JPH0834687B2 - High frequency link converter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Objects of the Invention (Field of Industrial Application) The present invention relates to a power conversion device having a high frequency link.

(Prior Art) FIG. 3 shows a configuration diagram of a conventional high-frequency link converter.

In the figure, SUP is an AC power supply, L _S is an AC reactor, C
C is a circulating current type cycloconverter, CAP is a high frequency phase advance capacitor, and LOAD is a load device. The cycloconverter CC is composed of a positive group converter SSP, a negative group converter SSN, and DC reactors L ₀₁ and L ₀₂ .

As the control circuit, the current detector CT _S , the voltage detector P
T _H , rectifier circuit D, voltage control circuit AVR, current control circuit ACR,
Phase control circuit PHC and the external oscillator O _SC are prepared.

The cycloconverter CC controls the input current I _S supplied from the AC power supply SUP so that the _peak values V _{cap of the} voltages Va, Vb, Vc applied to the phase advance capacitor CAP become substantially constant. The input current I _S is controlled to have a sine wave in phase with the power supply voltage V _S , and the operation can be performed with an input power factor of 1 and an extremely small harmonic component of the input current.

The phase control circuit PHC of the cycloconverter CC, external oscillator O _SC 3-phase reference signal from the e _a, e _b, e _c is given, and the signal e _a, e _b, the e _c to the reference, the cycloconverter CC
Phase control is performed.

The circulating current of the cycloconverter CC is adjusted so that the frequencies and phases of the voltages Va, Vb, and Vc applied to the phase-advancing capacitor CAP match the frequencies and phases of the reference signals e _a , e _b , and e _c. .

The load device LOAD uses the phase-advancing capacitor CAP as a high frequency power source, and may be a cycloconverter that drives an induction motor or a separately excited converter that drives a DC motor.

(Problems to be Solved by the Invention) The above-described conventional high-frequency link converter has the following problems.

That is, when the power supply SUP is a single-phase AC power supply, the power supply S
The current I _S supplied from UP is in phase with the power supply voltage V _S (power factor =
Even if the sine wave of 1) is controlled (the harmonics are small), the active power P _S = V _S · I _S supplied from the power supply SUP fluctuates at a frequency twice the power supply frequency _S as shown in the following equation. .

FIG. 4 shows respective waveforms of the voltage V _S , the current I _S, and the power P _S at that time.

This active power P _S is supplied to the high frequency phase advance capacitor CAP via the cycloconverter CC and stored as energy as in the following equation.

If the capacitance C _cap of the phase-advancing capacitor CAP is constant, the fluctuation of the active power P _S remains unchanged and the applied voltage V _{cap of the} phase-advancing capacitor V _cap
Will appear as a fluctuation. For this reason, it becomes impossible to supply a stable high-frequency voltage to the cycloconverter CC or load device that naturally commutates by using this voltage V _cap , which also causes commutation failure. The failure of the commutation of the cycloconverter hinders the establishment of the voltage of the phase advancing capacitor CAP and causes element destruction and the like.

The present invention has been made in view of the above problems, and keeps the high-frequency link voltage stable and performs commutation even when the power supply or the load is a single-phase AC, or even when the load is an unbalanced load. It is an object of the present invention to provide a high frequency link converter that does not fail.

[Structure of Invention]

(Means for Solving the Problems) In order to achieve the above object, the present invention provides an AC power supply, a first cycloconverter having an output terminal connected to the AC power supply, and a first cycloconverter. A high-frequency charging / discharging means connected to the input terminal, a load device connected to the high-frequency charging / discharging means, and a second cycloconverter having an input terminal connected to the high-frequency charging / discharging means,
DC charging / discharging means connected to the output side terminal of the second cycloconverter.

