JP2007215381A - Voltage converter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a voltage converter capable of suppressing the occurrence of a surge voltage. <P>SOLUTION: A comparison circuit 40 derives actual duty ratio of a step-up converter based on the voltage at the intermediate point of upper/lower arms of the step-up converter which is input from a voltage sensor. The comparison circuit 40 detects deviation between a command duty ratio DR_com from a duty ratio calculating part 52 for the converter and an actual duty ratio. It outputs a signal DET that indicates the detected deviation to a duty ratio correcting part 54 for converter. The duty ratio correcting part 54 for converter corrects by offsetting the command duty ratio DR_com by the amount of deviation so that the deviation indicated by the signal DET comes to be almost zero. A signal PWMC for turning on/off the upper and lower arms based on the corrected command duty ratio DR_com is generated, and output to a step-up converter 12. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a voltage converter, and more particularly to a voltage converter that can suppress the generation of a surge voltage.

  Usually, in a vehicle such as an electric vehicle (EV) or a hybrid vehicle (HV), the driving force by electric energy is converted from DC power supplied from a high-voltage battery to three-phase AC power by an inverter. This is obtained by rotating a three-phase AC motor. Further, when the vehicle is decelerated, the battery is stored with regenerative energy obtained by the regenerative power generation of the three-phase AC motor, so that the vehicle travels without wasting energy.

  In such a hybrid vehicle or electric vehicle, a configuration in which a DC voltage from a DC power source is boosted by a boost converter and the boosted DC voltage is supplied to an inverter that drives a motor has been studied (for example, Patent Document 1). To 3).

  The boost converter includes two switching elements connected in series between the power supply line and the earth line of the inverter, two diodes connected in parallel with each switching element in the forward direction toward the power supply line, It consists of a reactor having one end connected to the midpoint of the two switching elements and the other end connected to the power supply line of the DC power supply.

  The step-up converter turns on / off a switching element (upper arm) connected to the power supply line side and a switching element (lower arm) connected to the earth line side with a predetermined duty ratio, thereby supplying a DC voltage from the power supply. Is boosted and supplied to the inverter, and the DC voltage from the inverter is stepped down and supplied to the power source.

Since the upper arm and the lower arm constituting the boost converter are connected in series between the power supply line and the earth line, it is necessary to prevent the upper arm and the lower arm from being turned on simultaneously. Therefore, a dead time for preventing the upper arm and the lower arm from being turned on simultaneously is provided in the control signal for switching control of the upper arm and the lower arm.
JP 2005-51895 A Japanese Patent Laid-Open No. 9-47027 JP 2004-120844 A

  However, due to the dead time, in the boost converter, in the duty ratio of the upper arm and the lower arm, the command duty ratio calculated based on the optimum value of the inverter input voltage and the actual upper arm and lower arm are There is a problem that a deviation occurs between the duty ratio when turned on / off (hereinafter also referred to as an actual duty ratio).

  Since this deviation differs depending on the direction of the current flowing through the reactor, when the current direction is reversed, the actual duty ratio fluctuates discontinuously, and a surge voltage corresponding to the fluctuation amount is generated in the output voltage of the boost converter. there's a possibility that. This surge voltage may damage a load (such as an inverter) connected to the output side of the boost converter.

  Therefore, in the conventional motor drive device, in order to protect the load from the surge voltage, the smoothing capacitor connected between the boost converter and the inverter has a capacity large enough to absorb this surge voltage. The measure which consists of is taken. However, an increase in the capacity of the capacitor leads to an increase in the size and cost of the motor drive device.

  Therefore, the present invention has been made to solve such a problem, and an object of the present invention is to provide a voltage converter capable of suppressing the generation of a surge voltage.

  According to the present invention, the voltage converter varies the input voltage to the load. The voltage converter includes first and second switching elements connected in series between a power supply node and a ground node, and converts the voltage between the power supply and the load by the switching operation of the first and second switching elements. The actual duty ratio obtained as the on-period ratio of the first and second switching elements based on the voltage at the midpoint between the first and second switching elements, and the voltage command for voltage conversion Based on the value, the command duty ratio is corrected so as to maintain a constant deviation from the command duty ratio set as the command value of the ON period ratio of the first and second switching elements, and according to the corrected command duty ratio And a control device for controlling the switching operation.

  According to the voltage converter described above, since the deviation from the command duty ratio is maintained substantially constant, the actual duty ratio in the voltage converter is abrupt when the polarity of the direct current flowing through the voltage converter is reversed. Variations can be avoided. Thereby, it is possible to prevent a surge voltage from being generated on the output side of the voltage converter.

  Preferably, the voltage conversion device further includes a capacitive element that is disposed between the voltage converter and the load and connected between the power supply node and the ground node.

  According to the above-described voltage conversion device, since it is possible to reduce the capacity of a large-capacity capacitive element that has been conventionally provided on the input side of the load as a voltage surge protection means, the overall size and cost of the device can be reduced. Can be planned.

  Preferably, the control device sets the command duty ratio according to the voltage command value, and based on the voltage at the midpoint between the first and second switching elements, the actual duty ratio and the command duty are set. A comparison circuit that detects a deviation from the command duty ratio set by the ratio calculation unit, a command duty ratio correction unit that corrects the command duty ratio so as to maintain the deviation constant according to the detected deviation, and a correction And a control signal generator that generates a signal for controlling the switching operation based on the command duty ratio.

  According to the above voltage converter, the polarity of the direct current flowing through the voltage converter is reversed by detecting the deviation between the actual duty ratio and the command duty ratio and correcting the command duty ratio so as to keep it constant. Abrupt fluctuations can be avoided. Thereby, it is possible to prevent a surge voltage from being generated on the output side of the voltage converter.

  Preferably, the control device further includes a dead time adding unit that controls a switching operation so that a dead time during which both the first and second switching elements are turned off is provided for a predetermined period.

  According to the voltage converter described above, a surge voltage that can occur as a result of dead time can be prevented, so that both prevention of a short circuit of the voltage converter and suppression of the surge voltage can be realized.

  Preferably, the voltage conversion device further includes a voltage sensor that detects a voltage at an intermediate point between the first and second switching elements. The comparison circuit detects a deviation between the actual duty ratio derived from the detected voltage at the midpoint between the first and second switching elements and the command duty ratio. The command duty ratio correction unit corrects the command duty ratio so as to maintain the detected deviation at substantially zero. The control signal generation unit generates a signal for controlling the switching operation according to the corrected command duty ratio.

  According to the above-described voltage converter, the actual duty ratio is always substantially equal to the command duty ratio regardless of the direction of DC current flow, and therefore does not change suddenly when the direction of DC current flow is reversed. Thereby, it is possible to prevent a surge voltage from being generated on the output side of the voltage converter.

  Preferably, the voltage conversion device further includes a reactor disposed between the power source and an intermediate point between the first and second switching elements, and a current sensor that detects a reactor current flowing through the reactor. The control device includes a command duty ratio calculation unit that sets the command duty ratio according to the voltage command value, a current polarity determination circuit that determines the polarity of the reactor current, and a deviation that is substantially constant before and after the polarity of the reactor current is reversed. The command duty ratio correction unit that corrects the command duty ratio and a control signal generation unit that generates a signal for controlling the switching operation based on the corrected command duty ratio.

  According to the voltage converter described above, the deviation of the actual duty ratio from the command duty ratio is kept substantially constant regardless of the polarity of the reactor current. Therefore, when the polarity of the reactor current is reversed, the actual duty ratio suddenly increases. The fluctuation is avoided. Thereby, it is possible to prevent a surge voltage from being generated on the output side of the voltage converter.

  Preferably, the control device further includes a dead time addition circuit for controlling the switching operation so that a dead time during which both the first and second switching elements are turned off is provided for a predetermined period.

  According to the voltage converter described above, a surge voltage that can occur as a result of dead time can be prevented, so that both prevention of a short circuit of the voltage converter and suppression of the surge voltage can be realized.

  Preferably, when it is determined that the polarity of the reactor current is inverted, the current polarity determination unit holds the determination result for a predetermined latch period from the determined timing.

  According to the voltage converter described above, it is possible to prevent voltage conversion control from becoming unstable due to frequent switching of the polarity when the reactor current intersects the zero point.

  Preferably, the command duty ratio correction unit corrects the command duty ratio by adding a predetermined value set to approximately twice a predetermined period in response to the polarity of the reactor current being reversed from positive to negative.

  According to the voltage converter described above, the command duty ratio is corrected based on a known predetermined value in accordance with the reversal of the polarity of the reactor current, so that the actual duty ratio fluctuates rapidly when the polarity of the reactor current is reversed. Can be easily prevented.

  Preferably, the command duty ratio correction unit corrects the command duty ratio by subtracting a predetermined value set to approximately twice a predetermined period in response to the polarity of the reactor current being reversed from negative to positive.

