EP4315579A1

EP4315579A1 - Dc-to-dc converter device for a wind turbine, an electric drive system or an industrial dc supply system, and operating method

Info

Publication number: EP4315579A1
Application number: EP22719809.0A
Authority: EP
Inventors: Johannes Visosky; Heiko Bach-Preckwinkel
Original assignee: Keba Industrial Automation Germany GmbH
Current assignee: Keba Industrial Automation Germany GmbH
Priority date: 2021-03-31
Filing date: 2022-03-25
Publication date: 2024-02-07
Also published as: CN117223204A; WO2022207512A1; DE102021108280A1

Abstract

Disclosed is a DC-to-DC converter device (1) for operating a wind turbine, an electric drive system or an industrial DC-to-DC supply system (3) with electric power, in particular by means of a DC link of an AC-to-DC converter (400) of a DC energy source or DC energy store (8), said DC link being able to be coupled to the DC-to-DC converter device (1) which comprises: - an input DC link (500) that includes a number of DC link capacitors (501, 502) which are connected between a positive input conductor (401) and a negative input conductor (402); and - a DC-to-DC converter (600) which is connected in series to the input DC link (500) and includes a first half-bridge (H1) connected to the positive input conductor (401) as well as a second half-bridge (H2) connected to the negative input conductor (402), the center tap (M1) of the first half-bridge (H1) and the center tap (M2) of the second half-bridge (H2) being connected via a choke (605). A secondary aspect of the invention relates to a method for operating the DC-to-DC converter device, in particular to operate a pitch drive or yaw drive of a wind turbine, of an electric drive or of an industrial DC supply system.

Description

DC/DC CONVERTER DEVICE FOR A WIND TURBINE, ESN ELECTRICAL PROPULSION SYSTEM, OR FOR AN INDUSTRIAL DC SUPPLY NETWORK AND METHOD OF OPERATION

TECHNICAL AREA

The invention relates to a DC/DC converter device for a wind turbine, an electrical drive system, or for an industrial DC supply network with electrical energy by means of an intermediate circuit, which can be coupled to the DC/DC converter device, of an AC/DC converter, a DC Energy storage or an energy source. Furthermore, the invention relates to a method for operating such a DC/DC converter device.

STATE OF THE ART

The present technical field relates to a DC energy supply or support for a wind turbine, an interconnection of an intermediate circuit of at least one electrical drive or for the DC energy supply or support of a DC industrial network, preferably there a charging and discharging operation of an energy storage device or the coupling of DC -Subnets or network segments with different voltage levels. In a mains operation of a DC system such. B. a DC industrial network or an intermediate circuit of an electric drive, especially in high-security applications such as a pitch or yaw drive of a wind turbine ge, with a grid-side AC or DC supply, both an AC / DC converter and a DC / DC converters (DC converters) are used. In the area of electrical drives, DC intermediate circuits are used in frequency converters or for a DC power supply, which can be coupled to one another or to DC energy sources or energy sinks.

For this purpose, the document EP 2 515 424 B1 shows, for example, a DC voltage converter for stepping up and/or down voltages for supplying a third DC connection by a DC voltage source connected to a first connection and a DC voltage source connected to a second connection. Voltage source, for example two solar panels of a solar generator or two batteries. For this purpose, at least a first connection and at least a second connection circuit and at least one third connection, with an energy flow between the first and second connections on the one hand and the third connection on the other hand being possible, a first half-bridge which can be operated in a clocked manner, which is connected in parallel to the first connection and a series connection of at least one first switching device and a second switching device, and a second half-bridge that can be operated in a clocked manner, which is connected in parallel to the second terminal and has a series connection of at least one third switching device and at least one fourth switching device, the midpoints of the two half-bridges that can be operated in a clocked manner connected to one another via at least one inductor are connected, this at least one choke being operated as a flying inductance ben. The disadvantage is that an input potential of the first connection and, parallel thereto, an input potential of the second connection are galvanically connected to an output potential of the third connection via potential rails, so that the two inputs and the output cannot be switched freely. Furthermore, two input DC energy sources are to be provided for supplying an output DC energy sink.

In addition, DE 10 2014 203 157 A1 considers a bipolar high-voltage network for an aircraft or spacecraft, which has a reference potential connection. The circuit has two DC-DC converter modules that are switched into the converter circuit in such a way that they include two half-bridges that connect the input and output intermediate circuit rails, and their center taps each have a choke with a reference potential of the output intermediate circuit, which is related to ground potential , are connected. For this purpose, the output circuit is bipolar, and a reference potential is connected to ground for short-circuit detection. The two half-bridges of the two DC-DC converter modules are controlled separately, so that at least two chokes must be used, and the two chokes cannot be operated as flying inductors, since one connection is related to ground. Thus, no quasi-potential isolation can be achieved and both half-bridges are controlled separately, so that no potential isolation can be ensured between the input and output circuits. A short-circuit capability of the output connection to ground can therefore not be guaranteed.

Nevertheless, the present invention can also be used in a charging station for charging and/or discharging an energy store of an electric vehicle. DISCLOSURE OF THE INVENTION

It is an object of the present invention to provide an improved DC/DC converter device for operating a wind turbine, an electric drive system or a DC power grid.

The task is solved by a DC/DC converter device with and by a method with the features of the independent claims.

According to a first aspect, a DC/DC converter device, in particular a transformerless DC/DC converter device, is proposed for the operation of a wind turbine, an electric drive or an industrial DC supply network. The charging station comprises: an input intermediate circuit, which has a number of intermediate circuit capacitors connected between a positive input conductor and a negative input conductor, and a DC/DC converter connected downstream of the input intermediate circuit, which has a first half bridge connected to the positive input conductor and a first half bridge connected to the negative input conductor Input conductor connected second half-bridge, wherein the center tap of the first half-bridge and the center tap of the second half-bridge are connected via a choke.

The DC/DC converter device has, for example, a housing, in particular a waterproof housing, with an interior space in which a plurality of electrical and/or electronic components and a connection socket connected to at least one of the components for connecting a connection or La de connector for an energy store, such as an electric vehicle, are arranged.

The DC/DC converter device can be used, for example, as a charging connection device for an electric vehicle. The converter device can be designed in particular as a wall box. The converter device can be used to charge or regenerate an energy storage device in an electric vehicle, an emergency energy storage device in a wind power plant, the coupling or emergency energy support of intermediate circuits in electrical drives, or for adjusting voltage levels in DC industrial networks are used. The DC/DC converter device acts as a reference source for electrical energy for the energy store. The DC/DC converter device can also be referred to as an intelligent charger for an energy store.

Examples of the electrical and/or electronic components of the DC/DC converter device include a contactor, all-current-sensitive circuit breaker, direct current, overcurrent and fault current monitoring device, relay, connection terminal, electronic circuits and a control device, for example comprising a printed circuit board in which a plurality of electronic components are arranged for controlling and/or measuring and/or monitoring the energy states.

An AC/DC converter included in the DC/DC converter device for an AC or three-phase grid connection can also be referred to as a converter. The AC/DC converter is set up in particular for converting an AC voltage into a DC voltage and/or for converting a DC voltage into an AC voltage. The DC/DC converter device includes an input intermediate circuit which is connected downstream of a converter of this type in particular and has a number of intermediate circuit capacitors which are connected to an input intermediate circuit center point.

The polyphase three-phase network i has in particular a number of phases, for example L1, L2 and L3, and a neutral conductor (also denoted by N).

It should be noted that the “charging and/or discharging of an energy store” includes both supplying electrical energy and drawing electrical energy. This means that the energy store can act as a consumer or as a generator in the DC network of the wind turbine, an electric drive or the industrial network.

According to one embodiment, an AC/DC converter that can be coupled to a number of AC phases L1, L2, L3, in particular a 3-point AC/DC converter, can be connected upstream of the input intermediate circuit on the input conductors on the input side, or a DC energy source , In particular a solar generator, or a DC energy store, in particular a 3-point accumulator, to the input-side input conductors, ie to be connected to the source-side input intermediate circuit. Thus, in normal operation, DC energy can be taken from the DC output terminals of a mains rectifier or bidirectional AC/DC converter or stored again, or from a DC energy source, for example a fuel cell, a solar generator with solar cells, a flywheel mass storage device or ei ner battery are taken, or a DC energy storage, such as egg nem electrochemical accumulator, capacitor or flywheel storage are removed or recycled. This means that there are many possible uses for energy extraction and energy recovery between different DC voltage levels.

