JP2013198345A - Control device for ac electric machine driving system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively suppress variation of output of an AC electric machine ascribable to variation of power supply voltage after stepping up by a converter without incurring increase of switching loss or a calorific value.SOLUTION: A control device for an AC electric machine driving system, which includes a power supply, a converter, and an inverter that converts power supply voltage after stepping up by the converter into AC voltage and outputs the AC voltage to an AC electric machine M, calculates a duty ratio of PWM control based on target output of the AC electric machine, and controls the inverter based on the duty ratio. When the power supply voltage after the stepping up varies in a preset frequency range with a reference amplitude or greater (150), the control device corrects the duty ratio of the PWM control based on a command value VH# for the converter (160). When the power supply voltage after the stepping up does not vary in the preset frequency range with the reference amplitude or greater, the control device corrects the duty ratio of the PWM control based on a detection value VHd of the power supply voltage after the stepping up (170).

Description

  The present invention relates to a control device for a system for driving an AC electric machine such as an AC motor, and more particularly to a control device for an AC electric machine drive system including an inverter that converts a power supply voltage into an AC voltage and outputs the AC voltage to the AC electric machine. .

  As one of AC electric machine drive systems, an AC electric machine drive system including a power source, a converter, and an inverter that converts a power supply voltage boosted by the converter into an AC voltage and outputs the AC voltage to the AC electric machine is widely used. Also, a PWM control method is widely used as a control method for an AC electric machine drive system. In this control method, a duty ratio of PWM control for driving an AC electric machine is calculated, and based on the duty ratio. The inverter is controlled.

  The duty ratio of the PWM control is calculated based on the output required for the AC electric machine, and based on the power supply voltage after boosting so that the output of the AC electric machine does not fluctuate due to fluctuations in the power supply voltage after boosting by the converter. Will be corrected. For example, Patent Document 1 below describes a control device for an AC motor drive system configured such that the duty ratio of PWM control in an inverter is corrected based on a command value of a boosted power supply voltage.

JP 2006-320039 A

[Problems to be Solved by the Invention]
The actual value of the power supply voltage after boosting may not match the command value. For this reason, in the control device described in the above publication, fluctuations in the output of the AC motor due to fluctuations in the power supply voltage after boosting by the converter may not be effectively suppressed.

  Further, in order to solve the above-mentioned problem in the control device described in the above publication, the power supply voltage after boosting is detected, and the duty ratio of PWM control in the inverter is corrected based on the detected value. Can be considered. However, when the duty ratio is corrected based on the detected value, for example, in a situation where the actual value of the boosted power supply voltage greatly fluctuates at a relatively high frequency, fluctuations in the output of the AC motor On the other hand, it becomes bigger.

  Further, when the duty ratio is corrected based on the detected value, it is conceivable to increase the PWM control period in the inverter in order to prevent the fluctuation of the output of the AC motor from increasing. However, in such a case, the switching frequency of the switching element in the inverter increases, which causes a new problem of increased switching loss and heat generation.

The present invention has been made in view of the above-described problems in the control of an AC electric machine drive system including an inverter that converts a power supply voltage boosted by a converter into an AC voltage and outputs the AC voltage to the AC electric machine. And the main subject of this invention is suppressing the fluctuation | variation of the output of an alternating current electric machine resulting from the fluctuation | variation of the power supply voltage after the pressure | voltage rise by a converter, without causing the increase in a switching loss or the emitted-heat amount.
[Means for Solving the Problems and Effects of the Invention]

  According to the present invention, the main problem described above is the configuration of claim 1, that is, the power source, the converter, and the inverter that converts the power source voltage boosted by the converter into an AC voltage and outputs the AC voltage to the AC electric machine. A control apparatus for an AC electric machine drive system, comprising: calculating a duty ratio of PWM control based on a target output of the AC electric machine; and controlling the inverter based on the duty ratio. When the boosted power supply voltage fluctuates over a reference amplitude within a preset frequency range, the PWM control duty ratio is corrected based on the command value for the converter, and the boosted power supply voltage When the voltage does not fluctuate over the reference amplitude within the preset frequency range, the power supply voltage after boosting by the converter is detected. Modifying the duty ratio of the PWM control based on, it is achieved by a control apparatus for an AC electric drive system, characterized in that.

