JPH10225142A - Dead time compensation circuit for inverter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable to properly compensate for a defect caused by a dead time set for preventing a short between an upper and a lower arm which constitute an inverter. SOLUTION: A dead time compensation circuit 30 has a reverse vectored layer 21 which converts an output current command value of a two-phase rotary coordinate system to that of a two-phase polar coordinate system. The coordinate reference axis of the reverse vectored layer 21 is sin(ωt+ϕ) which leads a reference phase command value sinωt by ϕ. The output of the reverse vectored layer 21 is converted by a two-phase/three-phase converter 22 into an output current command value of a three-phase polar coordinate system and then is given to a current polarity detector 14. Or, the dead time compensation circuit 30 can have such a structure that, by means of an estimation and calculation circuit which estimates the magnitude of an output current command signal of the three-phase polar coordinate system at a time when the signal is ahead by the control delay time and the current polarity detector 14, a current polarity switching time is put ahead by the control delay time.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inverter dead time compensating circuit for compensating an adverse effect of a dead time provided for preventing a short circuit between upper and lower arms of a voltage-type pulse width modulation control inverter.

[0002]

2. Description of the Related Art FIG. 4 is a circuit diagram showing one phase of an inverter for converting a direct current to an alternating current, which is an anti-parallel connection of a gate turn-off thyristor (hereinafter abbreviated as GTO) and a freewheeling diode. Upper arm 5U
And the lower arm 5X, which is also an anti-parallel connection of a GTO and a freewheeling diode, connected in series,
This series circuit is connected to a DC power supply (capacitor) 6.
If the upper arm 5U and the lower arm 5X are alternately turned on and off, an output current _IL flows from a connection point between the two arms to a load (not shown). The polarity of the output current I _L, when the flow to the load direction is a positive polarity and when the reversed flow to the inverter direction as negative. Output voltage V _U appears at the point of attachment of both this time. By the way, upper arm 5
If the U and the lower arm 5X are simultaneously turned on even for a very short time, the DC power supply 6 is short-circuited through both arms, so that an excessive short-circuit current flows through both arms, and there is a risk of destroying the element. This is a so-called arm short circuit. Therefore, by providing a time period during which both the upper arm 5U and the lower arm 5X are turned off, it is possible to reliably prevent an arm short circuit. The period in which both arms are simultaneously turned off is referred to as dead time and is indicated as _Td .

FIG. 5 shows a dead timer in the inverter shown in FIG.
FIG. 4 is an operation waveform diagram showing the operation of each part when a time is provided.
FIG. 5 shows the change of the control signal λ and the carrier wave C.
FIG. 5 shows an ideal change in the gate signal of the upper arm 5U, and FIG.
Fig. 5 shows the ideal change of the gate signal of the lower arm 5X.
5 shows the change of the actual gate signal of the upper arm 5U, FIG.
Is the change of the actual gate signal of the lower arm 5X, and FIG.
Output current is positive (I _LActual output voltage when> 0)
V_UFIG. 5 shows that the output current is negative (I_L<0)
Actual output voltage V_UChange, each shows
I have. That is, the dead time T_dOutput current I_LBut
In the case of positive polarity, a negative voltage appears during the dead time (Fig.
5), output current I_LIs negative when
A positive voltage appears during the im period (see FIG. 5). as a result,
Output current I_LOutput voltage V if_UNegative bias
A difference occurs and the output current I_LOutput voltage V if
_UProduces a positive deviation.

FIG. 6 is a waveform diagram showing output voltage and output current waveforms of a conventional inverter when a dead time is provided in the inverter shown in FIG. FIG. 6 shows the output current I
_L waveform, FIG. 6 is a waveform of the output voltage V _U, both show an ideal waveform in solid line, shows the actual waveform by one-dot chain line. As is apparent in FIG. 6, the output voltage V _U If the polarity is negative the output current I _L is biased to the positive side,
Since the polarity of the output current I _L is positive when the output voltage V _U is biased to the negative side, time t ₁ the current passes through zero,
Output voltage V _U at t ₂ (i.e. when the current polarity is switched)
Causes a discontinuity in the Therefore, the current control is discontinuous at this point, and the current is distorted when passing through the zero point.

