JPS60223433A - Frequency converter - 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 frequency conversion device that connects power systems with different frequencies.

[Technical background of the invention]

Japan's electric power system can be broadly divided into the 60 Hz system in western Japan and the 59 Hz system in eastern Japan. As devices for connecting these two power systems and controlling the amount of power between the systems, there have long been known rotary layer wave number converters using an induction machine or the like, or stationary frequency converters using a mercury rectifier. Recently, static frequency converters using semiconductor-controlled rectifiers such as thyristors in place of mercury rectifiers have been put into practical use.

In addition, in order to compensate for the lack of capacity of existing rotary frequency converters, a method of operating static frequency converters in parallel has been adopted, and new problems have arisen due to the parallel operation.

FIG. 1 is a block diagram showing the configuration of a conventional frequency conversion device. This shows a case where a 50Hz system and 60H2 system are connected and the power flow rate between the two systems is controlled.

In Figure 1, BUS is the 3-phase power line of the 5QHz power system, BUS is the 3-phase power line of the 5QHz power system, and MG
is a motor generator device, SFC is a static power converter device, CA
PI l cxP, C advance phase:=7 nf n? ,5VC
1.8VC, C is a reactive power compensator.

The static power converter SFC includes a power transformer TR.

TI'L, separately excited converter (AC/DC power converter) SSl
SS! and DC reactor L. It consists of

In addition, the reactive power compensator 5VC1 includes a power transformer TR
, , a thyristor rectifier circuit SS, and a DC reactor L1, and the reactive power control circuit AQR controls the current flowing through the DC reactor L1 so that the reactive power Q1 at the receiving end becomes equal to the command value Q□ (=0). The engineering Ll is controlled. Similarly, the reactive power compensator 5VC2 is composed of a power transformer T, a thyristor rectifier circuit SS, and a DC reactor L, and the reactive power control circuit AQ changes the reactive power at the receiving end to a command value q: ( The current IL is controlled so that it is equal to =o).

On the other hand, the motor generator device MG is a 10-pole synchronous electric motor P! A
It is composed of a motor M and a 12-pole synchronous generator G, and the rotors (field poles) of each of the motor M and the generator G are directly connected mechanically. As the rotor rotates at a speed of 60 rpm, a three-phase AC voltage with a frequency of 5QHz is generated on the electric line BUS1 side, and a three-phase AC voltage with a frequency of 5QHz is generated on the electric line BUD side.
Phase alternating voltage is generated.

Usually, the electric line BU8. Several generators and loads are connected to and BUS, and the electric line BU81 shown here
．． BUD can be viewed as an alternating current voltage source. By keeping the field current IfM of the motor M of the MG device at the rated value and changing the field current Ifo of the generator G, the system BU
It is possible to control the transfer of power between 8□ and BUS.

That is, as Ifo increases, power is sent from 808m to BUS, and conversely, as Ifo decreases, power is sent from BUS to BUS. In addition, the power is BUS
, when the signal is being sent to BUS□, M of the MG device becomes a generator and G becomes an electric motor.

The same thing can be done by keeping IfG constant and changing IfM. In other words, as IfM increases, M becomes a generator and G becomes an electric motor, and the electric power changes from BUD to BUDK.
On the other hand, when IfM is decreased, M becomes a motor and G becomes a generator, and power is sent from BUS to BU8□.

As described above, it is possible to transfer power between the first power system BU8□ and the second power system using only the motor generator device [MO], but as the capacity of the power system has increased in recent years,
There is a growing need to increase the capacity of the MG device.

Therefore, a plan was devised to increase the conversion capacity by adding another MG device, but it was difficult to maintain the MG device because it has rotating parts, so it was not possible to apply a stationary frequency converter. It is now being considered. However, in order to make effective use of existing MG devices, a method has been adopted in which a static power converter and an MG device are operated in parallel as shown in FIG.

Next, the operation of the static power converter 8FC of the device shown in FIG. 1 will be explained.

