JPS61154481A - Distributing and controlling method for ignition pulse - Google Patents

Abstract

PURPOSE:To carry out overall stable follow-up control, by distributing and controlling pulse with delays, only when the polarity of output current is in the first range. CONSTITUTION:Delays are set by multi-vibrators 1, 2 to prevent upper and lower group arms from being simultaneously ignited on the starting of R phase ignition pulse, and the pulse is applied to AND gates 6, 7 in order to apply the pulse to the confronting arms. In the meantime, the polarity decision circuits 8, 9 of inverter output current organized by comparators 8, 9 are set, and the polarity of R phase output current is decided. The input of the decision signal to the AND gates 6, 7 is provided, and delays are arranged to be applied to U arm and X arm, only when R phase output current is in the first specified range.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention is applicable to a variable voltage variable frequency inverter (VVVF inverter) which is a power supply device for variable speed drive of an AC motor, or to power conversion for harmonic compensation in a power system. The present invention relates to a method for controlling the distribution of firing pulses to upper and lower group arms constituting an inverter section of a voltage source inverter that is preferably used as a device.

FIG. 4 is a well-known circuit diagram showing the main circuit of a voltage source inverter (more specifically, a variable voltage variable frequency inverter VVVF for driving an AC motor).

In the same figure, the forward conversion section includes diodes D1 to D6, and the inverter section includes first group arms U and V.

It consists of W and lower group arms x, y, and z. The mamaru can arm (for example U) is used for transistors and diodes (PrB
6 and D7) from the anti-parallel connection. .

Overall, the AC input voltage is rectified by a rectifier consisting of diodes D1 to D6, and further smoothed by a smoothing capacitor C1.
TR1 is connected in series to form a chopper, a smoothing circuit consisting of a reactor L and a capacitor C2 is provided on the output side of the chopper, a freewheeling diode FWD is connected in parallel with this smoothing circuit, and the output of the smoothing circuit is Power transistors PTR2 to PTR7 and diode D are on the side.
Through an inverter section consisting of 7 to D12, the induction motor M
is connected.

Here, the power transistor PT constituting the inverter section
R2 (U), PTRs (V), PrB6 (W) are each 120 @ phase difference, PrB6 and PrB7 (X), Pr
B3 and PTRs (Y), PrB6 and PrB6 (Z) each have a phase difference of 180@ (therefore PrB7.PTR
t5. When PrB6 is also turned on and off (with a phase difference of 120 degrees, respectively), alternating current is obtained at the output terminal of the inverter.

The present invention supplies and distributes firing pulses to each phase arm (specifically, to the base of the transistor belonging to each phase arm) so that each transistor constituting the inverter section operates on and off as described above. The present invention relates to a distribution control system for ignition pulses to achieve this goal.

Note that arms U and X belong to R phase, arms V and Y belong to S phase, and arms W and 2 belong to T phase (however, R, S, and T constitute three phases. ).

[Conventional technology]

FIG. 3 is a circuit diagram illustrating a conventional firing pulse distribution control method for upper and lower group arms constituting an inverter section, taking the R phase as an example.

In the figure, 1 and 2 are monostable multivibrators (MSl, MS2), 3 is an inversion gate (INV),
4.5 is each ant game) (AND 1 pA
ND2).

It should be noted that both monostable multivibrators 1 and 2 generate an output at the falling edge of an input signal (ignition pulse having two pulses of 1 and 0).

FIG. 6 is a waveform diagram showing pulse waveforms at various parts in FIG. 3.

The R-phase ignition pulse command (a) is generated by a common method using a sine wave control signal (a) and a triangular wave modulation signal (b).

Please refer to FIGS. 3 and 6. R-phase ignition pulse command (a
), it is recognized that a U-arm pace drive signal (d) as a firing pulse distributed to the U-arm and an X-arm base drive signal (e) as a firing pulse distributed to the X-arm are created. At 5°, there is a difference between the timing at which the drive signal (d) turns from on to off and the timing at which the drive signal (e) turns from off to on in relation to the time constants of monostable multivibrators 1 and 20. It will be seen from FIG. 6 that a delay period 15 has been inserted in . That is, if this delay period lS is zero, the on-state of the drive signal (d) and the on-state of the drive signal (e) overlap, and in this case, in FIG. This leads to the inconvenience of a short circuit between the two.

