JPH0419796B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a power conversion device comprising a DC voltage source supplied with power from an AC power supply and its load device.

[Technical Background of the Invention] Load devices using a DC voltage source as a power source include a pulse width modulation control (PWM) inverter + induction motor, or a DC chopper + DC motor. There are not many problems when using a battery as this DC voltage source, but when obtaining DC voltage from a commercial power supply via an AC/DC power converter, reactive power and harmonics generated on the commercial power supply side have recently become a problem. It's getting old.

In order to solve this problem, a method has been proposed in which a pulse width modulation control (PWM) converter is inserted between the commercial power supply and the DC voltage source (capacitor) as an AC/DC power converter (Japanese Patent Application No. 171886, etc.). ing.

FIG. 1 shows a configuration diagram of a conventional power conversion device using a PWM converter as an AC/DC power converter.

In the diagram, SUP is a single-phase AC power supply, L _s is an AC reactor, CONV is an AC/DC power converter,
C _d is a DC smoothing capacitor, and LAD is a load device. The converter CONV is an element with self-extinguishing capability (e.g. gate turn-off thyristor) S ₁
~ _S4 , wheeling diodes _D1 ~ _D4 , and DC reactors _L1 , _L2 , and the above elements _S1 ~
_S4 uses known pulse width modulation control to control the value of the AC side voltage Vo. In other words, the converter CONV is a DC voltage source (capacitor) C _d
When viewed from above, it becomes a pulse width modulation control (PWM) inverter, and in that case, the AC power supply SUP side can be seen as a type of load.

This conventional power exchange device uses the above DC voltage source C _d
The current Is supplied from the AC power supply is controlled so that the voltage _Vd of the AC power supply is approximately constant, and the _current Is supplied from the AC power supply is adjusted according to the power demand from the load device LAD.
Capable of quadrant operation.

The input current _Is is always controlled to be in phase with the power supply voltage _Vs , and the input power factor is 1.

Also, since the input current I _s is controlled in a sinusoidal manner, harmonics are extremely small.

is a feature.

The control operation of this device will be briefly explained below.

The following control circuits are available. CT _O is an AC current detector, R ₁ and R ₂ are voltage dividing resistors for detecting DC voltage, ISO is an isolation amplifier, VR is a DC voltage setting device, C ₁ to C ₃ are comparators, and G _V
(S) is a voltage control compensation circuit, ML is a multiplier, OA is an inverting operational amplifier, G _I (S) is a current control compensation circuit,
TRG is a carrier wave (triangular wave) generator, and GC is a gate control circuit.

First, the DC voltage V _d detected via the isolation amplifier ISO and the voltage command value V _d ^* from the voltage setting device VR
is input to the comparator C ₁ to find the deviation ε _V =V _d ^* −V _d . The deviation ε _V is input to the control compensation circuit G _V (S), where it is integrally amplified or proportionally amplified to reduce the input current.
This becomes the peak value command I _n of I _s .

The peak value command I _n is input to the multiplier ML and multiplied by the other input sin 〓 ^t . The input signal sin〓 ^t is a unit sine wave synchronized with the power supply voltage V _s =V _n・sin〓 ^t , and is obtained by detecting the power supply voltage V _s and multiplying it by a constant (1/V _n times). It will be done.

The output signal I _s ^* of the multiplier ML gives a command value of the current to be supplied from the power supply, and is expressed by the following equation.

I _s ^* = I _n・sin〓 ^t ...(1) The input current command value I _s ^* is inverted by the inverting amplifier OA, and the command value I _c ^* of the alternating current I _c supplied from the converter CONV to the power supply SUP is obtained. becomes. Hereinafter, I _c ^* will be referred to as a converter output current command value.

Converter output current I _c is detected by alternating current detector CT _c and input to comparator C ₂ . comparator
C ₂ compares the command value I _c ^* and the detected value I _c to obtain the deviation ε _I =I _c ^* −I _c . The deviation ε _I is input to the next control compensation circuit G _I (S), where it is proportionally amplified and becomes a control input signal for pulse width modulation control.
e _i becomes.

Pulse width modulation control is a known method, and is performed by a carrier wave generator TRG, a comparator _C3 , and a gate control circuit GC.

