JPS586391B2 - Inverter touch - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improvements in inverter devices, and in particular provides a new and improved control device for high frequency modulation inverter devices.

In inverter devices that control output voltage or output current, there is a so-called high-frequency modulation method in which a semiconductor switch of the inverter itself is controlled on-off at a frequency higher than its output frequency.

This method is simple because it does not require a separate output adjustment means such as a chopper or a variable voltage rectifier.

However, in this high frequency modulation method, there is a problem of output modulation frequency ripple.

An object of the present invention is to provide an inverter device whose characteristics are improved by providing a current detector in the positive side or negative side DC circuit of the inverter device.

More specifically, it is an object of the present invention to provide a novel modulation control method for reducing the modulation frequency ripple.

More particularly, it is an object of the present invention to provide a simple inverter device suitable for speed control of AC motors (including pulse motors).

FIG. 1 is a connection diagram showing an embodiment of the present invention. In the figure, a plurality of sets of semiconductor switch connections are connected in parallel between the terminals of a DC power supply 1, and each set has two semiconductor switches 2a to 2f. form a prizge inverter.

Each series connection point R, S, T is connected to an alternating current load 4, for example an alternating current motor.

In addition, diodes 3a to 3f forming separate paths (feedback or free circulation paths) for the load current are provided corresponding to the semiconductor switches 2a to 2f, respectively, to form a main circuit.

Furthermore, in the embodiment shown in FIG. 1, a smoothing reactor 9 is connected in series between the positive terminal P of the DC power supply and the DC input terminals of the semiconductor switches 2a, 2c, and 2e.

The first signal generator 5 for controlling conduction sequentially at the period of the output frequency is, for example, a ring counter triggered by a pulse train signal P, and the respective outputs a to f are approximately equal to the conduction of the semiconductor switches 2a to 2f. Decide on periods and their order.

In one embodiment of the present invention, the odd-numbered output signals a, c, and e of the first signal generator are directly connected to the positive semiconductor switch 2a.
, 2c, 2e are determined.

For example, the period is such that conduction is performed for 1/3 period and 1/3 period.
There is a phase difference of three periods each.

Alternatively, it is made conductive every 1/2 period and has a phase difference of every 1/3 period.

Alternatively, conduction is made for every 5/12 period and there is a phase difference for every 1/3 period.

In any case, in practice, in a three-phase bridge-connected inverter, conduction is carried out every 1/3 to 1/2 period, and
/3 periods of phase.

On the other hand, the negative-side semiconductor switches 2b, 2d, and 2f convert the even-numbered output signals b, d, and f of the first signal generator 5 and the conductive signal X of the second signal generator 6 into logical storage elements γb, respectively. γd,
Continuity is controlled by logical product via γf.

The even-numbered output signals b, d, and f have the same conduction time width as the odd-numbered output signals a, c, and e, respectively, and have a phase difference of 1/6.
Only the period is off.

On the other hand, the second signal generator 6 is used to issue a conduction/non-conduction command in the second period, and is used when generating at least both conduction and non-conduction signals periodically (for example, when controlling the output voltage to within the DC power supply voltage). case), it operates with a period substantially shorter than the output period, ie, 50 periods of the first signal generator.

However, if the smoothing reactor 9 is large, the cycle may be long.

When the output voltage is set to zero, a non-conduction command is continuously generated, and when the output voltage is maximized, a conduction command is continuously generated.

The second signal generator 6 that generates the second conduction control signal can use any time ratio control means, such as a pulse width modulator or an on-off controller using a comparator.

For example, when controlling the output current, the first
As in the embodiment shown in the figure, the input current detector 8 provided on the positive side common DC input circuit may detect the human power current to control the on time or off time of the second signal generator.

Now, the operation of the above embodiment will be explained in more detail.

In the case of 1/3 cycle energization control, when the first signal generator 5 issues a conduction signal for 173 cycles, that is, when supplying power to the load 4 mainly with an energization width of 120°, the positive semiconductor switches 2a, 2e, 2c is always energized, and the negative side semiconductor switches 2b, 2
One of d and 2f is always on-off controlled by the second signal generator.

Now, FIG. 2a shows a circuit state during a 1/6 cycle in which the semiconductor switch 2a is energized and the semiconductor switch 2b is controlled to be turned on and off.

That is, outputs a and b of the first signal generator 5 are in a conduction command state, the semiconductor switch 2a is energized, and the semiconductor switch 2b is controlled on-off (pulse width modulation) in response to the second signal X. ing.

When the R phase 4R and T phase 4T of the load 4 are supplied with power, when the semiconductor switch 2b is on, power is supplied as indicated by the solid line ion, and when the semiconductor switch 2b is off, the line iof
The output current (or output voltage) is controlled in response to the on-off signal X of the second signal generator 6 through the diode 3b as indicated by the arrow f.

