JPH0634581B2 - Multiplex pulse width modulation power converter - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a multiple pulse width modulation power converter of a system in which pulse width modulation single phase forward converters are connected in parallel to supply DC power. In particular, the present invention relates to a multiple pulse width modulation power converter suitable for a single-phase AC feeding type electric vehicle.

[Conventional technology]

Conventionally, in electric vehicles for railroads such as electric trains, even in AC electric vehicles, DC electric motors have been frequently used as electric motors for driving the AC electric vehicles, but in recent years, with the increase in output capacity, AC electric motors, In particular, there is an opportunity to drive an induction motor for driving.

By the way, in an AC electric vehicle using such an AC electric motor, a forward converter, in particular, a pulse width modulation forward converter is required as a power converter.

When applying this pulse-width modulation type forward converter to a large-capacity AC electric vehicle, from the viewpoint of the capacity of the semiconductor switching element that constitutes the main circuit and the reduction of harmonics on the single-phase AC power supply side, etc. , A so-called multiplex type pulse width modulation type forward converter in which a main circuit is divided and multiplexed is widely used.
Volume D, Vol. 107, No. 3 (1988) 304-311
Page, "Examination of high-performance AC vehicle system using PWM converter" and the like, which enables control to keep DC voltage and power supply power factor at predetermined values.

[Problems to be solved by the invention]

By the way, in a system using such a single-phase AC power supply, the electric power supplied from the system pulsates at a frequency twice the power supply frequency in the instantaneous value, and due to this, the DC side voltage of the forward converter is affected. It is necessary to suppress this without pulsation, but in the above-mentioned conventional technology, no particular consideration is given other than providing a smoothing capacitor on the DC side thereof, and therefore a large-capacity smoothing capacitor is required. Increasing the weight of the system and the space required to store it,
There are problems that it is difficult to mount it on a vehicle and the cost is significantly high.

An object of the present invention is to provide a multiple pulse width modulation power capable of sufficiently suppressing the pulsation of the above DC power without increasing the capacity of the smoothing capacitor, suppressing cost up, and reducing weight and volume. It is to provide a conversion device.

[Means for solving problems]

The above-mentioned object is to configure at least one terminal on the AC side of each pulse width modulation type forward converter (hereinafter referred to as a unit forward converter) which should constitute a multiplex pulse width modulation type forward converter. Connect to each other with an impedance element, so that the voltage appearing on this impedance element will be a predetermined value,
This is accomplished by controlling each unit converter.

[Work]

In order for the voltage of a predetermined value to appear in the impedance element,
By controlling each of the unit forward converters, it is possible to suppress the power pulsation at the DC side of these unit forward converters at a frequency twice as high as the frequency of the AC power source side. Therefore, even if the capacity of the smoothing capacitor is not increased. , It is possible to sufficiently reduce DC power pulsation.

〔Example〕

Hereinafter, the multiple pulse width modulation power conversion position according to the present invention will be described in detail with reference to the illustrated embodiment.

FIG. 1 is an embodiment in which the present invention is applied to a single-phase AC electric vehicle or the like using an induction motor as a drive motor, and in the figure, 1 is a single-phase AC power supply and 2 is a main transformer. Vessels, 3, 4 AC reactor, 5 auxiliary reactor, 6
~ 13 is a GTO thyristor, 14 ~ 21 is a diode, 22 is a smoothing capacitor, 23 is a load, 24 is a voltage regulator, 25 and 26 are current regulators, 27 and 28 are phase regulators, and 29 and 30 are phase difference detection. , 31 is a coordinate converter, 32 is a voltage synthesizer / coordinate converter, 33-
36 is a pulse width modulator.

The main transformer 2 has a primary winding 2P and two sets of secondary windings 2A, 2
It is a single-phase transformer having B and functions to convert the AC voltage ep received from the AC power supply 1 into two sets of secondary voltages es having a predetermined value.

The AC reactors 3 and 4 serve to reduce the interference between the AC input voltages e ₁ and e ₂ of the respective forward conversion units A and B.

The auxiliary reactor 5 acts to absorb the pulsating electric power, and its details will be described later.

The GTO thyristors 6 to 13 together with the diodes 14 to 21 form a main circuit of the unit forward conversion units A and B.

The smoothing capacitor 22 is connected in parallel to the DC output terminals of the unit forward conversion units A and B, and acts to suppress DC voltage pulsation.

Although not shown in the figure, the load 23 is a well-known load including an inverse converter (inverter) and an induction motor.

