JP2006094629A - Semiconductor power conversion device and its control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a semiconductor power conversion device that does not suffer an excessive current caused by magnetic deviation even if there occurs a large and steep disturbance, and to provide its control method. <P>SOLUTION: The semiconductor power conversion device comprises: a power converter 1 that forwardly or reversely converts the AC power of a load or an AC power supply via a transformer 2; a current detection means 3 that detects an output current of the power converter 1; a current control means 5 that controls the output current; an excited current detection means 4 that directly or indirectly detects an excited current of the transformer 2; a magnetic deviation suppression and control means 6 that prevents the magnetic deviation of the transformer 2 by using the excited current obtained by the excited current detection means 4; and a means 7 that generates a gate pattern of the power converter on the basis of outputs of the current control means 5 and the magnetic deviation suppression and control means 6. When at least either of the output current and the excited current exceeds a prescribed value, a control parameter of the magnetic deviation suppression and control means 6 is changed. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a self-excited semiconductor power conversion apparatus that performs forward conversion or reverse conversion by connecting to an AC power supply or a load, and a control method thereof.

  Conventionally, a semiconductor power conversion device connected to the AC power supply side or the load side via a transformer has been required to take measures against the magnetism of the transformer. This means that if there is even a small amount of direct current in the output of the semiconductor power converter, the direct current voltage will be integrated and the magnetic flux will be biased, preventing the transformer from operating in the saturation region of the iron core and causing overcurrent to flow. It is to do.

  For this reason, a so-called bias suppression control is employed in which the DC component of the exciting current flowing into the transformer is detected by some means and the output voltage is adjusted so that the DC component of the exciting current becomes zero.

In order to detect the direct current component of the excitation current described above, the normal bias suppression control needs to be integrated over one output cycle. For this reason, transients that require a quick response due to large power fluctuations or load disturbances are required. It was not possible to cope with typical bias. As a countermeasure against this, a proposal has been made to devise detection of a stationary part and a transient part of a biased DC component, and to control the output of the semiconductor power conversion device by a combined component of both (see, for example, Patent Document 1). .
Japanese Patent Laid-Open No. 7-298637 (page 5-6, FIG. 1)

  The technique disclosed in Patent Document 1 uses a filter circuit that extracts only a transient component in order to detect a transient portion of the bias. For this reason, the influence of delay due to the filter circuit is considered to be a problem, and since the transient part and the steady part are configured to have the same control input, the control effect is not necessarily sufficient. In other words, there were cases where it was not possible to cope with large and steep power disturbances or load disturbances.

  Accordingly, the present invention has been made in view of the above, and an object of the present invention is to provide a semiconductor power conversion device and a control method therefor that do not lead to overcurrent due to magnetic bias even when there is a large and steep disturbance. is there.

  In order to achieve the above object, a semiconductor power conversion device and a control method thereof according to a first invention of the present invention include a power converter that forward-converts or reverse-converts AC power of an AC power supply or a load via a transformer, Current detection means for detecting the output current of the power converter, current control means for controlling the output current, excitation current detection means for directly or indirectly detecting the excitation current of the transformer, and excitation current detection Based on the outputs of the demagnetization suppression control means for preventing the demagnetization of the transformer using the excitation current obtained by the means, and the current control means and the output of the demagnetization suppression control means, the gate pattern of the power converter In the semiconductor power conversion device comprising the means for generating the bias current, when at least one of the output current and the excitation current exceeds a predetermined value, the control parameter of the demagnetization suppression control means is set. It is characterized in that as further to.

Further, the second invention of the present invention is a power converter that forward-converts or reverse-converts AC power of an AC power source or a load via a transformer, current detection means that detects an output current of the power converter,
Using current control means for controlling the output current based on a current command value, excitation current detection means for directly or indirectly detecting the excitation current of the transformer, and the excitation current obtained by the excitation current detection means A demagnetization suppression control means for preventing the magnetism of the transformer, and a means for generating a gate pattern of the power converter based on outputs of the current control means and the demagnetization suppression control means. In the power conversion device, when at least one of the output current and the excitation current exceeds a predetermined value, the current command value or the control parameter of the current control means is changed.

  According to the present invention, it is possible to provide a semiconductor power conversion device and a control method therefor that do not lead to an overcurrent due to magnetic bias even when there is a large and steep disturbance.

