JP4915136B2 - Multiple power converter control device - Google Patents

Description

  The present invention relates to a control device that performs pulse width modulation (PWM) control of a multiple power conversion device.

FIG. 9 shows a conventional example of a power conversion system disclosed in Non-Patent Document 1, for example.
In FIG. 9, CNV surrounded by a broken line is a main circuit of the power converter, Q1 to Q4 are switching elements such as IGBTs (insulated gate bipolar transistors) that perform a switching operation, and C is a DC smoothing capacitor. PS is an AC power source, Ls is a reactor, CT is a current detector for detecting an AC current Ic of the power converter, PT is a voltage detector for detecting a DC voltage Ed of the power converter, and DL is a DC side. Is a load device connected to the.

FIG. 10 is an explanatory diagram of the operation of FIG.
In FIG. 10 (1), Vc ^* is a voltage command, TRIa is a triangular wave for performing a PWM operation necessary for the switching operation of Q1 and Q2 by comparison with the voltage command Vc ^*, and similarly TRIb is a switching operation of Q3 and Q4. This is a triangular wave for performing the PWM calculation necessary for the operation. These triangular waves TRIa and TRIb have a phase difference of ½ period (π) with respect to the period (2π) of the triangular wave as shown in FIG.

In the PWM calculation of FIG. 10A, when the voltage command Vc ^* is larger than any of the two triangular waves TRIa and TRIb, Q1 and Q4 are turned on (Q2 and Q3 are turned off), and the AC side voltage Vc is Positive (+ Ed). When the voltage command Vc ^* is equal to or greater than the triangular wave TRIa and equal to or less than TRIb, Q1 and Q3 are turned on (Q2 and Q4 are turned off), and the AC side voltage Vc is Vc = 0. When the voltage command Vc ^* is equal to or less than the triangular wave TRIa and equal to or greater than TRIb, Q2 and Q4 are turned on (Q1 and Q3 are turned off), and the AC side voltage Vc is Vc = 0. Further, when the voltage command Vc ^* is smaller than either of the two triangular waves TRIa and TRIb, Q2 and Q3 are turned on (Q1 and Q4 are turned off), and the AC side voltage Vc is Vc = −Ed.

FIG. 11 shows an example of a control block of the power converter shown in FIG.
In FIG. 11, Ed ^* is a DC voltage command, SUB1 is a subtractor that takes the difference between Ed ^* and Ed, AVR is a voltage regulator, sin ωt (ω is an angular frequency, and frequency is f [Hz], ω = 2πf [rad / s]) is a reference sine wave that is phase-synchronized with the power source, MUL is a multiplier that multiplies the AVR output and the reference sine wave sin ωt to calculate the current command Ic ^* , and SUB2 is the difference between the command value Ic ^* and the detected value Ic. A subtractor, ACR is a current regulator that calculates an AC voltage command Vc ^* , and PWM is a PWM calculator that performs a comparison operation on the voltage command Vc ^* that is the calculation result of ACR and a triangular wave. Here, the triangular wave input to the PWM calculator is only TRIa, but the triangular wave TRIb shown in FIG. 10A is generated by inverting the phase of TRIa inside the PWM calculator.

In the control system as shown in FIG. 11, the voltage regulator AVR operates so as to make the detected value (actual value) Ed of the DC voltage coincide with the command value Ed ^* , and determines the amplitude of the current command. The AC current control unit calculates the current command Ic ^* by multiplying the amplitude of the current command output from the previous stage by the reference sine wave sin ωt, and causes the current regulator ACR to match the detected current value (actual value) Ic with the command value. Such an AC voltage command Vc ^* is calculated. The PWM calculator calculates the PWM signal, and the alternating-side voltage Vc is determined as shown in FIG.

It is known that by using a power converter having a multiple connection configuration with a transformer, it is possible to supply several times the power to the DC side connected in parallel as compared with the case where the same power converter is provided.
FIG. 12 shows an example in which the AC sides of two power converters CNV1 and CNV2 are combined by a transformer and multiplexed. TR1 and TR2 are input side transformers of CNV1 and CNV2, respectively, and the other symbols are the same as those in FIG. Here, an example is shown in which one transformer is connected to each of two power converters, but a plurality of windings are provided on the secondary side, so that one transformer can be replaced.

