JPS6039371A - Cycloconverter device - Google Patents

Abstract

PURPOSE:To eliminate a circulating current detector by controlling the sum of the output currents of converters when controlling the reactive powers of a power receiving terminal. CONSTITUTION:A current detector CTS and a voltage detector PTS are mounted at a power terminal, and the reactive power Q is calculated by a reactive power calculator VAR. The command value Q* of the reactive power is normally set to zero, and a deviation epsilonQ=Q*-Q is generated by a comparator CQ. A control compensating circuit H(S) is used to set the normal deviation epsilonQ to zero, and the output IT* becomes the control command value of the sum IT=I1+I2+I3 of the output current of the converter. To control the sum current IT=I1+I2+I3, the sum V1+V2+V3 of the output voltage of the converter may be controlled, thereby eliminating the conventional circulating current detector. As a result, the reliability can be enhanced, thereby simplifying the circuit.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a triangular connection cycloconverter device capable of controlling reactive power at a receiving end.

[Technical background of the invention]

A cycloconverter is a frequency conversion device that directly converts alternating current power at one frequency into recurrent power at another frequency, and has recently been widely used as a drive power source for induction motors and synchronous motors.

The triangular connection cycloconverter has three AC/DC power converters (
A commonly used cycloconverter (a cycloconverter in which a positive group and a negative group converter are paired to form one phase of output ) has the advantage of requiring half the number of converters, and recently,
It has started to attract attention (Special application 1986-1586)
92).

Figure 1 shows a configuration diagram of a conventional triangular connection cycloconverter device.
It is described in 2.

In FIG. 1, BUS is a three-phase AC power supply line, C is a phase advance capacitor, TR is a power transformer, CC is a three-phase output cycloconverter body, and M is a three-phase AC motor. The cycloconverter main body CC has three AC/DC power converters (converters) s, sl, ss2° SS3 and DC reactors L1, L2 with intermediate taps.

It is composed of La. Power converter (converter) 8
AC input side of 81, 882, 883 is power transformer TR
The DC side is Δ-connected via DC reactors Ll+L, L3 so that a unidirectional circulating current flows. It constitutes a so-called triangular circulating current type cycloconverter. DC reactor f-1, L
2, the intermediate tap of La is connected to the three-phase winding of the three-phase AC motor M.

On the other hand, the control circuits include a current transformer C'rs that detects the three-phase AC current at the receiving end, and a transformer P that detects the three-phase AC voltage.
Ts, reactive power calculator VAa, control compensation circuit H(s),
Reactive power setting device Va, comparator CQ, co.

C1, C2, C3, adder A1. A2. A3, operational amplifier Ko, 1. 2. 3. Phase control circuit PH,,,P
H2゜PH3 and load current detector CTU, c'r■, C
Tw is used.

First, the operation of load current control will be explained.

FIG. 2 shows an equivalent circuit of the cycloconverter CC and the electric motor M shown in FIG. 1, and it is assumed that the electric motor M is Δ-connected. V,,V2゜v3 is converter s
s1. The output voltages of ss2 and SS3 can take positive and negative values. However, the output currents I, , I2 . I3 allows current to flow in only a certain direction. The electric motor M is wire-connected, and its windings are designated Ma, Mb, and Mc.

If the currents Ia, Ib, and Ic flowing through each winding are taken in the directions shown in the figure, and the relational expressions between the line currents IU, v, and w are calculated as follows.

Ia=(Iu Iv)/3 −・(1) Ib=(Iv
Iw )/3 -=...(2) Ic=(Iw Io
)/a +m・(3) In addition, IU + ■V r 工W
and Ia, Ib, and Ic are treated as balanced three-phase sinusoidal currents.

FIG. 3 shows waveform diagrams of various parts of FIG. 2. Phase currents Ia and Ib for line currents U, I■, and w.

Ic satisfies the above formulas (1,), (2), and (3). Since the output currents 1 p I2 HI11 of converters ss, , ss, and SS3 cannot flow in the negative direction, the line currents υ, Iv.

It changes as shown in the figure depending on the value of Iw. This can be divided into the following three modes.