  According to the voltage converter described above, the command duty ratio is corrected based on a known predetermined value in accordance with the reversal of the polarity of the reactor current, so that the actual duty ratio fluctuates rapidly when the polarity of the reactor current is reversed. Can be easily prevented.

  Preferably, when the polarity of the reactor current is positive, the command duty ratio correction unit corrects the command duty ratio by subtracting a predetermined value set to approximately twice the predetermined period, and the polarity of the reactor current is When negative, the command duty ratio is corrected by adding a predetermined value.

  According to the voltage converter described above, since the command duty ratio is corrected based on a known predetermined value according to the polarity of the reactor current, the actual duty ratio varies rapidly when the polarity of the reactor current is reversed. This can be easily prevented.

  Preferably, the load includes a motor and a drive circuit that drives and controls the motor. The control device includes: a first drive control unit that operates the motor at a first operating point that requires a motor drive current having a first current amplitude to generate the required torque; and a first drive control unit that generates the required torque. A second drive control means for operating at a second operating point that requires a motor drive current having a second current amplitude greater than the current amplitude; and a reactor current exceeding a predetermined set period within a predetermined current range including a zero point And switching means for controlling the drive circuit by switching from the first drive control means to the second drive control means in response to the determination that the vehicle is stagnant.

  According to the voltage conversion device, it is possible to prevent the control stability from being impaired due to the reactor current stagnating near the zero point.

  Preferably, the control device performs switching control of the first and second switching elements when it is determined that the reactor current has stagnated in a predetermined current range including a zero point over a predetermined setting period. The voltage converter is controlled by reducing the carrier frequency.

  According to the voltage conversion device, it is possible to prevent the control stability from being impaired due to the reactor current stagnating near the zero point.

  According to the present invention, since the deviation from the command duty ratio is kept substantially constant, the actual duty ratio is prevented from abruptly changing when the polarity of the direct current flowing through the voltage converter is reversed. . Thereby, it is possible to prevent a surge voltage from being generated on the output side of the voltage converter. As a result, it is possible to reduce the capacity of a large capacity capacitive element that has been conventionally provided on the input side of the load as a means for protecting against voltage surges, so that the entire apparatus can be reduced in size and cost.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same reference numerals indicate the same or corresponding parts.

[Embodiment 1]
FIG. 1 is a schematic block diagram of a motor drive device including a voltage conversion device according to Embodiment 1 of the present invention.

  Referring to FIG. 1, motor drive device 100 includes a battery B, voltage sensors 10 and 13, a current sensor 24, capacitors C <b> 1 and C <b> 2, a boost converter 12, an inverter 14, and a control device 30. .

  AC motor M1 is a drive motor for generating torque for driving drive wheels of a hybrid vehicle or an electric vehicle. Further, AC motor M1 is a motor that has a function of a generator driven by an engine and operates as an electric motor for the engine and can start the engine, for example.

  Boost converter 12 includes a reactor L1, IGBTs (Insulated Gate Bipolar Transistor) elements Q1, Q2, and diodes D1, D2.

  Reactor L1 has one end connected to the power supply line of battery B and the other end connected to the intermediate point between IGBT element Q1 and IGBT element Q2, that is, between the emitter of IGBT element Q1 and the collector of IGBT element Q2. .

  IGBT elements Q1, Q2 are connected in series between the power supply line and the earth line. The collector of IGBT element Q1 is connected to the power supply line, and the emitter of IGBT element Q2 is connected to the ground line. In addition, diodes D1 and D2 that allow current to flow from the emitter side to the collector side are arranged between the collectors and emitters of the IGBT elements Q1 and Q2, respectively.

  Inverter 14 includes U-phase arm 15, V-phase arm 16, and W-phase arm 17. U-phase arm 15, V-phase arm 16 and W-phase arm 17 are provided in parallel between the power supply line and the earth line.

  U-phase arm 15 includes IGBT elements Q3 and Q4 connected in series. V-phase arm 16 includes IGBT elements Q5 and Q6 connected in series. W-phase arm 17 includes IGBT elements Q7 and Q8 connected in series. Further, diodes D3 to D8 that flow current from the emitter side to the collector side are connected between the collectors and emitters of the IGBT elements Q3 to Q8, respectively.

  An intermediate point of each phase arm is connected to each phase end of each phase coil of AC motor M1. In other words, AC motor M1 is a three-phase permanent magnet motor, and is configured such that one end of three coils of U, V, and W phases is commonly connected to the midpoint. The other end of the U-phase coil is at the intermediate point between the IGBT elements Q3 and Q4, the other end of the V-phase coil is at the intermediate point between the IGBT elements Q5 and Q6, and the other end of the W-phase coil is at the intermediate point between the IGBT elements Q7 and Q8. Each is connected.

  Switching elements included in boost converter 12 and inverter 14 are not limited to IGBT elements Q1 to Q8, but may be constituted by other power elements such as MOSFETs.

  The battery B is a chargeable / dischargeable secondary battery, and is made of, for example, nickel metal hydride or lithium ion. Instead of the battery B, a chargeable / dischargeable battery other than the secondary battery, for example, a capacitor may be used. Voltage sensor 10 detects DC voltage Vb output from battery B, and outputs detected DC voltage Vb to control device 30.

  System relays SR1 and SR2 are turned on / off by signal SE from control device 30.

  Capacitor C1 smoothes DC voltage Vb supplied from battery B, and outputs the smoothed DC voltage Vb to boost converter 12.

  Boost converter 12 boosts DC voltage Vb supplied from battery B and supplies the boosted voltage to capacitor C2. More specifically, when boost converter 12 receives signal PWMC from control device 30, boost converter 12 boosts the DC voltage according to the period during which IGBT element Q2 is turned on by signal PWMC and supplies the boosted voltage to capacitor C2.

  Further, when boost converter 12 receives signal PWMC from control device 30, battery 12 is charged by stepping down the DC voltage supplied from inverter 14 via capacitor C2.

  Capacitor C <b> 2 smoothes the DC voltage from boost converter 12 and supplies the smoothed DC voltage to inverter 14. The voltage sensor 13 detects the voltage across the capacitor C2, that is, the output voltage VH of the boost converter 12 (corresponding to the input voltage to the inverter 14, the same applies hereinafter), and the detected output voltage Vm is controlled by the control device 30. Output to.

  When a DC voltage is supplied from the capacitor C2, the inverter 14 converts the DC voltage into an AC voltage based on the signal PWMI from the control device 30 and drives the AC motor M1. Thereby, AC motor M1 is driven to generate the required torque specified by torque command value TR.

  Further, the inverter 14 converts the AC voltage generated by the AC motor M1 into a DC voltage based on the signal PWMI from the control device 30 during regenerative braking of the hybrid vehicle or electric vehicle on which the motor drive device 100 is mounted, The DC voltage thus supplied is supplied to the boost converter 12 via the capacitor C2.

  Note that regenerative braking here refers to braking with regenerative power generation when the driver operating the hybrid vehicle or electric vehicle performs footbrake operation, or while not operating the footbrake, Including decelerating (or stopping acceleration) the vehicle while regenerating power.

  Current sensor 24 detects motor current MCRT flowing through AC motor M1 and outputs the detected motor current MCRT to control device 30.

  Control device 30 receives torque command value TR and motor rotation speed MRN from an externally provided ECU (Electric Control Unit), receives output voltage VH from voltage sensor 13, receives DC voltage Vb from voltage sensor 10, and supplies current. Motor current MCRT is received from sensor 24. Then, control device 30 performs switching control on IGBT elements Q3 to Q8 of inverter 14 when inverter 14 drives AC motor M1 based on output voltage VH, torque command value TR, and motor current MCRT by a method described later. Signal PWMI is generated, and the generated signal PWMI is output to inverter 14.

  Further, when inverter 14 drives AC motor M1, control device 30 uses IGBT element Q1 of boost converter 12 by a method described later based on DC voltage Vb, output voltage VH, torque command value TR, and motor rotation speed MRN. , Q2 is generated and output to boost converter 12 by generating a signal PWMC for switching control.

  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.

  Here, as is apparent from FIG. 1, the IGBT elements Q1 and Q2 constituting the boost converter 12 are connected in series between the power supply line and the earth line, so that the IGBT elements Q1 and Q2 are subjected to switching control. The signal PWMC for this purpose is provided with a dead time for preventing the IGBT elements Q1 and Q2 from being turned on simultaneously.

