JPS6231337A - Parallel operator for cycloconverter - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a parallel operation device for circulating current type cycloconverters.

[Technical background of the invention and its problems]

A cycloconverter is a power conversion device that directly converts AC power at a constant frequency into AC power at a different frequency.
It is commonly used as a Hz/60Hz frequency converter or as a drive power source for AC variable speed motors. Since the voltage of the AC power supply is used to commutate the elements (thyristor, etc.), it has the advantages of high reliability and easy capacity increase. On the other hand, it has the disadvantage that it takes a lot of reactive power from the power supply, and that reactive power constantly fluctuates in synchronization with the frequency of the load. For this reason, there have been problems such as increasing the capacity of the power supply system equipment and causing fluctuations in the power supply voltage, which have various adverse effects on electrical equipment connected to the same system.

In contrast, a method has been adopted in which an active filter, a reactive power compensator, or the like is installed at the receiving end of the cycloconverter to compensate for the high frequency and reactive power generated by the cycloconverter. However, the active filter and reactive power compensator described above require a large-capacity machine comparable to that of a cycloconverter (the equipment becomes expensive, and the equipment becomes large, creating new problems such as insufficient installation space). It's here.

Furthermore, in order to solve the above-mentioned problems, a reactive power compensation type cycloconverter device (Japanese Patent Publication No. 14988/1988) has been proposed. This device actively uses the circulating current of the cycloconverter, and the cycloconverter generates a cycloconverter so that the leading reactive power of the phase-advance capacitor connected to the receiving end of the cycloconverter is exactly equal to the lag reactive power of the cycloconverter. It controls the circulating current of the converter, and the fundamental wave power factor at the power receiving end is always maintained at I, eliminating any adverse effects on the power supply system. In addition, the conventionally required reactive power compensator and the like are no longer necessary, making the device smaller and lighter, which also leads to lower costs.

FIG. 5 shows a conventional system configuration diagram in which several reactive power compensation type cycloconverters are operated in parallel.

In the figure, BUS is the electrical line of the three-phase AC power supply, and CAP.

CAP, , --・-, CAPn is a phase advance capacitor, T
r It Tr2, "'Trn is the power transformer, CC
,, CC, , -, CCn is the circulating current type cycloconverter, Ml is the AC motor load, and Mn is the AC motor load. In addition, CT is used as a control circuit.

CT, , , , , c'rn are 13-phase AC current detectors, PT, , PT, .

--・, PTn is a three-phase AC voltage detector, VARl, V
AR2,...

VARn is a reactive power calculation circuit, AQRI I AQR
,l”・.

AQRn is a reactive power control circuit,
+ ``'+ 工0'' is the circulating current control circuit, ILCl f
f ILCl l "'l ILCn is a load current control circuit, PHC,, PHC, . . . PHCn is a phase control circuit.

Circulating current type cycloconverter CC1 is a three-phase motor M1
．． : It supplies alternating current power with variable voltage and variable frequency.
The above motor M81 by the load current control circuit LC+:
Controls the supplied three-phase load current.

On the other hand, a three-phase current detector CT and a three-phase voltage detector PT1 are installed at the power receiving end of the cycloconverter CC1, and send the next reactive power calculation circuit V A RC voltage and current detected value. The VA unit calculates the reactive power Q at the receiving end, and sends the calculated value Q□ to the reactive power calculation circuit QFL1.

The reactive power control circuit AQ bird is a circulating current control circuit that controls the circulating current of the bicycloconverter CC8 so that the reactive power Q□ at the receiving end becomes zero. C1 controls the circulating current of CC1 in accordance with a signal (circulating current command value) from the reactive power control circuit AQR.

The phase control circuit PHC is the load current control circuit ILC1 mentioned above.
and circulating current control circuit engineering. Output signal 1 of C1: Therefore, it controls the firing phase of the cycloconverter. The above operation is described in detail in Japanese Unexamined Patent Publication No. 56-133982.

The operations of other cycloconverters CC, . . . , can are similarly performed.

