JP4604557B2 - PWM cycloconverter and control method thereof - Google Patents

Description

  The present invention makes it possible to output a voltage as commanded by reducing or effectively correcting the commutation error that occurs during the inter-switch current commutation time, especially when the PWM cycloconverter is in a low current state. The present invention relates to a PWM cycloconverter and a control method thereof.

Since the PWM cycloconverter directly connects each phase of the AC power supply and each phase on the output side with a bidirectional switch with self-extinguishing capability, the three-phase AC power supply is directly converted to any voltage / frequency. It is possible.
However, in order to forcibly switch the current flowing through the switch, a unique switching operation is required. This series of switching operations is called commutation.
As a method of creating this commutation, there is a method of creating based on an output current direction signal obtained by an output current direction detection circuit that determines the direction of the output current flowing out of the switching element.
Also, the actual commutation is generally created in a logic circuit based on the PWM signal output.
However, when actually performing commutation, it is necessary to provide a certain delay time in consideration of the switching time of the switching element. Therefore, an error occurs between the output voltage command that should be output and the output voltage that is actually output.
Further, the error occurs depending on the state of the reference voltage of the power supply, the direction of the output current that becomes the information source of commutation, the magnitude relation of the power supply voltage, and the like.
For such a technical problem, a correction method has been proposed in which the current direction and voltage state are detected by a controller in advance, and the command voltage is corrected in advance to correct an error in the output voltage (see Patent Document 1). ).
JP 2003-309975 A

FIG. 7 is a diagram illustrating a method for creating a commutation operation by a conventional current direction detection method performed by the invention described in Patent Document 1. In FIG.
When the IGBT element has a reverse voltage blocking capability, the bidirectional switch has a configuration in which one arm is constituted by a circuit in which two IGBT elements are connected in reverse parallel as shown in configuration 8 in FIG. In the figure, two are shown.) The connected connection point may be connected to the load motor side, and the other end may be connected to each phase power line on the AC power supply side.
The case where the S1 command / S2 command and the S3 command / S4 command as shown in the figure are input to the gates of the two bidirectional switches will be described as an example.
The current direction signal and the commutation pattern are shown in the table as the state determination pattern 11.
In the table, first, when the state is 1, the pattern 1 is selected.
In the operation of the pattern 1, first, since the current flows in the command S1, the command S2 in which no current flows is turned off, and after a sufficient time has passed, the command S3 in which the current flows next is turned on.
Next, after a time has elapsed since the command S3 was turned on, the command S1 is turned off, and finally the command S4 is entered.
This series of operations completes commutation.
In the state 2, since the direction of the current is reversed, the commands S1 and S2 of the pattern 1 are replaced with the commands S3 and S4 as in the pattern 2.
However, conventionally, since there was only one current direction signal indicating the direction of the current, it was impossible to determine whether the current was a large value or near zero. For this reason, the actual minute current and the polarity of the commutation correction value do not match, which may cause overcompensation.

As described above, the correction method disclosed in Patent Document 1 is effective only when the direction of current can be detected correctly. However, if this detection itself is wrong, overcompensation is caused and voltage error is increased. There was a problem.
The present invention has been made to solve the above-described problems, and is capable of detecting the current direction in the vicinity of the zero current where the current direction is likely to be mistaken, and does not cause overcompensation even in the vicinity of the zero current. An object of the present invention is to provide a PWM cycloconverter that realizes a switching operation that reduces an error and a control method thereof.

In order to solve the above problem, the invention of the PWM cycloconverter according to claim 1 includes an LC power source and an LC filter on the input side, and each phase of the AC power source and each phase on the output side have a self-extinguishing capability. In a PWM cycloconverter that directly connects with a direction switch and PWM-controls an AC power supply voltage with a controller according to an output voltage command and outputs an arbitrary AC and DC voltage, a current detection device that detects an output current of the PWM cycloconverter And a current value detector capable of detecting the absolute value of the current based on the current signal output from the current detection device, wherein the controller has a certain value with an absolute value of the output current of the PWM cycloconverter. in the following cases, turning off the two switches connected in antiparallel constituting the bidirectional switch is turned on earlier time, after a certain time, And wherein the turning on simultaneously turned on should the two switches connected in antiparallel constituting a bidirectional switch.