According to one embodiment, at least one pitch drive or one yaw drive of a wind turbine, at least one intermediate circuit of one or more electric drives, or at least one DC network segment of a DC industrial network can be connected downstream to an output intermediate circuit of the DC/DC converter. This results in a wide range of advantages when using the DC/DC rectifier unit in the area of a wind turbine, a drive system or in a DC industrial network:

With direct current networks, using electronic frequency converters, the electrical supply in factories can be designed to be more energy-efficient, stable and flexible than with mains-side alternating current. If all electrical systems are coupled via an intelligent DC network, such as in the "DC Industry 2" joint project, this will also drive the energy transition in the industrial sector. In a DC industrial application, stepping up and stepping down a DC supply voltage bidirectionally seamlessly is possible with the aid of the proposed DC/DC converter device. In addition, there is a safe switch-off option and a short reaction time to short circuits and earth faults. This can be achieved in particular by the fact that the connection between the input and output of the DC/DC converter device is made exclusively by junction capacitances of semiconductor switching, i. H. there is no galvanic connection between input and output and quasi-potential isolation is possible. In this case, the DC converter device can continue to be operated without restriction in the event of a ground fault. In addition, there are the possibilities of connection and use in various applications which when connecting energy storage devices to, e.g. e.g.:

DC intermediate circuits of drive systems; Mains failure support, peak load reduction, braking energy absorption instead of braking resistance of electric drives in generator mode;

Bidirectional coupling of two or more DC intermediate circuits of drive systems, in particular at different voltage levels;

- Development of several DC network segments, in particular at different voltage levels, in an industrial hall;

Connection of different DC network segments in an industrial hall with the option of load shedding, pre-charging, voltage adjustment;

- Connection of photovoltaics, fuel cells, flywheel mass storage to a DC network segment in an industrial hall.

Furthermore, a quasi-potential separation between the input and load side is made possible, which means that increased safety, resistance to earth faults and short-circuits can be achieved.

In the area of a wind power plant, the use of the proposed DC/DC converter device is advantageous, in particular in the DC intermediate circuit network of a pitch and yaw drive of a wind power plant. A pitch drive determines the angle of attack of one or more rotor blades in relation to the wind, a yaw drive defines the horizontal alignment of the wind turbine's nacelle in relation to the wind.

For example, EP 1 852 605 B1 proposes adapting the voltage of an emergency energy store for a pitch drive to a DC intermediate circuit, so that a DC voltage level as in normal operation can be achieved largely independently of the voltage level of the emergency energy store in emergency operation and in generator operation Energy can be included in the emergency energy storage. The proposed DC/DC converter device thus enables the flexible connection of the emergency energy storage device for pitch and yaw drives in wind turbines, in particular for a large number of different types of emergency energy storage devices such as lead, lithium-ion batteries or capacitors, in particular SuperCaps or UltraCaps.

So far, there has been an upper limit for emergency energy storage voltage levels in comparison to the mains voltage in emergency energy storage devices, in particular it had to be the voltage level of the energy storage device must be lower than that of the rectified mains voltage at all times. Strong mains fluctuations, especially in a wind turbine or with electric drives, are problematic here and can mean that this condition cannot be met temporarily. As a result, an even greater restriction in the design of the emergency energy store may become necessary, so that the emergency energy store voltage must be designed to be significantly lower than the rectified setpoint mains voltage. With the aid of the proposed DC/DC converter device, this upper limit can be eliminated by a bidirectional step-up and step-down with a continuous transition. This gives the following advantages:

By means of a DC/DC converter device, different usage requirements can be satisfied, in particular high or low emergency energy storage voltages can be made available;

When the emergency energy storage voltage is high, lower currents can be used, which enables the use of more cost-effective cables with a smaller cable cross-section and a smaller space requirement for the interfaces, and thus easier and more cost-effective installation;

The operational safety with fluctuating mains voltage on the input side can be maintained or stabilized, which is particularly important when using wind turbines or for safety-critical electrical drives;

Several DC/DC converters and thus several pitch drives can be connected to an emergency energy store due to the quasi-potential separation that can be achieved;

A highly dynamic voltage exploitation up to near total discharge, for example of capacitor stores, enables both the coupling of energy stores, which provide significantly higher voltages than a DC intermediate circuit, and their operation until they are almost completely discharged, so that the energy content of the energy store is fully utilized can. In particular, a control unit is provided which can control individual or all elements and units of the DC/DC converter device. Furthermore, the choke of the DC/DC converter can preferably be operated as a flying inductance. In this case, the DC/DC converter with the flying inductance can advantageously function functionally like a quasi-potential isolation. For example, the DC/DC converter has a number of semiconductor switching elements, which are in the form of MOSFETs, for example. In particular, the DC/DC converter works as a voltage inverter, with the DC/DC converter preferably being controlled in such a way that the diodes of the MOSFETs never become conductive in an undesired manner during undisturbed operation. During operation, the inductance preferably flies back and forth between the input potential and the output potential. This functionally results in the quasi-potential separation. In the event of a ground fault on the output side, for example in an emergency energy store of a pitch drive (accumulator, battery), the potential of the energy store can shift freely relative to the potential of the intermediate input circuit of the DC/DC converter device. The regulation of the inductor current of the inductor in the event of a ground fault is preferably not affected. The duty cycle of the DC/DC converter does not have to be changed either.

The proposed DC/DC converter preferably behaves functionally like a DC/DC converter with a transformer. The output potential to ground can be freely shifted within certain limits during operation without affecting the function of the DC/DC converter. This is the case in particular when there is no galvanic connection between the input side and the output side outside of a connection through the two half-bridges.

In the case of a grounded input network, with appropriate dimensioning of the semiconductor switching elements of the DC/DC converter, it is possible for a person to touch one pole of the output of the DC/DC converter device without a significant direct current flowing through the person's body.

According to one embodiment, the inductor of the DC/DC converter can be operated as a flying inductance.

According to a further embodiment, the DC/DC converter device is a transformerless DC/DC converter device. According to a further embodiment, the DC/DC converter is designed as a bidirectional DC/DC converter for stepping up and/or stepping down voltages. The DC/DC converter can also be referred to as a DC voltage converter. In particular, the DC/DC converter is constructed symmetrically and can step-down and step-up in both directions.

According to a further embodiment, the respective half-bridge comprises a series connection of two semiconductor switching elements. The center tap of the half-bridge is between the two series-connected semiconductor switching elements.

According to a further embodiment, the respective semiconductor switching element is designed as a MOSFET, preferably as a SiC MOSFET, or as an IGBT or as a SiC cascode.

In particular, the present topology acts as a bidirectional voltage translation device (DC transformer), the voltage translation, which can be set by the control unit, depending on the ratio between the on-time and off-time of the semiconductor switching elements. With a duty cycle of 50%, the voltage transformation ratio is 1.

According to a further embodiment, the DC/DC converter device comprises a control unit which is set up to control the semiconductor switching elements in such a way that two corresponding semiconductor switching elements of the two half-bridges switch simultaneously, in particular switch with an identical switch-on delay.

In order to achieve a quasi-potential separation, the two input-side, i.e. source-side semiconductor switching elements of the two half-bridges can be switched simultaneously, and the two load-side, i.e. output-side semiconductor switching elements of the two half-bridges can be switched simultaneously.

In a further embodiment, the DC/DC converter device can have a control unit which is set up to control the two half-bridges H1 and H2 with a phase shift, in particular with a 180° phase shift. In particular, when a coupling line between the intermediate circuit center points of an input and output-side capacitor bridge is connected, such as described further below, in contrast to in-phase driving of the half-bridges, phase-shifted, in particular anti-phase driving of the half-bridges can take place. In this case, the quasi-potential isolation is abandoned, since a galvanic connection is established between the input and output side. Here by the efficiency of the DC / DC converter device can be increased significantly, and on the other hand, the choke can be made smaller and cheaper.