The voltage regulator 24 is also called AVR, and the smoothing capacitor 22
From the deviation between the average value E _d detected from the DC voltage ed appearing between the terminals and the DC voltage command value E _d ^* given thereto, the AC input of each unit forward conversion unit A, B It ^operates to calculate the current (converter input current) command value I _s ^* .

The current regulators 25 and 26 are called ACR, and the current command value I
The imaginary axis component command for each of the AC-side terminal voltages (converter input voltage) e _c1 and e _{c2 based} on the deviation between _s ^* and the detected values I _s1 and I _s2 of the actual input current to the unit forward conversion units A and B. _Functions to calculate and output the values E _1i ^* , E _2i ^* (based on the power supply voltage ep).

The phase adjusters 27 and 28 are called APRs, and are phase difference detectors (P
Where being by connexion detected DD) 29, 30, the phase difference phi ₁ between the power supply voltage ep the AC input current i _s1 and i _s2, phi
₂ and the command values φ ₁ ^* and φ ₂ ^{* corresponding} _thereto , the actual axis component command values E _1r ^* and E of the converter input voltages e _c1 and e _c2 are _calculated ^.
_Functions to output _2r ^* by calculation.

The coordinate converter 31 is called a CTR, and based on the command values E _o ^* , α ^* of the amplitude and phase of the voltage e ₀ to be applied to the auxiliary reactor 5, the real axis component command E _0r ^* and the imaginary axis component command of the voltage e ₀ are _calculated ^. Value E _0i ^*
Functions to output.

The voltage synthesizing / coordinate converter 32 is called VMX, and synthesizes respective command values E _1r ^* , E _1i ^* , E _2r ^* , E _2i ^* , E _0r ^* and E _0i ^* of the voltage e ₀ , and polar coordinate conversion. The command values E _1P ^{* to} E _2N ^* of the AC side terminal voltages of the unit order conversion units A and B are performed ^.
And the phase command values ∠ _IP ^{* to} ∠ _2N ^* are calculated and created.

The pulse width modulators 33 to 36 function to generate the gate signals G6 to G13 to be supplied to the GTO thyristors 6 to 13 of the unit order conversion units A and B from the above command values. The portion from the voltage regulator 24 to the pulse width modulator 36 is called a control unit CS.

First, the principle of reducing DC voltage pulsation will be described. The forward conversion unit will be referred to as a converter hereinafter.

FIG. 2 shows the main circuit portion of FIG. 1 taken out. As shown in the figure, the secondary voltage obtained by transforming the power supply voltage e _P by the main transformer 2 is e _s, the converter input voltage is e ₁ and e ₂ , and the converter input current is i _s1 and i _s2. Further, the inductances of the AC reactors 3 and 4 and the auxiliary reactor 5 are L ₁ , L ₂ , and L ₀ , respectively, and the auxiliary reactor 5
Let e ₀ be the voltage applied to V and i ₀ be the current flowing through it. Here, the middle point of the smoothing capacitor 22 is virtually grounded to a virtual ground point N, and the PWM for this virtual ground point N
If the electric potentials of the terminals P ₁ , N ₁ , P _2, and N ₂ of the AC side of the converter are e _1P , e _1N , e _2P , e _2N , the AC side circuit of FIG. The equivalent circuit shown in FIG. 3 (a) can be represented by the equivalent circuit shown in FIG. 3 (b) for the currents i _s1 , i _s2 and i ₀ . Can be represented.

Therefore, in order to explain the operation principle below, the broken line portions in the figure are represented by virtual converters CON1, CON2 and CON0.
I will call it.

First, regarding the virtual converters CON1 and CON2,
Secondary voltage _{e s,} the converter input voltage _e 1, _{e 2,} the fundamental wave vector of the converter input current i _s1, i _{s2 s,
Let 1} , ₂ , _s1 and _s2 .

Next, when trying to operate the PWN converter at a power factor of 1, in this case, each vector must satisfy the relationship shown in FIG. That is, the magnitudes and phases of the converter input voltages ₁ and ₂ must be adjusted so that the voltages jωL _{1 s1} and jωL _{2 s2} (ω: power source angular frequency) of the AC reactors 3 and 4 are orthogonal to the secondary voltage _s. . Where θ ₁ and θ ₂ are the phase angles of ₁ and ₂ (
_s standard). The converter input current _s1 and
_It is assumed that _s2 is controlled by the same command value I _s ^* and that _s1 = _s2 .

The relation of the vector diagram of FIG.
Figures (a) to (c) are shown.

