JPH0221219B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a reactive power control type cycloconverter device that freely controls the fundamental wave power factor seen from the power source side in accordance with a command value.

A cycloconverter is a device that directly converts alternating current power at a constant frequency into alternating current power at a different frequency, but because its component thyristor is commutated by the power supply voltage, it has the disadvantage of taking a large amount of reactive power from the power supply. There is. Moreover, the reactive power constantly fluctuates in synchronization with the frequency on the load side. This not only increases the capacity of current system equipment, but also
Reactive power fluctuations have various negative effects on electrical equipment connected to the same system.

FIG. 1 is a block diagram of a conventional reactive power control type cycloconverter device. In the figure, CC is the main body of the circulating current type cycloconverter, SS-P and SS-N are its positive group and negative group converters, Lo ₁ and Lo ₂ are DC reactors with intermediate taps, and LOAD is the load. Also, TR is a power transformer, C is Δ or a connected phase advance capacitor, and BUS is a three-phase electric line. The control circuit includes a current transformer CT _S that detects the three-phase AC current at the receiving end, a transformer PT that detects the three-phase AC voltage, a reactive power calculator VAR, and a control compensation circuit H.
(S), a current transformer CT _p that detects the output current I _p of the positive group converter SS-P, a current transformer CT _N that detects the output current I _N of the negative group converter SS-N, and adders A ₁ to A _Five ,
Operational amplifier K ₀ ~K ₂ , inverting amplifier K ₃ , comparator C ₁ ~
C ₃ , absolute value circuit ABS and phase control circuit PH-P,
PH-N is used.

Adder _A3 calculates I _p −I _N =I _L . This is the detected value of the load current. Also, adders A ₁ , A ₂
The following calculation is performed using the absolute value circuit ABS and the amplifier K ₀ (1/2 times).

I ₀ =(I _p + _IN − |I _L |)/2 (1) This is the detected value of the circulating current.

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

The phase control circuit compares the load current command I ^* _L with the detected value I _L of the load current that actually flows, and generates a voltage from the cycloconverter that is proportional to the deviation ε ₃ .
Controls PH-P and PH-N. The output phase α _N of PH-N with respect to the output phase α p of PH- _P is transferred from amplifier K ₂ to PH- _N via inverting amplifier K ₃ so as to maintain the relationship α _N = 180° − α p. is input.

In other words, the output voltage of positive group converter SS-P
V _p =K _v・V _S・cosα _p and the output voltage of negative group converter SS-N V _N =k _V・V _s・cosα _N =k _v・V _S・cos (180°−α _p ) is the load terminal Normal operation is carried out in a balanced state. When the load current command I _L is changed sinusoidally, the deviation ε ₃ also changes accordingly, and α _p and α _N are controlled so that a sinusoidal current I _L flows through the load. In this normal operation, the positive group converter SS-P
Since the output voltage of the negative group converter SS-N and the output voltage of the negative group converter SS-N are equally balanced, almost no circulating current I _O flows.

Next, the operation of circulating current control will be explained. A current detector CTs and a voltage detector PT are installed at the power supply terminal, and their reactive power Q is calculated by a reactive power calculator VAR. The reactive power command value Q ^* is normally set to zero, and the deviation ε ₁ = Q ^* −Q is determined by the comparator C ₁
is generated. The control compensation circuit H(S) normally uses an integral element in order to make the steady-state deviation ε ₁ zero, and its output I _O ^* becomes the command value of the circulating current I _O. comparator
The deviation ε ₂ =I _O ^* −I _O is taken by C ₂ and input to adders A ₄ and A ₅ via amplifier K ₁ .

Therefore, the inputs ε ₄ and ε ₅ to PH-P and PH-N
are as follows: However, K ₃ =-1.

