Redundancy of the resonant converter stage through frequency adaptation

Abstract

A resonant DC / DC converter includes: a first DC link, preferably including a first DC link capacitor; a DC / AC converter including a first plurality of N>1 converter bridges connected in parallel to the first DC link; each converter bridge including a plurality of switches, each of the plurality of switches being switchable between an on state and a non-conducting state; an AC intermediate circuit having an input connected to the output of the AC / DC converter and including: a transformer, preferably an intermediate frequency transformer, having a primary side and a secondary side; wherein the primary side includes at least one primary winding; and a first plurality of N capacitors, wherein for each converter bridge, different capacitors from the first plurality of capacitors are connected between the converter bridge and at least one primary winding. A control unit is configured to switch the semiconductor switches of the inverter bridge between an on state and an off state at a predetermined first switching frequency, or to switch the semiconductor switches of the inverter bridge between an off state and an on state at a predetermined first switching frequency, to provide AC current and / or voltage to an AC intermediate circuit; a plurality of N current sensing devices, wherein for each inverter bridge, different current sensing devices among the plurality of current sensing devices are provided for monitoring the current through the inverter bridge; wherein the control unit is configured to determine whether the current through one of the inverter bridges deviates from a expected value; and if the current through one of the inverter bridges deviates from the expected value, to adapt, in particular, to increase the predetermined first switching frequency.

Description

Technical Field

[0001] This invention belongs to the field of power electronics. According to the independent patent claims, this invention relates to a resonant DC / DC converter and a method for controlling such a converter. Background Technology

[0002] In distributed energy applications such as electric vehicle (EV) fast charging, photovoltaic (PV) solar energy, battery energy storage systems (BESS), wind power (onshore or offshore), or data centers, power converters such as inverters or rectifiers are needed to provide electrical insulation and handle large currents, particularly those exceeding 100A, or more specifically, exceeding 200A or even 500A. A large number of semiconductor switches must be connected in parallel to provide power switches that can be turned on and switched, particularly those that interrupt the required or desired current without unnecessary and / or significant losses, especially those required for building or employing solid-state transformers (SSTs). Due to parasitic effects and non-uniform temperature, geometry, and semiconductor characteristics, it is difficult to achieve a uniform distribution of losses and thus individual currents in parallel chips. This poses a particular challenge for future high-current applications of wide-bandgap semiconductors due to their high switching speeds, especially at frequencies above 1kHz, or more specifically above 5kHz or even 10kHz, and often due to relatively small chip sizes.

[0003] While paralleling a large number of semiconductor switches theoretically allows for the handling, particularly switching and / or conduction, of the large currents desired and / or required, this necessitates that losses within the paralleled chips be at least substantially uniformly distributed so that the current through each individual chip is at least substantially perfectly balanced. This at least substantially uniform distribution is difficult to achieve due to parasitic effects, non-uniform temperature, geometry, and / or (individual) semiconductor characteristics, or more precisely, due to (statistical) variations in these characteristics between the individual semiconductor chips contained within a semiconductor switch, for example, due to (non-zero) manufacturing tolerances. Relatively significant effort (including, for example, pre-selection of semiconductor switches, chips, and / or power modules, selection / development of specific module layouts, and selection / development of dedicated gate driver technologies) is required to adequately balance the current. Even so, balancing becomes increasingly difficult as the number of chips, particularly semiconductor switches, increases (e.g., it can be as low as 10, 5, or even 2), posing a challenge, especially for future high-current applications of wide-bandgap semiconductors.

[0004] As the number of components, especially semiconductor switches, increases, another problem that becomes increasingly serious is the potential decrease in system reliability due to the increased likelihood of any component failing.

[0005] Figge et al. (Power Electronics Experts Conference 2008, IEEE) described a half-bridge topology LLC resonant converter for a switch-mode power supply (Figure 8). The paper, "Paralleling of LLC resonant converters using frequency controlled current balancing," describes this. Figure 1 Each LLC resonant converter includes a transformer, a pair of switches S1 and S2 connected to the DC link, and a resonant capacitor Cs connected between the output of the half-bridge and the primary winding of each transformer. The difference between the currents measured at the output of each LLC is input to a load balancer, and the switching frequency of each LLC is adjusted to minimize the difference.

[0006] The purpose of this invention is to provide a resonant DC / DC converter with parallel-connected semiconductor switches that exhibits improved system reliability, and a control method for the resonant DC / DC converter with parallel-connected semiconductor switches that can increase system reliability. Summary of the Invention

[0007] This objective is achieved by a resonant DC / DC converter having a combination of features from the independent patent claims and a method for controlling such a converter. Other exemplary embodiments are clear from the dependent claims and the following description taken in conjunction with the accompanying drawings.