Therefore, in the conventional ignition pulse distribution control method, monostable multivibrators 1 and 2 are used, and their time constants are used to generate a signal between the U-arm base drive signal (d) and the X-arm base drive signal (e). In other words, a delay period ΔS was added to the delay period ΔS.

However, in such a conventional method, another problem occurs as follows. In FIG. 6, the two pulses B indicated by broken lines as the X-arm base drive signal (e) do not use a monostable multivibrator in the conventional firing pulse distribution control system, and therefore have a delay period. If ΔS were not provided, the firing pulse would naturally have occurred, but since monostable multivibrators 1 and 2 were used to provide the delay period ΔS, due to the configuration of the logic circuit, 1 would actually occur. This is a pulse that has disappeared.

Even if some ignition pulses do not actually occur, conventional voltage source inverters cannot achieve the required accuracy (the ability to make the output follow the current value set as the target). There were no practical problems in terms of accuracy (achievable accuracy).

However, in recent years, a new field of technology has emerged that attempts to use voltage source inverters not only as VVVFs, but also as power conversion devices that are directly connected to the power grid and supply power for harmonic compensation to the grid. It will be developed 5
It has become. As a result, in these new technical fields, the required precision has become even higher, and a technical situation has arisen in which conventional voltage type inverters cannot meet the requirements.

[Problem that the invention seeks to solve]

Since the present invention was conceived in view of the above-mentioned technical circumstances, the problems to be solved by the present invention are as follows:
In the method of controlling the distribution of firing pulses to the upper and lower group arms constituting the inverter section, it can be said that the aim is to further improve the accuracy of the voltage source inverter.

Therefore, it is an object of the present invention to provide an ignition pulse distribution control method that is improved as described above. As a result of studying the operation of the inverter, we found that the polarity level of the output current of the voltage source inverter falls into a first region consisting of a fixed range of upper and lower limits including zero level, and a second region where the polarity level is positive beyond the first region. and a third region of negative polarity lower than the first region, the polarity level of the output current is the same as that of the second region. When in the third region, if the R phase is present, a delay period ΔS is provided between the R phase U arm pace drive signal and the X arm base drive signal.
(The reason why it is not necessary to find out that distribution control of the ignition pulse is not necessary will be explained later), only when the polarity level of the output current is in the first region, the distribution control that causes the delay period is performed, and the 2. The accuracy of the voltage source inverter is improved by eliminating the delay period in the third region.

Next, the second. In the third region, the delay period ΔS
We will explain the reason why there is no need for distribution control to achieve this.

7 is a circuit diagram specifically showing the U arm and

Check Figures 7 and 7A. Generally, depending on the polarity of the output current of one inverter, even if firing pulses are applied alternately to the first group arm and the upper group arm, one of the arms will not fire.

In the figure, the inverter output current I is of positive polarity, but in this case, the first group arm U is conductive due to its firing pulse,
As shown in mode 1, current flows through the switching element (transistor), but when the firing pulse on the upper and lower arm U side disappears, the diode 5 on the upper group arm X side flows as shown in mode 2. Current flows through D12, and for the transistor on the upper group arm X side, the diode D1
A reverse bias is applied by the weir layer voltage of 2, and no current flows.

That is, as shown in FIG. 7A, according to the conventional method, a delay period ΔS is provided between the U-boo 4 firing pulse and the X-arm firing pulse, but even if this ΔS is set to zero, the inverter output current As long as the polarity of I is positive, the X-arm transistor will not conduct even if a firing pulse is applied, so it is meaningless to provide the delay period ΔS, and furthermore, if the X-arm is connected to the It will be understood that providing an arc pulse is in itself meaningless.

Similarly, as long as the polarity of the inverter output current I is negative, the U arm of the U arm and the X arm constituting the R phase will not conduct even if an ignition pulse is applied. Therefore, it can be seen that in this case as well, it is meaningless not only to provide the delay period ΔS but also to apply the ignition pulse to the U-arm.

Figure 8 shows the case where control is implemented to provide the above-mentioned delay period ΔS as [before improvement], and the case where it is not implemented (Δ5-0) as [after improvement]. This is a graph showing a comparison.

