JPH0683576B2 - High frequency power supply - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Object of the Invention (Industrial field of application) The present invention relates to a cycloconverter for driving an AC motor,
Alternatively, the present invention relates to a high frequency power supply device such as a separately excited converter that drives a DC motor.

(Prior Art) FIG. 8 shows a configuration diagram of a conventional high-frequency power supply device.

In the figure, SUP is an AC power supply, L _S is an AC reactor, CC−
Reference numeral 1 is a first cycloconverter, CC-2 is a second cycloconverter, TANK is a high frequency tank circuit, and IM is an induction motor.

The second cycloconverter CC-2 and the induction motor IM serve as a load of the high frequency power supply (first cycloconverter CC-1 + tank circuit TANK).

The first and second cycloconverters CC-1 and CC-2 are
Using the voltage of the tank circuit TANK, it commutates naturally.

The first cycloconverter CC-1 receives power from the AC power supply SUP, converts it into a high frequency, and supplies it to the tank circuit.

Also, the second cycloconverter CC-2 is a tank circuit TA.
NK is used as a high-frequency voltage source, converted into electric power of variable voltage and variable frequency, and supplied to the induction motor IM.

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

That is, when the load of the high-frequency tank circuit TANK is light, the frequency f _T ≈ is determined by the following formula by the capacitor C _T and the reactor L _T forming the tank circuit.
It will be constant.

However, as the load increases, the delay reactive power taken by the cycloconverters CC-1 and CC-2 increases accordingly, and the frequency f _T becomes larger than the value determined by (1). Therefore, the frequency f _T as a high frequency power supply device
Is not stable and affects the commutation limit of the cycloconverter performing natural commutation, in the worst case, it causes commutation failure and may even fall out of control.

Also, since the frequency of the high frequency power supply is not constant, the harmonic components of the output voltage of the cycloconverters CC-1 and CC-2 change, the filter constants for removing the harmonics are not fixed, and a wide range is covered. There is a drawback that it becomes a filter that can be used and the capacity increases.

In addition, the conventional high frequency power supply device is
Since no measures have been taken, the voltage of the high-frequency tank circuit fluctuates, causing the cycloconverter, which is performing natural commutation, to fail commutation, causing problems such as being out of control.

The present invention has been made in view of the above problems, stabilizes the frequency of the high frequency power supply device, and improves the control response even against a sudden load change, and keeps the high frequency voltage almost constant,
It is an object to provide a high frequency power supply device without commutation failure.

[Structure of Invention]

(Means for Solving Problems) In order to achieve the above object, the present invention provides an AC power supply,
A circulating current type cycloconverter having an output side terminal connected to the AC power supply, a phase advancing capacitor connected to an input side terminal of the cycloconverter, a load device using the phase advancing capacitor as a high frequency voltage source, and the phase advancing A means for controlling the peak value of the voltage applied to the capacitor to be substantially constant, a means for controlling the current supplied from the AC power supply by the output signal from the voltage peak value control means, and a means for controlling the current from the current control means. It comprises means for controlling the phase of the circulating current type cycloconverter according to the output signal, and an external oscillator for giving a phase reference signal to the phase control means.

(Function) The circulating current type cycloconverter controls the current supplied from the power supply so that the peak value of the voltage applied to the phase advancing capacitor becomes almost constant, and the circulating current is uncontrolled. . The phase reference signal provided to the phase control circuit of the cycloconverter is generated by an external oscillator. Therefore, the circulating current of the cycloconverter is automatically adjusted so that the frequency and phase of the voltage applied to the phase advancing capacitor match the frequency and phase of the phase reference signal provided from the external oscillator.

Therefore, the frequency and phase of the voltage applied to the phase-advancing capacitor are uniquely determined and are kept constant even if the load changes. The peak value of the voltage of the phase advancing capacitor is
It is controlled so as to match the command value, and is held substantially constant. Further, since the correction value of the amount proportional to the load power is added to the output signal from the voltage peak value control means and is applied to the current control means, the response is improved and a sudden change in the load is prevented. Also, the voltage peak value of the phase advancing capacitor is kept constant.

