JPS60128870A - Pulse width modulation converter - Google Patents

Abstract

PURPOSE:To reduce the harmonic component of an input current by controlling to modulate a plurality of pulse width modulation control converters with carrier which has a suitable phase difference. CONSTITUTION:A converter CONV1 compares an input current command value IS* with a detected value IS1, applies the deviation to a current controller G1 which converts it to a voltage command ei. A TRG1 generates a carrier and hence a triangular wave voltage of a pulse width modulation control (PWM) converter to control a converter CONV2 through a gate circuit GC1 by the amplitude relation between the command ei and the triangular voltage. A method of controlling the current of the converter CONV2 is similar. In this case, in one single phase converter, the carrier is displaced at 180 deg.C and applied, and controlled by displacing the carrier at suitable phase between the single phase pulse width modulation converters. Thus, the harmonic component of the input current can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a pulse width modulation converter capable of reducing harmonic components of an input current.

[Technical background of the invention l1II] Load 1 whose power source is a DC voltage source! The ill includes a pulse width modulation control ML (PWM) inverter + induction motor,
Alternatively, there are DC chopper devices and DC motors. There is not much of a problem when using a battery as this DC voltage source, but when obtaining DC voltage from a commercial power source via an AC/DC power converter, reactive power and harmonics generated on the commercial power source side This has become a problem in recent years.

In order to solve this problem, a method was developed in which a pulse width modulation control (P W N, 1) converter was inserted between the commercial power supply and the DC voltage source (capacitor) as an AC/DC power converter.
Japanese Patent Application No. 57-171886, etc.) have been proposed.

FIG. 1 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, LS is an AC reactor,
C0NV is an AC/DC power converter, Cd is a DC smoothing capacitor, and LOAD is a load device. Converter C0NV includes elements having self-extinguishing capability (for example, gate turn-off thyristors) S1-84. It is composed of wheeling diodes D1 to D4 and DC reactors L+ and L2, and the elements 81 to S4 are subjected to known pulse width modulation control in order to control the directivity of the AC side voltage VC. In other words, converter C0NV is controlled by pulse width modulation control (PW
M) It becomes an inverter, in which case the AC power supply SUP side can be seen as a kind of load.

This conventional power converter has a voltage V of the DC voltage source Cd.
It controls the current 1 s supplied from the AC power supply so that d is approximately constant. (1) It is capable of four-quadrant operation according to the power demand from the load device 1LoAD.

q) The input current 1s 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 1s is controlled in a sinusoidal manner,
Harmonics become extremely small.

is a feature.

The control operation of this device will be explained in detail below.

The following control circuits are available:

CTC is an AC current detector, R1 and R2 are voltage dividing resistors for detecting DC voltage, 180 is an isolation amplifier, VR is a DC voltage setter, C1-03 is a comparator, and Gv (S) is a voltage control supplement 1. ML is a multiplier, OA is an inverting amplifier, G and (S) are current control compensation circuits, TRG is a carrier wave (triangular wave) generator, and GO is a gate control circuit.

First, the DC voltage V detected via the isolation amplifier ISO
d and the voltage command value Vd' from the voltage setting device VR are input to the comparator C1, and the deviation εv=Vd'-Vd is calculated. The deviation εV is input to the control compensation circuit Gv (S),
It is integrally amplified or proportionally amplified to become a peak value command 1+n of the input current 1s.

The peak value command ll1l is input to the multiplier ML, and multiplied by the other input sinω1. The input signal sinωt is a unit sine wave synchronized with the power supply type avs = Vm - sinωt, and can be obtained by detecting the power supply voltage VS and multiplying it by a constant (1/'V m times).

The output signal @Is' of the multiplier 11ML gives a command value of the current to be supplied from the power supply, and is expressed by the following equation.

18' = I Ill ・Sin t, o t ・
...(1) The input current command value 1S-4 is the inverting amplifier O
At A, it is inverted and the power supply 5LI is output from the converter C0NV.
Command value of AC current 1c supplied to P) c%.

Hereinafter, c' will be referred to as converter output current command value.

Converter output current 1c is detected by alternating current detector CTc and input to comparator C2. , the command III I C' and the detected value 1c are compared by the comparator C2, and a deviation ε,=lc'-)c is determined. The said bias ε
1 is input to the next control compensation circuit G+(S), where it is proportionally amplified and becomes the control input signal ei for pulse width modulation control.

Pulse width modulation control is carried out by carrier wave generator TRG and comparator C3.
The control is performed by the gate control circuit GC.

