JP3395310B2 - Semiconductor power converter - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor power conversion device composed of semiconductor switching elements, and more particularly to a multiplex type semiconductor power conversion device in which a plurality of converters are connected in series via a transformer.

[0002]

2. Description of the Related Art A self-excited multiplex type semiconductor power conversion system composed of a self-extinguishing type semiconductor device is disclosed in Japanese Unexamined Patent Publication No. 56-15097. This power converter is suitable for obtaining high-voltage AC power from low-voltage DC power, for converting large-capacity power with a small-capacity converter, and for removing harmonic components.

Further, a transformer should be arranged on the output side when the output of the self-excited inverter device is electrically insulated and supplied, and when the output voltage is boosted and supplied. In order to solve the problem of magnetism and the problem of DC bias magnetization, a reactor is placed in parallel between the inverter and the transformer, and the voltage command value of the inverter is corrected by the DC component of the current flowing in the reactor. This is disclosed in Japanese Patent Laid-Open No. 4-322170.

However, it has not been known so far that the problem of DC bias magnetism in the transformer in the self-excited multiplex type semiconductor power converter exists and its solution.

[0005]

SUMMARY OF THE INVENTION The present invention adopts a self-excited multiplex type semiconductor power conversion device, and there is a problem of DC bias magnetization in a transformer, and the problem has been heretofore known. The inventors have found that the method applied to the case where there is only one converter and one transformer cannot solve the problem, and have reached the invention.

An object of the present invention is to provide a self-excited multiplex type semiconductor power converter that solves the problem of DC bias magnetism of a transformer that occurs when a plurality of self-excited converters and a plurality of transformers are used. There is.

Another object of the present invention is to provide a self-excited multiplex type semiconductor power conversion device in which variations in DC bias magnetism among a plurality of transformers are prevented.

Another object of the present invention will be apparent from the following description of the embodiments.

[0009]

The feature of the multiplex type semiconductor power converter of the present invention that achieves the above-mentioned object is that the converter uses the average value of the current flowing between each converter. The point is that the output control command of is corrected.
In order to realize this, the current detection means arranged between each converter and each transformer, the average value detection means for detecting the average value of the current detected by each current detection means, and the average value detection means It is necessary to prepare means for correcting the control command of the converter by the output signal.

Another feature of the multiplex type semiconductor power converter of the present invention is that, in addition to the above-mentioned configuration, the DC component of the exciting current of the transformer is derived from each current flowing between each converter and each transformer. Is obtained and is used to correct the control command of each converter. In order to realize this, AC current detection means for detecting the current flowing on the side opposite to the converter of the transformer, and the value obtained by converting the current detected by the AC current detection means into the current flowing on the converter side of the transformer. And the number of exciting current calculating means for calculating the exciting current of each transformer from the current value detected by the current detecting means arranged between each converter and each transformer, and the exciting current calculating means of each exciting current calculating means. Transformer DC component detecting means for detecting the DC component of the exciting current flowing in each transformer from the output signal, and means for correcting the input signal of each pulse generating circuit by the output signal of the transformer DC component detecting means are added. There is a need. In this case, an alternating current detecting means for detecting a current flowing on the side opposite to the converter of the transformer, and a means for calculating a value obtained by converting the current detected by the alternating current detecting means into a current flowing on the converter side of the transformer. Instead of the output signal of the current detection means arranged between each converter and each transformer and the output signal of the average value detection means for detecting the average value of the current detected by each current detection means, each transformer The exciting current may be calculated as the variation amount. In these cases, the DC component of the exciting current flowing through each transformer can be corrected by their average value.

The converter mentioned here is a converter for converting AC power into DC power and an inverter for converting DC power into AC power.

[0012]

The multiple semiconductor power converter of the present invention detects the current flowing through one winding of a plurality of transformers respectively connected to the plurality of converters, and uses the average value to detect the output of the converter. Since the control command is corrected, the current flowing through one winding of each transformer can be accurately detected, and as a result, DC bias magnetization of the transformer can be prevented with high control accuracy.
Further, if the DC component is detected from the average value and the output control command of the converter is corrected using the detected DC component, the DC bias magnetization of the transformer can be prevented with higher control accuracy.