Similarly, when other semiconductor switches are activated and power is supplied in other phases or with other polarities, a circuit state as shown in FIG. 2a is formed by successive semiconductor switches and successive loads.

Above, the operation waveform diagram in 1/3 period energization control is shown in the fifth figure.
As shown in the figure.

In the same figure, A and C indicate the conduction command periods of the first signals a to f, C indicates the on-off command of the second signal
3a shows the sections in which each of the parts 3a is energized.

The same <<H is the load voltage of the R phase, that is, the voltage that appears between the windings of the R phase 4R only when power is being supplied through each of the semiconductor switches 2a to 2f, and this voltage is synchronized with the second signal X.

Furthermore, the waveform shown by the dotted line is the voltage during the overlap period tu, which is a high load terminal voltage because the voltage is determined by the energization of the diode that does not pass through the smoothing reactor.

In the case of 1/2 period energization control, when the first signal generator 5 outputs a conduction signal for 1/2 period, three output signals out of the six output signals a to f are always conduction commands and other signals are Three output signals issue a non-conduction command,
This is a case where these states are sequentially cycled every 1/6 cycle.

In this case, there is a fourth state in which two of the positive semiconductor switches 2a, 2c, 2e and one of the negative semiconductor switches 2b, 2d, 2f are energized, and one of the positive semiconductor switches and one of the negative semiconductor switches are energized. and a second state in which two of them pass.

As a representative example of the first state, semiconductor switches 2a and 2
FIG. 2b shows a case where the semiconductor switch 2b is controlled to be turned on and off when the semiconductor switch 2b is energized.

In this case, the input current I is shunted to the loads 4R and 48 via the semiconductor switches 2a and 20, respectively, and flows to the load 4T.

On the other hand, if the output signal X of the second signal generator 6 is an ON command, power is supplied from the DC power supply 1 via the semiconductor switch 2b,
If it is an off command, the current flows back through the diode 3b.

That is, the loads 4R and 48 in parallel and the load 4T in series are combined and subjected to on-off control in the same manner as in FIG. 2a.

FIG. 2C shows the circuit state in the second state that follows the first state, that is, when the output signals b, c, and d of the first signal generator 5 are conduction commands and the others are non-conduction commands. .

During the weight period immediately after the transition from the state shown in FIG. 2b to the state shown in FIG.
Weight current iu flows.

When this weight period ends, the diodes 3a and 3f become non-conductive.

During the weight period, the current in the load 4S increases from I/2 to ■, the current in the load 4R changes to positive I/2, and the current in the load 4T decreases from ■ to I/2.

Thus, both the semiconductor switches 2b and 2d are controlled on and off by the second signal X, and the output voltage or output current is controlled.

In this case, the series body of loads 4T and 4R and the series body of load 4S are integrated, and the same control as in FIG. 2a is performed.

In FIG. 2B, the output terminals R and S are at the same potential, and in FIG. 2C, the output terminals R and T are controlled to the same potential.

In the case of 5/12 period energization control, this is the first period in which two successively connected output signals of the output signals of the first signal generator issue a conduction command, and the first period in which three successively connected output signals issue a conduction command. This is a case where the second section and the second section appear alternately.

That is, each output signal issues a conduction command for 5/12 periods, and each output signal has a phase difference of 1/6 period.

When such control is performed, the three circuit states shown in FIG. 2 appear one after another.

For example, the mode changes as shown in FIG. 2a→FIG. 2b→FIG. 2a, where the first signals b and C are in a conduction command state→FIG. 2C...

In the embodiment shown in FIG. 1, the circuit states shown in FIG.
The output can be controlled by the second signal X.

2 Now, as is clear from the embodiment in FIG. 1, according to the present invention, in the case of FIG. 2 a, the circuit current is not immediately cut off when the transistor 2b is turned off.
Since a current path passing through the diode 3b is formed, the instantaneous output voltage value is in a full voltage application state and a zero voltage state (reflux state).

On the other hand, in the conventional inverter control method in which the circuit current is cut off when the transistor is off, the inverter consists of a positive total voltage state and a negative total voltage state, and the output voltage is controlled by the time ratio of the positive total voltage state and the negative total voltage state.

Therefore, the output voltage ripple of the present invention is smaller, and the output current ripple is also smaller.

Furthermore, only one side of the semiconductor switch is required for on-off control using high frequency.

Furthermore, the number of semiconductor switches that are constantly on-off controlled at high frequency is one (or two), and the number of switching operations is small, so switching loss is small.

In particular, when using Cyrisk as the semiconductor switch 2, the commutation loss is reduced, and this effect is extremely significant.

Similarly, the thyristor arc extinguishing means can be simplified.

