JP2008211926A - Power converter and its control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power converter that reduces the occurrence of a harmonic current of an AC motor if there is a voltage difference when selecting a path between a plurality of DC power supplies and a motor, and that also reduces current ripples even in a mode in which one power supply is in power running, while the other is in regeneration. <P>SOLUTION: This power converter comprises: a means (44), which generates and synthesizes voltage pulses based on a command value of voltage pulse width using a plurality of switches; and a switch control means, which controls a plurality of the switches so as to charge at least one DC power supply, by changing over a mode 0, in which, when all switches of current flowing phases from the DC power supplies to the motor are at least in ON sate, a switch in the direction of conducting electric power from the motor to the positive electrode of the power supply is opened and the remaining DC power supplies are charged, and a mode 1, in which, when all switches of current flowing phases from the DC power supplies to the motor are at least in ON sate, a switch in the direction of conducting electric power from the motor to the positive electrode of the DC power supply concerned is turned on. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a power conversion device and a control method thereof, and more particularly to a power conversion device that reduces the generation of harmonic current of an AC motor and reduces current ripple even when a voltage difference exists during path selection. Regarding the method.

There is proposed a control method for a power converter that can reduce and reduce the overall volume and loss by using and distributing a plurality of power sources without using a DCDC converter, not limited to a combination of a fuel cell and a battery (Patent Literature). 1). In this proposed method, there is also proposed a control method for selecting whether a current flowing from the inductive load to the power supply bus flows through any of the buses (see Patent Document 2).
JP 2006-25520 A JP 2006-33955 A

  In the former proposed method, when multiple power sources are distributed, the carrier frequency component is used when the motor 10a (current value idc_a) is in power mode and the motor 10b (current value idc_b) is operating while regenerating. There was a problem that the current ripple increased. FIG. 14 is a diagram showing a current waveform (current ripple generation) in the power supply 10a powering and power supply 10b regeneration mode in the conventional technique. Furthermore, in the latter proposed method, when a current path is selected, there is a problem in that harmonics are generated because positive electrodes having different voltages are connected to each phase. FIG. 15 is a diagram showing generation of harmonics in the conventional technique. As shown in FIG. 15, the generation of harmonics is observed at the center of the figure.

  Therefore, an object of the present invention is to reduce the generation of harmonic current of an AC motor even when there is a voltage difference when selecting a route between a plurality of DC power supplies and an AC motor, and one power supply can be powered. It is to provide a control technique (apparatus and method) that reduces current ripple even in a mode in which the other power source is regenerative.

In order to solve the above-described problems, the power conversion device according to the first invention provides:
A power converter that generates voltage pulses for driving an AC motor from output voltages of a plurality of DC power sources,
Means (power converter) for generating and synthesizing the voltage pulse based on the command value of the voltage pulse width using a plurality of switches;
Among the plurality of DC power supplies, in each phase switch in the direction of conduction from the DC power supply to the AC motor, the power supply voltage is lower than or equal to that of the other DC power supplies. At least current flows from the DC power supply to the AC motor. When all the switches of a certain phase are in the ON state, the switch in the direction of conducting from the AC motor to the positive electrode of the DC power supply is opened (OFF), and the remaining DC power supplies are charged in mode 0, Among the DC power supplies, in each phase switch in a direction in which the power supply voltage is lower than or equal to that of the other DC power supplies and from the DC power supply to the AC motor, at least the phase in which current flows from the DC power supply to the AC motor Mode 1 in which the switch in the direction of conducting from the AC motor to the positive electrode of the DC power source is continuously turned on when all the switches of the AC motor are in the ON state. Switching, a switch control means for controlling said plurality of switches so as to charge the at least one DC power source of said plurality of direct current power source,
With

The power converter according to the second invention is
An open pulse width command value generating means for generating an open pulse width command value for defining an open time (off time) of a switch in a direction of conducting from the AC motor to at least one positive electrode of the plurality of DC power sources;
The switch control means;
A DC power supply to be charged is selected, and a charging path of a DC power supply other than the selected DC power supply to be charged is conducted to the positive electrode according to the open pulse width command value generated by the open pulse width command value generating means. Control to open the direction switch,
It is characterized by that.

A power converter according to a third aspect of the invention is
Carrier generating means for generating a carrier for defining an open time (off time) of a switch in a direction of conducting from the AC motor to at least one positive electrode of the plurality of DC power sources;
An open pulse width command value generating means for generating an open pulse width command value for defining an open time (off time) of a switch in a direction of conducting from the AC motor to at least one positive electrode of the plurality of DC power sources; Prepared,
The switch control means;
By comparing the carrier generated by the carrier generating means with the open pulse width command value generated by the open pulse width command value generating means, the opening time of the switch in the direction of conducting to the positive electrode is determined, and the determined Control to open the switch in the direction of conducting to the positive electrode according to the opening time,
It is characterized by that.

The power converter according to the fourth invention is
Further comprising voltage detection means for detecting voltages of the plurality of DC power supplies,
The switch control means;
Controlling to open a switch in a direction of conduction to at least one positive electrode of the plurality of DC power sources in the charging path of the lower voltage,
It is characterized by that.

The power converter according to the fifth invention is
Voltage pulse width command value correcting means for correcting a voltage pulse width command value based on a time for opening a switch in a direction to conduct to at least one positive electrode of the plurality of DC power supplies and a sign of a motor current;
Is further provided.

