JPS6348159A - Cycloconverter device - Google Patents

Abstract

PURPOSE:To reduce capacity of a power source transformer, by a method wherein input terminal of a positive group converter of a cycloconverter of each phase in three phases is connected to a common first phase advancing capacitor, and the terminal is connected to a secondary winding of the power source transformer. CONSTITUTION:A cycloconverter device is constituted by a power source transformer MTR, first-second phase advancing capacitors CAP, and a circulation current type cycloconverter CC. Each cycloconverter CC of U-phase-W-phase is constituted by positive group converters SSP and SDP, negative group converters SSN and SDN and a DC reactor LOU. In case of three-phase output, input terminals of the positive group converters SSP and SDP are connected to common first phase-advancing capacitors CAP11 and CAP12, and also connected to a secondary winding of the power source transformer MTR. The negative group converters SSN and SDN are also connected in similar manner. As a result, only active current flows in the secondary winding thereby capacity of the transformer can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a cycloconverter device in which the capacity of a power transformer is reduced.

(Prior art) A cycloconverter is a device that directly converts alternating current power at a constant frequency into alternating current power at a different frequency. However, since the thyristor, which is a component of the cycloconverter, is commutated by the power supply voltage, a large amount of reactive power is removed from the power supply. There is a disadvantage of taking Moreover, the reactive power constantly fluctuates in synchronization with the frequency on the load side. This not only increases the capacity of power supply system equipment, but also causes various adverse effects on electrical equipment connected to the same system due to reactive power fluctuations.

As a method of compensating for the reactive power of such a cycloconverter, there is a technique such as that disclosed in Japanese Patent Laid-Open No. 56-44382.

In other words, a phase advance capacitor that takes a certain amount of leading reactive power is installed at the receiving end of the cycloconverter, and the circulating current of the microconverter is adjusted so that the lag reactive power of the cycloconverter is always equal to the leading reactive power of the phase advance capacitor. It is something to do.

On the other hand, in this reactive power compensation type cycloconverter device, a power transformer is installed between the AC power supply and each converter for the purpose of lowering or increasing voltage, or for the purpose of insulating the converter, but the capacity of this power transformer is Therefore, a capacity was required that could also supply the delayed reactive power of each converter. That is, in addition to the power that can be supplied to the load, lagging reactive power opposite to the leading reactive power of the phase advancing capacitor must be supplied to the cycloconverter via the power supply lance. Therefore, the power transformer becomes large in size and expensive.

In view of this, Japanese Patent Application Laid-Open No. 57-80267 was proposed. FIG. 4 shows a main circuit configuration diagram of the conventional cycloconverter device.

In the figure, Bus is the electrical line of the three-phase AC power supply, TrU g T
rV *TrW is a power transformer, CApUl ~ CAP
LI4 + cApvl-CAPV4 tCAP-□~
CAPIN4 is a phase advance capacitor, cc-u, cc-
v.

CC-W is a circulating current type cycloconverter, U, V.

W represents a three-phase AC load, respectively.

The TJ phase converter CC-U has a positive group converter 5SPu, SDT'υ and a negative group converter SSNυ,
It consists of 5DNU and DC reactor I-L Loυ. This is a circulating current type cycloconverter with a so-called control phase number (control pulse number) of 12 pulses.

V-phase and W-phase cycloconverters cc-v, cc-
v is similarly configured.

On the input side of the TJ phase-success converter CC-U, phase advance capacitors CAPut to CAPU4 divided into four are connected to the secondary winding side of the power transformer TrU.

By connecting the phase advance capacitors CAP, CAPυ4 to the secondary winding side of the power transformer Trυ in this way, the lagging reactive power taken by the cycloconverters cr, -u and the leading reactive power taken by the phase advance capacitors CAPIJI~CAPU4 are reduced. They cancel each other out to some extent, which has the effect of reducing the capacity of the power transformer TrLI. The same applies to the (2) phase and the W phase.

Figure 5 shows the current value on the input side of the cycloconverter CC-U in Figure 4, where l5SPU is the input current of the positive group converter SSPυ, and l5SNυ is the input current of the negative group converter 5.
The input currents of SNu, ICaPUt and IcapU2, indicate the magnitude of the currents of the phase advance capacitors CAP, □ and CAPuz.

When the loads U, V, and W are AC motors, almost no back electromotive force is generated during startup and low-speed operation, the output voltage of the cycloconverter is small, and the control phase angle α is approximately 90''. , 5SPUy, 15SNIJ, etc. of each converter can be considered to be mostly delayed reactive currents.