[0008] A resonant DC / DC converter and a method for controlling a corresponding DC / DC converter according to the present invention may include the following features, components and / or steps: a first DC link preferably including a first DC link capacitor; a DC / AC converter including a first plurality of N>1 converter bridges connected in parallel to the first DC link; each converter bridge including a plurality of switches, each of the plurality of switches being switchable between an on state and a non-conducting state; an AC intermediate circuit having an input connected to the output of the DC / AC converter and including: a transformer, preferably an intermediate frequency transformer, having a primary side and a secondary side; wherein the primary side includes at least one primary winding; a first plurality of N capacitors, wherein for each converter bridge, the current from the first plurality of capacitors is not... A capacitor is connected between the converter bridge and at least one primary winding; a control unit is configured to switch the semiconductor switches of the inverter bridge between an on state and an off state at a predetermined first switching frequency, or to switch the semiconductor switches of the inverter bridge between an off state and an on state at a predetermined first switching frequency, to provide AC current and / or voltage to the AC intermediate circuit; a plurality of N current sensing devices, wherein for each inverter bridge, different current sensing devices among the plurality of current sensing devices are provided for monitoring the current through the inverter bridge; wherein the control unit is configured to determine whether the current through one of the inverter bridges deviates from a expected value; if the current through one of the inverter bridges deviates from the expected value, the predetermined first switching frequency is adapted, in particular, increased.

[0009] The first plurality of N>1 converter bridges can be considered as part of a DC / AC converter or inverter having inputs connected to a first DC link, which can in turn be connected to the grid via the converter, or to a DC power source such as a PV solar system or BESS, wherein the DC / AC converter is configured to provide AC voltage and / or current at the output of the DC / AC converter.

[0010] The transformer, as part of the AC intermediate circuit, may have an input and / or primary side connected to the output of the DC / AC converter. The AC intermediate circuit may include additional components, particularly capacitors or inductors connected in parallel or series with the input or output of the AC intermediate circuit and the transformer. In particular, the transformer may have only a single primary and / or a single secondary winding, but will typically include multiple primary windings and / or multiple secondary windings.

[0011] The output and / or secondary side of the AC intermediate circuit can be connected to the input of an AC / DC converter configured to convert the AC current and / or voltage output from the AC intermediate circuit into a DC voltage and / or (intermittent) DC current at the output of the AC / DC converter. The output of the AC / DC converter can then be connected to a second DC link, preferably a second DC link capacitor, at which a load can be connected. If the converter is suitable for bidirectional operation, particularly allowing bidirectional power flow, the load can also be used as a power source, at least temporarily.

[0012] The first DC link can provide at least a first voltage level and a second voltage level, particularly a zero or neutral level and a positive level. In particular, the first DC link can also provide a positive level, a zero or neutral level, and a negative voltage level.

[0013] The converter bridge can be, in particular, an active bridge of any topology that can apply at least one of two voltage levels provided by a first DC link to the input, specifically the input terminal, of the AC intermediate circuit. This can include half-bridges, full-bridges, midpoint clamping bridges, and any type of multi-stage topology. For example, a three-point bridge allows positive, negative, and zero voltages to be applied to the input of the AC intermediate circuit.

[0014] Therefore, the converter bridge includes multiple switches, each of which can switch between an on and off state; and corresponding switch connections that allow the establishment or termination of a connection between the input of the AC intermediate circuit and each voltage level. Specifically, the switches can operate under the control of a control unit, particularly a controller or control system, which can be internal to the DC / AC converter or provided externally. Control can be, in particular, open-loop control. The control unit can be configured to allow or provide zero-current switching (ZCS) or zero-voltage switching (ZVS) to minimize switching losses. The control unit can be configured to switch the switches between an on and off state at a first switching frequency, particularly a predetermined first switching frequency, or between an off and on state at a first switching frequency, particularly a predetermined first switching frequency, to provide AC current and / or voltage to the AC intermediate circuit.

[0015] All converter bridges connected in parallel to the first DC link can have the same topology. The corresponding switches of all converter bridges can be configured to operate in a manner that is at least substantially synchronous. Specifically, the controller or control system can turn all corresponding switches on at least substantially simultaneously and can turn all said corresponding switches off at least substantially simultaneously. Specifically, for example, all switches connected to a first voltage level can turn on at least substantially simultaneously, and in particular almost simultaneously, while all switches connected to a second voltage level can turn off at least substantially simultaneously; or all switches connected to the first voltage level can turn off at least substantially simultaneously, and in particular almost simultaneously, while all switches connected to the second voltage level can turn on at least substantially simultaneously.

[0016] The switch can be a semiconductor switch, including transistors, particularly BJT (bipolar junction transistor), MOSFET (metal-oxide-semiconductor field-effect transistor), IGBT (integrated gate bipolar transistor); or thyristors, particularly GTO (gate turn-off thyristor), GCT (gate commutated thyristor) or IGCT (integrated gate commutated thyristor).

