Drive unit and control method of electric motor

Abstract

To provide a drive unit which is excellent in responsiveness and realizes higher efficiency of an electric motor.SOLUTION: A drive unit according to an embodiment comprises a power converter, a voltage control unit and a phase adjustment unit. The power converter converts input power into AC power to be supplied to an electric motor. The voltage control unit applies drive voltage from the power converter to the electric motor by controlling an operation of the power converter. The phase adjustment unit executes first processing of advancing a phase of the drive voltage and second processing of delaying the phase of the drive voltage to adjust the phase of the drive voltage. The phase adjustment unit executes first phase control processing of receiving first information regarding a relation between the phase of current flowing in the electric motor and a rotational position of the electric motor to adjust the phase of the drive voltage on the basis of the first information, and second phase control processing of receiving second information regarding magnitude of current flowing in the electric motor, and third information regarding rotational speed of the electric motor to adjust the phase of the drive voltage on the basis of the second information and the third information.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] An embodiment of the present invention relates to a control method for a drive device and an electric motor. [Background technology]

[0002] To improve the efficiency of electric motor systems, synchronous motors using permanent magnets have become widespread, and various methods for controlling electric motors have been proposed. Examples of control methods for improving efficiency include a method of adjusting the voltage phase so that the induced voltage phase and current phase of the electric motor coincide, and a method of adjusting the voltage phase so that the current of the electric motor becomes small. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6935349 Summary of the Invention [Problem to be solved by the invention]

[0004] An embodiment of the present invention provides a drive device and a method for controlling an electric motor that are excellent in responsiveness and achieve high efficiency of the electric motor. [Means for solving the problem]

[0005] A drive device according to an embodiment includes a power converter, a voltage control unit, and a phase adjustment unit. The power converter converts input power into AC power and supplies it to the electric motor. The voltage control unit controls the operation of the power converter to apply a drive voltage from the power converter to the electric motor. The phase adjustment unit adjusts the phase of the drive voltage by executing a first process of advancing the phase of the drive voltage and a second process of delaying the phase of the drive voltage. The phase adjustment unit receives first information regarding a relationship between the phase of a current flowing through the electric motor and a rotational position of the electric motor, and executes a first phase control process of adjusting the phase of the drive voltage based on the first information, and receives second information regarding the magnitude of the current flowing through the electric motor and third information regarding the rotational speed of the electric motor, and executes a second phase control process of adjusting the phase of the drive voltage based on the second information and the third information. [Brief description of the drawings]

[0006] [Figure 1] Vector diagram of a permanent magnet motor. [Diagram 2] Vector diagram of a permanent magnet motor. [Diagram 3] FIG. 4 is a waveform diagram showing the relationship between the induced voltage of the motor and the current of the motor. [Figure 4] Vector diagram of a permanent magnet motor. [Diagram 5] 1 is a block diagram showing a drive device and a drive system according to a first embodiment. [Figure 6] 5 is a flowchart for explaining the driving operation of the driving device according to the first embodiment. [Figure 7] 5 is a flowchart showing a first phase control process of the drive device according to the first embodiment. [Figure 8] 5 is a flowchart showing an advance angle process of the drive device according to the first embodiment. [Figure 9] 5 is a flowchart showing a retardation process of the drive device according to the first embodiment. [Figure 10] 5 is a flowchart showing a second phase control process of the drive device according to the first embodiment. [Figure 11] FIG. 4 is a waveform diagram showing an example of current detection using a shunt resistor. [Figure 12] 10 is a flowchart showing a first phase control process of a drive device according to a second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0007] Hereinafter, the embodiments will be described with reference to the drawings. In the description, components having substantially the same functions and configurations are given the same reference numerals. The embodiments described below are merely examples of technical ideas. The materials, shapes, structures, arrangements, etc. of the components are not specified in the embodiments. Various modifications can be made to the embodiments.

[0008] (First embodiment) First, an overview of the drive control of an electric motor will be described. Figures 1 and 2 are vector diagrams of an electric motor using permanent magnets. Each of Figures 1 and 2 shows a magnetic flux vector Φ M The magnetic flux vector Φ M In addition, a drive voltage vector V applied to the motor from a power converter (inverter), an induced voltage vector E of the motor, and a current vector I flowing through the motor are shown.

[0009] Fig. 1 shows a state in which a drive voltage V is applied to a motor so that the drive voltage vector V is in phase with the induced voltage vector E. In this case, the phase difference θ of the current vector I flowing through the motor with respect to the induced voltage vector E is θa. The current vector I lags behind the induced voltage vector E by the phase difference θa.

[0010] FIG. 2 shows a state in which a drive voltage V is applied to the motor with the phase δ of the drive voltage vector V leading the induced voltage vector E by phase δa so that the phases of the current vector I and induced voltage vector E match. In the state of FIG. 2, the phase shift of the drive voltage from the state of FIG. 1 is phase δa. In this case, the drive voltage vector V leads the phase δa relative to the induced voltage vector E, so that the current vector I of the motor is in phase with the induced voltage vector E. Therefore, the phase difference θ of the current vector I with respect to the induced voltage vector E is zero.

[0011] Here, the torque T in a surface permanent magnet motor M can be expressed as formula (1) using the number of pole pairs P of the motor, the current I mentioned above, and the phase difference θ. In formula (1), the magnetic flux Φ M The current I flowing through the motor is expressed as a scalar quantity.

[0012]

number

[0013] On the right side of equation (1), the number of pole pairs P and magnetic flux Φ M is a constant. If we assume that the current I is also constant, then maximizing cosθ will produce the torque T M The maximum value of cosθ is 1 when θ=0 rad. In other words, in a surface permanent magnet motor, the maximum torque can be obtained when the conditions of the vector diagram shown in Figure 2 are met. Conversely, an arbitrary torque T M If you want to obtain, you can minimize the current I and improve the efficiency by setting θ = 0 rad.