That is, the carrier wave generator TRG generates a triangular wave e _T with a frequency of about 1 kHz, and the comparator _C3 generates the triangular wave
e _T and the input signal e _i are compared, and the deviation ε _T = e _i
-eT An on/off signal is given from the gate control circuit GC to the gate turn-off thyristors _S1 to _S4 .

When e _i >e _T , that is, when the deviation ε _T is positive, thyristors S ₁ and S ₄ are turned on (at this time, S ₂ and S ₃ are turned off), and the AC output voltage V _c of the converter becomes +V _d .

Also, when e _i <e _T , that is, when the deviation ε _T is negative,
Thyristors S ₂ and S ₃ are turned on (at this time, S ₁ , S ₄
is off), and V _c = -V _d .

Moreover, if e _i is a positive value and is large, the on periods of S ₁ and S ₄ will be longer, the on periods of S ₂ and S ₃ will be shorter, and the average value of V _c will be proportional to the input signal e _i. It becomes a positive value at the voltage. Conversely, when e _i is a negative value, S ₁ and
Since the on-periods of S ₂ and S ₃ are longer than the on-period of S ₄ , the average value of the output voltage V _c of the converter is a value proportional to the input signal e _i and becomes a negative value.

That is, the output voltage V _c of the converter is controlled to a value proportional to the input signal e _i .

The output current I _c of the converter (the inverted value of the input current I _s supplied from the current) is controlled by adjusting the output voltage V _c of the converter.

A differential voltage V _L =V s −V _c between the power supply voltage V _s and the output voltage _{V c} of the converter is applied to the AC reactor L _s .

When V _s > V _c , the power supply current I _s increases in the direction of the arrow in the figure. In other words, converter output current I _c
acts to decrease in the direction of the arrow in the figure. Conversely, when V _s <V _c , the converter output current I _c tends to increase in the direction of the arrow in the figure.

When the actual current I _c has a relationship of I _c ^* with respect to the converter output current command value I _c ^* , the deviation ε _I = I _c ^* − I _c becomes a positive value, and the control compensation circuit G _I (S) through
Increase the PWM control input signal e _i . Therefore, the converter output voltage V _c also increases in proportion to the input signal e _i , and V _c >V _s , causing the converter output current I _c to increase in the direction of the arrow in the figure. Conversely, when I _c ^* < I _c , the deviation ε _I takes a negative value and reduces e _i , that is, V _c, and V _c < V _s , reducing the output current I _c .
Therefore, the output current I _c of the converter is controlled to match the command value I _c ^* . If the command value I _c ^* is changed in a sinusoidal manner, the actual current I _c is also controlled in a sinusoidal manner following it.

The converter output current I _c is the input current from the power supply
The command value I _c ^{* of the converter output current is the inverted value of the command value I s *} _{of the} ^input current from the power supply. Therefore, the input current I _s is controlled to follow the command value I _s ^* .

Next, the control operation of the voltage V _d of the DC capacitor C _d will be explained.

The comparator C ₁ compares the detected DC voltage value V _d and its command value V _d ^* . When V _d ^* > V _d , the deviation ε _V becomes a positive value, and via the control compensation circuit G _V (S),
Increase the input current peak value I _n . Input current command value
I _s ^* is given by a sine wave that is in phase with the power supply voltage, as shown in equation (1). Therefore, if the actual input current I _s is controlled to I _s = I _s ^* as described above, when the above peak value I _n is a positive value, the effective power expressed by the following equation
P _s is supplied from the single-phase power supply SUP to the DC capacitor C _d via the converter CNV.

P _s = V _s × I _s = V _n・I _n・(sin〓 ^t ) ² = V _n・I _n・(1−cos2〓 ^t )/2 ……(2) Therefore, the energy P _s・t is a DC capacitor
It is accumulated in C _d as 1/2C _d V _d ² , and as a result, the DC voltage V _d increases.

Conversely, when V _d ^* < V _d , the deviation ε _V becomes a negative value, and the above peak value is reduced through the control compensation circuit G _V (S).
I _n is decreased until I _n <0. Therefore, the active power P _s also becomes a negative value, and this time, the energy P _s t
is regenerated from the DC capacitor C _d to the power supply. As a result, the DC voltage V _d decreases, and finally V _d = V _d
^* Controlled by *.

The load device LAD is, for example, a known PWM inverter-driven induction motor, and exchanges power with a DC capacitor _Cd , which is a current and voltage source. When the load device LAD consumes power, the DC voltage V _d decreases, but by the above control, the active power P _s is supplied from the power supply and the voltage is always controlled to be V _d ≈V _d ^* . Conversely, when power is regenerated from the load device LAD (when the induction motor is regenerated),
Although V _d increases once, by regenerating active power P _s to the power source SUP, V _d ≈V _d ^* . That is, the power _Ps supplied from the power source SUP is automatically adjusted according to the power consumption or power regeneration of the load device LAD.

At this time, the input current I _s is controlled to be a sine wave in phase or in phase with the power supply voltage (during regeneration), so naturally the input power factor is 1 and the harmonic component is an extremely small value.

[Problems with Prior Art] Such conventional power converters have the following problems.

In other words, in conventional power converters, the value of the current I _s supplied from the AC power supply is adjusted so that the DC voltage V _d applied to the smoothing capacitor is approximately constant.
Although it is controlled by a PWM converter, since disturbances due to the power supply voltage enter the current control system, it becomes impossible to accurately control the input current _Is , which is not the desired goal. There is a drawback that when the input power factor is 1, it is not possible to obtain an input current with few harmonic components.

FIG. 2 shows an equivalent circuit diagram of the power supply side of the device shown in FIG. In the figure, L _s and R _s are the inductance and resistance of the AC reactor, v _s , v _c , and i _s are the power supply voltage,
It represents the instantaneous values of converter output voltage and power supply current.

From this, the voltage equation can be expressed as: However, p is a differential operator.

v _s −v _c =(R _s +L _s ·p)・i _s (3) Therefore, the block diagram of the power supply current (input current) control system is as shown in FIG.

In FIG. 3, G _I (S) is the transfer function of the current control circuit, K _c · e ^{- s} is the transfer function of the PWM converter, K _c is the comparison constant, and τ represents the dead time. Note that S is a Laplace operator.

In the control system shown in Figure 3, the power supply current i _s is set to its command value I _s ^*
However, since a disturbance due to the power supply voltage V _s is introduced, i _s = I _s ^* does not hold.

For this reason, the power supply current command value I _s ^* is given as a sine wave current synchronized with the power supply voltage V _s as shown in equation (1), but the actual flowing current i _s has a phase and magnitude that is different from the above command. It will be different from the value I _s ^* . Therefore, there is a problem in that the initial goal of input power factor=1 and reduction of harmonic content cannot be achieved.

[Object of the Invention] The present invention has been made in view of the above problems, and eliminates the influence of power supply voltage disturbance entering the power supply current (input current) control system, and improves the power supply current i _s
An object of the present invention is to provide a power conversion device that is controlled to faithfully follow the command value I _s ^* .

[Summary of the Invention] In order to achieve the above object, the present invention provides a regenerative operation in which an AC voltage is applied through a reactor, the AC input current is controlled by pulse width modulation control, and a desired DC voltage is output. a converter, a capacitor connected to the output side of the converter to smooth the DC voltage, a voltage control means for comparing the output voltage with a reference voltage to obtain a current reference, and comparing the current reference with the input current. A current control means for outputting a control signal and a disturbance compensation means for obtaining a compensation signal from the alternating current voltage are provided, and the pulse width modulation control is performed by the sum of the control signal and the compensation signal, and the input current control system is This is a power converter that suppresses the effects of power supply voltage disturbances.

[Embodiment of the Invention] FIG. 4 is a configuration diagram showing an embodiment of the power conversion device of the present invention.

In the figure, SUP is a single-phase AC power supply, L _s is an AC reactor, CONV is a pulse width modulation control converter,
C _d is a DC smoothing capacitor, and LAD is a load device. The CNV of the pulse width modulation control converter is composed of elements having self-extinguishing capability (for example, gate turn-off thyristors) _S1 to _S4 , wheeling diodes _D1 to _D4 , and DC reactors _L1 and _L2 .

In addition, the control circuit includes a transformer PT for detecting the power supply voltage, a current transformer CT _c for detecting alternating current, voltage dividing resistors R ₁ and R ₂ for detecting direct current voltage, an isolation amplifier ISO, a direct current voltage setting device VR, and a comparison circuits C ₁ to C ₃ , voltage control compensation circuit G _V (S), multiplier ML, operational amplifier OA ₁ ,
OA ₂ , current control compensation circuit G _I (S), disturbance compensation circuit
H ₀ , adder AD, carrier wave generator TRG, and gate control circuit GC are provided.

By detecting the power supply voltage V _s by the transformer PT and multiplying it by (1/V _n ) by the operational amplifier OA ₁ , a unit sine wave sin〓 ^t synchronized with the power supply voltage is obtained.

Also, divider resistors R ₁ , R ₂ and isolation amplifier ISO
A direct current voltage V _d is detected via.

The relevant DC voltage detection value V _d and the DC voltage setting device VR
The voltage command value V _d ^{* from V d *} is input to the comparator C ₁ and its deviation ε _V =V _d ^* is determined. The deviation ε _V is input to the next voltage control compensation circuit G _V (S), where it is proportionally or integrally amplified to obtain the peak value I _n of the input current command value I ^* _s .
becomes.

The multiplier ML multiplies the unit sine wave sin〓 ^t by the peak value I _n to create a command value I _s ^* =I _n ·sin〓 ^t of the input current I _s supplied from the power supply. The input current command value I _s ^* is inverted by the inverting operational amplifier OA ₂ , and the converter's AC side output current I _c (input current I _s
(inverted value of ) becomes the command value I _c ^* .

The current transformer CT _c detects the converter output current I _c , and the detected value I _c is input to the comparator C ₂ together with the command value I _c ^* . Comparator C ₂ determines the deviation ε _I
＝I _c ^* −I _c is obtained, and the following current control compensation circuit G _I
(S) is proportionally amplified. The output e _i of the current control compensation circuit G _I (S) becomes one of the input signals for pulse width modulation control.

On the other hand, the unit sine wave sin ^t which is the output signal of the operational amplifier OA ₁ is also input to the disturbance compensation circuit H ₀ and multiplied by a constant to provide a compensation value e _s . The compensation value e _s
becomes the other input signal for pulse width modulation control.

That is, the adder AD adds the output signal e _i of G _I (S) and the output signal e _s of the disturbance compensation circuit H ₀ to obtain the input signal e _i ′=e _i +e _s for pulse width modulation control. It has gained.

The carrier wave generator TRG is a triangular wave with a frequency of about 1kHz.
It generates _eT and provides a carrier wave signal for pulse width modulation control.

Comparator C ₃ converts the input signal e _i ′ and the triangular wave e _T
According to the deviation ε _T =e _i ′−e _T , the component S ₁ of the converter CONV is changed from the gate control circuit GC to
~ _S4 is giving on and off signals.

A known method is used for pulse width modulation control, and a voltage V _c proportional to the input signal e _i ′ is applied to the converter CONV
is output from. That is, its proportionality coefficient is K _c ,
If the dead time associated with pulse width modulation control is τ, then V _c =K _c ·exp(−τS)·e _i ′ (4) S: Laplace operator relationship.

The output current I _c of the converter (the inverted value of the input current I _s supplied from the power supply) is controlled by adjusting the output voltage V _c of the converter.

A difference voltage V _L =V _s −V _c between the power supply voltage V _s and the output voltage of the converter is applied to the AC reactor L _s . When V _L is positive, the power supply current I _s increases in the direction of the arrow in the figure. In other words, the converter output current I _c acts to decrease in the direction of the arrow in the figure. Conversely, when V _L is negative, the converter output current tends to increase in the direction of the arrow in the figure.

The disturbance compensation circuit H ₀ multiplies the unit sine wave sin ^t by a constant (V _n /K _c times), and the compensation value e _s of the input signal for pulse width modulation control is given as shown in the following equation.

e _s = (V _n /K _c )・sin〓 ^t ……(5) V _n : Power supply voltage peak value K _c : Converter proportional constant Therefore, converter output voltage V _c can be calculated as follows from equation (4). become.

V _c = K _c・exp(−τS)・e _i ′ =K _c・exp(−τS)・(e _i +e _s ) =K _c・exp(−τS)・e _i +exp(−τS)・V _n・sin〓 ^t ……(6) In other words, assuming that the dead time τ associated with pulse width modulation control is sufficiently small, the relationship V _c =K _c・e _i +V _s ……(7) holds. , the voltage V _L applied to the AC reactor L _s is V _L = V _s −V _c = −K _c・e _i (8), and when controlling the input current I _s , the power supply voltage V _s
become unaffected by

When the actual current I _c has a relationship of I _c ^* > I _c with respect to the specified output current value I _c ^* of the converter, the deviation ε _I = I _c ^* =
I _c becomes a positive value and increases one of the input signals e _i for pulse width modulation control via the control compensation circuit G _I (S). Therefore, the AC reactor voltage shown by equation (8)
V _L is applied in the opposite direction to the arrow in the figure, increasing the converter output current I _c in the direction of the arrow in the figure. Therefore, the actual current I _c is controlled to match the command value I _c ^* .

Conversely, if I _c ^* < I _c , V _L becomes a positive value, and
Actual current I _c decreases. That is, the actual current I _c is still controlled to match the command value I c ^* .

In this case, the voltage applied to the AC reactor L _s
V _L is related only to the deviation ε _I I _c ^* −I _c and is not affected by the supply voltage V _s .

The converter output current I _c is the input current from the power supply
The command value I _c ^{* of the converter output current is the inverse value of the command value I s *} _{of the} ^input current from the power supply. Therefore, if the output current I _c of the converter is controlled to follow its command value I _c ^* , this means that the input current I _s from the power supply is controlled to follow its command value I _s ^* . .

The DC voltage V _d of the smoothing capacitor C _d is its command value
If the above input current command value I _s ^* is given as a sine wave current synchronized with the power supply voltage V _s so as to match V _d ^* , then
The actual input current I _s also follows this and is controlled in a sinusoidal manner.

[Effects of the Invention] As described above, according to the power conversion device of the present invention, the input current I _s supplied from the power supply can be made to follow the command value I _s ^* without being affected by the power supply voltage V _s . , can be faithfully controlled, smoothing capacitor
If the above input current command value I _S ^* is given as a sine wave current synchronized with the power supply voltage V _s so that the DC voltage V _d of C _d matches its command value V _d ^* , the actual input current
I _s also follows the command value I _s ^* , and the phase delay and amplitude error are controlled to be small. Therefore, the intended purpose of keeping the input power factor of the power converter at 1.0 and reducing the harmonic content of the input current is achieved.

In addition, since the input current control is no longer subject to power supply voltage disturbances, the control compensation circuit of the current control system
This also has the advantage of simplifying the design of G _I (S), making it easier to stabilize the control system and improve response.

Note that although the embodiments of the present invention have been described with respect to a single-phase power source, it goes without saying that the present invention can be similarly applied to a three-phase power source and other multi-phase power sources.

[Brief explanation of drawings]

Figure 1 is a block diagram of a conventional power converter, Figure 2 is an equivalent circuit diagram of the power supply side of the equipment shown in Figure 1, Figure 3 is a block diagram of the power control system of the equipment shown in Figure 1, and Figure 4 is a block diagram of the power supply control system of the equipment shown in Figure 1.
The figure is a configuration diagram showing an embodiment of the power conversion device of the present invention. SUP...Single-phase AC power supply, _Ls ...AC reactor, CNV...Pulse width modulation control converter,
C _d ...DC smoothing capacitor, LAD...Load device, _S1 to _S4 ...Gate turn-off thyristor,
D ₁ ~ _{D 4} ... Wheeling diode, L ₁ , L ₂ ...
...DC reactor, PT...Transformer, CT _c ...Current transformer, R ₁ , R ₂ ... Voltage dividing resistor, ISO... Isolation amplifier, VR ... DC voltage setting device, C ₁ to C ₃ ... ... Comparator, G _v (S) ... Voltage control compensation circuit, ML ... Multiplier, OA ₁ , OA ₂ ... Operational amplifier, G _I (S) ...
Current control compensation circuit, AD...adder, _H0 ...disturbance compensation circuit, TRG...carrier wave generator, GC...gate control circuit.

Claims (1)

[Claims] 1 A converter capable of regenerative operation to which an AC voltage is applied via a reactor, controls the AC input current by pulse width modulation control, and outputs a desired DC voltage; a capacitor for smoothing voltage; a voltage control means for comparing the output voltage and a reference voltage to obtain a current reference; a current control means for comparing the current reference and the input current and outputting a control signal; and the AC voltage. 1. A power conversion device comprising: a disturbance compensating means for obtaining a compensation signal from the control signal; and performing the pulse width modulation control based on an added value of the control signal and the compensation signal.