The invention of the PWM cycloconverter according to claim 2 comprises an AC power supply and an LC filter on the input side, and directly connects each phase of the AC power supply and each phase on the output side with a bidirectional switch having a self-extinguishing capability, In a PWM cycloconverter that performs PWM control of an AC power supply voltage with a controller in accordance with an output voltage command and outputs an arbitrary AC and DC voltage, a current detection device that detects an output current of the PWM cycloconverter, and a current detection device A current direction detection circuit for determining a current direction based on an output current signal; a current value detector capable of detecting an absolute value of a current based on a current signal output from the current detection device; and the current detection device A correction table related to the absolute value of the current signal output from the output voltage command and the controller detects the current direction detector. Switching the order of switching on the basis of the current direction signal, and, when the absolute value of the current signal is small, and performs the correction on the output voltage command by the correction table according to the absolute value.
According to a third aspect of the present invention, in the PWM cycloconverter according to the second aspect, when the current direction detector is configured by hardware, the controller determines the direction of the current signal that determines the correction value. The voltage direction is fetched from the detection result of the current direction detector, and the correction value corresponding to the fetched result is corrected for the voltage command.
According to a fourth aspect of the present invention, in the PWM cycloconverter according to the second aspect, in the case where the current direction detector is configured by hardware, the controller performs the operation of the current direction detector based on the output current signal. The same threshold value as the threshold value is configured by software, and even if the current direction signal is not detected, a direction signal corresponding to the threshold value is generated by software and used as a voltage correction determination signal.
According to a fifth aspect of the present invention, the PWM cycloconverter control method includes an AC power source and an LC filter on the input side, and each phase of the AC power source and each phase on the output side are directly connected by a bidirectional switch having a self-extinguishing capability. In the control method of the PWM cycloconverter that connects and performs PWM control of the AC power supply voltage with the controller according to the output voltage command, and outputs any AC and DC voltage, the output current of the PWM cycloconverter is detected and detected When the absolute value of the output current is calculated based on the output current signal and the absolute value of the output current is not more than a certain value, two switches connected in reverse parallel that constitute the bidirectional switch that is turned on at the same time The switch is turned off, and after a certain time, two switches connected in anti-parallel constituting a bidirectional switch to be turned on next are turned on simultaneously.

According to a sixth aspect of the present invention, there is provided an AC power supply and an LC filter on the input side, and each phase of the AC power supply and each phase on the output side are directly connected by a bidirectional switch having a self-extinguishing capability. In the control method of the PWM cycloconverter that connects and performs PWM control of the AC power supply voltage with the controller according to the output voltage command, and outputs any AC and DC voltage, the output current of the PWM cycloconverter is detected and detected If the direction of the output current and the absolute value of the output current are obtained based on the output current signal, and the absolute value of the current signal is small by the correction table related to the absolute value of the current signal output from the current detection device versus the output voltage command, The output voltage command is corrected by the correction table corresponding to the absolute value.
According to a seventh aspect of the present invention, in the method of controlling a PWM cycloconverter according to the sixth aspect, when the current direction detector is configured by hardware, the controller determines the direction of the current signal that determines the correction value. When determining, a voltage command is taken in as a detection result of the current direction detector, and a correction value corresponding to the fetched result is corrected for the voltage command.
According to an eighth aspect of the present invention, in the control method of the PWM cycloconverter according to the sixth aspect, when the current direction detector is configured by hardware, the controller detects the current direction based on the output current signal. The same threshold value as the threshold value of the detector is configured by software, and even if the current direction signal is not detected, a direction signal corresponding to the current direction signal is created in software and used as a voltage correction determination signal. And