(Operation) The first cycloconverter controls the input current supplied from the AC power supply so that the voltage of the DC charging / discharging means (normally composed of the DC smoothing capacitor) used as the DC voltage source becomes constant. . The input current is controlled to have a sine wave in phase with the power supply voltage, and the operation is performed in a state where the input power factor is 1 and the harmonic components of the input current are small. In the second cycloconverter, the high-frequency charging / discharging means used as a high-frequency voltage source (usually composed of a high-frequency phase-advancing capacitor or an LC resonance tank circuit) has a substantially constant peak value of voltage. The current supplied from the DC voltage source is controlled. When the load is a single-phase AC power supply and the load is a three-phase balanced load, active power that fluctuates at a frequency twice the power supply frequency is supplied from the AC power supply. Therefore, active power corresponding to the power fluctuation is supplied from the DC voltage source via the second cycloconverter. Therefore, the active powers flowing in and out of the high-frequency voltage source are balanced, so that substantial energy is not transferred in and out, and the high-frequency voltage is stabilized. Here, energy flows in and out of the DC voltage source by the fluctuation of the single-phase power, so that the DC voltage fluctuates. However, since it is easy to increase the energy storage capacity by using a DC smoothing capacitor or a battery as the DC voltage source, it is possible to easily suppress the fluctuation of the DC voltage. Similarly, when the load is a three-phase unbalanced load with a three-phase AC power supply,
The voltage of the high frequency power supply is stabilized, and it is possible to provide a high frequency link converter without commutation failure.

(Embodiment) FIG. 1 is a configuration diagram showing an embodiment of a high frequency link converter of the present invention.

In the figure, SUP is a single-phase AC power supply, L _S is an AC reactor, CC
-1 is a first circulating current type cycloconverter, CAP is a high frequency phase advancing capacitor, LOAD is a load device, CC-2 is a second circulating current type cycloconverter, L _d is a DC reactor,
C _d is a DC smoothing capacitor.

The first cycloconverter CC-1 is a positive group converter
It is composed of SP ₁ , negative group converter SN _1, and DC reactors L ₀₁ and L ₀₂ .

The second cycloconverter CC-2 includes a positive group converter SP ₂ , a negative group converter SN ₂ and a DC reactor.
It is composed of L ₀₃ and L ₀₄ .

As the control circuit, current detectors CT _s and CT _d , voltage detector P _TH , rectifier circuit D, comparators C _{1 to} C ₄ , adders A _{1 to} A ₅ ,
DC voltage control compensation circuit G _V1 , high frequency voltage control compensation circuit
G _V2 , Input current control compensation circuit G _I1 , DC current control compensation circuit
G _I2 , proportional amplifiers K ₁ and K ₂ , multiplier ML, phase control circuit PH
C ₁ , PHC ₂ , and external oscillator O _sc are prepared.

The load device LOAD may be, for example, a cycloconverter that drives an induction motor or a separately excited converter that drives a DC motor. Here, a three-phase balanced load is assumed.

The first cycloconverter CC-1 controls so that the power SUP supplies the power P _i commensurate with the active power P _L taken by the load device LOAD. At the same time, a DC smoothing capacitor connected to the output side terminal of the second cycloconverter CC-2.
Input current so that the voltage V _d applied to the C _d is substantially constant
Control I _S.

The second cycloconverter CC-2 is a high frequency capacitor
The direct current I _d is controlled so that the _peak values V _{cap of the} voltages V _a , V _b , and V _c applied to the CAP are almost constant. Also, the load device
When there is a difference between the power P _L taken by LOAD and the power P _i supplied from the power supply SUP, the DC voltage is adjusted so that the power corresponding to the difference P _L −P _i is temporarily supplied from the DC smoothing capacitor. Control the current I _d .

The signals of the three-phase reference voltages e _a , e _b , and e _c from the external oscillator O _sc are used for the phase control of the two cycloconverters CC-1 and CC-2, and the voltage applied to the capacitor CAP is used.
The frequencies and phases of V _a , V _b , and V _c are the same as the reference voltages e _a , e _b , and e _c.
Match the frequency and phase of.

