B is a means for detecting the rotation speed of the motor 4. For example, the rotation speed detection unit 16B calculates the rotation speed RV of the motor 4 based on information related to the rotation position of the motor from the rotation position detection unit 16A and a signal detected in accordance with the rotation speed of the motor 4. For example, the rotation speed detection unit 16B calculates the rotation speed RV from information related to the position of the rotor of the motor 4. The rotation speed detection unit 16B can supply the obtained rotation speed RV to the second phase adjustment unit 14, which will be described later.

[0016] The operation command setting unit 17 is a higher-level device that supplies an operation signal given from outside the motor system. Here, the operation command setting unit 17 is configured by means of giving a voltage amplitude (duty) DY from outside to a voltage control unit 18 (described later) and arbitrarily controlling the rotation speed of the motor 4.

[0017] The voltage control unit 18 receives a signal corresponding to the rotational position RP detected by the rotational position detection unit 16A, a signal corresponding to the rotational speed RV detected by the rotational speed detection unit 16B, a signal corresponding to the voltage amplitude DY from the operation command setting unit 17, and a signal corresponding to the phase adjustment amount CNT from the phase adjustment units 12 and 14 described below. The voltage control unit 18 generates on / off commands (e.g., PWM signals) for the multiple IGBTs 2 based on the rotational position RP, the rotational speed RV, the voltage amplitude DY, and the phase adjustment amount CNT described below.

[0018] The voltage detection unit 6 and the overvoltage detection unit 11 are mechanisms (devices) that detect overvoltage of the DC voltage Vx (also called inverter DC voltage) of the inverter circuit 1. The voltage detection unit 6 detects the DC voltage Vx supplied to the DC input side of the inverter circuit 1. The overvoltage detection unit 11 receives a signal corresponding to the DC voltage Vx detected by the voltage detection unit 6. When the DC voltage Vx exceeds a preset overvoltage detection threshold (first threshold), the overvoltage detection unit 11 recognizes the DC voltage Vx exceeding the detection threshold as an overvoltage. The function of the overvoltage detection unit 11 may be configured by a comparator as an analog circuit. Alternatively, the function of the overvoltage detection unit 11 may be configured by inputting DC voltage information from an ADC (Analog to Digital Converter) into a processor and comparing it with the detection threshold within the processor.

[0019] The first phase adjustment unit 12 is a control unit for suppressing overvoltage in the inverter circuit 1. The first phase adjustment unit 12 determines the amount of phase adjustment of the inverter circuit 1 based on the overvoltage determination result from the overvoltage detection unit 11. The first phase adjustment unit 12 receives the output signal of the overvoltage detection unit 11. The first phase adjustment unit 12 receives various parameters for the previous control from the phase adjustment selection unit 15. For example, the first phase adjustment unit 12 receives the previous phase adjustment amount CNT (and the previous advance angle control amount) of the drive voltage of the motor 4 output from the inverter circuit 1. For example, when an overvoltage is detected, the first phase adjustment unit 12 outputs a value obtained by incrementing (adding 1 to) the previous phase adjustment amount CNT generated by the phase adjustment selection unit 15.

[0020] The current detection unit 5 and the motor current detection unit 13 are mechanisms (devices) that detect the DC current Ix of the inverter circuit 1. The current detection unit 5 detects the DC current Ix flowing through the inverter circuit 1. The motor current detection unit 13 receives a signal corresponding to the DC current Ix detected by the current detection unit 5. The motor current detection unit 13 detects the motor current of at least one phase of the motor 4 based on the DC current Ix. The current detection unit 5 and the motor current detection unit 13 have a circuit function of detecting the three-phase current of the motor 4 based on the conduction states of the multiple IGBTs 2 that constitute the inverter circuit 1 using information about the DC current Ix. The current detection unit 5 and the motor current detection unit 13 may be substituted by a shunt resistor or a current sensor as long as they are capable of detecting the motor current. Furthermore, the current detection unit 5 and the motor current detection unit 13 may be configured by providing the above-mentioned detection means on the three-phase motor wiring of the inverter circuit 1, rather than in the DC section of the inverter circuit 1.

[0021] The second phase adjustment unit 14 is a control unit for controlling highly efficient operation of the motor 4. The second phase adjustment unit 14 receives an output signal from the motor current detection unit 13. The second phase adjustment unit 14 receives various parameters for the previous control from the phase adjustment selection unit 15. For example, the second phase adjustment unit 14 receives the previous phase adjustment amount CNT (and the previous advance angle control amount) of the drive voltage supplied to the inverter circuit 1. The second phase adjustment unit 14 outputs a value obtained by incrementing or decrementing (subtracting 1 from) the previous phase adjustment amount CNT generated by the phase adjustment selection unit 15 so as to reduce the motor current.

[0022] The phase adjustment selection unit 15 receives the output signal of the first phase adjustment unit 12 and the output signal of the second phase adjustment unit 14. The phase adjustment selection unit 15 receives the overvoltage detection result from the overvoltage detection unit 11. The phase adjustment selection unit 15 selects either the calculation result (output signal) of the first phase adjustment unit 12 or the second phase adjustment unit 14. The phase adjustment selection unit 15 outputs a signal according to the selection result to the voltage control unit 18. During normal operation, the phase adjustment selection unit 15 selects the output of the second phase adjustment unit 14 because it is required to control the motor 4 with high efficiency. When an overvoltage is detected and the motor system is to be immediately protected, the phase adjustment selection unit 15 selects the output of the first phase adjustment unit 12. The phase adjustment selection unit 15 feeds back the selected previous phase adjustment amount CNT to the phase adjustment units 12 and 14.