As described above, in the conventional parallel operation device for cycloconverters, the reactive power at the receiving end of each cycloconverter is controlled to maintain an input power factor of 11, and the input power factor as a whole is always kept at 1. can be kept. However, the following problems remain.

■ Even if the input power factor at the receiving end of each cycloconverter is maintained at 1, the overall input power factor is always 1:11:1 due to the connection of auxiliary equipment, etc. Not necessarily.

■Special? 2. If one or more of the cycloconverters is gated off due to an accident, the overall reactive power will advance due to the phase advance capacitor connected to the receiving end of the cycloconverter, leading to a rise in the power supply voltage. There is.

■ Reactive power control at the receiving end of each cycloconverter::
Usually, an integral element or the like is used, and a very fast control response cannot be expected. As a result, reactive power fluctuations synchronized with the output frequency cannot be suppressed, and sideband waves around the fundamental wave remain in the input current, which has various adverse effects on other electrical equipment.

■■fSecondly, a method has been proposed in which the circulating current of each cycloconverter is controlled based on a command value calculated from the output current value and the firing phase angle of the converter to increase the response of reactive power control ( Japanese Patent Publication No. 57-916
(No. 70) In this case, there is a tendency for the disadvantage (2) to become even more severe due to changes in calculation conditions, etc.

■ Power receiving end 1 of each cycloconverter: The capacity of the connected phase advance capacitor is determined when each cycloconverter takes the maximum load (when the delayed reactive power reaches its maximum) 1: The power factor of the power receiving end is 1 (: is designed to be, i.e.
Regardless of the operation mode of other cycloconverters, the capacitance of the phase advance capacitor is determined so as to obtain the leading reactive power that is sufficient to cancel out the maximum value of the delayed reactive power of the own cycloconverter, so it is a wasteful capacity from the overall perspective. The drawback was that even a phase advance capacitor was required.

■ Increasing the capacity of the phase advance capacitor means increasing the capacity of the power transformer, converter, etc., which causes unnecessary circulating current and causes inefficient operation.

[Purpose of the invention]

The present invention has been made in view of the above, and improves the response of reactive power control at the receiving end of each cycloconverter, as well as reliably controls the overall reactive power at the receiving end of an AC power supply, and prevents damage caused by an accident, etc. It is an object of the present invention to provide a cycloconverter parallel operation device that prevents a rise in power supply voltage from occurring even when one or several cycloconverters are gated off.

The present invention also provides a parallel operation device for cycloconverters, which integrates phase advancing capacitors connected to the power receiving end, reduces the capacitance of the capacitors, power transformers, etc., and allows efficient operation of the device as a whole. The purpose is to

[Summary of the invention]

In order to achieve the above object, the present invention connects a phase advance capacitor to the common magnetic receiving end C of a plurality of circulating current type cycloconverters, and calculates the output current value and firing phase angle of each cycloconverter. Calculate the first circulating current command value, detect the reactive power of the entire device, determine the second circulating current command value to be given to each cycloconverter so that it becomes zero, and calculate the sum of the two command values. (:Thus, the circulation tii flow of each cycloconverter is controlled.

Prepare the optimum value for the phase advance capacitor considering the operating mode of the entire system.

This improves the reactive power control response of each cycloconverter, eliminates reactive power fluctuations synchronized with the output frequency, and removes sidebands around the fundamental wave contained in the input current.

In addition, even if one of the cycloconverters is gated off due to an accident, reactive power control for the entire device can be continued by the remaining normally operating cycloconverters, and the fundamental wave power factor at the receiving end can always be maintained at 1. You will be able to do this. In addition, the capacitance of the phase advance capacitor is reduced, which eliminates the flow of wasteful circulating current in the system as a whole, allowing efficient operation.

[Embodiments of the invention]

FIG. 1 is a block diagram showing the configuration of an embodiment of the cycloconverter parallel operation device of the present invention.