In this context, the terms "input side" or "source side" and the terms "output side" or "load side" should only be understood as topological definitions of the two connection sides of the DC/DC inverter device, and thereby illustrate a direction of energy flow in normal operation . Nevertheless, in a bidirectional operation within the meaning of the invention, the energy flow can also take place from the output or load side to the input or source side. In an inverse operating mode of an application for supplying a pitch drive in emergency operation, energy can flow from the emergency energy store on the load side to the DC intermediate circuit on the source side, or in generator operation, energy can be transferred from a DC industrial network to an AC supply network, while in control operation the energy flow vice versa. In the case of coupled intermediate circuits in drive systems, for example, if required, energy can be routed from a first to a second intermediate circuit in the event of a high energy load in order to support the voltage level of the second intermediate circuit.

In particular, the control unit never turns on the semiconductor switching elements of a half-bridge at the same time in order to prevent a direct connection between the input and load sides.

According to a further embodiment, an interference suppression circuit is arranged between the input intermediate circuit and the DC/DC converter, which circuit has two interference suppression capacitors connected in parallel with the intermediate circuit capacitors. The node connecting the two interference suppression capacitors is connected to ground potential. The earth potential can also be referred to below as mass or earth.

According to a further embodiment, the DC/DC converter device comprises an intermediate output circuit connected downstream of the DC/DC converter with a number of output capacitors which are connected between a negative output potential tap and a positive output potential tap of the DC/DC converter device are switched.

To extend the previous embodiment, the intermediate circuit capacitors of the input intermediate circuit can advantageously form an input capacitor bridge with an input intermediate circuit center, and the output capacitors of the output intermediate circuit can form an output capacitor bridge with an output intermediate circuit center. The two intermediate circuit centers, i.e. the input intermediate circuit center can be connected to the output intermediate circuit center via a coupling line. Thus, the middle potential of the input and the output is galvanically coupled to each other. In particular, this improves the efficiency and the EMC robustness of the DC/DC inverter device. According to a further embodiment, an interference suppression circuit on the load side, i.e. on the output side, is arranged between the DC/DC converter and the intermediate output circuit. The load-side interference suppression circuit has two interference suppression capacitors connected in parallel with the number of output capacitors of the output intermediate circuit, the node connecting the two interference suppression capacitors being connected to ground potential. The coupling line also makes it possible to drive the half-bridges H1 and H2 out of phase, in particular out of phase by 180°, i.e. in phase opposition. With this control, on the one hand, a significantly increased efficiency of the DC/DC converter device can be achieved and, on the other hand, the inductor can be made smaller and more cost-effective.

According to a further embodiment, the control unit is set up to control the semiconductor switching elements in such a way that the input-side semiconductor switching element of the first half-bridge and the load-side semiconductor switching element of the second half-bridge have overlapping switch-on times (switch-on times) and/or that the input-side semiconductor switching element of the second half-bridge and the load-side semiconductor switching element of the first half-bridge have slightly overlapping turn-on times. In this case, the ratio of the switch-on times of the one output-side semiconductor switching elements to the switch-on times of the load-side semiconductor switching elements preferably corresponds to a predetermined quotient.

This control with the overlapping switch-on times causes a charge Shift in the interference suppression capacitors, which bear the reference numbers 651, 652 in the figures, in such a way that the potential of the output network can be adjusted with respect to ground potential. This allows the output potential to be balanced with respect to earth potential (ground). If an aforementioned coupling line is inserted between the capacitor bridges of the input and output, for example shown in FIG. 4a, an overlap with a 180° phase-shifted control can improve the efficiency. A phase shift that deviates slightly from 180° can change the symmetry of the output potential with respect to the input intermediate circuit center.

The control unit can be implemented in terms of hardware and/or software. In the case of a hardware implementation, the control unit can be designed as a device or as part of a device, for example as a computer or as a microprocessor or as a control computer. In the case of a software implementation, the control unit can be designed as a computer program product, as a function, as a routine, as part of a program code or as an executable object.

According to a further embodiment, the control unit is set up to switch off one of the input-side semiconductor switching elements of the two half-bridges earlier than the other input-side semiconductor switching element of the two half-bridges, so that coupling of an input-side primary circuit and a load-side secondary circuit via the inductor is made possible or is provided.

According to a further embodiment, the control unit is set up to turn off one of the load-side semiconductor switching elements of the two half-bridges earlier than the other load-side semiconductor switching element of the two half-bridges, so that - if no coupling line is provided and a quasi-potential isolation can be achieved - a coupling of an input-side Is made possible or is provided primary circuit and a load-side secondary circuit via the throttle.

According to a further embodiment, the semiconductor switching elements are MOSFETs. The control unit is set up to drive the gates of the MOSFETs of the half bridges with such phase-shifted control signals that - if no coupling line is provided and a quasi-potential isolation can be achieved - a coupling of an input-side primary circuit and a load-side secondary circuit is enabled or provided via the inductor.

In this embodiment, the symmetry of the output voltage with respect to ground can be regulated relative to one another by a slight phase shift in the drive signals of the first half bridge and of the second half bridge. - If no coupling line is provided and a quasi-potential separation can be achieved, the phase shift periodically results in a brief coupling of the input circuit and the output circuit. This is also the case when no real power is being transmitted by the DC/DC converter device.

According to a further embodiment, the control unit has a load current regulator, a balancing current regulator and a differential voltage regulator. Since the load current regulator is set up to set the ratio of the switch-on times of the input-side semiconductor switching elements to the switch-on times of the load-side semiconductor switching elements. The balancing current controller is configured to provide an adjustment signal for balancing the potential at the negative output potential tap and the potential at the positive output potential tap with respect to ground potential. Furthermore, the differential voltage controller is set up to provide a target value for the setting signal as a function of at least one measured voltage in the load-side secondary circuit.

According to a further embodiment, the differential voltage regulator is slower than the balancing current regulator.

According to a further embodiment, the anode of a first diode is coupled to the negative output potential tap and the cathode of the first diode is coupled to the input intermediate circuit center point. Furthermore, the anode of a second diode is coupled to the input intermediate circuit center and the cathode of the second diode is coupled to the positive output potential tap.

According to a further embodiment, the anode of the first diode is connected to the negative output potential tap and the cathode of the first diode is connected to the input intermediate circuit center point. Furthermore, the anode of the second diode is connected to the input intermediate circuit center and the cathode of the second diode is connected to the positive output potential tap. According to a further embodiment, an overvoltage protection element is coupled between the input intermediate circuit midpoint and a node to which the cathode of the first diode is connected and to which the anode of the second diode is connected. The overvoltage protection element is, in particular, a varistor or a bidirectional suppressor diode, such as a bidirectional transildiode.

According to a further embodiment, a series circuit comprising a first overvoltage protection element and the first diode is arranged between the input intermediate circuit center point and the negative output potential tap. Furthermore, a series circuit comprising a second overvoltage protection element and the second diode is arranged between the input intermediate circuit center point and the positive output potential tap.

According to a further embodiment, an EMC filter device and an LCL filter device connected downstream of the EMC filter device are coupled between three input-side connection terminals for the three phases of the multi-phase network and the AC/DC converter. The LCL filter device preferably includes at least three inductors and three capacitors.

According to a further embodiment, the AC/DC converter is designed as a 3-point AC/DC converter.

According to a further embodiment, a reversing capacitor is connected to the middle tap of the first half-bridge, which is connected in parallel to the input-side semiconductor switching element of the first half-bridge, with a further reversing capacitor being connected to the middle tap of the first half-bridge, which is connected in parallel to the load-side semiconductor switching element of the first half-bridge is. Furthermore, a reversing capacitor is connected to the center tap of the second half-bridge, which is connected in parallel to the input-side semiconductor switching element of the second half-bridge, with a reversing capacitor connected to the center tap of the second half-bridge, which is connected in parallel to the load-side semiconductor switching element of the second half-bridge. The reversing capacitors cause soft switching and thus a reduction in switching losses. The resonant capacitors can also be referred to as ZVS capacitors of the snubber capacitors (ZVS; zero-voltage switching). In this respect, haft be arranged parallel to each semiconductor switching element, a U tuning capacitor to implement a loss-reduced turn-off.

According to a further embodiment, the DC/DC converter device comprises a power switching device for safely disconnecting the number of input conductors from the input side, for example a multi-phase AC network. The power switching device may be in the form of an electromechanical element such as a contactor or a four-phase relay. The power switching device can be designed and controlled individually for a respective phase of the multiphase AC network and/or for a respective input conductor of the switching matrix, so that, for example, individual assignments can be interrupted by means of the power switching device.