[0023] For example, overvoltage detection unit 11, first phase adjustment unit 12, motor current detection unit 13, second phase adjustment unit 14, phase adjustment selection unit 15, and voltage control unit 18 may be functional blocks configured by microcomputer (or processor) 7. That is, microcomputer 7 realizes the functions of overvoltage detection unit 11, first phase adjustment unit 12, motor current detection unit 13, second phase adjustment unit 14, phase adjustment selection unit 15, and voltage control unit 18. Note that rotational position detection unit 16A and rotational speed detection unit 16B may be functional blocks configured by microcomputer 7.

[0024] In the motor driving device 100 of this embodiment, the voltage control unit 18 controls the operation of the inverter circuit 1 based on the phase adjustment amount CNT selected by the phase adjustment selection unit 15. The motor 4 is driven by the AC power generated by the inverter circuit 1.

[0025] (b) Principle The control principle of the motor driving device 100 of the first embodiment will be described with reference to FIGS.

[0026] 2 and 3 are vector diagrams relating to the motor drive device 100 of the first embodiment. The vector diagrams in Fig. 2 and 3 show a rotating coordinate system in which the magnetic flux direction of the motor rotor is the d-axis and the direction perpendicular to the d-axis is the q-axis. In Fig. 2 and 3, the inverter voltage vector V INV , motor induced voltage vector E M , motor current vector I M , and the motor flux vector Φ M is shown.

[0027] In Figure 2, without phase adjustment, the motor induced voltage vector E M In phase with the inverter voltage vector V INV is applied. The motor induced voltage vector E M and inverter voltage vector V INV is along the q-axis. In this case, the motor current vector I M is the motor induced voltage vector E M It is delayed by a phase difference of θ relative to the (q axis).

[0028] In Figure 3, compared to Figure 2, the inverter voltage vector V INV is the motor induced voltage vector E M As a result, in the vector diagram of FIG. 3, the motor current vector I M The phase of the motor induced voltage vector E M The phase is matched to that of

[0029] Here, the torque T in a surface magnet motor in which permanent magnets are attached to the surface of the rotor is M can be expressed as formula (f1) using the number of motor pole pairs P. Note that the motor magnetic flux Φ M and motor current I M is shown as a scalar quantity.

[0030]

number

[0031] On the right side of equation (f1), the number of motor pole pairs P and the motor magnetic flux Φ M is a constant specific to the motor. Furthermore, the motor current I M is also assumed to be constant, the torque T M The maximum value of cosθ is “1” when θ=0 [rad].

[0032] That is, in a surface permanent magnet motor, when the conditions of the vector diagram in Figure 3 are met, the maximum torque can be obtained. M If you want to obtain the motor current I M is minimized, and the efficiency of the motor can be increased.

[0033] Fig. 4 is a diagram showing the relationship between the phase of the motor induced voltage and the phase of the motor current for the motor drive device 100 of this embodiment. Fig. 4 shows the phase relationship between the motor induced voltage and the motor current during rotation.

[0034] The magnitude of the motor induced voltage changes depending on the rotational position of the motor.

[0035] As shown in Figure 4, a surface permanent magnet motor achieves maximum efficiency by matching the phase of the motor induced voltage with the phase of the motor current, as shown by the solid line current waveform in Figure 4. However, if the phase of the motor current lags, as shown by the dashed line current waveform in Figure 4, motor efficiency deteriorates and the motor current increases. Similarly, motor efficiency deteriorates when the motor current phase is advanced.

[0036] The phase of the motor current can be adjusted to lead or lag depending on the phase of the inverter voltage. Therefore, if the phase of the motor current lags the phase of the reference motor induced voltage, the inverter voltage is controlled to lead, and if the phase of the motor current leads, the inverter voltage is controlled to lag. This allows for simple motor control with excellent responsiveness.

[0037] On the other hand, the torque T in an interior permanent magnet motor with a permanent magnet embedded inside the rotor is M is expressed by the following equation (f2).

[0038]

number

[0039] In formula (f2), L d is the inductance of the d-axis component, and L q is the inductance of the q-axis component. Interior permanent magnet motors have saliency, so the relationship is Lq>Ld. In the case of surface permanent magnet motors, there is no saliency, so Lq=Ld, and so "L" in equation (f2) q -L d " becomes 0 (zero). Therefore, formula (f2), in which the 0 term has been deleted, becomes equivalent to formula (f1).

[0040] FIG. 5 is a vector diagram relating to the motor driving device 100 of this embodiment.

[0041] The vector diagram shown in Figure 5 is the inverter voltage vector V INV , motor induced voltage vector E M , motor current vector I M , motor flux vector Φ M 5, the inverter voltage vector V INV The phase of the motor current vector I M The phase of the motor induced voltage vector E M is advanced by a phase θ.

[0042] MTPA (maximum torque per ampere) control is known as a highly efficient control method for interior permanent magnet motors, and the motor current I M The optimum phase θ of the motor is to make the motor flux Φ M This is expressed by equation (f3).