In the figure, BUS is the electrical line of the three-phase AC power supply, CAP is the phase advancing capacitor, Tr L 'rr 2+ +++, Trn
l;! 'El source transformer, CC1+ CC1s...C
Cn is a circulating current type cycloconverter, J HM21
...Mn is the AC motor load.

In addition, as a control circuit, a three-phase current detector CTs, a three-phase electric current detector PTs, and an R1 comparator Cq to the reactive power calculation circuit V.
, reactive power setter VRQ, interval compensation circuit HQ(S), feedforward control circuit FF'1. FF...F
Fn, adder ADD, , ADD, , , person DDn,
Circulating current control circuit ■. C,,I. ni,..., engineering. Cn
, Output current side other circuit ■LC1+ If, + ”・+
II, Cn and phase control circuit PHC,.

P) IC,..., PHCn are prepared.

First, the normal operation of the cycloconverter CCI will be explained. FIG. 2C shows an embodiment of a 23-phase output cycloconverter. In the figure, TrU, TrV, and TrW are power transformers, and CC-U, CC-V, and CC-W are U-phase and V-phase, respectively.

W-phase circulating current type cycloconverter, LOADIJ.

LOAD, , LOAD are the armature windings of motor M1 in FIG.

The U-phase microconverter CC-U is composed of a positive group converter ssp, a negative group converter SSN, and a DC reactor LQI I Lot with an intermediate tap.

In addition, as the control circuit, C0NT-U, a load current detector CTL, and an output current detector C of the positive group converter.
T, negative group converter output current detector CTNυ, addition sinners 1 to 4, comparators C,, C,, 0°K for the operational amplifier, and phase control circuits PHP, PHN are used. .

The V-phase and W-phase cycloconverters are similarly configured, and the control circuits C0NT-V and C0 are surrounded by one-dot chain lines.
NT-W)-! It is configured similarly to the U-phase control circuit C0NT-U.

First, the operation of load current control of the circulating current type cycloconverter will be explained using the U phase as an example.

Compare the load current command IL[J and the detected value of the load current ILU that actually flows, and calculate the deviation ε2 ” IL U −I
The two-phase control circuits PHP and PHN are controlled so that a voltage proportional to LU is generated from the cycloconverter CC-U.

The output phase αN of PHN with respect to the output phase αPU of PHP
υ maintains the relationship αNυ = 180° − αPU,
PHN+2 is applied to the amplifier via the inverting circuit INV. That is, the output voltage of the positive group converter SSP, V de υ = VS - αPtl and the negative group converter S
SN output voltage vso = -1 (v'va - ■αPυ is balanced at the load terminal during normal operation. When the current command umbrella ILtl is changed sinusoidally, the deviation ε
3 also changes, the load (armature winding of 3-phase AC motor M,)
so that the sinusoidal current ILU flows through (: the αPU and α
, 4U is controlled. In this normal operation, since the SSP output voltage VPU and the SSN output voltage NU are equally balanced, almost no circulating current flows.

The V-phase and W-phase load current detectors +ILW are also controlled in the same way.

Next, the circulating electrician. The control operation will be explained. even here,
This will be explained by taking a U-phase cycloconverter as an example.

The circulating current Ion is detected as follows. That is, the sum of the detected value of the output current IPH of the positive group converter SSP and the detected value of the output current INU of the negative group converter SSN is calculated, and the absolute value of the detected value of the load current ILU is subtracted from it.
1/2') is the circulating current l0tl. The relational expression is as follows.

■. . =(IP+lN-l11.DI)/2 The circulating current IOU thus obtained is compared with its command value Ioυ. The deviation ε,=Ioυ−IOtl is applied to the amplifier via 1 to the adder A, and to 4+2.

Therefore, the inputs ε4 and ε to the phase control circuits PHP and PHN are of the fourth order.

1φε to ε4=,・ε3+.

ε, = -, ・ε, 10, ・ε.