Therefore, the current I flowing through the secondary winding of the power transformer TrU
T? The size of z is ITP2 = l l5spu Icapυ, l
And, the current ITr flowing through the primary winding of TrU is
The size of t is Itrz = 2 X I l5SPU'+l5SNU
-Icapul-IeapU21.

In this way, the capacitance of the power transformer TrLI can be reduced, but the phase advance capacitors CAPux to CAPU
While the leading current Icapυ, -ICaPU4 flowing through 4 is a constant value, the input current ISSPυ+l5SNLJ, etc. of each converter changes as shown in the figure according to the output current ■υ, so the difference between them is the current Flows into transformer TrU.

As the speed of the AC motor load increases, active power is consumed, and it goes without saying that the power supply l-lance TrLI must bear the burden of this active power in addition to the above-mentioned reactive power.

(Problems to be Solved by the Invention) The conventional cycloconverter device described above divides the phase advance capacitors CAPυ, ~CAPU4, etc., and converts the power transformer Tr.
By connecting to the secondary winding side of U etc., the capacity of the power transformer TrU etc. can be reduced to some extent.

However, while the current flowing through the phase advance capacitor is a constant value, the input current of each converter varies greatly depending on the output current of the cycloconverter, so the difference in reactive current must be borne by the power supply. However, the effect of reducing capacity was halved. Especially the transformer 2
At present, we cannot expect much reduction in the capacity of the next current.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a cycloconverter device in which the capacity of a power transformer is significantly reduced.

[Structure of the invention]

(Means for Solving the Problems) In order to achieve the above objectives, the present invention provides an AC power source, a load device insulated for each phase, and a positive group for supplying current to each phase of the load. and a cycloconverter having a negative group converter, a first phase advancing capacitor connected to the input side common terminal of each phase positive group converter of the cycloconverter, and a common input side of each phase negative group converter of the MiJ cycloconverter. A cycloconverter device is constituted by a second phase advance capacitor connected to the terminal and a power supply lance interposed between the AC power supply and the cycloconverter.

Also, the number of control phases (number of control pulses) of the cycloconverter
The first and second phase advancing capacitors are further divided according to the configuration.

(Function) In other words, when the number of output phases of the cycloconverter is three, the input side terminal of the positive group converter of each phase cycloconverter is connected to a common first phase advance capacitor, and that terminal is connected to the power supply l- By connecting to the secondary winding of the lance, 3
The delayed invalid input current of the positive group converter for the phase and the leading current of the first phase advancing capacitor cancel each other out, and the power supply 1
-Only active power flows through the secondary winding of the lance. The input side of the negative group converter operates in the same manner, and as a result, it becomes possible to significantly reduce the capacity of the power transformer.

At this time, the load of the cycloconverter is insulated for each phase to prevent a short circuit from occurring in the power supply.

When the number of control phases (number of control pulses) of the cycloconverter increases, the first and second phase advance capacitors are further divided accordingly, and operation with small output current ripple can be performed. Even in this case, the effect of reducing the capacity of the power lance is the same.

(Embodiment) Fig. 1 is a block diagram showing an embodiment of the cycloconverter device of the present invention.7 In the figure, SUP is a three-phase AC power supply, MTR is a power transformer,
CAP□□, CAP□2 are the first phase advance capacitors, C
AP2. .

CAP22 is the second phase advance capacitor, CC-U, CC-
V, CC-W are circulating current type cycloconverters, U, V
, W is a three-phase AC load.

U-phase zychroconverter CC-U is positive group converter 5S
PU, SDPυ and negative group converter SSNυ, SDN
υ and DC Liator LOυ (Lout −LOLIs
). The same applies to the V-phase and W-phase cycloconverters CC-V and CC-W.

In addition, CTs are current transformers for detecting 3-phase AC current, and PTs are 3-phase AC current detection current transformers.
Phase AC voltage detection transformer, VAR is reactive power calculation circuit,
CT, JHCTv + CTW is output current detector, cr
,v+CTNU+”TPVtCTNV+CTPWyC
TNW is an output current detector for each converter.

FIG. 2 is a block diagram showing an embodiment of the control circuit of the device shown in FIG.

In the figure, VRQ is a reactive power setting device, HQ (s) is a reactive power control compensation circuit, Gou (s) tGOV (s) +
GOW (s) is the load current control compensation circuit, Gu (s) +
Gv(s), Gw(s) are load current control compensation circuits, O
C1 to OC3 are circulating current calculation circuits, C and C7 are comparators, A1 to A6 are adders, and INV and INV are inverting amplifiers, respectively.

