JP3192858B2 - Control device for 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 control device for a power converter for controlling a total value of AC currents of a plurality of converters operated by connecting an AC terminal in a sinusoidal manner.

[0002]

2. Description of the Related Art FIG. 3 is a block diagram of a main circuit of a power converter to which the present invention is applied. In FIG. 3, 1 is an AC load, 2
Numerals 4 are capacitors. Reference numerals 5 to 8 denote unit converters (hereinafter, simply referred to as converters) for converting DC power into AC power, which are connected to the AC load 1 with common AC terminals and perform parallel operation. The capacitors 2 to 4 are used to absorb the switching surge of the converters 5 to 8. 9 to 32 are self-extinguishing type switching elements constituting the converters 5 to 8. Hereinafter, a case where a gate turn-off thyristor (hereinafter, simply referred to as GTO) is used as the self-extinguishing type switching element will be described. 33 to 40 are DC reactors for smoothing DC current,
41 to 44 are DC power supplies.

FIG. 4 is a configuration diagram of a conventional control circuit for controlling the power converter shown in FIG. In FIG.
Is a current command value generation circuit for the converters 5 to 8, 50 is a phase detection circuit, 51 is a triangular wave generator, 52 is a comparator, 53
Is a logic circuit for generating an AC current output command for the converters 5 to 8.

FIG. 5 is a waveform diagram when the power converter of FIG. 3 is controlled by the conventional control circuit shown in FIG. Hereinafter, the operation of the conventional embodiment will be described with reference to FIGS. 3, 4, and 5. FIG.

In FIG. 4, a current command value generating circuit 49
Generates an amplitude command value (1) and a phase angle command value of the AC current, and the amplitude command value (1) is given to the comparator 52. The phase angle command value is provided to the phase detection circuit 50 and the triangular wave generator 51. Signals (2) to (5) are output signals of the triangular wave generator 51 and are triangular waves having a cycle of 60 ° of the phase angle command value.
Also, it is assumed that the phases of the triangular waves (3) to (5) are each delayed by 15 ° with respect to the triangular wave (2). Comparator 52
Compares the amplitude command value (1) with the triangular waves (2) to (5), and sets a range in which the amplitude command value is larger than the triangular wave as an AC current output command. This output command is applied to the logic circuit 53, and the phase is discriminated based on the output of the phase detection circuit 50, thereby generating an AC current output command for each converter. That is, (6) is the U-phase output command of the converter 5, (7) is the X-phase output command of the converter 5, (8) is the converter 6
U-phase output command, (9) X-phase output command of converter 6, (10)
Is the U-phase output command of the converter 7, (11) is the X-phase output command of the converter 7, (12) is the U-phase output command of the converter 8, and (13) is the converter 8
X-phase output command.

By controlling the GTO of the converters 5 to 8 on and off based on the above output command, a current having a waveform shown in (14) is obtained as a U-phase output current. V phase, W
Similar control is performed on the phases by delaying the phases by 120 ° with respect to the U phase.

[0007]

As described above, when the AC terminals of the converters 5 to 8 are connected in parallel and the GTO is operated by delaying the conduction phase of the GTO by 15 °, the output current of each converter is reduced. Is a trapezoidal waveform as shown in FIG. 5 (14), and is a waveform including the fifth and seventh low-order harmonics.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a control device of a power conversion device capable of removing low-order harmonics by controlling a combined value of alternating currents of converters 5 to 8 in a sine wave shape. I do.

[0009]

In order to achieve the above-mentioned object, the present invention provides a six-arm switching element having a three-phase bridge.
The DC positive terminal and the negative terminal are respectively connected to a DC power supply via a DC reactor, and AC terminals are connected in parallel to obtain a three-phase AC output.
In a control device for a power converter having a plurality of unit converters, a three-phase AC current command for a three-phase AC current of the power converter is provided.
A current command value generating means for generating a value , a current phase detecting means for detecting a maximum phase in which the absolute value of the three-phase AC current command value is larger than the other two phases, and an absolute value of the three-phase AC current command value.
For detecting the positive / negative of the three-phase AC current command value that maximizes
And code detecting means, energizing arm number calculating means for determining the number of conduction arms of the n unit converter from the ratio of the DC current of the DC power source and the three-phase AC current command value, the current phase
The output of the detecting means, the output of the current sign detecting means and the communication
And the output of the current arm number calculating means,
Based on the output of the detecting means and the output of the current sign detecting means
The three-phase AC current finger for all of the n unit converters
Turn on either the positive or negative arm of the phase with the largest absolute value
The maximum current phase control function to be performed, and the n unit converters
The absolute value of the three-phase AC current command value is
The absolute value of the two-phase three-phase AC current command value is not
Energize the arm that is on in the phase and the arm on the opposite side
An alternating current control function to be turned on according to the number of arms;
For each of the n unit converters, the three-phase AC current
The two-phase three-phase AC current command in which the absolute value of the command value is not the maximum
Arm that is ON in the phase with the largest absolute value and the positive and negative sides
The three-phase AC when none of the arms
The arm that is turned on in the phase where the absolute value of the current command value is the largest
Bypass current control to turn on the opposite arm in series
It is characterized by having an energizing arm calculation means with a function .

