JPH0748951B2 - Power converter - Google Patents

Description

Description: TECHNICAL FIELD OF THE INVENTION The present invention relates to a power converter including a DC voltage source that receives power from an AC power source and a load device for the DC voltage source.

[Technical background of the invention] As a load device using a DC voltage source as a power supply, there are a pulse width modulation control (PWM) inverter + induction motor, or a DC chopper device + DC motor. When a battery is used as this DC voltage source, there is not much problem, but when a DC voltage is obtained from a commercial power source through an AC / DC power converter (converter), reactive power and harmonics generated on the commercial power source side have recently become a problem. It has become.

In order to solve this problem, a method of inserting a pulse width modulation control (PWM) converter as an AC / DC power converter between a commercial power source and a DC voltage source (capacitor) (Japanese Patent Application No. 57-171).
886) has been proposed.

FIG. 5 shows a configuration diagram of a conventional power converter using a PWM converter as an AC / DC power converter.

In the figure, SUP is a single-phase AC power supply, L _S is an AC reactor, CONV is an AC power converter (converter), Cd is a DC smoothing capacitor, and LOAD is a load device. Converter CONV includes an element with a self-extinguishing capacity (for example, a gate turn-off thyristor) S ₁ to S _4, consists wheeling diodes D ₁ to D ₄ and a DC reactor L ₁ ~L _2, the element S ₁ to S ₄ In order to control the value of the AC side voltage V _C , the well-known pulse width modulation control is performed. That is, the converter CONV is a pulse width modulation control (PW) when viewed from the DC voltage source (capacitor) Cd.
M) It becomes an inverter, in which case the AC power supply SUP side can be regarded as a kind of load.

In this conventional power converter, the current I _S supplied from the AC power supply is adjusted so that the voltage Vd of the DC voltage source Cd becomes almost constant.
It is capable of 4-quadrant operation according to the power demand from the load device LOAD.

The input power factor is controlled so that the input current I _S is always in phase with the power supply voltage V _S and becomes 1.

In addition, the input current I _S is controlled in a sinusoidal manner, so the harmonics are extremely small.

Is a feature.

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

The following are prepared as the control circuit. CT _C 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 setter, C _{1 to} S
₃ is a comparator, G _V (S) is a voltage control compensation circuit, ML is a multiplier, OA is an inverting operational amplifier, G _I (S) is a DC control compensation circuit, TRG is a carrier wave (triangular wave) generator, and GC is a gate. It is a control circuit.

First, the DC voltage Vd detected via the isolation amplifier ISO and the voltage command value Vd ^* from the voltage setting device VR are input to the comparator C ₁ to obtain the deviation ε _V = Vd ^* −Vd. The deviation ε _V is input to the control compensation circuit G _V (S) and integrated or amplified to become a peak value command Im of the input current I _S.

The peak value command Im is input to the multiplier ML and is multiplied by the other input sinωt. The input signal sinωt is a synchronized unit sine wave of the power supply voltage V _S = vm · sinωt, and is obtained by detecting the power supply voltage V _S and multiplying it by a constant (1 / Vm times).

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

I _S ^* = Im · sin ωt (1) The input current command value I _S ^* is inverted by the inverting amplifier OA and becomes the command value I _C ^* of the alternating current I _C supplied from the converter CONV to the power supply SUP. Hereinafter, I _C ^* will be referred to as a converter output current command value.

The converter output current I _C is input to the comparator C ₂ detected by the AC current detector CT _C. The comparator C ₂ compares the command value I _C ^* and the detected value I _C , and the deviation ε _I = I _C ^* −I _C
Is required. The deviation ε _I is calculated by the following control compensation circuit G
_It is input to _I (S), is proportionally amplified, and becomes a control input signal ei for pulse width modulation control.

The pulse width modulation control is a known method, and the carrier wave generator TRG, the comparator C ₃ and the gate control circuit GC perform the control.

