JP4220481B2 - PWM inverter device and control method thereof - Google Patents

Description

The present invention is a PWM that converts a DC voltage into an AC voltage by pulse width modulation (PWM).
The present invention relates to an inverter device, and more particularly, to a technique for eliminating disturbance of an output current even at a transient time such as repowering at high speed.

As a prior art, there is a PWM inverter device that controls an output voltage by a combination of an asynchronous bipolar modulation mode and an asynchronous overmodulation mode (see Patent Document 1). There is also a PWM inverter device (see Patent Document 2) that controls an output voltage by a combination of an asynchronous PWM mode and a synchronous PWM mode.

JP-A-7-227085 JP-A-9-261966

In a PWM inverter device used for driving a vehicle, the torque generated by the motor during acceleration or deceleration is constant, so that the fundamental frequency of the output voltage Finv and the output voltage command Vc, as shown in FIG. Control that keeps the ratio constant is common.
The range of the output voltage to be controlled is the entire range from 0 to the voltage having the maximum voltage utilization rate. In order to realize this control, control is performed by combining a plurality of PWM modes. The above prior art is an example of such a control method.
In the low output voltage region, in order to enable continuous control up to the output voltage 0, the asynchronous PWM mode in which the output timing of the voltage pulse does not depend on the phase of the output voltage fundamental wave is used, and in the operation region where the voltage utilization rate is maximum. The output voltage pulse waveform is controlled by a 1 pulse mode in which 180 ° energization with the same polarity as the fundamental wave is applied.

In Japanese Patent Application Laid-Open No. 7-227085, all control is performed in the asynchronous PWM mode except for the one-pulse mode. In this method, when the output cycle of the voltage pulse is sufficiently short compared to the cycle of the output voltage fundamental wave, that is, when the number of voltage pulses included in one cycle of the output voltage fundamental wave is sufficiently large, the output of the inverter Stable control with less current disturbance can be executed.
However, in the high output voltage region where the output voltage command is large and the frequency of the output voltage fundamental wave is high, the number of voltage pulses included in one cycle of the output voltage fundamental wave is reduced.
At this time, the output timing of the voltage pulse and the phase of the output voltage fundamental wave are asynchronous,
Low-frequency pulsations occur constantly in the output voltage of the inverter, and stable control cannot be performed.

In JP-A-9-261966, since synchronous PWM control is introduced in the high output voltage region, the output current of the inverter is steady without pulsation.
A transition must be made between the asynchronous PWM mode for controlling the low output voltage region and the synchronous PWM mode for controlling the high output voltage region. During the transition period, asynchronous P
Since the voltage pulse waveform in the WM mode and the voltage pulse waveform in the synchronous PWM mode coexist, the output current waveform of the inverter is somewhat disturbed at the moment of transition.
This disturbance is at a level that is not a problem during normal acceleration or deceleration, but when the transition period is passed in a short time, such as when repowering at high speed, the current jumps greatly, sometimes leading to overcurrent. is there.

An object of the present invention is to provide a PWM inverter device and a control method therefor that include means that does not cause steady pulsation in the output current in the entire operation region, and that does not disturb the output current even during transients such as high-speed repowering. It is to provide.

In order to solve the above problems, in a PWM inverter device including a PWM inverter that converts a DC voltage to an AC voltage by pulse width modulation, in a low output voltage region, an asynchronous bipolar modulation mode in which the voltage is controlled by a bipolar pulse is set to a high output voltage. Asynchronous PWM mode pulse pattern generation means that is in the asynchronous overmodulation mode, which outputs a voltage pulse pattern with the same polarity as the fundamental wave and wider than the voltage pulse near the fundamental zero crossing in the vicinity of the peak of the output voltage fundamental wave, Synchronous PWM that changes the pulse pattern of the output voltage at a predetermined phase of the output voltage fundamental wave in the output voltage region
Synchronous PWM mode pulse pattern generating means to become a mode, and either of the asynchronous bipolar modulation mode and the synchronous PWM mode or the asynchronous overmodulation mode depending on the frequency of the output voltage fundamental wave and the output voltage command in a predetermined output voltage command range The present invention proposes a PWM inverter device comprising a pulse pattern selection means for selecting a pulse pattern and causing a PWM inverter to transition.