  According to the above configuration, when the boosted power supply voltage fluctuates over a reference amplitude within a preset frequency range, the duty ratio of PWM control is corrected based on the command value for the converter. Therefore, even when the boosted power supply voltage fluctuates significantly within a preset frequency range, compared to the case where the duty ratio of PWM control is corrected based on the detected value of the boosted power supply voltage. And it can suppress effectively that the fluctuation | variation of the output of an alternating current electric machine becomes large on the contrary.

  Further, according to the above configuration, when the boosted power supply voltage does not fluctuate over the reference amplitude within the preset frequency range, the PWM control is performed based on the detected value of the boosted power supply voltage by the converter. The duty ratio is corrected. Therefore, when the boosted power supply voltage does not fluctuate significantly within the preset frequency range, the PWM control duty ratio is corrected based on the detected value of the boosted power supply voltage, and the boosted power supply voltage fluctuates. It is possible to effectively suppress fluctuations in the output of the AC electric machine due to the above.

  Furthermore, according to the above configuration, it is not necessary to increase the period of PWM control in the inverter. Accordingly, it is possible to effectively prevent the switching frequency of the switching element in the inverter from increasing, and the switching loss and the heat generation amount resulting from the switching frequency from being increased.

  Further, according to the present invention, in order to effectively achieve the main problems described above, there are an operation mode in which there is no command value for the converter with respect to the boosted power supply voltage and an operation mode in which the command value for the converter is not accurate. As the predetermined mode set in advance, when the AC electric machine drive system is operating in the predetermined mode, the duty ratio of the PWM control is corrected based on the detected value of the power supply voltage after boosting by the converter. (Constitution of Claim 2)

  According to the above configuration, when the AC electric machine drive system is operating in the predetermined mode, the duty ratio of the PWM control is corrected based on the detected value of the power supply voltage after being boosted by the converter. Therefore, in an operation mode where there is no command value for the converter or an operation mode where the command value for the converter is not accurate, it is certain that the duty ratio of PWM control cannot be properly corrected based on the power supply voltage after boosting. Can be avoided.

  According to the present invention, in order to effectively achieve the above-mentioned main problems, the inverter has a plurality of arms, each arm having an upper arm and a lower arm connected in series with each other, and The mode is configured to include an on-control mode of the upper arm (structure of claim 3).

  According to the above configuration, when the upper arm is in the on control mode, the duty ratio of the PWM control can be corrected based on the detected value of the boosted power supply voltage. Therefore, in a situation where there is no command value for the converter, it can be reliably avoided that the duty ratio of the PWM control cannot be properly corrected based on the boosted power supply voltage.

  According to the present invention, in order to effectively achieve the main problem described above, the AC electric machine drive system includes a first smoothing capacitor provided between the power source and the converter, the converter, and the A second smoothing capacitor provided between the first smoothing capacitor and the inverter, wherein the predetermined mode includes a discharge mode for discharging charges from the first and second smoothing capacitors. 4 configuration).

  According to the above configuration, when the operation mode of the AC electric machine drive system is the discharge mode in which charges are discharged from the first and second smoothing capacitors, the PWM control is performed based on the detected value of the power supply voltage after boosting by the converter. The duty ratio is corrected. Therefore, in the operation mode in which the command value for the converter is not accurate, it is possible to reliably avoid the fact that the duty ratio of the PWM control cannot be properly corrected based on the boosted power supply voltage.

  According to the present invention, in order to effectively achieve the above main problem, when the deviation between the command value for the converter and the detected value of the power supply voltage after boosting by the converter is larger than a reference value, the converter The duty ratio of the PWM control is modified based on the value obtained by reducing and correcting the command value for (configuration of claim 5).

  According to said structure, when the deviation of the command value with respect to a converter and the detected value of the power supply voltage after pressure | voltage rise is larger than a reference value, the correction amount of the duty ratio of PWM control can be reduced. Therefore, in a situation where the deviation between the command value for the converter and the detected value of the power supply voltage after boosting is larger than the reference value, the amount of correction of the duty ratio of PWM control becomes excessive, resulting in an AC electric machine output. The possibility that a surge will occur can be effectively reduced.