Mode I: Ivku0. In this case, the output current of SS1 becomes zero. Therefore, Kaya 1
=”V + Works = Iw flows.

) Mode II: Iw<O, Io>0 At this time, the output current factor 3 of S83 becomes zero. Therefore I
I ”IU + Work 2 = 'W flows.

Mode ■: IU<0. Iv>0 At this time, the output current Il of SSl becomes zero. Therefore I
z = IV, L = -IU.

Note that the above description has been made for the case where the circulating current 0 is not flowing through the cycloconverter CC, but if the circulating current 0 is flowing, the output current I! of each converter. .

I, , I, is a value on which the DC component IO is superimposed.

As can be seen from the equivalent circuit in Fig. 2, when the output voltage of each converter is in a three-phase balanced state, the following voltage equation holds true.However, the windings Ma, Mb,
The resistance of Me is FLa, Rb, 几C, the inductance is La, Lb, Lc, and the back electromotive force is Da, Fib.
, Ec.

Furthermore, p=d/dt is a differential operator.

V1=(Ra+La-p)-Ia+Ea +++++ (
4) From v2=(Rb+Lbφp)-+Eb...
(5) V3=(R,c+Lc @p)・Ic+Ec
...(6) Therefore, to control the current Ia, v
By changing l, the currents Ib and Ic can be controlled by changing v2 and v3, respectively.

Returning to the apparatus shown in FIG. 1, the control operation of the phase currents Ia, Ib, and Ic will be explained.

By the current detectors CTtr, CTv, CTw,
Detect the line currents Io, Iy, and w, (1), t2)
, +3+ calculate the phase current detection values Ia, Ib, and Ic.

These are input to comparators C1, C2, and C3 and compared with phase current command values, I"b, and Pc.Each deviation...
= f'a-I a , t2 = i'b-I b ,
tg = I * c - I c to amplifier Kl.

K2. 3 and input to phase control circuits PH1, Pi (and PH3), respectively.

For example, in the case of Ia minus IOb, G1·K1 increases, increasing the output voltage v1 of converter S81, and increasing the phase current Ia shown by equation (4). Finally Ia-? a
controlled so that Conversely, in the case of Ia) Ia, G
1.Kl decreases, vl decreases, and Ia decreases, and it is also controlled to -1.

Similarly, for other phase currents, I b = I”b, I
It is controlled so that c−I”c.

If Ia, Ib, and Ic are controlled as three-phase balanced sinusoidal currents as shown in Fig. 3, the line current ■U r ■V * ■W, which is the input current of the motor M, will naturally have the waveform shown in Fig. 3. It becomes a three-phase balanced pressure sinusoidal current as shown below.

Next, the control operation of reactive power at the power receiving end will be explained.

The power supply terminal has a current detector CTs and a voltage detector PTs.
is installed, and its reactive power Q is calculated by a reactive power calculator VA. The reactive power command* value Q is normally set to zero, and the comparator C calculates the deviation εci
=Q*-Q is generated. The control compensation circuit H(s) normally uses an integral element in order to make the steady-state deviation εQ zero, and its output formula becomes the command value of the circulating current IO. The deviation eoJo IO is taken by the comparator co and is passed through the amplifier KO to the adder A! , A2. Enter in A3. Therefore, the input ε4°G5, 66 of the phase control circuits PH, PH2, PH9 is as follows.

1+ε in G4−εl@.・Ko・・・・・・(7)εS
-ε21IK2+εo 'Ko ・-・i8) G6-G
3. 3+εG喀K. ... River (9) Therefore, the output type JE Vt, V2, v3 of each converter is the above ε
It becomes larger in a DC biased form by the amount of o-KO,
A circulating current 0 flows through the DC reactor L1 r ``2 + ''3.

The DC bias voltage is DC reactor L,, L2,
If the resistance of L* is sufficiently small, then it will settle down to almost zero.

In the steady state, the output voltage vl of each converter is
# v2 t ”3 is balanced and v, +v, +v
, =o...αe.

The circulating current Io of the cycloconverter appears as delayed reactive power when viewed from the power supply side, and does not affect the increase or decrease of active power.