  However, by providing the dead time, in boost converter 12, in the duty ratio of IGBT elements Q1 and Q2, the command duty ratio calculated based on the optimum value of the inverter input voltage and the actual IGBT elements Q1 and Q2 There is a problem that a deviation arises from the actual duty ratio when is turned on / off. Further, since the deviation shows a different value depending on the direction of the current flowing through the reactor L1, as described below, the actual duty ratio fluctuates discontinuously when the direction of the current is reversed. There is a risk of surge voltage depending on

  FIG. 2 shows a control signal for IGBT element Q1 (upper arm) and IGBT element Q2 (lower arm) when the reactor current is flowing in the positive direction, and is driven to an intermediate point between IGBT elements Q1 and Q2 in accordance with the control signal. It is a timing chart of the voltage to be performed. The positive direction represents the direction in which a direct current flows to the power line of inverter 14 via battery B, reactor L1, and IGBT element Q1. That is, the positive direction corresponds to a discharge direction in which boost converter 12 boosts a DC voltage and supplies the boosted voltage to inverter 14.

  Referring to FIG. 2, the upper arm and the lower arm are turned on / off at a predetermined command duty ratio (for example, 0.5) in each control cycle length T. The duty ratio represents the ratio of the on-period of the upper arm in the control cycle length T.

  At this time, if the lower arm is turned on until time t2, the upper arm is turned off until time t2, and then the upper arm is turned on at time t2 and the lower arm is turned off, the upper arm and the lower arm may be turned on simultaneously. Therefore, the lower arm is turned off at time t2, and the upper arm is turned on at time t3 after a certain dead time has elapsed. Similarly, the upper arm is turned off at time t4, and the lower arm is turned on at time t5 when a certain dead time has passed. It is assumed that the dead time is set to a length (0.1 T) that is 1/10 of the control cycle length T, for example.

  Since the reactor current flows in the positive direction, the reactor current flows to the power supply line of the inverter 14 via the diode D1 connected in parallel to the IGBT element Q1 during the dead time when the IGBT elements Q1 and Q2 are turned off. The IGBT element Q1 is substantially turned on.

  As a result, the actual duty ratio becomes longer by the dead time (= 0.6) than the on-duty defined by the command duty ratio (= 0.5). The voltage at the intermediate point between IGBT elements Q1 and Q2 is driven to output voltage VH only during the on-period of the upper arm in response to the actual duty ratio.

  As described above, when the reactor current is in the positive direction, the actual duty ratio increases from the command duty ratio by the dead time. On the other hand, when the reactor current is in the negative direction, as shown in FIG. 3, the actual duty ratio decreases from the command duty ratio by the dead time.

  FIG. 3 is a timing chart of the control signals of IGBT elements Q1 and Q2 when the reactor current is flowing in the negative direction, and the voltage driven to the intermediate point (node N1) between IGBT elements Q1 and Q2 according to the control signal. It is. Note that the negative direction represents the direction in which a direct current flows to battery B via the negative electrode of battery B, the ground line, and IGBT element Q2. That is, the negative direction corresponds to the charging direction in which the boost converter 12 steps down the DC voltage supplied from the inverter 14 and supplies it to the battery B.

  Referring to FIG. 3, the control signals of IGBT elements Q1, Q2 are the same as those in FIG. That is, the IGBT element Q2 is turned off at time t2, and the IGBT element Q1 is turned on at time t3 after a certain dead time has elapsed. Similarly, the IGBT element Q1 is turned off at time t4, and then the IGBT element Q2 is turned on at time t5 when a certain dead time has elapsed.

  However, since the reactor current flows in the negative direction, the reactor current flows to the reactor L1 through the diode D2 connected in parallel to the IGBT element Q2 during the dead time when the IGBT elements Q1 and Q2 are turned off. The IGBT element Q2 is turned on.

  As a result, the actual duty ratio becomes shorter by the dead time (= 0.4) than the on-duty defined by the command duty ratio (= 0.5). The voltage at the intermediate point between IGBT elements Q1 and Q2 is driven to output voltage VH only during the ON period of IGBT element Q1 in response to the actual duty ratio.

  As is apparent from FIGS. 2 and 3, the deviation between the command duty ratio and the actual duty ratio differs between when the reactor current flows in the positive direction and when the reactor current flows in the negative direction. Therefore, at the timing when the direction of the reactor current is switched from positive to negative, or from negative to positive, the actual duty ratio changes rapidly. As a result, a surge voltage shown in FIG. 4 is generated in the output voltage of boost converter 12. This surge voltage may damage a load (such as an inverter) connected to the output side of the boost converter 12.

  In order to protect the load from such a surge voltage, in a conventional motor drive device, a smoothing capacitor C2 connected between the boost converter 12 and the inverter 14 is large enough to absorb this surge voltage. Measures comprising capacity are taken. However, increasing the capacity of the capacitor C2 leads to an increase in size and cost of the motor drive device 100.

  Therefore, in motor drive device 100 according to the embodiment of the present invention, voltage conversion control of boost converter 12 is executed according to a correction of a command duty ratio generated based on a voltage command value. The configuration is as follows. Hereinafter, voltage conversion control of boost converter 12 will be described in detail.

  Referring to FIG. 1 again, motor drive device 100 further includes a comparison circuit 40 and a voltage sensor 11.

  Voltage sensor 11 detects a voltage V0 at node N1, which is an intermediate point between IGBT elements Q1 and Q2, and outputs the detected voltage V0 to comparison circuit 40. Comparison circuit 40 receives command duty ratio DR_com from control device 30 and receives voltage V0 at node N1 from voltage sensor 11.

Here, the command duty ratio DR_com refers to a DC voltage Vb that is an input voltage to the boost converter 12 and a target value of the output voltage of the boost converter 12 (hereinafter also referred to as a voltage command value) in the voltage conversion control of the boost converter 12. ) Is set based on the voltage conversion ratio. The command duty ratio DR_com indicates the ratio of the ON period of the IGBT element Q1 (upper arm) in one control cycle. For example, when the ON period of the IGBT element Q1 is Ton and the off period is Toff, the command duty ratio DR_com Is represented by Formula (1).
DR_com = Ton / (Ton + Toff) (1)
The comparison circuit 40 calculates the actual duty ratio DR_r in the boost converter 12 based on the voltage V0 of the node N1 from the voltage sensor 11. The actual duty ratio DR_r is a voltage ratio of the voltage V0 of the node N1 viewed from the output voltage VH of the boost converter 12. The actual duty ratio DR_r is calculated as a ratio of a period during which the voltage V0 in one control cycle is equal to the output voltage VH. For example the period in which the voltage V0 is an output voltage VH _{T VH,} when the period in which the voltage V0 becomes the ground voltage and _{T VL,} the actual duty ratio DR_r is represented by formula (2).
DR_r = T _VH / (T _VH + T _VL ) (2)
The comparison circuit 40 compares the magnitude relationship between the command duty ratio DR_com from the control device 30 and the actual duty ratio DR_r, and outputs a signal DET indicating the comparison result to the control device 30. Control device 30 corrects command duty ratio DR_com by a method to be described later according to signal DET from comparison circuit 40, and turns on / off IGBT elements Q1 and Q2 based on the corrected command duty ratio DR_com. The signal PWMC is generated and output to the boost converter 12.

FIG. 5 is a functional block diagram of the control device 30 in FIG.
Referring to FIG. 5, control device 30 includes inverter control means 301 and converter control means 302.

  Inverter control means 301 generates signal PWMI based on torque command value TR, motor current MCRT, and voltage VH, and outputs the signal to IGBT elements Q3-Q8 of inverter 14.

  More specifically, inverter control means 301 calculates the voltage to be applied to each phase of AC motor M1 based on torque command value TR, motor current MCRT and voltage VH, and based on the calculated voltage, A signal PWMI for turning on / off the IGBT elements Q3 to Q8 is generated. Then, inverter control means 301 outputs the generated signal PWMI to each IGBT element Q3 to Q8 of inverter 14.

  Thereby, each IGBT element Q3-Q8 of inverter 14 is switching-controlled, and controls the electric current which flows through each phase of AC motor M1 so that AC motor M1 may output the commanded torque. In this way, the motor drive current is controlled, and the motor torque corresponding to the torque command value TR is output.

  Converter control means 302 generates a signal PWMC based on torque command value TR, motor rotational speed MRN, voltage VH, DC voltage Vb and signal DET, and outputs the signal PWMC to IGBT elements Q1, Q2 of boost converter 12. To do.

FIG. 6 is a functional block diagram of converter control means 302 shown in FIG.
Referring to FIG. 6, converter control means 302 includes a voltage command calculation unit 50, a converter duty ratio calculation unit 52, a converter duty ratio correction unit 54, a converter PWM signal conversion unit 56, and a dead time addition. Part 58.

  Voltage command calculation unit 50 calculates an optimum value (target value) of the inverter input voltage, that is, voltage command value Vdc_com of boost converter 12 based on torque command value TR and motor rotation speed MRN from the external ECU, and calculates the calculation. The commanded voltage command value Vdc_com is output to the converter duty-ratio calculation unit 52.

Converter duty-ratio calculation unit 52 calculates a command duty ratio DR_com of boost converter 12 based on voltage command value Vdc_com from voltage command calculation unit 50 and DC voltage Vb from voltage sensor 10 using equation (3). To do.
DR_com = Vb / Vdc_com (3)
Then, converter duty-ratio calculation unit 52 outputs the calculated command duty ratio DR_com to converter duty-ratio correction unit 54 and comparison circuit 40.