  According to the present invention, the detected value of the power supply voltage after the boosting by the converter for correcting the duty ratio of the PWM control is effectively the boost detected by the detecting means in order to effectively achieve the main problem described above. It is configured to be a value obtained by filtering the subsequent power supply voltage (configuration of claim 6).

  According to the above configuration, the detected value of the boosted power supply voltage for correcting the duty ratio of the PWM control is a value obtained by filtering the boosted power supply voltage detected by the detecting means. Therefore, the fluctuation of the power supply voltage after boosting is not large, and in the situation where the duty ratio of PWM control should be corrected according to the detected value of the power supply voltage after boosting, it is caused by the fluctuation of the power supply voltage after boosting The possibility that the fluctuation of the output of the AC electric machine becomes large can be reduced.

It is a schematic block diagram which shows one Embodiment of the control apparatus of the alternating current electric drive system by this invention applied to the alternating current motor drive system. It is a control block diagram by the sine wave PWM control system performed by the control device in the embodiment. It is a flowchart which shows the control routine which sets the reference value VHref for reflecting the system voltage VH in the case of conversion from a shaft voltage command value to a phase voltage command value. It is a flowchart which shows the modification of the control routine which sets the reference value VHref.

  Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a schematic configuration diagram showing one embodiment of a control device for an AC electric machine drive system according to the present invention applied to an AC motor drive system.

  In FIG. 1, reference numeral 100 generally indicates an AC motor drive system. Drive system 100 includes a DC power supply B, a step-up / down converter 10, and an inverter 12 that converts a power supply voltage boosted by the converter into an AC voltage. The inverter 12 outputs the AC voltage to an AC motor M as an AC electric machine. And drive this.

  The direct current power source B may be any battery, for example, a secondary battery such as nickel metal hydride or lithium ion, a fuel cell, or a combination of both. In particular, when drive system 100 is mounted on a hybrid vehicle or an electric vehicle, DC power supply B is preferably a battery that can store electricity.

  The AC motor M is a drive motor that generates torque for driving the drive wheels of a hybrid vehicle or an electric vehicle, for example. Further, AC motor M may be configured to function as a motor generator that generates electric power when driven by an engine. Furthermore, AC motor M may operate as an electric motor for the engine, and may be incorporated in a hybrid vehicle so that the engine can be started, for example.

  One end of a power line 14 and a ground line 16 are connected to the positive terminal and the negative terminal of the DC power supply B, respectively. System relays SR1 and SR2 are provided for power line 14 and ground line 16 respectively, and first smoothing capacitor C1 is interposed between power line 14 and ground line 16 between system relays SR1 and SR2 and converter 10. Is provided.

  System relays SR1 and SR2 are turned on / off by a signal SE from control device 30. Specifically, the system relays SR1 and SR2 are turned on by an H (logic high) level signal SE from the control device 30, and are turned off by an L (logic low) level signal SE from the control device 30.

  The buck-boost converter 10 includes a reactor L1 provided on the power line 14, power semiconductor switching elements Q1 and Q2, and diodes D1 and D2 connected in antiparallel to the switching elements Q1 and Q2, respectively. The power power semiconductor switching element Q1 and the diode D1 are provided between the other end of the power line 14 and one end of the power line 18, and the power power semiconductor switching element Q2 and the diode D2 are connected to the other end of the power line 14 and the ground line 16. Between. On / off of the power semiconductor switching elements Q1 and Q2 is controlled by switching control signals S1 and S2 from the control device 30, respectively.

  In this embodiment, the power semiconductor switching element (hereinafter simply referred to as “switching element”) is, for example, an IGBT (Insulated Gate Bipolar Transistor), a power MOS (Metal Oxide Semiconductor) transistor, a power bipolar transistor, or the like. It may be.

  Inverter 12 is provided between the other end of power line 18 and the other end of ground line 16, and includes U-phase arm 20, V-phase arm 22, and W-phase arm 24. Each phase arm has a switching element connected in series between the power line 18 and the ground line 16. U-phase arm 20 has switching elements Q3 and Q4, V-phase arm 22 has switching elements Q5 and Q6, and W-phase arm 24 has switching elements Q7 and Q8. Further, diodes D3 to D8 are connected in reverse parallel to the switching elements Q3 to Q8, respectively.