[0010]

According to the present invention constructed as described above, for example, as shown in FIG. 2, during the period from time t1 to t8, the absolute value of the three-phase AC current command value RIV is different from those of the other two-phase RIW and RW.
Since the absolute value of IU is larger than the absolute value of IU, an ON signal is supplied to all the switching elements of the Y-phase arm connected to the V-phase of the unit converter shown in FIG. 3, that is, GTOs 13, 19, 25, and 31 during this period. In such a state, for example, at time t1, the switching element of the V converter of the unit converter 5, that is, the GTO 10
, The current supplied from the DC power supply 41 is bypassed via the GTOs 10 and 13 without flowing to the load 1. If the GTO 10 is turned off and the GTO 9 is turned on at time t2, the current supplied from the DC power supply 41 flows to the load 1. In this way, the GTO 15 is turned on at time t4, and the GTO 21 is turned on at time t6, whereby the U-phase current as the power converter gradually increases,
It looks like the IU in FIG. That is, IU is set to the U-phase current reference R
By controlling so as to follow the IU, the IU can be controlled to a sinusoidal current.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram of a control device showing an embodiment of the present invention for controlling the output current of the power conversion device shown in FIG. 3 in a sine wave shape.

In FIG. 1, 45 is a current command value generating means, 46 is a current phase detecting means, 47 is an energizing arm number calculating means, and 48 is an energizing arm calculating means. Processed by

FIG. 3 is a waveform diagram for explaining the operation of the embodiment of the present invention described with reference to FIGS. Hereinafter, the operation of the embodiment of the present invention will be described with reference to FIGS. Here, in order to make the description easy to understand, the converter 5 shown in FIG. 1 is the converter A, the converter 6 is the converter B, and the converter 7 shown in FIG.
Is a converter C, and the converter 8 is a converter D. The symbols of the positive arm of each converter are defined as U, V, W, and the symbols of the negative arm are defined as X, Y, Z.

In the figure, RIU, RIV and RIW are outputs of the current command value generating means 45, RIU is a U-phase current command value, RIV is a V-phase current command value and RIW is a W-phase current command value. IUX, IVX, IWX are outputs of the energizing arm number calculating means 47, IUX, is a command value of the energizing number corresponding to RIU, IVX, is a command value of the energizing number corresponding to RIV,
IWX, is a command value of the number of currents corresponding to RIW. I
UA to IZD are outputs of the energizing arm calculating means 48,
A, IVA, IWA, IXA, IYA, and IZA are U, V, W, X, Y, and Z phase energization commands of the converter A, IU
B, IVB, IWB, IXB, IYB, and IZB are U, V, W, X, Y, and Z phase energization commands for converter B, IU
C, IVC, IWC, IXC, IYC, and IZC are U, V, W, X, Y, and Z phase energization commands for converter C, IU
D, IVD, IWD, IXD, IYD, and IZD are energization commands for the U, V, W, X, Y, and Z phase arms of the converter D. Here, converter A, converter B, converter C, converter D
DC power supply 41, DC power supply 42, DC power supply 4
3. It is assumed that the DC power supply 44 controls the current values IDC to be equal to each other. The energization arm number calculation section 47 obtains the U-phase energization number command value IUX by the following calculation.

When RIU / IDC <−3.5, IUX = −4−3.5 ≦ RIU / IDC <−2.5, IUX =
−3−2.5 ≦ RIU / IDC <−1.5 IUX =
When −1.5−RIU / IDC <−0.5 IUX =
-1 -0.5 ≦ RIU / IDC <0.5 IUX =
0 When 0.5 ≦ RIU / IDC <1.5 IUX =
1 When 1.5 ≦ RIU / IDC <2.5 IUX =
2 When 2.5 ≦ RIU / IDC <3.5 IUX =
3 When 3.5 ≦ RIU / IDC IUX =
4 Similarly, a V-phase energization number command value IVX and a W-phase energization number command value IWX are determined.