In addition, in a PWM inverter device including a PWM inverter that converts a DC voltage to an AC voltage by pulse width modulation, an asynchronous bipolar modulation mode in which the voltage is controlled by a bipolar pulse in the low output voltage region is set, and the output voltage fundamental wave is in the high output voltage region. Asynchronous PW that becomes an asynchronous over-modulation mode that outputs a voltage pulse pattern that has the same polarity as the fundamental wave and a wider width than the voltage pulse near the fundamental zero crossing near the peak
M-mode pulse pattern generation means and synchronous PW which becomes a synchronous PWM mode in which the pulse pattern of the output voltage is changed at a predetermined phase of the output voltage fundamental wave in the high output voltage region
M-mode pulse pattern generation means, 1-pulse mode pulse pattern generation means for energizing the output voltage pulse waveform at 180 ° with the same polarity as the fundamental wave in the operation region where the voltage utilization rate is maximum, and within a predetermined output voltage command range Pulse pattern selection means for selecting one of the pulse patterns of the asynchronous bipolar modulation mode or the one-pulse mode and the synchronous PWM mode or the asynchronous overmodulation mode in accordance with the frequency of the output voltage fundamental wave and the output voltage command, and causing the PWM inverter to transition. A PWM inverter device comprising:

Furthermore, in a control method of a PWM inverter device including a PWM inverter that converts a DC voltage into an AC voltage by pulse width modulation, P for controlling an output voltage
Asynchronous bipolar modulation mode in which the timing of changing the pulse pattern of the output voltage is set independently of the fundamental wave phase of the output voltage and the voltage is controlled by bipolar pulses in the low output voltage region, and the high output voltage region. Asynchronous overmodulation mode that outputs a voltage pulse pattern that is wider than the voltage pulse near the fundamental wave zero cross with the same polarity as the fundamental wave near the peak of the output voltage fundamental wave, and the output voltage fundamental wave in the high output voltage region Synchronous PWM mode that changes the pulse pattern of the output voltage at a predetermined phase, and from the asynchronous bipolar modulation mode to the synchronous PWM mode according to the frequency of the output voltage fundamental wave and the output voltage command in the range of a predetermined high output voltage command Select a pulse pattern in either the asynchronous overmodulation mode or the PWM inverter to transition the PWM inverter. We propose a method of controlling the converter device.

According to the present invention, when a fundamental frequency is lower than a predetermined value in a PWM inverter device having a function of continuously controlling from an output voltage 0 to an output voltage region having a maximum voltage utilization rate by combining a plurality of PWM modes. When the method of transition from the pulse pattern of the asynchronous bipolar modulation mode to the pulse pattern of the synchronous PWM mode in the low output voltage region is selected to stabilize the output current during normal acceleration / deceleration, while the fundamental frequency is greater than the predetermined value Selects the method of transition from the asynchronous bipolar modulation mode pulse pattern in the low output voltage region to the asynchronous overmodulation mode, so there is no steady pulsation in the output current in the entire operation region, and at high speed repowering Thus, it is possible to realize control of the PWM inverter device in which the output current is not disturbed even during a transient state.

Next, the best mode of the PWM inverter device according to the present invention will be described with reference to FIGS.

FIG. 1 is a block diagram showing a system configuration of Embodiment 1 of a PWM inverter device according to the present invention.
The pulse pattern generation means 1 in the asynchronous PWM mode and the pulse pattern generation means 2 in the synchronous PWM mode generate the pulse pattern S1 and the pulse pattern S2 in accordance with the fundamental frequency Finv of the output voltage and the output voltage command Vc. The pulse pattern selection means 3 selects one of the pulse pattern S1 and the pulse pattern S2 as the switching pattern S according to the fundamental frequency Finv of the output voltage. The inverter 4 drives the induction motor 5 with voltage pulses according to the switching pattern S.

