JP2756049B2 - Inverter output voltage error correction device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an output voltage error correction device for an inverter which detects an output voltage error caused by a short-circuit prevention period in the output voltage of the inverter and corrects the error.

[0002]

2. Description of the Related Art FIG. 18 is a block diagram showing a control circuit of a conventional output voltage error correction device of an inverter device disclosed in Japanese Patent Application Laid-Open No. 3-7071. In the figure, 1 is an inverter main circuit, 2 and 3 are reactors and capacitors constituting an AC filter, 4 is a DC power supply, 5 is a load, 6 is a current detector connected in series to an inverter output circuit, and 7 is an inverter main circuit. 1 is a drive circuit, 8 is an AC reference voltage generation circuit for generating a sine wave reference voltage, 9 is an amplifier, and 10 is a PWM modulation circuit composed of a comparison circuit 10a and a carrier wave 10b.

Further, reference numeral 11 denotes a comparison circuit as current polarity judgment means for judging the polarity of the output current detected by the current detector 6, reference numeral 12 denotes a DC voltage sensor for detecting the voltage level of the DC power supply 4, and reference numeral 13 denotes a comparison circuit. 11 is a polarity inversion circuit that inverts the polarity of the output of the DC voltage sensor 12 in accordance with the output state of 11.

Next, the operation will be described. Capacitor 3
, A sine-wave output voltage corresponding to the control output of the PWM modulation circuit 10 is obtained, while the amplifier 9 and the PWM are controlled so that the sine-wave reference of the AC reference voltage generation circuit 8 matches the output voltage. The modulation circuit 10 controls the switching of the bridge-connected transistors of the inverter main circuit 1. At this time, generally, as shown in FIG. 19, overcurrent destruction of the transistor due to delay of the ON / OFF operation between the drive signal (b) and (c) of each transistor with respect to the predetermined PWM signal (a) is avoided. For this reason, a short-circuit prevention period Tb is provided at the time of transition, and all the bipolar transistors in each arm are turned off for a certain period to suspend the output voltage of the inverter device. An error voltage ΔV corresponding to the difference between the voltage value and the ideal inverter device voltage value is generated.

That is, when a current flows from the inverter device to the load 5, the voltage shown by oblique lines decreases during the short-circuit prevention period (FIG. 19 (e)), and conversely, when a current flows from the load 5 to the inverter device. In FIG. 19, a voltage indicated by oblique lines is added during the short-circuit prevention period (FIG. 19D), and each of them becomes an error voltage. As a result, a voltage deviating from an ideal sine wave as indicated by a dashed line in FIG. Will be applied.

Since the error average voltage in the short-circuit prevention period Tb has the same phase and opposite polarity as the output current of the inverter device, first, the output current of the inverter device is detected by the current detector 6, and the polarity is detected by the comparison circuit 11. Determine. The error average voltage corresponds to a time-averaged area of a voltage waveform of an actual inverter and an area of a waveform of an ideal inverter. Further, since the error average voltage is proportional to the DC power supply voltage, when the voltage level of the DC power supply 4 is detected by the DC voltage sensor 12 and applied to the polarity inversion circuit 13, the detected DC input voltage is compared with the comparison circuit. The output is inverted according to the output of No. 11.

That is, the polarity inversion circuit 13 outputs a positive polarity when the current polarity of the output signal of the comparison circuit 11 is positive, and outputs a negative polarity when the current polarity is negative. As a result, a signal having a polarity opposite to that of the error average voltage is obtained at the output of the polarity inversion circuit 13, and this polarity signal is output to the PWM modulation circuit 1
0 is given as a correction signal to automatically correct the output voltage error of the inverter device.

[0008]

Since the output error correction device of the conventional inverter device is constructed as described above, the polarity of the output current of the inverter device is determined by the output current at the zero current. Alternatively, the determination is made by determining the direction of the negative current. However, the current actually output from the inverter main circuit is the same as that shown in FIG.
Since there is a ripple as shown in (B), chattering occurs near the 0 current, and an error easily occurs in the polarity discrimination.
There is a problem that the error voltage cannot be properly corrected.

Further, when the current supplied to the load from the inverter main circuit increases or decreases, a delay occurs in the ON / OFF operation of the transistors constituting the inverter main circuit, and a period during which both the upper and lower arm transistors are actually turned off,
There is a problem that a deviation occurs from the preset short-circuit prevention period, and as a result, the error voltage is not correctly corrected.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and has as its object to provide an output voltage error correction device for an inverter device capable of appropriately correcting the output voltage error of the inverter device. I have.