With the configuration as described above, it is possible to reduce an output voltage error particularly in the vicinity of zero current.
Moreover, it is possible to suppress overcompensation due to detection error by accurately correcting the generated voltage error, and to suppress torque ripple of the load motor due to commutation error.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a circuit configuration diagram of a PWM cycloconverter for realizing the first embodiment of the present invention.
In the figure, 1 is a three-phase AC power source, 2 is an input filter, 3 is a matrix cycloconverter main circuit, 4 is a current direction detector group, 5 is a motor as a load, 6 is a gate driver, and 7 is a gate driver 6. The controller according to the present invention. The controller 7 includes a commutation creation logic 7-1, a PWM calculator 7-2, and a current direction detector 7-3.
The PWM cycloconverter has a shape in which a PWM cycloconverter main circuit 3 is connected from a three-phase AC power source 1 via an input filter 2. When driving the motor 5 as a load, the current detector group 4 is usually installed at the output stage of the PWM cycloconverter to detect the output current, and the controller 7 performs current control and overcurrent based on this output current. Provide protection.
The controller 7 performs A / D conversion on the current detected by the current detector group 4, and performs current control by the PWM calculator 7-2. The PWM signal output from the PWM calculator 7-2 is input to the commutation creation logic 7-1 in order to form a commutation operation unique to the PWM cycloconverter. As information for performing the commutation operation, the current direction information detected by the current direction detector 7-3 is required.
An output signal from the controller 7 is output as a bidirectional switch firing signal by the gate driver 6 to drive the bidirectional switch.

2A and 2B are diagrams for explaining the current direction detector 7-3 in FIG. 1. FIG. 2A shows the internal configuration, and FIG. 2B shows the detection of the current direction detector 7-3 in the case of a sine wave current signal. It is a figure which shows the relationship between the signal 1 to perform, and the signal 2.
By comparing the current signal with a positive reference voltage and a negative reference voltage, two types of current direction signal 1 for determining that the current direction is positive and current direction signal 2 for determining that the current direction is negative are created. To do. A current signal having a positive current direction is represented by (1.0), a current signal having a negative current direction is represented by (0.1), and a current signal having a positive reference voltage and a negative reference voltage or less is represented by (0.0).
Therefore, in the case of a sinusoidal current signal as shown in FIG. 2B, the states of the current direction signals 1 and 2 are (1.0), (0.1), and (0.0) 3. There will be a pattern.

FIG. 3 is a diagram showing what PWM pattern is selected based on the current direction signal detected by the current direction detector of FIG.
When the IGBT element has a reverse voltage blocking capability, the configuration of the bidirectional switch is configured as one arm by a circuit in which two IGBT elements are connected in antiparallel as shown in the configuration 8 in FIG. In the figure, two are shown.) The connected connection point may be connected to the load motor side, and the other end may be connected to each phase power line on the AC power supply side.
The case where the S1 command / S2 command and the S3 command / S4 command as shown in the figure are input to the gates of the two bidirectional switches will be described as an example.
The current direction signal and the commutation pattern are shown in the table as a state determination pattern 9.
In the table, first, when the state is 1, the pattern 1 is selected. In the operation of the pattern 1, first, since the current flows in the command S1, the command S2 in which no current flows is turned off, and after a sufficient time has passed, the command S3 in which the current flows next is turned on.
Next, after a time has elapsed since the command S3 was turned on, the command S1 is turned off, and finally the command S4 is entered.
This series of operations completes commutation.
In the state 2, since the direction of the current is reversed, the commands S1 and S2 of the pattern 1 are replaced with the commands S3 and S4 as in the pattern 2.
Further, when the state 3 which is a feature of the first embodiment is detected, the current flowing through the IGBT element is almost zero in the first place, so that it is not necessary to perform a complicated commutation operation like the patterns 1 and 2. In that case, the commands S1 and S2 are simultaneously turned off as in the pattern 3, and after a while, the commands S3 and S4 are simultaneously turned on to complete the switching.
Since it is difficult to accurately determine whether the current is positive or negative near the current zero, using this method makes it possible to perform more accurate switching operations, improving output voltage accuracy near the zero current. Connected.