Therefore, the relationship f2α, υ=180°−αPυ collapses, K1
- The output voltage vpt+ of the positive group converter SSP and the output voltage vNυ of the negative group converter SSN become unbalanced by an amount proportional to ε. The difference voltage is DC reactor LO8
゜Lo, l2 is applied, and a circulating current IOU flows. Circulating electrician. . is the command value. If it flows too much, the deviation ε!
becomes a negative value, and vPυ<vNυ, so ot1 is decreased. As a result, the circulating current l01J is controlled to be equal to its command value ■.υ.

Circulating current ZOV of the V@, W phase cycloconverter and ■. W is also controlled in the same way according to its command value O and ION.

Normally, the above circulating current command value is used. 0. Engineering 0 ma, engineering. W is given as the same value. However, in order to suppress the increase in the current capacity of the cycloconverter, a method has also been proposed in which the load current is distributed according to the magnitude of each phase load current (Japanese Patent Application Laid-Open No. 133982/1982).

Above, the basic operation of the cycloconverter CC-type shown in FIG. 1 has been explained. Other cycloconverters CC.

...CCn operates similarly.

Next, each cycloconverter CC1, CC,...C
Feedforward control circuits FF, , FF1. that control reactive power at the receiving end of Cn. ...The operation of FFn will be explained.

FIG. 3 is a configuration diagram showing an embodiment of a feedforward control circuit that controls reactive power at the receiving end of the cycloconverter CC1.

In the figure, s KffU+Kff'l'+ has 4W and Ka
is an operational amplifier, Lλ(0゜LMv, LMw is a limiter circuit, SQU, SQv, SQw is a square calculation circuit, SQ几u
, 5QRv, SQRw are square root calculation circuits, MypM
y, My is a multiplier, DIV is a divider, AD1 to AD8
is an adder, and VR is a reactive power setting device at the receiving end of CC.

First, the phase control input voltage Vα11 +”ay +vffW is taken out from the control circuit 900 shown in FIG.
The feedforward control circuit FF in the figure is operated by two people.

Vασ is the output signal of the amplifier Kt in FIG. 2, and takes a value proportional to the average value of αPU and αNu.

Therefore, by multiplying VαU by a constant by αυ in the amplifier, αU can be obtained as the cosine value of the ignition control angle αU. Next(
The limiter circuit LMυ determines the upper and lower limits of the signal αυ in the amplifier in order to satisfy the condition -1≦1αU≦1. This signal is divided into two by the square calculation circuit SQo.
Multiply, adder AD, l by two people. AD, the output signal of the SQυ is subtracted from the unit voltage 1, and as a result, 1
-) 9αU is found. This is passed through the next square root arithmetic circuit SQ⇠U to find sin αu=JT base 1C.

Similarly (from two Vetv sin αV is also VIx, from s
inαW is calculated.

Next (2) Take the absolute values IILIJI, l■Lvl, lxLwl of the load current of each phase cycloconverter in Fig. 2 and input them to the multiplier MO, My, M, and C of the feedforward control circuit FF in Fig. 3. .Multiplier Mυ
is the absolute value of the above load current IILOI +=the above 5ina
Multiplying by υ, we find 1ILol・sinαU,
Similarly 1: M ma C2, lxt, vl sin α ma,
Also, IILWI·sin αW can be obtained from Mwl2. These signals are added by adders AD and AD,-2 and input to the next adder D6. The reactive power setting device VR generates a signal Icap1 in response to a virtual phase advance capacitor (i.e., a flowing advance current Icapt). When setting the fundamental wave power factor at the power receiving end of the cycloconverter CC to 1, Icapt = 1 for Icapt/ is set as a conversion constant. However, in the device of the present invention, the phase advancing capacitor CAP is connected to the power receiving end of the entire cycloconverter, so Icapt does not exist.Cycloconverter CC8 , CC, . . . When the capacitances of CCn are the same, the virtual leading current Icap1 may be set to (1/n) of the current Icap flowing through the phase advancing capacitor CAP.If the capacitance of each cycloconverter is different, f Second, Icapx can be assumed to be proportional to its capacity jl.

To restate the above, Icap = 1capx
/, the cycloconverter CC, has a virtual lead current of 1. Is there enough delay current Ialm0 to cancel capl? -1 will be taken.