  Embodiments of the present invention will be described below with reference to the drawings.

  Hereinafter, a semiconductor power conversion device according to a first embodiment of the present invention will be described with reference to FIGS. 1 and 2.

FIG. 1A is a block configuration diagram of the semiconductor power conversion device according to the first embodiment of the present invention.

  The AC output of the power converter 1 is connected to a transformer 2, and the output of the transformer 2 is supplied to an AC power supply or a load. In the power converter 1, a main converter is configured by bridge-connecting an arm in which a diode is connected in reverse parallel to a self-extinguishing power device, and DC power (not shown) is supplied to the main converter.

  The output current of the power converter 1 is detected by the current detector 3. An exciting current detector 4 is provided for detecting the exciting current of the transformer 2. The excitation current detector 4 is usually obtained by subtracting the value obtained by converting the output current to the input side from the input current of the transformer 2. The excitation current detector 4 may detect the excitation current or the magnetic flux in the operating state of the transformer 2 directly or indirectly, regardless of the method.

  The output of the current detector 3 is given to the current controller 5. In the current controller 5, a voltage command is given to the gate pattern generator 7 so that the output current detected by the current detector 3 becomes a predetermined current reference (not shown). In addition, as a voltage command to the gate pattern generator 7, there is a case where so-called voltage control is performed together, for example, giving the current reference as a reference for obtaining a predetermined output voltage. .

  The output of the excitation current detector 4 is given to the demagnetization suppression control circuit 6. The demagnetization suppression control circuit 6 sends a correction voltage command to the gate pattern generator 7 so that the current component due to the demagnetization included in the excitation current is zero. give. For example, a proportional integration system is adopted for the bias suppression control circuit 6. Further, the output of the excitation current detector 4 is given to the excess detector 8. The excess detector 8 operates so as to change the control parameter of the bias suppression control circuit 6 when the excitation current exceeds a predetermined value. Hereinafter, the internal configuration of the bias suppression control circuit 6 will be described with reference to FIG.

  The excitation current, which is the output of the excitation current detector 4, is given to the DC amount detection circuit 9, and the DC amount detection circuit 9 calculates the average value of the output voltage of the power converter 1 in one cycle to several cycles to obtain the excitation current. The direct current amount is obtained, and this direct current amount is input to the average controller 10. The average controller 10 outputs a correction voltage command so that the direct current amount becomes zero. The excitation current that is the output of the excitation current detector 4 is given to the dead zone circuit 11. The output of the dead zone circuit 11 becomes an input of the instantaneous controller 12, and the instantaneous controller 12 outputs a correction voltage command so that the output of the dead zone circuit 11 becomes zero.

  The output of the excess detector 8 is given to the dead zone adjustment circuit 14, and the output of the dead zone adjustment circuit 14 is given to the dead zone circuit 11. Hereinafter, the dead zone adjustment operation will be described with reference to FIG.

  FIG. 2 shows the output characteristics of the dead zone circuit 11 with respect to the excitation current as an input. The dead zone circuit 11 during normal operation, that is, when the excess detector 8 is not operating, has an output characteristic having a wide dead zone width B1, as indicated by a broken line in FIG. That is, the instantaneous controller 12 responds sensitively to a small disturbance given to the exciting current to prevent the control from becoming unstable. When the excess detector 8 detects that the excitation current has exceeded a predetermined value, the dead zone circuit 11 switches to an output characteristic having a narrow dead zone width B2 as shown by the solid line in FIG.

  As described above, for example, when a large external disturbance is applied, the dead zone width of the dead zone circuit 11 is narrowed to make the operation of the instantaneous controller 12 sensitive so that the semiconductor power that does not lead to an overcurrent due to bias is generated. A conversion device can be realized.

  The above-described change in the dead band width is normally made to return to the original normal dead band width B1 when the excess detector 8 detects that the excitation current has recovered to a predetermined value or less. When the disturbance from the noise can be predicted in advance, it is possible to suppress the demagnetization more stably by holding the change of the dead band width by a timer for a predetermined time. The control method using this timer is not limited to the first embodiment, and can be applied to all embodiments described later.