[0014] FIG. 3 is a waveform diagram showing the relationship between the induced voltage of the motor and the current of the motor. The horizontal axis of the waveform diagram indicates time. The vertical axis indicates the value of the voltage or current. In FIG. 3, the waveform of the induced voltage E of the motor and the waveform of the current I of the motor are shown side by side. The current I is shown by a solid line when the current I and the induced voltage E are in phase, and by a dashed line when the phase of the current I lags behind the induced voltage E. In a surface magnet type motor, the highest efficiency is obtained by matching the phase of the induced voltage E with the phase of the current I. On the other hand, if the phase of the current I lags behind the phase of the induced voltage E, the efficiency deteriorates, and the current I becomes larger than when the phase of the induced voltage E and the phase of the current I are matched. The same is true when the phase of the current I leads the phase of the induced voltage E. The phase of the current I can be adjusted to be advanced or delayed by the phase of the drive voltage V. In other words, the phase of the drive voltage V can be adjusted so that the phase of the current I matches the phase of the induced voltage E. Specifically, if the phase of the current I lags behind the phase of the reference induced voltage E, the phase of the drive voltage V is advanced, and if the phase of the current I leads, the phase of the drive voltage V is delayed. This type of control is simple and has excellent responsiveness. As a method for determining the phase, for example, a method of determining the slope of the waveform of the current I based on the timing at which the induced voltage E reaches a positive peak can be considered. In this case, if the phase of the current I lags behind the phase of the induced voltage E, the slope will be positive, and if the phase of the current I leads behind the phase of the induced voltage E, the slope will be negative. In this way, by determining the reference timing and detecting the slope of the waveform of the current I, it is possible to determine whether the phase is delayed or advanced.

[0015] On the other hand, the torque T in an interior permanent magnet motor M is expressed by equation (2).

[0016]

number

[0017] In equation (2), inductance Ld is the d-axis component inductance. Inductance Lq is the q-axis component inductance. Interior permanent magnet motors have saliency, so the relationship is Lq>Ld. Note that in the case of surface permanent magnet motors, there is no saliency and Lq=Ld, so the term in equation (2) that includes (Lq-Ld) becomes 0, and equation (2) becomes equivalent to equation (1).

[0018] Figure 4 is a vector diagram of a motor using permanent magnets. In Figure 4, the magnetic flux vector Φ M The direction in which it acts is the d-axis, and the direction perpendicular to the d-axis is the q-axis. In Fig. 4, the phase of the drive voltage vector V is further advanced compared to Figs. 1 and 2, and the phase shift amount is set to δb, so that the phase of the motor current vector I is advanced by a phase θb ​​from the induced voltage vector E. Here, MTPA (Maximum Torque Per Ampere) control is known as a high-efficiency control method for interior permanent magnet motors, and the optimal phase θc of the motor current is expressed by equation (3) where Φa is the motor magnetic flux.

[0019]

number

[0020] Since the result of equation (3) is positive, the optimal phase θc of the current I of an interior permanent magnet motor leads the phase of the induced voltage E, as shown in Figure 4. Also, since the phase θ in equation (3) depends on the current I, the optimal phase θc of the current I of an interior permanent magnet motor changes depending on the load and operating state. Note that the control that matches the phase of the induced voltage E and the phase of the current I described above is a control that aims for θ = 0 rad, so for an interior permanent magnet motor whose optimal phase is not 0 rad, this control cannot achieve maximum efficiency.

[0021] Incidentally, the formula for finding the optimum phase θ of the current I in an interior permanent magnet motor, shown in equation (3), contains square roots and division. When configuring a drive system for an electric motor, this is not a problem if a CPU (Central Processing Unit) with relatively high processing power is used, but implementation is difficult when attempting to configure it using an inexpensive, small-sized IC (Integrated Circuit) with relatively low processing power. The following method, for example, can be given as a method for finding the optimum phase θc of the current I in an interior permanent magnet motor without performing square roots or division. Based on the principle of MTPA, it is sufficient to maximize the torque with respect to the current I, or minimize the current I with respect to the torque. Therefore, the torque T with respect to the current I is calculated as follows: M Ratio of I / T M is used as an indicator.

[0022] Index I / T M Torque T M However, as shown in equations (1) and (2), to express torque, it is necessary to set information such as the motor magnetic flux and inductance. In motor control using ICs with relatively low processing power, it is difficult to handle a large number of parameters. Therefore, we focus on the motor's equation of motion shown in equation (4). Note that 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 (i.e., T M -T L ).

[0023]

number

[0024] If we transform equation (4) from the perspective of the change from an arbitrary time and speed, that is, by replacing the term that partially differentiates ω with respect to t with Δω / Ts and further transforming the equation, we obtain equation (5), where Δω is the speed deviation and Ts is the control period.

[0025]

number

[0026] In equation (5), the control period Ts and the motor inertia constant M are constants, so the speed deviation Δω and the torque deviation ΔT are proportional to each other. M Based on the relationship in equation (5), the torque T M By replacing with the speed ω, the torque T M can be treated as an index η equivalent to the ratio of current I to

[0027]

number

[0028] Based on the index obtained from equation (6), the current I can be brought to the optimal phase by adjusting the phase of the drive voltage V so as to reduce this index. Note that although equation (6) includes division, the control system has a count value N (N is a positive integer, equivalent to the reciprocal of the speed) for observing the elapsed time of an arbitrary period in the control process to obtain the speed ω. Therefore, the index can be expressed by multiplication as in the following equation (7).

[0029]

number

[0030] The method of adjusting the phase of the current I using the index η determines the control direction in the next calculation cycle according to the change in the index η after executing a phase advance process (adjusting the phase of the drive voltage in the direction to advance it) or a phase delay process (adjusting the phase of the drive voltage in the direction to delay it), as shown in the table below.

[0031] [Table 1]

[0032] As shown in Table 1, if the index η decreases and the previous phase advance process was performed, the phase advance process is performed. If the index η decreases and the previous phase delay process was performed, the phase delay process is performed. If the index η increases and the previous phase advance process was performed, the phase delay process is performed. If the index η increases and the previous phase delay process was performed, the phase advance process is performed.