[0043]

number

[0044] Since the result of equation (f3) is positive, the motor current I M The optimum phase θ of the motor is determined by the motor induced voltage E M It leads the phase of

[0045] In addition, in equation (f3), the phase θ is the motor current I M Therefore, the motor current I of the interior permanent magnet motor depends on M The optimum phase θ of the motor varies depending on the load and operating conditions. M and the motor current I M Since the control to match the phase of is a control to aim for θ=0, an interior permanent magnet motor whose optimal phase is θ≠0 has a motor induced voltage E M and the motor current I M Therefore, maximum efficiency cannot be achieved by controlling the phase of the inverter.

[0046] On the other hand, the motor current I in the interior permanent magnet motor shown in equation (f3) M The formula for finding the optimal phase θ of (f3) includes square roots and division. This is not a problem if you have a CPU (central processing unit) with high processing power, but if you try to configure a motor drive device using an inexpensive, small integrated circuit (IC) with inferior processing power, implementing formula (f3) is difficult.

[0047] Therefore, the motor current I of the interior permanent magnet motor is measured using an IC with poor processing power. M Based on the principle of MTPA control, the motor current I M Torque T M or maximize the torque T M Whereas the motor current I M Therefore, the motor current I M Torque T M The proportion (IM / T M ) can be considered as an indicator.

[0048] Index I M / T M Torque T M However, as shown in equations (f1) and (f2), information such as motor magnetic flux and inductance is set. In motor control using an IC with poor processing power, it is difficult to handle a large number of parameters. Therefore, the motor equation of motion shown in equation (f4) is of interest. In equation (f4), M is the motor inertia constant, ω is the angular velocity, and T M is the motor output torque, T L indicates the load torque, and ΔT is the deviation between the motor output torque and the load torque.

[0049]

number

[0050] In this case, by transforming equation (4) from the viewpoint of the change from an arbitrary time and speed, the following equation (f5) is obtained. Note that Δω is the speed deviation, T s is the control period.

[0051]

number

[0052] In equation (f5), Ts and M are constants. Therefore, the speed deviation Δω and the torque deviation ΔT are proportional to each other. Therefore, the index I M / T M In this case, based on the relationship of equation (f5), the torque T M By replacing with the speed ω, the index η in the following equation (f6) is M Motor current I M can be treated as equivalent to the ratio of

[0053]

number

[0054] Based on the index η obtained from equation (6), the voltage phase is adjusted to reduce the index η, thereby deriving the optimal phase of the motor current.

[0055] Although equation (6) includes division, the control process for obtaining the speed ω has a count value N for measuring the elapsed time of an arbitrary period, so the index η can be expressed by multiplication as in the following equation (f7). Note that N is a positive integer and corresponds to the reciprocal of the speed.

[0056]

number

[0057] In the method of adjusting the phase of the motor current using the index η, the control direction in the next calculation cycle is determined according to the change in the index η after the phase of the motor current (or inverter voltage) is advanced or delayed, as shown in Fig. 6. In Fig. 6, an advance angle means adjusting the voltage phase in the positive direction, and a delay angle means adjusting the voltage phase in the negative direction.

[0058] In FIG. 6, advance or delay control is performed for the phase adjustment of the motor current as follows.

[0059] If the previous control was an advance angle and the index η has decreased, advance angle control is executed. If the previous control was an advance angle and the index η has increased, retard angle control is executed. If the previous control was a retard angle and the index η has decreased, retard angle control is executed. If the previous control was a retard angle and the index η has increased, advance angle control is executed. Note that a decrease in the index η indicates an improvement in efficiency, and an increase in the index η indicates a deterioration in efficiency.

[0060] In the above-mentioned method, when the change from the advance angle to the retard angle or the change from the retard angle to the advance angle is repeated in a short period of time, the phase of the motor current is considered to be near the optimum value. Here, the number of changes from the advance angle to the retard angle and the change from the retard angle to the advance angle is defined as the number of inflection points N infle The number of inflection points is defined as N infle By setting an arbitrary upper limit value for , the advance angle control (phase control) converges (ends) after a certain number of repeated trials. In this way, since it takes time for the control to converge due to repeated trials, the responsiveness of the control based on the efficiency is inferior to the control based on the phase of the motor induced voltage and the phase of the motor current. Note that when advance or retard angles are performed a certain number of times in succession, the number of inflection points N infle The value of is reset to 0 (zero), and the motor current is prevented from inadvertently converging to a phase other than the optimum phase.

[0061] In response to the control of the motor by motor drive device 100, regenerative braking occurs.

[0062] 7 and 8 are schematic diagrams illustrating the effects of regenerative braking in motor drive device 100 of this embodiment. The relationship between the locus of the current operating point and the constant voltage circle during operation and deceleration is shown in Fig. 7 and Fig. 8. It is assumed that control is applied to match the phase of the motor induced voltage and the phase of the motor current in the surface permanent magnet motor described above, and that the current operating point moves only on the q-axis current axis.

[0063] Figure 7(a) shows the current operating point (initial position) and constant voltage circle during operation as the initial state. The size of the constant voltage circle is proportional to the voltage / rotation speed. Figure 7(b) shows the change when the inverter voltage is reduced to slow down or stop the motor.

[0064] As shown in Figure 7, when a motor drives a load with inertia, such as a fan, a reduction in inverter voltage does not immediately reduce the motor's rotational speed. As a result, constant-voltage circle A1 shrinks. As the inverter voltage continues to decrease, a moment arrives when the constant-voltage circle and the q-axis intersect at a single point, the origin. Due to the constraints of high-efficiency control, constant-voltage circle B1 cannot be further reduced. However, as the inverter voltage continues to decrease, the rotational speed must be reduced to maintain or even expand the size of the constant-voltage circle. To reduce the rotational speed, braking is required, and regenerative braking is achieved by shifting the current operating point to the negative side of the q-axis current. If there is no regenerative load, the inverter circuit voltage will rise, as shown by constant-voltage circle B2, resulting in overvoltage.

