JPH0687662B2 - 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 is a block diagram of a conventional high frequency link converter.

In the figure, SUP is a three-phase AC power supply, L _S is an AC reactor, CC-
Reference numeral 1 is a first cycloconverter, CC-2 is a second cycloconverter, CAP is a high frequency advance capacitor, Tr1 and Tr2 are high frequency insulating transformers, and IM is an induction motor.

Further, as the control circuit, the current detector CT _S, CT _L, the voltage detector PT _S, ptcap, rotational speed detector PG, a rectifier circuit D, the voltage control circuit AVR, input current control circuit ACR _1, the phase control circuit PHC ₁ ,
PHC ₂ , external oscillator Osc, speed control circuit SPC, output current control circuit ACR ₂ are prepared.

The operation will be briefly described below.

The first cycloconverter CC-1 is a phase advance capacitor CA.
The current Is supplied from the power supply SUP is controlled so that the peak value Vcap of the voltage applied to P becomes substantially constant.

That is, through the voltage detector PTcap and the rectifier circuit D,
The voltage peak value Vcap of the phase advance capacitor CAP is detected and input to the voltage control circuit AVR. The AVR compares the detected voltage value Vcap with the command value ▲ V ^* _cap ▼, amplifies the deviation,
Create a peak value command ▲ I ^* _sm ▼ for the input current Is. A unit sine wave sinω synchronized with the power supply voltage Vs according to the _peak value command ▲ I ^* _sm ▼
Input current command value ▲ I ^* _s ▼ = ▲ I ^* _sm ▼ ・ sinω multiplied by st
Create st and input to the next current control circuit ACR ₁ . In ACR ₁ , the input current Is detected by the current detector CT _S and
The above command values ▲ I ^* _s ▼ are compared, the deviation is amplified, and the first
Input to the phase control circuit PHC ₁ of the cycloconverter CC-1. At this time, the three-phase reference voltage ea, eb, of the phase control circuit PHC ₁
ec is provided by the external oscillator Osc.

When ▲ V ^* _cap ▼> Vcap, the input current Is increases,
Active power Pi is supplied from the power supply SUP to the phase-advancing capacitor CAP, energy is accumulated by that amount, and Vcap is increased. On the contrary, if ▲ V ^* _cap ▼ <Vcap, the effective power Pi
Becomes a negative value, the energy stored in the phase advancing capacitor CAP is regenerated to the power supply SUP, and Vcap decreases. That is, the control is always performed so that Vcap≅V ^* _cap ▼.

At this time, since the input current Is is controlled to be a sine wave in phase with the power supply voltage Vs, the input power factor is always 1, and the harmonic component is extremely small.

The second cycloconverter CC-2 is for supplying a sinusoidal current I _L of the variable voltage variable frequency to induction motor IM, it can be variable speed operation of the motor IM. The operation will be briefly described below.

That is, the rotation speed ωr of the electric motor IM is detected by PG and is input to the speed control circuit SPC. In the SPC, the speed detection value ωr is compared with the command value ▲ ω ^* _r ▼, and the amplitude I _L m, the phase θ and the frequency ωe of the current I _L supplied to the electric motor IM are determined according to the deviation, Make the command value ▲ I ^* _L ▼.

In the output current control circuit ACR ₂ , the output current I _L detected by the current detector CT _L is compared with the above command value ▲ I ^* _L ▼,
The deviation is amplified and the second cycloconverter CC-2
Input to the phase control circuit PHC ₂ of. At this time, the three-phase reference voltages ea, eb, ec of the phase control circuit PHC ₂ are given by the external oscillator Osc.

The output current I _L of CC-2 is controlled so as to match its command value ▲ I ^* _L ▼, and as a result, the rotation speed ωr of the electric motor IM.
Are controlled so as to match the command value ^* ωr.

By setting at least one of the first and second cycloconverters as a circulating current type cycloconverter, the voltages Va, Vb, V applied to the phase advancing capacitor CAP are set.
The frequency fcap and phase of c are the output signal e of the external oscillator Osc.
The frequencies fc and phases of a, eb, and ec can be matched.

The operation will be briefly described as follows.