The power converter according to the sixth invention is
The voltage pulse width command value correcting means is
Only when the sign of the motor current is negative, the voltage pulse width command value is corrected.
It is characterized by that.

A power converter according to a seventh aspect of the invention is
The voltage pulse width command value correcting means is
Based on the voltage value of the DC power supply that does not have a path to charge from the AC motor, the voltage value of the DC power supply that has a path to charge from the AC motor, and the time to open the switch in the direction to conduct to the positive electrode, Correct the voltage pulse width command value,
It is characterized by that.

The power converter according to the eighth invention is
The opening pulse width command value generating means
(Comparing the minimum value of the voltage pulse width command value and the open pulse width command value generated by the open pulse width command value generating means) The value set below the minimum value of the voltage pulse width command value Generate open pulse width command value,
It is characterized by that.

The power converter according to the ninth aspect of the invention is
The carrier generated by the carrier generating means is a triangular wave.
The power conversion device according to the tenth invention is
The carrier generated by the carrier generating means is a sawtooth wave.

The power converter according to the eleventh invention is
The sign of the motor current is a sign of a motor current command value.
A power converter according to a twelfth aspect of the invention is
It further comprises a current measuring means for detecting the motor current,
The sign of the motor current is the sign of the detected motor current detection value.
It is characterized by that.

A power conversion device according to a thirteenth invention is
The apparatus further comprises means for adjusting the open pulse width command value based on the charge command value for the DC power source to be charged.

A power conversion device according to a fourteenth invention is
The apparatus further comprises means for calculating the open pulse width command value based on at least a motor current value and voltage values of the plurality of DC power supplies.

A power converter according to the fifteenth aspect of the present invention is
The adjustment or calculation of the open pulse width command value is performed by referring to a map created in advance.

As described above, the solution of the present invention has been described as an apparatus. However, the present invention can be realized as a method, a program, and a storage medium that stores the program substantially corresponding to these, and the scope of the present invention. It should be understood that these are also included.
For example, the control method of the power converter according to the sixteenth aspect of the present invention, which is realized as a method,
A method for controlling a power converter that generates a voltage pulse for driving an AC motor from output voltages of a plurality of DC power sources,
Generating and synthesizing the voltage pulse based on the command value of the voltage pulse width using a plurality of switches;
Among the plurality of DC power supplies, in each phase switch in the direction of conduction from the DC power supply to the AC motor, the power supply voltage is lower than or equal to that of the other DC power supplies. At least current flows from the DC power supply to the AC motor. When all the switches of a certain phase are in the ON state, the switch in the direction of conducting from the AC motor to the positive electrode of the DC power supply is opened (OFF), and the remaining DC power supplies are charged in mode 0, Among the DC power supplies, in each phase switch in a direction in which the power supply voltage is lower than or equal to that of the other DC power supplies and from the DC power supply to the AC motor, at least the phase in which current flows from the DC power supply to the AC motor Mode 1 in which the switch in the direction of conducting from the AC motor to the positive electrode of the DC power source is continuously turned on when all the switches of the AC motor are in the ON state. Switching and controlling the plurality of switches so as to charge at least one of the DC power source of said plurality of direct current power source,
Have

According to the present invention, by continuously switching between mode 0 and mode 1 to charge each DC power supply and control the charging power of the plurality of DC power supplies, for example, the voltages of the plurality of power supplies are equal. In some cases, when all the switches in the direction of output from one DC power source to the motor are in the ON state, the motor phase voltage becomes zero, and charging / discharging of a plurality of DC power sources can be controlled without applying an extra voltage to the motor. Even when the voltages of the respective DC power supplies are different, since only the difference voltage between the respective power supply voltages is applied to the motor, the harmonics can be reduced, and as a result, the torque ripple can be reduced. As a result, power source energy management in a vehicle having a plurality of power sources such as a fuel cell vehicle can be performed, and the charge / discharge control of the battery can be performed efficiently. Furthermore, since the ripple in the carrier frequency band of the motor current can be reduced and the motor copper loss and iron loss can be reduced, efficient operation becomes possible.
Furthermore, since the output voltage waveform becomes convex due to the continuous switching of the switches, noise generated by a steep voltage change can be reduced, and the reliability of the power converter can be improved.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
<First embodiment>
FIG. 3 shows a circuit diagram of the power conversion device according to this embodiment. The negative electrode of the power supply 10a and the negative electrode of the power supply 10b are connected to the common negative electrode bus 15. A pair of semiconductor switches 107a, 108a, 109a and diodes 107b, 108b, 109b is connected between the common negative electrode bus 15 and each phase terminal of the motor 20 in the same manner as a generally known lower arm of an inverter. . The positive electrode bus 14 of the power supply 10a and each phase terminal of the (alternating current) motor 20 are connected by semiconductor switches 101a / 101b, 102a / 102b, 103a / 103b capable of controlling bidirectional conduction. Further, semiconductor switches 104a / 104b, 105a / 105b, and 106a / 106b that can control bidirectional conduction are also connected between the positive electrode bus 16 of the power supply 10b and each phase terminal of the motor 20. A smoothing capacitor 12 is provided between the positive electrode bus 14 and the common negative electrode bus 15 of the power source 10a, and a smoothing capacitor 13 is also provided between the positive electrode bus 16 and the common negative electrode bus 15 of the power source 10b.