Also, since one side is high frequency on-off control, the other low frequency conduction control (first signal period control) side is not high frequency on/off control, so a smoothing reactor can be provided in the common manual DC circuit of the semiconductor switch.

Therefore, it is possible to further reduce the output ripple and conversely reduce the number of high frequency switching operations.

The conventional method of installing an AC smoothing reactor on the AC output side resulted in a drop in power factor and output, and there were limits to smoothing performance.

In this invention, the DC smoothing reactor 9 can be made arbitrarily large.

Therefore, on-off control can be performed using the second signal of any frequency without being restricted by the AC output frequency.

In other words, on-off control using the second signal has the same effect as providing an apparently independent DC chopper on the DC input side, and it can also be achieved by using a semiconductor switch for the inverter. By combining these functions, we have achieved functional integration.

FIG. 3 is a circuit connection diagram showing another embodiment of the present invention.
This is an example in which the non-modulation side semiconductor switch is a thyristor and the modulation side semiconductor switch is a transistor.

In the figure, 21a, 21c) 21o are Sairisk, 2
2a, 22o, and 22o are diodes, and 23 is an arc-extinguishing capacitor.

In this way, the semiconductor switch can be used for high-speed switches and low-speed switches, respectively.

FIG. 4 is a diagram showing another embodiment of the present invention, in which a common chopper 24 is provided for the modulation side semiconductor switches 21d72lb721f, and this is controlled on and off by the second signal X.

In this case, the series connection relationship of the chopper 24 to the semiconductor switches 2xb) 21d, 2if has the effect of the AND element 70.

Moreover, the semiconductor switch 21by2. When the dp21f is a thyristor, the chopper 24 can be turned off once, and the thyristors can be extinguished by turning off the chopper 24.

The logical NOT AND element 10, the monostable OR element 11, and the pulse differential element 12 are for extinguishing the arc, and the thyristor 2lb)2. When commutation is to be performed between d2 and f, that is, every time the output signal transfers between outputs b, d, and f of the first signal generator 5, the chopper 24 is turned off for a predetermined short time determined by the differential element 12. It is something to do.

As described above, according to the present invention, there is provided a plurality of series-connected bodies of semiconductor switches connected in series, which are connected in parallel between the positive and negative input terminals of a DC power supply, and the series connection point of the semiconductor switches is connected to an AC In the bridge-connected semiconductor switch device which serves as an output terminal, a first switch that determines the AC output frequency by periodically and sequentially controlling conduction of either the positive terminal side semiconductor switch or the negative terminal side semiconductor switch.
a first signal generator that generates a signal; a current detecting means provided in a DC circuit through which the sum of currents of a group of semiconductor switches whose conduction is controlled by the first signal flows; a first group of diodes each connected in antiparallel to a semiconductor switch whose conduction is controlled by a signal; a second group of diodes each connected in antiparallel to the other semiconductor switch; and a DC input detected by the current detection means. a second signal generator that generates a second signal for pulse width modulation control in accordance with the current; and a logic circuit that controls conduction of the other semiconductor switch based on a logic signal of the first signal and the second signal. By providing this, high frequency modulation with small ripples in the output voltage can be performed.

Furthermore, by inserting a current detection means into the DC input circuit,
A single current detection means can respond to an AC load current and detect continuous current.

[Brief explanation of the drawing]

FIG. 1 is a connection diagram showing an embodiment of the present invention, FIG. 2 is a partial state circuit diagram for explaining the operation of FIG. 1, and FIG.
FIG. 4 is a connection diagram showing other embodiments of the present invention, and FIG. 5 is a diagram showing an example of operating waveforms of the present invention. In the figures, the same reference numerals indicate the same parts. In the figure, 1 is a DC power supply, 2 is a semiconductor switch, 3 is a diode, and 4 is a load. 5 is a first signal generator of the first period, 6 is a second signal generator (on to
off modulation signal) generator.

Claims (1)

[Claims] 1. In a bridge-connected semiconductor switch device that has a plurality of series-connected semiconductor switches connected in parallel, which are connected in parallel between the positive and negative input terminals of a DC power supply, and the series connection point of the semiconductor switches is an AC output terminal. , a first signal generator that periodically and sequentially controls conduction of either the positive terminal side semiconductor switch or the negative terminal side semiconductor switch to generate a first signal that determines the AC output frequency; A current detection means provided in a DC circuit through which the sum of the currents of the semiconductor switches whose conduction is controlled by the signal flows, and a current detection means which is connected in antiparallel to the semiconductor switch whose conduction is controlled by the first signal through the current detection means. a first diode group connected in antiparallel to the other semiconductor switch, and a second diode group connected in antiparallel to the other semiconductor switch, and generates a second signal for pulse width modulation control according to the DC input current detected by the current detection means. and a logic circuit that controls conduction of the other semiconductor switch using an AND signal of the first signal and the second signal.