That is, the carrier wave generator TRG has a triangular wave e with a frequency of about 1 kHz.
_The comparator C ₃ compares the triangular wave e _T with the input signal ei, and the gate control circuit GC outputs the gate turn-off thyristors S _{1 to} S according to the deviation ε _T = ei−e _T. ON and OFF signals are given to ₄ .

When ei> e _T , that is, when the deviation ε _T is positive, the thyristor 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 + Vd.

When ei <e _T , that is, when the deviation ε _T is negative, the thyristors S ₂ and S ₃ are turned on (at this time, S ₁ and S ₄ are turned off), and V _C
= -Vd.

Moreover, if ei is a positive value and is large, the on period of S ₁ and S ₄ is long, the on period of S ₂ and S ₃ is short, and the average value of V _C is a voltage proportional to the input signal ei. Will be normal value. Conversely, when ei is a negative value, the on period of S ₂ and S ₃ is longer than the on period of S ₁ and S ₄ , and the average value of the converter output voltage V _C is proportional to the input signal ei. The value is the load value.

That is, the output voltage V _{C of the} converter is controlled to a value proportional to the input signal ei.

Converter output current I _C (input current supplied from power supply
The inverted value of I _S ) is controlled by adjusting the output voltage V _{C of the} converter.

And the supply voltage V _S to the AC inductor L _S, the difference voltage U _L = V _S -V _C between the output voltage V _C of the converter is applied.

When V _S > V _C , 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 so as to decrease in the direction of the arrow in the figure. On the contrary, when V _S <V _C , the converter output current I _C tries to increase in the arrow direction of the figure.

For the converter output current command value I _C ^* , the actual current I _C is I
_{When C} ^* > I _C , the deviation ε _I = Ic ^* −I _C becomes a positive value and the PWM control input signal e is output via the control compensation circuit G _I (S).
increase i. Therefore, the converter output voltage V _C also increases in proportion to the input signal ei, and V _C > V _S , and the converter output current I _C increases in the direction of the arrow in the figure. On the other hand, when I _C ^* <I _C , the deviation ε _I becomes the value of the load and ei, that is, V _C is decreased, and V _C <V _S , and the output current I _C is decreased.
Therefore, the output current I _{C of the} converter is controlled so as to match its command value I _C ^* . If the command value Ic ^* is changed in a sine wave shape, the actual current I _C is also controlled in a sine wave shape following the change.

The converter output current I _C is the inverted value of the input current I _S from the power source, and the converter output current command value I _C ^* is the inverted value of the input current command value I _S ^* from the power source. Therefore, the input current I _S is controlled by following the command value I _S ^* .

Next, the control operation of the voltage Vd of the capacitor Cd will be described.

DC voltage detection value Vd by comparison supply C ₁ and its command value Vd ^*
To compare. When Vd ^* > Vd, the deviation ε _V is a positive value,
The input current peak value Im is increased via the control compensation circuit G _V (S). The input current command value I _S ^* is given by a sine wave in phase with the power supply voltage, as shown in equation (1). Therefore, assuming that the actual input current I _S is controlled to I _S = I _S ^* as described above, when the peak value Im is a positive value, the active power P _S shown by the following equation is a single phase. It is supplied from the power supply SUP to the DC capacitor Cd via the converter CONV.

P _S = V _S × I _S = Vm ・ Im ・ (sinεt) ² = Vm ・ Im ・ (1-cos2εt) / 2 (2) Therefore, the energy P _S・ t is 1/2 CdV in the DC capacitor Cd.
It is stored as d ^{2, and} as a result, the DC voltage Vd rises.

On the contrary, when Vd ^* <Vd, the deviation ε _V becomes a negative value, and the peak value Im is decreased via the control compensation circuit G _V (S) until Im <0. Therefore, the effective power P _S becomes a negative value, in turn, the energy P _s t is regenerated to the power supply from the DC capacitor Cd. As a result, the DC voltage Vd drops and is finally controlled to Vd = Vd ^* .