  Switching elements Q3, Q5, Q7 and D3, D5, D7 constitute upper arms of U-phase arm 20, V-phase arm 22, and W-phase arm 24, respectively. Switching elements Q4, Q6, Q8 and D4, D6, D8 constitute lower arms of U-phase arm 20, V-phase arm 22, and W-phase arm 24, respectively. Switching elements Q3 to Q8 are turned on / off by switching control signals S3 to S8 from control device 30, respectively.

  An intermediate point of each phase arm is connected to each phase end of each phase coil of AC motor M. That is, the AC motor M is a three-phase permanent magnet motor, and one end of three coils of the U phase, the V phase, and the W phase is commonly connected to the middle point. Further, the other end of each phase coil is connected to the middle point of the pair of switching elements of each phase arm 20 to 24, that is, between the upper arm and the lower arm.

  The step-up / down converter 10 boosts the DC voltage Vb supplied from the DC power source B and supplies the boosted DC voltage to the inverter 12 during the boosting operation (in this specification, supplied to the inverter 12). This DC voltage is referred to as “system voltage” as necessary). Specifically, in response to the switching control signals S1 and S2 from the control device 30, the ON period of the switching element Q1 and the ON period of Q2 are alternately given, and the voltage boost ratio is the ratio of these ON periods. It becomes a value according to.

  A second smoothing capacitor C <b> 2 is provided between the power line 18 and the ground line 16 between the buck-boost converter 10 and the inverter 12. The smoothing capacitor C <b> 2 smoothes the DC voltage from the step-up / step-down converter 10 during the boosting operation, and supplies the smoothed DC voltage to the inverter 12.

  Further, during the step-down operation, the step-up / step-down converter 10 steps down the DC voltage (system voltage) supplied from the inverter 12 via the smoothing capacitor C2 and outputs it to the DC power supply B, thereby charging the DC power supply B. Specifically, in response to the switching control signals S1 and S2 from the control device 30, a period in which only the switching element Q1 is turned on and a period in which both the switching elements Q1 and Q2 are turned off are alternately given. The step-down ratio is a value corresponding to the duty ratio in the ON period.

  The inverter 12 converts the boosted DC voltage supplied from the smoothing capacitor C2 to an appropriate AC motor applied voltage by the switching operation of the switching elements Q3 to Q8 respectively responding to the switching control signals S3 to S8 from the control device 30. Convert. In particular, when the torque command value of AC motor M is positive, the boosted DC voltage from smoothing capacitor C2 is converted to an appropriate AC motor applied voltage so that AC motor M outputs a positive torque. . Further, when the torque command value of the AC motor M is zero, the inverter 12 applies an appropriate AC motor to the DC voltage after boosting from the smoothing capacitor C2 so that the output of the AC motor M becomes zero. Convert to voltage. Therefore, AC motor M is driven to generate zero or positive torque designated by the torque command value.

  Furthermore, when the motor drive system 100 is mounted on a hybrid vehicle or an electric vehicle and the vehicle is regeneratively braked, the torque command value of the AC motor M is set negative. In this case, the inverter 12 converts the AC voltage generated by the AC motor M into a DC voltage by a switching operation in response to the switching control signals S3 to S8, and converts the DC voltage (system voltage) through the smoothing capacitor C2. To the step-up / down converter 10. Regenerative braking is braking by converting a part of the kinetic energy of the vehicle into electric energy. Specifically, when braking is performed by the driver, braking that generates braking force by regenerative power generation in addition to friction braking force, or regenerative power generation when the accelerator pedal is turned off but no braking operation is performed. To decelerate (or stop acceleration) the vehicle.

  In addition, since the operation | movement at the time of regenerative braking of the motor drive system 100 does not make the summary of this invention, detailed description of the operation | movement at the time of regenerative braking is abbreviate | omitted.

  The DC power supply B is provided with a voltage sensor 32, and the voltage sensor 32 outputs a signal indicating the detected voltage Vb of the DC power supply B to the control device 30. Further, the smoothing capacitor C2 is provided with a voltage sensor 34 for detecting a voltage (system voltage) between both ends of the smoothing capacitor C2. The voltage sensor 34 detects the detected voltage, that is, the power supply voltage VH after being boosted by the step-up / down converter 10. The signal shown is output to the control device 30.