The operation of the apparatus of the present invention will be described below with reference to the embodiments shown in FIGS. 1 and 2.

First, the control operation of the load current IU+TV+I- will be explained. An example of a U-phase microconverter CC-UTE will be explained.

Load current Iυ is detected by current transformer CTU, and comparator C
Enter 1. Comparator C3 determines whether the current detector IU
and its command value ■v*, and its deviation Eυ=■♂−I
Find U. The deviation EU is converted to the following current control compensation circuit G
input to u(s) and amplify it. The output signal of GU(S) is
1 through the adder A, the positive group converter 5SPu,
Input to phase control circuit circle 1PU of 5DPu. G again
The other one of the output signals of U(s) is sent to the negative group converter SSNυ, 5D via the inverting amplifier INV1 and the adder A,
NU phase control circuit P) Input to INU.

Now, suppose the circulating current control circuit G. If the output signal from U(S) is ignored as being sufficiently small, the input signal tαP1 of the phase control circuit PHPU and the input signal tαP1 of the circle (Nu) and the gate αN
O has the following relationship. However, GU(S) has only υ as a proportional element.

In addition, the output voltage of the positive group and negative group converters VPU + VN
If we consider υ to be positive in the direction of the arrow in Figure 1, we have the following relationship.

Vpu" 1Iliv 'Vs' CO8(l
puVNu=-A v 1Vs 2cos αNU However, Mwa is the conversion constant, VS is the power supply voltage, αPUsαNU
are the control phase angles of the positive group and negative group converters.

Furthermore, cosapU=ffl φναPIJ+ CO
Since there is a relationship of 8αNU='A'tα, υ, VPU”
VNLI, and the control phase angle at this time is αN, =
180'-αI)U.

The voltage Vu applied to the load tJ is the average value of the output voltages Vpu+VNIJ of the positive group and negative group converters.

Vt+” (VPIJ+VNU) / 2=AV-A・
■8・Eυ・KI” In other words, a voltage VU proportional to the current deviation cU is applied to the load.

In the case of I,'>Iu, the deviation ε,J becomes a positive value, and the output voltage Vυ is increased and the current is increased by 11□, so that it is controlled to finally become ■uL9Iu'.

Conversely, when ■♂<I u, the deviation ε1'' becomes a negative value, making vU a negative value, reducing the current ■U, and the current command value settles as IU→■♂. When ■♂ is changed into a sinusoidal waveform, the actual current ■U is also controlled into an iE sinusoidal wave accordingly.

At this time, Vpu''VNυ is always satisfied, and there is no increase or decrease in the circulating current.

The load currents (I) of the (2) and W-phases are similarly controlled.

Next is the circulating current ■. The control operation of IJ + IOV + IOW will be explained.

Again, the explanation will be given by taking as an example the chromatic converter CC-U which supports the tJ phase.

Circulating current of U-phase microconverter■. 4. is the output current pU and INIJ of the positive group and load converter detected by the current transformers CTPU and CTNυ, and
It is obtained by inputting it into C1 and performing the following calculation.

l01J= (IPU+INU l (IP
U INLI) l) / 2 Here, there is a relationship IPU INLI=IIJ.

The thus obtained circulating current detection value IOυ is input to the comparator C2 and compared with the circulating current command value Io'u. The deviation E□υ=Io*u Iou is input to the current control compensation circuit G□υ(S) and amplified. Gou(s)
The output signals of are input to the phase control circuit circle (PU, Pl+Nυ) via adders A□ and A2, respectively.

Therefore, the input signal game αPυ of the circle (Pu, PHNu,
ναNO is changed as follows. However, Gou
Consider (s)=Kou.

9αPU: εU °KU+ t 01,1 °KO
UγαNU”−ευ0 to υ+ε0υ” KOU Therefore,
The output voltages VPU and VNυ of the positive group and negative group converters are unbalanced by 0υ with respect to the above ε0υ·, causing the circulating current l0tl to increase or decrease.

That is, ■o1. ．． *〉■. When υ, the deviation E
Qυ becomes a positive value, and VPU>VNIJ by that amount. Therefore, the circulating current becomes Iou=Iou* and settles down.

Conversely, if ■olJ*〈Iou, the deviation F. If υ becomes a negative value, V p u < V N U. Therefore ■. 0 decreases and again, Iou = Io
*U is controlled.

Circulating current of ■phase and W phase■. V+'Iow is similarly controlled.

” - Command value of circulating current: [o'ul In*ヮ+
Io~ is given by the output signal from the reactive power control circuit HQ(S).

