阅读说明：本技术 Dc/dc转换器和电网反馈单元 (DC/DC converter and grid feedback unit ) 是由 A·伊滕 B·费斯勒 C·施内根布格 D·舍库林 E·霍夫曼 于 2019-07-09 设计创作，主要内容包括：一种DC/DC转换器(1),具有：-第一连接极(U1+)和第二连接极(U1-),其中在所述第一连接极(U1+)和所述第二连接极(U1-)之间存在第一直流电压(U1),-第三连接极(U2+)和第四连接极(U2-),其中在所述第三连接极(U2+)和所述第四连接极(U2-)之间存在第二直流电压(U2),-第一换向单元(2),其中所述第一换向单元(2)具有电容器(3)、二极管(4)和半导体开关装置(5),-第二换向单元(6),其中所述第二换向单元(6)具有电容器(7)、二极管(8)和半导体开关装置(9),以及-用于对所述第一换向单元(2)的电容器(3)和所述第二换向单元(7)的电容器(7)进行预充电的预充电电路(11),其中所述预充电电路(11)具有预充电电阻器(12)和可控开关装置(13),其中所述预充电电阻器(12)和所述可控开关装置(13)并联连接,-其中所述第一换向单元(2)的电容器(3)、所述预充电电路(11)和所述第二换向单元(6)的电容器(7)串联地插入到所述第一连接极(U1+)和所述第二连接极(U1-)之间。(A DC/DC converter (1) having: -a first connection pole (U1 +) and a second connection pole (U1-), wherein a first direct voltage (U1) is present between the first connection pole (U1 +) and the second connection pole (U1-), -a third connection pole (U2 +) and a fourth connection pole (U2-), wherein a second direct voltage (U2) is present between the third connection pole (U2 +) and the fourth connection pole (U2-), -a first commutation unit (2), wherein the first commutation unit (2) has a capacitor (3), a diode (4) and a semiconductor switching device (5), -a second commutation unit (6), wherein the second commutation unit (6) has a capacitor (7), a diode (8) and a semiconductor switching device (9), and-a precharge circuit for precharging the capacitor (3) of the first commutation unit (2) and the capacitor (7) of the second commutation unit (7) An electrical pre-charge circuit (11), wherein the pre-charge circuit (11) has a pre-charge resistor (12) and a controllable switching device (13), wherein the pre-charge resistor (12) and the controllable switching device (13) are connected in parallel, -wherein the capacitor (3) of the first commutation cell (2), the pre-charge circuit (11) and the capacitor (7) of the second commutation cell (6) are inserted in series between the first connection pole (U1 +) and the second connection pole (U1-).)

1. A DC/DC converter (1) comprising:

-a first connecting pole (U1 +) and a second connecting pole (U1-), wherein a first direct voltage (U1) is present between the first connecting pole (U1 +) and the second connecting pole (U1-),

-a third connecting pole (U2 +) and a fourth connecting pole (U2-), wherein a second direct voltage (U2) is present between the third connecting pole (U2 +) and the fourth connecting pole (U2-),

-a first commutation cell (2), wherein the first commutation cell (2) has a capacitor (3), a diode (4) and a semiconductor switching device (5),

-a second commutation cell (6), wherein the second commutation cell (6) has a capacitor (7), a diode (8) and a semiconductor switching device (9), and

-a pre-charging circuit (11) for pre-charging the capacitor (3) of the first commutation cell (2) and the capacitor (7) of the second commutation cell (7), wherein the pre-charging circuit (11) has a pre-charging resistor (12) and a controllable switching means (13), wherein the pre-charging resistor (12) and the controllable switching means (13) are connected in parallel,

-wherein the capacitor (3) of the first commutation cell (2), the pre-charge circuit (11) and the capacitor (7) of the second commutation cell (6) are inserted in series between the first connection pole (U1 +) and the second connection pole (U1-).

