Synchronous motor drive device and drive control method

Abstract

A synchronous motor drive device according to an embodiment comprises a power conversion unit and a control unit. The power conversion unit supplies the power generated by control to a synchronous motor. The control unit selects either a first control or a second control on the basis of whether or not the control state of the synchronous motor satisfies a predetermined identification condition, said first control giving priority to linearity in a conversion request item of conversion processing and being applied to a first region, said second control giving priority to a request item other than the linearity in the conversion request item of the conversion processing and being applied to a second region, said first region and said second region being included within an application range of the conversion processing for generating a current reference for current control from a request torque reference related to control of the synchronous motor.

Description

Synchronous motor drive device and drive control method

[0001] An embodiment of the present invention relates to a synchronous motor drive device and a drive control method.

[0002] When a synchronous motor drive device drives a synchronous motor, there are various requirements, such as driving the synchronous motor more efficiently, improving the responsiveness of the synchronous motor to the required torque, and controlling the generated torque so that it is appropriate for the required torque standard. Although it is difficult to control the synchronous motor so that all of these requirements are satisfied simultaneously, there has been a desire to improve convenience by meeting these various requirements.

[0003] Japanese Patent Application Publication No. 2009-072056

[0004] An object of the present invention is to provide a synchronous motor drive device and a drive control method that can meet various requirements for controlling a synchronous motor and improve convenience.

[0005] According to an embodiment, a synchronous motor drive device includes a power conversion unit and a control unit. The power conversion unit supplies power generated by control to a synchronous motor. The control unit applies a first control that prioritizes linearity over requirements for the conversion of the synchronous motor within a range of application of the conversion process that generates a current reference for current control from a required torque reference for control of the synchronous motor, and a second control that prioritizes requirements other than linearity over requirements for the conversion of the conversion process. The control unit selects either the first control or the second control depending on whether a control state of the synchronous motor satisfies a predetermined discrimination condition.

[0006] The present invention relates to a synchronous motor drive device and a method for driving a synchronous motor, and more particularly to a synchronous motor drive circuit.

[0007] A synchronous motor drive device and a drive control method according to an embodiment will be described below with reference to the drawings. In the following description, components having the same or similar functions will be assigned the same reference numerals. Duplicate descriptions of those components may be omitted. Electrical connection may also be simply referred to as "connected."

[0008] FIG. 1 is a configuration diagram of a synchronous motor drive device 1 according to an embodiment. A control block diagram of the synchronous motor drive device 1 is shown in FIG. 1, and an overview of the control will be described. The synchronous motor drive device 1 includes, for example, an inverter unit 2 and a control unit 5. The inverter unit 2 includes a plurality of legs, each of which includes a plurality of semiconductor switching elements. For example, the plurality of legs are provided corresponding to the number of phases of the synchronous motor 3. The inverter unit 2 converts DC power into AC power under powering control from the control unit 5. There are no restrictions on the detailed configuration of the inverter unit 2, and any desired configuration may be applied.

[0009] The synchronous motor 3 is a synchronous motor such as a synchronous reluctance motor (referred to as SynRM). Because the SynRM does not have a permanent magnet or rotor conductor, it is expected to achieve higher efficiency, resource savings, and lower costs compared to an induction motor (IM). The type of synchronous motor 3 is not limited to the above-mentioned SynRM and may be selected appropriately. A phase detector such as a resolver that detects position is provided on the shaft of this synchronous motor 3.

[0010] The control unit 5 includes, for example, a torque reference generating unit 51, a magnetic flux reference generating unit 52, a current reference calculating unit 53, a current control unit 54, a coordinate conversion unit 55, a PWM control unit 56, a phase detection circuit 57, a differential calculation unit 58, and a phase reference generating unit 59.