  The power converter 30 is a DC-AC power converter that generates a voltage to be applied to the motor 20 based on the above three potentials, the common negative electrode bus, the positive electrode bus of the power source 10a, and the positive electrode bus of the power source 10b. A semiconductor switch provided in each phase is a switch means for generating a voltage to be output to each phase of the AC motor, and is connected alternatively from these potentials, and the proportion of the connection time is changed. Then, the necessary voltage is supplied to the motor.

  FIG. 2 is a block diagram showing the configuration of the control device 40 in this embodiment. The control device 40 is connected to the power converter 30. In response to a command value (pulse width command value) from the control device 40, the power converter 30 converts power from the power sources 10a and 10b constituting the power source unit 10 into alternating current and supplies it to the motor 20. The control device 40 includes a torque control means 41, a current control means 42, a power control / modulation rate calculation means 43, a PWM pulse generation means 44, a three-phase / dq conversion means 45, a dq / 3-phase conversion means 46, a correction gain calculator. 47. A feedback path opening command calculator 48 is provided. The torque control means 41 is a torque control means for calculating a d-axis current command value id * and a q-axis current command value iq * of the motor 20 from a torque command Te * and a motor rotation speed ω given from the outside. The torque control means 41 refers to a map with the torque command value Te * and the motor rotation speed ω prepared in advance as axes, and outputs d-axis and q-axis current target values id * and iq *. The current control means 42 performs current control for matching the d-axis current command value id * and q-axis current command value iq * with the d-axis current value id and q-axis current value iq. By this control, voltage command values vu *, vv *, vw * for each phase of the three-phase AC are output.

  FIG. 16 is a block diagram showing the internal configuration of the current control means 42. As shown in the figure, the current control means 42 includes a current control unit 201 and a dq / 3-phase converter 202. The current control unit 201 performs feedback control by PI control so that id and iq follow id * and iq *, respectively, and outputs a d-axis voltage command value vd * and a q-axis voltage command value vq *. id and iq are obtained from the U-phase current iu and the V-phase current iv by the three-phase / dq converter means 45. The dq / 3-phase converter 202 is dq / 3-phase voltage conversion means for converting a dq-axis voltage into a three-phase voltage command, and receives dq-axis voltage command values vd * and vq * as inputs, and a U-phase voltage command value vu. *, V phase voltage command value vv *, W phase voltage command value vw * are output.

Returning to the description of FIG. 2, the power control / modulation rate calculating means 43 performs power control using the distribution target values (rto_pa, rto_pb) of the power supplied from the power supplies 10 a and 10 b. The power distribution target value means the ratio of power between the power supply 10a and the power supply 10b when the correction voltage values vd_0 * and vq_0 * are 0. The power distribution target values rto_pa and rto_pb have the following relationship: .
rto_pa + rto_pb = 1
For this reason, if one power distribution target value is obtained, the other power distribution target value can be obtained from the above relationship. In FIG. 2, only rto_pa is shown as an input of the power control / modulation rate calculating means 43, and rto_pb is calculated based on the above equation by calculation inside the power control / modulation rate calculating means 43.

FIG. 17 is a block diagram showing an internal configuration of the power control / modulation rate calculating means 43. The multiplier 203 multiplies vu *, vv *, and vw * by rto_pa, respectively, to calculate vu_a, vv_a, and vw_a that are voltage command values on the power supply 10a side. Hereinafter, a voltage command generated from the power supply 10a is referred to as a power supply 10a divided voltage command, and a voltage command generated from the power supply 10b is referred to as a power supply 10b divided voltage command.
vu_a = vu * ・ rto_pa
vv_a = vv * ・ rto_pa
vw_a = vw * ・ rto_pa

On the other hand, the voltage command value on the power supply 10b side is obtained from the voltage command values vu *, vv *, vw * obtained from the control voltage of the motor current control, and the voltage command value values vu_a *, vv_a *, vw_a * on the power supply 10a side. Is subtracted by a subtracter 206.
vu_b * = vu *-vu_a *
vv_b * = vv *-vv_a *
vw_b * = vw *-vw_a *
The following description of the modulation factor calculation and PWM pulse generation is performed only for the U phase, but the same operation is performed for the V phase and the W phase. 17 inputs the voltage Vdc_a of the power source 10a and the voltage Vdc_b of the power source 10b, respectively, and instantaneous modulation rate commands mu_a *, mu_b *, mv_a *, mv_b *, which are standardized voltage commands, respectively. Modulation rate calculation means for generating mw_a * and mw_b *.

<Modulation rate calculating means 43a>
As shown in the figure, the power control / modulation rate calculation means 43 includes modulation rate calculation means 43a, and 43a includes multipliers 205 and 206. Here, the U-phase power supply 10a divided voltage command vu_a * and the power supply 10b divided voltage command vu_b * are normalized by half the value of each DC voltage so that the power supply 10a instantaneous modulation rate command mu_a * and the power supply 10b instantaneous A modulation factor command mu_b * is obtained.
mu_a * = vu_a * / (Vdc_a / 2)
mu_b * = vu_b * / (Vdc_b / 2)

<Modulation rate correction means 43b>
As shown in the figure, the power control / modulation rate calculation means 43 includes modulation rate correction means 43b. The modulation rate correction means 43b calculates the final modulation rate command value by allocating the time width of the PWM cycle and multiplying by the correction gain in order to output the obtained modulation rate. First, the modulation factor offset calculator 211 calculates the next modulation factor offsets ma_offset0 and mb_offset0 from the power supply voltages Vdc_a and Vdc_b and rto_pa. Here, rto_pb is calculated based on the above formula.
rto_pb = 1-rto_pa
The obtained modulation factor offsets ma_offset0 and mb_offset0 are added by the adders 209 and 210 to the instantaneous modulation factor command mu_a * for the power supply 10a and the instantaneous modulation factor command mu_b * for the power supply 10b, respectively.