According to a second aspect, a method for operating a DC / DC converter device for the operation of a wind turbine, an electric drive or an industrial DC supply network with electrical energy is proposed genes, wherein the DC / DC converter device has an intermediate circuit, which has a number of has intermediate circuit capacitors connected between a positive input conductor and a negative input conductor, and comprises a DC/DC converter connected downstream of the input intermediate circuit, which has a first half bridge connected to the positive input conductor and a second half bridge connected to the negative input conductor. The method includes operating an inductor of the DC/DC converter that connects the center tap of the first half bridge (H1) and the center tap of the second half bridge as a flying inductor.

This method has the same advantages as explained for the DC/DC converter device according to the first aspect. The embodiments described for the proposed DC/DC converter device apply correspondingly to the proposed method. Furthermore, the definitions and explanations for the DC/DC converter device also apply accordingly to the proposed method.

As used herein, "a" is not necessarily meant to be limited to just one element. Rather, a plurality of elements, such as two, three or more, can also be provided. Any other counting word used here should also not be understood to mean that there is a restriction to exactly the number of elements specified. Rather, numerical deviations are up and down possible below unless otherwise stated.

Further possible implementations of the invention also include combinations of features or embodiments described above or below with regard to the exemplary embodiments that are not explicitly mentioned. The person skilled in the art will also add individual aspects as improvements or additions to the respective basic form of the invention.

Further advantageous refinements and aspects of the invention are the subject matter of the dependent claims and of the exemplary embodiments of the invention described below. The invention is explained in more detail below on the basis of preferred embodiments with reference to the enclosed figures.

1a, 1b schematically shows two arrangements of a first embodiment of a DC/DC converter device for operating a DC industrial network and a wind power plant;

Fig. 2 shows a schematic circuit diagram of a second embodiment of a

DC/DC converter device for charging and/or discharging an energy store;

3 shows a schematic circuit diagram of another embodiment of a DC/DC converter device;

4a, 4b show schematic circuit diagrams of a third and fourth embodiment of a DC/DC converter device;

5a, 5b show schematic circuit diagrams of a fifth and a further embodiment of a DC/DC converter device;

6 shows a schematic circuit diagram of a sixth embodiment of a DC/DC converter device for supplying a DC network on the output side from a DC input circuit;

FIG. 7 shows the schematic circuit diagram of FIG. 6 with a primary circuit on the output side and a secondary circuit on the load side drawn in; FIG. 8 shows the schematic circuit diagram of FIG

circuit of symmetry current;

Fig. 9 shows diagrams to illustrate the inductor current and various

Signals of the DC/DC converter according to Figs. 7 and 8;

FIG. 10 shows the schematic circuit diagram of FIG. 6 with the balancing control drawn in; FIG. and

FIG. 11 shows a schematic flowchart of a method for operating a DC/DC converter device.

In the figures, elements that are the same or have the same function have been provided with the same reference symbols, unless otherwise stated.

1a and 1b show schematic arrangements with a first embodiment of a DC/DC converter device 1 for operating a DC industrial network (Fig. 1a) or an emergency energy store 2 of a pitch drive 3 of a wind turbine 3 (Fig.

1b).

In the first embodiment of FIG. 1a, a multi-phase AC network 4 is connected to a multi-phase power supply network 7 by means of a network connection point 6 . The multi-phase AC network 4 has in particular a number of phases, for example L1, L2 and L3. In this example, without loss of generality, it is a matter of three-phase power grids. A DC industrial network 3 with at least one or more DC network segments 2, preferably with different voltage levels and/or electrically isolated, is connected to the DC/DC converter device 1, which includes an AC/DC converter, to the AC grid 4 coupled. Further island grids 2 with the same or different voltage levels are conceivable via DC/DC converter devices 1 that can be connected in parallel. The industrial network 3 can be supplied with direct current energy via the DC/DC converter device, with the amount of energy being adjustable largely independently of the voltage level of the AC network 4 . It is conceivable that an energy store, for example a high-capacity accumulator and/or a solar generator with a large number of solar cells connected in parallel, can provide switchable energy at least for isolated operation via additional DC/DC converters included in the DC/DC converter device 1. can ask. Faster load shedding in the event of a fault is conceivable, as is the connection of various DC energy sources with different or fluctuating voltage levels, which is possible without risk thanks to the quasi-potential isolation.

According to the example in FIG. 1 b , a DC/DC converter device 1 is included in a wind power plant 3 which includes a plurality of rotor blades which can be adjusted by means of pitch drives 3 . The DC/DC converter device 1 couples a DC energy store 8 to an intermediate circuit of a pitch motor converter, which drives the pitch motors 2 in a controllable manner. A DC/DC converter device 1 can be provided for each pitch motor 2, each of which couples an energy store 8, but also couples a common energy store 8 to the three pitch motor Z intermediate circuits due to the quasi potential separation. The DC/DC converter device allows a desired DC voltage level to be provided steplessly and with a strongly fluctuating voltage level of the intermediate circuit, regardless of the nominal voltage or the charging capacity of the DC energy store 8. Due to the omission of an upper limit of the emergency energy store voltage in comparison Both energy stores 8 are used for the mains voltage, the nominal voltage of which is significantly higher than the DC intermediate circuit voltage of the pitch converter, and of the energy store 8, which provide a far lower voltage level. At high voltage levels, cables with smaller cross sections can be used due to reduced currents.

The DC/DC converter device 1 can have a number of electrical and/or electronic components (not shown in FIGS. 1a, 1b, see for example FIG. 2) and is particularly suitable for DC voltage conversion between the input and output sides the operation of a DC industrial network, or several network segments thereof, for coupling the intermediate circuit of one or more, in particular frequency-converted, drive systems, or to support the emergency supply of a pitch or yaw drive of a wind turbine by means of an intermediate circuit that can be coupled to a technical drive system Emergency energy storage provided..

Fig. 2 shows a schematic circuit diagram of a second embodiment of a DC / DC converter device 1 for DC supply of an industrial network 3 from a multi-phase network 4, which includes an AC / DC converter 400 connected upstream. The second 2 shows detailed features of the first embodiment according to FIG. 1a.

The DC/DC converter device 1 of FIG. 2 has three connection terminals 101, 102, 103 for the three phases L1, L2, L3 of the multiphase network 4. The DC/DC converter device 1 can also have another connection terminal (not shown) for have the neutral conductor.

According to FIG. 2, an EMC filter device 200 is connected downstream of the connection terminals 101, 102, 103. Furthermore, the DC/DC converter device 1 of FIG. to which a negative output potential tap 701 and a positive output potential tap 702 are connected.

In particular, an EMC filter device (not shown) can be connected between the negative output potential tap 701 and the positive output potential tap 702 .

3 shows a DC/DC converter 600 with an integrated input intermediate circuit capacitor 501 and output capacitor 703 of an embodiment of a DC/DC converter device 1, which explains the basic principle of DC/DC conversion. This includes two half-bridges H1, H2, each with two semiconductor switching elements 601, 602 or 603, 604, which are connected between the positive input conductor 401 and negative output potential tap 701 or between the negative input conductor 402 and positive output potential tap 702. A choke 605 is connected as a flying de inductance between the center taps M1, M2 of the two half-bridges H1, H2. An intermediate circuit capacitor 501 is connected in the input intermediate circuit 500 and an output capacitor 703 is connected to the output intermediate circuit 700 . The semiconductor switching elements 601 to 604 are controlled by a control unit 600. Depending on the control of the semiconductor switching elements 601 to 604 of the two half-bridges H1, H2 by the control unit 600, both a step-up and a step-down converter topology can be provided bidirectionally both from the input conductors 401, 402 to the output conductors 701, 702 and vice versa. This allows bidirectional DC energy from the input side 500 to the output 700 and vice versa, and the respective output voltages are continuously changed independently of the respective input voltages.

Fig. 4a shows a schematic circuit diagram of a third embodiment of a DC / DC converter device 1 which makes it possible with respect shiftable within certain limits, to convert DC voltage at the output potential taps 701, 702. A symmetrical GND center potential can be fed in on the input side, particularly if a 3-point AC/DC converter is used, but this can also be dispensed with. The third embodiment of FIG. 4a includes all the features of the second embodiment of FIG. FIG. 4a illustrates details of the DC/DC converter device 1. FIG.