The above-mentioned phenomenon can be ignored when the number of switching operations per unit time of the inverter is small. However, when the switching frequency is high as in a pulse width modulation control inverter, the ratio of dead time to the entire time increases. Therefore, the fluctuation of the output voltage greatly affects
Control performance will be degraded. Therefore, in a power converter having a high switching frequency, such as a PWM inverter, a circuit for compensating for a dead time must be provided to suppress a decrease in control performance.

FIG. 7 is a circuit diagram showing a conventional example of a circuit for compensating a dead time of an inverter.
62650. In recent inverters, vector control is generally used to improve the control performance. Therefore, the following description will be made on the assumption that the active current component and the reactive current component are orthogonal to each other. However, for simplicity of illustration, a circuit divided into two orthogonal axes and a three-phase circuit are represented by a single line.

The conventional circuit shown in FIG. 7 converts an output current command value in a two-axis rotating coordinate system into a two-axis polar coordinate system. A two-phase / three-phase converter 12 for converting to a current command value, a current regulator 13 for outputting a control signal λ for making a deviation between the output current command value and the actual output current value zero, and an adder 16 A current polarity detector 14 which comprises an output current control circuit 10 and a comparator and outputs +1 when the polarity of the output current command value is positive and outputs -1 when the polarity is negative. , An amplifier 15 as a compensation amount computing unit having a gain of the correction amount Δλ, and an inverse hysteresis setting unit 17 for setting an operating point of the current polarity detector 14. .

Here, by attaching the reverse hysteresis setting unit 17 to the current polarity detector 14, the polarity of the voltage command value corrected for the polarity switching timing of the actual output current value due to the control delay of the control device. The delay of the switching timing is prevented by arbitrarily setting the polarity switching timing of the correction voltage command value by setting the reverse hysteresis setting unit 17. The inverse vector drain 11 is given sinωt, which is a reference phase command value of the coordinate system when converting from the biaxial rotation coordinate system to the biaxial polar coordinate system. The adder 16 adds the control signal correction ± Δλ output from the amplifier 15 and the control signal λ from the current regulator 13 to output an output voltage command value.

From this output voltage command value and a separately obtained carrier wave C, power conversion is performed by distributing a pulse train generated by pulse width modulation to each arm and performing an on / off operation. FIG. 8 is an operation waveform diagram showing the operation of the conventional circuit in which the influence of the dead time shown in FIG. 7 is compensated. The left half of FIG. 8 shows the case where the output current _IL has a negative polarity, and the right half of FIG. The case where the output current _IL has a positive polarity is shown. FIG. 8 shows the magnitude relationship between the control signal λ and the carrier wave C when the control signal correction Δλ is added or subtracted, FIG. 8 shows an ideal voltage waveform, and FIG. 8 shows the voltage when the influence of the dead time is not corrected. FIG. 8 shows a waveform, and FIG. 8 shows a voltage waveform when the influence of dead time is corrected in the conventional circuit shown in FIG.

FIG. 9 is a voltage waveform diagram showing the effect of the conventional circuit in which the effect of the dead time shown in FIG. 7 is compensated. The dashed line indicates the output voltage waveform when the effect of the dead time is not corrected, and the broken line. Indicates the waveform of the correction voltage, and the solid line indicates the output voltage waveform when the influence of the dead time is corrected.

[0011]

FIG. 10 is an operation waveform diagram showing a dead time compensating operation in the conventional circuit shown in FIG. 7 when the current change rate is large. Although the time t ₁₀ which passes through the zero point is a polar switching time of the theoretical, by reverse hysteresis setting value, polarity switching point is moving from t ₁₀ to t _11.

FIG. 11 is an operation waveform diagram showing the dead time compensating operation in the conventional circuit shown in FIG. 7 when the current change rate is small, and the output current command value passes through the current zero point at t _10. Although time is a polar switching point of theoretical, since the reverse hysteresis setting current change rate becomes the same value as when the large, polarity switching time moving from t ₁₀ to t _12. That is, the polarity is switched at a point earlier than when the current change rate is large.