ε ₄ =K ₂・ε ₃ +K ₁・ε ₂ …(2) ε ₅ =−K ₂・ε ₃ +K ₁・ε ₂ …(3) Therefore, the relationship α _N = 180° − α _p breaks down. , the output voltage of the positive group converter SS-P is proportional to K ₁・ε ₂
V _p and the output voltage V _N of the negative group converter SS-N become unbalanced. The differential voltage is applied to DC reactors L _O1 and L _O2 , and a circulating current flows. If I _O flows too far below the command value I _O ^* , ε ₂ decreases, reducing the voltage difference. As a result, I _O is controlled to be equal to I _O ^* .

If reactive power Q is leading, ε ₁ =Q ^* −Q=−Q
becomes positive, increasing I _O ^* and increasing the delayed reactive current of the cycloconverter. Eventually Q=0
The circulating current I _O is controlled so that

Conversely, if Q is delayed, ε ₁ <0, and I _O is controlled so that I _O ^* is decreased so that Q=0 as well. In this way, the reactive power at the receiving end can be maintained at zero, that is, the fundamental wave power factor can be maintained at 1.

Figure 2 shows the voltage and current vector diagram at the receiving end of the cycloconverter shown in Figure 1, where V _S is the power supply voltage, I _cap is the current of the phase advancing capacitor C, I _ssp is the positive group converter input current, and I _SSN is the negative group converter input current, I _CC is the cycloconverter input current, I _REACT
is the reactive current of I _CC and I _S is the power supply current. This vector diagram is drawn at a certain point in time when the load current is changing moment by moment, and the values of the currents I _ssp , I _SSN and the phase angles α _P , α _N are changing moment by moment.

When the reactive power control described above is performed, the circulating current I _O is controlled so that I _cap = I _REACT , but I _REACT
is given as follows. However, α _N ≒180°−α _p .

I _REACT = I _ssp・sinα _p + I _SSN・sinα _N ≒ (I _ssp + I _SSN )・sinα _p = k ₁ (I _p + I _N )・sinα _p = k ₁ (2・I _O + | I _L | sinα _p ...(4) Here, k ₁ is the conversion constant of the converter. Therefore, when controlled so that Q = 0, that is, I _cap = I _REACT , the circulating current I _O satisfies the following equation .

I _O =I _cap −k ₁・|I _L |・sinα _p /2k ₁・sinα _p ...(5) FIG. 3 shows an equivalent circuit of the circulating current type cycloconverter body CC of FIG. 1. In the figure, V _p and V _N are the output voltages of the positive group and negative group converters, i _p and i _N are their output currents, i _L is the load current, Vd is the load terminal voltage,
Vc represents the back electromotive force in the case of a motor load, R _L and L _L represent the resistance and inductance of the load, and r, L and M represent the resistance and self and mutual inductance of the DC reactor, respectively.

Equations (6) to (8) are obtained by setting up voltage equations with voltage and current in the directions shown. However, P=d/dt
is a differential operator.

V _p = (r+LP)・i _p +MP・i _N +Vd ……(6) V _N =−MP・i _p −(r+LP)・i _N +Vd……(7) Vd=(R _L +L _L P)・i _L +Vc...(8) Also, if the circulating current is _iO , the current satisfies the following relational expression.

i _p −i _N = i _L ...(9) i _p +i _N =2・i _O + |i _L | ...(10) Here, equation (6) + equation (7) and equation (6) - Find equation (7) and (9),
Considering the relationship in equation (10), the following equations (11) and (12) are obtained.

V _p +V _N = {r+(L-M)・P}i _L +2・Vd ...(11) V _p −V _N {r+(L+M)P} ・(2・i _O + |i _L |) ... ...(12) Equation (11) is related to load current control, and equation (12) is related to circulating current control.