As one of the applications of the inverter device, when used for driving a vehicle in combination with an induction motor, in order to keep the torque generated by the induction motor during acceleration or deceleration constant,
In general, as shown in FIG. 2, control is performed so that the ratio between the fundamental frequency Finv of the output voltage and the output voltage command Vc is substantially constant. The range of the output voltage to be controlled is the entire range from 0 to the voltage having the maximum voltage utilization rate. To realize this, a plurality of PWs are used.
Combine M mode.
Asynchronous bipolar modulation that controls the voltage with bipolar pulses, which is a kind of asynchronous PWM mode in which the output timing of the voltage pulse does not depend on the phase of the fundamental voltage of the output voltage, in order to enable continuous control up to the output voltage 0 in the low output voltage range Conventionally, control using a one-pulse mode in which an output voltage pulse waveform is energized at 180 ° having the same polarity as the fundamental wave in an operation region where the voltage utilization rate is maximum is used. A method using an asynchronous over-modulation mode and a method using a synchronous PWM mode such as a 5-pulse mode and a 3-pulse mode are known between the asynchronous bipolar modulation mode and the 1-pulse mode.

Japanese Patent Laid-Open No. 7-227085 listed in the section of the prior art describes a method in which an asynchronous overmodulation mode is interposed between an asynchronous bipolar modulation mode and a one-pulse mode.
Asynchronous overmodulation mode means that the peak of the output voltage fundamental wave has the same polarity as the fundamental wave as shown in FIG. 3 for one phase when a pulse pattern of overmodulation mode is generated by triangular wave comparison PWM. This is a PWM mode in which the voltage pulse pattern is wider than the voltage pulse near the wave zero cross, and is a kind of asynchronous PWM mode.
Since the pulse pattern is obtained by thinning out the pulse corresponding to the peak of the fundamental wave from the pulse pattern of the asynchronous bipolar modulation, it is possible to continuously transition from the asynchronous bipolar modulation mode to the asynchronous overmodulation mode.

In this method, when the output cycle of the voltage pulse is sufficiently shorter than the cycle of the output voltage fundamental wave, that is, when the number of voltage pulses included in one cycle of the output voltage fundamental wave is sufficiently large, the output of the inverter Stable control with less current disturbance can be executed.
However, under operating conditions where the number of voltage pulses included in one cycle of the output voltage fundamental wave is small, such as in the high output voltage region where the output voltage command is large and the frequency of the output voltage fundamental wave is high, the voltage pulse output Since the timing and the phase of the output voltage fundamental wave are asynchronous, low-frequency pulsation constantly occurs in the output voltage of the inverter, and stable control cannot be performed.

On the other hand, Japanese Patent Laid-Open No. 9-261966 uses a synchronous PWM mode to control a high output voltage region. The synchronous PWM mode is a pulse pattern generation method in which the pulse pattern and the phase of the output voltage fundamental wave are synchronized.
An example of the pulse pattern in the synchronous PWM mode is shown in FIG. In the synchronous PWM mode, a stable current with no pulsation is steadily obtained. However, since the pulse pattern is significantly different from the asynchronous bipolar modulation mode that controls the low output voltage region, the asynchronous PWM modulation and the synchronous PWM mode are not used. There is always a transition period.

In the transition period, as shown in FIG. 5, the asynchronous PWM mode and the synchronous PW
Since the voltage pulse waveforms of the M mode are mixed, the output current waveform of the inverter is somewhat disturbed at the moment of transition. This disturbance is not so great during normal acceleration or deceleration, but when the transition period is passed in a short time, such as when repowering at high speed, a large current jumps, sometimes leading to overcurrent. .

1 includes both an asynchronous overmodulation mode and a synchronous PWM mode with respect to an asynchronous bipolar modulation mode for controlling a low output voltage region, and an output voltage command V
When c is in a predetermined range, one is selected with reference to the fundamental frequency of the output voltage.
In the first embodiment, when the fundamental frequency Finv of the output voltage is smaller than the boundary value Fm, the pulse pattern S2 in the synchronous PWM mode is used in order to obtain a steady and stable current.
Select. On the other hand, when Finv is greater than Fm, such as during repowering, the PWM mode switching is eliminated by selecting the pulse pattern S1 in the overmodulation mode,
It is possible to realize startup without current jump.

