Control device and motor drive system

Abstract

The present application provides a control device and a motor drive system that reduce the processing load of the control device and appropriately suppress high-order harmonic currents generated from an inverter of a drive motor. The control device (30) includes a prediction unit (310) and a command value determination unit (320). The prediction unit (310) predicts high-order harmonic currents from the second inverter (12) at each prediction point included in a prescribed prediction target period in the future from the present, based on control information of the second motor (M2) in at least the next carrier cycle of the second inverter (12). The command value determination unit (320) outputs, to an active filter unit (20), a current command value that generates a compensation current of an opposite polarity to the high-order harmonic current at the prediction point corresponding to the time of the next carrier cycle, based on the prediction result of the prediction unit (310). Each prediction point is set at a prescribed time interval from the start of the prediction target period, and the longer the next carrier cycle, the longer the time interval.

Description

Technical Field

[0001] The present invention relates to a control device for controlling an active filter section that suppresses high-order harmonic currents generated from the inverter of a drive motor, and a motor drive system equipped with the control device. Background Technology

[0002] In recent years, efforts to achieve a low-carbon or decarbonized society have become increasingly active as a concrete measure to address global climate change. Within the vehicle sector, there is a strong demand for CO2 emission reduction, leading to rapid development in the electrification of power sources. Specifically, the development of electric vehicles or hybrid electric vehicles (hereinafter also referred to as "electric vehicles"), which consist of a motor as the power source and a battery as the power supply to that motor, is underway.

[0003] Typically, the motors that drive electric vehicles use AC motors. Therefore, electric vehicles include inverters that convert the DC power supplied by the battery (which is a DC power source) into AC power and supply it to the motor. In this configuration, when the inverter switches on and off, high-order harmonic currents (hereinafter also simply referred to as "high-order harmonic currents") caused by surge-like noise currents may be generated on the power lines connecting the battery and the inverter. These high-order harmonic currents are a contributing factor to various malfunctions, such as abnormal noise, and therefore, it is desirable to suppress (reduce) them as much as possible.

[0004] Patent Document 1 describes a technique in which the current flowing through a power line connecting a DC power supply and a power converter is measured by a current sensor. A control device sequentially calculates a compensation current corresponding to an AC current of opposite polarity to the AC component of the current flowing through the current measured by the current sensor, generates a current command value for producing the compensation current, and provides it to an active filter. Furthermore, the active filter supplies the compensation current to the power line according to the current command value from the control device.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent Application Publication No. 2005-304235 Summary of the Invention

[0008] The problem that the invention aims to solve

[0009] However, in the prior art, there is room for improvement from the viewpoint of reducing the processing load of the control device and appropriately suppressing high-order harmonic currents. For example, as in the prior art described above, when the compensation current from the active filter is controlled by feedback control, the responsiveness of the compensation current to high-order harmonic currents becomes a problem. On the other hand, when the compensation current from the active filter is controlled by feedforward control, although it is foreseeable that the responsiveness of the compensation current to high-order harmonic currents will improve, the processing load of the control device may increase.

[0010] This invention provides a technique that can reduce the processing load of the control device and appropriately suppress high-order harmonic currents.

[0011] Methods for solving problems

[0012] This invention provides a control device that controls an active filter section to suppress high-order harmonic currents generated from the inverter of a drive motor, wherein...

[0013] The control device includes:

[0014] The prediction unit, based on the motor control information in at least the next carrier cycle of the inverter, predicts the higher harmonic currents at each prediction point within a specified prediction period from the present; and

[0015] The command value determination unit, based on the prediction result of the prediction unit, outputs a current command value to the active filter unit at a time corresponding to the prediction point contained in the next carrier cycle during the prediction period, to generate a compensation current with opposite polarity to the higher harmonic current at that prediction point, wherein...

[0016] Each prediction point is set at a predetermined time interval, starting from the beginning of the prediction period.

[0017] The longer the next carrier cycle, the longer the time interval.

[0018] Invention Effects

[0019] According to the present invention, the processing load of the control device can be reduced, and high-order harmonic currents can be appropriately suppressed. Attached Figure Description

[0020] Figure 1 This is a diagram illustrating an example of motor drive system 1.

[0021] Figure 2 This is a block diagram illustrating an example of the active filter control unit 300 included in the control device 30.

[0022] Figure 3This is a diagram showing a specific example of the prediction of high-order harmonic currents in the control device 30 (active filter control unit 300).

[0023] Figure 4 This is a diagram illustrating an example of the prediction period during overmodulated PWM control.

[0024] Figure 5 This is a diagram showing a modified example of motor drive system 1.