That is, the reference voltages ea, eb, ec of the phase control circuits PHC ₁ , PHC ₂
Therefore, when the phase of the voltage Va, Vb, Vc of the phase-advancing capacitor CAP is delayed (or when the frequency fcap is lower than fc), the ignition phase angle α of the cycloconverters CC-1 and CC-2 becomes smaller. , That much, circulating current of cycloconverter
It works to increase Io. Cycloconverter CC-1
When viewed from the phase advancing capacitor CAP side, CC and CC-2 can always be considered as an equivalent reactance Lcc that consumes delayed reactive power. In addition, the circulating current Io of the cycloconverter serves to increase the delayed reactive power and reduces the equivalent reactance Lcc. Therefore, the resonance frequency fcap of the phase advance capacitor CAP and the equivalent reactance Lcc is And increase fcap. Therefore, the phases of Va, Vb, and Vc are advanced and match the reference voltages ea, eb, and ec.

If the phases of Va, Vb, and Vc are too advanced, they will go through the opposite operation and will also coincide with ea, eb, and ec.

(Problems to be Solved by the Invention) In the above-described conventional power converter having a high-frequency link, the input current Is supplied from the power supply can be controlled to be a sine wave in phase with the power supply voltage Vs, and the input power factor = 1. Moreover, it is possible to obtain an input current having less harmonic components. Also electric motor
The current supplied to IM is controlled to a sine wave, which enables operation with less torque ripple. Further, the output frequency fo can be increased up to the frequency fcap of the voltage applied to the phase advancing capacitor CAP, and the electric motor IM has a frequency of 0 to several hundred Hz.
Can be supplied with current. That is, it has a feature that an ultra-high-speed AC variable speed electric motor can be driven.

Moreover, the cycloconverters CC-1 and CC-2 that constitute the converter are the phase-advancing capacitors CA that are high-frequency reactive power sources.
Since the voltage of P is used for spontaneous commutation, it has the feature that large capacity can be achieved very easily.

However, such a conventional power converter has the following problems.

That is, in order to reduce the capacity of the DC reactor that suppresses the pulsation of the circulating current of the AC reactor Ls and the cycloconverter, and further to increase the upper limit value of the output frequency,
It is necessary to increase the number of control phases (the number of control pulses) of the first and second cycloconverters, and therefore the insulating transformers Tr1 and Tr2 are required on the input side (high frequency side) of the cycloconverter.

Further, when the triangular connection linear cycloconverter is used as the first and second cycloconverters, there is an advantage that the number of elements constituting the converter can be reduced to half, but in that case, the other excitation constituting the cycloconverter is separately excited. The input side (high frequency side) of the converter (AC / DC power converter) must be insulated, and the high frequency isolation transformer is indispensable.

The capacity of the isolation transformers Tr1 and Tr2 is a phase advance capacitor.
It was comparable to the capacity of the CAP, and was one of the causes of increasing the cost of the device.

In addition, since it is a high frequency transformer, it is difficult to manufacture, and the loss is large, and the operating efficiency of the device is lowered. Phase-advancing capacitor even at light loads
Since the cycloconverter consumes the delayed reactive power that cancels the advanced reactive power of the CAP, the current flowing through the transformer does not decrease, and the extremely inefficient operation has been endangered.

The present invention has been made in view of the above problems, and in a high-frequency link conversion device using a triangular connection linear cycloconverter, the capacity of the high-frequency insulation transformer is reduced, and the operation efficiency of the device, particularly the operation at a light load, is performed. It is an object of the present invention to provide a high frequency link converter with improved efficiency.

[Structure of Invention]

(Means for Solving the Problems) In order to achieve the above object, the present invention provides a three-phase AC power supply, and a first triangular connection linear configuration in which an output side terminal is connected to the AC power supply via an AC reactor. A circulating current type cycloconverter, a three-phase AC load, a second triangular circulating current type cycloconverter in which an output side terminal is connected to the AC load, and separate excitations constituting the first and second cycloconverters. Input side terminals are connected to each converter (AC / DC power converter), and multiple sets of high frequency advance capacitors connected separately by common input side terminals are insulated from the multiple sets of phase advance capacitors. , And a high frequency transformer for electrical coupling.

(Operation) The first cycloconverter controls the magnitude of the current supplied from the AC power supply so that the peak value of the voltage applied to the phase advancing capacitor becomes substantially constant. At this time, by controlling the current supplied from the power source to be a sine wave having the same phase as the power source voltage, it is possible to perform operation with an input power factor of 1 and less harmonic components.

The second cycloconverter supplies a sine wave current having a variable voltage and a variable frequency to a load such as an AC motor.

The first and second cycloconverters are triangular connection linear circulating current type cycloconverters and are composed of the same number of separately excited converters. For example, when the number of control pulses is 6, the number of separately excited converters (three-phase bridge connection AC / DC power converters) is three.

Each of the separately excited converters forming the first and second cycloconverters is connected to the input side terminal one by one, and the phase advancing capacitor is installed for each input side terminal. Therefore, each separately-excited converter uses the voltage applied to the phase-advancing capacitor connected to each input-side terminal to spontaneously commutate.

The voltage applied to the multiple sets of phase advancing capacitors matches the frequency and phase of the reference voltage (given by the external oscillator) applied to the phase control circuits of the two cycloconverters. In other words, the circulating current of the first 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 reference voltage.

Although the peak value of the voltage applied to the plurality of sets of phase advancing capacitors changes every moment, a plurality of sets of phase advancing capacitors are coupled by a high frequency insulating transformer in order to maintain the voltage balance. As a result, the peak value of the voltage applied to the phase advancing capacitor becomes substantially constant, and its frequency and phase match the frequency and phase of the reference signal.

Since most of the delayed reactive power taken by each separately excited converter is canceled by the advanced reactive power taken by the phase advancing capacitor, the capacitance of the high frequency isolation transformer is significantly reduced as compared with the conventional transformer. Especially when the load is light, the electric power that goes in and out through the transformer becomes a very small value, and the loss becomes a very small value. In this way, operating efficiency can be improved.

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

In the figure, R, S, T are power receiving terminals of a three-phase AC power source, L _SR , L _SS , L _ST are AC reactors, CC ₁ is a first circulating current type cycloconverter, and CC ₂ is a second circulating current type. Cyclo converter,
M is 3-phase AC motor, CAP ₁ ~CAP ₃ is a high-frequency phase advancing capacitor, TR is a high frequency isolation transformer.

The first cycloconverter CC ₁ includes three separately excited converters (AC / DC power converters) SS _{1 to} SS ₃ and a DC reactor L ₁ to.
Composed of L ₃ . That is, it is a triangular connection linear circulating current type cycloconverter.

The second cycloconverter CC ₂ is composed of separate excitation of three converter SS ₄ ~ SS ₆ and DC reactor L ₄ ~L _5.

In the first and second cycloconverters, the input side terminals of the separately excited converters SS ₁ and SS ₄ are connected, and the phase advancing capacitor CAP ₁ is connected to the terminals.

Similarly, the input side terminals of the separately excited converters SS ₂ and SS ₅ are connected, and the phase advance capacitor CAP ₂ is connected to the terminals.
Further, the input side terminals of the separately excited converters SS ₃ and SS ₆ are connected, and the phase advance capacitor CAP ₃ is connected to the terminals.

Three sets of phase advancing capacitor CAP ₁ ~CAP ₃ is electrically coupled by a high frequency isolation transformer.

The output side terminal of the first cycloconverter CC ₁ is connected to the three-phase AC power supply terminals R, S, T via the AC reactors L _SR , L _SS , L _ST .

The output side terminal of the _second cycloconverter CC ₂ is
It is connected to the armature winding of the three-phase AC motor M.

Further, the following control circuits are prepared.

That is, CT _R , CT _S , CT _T are the input current detectors, CT _U , CT _V , CT _W
Is an output current detector, PTcap is a high frequency voltage detector, D is a rectifier circuit, PG is a rotation speed detector of the electric motor M, AVR is a voltage control circuit, ACR ₁ is an input current control circuit, SPC is a speed control circuit, ACR ₂ Is an output current control circuit, PHC ₁ and PHC ₂ are phase control circuits, and Osc is a reference voltage generator (external oscillator).

The operation will be described below.

The first cycloconverter CC ₁ has a phase advancing capacitor CAP ₁
~ Peak value Vcap of three-phase AC voltage va, Vb, Vc applied to CAP ₃
The currents I _R , I _S , and I _T supplied from the three-phase AC power supply are controlled so that V becomes almost constant.

The second cycloconverter CC ₂ supplies the AC motors M with 3-phase AC power of variable voltage and variable frequency by using the phase-advancing capacitors CAP _{1 to} CAP ₂ as 3-phase voltage sources.

The signals of the three-phase reference voltages ea, eb, and ec from the external oscillator Osc are used for the phase control of both cycloconverters CC ₁ and CC ₂ , and the voltage V applied to the phase advancing capacitors CAP _{1 to} CAP ₃ is used.
The frequencies and phases of a, Vb, and Vc match the frequencies and phases of the reference voltages ea, eb, and ec.

After the start operation for establishing the voltages va, Vb, Vc of the phase-advancing capacitors CAP _{1 to} CAP ₃ and the establishment of the voltages, the frequency and phase of the voltages Va, Vb, Vc are the frequencies of the reference voltages ea, eb, ec. For a detailed description of the operation that matches the phase, refer to Japanese Patent Application No. 61-165028.

After the voltage is established, the first cycloconverter CC ₁ is controlled as follows.

First, the high-frequency voltage detector PTcap is used to advance the phase-advancing capacitor CAP.
Three-phase voltages Va, Vb, Vc applied to _{1 to} CAP ₃ are detected, and a voltage peak value Vcap is obtained via the rectifier circuit D.

In the voltage control circuit AVR, compares the detected values of the voltage peak value Vcap and its command value ▲ V ^* _cap ▼, the deviation ω _{V =} ▲ _V ^*
_cap ▼ −Vcap is amplified (or integrated) to obtain the peak value ▲ I ^* _sm ▼ of the input current, and the value is multiplied by a unit sine wave synchronized with the power supply voltages V _R , V _S , and V _T , and The three-phase input current commands ▲ I ^* _R ▼, ▲ I ^* _S ▼, and ▲ I ^* _T ▼ are given to the current control circuit ACR ₁ .

▲ I ^* _R ▼ = ▲ I ^* _sm ▼ ・ sinωst… (1) ▲ I ^* _S ▼ ＝ ▲ I ^* _sm ▼ ・ sin (ωst-2π / 3)… (2) ▲ I ^* _T ▼ ＝ ▲ I ^* _sm ▼ · sin (ωst + 2π / 3) (3) where ▲ I ^* _sm ▼ = K _V · ε _V , where K _V is a proportional constant when voltage control is proportionally amplified.

On the other hand, the three-phase input currents I _R , I _S , and I _T are the current detectors CT _R , CT _S , and CT.
_It is detected by _T and input to the input current control circuit ACR ₁ .

In the input current control circuit ACR ₁ , the current detection values I _R , I _S , I _T and the current command values ▲ I ^* _R ▼, ▲ I ^* _S ▼, ▲ I ^* _T ▼ are compared with each other, and each deviation ε ^{_{R = ▲ I * R ▼ -I}} R, ε S = ▲ I * S ▼ -I S,
ε _T = ▲ I ^* _T ▼ the -I _T amplifying (K _I times). Further, the phase control input signals υ _{α 1 to} υ _{α 3} are obtained by the following calculation.

υ _{α 1} = K _I (ε _R −ε _S ) ... (4) υ _{α 2} = K _I (ε _S −ε _T ) ... (5) υ _{α 3} = K _I (ε _T −ε _R ) ... (6) ) Here, ν _{α 1} becomes the phase control input signal of the separately excited converter SS ₁ of the first cycloconverter CC ₁ . Similarly, υ _{α 2} and υ _{α 3} are the phase control input signals of the separately excited converters SS ₂ and SS ₃ , respectively.

These phase control input signal υ α ₁ ~υ α ₃ is input to phase control circuit PHC _1, the external oscillator Osc 3-phase reference signal ea given from, eb, is compared with ec, the first cycloconverter CC ₁ determining commutated converter SS ₁ ~ SS ignition phase angle alpha ₁ to? ₃ points ₃ forming.

The output voltage V ₁ ~V ₃ of the separately-excited converter SS ₁ ~ SS ₃ is that a value obtained by respectively proportional to the phase control input signal υ α ₁ ~υ α ₃ is that known.

First, the operation of current control will be described. The R phase will be described as an example.

When ▲ I ^* _R ▼> I _R , the deviation ε _R becomes a positive value,
Increase v _{α 1} and decrease v _{α 3} . Therefore, the output voltage V ₁ of SS ₁ increases in the direction of the arrow in the figure, and conversely the output voltage V ₁ of SS _3
3 is reduced. As a result, the output current I _{1 of} SS ₁ increases and SS _1
3 of the output current I ₃ is decreased, R-phase current I _R = I ₁ -I ₃ increases, approaches the command value ▲ I ^* _R ▼.

Conversely ▲ I ^* _R ▼ <If a I _R, the deviation epsilon _R takes a negative value, decreases the output voltage V ₁ of the SS _1, the output voltage V ₃ of the SS ₃ is increased. As a result, I _R = I ₁ -I ₃ decreases, and again approaches the command value ▲ I ^* _R ▼.

When the command value ▲ I ^* _R ▼ is changed in a sine wave shape as in the equation (1), the R-phase actual current I _R also follows it and is controlled to a sine wave.

The S-phase and T-phase currents are similarly controlled.

Next, the control operation of the voltage peak value Vcap will be described.

▲ V ^* _cap ▼> If a Vcap, deviation epsilon _V a positive value, increasing the crest value instruction ▲ I ^* _sm of the input current ▼. Input current _R, I _S, the command value I _T, as described above ▲ I ^* _R ▼, ▲
It is controlled according to I ^* _S ▼, ▲ I ^* _T , and is controlled to a sine wave in phase with the power supply voltages V _R , V _S , and V _T of each phase. Therefore, the active power Pi expressed by the following equation is supplied from the power source.

However, Vsm is the peak value of the power supply voltage, Ism is the input current peak value, and coincides with the command value ▲ I ^* _sm ▼.

Therefore, active power Pi is increased by Ism = ▲ I ^* _sm ▼.
Also increases and increases the energy stored in the high frequency phase-advancing capacitors CAP _{1 to} CAP ₃ as energy Pi · t. That is, Therefore, the voltage peak value Vcap is increased, and the command value ▲ V ^* _cap
Approach ▼.

On the contrary, when ▲ V ^* _cap ▼ <Vcap, the deviation ε _V becomes a negative value, and the active power Pi is decreased or set to a negative value (power regeneration), and the phase advance capacitors CAP _{1 to} CAP _{3 are made.} Reduce the stored energy of. Therefore, the voltage peak value Vcap decreases and is controlled so as to match the command value ▲ V ^* _cap ▼.

The second cycloconverter CC ₂ is controlled as follows.

First, the rotation speed detector PG detects the rotation speed ωr of the AC motor M and inputs it to the speed control circuit SPC.

In the speed control circuit SPC, the speed detection value ωr is compared with the speed command value ▲ ω ^* _r ▼, and the command value ▲ I ^* _U ▼, ▲ I ^* _V ▼, ▲ of the current supplied to the electric motor according to the deviation. Make I ^* _W ▼.

When the electric motor M is an induction motor, the current command value ▲ I
^* _U ▼, ▲ I ^* _V ▼, ▲ I ^* _W ▼ are obtained by means such as vector control.

When the motor M is a synchronous motor, the current command values ▲ I ^* _U ▼, ▲ I ^* _V ▼, ▲ I ^* _W ▼ are three-phase unit sine synchronized with the rotor (field) position of the motor. Wave velocity deviation ε _N
= ▲ ω ^* _r ▼ amplification (and K _N times) the -ωr value ▲ I ^* _Lm
▼ = K _N · ε _N is multiplied and it is made like the following formula.

▲ I ^* _U ▼ = ▲ I ^* _Lm ▼ ・ sinωot… (9) ▲ I ^* _V ▼ ＝ ▲ I ^* _Lm ▼ ・ sin (ωot-2π / 3)… (10) ▲ I ^* _W ▼ ＝ ▲ I ^* _Lm ▼ sin (ωot + 2π / 3) (11) where ωo = 2πfo is the rotational angular frequency of the synchronous motor.

The current command values ▲ I ^* _U ▼, ▲ I ^* _V thus obtained
▼ and ▲ I ^* _W ▼ are input to the next output current control circuit ACR ₂ and compared with the output currents I _U , I _V , and I _W detected by the current detectors CT _U , CT _V , and CT _W , respectively. It

The current deviation of each phase is amplified and input current control circuit ACR ₁
In the same manner as the above, the phase control input signals υ _{α 4 to} υ _{α 6}
The second cycloconverter as obtained, for generating a voltage V ₄ ~V ₆ in proportion to the phase control signal υ α ₄ ~υ α ₆ is
Ignition phase α _{4 of} separately excited converters SS _{4 to} SS ₆ that compose CC ₂
~ Α ₆ is determined.

The output currents I _U , I _V , and I _W are the respective current command values ▲ I ^* _U ▼, ▲ I
^The sine wave is controlled according to ^* _V ▼ and ▲ I ^* _W ▼. As a result, the rotation speed ωr of the electric motor M is controlled so as to match the command value ▲ ω ^* _r ▼.

The circulating current Io ₂ of the second cycloconverter CC ₂ is the reactive power Qcc ₂ of the input side (high frequency side) of the cycloconverter.
Is controlled to be almost constant.

In addition, the circulating current Io ₁ of the first cycloconverter CC1 is
The voltage Va, Vb, Vc applied to the phase-advancing capacitors CAP _{1 to} CAP ₃ are automatically adjusted so that the frequency and phase of them match the frequency and phase of the phase reference signals ea, eb, ec given from the external oscillator Osc. Adjusted to. That is, in the steady state, when the leading reactive power of the phase-advancing capacitors CAP _{1 to} CAP ₃ is Qcap, CC1
The circulating reactive current Io _{1 of} CC ₁ is automatically adjusted so that the delayed reactive power Qcc ₁ taken by Qcc ₁ = Qcap−Qcc ₂ (12).

FIG. 2 shows the second cycloconverter CC ₂ of the apparatus shown in FIG.
The current waveform of each part of is shown.

In the figure, (a) shows the output currents I _U , I _V , and I _W of CC ₂ , the peak value of which is Im.

(B) shows the output currents I _{4 to} I ₆ of each converter.
This is when a circulating current Io ₂ having a waveform as shown in (e) is applied.

(C) shows output currents ▲ I ⁰ ₄ ▼ to ▲ I ⁰ ₆ ▼ of each converter when the circulating current Io ₂ of CC ₂ is taken as an example. The output current ▲ I ⁰ ₄ ▼ of the separately excited converter SS ₄ has a waveform as shown by the solid line in (c).

(D) is the sum of the output currents of the converters of the waveform shown in (b) I _TOTAL = I ₄ + I ₅ + I ₆ and the sum of the output currents of the converters of the waveform shown in (c) ▲ I ⁰ _TOTAL ▼ = ▲ I ⁰ ₄ ▼ ＋ ▲ I ⁰ ₅
The waveform of ▼ + ▲ I ⁰ ₆ ▼ is shown. Input side of CC ₂ (high frequency side)
In order to make the reactive power Qcc ₂ of
_TOTAL is almost constant.

The circulating current Io ₂ of CC ₂ is ( _1/0 of the difference between I _TOTAL and ▲ I ⁰ _TOTAL ▼
3) flows and becomes a waveform as shown in (e).

In Fig. 2 (b), the output current I of the separately excited converter SS _4
4 is composed of a direct current component I _TOTAL / 3 and an alternating current component I _4AC , and the alternating current component I _4AC is expressed by the following equation when the _U -phase output current I _U is I _U = Im · sinωot.

Similarly, AC component I _5AC the output current I _5, I ₆ of SS ₅ and SS _6, I _6AC
Is expressed by the following equation.

As a _{result, I U = I 4 -I 6} , I V = I 5 -I 4, I W = 6 -I 5 holds.

The input current I _SS4 of the separately excited converter SS ₄ is a high frequency current having a value proportional to the output current I ₄ (frequency is the frequency fc of the reference signals ea, eb, ec given from the external oscillator Osc, for example, 1 kHz).
Becomes When each ignition phase of the converter SS ₄ is α ₄ , the active power P _SS4 taken by SS ₄ is proportional to I ₄ · cos α ₄ , and the reactive power Q _SS4 is proportional to I ₄ · sin α ₄ . This reactive power Q
_SS4 is canceled by half the value of the lead reactive power Qcap ₁ of the phase advancing capacitor CAP ₁ (the other half of Qcap ₁ is considered to cancel the reactive power Q _SS1 taken by SS ₁ of the first cycloconverter CC ₁ ).

The firing phase angle α ₄ of SS ₄ changes momentarily around 90 °, but here, in order to simplify the description, α ₄ ≈90 ° will be described. Thus reactive power Q _SS4 take the SS ₄ is proportional to the output current I ₄ of SS _4. As described above, the output current I ₄ of SS ₄ is composed of the direct current component I _TOTAL / 3 and the alternating current component I _4AC , and the reactive power Q _{SS4 (D of} SS ₄ corresponding to this direct current component I _TOTAL / 3 c ₎ is selected so that half the capacitance of the phase advancing capacitor CAP ₁ is canceled out.

As a result, the AC component reactive power Q _SS4 of SS ₄ corresponding to I _{4AC (A} c
_), But other converter SS ₅ via high frequency isolation transformer TR
And will enter and leave SS ₆ .

The above description is given by ignoring the active power P _SS4.
Similarly for _SS4 , DC component P _{SS4 (D} c ₎ and AC component P _{SS4 (A} c ₎
Therefore, the DC component is supplied from the converter SS _{1 of} the first cycloconverter CC ₁ and the AC component enters and leaves the other converters SS ₅ and SS ₆ via the transformer TR.

The same applies to the other converters SS ₅ and SS ₆ .

Similarly, for the first cycloconverter CC ₁ , active power and reactive power corresponding to the alternating current components of the output currents I _{1 to} I ₃ of the converters SS _{1 to} SS ₃ also enter and exit via the transformer TR.

In the conventional device, not only the active and reactive power corresponding to the AC component but also the active and reactive power corresponding to the DC component are
Since it goes in and out through the TR, there was a drawback that the capacity of the transformer TR was increased. On the other hand, in the device of the present invention, the electric power that goes in and out through the high frequency transformer is
Only the AC components corresponding to the AC components based on the AC output currents I _U , I _V , and I _W can be reduced, and the transformer capacity can be significantly reduced.

When the load becomes light, the AC output currents I _U , I _V ,
The peak value Im of I _W also becomes smaller, the AC component of the output current of each converter becomes smaller, and the electric power going in and out of the transformer TR becomes a very small value. As a result, the loss under light load is reduced, and the operating efficiency under light load, which is a drawback of the conventional device, can be significantly improved.

In the apparatus shown in FIG. 1, a 6-pulse cycloconverter has been described, but it goes without saying that 12-pulse, 18-pulse, 24-pulse, etc. can be similarly achieved. 12 pulses c /
In c, the number of divisions of the phase advancing capacitor is 6, and the number of windings of the high frequency transformer is also 6 is required. Similarly for 18,24 pulses c / c, the number of divisions increases to 9 and 12, respectively.

〔The invention's effect〕

As described above, the high-frequency link converter of the present invention can significantly reduce the capacity of the high-frequency insulation transformer, reduce the loss during light load, and significantly improve the operating efficiency. . Further, the number of windings of the transformer can be reduced, and the cost and the size and weight can be reduced.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of a high frequency link converter of the present invention, FIG. 2 is a current waveform diagram for explaining the operation of the device of FIG. 1, and FIG. 3 is a conventional high frequency link converter. It is a block diagram. R, S, T …… 3-phase AC power supply terminal L _SR , L _SS , L _ST …… AC reactor CC ₁ …… First triangular connection linear circulating current type cycloconverter SS ₁ 〜 SS ₃ …… Separately excited converter L _{1 to} L ₃ …… DC reactor CAP _{1 to} CAP ₃ …… High frequency advance capacitor TR …… High frequency isolation transformer CC ₂ …… Second triangular connection linear circulating current type cycloconverter SS ₄ 〜 SS ₆ …… Separately excited converter L _{4 to} L ₆ …… DC reactor M …… AC motor, PG …… Rotation speed detector CT _R , CT _S , CT _T …… Input current detector CT _U , CT _V , CT _W …… Output current detector PTcap …… High frequency voltage detector, D …… Rectifier circuit Osc …… External oscillator PHC ₁ , PHC ₂ …… Phase control circuit ACR ₁ , ACR ₂ …… Current control circuit AVR …… Voltage control circuit SPC …… Speed control circuit

Claims (1)

[Claims] 1. A three-phase AC power supply, a first triangular connection linear circulating current type cycloconverter having an output side terminal connected to the AC power supply via an AC reactor, and a three-phase AC load.
A second triangular connection linear circulating current type cycloconverter having an output side terminal connected to the AC load, and the first and second
The input side terminals are connected to each of the separately excited converters (AC / DC power converters) that make up the cycloconverter, and a plurality of sets of high-frequency phase advance capacitors connected separately for each common input side terminal, and the plurality of sets. High-frequency link conversion device comprising: a high-frequency transformer that insulates and electrically couples the phase-advancing capacitor.