A block diagram of the control system of the cycloconverter is drawn as shown in FIG. 4 based on the operating principle described above. In the figure, the part surrounded by the broken line is (8),
(11), which represents the relationship of Eq. Also, K _p・e ^- 〓 ^s
represents the gain K _p and dead time e ⁻ 〓 ^s of the positive group converter, and K _N · e ⁻ 〓 ^s represents the gain K _N and dead time e ⁻ 〓 ^s of the negative group converter. S is a Laplace operator. Note that there is a relationship of K _N =-K _p .

The reactive power Q at the receiving end can be expressed as a value obtained by multiplying the difference between the delayed reactive current I _REACT of the cycloconverter and the advanced reactive current I _cap of the phase advance capacitor by a coefficient K _Q.
I _REACT can be expressed by equation (4).

As can be seen from the block diagram of this control system, in the conventional reactive power control type cycloconverter device, the circulating current _iO is controlled so that the reactive power Q at the receiving end becomes equal to the command value Q ^* . , when a load current flows through the circulating current control system, a disturbance Δe _L expressed by the following equation is introduced.

Δe _L ={r+(L+M)S}·|i _L |...(13) In order to make the circulating current i _O respond faithfully to its command value i _O ^* , it is necessary to compensate for the above disturbance Δe _L. Ho(s) in FIG. 4 is the compensation circuit, which is specifically described in Japanese Patent Application No. 55-39911.

The compensation circuit ho(s) has a transmission relationship as shown by the following equation (14).

ho(s)={r+(L+M)S}/(2・K _p )...(14) In other words, since it contains a differential term proportional to (L+M), the noise is weak and a filter circuit is essential in actual circuits. As a result, complete compensation cannot be provided. Furthermore, even if the compensation shown in equation (14) can be achieved, accurate compensation cannot be achieved because an error due to the dead time e ^{- s} of the converter remains.

In other words, the circulating current i _O will no longer be able to follow the command value i _O , and the reactive power Q at the receiving end will follow the command value
It will deviate from Q ^* (=0).

The present invention has been made in view of the above, and an object of the present invention is to provide a reactive power control type cycloconverter device having reactive power control characteristics with good followability.

FIG. 5 is a configuration diagram showing an embodiment of the reactive power control type cycloconverter device of the present invention. 1st
The difference from the conventional device shown in the figure is that instead of controlling the circulating current I _O , the sum of the output current I _p of the positive group converter and the output current I _N of the negative group converter, I _pN = I _p + I _N , is controlled. be. In the figure, HPN is the command value of the above sum current I _pN
This is a current command circuit that generates I ^* _pN . Other symbols are the same as in Figure 1.

Figure 6 shows a specific example of the current command circuit HPN in Figure 5, where the input is the reactive power deviation ε ₁ =Q ^* -
Q and load current command value I _L ^* , output is sum current command value
I ^* _pN . In the figure, H(s) is the same control compensation circuit as in FIG. 1, K _H =2 is an amplifier, and ABS is an absolute value circuit. The output of H(s) is doubled by the circulating current command value I _O ^* , and the absolute value of the load current command value I _L ^* is added by the adder A _H. As a result, the sum current command value I ^* _pN is as follows.

I ^* _pN = 2I _O ^* + | I _L ^* | ...(15) Here, since 2・I _O ^* + | I _L ^* | = I _p + I _N ^* holds, equation (15) becomes as follows. can also be expressed.

I _pN = I _p + I _N ...(16) In other words, I ^* _pN found here is the command value I ^* _p of the output current I _p of the positive group converter and the command value I _N of the output current I _N of the negative group converter. It is in harmony with ^* .

By changing the reactive power Q at the receiving end, ε ₁
＝Q ^* −Q changes, command value of circulating current to flow
I _O ^* is given via the control compensation circuit H(s), but in the present invention, instead of directly controlling the circulating current I _O , the load current command I _L ^* is combined to control the positive group and negative group converters. The sum of output currents I _pN = I _p + _IN is controlled.