  FIG. 3 is a block diagram of a semiconductor power conversion device according to the second embodiment of the present invention. About each part of this Example 2, the same part as each part of the block block diagram of the semiconductor power converter concerning Example 1 of Drawing 1 (a) is shown with the same numerals, and the explanation is omitted. The second embodiment is different from the first embodiment in that the output of the current detector 3 is supplied to the excess detector 8A, and the control parameter of the bias suppression control circuit 6 is changed when the output current exceeds a predetermined value. This is the point that I tried to do.

  In this way, a disturbance that is demagnetized may be detected based on the instantaneous value of the output current instead of the instantaneous value of the exciting current. If detection is performed using the output current, there is an advantage that it is possible to prevent a delay in the excitation current detection circuit, particularly when the load current is small. Note that the output current detection of the second embodiment and the excitation current detection of the first embodiment may be used together using an AND condition or an OR condition.

  FIG. 4 is an internal configuration diagram of the bias suppression control circuit of the semiconductor power conversion device according to the third embodiment of the present invention. About each part of this Example 3, the same part as each part of the internal block diagram of the magnetic-bias suppression control circuit of the semiconductor power converter concerning Example 1 of FIG.1 (b) is shown with the same code | symbol, and the description is abbreviate | omitted. The third embodiment differs from the first embodiment in that a gain adjustment circuit 15 that operates with an excess current signal that is the output of the excess detector 8B is provided instead of the dead zone adjustment circuit 14, and the excitation current or output current is a predetermined value. This is the point that the gain of the instantaneous controller 12 is changed when the value exceeds.

  In the third embodiment, for example, when the gain at the time of overcurrent is switched to a large value, it is possible to more strongly suppress the magnetic bias of the transformer 2 than at the normal time, thereby suppressing the overcurrent. be able to. In addition, by reducing the gain in normal times, excessive response of the bias suppression control due to load fluctuations that occur normally is prevented, and the semiconductor power converter is operated stably.

  FIG. 5 is an internal configuration diagram of the bias suppression control circuit of the semiconductor power conversion device according to the fourth embodiment of the present invention. About each part of this Example 4, the same part as each part of the internal block diagram of the magnetic-bias suppression control circuit of the semiconductor power converter concerning Example 1 of FIG.1 (b) is shown with the same code | symbol, and the description is abbreviate | omitted. The fourth embodiment is different from the first embodiment in that a gain adjustment circuit 16 that operates with an excess current signal is provided instead of the dead band adjustment circuit 14, and when the excitation current or the output current exceeds a predetermined value, the average controller This is the point that the gain of 10 is changed.

  In the fourth embodiment, for example, when the gain at the time of excess current is switched to a large value, as in the case of the third embodiment, it is possible to suppress the magnetic bias of the transformer 2 more strongly than the normal time. Thus, overcurrent can be suppressed. In addition, by reducing the gain in normal times, excessive response of the bias suppression control due to load fluctuations that occur normally is prevented, and the semiconductor power converter is operated stably.

  Further, when applying the method of the fourth embodiment, it is more effective to use in combination with the first or third embodiment that makes the instantaneous control operation sensitive.

  FIG. 6A is a block diagram of a semiconductor power conversion device according to Embodiment 5 of the present invention. About each part of this Example 5, the same part as each part of the block block diagram of the semiconductor power converter device which concerns on Example 1 of Fig.1 (a) is shown with the same code | symbol, and the description is abbreviate | omitted. The fifth embodiment is different from the first embodiment in that the output of the excess detector 8B is input to the current control circuit 5 instead of the bias suppression control circuit 6.

  The internal configuration of the current control circuit 5 is shown in FIG. The current command value is given to the subtracter 18 via the multiplier 17 and compared with the output current detected by the subtractor 18. The output of the subtracter 18 becomes an input of the current controller 19, and the current controller 19 outputs a voltage reference so that the above difference becomes zero. The command value reduction circuit 20 that has received the excess current signal inputs α (α <1) to the multiplier 17 and corrects the current command value to be reduced when the excitation current or the output current exceeds a predetermined value.

  A semiconductor power conversion device capable of preventing overcurrent due to magnetic bias can also be provided by the method shown in the fifth embodiment.

  FIG. 7 is an internal configuration diagram of the current control circuit of the semiconductor power conversion device according to the sixth embodiment of the present invention. About each part of this Example 6, the same part as each part of the internal block diagram of the current control circuit of the semiconductor power converter concerning Example 5 of Drawing 6 (b) is denoted by the same numerals, and the explanation is omitted. The sixth embodiment differs from the fifth embodiment in that the multiplier 17 is omitted, and a gain adjustment circuit 21 that operates by an excess current signal is provided in place of the command value reduction circuit 20, and the current controller 19 is output from this output. The control gain is changed.