[0013] That is, in the prior art circuit described above in Figure 7, than the polarity switching time t ₁₀ theoretical polarity switching timing point of the correction voltage command value by the current polarity detector 14 reverse hysteresis setter 17 supplied with the However, depending on the magnitude of the change rate (di / dt) of the current command value, the polarity switching timing of the correction voltage command value with respect to the polarity switching timing of the actual output current value is not constant. There may be inconveniences such as being unable to switch, and being unable to output a correction voltage command value corresponding to the polarity of the output current that changes irregularly.

SUMMARY OF THE INVENTION An object of the present invention is to make it possible to appropriately compensate for a defect caused by a dead time set to prevent a short circuit between upper and lower arms constituting an inverter.

[0015]

In order to achieve the above object, a dead time compensating circuit for an inverter according to the present invention includes an upper arm and a lower arm corresponding to a magnitude relationship between a carrier wave and a control signal. When turning on and off alternately,
The output current signal of the voltage-source inverter for converting the power by preventing the upper and lower arms from being simultaneously turned on by providing a dead time or the polarity of the output current command signal of the voltage-source inverter is detected, and +1 corresponding to the detected polarity is detected. Or a current polarity detector that outputs -1 or -1, a compensation amount calculator that multiplies the output signal of the current polarity detector +1 or -1 by a compensation amount Δλ, and outputs the output signal of the compensation amount calculator to an inverter. A phase correction circuit for advancing the phase of the output current signal or the output current command signal by a control delay time in a dead time compensation circuit of an inverter having an addition circuit for adding to the output voltage signal; The polarity switching point is advanced by the control delay time by inputting the output signal to the current polarity detector.

Alternatively, there is provided a prediction operation circuit for estimating the magnitude of the output current signal or the output current command signal at a time preceding the control delay time by an amount corresponding to the control delay time. Input to the container,
The polarity switching time is advanced by the control delay time.

[0017]

The first invention comprises a phase correction circuit for advancing the phase of the output current signal or the output current command signal in a dead time compensation circuit of an inverter by a control delay time. The polarity switching point is advanced by the control delay time by inputting the output signal to the current polarity detector.

In a vector control inverter which is divided into an active current component and a reactive current component which are orthogonal to each other, an output current command value of a two-axis rotating coordinate system is converted into a two-axis polar coordinate for coordinate conversion dedicated to a dead time compensation circuit. Vector polarizer for converting the output current command value of the two-axis polar coordinate system into an output current command value of the three-phase polar coordinate system, and the output of the three-phase polar coordinate system A dead time compensating circuit is constituted by a current polarity detector for detecting a point in time when the current command value passes through a zero point, and an amplifier as a compensation amount calculator having a gain of the correction amount Δλ. At this time, by giving the coordinate reference axis sin (ωt + φ) to the inverse vector drain, the phase is advanced by φ from the reference phase command value sinωt. Φ is a phase corresponding to the control delay time of the control device. Thereby, the output current command value when converting from the two-axis polar coordinate system to the three-phase polar coordinate system is advanced by the control delay time.

According to a second aspect of the present invention, there is provided a prediction operation circuit for predicting the magnitude of the output current signal or the output current command signal in the inverter dead time compensating circuit at a point preceding the control delay time, and a current polarity detector. , And an amplifier serving as a compensation amount computing unit having a gain of the correction amount Δλ, thereby forming a dead time compensation circuit, and inputting an output signal of the prediction computing circuit to the current polarity detector.
The polarity switching point is advanced by the control delay time.

The predictive calculation circuit calculates the slope between the current value and the previous value from the current value and the previous value of the sampling data of the output current command value, and uses this slope to control the control delay from the current value. By predicting the magnitude of the output current command value ahead by the time and inputting the output signal of this prediction operation circuit to the current polarity detector, the polarity switching point is advanced by the control delay time.

FIG. 1 is a circuit diagram showing a first embodiment of the present invention. An inverse vector drain 11, a two-phase / three-phase converter 12, and a current regulator 1 constituting an output current control circuit 10 are shown.
3, the names, applications, and the like of the adder 16 and the current polarity detector 14 and the amplifier 15 constituting the dead time compensating circuit 30.
The function is the same as that of the conventional circuit described above with reference to FIG.