The adder AD receives the VR output signal Icap from the adder AD.
.

The output signal lILol-sinCtg+111yl-sinαV→
IL, which subtracts l-sin αW, is multiplied by 1/2 by the next amplifier Ka. On the other hand, the adder
and AD, by 5ina roju sinαmaju sinα
Find W and input it to the divider DIVc.

The output signal 01 of DIV is given as follows.

Circulating current engineering for each phase cycloconverter. . , Eng. . , Eng. 1 is the above command value r:+ =I:o ”I:ma=IOW
i2 is divided so that it is equal to .

Figure 4 shows the voltage and current vector for one phase on the input side of the cycloconverter CC1, where v8I is the power supply voltage,
■aI is the power supply current (virtual), and Icapz is the leading current (virtual) of the phase-advancing capacitor. . O)I. . V+I. .

7 is the input current of each phase cycloconverter, l8faP is the input current of the positive group converter SSP of the U-phase microconverter, and sss is the input current of the negative group converter SSN. -2 represents the delayed reactive current of the cycloconverter CC and the whole.

In the case of a U-phase microconverter, at a certain instant, a circulating current Ion and a load current I, υ flow through the positive group converter ssp at an ignition control angle αPυ. Therefore, if the conversion constant is set to 1, then s
The magnitude of the input current xssp of sp is ks (IO, +
lIL, l). In addition, the negative group converter has a firing control angle αNUS1
At 80°-αpu, a circulating current IOU flows. Therefore xs
The size of ss is kI·l0tl. Therefore, the input current I00υ of the U-phase microconverter becomes as shown in the figure, and its reactive current component, l1ll! AO? -0 is 1I
RIIA□? −u = l5P5jnαpo+l5s
H0sinαN.

= to 1 to Iot++1ILul) sin α0.

Similarly, the reactive current components of the V-phase and W-phase cycloconverters IRImuO? -V exist IRIImuO? -W is given as follows.

IRmaa chi v = kl to °Iov+ l IL
V l)'Sjnαma IRII□. T-W = kl・
・IOW+1IIiWI)・sin(Ew cycloconverter CC, total delayed reactive current IRIAO?-1
is a combination of these, and is as shown in the following equation.

I, Proverb A (1?-1” IRIAO Chi σ + IRjAO Ding-V + IRmAO Chi W = ni・IoU+lIr,
of)・sin αU+, to −Iov+111. Yl
)-sinctv+,ni・Iow+IILwl)si
nαW where, as mentioned above, the circulating current l0IJIIOV
When +IOW is controlled according to the circulating current command value IO,r2 from the feedforward control circuit FF1, the above process ag
The program 0i-1 becomes I: as follows.

IRIAQ? -1 = to + to @Iot + lI
Lt+ 1)-sin αU+, Ni・Iol +l
L, vl)・5 incty, ni・engine. 1 + II
LIF+)・5inc! y=2kl Iol (sin
α(1-4-sinαv+5inct,)+kt(
I ILo 1sinαg+ IIt, vl−” si
nαv+1ILIyls+nα=kl−Icap Icaps=Icapx /, l: If set, the delayed reactive current I of the cycloconverter CC, ■AO? −
1 is equal to the virtual lead current Icapt +=, so that the virtual supply current Is+ = Iaimu ot-t
+Icapt is the power supply voltage V8. There are only in-phase components. That is, the fundamental wave power factor at the receiving end of the CC is controlled as follows.

Actually, since Icapx does not exist, a constant delayed reactive current "nMAQT-1" flows through CCI, resulting in CC
1 and IRIIAQ? − flows, and the leading current Ic of the phase advancing capacitor CAP connected to the receiving end of the entire cycloconverter flows.
A part of ap Icapx and the above delay current 1111jAO
? -1 cancel each other out.