Further, the exciting current of each transformer is calculated from the current flowing through one winding of the plurality of transformers, the DC component thereof is detected, and the output control command of the converter is corrected using the detected DC component. By so doing, it is possible to prevent variations in DC bias magnetization between the transformers. In this case, if the output control command of the converter is corrected after correcting the DC component of the exciting current from its average value, it is possible to prevent the DC bias magnetization variation of the transformer with higher control accuracy. it can.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The multiple semiconductor power converter of the present invention will be described in detail below with reference to the drawings showing the embodiments.

FIG. 1 is a schematic configuration diagram showing an embodiment of the multiplex type semiconductor power converter of the present invention. In the figure, T ₁ and T ₂ are a pair of DC main terminals, T ₃ and T ₄ are AC main terminals whose number is determined by the number of AC phases, 11, 12, 13 and 1
4 is a pair of direct current terminals T _11A , T _11B , T _12A , T
_12B , T _13A , T _13B , T _14A , T _14B , AC terminals T _11C , T _11D , T _12C , T _12D , T _13C having the same number as the number of AC phases.
A bridge composed of T _13D , T _14C , T _14D , and an even number of self-extinguishing type semiconductor devices connected in series between the DC terminals, in parallel connected by a number (or an integral multiple thereof) determined by the AC phase. It has a circuit, an AC terminal is connected to the middle point of each bridge unit, and a pair of DC main terminals T ₁ and T ₂
4 converters in which each DC terminal is connected in parallel. Two
1, 22, 23 and 24 respectively have one winding W _21A ,
W _22A , W _23A and W _24A are connected to the AC terminals of each converter, and the other windings W _21B , W _22B , W _23B and W _24B are connected in series and connected between the AC main terminals T ₃ and T _4. The same number of transformers as the number of the converted converters, C is a control unit that controls on / off of the self-extinguishing type semiconductor device of the converter, 30 is a current transformer that detects the current flowing through the AC main terminal and applies the current to the control unit C, Reference numerals 31, 32, 33, and 34 denote current transformers that detect a current flowing in one winding of each transformer and apply the current to the control unit C, and S _REF is a command signal that controls the output of the converter.

The specific circuit configuration of the control section C will be described below. FIG. 2 shows an example of the control unit C. In the figure, 7 is a current control circuit that receives the command signal S _REF and controls the output current of the converter, and 81, 82, 83 and 84 are current control circuits 7.
Pulse generator circuit for controlling on / off of the self-extinguishing type semiconductor elements of the converters 11, 12, 13 and 14 by receiving a control signal from the transformers 41, transformers detected by the current transformers 31, 32, 33 and 34 An average value detection circuit for calculating the average value of the current flowing through one of the windings, and the output signal of this average value detection circuit is a signal for correcting the command signal S _REF input to the current control circuit 7 by the subtractor AD ₇ . Function as. By the current transformers 31, 32, 33 and 34, the average value detection circuit 41, the subtractor AD ₇ and the current control circuit 7, the DC component flowing in one winding of the transformer is set to 0, that is, the DC bias magnetism is reduced. A first control loop is constructed. Reference numeral 91 is a coefficient unit for converting the current flowing through the AC main terminal detected by the current transformer 30 into the current flowing through one winding of the transformer, AD ₆₁ , AD ₆₂ , and AD.
₆₃ and AD ₆₄ are calculated from the difference between the current flowing through one winding of each transformer detected by the current transformers 31, 32, 33 and 34 and the converted current flowing through the AC main terminal detected by the current transformer 30. Subtractors 61, 62, 6 for calculating the exciting current of each transformer
3 and 64 are DC component detection circuits for detecting the DC component contained in the exciting current from the output signal of the subtractor, 71, 7
2, 73 and 74 are DC component detection circuits 61, 62, 63
AD ₈₁ , AD ₈₂ , a control circuit for generating a signal for correcting the output signal of the current control circuit 7 based on the output signals of
AD ₈₃ and AD ₈₄ are control circuits 71, 72, 73 and 74.
Is a subtractor that corrects the output signal of the current control circuit 7 with the signal of. Current transformer 30, coefficient unit 91, current transformers 31, 32, 3
3 and 34, subtractors AD ₆₁ , AD ₆₂ , AD ₆₃ and A
D ₆₄ , control circuits 71, 72, 73 and 74, subtractor AD
₈₁ , AD ₈₂ , AD _83, and AD ₈₄ constitute a second control loop for reducing the variation of DC bias magnetism among the transformers.

