JPH0746855A - Two phase pwm controller for inverter - Google Patents

Abstract

PURPOSE:To reduce switching loss effectively by controlling the PWM signal generating operation for each phase based on a power factor angle determined to follow up the peak value of phase current in an inverter load for a predetermined interval. CONSTITUTION:A phase difference detecting section 30 detects the phase difference between a phase voltage VU and a line current IU, i.e., a power factor phi, for phase U. The power factor phi is fed to a current command generating section 32 which generates current commands IULAMBDA, IVLAMBDA, IWLAMBDA for controlling the switching stop interval of an inverter 10 depending on the power factor phi. An adder 34 generates a line current IV, being fed to a subtractor 18V, based on the line currents IU and IW and the phase difference detecting section 30 operates a power factor phi based on the line voltage VUV and the line current IU. The switching stop interval is set at 60 deg. which is equal not to the interval between the peaks of phase U voltage VU but to the interval between the peaks + or -30 deg. of phase U line current. Phase V and phase W are also subjected to similar processing. This constitution reduces switching loss effectively.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a two-phase PW inverter.
Device for controlling M (pulse width modulation), that is, two-phase PWM
Regarding the control device.

[0002]

2. Description of the Related Art FIG. 13 shows the configuration of a PWM control device according to a conventional example. The device shown in this figure
For example, it constitutes a part of the drive system of an electric vehicle.

The control target of the apparatus shown in this figure is the inverter 10. The inverter 10 converts DC power supplied from a DC power supply (not shown), for example, a main battery mounted on a vehicle, into AC power and supplies the AC power to a load. In this case,
A three-phase AC motor 12 having U, V, and W phases serves as a load of the inverter 10.

The inverter 10 has a switching element having a logarithm corresponding to the number of phases of the load in order to execute such a power conversion operation. The switching element is a high-power switching element such as an IGBT, and is driven by the base drive 14 placed in front of the inverter 10. The base drive 14 drives the inverter 10 based on the PWM signals e _U , e _V , and e _W of each phase supplied from the PWM generator 16.

The PWM generator 16 includes subtractors 18U, 1
A current command generator 20 is placed in front via 8V and 18W. The current command generator 20 supplies current commands I _U ^{^} , I _V ^{^} , and I _W ^{^} to the control device in this figure. The subtractors 18U, 18V, and 18W include the current commands I _U ^{^} , I _V ^{^} , and I _W ^{^} supplied from the current command generator 20 as well as the current sensors 22U, which are provided corresponding to the respective phases of the motor 12.
Line currents I _U , I _V detected by 22 V and 22 W,
Enter I _W. The subtractors 18U, 18V, 18W subtract the latter from the former and supply the result to the PWM generator 16. The PWM generator 16 includes subtractors 18U, 18V, 18
It has PI converters 24U, 24V, 24W for converting the output of W into voltage commands e _0U , e _0V , e _0W . The voltage commands e _0U , e _0V , e _0W obtained by the PI conversion units 24U, 24V, 24W are the comparators 26U, 26V, 2
Input to 6W respectively. Further, the comparator 26U, 26V, 26W has a carrier wave e _S from the oscillator 28.
Is being supplied. Comparators 26U, 26V, 26
W compares both, and the resulting voltage is PWM for each phase
The signals e _U , e _V , and e _W are supplied to the base drive 14.

FIG. 14 shows the contents of normal PWM control executed with reference to the phase voltage. As shown in this figure, in normal PWM control, a carrier wave e _S having a predetermined waveform such as a triangular wave is compared with each phase voltage command e _0U , e _0V , e _0W, and each phase PWM signal e _U, e _V, e _W is generated. The output voltages V _U , V _V , V _W of each phase from the inverter 10 to the motor 12 have a pulse width modulation waveform as shown in FIG. 14, and the line voltage of the motor 12, for example, the UV line voltage V _UV is a sine wave. The voltage is similar to a wave.