Voltage V _a of the phase advancing capacitor CAP, V _b, after starting operation and the voltage established for establishing V _c, the voltage V _a, V _b, V _c of the frequency and phase the reference voltage e _a, e _b, For the explanation of the operation in which the frequency and the phase of e _c coincide, see JP-A-63-23591, so please refer to them.

After the voltage is established, the first and second cycloconverters CC-
1, CC-2 is controlled as follows.

First, for convenience of explanation, the voltage V _d of the DC smoothing capacitor C _d
Has been established, the second cyclo converter
The control operation of CC-2 will be described.

The voltage detector PT _H, 3-phase voltage V _a applied to the high frequency phase advance capacitor CAP, detects V _b, V _c, via a rectifier circuit D, obtains the voltage peak value V _cap.

The comparator C ₃ has a voltage peak value V _cap and its command value ▲ V ^*
_{The cap} ▼ is compared, and the deviation ε ₃ = ▲ V ^* _cap ▼ −V _cap is input to the high frequency voltage control compensation circuit G _V2 . In G _V2 , the deviation ε ₃ is amplified or integrated, and the direct current command value ▲ I ^* _d ▼ is output via the adder A ₃ .

In the next comparator C ₄ , the DC detection value I _d detected by the current detector CT _d is compared with the DC current command value ▲ I ^* _d ▼,
The deviation ^{_{ε 4 = ▲ I * d ▼}} -I d the direct current control compensation circuit G _I2
To enter. In G _I2 , the deviation ε ₄ is amplified (or integrated), and the phase control input signal ν α ₂ is obtained via the adder A ₄ . Here, when G _I2 is an inverting amplifier (gain: −K _I2 ), να ₂ is given by the following equation.

ν α ₂ = -K _I2 · ε ₄ + E _d (1) E _d is a value proportional to the DC voltage V _d , and is used to output a voltage against V _d from the cycloconverter CC-2 in advance. .

The phase control circuit PHC _2, an external oscillator O _SC 3-phase reference signal from the e _a, e _b, e _c is given, the reference signal e _a, using e _b, e _c and the input signal Nyuarufa _2, By known means, firing phase angles α _P2 and α _N2 of the positive group converter SP ₂ and the negative group converter SN ₂ which constitute the cycloconverter CC-2 are given. In the steady state, there is a relationship of α _N2 ≈ 180 ° −α _P2 , and ν
The following equation holds for α ₂ .

ν ^α ₂ ^∝ cos α _P2 ≈−cos ^α _N2 (2) Further, when the output voltages V _P2 and V _N2 of the positive group and negative group converters are considered to be positive in the direction of the arrow in the figure, the following relationship holds.

V _P2 = K _v · V _cap · cos α _P2 ^∝ _ν ^α ₂ … (3) V _N2 = −k _v · V _cap · cos α _N2 ^∝ _ν ^α ₂ … (4) where V _cap is the high frequency voltage peak value and k _v is Proportional constant The output voltage of the cycloconverter CC-2 is the average value (V _P2 + V _N2 ) / 2 of the output voltage of the positive group and negative group converters.
Therefore, the output voltage of CC-2 has a value proportional to να ₂ .

A difference voltage between the DC voltage V _d and the output voltage (V _P2 + V _N2 ) / 2 of the CC-2 above is applied to the DC reactor L _{d.
V d - (V P2 + V} N2) / 2 by the DC current I _d is determined.

(1) always voltage against V _d by E _d of expression so generated from the cycloconverter CC-2, the voltage V _LD applied to L _d is a value proportional to K _I2 · ε _4.

▲ If a I ^* _d ▼> I _d, the deviation epsilon ₄ is a positive value, increasing the V _LD, increasing the DC current I _d. Conversely, ▲ I ^* _d ▼ <If a I _d, the deviation epsilon ₄ is a negative value, V _LD also reduces the DC current I _d becomes a negative value. Therefore, it is controlled so that I _d ≅ ▲ I ^* _d ▼.

The _peak value V _cap of the high frequency voltage is controlled as follows.

