JP2007020250A - Power converter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power converter which can perform high-speed power distribution ratio control, while reducing sounds, vibrations or losses generated from the power converter or a motor. <P>SOLUTION: The power converter outputs a pulsating AC voltage generated from a multioutput DC power supply (10) that outputs a voltage of three or more potentials, including a common potential; and the output voltage from its multilevel power supply comprises a voltage distribution (power control) means (44) for controlling the power distribution ratio, i. e. the ratio of power extracted from the voltage of each potential outputted from the multilevel power supply to follow up a target value, and a means for outputting 100% of electrical amount outputted from a power converter from any potential voltage within the time of 1 PWM period as a target value of power distribution ratio, from a first power distribution ratio target value given to the power control means, and making the power outputted from other potential voltage to 0%, thus generating a second power distribution target value, such that the ratio of time average of each potential output power becomes equal to the first power distribution ratio target value within a predetermined time equatl to an integral times of PWM. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a power conversion device, and particularly enables high-speed power distribution ratio control when necessary while reducing sound, vibration, or loss generated from a power converter or a power supply destination motor. It aims at providing such a power converter device.

A configuration for driving a motor with high efficiency and high response using a fuel cell as a main power source is disclosed in Japanese Patent Application Laid-Open No. 2002-118981 (see Patent Document 1). In this example, as shown in FIG. 1, a capacitor is connected in parallel with a fuel cell via a DC-DC converter, and the output efficiency as a power source is controlled by controlling the output voltage of the DC-DC converter. It aims to improve.
JP 2002-118981 A

  However, since this conventional example has a configuration in which a fuel cell and a battery are connected in parallel using a DC-DC converter, there are the following problems. Since a DC-DC converter is used, the size of the system increases and the cost is high. Since the battery voltage is converted by the DC-DC converter and further converted by the inverter and applied to the motor, the loss is large. In view of the above points, the present inventors can control the power supplied from each power source to an arbitrary value while making the motor drive system using a plurality of power sources lower in loss, smaller in size and lower in cost. Has already been developed (Japanese Patent Application No. 2004-316718).

However, in the power conversion device as described above, problems such as vibration, sound, loss due to the change in the power target value are not considered, and depending on the driving situation, the state of sound and vibration may change greatly. , There is a risk of increased sound and vibration and increased loss. In particular, in the case of an electric vehicle application in which the power conversion device is mounted on a passenger car or the like, such sound and vibration are problems that can greatly affect the comfort of passengers.
Therefore, the present invention provides power that enables high-speed power distribution ratio control when necessary while reducing sound, vibration, or loss generated from a power converter or motor in a power converter as described above. An object is to provide a conversion device.

In order to solve the above-described problems, the power conversion device according to the first invention provides:
A multi-output DC power source that outputs a voltage of three or more potentials including a common potential, and a power converter that generates and outputs a pulsed AC voltage (AC output voltage) from the output voltage of the multi-level power source,
Power control means (for example, a circuit) for controlling a power distribution ratio, which is a ratio of power (each potential output power) extracted from each potential voltage output from the multilevel power supply, to follow a target value;
As the target value of the power distribution ratio, 100% of the electric power output from the power converter from any potential voltage is output within the period of 1 PWM period from the first power distribution target value given to the power control means. The second output is such that the electric power output from other electric potential voltages is 0%, and the ratio of the time average of each electric potential output electric power is the same as the first electric power distribution target value within a predetermined time that is an integral multiple of PWM. A power distribution target value pre-processing unit (circuit) that generates a power distribution target value and gives the second power distribution target value to the power control unit as a target value of the power distribution ratio;
It is characterized by providing.

The power converter according to the second invention is
The power distribution target value pre-processing means is
Generating the second power distribution target value by performing PWM processing on the first power distribution target value;
It is characterized by that.

A power converter according to a third aspect of the invention is
The power distribution target value pre-processing means is
Depending on the state of a load (typically a motor) that is the output destination of the AC voltage and / or the state of the multi-output DC power source, the second power distribution target value is processed and the second power distribution target value is processed. The first power distribution target value is not generated, and the first power distribution target value is used as it is as the target value of the power distribution ratio. The through state and the first power distribution target value are processed. The second power distribution target value is generated and the pre-processing execution state in which the second power distribution target value is given to the power control unit as the target value of the power distribution ratio is provided.
It is characterized by that.