  For example, when the gain of the current controller 5 when the current is exceeded is made smaller than the normal gain, it is possible to prevent control interference between the current control and the bias suppression control. That is, when the transformer 2 is in the direction of demagnetization, the gain of the current controller 19 is reduced to make the demagnetization suppression control side dominant, thereby suppressing the demagnetization of the transformer 2 more effectively. And overcurrent due to biasing can be prevented.

  As can be seen from the above description, when the technique of the sixth embodiment is applied, it is more effective when used together with the control for increasing the sensitivity of the demagnetization suppression control as in the first and third embodiments.

  FIG. 8 is a block diagram showing a part of a semiconductor power conversion device according to Embodiment 7 of the present invention.

  In a three-phase semiconductor power conversion device, current control is generally performed on the dq axis, and the configuration of the seventh embodiment is the same as the configuration when the fifth and sixth embodiments are used together. The example implemented independently by q-axis is shown.

  In FIG. 8, the current detector 3 </ b> A decomposes the output current into a d-axis current having the same phase as the voltage and a q-axis current orthogonal thereto, and outputs the result to the current control circuit 5. As the current command, the d-axis current command value and the q-axis current command value are given independently, and the d-axis current detection value and the q-axis current detection value are respectively obtained by the subtractors 18D and 18Q via the multipliers 17D and 17Q, respectively. The outputs are compared and input to the d-axis current controller 19D and the q-axis current controller 19Q. The outputs of the current controller 19D and the current controller 19Q are not shown in the figure, but are converted back into three-phase components and input to the gate pattern generator 7.

  The excess current signal obtained by the excess detector 8 is given to the d-axis command value reduction circuit 20D and the gain adjustment circuit 21D, and the output of the command value reduction circuit 20D is given to the multiplier 17D. The output of the gain adjustment circuit 21D is given to the current controller 19D. Similarly, the excess current signal obtained by the excess detection circuit 8 is given to the q-axis command value reduction circuit 20Q and the gain adjustment circuit 21Q, and the output of the command value reduction circuit 20Q is given to the multiplier 17Q. The output of the gain adjustment circuit 21Q is given to the current controller 19Q.

If comprised as mentioned above, instantaneous demagnetization suppression control in current control can be performed independently for the d-axis and the q-axis. When such separation control is performed, it is not always necessary to perform both d-axis and q-axis instantaneous demagnetization suppression control. For example, when other transformers are inserted on the load side, most of the magnetizing inrush current is an ineffective component. Therefore, it is possible to prevent an overcurrent by reducing the q-axis current command value.

  In this embodiment, the current command value is reduced and the control gain of the controller is changed at the same time. However, it is obvious that either one may be used.

BRIEF DESCRIPTION OF THE DRAWINGS The block block diagram of the semiconductor power converter device which concerns on Example 1 of this invention. Explanatory drawing of the dead zone circuit of the semiconductor power converter device which concerns on Example 1 of this invention. The block block diagram of the semiconductor power converter device which concerns on Example 2 of this invention. The internal block diagram of the demagnetization suppression control circuit of the semiconductor power converter device which concerns on Example 3 of this invention. The internal block diagram of the demagnetization suppression control circuit of the semiconductor power converter device which concerns on Example 4 of this invention. The block block diagram of the semiconductor power converter device which concerns on Example 5 of this invention. The internal block diagram of the current control circuit of the semiconductor power converter device which concerns on Example 6 of this invention. The partial block block diagram of the semiconductor power converter device which concerns on Example 7 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Power converter 2 Transformer 3 Current detector 4 Excitation current detector 5 Current control circuit 6 Demagnetization suppression control circuit 7 Gate pattern generation circuit 8, 8A, 8B Excess detector 9 DC quantity detection circuit 10 Average controller 11 Dead zone Circuit 12 Instantaneous controller 13 Adder 14 Dead band adjustment circuit 15, 16 Gain adjustment circuit 17, 17D, 17Q Multiplier 18, 18D, 18Q Subtractor 19, 19D, 19Q Current controller 20, 20D, 20Q Command value reduction circuit 21, 21D, 21Q Gain adjustment circuit

Claims (10)