First, the operation of this device will be explained by taking as an example the case where power is sent from the 59 Hz power line BUD to the 59 Hz power line BU8.

Electric line BU8. A current detector CTs1 and a voltage detector FT are installed at the power receiving end to detect instantaneous values of three-phase voltages and currents. This is converted into the following active reactive power calculation circuit PQC
, and calculate the active power P and reactive power Q.

Similarly, a current detector C is also installed at the power receiving end from the power line BUD.
T8□ and voltage detector PTs□ are installed, and active reactive power calculation circuit PQC1,! :Total, effective power P.

and detect reactive power q.

The active power P is detected as positive in the incoming direction, and the active power P2 is detected as positive in the outgoing direction. In addition, reactive power Q,
, Q, detects delayed reactive power as positive and leading reactive power as negative.

Electric line BU8. From electric line BU8. When sending power to
The AC/DC power converter SS1 operates as a forward converter, and the AC/DC power converter SS operates as an inverse converter.

A power command value P>0 is given by the power flow rate setting device VRP. The Schmitt circuit 8H generates an output signal 111'' when the power command value p>o, and the switch SW
Connect l to the a side and switch SW2 to the b side. In other words, the forward converter SS has a power flow rate P"' (P1+
P1)/2 is equal to the command value Pi,
Its output voltage V is controlled, and the output voltage V of the inverter SS is controlled so as to generate a constant DC voltage V.

CTo is a DC current detector, and is the current I flowing through the DC reactor L0. Detect. The power control circuit APR is the average value (p, + Pg) of the power detection values P1 and P2 at both receiving mold ends.
The DC current ■ so that /2 is equal to the command value P
o.

Further, the constant voltage control circuit AVR controls the output voltage V of the inverter SS to a constant value V.
PH, PH2 are AC/DC power converters SS1 and SS, respectively.
, which is a phase control circuit.

When the output voltages of the AC/DC power converters SS and SS are taken in the direction of the arrow in the figure, V, =ky -V8. −cos α.

V,=-ky-V,, e cosα y. However, is a conversion constant, and v8□1Vl13 are AC side input voltages of AC/DC power converters SS and SS, respectively.

The firing control angle α of the forward converter SS is controlled in the range of 0° to 90', and the firing control angle α of the inverse converter SS is 90'.
-180' range. Firing control angle (W, = 1
80', the AC side input power factor of the inverter SS is 1, but it is necessary to shift the ignition timing by the commutation advance angle r to perform natural commutation. Therefore, the ignition control angle α
.

= 180°-r, and v*= kv-Vi2 ・CO
8 (180°-r). If the commutation advance angle r is constant, the output voltage V will also be a constant DC voltage.

DC electrician. is the voltage V applied to the DC reactor L0
, -V,. Output voltage V
! is controlled to be constant, so V,=,++ Vs,
a cos α.

It will be controlled by changing the Direct current■. If you want to increase the DC current I, control the ignition control angle α□ so that vI > v snow. If you want to decrease V, <V
The firing control angle α is controlled so that . Near the steady point, if the resistance of DC reactor L0 is ignored, Vi
”v Vl holds, Cogα, a-I-co
scX.

From α1→r.

Figure 2 (a) and (b) show electric line B of the 50Hz system.
It is a voltage-current vector diagram for one phase on the AC input side of each AC/DC power converter when power is being sent from U8□ to the electric line BUD of the 5QHz system. FIG. 2(a) shows the converter 88
FIG. 2(b) is a voltage-current vector diagram of converter 88.1.
The voltage and current vector diagrams of each are shown.

Considering a steady state with a direct current I0, V*'vV* holds, and the relationship α1zakigamma is established. Forward converter SS,
The input current 11181 lags the voltage v8□ by a phase α1, and its magnitude is I,8. == is −I0.

Also, an inverse transformer 88. The input current Iaag is the voltage v81
It is delayed by a phase angle α,=180°−γ, and its magnitude is IsH=K″IO.