[0025] Explanation of reference numerals in the attached figures:

[0026] M1 First Motor (Motor)

[0027] M2 Second Motor

[0028] 1. Motor drive system

[0029] 11. First Inverter (Inverter)

[0030] 12 Second Inverter (Inverter)

[0031] 20, 20' Active Filter Section

[0032] 30 Control device

[0033] 310 Forecasting Department

[0034] 320 Instruction Value Determination Unit. Detailed Implementation

[0035] Hereinafter, an embodiment of the control device of the present invention will be described in detail with reference to the accompanying drawings. The embodiment described below is an example of applying the control device of the present invention to the motor drive system of an electric vehicle.

[0036] [Motor drive system]

[0037] The electric vehicle of this embodiment (hereinafter also referred to as "vehicle V") has Figure 1 The motor drive system 1 shown is a battery BAT that serves as a DC power source; a drive motor MOT that serves as a drive source for the drive wheels (not shown) of a vehicle V; a power conversion unit 10 that converts the power received between the battery BAT and the drive motor MOT; an active filter unit 20; and a control device 30.

[0038] A battery (BAT) is an energy storage device capable of storing electricity used to drive a vehicle (V) (i.e., electricity used to drive the drive motor (MOT)). The positive terminal of the battery (BAT)... Figure 1 The battery BAT (represented by "P0" in the diagram) is connected to the high-potential side electric field line Lp, and the negative terminal of the battery BAT ( Figure 1The battery (shown as "N0") is connected to the low-potential side power line Ln. For example, the battery BAT is configured to connect multiple unit energy storage cells (not shown) implemented by lithium-ion batteries or the like in series or in parallel, and can output a high voltage of 100 to 400 [V] as the terminal voltage between the positive and negative terminals.

[0039] The drive motor MOT includes a first motor M1 and a second motor M2 with a higher output than the first motor M1. The first motor M1 and the second motor M2 are, for example, permanent magnet synchronous three-phase AC motors. The first motor M1 and the second motor M2 can drive a shared drive wheel or drive different drive wheels.

[0040] Both the first motor M1 and the second motor M2 are equipped with motor sensors (not shown) to detect their respective states. One example of a motor sensor is a rotary transformer that detects the rotation angle of the rotor. The motor sensor sends a detection signal indicating the detection result (e.g., the rotation angle of the rotor) to the control unit 30. Alternatively, the motor sensor can also send the detection signal to the control unit 30 via an in-vehicle network such as CAN (Controller Area Network).

[0041] The power conversion unit 10 includes a first inverter 11 and a second inverter 12 with a higher output than the first inverter 11. The first inverter 11 and the second inverter 12 are, for example, three-phase inverters equipped with six switching elements (not shown) driven according to control signals from the control device 30. The switching elements are IGBTs (Insulated Gate Bipolar Transistors), MOSFETs (Metal-Oxide-Semiconductor Field Effect Transistors), etc.

[0042] The high-potential side DC terminal of the first inverter 11 ( Figure 1 (Illustrated with "P1") is connected to the positive terminal of battery BAT via the high-potential side power line Lp. Additionally, the low-potential side DC terminal of the first inverter 11 (… Figure 1 (Illustrated with "N1") is connected to the negative terminal of battery BAT via the low-potential side power line Ln. Furthermore, the AC terminal of the first inverter 11 ( Figure 1 (U1, V1, W1) are shown in the diagram. The first motor M1 is connected via the first three-phase line L1.

[0043] The first inverter 11 converts the power (DC power) from the battery BAT, which is input via the high-potential DC terminal and the low-potential DC terminal, into three-phase AC power. Furthermore, the first inverter 11 outputs the converted AC power to the first motor M1 via the AC terminal. That is, the high-potential DC terminal and the low-potential DC terminal of the first inverter 11 can also be referred to as the input section of the first inverter 11, and the AC terminal of the first inverter 11 can also be referred to as the output section of the first inverter 11.

[0044] Additionally, a voltage sensor Sv1 is provided in the first inverter 11 to detect the voltage between the high-potential side DC terminals and the low-potential side DC terminals (i.e., the input voltage to the first inverter 11). The voltage sensor Sv1 sends a detection signal indicating the detection result to the control device 30 via the vehicle network or the like. Furthermore, a current sensor Si1 is provided on the high-potential side power line Lp connecting the battery BAT and the first inverter 11 to detect the value of the current flowing in that power line. The current sensor Si1 sends a detection signal indicating the detection result to the control device 30 via the vehicle network or the like. Alternatively, a current sensor that detects the value of the current flowing in each phase may also be provided on the first three-phase line L1 connecting the first inverter 11 and the first motor M1, and the detection signal from this current sensor may be sent to the control device 30.