When ▲ V ^* _cap ▼> _Vcap , the deviation ε ₄ has a positive value and is amplified (or integrated) by the control compensation circuit G _V2 to increase the direct current command value ▲ I ^* _d ▼. Actual current I _d
Since is controlled so as to coincide with the command value ▲ I ^* _d ▼, active power from the smoothing capacitor _{C d P d = V d ·} I d is supplied to the high frequency capacitor CAP. Therefore, the smoothing capacitor C _d
The stored energy of the high frequency capacitor CA
The accumulated energy of P increases, and the voltage peak value V _cap increases.

On the contrary, when ▲ V ^* _cap ▼ < _Vcap , the deviation ε ₃ has a negative value, and the direct current command value ▲ I ^* _d ▼ also has a negative value. Therefore, the active power P _d = V _d · I _d is high frequency capacitor CA
Regenerated from P to the smoothing capacitor C _d , the accumulated energy of C _d increases and the accumulated energy of CAP decreases. Therefore, V _{cap is} also reduced, and finally V _cap ≈ ▲ V ^* _cap ▼ is settled down.

As described above, the second cycloconverter CC-2
Controls the direct current I _d so that the voltage peak value V _{cap of the} high frequency capacitor CAP matches its command value ▲ V ^* _cap ▼.

Next, the voltage V _d applied to the DC smoothing capacitor C _d is controlled to be substantially constant by the first cycloconverter CC-1, and the power P _i commensurate with the active power P _L taken by the load device LOAD is set. The control operation supplied from the AC power supply SUP will be described.

The comparator C ₁ compares the detected value of the DC voltage V _d and its command value ▲ V ^* _d ▼ and obtains the deviation ε ₁ = ▲ V ^* _d ▼ -V _d. Therefore, the DC voltage control compensation circuit G _V1 input.

In G _V1 , the deviation ε ₁ is amplified (or integrated), and the peak value command ▲ I ^* _sm ▼ of the input current I _s is given via the adder A ₁ .

By a multiplier ML, and the peak value command ▲ I ^* _sm ▼, a unit sine wave sinωt synchronized with the power supply voltage V _s multiplied,
Calculate the input current command value ▲ I ^* _s ▼.

_{^{▲ I * s ▼ = ▲ I}} * sm ▼ sinωt ... (5) Next, the input current detector input current detected by the CT _s I _s and the current command value ▲ I ^* _s ▼ to comparator C _2, Deviation ε ₂
= ▲ seek the I ^* _s ▼ -I _s.

The deviation ε ₂ is inverted and amplified (gain: −K _I1 ) by the input current control compensation circuit G _I1 and input to the phase control circuit PHC _C1 via the adder A ₂ . Therefore, the phase control input signal να ₁ of PHC ₁ is as follows.

να ₁ = -K _I1 · ε ₂ + E _s (6) Here, E _S is a value proportional to the power supply voltage V _S , and a voltage for opposing V _S is output from the cycloconverter CC-1 in advance. It is a thing.

The phase control circuit PHC _1, the external oscillator O _SC 3-phase reference signal from the e _a, e _b, e _c is given, by a known method by using the reference signal and the input signal Nyuarufa _1, cycloconverter CC- 1 phase control is performed.

With respect to the firing phase angle α _P1 of the positive group converter SP _1, the firing phase angle α _N1 of the negative group converter SN ₁ has a relationship of α _N1 ≈180 ° −α _{P1 in} the steady state, and the above input Signal ν
The following relation holds for α ₁ .

να ₁ ∝cosα _P1 ≈−cosα _N1 (7) Also, if the output voltages V _P1 and V _N1 of the positive group and negative group converters are considered as positive values in the direction of the arrows in the figure, they become the following equations. .

V _P1 ^∝ K _V · V _cap · cosα _P1 ^∝ να ₁ … (8) V _N1 ^∝ −K _V · V _cap · cosα _N1 ^∝ να ₁ … (9) The output voltage of the cycloconverter CC-1 is positive and negative. The average value of the output voltage of the group converter (V _P1 + V _N1 ) / 2,
The value is proportional to the phase control input signal να ₁ .

