JPH03124265A - Input current control for pwm converter - Google Patents

Abstract

PURPOSE:To prevent the deterioration of a power factor by deviating the phase of first and second current commands with respect to the phase of an AC voltage respectively by a predetermined amount. CONSTITUTION:The phase of a first current command I is shifted so as to compensate a phase difference between an AC voltage Vm and a component corresponding to the first current command (effective current command) I among the current component constituting an input current while the phase of a second current command (power source compensating current command) I is shifted so as to make a current component corresponding to the AC voltage Vm inputted into a current control loop as an external turbulence zero. According to this method, the deviation of the phase of the input current cf a PWM converter with respect to the AC voltage Vm is compensated whereby the deterioration of a power factor can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a PWM converter, and particularly to a method for controlling input current of a PWM converter.

[Prior Art] Fig. 2 is a block diagram of a PWM converter; Fig. 3 is a block diagram of a conventional example of an input current control circuit for one phase of the three-phase main switching circuit shown in Fig. 2; The figure is an input current control vector diagram.
b) is a vector diagram during an inverse transformation operation.

In Fig. 2, the main switching circuit 1 of the PWM converter has U, V, and W phase switching circuits that turn on and off connections between each phase power source of a three-phase AC power source and the load, and the input current of each phase switching circuit. are connected to the U, V, and W phase currents of the AC power supply 2 via the input reactor 3, respectively. Further, a smoothing capacitor 4 is connected to the output current of the main switching circuit 1. The U, V, and W phase switching circuits each include a transistor switching element (
(hereinafter referred to as switching elements) Sl and S2. S3 and S
4. SL, and 86 are connected in cascade, and freewheeling diodes DI, D2 . ..., D6
are connected in parallel to the switching elements S and S8, respectively.

Each phase switching circuit is controlled on/off by a power conversion circuit shown in the block diagram of FIG. In FIG. 3, a DC voltage command V specifies the output voltage of the PWM converter. The deviation c or less between o and the detected value of the actual output voltage VOC (referred to as voltage deviation) Δ■ is input to the voltage amplifier 6, and an effective current amplitude command I; is generated. The operation for one U phase will be explained below. A sine table (sine wave generator) 10 has a U-phase power supply phase voltage V. is input, and a unit sine wave sinM is generated. Effective current amplitude command■
; is multiplied by the unit sine wave sinM, and the effective current command ■,
is generated. Furthermore, for the reasons described later, the power supply voltage compensation current amplitude command (hereinafter referred to as power supply compensation amplitude command)
Set the EMF to the command Ic. P and unit sine wave si
By multiplying by nM, a power supply voltage compensation current command (hereinafter referred to as power supply compensation current command) ICEMP is generated. The effective current command (2) is vector-subtracted from the power supply compensation current command I CEMF to generate a current command I rsf. The subtracter 9 calculates the current command I rat and the actual current input to the PWM converter (hereinafter referred to as converter input current). A current deviation ΔI is generated by vectorwise comparison. The current amplifier 7 inputs the current deviation Δt and generates a converter input voltage command (hereinafter referred to as voltage command) Vrer.

Hereinafter, the potential of each phase input current of the PWM converter with respect to the neutral point of the AC power supply voltage is referred to as the converter input voltage ■. It is written as The AC power supply has a vector difference VL between the AC power supply phase voltage (hereinafter referred to as AC voltage) V and the converter input voltage Vc.
(Reactor voltage) corresponding to the converter input current T.

Output.

If the inductance of the input reactor is L, then the converter input current is from the reactor voltage vL.

The transfer function that generates is 1/(Ls).

This input current Ic(s) is fed back to the subtracter 9, and a voltage command V rsf is generated so as to compensate for the current deviation Δ■. In the block diagram of FIG. 3, the PWM converter input voltage V. When generating the idle voltage VL, the alternating current voltage (i) acts as a disturbance, and the effective current command Ir and converter input current (i) are affected accordingly. There is a difference between In order to cancel this disturbance, as described above, the power supply compensation current command I ctwr is vector subtracted from the effective current command. When the load current IL>O (in the direction of the arrow in Fig. 2), the smoothing capacitor 4 is discharged, so the output voltage VOC tends to decrease, and as a result, the DC voltage command V COM> V o
c, voltage deviation ΔV = V COM −V Dc
> O, and the result is ■;>0. The effective current amplitude command ■; is multiplied by a unit sine wave having the same phase as the AC voltage V to become an effective current command Ir. Converter input current 1c
is this effective current command 1. Since it is controlled to follow the AC voltage Vm, it becomes approximately in phase with the AC voltage Vm, resulting in a forward conversion operation.