Therefore, the load power construction U of the cycloconverter.

Delayed reactive power based on IV+”W and the above circulating current IO
The circulating current 1. By controlling the value of IK, the input fundamental wave power factor can be maintained at IK.

In other words, the detected value Q of the reactive power at the receiving end is the command value Q.
- When εQ=♂-Q is a positive value, the command value of the circulating current via the control compensation circuit H(8) increases. Therefore, the actual circulating current IO increases, and the reactive power (delay) Q
will also increase. Finally, * is reduced to Q=Q, and control is performed so that Q=Q as well. If the command value Q is set to zero, Q=O, and the fundamental wave power factor at the receiving end is controlled to 1.

The above-described conventional device requires means for detecting the circulating current (i) of the cycloconverter CC.

Figure 4 shows a time chart when the circulating current Io is flowing through the device in Figure 1, where ■l is the converter 8S.
, the output current of 8G1. SG2. SG, are each line current I
A state diagram showing the positive or negative state of υ, work V, and Iw, swl
, sw2. sw3 is the above 8G, , S02. It represents the logic output of SG3.

FIG. 5 shows a specific circuit diagram for detecting the circulating current IO. 0 is an inverting operational amplifier with a gain of 1. Analog switch person S has three switches swl, sw
2. sw, and the logic outputs SW, , SWz shown in the operating mode of FIG.

It is turned on and off by SW3.

In FIG. 4, the output chamber iIt of the controller SS1 is connected to the output current 1 of S81 shown in FIG. The current value is obtained by superimposing the circulating current factor 0 on the current value.

That is, the current electrician l can be divided into the following three modes.

■ When IW <, 0, Iun 0, 11=Iυ11
0■ IUkuO, IV When 〉0 ■1=IO■ I
When y<o, Iw>o, ll--Iy+I.

Enter signal SG1 U〉0. Engineering SG2■〉0. SG3 I
By setting W>0 and performing the following logical operation, the signals sw1. sw2. sw3 is obtained.

■Signal of SW1,,=SG,・SG3 ■Signal of SW2=SG2・SG1 ■Signal of SW3=S03@SG2 Therefore, the analog switch A30 in Fig. 5, the three switch SWs, sw2. The detected value of the line current Io, the zero voltage, and the inverted value of the detected value of the line current IV are connected to each input of the signal S'vV1. sw2. By turning on and off according to sw3, the output current of converter SS1 when circulating current I0 does not flow can be determined. The circulating current ■ is obtained by subtracting the value obtained by the above calculation from the detected value of the actual converter SSl output current ■1.

be criticized.

[Problems with background technology]

Such conventional triangular connection cycloconverter devices have the following problems.

Ia) First, the circulating current of the cycloconverter CC is 0.
It is necessary to detect this, and therefore the calculations shown in FIGS. 4 and 5 must be performed. In particular, the stone signal SG for determining whether the currents It+, Iy, and Iw are positive or negative,
802. It is difficult to obtain SG3, and the current IU
, Iv, and Iw, the signal is disturbed and the circulating current ■. Problems arise, such as not being able to detect. Although other methods for detecting the circulating current (2o) are possible, all of them require complicated arithmetic circuits, lower the reliability of the device, and become economically expensive.

(b) In the conventional device, the circulating current command value I? from the reactive power control circuit? Circulating current of cycloconverter according to 0
However, the circulating current control system has a load current I
Disturbances occur due to the flow of U, Iy, and Iw.

Therefore, it becomes difficult to control the circulating current Io so that it matches the command value, which affects the reactive power control at the power receiving end.

Therefore, a control system that is not susceptible to disturbances is required.

[Purpose of the invention]

The invention was made in view of the above, and the reactive power at the receiving end of the triangular connection cycloconverter is
It is an object of the present invention to provide a cycloconverter device that can control a circulating current of a converter without relying on a detected value and has a control system that is not affected by disturbances caused by a load current.