Actually, these waveforms contain harmonic components, but as shown in Fig. 5, they are approximately sine waves, and the secondary voltage Based on Then, the electric power P converted to the DC side by the virtual converters CON1 and CON2 is as follows: p = e ₁ · i _s1 + e ₂ · i _s2 = 2E ₁ I _s sin ωt sin (ωt + θ ₁ ) + 2E ₂ I _s sin ωt sin (ωt + θ _{2 ) = E 1 I s {cosθ} 1 -cos (2ωt + θ 1)} + E 2 I s {cosθ 2 -cos (2ωt + θ 2)} a ... (3).

Here, in the equation (3), E ₁ I _s cos θ ₁ and E ₂ I
_s cos [theta] ₂ is the average power, expressed from equal to the product E _s I _s the effective value of the secondary voltage and the converter input current, (3) Further, as in the following equation.

Normally, the range of use of the phase angle of the converter input voltage is about ± 30 °, and even if there is a difference of about 10% between the values of the inductances L ₁ and L ₂ , cosθ ₁ / cosθ ₂ 1, Therefore, equation (4) is However, And the waveform is as shown in FIG. 5 (d).

In the equation (5), the first term on the right side is the average power converted from alternating current to direct current, and the second term on the right side indicates the pulsating component of the power. Then, since this pulsating power is injected into the smoothing capacitor 22, a pulsating voltage centered at twice the frequency of the power source is generated.

On the other hand, regarding the virtual converter CON0, the voltage e ₀ applied to the auxiliary reactor 5 is Then, the current i ₀ flowing in the auxiliary reactor 5 is Becomes

Therefore, from these equations (6) and (7), the power p ₀ consumed by the auxiliary reactor 5 is determined by the following equation.

In the equation (8), the first term is the average power and the second term is the pulsating power, and these powers are naturally supplied from the DC side.

Therefore, when the second term of equation (5) and the second term of equation (8) are equal, that is, When the above condition is satisfied, the pulsating component of the electric power supplied from the AC power source to the DC side is all absorbed by the auxiliary reactor 5. At this time, the voltage e ₀ to be applied to the auxiliary reactor 5
The execution value E ₀ and the phase angle α of are calculated from the equation (9) as follows.

By the way, even if the auxiliary reactor 5 is a general impedance element, it is possible to remove the pulsating power similarly to the above. In this case, the effective value E ₀ ′ of the voltage e ₀ ′ to be applied to the impedance element and the phase angle α ′.
Is However, R ₀ : resistance component, X ₀ : reactance component (X ₀ > 0: inductive, X ₀ <0: capacitive).

Next, the operation of this embodiment will be described.

The control unit CS in the embodiment of FIG. 1 uses the DC voltage E _d , the power factor angles φ ₁ and φ ₂ , and the voltage e ₀ applied to the auxiliary reactor 5.
It has a function of controlling the fundamental wave effective value E ₀ and the phase angle α. That is, the voltage regulator 24 calculates the command value I _S ^* of the input current of one of the converters A from the deviation between the detected value (average value) E _{d of} the DC voltage and its command value E _d ^* , and The imaginary axis component command value E _1i ^* of the converter input voltage e ₁ is created by the current regulator 25 from the deviation from the detected value I _s1 of the converter input current.

On the other hand, the phase difference φ ₁ between the power supply voltage e _P and the fundamental wave of the converter input current i _s1 is detected by the phase difference detector 29, and this and the phase difference command value φ ₁ ^* (power factor angle command value, usually force In order to set the ratio to 1, the phase adjuster 27 creates the actual axis component command value E _1r ^* of the converter input voltage e ₁ from the deviation from φ ₁ ^* = 0).

Similarly, for the other PWM converter B, the command values E _2i ^* and E _2r ^* of the converter input voltage e ₂ are created.

Further, the command values E ₀ ^* and α in polar coordinates of the voltage e ₀ to be applied to the auxiliary reactor 5 obtained by calculation based on the equation (10).
Regarding ^* , the command value is obtained by converting this into command values E _0i ^* (imaginary axis component) and E _0r ^* (real axis component) in Cartesian coordinates by the coordinate converter 31.

By the way, in this embodiment, as shown in FIG. 3, it is necessary to control the three voltages e ₁ , e ₂ and e ₀ by the four AC side terminal voltages e _1P , e _1N , e _2P and e _2N. . Therefore, the three voltage vector commands ₁ ^* (= E _1r ^* + jE _1i
^* ), ₂ ^* (= E _2r ^* + jE _2i ^* ) and ₀ ^* (= E _0r ^*)
+ JE _0i ^* ) for 4 AC side terminal voltage vector commands _1P
^* (= E _1Pr ^* + jE _1Pi ^* ), _1N ^* (= E _1Nr ^* + jE
_1Ni ^* ), _2P ^* (= E _2Pr ^* + jE _2Pi ^* ) and _2N ^* (=
E _2Nr ^* + jE _2Ni ^*) Synthesis, converts, it is necessary to obtain the command amplitude and phase angle of each voltage by further polar coordinate conversion.

Therefore, the fundamental wave vector _one of these voltages _e 1, _{e 2} and _{e 0, 2} and _0, AC terminal voltage e _1P,
e _1N , e _2P and e _2N fundamental wave vectors _1P , _1N , _2P
And with _2N Therefore, the terminal voltage vector of each AC side is However Then, given converter input voltage vector ₁ ,
It is possible to obtain a predetermined voltage vector ₀ while obtaining ₂ .

FIG. 6 shows the relation of the equation (13) at the time of vector, and the relation between each vector _s and ₁ and ₂ is the same as that of FIG. 4, so that the voltage vector _s and the current vectors _s1 and _s2
Are in phase, that is, the fundamental wave power factor is kept at 1. Also,
At the same time, it can be seen that the amplitude and phase angle of ₀ are also controlled to predetermined values.

Therefore, the command value of each AC side terminal voltage may be created according to the relationship of equation (13). Note that in (13), the reference vector _{b 1/2 2/2} of the average and the but,
_{If b} is in the vicinity of ( ₁ + ₂ ) / 4, then _b can be any vector.

From the command values obtained as a result of the above, pulse width modulators 33, 34
35 and 36 generate gate signals G6 to G13 to be supplied to the GTO thyristors 6 to 13, respectively. For example, the gate signals G6 and G7 given to the GTO thyristors 6 and 7 are as shown in FIG. 7 (b).
, The phase difference with respect to the power supply voltage e _P is θ _1P (= ∠
_1P ) and the amplitude is obtained by comparing the modulated sine wave y _m whose amplitude is proportional to E _1P (= | _1P |) with the carrier triangular wave y _c , The gate signal is sent so that As a result, the AC side terminal voltage e _1P has a waveform as shown in FIG. 7C when the influence of the pulsation of the DC voltage is ignored, and the modulated sine wave y _m
It is possible to generate a voltage e1P1 (fundamental wave) proportional to Further, the gate signals G8 to G13 given to the other GTO thyristors 8 to 13 can be obtained by the same method as described above.

As described above, the voltage shown in equation (13) is generated at each AC side terminal, and while maintaining the predetermined DC voltage and power factor, it is possible to sufficiently suppress the DC voltage pulsation of twice the frequency of the power supply. Is possible.

Therefore, according to this embodiment, the pulsating electric power, which has been directly injected into the smoothing capacitor 22 in the prior art and causes the DC voltage pulsation, is generated by the auxiliary reactor 5 provided between the AC side terminals of the PWM converter. As a result, it is almost absorbed, and not only the pulsation of the DC voltage can be removed with a simple main circuit configuration, but also the smoothing capacitor capacity can be reduced.

By the way, in the above-mentioned embodiment, the amplitude command value E ₀ ^* for the voltage e ₀ to be applied to the auxiliary reactor 5 is set in advance as a predetermined value, but instead of this, the actual converter It may be automatically set according to the operating state of.

Therefore, an embodiment thus configured will be described with reference to FIG.

In FIG. 8, reference numeral 37 denotes a pulsating current command value I _cr ^* to be flown into the smoothing capacitor 22 and a current i _c actually flowing into the smoothing capacitor 22 through a filter 38, which is twice the power supply. This is a current regulator that creates an amplitude command value E ₀ ^* of the voltage e ₀ to be applied to the auxiliary reactor 5 from the deviation from the frequency component I _cr, and all other parts are the same as the embodiment shown in FIG. .

The pulsation appearing in the DC voltage is obtained by integrating the pulsating component of the current i _c flowing into the smoothing capacitor 22, and pulsates at a frequency 2f _s which is twice that of the power supply. Was but connexion, pulsating current of the smoothing capacitor 22 as a main factor of the DC voltage ripple (2f _s component)
If I _cr is set to zero, the DC voltage ripple is eliminated.

Therefore, in the embodiment shown in FIG. 8, the command value I _cr ^* is set to 0 so that the amplitude command value E ₀ ^* with which the pulsating current I _cr becomes zero is automatically output. It is a thing.

According to this embodiment, in addition to the effects of the embodiment shown in FIG. 1, a reliable and responsive DC voltage ripple removing operation can be automatically given.

FIG. 9 shows still another embodiment. In the case of this embodiment, the pulsating component E _dr of the DC voltage ed appearing in the smoothing capacitor 22 is directly detected and the voltage regulator 39 is set so that it becomes zero. Outputs the amplitude command value E ₀ ^* , and other configurations are the same as those in FIG. The filter 40 has a function of extracting a frequency component twice the power supply frequency from the voltage ed, thereby obtaining the pulsation component E _dr .

Therefore, according to the embodiment of FIG. 9 as well, by setting the pulsating voltage command value E _dr ^* to zero, the same effect as that of the embodiment of FIG. Since there is no need to detect separately, the installation of a new detector can be unnecessary.

Next, in the above description, the converters A and B of the two systems are of the multiple type, and one auxiliary reactor is used. However, it goes without saying that the present invention is not limited to this and can be implemented. For example, FIG. 10 shows an embodiment in which two auxiliary reactors are provided, and 5A and 5B are auxiliary reactors.

Further, FIGS. 11 (a) and 11 (b) are multiplex type converters with three systems, and FIGS. 12 (a) and 12 (b) are multiplex type converters with four systems. C,
D, AC reactors 4A and 4B, and auxiliary reactors 5C and 5D are added thereto, which is also an embodiment of the present invention.

In the above embodiments, the main transformers 1 are all common one unit, but it goes without saying that each converter may be independent.

Further, the auxiliary reactor may be a general impedance element as described above, and may be, for example, a capacitor or a resistor.

〔The invention's effect〕

According to the present invention, the impedance element installed on the AC input side of the plurality of unit converters absorbs the pulsating portion of the power supplied from the single-phase AC power supply, so that the voltage in the DC power system of the power converter is reduced. The generation of pulsation is suppressed, high-quality DC power can be supplied to loads such as inverters and AC motors, and large-capacity electric vehicles can be fully supported.

Further, since the increase in the capacity of the smoothing capacitor can be suppressed, it can greatly contribute to downsizing and cost reduction.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a multiplex pulse width modulation power converter according to the present invention, FIG. 2 is an explanatory diagram showing a voltage relationship of a main circuit, and FIGS. 3 (a) and 3 (b) are operations. An equivalent circuit diagram for explanation, FIG. 4 is a vector diagram for explaining the condition of a power factor of 1,
5 (a) to 5 (g) are waveform diagrams for explaining the operation, FIG. 6 is a vector diagram for explaining the operation, FIG. 7 is a waveform diagram for explaining the pulse width modulation operation, FIG. 8 and FIG. The drawings are block diagrams, FIG. 10 and FIG. 11 for explaining other embodiments of the present invention.
Figures (a), (b) and Figures 12 (a), (b) are block diagrams showing another embodiment of the present invention. 1 ... Single-phase AC power supply, 2 ... Main transformer, 3, 4 ... AC reactor, 5 ... Auxiliary reactor, 6-13 ... GTO
Thyristor, 14-21 ... diode, 22 ... smoothing capacitor, 23 ... load, 24 ... voltage regulator, 25, 26 ... current regulator, 27, 28 ... phase regulator, 29, 30 ... Phase difference detector, 31 ... Coordinate converter, 32 ... Voltage combiner / coordinate converter,
33 to 36 ... Pulse width modulator, A, B ... Unit order conversion unit (converter), CS ... Control unit.

Claims (3)

[Claims] 1. At least two single-phase bridge-shaped pulses each comprising a semiconductor switching element, each of which is fed in parallel from a single-phase AC power source through a reactance element and is connected to feed a DC load having a smoothing capacitor in parallel. In a multiplex pulse width modulation power converter having a width modulation type unit forward converter, at least one impedance element connected between one terminals of each of the plurality of unit forward converters on the AC input side is connected. A multiplex pulse width modulation power conversion device, characterized in that the unit converters are pulse width modulation controlled so that the voltage appearing in the impedance element becomes a predetermined value. 2. The voltage according to claim 1, wherein the voltage appearing in the impedance element is 2 times the frequency of the single-phase AC power supply included in the current flowing in the smoothing capacitor.
A multiplex pulse width modulation power conversion device, which is configured to be adjusted according to a detection value of a double frequency component. 3. The voltage according to claim 1, wherein the voltage appearing in the impedance element is in accordance with a detected value of a frequency component that is twice the frequency of the single-phase AC power supply included in the terminal voltage of the smoothing capacitor. A multiplex pulse width modulation power conversion device, which is configured to be adjusted.