[0065] Figure 8(a) shows the initial state during operation, similar to Figure 7(a). Figure 8(b) is partially identical to Figure 7(b). As mentioned above, when a load with inertia, such as a fan, is driven, the motor rotation speed does not decrease immediately after the inverter voltage is reduced, so the constant voltage circle becomes smaller.

[0066] As the inverter voltage continues to decrease, there will come a moment when the constant voltage circle B1 and the q-axis intersect at only one point, the origin. From this state, the current operating point can be moved in the negative direction of the d-axis, allowing the constant voltage circle C1 to become even smaller. At this time, the current operating point does not move to the negative side of the q-axis, so regenerative braking does not occur. Therefore, no overvoltage occurs. The movement of the current operating point on the q-axis and d-axis is achieved by adjusting the inverter voltage phase δ to shift the motor current phase θ, as shown in Figures 1, 2, and 5.

[0067] Based on the above principles, the motor driving device 100 of this embodiment can suppress overvoltage and achieve highly efficient driving of the motor.

[0068] (c) Operation A control method for the motor driving device 100 of this embodiment will be described with reference to FIGS.

[0069] 9 is a flowchart of lead angle control (phase control) relating to the control method of motor drive device 100 of this embodiment. Lead angle control refers to a control function that adjusts the phase δ of the inverter voltage shown in FIGS. 1, 2, and 5. Leading the phase of the voltage (or current) is referred to as lead angle, and delaying the phase of the voltage (or current) is referred to as delay angle.

[0070] The advance angle control shown in the flowchart of FIG. 9 is made up of various processes in steps S91, S92, S93, and S94.

[0071] <s91> In step S91, motor driving apparatus 100 executes an overvoltage determination. Motor driving apparatus 100 detects the current inverter DC voltage Vx through the operation of voltage detection unit 6 and overvoltage detection unit 11 in FIG.

[0072] <s92> In step S92, the motor driving device 100 determines, in relation to the operation of the voltage detection unit 6 and the overvoltage detection unit 11, whether the current DC voltage Vx of the inverter circuit 1 exceeds a preset overvoltage detection threshold (first threshold).

[0073] <s93> In step S93, if the magnitude of DC voltage Vx exceeds the detection threshold (YES in S92), motor driving device 100 executes overvoltage suppression control, thereby suppressing the overvoltage generated in inverter circuit 1.

[0074] <s94> In step S94, if the magnitude of DC voltage Vx does not exceed the detection threshold (NO in S92), motor driving apparatus 100 executes high-efficiency control, thereby driving motor 4 with high efficiency.

[0075] While the motor 4 is in operation, the motor driving device 100 repeatedly executes the processes of steps S91, S92, S93, and S94.

[0076] The overvoltage suppression control in step S93 is a control process of the first phase adjustment unit 12 in Fig. 1. The overvoltage suppression control is a function that controls the current operating point in the negative direction of the d-axis to counter the overvoltage shown in Fig. 8, and forcibly advances the inverter voltage.

[0077] 10 is a flowchart of overvoltage suppression control relating to the control method of the motor drive device 100 of the first embodiment. The flowchart in FIG. 10 shows a more specific example of the overvoltage suppression control (S93) in FIG.

[0078] <s101> In step S101, the motor driving device 100 causes the voltage detection unit 6 and the overvoltage detection unit 11 to detect an overvoltage.

[0079] <s102> In step S102, the motor drive device 100 adjusts the lead angle control value θ obtained from the overvoltage suppression control (S93) or the high-efficiency control (S94) in the previous process by the first phase adjustment unit 12. n-1 A preset advance angle control amount M is added to

[0080] <s103> In step S103, the motor drive device 100 adjusts the previous lead angle control value θ by the first phase adjustment unit 12. n-1 and the sum of the advance angle control amount M (θ n-1 +M) to the new lead angle control value (current lead angle control value) θ n Set as.

[0081] The motor drive device 100 adjusts the set lead angle control value θ n =θ n-1 +M is output from the first phase adjustment unit 12 to the phase adjustment selection unit 15. When an overvoltage is detected, the phase adjustment selection unit 15 outputs the lead angle control value θ n =θ n-1 +M is output to the voltage control unit 18 as the phase adjustment amount CNT.

[0082] Through the above steps S101, S102, and S103, the overvoltage suppression control is executed.

[0083] The high-efficiency control in step S94 is a control process of the second phase adjustment unit 14 in FIG. 1. An example of high-efficiency control is the control of matching the phase of the motor induced voltage and the phase of the motor current in a surface permanent magnet motor, as described above. The second phase adjustment unit 14 adjusts the previous lead angle control value θ in accordance with the operating state of the motor 4 so that the operation of the motor 4 becomes more efficient. n-1 A preset advance angle control amount M is added to the input signal to advance the angle, or the advance angle control amount M is subtracted from the input signal to delay the angle.

[0084] 11 is a flowchart of high-efficiency control relating to the control method of motor drive device 100 of the first embodiment. The flowchart in FIG. 11 shows a more specific example of high-efficiency control (S94) in FIG.