[0045] Similar to the first inverter 11, the high-potential side DC terminal of the second inverter 12 ( Figure 1 (Illustrated as "P2") is connected to the positive terminal of battery BAT via the high-potential side power line Lp. Additionally, the low-potential side DC terminal of the second inverter 12 ( Figure 1 (Illustrated with "N2") is connected to the negative terminal of battery BAT via the low-potential side power line Ln. Furthermore, the AC terminal of the second inverter 12 ( Figure 1 (U2, V2, W2) are shown in the diagram. The second motor M2 is connected via the second three-phase line L2.

[0046] The second inverter 12 converts the power (DC power) from the battery BAT, which is input via the high-potential DC terminal and the low-potential DC terminal, into three-phase AC power. Furthermore, the second inverter 12 outputs the converted AC power to the second motor M2 via the AC terminal. That is, the high-potential DC terminal and the low-potential DC terminal of the second inverter 12 can also be referred to as the input section of the second inverter 12, and the AC terminal of the second inverter 12 can also be referred to as the output section of the second inverter 12.

[0047] Additionally, a voltage sensor Sv2 is provided in the second inverter 12 to detect the voltage between the high-potential side DC terminals and the low-potential side DC terminals (i.e., the input voltage to the second inverter 12). The voltage sensor Sv2 sends a detection signal indicating the detection result to the control device 30 via the vehicle network or the like. Furthermore, a current sensor Si2 is provided on the high-potential side power line Lp connecting the battery BAT and the second inverter 12 to detect the value of the current flowing in that power line. The current sensor Si2 sends a detection signal indicating the detection result to the control device 30 via the vehicle network or the like. Alternatively, a current sensor that detects the value of the current flowing in each phase can also be provided on the second three-phase line L2 connecting the second inverter 12 and the second motor M2, and the detection signal from this current sensor can be sent to the control device 30.

[0048] In the motor drive system 1, when the first inverter 11 and the second inverter 12 are switched on, high-order harmonic currents caused by surge-like noise currents may be generated on the high-potential side power line Lp. Because the high-order harmonic current generated by the first inverter 11, which operates at a low output, is relatively small, its impact on the battery BAT and the second inverter 12 is also relatively small. On the other hand, the second inverter 12, which operates at a high output, may generate relatively large high-order harmonic currents. Such large high-order harmonic currents may become a cause of failure in the battery BAT, the first inverter 11, etc.

[0049] Therefore, in the motor drive system 1, an active filter section 20 is provided to suppress high-order harmonic currents generated from the second inverter 12. The active filter section 20 includes: a low-voltage power supply 21, which serves as a DC power supply to enable the active filter section 20 to generate a compensation current with opposite polarity (opposite phase) to the high-order harmonic currents generated from the second inverter 12; and a single-phase inverter 22, which generates AC power equivalent to the compensation current from the power (DC power) supplied by the low-voltage power supply 21. The single-phase inverter 22, for example, includes four switching elements (not shown) driven according to control signals from the control device 30, and the compensation current is generated by switching these switching elements. The compensation current generated by the active filter section 20 (single-phase inverter 22) is supplied to the high-potential side power line Lp via an insulation transformer 23.

[0050] Furthermore, in this embodiment, an inductor 24 is provided between the battery BAT and the first inverter 11 and the second inverter 12, in addition to the active filter section 20. This allows the inductor 24 to suppress high-order harmonic currents generated from the second inverter 12. In other words, according to the structure of this embodiment, by using both the compensation current based on the active filter section 20 and the inductor 24, high-order harmonic currents generated from the second inverter 12 can be suppressed more effectively. Moreover, the inductor 24 is not a necessary component and can be omitted.

[0051] The control device 30 provides unified control over the entire vehicle V, including the motor drive system 1. For example, the control device 30 controls the drive (i.e., the on / off switching of switching elements) of the first inverter 11 and the second inverter 12 using triangular wave comparison-type PWM (Pulse Width Modulation) control, thereby controlling the power supplied from the first inverter 11 to the first motor M1 or from the second inverter 12 to the second motor M2. The control device 30 can control the drive of the first motor M1 by controlling the power supplied from the first inverter 11 to the first motor M1, and can also control the drive of the second motor M2 by controlling the power supplied from the second inverter 12 to the second motor M2.