Fig. 7 shows a block diagram of the control system of the device shown in Fig. 5.The main difference from the block diagram of Fig. 4 is that the control system of I _pN = I _p + I _N has a load current. The point is that no disturbance from I _L comes in at all. Therefore, the compensation circuit ho(s), which was indispensable in the conventional device, is no longer necessary, and control errors due to incomplete compensation are also eliminated.

The reason why no disturbance from I _L enters the I _pN control system can be explained as follows.

By substituting the relationship in equation (10) into equation (12), it can be rewritten as the following equation.

V _p −V _N = {r+(L+N)P} (i _p +i _N )……(16) Therefore, I _pN = I _p + _IN is the output voltage V _p of the positive group converter
It is determined by the difference between the output voltage V _N of the negative group converter and the output voltage V N of the negative group converter, and the influence of the load current I _L disappears.

On the other hand, the load current I _L can be controlled in the same way as before, and at this time, of course, I _pN
Disturbances associated with control do not enter.

That is, both control systems can be treated as completely independent systems, and there is an advantage that the control systems can be easily optimized.

The present invention exhibits even more remarkable effects when feedforward control is performed.

FIG. 8 is a configuration diagram showing another embodiment of the reactive power control type cycloconverter device of the present invention. 3
The reactive power at the receiving end of the phase output cycloconverter is controlled by feedforward. In the figure,
BUS is the electrical line of the three-phase AC power supply, C is Δ or the connected phase advance capacitor, TrU, TrV, TrW are the power transformer, CC-U, CC-V, CC-W are the circulating current type cycloconverter body, U , V, and W are three-phase loads. U-phase cycloconverter CC
-U is positive group converter SS-P, negative group converter
It consists of SS-N and DC reactors Lo ₁ and Lo ₂ . CC-V and CC-W are similarly configured. Also, CONT-U, CONT-V, CONT
-W are current control circuits of the cycloconverters of U, V, and W phases, respectively. The control circuit is CONT-U.
Operational amplifiers K ₁ , K ₂ , K ₃ , comparators C ₁ , C ₂ , adder
A ₁ , A ₂ , A ₃ and phase control circuit PH-P, PH-N
It consists of CONT-V, CONT-W
is similarly configured. Furthermore, the output current I _pU of the positive group converter SS-P, the negative group converter SS-N
AC generators CT _pU , CT _NU , and CT _LU are installed to detect each of the output current I _NU and load current I _LU . The same applies to the V and W phases.

The current control operation of the U-phase cycloconverter CC-U will be described as an example.

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

The load current command I ^* _LU is compared with the detected value I _LU of the load current actually flowing, and the phase control circuits PH-P and PH-N are controlled so that the cycloconverter generates a voltage proportional to the deviation ε ₂ . .

The output phase α _NU of the PH-N with respect to the output phase α _pU of the PH-P is changed from the amplifier K ₂ to the inverting amplifier K ₃ to the phase control circuit PH so as to maintain the relationship α _NU = 180° − α _pU . -N is input. In other words, the output voltage V _pU of the positive group converter SS-P and the negative group converter SS
-N output voltage _VNU is balanced at the load terminals for normal operation. When the load current command I ^* _LU is changed sinusoidally, the deviation _ε2 also changes accordingly, and the α _pU and α _NU are controlled so that the sinusoidal current I _LU flows through the load.

Next, the sum of the output current I _pU of the positive group converter SS-P and the output current I _NU of the negative group converter SS-N is I _pN-U =
The operation for controlling I _pU + I _NU will be explained.

The adder _A1 calculates the sum of _IpU and _INU , and the comparator _C1 compares it with the sum current command value I ^* _pN-U . The deviation ε ₁ =I ^* _pN-U −I _pN-U is amplified by amplifier K ₁ and input to adders A ₂ and A ₃ . As a result, the inputs ε ₃ and ε ₄ to the phase control circuits PH-P and PH-N
is as follows.