[0085] The high-efficiency control shown in the flowchart of FIG. 10 is composed of various processes in steps S111, S112, S113, S114, S115, S116a, S116b, S117a, S117b, S117c, S117d, S117e, S117f, S118a, S118b, S119a, S119b, S119c, S119d, S119e, and S119f.

[0086] <s111> In step S111, motor driving apparatus 100 acquires the current peak value of the motor current. For example, motor driving apparatus 100 acquires the current peak value for each cycle of the motor current through the operation of current detection unit 5 and motor current detection unit 13.

[0087] <s112> In step S112, motor drive device 100 acquires the rotation speed of motor 4 using rotation speed detection unit 16B.

[0088] <s113> In step S113, motor drive device 100 performs a period switching determination based on the current peak value and the rotation speed. Based on the determination results of the current peak value and the rotation speed, motor drive device 100 detects that one operation period of motor 4 has been completed. If a period switching has not occurred (NO in S113), motor drive device 100 ends the process.

[0089] In response to detection of the completion of one cycle of operation (YES in S113), motor drive device 100 causes second phase adjustment unit 14 to perform the following process once per cycle.

[0090] <s114> If a cycle change has occurred (YES in S113), in step S114, motor driving device 100 executes index calculation using second phase adjustment unit 14. Motor driving device 100 calculates the motor current peak value I p Using the speed count value N, the index η is calculated as shown in the following equation (f8). n Calculate (accumulate) η n-1 indicates the value of the previous calculation result.

[0091]

number

[0092] Accumulated index η n After the index determination (S117b, S119b) described later is completed, the previous index value η n-1 Update of (η n-1 =η n ) and the value of this index η n Initialization of (η n =0) is performed.

[0093] <s115> In step S115, motor driving device 100 performs stage determination. Motor driving device 100 executes one of a plurality of branched processes using second phase adjustment unit 14 according to the state of phase adjustment (stage value).

[0094] <S116a,S116b> If the value of the stage is 0, then in step S116a, motor driving device 100 advances the phase by a predetermined amount. In step S116b, motor driving device 100 sets the value of the stage to 1.

[0095] <S117a~S117f> If the stage value is 1, in step S117a, motor drive device 100 checks whether the number of cycles of motor 4 has passed a predetermined specified cycle. If the cycle of motor 4 has not passed the specified cycle (NO in S117a), motor drive device 100 does not execute the process.

[0096] If the period of the motor 4 has passed the specified period (YES in S117a), in steps S117b and S117c, the motor driving device 100 compares the indexes and determines the current value η of the index η. n and the previous value of the indicator η n-1 For example, the current value η n is the previous value η n―1 It is determined whether it is smaller than

[0097] η n <η n-1 If the above expression is true (YES in S117c), motor driving device 100 sets the stage value to 0 in step S117d.

[0098] η n <η n-1 If the above expression is not satisfied (NO in S117c), motor driving device 100 sets the stage value to 2 in step S117e.

[0099] In step S117f, motor driving device 100 updates the value of index η to the current value.

[0100] <S118a,S118b> If the value of the stage is 2, then in step S118a, motor driving device 100 delays the phase by a predetermined amount. In step S118b, motor driving device 100 sets the value of the stage to 3.

[0101] <S119a~S119f> If the stage value is 3, in step S119a, motor drive device 100 checks whether the number of cycles of motor 4 has passed a predetermined specified cycle. If the number of cycles of motor 4 has not passed the specified cycle (NO in S119a), motor drive device 100 does not execute the process.

[0102] If the number of cycles of the motor 4 has passed the specified cycle (YES in S119a), in steps S119b and S119c, the motor driving device 100 compares the indexes and calculates the current index value η n is the previous index value η n-1 Compares for less than.

[0103] η n <η n-1 If the above expression is true (YES in S119c), motor driving device 100 sets the stage value to 2 in step S119d.

[0104] η n <η n-1 If it is not true (NO in S119c), motor driving device 100 sets the stage value to 0 in step S119e.

[0105] In step S119f, motor driving device 100 updates the value of index η to the current value.

[0106] In this way, by setting the stage of the advance angle control based on the value of the index η, the motor driving device 100 can control the advance angle and delay angle of the phase of the inverter circuit 1 (or the motor 4) by the second phase adjustment unit 14.

[0107] By performing the above processing, the motor drive device 100 of the first embodiment can avoid the risk of overvoltage occurring when slowing down or stopping the motor 4 when a load 9 with large inertia, such as a fan, is connected to the motor 4 in controlling a synchronous motor that uses a permanent magnet, and can drive the motor 4 with high efficiency during normal operation.

[0108] (d) Summary Examples of control methods for increasing the efficiency of a motor system include a method of adjusting the voltage phase so that the phase of the motor's induced voltage matches the phase of the current, and a method of adjusting the voltage phase so that the motor's current becomes smaller.

[0109] A synchronous motor using permanent magnets generates electricity spontaneously from the induced voltage that occurs as the permanent magnets rotate. When high-efficiency control is applied to a synchronous motor using permanent magnets, regenerative braking can occur unintentionally depending on the operating conditions. If regenerative braking occurs and there is no way to consume the regenerative energy, the circuit voltage will rise, leading to overvoltage, and there is a risk of damage to various devices connected to the motor.