Other cycloconverters CC, . . . CCn are controlled in the same way.
imAay-s = kl @ Icap 3 engineering 1lAO
? -n = kl Icapn. The sum of the delayed currents of these cycloconverters, IRIA(+?-1+I
yvAo cheat +-+Ixmio? −n is equal to the leading current Icap flowing through the phase advancing capacitor CAP in FIG.
・If Icapn is given, the overall reactive power at the receiving end becomes zero, and operation with a power factor of 1 is possible.

In this way (2. Feedforward control C2), the value of the circulating current to be passed through the cycloconverter is calculated and given from the phase control signal and the value of the load current (output current), so it cannot be used for conventional reactive power detection. The accompanying detection delay and dead time are no longer a problem, and a control system with good followability can be constructed.

However, the cause of accidents (from the second point, cycloconverter C
When one or several units among C,, CC,...CCn are gated off, Icap = IasAa〒-+ + Iaiio'f
−t + −−−…+IFIIIλ0? -n relationship no longer holds true, and the power factor at the power receiving end becomes advanced, which has negative effects such as increasing the voltage of the grid.

Therefore, in the device of the present invention, the reactive power of the entire power receiving end is monitored and controlled so that it matches the command value.

The operation will be explained below.

In FIG. 1, reactive power Qy at the power receiving end of the entire device is detected. The three-phase current detector CTs and three-phase voltage detector PT shown in Fig. 1 detect the current and voltage at the receiving end,
Reactive power calculation circuit VAR (operated by two people).

In VAR, the phase of the three-phase detection voltage is shifted by 90',
Multiply that value by each phase detection current. Then, the value added for the three phases is the reactive power detection value (instantaneous value) at the receiving end Q? becomes.

The reactive power detection value Qv and its command value Q? Compare Cql by two people, and find the deviation εq=Q↑−Q? seek.

The deviation εq is input to the next control/compensation circuit HQ for proportional or integral amplification. ) I, (S) crab. ↑ is the second circulating current command value of the cycloconverter, and is added to the output signal from the feedforward control circuit FF1, that is, the first circulating current command value Io1, by the adder ADD, l2. , C.C.

Circulating current command value, engineering. ,+I. 1 is given. Circulation BRQ a I of each phase of cycloconverter CC3. U.J.
Qma.

Ioy is the above command value IO++IO? (I explained earlier that it is controlled to match.

The other cycloconverters CC, . . . CCn are controlled in the same manner.

When each cycloconverter CC,, CC,, -0, CCn is operating normally, lCa1)" Inmho!-+ +Inxhot-t is controlled by feedforward control.
−+ “−−−= + In*hat−.

is satisfied, and the reactive power command value Q? in Fig. 1 is satisfied. =O, Qv'=QT=0, and the deviation εq is almost zero. Therefore, the output signal r from H45)
ot is also approximately zero.

Here, assuming that the gate of CC is cut off due to an accident, ILIAO = 0, and the reactive power at the receiving end Q! becomes a leading value and becomes a negative value. Therefore, the deviation, εQ=Q? -Q〒 becomes a positive value and increases the second circulating current command value 10T. Therefore, the circulating current of other cycloconverters is IO? increases by the amount that increases,
Increases delayed reactive power. As a result, Qt is 4 from the beginning
+2, Qt = (h = O, and it settles down.

Next (Nicycloconverter CC1, CC, -0, CC
The control operation when one or more of n units is operated under overload will be explained.

In the apparatus of FIG. 1, adders ADD1. Person DD.

..., the output of ADDn is set to 1 through a limiter circuit so that the minimum circulating current always flows (to give two command values. In other words, the circulating current command value of CC,*
* ■Pull+IO? If is thicker than Δko, is it IO1+IO? If given as is, % 01 + ". T ΔI, then 1; is ΔI.

I try to give and receive.

If CC□ is operated with overload, pre-warning;
It is given as cap1=constant, and ■. It becomes 1 × 0. If Ioy”wO, then IC1l+IO?
0, and "o1 + work at < ΔIo. Therefore, 1
A constant circulating current command value ΔIo is given, Icap < rnm ot-r + IxmAoy-t
+-song+Immhot-a, and QT becomes delayed.