Next, the control of the phase at which the current is maximized, the control of the alternating current, and the control of the bypass current will be described step by step. (1) Control of the phase at which the current becomes maximum The current phase detection means 46 detects the absolute value of RIU or RIV.
Or the current phase at every 60 ° at which the absolute value of RIW becomes the maximum. For example, in the period from time t1 to time t8 in FIG. 3, the absolute value of RIV is maximum and RIV is negative. The energizing arm calculating means 48 includes a current phase detecting means 46
An energization command is generated as described below in accordance with the output signal.

When the absolute value of RIV is maximum and RIV is negative, the signals IYA, IYB, IYC, IYD become 1, and the arm Y of the converter A, the arm Y of the converter B, the arm Y of the converter C, The arm Y of the converter D is energized.

In the same manner for the other periods at intervals of 60 ° continuing from the time t1 to the time t8, when the absolute value of the RIU is maximum and the RIU is positive, IUA, IUB, IUA
The signals of UC and IUD become 1, and the arm U of the converter A, the arm U of the converter B, the arm U of the converter C, and the arm U of the converter D are energized.

When the absolute value of RIW is maximum and RIW is negative, the signals of IZA, IZB, IZC, and IZD become 1, and the arm Z of the converter A, the arm Z of the converter B, the arm Z of the converter C, The arm Z of the converter D is energized.

When the absolute value of RIV is maximum and RIV is positive, the signals of IVA, IVB, IVC and IVD become 1, and the arm V of the converter A, the arm V of the converter B, the arm V of the converter C, The arm V of the converter D is energized.

When the absolute value of RIU is maximum and RIU is negative, the signals of IXA, IXB, IXC, and IXD become 1, and the arm X of the converter A, the arm X of the converter B, the arm X of the converter C, The arm X of the converter D is energized.

When the absolute value of RIW is maximum and RIW is positive, the signals of IWA, IWB, IWC, and IWD become 1, and the arm W of the converter A, the arm W of the converter B, the arm W of the converter C, The arm W of the converter D is energized. (2) Control of AC Current During the period from time t1 to time t8, control is performed as follows. When IUX ≧ 1 The arm U of the converter A is energized by an IUA signal. When IUX ≧ 2 The arm U of the converter B is energized by an IUB signal. When IUX ≧ 3 The arm U of the converter C is energized by an IUC signal. When IUX ≧ 4 The arm U of the converter D is energized by an IUD signal. When IWX ≧ 1, the arm W of the converter D is energized by an IWD signal. When IWX ≧ 2 The arm W of the converter C is energized by an IWC signal. When IWX ≧ 3 The arm W of the converter B is energized by an IWB signal. When IWX ≧ 4 The arm W of the converter A is energized by an IWA signal. In the example shown in FIG. 3, at time t2, IUX becomes 1 and IUA becomes 1
become. At time t4, IUX becomes 2 and IUB becomes 1. At time t6, IUX becomes 3 and IUC
Becomes 1. At time t3, IWX becomes 2 and IWX
B becomes 0. At time t5, IWX becomes 1 and IWX becomes 1.
WC becomes 0. At time t7, IWX becomes 0 and IWD becomes 0. (3) Control of bypass current During the period from time t1 to time t8, control is performed as follows. The arm V of the converter A is energized by the signal of IVA obtained by IVA = 1-IUA-IWA. IVB = 1
-The arm V of the converter B is energized by the signal of IVB obtained by IUB-IWB. IVC = 1−IUC−IW
The arm V of the converter C is obtained from the IVC signal obtained by C.
Is turned on. The arm V of the converter D is energized by the signal of IVD obtained by IVD = 1-IUD-IWD. In the example shown in FIG. 3, during the period from time t1 to time t2, IUA and IWA are 0 and IVA is 1.
The period from time t3 to time t4 is IUB and IWB
Is 0 and IVB is 1. From time t5 to time t
In the period up to 6, IUC and IWC are 0, so IV
C becomes 1. The period from time t7 to time t6 is IU
Since D and IWD are 0, IVD is 1.