[Summary of the invention]

In order to achieve the above object, the present invention provides a circulating current type cycloconverter body connected to a three-phase load and triangularly connected by at least three AC/DC power converters, and a load current control circuit for controlling a load current, a means for detecting reactive power at a receiving end of the cycloconverter, and a sum for controlling 80 of the output current of each of the converters in accordance with a signal from the reactive power detecting means. A zycroconverter device consisting of a current control circuit and a phase control circuit that controls the firing phase of each contactor according to the output signals from the load current control circuit and the sum current control circuit. The difference is that the control amount is the sum of the output currents of each controller/unit.

[Embodiments of the invention]

FIG. 6 is a block diagram showing an embodiment of the cyclocondenser overnight device of the present invention.

In the figure, BUS is a three-phase AC power supply wire, CAP is a phase advancing capacitor, T is a power transformer, CC is a three-phase output cycloconverter body, and M is a three-phase AC motor (load). Cyclokonnoku Ichiyo main body CC has three AC/DC power converters (converters) 88. .

ss2. ss3 and DC reactor L' + L21
It is composed of L3. Power converter (Konno(-ri) SS,.

ss2. The AC input side of ss3 is insulated by a power transformer (R), and the DC side is connected to a DC reactor L1. L2. △ via L3
It is connected. It constitutes a so-called triangular circulating current type cycloconverter. DC reactors Ll, L2.
The center tap of L3 is connected to the three-phase winding of a three-phase AC motor M.

On the other hand, the control circuits include current transformers CTs that detect the three-phase AC current at the receiving end, and transformers PTs that detect the three-phase AC voltage.
, reactive magnetic force calculator VAJ reactive power control compensation circuit H(s)
, reactive power setter V IL, comparator CQ, CT, Cυ,
CV, Cw1 adder Al-A6, current control compensation circuit GT
, GU, Gv , Gw, phase 1 is also 11# circuit PH,,
PH2, PH3 and output current detector CT! .

CT2. CT is used.

First, the operation of load current control will be explained.

Installed on the output of converters SS, SS2 and SS3!
.

I2. I, the current detector CT1. Detected by CT2 and CT. The 'current detection values i, , I2. I3 is input to a current converter CLC (not shown), and the load current detection value U + V y IW is calculated by performing the following calculation.

IU = I, -I, ... (one IV = I, -
I, ... @ Iw=I3-I2 ... (g) Of course, the load electric construction U+■V+Iw may be detected directly.

The detected value of the load current ``U + W r IW and its command value 'TI, rS + W are compared to the comparators CU, Cv, C
Input into w and each individual difference εU = a ”U reV = trench - I
v, 6w4: set tw. The relevant deviations εU, εV, ε
After passing W through the following current control compensation circuits GU, GV, and Gw, the adder 1.83 and A5 generate a control signal ``lre(12re(I3)) expressed by the following equation.

eα1==Qg−εU−c+v・ε■ ・・・・・・α
荀ea 2 = Gy * 5 W −GW @g W
・-”αGe α3 = GW 11εW-GU@εu
−= □f9 Here, each current control compensation circuit GU, GV
By combining the control constants of , ow, Gtr=Gv=Gw=G(s)... can be replaced with α force, and the equation (a) becomes as follows.

ea1=(gtr gv)@G(s) +-+Qaeα
2=(εV−εW) −G(s) ・−・−αseα
3=(ε to ε.)・G(s) ...... These control signals eCLl, eα2. eα3 is the next adder A
2. A, , A6 are added to a signal ect (1) from a reactive power control circuit, which will be explained later, and input to phase control circuits PH, PH2 and PH3.

Here, for convenience of explanation, the explanation will be continued assuming that the value of the signal eaQ is zero.

For 3-phase 3-wire loads, IU +IV +Iw =
There is a relationship of 0. Therefore, the command value of the load current is also 4+
Give so that 4+4=o is satisfied. As a result, the current deviations of each phase εU, ε■, εW are εσ+εV+εw==Q
...Q→.

If you look at it as a specific value, for example, εU=2. ε
When y=1, 幇=-3. Therefore, the output voltage vl of converter SSl increases in proportion to (εU-εv)-1, the output voltage V2 of S82 increases in proportion to the value of (εV-εW)=4, and the output voltage of S83 increases in proportion to (εV-εW)=4. The voltage v3 is (ε
It decreases in proportion to the value of W-εo)=-5.