FIG. 6 is a block diagram showing a system configuration of the second embodiment including a pulse pattern generation means in asynchronous bipolar modulation mode and a pulse pattern generation means in 1 pulse mode.
The asynchronous PWM mode pulse pattern generation means 6 is a pulse pattern generation means common to the asynchronous bipolar modulation mode and the asynchronous overmodulation mode. When the output voltage command Vc is low, the asynchronous PWM mode pulse pattern generation means 6 generates a pulse pattern of the asynchronous bipolar modulation mode. When generating a pulse pattern in asynchronous overmodulation mode.
The pulse pattern selection means 3 selects a PWM mode according to the operating state according to the mapping shown in FIG. In FIG. 7, the boundary voltages Vc1 and Vc2 in the PWM mode are set to constant values. However, they may be made variable according to the fundamental wave frequency Finv of the output voltage. In addition, a region controlled in the asynchronous overmodulation mode may be included in a part of the low voltage region in the synchronous PWM mode.

Here, when the fundamental wave frequency Finv of the output voltage is in the vicinity of the boundary value Fm, it is possible to go back and forth between the asynchronous overmodulation mode and the synchronous PWM mode.
In such a state, pulse patterns of both modes are mixed, and a stable current without pulsation cannot be obtained.

Therefore, the pulse pattern selection means 3 in FIG.
In the state of Vc <Vc1 or Vc> Vc2, the transition between the asynchronous overmodulation mode and the synchronous PWM mode is allowed only through the asynchronous bipolar modulation mode or the one-pulse mode. Allow transition.

FIG. 8 is a PAD (Problem Analysis Diagram) showing an example of an algorithm when the pulse pattern selection means 3 of FIG. 6 is realized by software. The processing of FIG. 8 is executed at every elapse of a certain time, and the case is divided according to the previously selected PWM mode.

If the asynchronous bipolar modulation mode or 1-pulse mode was selected last time, refer to the output voltage command Vc, and if it falls within the range of Vc1 ≦ Vc ≦ Vc2, the fundamental frequency Finv of the output voltage is compared with the boundary frequency Fm Thus, it is determined which of the asynchronous overmodulation mode and the synchronous PWM mode should be selected.
When the previous asynchronous overmodulation mode or synchronous PWM mode is selected, the output voltage command Vc is compared with Vc1 and Vc2, and it is determined whether or not the transition to the asynchronous bipolar modulation mode or the one-pulse mode is possible.
When no transition is made, that is, when Vc1 ≦ Vc ≦ Vc2, the previous PWM mode is selected as it is.

According to the second embodiment, in a PWM inverter device having a function of continuously controlling from an output voltage 0 to an output voltage region where the voltage utilization rate is maximum by a combination of a plurality of PWM modes, the output current is constantly maintained in the entire operation region. It is possible to realize control of a PWM inverter device that does not disturb the output current even during a transient such as during high-speed re-powering without generating a significant pulsation.

The present invention has two types of PWM modes for controlling a high output voltage region: a synchronous PWM mode and an asynchronous overmodulation mode, which is a kind of asynchronous PWM mode, according to the fundamental frequency of the output voltage and the output voltage command. Means for selecting one of the pulse patterns. When the fundamental frequency is lower than the specified value, select the method to transition from the asynchronous bipolar modulation mode in the low output voltage range or the pulse pattern in the single pulse mode in the operating range where the voltage utilization is maximum to the pulse pattern in the synchronous PWM mode. And stabilize the output current during normal acceleration / deceleration.
On the other hand, when the fundamental frequency is greater than the predetermined value, select the method to transition from the asynchronous bipolar modulation mode in the low output voltage region or the pulse pattern in the one-pulse mode in the operation region where the voltage utilization is maximum to the asynchronous overmodulation mode. Thus, switching of the PWM mode is eliminated, and a jump in the output current is prevented.

