JPS5854745B2 - Inverter device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The purpose of the present invention is to provide an economical variable voltage, variable frequency inverter device that can be operated with good characteristics over a range from the low frequency region of AC output to the rated frequency range. be.

Conventionally, in order to improve the AC voltage waveform of impark, multiplexing has been carried out by providing a transformer or interphase reactor on the inverter output side.

On the other hand, motor control is generally performed by inverter output control, and in this case, there is usually a constant relationship E/f between impark AC voltage E and frequency f, as shown by curve a in FIG.

However, when starting the motor rotation speed from zero, in reality, a voltage drop occurs due to the impedance of the power supply line or the impedance of the motor coil. You may have to start from Eo.

In such a case, when the frequency becomes 11 or less, E/f increases, and in the multiplexing method described above, the voltage-time product applied to the output transformer or interphase reactor gradually increases, causing the iron core to become saturated and operation to be interrupted. becomes impossible.

For this reason, in the past, in order to obtain a three-phase output, for example, imparks 1uplu' were directly connected in series as shown in Figure 2.
Similarly, inverters 1 v + 1 v' constituted a V phase, and inverters Iw and 1w' constituted a W phase.

However, in such a configuration, inverter 1 u'
, 1v'.

Since the circuit potential of 1 w' is different, DC power supply 3
cannot be shared, and separate DC power supplies are required for each.
The number of DC power supplies has increased.

Furthermore, since the inverters 1 u', 1 v', and 1 vv' are single-phase, the ripple of the DC side current becomes large, and the capacitor 4C of the filter 4 needs to have a large capacity.

Therefore, a capacitor of large capacity is required for each DC power supply, and the capacitor capacity of the entire device becomes enormous.

In addition, to improve the waveform, it is necessary to operate with a voltage phase difference between the imparks connected in series, but in this case, the phase difference between the output voltage and load current of each impark becomes large, and the amount of reactive power increases. This will reduce the utilization rate of the inverter.

The present invention solves the problems of such conventional devices.The present invention is aimed at solving the problems of such conventional devices. This makes it possible to reduce the number of DC power supplies by reducing the capacity of the inverter DC filter capacitor without saturating the transformer on the inverter output side, and to easily adjust the voltage waveform against frequency changes in the range from zero to the rated frequency. The present invention provides an inverter device that can be improved.

This will be explained in detail below using examples.

FIG. 3 shows an embodiment of the invention.

1 is a non-insulated inverter, and the inverter arm 11P.

Consists of 11N, 12P, and 12N single-phase bridge connections.

The inverter arm 11P is composed of an anti-parallel connection of a cyrisk 11PT and a diode 11PD.

Thereafter, other inverter arms are constructed in the same manner.

Note that the commutation circuit of each impark arm is not clearly shown for simplicity.

AC terminals 3 and 4 and DC terminals 5 and 6 of inverter 1 are not electrically insulated.

For this reason, it is called a non-isolated inverter.

2 is an insulated impark, and the inverter arm 21P, 2
It consists of a single phase bridge connection of 1N, 22P, and 22N.

The AC side of the single-phase bridge circuit is connected to AC terminals 8 and 9 of the inverter 2 via a transformer 7.

10.13 indicates the DC terminal of the inverter 2.

In the inverter 2, AC terminals 8 and 9 and DC terminal 10
．． 13 is electrically isolated by a transformer 7.

For this reason, it is called an isolated inverter.

Inverters 1 and 2 are connected in parallel on the DC side and connected to a common DC power supply 15 via a filter 14.

AC terminals 3 and 8 of inverters 1 and 2 are connected so that the AC sides of inverters 1 and 2 are connected in series, and a combined AC output is obtained from terminals 4 and 9.

FIG. 4 shows operating waveforms of the embodiment of FIG.

The operation of the present invention will be explained below based on FIG.

Fig. 4a shows the operation when the frequency f shown in Fig. 1 is in the region f<fl and B/V is larger than the ratio EN/fN of the inverter rated voltage EN and the rated frequency fN. There is.

Ea is the AC voltage of inverter 1, Eb is the AC voltage of inverter 2, Bab is the combined output voltage of inverters 1 and 2,
■□ indicates the output current, and ■L' indicates the current on the primary side (impark bridge side) of the transformer 7, respectively.

The table at the bottom of the figure is for explaining the energization state of the inverter arm, for example at time t in Figure 4a.

to tl are inverter arms 11N and 12N. 21
This shows that P and 22P are energized.