2. The DC/DC converter (1) according to claim 1,

-the first commutation cell (2) is interposed between the first connection pole (U1 +) and the third connection pole (U2 +) and

-the second commutation unit (6) is inserted between the second connection pole (U1-) and the fourth connection pole (U2-).

3. The DC/DC converter (1) according to claim 1 or 2,

-the DC/DC converter (1) has a control unit (14) configured to manipulate a controllable switching device (13) of the pre-charging circuit (11) such that the controllable switching device (13) is opened during a pre-charging phase.

4. The DC/DC converter (1) according to any of the preceding claims,

-the pre-charge circuit (11) further has a capacitor (15), wherein the pre-charge resistor (12), the controllable switching means (13) and the capacitor (15) are connected in parallel.

5. The DC/DC converter (1) according to claim 4,

-the capacitance of the capacitor (15) of the pre-charge circuit (11) is smaller than the capacitance of the capacitor (3) of the first commutation cell (2) and smaller than the capacitance of the capacitor (7) of the second commutation capacitor (7).

6. The DC/DC converter (1) according to any of the preceding claims,

-the first commutation unit (2) has a coil (16), wherein the switching device (5) of the first commutation unit (2) and the coil (16) of the first commutation unit (2) are inserted in series between the first connection pole (U1 +) and the third connection pole (U2 +), and

-the second commutation unit (6) has a coil (17), wherein the switching device (9) of the second commutation unit (6) and the coil (17) of the second commutation unit (6) are inserted in series between the second connection pole (U1-) and the fourth connection pole (U2-).

7. The DC/DC converter (1) of claim 6,

-the capacitor (3) and the diode (4) of the first commutation cell (2) together form a first commutation path, which receives the current of the coil (16) of the first commutation cell (2) when the switching device (5) of the first commutation cell (2) is open,

-the capacitor (7) and the diode (8) of the second commutation cell (6) together form a second commutation path, which receives the current of the coil (17) of the second commutation cell (6) when the switching device (9) of the second commutation cell (6) is open.

8. The DC/DC converter (1) according to claim 7,

-the DC/DC converter is dimensioned such that the commutation current flowing through the pre-charge circuit (11) is smaller than the respective commutation currents in the first commutation cell (2) and in the second commutation cell (6), and the commutation current flowing through the pre-charge circuit (11) is smaller than the respective main currents flowing through the coil (16) of the first commutation cell (2) and the coil (17) of the second commutation cell (6).

9. The DC/DC converter (1) according to any of the preceding claims,

-the pre-charging circuit (11) is configured to limit the switch-on current upon switching-in of the first direct voltage (U1) if the semiconductor switching device (5) of the first commutation cell (2) is configured to be reverse blocking and the semiconductor switching device (9) of the second commutation cell (6) is configured to be reverse blocking.

10. The DC/DC converter (1) according to any of the preceding claims,

-the pre-charging circuit (11) is configured to limit the switch-on current when switching in the first direct voltage (U1) and/or the second direct voltage (U2) if the semiconductor switching device (5) of the first commutation cell (2) is configured to be switched in reverse and the semiconductor switching device (9) of the second commutation cell (6) is configured to be switched in reverse.

11. The DC/DC converter (1) according to any of the preceding claims,

-the pre-charge resistor (12) of the pre-charge circuit (11) is an ohmic resistance or a positive temperature coefficient resistor.

12. A grid feedback unit (100) configured to feed electrical energy from a voltage intermediate circuit (101) into a three-phase grid (102), wherein the grid feedback unit (100) has:

-at least one DC/DC converter (1) according to any of the preceding claims, and

-an inverter (10), the inverter (10) being electrically coupled on the input side with a third connection pole (U2 +) and a fourth connection pole (U2-) of the DC/DC converter (1) and on the output side with a three-phase power grid (102).

Technical Field

The present invention relates to a DC/DC converter and to a grid feedback unit with such a DC/DC converter.