FIG. 16 is an explanatory diagram of the operation of FIG.
In the PWM calculation of FIG. 16, the voltage commands Vc1 ^* and Vc2 ^* of the two power converters CNV1 and CNV2 are superposed as substantially the same sine wave. In actual operation, on the CNV1 side, as shown in FIG. 17 (1), Q11 to Q14 perform switching operation by comparing the voltage command Vc1 ^* with the triangular waves TRI1a and TRI1b, and as indicated by Vc1 in FIG. 17 (2). In the CNV2 side, as shown in FIG. 18 (1), Q21 to Q24 perform a switching operation by comparing the voltage command Vc2 ^* with the triangular waves TRI2a and TRI2b, and Vc2 in FIG. 18 (2). A voltage having a waveform as shown in FIG. The four triangular waves TRI1a, TRI1b, TRI2a, and TRI2b have a phase difference of ¼ period (π / 2) as shown in FIG. When the voltages on the primary side and the secondary side of the transformers TR1 and TR2 are the same, and the voltages Vc1 and Vc2 which are the voltages on the secondary side are synthesized on the primary side, a waveform like Vc in FIG. Is obtained.

FIG. 13 shows an example of a control block of the power converter shown in FIG.
The PHS in FIG. 13 is a phase delay device that delays the phase of the TRI2a with respect to the triangular wave TRI1a.
Since the DC power sides of the two power converters are connected in parallel, the DC voltage control unit is common. Also, in the AC current control unit, the two power converters operate with the same current command, but the current detection value (actual value) becomes a different instantaneous value, so that control is performed by the individual current regulators ACR1 and ACR2. Done. Further, different AC voltage commands Vc1 ^* and Vc2 ^* are output from the current regulators ACR1 and ACR2, respectively, and the operations shown in FIGS. 17 and 18 are performed on these voltage commands in the PWM1 and PWM2, respectively.

By multiply connecting two power converters, twice the power can be supplied to the DC side connected in parallel as compared with the case of one power converter having the same capacity. Further, by setting the phase delay device and operating with a phase difference of ¼ period (π / 2) between the triangular waves TRI1a and TRI2a as shown in FIG. The equivalent carrier frequency can be doubled compared to the case of one unit, and as a result, the proportion of harmonics on the power source side coupled by the transformer can be reduced.
The multiplexing configuration and operation of the power converter as described above are described in Non-Patent Document 2, for example.

Although the case of connecting to a common DC circuit has been described as a configuration for multiplex connection of power converters, a configuration in which an independent DC circuit is connected to each converter as shown in FIG. 14 may be considered as another configuration.
In the figure, PT1 and PT2 are voltage detectors for detecting DC voltages Ed1 and Ed2 of two converters CNV1 and CNV2, DL1 and DL2 are load devices of converters CNV1 and CNV2, respectively. Details are omitted because they are the same as in FIG.

In the configuration of FIG. 14, the operation of each power converter is completely independent. Therefore, as a control method applied to this, each of the converters CNV1 and CNV2 may be operated by the control block of FIG. When PWM operation of two converters is performed with a phase difference added to the triangular wave, the combined current of the AC side current can double the equivalent carrier frequency compared to the case of one, As a result, it can be easily analogized that the ratio of harmonics on the power source side coupled by the transformer can be reduced.
FIG. 15 is a control block diagram corresponding to FIG. 14. Basically, the same control block as that of FIG. 11 is applied to each converter, and a function of adding a phase difference to a triangular wave in two PWM operations is added. .

FIG. 20 shows another configuration example in which power converters are multiplex connected.
In FIG. 12, a current detector is installed for each power converter, but in this configuration, the combined current of the power converters is integrated by installing it on the primary side (left side of the figure) of the transformer. (This method is disclosed in, for example, Patent Document 1). As a PWM method in this case, as shown in FIG. 21, there is a method of comparing a voltage command with a plurality of triangular waves each biased according to the number of converters (see, for example, Non-Patent Document 3). In the converter CNV1, the triangular wave TRI3 of FIG. 21 is used for generating a PWM signal necessary for the switching operation of Q11 and Q12 by comparison with the voltage command Vc ^*, and the triangular wave TRI4 is also necessary for the switching operation of Q13 and Q14. It is a triangular wave for generating a PWM signal.

Negative when the output voltage Vc1 is positive when the voltage command Vc ^* greater than any of TRI3 and TRI4 (+ Ed), the voltage command Vc ^* is smaller than either of TRI3 and TRI4 (-Ed), voltage command Vc ^* Becomes zero when TRI3 or less and TRI4 or more.
In the converter CNV2, the triangular wave TRI1 of FIG. 21 is a triangular wave for switching Q21 and Q22 by comparison with the voltage command Vc ^*, and the triangular wave TRI2 is also a triangular wave for switching Q23 and Q24. The output voltage Vc2 is the voltage command Vc ^* is positive (+ Ed) when greater than any of the TRI1 and TRI2, negative (-Ed) when the voltage command Vc ^* is smaller than any of the TRI1 and TRI2, voltage command Vc ^* Becomes zero when TRI1 or less and TRI2 or more.

As a PWM system for a multiple converter having a configuration in which two power converters are coupled by a transformer, a triangular wave system with a phase difference as shown in FIG. 16 and a triangular wave system with a bias as shown in FIG. However, when these are compared with respect to harmonics on the AC side, it is known that the latter FIG. 21 can reduce harmonics.
FIG. 22 shows waveforms until a phase voltage is generated from R-phase and S-phase voltage commands and a combined line voltage is generated in a PWM system using a plurality of triangular waves with phase differences. Yes. Further, FIG. 23 shows waveforms until a phase voltage is generated from R-phase and S-phase voltage commands and a combined line voltage is generated in a PWM system using a plurality of biased triangular waves. Yes. Comparing the phase voltage waveforms of FIG. 22 and FIG. 23, it can be seen that the number of times the voltage level changes is the same, and the number of switching operations in both is the same. However, in the line voltage, FIG. 22 has a larger number of voltage changes within the same triangular wave period than FIG. Such a difference in line voltage indicates a difference in included harmonics, and as a result, the waveform in FIG. 23 has fewer harmonics than in FIG.

  The above-described difference in harmonics is described in detail, for example, in Non-Patent Document 4, which describes a graph for comparing harmonics due to differences in PWM methods as shown in FIG. This figure corresponds to the PWM method using a plurality of triangular waves with the horizontal axis representing the voltage magnitude and the vertical axis representing the harmonic, and the 5 Level-A curve having a phase difference, and the 5 Level-B curve is biased. This corresponds to a PWM method using a plurality of triangular waves. From the comparison of both curves, it is quantitatively clear that the PWM method using a plurality of triangular waves with a bias has fewer harmonics than the PWM method using a plurality of triangular waves with a phase difference.

"Semiconductor power conversion circuit" published by the Institute of Electrical Engineers of Japan, see pages 216-221 1985 Proceedings of the IEEJ National Convention, No. Refer to 547 “Examination of PWM converter control characteristics” See PESC 1990, Conference Record, p363-371 “A NEW MULTILEVEL PWM METHOD: A THEORETICAL ANALYSIS”. IEEJ Transactions, Department D, Vol. 119, no. 6, 1999, pp. 769-774 “Harmonic characteristics evaluation of multi-level PWM method using carrier wave” JP 2003-169477 A

As described above, as a method of multiplexing power converters, a method as shown in FIG. 12, 14 or 20 and a PWM method corresponding to these methods include a plurality of triangular waves with phase differences as shown in FIG. There are a method of calculating from a voltage command and a method of calculating from a plurality of triangular waves with a bias and a voltage command as shown in FIG.
Although it is advantageous to obtain a PWM signal from a plurality of triangular waves with a bias and a voltage command from the viewpoint of reducing harmonics, in FIGS. 12 and 14, calculation is performed from a plurality of triangular waves with a phase difference and a voltage command. The method to do is adopted.