Nowadays side t.

Looking at the state from to tl, since the inverter arms 11N, 12N, 21P, and 22P are energized, the voltages Ea and Eb are all zero, and the combined output voltage Eab
also becomes zero.

Also, since the current ■L' is negative, the inverter arm 21P
The diode 21PD is energized, and the thyristor 22PT is energized in the inverter arm 22P.

Next, at time t1, the inverter arm 11N becomes 11P.
Translocated to.

Therefore, the voltage Ea has a positive value.

On the other hand, in the inverter 2, since the inverter arms 21P and 22P continue to be energized, the voltage EblI'i continues to be zero.

Therefore, voltage Eab becomes equal to Ea.

Note that the current ■L' is reversed at time t2, so the diode 2
Thyrisk 21 instead of 1PD and thyristor 22PT
PT and diode 22PD are energized to continue the energized state of inverter arms 21P and 22P.

Next, at time t3, the impark arm 12N commutates to 12P and makes the voltage Ea zero.

On the other hand, invert arm 21P. Since 22P continues to be energized, both E b and Eab become zero.

Next, at time t4, inverter arms 11N, 12P, 21
P, 22P are energized, Ea is set to a negative value, and Eb is set to a negative value.
to zero.

As a result, Eab2Ea becomes a negative value.

At time t5, inverter arms 11N, 12N, 21P
, 22P is turned on again at time t.

Return to the state of In this way, inverter arm 21P
, 22P is always energized, transformer 7
The primary winding of the transformer 7 is maintained in a short-circuited state via the impark arm, and a current of 1 L' is caused to flow through the primary side in response to the load current IL. is not applied, so there is no worry that the iron core will become saturated.

Next, the frequency f increases and the frequency f shown in Fig. 1 becomes f≧11.
Then, E/f=EN/fN, and there is no need to worry about saturation of the iron core of the transformer 7, so the inverter 2 is also operated to output the output voltage.

FIG. 4b shows the operating state in this region, where the inverter is operated with a voltage pulse width γa1 and the inverter 2 is operated with a voltage pulse width γb.

Time t. During tl, inverter arm 11N, 1
Since 2N, 21N, and 22N are energized, Ea=Bb
=Bab20.

Between time t1 and t2, inverter arms 11P and 12
N.

Since 21N and 22N are energized, Ea=Bab, which is a positive value, and Eb=0.

Next, between time t2 and t3, the inverter arm 11P,
12N, 21P.

22N is energized, Ea and Eb are positive values, E a
b=E a +Eb.

Between time t3 and t4, inverter arm 1'IP, 1
2N, 21P, and 22F are energized, and Ea=Eab becomes a positive value, and Eb=0.

Between time t4 and t5, impark arms 11P, 1
2P, 21P, and 22P become energized, E a = E b
=E a b =0.

Between time t and t6, inverter arms 11N and 12
P, 21P.

22P becomes energized, Ba=Eab, negative value, Eb=
It becomes O.

Between time t6 and t7, the impark arms 11N and 12
P, 21N, and 22P are energized, and Ea and Eb have negative values, so that Ea b=Ea+Eb.

Between time t7 and t8, inverter arm 'IIN, 1
2P, 21N, and 22N become energized, and a negative value becomes Eb=o at Ea and Eab.

Next, at time t8, time t.

The state returns to the same state as Ea=Eb=Eab=o.

Thus, the voltage pulse widths γa and γb of the inverter 1°2
By controlling the output voltage Eab, it is possible to control the output voltage Eab.

Since the inverter 2 is an insulated impark type in which the AC terminals 8 and 9 and the DC terminals 10 and 13 are insulated by the transformer 1, the inverter 1 and the inverter 2 can share the Ifi filter 14 and the DC power supply 15.

Therefore, since the DC currents of the inverters 1 and 2 are combined, the ripple of the DC current is reduced, and the capacitance of the capacitor 14C of the filter 14 can be reduced.

Furthermore, the number of DC power supplies 15 and filters 14 is reduced.

The effects of the present invention will be even greater when applied to multiphase impark.

FIG. 5 shows an embodiment in which the present invention is applied to a three-phase inverter.

1 is a non-insulated three-phase impark, and the inverter arm U
P.I.

It consists of a three-phase bridge connection of UNl, VPI, VNI, WPI, and WNl.

The DC side of the impark 1 is connected to a DC power source 15 via a filter 14 .