A power converter that forward-converts or reverse-converts AC power from the AC power supply or load via a transformer
Current detection means for detecting an output current of the power converter;
Current control means for controlling the output current;
Excitation current detection means for directly or indirectly detecting the excitation current of the transformer;
Using the excitation current obtained by the excitation current detection means, the bias suppression control means for preventing the bias of the transformer,
Means for generating a gate pattern of the power converter based on the outputs of the current control means and the demagnetization suppression control means;
Comprising
The semiconductor power conversion device according to claim 1, wherein when at least one of the output current and the excitation current exceeds a predetermined value, a control parameter of the demagnetization suppression control means is changed. The demagnetization suppression control means includes
A first controller having as input an output of a DC amount detection means for detecting the DC amount from the excitation current;
A second controller that inputs the excitation current into a dead zone circuit with a dead zone and receives the output of the dead zone circuit;
An adder for adding the outputs of the first controller and the second controller;
The semiconductor power conversion device according to claim 1, wherein the control parameter is a dead band width of the dead band circuit. The demagnetization suppression control means includes
A first controller having as input an output of a DC amount detection means for detecting the DC amount from the excitation current;
A second controller that inputs the excitation current into a dead zone circuit with a dead zone and receives the output of the dead zone circuit;
An adder for adding the outputs of the first controller and the second controller;
The semiconductor power conversion device according to claim 1, wherein the control parameter is at least one of a control gain of the first controller and a control gain of the second controller.   2. The semiconductor power conversion device according to claim 1, wherein the change of the control parameter is continued for a predetermined time by a timer. A power converter that forward-converts or reverse-converts AC power from the AC power supply or load via a transformer
Current detection means for detecting an output current of the power converter;
Current control means for controlling the output current based on a current command value;
Excitation current detection means for directly or indirectly detecting the excitation current of the transformer;
Using the excitation current obtained by the excitation current detection means, the bias suppression control means for preventing the bias of the transformer,
Means for generating a gate pattern of the power converter based on the outputs of the current control means and the demagnetization suppression control means;
Comprising
A semiconductor power conversion device, wherein when at least one of the output current and the excitation current exceeds a predetermined value, the current command value or a control parameter of the current control means is changed.   6. The semiconductor power converter according to claim 5, wherein the control parameter is a control gain of a current controller used for the current control means. The current detection means is configured to obtain an output by decomposing the output current into a d-axis current in phase with the output voltage and a q-axis current orthogonal thereto.
The current command value includes a d-axis current command value and a q-axis current command value,
The current control means includes d-axis current control means for controlling the d-axis current;
The d-axis current control means comprises q-axis current control means for controlling the q-axis current independently of the d-axis current control means,
6. The control parameter according to claim 5, wherein the control parameter is at least one of a control gain of a current controller used for the d-axis current control means and a control gain of a current controller used for the d-axis current control means. The semiconductor power conversion device described.   6. The semiconductor power converter according to claim 5, wherein the change of the current command value or the control parameter of the current control means is continued for a predetermined time by a timer. A power converter that forward-converts or reverse-converts AC power from the AC power supply or load via a transformer
Current detection means for detecting an output current of the power converter;
Current control means for controlling the output current;
Excitation current detection means for directly or indirectly detecting the excitation current of the transformer;
Using the excitation current obtained by the excitation current detection means, the bias suppression control means for preventing the bias of the transformer,
In a semiconductor power conversion device comprising: means for generating a gate pattern of the power converter based on outputs of the current control means and the demagnetization suppression control means;
A control method for a semiconductor power conversion device, wherein when at least one of the output current and the excitation current exceeds a predetermined value, a control parameter of the demagnetization suppression control means is changed. A power converter that forward-converts or reverse-converts AC power from the AC power supply or load via a transformer
Current detection means for detecting an output current of the power converter;
Current control means for controlling the output current based on a current command value;
Excitation current detection means for directly or indirectly detecting the excitation current of the transformer;
Using the excitation current obtained by the excitation current detection means, the bias suppression control means for preventing the bias of the transformer,
In a semiconductor power conversion device comprising: means for generating a gate pattern of the power converter based on outputs of the current control means and the demagnetization suppression control means;
A control method for a semiconductor power conversion device, wherein when at least one of the output current and the excitation current exceeds a predetermined value, the current command value or a control parameter of the current control means is changed.

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