  Comparing circuit 40 receives command duty ratio DR_com from converter duty ratio calculation unit 52, and receives voltage V0 of node N1, which is an intermediate point between IGBT elements Q1 and Q2, from voltage sensor 11.

  The comparison circuit 40 calculates the actual duty ratio DR_r by the above equation (2) based on the voltage V0 of the node N1. Then, the comparison circuit 40 compares the calculated actual duty ratio DR_r with the command duty ratio DR_com, generates a signal DET indicating the comparison result, and outputs the signal DET to the converter duty ratio correction unit 54.

  A specific method for generating the signal DET in the comparison circuit 40 will be described below. As a method for generating the signal DET, any one of the methods shown in FIGS. 7 to 9 can be applied. The generated signal DET is converted into a digital signal by an A / D converter (not shown) and then input to the converter duty ratio correction unit 54.

FIG. 7 is a diagram illustrating an example of a method for generating the signal DET in the comparison circuit 40 of FIG.
Referring to FIG. 7, in a certain control cycle from time t1 to time t6 (control cycle length is T), command duty ratio DR_com is set to 0.5, whereas actual duty ratio DR_r Consider the case where becomes 0.6.

  Note that the case where the actual duty ratio DR_r is larger than the command duty ratio DR_com is, as described in FIG. 2, when the polarity of the reactor current IL flowing through the reactor L1 is positive, that is, the boost converter 12 is connected to the DC voltage Vb. Occurs when the voltage is boosted and supplied to the capacitor C2. The deviation ΔDR between the command duty ratio DR_com and the actual duty ratio DR_r corresponds to a dead time ratio (for example, 0.1 T) set in advance with respect to the control cycle length T.

In this case, the comparison circuit 40 calculates a deviation ΔDR between the command duty ratio DR_com and the actual duty ratio DR_r according to the equation (4), and supplies the calculated deviation ΔDR = −0.1 to the converter duty ratio correction unit 54. Output.
ΔDR = DR_com−DR_r (4)
Further, in another control cycle from the time t6 to the time t7, the comparison circuit 40 determines that the equation (in the case where the actual duty ratio DR_r is 0.4 while the command duty ratio DR_com is 0.5) The deviation ΔDR = 0.1 calculated in step 4) is output to the converter duty ratio correction unit 54.

  Note that the case where the actual duty ratio DR_r is smaller than the command duty ratio DR_com is, as described in FIG. 3, when the polarity of the reactor current IL is negative, that is, the boost converter 12 is connected to the inverter via the capacitor C2. This occurs when the DC voltage supplied from 14 is stepped down and supplied to battery B.

  That is, in the example of FIG. 7, the converter duty-ratio correction unit 54 receives the deviation ΔDR between the command duty ratio DR_com and the actual duty ratio DR_r for each control cycle.

FIG. 8 is a diagram illustrating another example of a method for generating the signal DET in the comparison circuit 40 of FIG.
In the example of FIG. 8, when the comparison circuit 40 detects the deviation ΔDR between the command duty ratio DR_com and the actual duty ratio DR_r, one of two preset potentials is selected according to the polarity of the detected deviation ΔDR. A signal DET1 consisting of is generated and output.

  Specifically, in a certain control cycle from time t1 to time t6, when the command duty ratio DR_com is smaller than the actual duty ratio DR_r, that is, the command duty ratio DR_com and the actual duty ratio DR_r calculated by Expression (4). The comparison circuit 40 generates and outputs a signal DET1 having a predetermined potential Vy.

  On the other hand, when the command duty ratio DR_com is larger than the actual duty ratio DR_r in another control cycle from time t6 to time t7, that is, when the deviation ΔDR between the command duty DR_com and the actual duty ratio DR_r is positive, the comparison is performed. The circuit 40 generates and outputs a signal DET1 having a predetermined potential Vx (Vx ≠ Vy).

  Therefore, in the example of FIG. 8, the converter duty-ratio correction unit 54 receives the polarity of the deviation ΔDR between the command duty DR_com and the actual duty ratio DR_r for each control cycle.

FIG. 9 is a diagram illustrating another example of the method for generating the signal DET in the comparison circuit 40 of FIG.
In the example of FIG. 9, the comparison circuit 40 is a signal having a predetermined potential in response to the polarity of the deviation ΔDR between the command duty ratio DR_com and the actual duty ratio DR_r calculated from the equation (4) being inverted. DET2 is generated and output.

  Specifically, the deviation ΔDR between the command duty ratio DR_com and the actual duty ratio DR_r is continuously negative in the control cycle from the time t6 to the time t7 in the figure and the control cycle before this, It is assumed that the deviation ΔDR in the control cycle from time t7 to time t8 is positively inverted. At this time, the comparison circuit 40 generates and outputs a signal DET2 having a predetermined potential Vx at the timing of time t8. The signal DET2 is held at a predetermined potential Vx until it is next determined that the polarity of the deviation ΔDR is inverted from negative to positive.

  The comparison circuit 40 then changes the polarity of the detected deviation ΔDR from positive to negative in a certain control cycle from time t8 to time t9 and another control cycle from time t9 to time t10. When it is determined that the signal has been inverted, a signal DET2 having a predetermined potential Vy (Vy ≠ Vx) is generated and output at the timing of time t10.

  That is, in the example of FIG. 9, every time the polarity of the deviation ΔDR between the command duty DR_com and the actual duty ratio DR_r is reversed, the converter duty ratio correction unit 54 reverses the polarity (from positive to negative or from negative to negative). Positive) is input.

  Referring to FIG. 6 again, when converter duty-ratio correction unit 54 receives signal DET (or DET1 / DET2) generated by one of the three methods described above, signal DET (or DET1) is received. The command duty ratio DR_com input from the converter duty ratio calculation unit 52 is corrected based on the content instructed to / DET2).

  Specifically, when the signal DET indicating the deviation ΔDR between the command duty ratio DR_com and the actual duty ratio DR_r is received according to the method described in FIG. 7, the converter duty ratio correction unit 54 is indicated by the signal DET. The command duty ratio DR_com is offset by an amount corresponding to the reverse polarity of the deviation ΔDR.

  That is, in FIG. 7, when the command duty ratio DR_com is 0.5 and the deviation ΔDR is −0.1, the command duty ratio DR_com is offset by +0.1 and corrected to 0.6. On the other hand, when the command duty ratio DR_com is 0.5 and the deviation ΔDR is +0.1, the command duty ratio DR_com is offset by −0.1 and corrected to 0.4.

  The corrected command duty ratio DR_com is output to the converter PWM signal conversion unit 56 as the corrected command duty ratio DR_0.

  On the other hand, when the signal DET1 or DET2 instructing the polarity of the deviation ΔDR or the polarity inversion is received according to the method described in FIGS. 8 and 9, the converter duty-ratio correcting unit 54 is set in advance based on the dead time. The command duty ratio DR_com is offset by the predetermined deviation ΔDR_std.

  Specifically, referring to FIG. 10, when receiving signal DET1 indicating the polarity of deviation ΔDR between command duty ratio DR_com and actual duty ratio DR_r, converter duty ratio correction unit 54 determines that signal DET1 is a predetermined value. If the potential is Vx, it is determined that the deviation ΔDR is positive. Then, converter duty-ratio correction unit 54 offsets command duty ratio DR_com in the positive direction by a predetermined deviation ΔDR_std. The corrected command duty ratio (= DR_com + ΔDR_std) is output to the converter PWM signal conversion unit 56 as the corrected command duty ratio DR_0.

  On the other hand, converter duty-ratio correction unit 54 determines that deviation ΔDR is negative if signal DET1 is a predetermined potential Vy, and offsets command duty ratio DR_com in the negative direction by predetermined deviation ΔDR_std. In this case, the correction command duty ratio DR_0 is (DR_com−ΔDR_std).

  Further, when the signal DET2 indicating the polarity inversion of the deviation ΔDR between the command duty ratio DR_com and the actual duty ratio DR_r is received, the converter duty ratio correction unit 54, if the potential of the signal DET2 is the predetermined potential Vx, It is determined that the deviation ΔDR is reversed from negative to positive. Then, converter duty-ratio correction unit 54 offsets command duty ratio DR_com in the positive direction by a predetermined deviation ΔDR_std.

  On the other hand, if the potential of signal DET2 is predetermined potential Vy, converter duty-ratio correction unit 54 determines that deviation ΔDR is inverted from positive to negative, and sets command duty ratio DR_com in the negative direction by predetermined deviation ΔDR_std. Offset. The command duty ratio DR_com offset in the positive direction or the negative direction is output to the converter PWM signal converter 56 as the corrected command duty ratio DR_0.