[0110] When driving a synchronous motor using permanent magnets, there is a risk of overvoltage occurring due to regenerative braking, especially when the motor drives a load with large inertia, such as a fan. The risk of overvoltage can be avoided or reduced by providing a resistor or other regenerative load to consume regenerative energy. However, in a configuration with a regenerative load, the motor system becomes larger because a regenerative load that is not used in normal operation is installed in the motor system.

[0111] On the other hand, if there is no mechanism to consume the regenerative energy, the circuit voltage will rise and become overvoltage. Therefore, measures such as increasing the insulation distance will be necessary to ensure sufficient withstand voltage margin for various devices, including inverter circuits. In this case, various devices will tend to become larger and their costs will increase.

[0112] As a result, the competitiveness of the motor system product is lost.

[0113] The motor drive device 100 of this embodiment does not accept the risk of overvoltage, but rather eliminates the risk of overvoltage by suppressing regenerative energy through an ingenious motor control method.

[0114] As described above, the motor drive device 100 of this embodiment controls the phase of the inverter voltage to suppress the overvoltage when an overvoltage is detected, and controls the phase of the inverter voltage to drive the motor 4 with high efficiency when an overvoltage is not detected.

[0115] As a result, the motor drive device 100 of this embodiment can eliminate the risk of overvoltage and achieve highly efficient operation while preventing the device from becoming larger and more expensive.

[0116] As described above, the motor drive device of this embodiment can provide a high-performance motor drive device.

[0117] (2) Second embodiment A motor drive device and a control method thereof according to the second embodiment will be described with reference to FIGS.

[0118] (a) Configuration An example of the configuration of a motor drive device according to the second embodiment will be described with reference to FIG.

[0119] FIG. 12 is a block diagram showing an example of the configuration of a motor driving device 100 according to this embodiment.

[0120] As shown in FIG. 12, motor driving device 100 of this embodiment differs from the configuration of motor driving device 100 of the first embodiment (see FIG. 1) in that it further includes a third phase adjustment unit 19.

[0121] The third phase adjustment unit 19 is a control unit that receives the motor current as an input and improves the efficiency of the operation of the motor 4. However, the third phase adjustment unit 19 is configured with a control law different from that of the second phase adjustment unit 14.

[0122] The phase adjustment selection unit 15 selects one of the calculation results from each of the first phase adjustment unit 12, the second phase adjustment unit 14, and the third phase adjustment unit 19. The phase adjustment selection unit 15 outputs the selected calculation result as the phase adjustment amount CNT to the voltage control unit 18. The phase adjustment selection unit 15 feeds back the selected previous phase adjustment amount CNT (and the advance angle control amount) to the first to third phase adjustment units 12, 14, and 19.

[0123] During normal operation of the motor, it is necessary to control the motor with high efficiency. Therefore, during normal operation, phase adjustment selection unit 15 selects either the output of second phase adjustment unit 14 or the output of third phase adjustment unit 19. When an overvoltage is detected and the motor system needs to be protected immediately, phase adjustment selection unit 15 selects the output of first phase adjustment unit 12.

[0124] Fig. 13 shows an example of a current waveform obtained by the current detection unit 5 in Fig. 12. In Fig. 13, three waveforms are depicted.

[0125] The waveform in the middle is the waveform when the phase of the inverter voltage and the phase of the motor current are the same. When the phase of the inverter voltage and the phase of the motor current are the same, the power factor is 1. When the power factor is 1, a relatively high efficiency state is achieved.

[0126] The waveform in the upper part has a downward sloping shape, which indicates that the motor current phase is more advanced than when the power factor is 1.

[0127] The waveform in the lower part has an upward sloping shape, which indicates that the motor current phase lags behind when the power factor is 1.

[0128] In this way, different waveforms (for example, current gradients) of the DC current Ix are observed depending on the state of the power factor (rotational position of the motor).

[0129] The phase state of the inverter voltage may be observed from the slope of the motor current waveform.

[0130] The third phase adjustment unit 19 performs control for increasing the efficiency of the motor 4 by advance angle control based on information obtained from the waveform of the motor current or the DC current Ix.

[0131] (b) Operation A control method for the motor driving device 100 of the second embodiment will be described with reference to FIGS.

[0132] 14 is a flowchart of high-efficiency control relating to the control method of the motor drive device 100 of this embodiment. FIG. 14 shows a flowchart of the control of the third phase adjustment unit 19 in FIG.

[0133] The control according to the flowchart of FIG. 14 is made up of various processes in steps S141, S142, S143, and S144.

[0134] <s141> In step S141, motor drive device 100 executes processing by current detection unit 5 and motor current detection unit 13 to detect the motor current.

[0135] <S142,S143> In step S142, motor drive device 100 evaluates the slope of the motor current using third phase adjustment unit 19. In step S143, motor drive device 100 uses third phase adjustment unit 19 to determine whether the index of the slope of the motor current is positive.

[0136] FIG. 15 is a schematic diagram illustrating an example of a method for evaluating the gradient of the motor current. The magnitude of the motor induced voltage changes depending on the rotational position of the motor. As shown in FIG. 15, for example, the motor drive device 100 uses the third phase adjustment unit 19 to evaluate the gradient of the motor current at the timing of the maximum positive amplitude (peak) of the motor induced voltage. When the phase of the motor current is lagging, the gradient of the motor current is positive. When the phase of the motor current is leading, the gradient of the motor current is negative. In this way, the phase state of the motor current can be determined from the gradient of the motor current.