In the figure, it is assumed that instantaneous current control is performed to keep the inverter output current within a range between an upper limit SU and a lower limit 3L that change in a sinusoidal manner.

First, [before improvement] will be explained. The inverter output current reaches the upper limit SU at point (a), so
The ignition pulse turns from on to off.

Thereafter, the X-arm firing pulse is applied after a delay period ΔS, but since the electric current reaches the lower limit SLK at the time (b), the X-arm firing pulse turns off. Then, after a delay period of ΔS, the U-boo 4 firing pulse is turned on, so the current I finally turns upward when it passes through the lower limit SL (c), and eventually has the characteristic shown by the broken line. (1) becomes.

Next K [after improvement] will be explained. The inverter output current reaches the upper limit SU at the time (a), and the U boo 4 ignition pulse turns from on to off. Next, when the electric current reaches the lower limit SLK at point (b), [Unlike the case before improvement, there is no delay period ΔS, so the U-Boo 4 ignition pulse immediately turns on, and then at point (d). Then the current I is again at the upper limit SL
K is reached, the U-boo 4 ignition pulse turns off, and thus K
In the end, the electric current worker has the characteristic (1) as shown by the solid line.

If characteristics (1) and (II) are compared, it will be clear that the improved characteristics exhibit better followability.

〔Example〕

The present invention will now be described in detail with reference to the drawings.

FIG. 1 is a circuit diagram showing an embodiment of the present invention.

In the figure, 1.2 is a monostable multivibrator, 3 is an inversion gate, 6, 7.10 is an antagonist), 8.9 is a comparator, 11.12 is an inversion gate, and 13.14 is an inversion gate. Nantes Gate.

Note that a circuit portion P surrounded by a broken line corresponds to a circuit portion according to the conventional method.

The firing pulse command is given according to a PWM (pulse width modulation) control method as shown in FIG. 6, or according to an instantaneous control method as shown in FIG.

The circuit configuration is roughly as follows.

A delay period ΔS is created using monostable multivibrators 1 and 2 to catch the falling edge of the R-phase firing pulse and prevent simultaneous firing of the upper and lower group arms, and an AND gate 6 is used to apply this to the paired arms. Add to ゜7. On the other hand, a polarity determination circuit for the inverter output current (R phase) consisting of comparators 8 and 9 is prepared, and a first region between a constant positive voltage V+ and a constant negative voltage V- is prepared. It is determined whether the polarity level of the R-phase output current is in a second region, which is a positive region exceeding V'', or a third region, which is a negative region below V''''.

This discrimination signal is given as an input to AND gate 6.7,
The firing pulse is applied to the upper bound arm U when it is on the positive side, that is, in the second region, and to the lower bound arm X, when it is on the negative side, that is, in the third region. Also, comparator 8
. and apply it to the X arm.

Figure 2 shows that the polarity level of the R-phase output current is in the first region (V
FIG.

As can be seen in the figure, when the output current I changes rapidly from positive to negative (Fig. 2 A) or from negative to positive (Fig. 2 B), the simultaneous firing of the upper and lower group arms is delayed for a period of time. Ensure prevention with ΔS, and when it ends (point A in the diagram)
It will be appreciated that this ensures that the upper group arm or the first group arm is fired quickly.

If the first region is limited to the zero level, all positive regions above the zero level are the second region, and all the negative regions below the zero level are the third region, then the difference in discrimination by the comparator Even though the actual current is, for example, in the third region, a situation may occur in which the determined output indicates the second region.

In this case, no ignition pulse will be applied. Then, the discrimination output indicates the third region and an ignition pulse is given.
Until this point, the inverter output current becomes a cage of almost zero, and the uncontrolled state continues for a long time, resulting in poor current followability. Therefore, a certain area between ■ and ■ is prepared as the first area to avoid the above-mentioned inconvenience.
That is to say.

FIG. 3 is a waveform diagram showing operation waveforms of each part of an embodiment of the present invention over one cycle period of the R-phase output current.