Reference numeral 65 is a DC component detection circuit for detecting a DC component contained in the output signal of the average value detection circuit 41, and 75 is a signal for correcting the output signal of the current control circuit 7 based on the output signal of the DC component detection circuit 65. The signal of the control circuit 75 is given to the subtracters AD ₈₁ , AD ₈₂ , AD ₈₃ and AD ₈₄ . 92 is a DC component detection circuit 65
And a control circuit 75, which is a coefficient unit for providing negative feedback. The signal of the control circuit 75 is the subtractor AD ₈₁ , A
Instead of applying to D ₈₂ , AD ₈₃ and AD ₈₄ , one subtractor may be provided at the output end of the current control circuit 7 and applied collectively thereto. This constitutes a first auxiliary control loop that complements the control accuracy of the first control loop.

Reference numeral 42 is a DC component detection circuit 61, 62, 63.
And the average value detecting circuit for calculating an average value of 64 output _{signals, AD 71, AD 72, AD} 73 and the DC component detecting circuit 61, 62 and 63 by the output signal of the AD ₇₄ is the average value detecting circuit 42
And 64 for correcting the output signals. This constitutes a second auxiliary control loop that supplements the control accuracy of the second control loop.

In this example, a four-multiplex type semiconductor conversion device composed of four converters and transformers is shown, but it can be applied to any other multiplex type semiconductor conversion device.

Next, the operation of the control unit shown in FIG. 2 will be described. Currents flowing through one winding of the four transformers 21 to 24 are detected by the current transformers 31 to 34. 4 in control unit C
AC currents I1, I2, I3, I detected by the current transformer of the table
The average value IAV = (I1 + I2 + I3 + I4) / 4 of 4 is obtained by the average value detection circuit 41, and the alternating current is controlled by the current control circuit 7 using the average value. At this time, there are a method of controlling by using the AC current as it is, and a method of controlling by converting the coordinates into two-axis rotational coordinates in the case of a three-phase converter. Is also alternating current controlled to use any control method, the DC current component also controlled to be 0 at the same time when an alternating current flowing through one winding of the transformer is controlled by a first control loop To be done. If the DC component remains in the AC current due to the characteristics of the converter or the performance of the control system,
By adding the first auxiliary control loop to detect the DC component of the average value and correcting the input signal of each pulse generation circuit, the DC current component flowing in one winding of the transformer can be more reliably reduced. You can For example, when the converter has a characteristic of generating a DC voltage due to an error in PWM control, the DC current component is set to 0 by the combined use of the first control loop and the first auxiliary control loop. Controlled.
It should be noted that even if the total value of the detected currents is used instead of the average value, the coefficient only changes, and the same effect is obtained.