2 is an insulated impark inverter arm UP2, U
It consists of a 3-phase bridge connection of N2, VF6, VH2, WF2, and WN2.

The inverter 2 has a DC input side and an AC output side electrically insulated by a transformer 7.

The DC input side of the inverter 2 is connected to a common DC power supply 15 via a filter 14 common to the impark 1 .

The AC sides of inverters 1 and 2 are connected in series, and the U phase, ■ phase,
W-phase output is obtained, but at this time non-isolated inverter II/i
Connect so that it is on the neutral point side of 3-phase AC U, V, and W.

In addition, inverters 1 and 2 are operated with a phase difference 30', and the phase voltages of inverter 1 are set to E, U, and E1.

BIW is the secondary voltage of transformer 7 of inverter 2.
When +E2V and E2W, the configuration is such that they are synthesized in a vector relationship as shown in Figure 6, and when the voltage magnitude is E1U = E1V = E1W = 1/2, E2U = E
Construct 2 tons so that the ratio is 2■2E2w-engine.

With this configuration, multiplexing can be performed without reducing the utilization rate of the inverter.

Next, the operation in the embodiment shown in FIG. 5 will be explained.

First, if the frequency is low and E/ f >E N/ f N, inverter arm UP2 of inverter 2. VP2
゜WF2 or inverter arm UN2. Any three pairs of arms of VN2°WN2 are always kept energized so that the primary side of the transformer 7 is short-circuited via the impark arm.

By doing this, there is no need to worry about the iron core of the transformer 7 becoming saturated.

On the other hand, invert 1 controls the output voltage by pulse width control, but since the output frequency flI'i is in the low region, 1
Since the number of commutations of the inverter per cycle can be increased, the number of voltage pulses in one cycle is increased by high-frequency pulse width control, and the width of each voltage pulse is controlled to obtain a sine wave voltage. I can do it.

Next, the output frequency increases and f>f, so E/f=EN/
When entering the region of fN, the inverter 2 also generates a voltage and operates so that the vector relationship shown in FIG. 6 is established.

As a result, the third, fifth, and seventh output voltages and their multiples of high frequencies are removed.

As described above, according to the present invention, even when E/f becomes large at low frequencies, there is no fear of saturation of the iron core of the transformer 7, and a good output voltage waveform can be obtained over the entire output frequency range. The utilization rate will also be good.

In the embodiment shown in Fig. 5, one set of two insulated inverters is used, but if multiple insulated inverters are connected in series on the AC side and operated in multiplex mode, an even better output voltage waveform can be obtained. .

Furthermore, a feature of the present invention in a multi-phase inverter is that the capacitance of the DC filter can be significantly reduced.

In the embodiment shown in FIG. 5, since the non-insulated inverter 1 is placed on the neutral point side, it can be made into a three-phase inverter.

Furthermore, since the inverter 2 is of an insulated type, the impark circuit can be constructed into a three-phase configuration regardless of the circuit potentials of the U-phase, ■-phase, and W-phase, and at the same time, the DC filter 14 and the DC power supply 15 are non-insulated. Can be used in common with Model Impark 1.

Therefore, the AC voltage of impark 1 and inverter 2 is 30'
By operating with a phase difference, a combined 12-phase operation is achieved, and the DC current IJ-tuple is greatly reduced.

Thus, the DC filter 14 is not for 12-phase operation, and the filter capacitors 14C are much smaller in width than those for single-phase operation in FIG. 2, and the number thereof can be reduced to 1/6.

In addition, by connecting the non-insulated type inverter to the neutral point side of the multi-phase AC, it is possible to create a multi-phase impark, so even if a DC filter is installed independently in the non-insulated type impark 1, a filter capacitor is required. It becomes possible to downsize.

Figure 7 shows an inverter device for supplying power to a three-phase load in which three phases are electrically isolated, and the U phase of non-isolated inverter 1 is connected to inverter arms UPI, UNl.
, UPI', and UNI', and similarly, the V and W phases are also connected to inverter arms VP1. ■N1. V.P.
1′, VN1′ and WPl.

It is composed of WN 1 , WP 1', and WN 1'.

Similarly, the insulated impark 2 has impark arms UP2゜UN2, UP2', UN2', VF6, VN2,
VP2'.

It is composed of VN2', WP2, WN2, WP2', WN2' and a transformer 7, and the transformer 7 insulates the AC side and the DC side.

AC output is U-U', V-V'. From W-W, the signal is sent to a three-phase AC load (not shown) whose phases are insulated.