A difference voltage between the power supply voltage V _S and the output voltage (V _P1 + V _N1 ) / 2 of the CC-1 is applied to the AC reactor L _S , and the difference voltage
The input current I _S is determined by V _S − (V _P1 + V _N1 ) / 2.

Since the voltage always opposes the supply voltage V _S by E _S of equation (6) is generated from the cycloconverter CC-1, the voltage V _LS applied to the AC reactor L _S is, a value proportional to K _I1 · ε ₂ Becomes

When ▲ I ^* _s ▼> I _S , the deviation ε ₂ has a positive value, and V _LS is increased to increase the input current I _S. Conversely ▲
When I ^* _s ▼ <I _S , the deviation ε ₂ becomes a negative value and V _LS
Also becomes a negative value to reduce the input current I _S. Therefore, I _S ≈
It is controlled so that ▲ I ^* _s ▼. If the command value ▲ I ^* _s ▼ is changed in a sine wave shape, the actual current I _S also follows it and becomes a sine wave current.

The input current command value ▲ I ^* _s ▼ is given by a sine wave in phase with the power supply voltage V _S = V _sm · sin ωt, as shown in equation (5), and as a result, the input power factor is always 1. , The harmonic components contained in the input current I _S almost disappear.

The DC voltage _Vd is controlled as follows.

First, a description will be given of a case in which a ^{_{▲ V * d ▼> V d}} . Deviation ε
₁ becomes a positive value, and the peak value command ▲ I ^* _sm ▼ of the input current is increased via the control compensation circuit G _V1 and the adder A ₁ . Therefore, the input current I _S ≅ ▲ I ^* _s ▼ increases, and the active power P _i = V _S · I _S is supplied from the power supply SUP to the high frequency capacitor CAP to increase the high frequency voltage V _cap . As a result, ▲ V ^* _cap ▼ < _Vcap , and the DC current command value ▲ I ^* _d ▼ becomes a negative value. I _d ≒ ▲ I
Since it is controlled to ^* _d ▼, the power P _d = V _d · I _d is regenerated to the DC smoothing capacitor C _d , increasing the DC voltage V _d , and V _d ≈V
^* _d ▼ becomes calm.

Further, ▲ V ^* _d ▼ <If a V _d, the deviation epsilon ₁ is a negative value, through a G _V1 and A _1, ▲ I ^* to _sm ▼ a negative value.
As a result, active power P _S = V _S · I _S is high frequency capacitor CAP
Is regenerated from the AC power supply SUP to reduce the high frequency voltage V _cap . Therefore, ▲ V ^* _cap ▼> V _cap , the DC current command value ▲ I ^* _d ▼ is increased, and the power P _d = V _d · I _d is supplied from the DC smoothing capacitor C _d to the high frequency capacitor CAP, and the DC smoothing is performed. The energy stored in the capacitor decreases and the DC voltage V _d decreases. After all, V _d = ▲ V ^* _d ▼ finally settles down.

As described above, the DC voltage V _d and the high frequency voltage V _cap
Are controlled to be substantially constant according to the respective command values.

When the load device LOAD takes active power P _L , temporarily,
▲ ^* _cap ▼> ▲ V ^* _cap ▼, and the DC current I _d is increased by CC-2 to control V _cap ≈ V _cap . As a result, V _d
There _{^{decreased, ▲ V * d ▼> V}} d becomes, increasing the input current I _S by CC-1, as described above, controlled to be ^{_{V d ≒ ▲ V * d ▼}} . Eventually, P _i = V _S · I _S ≈P _L and the overall settling down.

In order to improve the response to such sudden changes in load,
Positive control compensation is performed.