As described above, if the combined control of the first control loop and the first auxiliary control loop is performed, it is possible to prevent the demagnetization of the entire transformer. However, since the output characteristics vary from converter to converter, the amount of DC bias magnetism varies between the transformers, and some transformers may be saturated. For example, when the converter 11 has a characteristic of generating a positive DC voltage and the converter 12 has a characteristic of generating a negative DC voltage, the first control loop and the first auxiliary control loop are Although the DC voltage is not generated as a whole by the control in which the transformer is used in combination, the transformer 21 moves in the positive direction,
2 is demagnetized in the negative direction and reaches saturation. In such a case, the second control loop is added to the above control. The second control loop detects the amount of eccentricity of each transformer and performs control to prevent mutual variations. A method of detecting the exciting current of the transformer is used as a method of detecting the amount of magnetic bias. The exciting current Iex is the difference (Iexj) between the current flowing through one winding of the transformer detected by the current transformers 31 to 34 and the AC current IL detected by the current transformer 30 converted by the turns ratio of the transformer.
= Ij-kIL). However, j = 1 to 4 and k are turn ratio conversion factors. Next, the average value (IexAV =
The average value detection circuit 42 calculates (Iex1 + Iex2 + Iex3 + Iex4) / 4). The difference (ΔIexj = Iexj−IexAV) from the average value of the amount of magnetic bias is calculated for each transformer. This difference (ΔIex
The control circuits 71 to 74 are controlled so that j) becomes 0, and a DC voltage for correction is generated in each converter. As shown in the equation, the DC voltage correction amount of each converter is proportional to the deviation from the average value, so the sum of all converters is 0, and the DC value of the average value of the current flowing through one winding of the transformer is DC. No interference occurs with the control that causes the component to be zero. In addition, when the control for making the average value of the current flowing through one winding of the transformer 0 is added as in the present embodiment, the output current is controlled by the current transformer 30.
The current may be applied. For applications in which a DC current may flow to the AC main terminal side, the input of the coefficient unit 92 in front of the control circuit 75 is used as the output of the average value detection circuit 42, and the DC component of the average excitation current is set to 0. You can go.

Further, if the equation of the difference (ΔIexj) from the average value of the amount of magnetic bias for each transformer is modified, it will be as follows.

ΔIexj = (Ij−kIL) − (1 / n) Σ (Ii−kIL) Σ indicates that 1 is added to i for the number of transformers n. As a result, ΔIexj = Ij−IAV, and the result is that the deviation between the current detected by the current transformers 31 to 34 and its average value is obtained for each transformer, the DC component is detected, and each converter is correspondingly detected. This means that a method of applying a correction voltage to the above may be used. An embodiment to which this principle is applied is shown in FIG.

In FIG. 3, instead of the signals from the current transformer 30 and the coefficient unit 9 of FIG. 2, the output signal of the average value detection circuit 41 is given to the subtracters AD ₆₁ , AD ₆₂ , AD ₆₃ and AD ₆₄ . It is configured to do. Therefore, in this embodiment, there is an effect that the detection of the current flowing through the AC main terminal becomes unnecessary. Also in this case, the first auxiliary control loop may be added. Also,
According to the present invention, since the amount of magnetic bias of the transformer is made uniform, there is no method for performing output current control including control for setting the direct current component to 0 by using the current flowing through one winding of one representative transformer. Not possible.

An embodiment in which the embodiment of FIG. 3 is applied to a three-phase semiconductor power converter is shown in FIG. In this embodiment, an example in which two converters and two transformers are used to form a multiplex type is shown.
It will be described with reference to the drawings. Since the output of the semiconductor power converter does not include the zero-phase component, the three-phase alternating current can be converted into the combination of the two-phase alternating current. Therefore, the coordinates may be converted into orthogonal two-axis coordinates, and the above control may be performed for each axis component.
Currents flowing in two phases selected in one winding of the transformer are detected by current transformers 31, 35 and 32, 36. Current transformer 31,
The output signals of 35, 32 and 36 are converted into a three-phase / two-phase conversion circuit 5
Convert it to two phases at 1,52. The αβ axis conversion is generally used as the two-phase conversion. The conversion formula from the three-phase a, b, c to the two-phase α, β is given by the following formula.

[0026]

[Equation 1]

In FIG. 4, the current transformer detects only the currents of the a and c phases, but the current of the b phase is obtained by Ib = -Ia-Ic.