[0033] In the above method, when the process of advancing the phase to a process of delaying the phase, or the process of delaying the phase to an advance is repeated in a short period of time, the phase of the current I can be considered to be near the optimum value. The change from the process of advancing the phase to a process of delaying the phase, or from the process of delaying the phase to a process of advancing the phase, is defined as the number of inflection points Ninfle, and an arbitrary upper limit is set for this number, so that the phase control converges (ends) after a certain number of trial repetitions. As trials are repeated in this way, this method requires time for convergence. In addition, if the process of advancing the phase or the process of delaying the phase occur a certain number of times in succession, the number of inflection points Ninfle is reset to 0 to avoid convergence to a value other than the optimum phase.

[0034] Thus, phase control methods for driving an electric motor include matching the phase of the induced voltage E with the phase of the current I, and minimizing the index η. The former has excellent responsiveness, while the latter can drive even an interior permanent magnet type electric motor with high efficiency. In the first embodiment, by combining these two types of control methods, a drive device with excellent responsiveness and capable of driving an electric motor with high efficiency is realized.

[0035] A drive device according to a first embodiment and a drive system including the drive device and an electric motor that realizes these controls will be described below. Fig. 5 is a block diagram showing the drive device and drive system according to the first embodiment. As shown in Fig. 5, the drive system SYS includes an electric motor 4 and a drive device DRV.

[0036] The electric motor 4 is a three-phase synchronous motor. The electric motor 4 includes a rotor. The electric motor 4 is driven by a driving device DRV, and the rotor rotates.

[0037] The driving device DRV is a device that drives the electric motor 4. The driving device DRV includes a power converter 1, a rotor position detection unit 5, a current detection unit 6, a rotation speed calculation unit 7, a voltage control unit 8, a phase adjustment unit 9, a current value processing unit 10, and an operation command setting unit 11.

[0038] The power converter 1 converts a DC voltage into an AC voltage of any voltage and frequency. The power converter 1 includes, for example, six IGBTs (Insulated Gate Bipolar Transistors) 2 and six free wheeling diodes 3. The six IGBTs 2 are connected in a three-phase bridge to form a so-called inverter circuit. Each of the free wheeling diodes 3 is provided between the collector and emitter of each IGBT 2, with the anode connected to the emitter and the cathode connected to the collector. A DC voltage is supplied to the power converter 1 from a DC power supply Vdc, which is a driving power supply. Each of the three output terminals (three-phase output terminals) of the power converter 1 is connected to a corresponding one of the three stator windings (three-phase stator windings) of the electric motor 4.

[0039] The rotor position detection unit 5 detects the position (rotational position) of the rotor of the electric motor 4. For example, the rotor position detection unit 5 includes a rotary encoder or a Hall sensor attached to the electric motor 4, and detects the rotor position from the output of the rotary encoder or the Hall sensor. By detecting the rotor position, the phase of the three-phase induced voltage E generated in the electric motor 4 is detected. Information regarding the rotor position, i.e., information regarding the phase of the three-phase induced voltage E generated in the electric motor 4, is transmitted to the rotation speed calculation unit 7, the voltage control unit 8, and the current value processing unit 10.

[0040] The current detection unit 6 detects the current I flowing through the electric motor 4. The current detection unit 6 detects the current I for one or more phases of the electric motor 4. The current detection unit 6 includes a shunt resistor, a current sensor, or the like. In this embodiment, a so-called one-shunt system in which a shunt resistor is arranged at one location on the power supply line on the negative side (ground side) of the power converter 1 will be described as an example.

[0041] The rotation speed calculation unit 7 calculates the rotation speed from the amount of change in the rotation position. The rotation speed calculation unit 7 calculates the rotation speed based on the information on the rotor position received from the rotor position detection unit 5, and transmits it to the phase adjustment unit 9 as a count value N.

[0042] The current value processing unit 10 processes information about the current detected by the current detection unit 6. The current value processing unit 10 includes a zero-cross detection circuit and a peak hold circuit. The current value processing unit 10 detects a zero cross at which the current I switches from positive to negative, or a zero cross at which the current I switches from negative to positive, from information about the current I. The current value processing unit 10 then identifies the start and end of one period of the current I based on the detected zero cross. The current value processing unit 10 also detects a peak value Ip of the current I in one period. The current value processing unit 10 detects the peak value Ip for each period. The current value processing unit 10 transmits information about the period of the current and the peak value Ip to the phase adjustment unit 9. The current value processing unit 10 also detects the slope of the waveform of the current I, in other words, the direction of change of the current I over time. Based on information relating to the phase of induced voltage E received from rotor position detection unit 5, current value processing unit 10 detects the slope of the waveform of current I, for example, in accordance with the timing of the peak of induced voltage E. Detecting the slope of the waveform of current I means determining whether current I is increasing or decreasing over time. Current value processing unit 10 transmits information relating to the slope of the waveform of current I to phase adjustment unit 9.

[0043] The phase adjustment unit 9 determines the amount of phase shift from information related to the rotation speed and / or information related to the current. The phase adjustment unit 9 receives information related to the rotation speed from the rotation speed calculation unit 7 and information related to the current I from the current value processing unit 10. Based on this information, the phase adjustment unit 9 calculates the amount of phase shift, that is, how the phase of the drive voltage V should be relative to the phase of the induced voltage E, and transmits the calculated amount of phase shift to the voltage control unit 8.

[0044] The operation command setting unit 11 sets commands related to the operation of the electric motor 4. The operation command setting unit 11 includes, for example, a user interface, and commands related to the operation of the electric motor 4 are set by a user or the like. The commands set by the operation command setting unit 11 are transmitted to the voltage control unit 8. For example, a duty ratio is set by the operation command setting unit 11, and the set duty ratio is transmitted to the voltage control unit 8. Examples of the user interface provided in the operation command setting unit 11 include a touch panel, an operation button, a remote control, and the like.