As a result, not only does the commutation failure of the circulating current type cycloconverter itself disappear, but also the separately excited converter and the cycloconverter constituting the load device do not fail commutation.

Moreover, since the frequency is stable, the design of the filter and the like is simplified, and the capacity of the filter equipment can be reduced by selecting a more precise constant.

(Embodiment) FIG. 1 is a configuration diagram showing an embodiment of a high frequency power supply device of the present invention.

In the figure, SUP is an AC power supply, L _S is an AC reactor, CC is a circulating current type cycloconverter, CAP is a phase advancing capacitor, and LOAD is a load device.

As a control circuit, the current detector CT _S , the voltage detector P
T _S , PT _C , rectifier circuit D, voltage control circuit AVR, adder AD ₁ , AD ₂ ,
Multiplier ML, the current control circuit ACR, the phase control circuit PHC, external oscillator O _SC are prepared.

Circulating current type cycloconverter CC is
The current I _S supplied from the AC power supply SUP is controlled so that the _peak values V _{cap of the} voltages V _a , V _b , and V _c applied to P are almost constant.

Further, the load device LOAD is, for example, an induction motor driven by a cycloconverter, and supplies alternating-current power of a variable voltage variable frequency to the induction motor by the cycloconverter using the high-frequency advance capacitor CAP as a three-phase voltage source.

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 circulating current type cycloconverter CC, and the voltages V _a , V _b , V _{b of} the phase advancing capacitor CAP are used. The frequency and phase of V _c match the frequency and phase of the reference voltages e _a , e _b , and e _c .

FIG. 2 shows a concrete example of the main circuit configuration of FIG. 1, in which the circulating current type cycloconverter CC has an R phase, S
-Phase and T-phase cycloconverters CC-R, CC-S and CC-T
It consists of

R-phase cycloconverter CC-R is a positive group converter S
P _R , negative group converter S N _R and DC reactor L _O1-R , L
_O2-R is composed of, its output terminal via an AC reactor L _SR, and is connected to the secondary winding of the power transformer Tr.

The same applies to the S phase and T phase.

The input side terminal of each phase cycloconverter is connected to a high frequency phase advance capacitor (three phases), and the terminal is connected to a load device LOAD (for example, cycloconverter + induction motor).

The detailed operation will be described below.

First, the starting operation for establishing voltages V _a, V _b, V _c the phase advancing capacitor CAP.

The voltage of each phase of the three-phase AC power supply SUP can be expressed by the following equation. However, V _sm is the power supply voltage peak value, and ω _s = 2πf _s is the source angular frequency.

_{V R = V sm · sinω s} t ... (2) V S = V sm · sin (ω s t-2π / 3) ... (3) V T = V sm · sin (ω s t + 2π / 3) ... (4 ) with respect to the power of the frequency _{f s} (50 Hz or 60 Hz),
If the frequency f _cap on the input side (advancing capacitor side) of the cycloconverter CC is sufficiently high, the power supply voltages V _R , V _S , and V _T can be replaced with a DC voltage for a very small time.

Therefore, considering the period when the R-phase voltage is positive, the negative group converter
Through SN _R, explaining the operation to establish a voltage phase advance capacitor CAP.

Figure 3 is a R Aimakegun converter SN _R, phase advance capacitor C
_ab , C _bc , C _ca and AC reactor L _SR and R phase power supply voltage V _R
It is an equivalent circuit showing the relationship. As a matter of course, charging of the advance capacitors C _ab , C _bc , and C _ca is controlled through other S-phase and T-phase cycloconverters, but here, for simplification of description, the R-phase cycloconverter is used. The operation will be explained only with CC-R.