ε ₃ =K ₂・ε ₂ +K ₁・ε ₁ …(17) ε ₄ =−K ₂・ε ₂ +K ₁・ε ₁ …(18) Therefore, the above relationship α _NU = 180° − α _pU is Collapse, K ₁・
The output voltage V _pU of the positive group converter SS-P and the output voltage of the negative group converter SS-N become unbalanced by an amount proportional to ε ₁ . The difference voltage is the DC reactor
₍ i _{p +}
i _N ).

If I _pN-U < I ^* _pN-U , ε ₁ becomes positive and increases V _pU − V _NU , increasing I _pN-U = I _pU + I _NU , and I _pN-U ≒ I ^* _pN-U
to calm down. Conversely, if I _pN-U > I ^* _pN-U, ε ₁ becomes negative, V _pU −V _NU <0, and I _pN-U = I _pU +
Decrease I _NU and settle to I _pN-U ≒ I ^* _pN-U . As a result, the sum I _pN-U of the output currents of the positive group converter and the negative group converter is controlled to be equal to the command value.

Current control of the V-phase and W-phase cycloconverters also performs similar operations.

In the embodiment of the device of the present invention shown in FIG. 8, reactive power detection at the power receiving end is not performed. Instead, the load current command values I ^* _LU , I ^* _LV , I ^* _LW and phase control circuit inputs υ〓 _U , υ〓 _V , υ are set so that the reactive power at the receiving end becomes a predetermined value. 〓 By calculating from _W , the sum of the output currents of the positive group and negative group converters of each phase cycloconverter I _pN-U = I _pU + I _NU , I _pN-V = I _pV +
I _NV , I _pN-W = I _pW + I _NW command values I ^* _pN-U , I ^* _pN-V ,
We are looking for I ^* _pN-W . RIPN in FIG. 8 is a calculation circuit for the sum current command value, and its specific configuration is shown in FIG. 9. Note that VR is a setting device that determines the value of reactive power at the receiving end.

In Figure 9, K〓 _U , K〓 _V , K〓 _W , K _MU , K _MV ,
K _MW is an operational amplifier, LM _U , LM _V , LM _W are limiter circuits, SQ _U , SQ _V , SQ _W are square calculation circuits,
SQR _U , SQR _V , SQR _W are square root calculation circuits, M _U1 ,
M _V1 , M _W1 , M _U2 , M _V2 , M _W2 , M _U3 , M _V3 , M _W3
is a multiplier, DIV is a divider, ABS _U , ABS _V , ABS _W
is an absolute value circuit, and AD ₁ to AD ₁₂ are adders.

The inputs υ〓 _U , υ〓 _V , υ〓 _W are the outputs of the operational amplifier K ₂ shown in FIG. 8, and are the average value of the input signals of the phase control circuits PH-P and PH-N. That is, for example, υ〓 _U is
Output voltage of cycloconverter CC-U (V _pU +
V _NU )/2, α _NU ≒180°−α _pU
In the state where the relationship holds, υ〓 _U ∝cosα _pU ≒−
cosα _NU . Similarly, υ〓 _V ∝cosα _pV ≒−
cosα _NV , υ〓 _W ∝cosα _pW ≒−cosα _NW holds.

Therefore, in FIG. 9, cosα _U is obtained by multiplying υ〓 _U by a constant by the amplifier K〓 _U.
The limiter circuit LM _U is used to satisfy -1cosα _U +1, and is controlled by the square calculation circuit SQ _U.
Calculate cos ² α _U. The adder AD ₁ calculates 1-cos ² α _U , and the following square root calculation circuit SQR _U calculates sin α _U =√1- ² _U. Similarly, from υ〓 _V , sinαV=√1− ² , and from υ〓 _W ,
sinαW= ^√1−2 is found.

On the other hand, the load current command values I ^* _LU , I ^* _LV , I ^* _LW are RIPN
is input, and the following calculation is performed.