[0011]

An output voltage error correction device for an inverter device according to the present invention includes current detection means for detecting the output current of the inverter device, and detects the polarity of the current detected by the current detection means. The output voltage of the inverter device determined by the polarity determining means and set based on the frequency command is corrected by the voltage correcting means according to the polarity determination result, and the current polarity determining means sets a threshold value corresponding to the output current. It was made. Further, the threshold value is automatically set according to the output frequency of the inverter device.

Further, the output voltage error correction device of the inverter device according to the present invention includes current detection means for detecting the output current of the inverter device, and the polarity of the current detected by the current detection means is determined by the current polarity determination means. In addition, the output voltage of the inverter device set based on the frequency command is corrected by the voltage correction means according to the polarity determination result, and the correction means includes an arbitrarily set short-circuit prevention period and an actual OFF operation period. And a correction coefficient set from the following.

Further, the output voltage error correction device of the inverter device according to the present invention is provided with current detection means for detecting the output current of the inverter device, and the polarity of the current detected by the current detection means is determined by the current polarity determination means. Determine,
If the output current of the inverter device is outside the threshold with respect to the threshold set for the output current, the output voltage error is corrected based on the polarity of the determined output current. If the output current is within the threshold, the output voltage is corrected based on the polarity of the voltage command. Is provided.

Further, the output voltage error correction device of the inverter device according to the present invention is provided with current detection means for detecting the output current of the inverter device, and the polarity of the current detected by the current detection means is determined by the current polarity determination means. Determine,
If the output current of the inverter device is outside the threshold with respect to the set threshold, the output voltage error is corrected based on the polarity of the determined output current. If the output current is within the threshold, output voltage correction is performed based on the polarity of the voltage command. It is provided with voltage error correction means. Further, a device is provided for changing the current detected by the current detecting means to the magnitude of the current, and the magnitude of the previous threshold value is automatically set according to the magnitude.

[0015]

In the present invention, the output current of the inverter device is detected by the current detector, the polarity of the detected current is determined between a predetermined threshold value, and the error voltage calculated based on the DC power supply. Then, the output voltage is corrected in accordance with the polarity, and the PWM generation means generates a predetermined PWM based on the corrected output voltage to generate a short-circuit prevention period, and corrects the output voltage. Further, an error voltage is corrected based on a preset short-circuit prevention period of the inverter main circuit and an OFF period of the transistor due to an actual operation delay of the transistor, and the output voltage is corrected based on the error voltage.

In the present invention, the output current of the inverter device is detected by the current detector, and if the output current is within a predetermined threshold value, the DC power supply is determined based on the polarity of the voltage command calculated in the inverter device. The error voltage calculated in the above is corrected, and if it is outside the threshold value, the error voltage is corrected based on the determined current polarity, and the PWM generating means generates a predetermined PWM based on the corrected output voltage to short-circuit the upper and lower arms. A prevention period is generated to correct the output voltage.

In the present invention, the output current of the inverter device is detected by the current detector, and if the output current is within a predetermined threshold value, the DC power supply is determined based on the polarity of the voltage command calculated in the inverter device. Is corrected, and if it is outside the threshold, the error voltage is corrected based on the determined current polarity, and P is corrected based on the corrected output voltage.
The WM generation means generates a predetermined PWM to generate an upper and lower arm short prevention period, and corrects the output voltage. Further, according to the means for automatically setting the threshold value according to the magnitude of the output current, the error of the output voltage correction due to the change in the output current is eliminated.

[0018]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. FIG. 1 is an explanatory diagram showing a circuit configuration of the output voltage error correction device of the inverter device according to the first embodiment. In the figure, reference numeral 20 denotes an inverter main circuit formed by bridge-connecting a transistor combined with a diode;
21 is a converter for converting an AC voltage to a DC voltage, 22
Is a capacitor for smoothing the DC voltage, 23 is an induction motor connected to the output side of the inverter main circuit 20, 24 is a current detector provided on the output side of the inverter main circuit 20, and 25 is a frequency command. Output frequency / voltage calculating means for calculating the output frequency and voltage of the inverter main circuit based on the current, a current polarity judging means for judging the polarity of the output current detected by the current detector 24, and a current polarity judging means 27 obtained in advance by calculation. A voltage correcting means for correcting the output voltage based on the error voltage calculated from the DC voltage of the converter 21 and the output of the current polarity determining means 26.
The voltage calculating means 25, the current polarity discriminating means 26 and the voltage correcting means 27 are constituted by software in advance and stored in a microcomputer.