[0052] For example, the control device 30 derives the driving force required for the vehicle V to travel (hereinafter also referred to as "required driving force") based on the vehicle speed detected by a vehicle speed sensor (not shown) and the AP opening degree of the vehicle V detected by an AP (accelerator position) sensor (not shown). Moreover, the control device 30 uses the derived required driving force as a target value to control the output of the first motor M1 and / or the second motor M2.

[0053] Furthermore, the control device 30 controls the drive of the single-phase inverter 22 (i.e., the on / off switching of the switching elements) using, for example, triangular wave comparator-type PWM control, thereby controlling the compensation current supplied from the active filter section 20 to the high-potential side power line Lp. Based on control information from the drive motor MOT, the control device 30 predicts the high-order harmonic current generated by the switching operation of the inverter in the power conversion section 10, and controls the compensation current from the active filter section 20 through feedforward control. Therefore, compared to controlling the compensation current from the active filter section 20 through feedback control, an improvement in the responsiveness of the compensation current to high-order harmonic currents can be achieved.

[0054] More specifically, in this embodiment, the control device 30 controls the active filter unit 20 to generate a compensation current that suppresses high-order harmonic currents generated from the second inverter 12, based on the control information of the second motor M2. Here, the control information of the second motor M2 is information capable of predicting high-order harmonic currents generated from the second inverter 12, such as information representing the carrier signal (e.g., carrier period) of the second inverter 12, the dq-axis voltage and dq-axis current of the second motor M2, the motor electrical angle, speed, and Vpn voltage. The control information of the second motor M2 can be obtained based on the detection results of motor sensors (e.g., resolvers), voltage sensors Sv2, and current sensors Si2 installed on the second motor M2.

[0055] Furthermore, the control device 30 can be implemented, for example, through an ECU (Electronic Control Unit), which includes a processor for performing various calculations, a storage device for storing various information, and an input / output device for controlling the input and output of internal and external data of the control device 30. Additionally, the control device 30 can be implemented by one ECU or by multiple ECUs.

[0056] [Active Filter Control Section]

[0057] Next, an example of the active filter control unit 300, which is a functional unit of the control device 30 used to control the active filter unit 20, will be described. For example... Figure 2 As shown, the active filter control unit 300 includes a prediction unit 310 and a command value determination unit 320.

[0058] The prediction unit 310, for example, predicts the high-order harmonic current from the second inverter 12 at each prediction point included in a specified prediction period from now on, based on the control information of the second motor M2 in at least the next carrier cycle of the second inverter 12.

[0059] Specifically, the prediction unit 310 includes a motor model 311 that models the second motor M2, a speed prediction model 312 for predicting the speed of the second motor M2, and an inverter model 313 that models the second inverter 12.

[0060] The prediction unit 310 uses the motor model 311 to predict the output torque of the second motor M2 and the phase current flowing in each phase at a predetermined time (e.g., each prediction point included in the prediction period) that is closer to the future than the present, based on the control information of the second motor M2, the detection results of the voltage sensor Sv2 and the current sensor Si2, and the phase voltage derived from the inverter model 313.

[0061] Furthermore, the prediction unit 310 uses the speed prediction model 312 to predict the speed of the second motor M2 at a predetermined time (e.g., each prediction point included in the prediction period) closer to the present, based on the output torque of the second motor M2 predicted by the motor model 311. The control device 30 determines the carrier cycle of the second inverter 12 (e.g., the next carrier cycle of the second inverter 12) closer to the present, based on the speed of the second motor M2 predicted by the speed prediction model 312.

[0062] Furthermore, the prediction unit 310 uses the inverter model 313 to predict the high-order harmonic current generated from the second inverter 12 at a predetermined time closer to the future (e.g., each prediction point included in the prediction period) based on the phase current of the second motor M2 predicted by the motor model 311, the speed of the second motor M2 predicted by the speed prediction model 312, and the detection results of the current sensor Si2. Moreover, when the prediction unit 310 predicts the high-order harmonic current generated from the second inverter 12, it transmits the prediction result to the command value determination unit 320.

[0063] The command value determination unit 320, for example, based on the prediction result of the prediction unit 310, outputs a current command value to the active filter unit 20, which generates a compensation current with the opposite polarity to the higher harmonic current at the prediction point at the time corresponding to the prediction point contained in the next carrier cycle.

[0064] Specifically, the command value determination unit 320 generates voltage command values ​​for each frequency for generating a compensation current with the opposite polarity to the high-order harmonic current from the active filter unit 20, based on the high-order harmonic current obtained from the prediction result of the prediction unit 310. Furthermore, based on the generated voltage command values ​​for each frequency, the command value determination unit 320 performs PWM control on the single-phase inverter 22 via the PWM control unit 321, causing the single-phase inverter 22 to generate the compensation current.