In the present invention, the dead time compensating circuit 30 is composed of an inverse vector drain 21, a two-phase / three-phase converter 22, a current polarity detector 14, and an amplifier 15. The current command value of the rotating coordinate system is input. Here, it is assumed that the output current command value in the two-axis rotating coordinate system is represented by the following Equation 1. However, d is a d-axis current component (active current component), and q is a q-axis current component (reactive current component).

[0023]

D = I _d q = 0 The output current component is converted into a two-axis coordinate system by a rotation coordinate conversion matrix [A (t)] shown in the following Expression 2.

[0024]

(Equation 2)

The output current command value converted into the two-axis polar coordinate system by Expression 1 is expressed by Expression 3 below.

[0026]

(Equation 3)

Here, α and β in Expression 3 are as shown in Expression 4 below.

[0028]

Α = I _d × cos ωt β = 0 The output current command value of the biaxial polar coordinate system shown in Equation 3 is converted to the three-phase polar coordinate system by the two-phase / three-phase conversion matrix [B] shown in Equation 5 below. Is converted.

[0029]

(Equation 5)

The output current command value converted into the three-phase polar coordinate system is given by the following equation (6).

[0031]

(Equation 6)

Here, a, b, and c shown in Expression 6 are as shown in Expression 7 below.

[0033]

Equation 7] _{a = I d × cosωt b =} I d × cos (ωt - 2π / 3) c = I d × cos (ωt - 4π / 3) Next, when Advances the coordinate reference axis φ radians Equation 1 described above becomes Equation 8 below.

[0034]

(Equation 8)

When the output current command value of the two-axis rotating coordinate system represented by the formula 1 is converted into the three-phase polar coordinate system by using the formulas 8 and 5, the output current command value becomes the following formula 9.

[0036]

A = I _d × cos (ωt + φ) b = I _d × cos (ωt−2π / 3 + φ) c = I _d × cos (ωt−4π / 3 + φ) When Expression 7 is compared with Expression 9 It can be seen that each phase component of the three phases represented by Equation 9 is advanced by φ radians from that of Equation 7. Since φ radian corresponds to the control delay time of the control device, the output current command value can be advanced by the control delay time of the control device by advancing the coordinate reference axis by φ radian.

FIG. 2 is a circuit diagram showing a second embodiment of the present invention. An inverse vector drain 11, a two-phase / three-phase converter 12, and a current regulator 1 constituting an output current control circuit 10 are shown.
3, the names, applications, and the like of the adder 16 and the current polarity detector 14 and the amplifier 15 constituting the dead time compensation circuit 40.
The function is the same as that of the conventional circuit described above with reference to FIG.

According to the present invention, the dead time compensating circuit 40 is composed of the predicting operation unit 31, the two-phase / three-phase converter 22, the current polarity detector 14, and the amplifier 15, and the output is advanced by the control delay time. The current command value is predicted by the prediction calculator 31 and is advanced by the control delay time. This prediction calculator 31
Calculates the slope between two points, the current value and the previous value, from the current value and the previous value of the sampling data of the output current command value, and uses this slope to output the control delay time ahead of the current value by the control delay time. The magnitude of the current command value is predicted, and the output signal of the prediction operation circuit is provided to the current polarity detector 14. As a result, the output current command value input to the current polarity detector 14 is advanced by the control delay time. Therefore, a correction voltage command value having a polarity switching timing that always advances by a fixed time with respect to the polarity switching timing of the output current command value used in the current control system can be obtained. The output voltage command value is obtained by adding the correction voltage command value and the output signal of the current controller 13 by the adder 16.

FIG. 3 is an operation waveform diagram for explaining the operation of the circuit of the second embodiment shown in FIG. In FIG. 3, the previous value and the current value of the sampling data are present on the output current command waveform, and the predicted value at the time when the control delay time has elapsed from the current value is predicted on the same output current command waveform.
Since the output current command value predicted waveform from the predicted value at the time the advanced only the response delay time amount is obtained, the time t ₂₀ to the output current command value estimated waveform passes through the zero point is at the polarity switching time after the prediction operation . The time t _20, it is obvious that precedes by your delay time period than the polarity switching time t ₁₀ theoretical (when the output current command value waveform passes through the zero point).