  Converter PWM signal conversion unit 56 generates a signal PWMC for turning on / off IGBT elements Q1, Q2 of boost converter 12 based on correction command duty ratio DR_0 from converter duty ratio correction unit 54 to dead. The data is output to the time adding unit 58.

  When receiving a signal for turning on / off IGBT elements Q1, Q2, dead time adding unit 58 adds a preset dead time to this signal. The signal PWMC to which the dead time is added is output to the boost converter 12.

  Thus, for example, when the command duty ratio DR_com is 0.5 and the correction command duty ratio DR_0 is 0.4, the actual duty ratio DR_r obtained by the voltage conversion control according to the correction command duty ratio DR_0 is The correction command duty ratio DR_0 is increased by 0.1 to 0.5. Since this is equal to the original command duty ratio DR_com, it can be seen that the deviation ΔDR between them is suppressed to substantially zero.

  On the other hand, when the command duty ratio DR_com is 0.5 and the correction command duty ratio DR_0 is 0.6, the actual duty ratio DR_r obtained by the voltage conversion control according to the correction command duty ratio DR_0 is the correction command duty ratio. The ratio DR_0 is decreased by 0.1 to 0.5. Also in this case, the actual duty ratio DR_r is equal to the original command duty ratio DR_com, and the deviation ΔDR is suppressed to substantially zero.

  In the next control cycle, the deviation ΔDR between the original command duty DR_com and the actual duty ratio DR_r adjusted by the correction command duty ratio DR_0 is detected again. The command duty ratio DR_com is corrected according to the signal DET (or DET1 / DET2) generated based on the detected deviation ΔDR, and the voltage conversion control is continuously executed according to the corrected command duty ratio DR_.

  In this way, by correcting the command duty ratio DR_com in accordance with the deviation between the command duty ratio DR_com and the actual duty ratio DR_r for each control period, the actual duty ratio DR_r is less affected by the dead time, and the command duty ratio is reduced. Deviation from DR is maintained at approximately zero. Therefore, in the conventional voltage conversion control, the discontinuous change in the actual duty ratio DR_r that appears when the polarity of the reactor current IL is reversed, that is, when the discharge direction and the charge direction in the boost converter 12 are switched is suppressed. can do. As a result, it is possible to prevent a surge voltage from occurring at such timing.

  Further, since it is not necessary to increase the capacity of the capacitor C2 for absorbing the surge voltage, the capacitor C2 can be configured with a small size, and the apparatus can be reduced in size and cost.

  FIG. 11 is a flowchart for explaining the voltage conversion control operation in converter control means 302.

  Referring to FIG. 11, when a series of operations for voltage conversion is started, converter duty ratio calculation unit 52 calculates command duty ratio DR_com based on voltage command value Vdc_com from voltage command calculation unit 50. (Step S01).

  When the comparison circuit 40 receives the command duty ratio DR_com from the converter duty ratio calculation unit 52 and receives the voltage V0 at the node N1 from the voltage sensor 11, it calculates the actual duty ratio DR_r based on the voltage V0 (step S02). Then, comparison circuit 40 generates signal DET (or DET1 / DET2) based on deviation ΔDR between command duty ratio DR_com and actual duty ratio DR_r, and outputs the signal to converter duty ratio correction unit 54 (step S03).

  Converter duty-ratio correction unit 54 corrects command duty ratio DR_com based on signal DET (or DET1 / DET2) from comparison circuit 40, and generates corrected command duty ratio DR_0 (step S04).

  Converter PWM signal converter 56 generates signal PWMC in accordance with correction command duty ratio DR_0. Dead time adding unit 58 adds a predetermined dead time to the generated signal PWMC and outputs it to IGBT elements Q1, Q2 of boost converter 12. Thereby, IGBT elements Q1 and Q2 are subjected to switching control with a duty ratio substantially equal to the command duty ratio DR_com, with the influence of the dead time removed (step S05). Therefore, no surge voltage is generated even when the polarity of the reactor current IL is reversed, so that the circuit element can be protected with a small and inexpensive device configuration.

[Example of change]
The voltage conversion control described in the first embodiment of the present invention is actually performed by each step of the flowchart shown in FIG. 11 in the CPU configured to include the control device 30 (however, step S03 by the comparison circuit 40). Is removed from the ROM, and the read program is executed.

  Note that steps S03 and S04 in the flowchart shown in FIG. 11 may be executed by a comparison circuit 40 and a correction circuit 60 externally attached to the control device 30, as shown in FIG.

  FIG. 12 is a functional block diagram for explaining a modified example of converter control means 302 in FIG.

  Referring to FIG. 12, converter control means 302 </ b> C includes a voltage command calculating unit 50, a converter duty ratio calculating unit 52, and a converter PWM signal converting unit 56. The converter control unit 302C is obtained by changing the converter duty ratio correction unit 54 in the converter control unit 302 of FIG. 6 to a correction circuit 60 provided outside the control device 30.

  The correction circuit 60 has a function equivalent to that of the converter duty ratio correction unit 54 of FIG. That is, when the correction circuit 60 receives the command duty ratio DR_com and the signal DET (or DET1 / DET2) from the comparison circuit 40, the correction circuit 60 sets the correction command duty ratio DR_0 based on the polarity of the deviation ΔDR or the deviation ΔDR indicated by the signal DET. It is generated and output to the converter PWM signal converter 56.

  As a merit of configuring the correction circuit 60 by hardware as described above, it is possible to cope with various boost converters 12 having different dead times by being integrated with the comparison circuit 40 and externally attached to the control device 30. The point that property is improved is mentioned.

  As described above, according to the first embodiment of the present invention, since the deviation between the command duty ratio and the actual duty ratio is always kept substantially zero, the influence of the dead time when the polarity of the reactor current is reversed. In response, the actual duty ratio can be suppressed from becoming discontinuous. As a result, it is possible to prevent a surge voltage from occurring at such timing.

  Furthermore, since it is not necessary to increase the capacity of the capacitor C2 for absorbing the surge voltage, the capacitor C2 can be configured with a small size, and the apparatus can be reduced in size and cost.

[Embodiment 2]
FIG. 13 is a schematic block diagram of a motor drive device including a voltage conversion device according to Embodiment 2 of the present invention.

  Referring to FIG. 13, motor drive device 100A includes battery B, voltage sensors 10 and 13, current sensors 24 and 26, capacitors C1 and C2, boost converter 12, inverter 14, and control device 30A. And a determination circuit 70.

  The motor drive device 100A in FIG. 10 is obtained by changing the voltage sensor 11, the comparison circuit 40, and the control device 30 to the current sensor 26, the determination circuit 70, and the control device 30A, respectively, with respect to the motor drive device 100 in FIG. is there. Therefore, a detailed description of portions common to FIG. 1 is omitted.

  Current sensor 26 detects a reactor current IL that flows through reactor L 1, and outputs the detected reactor current IL to determination circuit 70.

  Determination circuit 70 determines the polarity of reactor current IL, generates a signal IPD indicating the determined polarity, and outputs the signal IPD to control device 30A. Specifically, when reactor current IL flows in the positive direction, determination circuit 70 determines that the polarity of reactor current IL is positive. On the other hand, when reactor current IL flows in the negative direction, determination circuit 70 determines that the polarity of reactor current IL is negative.

  As described above, the positive direction represents a direction in which boost converter 12 boosts DC voltage Vb and supplies it to capacitor C2. In the positive direction, reactor current IL flows through the power supply line of battery B to reactor L1 to IGBT element Q1 to inverter 14 as a current path. Further, the negative direction represents a direction in which the boost converter 12 steps down the DC voltage supplied from the inverter 14 via the capacitor C2 and supplies it to the battery B. In the negative direction, reactor current IL flows in the current path from negative electrode of battery B to ground line to IGBT element Q2 to reactor L1 to power supply line to battery B.

  Control device 30A receives torque command value TR and motor rotational speed MRN from an external ECU, receives output voltage VH from voltage sensor 13, receives DC voltage Vb from voltage sensor 10, receives motor current MCRT from current sensor 24, Signal IPD is received from determination circuit 70. Then, control device 30A provides a signal PWMI for switching control of IGBT elements Q3 to Q8 of inverter 14 when inverter 14 drives AC motor M1 based on output voltage VH, torque command value TR, and motor current MCRT. And the generated signal PWMI is output to the inverter 14.

  In addition, when inverter 14 drives AC motor M1, control device 30A provides a method for boost converter 12 using a method described later based on DC voltage Vb, output voltage VH, torque command value TR, motor rotational speed MRN, and signal IPD. A signal PWMC for switching control of IGBT elements Q1, Q2 is generated and output to boost converter 12.

  Further, control device 30A generates signal SE for turning on / off system relays SR1, SR2 and outputs the signal SE to system relays SR1, SR2.

FIG. 14 is a functional block diagram of control device 30A in FIG.
Referring to FIG. 14, control device 30A includes inverter control means 301A and converter control means 302A.