FIG. 4 is a block diagram showing the inside of the controller for realizing the second embodiment of the present invention.
As shown in FIG. 1, the controller 7 includes a commutation generation logic 7-1, a current direction detector 7-3, and a PWM calculator 7-2 according to the second embodiment.
The voltage command is corrected by the current signal taken in the PWM calculator 7-2. Based on the detected current signal, a correction value is determined from a correction table that has been facilitated in advance. The determined correction value is added to the voltage command to be originally output.
The voltage actually output in response to the voltage command includes an error depending on the direction and absolute value of the current. Therefore, in order to correct this error, an error due to the current value is calculated in advance and a correction value table is created. In the correction table of FIG. 4, the horizontal axis represents the current value and the vertical axis represents the correction value. Therefore, the detected current value is input to this correction table, and the correction is performed by adding or subtracting the output correction value to the voltage command.
This addition can be performed by either a dq axis control system or a three-phase voltage command.
A PWM is created based on the voltage command with these corrections added, and the IGBT element is driven as shown in FIG.

FIG. 5 is a block diagram showing the inside of the controller for realizing the third embodiment of the present invention.
The third embodiment is characterized in that the correction is not made based on the current detected for calculation in the PWM calculator but based on the detection signal of the current direction detector.
The detection result of the current direction detector 7-3 is input to the PWM calculator, and a correction value is determined according to the state and added to the voltage command to perform correction. When the actual current direction signal and the calculated current direction as shown in FIG. 4 are different, the correction is performed in the opposite direction, resulting in overcompensation and increasing the voltage error.
However, if the method as shown in FIG. 5 is used, the commutation is generated and the error is corrected based on the same signal, so that there is an advantage that the correction direction is not mistaken. The actual voltage error has its polarity determined by the direction of current and its value by its absolute value. Further, since the value is the same for a certain current or more, the influence when the direction is wrong due to the current value is large. Therefore, more accurate correction is performed by performing only the direction determination using the actual signal.

FIG. 6 is a block diagram showing the inside of the controller for realizing the fourth embodiment of the present invention.
Here, the current signal taken into the PWM controller is introduced with the same noise removal method as the current direction detector, and the actual current direction signal as described above is different from the calculated current direction. Suppress. That is, since the current direction detector 7-3 is configured by hardware, it is easily affected by actual noise, and therefore a noise removal method such as hysteresis is used. Therefore, by using equivalent hysteresis for the current direction discriminator, the difference from the output of the current direction detector 7-3 can be suppressed as a result.

FIG. 2 is a circuit configuration diagram of a PWM cycloconverter for realizing the first embodiment of the present invention. 1A and 1B are diagrams for explaining the current direction detector 7-3 of FIG. 1, in which FIG. 1A shows its internal configuration, and FIG. 1B shows a signal 1 detected by the current direction detector 7-3 in the case of a sine wave current signal. FIG. It is a figure explaining PWM patterns 1-3 concerning the present invention selected by an output current direction signal. The block diagram inside a controller for implement | achieving the 2nd Example of this invention is shown. The block diagram inside a controller for implement | achieving the 3rd Example of this invention is shown. The block diagram inside a controller for implement | achieving the 4th Example of this invention is shown. It is a figure which shows the preparation method of the commutation operation | movement by the conventional current direction detection method.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Three-phase alternating current power supply 2 Input filter 3 PWM cycloconverter main circuit 4 Current direction detector 5 Load motor 6 Gate driver 7 Controller 7-1 Commutation creation logic 7-2 PWM calculator 7-2-1 Current direction discriminator 7 -3 Current direction detector 8 Bidirectional switch configuration 9 State determination pattern 10 Commutation operation creation example 11 Conventional state determination pattern 12 Conventional commutation operation creation example

Claims (8)