The load device LOAD is, for example, a known PWM inverter drive induction motor or the like, and exchanges electric power with a DC capacitor Cd that is a DC voltage source. If the load device LOAD consumes power, the DC voltage Vd drops, but by the above control, the active power P _S is supplied from the power supply and is always controlled to Vd = Vd ^* . Conversely, when power is regenerated from the load device LOAD (when the induction motor is regeneratively operated), Vd rises once, but by regenerating the active power P _S to the power supply SUP, Vd ≈ Vd ^* Becomes. That is, the load device LOAD
The power P _S supplied from the power supply SUP is automatically adjusted according to the power consumption or power regeneration of the power supply.

At this time, since the input current I _S is controlled to have a sine wave having the same phase as the power supply voltage or an opposite phase (during regeneration), the input power factor = 1 and the harmonic component is of course a very small value.

[Problems of Prior Art] Such a conventional power conversion device has the following problems.

That is, in the conventional power converter, the current I _S supplied from the AC power supply is in phase with the power supply voltage V _S so that the DC voltage Vd applied to the smoothing capacitor is almost constant (input power factor =
Although the sine wave of 1) is controlled (the harmonics are small), the current control is always accompanied by a phase delay, and the current command value I _S ^* does not match the actual current I _S. It was difficult to operate with the input power factor of 1, which is the desired goal.

FIG. 3 shows a current control waveform by the conventional device. The broken line shows the current command value I ₁ ^* , and the solid line shows the actual current I _S. Due to the control delay, the actual current I _S lags behind the command value I _S ^* by the phase angle φ. Therefore, the actual current I _S does not have the same phase as the power supply voltage V _S, and the input power factor also becomes delayed, which delays reactive power from the power supply and increases the installed capacity of the power supply system.

[Object of the Invention] The present invention has been made in view of the above problems, and compensates for the phase delay of the current control, and the power supply current I _S to the command value thereof.
An object is to provide a power conversion device controlled so as to faithfully follow I _S ^* .

[Summary of the Invention] In order to achieve the above object, the present invention connects an AC power supply, a pulse width modulation control converter connected to the AC power supply via an AC reactor, and a DC side of the pulse width modulation control converter. Smoothing capacitor, a load device using the smoothing capacitor as a voltage source, a DC voltage control circuit that detects the DC voltage of the smoothing capacitor and controls the DC voltage to a value according to a reference voltage, and an output signal of the DC control circuit. An input current control circuit that controls a current supplied from the AC power supply according to the above, a compensation circuit that outputs a compensation signal for the voltage of the AC power supply and a voltage drop of the AC reactor, and an output signal of the input current control circuit. Is provided with an adder for obtaining the control input signal of the pulse width modulation control converter by adding the compensation signal to the It is a power conversion device in which the supplied current I _S is controlled so as to faithfully follow the command value I _S ^* .

[Embodiment of the Invention] FIG. 1 is a main circuit configuration diagram showing an embodiment of a power converter of the present invention.

In the figure, SUP is AC current, L _S is AC reactor, CONV is pulse width modulation control converter, Cd is DC smoothing capacitor,
LOAD is a load device.

FIG. 2 is a block diagram showing an embodiment of the control circuit of the apparatus shown in FIG.

In the figure, C ₁ and C ₂ are comparators, G _V and G _I are control compensation circuits, A _{1 to} A ₃ are adders, ML ₁ and ML ₂ are multipliers, OA _{1 to} OA ₄ are operational amplifiers, S / C
Is a sine / cosine converter, and PWM is a pulse width modulation control circuit.

Detecting a power supply voltage V _S by the converter or the like, an operational amplifier OA ₂
By multiplying by (1 / Vm), a unit sine wave sinωt synchronized with the power supply voltage can be obtained.

The DC voltage detection value Vd and its command value Vd ^* are input to the comparator C ₁ to obtain the deviation ω _V = Vd ^* −Vd. The deviation ω _V is input to the next voltage control compensation circuit G _V , and is proportionally amplified or integratedly amplified to become the peak value ΔIm of the input current command value I _S ^* .

Incidentally, in order to prevent the DC voltage Vd by the abrupt change in the load current I _L varies greatly, the load current I _L equivalent Imo is added to the peak value ΔIm of the input current command value. Operational amplifier OA ₁
And adder A ₁ is used for that.

That is, the output Im = Imo + ΔIm of the adder A ₁ becomes the peak value of the actual input current command value.

The multiplier ML ₁ uses the unit sine wave sinωt and the peak value signal.
Input current Is supplied from the power supply is multiplied by Im
Command value I _s ^* = Im · sin ωt is created.

The input current I _S is detected by the current transformer CT _S and compared with the command value I _S ^* by the comparator C ₂ . The deviation ε _I
= I _S ^* −I _S is input to the next current control compensation circuit G _I , inverted and amplified (here, G ₁ is a proportional element only for simplification of explanation), and the pulse width modulation control circuit PWM Input signal e
It will be one of i. The pulse width modulation control circuit PWM is known, and for example, a 1 kHz triangular wave (carrier wave) and the input signal ei
Are compared and the ON / OFF signals of the elements that constitute the converter CONV are generated. The AC side output voltage V _C of the converter CONV generates a voltage proportional to the input signal ei.

_{V C E ≒ K C · ei} : K C whereas in a proportional constant, a unit sine wave sinωt synchronized with the power supply voltage V _S is converted into a unit cosine wave cosωt by sine / cosine converter S / C.

The multiplier ML ₂ has the unit cosine wave cosωt and the input current high value.
By multiplying by Im, the compensation signal V _L ′ represented by the following equation is generated via the operational amplifier OA ₄ .

V _L ′ = −Im × (ωL _S / K _C ) · cosωt where ω is the angular frequency of the AC power supply, L _S is the inductance value of the AC reactor, and K _C is the conversion constant of the PWM converter.

The unit sine wave sinωt forms the power supply voltage compensation signal V _S ′ through the operational amplifier OA ₃ .

V _S ′ = (V _m / K _C ) · sin ωt These two compensation signals V _s ′ and V _L ′ are added to the output signal of the current control compensation circuit G _I by adders A ₂ and A ₃ and pulse width modulated. The following input signal ei is given to the compensation circuit PWM.

ei = −K _I · ω _I + V _S + V _L ′ where −K _I is the transfer function of the current control compensation circuit.

The operations of the DC voltage control and the input current control have been described in detail in the conventional device, so please refer to them.

Further, the operation and effect of the compensating component V _S ′ for the power supply voltage are described in detail in Japanese Patent Application No. 58-151508, so please refer to it. That is, simply explaining, the power supply voltage V _S acts as a kind of disturbance in controlling the input current. In order to cancel this, a power supply voltage V _S is generated in advance as the AC side voltage V _C of the converter CONV, and then the input current I _S is controlled to match the command value _S ^* , The effect of V _S can be eliminated.

Here, the compensation method in the case where the actual current I _S is controlled to be slightly delayed from the command value I _S ^* after the compensation for the power supply voltage V _S is performed will be described in detail.

FIG. 3 shows the waveforms of the input current command value I _S ^* and its actual current I _S , and the ripples are omitted. Fourth
The figure shows the voltage-current vector diagram on the power supply side at this time.

In FIG. 4, V _S is the power supply voltage and V _L is the AC reactor L _S
, V _S is the AC side output voltage of the converter,
I _S ^* represents the input current command value, and I _S represents the input current.

The converter output voltage V _C is represented by the vector difference between the power supply voltage V _S and the AC reactor applied voltage V _L.

V _C = V _S −V _L The AC reactor applied voltage V _L has the following relationship with the input current I _S.

V _L = jωL _S I _{S In} the case where only the compensation V _S for the power supply voltage V _S is added, the applied voltage V _L of the AC reactor L _S is given from the current control circuit.

That is, the deviation between the current command value I _S ^* and the actual current I _S ε _I = I _S ^* −I
_It amplifies _S and inputs it to the PWM control circuit to generate an amount corresponding to V _L from the converter, and V _L ≈ K _C · K _I · ε _I. K _C is the conversion constant of the converter.

Therefore, the deviation ε _I = ΔI _S is required to generate V _L, and as a result, the input current I _S is always delayed by the phase angle φ with respect to the command value.

The present invention is configured such that the power supply voltage V _S and the AC reactor applied voltage V _L are generated in advance as the output voltage V _C of the PWM converter in a feedforward manner, and the current deviation for generating the V _L is generated. ε _I = ΔI _S is unnecessary.

In FIG. 2, the input signal ei of the PWM control circuit is ei = -K _I · ε _I + V _S ′ + V _L ′ as described above.

V _S ′ = (Vm / K _C ) · sin ωt causes the converter to generate an amount corresponding to the power supply voltage V _S, and V _L ′ = − (ω _{L S} / K _C ) · Im × cos ωt
Generates a voltage equivalent to the AC reactor applied voltage V _L from the converter.

Therefore, the output signal -K _I · ε _I from the current control circuit does not need the element for generating _VL . That is, the deviation ε _I = 0 in a steady state (when the peak value Im of the input current command value L _S ^* is constant), and the phase difference φ of the actual current I _S with respect to the command value I _S ^* becomes zero. When the peak value Im changes and the actual current I _S has a different value with respect to the command value I _S ^* , ε _I ≠ 0 and the feedback control controls I _S = I _S ^*. The same as before.

Although the single-phase power source has been described above, the same applies to the three-phase or multi-phase power source. Especially in the case of a multi-phase power source, it goes without saying that it is easy to create a unit cosine wave (for one phase) cosωt for a unit sine wave (for one phase) sinωt.

[Effects of the Invention] As described above, according to the power converter of the present invention, it becomes unnecessary to include the AC reactor applied power in the output signal from the current control circuit, and the current command value I _S ^* The phase delay of the actual current I _S disappears. That is, the smoothing capacitor Cd
When the DC voltage Vd of gave the input current command value I _S ^* to match the command value Vd ^* as the sinusoidal current synchronized with the power supply voltage V _S, the actual input current I _S is also the command value I Control is performed by faithfully following _S ^* , which enables control without phase delay. Therefore, the intended purpose of keeping the input power factor of the power converter at 1.0 and reducing the input current harmonics is achieved.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a main circuit configuration diagram showing an embodiment of a power conversion device of the present invention, FIG. 2 is a configuration diagram showing an embodiment of a control circuit of the device of FIG. 1, and FIG. Is a current waveform diagram for explaining the operation of the conventional device and the device of the present invention, FIG. 4 is a voltage-current vector diagram for explaining the operation of the device of the present invention, and FIG. 5 is a configuration diagram of the conventional power conversion device. . SUP …… AC power supply, L _S …… AC reactor, CONV …… PWM
Converter, Cd …… Smoothing capacitor, LOAD …… Load device, C ₁ , C ₃ …… Comparator, G _V , G _I …… Control compensation circuit, A _{1 to} A ₃
…… Adder, ML ₁ , ML ₂ …… Multiplier, K _L , K _S …… Operational amplifier, PWM …… Pulse width modulation control circuit, S / C …… Sine / cosine converter.

Claims (1)

[Claims] 1. An AC power supply, a pulse width modulation control converter connected to the AC power supply via an AC reactor, a smoothing capacitor connected to the DC side of the pulse width modulation control converter, and a voltage across the smoothing capacitor. A load device as a power source, a DC voltage control circuit that detects a DC voltage of the smoothing capacitor and controls the DC voltage to a value according to a reference voltage, and a current supplied from the AC power supply according to an output signal of the DC voltage control circuit. An input current control circuit that controls the voltage of the AC power supply and a compensation circuit that outputs a compensation signal for the voltage drop of the AC reactor; and the pulse by adding the compensation signal to the output signal of the input current control circuit. A power conversion device comprising an adder circuit for obtaining a control input signal of a width modulation control converter.