[0045] The voltage control unit 8 controls the power converter 1 to supply AC power from the power converter 1 to the electric motor 4. The voltage control unit 8 controls the on / off of each of the six IGBTs 2 included in the power converter 1 to cause the power converter 1 to convert the DC power supply Vdc into an AC voltage of a given voltage and frequency and output it to the electric motor 4. In other words, the voltage control unit 8 controls how the power converter 1 outputs the drive voltage V. The control of the six IGBTs 2 by the voltage control unit 8 is based on information about the rotor position received from the rotor position detection unit 5, the amount of phase shift received from the phase adjustment unit 9, and the duty ratio received from the operation command setting unit 11.

[0046] The rotation speed calculation unit 7, the voltage control unit 8, the phase adjustment unit 9, and the current value processing unit 10 are implemented in, for example, an integrated circuit 12. The integrated circuit 12 is an IC (Integrated Circuit) chip. The integrated circuit 12 includes a processor and a storage medium. The integrated circuit 12 may be a microcomputer including a CPU, an ASIC (Application Specific Integrated Circuit), or an FPGA (Field Programmable Gate Array). The integrated circuit 12 including the processor performs the processing described below by executing a program or the like stored in a storage medium or the like.

[0047] 6 is a flowchart for explaining the driving operation of the drive device according to the first embodiment. The driving operation is an operation in which the drive device DRV drives the electric motor 4.

[0048] When the driving operation is started (START), the phase adjustment unit 9 initializes each variable (S61). Specifically, the variables Pa, Pb, C, ηa, ηb, Stage, and α are initialized to 0, and the inflection point number Ninfle is initialized to -1. The variables Pa and Pb are variables used in the advance angle processing and the retardation angle processing described later. The variable Pa is a variable indicating whether the processing currently being executed is the advance angle processing or the retardation angle processing, and 1 is assigned to the variable Pa in the case of the advance angle processing, and -1 is assigned to the variable Pb in the case of the retardation angle processing. The variable C is a variable that is counted up when the processing for advancing the phase is executed consecutively, or when the processing for retarding the phase is executed consecutively. The variables ηa, ηb, Stage, and α are variables used in the second phase control processing described later. The variable ηa stores a value obtained by accumulating the index η shown in the formula (7) multiple times. The variable ηb stores an accumulated value held by the variable ηa before the variable ηa is reset to accumulate the current variable ηa. The variable Stage stores the current stage of the phase adjustment. Details of each stage will be described later. The variable α is a variable indicating the progress of the period, and is incremented by 1 or reset to 0 when the process of each stage is executed. The inflection point count Ninfle is a variable that is counted up when switching from a process of advancing the phase to a process of delaying the phase, or from a process of delaying the phase to a process of advancing the phase. The inflection point count Ninfle is initialized to −1 instead of 0 in order to cancel the effect of counting up the inflection point count Ninfle when either the advance angle process or the delay angle process described later is executed for the first time.

[0049] Next, the phase adjustment unit 9 determines whether the number of inflection points Ninfle is smaller than 1 (S62). By determining whether the number of inflection points Ninfle is smaller than 1, it is determined whether the current phase is in the vicinity of an optimal phase. Note that the number 1 compared with the number of infle of infle in S62 is a threshold value, and may be, for example, 2 or 3. The threshold value compared with the number of infle of infle in S62 can be set to any value.

[0050] If the inflection point count Ninfle is smaller than 1 (S62, Yes), the phase adjustment unit 9 executes the first phase control process (S63). The first phase control process is a process for adjusting the phase of the drive voltage V in a direction in which the phase of the current I and the phase of the induced voltage E coincide with each other. In other words, the first phase control process is a process for adjusting the phase of the drive voltage V based on the relationship between the phase of the current I and the rotational position information of the motor 4. Since the inflection point count Ninfle is smaller than 1, the phase adjustment unit 9 can estimate that the current phase of the drive voltage V is far from the optimal phase. Therefore, the phase adjustment unit 9 executes the first phase control process, which is more responsive than the second phase control process. The details of the first phase control process will be described later. When the first phase control process is completed, the phase adjustment unit 9 executes the process of S65.

[0051] On the other hand, if the inflection point count Ninfle is not smaller than 1 (S62, No), the phase adjustment unit 9 executes the second phase control process (S64). The second phase control process is a process for adjusting the phase of the drive voltage V in a direction in which an index calculated from the peak value of the current I and the rotation speed of the motor 4 decreases. In other words, the second phase control process is a process for adjusting the phase of the drive voltage V based on the magnitude of the current I and the rotation speed of the motor 4. Since the inflection point count Ninfle is not smaller than 1, that is, it has been counted up to 1 or more, the phase adjustment unit 9 can infer that the current phase of the drive voltage V is in the vicinity of the optimal phase. Therefore, the phase adjustment unit 9 executes the second phase control process that can drive the motor more efficiently than the first phase control process. The details of the second phase control process will be described later. When the second phase control process is completed, the phase adjustment unit 9 executes the process of S65.

[0052] In the process of S65, the phase adjustment unit 9 determines whether the variable C is greater than the threshold value Cref (S65). By determining whether the variable C is greater than the threshold value Cref, it is determined whether the process of advancing or delaying the phase is being executed continuously.

[0053] If the variable C is greater than the threshold Cref (S65, Yes), the phase adjustment unit 9 assigns 0 to the inflection point count Ninfle and assigns 0 to the variable C (S66). Since the variable C is greater than the threshold Cref, it can be seen that the phase advance process or phase delay process has been executed consecutively a number of times greater than the threshold Cref. To avoid convergence to a value other than the optimal phase, the phase adjustment unit 9 sets the inflection point count Ninfle to 0 and initializes the variable C to 0. When the process of S66 is completed, the process of S62 is executed.

[0054] On the other hand, if the variable C is not greater than the threshold Cref (S65, No), the process of S62 is executed. If the variable C is not greater than the threshold Cref, that is, if the variable C is equal to or less than the threshold Cref, the process proceeds to the next step without changing the variable.