[0065] Furthermore, the active filter control unit 300, which includes the prediction unit 310 and the instruction value determination unit 320, can be implemented, for example, by having the processor of the ECU that implements the control device 30 execute a program pre-stored in a storage device.

[0066] [Specific example of high-order harmonic current prediction in a control device]

[0067] Next, refer to Figure 3 A specific example of predicting high-order harmonic currents in the control device 30 (active filter control unit 300) will be explained.

[0068] exist Figure 3In the example shown, the carrier signal used by the control device 30 to drive the second inverter 12 (i.e., the second motor M2) has three carrier cycles: a first cycle Cc1 from time t0 to time t1, a second cycle Cc2 from time t1 to time t2, and a third cycle Cc3 from time t2 to time t3.

[0069] In addition, Figure 3 In the example shown, the rotational speed of the second motor M2 is ( Figure 3 The speed of the motor (as shown in the diagram) increases as it progresses later in the time series, and correspondingly, the carrier period decreases as it progresses later in the time series. Specifically, when the length of the first period Cc1 is set to T1[s], the length of the second period Cc2 is set to T2[s], and the length of the third period Cc3 is set to T3[s], T1 > T2 > T3.

[0070] Since the compensation current generated from the active filter unit 20 is controlled by feedforward control, the control device 30 predicts the high-order harmonic currents at each prediction point within a predetermined prediction target period from the present (i.e., the prediction start time) when the predetermined prediction start time arrives. Here, the prediction target period can be, for example, set to the period of at least the next carrier cycle of the inverter (here, the second inverter 12), which is the source of the high-order harmonic current that is to be suppressed.

[0071] In this embodiment, the prediction target period can be set as the time period from the predicted start time to the end time of the next carrier cycle, i.e., the time before the start time of the next carrier cycle. Furthermore, the predicted start time is set to a time when the prediction of the higher harmonic currents for the prediction target period including that carrier cycle can be completed before the start time of the next carrier cycle.

[0072] Specifically, with the start of the first cycle Cc1, the control device 30 first determines various command values ​​to be used in order to control the second inverter 12, etc., in the next carrier cycle (i.e., the second cycle Cc2). Figure 3 The diagram shows "Command Value Determination (t1)"). This determines the length of the second cycle Cc2, the switching content of the second inverter 12 in the second cycle Cc2, and so on.

[0073] Furthermore, after determining the various command values ​​in the second cycle Cc2, the control device 30 begins predicting the higher harmonic currents generated in the second cycle Cc2 when the prediction start time, i.e., time t10, arrives. Figure 3 The diagram in the middle is titled "Prediction of Higher Harmonics (t1~t2)").

[0074] When predicting the higher harmonic current generated in the second period Cc2, the control device 30 uses the period from time t10 to time t2 as the prediction period. Figure 3 The diagram shows the prediction of the high-order harmonic currents at each prediction point within the predicted object period (α). Figure 3 As shown, the prediction period α includes the second period Cc2.

[0075] Each prediction point is set at a predetermined time interval starting from the beginning of the prediction period (i.e., the prediction start time). This time interval (hereinafter also referred to as the "prediction point interval") is proportional to the length of the next carrier cycle; the longer the next carrier cycle, the longer the time interval. As an example, in this embodiment, when the length of the next carrier cycle is set to Tx[s] and the prediction point interval is set to Sx[s], Sx = Tx / 10. That is, in this embodiment, the number of prediction points included in the next carrier cycle is a constant 10, regardless of the length of the carrier cycle.

[0076] Specifically, in Figure 3 During the prediction period α shown, prediction points are marked with black circles in the diagram. The earliest prediction point p1 in the time series is T2 / 10 [s] after time t10, and the next prediction point p2 is T2 / 10 [s] after prediction point p1. Similarly, the next prediction point p3 is T2 / 10 [s] after prediction point p2, the next prediction point p4 is T2 / 10 [s] after prediction point p3, and the next prediction point p5 is T2 / 10 [s] after prediction point p4. Prediction points after prediction point p5 are also set at T2 / 10 [s] intervals up to the end of the second period Cc2, i.e., time t2.

[0077] Similarly, with the start of the second cycle Cc2, the control device 30 determines various command values ​​to be used in order to control the second inverter 12 in the next carrier cycle (i.e., the third cycle Cc3). Figure 3 The diagram in the middle is labeled "Command Value Determination (t2)"). Furthermore, after determining the various command values ​​in the third cycle Cc3, the control device 30 predicts the higher harmonic currents generated in the third cycle Cc3. Figure 3 The diagram in the middle shows "Higher Harmonic Prediction (t2~t3)"). The prediction period in this case is ( Figure 3 The interval between prediction points in the diagram (showing the prediction period β) is proportional to the length of the third period Cc3. Specifically, as shown in the diagram... Figure 3 As shown, it is T3 / 10[s].