<Input voltage command correction means 49>
The input voltage command correcting means 49 in FIG. 17 is a voltage command value correcting means for correcting an output voltage error that occurs due to the opening of the return path of the motor. The input voltage command correction means 49 corrects the voltage command value by adding the voltage command value correction values Vu_comp, Vv_comp, and Vw_comp of each phase to the voltage command values Vu *, Vv *, and Vw *, respectively. The voltage command value correction value is calculated by the voltage command value correction value calculator 213 as follows.
Vu_comp = 0 (iu ≥ 0)
Vu_comp = (Vdc_b-Vdc_a) * m_R * / 4 (iu <0)
Vv_comp = 0 (iv ≥ 0)
Vv_comp = (Vdc_b-Vdc_a) * m_R * / 4 (iv <0)
Vw_comp = 0 (iw ≥ 0)
Vw_comp = (Vdc_b-Vdc_a) * m_R * / 4 (-iu-iv <0)
Here, iu and iv may be current detection values or current command values. Note that m_R * is a command value for opening the reflux path in stages, which will be described later.

Apply the appropriate voltage pulse corresponding to the voltage command value to the motor by estimating the motor current path from the motor current sign and correcting the error of the output voltage pulse by the above input voltage command correction means. It becomes possible to suppress the generation of harmonic current of the motor phase current. As a result, the loss of the motor can be reduced, and if this configuration is applied to a fuel cell electric vehicle, the fuel efficiency of the fuel cell electric vehicle can be improved. Further, by suppressing the generation of unnecessary harmonic current, torque ripple is reduced and the ride comfort of the vehicle is improved.
Furthermore, the pulse width is corrected only when the sign of the motor current is negative. When the sign of the motor current is positive, unnecessary correction is not performed, and the pulse width is corrected in the necessary current state. Therefore, generation of harmonic current can be suppressed.

  Furthermore, the pulse width can be corrected by correcting the modulation factor command value from the power supply voltage value of the power supply that does not have a path for charging from the motor, the voltage value of the power supply having the path for charging from the motor, and the open time. Can be performed with high accuracy, and generation of harmonic current can be suppressed. Furthermore, by using the motor current command value for the determination of the sign of the motor current, it is possible to determine the current sign without being affected by the noise of the motor current. Thus, by accurately determining the current code, the pulse width can be corrected with high accuracy, and the generation of harmonic current can be suppressed.

  Furthermore, by using the motor current detection value measured by the current detection means provided in the motor to determine the sign of the motor current, even when the follow-up to the command value of the motor current is slow, it is based on the actual current path. The current code can be discriminated. Using this sign discrimination, the pulse width can be corrected for the error of the output voltage pulse caused by the current path, and the generation of harmonic current can be suppressed.

<PWM pulse generating means 44>
FIG. 5 shows a triangular wave used in the PWM pulse generating means. As shown in the figure, the carrier for the power source 10a is supplied with each switch (A, B, C, D, E in FIG. 4 or the semiconductor switch 101a in FIG. 1) in order to output a voltage pulse from the voltage Vdc_a of the power source 10a. / 101b / 107a / 104a / 104b, etc.) for generating a PWM pulse. Similarly, a triangular wave is provided as a carrier for the power supply 10b. These two triangular wave carriers have values of an upper limit of +1 and a lower limit of -1, and have a phase difference of 180 degrees. In this embodiment, the carrier is a triangular wave, but a “sawtooth wave” as shown in FIG. 6 may be used.

FIG. 7 shows a configuration diagram in which only the U phase is extracted from FIG. Here, drive signals for driving the U-phase switches are set as follows based on FIG.
Drive signal A: Drive signal of the switch (101a) conducting from the power source 10a to the output terminal Drive signal B: Drive signal of the switch (107a) conducting from the output terminal to the negative electrode Drive signal C: Power source 10a from the output terminal Drive signal for switch (101b) that conducts in the direction of the drive signal D: Drive signal for switch (104a) that conducts in the direction from the power supply 10b to the output terminal Drive signal E: Switch (104b that conducts in the direction from the output terminal to the power supply 10b ) Drive signal

  First, a pulse generation method when a voltage pulse is output from the power supply 10a will be described. When outputting a PWM pulse from the power supply 10a, it is necessary to turn on A. When there is a potential difference between the positive electrode and the positive electrode and Vdc_a> Vdc_b, when both A and E are turned on, a current that short-circuits between the positive electrodes flows. For example, when A is switched from on to off at the same time and E is switched from off to on, it takes time for A to completely turn off. A short-circuit current flows, and the amount of heat generated by the semiconductor switch installed in this path increases. In order to prevent such an increase in heat generation, A and E are switched from OFF to ON after a time during which both the drive signals A and E are turned off. In this way, pulse generation is performed by adding a short-circuit prevention time (dead time) to the drive signal. Similar to adding dead time to the driving signals of A and E, dead time is added to E and C, and in order to prevent a short circuit between the positive and negative electrodes, dead to A and B and E and B. Add time.