In such a configuration, in the low frequency range 1, the inverter 2 has impark arms UP2, UP2', VF6,
VP2', WP2.

WP2' or UN2, UN2', VN2, V
N2'WN2. By always keeping the WN2'(7)6 arm energized, the primary winding of the transformer 7 is operated so as to be short-circuited via the inverter arm.

As explained above, the present invention connects a non-isolated inverter and an isolated inverter in series on the AC side, and in the low range of output frequency f, the primary side of the isolated impark transformer is connected to the inverter arm. is short-circuited through the inverter, and the output voltage is obtained by a non-isolated inverter, and the output frequency
As the voltage increases, the isolated inverter and the non-isolated inverter jointly generate an output voltage to perform multiplexed operation.

As a result, even if characteristics such as a large E/f are required in a low output frequency region, there is no need to worry about transformer iron core saturation or a drop in inverter utilization, and multiplexing in any combination becomes possible.

Furthermore, since both the non-insulated inverter and the isolated impark can be made multi-phase or use a common DC power supply, the capacitor of the DC filter can be made smaller, and the number of DC power supplies and DC filters can be reduced.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing the characteristics of an inverter device, Fig. 2 is a schematic diagram showing a conventional impark device, Fig. 3 is a schematic configuration diagram showing an embodiment of the present invention, and Fig. 4 is a diagram similar to Fig. 3. The operating waveforms of the embodiment are shown, with FIG. 4a showing the operating waveforms in a low frequency range, and FIG. 4b showing the operating waveforms in the high frequency range. FIG. 5 is a schematic configuration diagram showing another embodiment of the present invention, and FIG. 6 is a voltage vector diagram in the embodiment of FIG. FIG. 7 is a schematic configuration diagram showing still another embodiment of the present invention. In the diagram, 1...Non-insulated impark, 2...
・Insulated inverter, 3, 4, 8.9...AC terminal, 5゜6.10,13...DC terminal, 7.
...Transformer, 11P, 11N, 12P, 12N,
21P, 21N, 22P, 22N... Inverter arm, 14... Filter, 14C...
...Filter capacitor, 15...DC power supply,
UP I, UP I', VP1VPI', WP1
, WP1', UNI, UN1', VNl. VNI', WNl, WN1', UP2. UP2',V
F6°VP2', WF2. WP2', UN2. UN2'
, VN2゜VN2', WN2, WN2'...
Both show inverter arms. LN・・・Inverter rated AC voltage, E a s
E b y E a b t EI Uy E 1
y +EIWI E2U j E2V I E2W”
"" Impark AC voltage, IL, I□'...Impark AC current. Note that the same reference numerals in the drawings indicate the same or equivalent parts.

Claims (1)

[Claims] 1. An inverter circuit consisting of a plurality of sets of impark arms, a primary winding connected to the AC side of the inverter circuit, and one or more sets connected to the AC output circuit of the impark device. a first inverter device comprising a transformer having a secondary winding, and a DC input terminal and an AC output terminal are electrically insulated by the transformer; and an inverter comprising a plurality of sets of inverter arms. The circuit includes a second impark device in which a transformer having an electrical insulation function is not interposed between the DC input terminal and the AC output terminal, and the first impark device and the second inverter device An inverter device characterized by being connected in series on the alternating current side. 2. The first impark device and the second inverter device are configured to derive a multiphase AC output, and the second
2. The inverter device according to claim 1, wherein the inverter devices are connected in series so as to be closer to the neutral point than the first impark device. 3 An impark circuit consisting of multiple sets of inverter arms, a primary winding connected to the AC side of the impark circuit, and one or more sets of secondary windings connected to the AC output circuit of the inverter device. an inverter circuit comprising a first impark device having a transformer having a transformer and a DC input terminal and an AC output terminal electrically insulated by the transformer; and a plurality of sets of impark arms. , a second inverter device having no intervening transformer having an electrical insulation function between the DC input terminal and the AC output terminal and connected in series with the first inverter device on the AC side; The impark device and the second inverter device are operated with alternating current output at a variable frequency, and in a low frequency region, the primary winding of the transformer of the first inverter device is connected via the impark arm. An impark device characterized by operating in such a way that it is short-circuited. 4 The first inverter device and the second inverter device are configured to derive a multiphase AC output, and the second inverter device
4. The inverter device according to claim 3, wherein the inverter devices are connected in series so as to be closer to the neutral point than the first inverter device.