In the same figure, from the output waveform of AND gate 6.7, R
In the period when the phase output current is in the first region (that is, the period TU in which the firing pulse is applied to the first group arm U and the period TX in which the firing pulse is applied to the upper group arm X overlap) , as in the conventional system, a delay period ΔS is provided to prevent short circuits between the upper and lower group arms;
It will be understood that when the R-phase output current is in the region, the delay period ΔS is not provided and good followability of the output current to the target value is achieved.

〔Effect of the invention〕

According to the present invention, in the distribution control method of firing pulses to the upper and lower group arms constituting the inverter section, the polarity level of the inverter output current falls into a first region consisting of a fixed range of its upper and lower limits including zero level; It is determined which region is located between a second region of positive polarity exceeding the first region and a third region of negative polarity below the first region, and the second region or third region is located. When in the region, a firing pulse is given only to the arm of the first group or the upper group accordingly, and when it is in the first region, a firing pulse is given alternately to the arm of the first group and the arm of the upper group. It was decided to provide a delay period so that an overlapping period in which both arms of the upper and lower groups fire at the same time would not occur.

According to K, when the inverter is required to operate at a high frequency, when the polarity level of the inverter output current is in the second or third region, there is no control delay due to the delay period, Accurate control, that is, control with good followability, becomes possible. At the same time, since no firing pulse is given to either arm of the first group or the upper group,
The loss in the ignition pulse drive circuit is reduced accordingly.

On the other hand, when the polarity level of the inverter output current is in the first region, a delay period is reliably provided to prevent the firing pulses applied alternately to the first group arm and the upper group arm from overlapping, and the output current It is possible to shorten the countless non-control times that may occur during control when transitions from positive to negative or from negative to positive.

In this manner, the present invention has the advantage that stable control with good followability is possible over the entire control of the output current of the voltage source inverter.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, and FIG. 2 is a waveform diagram showing operation waveforms of each part of the embodiment of the present invention when the polarity level of the R-phase output current is in the first region. FIG. 3 is a waveform diagram showing operation waveforms of each part of an embodiment of the present invention over one cycle period of the R-phase output current, FIG. 4 is a well-known circuit diagram showing the main circuit of a voltage source inverter, and FIG. Figure 6 is a waveform diagram showing the pulse waveforms of each part in Figure 3. Figure 7 is a diagram showing the conventional distribution control system of firing pulses for the upper and lower group arms that make up the U-arm that constitutes the R phase. 7A is a waveform diagram showing the operating waveforms of each part in FIG. 7, and FIG. 8 is an inverter output current with and without implementing the present invention. 2 is a graph showing a comparison of the quality of tracking performance with respect to the target directness. Code explanation 1.2... Monostable multivibrator, 3...
...Inversion gate, 4.5.6.7...And gate, 8.9...Comparator, 10...
...And Gate, 11.12...Reverse Gate, 13.14...Nant Gate Agent Patent Attorney Akio Namiki Agent Patent Attorney Kiyota Matsuzaki III 2WI (A )
CB No. 6! I! J JI 7 Figure M7Ali! ! l Todoroki□ avA

Claims (1)

[Scope of Claims] 1) A distribution control system for firing pulses to an upper group arm and a lower group arm constituting an inverter section of a voltage source inverter, comprising means for monitoring the polarity level of the output current of the voltage source inverter. , a first region consisting of a certain range of upper and lower limits including the zero level, a second region of positive polarity exceeding the first region, and a third region of negative polarity below the first region. When the monitoring means detects that the polarity level of the output current is in the second or third region among the regions, only one of the upper group arm or the lower group arm is connected accordingly. When the monitoring means detects that the polarity level of the output current is in the first region, the firing pulse is distributed alternately to the upper group arm and the lower group arm; Moreover, a certain first arm belonging to the upper group and a second arm belonging to the lower group and forming a pair with the first arm each receive the ignition pulse and are switched on and off. There is a delay between the timing at which the first arm turns off (or on) and the timing at which the second arm turns on (or off) so that an overlapping period in which the arms turn on at the same time does not occur when the first arm turns off (or on). A distribution control method for an ignition pulse, characterized in that it has a period of time. 2) The ignition pulse distribution control method according to claim 1, wherein the arm is composed of an antiparallel connection of a switching element such as a transistor or a thyristor and a diode. method.