Background

WO 2017/072297 a1 shows a grid feedback unit which is configured to feed electrical energy from a voltage intermediate circuit into a three-phase grid. The grid feedback unit has a step-down converter unit having a first DC/DC converter in the form of a step-down converter and a second DC/DC converter in the form of a step-down converter, wherein the first and second step-down converters are connected in parallel and are each electrically coupled on the input side to the voltage intermediate circuit.

Disclosure of Invention

The object on which the invention is based is to provide a DC/DC converter and a grid feedback unit having such a DC/DC converter, which can be produced cost-effectively and/or have a low power loss.

The invention solves this object by a DC/DC converter according to claim 1 and a grid feedback unit according to claim 12.

The DC/DC converter generally has a first connection pole and a second connection pole, a first direct voltage being present or output or being applied between the first connection pole and the second connection pole.

The DC/DC converter also has a third connection pole and a fourth connection pole, a second direct voltage being present or being output or being applied between the third connection pole and the fourth connection pole.

The first direct voltage and the second direct voltage typically have different voltage levels.

The DC/DC converter also has a first commutation cell, wherein the first commutation cell has a capacitor, a diode and a controllable semiconductor switching device, for example in the form of a field effect transistor or an IGBT.

The DC/DC converter also has a second commutation cell, wherein the second commutation cell has a capacitor, a diode and a semiconductor switching device, for example in the form of a field effect transistor or an IGBT.

The semiconductor switching devices of the first and second commutation cells are preferably controlled or clocked in such a way that the level of the first or second dc voltage has a predetermined value.

The capacitor of the first commutation cell and the capacitor of the second commutation cell may together form a buffer capacitor to be pre-charged.

The DC/DC converter further has a precharge circuit for precharging the capacitor of the first commutation cell and the capacitor of the second commutation cell. The pre-charging circuit has a pre-charging resistor and a controllable switching means, for example in the form of a relay, wherein the pre-charging resistor and the controllable switching means are connected in parallel.

The capacitor of the first commutation cell, the pre-charge circuit (i.e. the pre-charge resistor and the parallel controllable switching means) and the capacitor of the second commutation cell are inserted in series between the first and second connection pole.

According to one embodiment, the first commutation cell is inserted between the first and third connecting poles and the second commutation cell is inserted between the second and fourth connecting poles.

According to one specific embodiment, the DC/DC converter has a control unit, which is designed to actuate the controllable switching devices of the pre-charging circuit in such a way that they are opened during a pre-charging phase of the capacitors of the first and second commutation cells. The precharge phase may have a predetermined duration. The precharging phase can be terminated as soon as a predefined threshold voltage is established across the capacitor to be precharged. The opening of the switching means of the pre-charge circuit causes a limitation of the switched-on current when switching in or switching on the first direct voltage and/or the second direct voltage, since the pre-charge resistor is active in the charging current path, i.e. without a short circuit.

According to one embodiment, the pre-charge circuit has a capacitor, wherein the pre-charge resistor, the controllable switching means and the capacitor are connected in parallel. The capacitance of the capacitor of the precharge circuit may be smaller than the capacitance of the capacitor of the first commutation cell and may be smaller than the capacitance of the capacitor of the second commutation cell.

According to one specific embodiment, the first commutation cell has a coil, wherein the switching device of the first commutation cell and the coil of the first commutation cell are inserted in series between the first connection pole and the third connection pole. Correspondingly, the second commutation cell has a coil, wherein the switching device of the second commutation cell and the coil of the second commutation cell are inserted in series between the second connection pole and the fourth connection pole.

According to one embodiment, the capacitor and the diode of the first commutation cell together form a first commutation path, which receives a current flowing through the coil of the first commutation cell when the switching device of the first commutation cell is open. Correspondingly, the capacitor and the diode of the second commutation cell together form a second commutation path, which receives the current flowing through the coil of the second commutation cell when the switching means of the second commutation cell are open.