Such PWM control is performed by the inverter 10
Is a widely used driving method. In recent years, for example, Proceedings of the Annual Meeting of the Institute of Electrical Engineers of Japan 1983 [6], April 1983, No. 298, pages 574-575, Kim et al. Have developed two-phase PWM control. In the two-phase PWM control, the number of times of switching is reduced, so that it is possible to reduce switching loss, which is increased as the current increases, such as copper loss.

FIG. 15 shows the contents of the two-phase PWM control executed with the line voltage as a reference. The control shown in this figure can be executed by the device configuration shown in FIG.

As shown in this figure, in the voltage commands e _0U , e _0V , and e _0W in the two-phase PWM control, that value is set to the peak value of the carrier wave e _S for a period of about 60 ° in electrical angle. ing. When such a period is determined, the switching in the inverter 10 is stopped in this period, and as a result, the output voltage of each phase as shown in FIG. 15 is obtained.

[0010]

However, in the conventional two-phase PWM control, the switching stop period is fixedly set near the peak of the voltage as shown in FIG. Therefore, when the phase difference between the current and the voltage is large, that is, when the power factor of the load of the inverter is reduced, the effect of reducing the switching loss is not so large. In a remarkable case, since the switching is performed at the maximum current, the loss is hardly reduced. Furthermore, when a motor is considered as the load of the inverter, the power factor of the motor fluctuates due to an increase in its rotation speed, an increase in torque, and the like. Therefore, when driving such a load, the switching loss is not significantly reduced even if the switching stop period is fixed and set at the time of the peak voltage.

The present invention has been made to solve the above problems, and an object thereof is to make it possible to suitably reduce the switching loss by following the current peak during the switching stop period. To do.

[0012]

In order to achieve such an object, a two-phase modulation PWM control device for an inverter according to the present invention is configured so that switching of each phase of the inverter is stopped alternately for a predetermined period. Means for generating a PWM signal and supplying it to the inverter as a signal for controlling switching; means for detecting a phase voltage and line current for at least one of the phases to obtain a power factor angle that is a phase difference between the two; Means for controlling the generation operation of each phase PWM signal based on the obtained power factor angle so as to follow the peak of the phase current flowing through the load.

The two-phase modulation PW of the inverter of the present invention
The M control device detects a state of a load of the inverter and a means for generating a PWM signal of each phase so that the switching of each phase of the inverter is alternately stopped for a predetermined period and supplying the inverter as a signal for controlling the switching. A means for obtaining a power factor based on the detected state, and a means for controlling the generation operation of each phase PWM signal based on the obtained power factor so that the above period follows the peak of the line current flowing through the load of the inverter. It is characterized by being provided.

[0014]

According to the present invention, each phase PWM signal is generated and the inverter switching is controlled so that the switching of each phase of the inverter is alternately stopped for a predetermined period, that is, the two-phase PWM control is executed. It At that time, the phase voltage and the line current are detected for at least one of the phases, and the phase difference (power factor angle) between them is obtained.
The obtained power factor angle is used for controlling the generation operation of each phase PWM signal. This control is executed so that the switching stop period of each phase of the inverter follows the peak of the line current flowing through the load of the inverter. Therefore, in the present invention, since the switching stop period follows the peak of the current, it is possible to preferably suppress the switching loss that increases as the current increases.

Further, in the present invention, as the means for obtaining the power factor, not only the means for detecting the phase voltage and the line current but also the means for detecting the load state of the inverter can be used. The load of the inverter, for example, the state of the motor can be estimated from the rotation speed and torque. In the present invention, the power factor is obtained based on the load state thus detected, and the follow-up control of the switching stop period is executed based on the obtained power factor. By executing such control, in the present invention, the switching loss reduction control according to the load state of the inverter is preferably realized.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described below with reference to the drawings. The same components as those in the conventional example shown in FIGS. 13 to 15 are designated by the same reference numerals and the description thereof will be omitted.