[0055] Thereafter, the processes of S62 to S66 are repeatedly executed while the driving operation is being performed.

[0056] FIG. 7 is a flowchart showing the first phase control process of the drive device according to the first embodiment.

[0057] When the first phase control process is started (START), the phase adjustment unit 9 detects the gradient of the current based on the output of the current value processing unit 10 (S71). Specifically, the phase adjustment unit 9 receives information on the gradient of the waveform of the current I from the current value processing unit 10.

[0058] Next, the phase adjustment unit 9 determines whether the detected gradient is positive (S72).

[0059] If the detected gradient is positive (S72, Yes), the phase adjustment unit 9 executes advance angle processing (S73). Advance angle processing is processing for advancing the phase of the drive voltage V and updating the number of inflection points Ninfle and / or the variable C based on the previous advance angle processing or delay angle processing. Details of advance angle processing will be described later. Because the detected gradient is positive, it is estimated that the phase of the current I lags behind the phase of the induced voltage E. Therefore, by executing advance angle processing to advance the phase of the drive voltage V, it is possible to bring the phase of the drive voltage V closer to the optimal phase. When the advance angle processing is completed, the first phase control processing ends (end).

[0060] On the other hand, if the detected slope is not positive in S72 (S72, No), the phase adjustment unit 9 executes a retard process (S74). The retard process is a process for delaying the phase of the drive voltage V and updating the number of inflection points Ninfle and / or the variable C based on the previous advance process or retard process. The details of the retard process will be described later. Since the detected slope is not positive, i.e., negative, it is estimated that the phase of the current I is advanced relative to the phase of the induced voltage E. Therefore, by executing the retard process and retarding the phase of the drive voltage V, it is possible to bring the phase of the drive voltage V closer to the optimal phase. When the retard process is completed, the first phase control process ends (ends).

[0061] FIG. 8 is a flowchart showing the advance angle processing of the drive device according to the first embodiment.

[0062] When the advance angle process is started (START), the phase adjustment unit 9 adds the phase shift amount to advance the phase of the drive voltage V (S81).

[0063] Next, the phase adjustment unit 9 assigns 1 to the variable Pa (S82).

[0064] Next, the phase adjustment unit 9 determines whether the variable Pa is equal to the variable Pb (S83).

[0065] If the variable Pa is equal to the variable Pb (S83, Yes), the phase adjustment unit 9 adds 1 to the variable C (S84). That is, the phase adjustment unit 9 counts up the number of consecutive executions of the phase advance process. When the process of S84 is completed, the phase adjustment unit 9 executes the process of S86.

[0066] On the other hand, if the variables Pa and Pb are not equal (S84, No), that is, if the variables Pa and Pb are different, the phase adjustment unit 9 adds 1 to the inflection point count Ninfle and assigns 0 to the variable C (S85). Since the variables Pa and Pb are different, it is understood that the retardation process was performed last time and the advancement process was performed this time. Therefore, the inflection point count Ninfle is counted up and the variable C is reset to 0. When the process of S85 is completed, the phase adjustment unit 9 executes the process of S86.

[0067] In the process of S86, the phase adjustment unit 9 assigns the variable Pa to the variable Pb (S86). This process makes it possible to refer to the process that was executed this time when the advance angle process or the retard angle process is executed next time. When the process of S86 is completed, the advance angle process ends (END).

[0068] FIG. 9 is a flowchart showing the retardation process of the drive device according to the first embodiment.

[0069] When the retardation process is started (START), the phase adjustment unit 9 subtracts the phase shift amount to retard the phase of the drive voltage (S91).

[0070] Next, phase adjustment unit 9 assigns -1 to variable Pa (S92).

[0071] Next, the phase adjustment unit 9 determines whether the variable Pa is equal to the variable Pb (S93).

[0072] If the variables Pa and Pb are equal (S93, Yes), the phase adjustment unit 9 adds 1 to the variable C (S94). That is, the phase adjustment unit 9 counts up the number of consecutive executions of the phase delay process. When the process of S94 is completed, the phase adjustment unit 9 executes the process of S96.

[0073] On the other hand, if the variables Pa and Pb are not equal (S93, No), that is, if the variables Pa and Pb are different, the phase adjustment unit 9 adds 1 to the number of inflection points Ninfle and assigns 0 to the variable C (S95). Since the variables Pa and Pb are different, it is understood that advance angle processing was performed last time and retard angle processing was performed this time. Therefore, the number of inflection points Ninfle is counted up and the variable C is reset to 0. When the process of S95 is completed, the phase adjustment unit 9 executes the process of S96.

[0074] In the process of S96, the phase adjustment unit 9 substitutes the variable Pa for the variable Pb (S96). When the process of S96 is completed, the retardation process ends (END).

[0075] FIG. 10 is a flowchart showing the second phase control process of the drive device according to the first embodiment.

[0076] When the second phase control process is started (START), the phase adjustment unit 9 acquires the peak current value Ip (S101). Specifically, the phase adjustment unit 9 receives the peak current value Ip from the current value processing unit 10.

[0077] Next, the phase adjustment unit 9 acquires the count value N (S102). Specifically, the phase adjustment unit 9 receives the count value N from the rotation speed calculation unit 7.

[0078] Next, the phase adjustment unit 9 determines whether the current I has switched to the next period (S103). Specifically, the phase adjustment unit 9 determines whether the current I has switched to the next period based on the zero-cross detection result in the rotation speed calculation unit 7. Depending on the result of this determination, it is determined whether or not the processing from S104 onwards is executed. Also, depending on this determination, the processing from S104 onwards is executed once per period of the current I.

[0079] If the current I has not been switched to the next period (S103, No), the second phase control process ends (END).

[0080] When the current I is switched to the next cycle (S103, Yes), the phase adjustment unit 9 assigns the calculation result to the variable ηa (S104). The variable ηa(n) in the nth cycle is expressed as in equation (8) using the variable ηa(n-1) in the n-1th cycle and the index η(n) in the nth cycle. In other words, the value assigned to the variable ηa is a value obtained by accumulating the index η shown in equation (7) multiple times.