[0040]

The output current is distorted due to the provision of the dead time for preventing the upper and lower arms of the inverter from being short-circuited. In the first invention, the phase of the output current command signal is changed by the control delay time. The phase change timing of the output current command value is always synchronized with the polarity switch timing of the actual output current value even if the rate of change of the output current command value changes. Even if the polarity changes irregularly, a correction voltage command value corresponding to this can be output, so that even if the rate of change of the output current fluctuates, distortion near the output current passing through the zero point can be greatly improved. The effect is obtained. In the second invention, the same effect as that of the first invention is obtained by providing the prediction operation circuit for predicting the magnitude of the output current command signal at the time preceding the control delay time by the control delay time. Even when the value includes the negative phase current component, the polarity switching timing of the correction voltage command value always synchronized with the polarity switching timing of the actual output current value can be obtained.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a first embodiment of the present invention.

FIG. 2 is a circuit diagram showing a second embodiment of the present invention.

FIG. 3 is an operation waveform diagram for explaining the operation of the circuit of the second embodiment shown in FIG. 2;

FIG. 4 is a circuit diagram showing one phase of an inverter that converts DC to AC.

FIG. 5 is an operation waveform diagram showing the operation of each unit when a dead time is provided in the inverter shown in FIG. 4;

FIG. 6 is a waveform diagram showing output voltage and output current waveforms of a conventional inverter when a dead time is provided in the inverter shown in FIG. 4;

FIG. 7 is a circuit diagram showing a conventional example of a circuit for compensating a dead time of an inverter.

8 is an operation waveform diagram showing the operation of the conventional circuit in which the influence of the dead time shown in FIG. 7 is compensated.

9 is a voltage waveform diagram showing the effect of the conventional circuit in which the influence of the dead time shown in FIG. 7 has been compensated.

10 is an operation waveform diagram showing a dead time compensation operation in the conventional circuit shown in FIG. 7 when the current change rate is large.

11 is an operation waveform diagram showing a dead time compensation operation in the conventional circuit shown in FIG. 7 when the current change rate is small.

[Explanation of symbols]

 5U Upper arm 5X Lower arm 6 DC power supply 10 Output current control circuit 11,21 Inverted vector drain 12,22 Two-phase / three-phase converter 13 Current regulator 14 Current polarity detector 15 Amplifier as compensation amount calculator 16 Addition Unit 17 reverse hysteresis setting unit 20, 30, 40 dead time compensation circuit 31 prediction operation unit

Claims (2)

[Claims] When an upper arm and a lower arm are alternately turned on and off corresponding to the magnitude relationship between a carrier wave and a control signal, a dead time is provided to prevent simultaneous turning on of the upper and lower arms. The polarity of the output current signal of the voltage-source inverter for power conversion or the output current command signal of the voltage-source inverter is detected, and +1 or -1 is determined according to the detected polarity.
, A compensation amount calculator for multiplying the output signal of the current polarity detector +1 or -1 by a compensation amount Δλ, and an output signal of the compensation amount calculator for an output voltage signal of an inverter. An inverter dead time compensating circuit, comprising: a phase correction circuit for advancing the phase of the output current signal or the output current command signal by a control delay time; and an output of the phase correction circuit. A dead time compensation circuit for an inverter, wherein a signal is input to the current polarity detector. 2. A dead time is provided for alternately turning on and off an upper arm and a lower arm in accordance with the magnitude relationship between a carrier wave and a control signal to prevent simultaneous turning on of the upper and lower arms. The polarity of the output current signal of the voltage-source inverter for power conversion or the output current command signal of the voltage-source inverter is detected, and +1 or -1 is determined according to the detected polarity.
, A compensation amount calculator for multiplying the output signal of the current polarity detector +1 or -1 by a compensation amount Δλ, and an output signal of the compensation amount calculator for an output voltage signal of an inverter. A dead time compensating circuit for an inverter, the predicting operation circuit predicting a magnitude of the output current signal or the output current command signal at a time preceding the control delay time by a control delay time. A dead time compensation circuit for an inverter, wherein an output signal of the prediction operation circuit is input to the current polarity detector.