A vector diagram during this forward conversion operation is shown in FIG. 4(a).

When the load current IL<O, the smoothing capacitor 4 is charged, so the output voltage VDC tends to increase, and as a result, the DC voltage command V COM < V oc becomes, and the voltage deviation ΔV=V C
OM −V oc<O, and as a result, the effective current amplitude command x;<o. The effective current amplitude command I7 is multiplied by a unit sine wave having the same phase as the AC voltage V, and becomes an effective current command Ir. Since the converter input current Ic is controlled to follow this effective current command, the AC voltage v,
, the phase is almost reversed, resulting in an inverse conversion operation. A vector diagram during this inverse conversion operation is shown in FIG. 4(b). Like this P
WM converter is capable of forward and reverse power conversion.

In Fig. 4, in order to simplify the explanation, in the case of forward conversion operation (Fig. 4 (a)), the converter input current ■ and the AC voltage V, , are shown to be in phase. As shown, generally vffi and ■. There is a phase difference. Similarly, in the case of the inverse conversion operation (FIG. 4(b)), the phase difference between V and Ic is not 180''. Therefore, the absolute value of the power factor is generally not strictly 1.

The operation of the input current control circuit shown in FIG. 3 is as follows.

From the block diagram in Figure 3, converter input current ■. Calculating the relationship between this and the effective current command ■1 results in the following equation.

(2) When the phase switching circuits that generate . Here, GPWM is a scalar quantity. (Actually, it is difficult to completely linearly convert the voltage command V r 11 f into the converter input voltage V due to the effects of the upper and lower short circuit prevention periods of the main switching circuit elements, but it is possible to prevent upper and lower short circuits by using high-speed switching elements. Keep the period as short as possible,
Further, it is assumed that the carrier frequency is sufficiently high, that V ref is converted almost linearly to vc, and that there is no delay in PWM conversion. ) The first and second terms on the right side of equation (5), that is, the transfer function of the current amplifier 7 here, are set as -G1(S), and the voltage command V r
Converter input voltage from sf■.

(PWM control circuit 8 in FIG. 3 and P
When the WM signal is input, the converter input voltage is a current component corresponding to the active current command Ir and the power supply compensation current command ICEMP, respectively.

Now, the proportional gain of current amplifier 7 is g! When the −th lag time constant is T, the transfer function G r (s) is expressed by the following equation.

In addition, as described above, the power supply compensation current command I CEMP
is a signal input to compensate for the AC voltage V, , which acts as a disturbance, and is used for power factor 1 control (controlling the phase difference between the AC voltage and the converter input current to 0° or 180°). In this case, it is applied in phase with the alternating current voltage V, so it is set so that the following equation holds true.

Vm(s)=g+ GPWM ICEMF
(9) Formula (8) is replaced by formula (6), and formula (8), (
9) into Equation (7) and further set s=jω, it is about 100 μsec, L is about several mH, and ω=2π・60
Therefore, TlO2(GPWM9g, (12)). Therefore, the following equation holds true.

Therefore, ■ for ■. The gain G1 and phase difference ψ1 of , are expressed by the following equations.

Similarly, the gain G2 and phase difference ψ2 of I C2 with respect to I CEMP are expressed by the following equations.

Normally, each Gpwyzgr is about several dozen, and T is a mathematical formula (
16), the parts corresponding to the independent variables of the arctangent function on the right side of (18) are mutually reciprocals and have opposite signs, so as is clear from the trigonometric formula, ψ, (ω) and ψ2(ω) The difference is always 90° regardless of ω. Here, in the case of the ideal state ωL < G p y g 1 (+9) T = O (19a), G+=1. ψ1=○, G2=O, converter input current ■. and effective current command.

The phase difference with that is Oo. In the case of power factor 1 control, the AC voltage □ and the active current command are in phase when the power is on. Therefore, the alternating voltage ■, and the converter input current ■. is in phase with . Figure 4(a) shows the solid patterns 1 to 1 in such a case.
This is a diagram. Further, in the case of power factor 1 control, during regeneration, the effective current command (2) and the AC voltage (2) are in opposite phases. Therefore, the converter input current factor. is the AC voltage vffl
It is in reverse phase with respect to FIG. 4(b) is a vector diagram in such a case. However, equation (19).

If the condition expressed in (19a) is not met, the converter input current ■. Each current component 1c+,
There are equations (16) and (18) between Icz and AC voltage V.
A phase difference shown by is generated.

In this way, in the case of power factor 1 control, the effective current command Ir changes in phase with the AC voltage (during power) or in opposite phase (during regeneration), so the vector diagram is shown in Figure 5. You will be able to do it.