FIG. 8 shows A and E pulse generation by triangular wave comparison. A method of adding dead time to the A and E drive signals will be described below with reference to FIG. In order to generate a drive signal with a dead time added, mu_a_c_up * and mu_a_c_down * offset from the mu_a_c * by the dead time are obtained as follows.
mu_a_c_up * = mu_a_c * + Hd
mu_a_c_down * = mu_a_c * − Hd
Here, Hd is obtained from the amplitude of the triangular wave (from the base to the apex) Htr, the period Ttr, and the dead time Td as follows.
Hd = 2Td · Htr / Ttr
The carrier and mu_a_c *, mu_a_c_up *, mu_a_c_down * are compared, and the drive signals for the A and E switches are obtained according to the following rules.
If mu_a_c_down * ≥ carrier for power supply 10a, A = on mu_a_c * ≤ A if carrier for power supply 10a A = off mu_a_c * ≥ If carrier for power supply 10a E = off mu_a_c_up * ≤ carrier for power supply 10a E = on In addition, by generating the drive signal, a dead time of Td can be provided between A and E, and a short circuit between the positive electrodes can be prevented. The pulse generation method for outputting voltage pulses from the power supply 10b is the same as that of the power supply 10a, and the following mu_b_c_up * and mu_b_c_down * are obtained and compared with the carrier for the power supply 10b. FIG. 9 shows pulse generation of D and C by the triangular wave comparison.
mu_b_c_up * = mu_b_c * + Hd
mu_b_c_down * = mu_b_c * − Hd

The drive signals D and C are obtained according to the following rules.
If mu_b_c_down * ≥ carrier for power supply 10b, D = on mu_b_c * ≤ D for carrier for power supply 10b, D = off mu_b_c * ≥ If carrier for power supply 10b, C = off mu = b_c_up * ≤ carrier for power supply 10b, C = on Thus, a dead time of Td can also be provided between D and C, and a short circuit between the positive electrodes can be prevented.

The drive signal B is generated from AND (logical product) of the generated drive signals E and C.
B = E ・ C
E is a drive signal with a dead time added to A, and C is a drive signal with a dead time added to D. Therefore, by generating B from the AND of E and C, it is possible to generate dead time for B and A and B and E as well. FIG. 10 shows an example of pulse generation with a dead time added. Based on the PWM pulse generated in this way, each switch of the power converter is turned on / off to generate an output voltage pulse. Taking the average of the voltage pulse generated from the voltage Vdc_a of the power supply 10a and the voltage pulse generated from the voltage Vdc_b of the power supply 10b for each period, the original three-phase voltage command values vu *, vv *, vw * Thus, a voltage pulse that realizes is generated.

<Stepwise switching of charging path>
Here, a method of continuously opening the return current path of the motor will be described with reference to FIGS. 11 and 12 do not show the dead time for the sake of simplicity, it is assumed that the dead time is taken into account. FIG. 11 shows a state where the power distribution target value on the power supply 10b side is zero. A, B, C, D, and E in the figure indicate the switches shown in FIG. In this state, the switches D and E are not passed, and power distribution from the power source 10b is not performed. In this case, there are a total of four switching modes (switch element states), and switching modes 1, 2, 3, and 4 as shown in FIG. 11 appear.

Here, the return path to the power source 10a is switched using the return path open command m_R * as shown in FIG. That is, switching is performed as follows.
If Vdc_b ≥ Vdc_a, if power carrier 10a <m_R *, turn on E, turn off C If power carrier 10a carrier ≥ m_R *, turn off E, turn on C
When Vdc_b <Vdc_a <br /> If power carrier 10b <m_R *, turn off E, turn on C If power carrier 10b ≥ m_R *, turn on E, turn off C Switching mode by switching in this way It is set to 0, and switching is performed so as to charge the power supply having the higher voltage in the negative phase of the motor current. Note that when switching between the switches E and C, an overlap time is set so as not to interrupt the motor current path.

  When a sawtooth wave is used for the carrier, the switching is as shown in FIG. Further, the return path opening command m_R * is set so that the smallest one of the modulation rate command mu_a_c *, the modulation rate command mv_a_c *, and the modulation rate command mw_a_c * is the same or a small value.

  FIG. 4 shows a state transition diagram showing the current flow of each phase in the case of such a configuration when Vb ≧ Va, that is, the current flow of each phase. In switching mode 0 (Mode_0), the power source 10a outputs only the U phase where the motor current is positive, and the power source 10b is charged from the V phase and W phase where the motor current is negative. In this operation mode, the power supply 10a is discharged and the power supply 10b is charged. In the switching modes 0 to 5 (Mode_1 to Mode_5), the same switching as that of a normal three-phase inverter is performed, and a necessary voltage is applied to each phase of the motor. The current state of the motor is positive in the U phase, negative in the V and W phases, but the same is true when the positive and negative motor currents are switched.

  Furthermore, FIG. 1 shows an output voltage waveform in a phase where the motor current is negative. As shown in FIG. 1A, in the phase where the motor current is negative, when 107a is off and both 101b and 104b are on, the current flows to the power source 10a having the lower voltage, so the output voltage is Vdc_a To be clamped. Further, when 101b is turned off from this state, the motor current flows to the power supply 10b, so that the output voltage is clamped to Vdc_b. As a result, the output voltage has a convex waveform as shown in FIG.