The AC power supply is equipped with an LC filter on the input side, and each phase of the AC power supply and each phase on the output side are directly connected by a bidirectional switch with self-extinguishing capability, and the AC power supply voltage is controlled by the controller according to the output voltage command. In a PWM cycloconverter that performs PWM control and outputs an arbitrary AC and DC voltage,
A current detection device that detects an output current of the PWM cycloconverter, and a current value detector that can detect an absolute value of a current based on a current signal output from the current detection device;
When the absolute value of the output current of the PWM cycloconverter is below a certain value, the controller simultaneously turns off the two switches connected in reverse parallel that constitute the bidirectional switch that is turned on first. A PWM cycloconverter characterized in that, after time, two switches connected in reverse parallel constituting a bidirectional switch to be turned on next are simultaneously turned on. The AC power supply is equipped with an LC filter on the input side, and each phase of the AC power supply and each phase on the output side are directly connected by a bidirectional switch with self-extinguishing capability, and the AC power supply voltage is controlled by the controller according to the output voltage command. In a PWM cycloconverter that performs PWM control and outputs an arbitrary AC and DC voltage,
A current detection device that detects an output current of the PWM cycloconverter; a current direction detection circuit that determines a current direction based on a current signal output from the current detection device; and a current signal output from the current detection device A current value detector capable of detecting the absolute value of the current based on the current value, and a correction table relating to the absolute value of the current signal output from the current detection device versus the output voltage command,
When the controller switches the order of switching based on the current direction signal detected by the current direction detector, and the absolute value of the current signal is small, an output voltage command is issued by the correction table according to the absolute value. PWM cycloconverter characterized by performing correction on   When the current direction detector is configured by hardware, when the controller determines the direction of the current signal for determining the correction value, the detection result of the current direction detector is acquired as a voltage command, and the acquired result The PWM cycloconverter according to claim 2, wherein a correction value corresponding to the voltage command is corrected for the voltage command.   When the current direction detector is configured by hardware, the controller configures the same threshold value as that of the current direction detector by software based on the output current signal, and the current direction signal 3. The PWM cycloconverter according to claim 2, wherein even if the signal is not detected, a direction signal corresponding to the signal is generated by software and used as a voltage correction determination signal. The AC power supply is equipped with an LC filter on the input side, and each phase of the AC power supply and each phase on the output side are directly connected by a bidirectional switch with self-extinguishing capability, and the AC power supply voltage is controlled by the controller according to the output voltage command. In a control method of a PWM cycloconverter that performs PWM control and outputs an arbitrary AC and DC voltage,
The output current of the PWM cycloconverter is detected, the output current absolute value is calculated based on the detected output current signal,
When the absolute value of the output current is less than a certain value, the two switches connected in reverse parallel constituting the bidirectional switch that is turned on first are turned off at the same time. A control method for a PWM cycloconverter, wherein two switches connected in antiparallel constituting a direction switch are simultaneously turned on. The AC power supply is equipped with an LC filter on the input side, and each phase of the AC power supply and each phase on the output side are directly connected by a bidirectional switch with self-extinguishing capability, and the AC power supply voltage is controlled by the controller according to the output voltage command. In a control method of a PWM cycloconverter that performs PWM control and outputs an arbitrary AC and DC voltage,
The output current of the PWM cycloconverter is detected, the direction of the output current and the absolute value of the output current are obtained based on the detected output current signal, and the absolute value of the current signal output from the current detection device versus the output voltage command When the absolute value of the current signal is small according to the correction table for the output, the PWM cycloconverter control method corrects the output voltage command using the correction table corresponding to the absolute value.   When the current direction detector is configured by hardware, when the controller determines the direction of the current signal for determining the correction value, the detection result of the current direction detector is acquired as a voltage command, and the acquired result 7. The method of controlling a PWM cycloconverter according to claim 6, wherein a correction value corresponding to the voltage command is corrected for the voltage command.   When the current direction detector is configured by hardware, the controller configures the same threshold value as that of the current direction detector by software based on the output current signal, and the current direction signal 7. The method of controlling a PWM cycloconverter according to claim 6, wherein a direction signal corresponding to the detected signal is generated by software and used as a voltage correction determination signal even if the signal is not detected.

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