[0081]

number

[0082] Next, the phase adjustment unit 9 judges which stage the phase adjustment of the driving voltage V is in (S105). The stage includes, for example, four states, 0, 1, 2, and 3. Stage 0 is a state in which the phase is advanced and Stage 1 is set to be executed next. Stage 1 is selected after the processing of advancing the phase is completed in Stage 0. Stage 1 is a state in which it is judged whether the variable ηa is smaller than the previous integrated value or equal to or greater than the previous integrated value, and it is set to select Stage 0 or Stage 2 in the next processing based on the judgment. Stage 2 is a state in which the phase is delayed and it is set to execute Stage 3 next. Stage 3 is selected after the processing of delaying the phase is completed in Stage 2. Stage 3 is a state in which it is judged whether the variable ηa is smaller than the previous integrated value or equal to or greater than the previous integrated value, and it is set to select Stage 0 or Stage 2 in the next processing based on the judgment.

[0083] In S105, when Stage is 0 (S105, Stage = 0), the phase adjustment unit 9 executes advance angle processing (S106a). This advance angle processing is similar to that described with reference to FIG. 8. Next, the phase adjustment unit 9 sets Stage to 1 (S106b). Next, the phase adjustment unit 9 adds 1 to the variable α (S106c). When the processing of S106c is completed, the second phase control processing ends (End).

[0084] In S105, when Stage is 1 (S105, Stage = 1), the phase adjustment unit 9 judges whether the variable α is equal to or greater than a reference value αref (S107a). The reference value αref is a value that determines how many times the index η is accumulated when calculating the variable ηa. If the variable α is not equal to or greater than the reference value αref (S107a, No), the phase adjustment unit 9 adds 1 to the variable α (S107f). When the process of S107f is completed, the second phase control process ends (End).

[0085] On the other hand, in S107a, if the variable α is equal to or greater than the reference value αref (S107a, Yes), the phase adjustment unit 9 determines whether the variable ηa is smaller than the variable ηb (S107b). If the variable ηa is smaller than the variable ηb (S107b, Yes), the phase adjustment unit 9 sets Stage to 0 (S107c). That is, the phase adjustment unit 9 makes the advance angle process be performed the next time the second phase control process is executed and the processes from S105 onwards are executed. When the process of S107c is completed, the phase adjustment unit 9 executes the process of S107e.

[0086] On the other hand, if the variable ηa is not smaller than the variable ηb (S107b, No), the phase adjustment unit 9 sets Stage to 2 (S107d). That is, the phase adjustment unit 9 performs the retardation process when the second phase control process is executed next time and the processes after S105 are executed. When the process of S107d is completed, the phase adjustment unit 9 performs the process of S107e.

[0087] In the process of S107e, the phase adjustment unit 9 assigns 0 to the variable α, assigns the variable ηa to the variable ηb, and assigns 0 to the variable ηa (S107e). Looking back at the process up to this point, the process of S107a confirmed that the variable ηa had been accumulated for a specified period, the magnitude relationship between the variables ηa and ηb was confirmed in S107b, and the stage was changed by the process of S107c or S107d. Therefore, the purpose of S107e is to reset or update each variable to prepare for the next operation. In S107e, the phase adjustment unit 9 resets the variable α to 0, saves the value of the variable ηa in the variable ηb, and resets the variable ηa to 0. When the process of S017e is completed, the second phase control process ends (end).

[0088] In S105, when Stage is 2 (S105, Stage = 2), the phase adjustment unit 9 executes the retardation process (S108a). This retardation process is similar to that described with reference to FIG. 9. Next, the phase adjustment unit 9 sets Stage to 3 (S108b). Next, the phase adjustment unit 9 adds 1 to the variable α (S108c). When the process of S108c is completed, the second phase control process ends (End).

[0089] In S105, when Stage is 3 (S105, Stage = 3), the phase adjustment unit 9 judges whether the variable α is equal to or greater than the reference value αref (S109a). If the variable α is not equal to or greater than the reference value αref (S109a, No), the phase adjustment unit 9 adds 1 to the variable α (S109f). When the process of S109f is completed, the second phase control process ends (End).

[0090] On the other hand, in S109a, if the variable α is equal to or greater than the reference value αref (S109a, Yes), the phase adjustment unit 9 determines whether the variable ηa is smaller than the variable ηb (S109b). If the variable ηa is smaller than the variable ηb (S109b, Yes), the phase adjustment unit 9 sets Stage to 2 (S109c). That is, the phase adjustment unit 9 performs the retardation process the next time the second phase control process is performed and the processes from S105 onward are performed. When the process of S109c is completed, the phase adjustment unit 9 performs the process of S109e.

[0091] On the other hand, if the variable ηa is not smaller than the variable ηb (S109b, No), the phase adjustment unit 9 sets Stage to 0 (S109d). That is, the phase adjustment unit 9 causes the advance angle process to be executed the next time the second phase control process is executed and the processes after S105 are executed. When the process of S109d is completed, the phase adjustment unit 9 executes the process of S109e.

[0092] In the process of S109e, the phase adjustment unit 9 assigns 0 to the variable α, assigns the variable ηa to the variable ηb, and assigns 0 to the variable ηa (S109e). Looking back at the process up to this point, the process of S109a confirmed that the variable ηa had been accumulated for a specified period, the magnitude relationship between the variables ηa and ηb was confirmed in S109b, and the stage was changed by the process of S109c or S109d. Therefore, the purpose of S109e is to reset each variable to prepare for the next operation. In S109e, the phase adjustment unit 9 resets the variable α to 0, saves the value of the variable ηa in the variable ηb, and resets the variable ηa to 0. When the process of S109e is completed, the second phase control process ends (end).

[0093] By operating the phase adjustment unit 9 in this manner, the phase of the current I can be adjusted in the manner shown in Table 1.