Next, the operation of the reactive power control will be explained. Current transformer CTs and transformer P installed at the receiving end of Cygro converter
T8 detects the three-phase AC current and three-phase AC voltage and inputs them to the reactive power calculation circuit VAR. The reactive power Qs at the receiving end is -1-distribution power voltage 'l'R+vS+ +1)
The phase of T is delayed by 90°, and each phase current) - RrIgt
Multiply each by fT and add the three phases. i.e.
Qs-vR"LR+v3'"ノS+vT" j-T
vR' - bs yr) /J3Vs'"'
(VT-vR) /1/3vT' ”” b
Instantaneous reactive power QS is detected by lg Vs) /V3.

The reactive power detection value O8 is input to the comparator CI and compared with the command value Qs* from the reactive power setting device VRQ.

The relevant deviation EQ=QS*Qs is calculated by the reactive power control compensation circuit It.
Q(s) and performs integral amplification or proportional amplification.

Usually, an integral element is used for IQ(s) (in order to make the steady-state deviation ε1, zero).

The output of IQ(s) is the command value of the circulating current of each phase zyroconductor■. −+ IO＊ヮ + IO□.

If OS*>Qs, the deviation EQ will be a positive value,
Increase the circulating current command value IO'lJ + IO□, ■o-. Actual circulating current■Button JI Ii', )V+ 1
As mentioned before, Iou 'q Io*u t
Since it is controlled so that Iov 'F ro*v r Iow sakiIo'ti, the circulating current ■. Ll+几ヮ+IOW also increases, increasing the delayed reactive power (h) at the power receiving end, causing Qs=Qs* to fall.

Conversely, when Q, □;*<Qs, the deviation E Gl becomes a negative value, and each phase @ ring current ■. Ll+ Iov+ Io
By increasing w and reducing the delayed reactive power Qs at the receiving end, is it still OSSO3? I want to be able to control how I yell.

Note that in this case, the reactive power detection value QJ delay is treated as a positive value.

In addition, in general, the reactive power command value Qs is given as ``O'' in order to perform a power conversion with an input power factor of 1.

Zychroconverters CC-U, CC-V, C (Jl uses the power supply voltage to perform natural commutation, The current ■0.

Depending on the value of IV+I, the control phase angle of each converter at that time αPLl+ ” NIJ+ αl'V+
Although it varies depending on the value of It NV + αpHl + αNL, Qcc can be kept at a constant value by adjusting the circulating current (Ovr 'IOV and l0Ill ) of each phase cycloconverter as described above.

This is divided into the secondary winding side of 5 power supply I/Lanos penalty) and connected to 'C'. C
AP1. .

CAP7. , CA, j is −・constant leading reactive power Q c
a T1, 1. J, it is sufficient to supply the active power Psr from the power source SUI+ by canceling out the delayed reactive power Qcc.

Now, in the cyglo converter device of the present invention, C,
Positive group converter 5SPII for C-U, positive group converter 5SP for CC-V and positive group converter 5SP for CCMU
The input side terminal of y is connected to a common phase advancing capacitor CAP, □, and the leading reactive power Qcap11 and s of CAP, ,
spυ, the sum of the delayed reactive powers of 5SPV and 5SPIll, Q S S P x , cancel each other out L.

At this time, Qssp+ can be expressed as the following equation.

Qsspn = IA Q(Ipu-sin a pu
+Tpu'sjn a py+Ipvsin fk p
u) However, stones. When the proportional loads U, V, and W are the electric motor f and the winding of an AC motor, the speed electromotive force is small during starting and low-speed operation, so the output voltage of the zycroconverter, Vυ+VV+V, is small, and the control phase angle αpU+ aPv"= αpHl'F90
'It is operated under the condition of '. At this time, the delayed reactive power Qs taken by the zycroconverter becomes maximum, and the circulating current Iou
+ Iov + Iow is the minimum value.

Phase advance capacitor CAP, □, CAP1□, CAP, □,
CAP22 is α1) tl-α=αpv=αNV-
When αpw = aNv = 90'', the delayed reactive power of the microconverter when the load current ■υ+IV*Iψ takes the maximum (11'i) is
Qcap = Qcapx □→-Qcapx 2 +
Prepare Qcapz IIQcapz 2. Therefore Q
cap, 1: Qcgip/4.

Figure 3 shows the circulating current Iou = Iov = Iow
”= O, 1st group converter 5SPU, 5SPV
, SS['1. output current t o +−+ +I
The waveforms of OV+IOW and delayed reactive power Ossp□ are shown below.