According to FIG. 4a, the input intermediate circuit 500 has two intermediate circuit capacitors 501, 502, which are connected between a positive input conductor 401 and a negative input conductor 402 and a symmetrical center potential GND of the intermediate circuit center point 503.

The DC/DC converter 600 connected downstream of the input intermediate circuit 500 has a first half-bridge H1 and a second half-bridge H2. The first half-bridge H1 is connected to the positive input conductor 401 and includes a series connection of two semiconductor switching elements 601, 602. The first half-bridge H1 is also connected to the negative output potential tap 701.

The second half-bridge H2 is connected to the negative input conductor 402 and includes a series connection of two semiconductor switching elements 603, 604. The respective semiconductor switching element 601, 602, 603, 604 is in the form of a MOSFET, for example. In addition, the second half-bridge H2 is connected to the positive output potential tap 701 .

The center tap M1 of the first half-bridge H1 and the center tap M2 of the second half-bridge H2 are connected via a choke 605.

The inductance of the choke 605 is preferably between 10 mH and 100 mH. Included the value of the inductance of the choke 605 is selected in particular depending on the power of the DC/DC converter device 1 and the selected switching frequency from the range between 10 mH and 100 mH's.

The choke 605 of the DC/DC converter 600 can be operated in particular as a flying inductance.

Furthermore, the DC/DC converter device 1 of Fig. 4a has a control unit 610. The control unit 610 is set up to control the semiconductor switching elements 601, 602, 603, 604 and in particular to control them in such a way that two corresponding semiconductor switching elements 601, 603 and 602, 604 of the two half-bridges H1, H2 in phase or antiphase, also phase-shifted, switch, in particular switch with an identical switch-on delay.

In particular, the two input-side, i.e. source-side semiconductor switching elements 601, 603 of the two half-bridges H1, H2 can be switched simultaneously, and the two load-side, i.e. output-side semiconductor switching elements 602, 604 of the two half-bridges H1, H2 can also be switched simultaneously, in particular in phase or in phase opposition. The half-bridges H1 and H2 are thus operated in phase. Alternatively, the half-bridges H1 and H2 can also be operated with a 180° phase shift, i.e. in phase opposition.

An intermediate output circuit 700, which has a number of output capacitors 703, 704, is connected downstream of the DC/DC converter 600. In the example of Fig. 4a, the intermediate output circuit 700 has - without loss of generality - an output capacitor bridge with two series-connected capacitors 703, 704 which is connected between the negative output potential tap 701 and the positive output potential tap 702 of the DC/DC converter device 1, between tween which an output intermediate circuit center 705 is defined. The input intermediate circuit center point 503 and the output intermediate circuit center point 705 are connected to one another via a coupling line 750 . The coupling line 750 equalizes the middle potentials of the intermediate circuit center points 503, 705, so that no potential differences occur in this respect and the input and output potential thus receive a common middle potential. This is particularly advantageous with regard to the degree of efficiency and the EMC resistance of the DC/DC converter device. In Fig. 4b is a schematic circuit diagram of a fourth embodiment of a DC / DC converter device 1, which is designed for charging and discharging a DC energy store 8 by means of an AC network 4. The fourth embodiment of Fig. 4b includes essential features of the third embodiment of Fig. 4a, but differs from it in a few points:

The intermediate input circuit 500 is preceded by a 3-point AC/DC converter 400, which provides an input potential symmetrical about a GND center tap from mains-side three-wire phases of a subscriber network 4, which are smoothed by an LCL filter device 400.

The intermediate output circuit 700 includes a single output capacitor 703 and the coupling line 750 is omitted. As a result, the center potential between the output potential taps 701, 702 can be freely shifted independently of the center potential at the input intermediate circuit center point 503 and is generally kept at ground potential during operation. In the event of a ground fault, one of the output potential taps 701 or 702 can be brought to ground potential without impairing operation, which enables protection against accidental contact.

In addition, the DC/DC converter device 1 of Fig. 4b has an interference suppression circuit 550 arranged between the input intermediate circuit 500 and the DC/DC converter 600. The interference suppression circuit 550 comprises two interference suppression capacitors 551, 552 connected in parallel with the intermediate circuit capacitors 501, 502. The node 553 connecting the two suppression capacitors 551, 552 is connected to earth potential (mass). Furthermore, the DC/DC converter device 1 of Fig. 4b has a load-side interference suppression circuit 650 arranged between the DC/DC converter 600 and the output intermediate circuit 700. The load-side, i.e. output-side interference suppression circuit 650 has two parallel to the output capacitor 703 of the output intermediate circuit 700 switched interference suppression capacitors 651, 652. The node 653 connecting the two interference suppression capacitors 651, 652 is connected to earth potential (ground).

5a shows a schematic circuit diagram of a fifth embodiment of a DC/DC converter device 1 for charging and/or discharging an energy store 8 from an AC network 4. The energy store 8 can also be powered by a DC industrial network 3 or an emergency energy store of an intermediate circuit a pitch drive 2 can be replaced, in which case no AC mains 4 but an intermediate circuit of the control Circuit of the pitch drive 2 is connected.

The fifth embodiment of FIG. 5a comprises all features of the fourth embodiment according to FIG. 4b, although the interference suppression circuit 550 on the input side and the interference suppression circuit .650 on the output side are omitted.

The DC/DC converter device 1 of FIG. 5a also has a first diode 801 and a second diode 802. The anode of the first diode 801 is connected to the negative output potential tap 701, and the cathode of the first diode 801 is connected to the input Intermediate circuit center 503 connected. The anode of the second diode 802 is connected to the input intermediate circuit center point 503 and the cathode of the second diode 802 is connected to the positive output potential tap 702 .

According to FIG. 5a, a resonant capacitor 606 is connected to the center tap M1 of the first half-bridge H1 and is connected in parallel with the semiconductor switching element 601. FIG. Furthermore, an oscillating capacitor 607 is connected to the center tap M1 of the first half-bridge H1 and is connected in parallel to the semiconductor switching element 602 .

Analogously, a reversing capacitor 608 is connected to the center tap M2 of the second half-bridge H2 and is connected in parallel to the semiconductor switching element 603 . Correspondingly, an oscillating capacitor 609 is connected to the center tap M2 of the second half-bridge H2 and is connected in parallel to the semiconductor switching element 604 .

The reversing capacitors 606, 607, 608, 609 limit the rate at which the voltage rises and thus reduce the turn-off losses and improve the EMC behavior with regard to interference emissions. The resonant capacitors can also be referred to as ZVS capacitors or snubber capacitors (ZVS; zero-voltage switching).

5b shows the fifth embodiment shown in FIG. 5a for a general DC/DC conversion as a further embodiment and enjoys the advantages shown with respect to the fifth embodiment, in particular with regard to the efficiency, the EMC and the ZVS switching behavior . On the input side, a DC source, for example a drive intermediate circuit, a DC energy source such as a Solar generator or a DC energy storage can be connected. On the output side, for example, a DC industrial network segment 2 of a DC industrial network 4 or an emergency energy store of a pitch drive 2 can be connected.

Advantageously, a DC voltage is provided on the input side on the positive and negative input conductors 401, 402, and a center voltage symmetrical thereto is provided on the GND input. Deviating from the fifth embodiment of FIG. 5a, an intermediate output circuit with an output capacitor bridge 703, 704 is arranged on the output side. As in FIG. 4a, the output intermediate circuit center point 705 is connected to the input intermediate circuit center point 503 via a coupling line 750, so that what was said about the embodiment of FIG. 4a applies in this regard.

The GND connection does not necessarily have to be used. The control unit 610 is preferably set up to control the semiconductor switching elements 601, 602, 603, 604 in such a way that the first half-bridge H1 and the second half-bridge H2 are controlled in phase or preferably in phase opposition with a 180° phase shift. The ratio of the switch-on times of the input-side semiconductor switching elements 601, 603 to the switch-on times of the load-side semiconductor switching elements 602, 604 is in particular adjustable or constant, ie has a predetermined quotient. The symmetry of the average output voltage at the output potential taps 701 and 702 with respect to GND can be achieved by a phase shift that deviates slightly from in-phase or from 180°. In addition, the control unit 610 is preferably set up to turn off one of the semiconductor switches 601, 602, 603 and 604 somewhat earlier in order to achieve symmetry of the average output voltage at the output potential taps 701 and 702 with respect to GND.