That is, the carrier wave generator TRG generates a triangular wave e■ with a frequency of about 1 kHz, and the comparator C3 compares the triangular wave e with the input signal ei, and calculates the deviation ε.
According to 7=ei-C7, from the game-1 control circuit GO,
On/off signals are given to the gate turn-off thyristors 81 to S4.

When ei>e, that is, when the deviation 8 is positive, thyristors S1 and 84 are turned on (at this time, 82, S
3 is off) The AC output voltage VC of the converter becomes +Vd.

Further, when ei<eT, that is, when the deviation εT is negative, the thyristors 82 and 83 are turned on (at this time, 81.
84 is off), Vc--Vd.

Moreover, if ei is a positive value and is large, the on-periods of S1 and 84 become longer, the on-periods of S2 and 83 become shorter, and the average value of VC is a positive value with a voltage proportional to the input signal el. becomes. Conversely, when ei is a negative value, the on periods of 82 and 83 are longer than the on periods of Sl and 84, and the average value of the output voltage VC of the converter is equal to the input signal ei
It is a value proportional to , and is a negative value.

In other words, the converter is converted to a value proportional to the input signal e1. The output voltage 0 of the motor is controlled.

The output current 1c of the converter (the inverted value of the input current is supplied from the power supply) is controlled by adjusting the output voltage VC of the converter.

A difference voltage VL=VS-VC between the power supply voltage Vs and the output voltage VC of the converter is applied to the AC lick Is.

When Vs > Vc, the power supply current ■S increases in the direction of the arrow in the figure. In other words, the converter output current 1c acts to decrease in the direction of the arrow in the figure. On the contrary, VS <
When VC, the converter output current 1c works to increase in the direction of the arrow in the figure.

Actual current l for converter output current command value 1 cH
When c is in the relationship lc'> ■a, the deviation ε+
-1C''-1c is a positive value, and control compensation circuit a, (S
) to increase the input signal ei of the PWM control. Therefore, the converter output voltage Vc also increases in proportion to the input signal ei, VC>VS, and the converter output current 1c increases in the direction of the arrow in the figure. On the contrary, lc'<)
c, the deviation ε1 becomes a negative value, decreasing ei, that is, VC, and VC<V, S, and the output current 1
Decrease c. Therefore, the output current 1c of the converter is controlled to match the command value ■cH. If the command value 1 cM is changed in a sinusoidal manner, the actual current IC is also controlled in a sinusoidal manner following it.

The output current 1c of the converter is the inverted value of the input current IS from the power supply, and the command value 1c of the converter output current is
H is the inverted value of the input current command value ls' from the power source. Therefore, the input current is follows the command value 1sM and becomes l.
l11 Ill will be.

Next, the control operation of the voltage d of the DC capacitor Cd will be explained.

By comparison C1, the detected DC voltage value Vd and its command value V
Compare d masu. When Vd'>Vd, the deviation εV takes a positive value and increases the input current peak value 1m via the control compensation circuit Gv (S). The input current command value Is' is
As shown in equation (1), it is given by a sine wave that is in phase with the voltage. Therefore, as mentioned above, the actual input current IB is 1s
=ls', the above wave height value ll1
When l is a positive value, active power ps expressed by the following equation is supplied from single-phase power supply SUP to DC capacitor Cd via converter C0NV.

PS=VSXIS=Vllll 'Im' (Sill ωt) 2
=Vm-In+-(1-cos 2ωt)/2...
・(2) Therefore, the energy ps ・[is the DC capacitor Cd
i,: 3 ACd Vd 2, so that
DC voltage Vd increases.

Conversely, when Vd'<Vd, the deviation εV becomes a negative value, and the above-mentioned peak value Is
, and finally set it to lll1 minus 0. Therefore, the active power ps also becomes a negative value, and the energy pst is now regenerated from the DC capacitor Cd to the power supply. the result,
The DC voltage Vd decreases and is finally controlled to Vd -1'.

The load device 10 AD is, for example, a known PWM inverter-driven induction motor, and exchanges power with a DC capacitor Cd, which is a DC voltage source.

If the load device Lo AD consumes power, the DC voltage Vd
However, due to the above control, the effective power P from the power source decreases.
s and is always controlled to Vd:Vd''.On the other hand, when power regeneration is performed from the load device (when an induction motor is operated regeneratively), Vd increases temporarily, but the power supply By regenerating the active power ps to the SUP, it becomes Vd~Vd''. That is, load device Lo
Depending on AD power consumption or power regeneration, power supply SUP
This means that the power Ps supplied from the controller is automatically adjusted.