Reference numeral 28 denotes a PWM generator for generating a PWM corresponding to the corrected output voltage, and 29 denotes an upper and lower arm for setting an upper and lower arm short circuit prevention time of the inverter main circuit 20 based on the output of the PWM generator 28. In the short-circuit prevention period generating section, each of the generating sections is configured by a gate array.

Next, the operation of the above embodiment will be described with reference to FIGS. The AC voltage input to the converter 21 is converted to a DC voltage, smoothed by the capacitor 22, and input to the inverter main circuit 20. In the inverter main circuit 20, a bridge-connected transistor is driven based on a drive signal output from the upper and lower arm short-circuit prevention period generation unit 28, and converts a DC voltage into an AC voltage having a predetermined frequency and voltage to convert the DC voltage into an AC voltage. Apply to.

At this time, the output current of the inverter main circuit 20 is detected by the current detector 24, and the output is input to the current polarity determining means 26. On the other hand, as shown in FIG. 4, when the output frequency / voltage calculating means 25 receives the frequency command (S
41) The command value is set as the output frequency f _OUT of the inverter main circuit 20 (S42), and based on this output frequency, the output voltage V _OUT is calculated so that the output voltage / output frequency becomes constant (S43).

When the current polarity discriminating means 26 receives the current positive / negative information and the output frequency f _OUT as shown in FIG. 5 (S51), the current polarity judging means 26 determines the current value from the relationship between the output frequency and the threshold shown in FIG. Is determined (S52) with respect to
The current values a and b which are increased or decreased from the 0 current by the threshold value Δi as shown in FIG. At this time, the threshold Δi is set to be larger than the ripple of the output current depending on the magnitude of the ripple, thereby preventing chattering.
The ripple of the output current apparently changes depending on the output frequency, and its magnitude increases as the frequency increases.

Therefore, it is determined whether or not the current value is larger than the negative threshold value b (S53). If the current value is smaller, the current polarity is set negative (S54). If the current value is larger, it is further determined whether the current polarity is larger than the positive threshold value a. Is determined (S55), and if so, the current polarity is made positive (S56). Then, each threshold a, b
If it is, it is determined whether the current is increasing (S57),
If the current polarity is increasing, the current polarity is determined to be positive (S58), and if the current polarity is decreasing, the current polarity is determined to be negative (S5).
9).

When the polarity of the output current thus obtained is positive, the voltage correction means 27 first receives the calculated output voltage V _OUT from the output frequency / voltage calculation means 25, as shown in FIG. (S61), whereas, the upper and lower arm short-circuit prevention period Tb that is set in advance corresponding to the inverter main circuit 20, and the carrier frequency f _c, and a DC voltage V _DC, the error voltage ΔV ΔV = Tb × V _DC × calculated as f _c (S62). Then, the polarity of the output current, which is the output of the current polarity discriminating means 26, is confirmed (S63). If the current polarity is positive, V _OUT + ΔV is set as the voltage V ′ _OUT actually output by the inverter main circuit 20 (S65). ), If the current polarity is negative, V _OUT -ΔV
, And corrects the output voltage so that the voltage V ′ _OUT is actually output (S64), and based on a signal corresponding to the corrected voltage value, the PWM main unit 20 determines whether the inverter main circuit 20 In step S66, an upper and lower arm short-circuit prevention period is generated so as to output the predetermined voltages, and is output to the inverter main circuit 20.

In the above embodiment, a method of determining the actual threshold value Δi from the relationship between the output frequency and the threshold value shown in FIG. 3 will be described. That is, in the inverter device, the output frequency f _OUT and the output voltage V _OUT are, for example, V _OUT / f
_{When OUT} = constant relation, as the output frequency f _OUT increases, the output voltage V _OUT also increases. On the other hand, since the error voltage ΔV is substantially constant regardless of the output frequency f _OUT , the error voltage ΔV relative to the output voltage V _{OUT is} relatively large.
The ratio of V decreases as the output frequency f _OUT increases. When the output current of the inverter device increases and reaches the negative threshold value b, it is considered that the polarity of the output current has been inverted, and the polarity of the voltage to be corrected is inverted and added. Therefore, the output current changes abruptly when it reaches the negative threshold value b.