[0137] If the exact phase of the motor induced voltage cannot be obtained, motor drive device 100 determines the gradient of the motor current based on the upward or downward slope of the waveform of DC current Ix shown in FIG.

[0138] <s144> In step S144, if the slope of the motor current is positive or the waveform of the DC current is rising (YES in step S143), motor drive device 100 performs an advance angle determination using third phase adjustment unit 19. As a result, processing is performed to add +1 step to the previous advance angle control value.

[0139] <s145> In step S145, if the slope of the motor current is negative or the waveform of the DC current is downward sloping (NO in step S143), motor drive device 100 performs a delay angle determination using third phase adjustment unit 19. As a result, processing of -1 step is performed on the previous advance angle control value.

[0140] Through the above-described various processes, the control by the third phase adjustment unit 19 in the motor drive device 100 of this embodiment is completed.

[0141] Fig. 16 is a flowchart of lead angle control relating to the control method of motor drive device 100 of this embodiment. The flowchart in Fig. 16 shows the processing of phase adjustment selection unit 15. The control according to the flowchart in Fig. 16 is made up of various processes in steps S161, S162, S163, S164, S165, S166, S167, and S168.

[0142] The flowchart shown in Figure 16 is the control flowchart for motor drive device 100 of the first embodiment shown in Figure 9, to which a switching condition to high-efficiency control based on the observation results of the current waveform processed by third phase adjustment unit 19 has been added.

[0143] <S161,S162> In steps S161 and S162, similar to the above-mentioned steps S91 and S92, the motor driving device 100 determines whether the current DC voltage Vx of the inverter circuit 1 exceeds a preset overvoltage detection threshold (first threshold) through the operation of the voltage detection unit 6 and the overvoltage detection unit 11.

[0144] <s163> If the value of the DC voltage Vx of the inverter circuit 1 exceeds the detection threshold (YES in S162), the motor drive device 100 performs overvoltage suppression control based on the processing of Figure 10 described above, using the output of the first phase adjustment unit 12 in accordance with the selection of the phase adjustment selection unit 15, similar to step S93 in Figure 9.

[0145] <S164,S165> If the value of DC voltage Vx of the inverter circuit does not exceed the detection threshold (NO in S162), motor driving device 100 executes processing for high efficiency control in accordance with the selection of phase adjustment selection unit 15.

[0146] In step S164, the motor driving device 100 determines the number of inflection points N infle The motor driving device 100 detects the number of times the angle changes from an advance angle to a delay angle and the number of times the angle changes from a delay angle to an advance angle.

[0147] In step S165, the motor driving device 100 detects the number of inflection points N infle is smaller than a threshold (second threshold). For example, infle The threshold value for is set to 1.

[0148] <s166> Number of inflection points N infle If is smaller than the threshold value (YES in S165), motor drive device 100 performs high-efficiency control using a current waveform based on the processing in Figure 14 described above, using the output of third phase adjustment unit 19 in accordance with the selection of phase adjustment selection unit 15.

[0149] <s167> Number of inflection points N infle If is greater than or equal to the threshold value (NO in S165), motor drive device 100 performs high-efficiency control using the index based on the output of second phase adjustment unit 14 in accordance with the selection of phase adjustment selection unit 15, based on the processing in Figure 11 described above.

[0150] <s168> After the various controls have been selected, in step S168, the motor driving device 100 infle Integration process and number of inflection points N infle Execute the reset process.

[0151] While the motor 4 is in operation, the motor driving device 100 repeatedly executes the processes of steps S161, S162, S163, S164, S165, S166, S167, and S168.

[0152] (c) Summary Motor drive device 100 of this embodiment further includes a third phase adjustment unit 19 that performs high-efficiency control based on the observation results of the current waveform.

[0153] In the control method of motor drive device 100 of this embodiment, lead angle control (see FIG. 14) using the added waveform shape of the motor current (or DC current) has better responsiveness than lead angle control using the index of FIG.

[0154] However, in the case of lead angle control based on the current waveform, it is difficult to converge the phase state to the optimum lead angle (operating point), whereas lead angle control based on an index is superior in terms of converging to the optimum lead angle.

[0155] Therefore, motor drive device 100 of this embodiment can achieve both responsiveness and convergence by combining lead angle control based on an index and lead angle control based on the current waveform shape.

[0156] As described above, when controlling a synchronous motor using a permanent magnet, the motor drive device 100 of the second embodiment can avoid the risk of overvoltage occurring when slowing down or stopping the motor when a load with large inertia, such as a fan, is connected to the motor, and can also achieve highly efficient control with excellent responsiveness and convergence during normal motor operation.

[0157] As a result, the motor driving device 100 of this embodiment can provide a high-performance motor driving device.

[0158] (3) Other The motor drive device of this embodiment can be applied to home appliances, railway vehicles, electric vehicles, power generation systems, and the like.

[0159] Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, and are also included in the scope of the invention and its equivalents as defined in the claims. [Explanation of symbols]

[0160] 1: inverter circuit, 2: IGBT (Insulated Gate Bipolar Transistor), 3: freewheel diode, 4: motor, 5: current detection unit, 6: voltage detection unit, 11: overvoltage detection unit, 12: first phase adjustment unit, 13: motor current detection unit, 14: second phase adjustment unit, 15: phase adjustment selection unit, 16A: rotation position detection unit, 16B: rotation speed detection unit, 17: operation command setting unit, 18: voltage control unit, 19: third phase adjustment unit, 9: load unit, 100: motor drive device.