Icapl and Icapg are currents flowing into the phase advance capacitors CAP and CAP, '88B and xss4 are lag currents flowing into the reactive power compensators 8VC and SVC, respectively.

If input current Ias l is divided into effective component Ipt and reactive component IqI, Ipl::l5st -cosα, =k @I0- c
osα11ql=I, , −sinα,=k −Io
・Sin α1. If the lagging current I8am is controlled so that the lagging current Iql+l5ss becomes equal to the advancing current Icapt, the current IAOI that enters from the electric line BUS becomes only the effective portion Ipt, and operation can be performed with the fundamental wave power factor always being 1.

Similarly, the input current ■,. The valid part 11) 2 and the invalid part fq
When divided into 2, 11) 2 = I, 8. - cosα2Iq2 = I
8. , -sin α2, and if the delay current generator 84 is controlled so that Iqz+l1ls,==Icap2, the input current IAoffi from the electric line BUS becomes equal to the effective component Ip2.

The effective component Ip2 is the voltage v8. Since the phase is shifted by 180 degrees with respect to the power line BUD, the fundamental wave power factor is 1, indicating that the power is returning in the direction of the electric line BUD.

When the set value P of the power flow rate is increased, the DC type) current 1.
In order to increase the ignition control angle, the ignition control angle is changed transiently, but when the DC current approaches I'o, which corresponds to P=(Pl+P,)/2, it settles at α1''v7. At this time, the invalid part on the input side is I'q1=k * Is *
sin α, and I'a8j=Icap1- fq
If l is decreased, em o,=I″pt==−I′
0-CO8α8, and only the power flow amount can be increased. Phase advance capacitors CAP and CA
The currents Icaps and Icapz of P may be prepared in amounts commensurate with the maximum power flowing.

When the set value P of the power flow rate is set to a negative value, the switch SW is connected to the b side, and the switch 8W2 is connected to the a side, and this time the electric line BUS of the 60Hz system is connected to the electric line Bus of the 5QHz system, Electricity will be sent to. At this time, SS is used as an inverse converter to perform constant output pressure control, and SS is used as a forward converter to perform DC current control.

[Problems with background technology]

Such conventional frequency conversion devices have the following problems.

(a) First, in order to adjust the power flow rate, the DC current of the stationary power converter SFC is installed. is increased or decreased, and as the change occurs, the reactive component Iqt on the input side (AC side) of the converters SS and SS.

Iqz changes, and the reactive power compensator s
vc, Oyobi SVC, Nomi m l5ss * l5s4
You need to control it.

As mentioned earlier, the capacity of the reactive power compensators svc, , svc,
) and 1, then I,,, =Icap1− Iql == k −(I.(max) −I.) −sinα
.

l811. = Icapi −Iq2=k −(Io
(max) -I. ) -sin Q.

Then, phase angle α1 ``q r+ Phase angle false = 180'
-r relationship, the DC current ■. is 0~I0(m
Considering that it changes between l56g ""8114 Sk # I6 (rrla
X) Sin 7 is required.

As mentioned above, r is the commutation advance angle required to naturally commutate the thyristor of the power converter, and is related to the inductance on the power supply side and the turn-off time of the thyristor.

In particular, the former value is quite large in order to prepare for short-circuiting of the converter arm. Therefore, the commutation advance angle γ usually reaches a value of 30' to 40°. Even if the commutation advance angle r = 30°, sin r = 0.5, and the reactive power compensator S VC
, and S VC, are the capacities of power converters SS1 and 8
8. The value of H becomes the capacitance of .

Therefore, there is a drawback that the device is expensive and complicated.

(b) Furthermore, when the motor generator device MG and the static power converter device 8FC are operated in parallel, the response of the power flow rate control of src becomes a problem. For example, in FIG. 1, system BU8. If a sudden load change occurs on the side, the load on the motor generator MG can be reduced by preparing a static power converter 8FC that can follow the load change, but if the SFC response is slow, The above load fluctuations are all M
This places a burden on G, and there is no point in installing 8 PCs of static power converters.