  A current sensor 36 is provided on the power line between the inverter 12 and the AC motor M. The current sensor 36 detects a motor current flowing through the AC motor M, and outputs a signal indicating the detected motor current to the control device 30. Since the sum of the instantaneous values of the three-phase currents iu, iv, iw flowing through the three power lines is zero, the current sensor 36 has a motor current (for example, V-phase) for two phases as shown in FIG. It only needs to be arranged so as to detect the current iv and the W-phase current iw).

  The AC motor M is provided with a rotation angle sensor (resolver) 38 that detects the rotor rotation angle θ. The rotation angle sensor 38 outputs a signal indicating the rotor rotation angle θ of the AC motor M to the control device 30. . The control device 30 calculates the rotational speed (rotational speed) of the AC motor M based on the rotational angle θ.

  Control device 30 also receives torque command value Tqcom of AC motor M from an electronic control unit (ECU) provided outside. Based on the torque command value, power supply voltage Vb detected by each sensor, system voltage VH, motor currents iv and iv, and rotation angle θ, control device 30 outputs torque corresponding to the torque command value. Thus, the buck-boost converter 10 and the inverter 12 are controlled. That is, the control device 30 generates switching control signals S1 to S8 for controlling the step-up / step-down converter 10 and the inverter 12 as described above, and outputs them to the step-up / down converter 10 and the inverter 12.

  During the step-up operation of the step-up / step-down converter 12, the control device 30 feedback-controls the output voltage VH of the smoothing capacitor C1, and generates the switching control signals S1, S2 so that the output voltage VH becomes a voltage command value to generate the step-up / step-down converter. 12 is output. Furthermore, control device 30 generates signal SE for turning on / off system relays SR1, SR2 and outputs the signal SE to system relays SR1, SR2.

  Next, power conversion controlled by the control device 30 and executed in the inverter 12 will be described in detail. The power conversion in the inverter 14 is controlled by a sine wave PWM control method.

  The sine wave PWM control method is used as a general PWM control. The on / off of the switching element in each phase arm is determined by a sine wave voltage command value and a carrier wave (typically a triangular wave). Control according to voltage comparison. As a result, for a set of a high level period corresponding to the on period of the upper arm element and a low level period corresponding to the on period of the lower arm element, the duty is set so that the fundamental wave component becomes a sine wave within a certain period. The ratio is controlled.

  In the AC motor M, the induced voltage increases as the rotation speed and output torque increase, and the required voltage increases. The boosted voltage by the converter 10, that is, the system voltage VH needs to be set higher than this motor required voltage (induced voltage). On the other hand, there is a limit value (VH maximum voltage) in the boosted voltage by the converter 10, that is, the system voltage.

  Therefore, the maximum torque control by the sine wave PWM control method is applied, and the output torque is controlled to the torque command value Tqcom which is the target value by the motor current control according to the vector control. Note that torque command value Tqcom of AC motor M is calculated from the vehicle request output based on the accelerator opening and the like by an ECU not shown in the figure.

  FIG. 2 is a control block diagram according to the sine wave PWM control method executed by the control device 30. The control in the control block diagram shown in FIG. 2 is realized by a control calculation process according to a predetermined program executed by the control device 30.

  As shown in FIG. 2, the PWM control block 200 includes a current command generation unit 210, coordinate conversion units 220 and 250, a rotation speed calculation unit 230, a PI calculation unit 240, and a PWM signal generation unit 260. Contains.

  The current command generation unit 210 generates a d-axis current command value Idcom and a q-axis current command value Iqcom corresponding to the torque command value Tqcom of the AC motor M according to a table created in advance.

  The coordinate conversion unit 220 performs the v-phase current iv and the W-phase current detected by the current sensor 36 by coordinate conversion (3 phase → 2 phase) using the rotation angle θ of the AC motor M detected by the rotation angle sensor 38. Based on iv, the d-axis current id and the q-axis current iq are calculated.

  The rotation speed calculation unit 230 calculates the rotation speed Nmt of the AC motor M based on the rotation angle θ of the AC motor M input from the rotation angle sensor 38.