The equivalent circuit of the main circuit of the device shown in FIG. 6 can be expressed similarly to that shown in FIG.

Therefore, the current Ia increases in proportion to the increase lII in vl, the current Ib also increases in proportion to the increase I4 in V2, and the current Ic decreases in proportion to the decrease 1-51 in ■3. Here, load current (line current) ■U+ IV +
'W and the above-mentioned phase currents Ia, Ib, and Ic are expressed by the following relational expression (%) () This relational expression holds true regardless of whether or not a circulating current is flowing through the Δ-connected load.

Therefore, IU increases by w6m and Iyld “3’
The bamboo increases and the work w decreases by 1-91. These increases and decreases △WorkUr△IV, △1w are each △IU: ``6'' (X: ε, == 121 △: tv''
3 'oegy = w 1 w △ engineering w - 1 - 91 father εW = ' 3 ', and it can be seen that it is proportional to each deviation.

In this way, the load electric construction U, IV, and iW can be directly controlled.

Next, the operation of reactive power control at the power receiving end of the cycloconverter CC will be explained.

The power supply terminal has a current detector CTs and a voltage detector PTs.
is installed, and its reactive power Q is calculated by a reactive power calculator VAR. The reactive power command value φ is normally set to zero, and a deviation *εQ=QQ is generated by the comparator cQ. Control compensation circuit H(s)
An integral element is usually used to make the steady-state error εQ zero,
The output IF is the sum of the converter output currents IT #sum current detection value IT is the output of each converter current L
This is simply the sum of the three detected values and does not require any complicated calculations.

The comparator CT compares the sum current command value F and the sum current detected value IT, and the deviation εT=? Input T-IT to the current control compensation circuit GT.

The current control compensation circuit GT is often composed of an integral element or a proportional element, but for the sake of simplicity, only the proportional element (amplification factor KT) will be explained here.

Therefore, the deviation ε1 is multiplied by KT and input to adders A, , A, and A6.

In the case of silicone T, the deviation εT is a positive value9, εT・KT
The output voltage of each converter is increased by a value proportional to V1. v2.
Increase v3 in the direction of the arrow in FIG.

As a result, the circulating current I of the cycloconverter CC.

increases, and the output current of each converter I, ,
I2. I3 increases and the sum current IT =I! +I2+I3
will also increase. Therefore, it is controlled so that IT=IT.

On the other hand, when I''; .Therefore, the sum current IT decreases and IT = IT K
controlled so that

When the firing phase angle of each converter at a certain instant is αl+ct2 and q3, the reactive power Qc at the receiving end of the cycloconverter cc is expressed as the following equation.

QCC=kQ ・(Il ・sin αr +I, a
sir+a, +I, 115ina3)...
Here, the ignition phase angle α1. α2. α3 changes moment by moment in synchronization with the frequency on the load side, but in a naturally commutated converter, it is normally controlled within a range of 20° to 15o0, and its sine values sinα1, sinα2, and Sjnα3 are always positive values. In addition, the output current of each converter is 11°I
2. Since I3 also always takes a positive value, increasing the sum of the currents air will increase the delayed reactive power Q mentioned above. C is increased, and the summation flow command value *IT is increased via the control compensation circuit H(s). As mentioned above, the sum current IT is the *command value■. Since h is controlled to be equal to , h also increases, and the delayed reactive power Q taken by the cycloconverter CC. Increase 0.

The reactive power Q at the receiving end is the delayed reactive power Q of the cycloconverter. If the delay is expressed as a positive value by the sum of 0 and the leading reactive power Qcap of the phase advancing capacitor CAP, the following equation is obtained.

Q = Qcc -Qcap ·-H Therefore, since Qcap is almost constant, the reactive power at the receiving end increases by the amount that Qcc increases. is controlled so that the cal increases and Q* = QK.

On the other hand, when Q*<Q, the deviation εQ becomes a negative value, and the total current force T=equipment decreases. =Q*.