FIG. 5(a) is a vector diagram during power travel, and FIG. 5(b) is a vector diagram during regeneration. When the power is on, the converter input current ■. The phase of is delayed or advanced with respect to the effective current command Ir. During regeneration, the phase of converter input current Ic always lags behind the effective current command.

[Problem to be solved by the invention]

The above conventional PWM converter input current control method is as follows:
Converter input current engineer. Since the phase of converter input current ■ is shifted from the effective current command ■. There is a problem in that the phase of the AC voltage (1) is not in phase with the AC voltage (1) during power generation, and is no longer in opposite phase during regeneration, resulting in a decrease in the power factor.

Such a delay of Ic+ itself, and a vector E leading by 90° from Ic+ or 1 2 . Among the phase shifts caused by
), the larger the inductance L of the input reactor 3 is, and the smaller GPWM-gl is, the larger the value becomes.Furthermore, the magnitude G2 of the vector Ic+, which leads 90" from ICI, is the current The larger the first-order lag time constant T of the amplifier 7 is, the larger it becomes.

The object of the present invention is to reduce the inductance and reduce the converter input current even when the time lag time constant T is large and Gp and gl are small. follows the effective current command (■) without any phase difference, so that the AC voltage (V) and the converter input current (V). An object of the present invention is to provide an input current control method for a PWM converter that does not cause a decrease in power factor due to a phase shift.

[Means for Solving the Problems] The input current control method for a PWM converter of the present invention includes: a first current amplitude command corresponding to a voltage deviation of a DC voltage output from a PWM converter with respect to a set voltage; and an AC voltage of an AC power supply. A first current command is generated by multiplying a first sine wave signal having the same frequency as the second current amplitude command set to compensate for the AC voltage acting as a disturbance, and the AC voltage. A second current command is generated by multiplying a second sine wave signal having the same frequency as the first . For the third current command formed by combining the second current designation,
In order to compensate for the current deviation of the input current of the PWM converter, an input voltage of the PWM converter that is PWM-controlled is generated corresponding to the current deviation, and a PWM converter is generated from the AC power supply via the input reactor in accordance with the input voltage. An input current control method for a PWM converter that controls the input current input to the converter, the method comprising: determining the position of the AC voltage and the component corresponding to the first current command among the current components constituting the input current; Shifting the phase of the first current command so as to compensate for the phase difference, and setting the current component corresponding to the AC voltage input as a disturbance to the current control loop included in the input current control method to zero. , the phase of the second current command is shifted.

[Function] The phase of the first sine wave signal is advanced to compensate for the phase difference with the AC voltage, and the first current command (effective current command) of the advanced phase is changed to the original first current command. , it is possible to make the phase of the input current II+ of the PWM converter corresponding to the leading phase of the first current command (1) in phase with the original first current command (2). Therefore, the phase of the input current generator 3° is in phase with the alternating current voltage vm when the power is in the dark, and is in the opposite phase during the regeneration, resulting in power factor control of 1.

Furthermore, by advancing the phase of the second sine wave signal and using the second current command (power supply compensation current command) ISEMF of the advanced phase in place of the original second current command ICEMP, the phase of the advanced phase can be increased. Second current command I: The input current ■3□ corresponding to EMF can be set to O. the result,
PWM converter input current for AC voltage
. The phase shift of is compensated, and power factor unity control is realized.

[Example] Next, an example of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram of an input current control circuit for one phase for implementing the input current control method for a PWM converter according to the present invention.

The deviation (voltage deviation) ΔV between the DC voltage command V COM and the detected value of the actual output voltage VOC is input to the voltage amplifier 6, and an effective current amplitude command (first current amplitude command) F is generated. In addition, the sine table (sine wave generator) 12 inputs the AC voltage ■Y output from the AC power supply, and inputs the AC voltage v
1 and has the same frequency ω and angle a + = ta
A unit sine wave (first sine wave signal) sinMl whose phase is advanced by n-'(ωL/g IGPWM) is generated.