  The PI calculation unit 240 receives a deviation ΔId (ΔId = Idcom-id) with respect to the command value of the d-axis current and a deviation ΔIq (ΔIq = Iqcom-iq) with respect to the command value of the q-axis current. The PI calculation unit 240 performs a PI calculation with a predetermined gain for each of the d-axis current deviation ΔId and the q-axis current deviation ΔIq to obtain a control deviation, and the d-axis voltage command value Vd # and the q-axis corresponding to the control deviation Voltage command value Vq # is generated.

  The coordinate conversion unit 250 converts the d-axis voltage command value Vd # and the q-axis voltage command value Vq # to the U-phase, V-phase, W-phase by coordinate conversion (2 phase → 3 phase) using the rotation angle θ of the AC motor M. The phase voltage command values Vu, Vv, Vw of the phases are converted. In order to convert the shaft voltage command value to the phase voltage command value so that the fluctuation does not affect the output torque of the AC motor M even if the system voltage VH varies, the reference value of the system voltage VH will be described later in detail. VHref is reflected.

  The PWM signal generator 260 generates the switching control signals S3 to S8 shown in FIG. 1 based on the comparison of the voltage command values Vu, Vv, Vw of each phase and a predetermined carrier wave. The switching elements Q3 to Q8 of the inverter 14 are switching-controlled by the switching control signals S3 to S8 generated by the PWM control block 200, so that the AC motor M outputs a torque corresponding to the torque command value Tqcom. A voltage is applied to the AC motor M.

  As described above, the reference value VHref of the system voltage VH is reflected in the conversion from the shaft voltage command values Vd #, Vq # to the phase voltage command values Vu, Vv, Vw, and the voltage command value of each phase after conversion and a predetermined value Switching control signals S3 to S8 are generated based on the comparison with the carrier wave. Therefore, the duty ratio of the PWM control in the inverter 12 is calculated based on the phase voltage command value so that the torque command value of the AC motor M is achieved, and the fluctuation of the system voltage affects the output torque of the AC motor M. Is corrected based on the reference value VHref.

  As shown in FIG. 2, the control device 30 of the AC motor drive system 100 according to the embodiment further includes a VH command value generation unit 310, a PWM signal generation unit 360, and a reference value setting unit 370. ing.

  VH command value generation unit 310 generates control command value VH # (hereinafter also referred to as voltage command value VH #) of system voltage VH in accordance with torque command value Tqcom and rotation speed Nmt of AC motor M.

  The PWM signal generation unit 360 is a predetermined PWM control method based on the power supply voltage Vb detected by the voltage sensor 32 and the current voltage command value VH # so that the output voltage of the converter 10 matches the voltage command value VH #. The switching control signals S1 and S2 are generated according to

  With this configuration, feedback control of the motor current (id, iq) is performed so that the output torque of AC motor M coincides with torque command value Tqcom.

  The reference value setting unit 370 for the system voltage is a reference value VHref for reflecting the system voltage VH in the conversion from the axial voltage command value to the phase voltage command value in the coordinate conversion unit 250 according to the flowchart shown in FIG. And the reference value VHref of the set system voltage is output to the coordinate conversion unit 250. The coordinate conversion unit 250 converts the shaft voltage command value into the phase voltage command value so that the influence of the system voltage fluctuation is reduced based on the input reference value VHref of the system voltage VH.

  As shown in FIG. 3, first, control is started from step 100. In step 110, it is determined whether or not the drive system 100 is in a discharge operation in which charges are discharged from the smoothing capacitors C1 and C2. Done. When an affirmative determination is made, control proceeds to step 170, and when a negative determination is made, control proceeds to step 120.

  In step 120, it is determined whether any upper arm of the inverter 12 is on, that is, whether any of the switching elements Q3, Q5, Q7 is on. . When an affirmative determination is made, control proceeds to step 170, and when a negative determination is made, control proceeds to step 130.

  In step 130, it is determined whether or not deviation ΔVH between voltage command value VH # and detected value VHd of system voltage VH is larger than reference value α (for example, 10% of voltage command value VH #). . When a positive determination is made, in step 140, β is set to, for example, 10% of the voltage command value VH #, and the voltage command value “VH # −β after the reference value VHref is reduced and corrected by β is determined. When the determination is negative, the control proceeds to step 150.