That is, the active power P _L taken by the load device LOAD is detected (or calculated by calculation or the like), the value is input to the proportional amplifier K _1, and the peak value command ▲ I of the input current corresponding to the active power P _{L of the} load is input. _Input ^* _smo ▼ into adder A ₁ . In the case of the single-phase power supply SUP, ▲ I ^* _smo ▼ is obtained by the following equation.

However, V _sm is the _peak value of the power supply voltage, and as a result, when the load LOAD takes active power P _L , immediately,
Active power _i (average value) is supplied from the AC power supply SUP,
Moreover, Therefore, it becomes possible to control the applied voltage V _cap of the high frequency capacitor CAP so as not to fluctuate.

However, in the case of a single-phase power supply, the supplied active power P _i is exactly as follows.

Therefore, the component of the second term on the right side of the equation (12) remains, and the high frequency voltage V _{cap tends} to be changed.

FIG. 2 shows the waveforms of the voltage, current and power of each part of the device of FIG. 1, where V _S is the power supply voltage, I _S is the input current, P _i is the input power, P _L is the load power, and V is the load power. _d represents a DC voltage and I _d represents a DC current.

The input current I _S is controlled by a sine wave in phase with the power supply voltage V _S ,
When the input power factor is 1, the current has few harmonics.

The input power P _i = V _S · I _S changes at a frequency twice the power supply frequency _S. The average value _i substantially matches the load power P _L.

Input power P _i and load power P _L
The difference between the two comes in and out, and as a result, the _peak value V _{cap of the} high frequency voltage _tends to change. However, with the second cycloconverter, the DC current is adjusted so that V _cap ≈ ▲ V ^* _cap ▼ = constant
The high frequency voltage V _cap is kept substantially constant in order to control I _d . Therefore, this time, the difference P _i −P _{L of the} power flows in and out of the DC smoothing capacitor C _d , and the DC voltage V _d changes.
However, since it is easy to increase the energy storage capacity of the DC smoothing capacitor C _d , by preparing a capacitor capacity sufficient to absorb the fluctuation of the active power associated with the single-phase power supply, the DC voltage V The fluctuation of _d can be suppressed small.

Here, if the direct current I _d is controlled by waiting for the change of the high frequency voltage V _cap as described above, it is inevitable that the high frequency voltage V _cap fluctuates to some extent due to a control delay or the like.

Therefore, the direct current I _d is controlled in a positive manner according to the power difference P _L −P _i to suppress the fluctuation of the high frequency voltage V _cap .

That is, in FIG. 1, active power taken by the load LOAD.
The input power P _i from P _L and the power supply SUP is detected, input to the adder A ₅ , the calculation of P _L −P _i is performed, and the direct current command value ▲ I ^* _do ▼ is calculated via the proportional amplifier K _2. And

The adder A ₃ adds the output signal of the high frequency voltage control compensation circuit G _V2 and the above-mentioned ▲ I ^* _do ▼ to obtain a DC command value ▲ I ^* _d ▼.

▲ V ^* _cap ▼ output signal of the G _V2 as ≒ V _cap is When sufficiently _{^{small, ▲ I * d ▼ ≒ ▲}} I * do ▼ , and the like of FIG. 2, the direct current I _d is changed, the single Phase power fluctuation P _L −P _i
Flows so as to immediately cancel. As a result, the high-frequency voltage ▲ V ^* _cap ▼ fluctuations of no longer, the V _cap ≒ V _cap.

In the above, the single-phase AC power supply SUP and the three-phase balanced load LOAD have been described, but the same can be applied when the power supply is three-phase and the load is a single-phase or unbalanced load. That is, if there is a difference between the input power P _i and the load power P _L ,
It is possible to stabilize the high frequency voltage V _cap by supplying the effective power of the difference by CC-2.

Also, as a high frequency voltage source, a high frequency advance capacitor CA
When P is used, it is sufficient if at least one of the first and second cycloconverters is a circulating current type cycloconverter. That is, high frequency capacitors
Voltage V _a applied to the CAP, V _b, V _c of the frequency and phase external oscillator O 3 phase reference signal supplied from the _SC e _a, e _b, to match the frequency of e _c and phase, the Cyclo This is because the circulating current of the converter is controlled. For details, see JP-A-63
See −23591 publication.