The command value I _*U of the U-phase load current becomes its absolute value |I ^* _LU | by the absolute value circuit ABS _U , and the multiplier M _U1 ,
It is input to an operational amplifier _KMU and an adder _AD10 .
The operational amplifier K _MU normalizes the load current I _LU , and when I _M is selected as the maximum output current of a cycloconverter, for example, it multiplies the above |I ^* _LU | by (1/I _M ). Then, by the next adder AD ₄ , K _U (1−|
I ^* _LU |/I _M ) is being calculated. k _U is the multiplier M _U2 ,
Input to M _U3 .

I ^* _LV and L ^* _LW are calculated in the same way, k _V = (1 - | I ^* _LV
|/I _M ) and k _W =(1−|I ^* _LW |/I _M ) are obtained.

By the multipliers M _U1 , M _V1 , M _W1 respectively |I ^* _LU |
sinα _U , |I ^* _LV |・sinα _V and |I ^* _LW |・sinα _W are determined, and by the next adder AD ₇ |I ^* _LU |・sinα _U +
|I ^* _LV |・sinα _V + |I ^* _LW |・sinα _W is calculated, and the next adder AD ₈ calculates the difference from the output I ^* _cap of the external reactive power setting device VR. Ru.

a=I ^* _cap −{|I ^* _LU |・sinα _U +|I ^* _LV |・sinα _V
+|I ^* _LW |・_sinαW }...(19) a is input to the divider DIV.

In addition, multipliers M _U2 , M _V2 , M _W2 each
k _U・sinα _U , k _V・sinα _V , k _W・sinα _W are calculated,
By the next adder AD ₉ b=k _U・sinα _U +k _V・sinα _V +k _W・sinα _W
...(20) is calculated and input to the divider DIV.

The divider DIV calculates I _O ^*2 = a/b, and the next multipliers M _U3 , M _V3 , M _W3 calculate k _U・I _O
^* ₂ , k _V · I _O ^* ₂ and k _W · I _O ^* ₂ are calculated.

Finally, by adders AD ₁₀ , AD ₁₁ , AD ₁₂ ,
A command value of the sum of the output currents of the positive group and negative group converters of each phase cycloconverter is output as shown by the following equation.

I ^* _pN-U = | I ^* _LU | +k _U・I _O ^* ₂ ......(21) I ^* _pN-V = | I ^* _LV | +k _V・I _O ^* ₂ ......(22) I ^* _{pN- W} = |I ^* _LW | +k _W・I _O ^* ₂ ...(23) Command values obtained in this way I ^* _pN-U , I ^* _pN-V ,
I _pN-U of each phase cycloconverter according to I ^* _pN-W ,
I _pN-V and I _pN-W are controlled, but as mentioned earlier, no disturbance due to the flow of load current enters this control system, so control with extremely good followability can be expected.

Here, I _pN-U = I ^* _pN-U , I ^* _pN-V = I ^* _pN-V , I _pN-W =
Consider the reactive power at the receiving end when controlled to I ^* _pN-W .

The reactive power Q at the receiving end of the three-phase output cycloconverter is the delayed reactive current of the cycloconverter.
It can be expressed as the value obtained by multiplying the difference between I _REACT and the leading reactive current I _cap of the phase advancing capacitor by a coefficient K _Q. I _REACT is the following (2
4) It becomes like the formula. However, α _NU ≒180°−α _pU ,
Assume that α _NV ≒180°−α _pV and α _NW ≒180°−α _pW hold.

I _REACT =k ₁ (I _pU +I _NU )・sinα _U +k ₁ (I _pV +I _NV )・sinα _V +k ₁ (I _pW +I _NW )・sinα _W …(24) Above (I _pU + I _NU )=I _pN-U is controlled equal to the command value I ^* _pN-U , (I _pV + I _NV ) = I _pN-V is controlled equal to the command value I ^* _pN-V , (I _pW + I _NW ) = I _pN- Since _W is controlled to be equal to the command value I ^* _pN-W , by substituting the relationships in equations (21) to (23) into equation (24), the reactive power at the receiving end Q = K _Q (I _REACT −I _cap ) is calculated. I _REACT is changed as follows.