[0011] For example, the torque reference generation unit 51 (ASPR) generates and outputs a torque reference (T_R) by speed control based on the input speed reference. This torque reference (T_R) corresponds to the required torque. The flux reference generation unit 52 (FLUX WEAK) generates a flux reference using a predetermined control method determined by control. Flux reference by the flux reference generation unit 52: For example, the flux reference generation unit 52 selects either the constant Id method or the constant current angle method and generates a flux reference using the selected control method. The current reference calculation unit 53 calculates the D-axis and Q-axis current references based on the flux reference generated by the flux reference generation unit 52. The current control unit 54 (ACR) calculates the D-axis and Q-axis voltage references so that the respective errors become zero through current control based on the D-axis and Q-axis current references calculated by the current reference calculation unit 53 and the D-axis and Q-axis current feedback values. The D-axis and Q-axis current feedback values ​​may be generated based on detected values ​​of the drive currents flowing through the synchronous motor 3 or estimated values ​​of the drive currents flowing through the synchronous motor 3. The method for generating the D-axis and Q-axis current feedback values ​​is not limited and may be selected appropriately. The coordinate conversion unit 55 (2Φ / 3Φ) converts the D-axis and Q-axis voltage references calculated by the current control unit 54 into a three-phase voltage reference based on the phase reference θ generated by the phase reference generation unit 59. The PWM control unit 56 (PWM) generates gate pulse signals for each phase for PWM control based on the three-phase voltage reference and outputs the gate pulse signals (GATE) for each phase to the inverter unit 2, thereby driving the synchronous motor 3. The phase detection circuit 57 receives signals from a phase detector associated with the synchronous motor 3, converts them into mechanical angle data, and outputs the data. The differentiation unit 58 (d / dt) differentiates the mechanical angle generated by the phase detection circuit 57 to generate a speed value (referred to as speed FBK). For example, the differential calculation unit 58 (d / dt) may use the amount of change in the mechanical angle per unit time as the speed FBK. The phase reference generation unit 59 converts the mechanical angle generated by the phase detection circuit 57 into an electrical angle based on the mechanical angle. The phase reference generation unit 59 corrects the electrical angle using the magnetic pole position correction angle to generate a phase reference θ.

[0012] The current reference calculation unit of the embodiment will be described with reference to Fig. 2. Fig. 2 is a schematic configuration diagram of the current reference calculation unit of the embodiment. For example, the current reference calculation unit 53 includes a cosine wave generation unit 531, a sine wave generation unit 532, multipliers 533 and 534, an absolute value calculation unit 535, and a torque reference adjustment unit 536.

[0013] The cosine wave generator 531 generates a cosine wave (cos) by setting a current angle based on the phase reference θ generated by the phase reference generator 59. The sine wave generator 532 generates a sine wave (sin) by setting a current angle based on the phase reference θ generated by the phase reference generator 59. The multiplier 533 multiplies the cosine wave (cos) generated by the cosine wave generator 531 by the output value of the absolute value calculator 535 to generate a D-axis current reference. The multiplier 534 multiplies the sine wave (sin) generated by the sine wave generator 532 by the output value of the torque reference adjuster 536 to generate a Q-axis current reference. The absolute value calculator 535 converts the output value of the torque reference adjuster 536 into an absolute value. The torque reference adjuster 536 generates a required torque reference T_R. The coefficient generated by the torque reference adjuster 536 is called the required torque reference T_R.

[0014] The operation of the current reference calculation unit 53 of the embodiment will be described with reference to Figures 3 and 4. Figure 3 is a diagram for explaining the operation of the current reference calculation unit 53 of the embodiment.

[0015] The graph shown in Figure 3 shows the relationship between the torque T (vertical axis) and the required torque reference T_R (torque reference: horizontal axis). The required torque reference T_R varies from 0 to over 100%. The straight line passing through the origin of this graph represents an ideal state in which the magnitude of the torque T generated is equal to the required torque reference T_R. The curve passing through the origin of this graph is a parabola, which represents a case in which the magnitude of the torque T generated relative to the required torque reference T_R is a quadratic function. The magnitude of the torque T is normalized such that a torque T with a magnitude of 1 is generated when the required torque reference T_R is 100%.

[0016] As described above, this parabola has a downward convex shape, so the value indicated by this parabola is smaller than the value indicated by the straight line when the required torque reference T_R is in the range from 0 to 100%, and is larger than the value indicated by the straight line when the required torque reference T_R exceeds 100%.

[0017] (Required torque standard T_R(T ＊ ) and the torque T generated. Here, the required torque reference T_R (T ＊ The relationship between the required torque reference T_R (T) and the generated torque T is shown in the following equation (1). In equation (1), ID and IQ are the current references for the D axis and the Q axis. a and b are predetermined proportional coefficients. For ease of explanation, the required torque reference T_R (T ＊ ) The current references for the D and Q axes are calculated by proportional calculation.