However, αPLI”αI)V'Fαpt+: (')
It is treated as such.

The same applies to the delayed reactive power Qsnpt of the positive group converter SDPυ, 5l)Pv, 5DP6j connected to the secondary line of the Δ result of the power supply 1-lance MTR. That is, QSDPI = Qssp+.

On the other hand, negative group converters SSN, , SSNν and SSN
, the output current INU + INV + INW is the current waveform IPLl + IPV and II)W shown in Fig. 3, whose phase is 180°, but the reactive power QSSN□ is (r
NU JuchoNu”sin rtNVJuchoNvSinαN
Warning) Reactive power Q3S taken by the positive group converter
・Do with N1.

That is, Qssp+″Qsr+pt = QSssx = Q
SDNI=Qcc/4 holds true. Phase advance capacitor CAI)□1. CAP,
2. CAP2. −.

The maximum value Q of the delayed reactive power Qcc that the cycloconverter can take from the leading reactive power Qcap taken by CAP. C(
I! If you prepare only 1aX), it will always be Q. c"Qca
Circulating current 1゜υ+IOshi, ■ollI flows so that Q 3 S P 1. ” Q CaP x s
will be satisfied.

That is, on the secondary side of the power transformer MTR, the leading reactive power QCap1s taken by the phase advance capacitor CAP, □ and the lagging reactive power Qsspt taken by the positive group converters 5SPUISSPV, 5SPII+ completely cancel each other out, and the secondary winding of the transformer MTR Only active current will flow.

The same applies to other secondary windings.

CYC 0” J converter cc-u, c (knee v, cc-u
The output terminals are separated for each phase of the load, so no short-circuit current will flow even if the input terminals are shared.

The device shown in Fig. 1 has been described for a 12-pulse cycloconverter, but for a 6-pulse cycloconverter,
It is sufficient to prepare a first phase advance capacitor CAP1 and a second phase advance capacitor CAP2, and in a 24-pulse cycloconverter, divide the first phase advance capacitor into four,
cAPl, ,CAP,2. CAP13. CAP...

Then, the second phase advance capacitor is also divided into four parts, CAP2. .

Pzz + cAp23 to C. c8)), 4.

Although the device shown in FIG. 1 has been described for a circulating current type cycloconverter, it goes without saying that the same effect can be achieved even when applied to power factor improvement of a non-circulating current type cycloconverter.

〔Effect of the invention〕

As described above, in the cycloconverter device of the present invention,
The reactive power can be completely canceled out on the secondary side of the power transformer MTR, making it possible to significantly reduce the capacity of the lance. In particular, the current flowing through the secondary winding is only the effective current, and there is no need to increase the current capacity of the secondary winding as in conventional devices.

In addition, the number of power supplies per lance is 173 compared to the conventional device, and the cost can be reduced accordingly.

Furthermore, during light load operation, the current flowing through the power transformer is also reduced, and losses are correspondingly reduced, allowing for efficient operation.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing an embodiment of the cycloconverter device of the present invention, Fig. 2 is a block diagram showing an embodiment of the control circuit of the device of Fig. 1, and Fig. 3 shows the operation of the device of Fig. 1. FIG. 4 is a waveform diagram for explaining the configuration of a conventional cycloconverter device, and FIG. 5 is a waveform diagram for explaining the operation of the device shown in FIG. 4. 5U11...3-phase AC power supply MTR...Power supply 1-Lance CAP, 1. CAI), 2... First phase advance capacitor CAP2□, CAP, 2... Second phase advance capacitor CC-U, CC-V, CC-W... Circulating current type cycloconverter U, V, υ... AC load agent Patent attorney Nori Ken Chika Yudo Hirofumi Mitsumata Figure 2 Ipu Ipv I-pw Figure 3 Lsspty = A:・Ipu Figure 5 tAPwJ Yuyu CAPw4 Figure 4

Claims (2)

[Claims] (1) An AC power supply, a load device insulated for each phase, a cycloconverter having a positive group converter and a negative group converter for supplying current to each phase of the load, and a positive group converter for each phase of the cycloconverter. a first phase advance capacitor connected to the input side common terminal of the cycloconverter, a second phase advance capacitor connected to the input side common terminal of each phase negative group converter of the cycloconverter, and the alternating current and the cycloconverter A cycloconverter device consisting of a power transformer interposed between the (2) The cycloconverter device according to claim 1, wherein the first and second phase advance capacitors are divided according to the number of control pulses of the cycloconverter.