On the other hand, FIG. 20 employs a PWM system that calculates from a plurality of biased triangular waves and voltage commands. However, since this method detects the current on the primary side of the transformer, accurate control cannot be performed for each power converter, resulting in a problem that an error occurs in the output voltage and abnormalities such as magnetic bias occur.
Therefore, an object of the present invention is to make it possible to apply a PWM system that calculates from a plurality of biased triangular waves and voltage commands even when a power converter is multiplexed using a transformer.

  In order to solve such a problem, in the present invention, a plurality of power converters having a configuration in which the AC sides of a plurality of power converters connected to individual or common DC circuits are coupled by a transformer are biased. A PWM calculation method using a triangular wave is applied, and the result of current control based on the current detection value for each power converter is reflected as a correction value on the PWM signal. Further, the timing of the PWM signal is adjusted so that a plurality of power converters can be switched evenly.

  According to the present invention, a PWM system using a plurality of biased triangular waves can be applied to a multiple power conversion device in which the AC sides of a plurality of power converters connected to individual or common DC circuits are coupled by a transformer. By doing so, sufficient current control can be performed for each power converter, and the multiple power converter can be operated safely and stably. By adjusting the timing of the PWM signal so that the plurality of power converters can be switched evenly, the power sharing of the plurality of power converters can be made uniform.

FIG. 1 is a control block configuration diagram showing an embodiment of the present invention, and a multiplexing configuration is the same as FIG. The PWM shown in FIG. 1 is based on the voltage command Vc ^* and the triangular wave TRI, and is a PWM calculator that performs PWM calculation using a biased triangular wave as shown in FIG. 21. SUB1 is a DC voltage command Ed ^* and a detected value Ed. AVR is a voltage regulator for controlling the DC voltage based on the output of SUB1, MUL is a multiplier that multiplies the output of AVR and a reference sine wave, and SUB2 is a power converter of two power converters. A subtractor that takes the difference between the current detection value Ic1 on one side (CNV1 in FIG. 12) and the current command Ic ^* , SUB3 is the current detection value Ic2 and current command Ic on the other (CNV2 in FIG. 12) of the two power converters. ^* taking a difference between the subtractor, ACR1, ACR2 each SUB1, SUB2 current regulator for controlling the current based on the output of, PCOM1, PCOM2 each ACR1, ACR2 of Based on the force which is a correction calculator for correcting the PWM calculation result.

Here, the operation of FIG. 1 will be described.
In PWM, a voltage command Vc ^* and a triangular wave TRI are input, and a PWM signal necessary for switching is generated by a comparison operation between the voltage command and a plurality of triangular waves with a bias. Here, the voltage command Vc ^* may be a sine wave having the same magnitude and phase as the phase voltage on the power supply side. In the DC voltage control unit, the difference between the DC voltage command value Ed ^* and the detected value Ed is amplified by AVR and output. Since the output of AVR is a direct current amount, it is multiplied by a reference sine wave sin ωt by MUL to be converted into an alternating current amount, which is used as a current command Ic ^* .

  In the AC control unit, the current command calculated in the previous stage is given in common to the two power converters CNV1 and CNV2, and the current control calculation is executed independently by ACR1 and ACR2 based on the detected current values Ic1 and Ic2. In PCOM1 and PCOM2, the result calculated by ACR1 and ACR2 is reflected in the PWM calculation result, and the final PWM signal for actually switching CNV1 and CNV2 is output.

  FIG. 2A is an example in the case where the alternating current control unit outputs a constant value on the positive side in the control block diagram shown in FIG. In FIG. 2 (a), the output from the PWM calculation unit shown in (1) is changed to the output shown in FIG. 2 (a) from the AC current control unit shown as the correction amount. ) Is corrected as in (3). In the case of FIG. 2B in which the AC current control unit outputs zero, and in the case of FIG. 2C in which the AC current control unit outputs a constant value on the negative side, the same arithmetic operation as described above is performed. .

FIG. 3 is a waveform diagram showing an output signal to each power converter obtained as a result of the correction calculation.
Vc1 and Vc2 in FIGS. 3 (1) and 3 (2) respectively indicate the outputs of the PWM calculator before correction, and FIGS. 2 (3) and 2 (4) Vc1 and Vc2 respectively indicate voltage waveforms after the correction calculation. . As a result of the correction calculation, the voltages of both Vc1 and Vc2 change as indicated by the hatched portion, and switching control of each element of the power converter is performed.

FIG. 4 shows an example of a control block when the AC side of the power converter from which the DC part is separated is combined by a transformer and multiplexed.
Here, since the DC voltage is individually detected because the DC part is separated, voltage regulators are individually provided as AVR1 and 2, and MUL1 and 2 are multiplied by the reference sine wave sinωt, respectively. It is the same as FIG. 1 except that it is converted into a quantity and current commands Ic1 ^* and 2 ^* are obtained.

By the way, in the control system of FIG.1 and FIG.4, the magnitude | size of the alternating current side voltage with respect to each power converter is clear when comparing (1) and (2) or (3) and (4) of FIG. Are different from each other, and as a result, there is a possibility that the power of the plurality of power converters may be unbalanced.
FIG. 5 shows another embodiment that may address such issues. As is apparent from FIG. 5, the feature shown in FIG. 5 is that an equalization computing unit PEQ is added to that shown in FIG. The equalization computing unit PEQ distributes PWM signals so that the switching operations of the two power converters are equalized with respect to the output of the PWM computing unit. Other details are the same as in FIG.

  The operation of FIG. 5 will be described with reference to FIG. Now, when the two power converters CNV1 and CNv2 are operated without any change to the output of the PWM calculator, the output voltage for CNV1 and CNv2 is from the PWM calculation to the AC side voltage. As in FIG. 21, the waveforms are as Vc1 and Vc2 before equalization in FIGS. 7 (2) and (3). Here, when comparing the waveforms of Vc1 and Vc2 before equalization, the period during which a positive (+ Ed) or negative (-Ed) voltage is output in one cycle of the voltage command is different. The power burden on the converter is also different.

  For this reason, the equalization computing unit PEQ is configured so that the operation in which the output voltage changes from zero to positive and the operation in which the output voltage changes from positive to zero are alternately performed by the two power converters during the positive period of the voltage command. Adjust the timing. By carrying out such an operation, the AC side voltages of the two power converters have waveforms such as Vc1 and Vc2 after equalization in FIGS. 7 (4) and (5), and the voltage output period is As a result, the power burden is also equalized. The combined output voltage of the two power converters is Vc in FIG. 7 (6), which is the same with and without the equalization operation.

FIG. 8 is a waveform diagram showing correction calculation results by the correction calculators PCOM1 and PCOM2 for the above equalization calculation.
8 (1) and (2) are the same as the Vc1 and Vc2 waveforms after equalization in (4) and (5) of FIG. 7, and by performing a correction operation on this, FIG. 8 (3) , (4) is corrected as indicated by hatching.
FIG. 6 is the same as that shown in FIG. 4 except that an equalization computing unit PEQ is added to the one shown in FIG.

Control block diagram showing an embodiment of the present invention when a DC circuit is shared Waveform diagram illustrating the concept of correction calculation in FIG. Waveform diagram showing an output signal to each power converter obtained as a result of the correction calculation as shown in FIG. Control block diagram when there is an independent DC circuit for each power converter Control block diagram showing a modification of FIG. Control block diagram showing a modification of FIG. Waveform diagram explaining equalization calculation Waveform diagram explaining the result of applying correction calculation to equalization calculation General system configuration diagram with one power converter connected to AC power supply FIG. 9 illustrates the operation Control block diagram of the power converter of FIG. System configuration diagram of multiple power converter with common DC circuit Control block diagram corresponding to FIG. System configuration diagram of multiple power converter when DC circuit is individual Control block diagram of the power converter shown in FIG. Control operation explanatory diagram of FIGS. Explanatory drawing of the PWM calculation method with respect to one power converter of FIG. Explanatory drawing of the PWM calculation method with respect to the other power converter of FIG. Triangular wave carrier phase diagram Configuration diagram showing another example of a multiple power converter system 20 is an explanatory diagram of the PWM control method of FIG. Explanation of PWM method using multiple triangular waves with phase difference Explanation of PWM method using multiple triangular waves with bias Graph showing differences in harmonics due to differences in PWM method