FIG. 1 shows the configuration of a control device according to the first embodiment of the present invention. In this embodiment, U
A phase difference detection unit 30 that detects a phase difference between the phase voltage V _U and the line current I _U , that is, a power factor angle φ is provided for each phase. The power factor angle φ output from the phase difference detection unit 30 is supplied to the current command generation unit 32, and the current command generation unit 32 controls the switching stop period of the inverter 10 according to the power factor angle φ. Current commands I _U ^{^} , I _V ^{^} , I _W ^{^}
To generate. Also, in this embodiment, the subtractor 18
The line current I _V input to _V is generated by the adder 34 based on the line currents I _U and I _W. Phase difference detector 3
0 is the power factor angle φ based on the line voltage V _UV and the line current I _U.
Is calculated.

2 to 4 show the contents of the switching stop period follow-up control in this embodiment. In particular, FIG. 2 shows the switching stop period when φ <30 ° (power factor> 0.866), and FIG. 3 shows the switching stop period when φ ≧ 30 ° (power factor ≦ 0.866). Figure 4
Shows the flow of control, respectively.

Considering the U phase as an example, the switching stop period in the conventional two-phase modulation PWM control is fixedly set to the peak of the U phase voltage V _U of the motor 12. That is, the switching stop period was set so that the peak of the U-phase voltage V _U was ± 30 °. In this embodiment, the switching stop period is not the U-phase voltage V _U but the peak ± of the U-phase line current I _U.
Follow-up is set to be a period of 30 °, a total of 60 °.
That is, the switching stop period is set according to the power factor angle φ that is the phase difference between the U-phase voltage V _U and the U-phase line current I _U ,
As a result, the switching stop period follows the peak of the U-phase line current I _U. In the present embodiment, this control is also executed for the V phase and the W phase.

As described above, in the present embodiment, since the switching stop period is controlled so as to be near the peak of the line current, for example, I _U , the switching loss which increases with the increase of the current is effective. As a result, effects such as downsizing of the cooling system of the inverter 10 and reduction of heat mass can be realized.

Further, the follow-up control of the switching stop period as shown in FIG. 2 has a predetermined limit. That is, the switching stop period cannot be set beyond the section where the three differential relationship is established, that is, beyond the switching stoppable section shown in the figure. Therefore, when the power factor angle φ is 30 ° or more, as shown in FIG. 3, during the switching stop period, the line current (for example, U phase line current) is changed from the peak of the phase voltage (for example, V phase voltage V _U ). It is set in the range of 60 ° near the peak of I _U ). Such a setting corresponds to setting the switching stop period so that the switching loss is most reduced in the switching stoppable section having a spread of 120 °.

Such control is possible by detecting the power factor angle φ. In FIG. 4, the flow of control in this embodiment is described focusing on the method for detecting the power factor angle (phase difference) φ.

As shown in this figure, in this embodiment, the UV line voltage V _UV is first detected by the phase difference detecting section 30.
And the U-phase line current I _U is measured (100, 102).
The measured line voltage V _UV is converted into a phase voltage V _U (10
4) The phase difference between the obtained U-phase voltage V _U and the U-phase line current I _U , that is, the power factor angle φ is detected (106). The phase difference detection unit 30 uses the detected power factor angle φ as the current command generation unit 32.
Supply to. The current command generator 32 sets this power factor angle φ to 3
It is compared with 0 ° (108), and either process A or B is executed according to the result (110, 112). Process A is an operation when the power factor angle φ is less than 30 °, that is, FIG.
The process B is the follow-up control of the switching stop period, and the process B is the operation when the power factor angle φ is 30 ° or more, that is, the control operation as shown in FIG.

FIG. 5 shows the voltage command e in this embodiment.
_0U, e _0V, the waveform of e _{0 W} is shown. The current command generation unit 32 uses the power factor angle φ detected by the phase difference detection unit 30.
By generating the current commands I _U ^{^} , I _V ^{^} , and I _W ^{^ in accordance} with the above, the voltage commands e _0U , e _0V , e _0W as shown in FIGS. 5A to 5C are generated. This voltage command e _U ,
Each of e _V and e _W includes a switching stop period that follows the power factor angle φ. As shown in FIGS. _6A to 6C, the voltage commands e _0U , e _0V , and e _0W are generated by the carrier wave e _S output from the oscillator 28 and the comparator 26U, respectively.
It is compared at 26V and 26W. The resulting PWM signals e _U , e _V , e _W are supplied to the base drive 14, and as a result, the switching stop period becomes the phase currents I _U , I _V , I _W as shown in FIG. 2 or 3. The follow-up two-phase PWM control is realized.