In the circuit of FIG. 3, when the firing pulse is applied to the thyristors S ₂ and S ₄ , the charging current I _R is the power supply V _R ⁺ → reactor L _SR → thyristor S ₄ → capacitor C _ab → thyristor S ₂ → power supply. V _R ^- and path of the power source V _R ⁺ → reactor L _SR → thyristor S ₄ → capacitor C _ca → capacitor C _bc → thyristor S ₂ → power V _R ^- flows through a path of. As a result, the capacitor C _ab, the power supply voltage V
_R is charged, and a voltage of −V _R / 2 is applied to the capacitors C _bc and C _ca.

Figure 4 (a) is a thyristor S ₁ to S of the negative group converter SN _R
Shows the ₆ arc mode point, 3-phase reference signal e _a from an external oscillator O _SC of FIG. 1, e _b, firing pulse is applied in synchronization with the e _c. After the mode of FIG. 3, the thyristor S ₃ is given a firing pulse. Then, the reverse bias voltage is applied to the thyristor S ₂ by the voltage charged in the capacitor C _bc , and S ₂ is turned off. That is, the phase advancing capacitor CAP functions as a commutation capacitor at startup. When the thyristors S ₄ and S ₃ are turned on, the voltage applied to the capacitors C _ab , C _bc and C _ca also changes.

FIG. 4B shows the waveforms of the voltage V _ab and the phase voltage V _a between the terminals a and b of FIG. 3 when the ignition is performed in the mode of FIG. Since the voltage V _ab is charged via the reactor L _SR , the voltage V _ab gradually rises as shown by the broken line. When the time is set to 2δ, the fundamental wave component of V _ab is delayed by δ. The phase of the phase voltage V _a is delayed by (π / 6) radian with respect to the line voltage V _ab .

As can be seen by comparing the ignition mode and the phase voltage V _a in FIG. 4, the phase control angle α _NR at startup is α _NR = π−δ (radian) (5). Since δ is not so large, it means that the operation is approximately α _NR ≈180 °. Output voltage V _NR converter SN _R in this case, given the direction of the arrow of FIG. 3 as positive, and has a _{V NR = -k · V cap ·} cosα NR ... (6). However, k is a proportional constant and _Vcap is the _peak value of the phase voltage of the capacitor.

The output voltage V _NR is balanced with the power supply voltage V _R. However, as it is, the phase advancing capacitor CAP is not charged with a voltage equal to or higher than the power supply voltage V _R.

Therefore, the firing phase angle α _NR is slightly shifted in the direction of 90 °. Then, the output voltage V _NR represented by the equation (6) decreases, and V _R > V _NR . As a result, the charging current I _R increases,
The capacitor voltage V _cap is increased, and V _R = V _NR, and then settles down. At this time, I _R = 0. When it is desired to further increase V _cap , it can be achieved by shifting α _NR further by 90 ° and decreasing the output voltage V _NR . α _NR = 9
At 0 °, V _NR = 0 ^V , and theoretically, the capacitor voltage V _cap can be charged to a large value even if the power supply voltage V _R is a very small value. However, in reality, since there is a circuit loss, power supply for that amount is indispensable.

In this way, the voltage V _cap of the phase advancing capacitor CAP can be charged to an arbitrary value.

When the power supply voltage V _R is a negative value, positive group converter
Charging is controlled similarly via SP _R.

Similarly, the charging currents I _S and I _T are supplied to the phase advancing capacitor CAP through the S-phase and T-phase cycloconverters CC-S and CC-T.

From a macro perspective, active power supplied from a three-phase power source
When the input power factor is 1, P _S is P _S = V _R · I _R + V _S · I _S + V _T · I _R (7), and the energy P _S · t is stored in the phase advance capacitor CAP. Will be accumulated. To increase the voltage V _cap applied to the phase-advancing capacitor CAP, increase the active power P _{S in} equation (7). Conversely, if you want to lower V _cap , set P _S to a negative value. do it. The circulating current type cycloconverter CC performs this control.

The voltage V of the advance capacitor CAP established in this way
_a , V _b , V _c are given to the phase control circuit PHC of FIG. 1 3
It will be described below that the phase reference voltages e _a , e _b , and e _c match the frequency and phase.