[0078] In this way, when predicting the high-order harmonic current generated in the next carrier cycle, by predicting the high-order harmonic current at the prediction point set at a time interval proportional to the length of the carrier cycle, the high-order harmonic current generated in the carrier cycle can be predicted with high accuracy, and the processing load of the control device 30 used to perform the prediction can be reduced.

[0079] Suppose that when predicting the higher harmonic currents generated in the next carrier cycle, the higher harmonic currents are predicted at prediction points set at regular time intervals, independent of the length of the carrier cycle. In this case, to predict the higher harmonic currents generated in the next carrier cycle with high accuracy, the interval between prediction points needs to be shortened to some extent. However, when the carrier cycle is relatively long, the variation of the higher harmonic currents generated in that carrier cycle becomes gradual, so even without predicting the higher harmonic currents at such short intervals, it is possible to predict the higher harmonic currents generated in that carrier cycle with high accuracy.

[0080] Therefore, in this embodiment, by predicting the high-order harmonic current at prediction points set at time intervals proportional to the length of the next carrier cycle, the prediction of high-order harmonic current at excess prediction points is reduced, thereby reducing the processing load of the control device 30 when predicting the high-order harmonic current generated in the next carrier cycle.

[0081] Furthermore, by setting prediction points at time intervals proportional to the length of the next carrier cycle, the number of prediction points can be kept approximately constant regardless of the length of the carrier cycle. Therefore, the higher harmonic currents generated in a carrier cycle can be predicted with a approximately constant processing load, independent of the length of the next carrier cycle. Consequently, regardless of how the carrier cycle changes, the power consumption of the control device 30 used to predict the higher harmonic currents generated in each carrier cycle can remain approximately constant. Moreover, by setting the power consumption of the control device 30 used to predict the higher harmonic currents generated in each carrier cycle to be approximately constant, the estimation of this power consumption can be facilitated.

[0082] However, as mentioned above, the prediction start time, which serves as the starting point of the prediction target period, is earlier than the start time of the next carrier cycle. Therefore, for example, the prediction target period α also includes prediction points outside the second cycle Cc2, such as prediction point p1 and prediction point p2. Moreover, the prediction results of higher harmonic currents at such prediction points outside the next carrier cycle are not used to suppress the generation of compensation currents for higher harmonic currents generated in the next carrier cycle. Therefore, it is desirable to minimize such useless prediction points as much as possible.

[0083] Therefore, in this embodiment, the first period from the completion time of the prediction of the higher harmonic currents at each prediction point included in the prediction target period to the start time of the next carrier cycle is shorter than the second period from the time when the command value for driving the inverter in the next carrier cycle is determined to the start time of the prediction of the higher harmonic currents at each prediction point included in the prediction target period.

[0084] Specifically, such as Figure 3 As shown, the time at which the various command values ​​for driving the second inverter 12 in the second cycle Cc2 are determined is set as t11, and the completion time of the prediction of the higher harmonic currents at each prediction point included in the prediction target period α of the second cycle Cc2 is set as t12. In this case, the period tb from time t12 to time t1 corresponds to the first period described above, and the period ta from time t11 to time t10 corresponds to the second period described above. Moreover, the period tb is shorter than the period ta.

[0085] In this way, by setting the prediction start time as late as possible within the range that the prediction of the high-order harmonic current during the prediction period including the prediction object can be completed up to the start time of the next carrier cycle, the aforementioned useless prediction points can be reduced, and the processing load of the control device 30 for predicting the high-order harmonic current generated in the next carrier cycle can be further reduced.

[0086] On the other hand, assuming that the prediction start time for the higher harmonic current generated in the second cycle Cc2 is set to the time t11 that determines the various command values ​​used to drive the second inverter 12 in the second cycle Cc2, Figure 3 The number of useless prediction points, such as those indicated by the white circles in the middle, increases, and consequently the processing load on the control device 30 increases accordingly.

[0087] In addition, the control device 30 can also switch between two modulation methods, sinusoidal PWM control and overmodulation PWM control, to drive the second inverter 12 (i.e., the second motor M2). Figure 4 An example is shown of the gate signal applied by the control device 30 to the gate terminal of the switching element of the second inverter 12 and the high-order harmonic current generated from the second inverter 12 during overmodulated PWM control.