When the transformer is composed of, for example, a ΔΔ winding and a ΔY winding as in this example, for example, the phase angle of the current flowing through one winding on the ΔY winding side. 30
The control may be advanced and the control described above may be performed in accordance with the same coordinate axis as the transformer of the ΔΔ winding. Therefore, the phase conversion circuit 5
5 is installed. The phase conversion of the angle θ can be performed by the following equation.

[0029]

[Equation 2]

By performing the phase conversion in this way, the two-phase vectors of both converters can be made to have the same direction, and can be handled separately for each phase. The following control is the same as that in FIG. Control result is △ Y
On the winding side, the phase angle conversion circuit 56 reverses the phase to restore the original phase. Next, the two-phase / three-phase conversion circuits 53 and 54 restore the three-phase to operate each converter. In the present embodiment, the control of the output current is also performed by the two-phase control of two axes of α and β by the control devices 7 and 70. However, the output current is further converted into the rotational coordinate system for control, and the inverse conversion is performed again. You may carry out.

In the case of three-phase AC, if a three-phase AC voltage is generated all at once when the converter is started, the transformer will be biased even if the initial condition is zero. To prevent this, a voltage may be generated for each of the two orthogonal phase components at the time when the phase angle of the fundamental wave sine wave becomes 90 degrees. If the initial condition is 0, it is possible to start up the transformer without causing magnetic bias. An example of the waveform is shown in FIG. The voltages on the α and β axes are generated from the phase angle of 90 degrees of the sine wave as shown in the figure. This is converted into a voltage of three phases a, b, and c to generate a voltage of each phase. For this reason, in the embodiment shown in FIG.
Synchronous starting circuits 58 and 59 for starting at 0 degrees are added.

[0032]

According to the present invention, the DC bias magnetism of a plurality of transformers arranged on the AC main terminal side of the converter is reduced as much as possible,
As a result, it is possible to realize a multiplex type semiconductor power conversion device which eliminates the inconvenience associated with DC bias magnetization.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a schematic configuration of a semiconductor power conversion device of the present invention.

FIG. 2 is a schematic circuit diagram showing details of a control unit of the semiconductor power conversion device of FIG.

FIG. 3 is a schematic circuit diagram showing another embodiment of the semiconductor power conversion device of the present invention.

FIG. 4 is a schematic circuit diagram showing still another embodiment of the semiconductor power conversion device of the present invention.

5 is a waveform chart for explaining the operation of the embodiment of FIG.

[Explanation of symbols]

10 ... Load, 11-14 ... Converter, 21-24 ... Transformer, 30-36 ... Current transformer, 41-43 ... Average value detection circuit, 51, 52 ... Three-phase / two-phase conversion circuit, 53, 54 ... Two-phase / three-phase conversion circuit, 55, 56 ... Phase conversion circuit, 57 ...
Sync detection circuit, 58, 59 ... Sync start circuit, 61-67
... DC component detection circuit, 70-77 ... Control circuit, 81-8
4 ... Pulse generating circuit, 91, 92 ... Coefficient multiplier.

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hironari Kawazoe 7-1-1, Omika-cho, Hitachi-shi, Ibaraki Hitachi Ltd. Hitachi Research Laboratory (56) Reference JP-A-4-322170 (JP, A) Kaihei 4-261366 (JP, A) JP 4-4756 (JP, A) JP 5-300750 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H02M 7 / 537 H02M 7/48

Claims (11)