Here, too, the R-phase cycloconverter CC-R will be described as an example.

Since the R-phase cycloconverter CC-R controls the input current I _R supplied from the power supply, its output voltage V _CR is changed according to the power supply voltage V _R. Output voltage V _CR of CC-R is an average value of the output voltage V _NR the output voltage V _PR and negative group capacitor SN _R of positive group converter SP _R, is expressed as follows.

V _CR = (V _PR + V _NR ) / 2 (9) Further, as for the circulating current I _OR , the difference V _PR −V _NR between the output voltages of the positive group and negative group converters is the DC reactor L _O1-R , L _O2. It flows by being applied to _-R . That is, when V _PR > V _NR , I _OR increases, and conversely, when V _PR <V _NR , I _OR decreases.

Normally, V _PR ≈V _NR and the circulating current I _OR does not increase or decrease.
At this time, the firing phase angle satisfies the condition of α _NR ≈180 ° −α _PR (10).

FIG. 5 shows the phase control reference signals e _a , e _b , e _{c in} the case of α _PR = 45 ° and α _NR = 135 ° and the ignition pulse signals of the positive group and negative group converters.

Reference signal e _a, e _b, e _c is intended to be supplied from an external oscillator O _SC, expressed as follows.

e _a = sin (ω _C · t) (11) e _b = sin (ω _C · t-2π / 3) (12) e _c = sin (ω _C · t + 2π / 3) (13) where , Ω _C = 2πf _C is a high-frequency angular frequency, for example,
f _C = 1 kHz is selected.

Phase voltage V _a of the phase advancing capacitor CAP, V _b, V _c is the reference voltage e
_When the frequencies and phases of _a , e _b , and e _c match, the output voltages of the converters SP _R and S N _R are as follows.

V _PR = k · V _cap · cosα _PR (14) V _NR = −k · V _cap · cos α _NR (15) Therefore, as long as equation (10) is satisfied, V _PR ≈ V _NR There is no increase or decrease in circulating current I _OR .

Frequency f _cap of if the capacitor voltage in this state is lowered, the V _'a, V' shown by the broken line of FIG. 5 _b, consider the case where a V _'c.

Ignition phase angle of the converter SP _R is, alpha from _PR alpha 'in _PR, also the ignition phase angle of the SN _R is alpha from alpha _NR' changes _NR. As a result, V _PR > V _NR and the R-phase cycloconverter CC-
Increase the circulating current I _{OR of} R.

Similarly, S-phase and T-phase cycloconverters CC-S and
The circulating currents I _OS and I _{OT of} CC-T also increase.

The circulating currents I _OR , I _OS , and I _OT become delayed reactive power on the input side of the cycloconverter CC when viewed from the phase advancing capacitor CAP side.

FIG. 6 shows an equivalent circuit for one phase on the input side of the cycloconverter CC. The cycloconverter CC is replaced with a variable inductance _Lcc that takes a delay current. The resonance frequency f _cap of this circuit is as follows.

The increase of the circulating current is equivalent to the decrease of the equivalent inductance L _cc , and the frequency f _cap is increased,
_{V 'a, V' b,} V ' frequency f _cap the reference voltage e _a of _c, e _b, near Nuisance frequency _{f c} of e _c.

Similarly, when a f _cap> f _c is the circulating current I _OR, I
_OS , I _OT decreased, L _cc increased, and again f _cap
= Settle down and become a _{f c.}

If the phase of the voltage of the phase advancing capacitor CAP is delayed from the phase of the reference voltage, the f _cap <Similarly circulating current and when it becomes f _c increases, it advances the voltage phase of the phase advancing capacitor CAP. If the voltage phase opposite to the phase advance capacitor CAP is advanced from the reference voltage, as well as when a the f _cap> f _c, the circulating current is reduced, delaying the voltage phase of the phase advancing capacitor CAP. In this way, the phase advance capacitor CAP
The voltages V _a , V _b , and V _c of are automatically adjusted in magnitude of the circulating current so that they have the same frequency and phase as the reference voltages e _a , e _b , and e _c . Therefore, the capacitor voltages V _a , V _b ,
V _c is expressed by the following equation.