<Effect of stepwise switching of charging path>
With this configuration, the power supply is charged by continuously switching between mode 0 and mode 1, so that the charging power of a plurality of power supplies can be controlled. By configuring in this way, for example, when the voltages of multiple power supplies are equal, the motor phase voltage becomes zero when all switches in the direction of output from one power supply to the motor are on, and an extra voltage is applied to the motor. It is possible to control charging / discharging of multiple power supplies without having to do so. Even when a plurality of power supply voltages are different, only a difference voltage between the respective power supply voltages is applied to the motor, so that the harmonics can be reduced, and as a result, the torque ripple can be reduced. As a result, power source energy management in a vehicle having a plurality of power sources such as a fuel cell vehicle can be performed, and the charge / discharge control of the battery can be performed efficiently. Furthermore, the ripple in the carrier frequency band of the motor current, which has been a problem of the prior art, can be reduced, and the motor copper loss and iron loss can be reduced, so that efficient operation is possible. Furthermore, since the output voltage waveform becomes convex due to the continuous switching of the switches, noise generated by a steep voltage change can be reduced, and the reliability of the power converter can be improved. Furthermore, the power of the power source to be charged can be controlled by opening a charging path to a power source other than the power source to be charged for a certain period of time. Therefore, charging / discharging of a plurality of power supplies can be easily controlled by controlling the open time. Further, the power supply voltage is detected, and the charging path with the lower power supply voltage is opened. Therefore, even when the magnitude relation of the power supply voltage is switched, the charging path can be appropriately opened. Further, since the carrier is a simple one such as a triangular wave or a sawtooth wave, the control device can be configured at low cost.

  FIG. 15 shows motor phase currents iu and iv, dq axis currents id and iq, and power source currents idc_a and idc_b when a simulation of charging the power source 10b is performed with the distribution target value of the power source 10b being negative. After starting the power supply 10b charging mode, it is possible to output a current with less distortion by performing correction to reduce the motor harmonics.

<Reflux path opening command calculation unit 48>
Next, a calculation method of the reflux path opening command calculation unit 48 and its effect will be described. When performing stepwise switching of the return path, as described above, the power supply 10b can be charged even if the power distribution target value on the power supply 10b side is zero. That is, there is a difference between the power distribution target value and the actual power distribution. In this configuration, the return path opening command calculation unit 48 is used to control the amount of power on the power supply 10b side in accordance with the command value Pb *. The description will be made assuming that Vdc_b ≧ Vdc_a, and charging to the power supply 10b side. However, the magnitude relationship of the voltage changes, and the same method can be used when charging the power supply 10a.

  The return path open command calculation unit (power command generation unit) 48 receives the power command value Pb * of id, iq, Vdc_a, Vdc_b, and the power supply 10b as input, and calculates the return path open command m_R *. . A reflux path opening command is obtained by the calculation of the reflux path opening command calculation unit 48, and the power of the power source 10b is controlled. Also, m_R * may not be calculated online, but may be calculated in advance and incorporated into the controller as a map.

<Effects of power command generator>
By configuring the reflux path opening command calculation unit in this way, it is possible to charge the power amount according to the power command value of the power source by adjusting the opening time according to the power amount required for the power source. Further, since the open pulse width command value is obtained from the motor current and the power supply voltage, a sensor or the like for detecting the output of the motor or the power supply is not used, so that an inexpensive control device can be configured. Further, the calculation of the open pulse width command value is performed only by referring to a previously created map. Therefore, the calculation time can be shortened. When the control of the present invention is calculated by a microcomputer, an inexpensive microcomputer can be used by shortening the calculation time.

  The advantages of the present invention are summarized as follows. First, according to the present invention, for example, the voltage of a plurality of power supplies is controlled by charging each DC power supply by continuously switching between mode 0 and mode 1 and controlling the charging power of the plurality of DC power supplies. If the switches are in the ON state, the motor phase voltage is zero, and charging / discharging of multiple DC power supplies can be controlled without applying extra voltage to the motor. .

  Furthermore, according to the embodiments of the present invention (the second to fifteenth inventions), there are the following advantages. According to the second aspect of the present invention, it is possible to control the power of the power source to be charged by opening a charging path to a power source other than the power source to be charged for a predetermined time. Therefore, charging / discharging of a plurality of power supplies can be easily controlled by controlling the open time. According to the third invention, the release time is generated by comparing the carrier and the release pulse width command value. Therefore, it can be configured with an inexpensive control device. According to the fourth invention, the power supply voltage is detected, and the charging path with the lower power supply voltage is opened. Therefore, even when the magnitude relation of the power supply voltage is switched, the charging path can be appropriately opened. According to the fifth aspect of the present invention, the motor current path is estimated from the motor current code, and the error of the output voltage pulse is corrected, whereby an appropriate voltage pulse corresponding to the voltage command value is applied to the motor. It becomes possible to apply, and it becomes possible to suppress generation | occurrence | production of the harmonic current of a motor phase current. As a result, the loss of the motor can be reduced, and if the present invention is applied to a fuel cell electric vehicle, the fuel efficiency of the fuel cell electric vehicle can be improved. Further, by suppressing the generation of unnecessary harmonic current, torque ripple is reduced and the ride comfort of the vehicle is improved.