Explanation of symbols

  PS: AC power supply, PWM: PWM calculator, AVR, AVR1, AVR2 ... Voltage regulator, ACR, ACR1, ACR2 ... Current regulator, PCOM1, PCOM2 ... Correction calculator, SUB, SUB1, SUB2, SUB3, SUB4 ... Subtract MUL, MUL1, MUL2 ... multiplier, Ls, Ls1, Ls2 ... reactor, DL, DL1, DL2 ... load device.

Claims (4)

In a control apparatus for a multiple power converter that controls a multiple power converter in which AC terminals of a plurality of power converters connected to the same DC circuit are coupled via a transformer,
One PWM calculation means for generating a PWM (pulse width modulation) signal by comparing a plurality of biased triangular waves and a voltage command for the plurality of power converters, a common DC voltage command and a common DC voltage generate individual control amount by the control operation by the control calculation to zero a deviation between the detection value to generate a common alternating current command value, the deviation between the AC current command value and the individual alternating current detected value to zero And a control means for individually correcting the pulse width of the PWM signal based on the output from the control calculation means, and each power converter is controlled based on the output from the correction means. A control device for a multiple power converter. In a control apparatus for a multiple power converter that controls a multiple power converter in which AC terminals of a plurality of power converters connected to individual DC circuits are coupled via a transformer,
One PWM calculation means for generating a PWM (pulse width modulation) signal by comparing a plurality of biased triangular waves and a voltage command for the plurality of power converters, a common DC voltage command and individual DC voltages generate individual control quantity by a control operation to generate individual alternating current command value to zero a deviation between the alternating current command value and the individual alternating current detected value by controlling operation to zero the deviation between the detection value And a control means for individually correcting the pulse width of the PWM signal based on the output from the control calculation means, and each power converter is controlled based on the output from the correction means. A control device for a multiple power converter. In a control apparatus for a multiple power converter that controls a multiple power converter in which AC terminals of a plurality of power converters connected to the same DC circuit are coupled via a transformer,
One PWM calculation means for generating a PWM (pulse width modulation) signal by comparing a plurality of biased triangular waves and a voltage command with respect to the plurality of power converters, and the generated PWM signal to a plurality of power converters A common AC current command value is generated by an equalization calculation means for performing a calculation for evenly distributing the output and a control calculation for setting the deviation between the common DC voltage command and the common DC voltage detection value to zero. Control calculation means for generating individual control amounts by control calculation that makes the deviation between the AC current command value and the individual AC current detection value zero, and the pulse width of the output from the equalization calculation means from the control calculation means And a correction unit that individually corrects the power converter based on the output of the power, and controls each power converter based on the output from the correction unit. In a control apparatus for a multiple power converter that controls a multiple power converter in which AC terminals of a plurality of power converters connected to individual DC circuits are coupled via a transformer,
One PWM calculation means for generating a PWM (pulse width modulation) signal by comparing a plurality of biased triangular waves and a voltage command with respect to the plurality of power converters, and the generated PWM signal to a plurality of power converters Individual AC current command values are generated by an equalization calculation means for performing an operation for evenly distributing to each other, and a control calculation for making a deviation between a common DC voltage command and an individual DC voltage detection value zero, Control calculation means for generating individual control amounts by control calculation that makes the deviation between the AC current command value and the individual AC current detection value zero, and the pulse width of the output from the equalization calculation means from the control calculation means And a correction unit that individually corrects the power converter based on the output of the power, and controls each power converter based on the output from the correction unit.

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