[0018] T=ID×IQ (1)

[0019] ID = a × T ＊ , IQ=b×T*, and substituting this into the above equation (1) and rearranging, the following equation (2) is obtained: where c is a predetermined proportionality coefficient.

[0020] T = c × (T * ) 2 , c=a×b (2)

[0021] In the above formula (2), (T * ) 2　 If is less than 1, the following equation (3) holds.

[0022] (T * ) 2 <1(3)

[0023] The inequality holds even if we take the square root of both sides of the above equation (3).

[0024] The square root of the left side of the above equation (3) can be transformed into the following equation (4).

[0025] √((T * ) 2 ) → (T * ) (4)

[0026] Therefore, if the required torque reference T_R is in the range of 0 to 100%, the required torque reference T_R (T ＊ ) it can be seen that the generated torque T can be approximated based on

[0027] Incidentally, the above approximation has a tendency that the approximation error is small for values ​​near 0, but the error increases as the value moves away from 0. This tendency is clear from the graph in FIG.

[0028] (Priority Setting) Next, the setting of control priorities will be described. For example, a case will be described in which the priorities of requests to the control system are set so that priority is given to more accurate generation of torque T when the required torque reference T_R is in the range of 0 to 100%, and priority is given to tracking when the required torque reference T_R exceeds 100%. If a graph simulating such set priorities is shown by a solid line, the range of the required torque reference T_R from 0 to 100% is a straight line, and the range of the required torque reference T_R exceeding 100% is a parabola. By switching the loop gain of the control system according to the magnitude of the required torque reference T_R, adaptive control according to the magnitude of the required torque reference T_R is possible.

[0029] FIG. 4 is an explanatory diagram of the generated torque error when the current reference calculation unit 53 of the embodiment is applied. FIG. 4 shows the calculated generated torque error using the constant Id method and the constant current angle method. The graph shown in FIG. 4 shows the relationship between the required torque reference T_R (torque reference: horizontal axis) and the generated torque error (vertical axis). This graph shows the results of trial calculation of the generated torque error using the priority policy described in the description of FIG. 3.

[0030] The results are shown when the constant current angle method is applied in the range where the required torque reference T_R exceeds 100%.

[0031] There are two curves in the range of the required torque reference T_R from 0 to 100%. The graph indicated by black dots shows the results for the constant current angle method. The graph indicated by white dots shows the results for the constant current angle √T_R method.

[0032] The trends of the two curves in the range of the required torque reference T_R from 0 to 100% are similar to those shown in FIG. 3 . However, in FIG. 3 , the generated torque T was approximated by a straight line, assuming that the generated torque error in the constant current angle method would be small. FIG. 4 also shows the calculation results for the constant current angle method. It can be seen that in the constant current angle method, a positive error occurs in the range of the required torque reference T_R from 0 to 100%. Comparing the magnitude of the error between the two methods in the range of the required torque reference T_R from 0 to 100%, it can be seen that the constant current angle method has a smaller error. In this embodiment, by switching the calculation rule used by the current reference calculation unit 53 depending on the magnitude of the required torque reference T_R, it is expected that the error in the generated torque T in the range of the required torque reference T_R from 0 to 100% can be reduced and responsiveness can be improved in the range of the required torque reference T_R exceeding 100%. In this way, it is possible to improve the responsiveness in the range where the required torque reference T_R exceeds 100%, while maintaining the advantages of the constant current angle method in the range of 0 to 100% of the required torque reference T_R.

[0033] Next, we will consider the influence of the generated torque error becoming negative. A negative generated torque error leads to a request that the synchronous motor 3 does not rotate fast enough. Therefore, the constant current angle method is applied when the required torque reference T_R is in the range from 0 to 100%. This makes it possible to prevent the generated torque error from becoming negative.

[0034] According to the above embodiment, the power conversion unit of the synchronous motor drive device 1 supplies the synchronous motor with power generated through control. The control unit 5, within the application range of the conversion process for generating a current reference for current control from a required torque reference for control of the synchronous motor 3, includes a first region in which a first control that prioritizes linearity among the conversion requirements of the conversion process is applied, and a second region in which a second control that prioritizes requirements other than linearity among the conversion requirements of the conversion process is applied. Either the first control or the second control is selected depending on whether the control state of the synchronous motor 3 satisfies a predetermined discrimination condition. This improves convenience in meeting various requirements for synchronous motor control.