  Inverter control means 301A includes a motor control phase voltage calculator 80A and an inverter PWM signal converter 82A.

  Motor control phase voltage calculation unit 80A receives output voltage VH of boost converter 12 from voltage sensor 13, receives motor current MCRT from current sensor 24, and receives torque command value TR from an external ECU. Based on these input signals, motor control phase voltage calculation unit 80A calculates a voltage to be applied to each phase coil of AC motor M1, and outputs the calculated result to inverter PWM signal conversion unit 82A. To do.

  Based on the calculation result received from motor control phase voltage calculation unit 80A, inverter PWM signal conversion unit 82A generates a signal PWMI for turning on / off each IGBT element Q3-Q8 of inverter 14, and the generated signal PWMI is output to IGBT elements Q3 to Q8 of inverter 14.

  Converter control means 302A includes a voltage command calculation unit 50, a converter duty ratio calculation unit 52, a converter duty ratio correction unit 54A, a converter PWM signal conversion unit 56, and a dead time addition unit 58. The converter control unit 302A is obtained by changing the converter duty ratio correction unit 54 in the converter control unit 302 of FIG. 3 to a converter duty ratio correction unit 54A.

  Converter duty-ratio correction unit 54A receives command duty ratio DR_com from converter duty-ratio calculation unit 52, and receives signal IPD indicating the polarity of reactor current IL from determination circuit 70. Then, converter duty-ratio correction unit 54A corrects command duty ratio DR_com based on the polarity of reactor current IL, and outputs the corrected command duty ratio DR_com to converter PWM signal conversion unit 56 as corrected command duty ratio DR_0. To do.

  Thus, converter control means 302A according to the present embodiment has a characteristic configuration in which command duty ratio DR_com is corrected based on the polarity of reactor current IL. Hereinafter, the voltage conversion control by the converter control unit 302A will be described in detail.

  First, a method for determining the polarity of the reactor current IL executed by the determination circuit 70 will be described.

  FIG. 15 is a timing chart for explaining reactor current IL and output signal IPD of determination circuit 70 based thereon.

  Referring to FIG. 15, reactor current IL gradually decreases while repeating increase and decrease in response to on / off of IGBT elements Q1 and Q2. In the period up to time t11, reactor current IL is always positive in one switching cycle.

  Then, the reactor current IL crosses the zero point for a predetermined period from the time t11, that is, a state where the maximum value of the reactor current IL is positive and the minimum value is negative in one switching cycle. Thereafter, the reactor current IL shows a state that is always negative in one cycle of switching.

  The polarity of the reactor current IL based on such a state is positive until time t11 as shown in the middle part of the figure, and is positive as the reactor current IL crosses the zero point in a predetermined period from time t11. A waveform that frequently repeats negative and negative. And it becomes negative after a predetermined period.

  Determination circuit 70 generates and outputs signal IPD based on the polarity of reactor current IL. Specifically, L (logic low) level signal IPD is output in response to reactor current IL being in a positive state. Then, in response to the polarity being switched from positive to negative at time t11, it is determined that reactor current IL is in a negative state, and H (logic high) level signal IPD is output.

  When signal IPD rises from L level to H level in response to the polarity of reactor current IL being inverted from positive to negative at time t11, the logic level is maintained for a predetermined latch period dt_rat. Then, at time t12 when the predetermined latch period dt_rat has elapsed, the signal IPD continues to show the H level in response to the reactor current IL being in a negative state.

  The reason why the predetermined latch period dt_rat is provided for the output of the signal IPD is that the polarity of the signal IPD is changed accordingly during the predetermined period in which the reactor current IL crosses the zero point. This is to prevent the voltage conversion control executed based on the signal IPD from becoming unstable due to frequent switching. Therefore, the predetermined latch period dt_rat is set so as to include a predetermined period in which reactor current IL crosses the zero point.

  Next, converter duty-ratio correction unit 54A receives signal IPD from determination circuit 70 and corrects command duty ratio DR_com based on the logic level of signal IPD.

  Specifically, converter duty-ratio correction unit 54A corrects command duty ratio DR_com in response to the logic level of signal IPD rising from “L” to “H”. For example, as shown in FIG. 15, when signal IPD rises from L level to H level at time t12, converter duty-ratio correction unit 54A adds a predetermined deviation set in advance to command duty ratio DR_com.

  The predetermined deviation at this time includes a deviation ΔDR between the command duty ratio DR_com and the actual duty ratio DR_r that occurs when the polarity of the reactor current IL is positive, and a command duty ratio DR_com that occurs when the polarity of the reactor current IL is negative. It is set to the sum of absolute values of deviation ΔDR from actual duty ratio DR_r.

  Therefore, as shown in FIG. 2, when the command duty ratio DR_com is 0.5 and the dead time is 0.1, the actual duty ratio DR_r is 0.6 when the reactor current IL is positive, Since the actual duty ratio DR_r is 0.4 when the reactor current IL is negative, the sum of the absolute values of the deviations is 0.2. Correction when reactor current IL is negative by adding 0.2, which is the sum of absolute values of this deviation, to command duty ratio DR_com in response to the polarity of reactor current IL reversing from positive to negative The command duty ratio DR_0 is set to 0.5 + 0.2 = 0.7. As a result, the actual duty ratio DR_r when the reactor current IL is negative is obtained as a value 0.6 (= 0.7−0.1) that is reduced by the deviation ΔDR with respect to the correction command duty ratio DR_0. In other words, the actual duty ratio DR_r is kept constant (= 0.6) before and after the polarity inversion of the reactor current IL. As a result, since the actual duty ratio DR_r does not become discontinuous when the polarity of the reactor current IL is reversed, generation of a surge voltage can be prevented.

  In the embodiment of the present invention, the actual duty ratio DR_r always has a constant deviation (for example, +0.1) with respect to the command duty ratio DR_com. This deviation is common in motor drive control. Since it can be absorbed by the adjustment of the PI gain in the PI control executed at the same time, it can be determined that no particular problem occurs.

  In the embodiment of the present invention, the sum of the absolute values of deviations in each polarity is added to the command duty ratio DR_com in response to the polarity of the reactor current IL being inverted from positive to negative. In addition to the configuration, the same effect can be obtained by a configuration in which the sum of the absolute values of the deviations is subtracted from the command duty ratio DR_com in response to the polarity of the reactor current IL being inverted from negative to positive. In this case, the actual duty ratio DR_r always has a constant deviation (for example, −0.1) with respect to the command duty ratio DR_com.

  Furthermore, a configuration may be adopted in which the deviation is subtracted from the command duty ratio DR_com when the polarity of the reactor current IL is positive, and the deviation is added to the command duty ratio DR_com when the reactor current IL is negative. According to this, the actual duty ratio DR_r is always substantially equal to the command duty DR_com.

  FIG. 16 is a flowchart for explaining the voltage conversion control operation in converter control means 302A.

  Referring to FIG. 16, when a series of operations for voltage conversion is started, converter duty ratio calculation unit 52 calculates command duty ratio DR_com based on voltage command value Vdc_com from voltage command calculation unit 50. (Step S11).

  When receiving the reactor current IL from the current sensor 26, the determination circuit 70 determines its polarity and generates a signal IPD indicating the determination result (step S12). Determination circuit 70 outputs generated signal IPD to converter duty ratio correction unit 54A.

  The converter duty-ratio correction unit 54A adds the predetermined deviation described above to the command duty ratio DR_com in response to the signal IPD from the determination circuit 70 rising from the L level to the H level, thereby correcting the corrected command duty ratio DR_0. Is generated (step S13).

  Converter PWM signal converter 56 generates signal PWMC in accordance with correction command duty ratio DR_0. Dead time adding unit 58 adds a predetermined dead time to the generated signal PWMC and outputs it to IGBT elements Q1, Q2 of boost converter 12. As a result, the IGBT elements Q1 and Q2 are subjected to switching control with the duty ratio maintained at a substantially constant value, with the influence of the dead time removed (step S14). Therefore, no surge voltage is generated when the polarity of the reactor current IL is reversed, so that the capacitor C2 can be reduced in size. As a result, the circuit element can be protected with a small and inexpensive apparatus configuration.

  Here, in the reactor current IL flowing through the reactor L1, as shown in the upper part of FIG. 17, in addition to the waveform in which the polarity is inverted through the state intersecting with the zero point for a predetermined period as shown in FIG. There may be a waveform stagnating near the zero point over a period of time. When such a current waveform is input to the determination circuit 70, the reactor current IL still crosses the zero point even when the predetermined latch period dt_rat has elapsed, so that the signal IPD generated according to the switching of the polarity The logic level is frequently switched. Therefore, the possibility that the voltage conversion control executed based on the signal IPD becomes unstable is further increased.