V _a = V _cap · sin (ω _C · t) (17) V _b = V _cap · sin (ω _C · t-2π / 3)… (18) V _c = V _cap · sin (ω _C · t + 2π / 3) (19) However, V _cap is the voltage peak value.

Next, returning to FIG. 1, the operation of controlling the voltage peak value V _cap of the phase advance capacitor CAP to be constant will be described.

First, the voltage detector PT _C, detects the voltage V _a, V _b, V _c the phase advancing capacitor CAP, via the rectifier D it detects the voltage peak value V _cap.

In the voltage control circuit AVR, it compares the command value ▲ V ^* _c ▼ _ap and the voltage detection value V _cap, the deviation _{^{ε V = ▲ V * c ▼}} ap -V
_cap is amplified (and K _V times), and inputs _{ΔI m = K V · ε V} ... (20) to the adder AD _1.

On the other hand, the active power P _L consumed by the load LOAD is detected, and I _mo = K _L · P _L (21) is input to the adder AD ₁ through the proportional amplifier K _L.

The adder AD ₁ adds the above I _mo and ΔI _m to obtain I _m = I _mo + ΔI
Input _m to the multiplier ML.

Further, the power supply voltages V _R , V _S , and V _T are detected by the voltage detector PT _S , and the following three-phase unit sine wave φ is detected via the proportional amplifier K _S.
Find _R , φ _S , and φ _T.

_{φ R = (V R / V} sm) = sinω S t ... (22) φ S = (V S / V sm) = sin (ω S t-2π / 3) ... (23) φ T = (V T / _{V sm) = sin (ω S} t + 2π / 3) ... (24) multiplier ML is the 3-phase unit sine wave phi _R, phi _S, multiplied by the phi _L and the input current peak value command I _m, the following Input current command value ▲ I ^* _R ▼, ▲ I ^* _S ▼, ▲ I ^* _T ▼ to current control circuit ACR.

^{_{▲ I * R ▼ = I m}} × φ R = I m · sinω S t ... (25) ▲ I * S ▼ = I m × φ S = I m · sin (ω S t-2π / 3) ... (26 ) ▲ I ^* _T ▼ = In _{I m × φ T = I m} · sin (ω S t + 2π / 3) ... (27) current control circuit ACR, the current command value _{^{▲ I * R ▼, ▲ I}} * S
▼, ▲ I ^* _T ▼ and the input currents I _R , I _S , I _T detected by the current detector CT _S are compared with each other, and each deviation ε _R = ▲ I ^* _R ▼ −
I _R , ε _S = ▲ I ^* _S ▼ −I _S , ε _T = ▲ I ^* _T ▼ − I _T is amplified,
Input to phase control circuit PHC.

Figure 7 is shows a current control circuit and the phase control circuit of the R-phase cycloconverter, C _R is a comparator, G _I (S) is a current control compensation circuit, AD _R adder, INV inverting amplifier, PHP _R is the phase control circuit of the positive group converter, PHN _R denotes a phase control circuit of the negative group converter.

Depending on the comparator C _R , the R phase current command value ▲ I ^* _R ▼ and the actual current I _R
There are compared, deviation ^{_{ε R = ▲ I * R ▼}} -I R current control compensation circuit
Input to G _I (S).

G _I (S) is an inverting amplifier that multiplies ε _R by −K _I. Its value − K _I
The · epsilon _I input to the adder AD _R, one alignment added and the compensation amount e _R proportional to the power supply voltage V _R is input to the phase control circuit PHP _R direct positive group converter, the other one inverting amplifier Input to the phase control circuit PHN _R of the negative group converter via INV.

The input signals v _αP and v _αN to the PHP _R and _{PH N R} are as follows.