  In step 150, it is determined whether or not the fluctuation of the detected value VHd of the system voltage VH is larger than a threshold value. When an affirmative determination is made, the control proceeds to step 160, and when a negative determination is made, the control proceeds to step 170. In this case, when the detected value VHd of the system voltage VH varies over a reference amplitude within a preset frequency range, it may be determined that the variation of the detected value VHd is larger than the threshold value.

  Note that the frequency range and the reference amplitude are a frequency range in which fluctuations in the output torque of the AC motor increase due to fluctuations in the system voltage when the reference value VHref is set to the detection value VHd or its filtered value VHdf. The amplitude may be obtained experimentally, for example.

  In step 160, reference value VHref is set to voltage command value VH #, and in step 170, reference value VHref is set to a value VHdf obtained by filtering detected value VHd of system voltage VH. The filtering process may be an arbitrary filtering process as long as a value obtained by reducing the fluctuation of the system voltage VH is obtained.

  As described above, when the detected value VHd of the system voltage VH, which is the boosted power supply voltage, fluctuates over a reference amplitude within a preset frequency range, the reference value VHref is determined as a voltage command in step 160. Set to the value VH #. That is, when the fluctuation of detected value VHd of system voltage VH is larger than the threshold value, the duty ratio of PWM control in inverter 12 is corrected based on voltage command value VH # for converter 10.

  Accordingly, when the fluctuation of the system voltage VH is large and the duty ratio of the PWM control is corrected based on the detected value VHd of the system voltage VH, the output of the AC motor M is greatly changed instead of the output torque of the AC motor M. Torque fluctuations can be reduced.

  When the detected value VHd of the system voltage VH does not fluctuate over the reference amplitude within the preset frequency range, the reference value VHref filters the detected value VHd of the system voltage VH in step 170. Set to the value VHdf. That is, when the fluctuation of the detected value VHd of the system voltage VH is equal to or less than the threshold value, the duty ratio of the PWM control in the inverter 12 is corrected based on the filter processing value VHdf of the system voltage detected value VHd.

  Therefore, in the situation where the fluctuation of the system voltage VH is not large and the duty ratio of the PWM control should be corrected according to the detected value of the power supply voltage after boosting, the AC motor M is caused by the fluctuation of the system voltage VH. It is possible to reduce the possibility that the fluctuation of the output torque becomes large.

  Further, the reference value VHref is set not to the detected value VHd of the system voltage VH but to a value VHdf obtained by filtering the detected value VHd. Therefore, compared with the case where the reference value VHref is set to the detection value VHd of the system voltage VH, the control cycle of the inverter 14 is lowered, the switching frequency of the switching elements Q3 to Q8 is reduced, and the switching loss and the heat generation amount are high. Can be effectively suppressed.

  Further, according to the above-described embodiment, even when the driving system 100 is in a discharging operation for discharging electric charges from the smoothing capacitors C1 and C2, or when any one of the upper arms of the inverter 12 is on, step 170 is performed. Is executed. Therefore, the duty ratio of PWM control is set to the system voltage as much as possible even in an operation mode in which voltage command value VH # for converter 10 does not exist for the boosted power supply voltage or in an operation mode in which voltage command value VH # for converter 10 is not accurate. Corrections can be made based on VH.

  Further, according to the above-described embodiment, when the difference ΔVH between the voltage command value VH # and the detected value VHd of the system voltage VH is larger than the reference value α, the reference value VHref is corrected to be reduced by β in step 140. Is set to the voltage command value “VH # −β”. Therefore, in a situation where the duty ratio of PWM control has reached the lower limit value, a surge occurs in the output torque of AC motor M by setting reference value VHref to voltage command value VH #. Can be effectively suppressed.

  In particular, according to the above-described embodiment, the reference value α and the reduction correction amount β are variably set according to the voltage command value VH #, for example, as a value of 10% of the voltage command value VH #. Therefore, it is possible to appropriately suppress a sudden change in the output torque of AC motor M, as compared with the case where these values are constant.

  Although the present invention has been described in detail with respect to specific embodiments, the present invention is not limited to the above-described embodiments, and various other embodiments are possible within the scope of the present invention. It will be apparent to those skilled in the art.

  For example, in the above-described embodiment, the AC electric machine is a three-phase AC motor, but the AC electric machine has an arbitrary voltage as long as the power supply voltage after being boosted by the converter is converted into an AC voltage by an inverter and driven by the AC voltage. It may be an AC electric machine.