In this respect, the conventional static power converter 8FC has a problem. That is, in the conventional 8FC, the DC voltage V1 or V2 is almost constant, and the amount of power flow is controlled by the DC current regulator. We are changing the. Naturally, therefore, when the power flow rate is zero, l0==Q, and if the power flow rate is suddenly increased from this state, the DC current I0 will rise from zero current. When the DC current I0 is a small value, power converters SS□ and S
The operation of S is interrupted from time to time, resulting in so-called intermittent current. Power converter S in this intermittent current state
It is known that the control response of S and SS is one order of magnitude worse than the control response under normal continuous current conditions. Methods such as making the gain of the control system variable have been proposed in order to improve this response, but this requires extremely advanced technology.

Furthermore, the conventional static power converter 8PC also has a problem when reversing the amount of power flow. As described above, when transmitting power from the system BUD to the system BUs, the converter SS performs constant voltage control, and the converter SS performs power control (current control).

If it becomes necessary to send power from BUD2 to BUS□ in this state, the Schmitt circuit 8H will switch s
w1. By switching sw, converter SS is switched to constant voltage control and converter SS is switched to power control. Therefore, the dead time at the time of switching inevitably results in a delay in control, which has the drawback of imposing a burden on the motor generator device MG during that time.

[Purpose of the invention]

The present invention has been made in view of the above, and it maintains the fundamental wave power factor at the power receiving end at 1 without using a conventionally required reactive power compensator, and also maintains the power flow rate of a stationary power converter. An object of the present invention is to provide a frequency conversion device that reduces the burden on a motor generator device by improving control response.

[Summary of the Invention] In order to achieve this object, the present invention calculates the value of the DC current of the static power converter and the value of the active power transferred between the first power system and the second power system. The present invention is characterized in that the value of the DC voltage is adjusted to simultaneously control the value of the reactive power of each AC/DC power converter and the value of the active power to be transferred by the power converter.

[Embodiments of the invention]

FIG. 3 is a block diagram showing the configuration of an embodiment of the frequency conversion device of the present invention.

In the figure, BUD is the three-phase power line of the 50Hz power system, BO
2° is a 60Hz Q-power system three-phase power line, MG is a motor generator device, 8FC is a static power converter, CAP,
CAP.

is a phase advance capacitor.

The motor generator device MG is composed of a 10-pole synchronous motor mm and a 12-pole synchronous generator G, and the rotor (field pole) of each of the motor M and the generator G is mechanically directly connected. As the rotor rotates at a speed of 60 rpm, the electric line B
A three-phase AC voltage with a frequency of 5QI (z) is generated on the USl side, and a three-phase AC voltage with a frequency of 59Hz is generated on the electric line BU8. side.

As described above, the power flow rate control by the motor generator device MG is performed by adjusting the field current IfM IIfo of M or G.

On the other hand, the static power converter 8FC has a power transformer TR
,,TR,, separately excited converter (AC/DC power converter) ssl
, ss, and a DC reactor L0.

As a control circuit, AC current detector c'r, 11 c'
r8. ICTL1 AC voltage detector PT□, FT,...
PT active reactive power calculation circuit, PQCl, PQC8,
PQC, DC current detector CTO, reactive power setting device VR
Q, comparator CItCIlcal control compensation circuit Hq(s)
s Hp(s), operational amplifier K. , K1. Five KL adders and 89 adders and phase control circuits PH1 and PH are provided.

First, the operation of the static power converter SFC of the present invention will be explained.

Direct current I. is controlled as follows.

DC current ■ by DC current detector CTo. detect,
The command value of DC current is calculated by comparator C8. Compare with.

The deviation εfl=IOIO is calculated by the operational amplifier K. The signal is amplified by and input to the phase control circuits PH1, PH. The phase control circuits PH, PH, control the converters S81 and SS to generate voltages proportional to their respective inputs ε and ε.