  Therefore, the motor drive device 100A according to the embodiment of the present invention is configured to intentionally increase energy loss while keeping the output torque of the AC motor M1 constant in response to the reactor current IL stagnating near the zero point. To do. According to this, the reactor current IL increases by the amount of energy loss, so that the reactor current IL can escape from the stagnation near the zero point.

  FIG. 18 is a diagram for explaining control of AC motor M1 according to the second embodiment of the present invention.

  Referring to FIG. 18, the relationship between torque of AC motor M1 and current phase θ of the current flowing through the motor is represented by curves k1 and k2. The curves k1 and k2 have different motor current amplitudes, and the curve k2 has a relatively larger amplitude than the curve k1 (assumed that the amplitude is I1) (amplitude I2 (I2> I1)).

  In each of the curves k1 and k2, the torque changes so as to become maximum with respect to a certain current phase θopt. That is, the maximum torque can be obtained by passing a current through AC motor M1 at current phase θopt. Hereinafter, the control mode in which the current phase θ is changed so as to obtain the maximum torque is also referred to as a maximum torque control mode. Further, the operating point A of AC motor M1 when current phase θ = θopt is also referred to as an optimal operating point.

  On the other hand, when the current phase θ is shifted from θopt that gives the optimum operating point A in each of the curves k1 and k2, the torque gradually decreases. That is, the motor efficiency is lowered by shifting the current phase θ from θopt.

  In addition to the above-described maximum torque control mode, the motor drive device according to the embodiment of the present invention further includes a control mode for controlling AC motor M1 so as to increase energy loss while keeping the output torque constant. It is characterized by. Hereinafter, the control mode in which the torque is constant and the energy loss is increased is also referred to as a loss increase control mode.

  Specifically, in the loss increase control mode, as shown in FIG. 18, the current amplitude is set to a current amplitude I2 larger than the current amplitude I1 at the optimum operating point A, and the current phase is set to the optimum operating point A. AC motor M1 is driven at operating point B with current phase θi shifted from current phase θopt. As apparent from FIG. 15, at this operating point B, AC motor M1 outputs a torque equivalent to the output torque at optimal operating point A. Hereinafter, this operating point B is also referred to as a motor loss increasing point. The current phase θi at the motor loss increase point B may be either a high phase or a low phase with respect to the current phase θopt.

  When it is determined that the reactor current IL is stagnating near the zero point, the inverter control means 301A of the control device 30A switches the control mode from the maximum torque control mode to the loss increase control mode. As a result, in AC motor M1, the current amplitude of the motor current increases from amplitude I1 to amplitude I2. When the AC motor M1 is driven at the loss increase point B, the copper loss generated in the three-phase coil increases due to the increase in the current amplitude of the motor current.

  Along with this, in the battery B, electric power corresponding to copper loss is discharged, and the direct current flowing through the battery B increases in accordance with the electric power. At this time, the reactor current IL also increases as the direct current increases, so that the reactor current IL can escape from the stagnation near the zero point as shown in the lower part of FIG.

  FIG. 19 is a flowchart for explaining the voltage conversion control operation in converter control means 302A.

  Referring to FIG. 19, when a series of operations for voltage conversion is started, converter duty-ratio calculation unit 52 calculates command duty ratio DR_com based on voltage command value Vdc_com from voltage command calculation unit 50. (Step S11).

  When receiving the reactor current IL from the current sensor 26, the determination circuit 70 determines whether or not the reactor current IL is included in a predetermined current range ΔIL_std set near the zero point (step S111). If it is determined in step S111 that the reactor current IL is included in the predetermined current range ΔIL_std, the determination circuit 70 further determines whether or not a predetermined period T_std set in advance has elapsed (step S112).

  When it is determined in step S112 that the predetermined period T_std has elapsed, the determination circuit 70 determines that the reactor current IL is stagnating near the zero point, and outputs a signal ICD indicating the determination result of the inverter control means 301A. Output to motor control phase voltage calculation unit 80A.

  When receiving the signal ICD, the motor control phase voltage calculation unit 80A switches the control mode of the AC motor M1 from the maximum torque control mode to the loss increase control mode. The switching of the control mode in the motor control phase voltage calculation unit 80A is actually performed by using a current command set based on the optimum operating point A in FIG. 15 from the current amplitude I1 when the current amplitude is the optimum operating point A. Is changed to a current command set based on the loss increase point B with the current phase θi shifted from the current phase θopt of the optimum operating point A (step S113). ).

  By switching the control mode of AC motor M1, reactor current IL increases to escape from the stagnation near the zero point. The determination circuit 70 determines the polarity of the reactor current IL and generates a signal IPD indicating the determination result (step S12). Determination circuit 70 outputs generated signal IPD to converter duty ratio correction unit 54A.

  If it is determined in steps S111 and S112 that reactor current IL is not stagnating near the zero point, the control mode of AC motor M1 is maintained in the normal maximum torque control mode. In step S12, the determination circuit 70 generates a signal IPD based on the polarity of the reactor current IL.

  The converter duty-ratio correction unit 54A adds the predetermined deviation described above to the command duty ratio DR_com in response to the signal IPD from the determination circuit 70 rising from the L level to the H level, thereby correcting the corrected command duty ratio DR_0. Is generated (step S13).

  Converter PWM signal conversion unit 56 generates signal PWMC in accordance with correction command duty ratio DR_0 and outputs the signal to IGBT elements Q1, Q2 of boost converter 12. As a result, the IGBT elements Q1 and Q2 are subjected to switching control with the duty ratio maintained at a substantially constant value, with the influence of the dead time removed (step S14).

[Example of change]
In this modified example, another method for causing the reactor current IL to escape from the stagnation near the zero point will be described.

  FIG. 20 is a functional block diagram of converter control means 302B in a modification of the second embodiment of the present invention.

  Referring to FIG. 20, converter control means 302B includes voltage command calculation unit 50, converter duty ratio calculation unit 52, converter duty ratio correction unit 54B, converter PWM signal conversion unit 56B, and dead time addition. Part 58.

  Converter control means 302B is obtained by changing converter duty ratio correction unit 54 and converter PWM signal conversion unit 56 of converter control means 302 of FIG. 6 to converter duty ratio correction unit 54B and converter PWM signal conversion unit 56B. It is.

  When receiving the reactor current IL from the current sensor 26, the determination circuit 70 determines the polarity of the reactor current IL according to the method described in FIG. 15, and generates a signal IPD indicating the determination result. Then, determination circuit 70 outputs generated signal IPD to converter duty ratio correction unit 54B.

  Converter duty-ratio correction unit 54B has the same configuration as converter duty-ratio correction unit 54A in FIG. That is, converter duty-ratio correction unit 54B adds a predetermined deviation to command duty ratio DR_com in response to signal IPD from determination circuit 70 rising from the L level to the H level, thereby correcting correction command duty ratio DR_0. Is generated.

  Determination circuit 70 further determines whether or not reactor current IL is stagnating near the zero point. Specifically, as shown in the upper part of FIG. 21, when it is determined that the reactor current IL is included in the predetermined current range ΔIL_std and the period exceeds the predetermined period T_std, the reactor current IL approaches the zero point. It determines with stagnating, and outputs the signal ICD which shows the determination result to the converter PWM signal conversion part 56B.

  Converter PWM signal conversion unit 56B sets the carrier frequency to a relatively low carrier frequency in response to input of signal IPD from determination circuit 70. Note that the relatively low carrier frequency is set to a frequency that can suppress the generation of noise accompanying a decrease in the carrier frequency.

  By reducing the carrier frequency in this way, the waveform of the reactor current IL increases the cycle length of one cycle as shown in the lower part of FIG. Reduced. Therefore, frequent switching of the polarity of reactor current IL is suppressed, and the logic level of signal IPD generated according to the switching of the polarity can be stabilized. As a result, it is possible to stably perform voltage conversion control executed based on the signal IPD.

  FIG. 22 is a flowchart for explaining the voltage conversion control operation in converter control means 302B.

  Referring to FIG. 22, when a series of operations for voltage conversion is started, converter duty-ratio calculation unit 52 calculates command duty ratio DR_com based on voltage command value Vdc_com from voltage command calculation unit 50. (Step S11).

  When receiving the reactor current IL from the current sensor 26, the determination circuit 70 determines whether or not the reactor current IL is included in a predetermined current range ΔIL_std set near the zero point (step S111). If it is determined in step S111 that the reactor current IL is included in the predetermined current range ΔIL_std, the determination circuit 70 further determines whether or not a predetermined period T_std set in advance has elapsed (step S112).

  When it is determined in step S112 that the predetermined period T_std has elapsed, the determination circuit 70 determines that the reactor current IL is stagnating near the zero point, and converts the signal ICD indicating the determination result to the converter PWM signal conversion. To the unit 56B.

  When receiving signal ICD, converter PWM signal conversion unit 56B sets the carrier frequency to a relatively low frequency (step S114). Then, converter PWM signal conversion unit 56B generates signal PWMC using the set carrier frequency and correction command duty ratio DR_0 from converter duty ratio correction unit 54B, and uses the generated signal PWMC as a boost converter. It outputs to 12 IGBT elements Q1, Q2.