[0088] Furthermore, the control device 30 can also switch the desired prediction period using a modulation method. Specifically, when the control device 30 drives the second inverter 12 using sinusoidal PWM control, as... Figure 3 As shown, the prediction target period is set to include the next carrier cycle (i.e., one carrier cycle).

[0089] On the other hand, when the control device 30 drives the second inverter 12 via overmodulated PWM control, it extends the prediction period compared to when the second inverter 12 is driven via sinusoidal PWM control. Specifically, in this case, as... Figure 4 As shown, the control device 30 sets a prediction target period including one-sixth (i.e., Tf / 6) of the fundamental period Tf of the second inverter 12. Here, the fundamental period Tf of the second inverter 12 is the reciprocal of the fundamental frequency obtained by dividing the rotational frequency of the second motor M2 by the number of pole pairs (the number of switching elements of the second inverter 12). Moreover, in this case, the control device 30 sets the prediction point (in the time interval obtained by further dividing one-sixth of the fundamental period Tf by 10) to obtain the prediction point. Figure 4 (Refer to the black circle in the middle).

[0090] In this way, the control device 30 can set an appropriate prediction period and prediction point through a modulation method, enabling high-precision prediction of higher harmonic currents and reducing the processing load for such prediction. Specifically, in overmodulated PWM control, compared to sinusoidal PWM control, the frequency of the higher harmonic current is lower, and the fluctuation of the higher harmonic current becomes smoother. Therefore, even without predicting the higher harmonic current at short intervals, high-precision prediction of the higher harmonic current is possible. Therefore, when driving the second inverter 12 using overmodulated PWM control, the control device 30 can reduce the prediction of higher harmonic currents at excessive prediction points by setting the prediction period and prediction point as described above.

[0091] [Variation Example]

[0092] Next, variations of the above embodiments will be described. Furthermore, in the following, structures identical to those described above will be labeled with the same reference numerals, and their descriptions will be omitted or simplified as appropriate.

[0093] In the example above, only an active filter section 20 is provided to generate a compensation current with the opposite polarity to the high-order harmonic current generated from the second inverter 12, but the present invention is not limited thereto. For example, as Figure 5 As shown, in addition to the active filter section 20 that generates a compensation current with the opposite polarity to the high-order harmonic current generated from the second inverter 12, an active filter section 20' that generates a compensation current with the opposite polarity to the high-order harmonic current generated from the first inverter 11 can also be provided. That is, as Figure 5As shown, the motor drive system 1 can also be configured such that the first motor M1, the first inverter 11, and the active filter unit 20' are connected in parallel with the second motor M2, the second inverter 12, and the active filter unit 20' relative to the battery BAT that supplies power to each inverter 11, 12. When the active filter unit 20' is provided, the control device 30, similar to the example described above, predicts the high-order harmonic current generated from the first inverter 11 based on control information of the first motor M1, and causes the active filter unit 20' to generate a compensation current of opposite polarity. This also suppresses the high-order harmonic current generated from the first inverter 11. Therefore, the high-order harmonic current in the motor drive system 1, which consists of the first motor M1, the first inverter 11, and the active filter unit 20', and the second motor M2, the second inverter 12, and the active filter unit 20' connected in parallel with the battery BAT, can be suppressed more appropriately.

[0094] In addition, such as Figure 5 As shown, a passive filter 50 can be provided instead of the aforementioned inductor 24. Furthermore, a passive filter 50 can also be provided between the battery BAT and the active filter section 20'.

[0095] As explained above, according to the present invention, the processing load of the control device can be reduced, and high-order harmonic currents can be appropriately suppressed.

[0096] Various embodiments of the present invention have been described above with reference to the accompanying drawings, but the present invention is not limited to such examples. It is obvious that those skilled in the art will conceive of various modifications or alterations within the scope of the technical solutions described, and these modifications or alterations naturally fall within the technical scope of the present invention. Furthermore, the constituent elements of the above embodiments can be combined arbitrarily without departing from the spirit of the invention.

[0097] At least the following items are described in this specification. Furthermore, the constituent elements corresponding to those in the above embodiments are shown in parentheses, but the present invention is not limited thereto.

[0098] (1) A control device (control device 30) that controls an active filter section (active filter section 20, active filter section 20') that suppresses high-order harmonic currents generated from the inverters (first inverter 11, second inverter 12) of the drive motors (first motor M1, second motor M2), wherein,

[0099] The control device includes:

[0100] The prediction unit (prediction unit 310) predicts, based on the motor control information in at least the next carrier cycle of the inverter, the higher harmonic currents at each prediction point included in a predetermined prediction period from the present.