Therefore, if the direct current (command value) Io > (detected value) IO, the deviation ε, 〉0, and ε, -ε, = ε, ·Ko enters the phase control circuits PH1 and PH, and the conversion is performed. The output voltage v1 of the converter 881 is in the direction of the arrow in FIG. 3, and the output voltage V of the converter SS is in the opposite direction to the arrow in FIG. 3, and a voltage proportional to the deviation ε is generated. .

Therefore, the voltage applied to DC reactor L0 is Vt-
Vt > 0, and DC current ■. increase.

Conversely, (command value) IO < (detected value) of DC current. When the deviation ε becomes zero, the output voltage vI Vt<0 and the DC current I0 decreases.

As a result, DC current ■. = Engineering. It calms down.

At this time, DC reactor L. If the resistance is sufficiently large, VI→V.

FIGS. 4(a) and 4(b) are voltage and current vector diagrams for one phase at the receiving end of 8F'C.

FIG. 4(a) is a vector diagram of the power receiving end of converter SSl, and FIG. 4(b) is a vector diagram of the power receiving end of converter SS.

Next, the power flow control operation and the reactive power control operation will be explained with reference to FIGS. 3 and 4 (a) and (b).

3-phase AC current detector CT8. and 3-phase AC voltage detector P
T,1 detects the instantaneous values of voltage and current at the receiving end of converter SS1. This is the active reactive power calculation circuit PQ
Enter C□ and calculate active power P and reactive power Q□.

Similarly, the voltage and current at the receiving end of the converter 88□ are detected by CTa and FT, and the active power P is detected by PQC.
.

and reactive power Q.

The effective power P,,P, is from the power line BUS1 to the power line BUD.
The direction of the current toward , is taken as a positive value. Also, reactive power Q1
+ + indicates the delayed reactive power as positive.

Note that the detected values of the active power and reactive power may be controlled by using the detected values at the power receiving end of either one of the converters. BOD5
In order to reduce the influence of each voltage fluctuation, etc., the following average values are used for control.

P=(P1+P,)/2 Q=(Q1+Qri/2) Comparator C8 compares the reactive power detection value Q and its command value Q, and its output deviation εt""Q is determined by the following control compensation circuit. 11q(s).The output signal I of the control compensation circuit Hq(s) becomes the command value of the DC current generator.

Further, the comparator C5 compares the active power detection value P and its command value P, and its output deviation ε,=p''-P is integrated or amplified by the next control compensation circuit H〆S). One of the output signals ε4 of the core control compensation circuit 11 p(s) is inputted to the phase control circuit PH, via the filter, and the other is inputted to the inverting amplifier and the adder A. , to the phase control circuit PH,l.

Therefore, the input ε of the phase control circuit PH□ and the input ε6 of the phase control circuit PH can be expressed as follows.

ε,=84+ε,・dog ε,=−ε,+6. 0 for @ For the sake of explanation, if we consider the case where I0 = ■o, ε, = 0 and the deviation ε, = ε4. The relationship ε6=-ε4 holds, and the output voltage V, = V. Conversion constant: kV + AC side input voltage: Vs = V8. =V, , then V1=ky-V,-cosα,oc6”.

"F=-kV "a"Co!10-oc-ε60
(No. 6, the cosine value of the firing control angle α of converter SS is proportional to the deviation ε4, and the cosine value of the firing control angle α of converter 88 is proportional to the negative value of the deviation ε4. .Therefore, the firing control angle α1 of the converter SS1 and the firing control angle false of the converter SS have the relationship α, j−f180°−α.The DC current is Io to Io, and the deviation is When ε!~O, the relationship between the ignition control angle αB ``q l g Qo-(IIs breaks down, and the output voltage becomes v1~V, which increases or decreases the DC current ■. Steadyly, the output voltage V1 ``q V2 I mentioned this earlier.