Further, as the high frequency voltage source, an LC tank circuit using a resonance circuit of the reactor L and the capacitor C may be used. In that case, both the first and second cycloconverters may be non-circulating cycloconverters. However, the frequency of the high-frequency voltage source is related to the constants of L and C and the value of the reactive power taken by the cycloconverter, and cannot be set constant from the outside. Further, as the reference signal of the phase control circuit, it is necessary to directly detect the high frequency voltage and use a signal synchronized with the voltage.

The case where the DC smoothing capacitor C _d is used as the DC voltage source has been described, but the same can be applied to the case where a battery having a larger energy storage capacity is used. If the power fluctuation of the load is large, the power fluctuation can be
AC power supply via the cycloconverter CC-2
The SUP can supply time-averaged power with little fluctuation. As a result, the capacity of the first cycloconverter and the equipment capacity of the power supply system can be reduced.

〔The invention's effect〕

As described above, according to the high frequency link converter of the present invention, even if the power supply SUP is a single-phase AC power supply or the load becomes an unbalanced load, the DC voltage source is generated via the second cycloconverter. The compensation power can be supplied from the device, and the voltage of the high frequency voltage source can be kept stable. Therefore, the commutation failure of the cycloconverter that spontaneously commutates using the voltage of the high frequency voltage source is eliminated, and a highly reliable system can be provided.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a high frequency link converter of the present invention, FIG. 2 is a waveform diagram of voltage, current and power of each part for explaining the operation of the device of FIG. 1, and FIG. FIG. 4 is a configuration diagram of the high frequency link converter of FIG. 4, and FIG. 4 is a time chart diagram for explaining the operation of the device of FIG. SUP ... AC power source, L _S ... AC reactor CC-1 ... first cycloconverter CAP ... high frequency power capacitor LOAD ... loading device C _d ... DC smoothing capacitor L _d ... DC reactor CC-2 ... second cycloconverter CT _S, CT _d ... current detector PT _H ... voltage detector, D ... rectifier circuit C ₁ -C ₄ ... comparator, A ₁ ~A ₅ ... adder _{G V1, G V2, G I1} , G I2 ... control compensation Circuit K ₁ , K ₂ … Proportional amplifier, ML… Multiplier PHC ₁ , PHC ₂ … Phase control circuit O _SC … External oscillator

Claims (7)

[Claims] 1. An alternating current power supply, a first cycloconverter having an output side terminal connected to the alternating current power supply, a high frequency charging / discharging means connected to an input side terminal of the first cycloconverter, and the high frequency charging / discharging means. A load device connected to the discharging means; a second cycloconverter having an input side terminal connected to the high frequency charging / discharging means; and a DC charging / discharging means connected to the second cycloconverter. Characteristic high-frequency link converter. 2. The high frequency link converter according to claim 1, wherein the high frequency charging / discharging means is composed of a high frequency advance capacitor. 3. The high frequency link according to claim 1, wherein at least one of the first and second cycloconverters is a circulating current type cycloconverter. Converter. 4. The first cycloconverter comprises means for controlling a current supplied from the AC power supply so that the voltage of the DC charging / discharging means becomes substantially constant. The high frequency link converter according to 1). 5. The second cycloconverter comprises means for controlling a current supplied from the direct current charging / discharging means so that the voltage peak value of the high frequency charging / discharging means becomes substantially constant. The high frequency link converter according to any one of claims (1) to (4). 6. The first cycloconverter comprises means for controlling a current supplied from the AC power supply according to active power taken by the load device. The high frequency link converter according to claim 4. 7. The second cycloconverter means for controlling a current supplied from the DC charging / discharging means in accordance with a difference between active power taken by the load device and active power supplied from the AC power supply. The high frequency link converter according to claim 1 or 5, further comprising: