JPH0789742B2 - Power converter - Google Patents

Description

TECHNICAL FIELD The present invention relates to a power converter that converts three-phase AC power into DC power.

[Conventional technology]

FIG. 9 is a circuit configuration diagram showing the principle of a conventional power conversion device shown in, for example, the 1986 National Conference of the Institute of Electrical Engineers of Japan (Page 574). In the figure, 1 is a diode rectifier, which is configured by a single-phase bridge circuit, and the AC side is connected to a commercial AC power source AC via a reactor 2. Three
Is a DC switch and is connected in parallel to the DC side of the diode rectifier 1. Reference numeral 4 denotes a diode, the anode side of which is connected to the positive output terminal (P) of the diode rectifier 1. A capacitor 5 is connected to the cathode side of the diode 4 and the negative output terminal (N) of the diode rectifier 1. A load 6 is connected in parallel to the capacitor 5.

Next, the operation will be described based on the operation waveform chart of FIG. First, the conventional example shown in FIG. 9 shows a case where single-phase AC power is converted into series power. The DC switch 3 is turned on / off by a high-frequency switching operation, and the current flowing in the AC power supply is waveform-controlled in a sinusoidal waveform. At the same time, the power factor is controlled to be close to 1. Here, as the DC switch 3, a self-extinguishing type switching element, for example, a transistor, a gate turn-off thyristor, a MOSFET, etc. is generally used, and on / off control is performed at a switching frequency of several KHz to several tens KHz. In addition, in FIG. 10, the AC power supply current I _ac is in phase with the AC power supply voltage V _ac , and its magnitude depends on the equilibrium condition of power between the input and output. Controlled according to the relationship. Here the AC power supply voltage V _c is the average DC voltage of the capacitor 5, the I _L indicates the average DC current of the load 6. The direct current I _P is the arm element of the diode rectifier ₁ during the positive half cycle period (t _{1 to} t ₂ ) of the AC power supply voltage V _ac.
Flow through D ₁ , D ₄ and also negative half cycle period (t ₂ ~
At t ₃ ), since it flows through the arm elements D ₂ and D ₃ , the full-wave rectified waveform of the alternating current I _ac is obtained. Further, the periods t _{4 to} t ₆ show the switching cycle of the DC switch 3, and a part of the switch operation waveform is shown by I _SW and I _D. Here, I _SW is the current waveform of the DC switch 3, and I _D is the current waveform of the diode 4. When the DC switch 3 is turned on during the period from time t _{4 to} t ₅ , the current I _SW of the DC switch 3 flows through the reactor 2 and the diode rectifiers D ₁ and D ₄ , and energy is stored in the reactor 2. Next time t ₅ ~t ₆ period, if off the DC switch 3, the energy of the reactor 2 is discharged to the capacitor 5 through the diode 4. Therefore, the voltage of the capacitor 5 is always kept at a voltage level higher than the AC power supply voltage V _ac .

Even if the reactor 2 is inserted between the output end of the diode rectifier 1 and the DC switch 3, the same operation of the boost chopper is performed.

[Problems to be solved by the invention]

Since the conventional power conversion device is configured as described above, the conduction period of each arm element that performs the step-up chopper operation via the diode rectifier is 180 °, and the alternating current is controlled in a sinusoidal shape. . However, when this is applied to a three-phase AC power supply, if the diode rectifier is simply a three-phase bridge structure, the conduction period of each arm will be 120 °, and the AC current cannot be controlled in a sinusoidal manner. There has been a problem that many low-order harmonic components such as the order are included.

The present invention has been made to solve the above problems, and provides a three-phase AC power converter capable of controlling an alternating current in a sine wave shape and controlling a power factor of a power source to approximately 1. The purpose is to

[Means for solving problems]

In the power converter according to the present invention, a step-up chopper cascade-connected in two stages is connected in parallel to the DC output side of a diode rectifier having a three-phase bridge configuration, and a bidirectional connection is provided between an intermediate point of the step-up chopper and a three-phase AC power source. An energization type three-phase AC switch is provided, and each step-up chopper is controlled so as to flow a current having a current waveform similar to the voltage waveform of the corresponding three-phase half-wave rectification, and the input current of each step-up chopper is changed. A main circuit section of the power converter in which the difference is passed through a three-phase AC power supply through a three-phase AC switch, and a voltage controller for the output voltage of the boost chopper and a current controller for the AC power supply current are provided. Is.

[Work]

The power converter according to the present invention calculates an AC power supply current reference from the output signal of the voltage controller and the load current value, and further calculates a current reference of the positive and negative group both step-up choppers from this AC power supply current reference to obtain both the step-up choppers. Are in phase with each other
Waveform control of P-side and N-side output currents of the diode rectifier by a current controller in a three-phase half-wave rectified wave form shifted by 180 °, and the difference between the P-side and N-side DC currents is passed through a 3-phase AC switch. Control to flow to AC power.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. In the figure, the same parts as in FIG.
In the figure, 10 is a diode rectifier connected in a three-phase bridge, and its AC end is connected to a three-phase AC power supply ( _eu , _ev , _ew ). 2P and 2N are reactors respectively connected to the positive output terminal (P) and the negative output terminal (N) of the diode rectifier 10, and 3P and 3N are boost choppers connected in series between both ends of the reactors 2P and 2N. 8P, 8N DC switch, 4P, 4N are respectively connected to the connection point of the reactor 2P and the DC switch 3P and the connection point of the reactor 2N and the DC switch 3N, in the forward direction with respect to the DC circuit of the diode rectifier 10. The diodes 5P and 5N are capacitors connected in series between the output terminals of the diodes 4P and 4N, and the intermediate connection point of the capacitors 5P and 5N is connected to the intermediate connection point of the DC switches 3P and 3N. 6 is a load connected to both ends of both capacitors 5P and 5N, and 7 is a three-phase AC switch, which is an intermediate connection point between the DC switches 3P and 3N of the step-up choppers 8P and 8N and the three-phase AC power supply (e _u , _ev , _ew )).

Next, the operation will be described with reference to the operation waveform diagram shown in FIG. In the figure, _eu , _ev , _ew are three-phase AC power supplies ( _eu , _ev ,
e _w ) shows the phase voltage waveform. I _P shows the current waveform of reactor 2P, reactor 2P, DC switch 3P, diode 4P
The step-up chopper 8P of positive group composed of the three-phase AC power source _{(e u, e v, e} w) is controlled in the positive polarity of the three-phase half-wave rectified voltage waveform, similar to a current waveform. I _N represents the current waveform of the reactor 2N, and by the negative group boost chopper 8N composed of the reactor 2N, the DC switch 3N, and the diode 4N,
The current waveform is controlled to be similar to the voltage waveform of the negative polarity three-phase half-wave rectification of the three-phase AC power supply ( _eu , _ev , _ew ). Here, the current ripples I _P and I _N of the reactors 2P and 2N are actually superimposed with the current ripple components of the switching frequency components of the boost choppers 8P and 8N of the positive group and the negative group, respectively. It is omitted in FIG. I _O is a three-phase AC switch 7
Shows the current waveform of I _O = I _P −I _N. Here, since I _P and I _N have a ripple component of a frequency three times the power supply frequency _{ac with} a phase difference of 180 ° and have the same magnitude, I _O is 3
It becomes AC waveform of the _ac. The peak value when the ripple of I _P and I _N is ignored If so, the peak value of the current waveform I _O of the three-phase AC switch 7 is Becomes I _u , I _v , and I _w represent the current waveform of the AC power supply. I _u is u
It is a phase current, and is a three-phase AC switch 7 during the period from time t _{1 to} t _2.
The current I _{O is made} to flow by turning on the arm element S _u of the diode, the current I _{P is made} to flow by the arm element D _u of the diode rectifier 10 during the period of time t _{2 to} t ₄ , and the period I of time t _{4 to} t ₅ is again set. turn on the arm element S _u of the three-phase AC switch 7 electric current I _O, the period of time t ₅ ~t ₇ depending arm element D _X of diode rectifier 10 an alternating current waveform of the sinusoidal electric current I _N Obtainable. If there is no 3-phase AC switch 7 here,
It can be seen that a sinusoidal current cannot be obtained because the alternating current I _u can only flow through the diode rectifier 10. The v-phase AC current I _v is 120 with respect to the u-phase AC current I _u .
A phase lag waveform of .degree., And similarly, a sinusoidal waveform is obtained by the arm elements D _v and D _{y of} the diode rectifier 10 and the arm element S _v of the three-phase AC switch 7. The w-phase AC current I _w has a waveform with a phase delay of 240 ° with respect to the u-phase AC current I _u , and similarly, the arm elements D _w and D _{z of} the diode rectifier 10 and the arm of the three-phase AC switch 7 are formed. sinusoidal waveform is obtained by the element S _w. The commutation of each arm element (D _u , D _v , D _w , D _x , D _y , D _z ) of the diode rectifier 10 is similar to the operation of a normal diode rectifier, and the voltage (e _u , e _v , _ew ), but commutation of each arm element (S _u , S _v , S _w ) of the three-phase AC switch 7 must be forced. For example, at time t ₅ , the switch
Considering the commutation from S _u to switch S _w , at this time e _u =
not be the power supply commutation because it is a e _w. The same applies to other commutation timings, and power commutation cannot be performed because commutation must be performed at the cross point of each phase voltage. Time t ₁ ~t ₇ corresponds to that 6 equal one cycle of the AC power supply, the AC switch _{(S u, S v, S} w) is conducting at a time between 60 DEG. Since each arm element (D _u , D _v , D _w , D _x , D _y , D _z ) of the diode rectifier 10 conducts by 120 ° like a normal diode rectifier, the arm element of the diode rectifier 10 conducts. During the rest period, the AC current may be passed by each AC switch (S _u , S _v , S _w ).

Next, an embodiment of a control device for a power converter according to the present invention will be described with reference to the drawings. Figure 3 is the positive group and negative group of the step-up chopper 8P and 8N switching means 3-Way, (hereinafter abbreviated as GTO) gate turn-off thyristor as a 3N 3-Way, obtained by applying the 3N, 3-phase AC switch (S _u, S _v , S _w ), GTO3P, 3N is connected between the DC ends of the single-phase diode bridge, and the circuit is configured so that bidirectional conduction is possible. Also, 20P, 20N, 20
L is a current detector, which detects the positive electrode output current, the negative electrode output current, and the load 6 current of the diode rectifier 10,
Current detection signals of _Pb , _INb and _ILb are obtained. twenty two
Is an isolation transformer, the primary side is connected to an AC power source (AC), and the secondary side is a three-phase signal (e _u1 ,
e _v1 , e _w1 ). Further, the logical operation means is configured as follows. That is, 23 is a zero-cross comparator, which is a three-phase signal (e _u1 , e _v1 ,
Determine the positive and negative polarities of e _w1 ). _{Reference numeral} 24 is an exclusive OR circuit, and among the three-phase output signals (e _u2 , e _v2 , e _w2 ) of the zero-cross comparator 23, the exclusive-OR NOT is provided for every two phases.
_Is performed to obtain a three-phase signal (e _u3 , e _v3 , e _w3 ). 2
_{Reference numeral} 5 denotes a gate amplifier which amplifies the output signal (e _u3 , e _v3 , e _w3 ) of the exclusive OR circuit 24 and _supplies it as a gate signal to the three-phase AC switch (S _u , S _v , S _w ). (23 to 25 are referred to as logical operation means). Reference numeral 21 is a voltage detector that detects both output voltages V _c of the positive group and negative group boost choppers 8P, 8N,
A voltage detection signal of V _cb is obtained. A voltage controller 29 amplifies the deviation between the reference signal V _cre and the detection signal V _cb of the output voltages V _c of both the positive group and negative group boost choppers 8P and 8N. 30 is a multiplier, which is a load current detection signal I _Lb
And the output voltage detection signal V _{cb of} both boost choppers 8P and 8N
Is multiplied by. 26 is an isolation transformer, the primary side of which is connected to an AC power supply (AC), and the secondary side of which is a six-phase voltage signal (e _u4 , e _v4 , e _w4 , e _x4 , e _y4 ) in phase with the primary side. , e _z4 ). 28
Is a peak value detector, which rectifies the 6-phase signal on the secondary side of the insulation transformer 26 and smoothes it with a capacitor to obtain a signal V _acp ′ proportional to the _peak value V _acp of the phase voltage V _ac of the AC power supply AC. ing. _{Reference numeral} 31 is a divider, which _divides the output signal of the multiplier 30 by the peak value detection signal V _acp ′ to obtain the AC current _peak value converted signal I _acp ′ via the variable resistor 32. _{Reference numeral} 33 is an adder, which converts the AC current _peak value conversion signal I _acp ′ and the voltage controller 29.
It adds the output signal [Delta] I _c, alternating current peak value reference signal I
_{The acpre} is the AC current _peak value reference signal control means 29 to 3
You're getting by 3. 27P and 27N are three-phase half-wave rectification circuits (three-phase half-wave rectification means), which are secondary voltages (e _u4 , e _v4 , e _w4 ) and (e _x4 , e _y4 , e) of the insulating transformer 26, respectively. _The three-phase half-wave AC signals e _27P and e _27N are obtained by rectifying _z4 ). 34P, 34N
Is a multiplier, and these three-phase half-wave rectified signals e _27P and e _27N
And the AC current _peak value reference signal I _acpre are multiplied to obtain the current reference signals I of the positive and negative group boost choppers 8P and 8N.
I got _pre and I _Nre . 35P, the deviation of 35N both boost chopper 8P, a current controller of 8N, this both boost chopper current reference signal I _Pre and I _Nre the positive electrode and the negative electrode output current detection signal of the diode rectifier 10 I _Pb and I _Nb Is amplified (step-up chopper current control means). 36P,
36N is a pulse width modulation circuit (hereinafter abbreviated as PWM circuit), which outputs the output signals of the current controllers 35P and 35N and the triangular wave carrier signal.
Compare V _ca levels. 37P and 37N are gate amplifiers which amplify the output signals of the PWM circuits 36P and 36N and give them as gate signals to the GTOs 3P and 3N of the step-up choppers 8P and 8N (step-up chopper element control means).

Next, the operation of the control device for the power converter shown in FIG. 3 will be described. FIG. 4 is an operation waveform diagram showing formation of gate signals of the three-phase AC switches (S _u , S _v , S _w ). The secondary side voltage (e _u1 , e _v1 , e _w1 ) of the isolation transformer 22 is the AC power supply voltage (e _u ,
e _v, e _w) from 30-degree phase are delayed, the output signal of the zero-cross comparator _{23 (e u2, e v2,} e w2) is a rectangular wave signal of 180 ° width, the AC power supply voltage (e _u, The phase is delayed by 30 degrees from e _v , e _w ). Output signal of exclusive OR circuit 24 (e _u3 , e _v3 , e _w3 ).
_Are the output signals e _u2 and e _v2 , e _{v2 of the} zero-cross comparator 23, respectively.
And e _w2, obtained by the operation of the NOT exclusive OR of e _w2 and e _u2, occurs twice during one cycle of the AC power supply in the rectangular wave signal of each 60 ° wide. Turn on the three-phase AC switch (S _u , S _v , S _w ).
The gate signal is the output signal (e _u3 ,
e _v3 , e _w3 ), which corresponds to the operation waveform of the main circuit section shown in FIG.

Next, the current reference signals I _Per and I _{Ner of the} boost choppers 8P and 8N
Is obtained from the balance condition of the AC power supply and the load power. If the power factor of the AC power P _ac is 1, Here, V _acp and I _acp represent the peak value of the phase voltage of the AC power supply and the peak value of the AC power supply current, and are represented by the following equations.

On the other hand, the load voltage P _L is shown by P _L = I _L · V _C (2) P _ac = P _{L in} steady state due to power balance condition
Then, from equations (1) and (2) The relational expression of is obtained. By substituting the detection signals corresponding to the voltage and current values of the equation (3), the equation (4) can be obtained.

I _acp ′ = K ₁ I _Cb · V _Cb / V _acp ′ (4) where K ₁ is a proportional constant. V _acp ′ is obtained from the peak value detector 28, and the operation of the equation (4) is executed by the multiplier 30, the divider 31 and the variable resistor 32, and the AC current peak value conversion signal I
_acp ′ is obtained. The voltage controller 29 controls the voltage V _C across the capacitors 5P and 5N to a value corresponding to the reference signal V _Cre. The output signal ΔI _c of the voltage controller 29 is the capacitor 5P.
The reference signal of the current component injected into P and 5N is shown. The alternating current _peak value reference signal I _acpre is given by I _acpre = ΔI _c + I _acp (5) and executed by the adder 33.

This AC current _peak value reference signal I _acpre is a current reference signal I _Pre of the boost choppers 8P and 8N of the positive group and the negative group according to the following equation.
And I _Nre .

Expression (6) is executed by the multipliers 34P and 34N. FIG. 5 shows the operation waveform diagram. The secondary voltage of the isolation transformer 26 is a six-phase waveform with a phase difference of 60 °, of which the three-phase signals with a phase difference of 120 ° (e _u4 , e _v4 , e _w4 ) and (e _x4 , e _y4 , e _z4 ) By the three-phase half-wave rectification circuits 27P and 27N, the three-phase half-wave rectification signals _e27P and _{e27N that} are similar to the positive polarity and the negative polarity and are synchronized with the AC power supply voltage are obtained. These signals and AC current _peak value reference signal I _acpre
Is multiplied to obtain current reference signals I _Pre and I _{Nre of the} positive group and negative group choppers 8P and 8N. If the AC current _peak value reference signal I _acpre has a flat waveform, the waveforms of the current reference signals I _Pre and I _Nre are three-phase half-wave rectified signals.
The waveforms are similar to those of e _27P and e _27N and correspond to the currents I _P and I _N of the reactors 2P and 2N shown in the operation waveform diagram of the main circuit portion of FIG.

The currents I _P and I _C of the positive and negative group boost choppers 8P and 8N are controlled by the current controllers 35P and 35N according to the current reference signals I _Pre and I _Nre . The output signal e of this current controller 35P, 35N
_{The 35P} and e _35N are modulated into high frequency switching signals by the PWM circuits 36P and 36N. This modulation frequency is a triangular wave modulation signal
Although it is determined by V _ca , this PWM circuit is publicly known and therefore detailed description thereof is omitted.

Instead of the combination of the current controllers 35P and 35N and the PWM circuits 36P and 36N, a known hysteresis comparator may be provided to control the instantaneous value of the current.

Further, in the above embodiment, a mechanical switch or GTO is provided as the switch means of the positive group and negative group boost chopper switches 3P, 3N, but a self-extinguishing type capable of high frequency switching such as a transistor MOSFET is shown. A semiconductor element may be used, and the switching means of the three-phase AC switch 7 may also be a self-extinguishing semiconductor element other than GTO. Further, the self-extinguishing semiconductor element is connected in antiparallel. It may be one.

In the embodiment of the control device shown in FIG. 3, an analog circuit is mainly constituted, but it can be easily realized by a digital circuit using a microprocessor. Further, FIG. 6 shows a circuit configuration diagram of a control device constituted by a digital circuit. Reference numeral 41 is a single-phase transformer, the primary side of which is connected between the w and v phases of the AC power supply. Reference numeral 42 denotes a filter circuit, which is connected to the secondary side of the single-phase transformer 41 and generates a voltage signal V _ac ′ with a 90 ° phase delay. 43 is the PLL (Phase
Output signal V of the filter circuit 42 in the (looked loop) circuit.
_The phase signal θ synchronized with the signal obtained by converting _ac ′ into a rectangular wave through a zero-crossing comparator is used as PLL, filter, VCO,
This is a well-known circuit that is generated in the PLL circuit 43 configured by a counter. 44 is the (first) ROM table,
Corresponding to this phase signal, a three-phase AC switch (S _u , S _v ,
It is _tabulated so as to generate the ON signal (e _u3 , e _v3 , e _w3 ) of S _w ). 45 is a (second) ROM table, which corresponds to the phase signal θ and is a three-phase half-wave rectified signal e _27P ′, e
_{It is tabulated} to generate _27N '. An interrupt control circuit 46 generates an interrupt signal INT at a predetermined phase corresponding to the phase signal θ, and a microprocessor (μ-
P and abbreviated below) 49. 47 is a multiplexer (MPX abbreviated hereinafter), an AC voltage signal V _ac ', the detection signal I _Pb of the step-up chopper current of positive _group, the detection signal I _Nb of the step-up chopper current of the negative _group, the detection signal of the load current I
_Lb , output voltage detection signal V across both boost choppers
Each signal of _Cb is selected according to the command from the μ-P 49 and is given to the μ-P 49 via the A / D converter 48. 36 is PWM
It is a circuit and produces a modulation signal based on the output signal of the μ-P 49, and gives an ON signal to the switches 3P and 3N via the gate amplifier 37. FIG. 7A shows the operation waveforms of the (first) ROM table 44 and the (second) ROM table 45 in an analog expression. The primary-side voltage e _wv of the single-phase transformer 41 has a 90 ° lead phase with respect to the U-phase voltage _eu of the AC power supply, and the signal V _ac ′ with a 90 ° phase delay in the filter circuit 42 eventually _results in the U-phase voltage e _u . _u
And the same phase is obtained. The result is the output signal θ of the PLL circuit 43 will signal synchronized with the U-phase voltage e _u of the AC power supply, in this example shows the waveform of the up-count analog representation. The phase signal θ is not particularly required to be synchronized with the U-phase voltage, it may be synchronized with the voltage of another phase, and the filter circuit 42 does not have to delay it by 90 °. (First) ROM table 4
4 is a three-phase logic signal (e _u3 , e _v3 , e) with respect to this phase signal θ.
_w3 ) is generated. For example, the logic signal e _u3 the phase signal θ is 0 ° to 30 °, 150 ° to 210 °, it is tabulated to output a signal of high level "H" between 330 ° to 360 °.
The (second) ROM table 45 outputs an output signal having a waveform similar to the positive and negative three-phase half-wave rectified waveform with respect to the phase signal θ.
It is _tabulated to output as e _27P ′, e _27N ′. For example, in the positive three-phase half-wave rectified waveform signal e _27P ′, the phase signal θ is cos (θ + 30 °) between 0 ° -30 °, cos (θ-90 °) between 150 ° -150 °, and 150 ° -270 °. Between degrees, cos (θ−210
)), Between 270 ° and 360 ° is tabulated by the function of cos (θ-330 °). The interrupt control circuit 46 provides an interrupt signal INT to the μ-P49 in response to the phase signal θ, and the μ-P49 performs arithmetic processing in response to this interrupt signal INT. It may be present, and the priorities in this case are generally set as follows. For example, interrupt signal INT that occurs only at θ = 90 ° 90 ° interrupt signal IN that occurs every 30 °
Three types of interrupt signals, INT _PWM generated at every T _{30 °} , 360 ° / 256, cause μ-P49 to execute the operation according to the control flow shown in Fig. 7 (B). Performs the same calculation as the analog circuit of FIG. 3 by time sharing. The arithmetic processing of the PWM circuit 36 can also be executed by μ-P49. In addition, the voltage controller 29 and the current controller 35P,
The operation of 35N may be an operation method based on a well-known classical control logic such as P, PI, or PID, or an operation method based on modern control theory such as dead beat control.

FIGS. 8 (a) and 8 (b) show examples of circuits in the case where a gate turn-off thyristor is applied as the switching means of the three-phase AC switch 7. The switch means may be a self-arc-extinguishing type semiconductor element such as a gate turn-off thyristor or a transistor MOSFET, and it is necessary to be able to energize in both directions. FIG. 9 (a) shows an arm element (S _u , S _v , S _w ).
Is an example in which gate turn-off thyristors are connected in anti-parallel. FIG. 8 (b) shows an example in which one gate turn-off thyristor is connected between the DC ends of the single-phase diode bridge, and the same effect as that of the above embodiment is obtained. The duty of operation of the switch means of the three-phase AC switch 7 may be low current and low frequency as compared with the switch means 3P and 3N of the step-up chopper.

Further, the load 6 is shown as an example of a DC load, but an AC load may be connected via a DC-AC power converter (inverter), and the same effect as that of the above-described embodiment is obtained. .

In addition, the positive group and negative group boost choppers 8P and 8N are installed on the AC power supply side.
There may be provided a filter for controlling a harmonic component of the alternating current (generally, an integral multiple of the switching frequency) depending on the switching frequency.

〔The invention's effect〕

As described above, according to the present invention, the boost choppers cascade-connected in two stages are connected in parallel to the DC output side of the diode rectifier having the three-phase bridge configuration, and the intermediate point of the boost chopper and the three-phase AC power supply are connected. Two-way energizing type 3
A phase AC switch is provided, and each boost chopper is controlled so that a current with a current waveform similar to the current waveform of the corresponding three-phase half-wave rectification of the polarity is flowed, and the difference in the input current of each boost chopper is calculated as three phases. A main circuit unit is configured to flow a three-phase AC current through an AC switch, and as a control method thereof, an AC current peak value reference signal calculation means, a three-phase half-wave rectified wave-shaped current reference signal calculation means, The control device is constituted by means for controlling the positive and negative output currents of the diode rectifier by the boost chopper based on the current reference signal and the logical operation means for the ON signal of the three-phase AC switch. Not only can the power factor of the AC power supply be set to 1 by the operation of, but the corresponding polarity of 3
The AC power supply can be controlled in a sinusoidal shape by providing boost choppers that are controlled so that currents with a current waveform similar to the voltage waveform of phase half-wave rectification can be controlled, thereby reducing the harmonic current in the output current. There is an effect that a power conversion device can be obtained.

[Brief description of drawings]

FIG. 1 is a circuit configuration diagram of a power converter according to an embodiment of the present invention, FIG. 2 is a waveform diagram of a main part showing the operation of FIG. 1, and FIG. 3 is a power converter according to an embodiment of the present invention. 4 and 5 are operation waveform diagrams of FIG. 3, FIG. 6 is a circuit configuration diagram of a control device according to another embodiment of the present invention, and FIG. ) And (B) are operation waveform diagrams and control free diagrams of FIG. 6, FIG. 8 is a circuit diagram showing a specific example of a three-phase AC switch, and FIG. 9 is a circuit configuration diagram showing a conventional power conversion device. FIG. 10 is an operation waveform diagram of FIG. In the figure, 1, 10 are diode rectifiers, 2, 2P, 2N are reactors, 3, 3P, 3N are DC switches, 4, 4P, 4N are diodes,
5,5P and 5N are capacitors, 6 is a load, 7 is a three-phase AC switch, 8P and 8N are boost choppers for positive and negative groups, 20P, 20N and 20L are current detectors, 21 is a voltage detector, 22, 26 is an isolation transformer, 2
3 is a zero cross comparator, 24 is an exclusive OR circuit, 25,
37P, 37N, 37 are gate amplifiers, 27P, 27N are three-phase half-wave rectifier circuits, 28 is a peak value detector, 30, 34P, 34N are multipliers, 31 is a divider, 32 is a variable resistor, 33 is Adder, 29 is a voltage controller, 35
P and 35N are current controllers, 36P and 36N are PWM circuits, 37 is a gate amplifier, 43 is a PLL circuit, 44 and 45 are first and second ROM tables, and 49 is a microprocessor.

Claims (12)

[Claims] 1. A three-phase bridge-connected diode rectifier connected to a three-phase AC power supply, and positive and negative boost choppers connected in two stages in cascade between the positive and negative output terminals of the diode rectifier, The step-up chopper of the positive group is similar to the voltage waveform of the positive polarity three-phase half-wave rectification of the three-phase AC power supply, which is provided with a three-phase AC switch connected between the connection intermediate points of both choppers and the AC power supply end. Is controlled so that a current having a different current waveform is passed, and the boost chopper of the negative group has
It is controlled so that a current having a current waveform similar to the voltage waveform of the negative polarity three-phase half-wave rectification of the phase-phase AC power supply is passed, and the input current of the positive group boost chopper and the negative group boost chopper A power conversion device characterized in that the difference is caused to flow to the three-phase AC power source through the three-phase AC switch. 2. A gate turn-off thyristor, a transistor, and a MOSFET as switching means of the three-phase AC switch.
The power conversion device according to claim 1, wherein a self-arc-extinguishing type semiconductor element such as is used. 3. The power conversion device according to claim 1, wherein self-extinguishing type semiconductor elements are connected in antiparallel as a configuration of the three-phase AC switch. 4. A self-extinguishing type semiconductor device such as a gate turn-off thyristor is connected between the direct currents of a single-phase bridge as a constitution of the three-phase AC switch. Power converter. 5. A three-phase bridge-connected diode rectifier connected to a three-phase AC power supply, and positive and negative boost choppers connected in two stages between the positive and negative output terminals of the diode rectifier, A three-phase AC switch connected between the connection intermediate point of both choppers and the AC power source end, a load connected between the boost choppers of the positive group and the negative group and driven by DC power, a current of the load, and the load. AC current peak value reference signal control means for calculating the current peak value of the AC power supply from the voltage across both boost choppers, the voltage peak value of the AC power supply, and the voltage across the choppers, and is synchronized with the AC power supply. From the three-phase half-wave rectifying means for deriving positive and negative three-phase half-wave rectified waveform signals, the rectified waveform signal by the three-phase half-wave rectifying means and the AC voltage peak value signal, the positive group and the negative Boost chopper current control means for calculating the current reference of the boost chopper, step-up chopper element control means for controlling the currents of the boost choppers of the positive group and the negative group based on the current reference by the step-up chopper current control means, and the diode. A step-up chopper of the positive group, which has a positive polarity 3 of the three-phase AC power supply.
The boost chopper of the negative group is controlled so that a current having a current waveform similar to the voltage waveform of the half-phase half-wave rectification is supplied, and the boost chopper of the negative group has a current waveform similar to the voltage waveform of the negative three-phase half-wave rectification of the three-phase AC power supply. Of the positive group boost chopper and the input current of the negative group boost chopper are passed through the three-phase AC switch to the three-phase AC power supply. A power converter characterized by the above. 6. The power converter according to claim 5, wherein the AC current peak value reference signal control means is composed of a multiplier, a voltage controller, a divider, an adder and the like. 7. A diode is connected to each secondary side terminal of an insulating transformer having a three-phase AC power supply as a primary as the three-phase half-wave rectifying means, and positive and negative three-phase half-wave rectified signals are output. The power conversion device according to claim 5, wherein 8. A current controller for controlling an output signal of a three-phase half-wave rectifying means as the step-up chopper current control means and controlling the signal through a multiplier. The power converter according to the item. 9. The power conversion device according to claim 5, wherein the boost chopper element control means comprises a pulse width modulation circuit and a gate amplifier. 10. The power conversion device according to claim 5, wherein the logical operation means comprises a zero-cross comparator, an exclusive OR circuit, and a gate amplifier. 11. A three-phase bridge-connected diode rectifier connected to a three-phase AC power supply, and positive and negative boost choppers connected in two stages between the positive and negative output terminals of the diode rectifier, An AC switch connected between the connection intermediate point of both choppers and the AC power source terminal, an insulating transformer connected to the three-phase AC power source, and a secondary voltage of the insulating transformer to a zero cross comparator via a filter circuit. A PLL circuit for guiding a sawtooth wave from the output of the zero-cross comparator and an output of the PLL circuit
It is input to the ROM table, is amplified by the output of the ROM table and is applied as a gate signal of a three-phase AC switch, and is guided to a multiplexer via the filter circuit, and is input from the multiplexer via an A / D converter. A microprocessor for digitally processing the received signal, and
A second ROM table and interrupt control circuit connected in parallel to receive the output signal of the PLL circuit, and the outputs of the second ROM table and interrupt control circuit are input to and output from the microprocessor. A positive amplifier of the positive polarity of the three-phase alternating current power supply, the positive group boost chopper having a positive polarity of the three-phase AC power source. The boost chopper of the negative group is controlled so that a current having a current waveform similar to the voltage waveform of the three-phase half-wave rectification is passed, and the boost chopper of the negative group has a current similar to the voltage waveform of the negative-polarity three-phase half-wave rectification of the three-phase AC power supply. It is controlled to flow a waveform current,
A power conversion device, wherein a difference between an input current of the positive group boost chopper and an input current of the negative group boost chopper is made to flow to the three-phase AC power supply via the AC switch. 12. The PLL circuit comprises a zero cross comparator, PL
12. The power conversion device according to claim 11, comprising a circuit having L, a voltage controlled oscillator, and a counter.