FIG. 7 shows an equivalent circuit of the cycloconverter CC and the load (motor M) of the device shown in FIG. 6, and it is assumed that the load is connected in a large manner.

The voltage equation can be calculated from this equivalent circuit as follows.

However, p is a differential operator.

vl = (R, +L1 p)-il +M, pi2+M
31 pi3+VUy...Kan v2 = (EL2 +L2 p)* i2 +M, 2p
i1 +M23pi3 +VVW... (a) V3 = (Ft3 +L3 p) * i3 10M,,
p i, +MBpi2 +VWU... 翰MU =(RL +LL p) +() +vQU,
"," (1) VV = (RL + LT, I) ) ・
iv +Vcv =-C(1)Vw-(RL+LL
I) ) ・jw + #CW =・(M where R1,
``2,'' 3 and Ll r L2 + ''3 are the resistance and self-inductance values of the DC reactor, Ml2,
M23, M3□ are mutual inductance values, RL
.

LL is the resistance and inductance value for one phase of load.

Further, vCU + vcv l vcw represents the back electromotive force of the crawler, Vg, 'lay, VW represent the phase' solder pressure applied to the load, and vuv + vVW, vwU represent the line voltage of the load. Therefore, we have the following relational expression.

VOy = VU −vv −...n vvW ”= VvMW ””・CHIVWU ==
l/W -vU-...% Also, converter output current 1
1+'2+'3 and the load currents iσ, iv, and iW satisfy the following relational expression as described above. This is not related to the presence or absence of the circulating current Io.

io = il-il ... (g) iy = i
2-il...(b)iw=i3-i2...
...(To) Here, R1=R2=R3=L, =L2=L3
=: [,.

As Ml, :M, 3==M31==M, (a) formula -,'
Putting in equation A, vl −Vg = (R0Lp) (il
-il) -MP(il -il) 12V UV
y V W −(R+(LM)p)(it −il )+3VU=
(R+(LM)p)iU+3((RT,+LLp)i
U+vcU) =3[几/30R,+((LM)/3+LL'1[
) J 'u 13VCU... (c) becomes. However, the relationship vU+VV+VW=0 was used.

Therefore, it can be seen that in order to control the flow jU of the load', it is sufficient to use the relationship of equation (A) and control vl-v3.

Similarly, if we add the Kan-shiki-i-shiki and the Kan-shiki-(to)-shiki, we get the following.

V 2-vl -3(R/ 3 + RL + ((L
M) / 3 +LT,)p)iv+3°vCv
...) Va Vz = 3 (R/'3+RL+ ((LM)
/3 +TJL) T) ) 'w+3#Vow
...... (41) From the relationship in equation (7), to control the load current 1y, the voltage V
2 Vl may be controlled, and from the relationship expressed in equation 411, it can be seen that in order to control the load current iw, it is sufficient to control the voltage V3-v2.

The load current control circuit shown in FIG. 6 uses the above principle.

Also, if we consider the relationship between Kashiki + Kanni 11-shiki, we get the following.

v1±Vg +v3 = (R, +Lp) (il +
i2 +13) +zMp (il+ t□+js) +vU■+■■t+vwU = (几+(L+2M) p) (j+ + j+ +
's )... (4 forces, that is, the sum current 'T '' L l+j2 + il
To control the output of the converter, the sum of voltages Vl +
It can be seen that it is sufficient to control VB +v3. Moreover,
The transfer function of the control system is determined by the resistance value R of the DC reactor and the value of the inductance (L+2M), and the control system is free from external disturbances.

In the conventional device, the output current of each converter +1゜i,...
+3 is the circulating current i6 and the load current dependent component 'l
p F Hj3' and il = i6 + il
・・・・・・(Belief 1□−I.+12 ・・・−・(44)
i3=i, +i3... (It is treated as Tsukuda, and (formula 43 is treated as follows.

Ml +v2 +v3 = (R+ (L+2M) p
) (3io+i+'+i2'+1s)=(R0(L
+2M) p) Sleep 3 i.