According to one embodiment, the DC/DC converter or its pre-charge circuit is dimensioned such that the commutation current flowing through the pre-charge circuit is smaller than the respective commutation currents in the first and second commutation cells, and the commutation current flowing through the pre-charge circuit is smaller than the respective main currents flowing through the coils of the first and second commutation cells. The commutation current is here typically the current that passes from one conducting branch to the other conducting branch. For example, the commutation current flows to a closed contact or with a switching device of the precharge circuit closed. The remainder of the patent application refers to the relevant technical literature.

According to one specific embodiment, the precharge circuit is designed to limit the switching-on current when the first direct current voltage is switched on if the semiconductor switching device of the first commutation cell is designed to be switched off in the reverse direction and the semiconductor switching device of the second commutation cell is designed to be switched off in the reverse direction. This is achieved, for example, by opening the switching means of the pre-charge circuit and dimensioning the pre-charge resistor accordingly.

According to one specific embodiment, the precharge circuit is designed to limit the switching-on current when the first direct voltage is switched on and/or when the second direct voltage is switched on if the semiconductor switching device of the first commutation cell is designed to be switched on in the reverse direction and the semiconductor switching device of the second commutation cell is designed to be switched on in the reverse direction. This may be achieved, for example, by opening the switching means of the pre-charge circuit and dimensioning the pre-charge resistor accordingly.

According to one embodiment, the pre-charge resistor of the pre-charge circuit is an ohmic resistor or a positive temperature coefficient resistor.

The grid feedback unit according to the invention is designed to feed or feed back electrical energy from the voltage intermediate circuit into the three-phase grid.

The grid feedback unit has at least one DC/DC converter as described above. The grid feedback unit preferably has two DC/DC converters connected in parallel, which are controlled with a clock offset from one another.

The grid feedback unit also has an inverter which is electrically coupled on the input side to the third and fourth connection poles of the DC/DC converter and on the output side to the three-phase grid.

Drawings

The present invention is described in detail below with reference to the accompanying drawings. Here:

fig. 1 shows a circuit diagram of a DC/DC converter according to the invention, an

Fig. 2 shows a circuit diagram of a grid feedback unit with parallel-connected DC/DC converters according to the invention.

Detailed Description

Fig. 1 shows a circuit diagram of a DC/DC converter 1.

The DC/DC converter 1 has a first connecting pole U1+ and a second connecting pole U1-, wherein a first direct voltage U1 is present between the first connecting pole U1+ and the second connecting pole U1-.

The DC/DC converter 1 also has a third connecting pole U2+ and a fourth connecting pole U2-, wherein a second DC voltage U2 is present between the third connecting pole U2+ and the fourth connecting pole U2-.

The DC/DC converter 1 further has a first commutation cell 2, which first commutation cell 2 has a capacitor 3, a diode 4, a semiconductor switching device 5 and a coil 16. An optional diode 18 is connected in parallel with the semiconductor switching device 5 and is inserted in the blocking direction between the first connection pole U1+ and the third connection pole U2 +. If the semiconductor switching device 5 is implemented as a field effect transistor, the diode 18 may be a so-called body diode. The semiconductor switching device 5 and the coil 16 are inserted in series between the first connecting pole U1+ and the third connecting pole U2 +. The cathode of the diode 4 is electrically connected to the semiconductor switching device 5, the anode of the diode 18, and the coil 16, and the anode of the diode 4 is electrically connected to the capacitor 3 and the precharge circuit 11.

The DC/DC converter 1 further has a second commutation cell 6, the second commutation cell 6 having a capacitor 7, a diode 8, a semiconductor switching device 9 and a coil 17. An optional diode 19 is connected in parallel with the semiconductor switching device 9 and is inserted in the direction of conduction between the second connection pole U1 "and the fourth connection pole U2". If the semiconductor switching device 9 is implemented as a field effect transistor, the diode 19 may be a so-called body diode. The semiconductor switching device 9 and the coil 17 are inserted in series between the second connection pole U1-and the fourth connection pole U2-. The anode of the diode 8 is electrically connected to the semiconductor switching device 9, the cathode of the diode 19, and the coil 17, and the cathode of the diode 8 is electrically connected to the capacitor 7 and the precharge circuit 11.