The active current amplitude command ■; is multiplied by the unit sine wave sinMl, and the active current command of the leading phase (the first current command of the leading phase) ■? is generated. The sine table (sine wave 5 6 generator) 13 is an AC voltage V. input, has the same frequency ω as the AC voltage, and angle α2='jan-'
A unit sine wave (second sine wave signal) sinM2 whose phase is advanced by (ωT) is generated. The unit sine wave sinM2 is the set power supply compensation amplitude command (second current amplitude command)
By multiplying by ICEMP, an advanced phase power supply compensation current command (second advanced phase current command) cm is generated. The current command I tar is generated by vector subtracting the power supply compensation current command I3□ from the effective current command I. A subtracter 9 calculates the input current of the PWM converter from the current command Iref. vector subtraction, the current deviation ΔI
generate. The current amplifier 7 inputs the current deviation Δ and generates a voltage command V r a f. The PWM control circuit 8 oscillates a PWM carrier, and generates a voltage command V r with the carrier.
Generate a PWM signal by comparing II f;
It is output to the main switching circuit 1 of the PWM converter.

The main switching circuit 1 turns on and off the connection between the input end and the output end of the PWM converter to generate a converter input voltage Vc. As a result, the converter input current is proportional to the reactor voltage Vt. is generated. Converter input current Ic is fed back to subtracter 9.

Next, the operation of this embodiment will be explained.

First, at = tan-' (ωL/g+ Gpwll)
(20) α2 = t a n−'ωT
(21) is set.

The converter input current Ic is determined from the block diagram of FIG. 1 as shown in the following equation.

Here, by substituting equation (8) into equation (23) and setting it as Sjω and setting it as TLω2(gIGPwl, I), and assuming that the first and second terms of equation (24) are respectively ■21°G2 , IS2 are expressed by the following equation.

The converter input current 11C+ corresponding to the leading phase active current command ■ becomes in phase with the original active current command (active current command having the same phase as the AC voltage vm) ■.

Moreover, I3□ is expressed by the following formula.

The numerator of Gz is transformed from formula (21) as follows.

Vm(1+jωT) Icgupg+GpwM(V,
, [+ω2T2)"2-IcEMrg+GpwM))e
ja' (26a) Since ω2T2<1, the formula (
22), I3□=O Therefore, Ic is in phase with Ir, and converter input current ■. is an AC voltage V when the power is on. The PWM converter of this embodiment performs power factor 1 control because the phase is the same as that and the phase is opposite during regeneration.

〔Effect of the invention〕

As explained above, the present invention has the following features: By shifting the phase of the second current command by a predetermined amount with respect to the phase of the AC voltage, the inductance of the input reactor,
And, the influence of the current follow-up delay caused by the first-order delay time constant of the current amplifier can be completely removed, and power factor control can be achieved. Even when the power factor is smaller than 1, there is an effect that the converter input current can follow the AC voltage at a predetermined phase angle, and the power factor can be controlled to a desired value.

[Brief explanation of drawings]

9 0 Fig. 1 is a block diagram of an input current control circuit for one phase for carrying out the input current control method of a PWM converter of the present invention, Fig. 2 is a block diagram of a PWM converter configuration diagram, and Fig. 3 is a block diagram of a PWM converter input current control circuit. A block diagram of a conventional example of an input current control circuit for one phase of the three-phase main switching circuit shown in the figure, Figure 4 is a vector diagram of input current control, and Figure 4 (a) is a diagram for forward conversion operation. ,
Fig. 4(b) is a vector diagram during inverse conversion operation, Fig. 5 is a vector diagram explaining the phase relationship between the converter input current and AC voltage, and Fig. 5(a) is a vector diagram when b) is a vector diagram during regeneration. DESCRIPTION OF SYMBOLS 1... Main switching circuit, 2... AC power supply, 3... Input reactor, 4... Smoothing capacitor, 5... Power conversion circuit, 6... Voltage amplifier, 7... Current amplifier , 8...P
WM control circuit, 9... subtractor, 10.12.13...
・Sign table. (a) (b) Figure (b) Figure

Claims (1)

[Claims] Multiplying the first current amplitude command corresponding to the voltage deviation of the DC voltage output from the PWM converter with respect to the set voltage by the first sine wave signal having the same frequency as the AC voltage of the AC power supply. a second current amplitude command set to compensate for the alternating current voltage acting as a disturbance and a second sine wave signal having the same frequency as the alternating voltage; to generate a second current command, and for a third current command formed by combining the first and second current commands,
In order to compensate for the current deviation of the input current of the PWM converter, an input voltage of the PWM converter that is PWM-controlled is generated corresponding to the current deviation, and a PWM converter is generated from the AC power supply via the input reactor in accordance with the input voltage. In an input current control method for a PWM converter that controls the input current input to a converter, the phase difference between a component corresponding to the first current command and the AC voltage among the current components constituting the input current is determined. shifting the phase of the first current command so as to compensate, and zeroing out the current component corresponding to the alternating current voltage input as a disturbance to a current control loop included in the input current control method; An input current control method for a PWM converter, characterized in that the phase of the second current command is shifted.