I _REACT = k ₁ {(|I ^* _LU | +ku・I _O ^* ₂ )・sinα _U + (|I ^* _LV | +k _V・I _O ^* ₂ )・sinα _V + (|I ^* _LW | +k _W・I _O ^* ₂ )・sinα _W } =k ₁ {|I ^* _LU |・sinα _U +|I ^* _LV |・sinα _V +|I ^* _LW |・sinα _W +I _O ^* ₂・(k _U・sinα _U +k _V・sinα _V +k _W・sinα _W )} ...(25) I _O ^* ₂ = a/b, and b is given by equation (20), so I _O ^* ₂・(K _U・sinα _U +k _V・sinα _V +K _W・sinα _W )=
It becomes a. Also, by substituting the relationship in equation (19) into equation (25), I _REACT = k ₁ {I ^* _cap −a+a} = k ₁ · I ^* _cap (26).

In order to make the reactive power Q at the receiving end zero, I ^* _cap should be set so that I _REACT = I _cap = k ₁ · I ^* _cap (27) holds true.

In the above control, k _U , k _V , and _kW are coefficients that distribute the value of the circulating current of each phase cycloconverter according to the magnitude of the load current.

As shown in equation (21), the sum of the output currents of the positive group and negative group of the U-phase cycloconverter I _pN-U = I _pU
When +I _NU is controlled I _pU +I _NU = |I _LU | +2・I _OU (28) From the relationship, the circulating current I _OU is the same as being controlled to the following value.

I _OU = (K _U・I _O ^* ₂ )/2 = 1/2 (1 − | I ^* / _LU | / I _M I _O ^*2 ...(29) I ^* _LU = I _n・sin 〓 ^t If I _M = I _n is selected, the circulating current I _OU becomes zero when I ^* _LU reaches the maximum value I _n , and conversely, when I ^* _LU = 0, I _OU = I _O ^* ₂ /2. In other words, when the absolute value of the load current |I _LU | is large, the value of the circulating current I _OU is small, and conversely |
When I _LU | is small, the value of I _OU is controlled to be large. The value of the output current I _pU of the positive group converter SS-P or the output current I _NU of the negative group converter SS-N is the value obtained by adding the above circulating current I _OU to the positive or negative half-wave value of the load current I _LU . However, by distributing the value of the circulating current I _OU according to the magnitude of the load current I _LU as described above, it is possible to reduce the increase in the maximum current capacity of the converter.

Circulating current of V-phase and W-phase cycloconverter
I _OV and I _OW are similarly distributed by k _V and _kW . In this case, the load currents of each phase are out of phase by 120°, so the circulating current will not reach zero or the maximum at the same time. For example, when I _OU becomes small, I _OV or I _OW will become large. Therefore, the reactive power Q at the receiving end is held constant.

If you want to control the circulating currents I _OU , I _OV , and I _OW of each phase to the same value, you can select the normalization constant I _M to be ∞. Specifically, the operational amplifier shown in Fig. 9
The gains of K _MU , K _MV , and K _MW should be made zero.

As described above, the device of the present invention using the feed forward control shown in FIG.
It is not necessary to detect this, and the control delay associated with this detection can be eliminated. On the other hand, if the response of current control is poor, the response of reactive power control at the receiving end will remain as an error to that extent, so control with good followability is required. Circulating current I _OU as before,
When trying to directly control I _OV and I _OW themselves, disturbances are introduced due to the flow of load currents I _LU , I _LV , and I _LW , making it difficult to improve control responsiveness. In this respect, in the present invention, the load current control system and the control system for the sum of the positive group and negative group output currents can be treated as independent systems, and a response with good followability can be obtained. Therefore, by applying the device of the present invention to feed forward control, its effects can be fully exhibited.