The DC/DC converter 1 has a precharge circuit 11 for precharging the capacitors 3 and 7, wherein the precharge circuit 11 has a precharge resistor 12, a controllable switching means in the form of a relay 13 and optionally a capacitor 15, wherein the precharge resistor 12, the controllable switching means 13 and the capacitor 15 are connected in parallel.

The capacitor 3 of the first commutation cell 2, the precharge circuit 11, i.e. the parallel circuit consisting of the precharge resistor 12, the controllable switching device 13 and the capacitor 15, and the capacitor 7 of the second commutation cell 6 are inserted in series between the first connection pole U1+ and the second connection pole U1-.

The DC/DC converter 1 has a control unit 14, for example in the form of a microprocessor, which control unit 14 is configured to actuate the controllable switching means 13 of the precharge circuit 11 such that the controllable switching means 13 are opened during a precharge phase of the capacitors 3 and 7 in order to charge the capacitors 3 and 7 up to a desired precharge voltage.

The DC/DC converter 1 may be configured as a buck converter, i.e. applicable U1> U2.

The capacitance of capacitor 15 is typically chosen to be smaller than the capacitance of capacitor 3 or 7.

Fig. 2 shows a circuit diagram of a grid feedback unit 100 according to the invention, the grid feedback unit 100 having two DC/DC converters 1 connected in parallel, wherein the respective DC/DC converter 1 corresponds to the DC/DC converter 1 shown in fig. 1.

The grid feedback unit 100 is configured to feed electrical energy from the voltage intermediate circuit 101 into the three-phase grid 102. The grid feedback unit 100 is based on the grid feedback unit shown in WO 2017/072297 a1 and is extended in particular with respect to the pre-charging circuit 11. Reference is therefore also made to the disclosure of WO 2017/072297 a1 regarding the basic functionality of the grid feedback unit 100.

The grid feedback unit 100 has two DC/DC converters 1 as shown in fig. 1 and an inverter 10 which is electrically coupled on the input side to the respective third connection U2+ and the respective fourth connection U2+ of the DC/DC converter 1 and on the output side to the three-phase grid 102 of the three phases. It is understood that instead of two DC/DC converters 1, only a single DC/DC converter may be provided, or more than two DC/DC converters may be connected in parallel.

The filter capacitors 24 are inserted in series between the respective third connection pole U2+ and the respective fourth connection pole U2 "of the DC/DC converter 1 together with a pre-charge circuit having a resistor 25 and a controllable switching device 26. To precharge the filter capacitor 24, the switching device 26 is opened. The switching device 26 may be designed as a relay.

The inverter 10 has conventional semiconductor switching devices 22 in a bridge circuit. A grid choke 23 is provided on the grid side. The inverter 10 may be operated, for example, at a switching frequency >60kHz or clocked with the grid frequency.

The precharge circuit 11 is arranged in the field of circuits dedicated to low-frequency equalization currents. The equalizing current or ripple current generated during operation is significantly smaller than the current to be transmitted by the DC/DC converter, so that only a small proportion of the commutation current flows through the respective switching device 13. Therefore, no additional impedance is added in the commutation path and oscillations or overvoltages at the semiconductor switching devices 5 and 9 can be avoided. Only a single switching device or pre-charge relay 13 is sufficient per DC/DC converter 1.

This makes it unnecessary to design the precharge circuit 11 to bear the entire device power. Due to the resulting low loss power, the pre-charge circuit 11 and its peripherals can be implemented on a printed circuit board without additional cooling.

The diodes 20 and 21 prevent reverse charging from the three-phase network 102 to the intermediate circuit 101.

The following advantages can be achieved by means of the invention:

-space saving

Reduction of costs

Low loss power, so that it can be implemented on uncooled printed circuit boards

-laying out within the intermediate circuit capacitor area and thus at a location where the required installation height of the relay is already present.