Current-supplied inverter for island or network operation

(10) Number: AT 409 570 B (19)

REPUBLIC

AUSTRIA

Patent office

PATENT LETTERING

<td> (21)</td><td>Application number:</td><td>A 1503/97</td>

<td> (22)</td><td>Registration date:</td><td> 09.09.1997</td>

<td> (42)</td><td>Start of the patent term:</td><td> 15.01.2002</td>

<td> (45)</td><td>Issue date:</td><td> 25.09.2002</td>

(51) mt ci 'H02M 7/538 (56)

Citations:

(73)

Patent holder:

US5113334A US5151851A

ZACH FRANZ DIPL.ING. DR.TECHN. A-1180 VIENNA (AT).

(72) Inventor:

HIMMELSTOSS FELIX DIPL.ING. DR.TECHN. WR. NEUDORF, LOWER AUSTRIA (AT). EDELMOSER KARL DIPL.ING. DR.TECHN. VIENNA (AT).

ZACH FRANZ DIPL.ING. DR.TECHN.

VIENNA (AT).

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<td>CQ</td><td> (57)</td>

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POWER SUPPLIED INVERTER FOR ISLAND AND GRID OPERATION

The invention relates to a converter circuit (Fig. 1) for converting DC voltages (U_DC) into alternating currents with the help of a transformer (Tr) with a central tapped primary winding, a split inductance (La, L_b) and two bidirectional circuit breakers (Si &amp; Dsi, S2 &amp; DS2)

A conventional 50 Hz mains transformer can be used for the transformer. In contrast to transformers operated with switching frequency, this leads to a cost reduction. Depending on the application, the input DC voltage can be supplied by a battery, solar cells, fuel cells, or by rectification from the single or multi-phase network, or can be obtained by rectifying the output voltage of alternators or three-phase generators and subsequent, possibly only coarse filtering.

In the circuit discussed here, an output alternating current of any form (mean value must be zero) is generated from an input direct voltage by means of a corresponding control. The field of application of the circuits in question is, for example, the feeding of electrical energy into a single-phase alternating voltage network.

<img file="AT409570B_D0001.tif" />

DVR 0078018

AT 409 570 B

The invention relates to a converter circuit (FIG. 1) for converting direct voltages into alternating currents with the aid of a transformer with a central tapped primary winding, a split inductance and two bidirectional power switches.

In contrast to the solution presented here, the converter circuits currently used in technology, such as those disclosed in US Pat. No. 5,113,334 or US Pat. The solution according to Fig. 1 a decisive advantage.

Depending on the application, the input DC voltage can be supplied by a battery, solar cells, fuel cells, or by rectification from the single or multi-phase network, or by rectifying the output voltage of alternators or three-phase generators and subsequent, possibly only coarse filtering.

Particularly advantageous in the circuit discussed here is the fact that output currents of different polarity can be generated from an input direct voltage and alternating currents of any shape (mean value must be zero) can also be generated by appropriate control. A particularly interesting field of application of the circuits in question is the feeding of electrical energy obtained, for example, with solar cells into a single-phase alternating voltage network. The generation of sinusoidal currents with a definable frequency for controlling alternating current machines, for example, is also of practical importance. Further applications are the implementation of highly dynamic controls for actuators and power amplifiers.

The mode of operation of the circuit will now be discussed with reference to FIG. 2, with self-locking MOSFETs being drawn as active switches (S ^) by way of example. The body diode contained in the MOSFET is shown with an extra dashed line for clarity (D._S1, D_S.2) · If switches are used without a built-in diode, this must be added externally in order to implement the current-bidirectional switch.

For the positive half-wave in the output current (i_AC) is switched on in the driving phase S ·). The current flow on the primary side takes place from the source (U_D.c) via the transformer (Tr), the partial inductance (L_A.) and the switch (Sf). The current rises. If the switch (SO is now switched off, freewheeling takes place as shown in FIG. 2.b, ie the current commutates into the second partial inductance (L_B.) and the freewheeling diode (Ds2). The direction of flow in the transformer does not change between Fig.2.a and Fig.2.b. During the generation of the positive half-wave of the output current, the two states alternate.

For the negative half-wave in the output current (i_AC) is in the driving phase S₂ switched on. The current flow on the primary side takes place from the source (U_DC) via the transformer (Tr), the partial inductance (L_B.) and the switch (p₂). The current increases in amount. If the switch (p₂) is switched off, freewheeling takes place as shown in FIG_A.) and the freewheeling diode (D_S.i). The flow direction in the transformer does not change between Fig.2.c and Fig.2.d. During the generation of the negative half-wave of the output current, the two states alternate.