[0035] In the synchronous motor drive device 1, it is preferable that a required torque standard related to the control of the synchronous motor 3 is associated as an index of the control state of the synchronous motor 3.

[0036] In addition, if the required torque reference value is included in the second region, the control unit 5 uses the magnitude of the required torque reference value to generate the current reference value, and if the required torque reference value is included in the first region, the control unit 5 calculates the square root of the required torque reference value and uses the magnitude of the square root value to generate the current reference value.

[0037] According to at least one of the above-described embodiments, the synchronous motor drive device includes a power conversion unit and a control unit. The power conversion unit supplies power generated by control to the synchronous motor. The control unit applies a first control that prioritizes linearity over requirements for the conversion of the synchronous motor, within a range of application of the conversion process that generates a current reference for current control from a required torque reference for control of the synchronous motor. The control unit applies a second control that prioritizes requirements other than linearity over requirements for the conversion of the synchronous motor. The control unit selects either the first control or the second control depending on whether the control state of the synchronous motor satisfies a predetermined discrimination condition. This improves convenience by meeting various requirements for synchronous motor control.

[0038] 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 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 within the scope and spirit of the invention, as well as within the scope of the invention described in the claims and their equivalents.

[0039] REFERENCE SIGNS LIST 1... Synchronous motor drive device 2... Inverter unit 3... Synchronous motor 5... Control unit 51... Torque reference generation unit 52... Magnetic flux reference generation unit 53... Current reference calculation unit 531... Cosine wave generation unit 532... Sine wave generation unit 533, 534... Multiplier 535... Absolute value calculation unit 536... Torque reference adjustment unit

Claims

1. A power conversion unit that supplies power generated by control to a synchronous motor, The scope of application of a conversion process that generates a current reference for current control from a required torque reference related to the control of the synchronous motor includes, in the conversion request items of the conversion process, a first region in which a first current control is applied to the required torque reference by prioritizing the linearity of the relationship between the required torque reference and the torque generated by the synchronous motor, and a second region in which a second current control is applied to the required torque reference by prioritizing a request item other than linearity in the conversion request items of the conversion process, and a control unit that selects either the first current control or the second current control depending on whether the control state of the synchronous motor satisfies predetermined identification conditions, Equipped with, In the first region, when linearity is prioritized as the required item, the error between the required torque reference and the generated torque becomes smaller than when other properties are prioritized. In the second region, when linearity is prioritized as the required item, the error between the required torque standard and the generated torque becomes larger than when a requirement other than linearity is prioritized. Synchronous motor drive device.

2. The required torque standard related to the control of the synchronous motor is associated with the control state of the synchronous motor. The synchronous motor drive device according to claim 1.

3. The control unit, If included in the second region, the magnitude of the required torque reference is used to generate the current reference. If it falls within the first region, the square root of the value of the required torque reference is calculated, and the magnitude of the square root is used to generate the current reference. The synchronous motor drive device according to claim 2.

4. A drive control method for a synchronous motor driven by power generated by control, A current reference for current control is generated from a required torque reference related to the control of the synchronous motor, and the scope of application of the conversion process includes a first region in which a first current control is applied to the required torque reference by prioritizing the linearity of the relationship between the required torque reference and the torque generated by the synchronous motor, and a second region in which a second current control is applied to the required torque reference by prioritizing requirements other than linearity in the conversion requirements of the conversion process, and either the first current control or the second current control is selected depending on whether the control state of the synchronous motor satisfies predetermined identification conditions. Includes, In the first region, when linearity is prioritized as the required item, the error between the required torque reference and the generated torque becomes smaller than when other properties are prioritized. In the second region, when linearity is prioritized as the required item, the error between the required torque standard and the generated torque becomes larger than when a requirement other than linearity is prioritized. A method for controlling the drive of a synchronous motor.

5. The required torque standard related to the control of the synchronous motor is associated with the control state of the synchronous motor. A method for controlling the drive of a synchronous motor according to claim 4.

6. If included in the second region, the magnitude of the required torque reference is used to generate the current reference. If it falls within the first region, the square root of the value of the required torque reference is calculated, and the magnitude of the square root is used to generate the current reference. A method for controlling the drive of a synchronous motor according to claim 5.