Figure 4(a) shows the converter SS at DC voltage V1+V.
1 shows a voltage and current vector diagram at the power receiving end of the power source. The input current l8111 of the converter SS1 has a magnitude k·Io and a supply voltage v8. The flow is delayed by an angle α□.

Moreover, FIG. 4(b) shows a voltage-current vector diagram at the receiving end of the converter SS, where the input current of 8S2, 8°, is of a magnitude, Io is the power supply voltage V8! Angle α, +18
The flow is delayed by 0'-α1.

When current 111111 is divided into effective component Ipt and reactive component Iql, Ips=Isa1-cos α1=k-I. -co
s α11q1=I, , m sin α,=k −Io
-sinαl, electrician, a! The valid minute Ipg and the invalid minute Iq! Dividing into Io2 = IH1, -CO8 (Xffi = k - I. -
cos c&.

Iq2::Iss*-5in α, =k e I.

m sin α.

Tonaru. When the relationship between the phase control angle α and +180°−α is included, Ip2=−Ipt Iq2 == −Iqt. Note that the lagging reactive current Iq1=Iqg is the leading reactive current I of the phase advancing capacitors CAP and CAP.
It is controlled to be equal to cap1°Icapz.

Consider the case where the command value P'' of the power flow rate shown in FIG. 3 is increased from this state.

The deviation εs=P p>o, and the output ε4 of the control compensation circuit Hp(s) increases. Therefore, the output voltages V, 4-qV, of converters SS1 and SS increase, and CO5α1 and -
Coa 4 also increases. Therefore, Ipl+-11)2 increases, the effective power P increases, and finally P=P.

Since the firing control angles α1 and α2 of the converters SS1 and SS change in the process where the active power becomes p=p, the reactive power side of the power receiving end also has an influence. i.e. aOS
When α1 and -cos c4 become large, sin α1 and sin α.

decreases, Iqt=to・Io−sinα, < IcoptIq2
=k-I. −sin α, < Icapz.

Therefore, the reactive power Q at the power receiving end advances and a negative value is detected. Therefore, ε+=Q-Q>o, and the DC current command value I is the output of the next control compensation circuit) 1q(s). increase. DC electrician. The control is as described above, ■.

=Io. As a result, the invalid portion Iqr
and IQ2 increases, - eventually the reactive power Q=Q=o
controlled so that

However, DC electrician. When increases, the effective part Ipl =-
Ip2 also increases and the active power P becomes larger than its command value P. Therefore, this time it operates to reduce cosα1 and -cosα2, and the DC current I. will also decrease slightly.

That is, when the command value P of the power flow rate is increased,
Output voltage and DC current I of power converter 88m and SS. While changing, active power control and reactive power control are performed simultaneously, and finally active power P=P, reactive power Q
Output voltage v1kqvt and DC current so that =Q. The value is . In the Guchtl diagrams in Figures 4(a) and 4(b), as a result of increasing the command value P of the power flow rate, the input current of the converter SS is changed from E as I to 11111
1, and the input current of converter SS changes from 8° to Pss2, and only the effective component is I p 1-- I
It shows that px has increased to fi'pl=-I'pz.

Even when the active power command value P is decreased, the DC current I is controlled in the same way so that the effective component p=p and the reactive component Q=Q=0. and the output voltage V1+V.

If the active power command value P is set to a positive value, the power P becomes 59Hz.
Power system BU8. If P is set to a negative value, power P will be sent from BUS to BUS. When P is changed from a positive value to a negative value, the power converter 88. and SS, DC ton field V*
SV@ automatically becomes a negative value, and there is no need for a changeover switch like in conventional devices.

Above, we set the reactive power command value Q = 0 and controlled so that the reactive power at the receiving end becomes zero, that is, the input fundamental wave power factor becomes 1. Needless to say, the motor-generator device MG and the static power converter SF
The control operation for parallel operation with C will be explained.

In order to detect the active power PL going out to the 59Hz power system BU8□, a three-phase AC current detector CTL, a three-phase AC voltage detector PTL, and a ringing reactive power calculation circuit PQC11
are available.