[0094] The drive device according to the first embodiment executes a first phase control process that adjusts the phase of the drive voltage V based on the relationship between the phase of the current I and the rotational position information of the motor 4, and a second phase control process that adjusts the phase of the drive voltage V based on the magnitude of the current I and the rotational speed of the motor 4. The first phase control process is simple in control, so it can be executed faster than the second phase control process and has excellent responsiveness. The second phase control process controls based on the index η, so that even an embedded magnet type motor can be driven with high efficiency. The drive device according to the first embodiment combines these processes, approaches high speed by the first phase control process until it is close to the optimal phase, and then executes the second phase control process, thereby achieving both responsiveness of the phase control and highly efficient driving of the motor.

[0095] Moreover, the drive device according to the first embodiment switches between the first phase control process and the second phase control process according to the inflection point number Ninfle. Specifically, when the inflection point number Ninfle is smaller than the threshold, that is, when advance angle processing or retard angle processing that changes the shift amount toward the vicinity of the optimal value is performed continuously, the first phase control process that has excellent phase control responsiveness is executed. On the other hand, when the inflection point number Ninfle is larger than the threshold, that is, when the shift amount has reached the vicinity of the optimal value, the second phase control process that can drive the electric motor with high efficiency is executed. In this way, the drive device according to the first embodiment can achieve both phase control responsiveness and high-efficiency driving of the electric motor.

[0096] Second embodiment The drive device according to the second embodiment differs from the drive device according to the first embodiment in the content of the first phase control process. The drive device according to the second embodiment will be described below in terms of the differences from the first embodiment.

[0097] The principle used in the first phase control process in the drive device according to the second embodiment will be described. FIG. 11 is a waveform diagram showing an example of current detection using a shunt resistor. FIG. 11 shows a number of examples of current waveforms detected when a shunt resistor is used in the current detection unit 6. In FIG. 11, three types of current waveforms are vertically arranged from the top, in order, when the phase of the drive voltage V is advanced, when the power factor is 1, and when the phase of the drive voltage V is delayed. As shown in FIG. 11, when the motor current is detected using a shunt resistor, the waveform shape is divided into six parts per period with respect to the output voltage phase of the power converter 1. At this time, if the phase of the drive voltage V and the phase of the current I are in phase, as shown in the center of FIG. 11, the waveform shape is convex in the center in each divided part. Note that if the phase of the drive voltage V and the phase of the current I are in phase, the power factor is 1 operation. If the phase of the drive voltage V is more advanced than the power factor 1, the position of the convex part of the waveform advances, and the waveform shape is sloping downward to the right as shown in the upper part of FIG. 11. When the phase of the drive voltage V lags behind a power factor of 1, the position of the convex part of the waveform is delayed, resulting in a waveform shape that rises to the right as shown in the lower part of Fig. 11. In the second embodiment, this difference in waveform shape is utilized to execute the first phase control process.

[0098] A current value processing unit 10 included in the drive device according to the second embodiment differs from the current value processing unit 10 included in the drive device according to the first embodiment in that it further has a function of transmitting a current value to a phase adjustment unit 9. Specifically, the current value processing unit 10 according to the second embodiment transmits the value of current I detected by a current detection unit 6 to the phase adjustment unit 9. The other configurations of the drive device according to the second embodiment and the drive system including the drive device and the electric motor are similar to those of the first embodiment.

[0099] FIG. 12 is a flowchart showing the first phase control process of the drive device according to the second embodiment.

[0100] When the first phase control process is started (START), the phase adjustment unit 9 initializes variables β, Ia, Ib, and Id to 0 (S121). The variable β is a variable that is counted up when a variable Id described later is positive, and is counted down when the variable Id is not positive. The variable Ia is a variable that stores the current value acquired from the current value processing unit 10. The variable Ib is a variable that stores the previously acquired current value. The variable Id is a variable that stores the value obtained by subtracting the variable Ib from the variable Ia.

[0101] Next, the phase adjustment unit 9 obtains the current value from the current value processing unit 10 and substitutes it for the variable Ia (S122). Specifically, the phase adjustment unit 9 obtains the current value of the current I from the current value processing unit 10 and substitutes it for the variable Ia.

[0102] Next, the phase adjustment unit 9 subtracts the variable Ib from the variable Ia and assigns the result to the variable Id (S123). The variable Ib is a variable that stores the previously acquired current value. Therefore, the difference between the variable Ia, which is the currently acquired current value, and the variable Ib, which is the previously acquired current value, is assigned to the variable Id by this process.

[0103] Next, the phase adjustment unit 9 determines whether the variable Id is positive (S124). If the variable Id is positive (S124, Yes), the phase adjustment unit 9 adds 1 to the variable β (S125a). When the process of S125a is completed, the phase adjustment unit 9 executes the process of S126. On the other hand, when the variable Id is not positive in S124 (S124, No), the phase adjustment unit 9 subtracts 1 from the variable β (S125b). When the process of S125b is completed, the phase adjustment unit 9 executes the process of S126.

[0104] In S126, the phase adjustment unit 9 assigns the value of the variable Ia to the variable Ib (S126). Through this process, the currently acquired current value is assigned to the variable Ib, and is used as the previously acquired current value in the next process.

[0105] Next, the phase adjustment unit 9 determines whether the current I has switched to the next cycle (S127). If the cycle has not switched (S127, No), the process of S122 is executed. That is, the processes of S122 to S126 are repeatedly executed until the cycle is switched.

[0106] On the other hand, when the cycle is switched in S127 (S127, Yes), the phase adjustment unit 9 judges whether the variable β is positive (S128). The variable β is counted up when the variable Id is positive by the processes of S124, S125a, and S125b, and is counted down when the variable Id is negative. Then, these processes are repeated until the cycle of the current is switched by the process of S127. As a result, the variable β holds whether the variable Id was often positive or not, depending on whether the number is positive or negative. Since the variable Id is the difference between the current value this time and the current value the previous time, when the variable β is positive, it means that the current I was on an increasing trend. When the variable β is not positive, it means that the current I was on a decreasing trend. As described with reference to FIG. 11, when the phase of the driving voltage V is delayed, the current waveform has a right-shouldered upward shape, and when the phase of the driving voltage V is advanced, the current waveform has a right-shouldered downward shape. Therefore, since the variable β is positive, the phase adjustment unit 9 can estimate that the phase of the drive voltage V is delayed, and since the variable β is not positive, the phase adjustment unit 9 can estimate that the phase of the drive voltage V is advanced.