10 (几+(L” 2M) p ) (it 10+≦+1
3)... (46) In other words, the sum of converter output voltages Vl +v2+v3
The circulating current io is controlled by ΔeL=(I%+(L+2M)p)("1'+i2
jB ) ”・(47) enters and disturbs the control of the circulating current io. Here, i'l + i; +
il changes at a frequency three times the frequency on the load side, and the disturbance ΔeL increases in proportion to the frequency, and is also proportional to the magnitude of the load current 'U+'V+'W.

Disturbances in the control of the circulating current io appear as reactive power fluctuations at the receiving end, which become sideband waves around the power supply frequency (fundamental wave), causing various adverse effects on the power supply system.

On the other hand, in the device of the present invention, which uses the relationship of Equation 421 as is, there is no disturbance from other sources, so the sum current jT-1
In addition to keeping 1+12 + j3 constant, it is also possible to freely change it according to reactive power control.

As described above, in the embodiment shown in FIG. 6, the cycloconverter main body CC is composed of AC/DC power converters (converters) 881, 882, and 883, but in order to increase the number of control pulses of the cycloconverter, a group of converters connected in cascade is arranged in a triangular manner. The same applies to wired items.

〔Effect of the invention〕

As described above, in the device of the present invention, the reactive power jl+!
By configuring the system to control the sum of the output currents of each converter during total control, the following effects are produced.

(a) The conventional circulating current detection circuit is not required, and as a result, a highly reliable and economical system can be provided.

(b) Conventionally, accurate circulating current control was not possible due to disturbances entering the circulating current control system, and as a result, reactive power fluctuations remained at the power receiving end, which had various negative effects on the power supply system. The device of the present invention can configure a control system without disturbance, achieve accurate sum current control, and have extremely small fluctuations in reactive power at the receiving end, making it possible to obtain a cycloconverter device that does not adversely affect the power supply system. can.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of a conventional triangular-connected cycloconverter device, Fig. 2 is an equivalent circuit diagram of the main circuit of the device in Fig. 1, Fig. 3 is a waveform diagram of Fig. 2, and Fig. 4 is a diagram of each waveform in Fig. 2. 1 is a time chart for explaining the operation of the device, FIG. 5 is a circulating current detection circuit diagram necessary for the device in FIG. 1, and FIG. 6 is a configuration showing an embodiment of the cycloconverter device of the present invention. Figure, 7th
This figure is an equivalent circuit diagram for explaining the apparatus of FIG. 6. BUS...3-phase AC power supply line CAP...
・Phase advance capacitor TR...Power transformer CC...Three-phase output
- 3-phase AC motor (load) ssl, ss, ss3...AC/DC power converter (converter) Ll, Ll, Ls...DC reactor CTs, CT4, GT2. GT3-
Current transformer PTs・-Transformer VAR・・Reactive power calculator H(s)・・Reactive power control compensation circuit V ・・Reactive power setting device cQ, cT, cU, Cv, Cw ...Comparator A1~
A6... Adder GT, GU, Gv, Gw... Current control compensation circuit P
H1, PH2, PH3... Phase control circuit (731
7) Agent: Kensuke Chika, patent attorney (and 1 other person)
Fig. 2 CC Itt M Fig. 3 Fig. 4 Fig. 11 = -IP It-1υ I/≠θ It knee 17 Fig. 5

Claims (2)

[Claims] (1) A circulating current type cycloconvert connected to a three-phase load and triangularly connected by at least three AC/DC power converters, and load current control that controls the load current to be supplied to the three-phase load. a circuit, means for detecting reactive power at the receiving end of the cycloconverter, a sum current control circuit for controlling the sum of output currents of the respective converters in accordance with a signal from the reactive power detecting means, and the load current control circuit. A cycloconverter device comprising a circuit and a phase control circuit that controls the firing phase of each converter according to the output signal from the sum current control circuit. (2) Connect a phase advance capacitor to the power receiving end of the cycloconverter, and adjust the output current of each converter so that the leading reactive power taken by the phase advance capacitor and the lagging reactive power taken by the cycloconverter exactly cancel each other. The cycloconverter device according to claim 1, characterized in that the sum is controlled.