FIG. 7 shows the two-phase PWM in this embodiment.
The relationship between the voltage command waveform relating to control and the voltage command waveform relating to normal PWM control is shown. As shown in this figure, in this embodiment, the switching stop period is set according to the power factor angle φ. This figure shows φ <3
It is a figure in case of 0 degree.

FIG. 8 shows the configuration of the control device according to the second embodiment of the present invention. The device shown in this figure
This is a configuration in which the function of the phase difference detection unit 30 in the first embodiment is added to the current command generation unit 36. Even in such a configuration, the above-mentioned effects can be obtained.

FIG. 9 shows the configuration of the control device according to the third embodiment of the present invention, and FIG. 10 shows the control flow thereof.

In this embodiment, the power factor angle φ is not detected on the basis of the line current and the phase voltage (directly the line voltage), but the current command generator 40 is supplied from a controller (not shown). Based on the torque command T and the rotation speed of the motor 12 detected by the rotation speed sensor 38, the ROM 4
The power factor angle φ is obtained by referring to the table above.

That is, as shown in FIG. 10, the torque command generator 40 inputs the torque command T (114),
Further, the rotation speed N is detected (116). The torque command T is a torque command value for the motor 12, that is, a value indicating a torque value to be output from the motor 12 by current control by the inverter 10. Power factor angle φ of motor 12
Generally depends on the state of the motor 12, for example, torque and rotation speed. Therefore, the values of the torque command T and the rotation speed N can be associated with the power factor angle φ of the motor 12. The table stored on the ROM 42 is
5 is a table in which a torque command T and a rotation speed N are associated with a power factor angle φ. In this embodiment, the table on the ROM 42 is referred to by the torque command T and the rotation speed N, and the power factor angle φ is read (118). The read power factor angle φ is subjected to the same determination as in the first embodiment, and the processes A and B are selectively executed.

Therefore, also in this embodiment, the same effects as those of the above-mentioned embodiments can be obtained. Moreover, since the switching stop period can be set according to the state of the motor 12 that is the load of the inverter 10, it is possible to suitably reduce the switching loss according to the state of the motor 12. This leads to improvement of controllability, elimination of the phase difference detection unit 30 for phase difference detection, which leads to cost reduction and speedup of control. In addition, since the change of the conventional device is small, it is easy to realize.

FIG. 11 shows the configuration of a control device according to the fourth embodiment of the present invention. In this embodiment, the phase difference detector 30 is used to detect the power factor angle φ and the power factor angle φ is used to control the carrier wave e _S , thereby realizing the follow-up control of the switching stop period. ing. Therefore, the PWM generation unit 44 includes a carrier wave control unit 46 that controls the oscillation operation of the carrier wave e _S based on the power factor angle φ.

More specifically, in this embodiment, the offset of the carrier wave e _S is controlled based on the power factor angle φ output from the phase difference detecting section 30. That is, the offset is controlled so that the amplitude of the carrier wave e _S matches the amplitude of the voltage command during the switching stop period. Thus, voltage e _0U, e _0V, instead of e _{0 W,} by applying predetermined processing to the carrier e _S, it is possible to realize the follow-up control of the switching stop period.

FIG. 12 shows the configuration of a control device according to the fifth embodiment of the present invention. Also in this example,
The PWM generation unit 48 includes a carrier wave control unit 50, and the carrier wave control unit 50 realizes offset control of the carrier wave e _S , thereby realizing follow-up control to the phase current during the switching stop period. However, the carrier wave control unit 50 in this embodiment does not control the carrier wave e _S based on the power factor angle φ detected by the phase detection unit 30, but rather the torque command T and the rotation supplied from the control device (not shown). Motor 1 detected by the number sensor 38
Information on the power factor angle φ is obtained by referring to the table on the ROM 42 based on the rotation speed of 2.