At this time, since the input current Is is controlled to be a sine wave in phase or in phase with the power supply voltage (during regeneration), the input power factor is -1 and the harmonic components are of extremely small value.

[Problems with the prior art] In conventional devices, when a gate turn-off thyristor is used, there is a limit to the turn-off time and a limit to the reverse blocking recovery time of the diode. This is the only thing that can be done. The same applies when using a thyristor with a forced commutation circuit. Therefore, there is a drawback that the input current (S) taken from the power supply contains many harmonics.

[Summary of the present invention] The present invention sets the frequency of the carrier wave of one pulse width modulation converter to about Ikl-12, prepares a plurality of pulse width modulation converters, and sets each converter to have an appropriate phase difference. Modulation control is performed using a carrier wave, and substantially the modulation effect is several times that of a single converter, and harmonic components of the input current are reduced by 11.

[Embodiment of the Invention] FIG. 2 is a block diagram showing an embodiment of the present invention, in which two pulse width modulation converters (PWM converters), ie, C0N
This is the case where V,1 and C0NV,2 are present. 5LJP is a single-phase power supply, and TR is a transformer with two secondary windings. The first secondary winding is connected to converter C0NV,1 via AC reactor L81. A capacitor C is connected to the DC side of the converter, and then a load device using the capacitor C as a voltage source is connected. Similarly, the second secondary winding is also connected to the AC reactor LS2, converter C0NV,
2 is connected, and its DC side terminals are connected to both ends of the capacitor C.

The operation of the embodiment will be explained using FIGS. 3 to 5. FIG. 3 is a control block diagram of converters C0NV,1 and C0NV,2. The basic idea is the same as that shown in Figure 1, but a common input current command 1s' is given to the two converters so that converters C0NV,1 and C0NV,2 handle the same power, and two independent current series control routes are used. / constitutes.

The command value V (1' of the DC voltage of the capacitor) is compared with the detected value Vd, and the deviation is given to the current control device Qv.
If the result is Is', then lsW is the input current command necessary to make the capacitor voltage match the command value. Input current command 1s+4 is DC voltage deviation Vd
It is an effective current command that has a peak value proportional to -Vd and is in phase with the power supply voltage. The input current command 18'' is given in parallel to the current control device of converter IcONV, 1 and the current control device of C0NV, 2.Converter C0NV, 1
To describe the input current command value isN and the detected value 1St
are compared, and the deviation is given to the current control device G1 and converted into a voltage command e:.

TRG5 generates the carrier wave of the PWM converter, that is, the triangular wave voltage, and the voltage command e1 and the magnitude of the triangular wave voltage,
The converter C0NV,1 is controlled via the gate circuit GC1 by a small relationship. The current control method of converter C0NV,2 is also exactly the same.

The key to realizing the present invention lies in the modulation control method of two PWM converters. Two converters C0NV, 1
The modulation method will be explained for converter C0NV,1 assuming that and C0NV,2 are in a balanced state (ISt=IS2).

FIG. 4 is a waveform showing the relationship between the voltage command 2i and the triangular carrier wave in FIG. 3. The carrier wave generator TRG1 outputs two 313-angle waves a and b having 1806 phases different from each other. By comparing the voltage command ei and the triangular wave a, a control number 1M is obtained, and the thyristor St1. Controls S12. The control signal y is obtained by comparing the voltage command 2i and the triangular wave 1) and the game
1. Thyristor 81B, St 4 via circuit GC1
control. When the voltage command 2i is positive, the input voltage of the PWM converter is as shown in the figure e0. On the other hand, when the voltage command is square, the signal x = y-1, and PW
The input voltage of the M converter is 80''.

When the control input signal e1 has a positive value, the on period of thyristor 811 is longer than the on period of thyristor 812, and the on period of thyristor 814 is better than the on period of thyristor 81B. Furthermore, the on period of thyristor S13 occurs only once during the on period of thyristor S1t, and the on period of thyristor 812 occurs only once during the on period of thyristor 814. Therefore, the following three modes exist.

(a) 811 on (S12 off).

814 on (S13 off) 14- (b) 811 on (812 off).

813 on (S14 off) (c) 812 on (811 off).

814 ON (Ss 3 OFF) In the above mode (A), the capacitor voltage Vrl is generated at the input terminal of the converter and becomes 2o-Vd.