_{v αP = e R -K I εR} ... (28) v αN = - (e R -K I εR) ... (29) positive group converter SR output voltage of the _R V _PR is the input signal v _.alpha.P
In addition, the output voltage V _NR of the negative group converter SN _R becomes a value proportional to the inverted value of the input v _αN when the direction of the arrow in FIG. 1 is a positive value.

When deviation ε _R = 0 in equations (28) and (29), the phase control input signal is v _αP = e _R , v _αN = -e _R , and the output voltage of each converter is V _PR = k _C v _αP = k _C · e _R (30) V _NR = −k _C · v _{α N} = k _C · e _R (31) and the output voltage V _{CR of the} R-phase cycloconverter CC-R
As a result, V _CR = (V _PR + V _NR ) / 2 = k _C · e _R (32). Make this voltage equal to the R-phase power supply voltage V _R
e _R is given, V _CR = V _R, and the input current I _R does not increase or decrease.

When ▲ I ^* _R ▼> I _R , the deviation ε _R becomes a positive value and R
Output voltage V _CR phase cycloconverter is smaller than the power supply voltage V _R, increase the input current I _R.

On the contrary, when ▲ I ^* _R ▼ <I _R , the deviation ε _R becomes a negative value, V _CR becomes larger than V _R , and the input current I _R is decreased.

Therefore, it is controlled so that I _R ≅ ▲ I ^* _R ▼.

The input currents I _S and I _{T of the S} and T phases are also the command values ▲ I ^*
Controlled to match _S ▼, ▲ I ^* _T ▼.

The command values ▲ I ^* _R ▼, ▲ I ^* _S ▼, and ▲ I ^* _T ▼ are (25) to (2
Since it is given by a sine wave synchronized with the power supply voltages V _R , V _S , and V _T as shown in equation (7), the input power factor is always 1, and the input current has few harmonic components.

Now, consider the case where ▲ V ^* _c ▼ _ap > _Vcap in the control circuit of FIG.

The deviation ε _V = ▲ V ^* _c ▼ _ap −V _cap has a positive value, and the output ΔI _m of the voltage control circuit AVR = K _V · ε _V also has a positive value and increases.
Therefore, the input current peak value I _m also increases, and the active power P _S supplied from the power supply SUP increases. Therefore, the energy shown by the equation (8) is accumulated in the phase advancing capacitor CAP, and the voltage peak value V _cap is increased. Eventually V _cap ≒ ▲ V ^* _c ▼ _ap and settle down.

Conversely ▲ V ^* _c ▼ _ap <If a V _cap, deviation epsilon _V becomes a negative value, [Delta] I _m also becomes a negative value to reduce the input current peak value I _m. Therefore, the active power P _S supplied from the power supply SUP decreases, and the peak value V of the voltage applied to the phase-advancing capacitor CAP is reduced.
_{The cap} is reduced, and V _cap ≅ ▲ V ^* _c ▼ _ap is also controlled.

As described above, the voltage V _cap of the phase-advancing capacitor CAP is held substantially constant, but the operation when the load suddenly changes will be described here.

To be precise, the energy stored in the phase-advancing capacitor CAP is determined by the difference between the power P _S supplied from the power supply SUP and the power P _L consumed by the load device LOAD, as in the following equation. However, we consider that the loss of the converter can be ignored.

If the load P _L increases, the voltage V _{cap of the} phase advance capacitor CAP
Decreases, and ▲ V ^* _c ▼ _ap > _Vcap, and ΔI _m increases,
The power P _S supplied from the power supply SUP increases, and the voltage V _cap is restored.

Therefore, when the change of the load P _L is slow, the voltage control follows and V _cap = ▲ V ^* _c ▼ _ap holds,
If the load P _L changes suddenly, V
_cap ≠ ▲ V ^* _c ▼ _ap . If the sudden change in the load P _L is large, the difference also becomes large, and commutation failure of the cycloconverter performing natural commutation may be caused.

The compensation amount I _mo added to the adder AD ₁ in FIG. 1 improves the followability of the voltage control so that V _cap = ▲ V ^* _c ▼ _ap even when the load changes suddenly. Operate.