  Further, in the above-described embodiment, the reference value VHref of the system voltage for power conversion in the inverter is set according to the flowchart shown in FIG. 3, but the flowchart shown in FIG. May be modified to be set according to In FIG. 4, the same step numbers as those in FIG. 3 are assigned.

  In the above-described embodiment, the power conversion in the inverter is controlled by the sine wave PWM control method. However, other control methods such as a modulation PWM control method can be used depending on the situation. It may be modified to be controlled by.

DESCRIPTION OF SYMBOLS 10 ... Converter, 12 ... Inverter, 14, 18 ... Power line, 16 ... Ground wire, 20 ... U-phase arm, 22 ... V-phase arm, 24 ... W-phase arm, 30 ... Control device, 32, 34 ... Voltage sensor, 36 DESCRIPTION OF SYMBOLS ... Current sensor, 38 ... Rotation angle sensor, 100 ... AC motor drive system, 200 ... PWM control block, 210 ... Current command generation part, 260 ... PWM signal generation part (inverter), 270 ... Control mode determination part, 310 ... Control Mode determining unit, VH command value generating unit, 320 ... VH command value correcting unit, 350 ... PWM signal generating unit (converter), 370 ... reference value setting unit,
B: DC power supply, C1, C2: smoothing capacitor, D1 to D8: diode (anti-parallel diode), id: d-axis current, Idcom: d-axis current command value, iq: q-axis current, Iqcom: q-axis current command value , Iu, iv, iw ... motor current (three-phase current), L1 ... reactor, M ... AC motor, Nmt ... motor speed, Q1-Q8 ... power switching element, S1-S8 ... switching control signal, SR1, SR2 ... System relay, Tqcom ... Torque command value, Vb ... DC voltage, Vd ... d-axis voltage, Vd # ... d-axis voltage command value, VH ... System voltage (inverter input voltage), VH # ... System voltage command value, Vq ... q-axis voltage, Vq #, q-axis voltage command value, Vu, Vv, Vw, phase voltage command values, ΔId, d-axis current deviation, ΔIq, q-axis current deviation, θ, rotor rotation angle

Claims (6)

A control device for an AC electric machine drive system including a power supply, a converter, and an inverter that converts a power supply voltage boosted by the converter into an AC voltage and outputs the AC voltage to an AC electric machine, based on a target output of the AC electric machine In a control device for an AC electric machine drive system that calculates a duty ratio of PWM control and controls the inverter based on the duty ratio.
When the boosted power supply voltage fluctuates over a reference amplitude within a preset frequency range, the duty ratio of PWM control is corrected based on the command value for the converter,
When the boosted power supply voltage does not fluctuate over the reference amplitude within the preset frequency range, the duty ratio of PWM control is corrected based on the detected value of the boosted power supply voltage by the converter ,
A control device for an AC electric machine drive system.   The operation mode in which there is no command value for the converter with respect to the boosted power supply voltage and the operation mode in which the command value for the converter is not accurate are set as the predetermined mode set in advance, and the AC electric machine drive system is changed to the predetermined mode. 2. The control device for an AC electric machine drive system according to claim 1, wherein the duty ratio of the PWM control is corrected based on a detected value of the power supply voltage boosted by the converter.   The inverter includes a plurality of arms, each arm having an upper arm and a lower arm connected in series with each other, and the predetermined mode includes an on control mode of the upper arm. Item 3. A control device for an AC electric machine drive system according to Item 2.   The AC electric machine drive system includes a first smoothing capacitor provided between the power source and the converter, and a second smoothing capacitor provided between the converter and the inverter, 3. The control device for an AC electric machine drive system according to claim 2, wherein the mode includes a discharge mode for discharging electric charges from the first and second smoothing capacitors.   When the deviation between the command value for the converter and the detected value of the power supply voltage after boosting by the converter is larger than a reference value, the duty ratio of PWM control is corrected based on the value obtained by reducing and correcting the command value for the converter The control device for an AC electric machine drive system according to any one of claims 2 to 4.   The detection value of the boosted power supply voltage by the converter for correcting the duty ratio of PWM control is a value obtained by filtering the boosted power supply voltage detected by the detecting means. 4. The control apparatus for an AC electric machine drive system according to any one of 4 above.

Images