The figure which shows the structure of Example 1 of the PWM inverter apparatus by this invention. Relationship diagram between fundamental frequency of output voltage of PWM inverter and output voltage command Diagram showing an example of pulse pattern in asynchronous overmodulation mode The figure which shows an example of the pulse pattern of synchronous PWM mode Mixed diagram of asynchronous overmodulation mode and synchronous PWM mode pulse patterns The figure which shows the structure of Example 2 of the PWM inverter apparatus by this invention. The figure which shows the PWM mode which should be selected according to the operating state PAD diagram showing an example of the algorithm of the pulse pattern selection means

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Asynchronous overmodulation mode pulse pattern generation means, 2 ... Synchronous PWM mode pulse pattern generation means, 3 ... Pulse pattern selection means, 4 ... PWM inverter, 5 ...
Induction motor, 6... Asynchronous PWM mode pulse pattern generation means, 7... 1 pulse mode pulse pattern generation means

Claims (3)

P including a PWM inverter that converts DC voltage to AC voltage by pulse width modulation
In the WM inverter device,
Asynchronous bipolar modulation mode in which voltage is controlled by bipolar pulses in the low output voltage region, and wider in the high output voltage region than the voltage pulse near the fundamental wave zero cross with the same polarity as the fundamental wave near the peak of the output voltage fundamental wave Asynchronous PWM mode pulse pattern generation means for an asynchronous overmodulation mode for outputting a voltage pulse pattern;
Synchronous PWM mode pulse pattern generating means that becomes a synchronous PWM mode for changing the pulse pattern of the output voltage at a predetermined phase of the output voltage fundamental wave in the high output voltage region;
When the frequency of the output voltage fundamental wave is low according to the frequency of the output voltage fundamental wave and the output voltage command within a predetermined output voltage command range, the pulse pattern of the asynchronous bipolar modulation mode and the synchronous PWM mode is selected. And a pulse pattern selection means for selecting the pulse pattern of the asynchronous bipolar modulation mode and the asynchronous overmodulation mode when the frequency of the fundamental voltage of the output voltage is high, and causing the PWM inverter to transition. PWM inverter device. P including a PWM inverter that converts DC voltage to AC voltage by pulse width modulation
In the WM inverter device,
Asynchronous bipolar modulation mode in which voltage is controlled by bipolar pulses in the low output voltage region, and wider in the high output voltage region than the voltage pulse near the fundamental wave zero cross with the same polarity as the fundamental wave near the peak of the output voltage fundamental wave Asynchronous PWM mode pulse pattern generation means for an asynchronous overmodulation mode for outputting a voltage pulse pattern;
Synchronous PWM mode pulse pattern generating means that becomes a synchronous PWM mode for changing the pulse pattern of the output voltage at a predetermined phase of the output voltage fundamental wave in the high output voltage region;
Output voltage pulse waveform with the same polarity as the fundamental wave in the operating range where the voltage utilization rate is maximum 1
1 pulse mode pulse pattern generating means for energization at 80 °,
When the frequency of the output voltage fundamental wave is low according to the frequency of the output voltage fundamental wave and the output voltage command in a predetermined output voltage command range, the asynchronous bipolar modulation mode, the synchronous PWM mode, and the one-pulse mode When the frequency of the output voltage fundamental wave is high, select the pulse pattern of the asynchronous bipolar modulation mode, the asynchronous overmodulation mode, and the one-pulse mode,
A PWM inverter device comprising: a pulse pattern selection means for causing the PWM inverter to transition. P including a PWM inverter that converts DC voltage to AC voltage by pulse width modulation
In the control method of the WM inverter device,
As a PWM mode for controlling the output voltage, the timing at which the pulse pattern of the output voltage changes is set independently from the fundamental phase of the output voltage,
Asynchronous bipolar modulation mode in which voltage is controlled by bipolar pulses in the low output voltage region, and the same polarity as the fundamental wave in the vicinity of the peak of the output voltage fundamental wave in the high output voltage region, compared with the voltage pulse in the vicinity of the fundamental zero cross. Asynchronous overmodulation mode that outputs a wide voltage pulse pattern, and synchronous PWM mode that changes the pulse pattern of the output voltage at a predetermined phase of the fundamental voltage of the output voltage in a high output voltage region,
When the frequency of the output voltage fundamental wave is low according to the frequency of the output voltage fundamental wave and the output voltage command in a predetermined high output voltage command range, the pulse patterns of the asynchronous bipolar modulation mode and the synchronous PWM mode are changed. When the frequency of the fundamental voltage of the output voltage is high, the pulse pattern of the asynchronous bipolar modulation mode and the asynchronous overmodulation mode is selected, and the PWM inverter is transitioned. Method.

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