First, the active power P _L consumed by the load LOAD is detected. This includes, for example, the voltages V _a , V _b , V _{c of} the phase advancing capacitor CAP,
The instantaneous active power is calculated by detecting the instantaneous values of the currents I _La , I _Lb , and I _Lc that flow into the load device LOAD and performing the calculation of the following equation.
Detect P _L.

P _L = V _a · I _La + V _b · I _Lb + V _c · I _Lc (34) This detected value P _L is input to the proportional amplifier K _L and the following equation is calculated to calculate the compensation amount I _mo . Ask.

As a result, when ΔI _m = 0, I _m = I _mo , and the input currents I _R , I _S , and I _T of each phase of the power supply are controlled as follows.

Therefore, the active power P _S supplied from the power supply SUP is P _S = V _R · I _R + V _S · I _S + V _T · I _T = P _L (39) from the equation (7).

Therefore, when the load P _L suddenly changes, the effective power P _S = P _L corresponding to this is immediately supplied from the power supply SUP, and the voltage V _cap of the phase advance capacitor CAP represented by the equation (33) does not change.

As a result, V _cap ≒ ▲
It is controlled to V ^* _c ▼ _ap, and a stable high frequency voltage source can be achieved.

In reality, P _S and P _L cannot be made to completely match due to the calculation error of equation (35), etc.
It will be controlled so that V _cap ≈ ▲ V ^* _c ▼ _ap via the AVR.

〔The invention's effect〕

As described above, in the high frequency power supply device of the present invention, the frequency and phase of the voltage applied to the phase advancing capacitor are determined by the external oscillator _OSC.
It matches the frequency and phase of the phase reference signals e _a , e _a , e _c given by and remains constant even if the load changes.

Further, the peak value V _cap of the voltage of the phase advancing capacitor is controlled so as to match the command value ▲ V ^* _c ▼ _ap , and is maintained substantially constant without fluctuating even when the load suddenly changes.

As a result, not only the commutation failure of the circulating current type cycloconverter itself can be prevented, but also the commutation failure of the separately excited converter and the cycloconverter constituting the load device can be prevented.

Further, since the frequency becomes stable, the design of the filter and the like becomes simple, and the capacity of the filter equipment can be reduced by selecting a more precise constant.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a high-frequency power supply device of the present invention, FIG. 2 is a block diagram showing an embodiment of the main circuit section of FIG. 1,
FIG. 3 is an equivalent circuit diagram for explaining the operation of the device of FIG. 1, FIG. 4 is a time chart diagram thereof, and FIG. 5 is a time chart diagram for explaining the operation of the device of FIG. 6
7 is an equivalent circuit diagram, FIG. 7 is a configuration diagram showing a part of a control circuit of the device of FIG. 1, and FIG. 8 is a configuration diagram of a conventional high frequency power supply device. SUP ... AC power supply, L _S ... AC reactor CC ... Circulating current type cycloconverter CAP ... High frequency advance capacitor LOAD ... Load device, CT _S ... Current detector PT _S , PT _C ... Voltage detector, D ... Rectifier AVR ... Voltage control circuit ACR ... current control circuit PHC ... phase control circuit, O _SC ... external oscillator K _S, K _L ... proportional amplifier AD _1, AD ₂ ... adder, ML ... multiplier

Claims (1)

[Claims] 1. An AC power source, a circulating current type cycloconverter having an output terminal connected to the AC power source, a phase advancing capacitor connected to an input side terminal of the circulating current type cycloconverter, and the phase advancing capacitor. A load device as a high frequency voltage source, a means for calculating an AC power supply side current peak value command of the circulating current type cycloconverter from the peak value of the voltage applied to the phase advancing capacitor, and the circulation from the current peak value command. Means for calculating the AC power supply side current command of the current type cycloconverter, means for controlling the phase of the circulating current type cycloconverter according to the current command, and an external oscillator for giving a phase reference signal to the phase control means. A high-frequency power supply characterized by being provided.