The power converter according to the fourth invention is
The power distribution target value pre-processing means is
The frequency of the carrier used when generating the pulse voltage to be applied to the load differs between the case of the through state and the case of the preprocessing implementation state,
It is characterized by that.
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.

  In the first invention, power distribution target value preprocessing means for preprocessing the power distribution target value is provided, and the power distribution target value is set to either 0% or 100% within one PWM period. A second power distribution target value is determined by determining 0% time and 100% time so that the time average value of each potential output power within a predetermined time that is an integral multiple of the cycle is the same as before processing. Is used as the final power distribution target value. By doing so, a PWM pulse is generated from a DC voltage formed by a common potential and one potential other than the common potential within one PWM period, and pulse generation is performed using a potential voltage other than these. Absent. Accordingly, since the number of times of switching in one PWM cycle does not change, the sound and vibration do not change greatly due to the change of the number of times of switching. In addition, since the number of times of switching is constant, loss due to a large change in the number of times of switching can be prevented.

  In the second invention, the power distribution target value pre-processing means generates the second power distribution target value by performing PWM processing on the first power distribution target value. By doing so, the power distribution target value pre-processing means shown in the first invention can be configured easily and simply.

  In the third aspect of the invention, the power distribution target value preprocessing means outputs the first power distribution target value without performing processing (through state) and processing according to the state of the motor and the state of the power supply. The function to switch the state of applying (pre-processing implementation state). In this way, the power distribution target value that has been pre-processed is normally used, and the power distribution target value in the through state can be used when changing the power distribution ratio at high speed. Is capable of performing low-loss operation while preventing generation of sound and vibration, and performing high-speed power distribution control when necessary.

  In the fourth invention, the carrier frequency used when generating the pulse voltage applied to the motor is different depending on whether the power distribution target value preprocessing means is in the through state or in the preprocessing state. did. By doing in this way, the total frequency | count of power converter switching per unit time can be made constant by changing a carrier frequency by the case where high-speed power distribution control is performed, and the case other than that. That is, it is possible to prevent a large change in sound and loss from occurring when high-speed power distribution control is performed and when it is not.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
First embodiment (equivalent to the first and second inventions)
The configuration of the first embodiment of the present invention is shown in FIG. In this embodiment, a multi-output DC power supply 10 composed of a first DC power supply 10a and a second DC power supply 10b, and a power converter 30 for generating a voltage to be applied to a motor using the voltage of the power supply, The motor 20 and the controller 40 that controls the torque of the motor 20 by driving the power converter 30 and controls the distribution ratio of the power supplied from each of the DC power supplies 10a and 10b. In the multi-output DC power source 10, a low potential side terminal of the DC power source 10a and a low potential side terminal of 10b are connected to form a common potential (hereinafter referred to as GND potential). This power supply is a power supply that outputs three potentials, that is, a GND potential, a potential Vdc_a of the DC power supply 10a, and a potential Vdc_b of the DC power supply 10b. The motor 20 is a three-phase AC motor. This motor is driven by an AC voltage output from a power converter 30 described later.

  The power converter 30 is a DC-AC power converter that generates a voltage to be applied to the motor based on three potential voltages output from the multi-output DC power supply 10. As shown in FIG. 4, this power converter is composed of switch means having the same configuration for each phase. This will be described using the U-phase switch means 30U. This switch is switch means for generating a voltage to be output to the U phase of the motor 20. It is a switch that is alternatively connected from among the GND potential, Vdc_a, and Vdc_b, and supplies the necessary voltage to the motor by changing the proportion of time to connect to each potential. The same applies to the V-phase switch means 30V and the W-phase switch means 30W.

  Returning to FIG. 2, the configuration of the control device 40 will be described. Reference numeral 41 denotes torque control means for calculating a command value id * of the motor d-axis current and a command value iq * of the q-axis current from a torque command given from the outside and the rotational speed of the motor. Reference numeral 42 denotes current control means for calculating voltage command values vd * and vq * for matching the dq-axis current command values id * and iq * and the dq-axis current values id and iq. id and iq are obtained from the three-phase currents iu and iv by the three-phase / dq conversion means 48. Reference numeral 43 denotes dq / 3-phase voltage conversion means for converting the dq-axis voltage command values vd * and vq * into three-phase voltage commands vu *, vq * and vw *. 44 is a U-phase voltage generated from the voltage of each power supply in accordance with the distribution target value (rto_pa *, rto_pb *) of the power Pa supplied from the power supply 10a and the power Pb supplied from the power supply 10b. Voltage distribution (power control) means for generating commands vu_a *, vu_b *, V-phase voltage commands vv_a *, vv_b *, W-phase voltage commands vw_a *, vw_b * (hereinafter referred to as voltage commands generated from the power supply 10a) The power supply 10a voltage command and the voltage command generated from the power supply 10b are referred to as the power supply 10b voltage command). 45, the voltage Vdc_a of the power source 10a and the voltage Vdc_b of the power source 10b are input, and the instantaneous modulation rate command mu_a *, which is a standardized voltage command, vu_a *, vu_b *, vv_a *, vv_b *, vw_a *, vw_b *, Modulation rate calculation means for generating mu_b *, mv_a *, mv_b *, mw_a *, mw_b *. Reference numeral 46 denotes a modulation rate correction unit that performs processing before performing PWM on the instantaneous modulation rate command and generates final instantaneous modulation rate commands mu_a_c *, mu_b_c *, mv_a_c *, mv_b_c *, mw_a_c *, and mw_b_c *. 47 is PWM pulse generation means for generating a PWM pulse for turning on / off each switch of the power converter 30 based on the final instantaneous modulation rate command. Reference numeral 49 denotes power distribution preprocessing means that is the center of the present invention. The power distribution target value rto_pa1 * given from the outside is processed to generate power distribution target values rto_pa * and rto_pb * to be given to the 44 voltage distribution means.

  Next, the operation will be described. The power converter 30 is a power converter configured with three arms per phase as shown in FIG. The control device 40 can freely change the proportion of power supplied from the two power sources 10a and 10b according to the command value while controlling the torque of the motor, but performs preprocessing on the power distribution target value. This prevents the sound from changing greatly. In addition, since the total number of switching times per unit time is not changed, the loss can be prevented from changing greatly. That is, it is possible to always drive at the optimum switching frequency.

In FIG. 2, the voltage distribution unit 44 and the standardized voltage command generation unit 45 generate a voltage command value for setting the power distribution to a desired value. The power distribution means 44 performs calculations based on the following principle. In order to change the ratio of the electric power Pa supplied from the power source 10a and the electric power Pb supplied from the power source 10b while controlling the motor torque in accordance with the command value, the following two conditions may be satisfied.
Voltage condition Vu * = Vu_a * + Vu_b *
Vv * = Vv_a * + Vv_b *
Vu * = Vw_a * + Vw_b *
Power condition Pa: Pb = Vu_a *: Vu_b *
Pa: Pb = Vv_a *: Vv_b *
Pa: Pb = Vw_a *: Vw_b *

FIG. 8 shows a U-phase voltage command Vu *, a power supply 10a divided voltage command Vu_a *, and a power supply 10b divided voltage command Vu_b *. When the above two conditions are represented by voltage vectors, the result is as follows.
Voltage condition V * = Va * (Vu_a *, Vv_a *, Vw_a *) + Vb * (Vu_b *, Vv_b *, Vw_b *)
Power condition Pa: Pb = sgn (Va *) | Va * (Vu_a *, Vv_a *, Vw_a *) |
: Sgn (Vb *) (| Vb * (Vu_b *, Vv_b *, Vw_b *) |
However, sgn (Va *) and sgn (Vb *) define the same direction as the voltage vector V as 1 and the opposite direction as -1.
This is expressed as a voltage vector as shown in FIG.

Now, returning to FIG. 2, the operation of the voltage distribution means 44 will be described. If the sum of the power supplied from the two power sources is P,
P = Pa + Pb.
Here, Pa = rto_pa * · P and Pb = rto_pb * · P are defined.
Voltage command vu *, vv *, vw * and distributed power command value rto_pa2 * (= 1−rto_pb2 *) are input to the voltage distribution means 44. From these, the power supply 10a voltage command and the power supply 10b voltage command are obtained by the following calculation.
vu_a * = rto_pa * ・ vu *
vu_b * = rto_pb * ・ vu *
vv_a * = rto_pa * ・ vv *
vv_b * = rto_pb * ・ vv *
vw_a * = rto_pa * ・ vw *
vw_b * = rto_pb * ・ vu *

  Hereinafter, the modulation factor calculating unit 45, the modulation factor correcting unit 46, and the PWM pulse generating unit 47 will be described in detail with reference to FIG. 10, FIG. 11, and FIG. FIG. 10 is a diagram in which one phase portion extracted from the means 45 to 47 in FIG. 2 is extracted. FIG. 11 is a flowchart showing the calculation performed by each means of FIG. FIG. 12 shows a method for generating a PWM pulse. The following description is performed only for the U phase, but the same operation is performed for the V phase and the W phase.

Modulation rate calculation means 45
The modulation factor calculation means 45 performs calculation 2 shown in FIG. By normalizing the U-phase power supply 10a voltage command vu_a * and the power supply 10b voltage command vu_b * with half of each DC voltage, the power supply 10a instantaneous modulation rate command mu_a * and the power supply 10b instantaneous modulation rate command Find mu_b *.
mu_a * = vu_a * / (Vdc_a / 2)
mu_b * = vu_b * / (Vdc_b / 2)

Modulation rate correction means 46
The modulation factor correction means 46 performs calculation 3 shown in FIG. The final instantaneous modulation rate commands mu_a_c * and mu_b_c * are obtained by subtracting the power distribution ratio and the offset corresponding to each power supply voltage from the instantaneous modulation rate command mu_a * for the power supply 10a and the instantaneous modulation rate command mu * _b for the power supply 10b. Ask.
mu_a_c * = mu_a *-| rto_pb * / Vdc_b | / (| rto_pa * / Vdc_a | ・ | rto_pb * / Vdc_b |)
mu_b_c * = mu_b *-| rto_pb * / Vdc_b | / (| rto_pa * / Vdc_a | ・ | rto_pb * / Vdc_b |)

PWM pulse generation means 47
The PWM pulse generation means 47 performs calculation 4 (FIG. 12) shown in FIG. The operation will be described with reference to FIG. First, from the voltage Vdc_a of the power source 10a, the carrier for the power source 10a used when generating the PWM pulse based on the final instantaneous power source modulation factor command mu_a_c * for the power source 10a, and the final instantaneous power source modulation factor command mu_b_c * for 10b. There is a power supply 10a carrier used when generating a PWM pulse based on a power supply 10b voltage command, and these phases are inverted. The mu_a_c * and the carrier for the power source 10a are compared to generate vu_pwm1. Also, mu_b_c * and the power supply 10b carrier are compared to generate vu_pwm2. vu_pwm1, vu_pwm2, and vu_pwm3 (NO of vu_pwm1 and vu_pwm2) are generated. These signals are applied to SW1, SW2, and SW3 in FIG.

  In this embodiment, the time Tp1 for generating a pulse based on the instantaneous modulation factor for the power source 10a and the time Tp2 for generating a pulse based on the instantaneous modulation factor for the power source 10b are changed in accordance with the power distribution ratio. By doing so, it is possible to increase the ON time of the pulse generated from the power supply that extracts the large power up to 1 PWM cycle time and to decrease the ON time of the pulse generated from the power supply that extracts the small power to 0. Even when the ratio of the magnitudes of the two distributed output power target values differs greatly, the power supply voltage can be used effectively.

  However, when the power distribution target value rto_pa * = 0, 1 (or rto_pb * = 1, 0), that is, when all power is extracted from one power supply voltage, one of the pulses of vu_pwm1 and vu_pwm2 disappears. (FIG. 5). When this case is compared with the case where the power distribution target value is other than this value (FIG. 6), the total number of times of switching of SW1, SW2, and SW3 is halved. If the carrier frequency is set to a frequency in the vicinity of the lower limit of the level at which the audible sound does not cause a problem in the latter case, the frequency is halved in the former case, and an audible sound is generated. If the carrier frequency is set to a frequency that does not cause an audible sound problem in the former case, the switching frequency is doubled in the latter case, so that the loss of the switching element increases. Also, the current response is greatly different between the two.

  As means for improving this point, power distribution preprocessing means 49 is provided. The configuration of 49 is shown in FIG. As shown in the figure, a pulse distribution signal rto_pa * of 0/1 is generated for each PWM cycle by PWM using a power distribution target value rto_pa * given from the outside and a carrier having a power control cycle Ts_pwm longer than the PWM cycle. Since the power distribution target command processed in this way can only have a value of 0 or 1, the switching frequency is always constant. Therefore, if the carrier frequency is set to an appropriate value, the problem of audible sound will occur regardless of whether the power distribution target value given from the outside is 0/1 or a value other than 0/1. Absent. In addition, it is possible to prevent a change in loss and a change in current response due to a change in switching frequency.

Second embodiment (equivalent to the first to fourth inventions)
This embodiment differs from the first embodiment in the configuration of the power distribution preprocessing means 49 in FIG. The other parts are the same as in the first embodiment. The configuration of the power distribution preprocessing means 49 is shown in FIG. As can be seen by comparing the power distribution preprocessing means of the second embodiment (FIG. 7) with that of the first embodiment (FIG. 6), the final power distribution target value rto_pa * The power distribution target value rto_pa1 * given from the outside is configured to switch between a case where processing similar to that in the first embodiment is performed and a case where processing is not performed. Normally, the signal in the former case (execution of preprocessing) is output via a path Rt1 by some switch, and if the power control is to be performed at high speed, the signal of the latter signal (no preprocessing is performed) is routed by the switch. Output via Rt2. In the latter case, the carrier frequency is preferably halved to prevent the loss from increasing. By doing as described above, it is possible to perform high-speed power control when necessary while preventing problems of sound, loss, and current responsiveness.

  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 member, each means, each step, etc. can be rearranged so that there is no logical contradiction, and a plurality of members, means, steps, etc. can be combined or divided into one. Is possible.

It is a figure which shows the structure of the conventional motor control system. It is a figure which shows the structure of the control system of a 1st Example. It is a figure which shows a switching pulse in case electric power distribution command value is other than 0/1. It is a figure which shows the structure of a power converter. It is a figure which shows a switching pulse in case an electric power distribution command value is 0/1. It is a figure which shows the structure of the power distribution pre-processing means of a 1st Example. It is a figure which shows the structure of the power distribution pre-processing means of a 2nd Example. It is a figure explaining voltage distribution with a phase voltage waveform. It is a figure explaining voltage distribution by a voltage vector. It is a figure which shows the structure (for 1 phase) of a 1st Example. It is a figure which shows the flow which shows the calculation of each block of FIG. It is a figure which shows the calculation in the PWM pulse production | generation means of 1st Example.

Explanation of symbols

10 Multi-output DC power supply
10a First DC power supply
10b Second DC power supply
20 Motor
30 Power converter
30U switch means
30V switch means
30W switch means
40 Control unit
41 Torque control means
42 Current control means
43 dq / 3-phase conversion means
44 Voltage distribution means
44 Power distribution means
45 Standardized voltage command generation means
45 Modulation rate calculation means
46 Modulation rate correction means
47 Pulse generation means
48 Three-phase / dq conversion means
49 Power distribution pre-processing means

Claims (4)

A multi-output DC power source that outputs a voltage of three or more potentials including a common potential, and a power converter that generates and outputs a pulsed AC voltage from the output voltage of the multi-level power source,
Power control means for controlling a power distribution ratio, which is a ratio of power extracted from each potential voltage output from the multi-level power supply, to follow a target value;
As the target value of the power distribution ratio, 100% of the electric power output from the power converter from any potential voltage is output within the period of 1 PWM period from the first power distribution target value given to the power control means. The second output is such that the electric power output from other electric potential voltages is 0%, and the ratio of the time average of each electric potential output electric power is the same as the first electric power distribution target value within a predetermined time that is an integral multiple of PWM. A power distribution target value pre-processing unit that generates a power distribution target value and gives the second power distribution target value to the power control unit as a target value of the power distribution ratio;
A power conversion device comprising: The power conversion device according to claim 1,
The power distribution target value pre-processing means is
Generating the second power distribution target value by performing PWM processing on the first power distribution target value;
The power converter characterized by the above-mentioned. In the power converter device according to claim 1 or 2,
The power distribution target value pre-processing means is
The second power distribution target value is generated by processing the first power distribution target value according to the state of the load that is the output destination of the AC voltage and / or the state of the multi-output DC power supply. Without processing, the first power distribution target value is directly applied to the power control means as the target value of the power distribution ratio, and the second power distribution is performed by processing the first power distribution target value. A function of generating a target value and switching a pre-processing execution state in which the second power distribution target value is given to the power control means as a target value of the power distribution ratio;
The power converter characterized by the above-mentioned. The power conversion device according to claim 3,
The power distribution target value pre-processing means is
The frequency of the carrier used when generating the pulse voltage to be applied to the load differs between the case of the through state and the case of the preprocessing implementation state,
The power converter characterized by the above-mentioned.

Images