At this time, the output frequency f of the inverter device
_{If OUT} is small, the amount of change in the output current is large because the value of the correction voltage with respect to the output voltage V _OUT is large. Even if the threshold value is small, the polarity of the output current goes between positive and negative around 0 (A). And the chattering at the time of polarity determination is prevented. However, if the output frequency f _OUT is large, the ratio of the correction voltage to the output voltage V _OUT is small, so that the output current when the negative threshold b is reached is obtained. Change is small and 0
(A) Since the polarity easily moves between positive and negative in the vicinity, the threshold value is increased to a value sufficiently larger than the ripple of the output current,
Since it is necessary to switch the polarity early to prevent chattering, as shown in the range B of FIG.
_OUT needs to increase the threshold value Δi.

However, even if the output frequency f _OUT becomes very small, the ripple of the output current does not become zero.
As shown in the range A, the threshold value has a certain value or more even when the output frequency f _OUT becomes zero. Also, the output frequency f
_{When OUT} is equal to or higher than the base frequency, the output voltage V _OUT does not change, so that the ratio of the correction voltage to the output voltage V _OUT does not change. Therefore, it is not necessary to change the threshold as shown by C in FIG. Output current decreases and positive threshold a
A similar phenomenon occurs when the threshold is reached.

Next, as a second embodiment, in the operation of the inverter main circuit 20, a time delay actually occurs between the ON operation and the OFF operation of each transistor. That is, each ON / OF of the upper arm transistor and the lower arm transistor
A delay of T _ON and T _OFF occurs as shown in FIG.
Since a deviation occurs in the short-circuit prevention period of the upper and lower arms, that is, the time during which both the upper and lower arm transistors are OFF, the error voltage actually changes. Therefore,
In order to properly correct the error voltage in the operation, it is necessary to further consider the deviation of the ON / OFF operation.

Actually, both the upper and lower arm transistors are O
Since the time during which the FF is performed is Tb- (T _ON -T _OFF ), the coefficient k indicating the relationship with the preset short-circuit prevention period is set.
Is k = Tb− (T _ON −T _OFF ) / Tb. Note that T
_ON and T _OFF are obtained by sampling and measuring the transistor alone in advance, and this relationship is shown in FIG.

Therefore, when the error voltage is calculated by the voltage correcting means 27, the error voltage is further corrected by using the coefficient k obtained in advance, and the error voltage is calculated during the time when the upper and lower arm transistors are actually OFF. The corresponding error voltage is calculated. Then, correcting the output voltage in consideration of the polarity of the output current based on the error voltage,
This is the same as in the first embodiment. The operation in this case will be described with reference to the flowchart shown in FIG.

The voltage to be applied to the induction motor is calculated (S
71), and the error voltage is calculated based on it (S71).
72). Next, a calculation of coefficient × error voltage (ΔV) is performed (S73), and the polarity is determined (S74). Here, when it is determined that the polarity is negative, the voltage actually output is V ′.
_OUT = V _OUT −ΔV (S75) On the contrary, when it is determined that the polarity is positive, the voltage actually output is V ′ _OUT = V
_OUT + ΔV (S76), and V ′ _OUT is output (S77), thereby ending a series of processing.

Incidentally, the voltage for correcting the output voltage of the inverter main circuit 20 may be a value including an error voltage based on a short-circuit prevention period of the upper and lower arm transistors and a forward voltage drop of the upper and lower arm transistors and the diode. Further, the forward voltage drop of each transistor and diode is determined by sampling and measuring in advance. First, when the output current is positive and the upper arm transistor is ON, the output voltage decreases by the forward voltage drop (V _Tr ) of the upper arm transistor, and when the lower arm transistor is ON, the diode The output voltage decreases by the forward voltage drop (V _D ). Therefore, correction is performed by adding (V _Tr + V _D ) / 2 on average. When the output current is negative, the operation is reverse to that when the output current is positive.

Next, a third embodiment will be described. FIG.
FIG. 9 is a circuit diagram showing an output voltage error correction device for an inverter device according to a third embodiment. In the figure, 30 is a current threshold value discriminating means for discriminating whether the absolute value of the output current is larger or smaller than a threshold value set in advance to a predetermined value, 31
Is a voltage command polarity determining means for determining the polarity of the voltage command. The output frequency / voltage calculating means 25, current polarity determining means 26, voltage correcting means 27, current threshold value determining means 30, and voltage command polarity determining means 31 are software. And stored in the microcomputer. The rest of the configuration is the same as the configuration of FIG. 1 describing the first embodiment.