Therefore 1 = deviation εQ = Q? Qt becomes a negative value, and the second
The circulating current command value ot is set to a negative value I:. Therefore, other cycloconverters cc, , cc, ,...C
The circulating current command value of Cn also decreases, resulting in Q? ”w
It is controlled so that Qt=Ol2.

That is, the cycloconverters CC,, CC,...
Even if one or several CCn units are in overload operation, if other cycloconverters are under light load, the circulating current of the cycloconverter during light load operation is reduced,
The power factor of the entire receiving end is maintained at 1. At this time, since the minimum circulating current is controlled to flow even in the cycloconverter which is being overloaded, each cycloconverter does not lose its good characteristics as a circulating current type cycloconverter.

Furthermore, when most of the cycloconverters in the device are operated under overload, each cycloconverter is mini-controlled so that only the minimum circulating current flows, resulting in reactive power Q at the receiving end! becomes delayed, and power factor = 1 is no longer satisfied.

However, overload operation does not occur frequently;
Moreover, most cycloconverters are rarely overloaded. Therefore, the influence on the power supply system is also small.

〔Effect of the invention〕

As described above, according to the device of the present invention, the following effects can be expected.

■ Even if non-circulating current type cycloconverters, auxiliary equipment, etc. are connected to the power supply system, the input power factor as a whole including them can be maintained at 1.

■ Accident 1: Even if one or several cycloconverters are gated off, the other normal cycloconverters can continue to control the reactive power at the power receiving end, and are connected to the power system. The impact of 1: can be prevented to a minimum.

■ During normal operation, feedforward control enables reactive power control with good followability, and output frequency 1 = synchronized reactive power fluctuations are eliminated, and around the fundamental wave of input current, which was conventionally considered to be extremely harmful. harmonics (sidebands) can be removed.

■ The capacitance of the phase advance capacitor connected to the power receiving end can be selected to the optimum value by considering the operation modes of multiple cycloconverters, and the capacitance can be reduced.

■ Also, unnecessary circulating current is no longer allowed to flow, and the capacity of power transformers and converters can be reduced. At the same time, efficient operation becomes possible.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the cycloconverter parallel operation device of the present invention, FIG. 2 is a block diagram showing an embodiment of the cycloconverter of the device in FIG. 1, and FIG. FIG. 4 is a block diagram showing an embodiment of the feedforward control circuit of the device. FIG. 4 is a voltage and current vector diagram at the receiving end to explain the operation of the circuit in FIG. 3. FIG. FIG. 2 is a configuration diagram showing a parallel operation device. BUS... Electric line of three-phase AC power supply CAP... Phase advance capacitor Trl, Tr21..., Trn,... Power transformer CC,, CC,..., CCn... Cyclo converter M19M! ,...Mn...AC motor load CTII...3-phase current detector PT,...3-phase voltage detector VAR...Reactive power calculation circuit FF, , FF, ,...FFn...・Feedforward division circuit ADD, , ADD, , J)Dn
98. Adder oC+ + Io”!+ −+ Io
Cn - circulating current control circuit ILC1, ILC,...
・, ILCn ・・・Output current control circuit PHC,,
PHC,,--0,PI-ICn-Phase control circuit agent Patent attorney Nori Chika Ken Yudo Wang Hou Hongbun Figure 2

Claims (1)

[Claims] An AC power supply, a plurality of circulating current type cycloconverters connected in parallel to the AC power supply, a plurality of loads receiving power from each of the cycloconverters, and a phase advancing capacitor connected to the receiving end of the AC power supply. a means for controlling the output current of each of the cycloconverters; a means for controlling the circulating current of each of the cycloconverters; means for controlling an ignition phase angle; means for calculating a first circulating current command value given to each of the circulating current control means based on the output current value and the ignition phase angle of each of the cycloconverters; and the AC power source. A parallel operation device for cycloconverters, comprising means for applying a second circulating current command value to circulating current control means of each of the cycloconverters, in order to control the entire reactive power at the power receiving end of the cycloconverters.