Therefore, in this embodiment, the same effect as that of the above-mentioned third embodiment can be obtained.

The present invention is not limited to the configuration of each embodiment described above. For example, the inverter 10
The load of is not limited to the motor 12. Furthermore, the power factor angle φ
The phase on which detection is based is not limited to the U phase.
The switching stop period may be less than 60 °.

[0036]

As described above, according to the present invention,
The phase voltage and line current are detected, the phase difference (power factor angle) between them is calculated, and the switching stop period is controlled so as to follow the peak of each phase line current. Therefore, switching loss that increases as the current increases It is possible to effectively reduce the size of the cooling system of the inverter and to reduce the heat mass.

Further, according to the present invention, the state of the load (for example, the motor) of the inverter is detected, and the switching stop period is controlled so as to follow the peak of the line current according to the detection result. Besides, it is possible to obtain the effect of improving the controllability of the load.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a control device according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a switching stop period when the power factor angle φ is less than 30 ° in this embodiment.

FIG. 3 is a diagram showing a switching stop period when the power factor angle φ is 30 ° or more in this embodiment.

FIG. 4 is a diagram showing a control flow in this embodiment.

5A to 5C are diagrams showing voltage command waveforms of respective phases in this embodiment, and FIGS. 5A to 5C are diagrams showing voltage command waveforms of U, V, and W phases, respectively.

FIG. 6 is a diagram showing a generation process of each phase PWM signal in this embodiment, and FIGS. 6 (a) to 6 (c) show U and U, respectively.
It is a figure which shows the PWM signal generation process of V phase and W phase.

FIG. 7: Voltage command waveform and normal PW in this embodiment
It is a figure which shows the relationship of the voltage command waveform in M control.

FIG. 8 is a block diagram showing a configuration of a control device according to a second embodiment of the present invention.

FIG. 9 is a block diagram showing a configuration of a control device according to a third embodiment of the present invention.

FIG. 10 is a diagram showing a control flow in this embodiment.

FIG. 11 is a block diagram showing a configuration of a control device according to a fourth embodiment of the present invention.

FIG. 12 is a block diagram showing a configuration of a control device according to a fifth example of the present invention.

FIG. 13 is a block diagram showing a configuration of a control device according to a conventional example.

FIG. 14: Normal PWM executed with reference to phase voltage
It is a figure which shows the content of control.

FIG. 15 is a two-phase PWM executed with reference to a line voltage.
It is a block diagram which shows the structure of control.

[Explanation of symbols]

 10 Inverter 12 Motor 14 Base drive 16, 44, 48 PWM generator 20, 32, 36, 40 Current command generator 22U, 26V, 22W Current sensor 26U, 26V, 26W Comparator 28 Oscillator 30 Phase difference detector 38 Rotation speed sensor 42 ROM 44, 50 Carrier wave control section φ Power factor angle Switching stoptable section Switching stop period

Claims (2)

[Claims] 1. A means for generating a pulse width modulation signal for each phase so that switching of each phase of the inverter is alternately stopped for a predetermined period and supplying the pulse width modulation signal for each phase to the inverter as a signal for controlling the switching, and at least one of the phases. A means to detect the phase voltage and the line current and obtain the power factor angle that is the phase difference between them, and the pulse width of each phase based on the obtained power factor angle so that the above period follows the peak of the line current flowing to the load of the inverter. A two-phase PWM control device for an inverter, comprising: a unit that controls a generation operation of a modulation signal. 2. A means for generating a pulse width modulation signal for each phase so that the switching of each phase of the inverter is alternately stopped for a predetermined period, and supplying it to the inverter as a signal for controlling the switching, and a state of the load of the inverter. A means for obtaining a power factor based on the detected state and controlling the generation operation of each phase pulse width modulation signal based on the obtained power factor so that the above period follows the peak of the line current flowing in the load of the inverter. A two-phase PWM control device for an inverter, comprising: