Device, method for operating such a device and application of such a device

Abstract

A converter (6) comprising an input (61, 62) connectable to a DC power source (2), at least one converter module (1, 1'-1"') having a first, a second and a third bridge branch (11, 12, 13), and a common DC voltage intermediate circuit (14) for the bridge branches (11, 12, 13), wherein each of the bridge branches (11, 12, 13) has a phase output (113, 123, 133), wherein the first and second bridge branches (11, 12) are configured to provide a first power (51) in the form of an alternating current to the phase output (113, 123), and an energy storage ( The invention also relates to a method for operating a converter (6) and a use of such a converter (6).

Description

Technical Field

[0001] The invention relates to a converter having at least one converter module with a first, a second and a third bridge branch, wherein each of the bridge branches has a phase output and a control unit for actuating the bridge branches, wherein a common DC voltage intermediate circuit is provided for all bridge branches. The invention also relates to a method for operating a converter and to the use of such a converter. Background Art

[0002] Such converters are usually used as inverters to convert a DC voltage (e.g. from a photovoltaic (PV) system) into a grid-compatible AC current for feeding a three-phase AC power grid. The power supply grid is usually designed as a three-phase grid at all voltage levels, wherein the grid provider's feed-in guidelines allow only limited power differences for the three phases. For this reason - except for converters for special applications - converters are usually equipped with three bridge branches, since these three bridge branches are required for most applications.

[0003] Document DE 10 2014 104 216 B3 discloses a three-phase inverter which can be operated in single-phase emergency mode in the event of a fault in the power supply network. In this emergency mode, two of the three bridge branches are operated in such a way that a single-phase alternating current for emergency power supply (for example, of a house) can be supplied between the two bridge branches on at least one network phase. The third bridge branch remains unused.

[0004] EP 2 950 439 A1 discloses a power router, which consists of bidirectional power converter subunits connected on the DC side via a DC bus, wherein the power converter subunits provide different loads or feed power into a battery or a network. Here, each of the subunits must be designed for a power that corresponds to the power source or load connected respectively.

[0005] When converting direct current into three-phase alternating current, the energy is extracted very evenly from the direct current source, so that the DC intermediate circuit, which can be designed as a film capacitor, for example, is only slightly loaded. In this case, only the fluctuations caused by the switching operation of the semiconductor switches (commonly referred to as "ripple") need to be buffered against the constantly output direct current power. This does not apply when converting to single-phase alternating current, where only the sinusoidal current is output. 2 The DC link circuit of an inverter sized for three-phase AC is therefore usually too small for single-phase applications.

[0006] For reasons of efficiency, it is desirable to configure and operate the converter in such a way that the energy output from the connected PV system is as uniform as possible over the entire cycle of the generated alternating current. At the same time, it is also desirable to use converters that are cost-effective and, if possible, always of the same type. In particular, it is desirable to use "standard three-phase inverters" that are inexpensively produced for the application and are fed into the interconnection network via a conventional three-phase AC feed. In this context, the connection of storage systems should first be mentioned, since the storage of electrical energy and regenerative energy sources are becoming increasingly important due to their highly fluctuating energy generation. Summary of the invention

[0007] The object of the present invention is therefore to provide a converter having a converter module with three bridge branches, which provides an AC voltage and a DC voltage for a storage system when the DC source is evenly loaded. Another object is to specify an operating method for such a converter.

[0008] This object is achieved by a converter having the features according to the invention and a method for operating a converter. Advantageous embodiments and refinements are optional embodiments.

[0009] In the converter according to the invention, an alternating voltage power is provided between the phase outputs of the first bridge branch and the second bridge branch, and an energy storage device can be connected to the third bridge branch in order to charge and / or discharge the energy storage device. A DC power source (e.g., a PV generator) can be connected to the input of the converter. The converter comprises at least one converter module having a first, second, and third bridge branch, wherein each of the bridge branches has a phase output. The converter module also comprises a common DC voltage intermediate circuit for the bridge branches. The first bridge branch and the second bridge branch are configured to output a first power from the DC power source and provide the first power as an alternating current to the phase output. The energy storage device can be connected to the phase output of the third bridge branch, and the third bridge branch is configured to exchange a second power between the DC power source and the energy storage device and between the energy storage device and the common DC voltage intermediate circuit. The energy storage device can output and store electrical power from the DC power source through the DC voltage intermediate circuit, and vice versa, the electrical power can flow back from the energy storage device into the DC voltage intermediate circuit and further flow back through the first and second bridge branches, for example, into a network connected there.

[0010] The converter further comprises a control unit, which is arranged to control the bridge branches or their semiconductor switches in such a way that the sum of the first power and the second power corresponds to a constant desired value, thereby minimizing the power flow into or out of the common DC voltage intermediate circuit. The balance of the sum of the first power and the second power depends on the instantaneous amplitude and direction of the energy flow and occurs in the common DC voltage intermediate circuit, which should remain virtually unloaded by this balance. According to the invention, the control unit is arranged to control the bridge branches in such a way that the geometric sum of the second power flowing through the third bridge branch and the first power flowing through the first and second bridge branches in the common DC voltage intermediate circuit at any time results in a constant desired value, which is output from the DC power source and output as alternating current to the phase output. In summary, small fluctuations of the sum of the instantaneous values ​​should be compensated at least over the duration of the network cycle.

[0011] This means that the instantaneous value of the power flowing into or out of the energy store compensates for the AC voltage power on a time scale that is dependent on the network frequency.

[0012] The method according to the invention relates to a control of a converter, to which a DC power source can be connected to the input of the converter. The converter comprises at least one converter module having a first, second and third bridge branch and a common DC voltage intermediate circuit for the bridge branch, wherein each of the bridge branches has a phase output terminal, and the converter further comprises a control unit for controlling the bridge branch or its semiconductor switch. An energy storage device can be connected to the third bridge branch. According to the invention, the first bridge branch and the second bridge branch are controlled in such a way that a first power is output from the DC power source and the first power is provided to the phase output terminal as an alternating current, in other words, AC power can be fed into the network or electrical power can be provided to AC electrical appliances. The third bridge branch is controlled in such a way that a second power can be exchanged between the DC power source and the energy storage device and between the energy storage device and the common DC voltage intermediate circuit.

[0013] The control of the bridge branches is characterized in that the sum of the first power and the second power corresponds to a constant desired value, so that the power flow into or out of the common DC voltage intermediate circuit is minimized. In other words, the third bridge branch is controlled in such a way that the instantaneous value of the power flowing into or out of the energy storage compensates the generated AC voltage power on a time scale that is dependent on the network frequency. For this purpose, the power flowing into or out of the energy storage and the AC voltage power are preferably operated in anti-phase.

[0014] In this way, the alternating voltage power is compensated during each network frequency cycle by the varying power flowing into or out of the energy storage device, so that the direct current source is constantly loaded. In this way, the energy storage device can at least partially take over the function of a capacitor that is usually arranged in a direct current (DC) intermediate circuit in devices according to the prior art. By means of the method according to the invention, the capacitor does not need to withstand power fluctuations of the alternating current power that occur at twice the network frequency, but only current ripples that occur at a much higher frequency due to the switching of semiconductor power switches. Accordingly, the capacitance in the DC intermediate circuit can be kept small, in particular so small that it can be applied economically and in view of the lower space requirement by means of film capacitors, which have a longer service life and lower losses than, for example, electrolytic capacitors.

[0015] In an advantageous embodiment, the constant desired value corresponds to the maximum power point (MPP) of the DC source (eg PV generator), which is important for the maximum energy yield of the DC source and leads to an optimized efficiency of the entire system consisting of the DC source and the converter.

[0016] In a further advantageous embodiment of the converter, the first, second and third bridge branches have the same type of construction. This offers the advantage of using a "standard three-phase inverter" in combination with an energy store (e.g. a battery), which was not previously possible, which can be produced cheaply and in large quantities. Furthermore, the bridge branches are preferably designed for bidirectional operation so that, if necessary, a current return from the energy store into the DC intermediate circuit is also possible, which brings the additional advantage of being able to connect the energy store to any bridge branch. Thus, reactive current can also be provided on other bridge branches - for example for network support.

[0017] In a further advantageous embodiment, the converter according to the invention comprises exactly one converter module with three bridge branches, whereby a single-phase alternating current can be realized at the phase output of two of the three bridge branches - for example for direct supply of local loads or for feeding into an independent supply network (Inselnetz) or a higher-level connection network. Nevertheless, this function can be provided by means of a "standard three-phase inverter", the DC intermediate circuit of which is formed, for example, with inexpensive and space-saving film capacitors. According to the invention, the intermediate circuit capacity that is missing compared to conventional inverters for single-phase applications is realized by the power consumption and output from the storage unit to the intermediate circuit, which is carried out by controlling the third bridge branch.

[0018] Advantageously, the converter according to the invention can also include at least three converter modules, each converter module having three bridge branches, wherein a three-phase AC voltage is provided on the output side and each phase of the three-phase AC voltage is provided by two bridge branches of different converter modules, wherein the third bridge branch can be coupled to an energy storage device. This can be an energy storage device on one of the third bridge branches of the three converter modules, thus involving a total of three energy storage devices. Alternatively, all third bridge branches of the three converter modules can be connected to a common energy storage device.

[0019] Converters having at least three (structurally identical) converter modules, each having three bridge branches, are common on the market, wherein the converter modules are usually operated in parallel in order to be able to provide higher powers.

[0020] In an advantageous embodiment of the converter, the energy store comprises a (rechargeable) battery, also called an accumulator. The phase output of a third bridge branch or the phase outputs of a plurality of third bridge branches can also form part of the energy store.

[0021] The method described can be used particularly advantageously in a converter for feeding AC power into a single-phase power supply network for rail transit. This applies in particular because lower network frequencies are often used in rail transit, for example around 16 Hz (hertz), instead of 50 or 60 Hz in other power supply networks. If the PV generator is to be loaded as evenly as possible over the course of a network cycle, according to the prior art, the lower the network frequency, the higher the capacity that needs to be used in the DC intermediate circuit. The method according to the invention makes it possible to feed even greater power into a power supply network that is only single-phase for the DC intermediate circuit with reasonable component expenditure, because the intermediate circuit capacitance that is missing in a "standard three-phase inverter" with film capacitors is "emulated" by a battery, for example. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The present invention will be further described below based on embodiments with the aid of the accompanying drawings. The accompanying drawings show:

[0023] Figure 1 A schematic diagram showing a device having a converter in a first embodiment;

[0024] Figure 2 A schematic diagram showing the power distribution during half an alternating current cycle in the case of the device of the first embodiment;

[0025] Figure 3 A schematic diagram showing a device with a converter in a second embodiment;

[0026] Figure 4 A schematic diagram shows the power distribution during half an alternating current cycle in the case of an arrangement of the second embodiment. DETAILED DESCRIPTION

[0027] exist Figure 1 Detailed Description of the Invention A device having a converter 6 in a first exemplary embodiment is shown in a schematic circuit diagram.

[0028] The converter 6 has a converter module 1 having three bridge branches, a first bridge branch 11, a second bridge branch 12 and a third bridge branch 13. Each of these bridge branches 11-13 comprises two semiconductor switches 111, 112 or 121, 122 and 131, 132 connected in series. A DC input voltage is supplied to the bridge branches 11-13 at the inputs 61, 62 of the converter 6, which DC input voltage is provided here by way of example by a photovoltaic (PV) generator 2. In the topology shown, the center tap between the two semiconductor switches 111, 112 or 121, 122 or 131, 132 of each bridge branch 11-13 represents the phase output 113, 123, 133 of the bridge branch 11-13, respectively.

[0029] PV generator 2 in Figure 1 It is understood that the PV generator 2 may include a plurality of PV cells arranged in a plurality of PV modules, wherein the PV modules for their part may in turn be connected in series and / or in parallel in order to form the photovoltaic generator 2 .

[0030] In parallel with the PV generator 2, a DC intermediate circuit 14 is formed as part of the converter module 1, which DC intermediate circuit Figure 1 It is represented by the circuit symbol of a capacitor.

[0031] The individual semiconductor switches 111, 112, 121, 122, 131, 132 are preferably driven by a control unit 17 using a pulse width modulation method (PWM method) in order to convert the supplied direct current. In the example shown, the semiconductor switches 111, 112, 121, 122, 131, 132 are IGBTs (insulated gate bipolar transistors) with anti-parallel connected freewheeling diodes. The semiconductor switches 111, 112, 121, 122, 131, 132 are driven in Figure 1 It is shown very schematically in FIG.

[0032] In order to correctly determine the switching instants of the PWM method, suitable current and / or voltage measurements at the outputs of the bridge branches 11-13 and / or the converter 6 are required. Figure 1Schematically shown in FIG. 1 are current measuring devices 114, 124 and 134 for measuring the output current of each bridge branch 11-13. The current measuring devices can be, for example, shunts or sensors (for example, Hall sensors) which detect the current as a function of the measured magnetic field. The measured current values ​​are evaluated in the control unit 17. For the sake of clarity, the current measuring devices 114, 124 and 134 are shown in FIG. 114, 124 and 134 for measuring the output current of each bridge branch 11-13. The current measuring devices can be, for example, shunts or sensors (for example, Hall sensors) which detect the current as a function of the measured magnetic field. The measured current values ​​are evaluated in the control unit 17. Figure 1 The illustration of corresponding voltage measuring devices for measuring the output voltages at the phase outputs 113 , 123 and 133 has been omitted.

[0033] In the converter 6 shown by way of example, the center tap represents the phase outputs 113, 123, 133 of the converter 6. In principle, in addition to the so-called B6 topology shown with three bridge branches each having two semiconductor switches and a center tap, other topologies can also be implemented in the converter 6. Thus, converters with three or more levels such as "neutral point clamped" (NPC), "bipolar switch neutral point clamped" (BSNPC), "active neutral point clamped" (ANPC) or "flying capacitor" (FLC) can also be used. Compared to the B6 topology, these topologies may require more semiconductor switches per bridge branch, but generally have advantages in terms of efficiency.

[0034] The converter 6 with three bridge branches 11-13 is basically suitable for converting the direct current supplied at the input into a three-phase alternating current. Since this is a frequently used purpose of the converter, converters with three bridge branches are common on the market. Usually, the three bridge branches are constructed identically and have the same current and voltage load capacity respectively.

[0035] exist Figure 1 In the application shown, only two of the bridge branches (here the first bridge branch 11 and the second bridge branch 12) are used in the manner of an H-bridge for converting the delivered input direct current into a single-phase alternating current. For this purpose, the phase outputs 113, 123 of the two bridge branches 11, 12 are coupled to the phases of the power supply network 3 via a filter 15. The two bridge branches 11, 12 can therefore be regarded as part of the AC branch of the converter 6.

[0036] In the present case, the transformer 31 is provided for coupling to the power supply network 3. Furthermore, a switching element 32 is also present, for example, as a network separator. In addition, a safety or measuring device (not shown here) can be arranged between the converter 6 and the power supply network 3.

[0037] The filter 15 comprises two chokes (coils) 151 arranged in series in the line between the phase output terminals 113, 123 and the power supply network 3 and a capacitor 152 arranged in parallel with the primary winding of the transformer 31. The filter 15 acts as a so-called sinusoidal filter and is used to smooth the generated single-phase alternating current. It should be understood that other combinations of chokes and capacitors can be used as the filter 15.

[0038] Here, the third bridge branch 13 is not provided for the alternating current direction, but is connected to a direct current unit (DC unit) 4. The coupling is carried out via a filter 16, which likewise comprises a series-connected inductor (coil) 161 and a capacitor 162 connected in parallel with the DC unit 4. The bridge branch 13 can therefore be regarded as part of the DC branch of the converter 6.

[0039] In this case, the components of the filter 16 together with the semiconductor switches 131 , 132 of the third bridge branch 13 serve as a DC / DC converter having a step-up and / or step-down function.

[0040] The names "DC unit" and "DC / DC converter" are not to be understood here as meaning that current and power flow in only one direction. Quite the contrary, the converter according to the present application or the method according to the present application is characterized in that the current flowing into or out of the DC unit 4 can change its current intensity and possibly its polarity on a time scale that is in the order of magnitude of the period duration of the alternating current frequency in the power supply network 3.

[0041] In this case, the DC unit 4 comprises a switching element 41 for coupling or decoupling a battery 42. The battery 42 is a rechargeable battery, which is here represented by way of example by a plurality of battery cells connected in series. By suitable actuation of the semiconductor switches 131, 132, a current flow from the PV generator 2 or from the DC intermediate circuit 14 to the battery 42 or vice versa is achieved from the battery 42 to the DC intermediate circuit 14.

[0042] According to the present application, battery 42 represents an energy store for supporting or relieving the energy store of DC link 14. It should be noted that components of filter 16 also perform an energy storage function and therefore also form part of the energy store in addition to battery 42.

[0043] In the following, the coupling of the converter 6 to the supply network 3 is also referred to as an AC branch, and the coupling of the converter 6 to the DC unit 4 , in particular the energy store, is also referred to as a DC branch.

[0044] Figure 1The arrangement shown in FIG. 1 makes it possible to feed the alternating current supplied by the PV generator 2 into the single-phase power supply network 3 .

[0045] according to Figure 1 The field of application of the device is to feed the current generated by the PV generator 2 into a single-phase upper power supply network 3. Such a single-phase upper power supply network 3 exists, for example, when feeding the track line in rail traffic, so that the current generated by the PV generator 2 can be fed into a single-phase upper power supply network 3. Figure 1 The device shown is used, for example, in conjunction with a free-field PV system along a track line.

[0046] In a converter according to the present application having three bridge branches (e.g. Figure 1 In the operating method of the converter 6) shown in the figure, the power transmitted by the converter through the DC branch is adjusted according to the AC power transmitted. The power that changes instantaneously in the AC during the AC cycle is also reflected in the transmitted power in the DC branch. During the AC cycle, the AC power changes twice between the minimum and maximum values. Accordingly, the power transmitted in the DC branch also changes with twice the frequency of the AC, but correspondingly in anti-phase.

[0047] This is Figure 2 Schematically illustrated in a diagram, wherein the variation of the power P transmitted in the AC or DC branch of the converter is shown as being related to the phase angle Φ of the output alternating current. The power P is marked on the vertical axis of the diagram and the phase angle Φ is marked on the horizontal axis of the diagram. Figure 1 The structure of the converter 6 is exemplarily described Figure 2 .

[0048] Three curves are plotted in the figure, namely the instantaneous first power 51 transmitted during the illustrated half-cycle of the alternating current in the AC branch, also referred to below as AC power 51 (corresponding to the power of one phase of the three-phase network), the second power 52, which is instantaneously transmitted into the battery 42 (positive values) or out of the battery 42 (negative values) in the DC branch. The power 52 transmitted in the DC branch is also referred to below as storage power 52. A third power 53 is also shown, which corresponds to the average power 53 output from the PV generator 2. The illustrated curve depicts the transmitted power. If possible losses in the converter 6 are neglected, the curve also depicts the power consumed from the respective AC or DC branch and output from the DC intermediate circuit 14 in the same way.

[0049] The AC power 51 shows a typical sine-squared curve. Depending on the application, the switching elements 131, 132 of the third bridge branch 13 as part of the DC / DC converter are controlled so that the transmitted storage power 52 is operated in antiphase with the transmitted AC power 51, so that the total transmitted power 53 and thus supplied by the PV generator 2 is constant.

[0050] The DC intermediate circuit 14 is thus loaded evenly over the cycle of the output alternating voltage, thereby avoiding voltage dips and always operating the PV generator at the MPP (maximum power point). This is achieved by varying the power fed into or out of the battery 42 during the illustrated half-cycle duration of the generated alternating current in such a way that the sum of the AC power 51 and the storage power 52 is constant.

[0051] In this case, in the example shown, power can also be temporarily output in the range between the phase angle Φ of 105° to 195° of the battery 42, which then flows into the AC branch. Accordingly, energy is transferred back from the battery 42 to the DC intermediate circuit 14. In this case, the DC branch of the converter 6 supports the DC intermediate circuit 14.

[0052] Especially according to Figure 1 This procedure is meaningful when the converter 5 is used to feed the power supply network 3 of a railway, because the power supply network of a railway usually operates at a low frequency (e.g. 16.6 Hz), and therefore the DC intermediate circuit 14 of a converter that is dimensioned for three-phase conversion at a higher frequency of 50 or 60 Hz usually does not have sufficient capacitance. A capacitor dimensioned appropriately in the DC intermediate circuit 14 would be very large and cost-intensive. By means of the method according to the application, the capacitance in the DC intermediate circuit 14 can be kept so small that it can be applied economically and in view of the space requirements by film capacitors, which have a longer service life and lower losses than, for example, electrolytic capacitors.

[0053] exist Figure 2 The case where the AC power transmitted is pure active power is shown in FIG. However, in addition to active power, reactive power can also be exchanged with the supply network through the converter. In this case, the phase of the direct current transmitted by the DC / DC converter follows the phase of the total current transmitted in the AC branch.

[0054] In one embodiment of the converter, the converter may include a plurality of converter modules each having three bridge branches. Two bridge branches of each converter module, one in the AC branch and one in the DC branch, may then be used. The AC branch may provide a total of one or more alternating currents (e.g., three alternating current phases), wherein the two bridge branches assigned to one phase do not necessarily need to be assigned to one converter module.

[0055] Figure 3 Such a converter 6 is shown, which comprises three three-phase converter modules 1 ′, 1 ″ and 1 ″′, which are connected on the input side to a common PV generator 2 . The arrangement of three (structurally identical) three-phase converter modules in a converter is common on the market in order to be able to provide higher powers and to be able to use already developed devices. Figure 3 In the example of Figure 1 For the sake of clarity, it is not Figure 3 All elements are provided with reference numerals. Some elements are omitted from the illustration, such as the control unit (see Figure 1 The control unit may include three control units that communicate with each other - this is very similar to Figure 1 The converter shown with the converter modules or a common control unit for all converter modules can provide control signals for all included semiconductor switches.

[0056] Each converter module 1', 1" and 1"' is similar to Figure 1 The converter modules 1 are each constructed with three bridge branches. The three bridge branches (one each in each converter module 1', 1", and 1"') are connected to a common capacitor 162 via a choke 161 and are coupled to a battery 42. The other two bridge branches of the converter modules 1', 1", and 1"' are each connected via a choke 151 and a capacitor 152 to three phase output terminals L1, L2, and L3, at which three-phase alternating current is provided for feeding into a three-phase power supply network. However, unlike Figure 1 In contrast to the embodiment in FIG. 1 , a different connection of the bridge branches to the phases L1, L2 and L3 has been chosen here, which can be described as "crossed". Two bridge branches of different converter modules are each fed into one phase. Figure 3 For example, the bridge branches of the converter module 1 ′ and the bridge branches of the converter module 1 ″ generate alternating current in phase L1 . This further reduces the need for compensation between the output AC power and the power provided by the DC branch.

[0057] Figure 4 Similar to Figure 2The diagram shows the operation according to the present invention Figure 3 Once again, one of the curves shown shows the AC power 51 fed into the supply network, one shows the storage power 52 flowing into the battery 42, and one shows the PV power 53 output from the PV generator. In pure three-phase operation, the AC power 52 is a DC power that is superimposed by a sinusoidal power component having half the amplitude of the DC power and twice the network frequency.

[0058] According to the invention, the bridge branches connected to the battery 42 are now adjusted in such a way that the storage power 52 is operated in antiphase with the AC power, whereby the PV power 53 output from the PV generator 2 is constant. Analogously to the first embodiment, a power output of the PV generator that is as uniform as possible within each network cycle (i.e. on the time scale of the network cycle) is advantageously achieved.

[0059] The current in the battery 42 is direct current since the individual currents of the three third bridge branches are adjusted in such a way that they are offset by 60 degrees (with respect to the network fundamental frequency) relative to their sinusoidal components.

[0060] Reference numerals list

[0061] 1, 1'-1"' converter module

[0062] 11 First bridge branch

[0063] 111, 112 Semiconductor switch

[0064] 113 Phase output terminal

[0065] 114 Current measuring device

[0066] 12 Second bridge branch

[0067] 121, 122 Semiconductor switch

[0068] 123 Phase output terminal

[0069] 124 Current measuring device

[0070] 13 The third bridge branch

[0071] 131, 132 Semiconductor switch

[0072] 133 Phase output terminal

[0073] 134 Current measuring device

[0074] 14 DC intermediate circuit

[0075] 15 Filter

[0076] 151, 161 Choke

[0077] 152, 162 Capacitors

[0078] 16 Filter

[0079] 17 Control Unit

[0080] 2 PV generator

[0081] 3 Power supply network

[0082] 31 Transformer

[0083] 32 Switching elements

[0084] 4 DC units

[0085] 41 Switching elements

[0086] 42 Batteries

[0087] 51 First Power

[0088] 52 Second Power

[0089] 53 Expected value

[0090] 6 Converter

[0091] 61, 62 Input terminal

Claims

1. A device comprising a converter (6) and a filter (16), wherein: The converter (6) comprises an input (61, 62) which can be connected to a DC power source (2), at least one converter module (1, 1'-1'") and a common DC voltage intermediate circuit (14), wherein the input is connectable to a DC power source (2), the at least one converter module having a first, a second and a third bridge branch (11, 12, 13), wherein each of the bridge branches (11, 12, 13) has a phase output (113, 123, 133), and the common DC voltage intermediate circuit is used for the bridge branches (11, 12, 13), wherein The first and second bridge branches (11, 12) are configured to supply a first power (51) in the form of an alternating current to the phase output terminals (113, 123), An energy storage device (42) is connectable to a phase output (133) of the third bridge branch (13), wherein the filter (16) is connected between the energy storage device (42) and the phase output (133), wherein components of the filter (16) and semiconductor switches (131, 132) of the third bridge branch (13) cooperate to operate as a DC / DC converter with a step-up and / or step-down function, wherein the third bridge branch (13) is provided for exchanging a second power (52) between the DC power source (2) and the energy storage device (42) and between the energy storage device (42) and the DC voltage intermediate circuit (14), wherein: The converter (6) comprises a control unit (17) which is configured to control the bridge branches (11, 12, 13) in such a way that the sum of the first power (51) and the second power (52) corresponds to a constant desired value (53) at any time. The control unit (17) is designed to control the third bridge branch (13) in such a way that the second power (52) and the first power (51) run in antiphase with respect to one another on a time scale that is dependent on the network frequency.

2. The device according to claim 1, wherein: The constant desired value (53) corresponds to the maximum power point (MPP) of the DC source (2).

3. The device according to claim 1 or 2, wherein: The first, second and third bridge branches (11, 12, 13) are of the same construction type.

4. The device according to claim 1 or 2, wherein: The first, second and third bridge branches (11, 12, 13) are designed for bidirectional operation.

5. The device according to claim 1 or 2, wherein: The converter (6) has exactly one converter module (1) having three bridge branches (11, 12, 13).

6. The device according to claim 1 or 2, wherein the converter (6) of the device comprises at least three converter modules (1, 1'-1''), wherein: A three-phase AC voltage is provided on the output side, and each phase of the three-phase AC voltage is provided by two bridge branches (11, 12) of different converter modules (1, 1'-1''), wherein the third bridge branch (13) is coupled to an energy storage device (42).

7. The device according to claim 1 or 2, wherein: The DC voltage intermediate circuit (14) has a film capacitor.

8. The device according to claim 1 or 2, wherein: The bridge branches (11, 12, 13) are composed of a neutral point clamped (NPC) branch, a bipolar switch neutral point clamped (BSNPC) branch, an active neutral point clamped (ANPC) branch or a flying capacitor (FLC) branch.

9. A method for operating a device, the device comprising a converter (6) and a filter (16), the converter comprising an input (61, 62), at least one converter module (1, 1'-1'") and a common DC voltage intermediate circuit (14), the input being connectable to a DC power source (2), the at least one converter module having a first, a second and a third bridge branch (11, 12, 13), wherein: Each of the bridge branches (11, 12, 13) has a phase output (113, 123, 133), the common DC voltage intermediate circuit is used for the bridge branches (11, 12, 13), an energy storage device (42) is connected downstream of the third bridge branch (13), the converter (6) further comprises a control unit (17) for controlling the bridge branches (11, 12, 13), wherein: The first and second bridge branches (11, 12) are controlled in such a way that a first power (51) in the form of an alternating current is provided to the phase output (113, 123), The filter (16) is connected between the energy storage device (42) and the phase output terminal (133), wherein components of the filter (16) cooperate with the semiconductor switches (131, 132) of the third bridge branch (13) to operate as a DC / DC converter with a step-up and / or step-down function, wherein: The third bridge branch (13) is controlled in such a way that a second power (52) is exchanged between the DC power source (2) and the energy storage device (42) and between the energy storage device (42) and the DC voltage intermediate circuit (14). wherein the sum of the first power (51) and the second power (52) corresponds to a constant desired value (53) at any time, The control unit (17) is designed to control the third bridge branch (13) in such a way that the second power (52) and the first power (51) run in antiphase with respect to one another on a time scale that is dependent on the network frequency.

10. The method according to claim 9, wherein: The constant desired value (53) corresponds to the maximum power point (MPP) of the DC source (2).

11. The method according to claim 9 or 10, in which the first power (51) is fed into a single-phase power supply network for rail traffic.

12. Use of a device according to any one of claims 1 to 5, comprising a converter (6) and a filter (16), the converter being used to feed AC power into a single-phase power supply network for rail traffic.

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