  According to the sixth aspect of the invention, the pulse width is corrected only when the sign of the motor current is negative. When the sign of the motor current is positive, unnecessary correction is not performed. In the current state, the generation of the harmonic current can be suppressed by correcting the pulse width.

  According to the seventh aspect of the invention, the modulation factor command value is corrected from the power supply voltage value of the power supply not having a path for charging from the motor, the voltage value of the power supply having a path of charging from the motor, and the open time. By doing so, the pulse width can be corrected with high accuracy, and the generation of harmonic current can be suppressed.

  According to the eighth aspect of the invention, the open pulse width command value is set to be equal to or smaller than the minimum value of the output pulse width command value. As a result, since the open pulse width is not wider than the output pulse width, generation of voltage that causes harmonics can be suppressed, and torque ripple can be reduced. According to the ninth invention, the carrier is a triangular wave. Therefore, it can be configured with an inexpensive control device. According to the tenth aspect, the carrier is a sawtooth wave. Therefore, it can be configured with an inexpensive control device. Further, according to the eleventh aspect, by using the motor current command value for determining the sign of the motor current, it is possible to determine the current sign without being affected by the noise of the motor current. Thus, by accurately determining the current code, the pulse width can be corrected with high accuracy, and the generation of harmonic current can be suppressed. Further, according to the twelfth aspect, by using the detected value of the motor current to determine the sign of the motor current, the current sign based on the actual current path can be obtained even when the follow-up to the command value of the motor current is slow. Can be determined. Using this sign discrimination, the pulse width can be corrected for the error of the output voltage pulse caused by the current path, and the generation of harmonic current can be suppressed.

  Further, according to the thirteenth aspect, by adjusting the open time according to the amount of power required for the power source, the amount of power according to the power command value of the power source can be charged. According to the fourteenth aspect of the invention, since the open pulse width command value is obtained from the motor current and the power supply voltage, a motor or a sensor for detecting the output of the power supply is not used. . According to the fifteenth aspect of the invention, the calculation of the open pulse width command value is performed only by referring to a previously created map. Therefore, the calculation time can be shortened. When this control is calculated by a processor such as a microcomputer, an inexpensive processor can be used by reducing the calculation time.

  Although the present invention has been described based on the drawings and examples, it should be noted that those skilled in the art can easily make various modifications and corrections based on the present disclosure. Therefore, it should be noted that these variations and modifications are included in the scope of the present invention. For example, the functions included in each means, each step, etc. can be rearranged so as not to be logically contradictory, and a plurality of members, means, steps, etc. can be combined or divided into one. is there.

FIG. 3 is a schematic diagram showing an output voltage waveform of Example 1. 3 is a block diagram showing a configuration of a control device 40. FIG. The circuit diagram of the power converter device is shown. It is a state transition diagram which shows the flow of the electric current of each phase. It is a figure which shows the triangular wave used with a PWM pulse production | generation means. It is a figure which shows the sawtooth wave used with a PWM pulse production | generation means. It is the block diagram which extracted only the U phase from FIG. It is a figure which shows the pulse generation of A and E by a triangular wave comparison. It is a figure which shows the pulse generation of D and C by a triangular wave comparison. It is a figure which shows the example of the pulse generation to which the dead time was added. It is a figure which shows the switching pattern (The dead time is abbreviate | omitted) for three phases. It is a figure which shows the switching pattern (triangular wave) of Example 1. FIG. It is a figure which shows the switching pattern (sawtooth wave) of Example 1. FIG. It is a figure which shows the current waveform of the power supply 10a powering and the power supply 10b regeneration mode in the prior art. It is a figure which shows generation | occurrence | production of the harmonic in a prior art. 3 is a block diagram showing an internal configuration of current control means 42. FIG. 4 is a block diagram showing an internal configuration of a power control / modulation rate calculating means 43. FIG.

Explanation of symbols

101a / 101b / 107a / 104a / 104b semiconductor switch
102a / 102b / 108a / 105a / 105b semiconductor switch
103a / 103b / 109a / 106a / 106b semiconductor switch
107b / 180b / 109b diode
10a, 10b power supply
12,13 Smoothing capacitor
14 Positive bus
15 Common negative electrode bus
16 Positive bus
20 Motor
30 Power converter
40 Control unit
41 Torque control means
42 Current control means
43 Power control / modulation rate calculation means
43a Modulation rate calculation means
43b Modulation rate correction means
44 Pulse generation means
45 Three-phase / dq conversion means
46 dq / 3-phase conversion means
47 Correction gain calculator
48 Feedback path open command calculator
49 Input voltage command correction means
A, B, C, D, E switch
201 Current controller
202 dq / 3 phase converter
203,205 multiplier
206 Subtractor
209 Adder
211 Modulation rate offset calculator
213 Voltage command value correction value calculator

Claims (16)