Next, this operation will be described with reference to the flowchart of FIG. The AC voltage input to the converter 21 is converted to a DC voltage, smoothed by the capacitor 22, and input to the inverter main circuit 20. In the inverter main circuit 20, a bridge-connected transistor is driven based on a drive signal output from the upper and lower arm short-circuit prevention period generation unit 28, and converts a DC voltage into an AC voltage having a predetermined frequency and voltage to convert the DC voltage into an AC voltage. Is applied.

First, a voltage command V _OUT is received (S8).
1) The error voltage ΔV is calculated (S82). Then, the output current of the inverter main circuit 20 is detected by the current detector 24, and the output is input to the current threshold value judging means 30. The current threshold value determining means 30 determines whether or not the absolute value of the output current is smaller than a threshold value Δi set to a predetermined value in advance (S
83). Here, when it is determined that the absolute value of the output current is larger than the threshold value, the output of the current detector 24 is input to the current polarity determining means 26, and the polarity of the current is determined (S8).
7). When it is determined that the polarity of the output current is positive, the voltage correction means 27 adds a voltage error ΔV to the voltage command V _OUT to obtain V ′.
_OUT is set as an actual output voltage (S88). Conversely, if the polarity of the output current is determined to be negative, the voltage error ΔV is subtracted from the voltage command V _OUT to make V ′ _{OUT the} actual output voltage (S89).

In step S83, when the current threshold value determining means 30 determines that the absolute value of the output current is smaller than the threshold value Δi, the polarity of the voltage command V _OUT is ignored, ignoring the current polarity. The determination is made by the determination means 31 (S84). If the polarity of the voltage command is determined to be positive, the voltage correction means 27 adds the voltage error ΔV to the voltage command V _OUT to make V ′ _{OUT an} actual output voltage (S86). Conversely, if the polarity of the voltage command is determined to be negative, the voltage correction means 27 subtracts the voltage error ΔV from the voltage command V _OUT to obtain V ′.
_OUT is set as an actual output voltage (S85).

As described above, when the absolute value of the current is smaller than the threshold value, that is, the polarity of the current is not observed when the current exceeds 0, the chattering around the current 0 is ignored, and the voltage error is ignored. Whether to add or subtract ΔV can be determined as shown in FIG.

Next, a fourth embodiment of the present invention will be described. Since the output error correction device of the inverter device in the above embodiment is configured as described above, the correction of the output voltage of the inverter device is performed in a section where chattering occurs near 0 current by a threshold value Δi set to a predetermined value in advance. Is performed by determining the voltage polarity, and determining the current polarity for a current larger than the threshold value Δi.

However, when the output current of the inverter device is small, such as when the motor capacity is too small, the wiring length is long, or the motor temperature is high relative to the capacity of the inverter device, chattering becomes small. As shown in FIG. 13, the threshold value Δi set to a predetermined value with respect to the output current of the inverter device is no longer appropriate, and an error occurs in the polarity determination, and the error voltage cannot be corrected properly.

FIG. 14 is an explanatory diagram showing a circuit configuration of an output voltage error correction device of an inverter device according to a fourth embodiment which solves the above-mentioned problem. In the figure, reference numeral 32 denotes a threshold correction means for correcting a threshold according to the magnitude of the output current;
Is a current value calculating means for calculating the magnitude of the output current from the output current detected by the current detector 24. The output frequency / voltage calculating means 25, current polarity determining means 26, voltage correcting means 27, current threshold value determining means The means 30, the voltage command polarity discriminating means 31, the threshold value correcting means 32 and the current value calculating means 33 are constituted by software and stored in a microcomputer. Other configurations are the same as the configurations in FIGS. 1 and 10 that describe the first and third embodiments.

Next, this operation will be described with reference to the flowchart shown in FIG. The AC voltage input to the converter 21 is converted to a DC voltage, smoothed by the capacitor 22, and input to the inverter main circuit 20. In the inverter main circuit 20, the upper and lower arm short-circuit prevention period generation unit 28
The bridge-connected transistor is driven based on the drive signal output from the inverter, converts a DC voltage into an AC voltage having a predetermined frequency and voltage, and applies the AC voltage to the induction motor 23.