In modes (b) and (c), the input terminals are short-circuited, so eo=o. Therefore, when the output voltage e0 is expressed in units, the input voltage of the converter has a waveform of e0 in the figure.

The input voltage e0 is always a positive value, and its average value is proportional to the voltage command 2i. The control frequency of the input voltage e0 is the control frequency of the thyristor 8.
11 to 814, that is, twice the carrier wave frequency.

When the voltage command becomes a negative value such as 2i-, the on-period of thyristor S12 becomes longer than the on-period of Sll, and the on-period of thyristor S13 becomes longer than the on-period of 814. Moreover, during the on period of thyristor S12, 814 is turned on only once, and thyristor 81
The ON period of Sl occurs only once during the ON period of B.

Therefore, the following three modes are possible.

(b) 811 on (812 off).

81s on (S14 off) (b) S52 on (S11 off).

SlB on (S14 off) (c) 812 on (Ss t off).

814 ON (S13 OFF) In the above modes (A) and (C), the input terminal of the converter is short-circuited and becomes zero, and in the mode (B), the input voltage becomes 2o=-vd. Therefore, when the converter input voltage is expressed as ψ grains, it becomes as shown in FIG. 2o'. The voltage e0- is always a negative value, and its average value is proportional to the voltage command 2i-.

In this case as well, the control frequency of the input voltage 2o=is twice the carrier wave frequency.

The modulation control method for converter C0NV,2 is also exactly the same as the method for converter C0NV,1. However, the converter C0NV.

The difference is that the phase of the triangular wave output from the carrier wave generator TRG2 when modulating with respect to the voltage command e1 is delayed by 90'' with respect to the output of the carrier wave generator TRG5, as shown in FIG. Thyristor S21.S is transmitted via gate circuit GC2 depending on the magnitude relationship of carrier wave a'.
22, and also controls the voltage command e1 and the magnitude of the carrier wave b',
Thyristors 823 and 824 are controlled by the small relationship.

As can be understood from Fig. 5, converter C0NV,1 and C0NV,2 are 90% for one input current command Is.
°Modulation is controlled with delay. Considering that within one converter, it is controlled at twice the frequency of the carrier wave as mentioned above, the current Is flowing through the primary winding of the overall transformer is essentially four times the frequency of the carrier wave. It will be controlled.

Although the example for two PWM converters was explained, n
180'/n converters are introduced, and each converter is
By performing modulation control using a carrier wave having a phase difference of , it is possible to increase the frequency of one apparent carrier wave to 2n fc <fc: 17-thyristor control frequency).

[Effects of the Invention] According to the present invention, a plurality of PWM converters are used to modulate each converter with a carrier wave having an appropriate phase difference, and the modulation effect is substantially several times that of a single PWM converter. This reduces the harmonic components of the input current.

Further, although not described in detail above, if AC to DC conversion is realized using a plurality of converters, a system with excellent control redundancy can be constructed. In other words, if one converter breaks down for some reason, disconnecting that converter will inevitably result in a slight reduction in capacity, but it will avoid a major accident in which the entire system becomes inoperable. The present invention deals with the case where the power source is a medium-phase power source, and considering that the present invention is applied to an AC train or the like, such control redundancy is an extremely important element.

[Brief explanation of drawings]

Fig. 1 is a block diagram of a conventional power converter, Fig. 2 is a block diagram showing an embodiment of the present invention, Fig. 3 is a control block diagram of Fig. 2, and Figs. FIG. 2 is a diagram for explaining the present invention in detail. SUP...power supply, TR...transformer, Ls, Lsl
. LS2...AC reactor, C0NV, C0NV. 1, C0NV, 2...Converter, Cd, C...Capacitor, R1, R2...Resistor, 180...Isolation amplifier, TRG, TRG! , TRG2...Carrier wave generator, VR...Variable resistor, Qv, G+...Control device, Ml-...Multiplier, GC, GCI, GC2...
・Gate control circuit. Applicant's agent Patent attorney Takehiko Suzue = 19- Meichi 385- →; 5

Claims (1)

[Claims] At least 2 semiconductor switching elements! A plurality of single-phase pulse width modulation converters are connected in parallel, in which two pairs are connected in series, the converters are connected in parallel to a DC voltage source, and the midpoint of the series connection is connected to a single-phase AC power source. 1
A pulse-width modulation converter that controls the control carrier waves of two sets of switching elements connected in series with a 180 degree shift in one single-phase converter, and shifts the carrier waves by an appropriate phase between the single-phase pulse-width modulation converters. .