Here, the field current IfM+If of the motor generator device MG
It is assumed that approximately the rated current is passed through o, and the amount of power flow is not controlled depending on the MG device.

First, a case will be described in which power PL is being sent from the 59Hz '@ power system BU81 to the 6QHz power system BUS.

The active power PL output to the system BUS is detected and input to the operational amplifier KL. For example, KL is a (1/2) times amplifier, and its output signal P - (1/2) PL becomes the command value of the active power P exchanged by the static power converter 8FC1. As explained earlier, since p=p l is controlled, out of the active power PL output to the grid BUD, (
1/2) is borne by the static power converter 8FCl, and the remaining (1/2) PL is borne by the motor generator device.

This means that PL is a negative value, that is, from 60H2ii power system BUS2 to 5QIIz power system BU8. This also holds true when sending power to.

That is, the motor generator device MG and the static power converter device 8
The load sharing ratio of the FC is uniquely determined by the operational amplifier KL, which has the advantage that the capacity of the frequency conversion device can be easily increased.

Naturally, for the above distribution to be successful, the power control response of the static power converter SFC must be good.

The static power converter 8FC in the device of the present invention always generates a DC current I of sufficient magnitude to control the reactive power at the receiving end of the power converters ss, , ss. is flowing.

Therefore, even when the power flow rate p=0, the DC current I0 is not interrupted (the conventional problem of decreasing the gain of the control system when the current is interrupted is eliminated, and a good control response can always be obtained).

In addition, even if the power command value P rapidly changes from positive to negative or from negative to positive, there is no need to switch the control operation using a switch circuit as in conventional devices, and there is no wasted time for this, so the motor generator device MG This eliminates the need to place an extra burden on

FIG. 5 shows another embodiment of the device of the present invention, (a)
is a control circuit block diagram, and (b) and (C) are diagrams explaining its operation.

In FIG. 5(a), V)tp is a power setting device, A is an adder, and other symbols are the same as those explained for the control circuit in FIG. 3.

The power setting device VRp indicates that the motor generator device MG is connected to the system BU8.
A command value Po of active power to be sent from BO2 to BO2 is given.

If the active power supplied to the load connected to the grid BUD is PL, then the adder A3 calculates the load power P
L and the inverted value of the above power command value Po are added.

The value P =:PL-7Po is converted to static power converter 8F.
This is the command value of the active power transmitted and received by C.

Figure 5(b) and (C) show the active power P supplied to the load.
1 is a time chart showing the relationship between L and the active power pp exchanged by the static power converter SFC.

Active power P exchanged by static power converter SFC
is controlled so that it becomes equal to its command value P=pL-pG. When pa is set constant, the SFC operates to compensate for all fluctuations in the load power PL, and as a result, the motor generator device MG always supplies a constant active power Po=P. In particular, if Po is selected to match the rated value of the MG device, efficient operation is possible.

FIG. 6 shows another embodiment of the device of the present invention, (
a) is a control circuit block diagram, and ←) and (C) are diagrams explaining its operation.

In FIG. 6(a), LB is a level setter, and other symbols are similar to those in FIG. 3.

The detected value PL of the active power to be supplied to the load (assumed to be connected to the grid BU8. side) is input to the level setter LB. The level setter LB is for setting the highest value PM of the active power transferred by the motor generator device MG, and is used to set the load power p,
When the value of is -P and <PL<+1M, the command value of the active power transferred by the static power converter 8FC is given as p=Q, and when PL<PM
In the case of , it is given as P=PL (PM), and further PL>
In the case of +1M, it is given as P=PL−p.

That is, as long as the load power PL does not exceed the absolute value of the set power PM, the active power P exchanged by the static power converter SFC becomes zero, and the motor generator device MG bears all of the PL. . When the absolute value of PL becomes larger than the absolute value of PM, power is exchanged by src by the excess amount, and the burden on the MG device does not exceed +2M.