First, the voltage command V _OUT is received (S9).
1 ) The error current ΔV is calculated (S92). Next, the output current of the inverter main circuit 20 is detected by the current detector 24, and the AC amount is directly converted by converting the stator coordinates into the rotor coordinates (dq orthogonal coordinates) according to the following equation (1). From the equation (2) shown below, the magnitude of the output current | I |
Is calculated (S93).

[0043]

(Equation 1)

[0044]

(Equation 2)

When the magnitude of this current is smaller than the reference current | I _o |, the coefficient k given in FIG. 16 is multiplied by a reference threshold Δio according to the following equation (3) with respect to a preset threshold. (S94).

[0046]

(Equation 3)

The current threshold value judging means 30 judges whether the current value is smaller than the set threshold value Δi (S95). here,
When it is determined that the absolute value of the output current is larger than the threshold value, the output of the current detector 24 is input to the current polarity determining means 26, and the polarity of the current is determined (S99). If the polarity of the output current is determined to be positive, the voltage correction means 27 adds the voltage error ΔV to the voltage command V _OUT to obtain a V ′ _OUT block output voltage (S100). Conversely, if the polarity of the output current is determined to be negative, the voltage error ΔV is subtracted from the voltage command V _OUT, and V ′ _OUT is set as the actual output voltage (S101).

In step S95, when the current threshold value judging means 30 judges that the absolute value of the output current is smaller than the threshold value Δi, the current command is ignored and the voltage command V
The polarity of _OUT is determined by the voltage command polarity determining means 31 (S96). If the polarity of the voltage command is determined to be positive, the voltage correction means 27 adds the voltage error ΔV to the voltage command V _OUT to make V ′ _{OUT an} actual output voltage (S98). Conversely, if the polarity of the voltage command is determined to be negative, the voltage correction means 27 subtracts the voltage error ΔV from the voltage command V _OUT to obtain V ′.
_OUT is set as an actual output voltage (S97).

As described above, when the absolute value of the current is smaller than the threshold value, that is, since the polarity of the current is not observed when the current exceeds 0, even if the current is chattered around 0, the chattering is ignored. It is possible to determine whether an error is to be added or subtracted. When the output current is small, the threshold value Δi is corrected as shown in FIG. 17, thereby preventing erroneous polarity determination.

Although the above embodiment has been described using a three-phase induction motor, a multi-phase induction motor having another configuration may be used.

[0051]

As described above, according to the present invention, since the polarity of the output current of the inverter main circuit can be accurately determined, the error voltage based on the short-circuit prevention period can be properly corrected.

Further, since the correction is performed based on the error voltage corresponding to the short-circuit prevention period in the actual operation of the inverter main circuit, a more appropriate output voltage can be obtained.

Further, the error voltage caused by the upper and lower arm short-circuit prevention period is corrected by using either the polarity of the output current of the inverter device or the polarity of the voltage command.
There is an effect that a more appropriate error voltage can be corrected.

The error voltage caused by the upper and lower arm short circuit prevention period is corrected by using either the polarity of the output current of the inverter device or the polarity of the voltage command, and the threshold value for switching between the output current polarity determination and the voltage command polarity determination is set. Correction based on the magnitude of the output current has the effect of making it possible to correct the error voltage appropriately.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a schematic configuration of an output voltage error correction device of an inverter device according to the present invention.

FIG. 2 is a graph showing a waveform of an output current of an inverter main circuit according to the present invention.

FIG. 3 is a graph showing a relationship between an output frequency and a threshold according to the present invention.

FIG. 4 is a flowchart showing the operation of the output frequency / voltage calculating means according to the present invention.

FIG. 5 is a flowchart showing the operation of the current polarity discriminating means according to the present invention.

FIG. 6 is a flowchart showing the operation of the voltage correction means according to the present invention.

FIG. 7 is a waveform chart showing the operation of the upper and lower arm transistors according to the present invention.

FIG. 8 shows an OF of the upper and lower arm transistors according to the present invention;
It is a graph which shows the relationship between F time and a short circuit prevention period.

FIG. 9 is a flowchart showing the operation of the voltage correction means in another embodiment according to the present invention.

FIG. 10 is an explanatory diagram showing a schematic configuration of an output voltage error correction device of an inverter device according to another embodiment of the present invention.

FIG. 11 is a flowchart showing the operation of the voltage correction means shown in FIG.

FIG. 12 is a graph showing output current and voltage command waveforms of the inverter device according to the present invention.