  When the frequency of switching the polarity of reactor current IL is reduced due to the decrease in carrier frequency, determination circuit 70 determines the polarity of reactor current IL and generates signal IPD indicating the result of the determination (step S12). Determination circuit 70 outputs generated signal IPD to converter duty-ratio correction unit 54B.

  When it is determined in steps S111 and S112 that the reactor current IL is not stagnating near the zero point, the carrier frequency is held at a normal frequency. In step S12, the determination circuit 70 generates a signal IPD based on the polarity of the reactor current IL.

  The converter duty-ratio correction unit 54B adds the predetermined deviation described above to the command duty ratio DR_com in response to the signal IPD from the determination circuit 70 rising from the L level to the H level, thereby correcting the correction command duty ratio DR_0. Is generated (step S13).

  Converter PWM signal conversion unit 56 generates signal PWMC in accordance with correction command duty ratio DR_0 and outputs the signal to IGBT elements Q1, Q2 of boost converter 12. As a result, the IGBT elements Q1 and Q2 are subjected to switching control with the duty ratio maintained at a substantially constant value, with the influence of the dead time removed (step S14).

  As described above, according to the second embodiment of the present invention, the deviation between the command duty ratio and the actual duty ratio is kept substantially constant before and after the polarity of the reactor current is reversed. In response, the actual duty ratio can be suppressed from becoming discontinuous. As a result, it is possible to prevent a surge voltage from occurring at such timing.

  Furthermore, since it is not necessary to increase the capacity of the capacitor C2 for absorbing the surge voltage, the capacitor C2 can be configured with a small size, and the apparatus can be reduced in size and cost.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  The present invention can be applied to a voltage conversion device and a motor drive device including the same.

1 is a schematic block diagram of a motor drive device including a voltage conversion device according to Embodiment 1 of the present invention. It is a timing chart of the voltage driven to the middle point of the upper and lower arms according to the control signal of the upper arm and the lower arm when the reactor current is flowing in the positive direction. It is a timing chart of the voltage driven to the middle point of the upper and lower arms according to the control signal of the upper arm and the lower arm when the reactor current is flowing in the negative direction, and the control signal. It is a timing chart of the output voltage waveform of the boost converter. It is a functional block diagram of the control apparatus in FIG. It is a functional block diagram of the converter control means shown in FIG. FIG. 7 is a diagram illustrating an example of a method for generating a signal DET in the comparison circuit of FIG. 6. FIG. 7 is a diagram illustrating another example of a method for generating a signal DET in the comparison circuit of FIG. 6. FIG. 7 is a diagram illustrating another example of a method for generating a signal DET in the comparison circuit of FIG. 6. It is a figure for demonstrating the correction method of the command duty ratio based on the signal DET. It is a flowchart for demonstrating the voltage conversion control operation | movement in a converter control means. It is a functional block diagram for demonstrating the example of a change of the converter control means of FIG. It is a schematic block diagram of a motor drive device provided with the voltage converter by Embodiment 2 of this invention. It is a functional block diagram of the control apparatus in FIG. It is a timing chart for demonstrating reactor current IL and the output signal IPD of the determination circuit based on this. It is a flowchart for demonstrating the voltage conversion control operation | movement in a converter control means. It is a timing chart for demonstrating the output waveform of the reactor current IL. It is a figure for demonstrating control of the AC motor by Embodiment 2 of this invention. It is a flowchart for demonstrating the voltage conversion control operation | movement in a converter control means. It is a functional block diagram of the converter control means in the modification of Embodiment 2 of this invention. It is a timing chart for demonstrating the output waveform of the reactor current IL. It is a flowchart for demonstrating the voltage conversion control operation | movement in a converter control means.

Explanation of symbols

  10, 11, 13 Voltage sensor, 12 Boost converter, 14 Inverter, 15 U-phase arm, 16 V-phase arm, 17 W-phase arm, 24, 26 Current sensor, 30, 30A Control device, 40 Comparison circuit, 50 Current command conversion Unit, 52 converter duty ratio calculation unit, 54, 54A, 54B converter duty ratio correction unit, 56, 56B converter PWM signal conversion unit, 58 dead time addition unit, 60 correction circuit, 70 determination circuit, 301, 301A inverter Control means, 302, 302A to 302C Converter control means, Q1 to Q8 IGBT elements, D1 to D8 diodes, C1 and C2 capacitors, B battery, L1 reactor, M1 AC motor.

Claims (13)

A voltage converter that varies an input voltage to a load,
A voltage including first and second switching elements connected in series between a power supply node and a ground node, and performing voltage conversion between the power supply and the load by the switching operation of the first and second switching elements A converter,
Based on the actual duty ratio obtained as the actual on-period ratio of the first and second switching elements based on the voltage at the intermediate point of the first and second switching elements, and the voltage command value for the voltage conversion The command duty ratio is corrected so as to maintain a constant deviation from a command duty ratio set as a command value of the ON period ratio of the first and second switching elements, and the command duty ratio is corrected according to the corrected command duty ratio. A voltage converter comprising: a control device that controls a switching operation.   The voltage conversion device according to claim 1, further comprising a capacitive element that is arranged between the voltage converter and the load and connected between the power supply node and the ground node. The controller is
A command duty ratio calculation unit for setting the command duty ratio according to the voltage command value;
A comparison circuit for detecting a deviation between the actual duty ratio and the command duty ratio set by the command duty ratio calculation unit based on a voltage at an intermediate point between the first and second switching elements;
A command duty ratio correction unit that corrects the command duty ratio so as to maintain the deviation constant according to the detected deviation;
The voltage conversion device according to claim 1, further comprising: a control signal generation unit configured to generate a signal for controlling the switching operation based on the corrected command duty ratio.   The voltage conversion according to claim 3, wherein the control device further includes a dead time adding unit that controls the switching operation so that a dead time during which both the first and second switching elements are turned off is provided for a predetermined period. apparatus. A voltage sensor for detecting a voltage at an intermediate point between the first and second switching elements;
The comparison circuit detects the deviation between the actual duty ratio derived from the detected midpoint voltage of the first and second switching elements and the command duty ratio;
The command duty ratio correction unit corrects the command duty ratio so as to maintain the detected deviation substantially at zero,
The voltage conversion device according to claim 4, wherein the control signal generation unit generates a signal for controlling the switching operation according to the corrected command duty ratio. A reactor disposed between the power source and an intermediate point between the first and second switching elements;
A current sensor for detecting a reactor current flowing through the reactor,
The controller is
A command duty ratio calculation unit for setting the command duty ratio according to the voltage command value;
A current polarity determination circuit for determining the polarity of the reactor current;
A command duty ratio correction unit that corrects the command duty ratio so that the deviation is maintained substantially constant before and after the polarity of the reactor current is reversed;
The voltage conversion device according to claim 1, further comprising: a control signal generation unit configured to generate a signal for controlling the switching operation based on the corrected command duty ratio.   The voltage conversion according to claim 6, wherein the control device further includes a dead time addition circuit that controls the switching operation so that a dead time during which both the first and second switching elements are turned off is provided for a predetermined period. apparatus.   The voltage conversion device according to claim 7, wherein when it is determined that the polarity of the reactor current is inverted, the current polarity determination unit holds the determination result for a predetermined latch period from the determined timing.   The command duty ratio correction unit corrects the command duty ratio by adding a predetermined value set to approximately twice the predetermined period in response to the polarity of the reactor current being reversed from positive to negative. The voltage converter according to claim 8.   The command duty ratio correction unit corrects the command duty ratio by subtracting a predetermined value set to approximately twice the predetermined period in response to the polarity of the reactor current being reversed from negative to positive. The voltage converter according to claim 8.   The command duty ratio correction unit corrects the command duty ratio by subtracting a predetermined value set to approximately twice the predetermined period when the polarity of the reactor current is positive, and the reactor current The voltage converter according to claim 8, wherein when the polarity is negative, the command duty ratio is corrected by adding the predetermined value. The load is
A motor,
A drive circuit for driving and controlling the motor,
The controller is
First drive control means for operating the motor at a first operating point that requires a motor drive current of a first current amplitude to generate the required torque;
Second drive control means for operating the motor at a second operating point that requires a motor drive current having a second current amplitude larger than the first current amplitude to generate the required torque;
When it is determined that the reactor current has stagnated in a predetermined current range including a zero point over a predetermined set period, the first drive control means is switched to the second drive control means. The voltage conversion apparatus according to claim 7, further comprising switching means for controlling the drive circuit.   The control device performs switching control of the first and second switching elements in response to a determination that the reactor current has stagnated in a predetermined current range including a zero point over a predetermined setting period. The voltage converter according to claim 7, wherein the voltage converter is controlled by reducing a carrier frequency.

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