(57) [Claims] 1. A bridge unit in which an even number of semiconductor switching elements are connected in series between a pair of DC main terminals, a plurality of main AC terminals, a pair of DC terminals , a plurality of AC terminals , and a pair of DC terminals. It consists of a plurality of bridge circuits connected in parallel, an AC terminal is connected to the middle point of each bridge unit, and a plurality of converters in which each DC terminal is connected in parallel to a pair of DC main terminals, respectively. It has a pair of windings, and one winding has a plurality of windings.
Is connected to the AC terminals of each transducer of the transducer, on-off control the same number of transformer and the transformer and the other winding are connected in series are connected between the main AC terminals, the semiconductor switching element of the transducer In the semiconductor power conversion device including a control unit, the control unit generates a pulse signal for turning on and off a semiconductor switching element of the converter, and an output for controlling the output of the converter in the pulse generation circuit. and means for applying a command signal via the control circuit, the same number of transformer current detecting means and a transformer for detecting the current flowing in one of the windings of the plurality of transformers respectively, said respective transformer current detecting means Sum the above currents detected in
The semiconductor power conversion device, characterized by comprising: a mean value detecting means for obtaining an average value, and means for correcting the command signal at the output signal of the average value detecting means, a Te. 2. The method of claim 1, Bei the DC component detecting means for detecting a DC component from the output signal of said average value detecting means
For example, a semiconductor power conversion device and correcting the output signal of the output control circuit by an output signal of the DC component detecting means. 3. The claim 1 or 2, a main AC alternating current detecting means for detecting a current flowing through the terminal, the current value detected by the current and the transformer current detecting means detected by the alternating current detecting means The same number of exciting current calculating means as the converter for calculating the exciting current of each transformer, and the transformer direct current component detecting means for detecting the direct current component flowing in each transformer from the output signal of each exciting current calculating means are provided. the semiconductor power conversion device by the output signal of the vessels DC component detecting means and corrects the input signal of the respective pulse generating circuits. 4. The DC current average value detecting means for detecting the average value of the DC current flowing through the transformer from the output signal of each transformer DC component detecting means according to claim 3, and the DC current average value detecting means. A semiconductor power conversion device, characterized in that the output signal of each transformer DC component detecting means is corrected by the output signal of. 5. In any one of claims 1 to 4, a semiconductor power conversion device, wherein the semi <br/> conductor switching element is a self-extinguishing type semiconductor device. 6. The semiconductor power conversion device according to claim 1, wherein the converter is a converter that converts AC power into DC power. 7. The semiconductor power converter according to claim 1, wherein the converter is an inverter that converts DC power into AC power. 8. A bridge unit in which an even number of semiconductor switching devices are connected in series between a pair of DC main terminals, a plurality of main AC terminals, a pair of DC terminals , a plurality of AC terminals , and a pair of DC terminals. It consists of a plurality of bridge circuits connected in parallel, an AC terminal is connected to the middle point of each bridge unit, and a plurality of converters in which each DC terminal is connected in parallel to a pair of DC main terminals, respectively. It has a pair of windings, and one winding has a plurality of windings.
Is connected to the AC terminals of each transducer of the transducer, on-off control the same number of transformer and the transformer and the other winding are connected in series are connected between the main AC terminals, the semiconductor switching element of the transducer In the semiconductor power conversion device including a control unit, the control unit generates a pulse signal for turning on and off a semiconductor switching element of the converter, and an output for controlling the output of the converter in the pulse generation circuit. and means for applying a command signal via the control circuit, the same number of transformer current detecting means and a transformer for detecting the current flowing in one of the windings of the plurality of transformers respectively, said respective transformer current detecting means Sum the above currents detected in
From the mean value detecting means for obtaining an average value, and means for correcting the command signal with an output signal of said mean value detecting means, a current value detected by the output signal and the converter current detecting means of the average value detecting means Te a converter as many excitation current calculating means for calculating the variation of the exciting current of each transformer, the transformer DC for detecting a DC component of the variation of the exciting current of each transformer from the output signals of the respective exciting current calculation means A semiconductor power conversion device comprising: component detecting means; and means for correcting an input signal of each pulse generating circuit by an output signal of each transformer DC component detecting means. 9. The semiconductor power conversion device according to claim 8, wherein the semiconductor switching element is a self-extinguishing type semiconductor element. 10. In any one of claims 8 or 9, before
The semiconductor power conversion device, wherein the serial converter is converter for converting AC power into DC power. 11. A claim 8 or 9, before
The semiconductor power conversion device, wherein the serial converter is an inverter that converts DC power to AC power.