FIG. 13 is a graph showing waveforms of an output current and a voltage command of the inverter device.

FIG. 14 is an explanatory diagram showing a schematic configuration of an output voltage error correction device of an inverter device according to another embodiment of the present invention.

FIG. 15 is a flowchart showing the operation of the voltage correction means shown in FIG.

FIG. 16 is a graph showing a relationship between a current magnitude and a correction coefficient in the present invention.

FIG. 17 is a graph showing a relationship between an output current of an inverter and a threshold according to the present invention.

FIG. 18 is a block diagram showing a schematic configuration of a conventional output voltage error correction device for an inverter device.

FIG. 19 is a waveform diagram showing an operation of a conventional output voltage error correction device of an inverter device.

FIG. 20 is a waveform diagram showing a current voltage of a conventional output voltage error correction device of an inverter device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 20 Inverter main circuit 21 Converter 22 Capacitor 23 Induction motor 24 Current detector 25 Output frequency / voltage calculation means 26 Current polarity discrimination means 27 Voltage correction means 28 PWM generation part 29 Upper and lower arm short circuit prevention period generation part 30 Current threshold value discrimination means 31 Voltage Command polarity determining means 32 Threshold value correcting means 33 Current value calculating means

Claims (4)

(57) [Claims] 1. An output voltage error correction device for an inverter device for correcting an output voltage error caused by a short-circuit prevention period of an output voltage of an inverter device for converting a direct current to an alternating current, wherein a current detection for detecting an output current of the inverter device. Means, a current polarity determining means for determining the polarity of the output current of the inverter device detected by the current detecting means, and an output voltage of the inverter device set based on a frequency command and a determination result of the current polarity determining means. And a voltage correcting means for correcting the output voltage according to the current polarity. The current polarity determining means sets a threshold value for the output current.
And set a current value increased or decreased from the zero current by the threshold value.
By determining the current polarity, the threshold
Automatically set according to the output frequency of the inverter device. 2. An output voltage error correction device for an inverter device for correcting an output voltage error caused by a short-circuit prevention period of an output voltage of an inverter device for converting a direct current to an alternating current, wherein a current detection for detecting an output current of the inverter device. Means, current polarity determining means for determining the polarity of the output current of the inverter device detected by the current detecting means, and the output voltage of the inverter device set based on the frequency command and the determination result of the current polarity determining means. Voltage correction means for inputting and correcting the output voltage according to the current polarity, wherein the voltage correction means comprises a short-circuit prevention period arbitrarily set in advance.
Both the upper and lower arm transistors actually turn off.
The inverter based on the correction factor set from the
Corrects the output voltage error of the device from the theoretical value and the true value of the error
And correcting the output voltage accordingly. 3. An output voltage error correction device for an inverter device for correcting an output voltage error caused by a short-circuit prevention period of an output voltage of an inverter device for converting a direct current to an alternating current, wherein a current detection for detecting an output current of the inverter device. Means, current polarity determining means for determining the polarity of the output current of the inverter device detected by the current detecting means, and current threshold value determining means for determining whether the value of the output current is larger or smaller than a preset threshold value When, a voltage command polarity discriminating means for discriminating the polarity of the voltage command, and to determine the polarity of the detected current, is set for the output current
The output current of the inverter device is outside the threshold
If this is the case, the output voltage error is compensated by the determined polarity of the output current.
Performs positive and outputs within the threshold value according to the polarity of the voltage command
An output voltage error correction device for an inverter device, which performs voltage correction . 4. An output voltage error correction device for an inverter device for correcting an output voltage error caused by a short-circuit prevention period of an output voltage of an inverter device for converting a direct current to an alternating current, wherein a current detection for detecting an output current of the inverter device. Means, current polarity determining means for determining the polarity of the output current of the inverter device detected by the current detecting means, and current threshold value determining means for determining whether the value of the output current is larger or smaller than a set threshold value. A voltage command polarity determining means for determining the polarity of the voltage command; a current value calculating means for calculating the magnitude of the output current from the output current detected by the current detecting means; and an output current calculated by the current value calculating means. And a threshold value correcting means for correcting the threshold value based on the magnitude .
If the output current of the inverter device is outside the threshold value,
The output voltage error is corrected based on the polarity of the output current.
Output voltage correction according to the polarity of the voltage command if within the threshold
And the output of the inverter device
An output voltage error correction device for an inverter device, wherein the output voltage error correction device automatically corrects according to the magnitude of a current .