[Brief explanation of drawings]

Fig. 1 is a configuration diagram of a conventional reactive power control type cycloconverter device, Fig. 2 is an input side voltage and current vector diagram to explain its operation, and Fig. 3 is also a diagram to explain the operation of Fig. 1. The equivalent circuit diagram of
Fig. 4 is a block diagram of the control system shown in Fig. 1, Fig. 5 is a block diagram showing an embodiment of the reactive power control type cycloconverter device of the present invention, and Fig. 6 is the current command circuit HPN of Fig. 5. 7 is a block diagram of the control system of FIG. 5, FIG. 8 is a block diagram showing another embodiment of the reactive power control type cycloconverter device of the present invention, and FIG. 9 is a block diagram of the control system of FIG. 8 is a specific configuration diagram of the sum current command value calculation circuit of FIG. 8. FIG. BUS...3-phase power line, TR, TR-U, TR-
V, TR-W...Power transformer, C...Phase advance capacitor, CC, CC-U, CC-V, CC-W...Cyclo converter body, LOAD, U, V, W...
...Load, Lo ₁ , Lo ₂ ...DC reactor, SS-P
...Positive group converter, SS-N...Negative group converter, CONT-U, CONT-V, CONT-W...
Current control circuit, PH-P, PH-N...Phase control circuit, _K1 , _K2 , _K3 ...Operation amplifier, _C1 to _C3 ...
Comparator, A ₁ to _{A 5} ... Adder, VAR ... Reactive power calculator, HPN ... Current command circuit, RIPN ... Sum current command value calculation circuit, VR ... Reactive power setting device.

Claims (1)

[Claims] 1. A circulating current type cycloconverter consisting of a positive group converter, a negative group converter, and a DC reactor, a load device receiving current supply from the cycloconverter, and a firing phase of the positive group and negative group converters. A phase control circuit to control, a circuit to control the load current to be supplied to the load device, a circuit to control the reactive power on the input side of the cycloconverter, an output signal from this reactive power control circuit, and the load current. A reactive power control type cycloconverter device comprising a circuit that creates a command value from a command value signal of a control circuit and controls the sum of the output current of the positive group converter and the output current of the negative group converter of the cycloconverter. . 2. A circulating current type cycloconverter consisting of a positive group converter, a negative group converter, and a DC reactor, a load device that receives current supply from this cycloconverter, and a phase control circuit that controls the firing phase of the positive group and negative group converters. , a circuit for controlling the load current to be supplied to the load device, and a value of the sum of the output current of the positive group converter and the output current of the negative group converter of the cycloconverter for controlling the reactive power on the input side of the cycloconverter. and calculating a command value of the sum of the output current of the positive group converter and the output current of the negative group converter from the command value of the load current and the input signal value of the phase control circuit. Characteristic reactive power control type cycloconverter device. 3. A circulating current type cycloconverter consisting of a positive group converter, a negative group converter, and a DC reactor provided according to the number of phases of the load, each phase load device each receiving current supply from this cycloconverter, and the above-mentioned cycloconverter provided for each phase. a phase control circuit that controls firing phases of the positive group and negative group converters;
In order to control the reactive power on the input side of the cycloconverter, a circuit is provided for controlling the sum of the output current of the positive group converter and the output current of the negative group converter of the cycloconverter of each phase, and The command value of the sum of the output current of the group converter and the output current of the negative group converter is calculated from the command value of the load current of each phase and the input signal value of the phase control circuit of each phase, and the circulating current of the cycloconverter of each phase is calculated. The value of the sum of the output current of the positive group converter and the output current of the negative group converter of each phase is controlled so that the value is distributed in inverse proportion to the magnitude of the load current command value of each phase. Characteristic reactive power control type cycloconverter device.