The same control is performed for the other 60 ° periods that continue from the time t1 to the time t8, so that the output signals IUA and IV of the energizing arm operation means 48 are controlled.
A, IWA, IXA, IYA, IZA, IUB, IV
B, IWB, IXB, IYB, IZB, IUC, IV
C, IWC, IXC, IYC, IZC, IUD, IV
D, IWD, IXD, IYD, IZD operate as shown in FIG. IUA, IVA, IWA, IXA, IY
A, U, V, W,
X, Y and Z are controlled. IUB, IVB, IWB, IX
Based on the signals of B, IYB and IZB, the arms U,
V, W, X, Y, and Z are controlled. IUC, IVC, IW
The arms U, V, W, X, Y and Z of the converter C are controlled by the signals of C, IXC, IYC and IZC. IUD, IV
The arms U, V, W, X, Y and Z of the converter D are controlled by the signals D, IWD, IXD, IYD and IZD.

IU is the total value of the U-phase currents of converter A, converter B, converter C, and converter D obtained by the above control. A sinusoidal current following the U-phase current command value RIU is obtained. The V-phase current IV and the W-phase current IW are similarly controlled.

In the above-described embodiment, the case where four unit converters are operated in parallel has been described. However, the present invention is similarly applied to the case where a plurality of unit converters other than four are operated in parallel. It can be implemented.

[0026]

As described above, according to the present invention, the DC positive terminal and the negative terminal are respectively connected to the DC power supply via the DC reactor, and the AC terminals are connected in parallel to form a three-phase AC output. The output current of the power converter composed of n unit converters can be controlled in a sinusoidal manner, so that a large number of converters can be connected in parallel to perform a large-capacity power conversion. Can be made very small. Also, as shown in FIG. 2, IUA, IXA, IVA,
Since IWA, IZA,..., IZD are turned on and off twice for an output frequency of 1 Hz and each waveform is regularly controlled, for example, when the output frequency is 50 Hz, the switching frequency of each arm of the converter is 100 Hz, which is low. The output current can be controlled in a sine wave shape at the switching frequency. Therefore, the switching loss can be reduced, so that a highly efficient power converter can be realized.

[Brief description of the drawings]

FIG. 1 is a block diagram of a control circuit showing one embodiment of the present invention.

FIG. 2 is a diagram for explaining the operation of one embodiment of the present invention.

FIG. 3 is a main circuit configuration diagram of a power converter to which the present invention is applied.

FIG. 4 is a block diagram of a control circuit of a conventional power converter.

FIG. 5 is a waveform chart for explaining an operation of a control device of the conventional power converter.

[Explanation of symbols]

1 ... AC load 2-4 ...
Capacitors 5 to 8 Unit converters 9 to 32
GTO 33-40 DC reactor 41-44 ...
DC power supply 45 ... current command value generating means 46 ...
Current phase detecting means 47 ... means for calculating the number of energized arms 48 ...
Power supply arm calculation means

Claims (1)

(57) [Claims] 1. A six-arm switching element comprising a three-phase bridge.
The DC positive terminal and the negative terminal are each connected to a DC power supply via a DC reactor, respectively.
A control device for a power conversion device having n unit converters configured to obtain a three-phase AC output by connecting AC terminals in parallel, the three-phase AC current of the power conversion device being three-phase A current command value generating means for generating an AC current command value , a maximum value of the three-phase AC current command value being larger than the other two phases;
Current phase detecting means for detecting a large phase , and three-phase AC in which the absolute value of the three-phase AC current command value is maximum.
Current sign detecting means for detecting whether the current command value is positive or negative; and energizing arm number calculating means for determining the energizing arm number of the n unit converters from a ratio of the three-phase AC current instruction value and the DC current of the DC power supply And the output of the current phase detecting means and the current sign detecting means.
An output and an output of the energizing arm number calculating means are input,
The output of the current phase detection means and the output of the current sign detection means
And the output of the n unit converters.
The absolute value of the phase AC current command value is
A current maximum phase control function for turning on the arm;
For any of the unit converters, the three-phase AC current command value
Absolute value of two-phase three-phase AC current command value whose absolute value is not maximum
The arm that is turned on in the phase with the largest pair value and the arm that is
AC current control for turning on the arm according to the number of the energizing arms
The function and the three units for each of the n unit converters
Above three-phase two-phase AC current command value absolute value is not maximum
An arc that is turned on in the phase where the absolute value of the AC
If neither the arm nor the opposite arm is on,
Turn on in the phase where the absolute value of the three-phase AC current command value is the maximum
To turn on the opposite arm in series with the arm
Energizing arm computing means having a path current control function.
A control device for a power conversion device, comprising: