JP3261952B2 - PWM converter control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pulse width modulation (hereinafter referred to as "PWM") converter connected to an AC power supply via a reactor, and a voltage control device for controlling a voltage of a load device connected to a DC output side of the PWM converter to a set value. In particular, even if voltage distortion occurs in the AC power supply, the power supply current has few harmonics,
Also, the present invention relates to a PWM converter control device suitable for controlling to a power factor of 1.

[0002]

2. Description of the Related Art A PWM converter having a power regeneration function has been put into practical use as one of devices for converting AC power into DC power. The PWM converter is designed so that the DC voltage of the smoothing capacitor connected to its DC side becomes a set value.
JP-A-60-46773 discloses a device for controlling the input current of a PWM converter in a substantially sinusoidal waveform. The current control system for controlling the input current is designed to improve the power factor without increasing the response. A control method is disclosed. FIG. 3 shows the configuration of the control circuit.

Although the PWM converter and the control circuit shown in FIG. 3 have a single-phase or three-phase configuration according to the number of power supply phases, only one phase is shown for simplicity.

In FIG. 3, 1 is an AC power supply, 2 is an AC reactor, 3 is a PWM converter constituted by using a self-extinguishing element such as an IGBT (insulated gate bipolar transistor), 4 is a smoothing capacitor, 5 is a smoothing capacitor. 4
And a PWM inverter 51 having the same configuration as the PWM converter 3, and a motor 52 driven by the PWM inverter 51.

Reference numeral 6 denotes an AC voltage detector which insulates and extracts the voltage of the AC power supply 1 and generates a unit sine wave signal e _s0 * having the same phase as that of each phase voltage of the AC power supply 1 and having the same phase.

Reference numeral 7 denotes a current detector for detecting an input current flowing to the AC side of the PWM converter 3, and 8 denotes a smoothing capacitor 4.
Is a DC voltage detector that detects the voltage of the DC voltage.

Reference numeral 9 denotes a control circuit for the PWM converter 3, which is a PWM circuit for driving the PWM converter so that the voltage of the smoothing capacitor 4 serving as a voltage source of the load device 5 is set to a set value.
An M pulse signal _Pc is output.

[0008] 10 is a gate circuit which outputs a gate signal G _p that drives the PWM converter of the self-turn-off devices receives the PWM pulse signal P _c, which is output by the control circuit 9.

Next, the function of each element constituting the control circuit 9 will be described.

First, reference numeral 901 denotes a DC voltage setting unit for instructing the voltage of the smoothing capacitor 4 connected to the DC side of the PWM converter 3, and 902 denotes a DC voltage command E _d * output from the DC voltage setting unit 901 and a DC voltage command. adding unit for determining the deviation of the DC voltage detected value E _d by the voltage detector 8, 903 voltage control section for outputting a * amplitude value I _m of the input current flowing through the AC side of PWM converter 3 as the deviation becomes zero , 90
4 inputs the unit sine wave signal e _s0 * from the amplitude value I _m * and an AC voltage detector 6 by the multiplication unit, consequently instructs the current flowing through the AC side of PWM converter input current command i _s * output I do.

[0011] 905 adding unit for determining the deviation of the actual value i _s of the input current detected from the input current command i _s * and the input current detector 7, 906 PWM as the deviation becomes zero
It is a current control unit for instructing the AC-side generated voltage of the converter.

Further, a power supply voltage compensating unit 907 receives the unit sine wave signal e _s0 * from the AC voltage detecting unit 6 and adjusts its magnitude so as to match the control system. voltage signal .DELTA.e _c * and the voltage compensation signal e _s * a adder for vector addition output from the supply voltage compensating unit 907 is, 909 carrier signal e _t consisting of a triangular wave
Carrier wave generator for generating a, 910 outputs a PWM pulse P _s by comparing the voltage signal e _c * and the carrier wave signal e _t PWM
It is a pulse generator.

From the above, the control circuit 9 is configured, and the input current flowing to the AC side of the PWM converter 3 is controlled by the following operation so that the voltage of the smoothing capacitor 4 becomes the set value.

[0014] First, the voltage E _d of the smoothing capacitor 4 is the same as the DC voltage command E _d *, shows the case where the load device 5 does not require a current. In this case, the current control unit 906
The output Δe _c * of the power supply voltage compensator 907 is zero.
, A voltage based on the voltage compensation signal e _s * is generated on the AC side of the PWM converter 3.

In this configuration, the AC side voltage of the PWM converter 3 is generated at a voltage corresponding to the AC power supply voltage, thereby canceling the disturbance entering the control system.

Next, when the load current _IL flows into the load device 5 and the voltage of the smoothing capacitor 4 drops, the voltage is controlled so as to match the DC voltage command E _d * from the DC voltage setter 901.

Firstly, direct current detection value E _d from DC voltage command E _d * and the DC voltage detector 8 from the voltage setting unit 901 are added by an adder 902, a voltage control unit 903 so that the deviation becomes zero Outputs the amplitude value I _m * of the input current flowing to the AC side of the PWM converter 3. Unit sine e _s0 * is multiplication unit 90 from the amplitude value I _m * AC power supply detector 6
4 went out together is to output the input current command i _s *.

[0018] The input current command i _s * and the actual value i _s is detected by the current detector 7 is abutted by the adder 905, the AC of the PWM converter 3 from the current controller 906 so that the deviation becomes zero Voltage signal Δe for adjusting side voltage
Output _c *.

The voltage signal Δe _c * and the voltage compensation signal e _s * are vector-added by the adder 908 to become a voltage command e _c * for indicating the AC-side generated voltage of the PWM converter.

In the PWM pulse generator 910, the voltage signal e
_c * and generates a PWM pulse signal P _s based on the carrier signal e _t from the carrier generator 909. Further, P _s is applied to the PWM converter 3 via the gate circuit 10.

As a result, a voltage based on the voltage signal e _c * is generated on the AC side of the PWM converter 3, and the input current is controlled.

[0022]

In the above prior art, the power factor can be improved without increasing the response of the control system by adding a value equivalent to the AC power supply voltage to the output of the current control unit as a compensation value. No consideration is given to a control method when a voltage fluctuation including voltage distortion occurs in the power supply 1.

That is, when the input current command is created by a unit sine wave based on the AC power supply, the waveform becomes distorted under the influence of the voltage distortion.

The input current is controlled based on the distorted input current command, and as a result, there is a problem that the current becomes distorted, that is, a current containing a harmonic component.

An object of the present invention is to provide a sinusoidal current having a power supply power factor of 1 and a small number of harmonic components without being affected by the input current even if a voltage fluctuation including voltage distortion occurs in the AC power supply. Control.

[0026]

SUMMARY OF THE INVENTION The present invention comprises a PWM converter connected to an AC power supply via an AC reactor;
In a load device using a smoothing capacitor connected to the DC side of the PWM converter as a voltage source, and a PWM converter control device that detects a DC voltage of the smoothing capacitor and controls an input current of the PWM converter so as to reach a set voltage, Voltage control means for controlling a DC side voltage to a set value; phase calculation means for detecting an AC power supply and calculating a phase synchronized with the AC power supply; amplitude value by the voltage control means; Current command calculation means for calculating an input current command from a function, current control means for controlling an input current according to the input current command, and power supply voltage compensation for detecting an AC power supply and outputting a value corresponding to the instantaneous voltage of the AC power supply Means for controlling an AC-side generated voltage of the PWM converter based on a vector composite value of an output of the current control means and an output of the power supply voltage compensating means. Providing a PWM pulse generating means. With this configuration, even when a voltage fluctuation including a voltage distortion occurs in the power supply, the power supply voltage compensating means changes the AC side voltage of the PWM converter to a PWM equivalent to the AC voltage according to the fluctuation.
And operates to output a signal for generating a converted voltage.

On the other hand, a sine-wave input current command which is synchronized with the AC power supply and does not depend on the voltage fluctuation is issued from the current command calculating means, and the current control means controls the AC side voltage of the PWM converter so that the current according to the current command flows. To output a signal for adjusting.

Therefore, the input current is not affected by the voltage fluctuation, and the power factor according to the input current command is 1,
In addition, the current is controlled to a sinusoidal current having a low harmonic content.

[0029]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a PWM converter control device according to the present invention will be described below with reference to FIG.

Although the PWM converter and the control circuit shown in FIG. 1 have a single-phase or three-phase configuration corresponding to the number of power supply phases, similarly to the configuration shown in FIG. it's shown.

In FIG. 1, reference numeral 911 denotes an AC voltage detector 6.
The power supply phase calculation unit calculates the phase θ _s * synchronized with the AC power supply based on the unit sine wave signal e _s0 from the power supply, and obtains the phase θ _s * by the processing shown in FIG.

First, a point where the unit sine wave signal e _s0 * changes from a negative value to a positive value, that is, a zero crossing point is detected. The phase θ _s * synchronized with the AC power supply 1 is calculated by integrating a predetermined angular frequency ω * corresponding to the frequency of the AC power supply 1 at a fixed period Δt with the detection point as a base point. . Therefore, when the unit sine wave signal resulting voltage distortion to the AC power supply 1 becomes a voltage waveform e _sox * including a voltage distortion as shown in FIG. 2 also, for computed by the phase, it is affected There is no.

Next, reference numeral 912 denotes a current command calculation unit which outputs a current command i _s * for specifying an input current of the PWM converter 3. In the current command calculation unit 912, the amplitude value _Im * of the voltage control unit 903, the phase θ _s * of the power supply phase calculation unit 911, and the sine
Based on the (sin) function, a current command determined by the following equation is output.

[0034]

[Number 1] _{i s * = I m * ·} sinθ s * ... ( Equation 1) Thus, although the current command i _s * matches the phase AC power supply 1 always sinusoidal unaffected by fluctuations in the power supply voltage Command.

In the above configuration, when the voltage of the smoothing capacitor 4 connected to the DC side of the PWM converter 3 is set to the set value by the following operation, the power supply according to the input current command is not affected by the voltage fluctuation. It is controlled to a sinusoidal current with a power factor of 1 and a low harmonic content.

[0036] First, the voltage E _d of the smoothing capacitor 4 is the same as the DC voltage command E _d *, shows the case where the load device 5 does not require current, in this case, as explained in the conventional example current The output Δe _c * of the control unit 906 is zero, and a voltage based on the voltage compensation signal e _s * from the power supply voltage compensating unit 907 is generated on the AC side of the PWM converter 3.

That is, the power supply voltage compensating unit 907, which receives the unit sine wave signal e _s0 *, converts the AC side voltage of the PWM converter 3 into a voltage compensating signal e _s * for generating a voltage of the AC power supply phase and the like, and a carrier wave generating unit. by the 909 carrier signal e _t from the PWM pulse generating unit 910 PWM pulse P _s
And the PWM converter 3 via the gate circuit 10
Is added to As a result, the AC side voltage of the PWM converter 3 is set to a PWM voltage such as an AC voltage phase using the voltage of the smoothing capacitor as a voltage source.

Next, a load current flows, and the smoothing capacitor 4
When the voltage of the drops, the voltage value E _d adder from the DC voltage detector 8 and the voltage command E _d * from the DC voltage setter 901
The voltage control unit 903 matches the amplitude value I of the input current of the PWM converter so that the difference becomes zero.
_m * is output.

On the other hand, a phase θ _s * synchronized with the AC power supply 1 is output from the power supply phase calculation section 911. Current command calculator 9
At 12, an input current command i _s * indicating the input current flowing to the AC side of the PWM converter 3 is output from the amplitude value _Im * from the voltage control unit 903, the phase θ _s * from the power supply phase calculation unit 911, and the sine function. Is done.

This input current matches the phase of the AC power supply,
It becomes a sine-wave-shaped current command that is not affected by voltage fluctuations.

Next, the input current command i _s * and the actual value i _{s of the} input current detected by the current detector 7 are matched by an adder 905, and the deviation of the adder 905 from the current control unit 906 is obtained. voltage signal to adjust the AC side voltage of the PWM converter 3 so as to zero .DELTA.e _c * is output.

This voltage signal Δe _c * is the power supply voltage compensation signal e
_s * is the vector adder 908, a PWM pulse P _s is generated from the PWM pulse generating section 910 by the carrier signal e _t of the voltage signal e _c * and carrier wave generating unit 909 is added, via a gate circuit 10 To the PWM converter 3.

As a result, the AC side voltage of the PWM converter 3 generates a voltage having a magnitude based on the voltage compensation signal e _s * and the voltage signal Δe _c * for setting the DC voltage to a set value.
Input current i _s to the set value a DC voltage is controlled.

[0044] As described above, the input current i _s is not affected by the voltage fluctuation, power factor according to the input current command 1
, And is controlled to a sinusoidal current with a low harmonic content. In the embodiment, the input current command i _s * is created by the current command calculation unit 912 based on a sine wave function. However, the present invention is not limited to this. Sine wave data is stored in advance in a ROM (read only memory) or the like. Alternatively, a method of reading out according to the phase θ _s * output from the power supply phase calculation unit 911 may be used.

[0045]

According to the present invention, the voltage on the AC side of the converter is obtained by the voltage signal based on the instantaneous voltage equivalent value of the AC power supply and the voltage signal based on the input current command synchronized with the AC power supply and created using a sine function. Is adjusted, the input current can be controlled to a sinusoidal current having a power supply power factor of 1 and a small harmonic component even if a voltage fluctuation including voltage distortion occurs in the AC power supply.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of a PWM converter control device according to the present invention.

FIG. 2 is an explanatory diagram of a power supply phase calculation unit.

FIG. 3 is a block diagram showing a conventional PWM converter control device.

[Explanation of symbols]

903: voltage control unit, 906: current control unit, 907: power supply voltage compensation unit, 910: PWM signal generation unit, 911: power supply phase calculation unit, 912: current command calculation unit.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-7-200084 (JP, A) JP-A-7-231649 (JP, A) JP-A-4-285472 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) H02M 7/155 H02M 7/48 H02M 7/72 H02P 7/63

Claims (1)

(57) [Claims] 1. A pulse width modulation to control said pulse width modulation converter such that the voltage of the connected smoothing capacitor dc side of the pulse width modulation converter connected to an AC power source via an AC reactor becomes set voltage In the converter control device, voltage control means for controlling the DC side voltage to a set value, and a preset value is set based on a zero cross point of the AC power supply voltage.
Phase calculating means for calculating the phase of the AC power supply voltage by integrating the angular frequency at a constant period, a current amount of the AC power supply , the calculated phase, and a sine.
Current control means for controlling an input current according to an input current command based on a function; power supply voltage compensation means for outputting an instantaneous voltage equivalent value of the AC power supply; output of the current control means and the power supply voltage compensation means A pulse width modulation converter control device, comprising: a pulse width modulation pulse generation means for controlling an AC-side generated voltage of the pulse width modulation converter based on the output of the pulse width modulation converter.