[0107] If the variable β is positive in S128 (S128, Yes), the phase adjustment unit 9 executes advance angle processing (S129a). This advance angle processing is similar to that described with reference to FIG. 8. Since the variable β is positive, it is estimated that the phase of the drive voltage V is delayed. Therefore, by executing the advance angle processing to advance the phase of the drive voltage V, it is possible to bring the phase of the drive voltage V closer to the optimal phase. When the processing of S129a is completed, the first phase control processing ends (End).

[0108] If the variable β is not positive in S128 (S128, No), the phase adjustment unit 9 executes a retardation process (S129b). This retardation process is the same as that described with reference to FIG. 9. Since the variable β is not positive, it is estimated that the phase of the drive voltage V is advanced. Therefore, by executing the retardation process to retard the phase of the drive voltage V, it is possible to bring the phase of the drive voltage V closer to the optimal phase. When the process of S129b is completed, the first phase control process ends (END).

[0109] In this way, the first phase control process can be implemented based on the waveform shape of the current I as well.

[0110] Furthermore, even when the first phase control process is implemented in this manner, the drive device according to the second embodiment can achieve both responsiveness and highly efficient drive, similar to the first embodiment.

[0111] (Variations, etc.) In the above embodiment, the rotor position detection unit 5 includes a rotary encoder or a Hall sensor attached to the electric motor 4. The rotor position detection unit 5 may adopt a so-called sensorless system in which no sensor is provided. For example, in one example, the rotor position detection unit 5 directly detects the induced voltage E of the electric motor 4 and detects the position of the rotor based on the phase of the induced voltage E. In another example, the rotor position detection unit 5 acquires information on the current I flowing through the electric motor 4 from the current detection unit 6. Then, the rotor position detection unit 5 estimates the position of the rotor using the operating state of the electric motor 4 such as the current I and fixed constants. When the rotor position detection unit 5 adopts the sensorless system, the rotor position detection unit 5 may be implemented in the integrated circuit 12 together with the rotation speed calculation unit 7, the voltage control unit 8, the phase adjustment unit 9, and the current value processing unit 10.

[0112] The above embodiment has been described by taking as an example a so-called one-shunt system in which the current detection unit 6 has a shunt resistor disposed at one location on the power line on the negative side (ground side) of the power converter 1. The current detection unit 6 may adopt a three-shunt system in which shunt resistors are disposed at three locations by disposing a shunt resistor between the emitter of each of the three IGBTs 2 on the negative side (ground side) of the power converter 1 and the negative power line.

[0113] 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 implemented 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 in the scope and spirit of the invention, and are included in the scope of the invention and its equivalents described in the claims. [Explanation of symbols]

[0114] 1...power converter, 3...freewheeling diode, 4...electric motor, 5...rotor position detection unit, 6...current detection unit, 7...rotation speed calculation unit, 8...voltage control unit, 9...phase adjustment unit, 10...current value processing unit, 11...operation command setting unit, 12...integrated circuit, DRV...drive device, SYS...drive system.

Claims

1. a power converter that converts input power into AC power and supplies the AC power to the electric motor; a voltage control unit that controls an operation of the power converter to apply a drive voltage from the power converter to the electric motor; a phase adjustment unit that adjusts the phase of the drive voltage by executing a first process of advancing the phase of the drive voltage and a second process of delaying the phase of the drive voltage; Equipped with The phase adjustment unit is a first phase control process for receiving first information relating to a relationship between a phase of a current flowing through the electric motor and a rotational position of the electric motor, and adjusting a phase of the drive voltage based on the first information; a second phase control process for receiving second information related to a magnitude of a current flowing through the electric motor and third information related to a rotation speed of the electric motor, and adjusting a phase of the drive voltage based on the second information and the third information; A driving device that performs the above.

2. 2. The driving device according to claim 1, wherein the phase adjustment unit executes the first phase control process or the second phase control process based on a first number of times that the second process is executed after the first process, or the first process is executed after the second process.

3. The drive device according to claim 2 , wherein the phase adjustment unit executes the first phase control process when the first number of times is smaller than a first threshold value, and executes the second phase control process when the first number of times is equal to or greater than the first threshold value.

4. 3. The drive device according to claim 2, wherein the phase adjustment unit resets the first number of times when the first process has been executed consecutively more times than a second threshold value or when the second process has been executed consecutively more times than the second threshold value.

5. 2. The drive device according to claim 1, wherein the phase adjustment unit controls the phase of the drive voltage in the first phase control process so that the phase of the current flowing through the motor coincides with the phase of an induced voltage detected from the rotational position of the motor.

6. 2. The drive device according to claim 1, wherein the second information includes information relating to a peak value in one period of an AC current flowing through the electric motor, and the third information includes information relating to an inverse of a rotation speed of the electric motor.

7. The drive device according to claim 6 , wherein the phase adjustment unit controls the phase of the drive voltage in the second phase control process so that a product of the peak value and a reciprocal of the rotation speed becomes small.

8. converting input power into AC power by a power converter and supplying the converted AC power to an electric motor; Detecting a current flowing through the motor, a rotational position of the motor, and a rotational speed of the motor; adjusting a phase of the drive voltage by executing a first process of advancing a phase of the drive voltage applied from the power converter to the electric motor and a second process of delaying the phase of the drive voltage based on the detected current and the detected rotational position; when the number of times the second process is executed after the first process, or the number of times the first process is executed after the second process, becomes equal to or greater than a first threshold value, executes the first process and the second process based on the detected current and the detected rotation speed, thereby adjusting the phase of the drive voltage; A method for controlling an electric motor comprising:

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