A power converter that generates voltage pulses for driving an AC motor from output voltages of a plurality of DC power sources,
Means for generating and synthesizing the voltage pulse based on the command value of the voltage pulse width using a plurality of switches;
Among the plurality of DC power supplies, a current flows at least from the DC power supply to the AC motor in each phase switch in a direction in which the power supply voltage is lower than or equal to other DC power supplies to the AC motor. When all the switches of the phase are in the ON state, the switch in the direction of conduction from the AC motor to the positive electrode of the DC power supply is opened, and the mode 0 in which the remaining DC power supplies are charged, and among the plurality of DC power supplies In the switches of the respective phases in the direction in which the power supply voltage is lower than or equal to that of the other DC power supply and from the DC power supply to the AC motor, at least all of the phase switches in which current flows from the DC power supply to the AC motor are all. When in the ON state, the mode is continuously switched to mode 1 in which the switch in the direction of conducting from the AC motor to the positive electrode of the DC power source is conducted. A switch control means for controlling said plurality of switches so as to charge the at least one DC power source of said plurality of direct current power source,
A power conversion device comprising: The power conversion device according to claim 1,
An open pulse width command value generating means for generating an open pulse width command value for defining an open time of a switch in a direction of conducting from the AC motor to at least one positive electrode of the plurality of DC power supplies;
The switch control means;
A DC power supply to be charged is selected, and a charging path of a DC power supply other than the selected DC power supply to be charged is conducted to the positive electrode according to the open pulse width command value generated by the open pulse width command value generating means. Control to open the direction switch,
The power converter characterized by the above-mentioned. The power conversion device according to claim 1,
Carrier generating means for generating a carrier for defining an opening time of a switch in a direction of conducting from the AC motor to at least one positive electrode of the plurality of DC power sources;
An open pulse width command value generating means for generating an open pulse width command value for defining an open time of a switch in a direction of conducting from the AC motor to at least one positive electrode of the plurality of DC power sources;
The switch control means;
By comparing the carrier generated by the carrier generating means with the open pulse width command value generated by the open pulse width command value generating means, the opening time of the switch in the direction of conducting to the positive electrode is determined, and the determined Control to open the switch in the direction of conducting to the positive electrode according to the opening time,
The power converter characterized by the above-mentioned. In the power converter device according to any one of claims 1 to 3,
Further comprising voltage detection means for detecting voltages of the plurality of DC power supplies,
The switch control means;
Controlling to open a switch in a direction of conduction to at least one positive electrode of the plurality of DC power sources in the charging path of the lower voltage,
The power converter characterized by the above-mentioned. In the power converter device according to any one of claims 1 to 4,
Voltage pulse width command value correcting means for correcting a voltage pulse width command value based on a time for opening a switch in a direction to conduct to at least one positive electrode of the plurality of DC power supplies and a sign of a motor current;
The power converter characterized by further comprising. The power conversion device according to claim 5,
The voltage pulse width command value correcting means is
Only when the sign of the motor current is negative, the voltage pulse width command value is corrected.
The power converter characterized by the above-mentioned. In the power converter of Claim 5 or 6,
The voltage pulse width command value correcting means is
Based on the voltage value of the DC power supply that does not have a path to charge from the AC motor, the voltage value of the DC power supply that has a path to charge from the AC motor, and the time to open the switch in the direction to conduct to the positive electrode, Correct the voltage pulse width command value,
The power converter characterized by the above-mentioned. In the power converter device according to claim 2 or 3,
The opening pulse width command value generating means
Generating the open pulse width command value set below the minimum value of the voltage pulse width command value;
The power converter characterized by the above-mentioned. The power conversion device according to claim 3,
The carrier generated by the carrier generation means is a triangular wave.
The power converter characterized by the above-mentioned. The power conversion device according to claim 3,
The carrier generated by the carrier generating means is a sawtooth wave,
The power converter characterized by the above-mentioned. The power converter according to any one of claims 5, 6, and 7,
The sign of the motor current is a sign of a motor current command value.
The power converter characterized by the above-mentioned. The power converter according to any one of claims 5, 6, and 7,
It further comprises a current measuring means for detecting the motor current,
The sign of the motor current is the sign of the detected motor current detection value.
The power converter characterized by the above-mentioned. In the power converter device according to any one of claims 1 to 12,
Means for adjusting the open pulse width command value based on the charge command value to the DC power source to be charged;
The power converter characterized by further comprising. The power conversion device according to claim 13,
Means for calculating the open pulse width command value based on at least the motor current value and the voltage values of the plurality of DC power supplies;
The power converter characterized by further comprising. The power conversion device according to claim 13 or 14,
The adjustment or calculation of the opening pulse width command value is executed by referring to a map created in advance.
The power converter characterized by the above-mentioned. A method for controlling a power converter that generates a voltage pulse for driving an AC motor from output voltages of a plurality of DC power sources,
Generating and synthesizing the voltage pulse based on the command value of the voltage pulse width using a plurality of switches;
Among the plurality of DC power supplies, in each phase switch in the direction of conduction from the DC power supply to the AC motor, the power supply voltage is lower than or equal to that of the other DC power supplies. At least current flows from the DC power supply to the AC motor. When all the switches of a certain phase are in the ON state, the switch in the direction of conduction from the AC motor to the positive electrode of the DC power supply is opened, and the mode 0 for charging the remaining DC power supplies, and the plurality of DC power supplies Among the switches in each phase in the direction of flowing from the DC power supply to the AC motor, the power supply voltage is lower than or equal to the other DC power supply, and at least the phase switch in which current flows from the DC power supply to the AC motor. When all the switches are in the ON state, the mode is switched continuously to the mode 1 in which the switch in the direction of conducting from the AC motor to the positive electrode of the DC power supply is conducted. And controlling the plurality of switches so as to charge at least one of the DC power source of said plurality of direct current power source,
A control method for a power conversion device having

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