[0101] The command value determination unit (command value determination unit 320), based on the prediction result of the prediction unit, outputs to the active filter unit a current command value that generates a compensation current with opposite polarity to the higher harmonic current at the prediction point at a time corresponding to the prediction point contained in the next carrier cycle during the prediction period, wherein...

[0102] Each prediction point is set at a predetermined time interval, starting from the beginning of the prediction period.

[0103] The longer the next carrier cycle, the longer the time interval.

[0104] According to (1), the processing load of the control device can be reduced and high-order harmonic currents can be appropriately suppressed.

[0105] (2) The control device according to (1), wherein,

[0106] The control device is configured to switch between two modulation methods, sinusoidal PWM control and overmodulation PWM control, to drive the inverter.

[0107] When the inverter is driven by the overmodulated PWM control, the control device extends the prediction period compared to when the inverter is driven by the sinusoidal PWM control.

[0108] According to (2), by setting an appropriate prediction period through modulation method, high-order harmonic currents can be predicted with high accuracy, and the processing load of the control device used to make the prediction can be reduced.

[0109] (3) The control device according to (2), wherein,

[0110] The prediction period during which the inverter is driven by the sinusoidal PWM control includes the next carrier cycle, and

[0111] The predicted period during the case where the inverter is driven by the overmodulated PWM control includes one-sixth of the fundamental cycle of the inverter.

[0112] According to (3), by setting an appropriate prediction period through modulation, high-order harmonic currents can be predicted with high accuracy, and the processing load of the control device used for making the prediction can be reduced.

[0113] (4) The control device according to any one of (1) to (3), wherein,

[0114] The number of prediction points included in the next carrier cycle is constant and independent of the length of the next carrier cycle.

[0115] According to (4), it is possible to predict the higher harmonic current generated in the next carrier cycle with a roughly constant processing load, regardless of the length of the next carrier cycle.

[0116] (5) The control device according to any one of (1) to (4), wherein,

[0117] The period from the completion time of the prediction of the higher harmonic current at each prediction point to the start time of the next carrier cycle is shorter than the period from the time when the command value for driving the inverter in the next carrier cycle is determined to the start time of the prediction of the higher harmonic current at each prediction point.

[0118] According to (5), the processing load of the control device used to predict the high-order harmonic current generated in the next carrier cycle can be reduced.

[0119] (6) A motor drive system (motor drive system 1) comprising the control device described in any one of (1) to (5), wherein,

[0120] The plurality of motors, the inverters that drive the motors, and the active filter section that suppresses the high-order harmonic currents generated from the inverters are connected in parallel with the power supply that supplies power to each inverter.

[0121] According to (6), the high-order harmonic current in the motor drive system is formed by connecting multiple motors, the inverter that drives the motors, and the active filter section that suppresses the high-order harmonic current generated from the inverter in parallel with the power supply that supplies power to each inverter.

Claims

1. A control device that controls an active filter section that suppresses high-order harmonic currents generated from an inverter driving a motor, wherein, The control device includes: The prediction unit, based on the motor control information in at least the next carrier cycle of the inverter, predicts the higher harmonic currents at each prediction point included in a specified prediction period from now on. as well as The command value determination unit, based on the prediction result of the prediction unit, outputs a current command value to the active filter unit at a time corresponding to the prediction point contained in the next carrier cycle during the prediction target period, and generates a compensation current with opposite polarity to the higher harmonic current at that prediction point. Each prediction point is set at a predetermined time interval, starting from the beginning of the prediction period. The longer the next carrier cycle, the longer the time interval.

2. The control device according to claim 1, wherein, The control device is configured to switch between two modulation methods, sinusoidal PWM control and overmodulation PWM control, to drive the inverter. When the inverter is driven by the overmodulated PWM control, the control device extends the prediction period compared to when the inverter is driven by the sinusoidal PWM control.

3. The control device according to claim 1 or 2, wherein, The number of prediction points included in the next carrier cycle is constant and independent of the length of the next carrier cycle.

4. The control device according to claim 1 or 2, wherein, The period from the completion time of the prediction of the higher harmonic current at each prediction point to the start time of the next carrier cycle is shorter than the period from the time when the command value for driving the inverter in the next carrier cycle is determined to the start time of the prediction of the higher harmonic current at each prediction point.

5. A motor drive system comprising the control device according to any one of claims 1 to 3, wherein, The plurality of motors, the inverters that drive the motors, and the active filter section that suppresses the high-order harmonic currents generated from the inverters are connected in parallel with the power supply that supplies power to each inverter.

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