Claims

1. a three-phase synchronous motor; a power conversion device that converts a DC voltage into three-phase AC power of a certain voltage and a certain frequency by switching operations of a plurality of semiconductor elements and supplies the converted three-phase AC power to the three-phase synchronous motor; a voltage detection unit that detects a voltage on a DC input side of the power conversion device; a voltage control unit that issues ON / OFF commands to the plurality of semiconductor elements in order to apply a drive voltage of a certain voltage and a certain frequency from the power conversion device to the three-phase synchronous motor; a plurality of phase adjustment units that adjust the phases of the drive voltages, respectively; a phase adjustment selection unit that selects one of the calculation results of the plurality of phase adjustment units and outputs the selected calculation result to the voltage control unit; Equipped with a first phase adjustment unit among the plurality of phase adjustment units performs control so as to advance the phase of the drive voltage when a voltage detection value obtained from the voltage detection unit exceeds a first threshold; the phase adjustment selection unit selects the output of the first phase adjustment unit when the voltage detection value exceeds the first threshold value. Motor drive device.

2. a current detection unit that detects a motor current of at least one phase of the three-phase synchronous motor; a rotation speed detection unit that detects the rotation speed of the three-phase synchronous motor; Further comprising: a second phase adjustment unit among the plurality of phase adjustment units sets an index based on a ratio between the magnitude of the motor current obtained by the current detection unit and the magnitude of the rotation speed obtained by the rotation speed detection unit, and determines whether to advance or delay the phase of the drive voltage based on the magnitude of the index; the phase adjustment selection unit selects the output of the second phase adjustment unit when the voltage detection value is equal to or less than the first threshold value. The motor drive device according to claim 1 .

3. a rotational position detection unit that detects a signal synchronized with a rotational position of the three-phase synchronous motor; Furthermore, a third phase adjustment unit among the plurality of phase adjustment units evaluates a gradient of the motor current obtained by the current detection unit in accordance with the rotational position of the motor obtained by the rotational position detection unit, and determines whether to advance or delay the phase of the drive voltage based on a result of the evaluation of the gradient; the phase adjustment selection unit selects one of the outputs of the second and third phase adjustment units when the voltage detection value is equal to or less than the first threshold value. The motor drive device according to claim 2 .

4. the third phase adjustment unit evaluates the gradient of the motor current based on a waveform of the motor current. The motor drive device according to claim 3 .

5. the third phase adjustment unit evaluates the gradient of the motor current based on an observation result of the motor current at a certain timing. The motor drive device according to claim 3 .

6. the phase adjustment selection unit selects the output of the second phase adjustment unit when the number of times the phase of the motor current changes between the advance angle and the delay angle exceeds a second threshold, and selects the output of the third phase adjustment unit when the number of times is equal to or less than the second threshold. The motor drive device according to claim 3 .

7. a three-phase synchronous motor; a power conversion device that converts a DC voltage into three-phase AC power of a certain voltage and a certain frequency by switching operations of a plurality of semiconductor elements and supplies the converted three-phase AC power to the three-phase synchronous motor; a current detection unit that detects a motor current of at least one phase of the three-phase synchronous motor; a voltage detection unit that detects a voltage on a DC input side of the power conversion device; a rotational position detection unit that detects a signal synchronized with a rotational position of the three-phase synchronous motor; a rotation speed detection unit that detects the rotation speed of the three-phase synchronous motor; a voltage control unit that issues ON / OFF commands to the plurality of semiconductor elements in order to apply a drive voltage of a certain voltage and a certain frequency from the power conversion device to the three-phase synchronous motor; a plurality of phase adjustment units that adjust the phases of the drive voltages, respectively; a phase adjustment selection unit that selects one of the calculation results of the plurality of phase adjustment units and outputs the selected calculation result to the voltage control unit; Equipped with The plurality of phase adjustment units include: a first phase adjustment unit configured to advance the phase of the drive voltage when a voltage detection value obtained by the voltage detection unit exceeds a preset first threshold; a second phase adjustment unit that sets an index based on a ratio between the magnitude of the motor current detected by the current detection unit and the magnitude of the rotation speed detected by the rotation speed detection unit, and determines whether to advance or delay the phase of the drive voltage based on the magnitude of the index; a third phase adjustment unit that evaluates a gradient of the motor current obtained by the current detection unit in accordance with the rotational position of the motor obtained by the rotational position detection unit, and determines whether to advance or delay the phase of the drive voltage based on the result of the evaluation of the gradient; Including, the phase adjustment selection unit selects control of the phase of the drive voltage based on the calculation result of the first phase adjustment unit when the voltage detection value obtained from the voltage detection unit exceeds the first threshold, and selects control of the phase of the drive voltage based on the calculation result of either the second or third phase adjustment unit when the voltage detection value is equal to or less than the first threshold. Motor drive device.

8. the phase adjustment selection unit selects the calculation result of the second phase adjustment unit when the number of times the phase of the motor current changes between the advance angle and the delay angle exceeds a second threshold, and selects the calculation result of the third phase adjustment unit when the number of times is equal to or less than the second threshold. The motor drive device according to claim 7.

9. the third phase adjustment unit evaluates the gradient of the motor current based on a waveform of the motor current. The motor drive device according to claim 7.

10. the third phase adjustment unit evaluates the gradient of the motor current based on an observation result of the motor current at a certain timing. The motor drive device according to claim 7.

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