In the case of Fig. 5, the power PG exchanged by the MG device is always constant, whereas in the embodiment of Fig. 6, 8FC operates only during heavy loads, does not operate during light loads, and furthermore, The power PG delivered and received by the device is also reduced. Therefore, even more efficient operation can be expected.

〔Effect of the invention〕

As described above, according to the frequency converter of the present invention, the fundamental wave power factor at the receiving end from both systems can be always maintained at 1 without using a reactive power compensator that is conventionally required. This has the advantage of being able to freely control the amount of power flow between both systems.

In particular, the static power converter spc in the device of the present invention has a DC current converter of sufficient size for reactive power control at the receiving end. is flowing, so the current will not be intermittent even when the power flow rate is P-0, and the conventional problem of decreasing the gain of the control system when the current is intermittent is eliminated, making it possible to always obtain a good control response. can. In addition, power command value P
Even if the current changes from positive to negative or from negative to positive, there is no need to switch the control operation using a switch circuit as in conventional devices, eliminating dead time and eliminating unnecessary burden on the motor generator device MG. It will be done.

In addition, a motor generator device MG and a static power converter device SFC
You can freely choose to share the burden with the MG.
It is also possible to perform efficient operation by keeping the effective power delivered and received by the device constant.

Furthermore, by operating the static power converter SFC only when overloaded, the system as a whole can operate more efficiently.

[Brief explanation of drawings]

Figure 1 is a block diagram showing the configuration of a conventional frequency conversion device, Figures 2 (a) and (b) are voltage and current vector diagrams at the receiving end to explain the operation of Figure 1, and Figure 3 4(a) and 4(b) are voltage and current vector diagrams at the receiving end for explaining the operation of the device shown in FIG. 3, respectively. 5 and 6 are a control circuit diagram and an explanatory diagram thereof showing another embodiment of the device of the present invention. BI3. ... Electric line Bus of the first power system, ...
Electrical line MG of the second power system...Motor generator device SFC...Static power converter device CAP, , CAP, 8. Phase advance capacitor TR,,
TR,...Power transformer ss, , ss,...AC/DC power converter Lo...
・・・・・・・・・DC reactor CTl1l
,c'ra, ,c'rL"'AC current detector PT, ,
, FT, PTL...AC voltage detector PQC1,
PQC1, PQC3...active reactive power calculation circuit CTo
...DC current detector VRq...Reactive power setter C, C1...Comparator Hq(s), Hp(s)...Control compensation circuit KOIK
IIKL...Operation amplifier A,,A,,A1°...Adder PHth PHt...Phase side - circuit VRp...Active power setter LB...Level setter (7317) Agent Patent attorney Kensuke Chika (1 person) 7 3 (+Q+-JNN))

Claims (4)

[Claims] (1) A motor generator device interposed between a first power system and a second power system and an AC side of a first AC/DC power converter are connected to the first power system, and a second power system is connected to the AC side of the first AC/DC power converter. A static power source in which the AC side of an AC/DC power converter is connected to the second power system, and the DC sides of the two power converters are connected so that a DC current flows in a fixed direction via a DC reactor. A frequency converter configured with a converter, the value of the DC current of the static power converter and the value of the active power exchanged between the first power system and the second power system. A frequency conversion device characterized in that the value of the DC voltage is adjusted to simultaneously control the value of the reactive power of the two AC/DC power converters and the value of the active power to be transferred and received by the power conversion device. (2) The value of the active power transferred by the static power converter device is controlled in proportion to the value of the active power transferred by the motor generator device. frequency converter. (3) A patent claim characterized in that the value of the active power transferred by the static power converter ff is controlled so that the value of the active power transferred by the motor generator device is a constant value. The frequency conversion device according to item 1. (4) A patent characterized in that the value of active power exchanged by the static power converter device is controlled so that the value of active power exchanged by the motor generator device does not exceed a set level. A frequency conversion device according to claim 1.