6 shows a schematic circuit diagram of a sixth embodiment of a DC/DC converter device 1 for providing a variably adjustable DC output potential on the output side. The sixth embodiment of FIG. 6 includes all features of the fifth embodiment of FIG. 5a.

Furthermore, the DC/DC converter device 1 according to FIG. 6 has an overvoltage protection element 803, which is coupled between the input intermediate circuit center point 503 and a node 804, to which the cathode of the first diode 801 is connected and to which the anode of the second Diode 802 is connected. The overvoltage protection element 803 is, for example, a varistor or a bidirectional suppressor diode, such as a bidirectional transildiode.

The functionality of the diodes 801, 802 and the overvoltage protection element 803 is the protection of the semiconductor switching elements 601, 602, 603, 604 against overvoltage. This overvoltage can arise if the mean potential of the output potential taps 701 and 702 should shift sharply in relation to the input intermediate circuit center point 503. The diodes 801, 802 and the overvoltage protection element 803 achieve this in particular in that the potential of the output potential tap 702 cannot become more negative than the potential of the input intermediate circuit center point 503 and the potential at the output potential tap 701 cannot become more positive than that Potential of the input intermediate circuit center point 503.

As an alternative and not shown, a series circuit comprising a first overvoltage protection element and the first diode 801 can be arranged between the input intermediate circuit center point 503 and the negative output potential tap 701, and a series circuit comprising a second overvoltage can be arranged between the input intermediate circuit center point 503 and the positive output potential terminal 702 voltage protection element and the second diode 802 can be arranged.

For the embodiment shown in Fig. 6, the control unit 610 is preferably set up to control the semiconductor switching elements 601, 602, 603, 604 in such a way that the input-side semiconductor switching element 601 of the first half-bridge H1 and the load-side semiconductor switching element 604 of the second half-bridge H2 are low have slightly overlapping turn-on times and/or that the input-side semiconductor switching element 603 of the second half-bridge H2 and the load-side semiconductor switching element 602 of the first half-bridge H1 have slightly overlapping turn-on times. In this case, the ratio of the switch-on times of the input-side semiconductor switching elements 601, 603 to the switch-on times of the load-side semiconductor switching elements 602, 604 is in particular adjustable or constant, that is to say it has a specific quotient.

In addition, control unit 610 is preferably set up to turn off one of the output-side semiconductor switching elements 601, 603 of the two half-bridges H1, H2 earlier than the other input-side semiconductor switching element 603, 601 of the two half-bridges H1, H2, so that a coupling of an input-side primary circuit K1 (see FIG. 7) and a load-side secondary circuit K2 (see FIG. 7) via the inductor 605 is provided. Such a coupling for the circuit K3 of a balancing current is shown in FIG. Details on this are explained below.

As FIG. 6 shows, the semiconductor switching elements 601, 602, 603, 604 can be in the form of MOSFETs. The control unit 610 can preferably be set up to control the gates of the MOSFETs 601, 602, 603, 604 of the half-bridges H1, H2 with such phase-shifted control signals G1, G2, G3, G4, so that the input-side primary circuit K1 (See Fig. 7) and the load-side secondary circuit K2 (see Fig. 7) via the choke 605 is provided.

The above, in particular the mode of operation of the choke 605 that can be operated as a flying inductor and the output potential control, is explained in more detail below with reference to the diagrams in FIG. For this purpose, FIG. 9a shows the current in the inductor 605 and FIG. 9b shows the output voltage denoted as U1, plus to ground denoted as U2, minus to ground denoted as U3 and the average output voltage denoted as U4. Furthermore, Fig. 9c shows the reverse voltages of MOSFETs 601, 602, 603 and 604, where V1 is the reverse voltage across MOSFET 601, V2 is the reverse voltage across MOSFET 602, V3 is the reverse voltage across MOSFET 603 and V4 is the reverse voltage across MOSFET 604 is. Furthermore, FIG. 9d shows the gate signals of the MOSFETs 601, 602, 603 and 604. Here the gate signal G1 is assigned to the MOSFET 601, the gate signal G2 is assigned to the MOSFET 602, which is the gate signal G3 associated with MOSFET 603 and gate signal 604 associated with MOSFET 604 .

As shown in Fig. 9a, the mean value of the current flowing through the choke 605 is 60 A. This is the sum of the mean input current of the primary circuit K1 (see Fig. 7) and the mean output current of the secondary circuit K2 (see 7). With reference to FIG. 9d, times A are provided in the gate signals G1, G2, G3, G4 of the MOSFETs 601, 602, 603, 604 for the charge reversal of the reversing capacitors 606, 607, 608 and 609. The charge reversal can be seen on edge B of the MOSFET blocking voltages according to FIG. 9c. The maximum current of + 150 A according to Fig. 9a in the inductor 605 causes rapid charge reversal, the minimum current of -30 A according to FIG. 9a in the inductor 605, on the other hand, causes a slow charge reversal and thus a flat edge B of the MOSFET blocking voltages in FIG. 9c. The MOSFETs switch on, see A in FIG. 9d, always takes place when the blocking voltage of the MOSFETs is zero in order to reduce or avoid turn-on losses. When the MOSFETs turn off (see A in Fig. 9d), the MOSFET blocking voltage across them increases so slowly during charge reversal that the blocking voltage remains low during turn-off, i.e. there is a dU/dt-limited turn-off. Compared to hard turn-off, this results in far fewer turn-off losses.

ZVS switching of MOSFETs 601, 602, 603 and 604 is characterized by zero-loss turn-on and zero-loss turn-off with slew-rate limited by resonant capacitors 606, 607, 608 and 609. ZVS switching presupposes that the inductor current according to FIG. 9a has at least one zero crossing between two switching operations of the MOSFETs 601, 602, 603 and 604.

At time C in FIG. 9d, MOSFET 603 is switched off earlier than MOSFET 601. This results in the above-mentioned coupling (see circuit K3 in FIG. 8) of the circuits. The symmetry of the output voltage to ground shifts with each switching process (cf. FIG. 9b at time C). A symmetry control can thus take place.

As already explained above, there are two possibilities for symmetry control: firstly, turning off one or more MOSFETs slightly earlier and secondly, slightly shifting the phase of the gate signals G1, G2, G3, G4 of the two half-bridges H1, H2 relative to one another.

As shown in FIGS. 6, 7, 8 and 10, the control unit 610 can have two current regulators, which in particular are independent of one another. In particular, control unit 610 includes a load current controller 611 and a balancing current controller 612. Control unit 610 also includes a differential voltage controller 613.

The load current controller 611 is set up in particular to set the ratio of the switch-on times of the input-side MOSFETs 601, 603 to the switch-on times of the load side MOSFETs 602, 604 set. The symmetry current regulator 612 provides a symmetry current (see circuit K3 of FIG. 8 and SY in FIG. 10) for symmetrizing the potential at the negative output potential tap 701 and the potenti as at the positive output potential tap 702 with respect to ground potential.

The differential voltage controller 613 is set up in particular to provide a setpoint value SWS (see FIG. 10) for a setting signal SY depending on at least one measured voltage U2, U3 (see FIG. 10) in the load-side secondary circuit K2. The differential voltage controller 613 is slower than the balancing current controller 612.

As explained above, the fast load current controller 611 influences the ratio of the switch-on times (switch-on durations) of the input-side MOSFETs 601, 603 to the switch-on times of the load-side MOSFETs 602, 604. If the ratio is less than 1, the input voltage is reduced, if the ratio is greater than 1 it is boosted, with a ratio of 1 the input voltage is only inverted.

The differential current controller influences the switch-off time of individual MOS-FETs 601, 602, 603, 604 or the phase shift. As explained above, the balancing current regulator 612 can set a balancing current according to FIGS. 8 and 10. The differential voltage controller 613 supplies the target value SWS for the setting signal SY. For example, this can ensure that an earth leakage current caused by unequal soiling of the output potential taps 701 and 702 to earth is compensated for by the balancing current regulator 612 and the output voltage thus remains earth-symmetrical. It is also preferably suitable for compensating for the tendency towards asymmetry caused by timing tolerances in the gate signals G1, G2, G3, G4. Details on this are explained with reference to FIG. 10 .

Here, FIG. 10 shows the schematic circuit diagram of FIG. 6 with the balancing control drawn in, with some of the reference symbols drawn in FIG. 6 being omitted in FIG. 10 for reasons of clarity.

The control unit 610 shown in FIG. 10 can also be referred to as a control unit or control device and is set up for balance control. The control unit 610 of FIG. 10 includes a load current controller 611, a balancing current controller 612 and a differential voltage controller 613. the DC/DC converter device 1 according to Fig. 10 includes a first current measuring device 614, a second current measuring device 615, a first voltage measuring device 616, a second voltage measuring device 617, a first subtraction unit 618, a summation unit 619, a second subtraction unit 620, a halving unit 621 as well a PWM generator 622 (PWM; pulse width modulation).

The first current measuring device 614 is set up to measure the current I3 flowing from the first half bridge H1 to the negative output potential tap 701 . Correspondingly, the second current measuring device 615 is set up to measure the current I2 flowing from the second half-bridge H2 to the positive output potential tap 702 .

The first subtraction unit 618 is suitable for providing a first differential signal DS1 from a difference between the current I2 and the current I3 on the output side. The summing unit 619, on the other hand, sums the currents I2 and I3 and, depending on this, provides a sum signal SS1 on the output side.

The halving unit 621 halves the first sum signal SS1 provided by the summing unit 619 and provides a second sum signal SS2 on the output side (SS2=0.5*SS1).

The first voltage measuring device 616 is set up to measure a voltage drop between the negative output potential tap 701 and ground and to provide a first voltage value U3 (negative to ground) on the output side as a function of this measurement.

Furthermore, the second voltage measuring device 617 is set up to measure a voltage drop between the positive output potential tap 702 and ground and to provide a second voltage signal U2 (plus to ground) on the output side as a function of the measurement. The second subtraction unit 620 forms a second difference signal DS2 from the difference between U2 and U3 and makes this available on the output side.

The differential voltage controller 613 receives on the input side the second differential signal DS2 from the second subtraction unit 620 and a differential voltage setpoint value DSS and, depending on this, sets the balancing current setpoint on the output side. value SWS and feeds it to the balancing current controller 612. The balancing current controller 612 receives the balancing current setpoint SWS on the input side and the first differential signal DS1 from the first subtraction unit 618. Depending on these received signals DS1, SWS, the balancing current controller 612 provides the setting signal SY on the output side and feeds this to the PWM generator 622 to.

On the input side, the load current controller 611 receives the halved sum signal SS2 and a load current setpoint value LSS and, depending on this, provides a setting signal on the output side for setting the switch-on times of the MOSFETs 601, 602, 603, 604.

The PWM generator generates the gate signals G1, G2, G3, G4 for the MOSFETs 601, 602, 603, 604 depending on the received setting signal ES and the received setting signal SY.

In particular, the differential voltage controller 613 is so slow that it cannot initially change the balancing current in the event of a fault current suddenly occurring. The charge reversal of the capacitors 651 and 652 is preferably not disturbed in this case. As a result, the system behaves like a system that is galvanically isolated from the network 4. Before the differential voltage controller 613-balancing current controller 612 can react in such a case, the DC/DC converter 600 is preferably switched off. If desired, the system could continue to operate with a ground fault if necessary, without driving a current into the ground fault.

In the embodiments shown in Figures 3, 4b, 5a, 6, 7, 8, 10, if there is no line 750, i.e. if there is quasi-potential isolation and there is no galvanic connection between the input side and the output side outside of the semiconductor bridges H1 , H2 the DC converter device 1 can continue to be operated without restrictions in the event of a ground fault. This circumstance is an important aspect, particularly with regard to personal protection and operational safety.

11 also shows a schematic flowchart of a method for operating a DC/DC converter device 1 for operating a wind turbine or an industrial DC supply network 3. The DC/DC converter device 1 is explained, for example, as in the preceding figures educated. In step S1, the DC/DC converter device 1 is connected to a DC energy source such as an AC/DC converter 400 of a multi-phase network 4, an intermediate drive circuit, a solar generator, a DC energy store or the like and a DC energy sink. for example a DC. Energy store 8, for example an electric vehicle, a network segment 2 of a DC industrial network 3, an emergency energy store, etc. coupled. It is also conceivable to place the DC/DC converter device between an emergency energy store and the intermediate circuit of one or more pitch or yaw drives 2 of a wind turbine 3, between intermediate circuits of electrical drives for intermediate circuit coupling or support by means of an energy store or an energy source, between to use different network segments 2 of a DC industrial network 3 or the like, in which, preferably bidirectionally, electrical energy can be passed to the same or different, preferably variable, voltage levels.

In step S2, the inductor 605 of the DC/DC converter 600 connecting the center tap M1 of the first half-bridge H1 and the center tap M2 of the second half-bridge H2 is operated as a flying inductor.

Although the present invention has been described on the basis of embodiments, it can be modified in many ways.

REFERENCE LIST

DC/DC converter device

Pitch drive or DC industrial network segment

Wind turbine or DC industrial grid

AC grid

charging cable

Grid connection point for multi-phase power supply grid

DC energy storage

terminal block

EMC filter device

LCL filter device

AC/DC converter positive input lead negative input lead

input intermediate circuit

intermediate circuit capacitor

Input intermediate circuit center

suppression circuit

suppression capacitor

node

DC/DC converter

semiconductor switching element

throttle

reversing capacitor

control unit

load current controller

balancing current controller

differential voltage regulator first current measuring device second current measuring device first voltage measuring device second voltage measuring device first subtraction unit

summation unit second subtraction unit

bisection unit

PWM generator

suppression circuit > m

651 anti-interference capacitor

652 anti-interference capacitor

653 knots

700 output intermediate circuit

701 output potential tap

702 output potential tap

703 output capacitor

704 output capacitor

705 output intermediate circuit center 750 coupling line 801 diode 802 diode

803 overvoltage protection element

804 knots

, B, C times

adjustment signal

G1 gate signal for semiconductor switching element 601

G2 gate signal for semiconductor switching element 602

G3 gate signal for semiconductor switching element 603

G4 gate signal for semiconductor switching element 604

H1 first half bridge

H2 second half bridge

current

12 electricity

13 current K1 circuit K2 circuit K3 circuit L1 phase L2 phase L3 phase M1 center tap of the first half bridge M2 center tap of the second half bridge s Time in seconds

S1, S2 method steps

SY setting signal ui output voltage

U2 plus to earth

U3 negative to earth

U4 Average output voltage

V1 Voltage at the semiconductor switching element 601

V2 voltage at the semiconductor switching element 602

V3 voltage at the semiconductor switching element 603

V4 voltage at the semiconductor switching element 604

GND Center potential at the input intermediate circuit center

Claims

patent claims

1. DC/DC converter device (1) for operating a wind turbine, an electrical drive system, or an industrial DC supply network (3) with electrical energy, having: an input intermediate circuit (500) which has a number of intermediate circuits between a positive input conductor ( 401) and a negative input conductor (402) has switched intermediate circuit capacitors (501, 502), and a DC/DC converter (600) which is connected downstream of the input intermediate circuit (500) and which has a first half-bridge (H1 ) and a second half-bridge (H2) connected to the negative input conductor (402), the center tap (M1) of the first half-bridge (H1) and the center tap (M2) of the second half-bridge (H2) being connected via a choke (605). are.

2. DC / DC converter device (1) according to claim 1, characterized in that with a number of AC phases (L1, L2, L3) can be coupled AC / DC converter (400), in particular a 3-point AC/DC converter is connected upstream on the input intermediate circuit (500) on the input conductors (401, 402), or a DC energy source, in particular a solar generator, or a DC energy store (3), in particular an accumulator, on the input intermediate circuit (500 ) is connected to the input conductors (401, 402).

3. DC / DC converter device (1) according to claim 1 or 2, characterized in that at least one pitch drive (3), or a yaw drive of a wind turbine (3), an intermediate circuit of an electrical drive or at least one DC Network segment of a DC industrial network (3) is connected downstream to an intermediate output circuit (700) of the DC/DC converter (600).

4. DC/DC converter device (1) according to one of the preceding claims, characterized in that the inductor (605) of the DC/DC converter (600) can be operated as a flying inductance. 5. DC / DC converter device (1) according to any one of the preceding claims, characterized in that the DC / DC converter device (1) is a transformerless DC / DC converter device.

6. DC / DC converter device (1) according to any one of the preceding claims, characterized in that the DC / DC converter (600) is designed as a bidirectional DC / DC converter for stepping up and / or stepping down voltages.

7. DC/DC converter device (1) according to one of the preceding claims, characterized in that the respective half-bridge (H1, H2) has a series connection of two semiconductor switching elements (601, 602, 603, 604).

8. DC / DC converter device (1) according to claim 7, characterized in that the respective semiconductor switching element (601, 602, 603, 604) as a MOSFET, preferably as a SiC MOSFET, or as an IGBT or as a SiC Cascode is formed.

9. DC/DC converter device (1) according to claim 7 or 8, characterized in that the DC/DC converter device (1) has a control unit (610) which is set up to switch the semiconductor switching elements (601, 602, 603, 604) to control such that two corresponding semiconductor switching elements (601, 603, 602, 604) of the two half-bridges (H1, H2) switch simultaneously, in particular switch with an identical switch-on delay.

10. DC/DC converter device (1) according to claim 7 or 8, characterized in that the DC/DC converter device (1) has a control unit (610) which is set up to control the half-bridges H1 and H2 out of phase, in particular with 180° phase shift.

11. DC / DC converter device (1) according to any one of the preceding claims, characterized in that between the input intermediate circuit (500) and the DC / DC converter (600) an interference suppression circuit (550) is arranged, which two to the intermediate circuit capacitors (501, 502) has interference suppression capacitors (551, 552) connected in parallel, with the node (553) connecting the two interference suppression capacitors (551, 552) being connected to ground potential. 12. DC / DC converter device (1) according to any one of the preceding claims, characterized by a DC / DC converter (600) downstream output intermediate circuit (700) with a number of output capacitors (703, 704) which between a negative Output potential tap (701) and a positive output potential tap (702) of the DC/DC converter device (1) are connected.

13 DC/DC converter device (1) according to Claim 12, characterized in that the intermediate circuit capacitors (501, 502) of the input intermediate circuit (500) form an input capacitor bridge with an input intermediate circuit center point (503), and the output capacitors (703, 704 ) of the output intermediate circuit (700) form an output capacitor bridge with an output intermediate circuit center (705), the input intermediate circuit center (503) being connected to the output intermediate circuit center (705) via a coupling line (750).

14. DC/DC converter device (1) according to claim 12 or 13, characterized in that a load-side interference suppression circuit (650) is arranged between the DC/DC converter (600) and the intermediate output circuit (700), which has two Number of output capacitors (703, 704) of the intermediate output circuit (700) has suppression capacitors (651, 652) connected in parallel, the node (653) connecting the two suppression capacitors (651, 652) being connected to ground potential.

15. DC / DC converter device (1) according to any one of claims 9 to 14, characterized in that the control unit (610) is set up to control the semiconductor switching elements (601, 602, 603, 604) such that the input-side semiconductor switching element (601) of the first half-bridge (H1) and the load-side semiconductor switching element (604) of the second half-bridge (H2) have overlapping switch-on times and/or that the input-side semiconductor switching element (603) of the second half-bridge (H2) and the load-side semiconductor switching element (602) of first half bridge (H1) have overlapping turn-on times, the ratio of the turn-on times of the input-side semiconductor switching elements (601, 603) to the turn-on times of the load-side semiconductor switching elements (602, 604) preferably having a predetermined quotient. 16. DC/DC converter device (1) according to one of claims 9 to 15, characterized in that the control unit (610) is set up to switch one of the output-side semiconductor switching elements (601, 603) of the two half-bridges (H1, H2) earlier turn off than the other input-side semiconductor switching element (601, 603) of the two half-bridges (H1, H2), so that a coupling of an input-side primary circuit (K1) and a load-side secondary circuit (K2) via the inductor (605) is provided .

17. DC/DC converter device (1) according to any one of claims 9 to 16, characterized in that the semiconductor switching elements (601, 602, 603, 604) are MOSFETs and the control unit (610) is set up to switch the gates of the MOSFETs ( 601, 602, 603, 604) of the half-bridges (H1, H2) with such phase-shifted control signals (G1, G2, G3, G4), so that a coupling of an input-side primary circuit (K1) and a load-side secondary circuit (K2) is provided via the throttle (605).

18. DC/DC converter device (1) according to one of Claims 9 to 17, characterized in that the control unit (610) has a load current controller (611), a balancing current controller (612) and a differential voltage controller (613). has, wherein the load current controller (611) is set up to set the ratio of the switch-on times of the input-side semiconductor switching elements (601, 603) to the switch-on times of the load-side semiconductor switching elements (602, 604), the balancing current controller (612) being used for this purpose is set up to set a setting signal (SY) for balancing the potential at the negative output potential tap (701) and the potential at the positive output potential tap (702) with respect to ground potential, and the differential voltage regulator (613) is set up to do this, provide a target value (SWS) for the setting signal (SY) depending on at least one measured voltage (U2, U3) in the load-side secondary circuit (K2).

19. DC/DC converter device (1) according to claim 18, characterized in that the differential voltage controller (613) is slower than the balancing current controller (612). 20. DC/DC converter device (1) according to one of claims 12 to 19, characterized in that the anode of a first diode (801) is coupled to the negative output potential tap (701) and the cathode of the first diode (801). is coupled to the input intermediate circuit center point (503) and the anode of a second diode (802) is coupled to the input intermediate circuit center point (503) and the cathode of the second diode (802) is coupled to the positive output potential tap (702).

21. DC/DC converter device (1) according to claim 20, characterized in that the anode of the first diode (801) is connected to the negative output potential tap (701) and the cathode of the first diode (801) is connected to the input intermediate circuit center point (503) and the anode of the second diode (802) is connected to the input intermediate circuit center point (503) and the cathode of the second diode (802) is connected to the positive output potential tap (702).

22. DC / DC converter device (1) according to claim 20, characterized in that a

Overvoltage protection element (803) between the input

Intermediate circuit center (503) and a node (804) is coupled to which the cathode of the first diode (801) is connected and to which the anode of the second diode (802) is connected.

23. DC/DC converter device (1) according to claim 20, characterized in that a series connection of a first overvoltage protection element and the first diode (801) is arranged between the input intermediate circuit center point (503) and the negative output potential tap (701). and a series connection made up of a second overvoltage protection element and the second diode (802) is arranged between the input intermediate circuit center point (503) and the positive output potential tap (702).

24. DC/DC converter device (1) according to one of the preceding claims, characterized in that an EMC filter device (200) and an LCL filter device (300) connected downstream of the EMC filter device (200) between three input-side connection terminals (101 , 102, 103) for the three phases (L1, L2, L3) of the multi-phase network (4) and the AC/DC converter (400). 25. DC/DC converter device (1) according to one of the preceding claims, characterized in that the AC/DC converter (400) arranged on the input side is designed as a 3-point AC/DC converter.

26 DC / DC converter device (1) according to any one of the preceding claims, characterized in that connected in parallel with each semiconductor switching element (601, 602, 603, 604) a resonant capacitor (606, 607, 608, 609) to implement a ZVS switching behavior is.

27. A method for operating a DC/DC converter device (1) for operating a wind turbine, an electrical drive system or an industrial DC supply network (3) with electrical energy, preferably according to one of the preceding claims, wherein the DC/DC Converter device (1) has an input intermediate circuit (500) which has a number of intermediate circuit capacitors (501, 502) connected between a positive input conductor (401) and a negative input conductor (402), and a DC connected downstream of the input intermediate circuit (500). / DC converter (600), which one with the positive input conductor

(401) connected first half bridge (H1) and one to the negative input conductor

(402) connected second half-bridge (H2), with:

Operating a choke (605) of the DC/DC converter (600) connecting the center tap (M1) of the first half-bridge (H1) and the center tap (M2) of the second half-bridge (H2) as a flying inductor.