[0017] N capacitors connected between N converter bridges and at least one primary winding, along with any other capacitors that may be connected between the N converter bridges and at least one primary winding, as detailed further below, collectively serve as the resonant capacitors of the resonant DC / DC converter, similar to the (single) resonant capacitor of a conventional resonant DC / DC converter. These capacitors can therefore be considered as discrete resonant capacitors, where each individual capacitor serves as a partial resonant capacitor. Due to the presence of these partial resonant capacitors, the current through each active half-bridge or arm is not defined by the parasitic, non-uniform temperature distribution of the power module and / or the semiconductor switching characteristics (not perfectly equal for all chips), but by the resonant circuit (defined by the transformer stray flux (approximately equal for all parallel wires)) and the discrete resonant capacitors (with a limited maximum deviation from the reference capacitor, e.g., 5%) within a defined range. This results in a uniform and stable current distribution among the individual converter bridges without the need for additional measures or effort.

[0018] Provide multiple N current sensing devices to monitor, in particular measure, or otherwise acquire the current I through the i-th converter bridge in the converter bridge. sensed,iThe indication, in particular, is the AC current output by or from the i-th converter bridge, where i ∈ {1,…,N}. Each current sensing device can be a current sensor, particularly an AC current sensor capable of and / or configured to measure the AC current output by one of the converter bridges. Any kind of device capable of providing at least a coarse indication of the current, particularly an indication of the current magnitude, is sufficient to serve as a current sensing device. The sensed current value I sensed,i Specifically, it can be the root mean square value or the average value of the absolute current.

[0019] The control unit is configured to determine the current I through the i-th converter bridge, specifically the first converter bridge. sensed,i Does it deviate from the expected value; especially the current I? sensed,i Is the absolute value less than, especially significantly less than, the expected value I? expected That is, whether or not |I sensed,i |< expected The expected value I expected It can be derived from the nominal, rated, and / or maximum current of the DC / DC converter or any of its components, particularly semiconductor switches or one or more transformer windings, especially by selecting I. expected The value is significantly smaller than any such nominal, rated, and / or maximum current. Alternatively, it can be I. expected Select a value less than 1A, 100mA, 10mA, or 1mA. The control unit determines the current I. sensed,i The absolute value is less than, especially significantly less than, the expected value I. expected It can also be derived from sensing or observation other than current measurement; for example, by frequency measurement, particularly at the output of the i-th converter bridge in the converter bridge, especially in cases where such frequency measurement produces unexpected or uncertain values, or from signals from the gate drivers of the semiconductor switches included in the i-th converter bridge in the converter bridge.

[0020] If the current I through the i-th converter bridge is found... sensed,i Deviation from expected value; in particular, if current I is found sensed,i The absolute value is less than, especially significantly less than, the expected value I. expected Therefore, it can be assumed that the i-th converter bridge is defective. The control unit will then adapt, in particular, increase the switching frequency of the remaining converter bridges, i.e., all j-th converter bridges i ≠ j ∈ {1,…,N} are switched. Furthermore, the i-th converter bridge can be actively deactivated by the control system, particularly by the control system ceasing to send switching signals, and / or by setting or attempting to set the bridge's switch to a non-conducting state.

[0021] ​In particular, the switching frequency can be adapted as follows, especially in the case where exactly N capacitors are connected between N converter bridges and at least one primary winding: for an initial switching frequency f applied when all N converter bridges are active and / or operating normally res , it is possible to determine and / or set a first adapted switching frequency f according to res adapted,1 , which will subsequently apply to switching the remaining N - 1 converter bridges after a first converter bridge has failed. In the unlikely case where 1 < n < N converter bridges should or have become defective, a second adapted switching frequency f can be determined and / or set according to res adapted,2 , which subsequently applies to switching the remaining switches, i.e., the N - n non-defective converter bridges.

[0022] Preferred embodiments of the present invention, in particular those described above, can be implemented according to the items listed below, advantageously in combination with one or more of the features detailed above, or according to the drawings and the detailed description of the preferred embodiments and / or claims presented below, as detailed in the numbered embodiments.

[0023] 1) A resonant DC / DC converter, comprising

[0024] a) A first DC link, preferably including a first DC link capacitor;

[0025] b) A first plurality of N > 1 converter bridges connected in parallel to the first DC link; each converter bridge includes a plurality of switches, especially semiconductor switches, and each of the plurality of switches can be switched between a conducting state and a non-conducting state;

[0026] c) A transformer, preferably an intermediate frequency transformer, having a primary side and a secondary side; wherein the primary side includes at least one primary winding;

[0027] d) A first plurality of N capacitors, wherein

[0028] e) For each converter bridge, a different capacitor from the first plurality of capacitors is connected between the converter bridge and at least one primary winding;

[0029] f) A control unit configured to switch the switches of the inverter bridge between a (predetermined) first switching frequency f res between a conducting state and a non-conducting state, or to switch the switches of the inverter bridge between a (predetermined) first switching frequency f res between a non-conducting state and a conducting state;

[0030] g) A plurality of N current sensing devices, wherein for each inverter bridge, different current sensing devices among the plurality of current sensing devices are provided for monitoring the current through the inverter bridge;

[0031] h) The control unit is configured to determine whether the current through one of the converter bridges deviates from the expected value; and if the current through one of the inverter bridges deviates from the expected value, to adapt, in particular, to increase (predetermined) a first switching frequency.

[0032] 2) A resonant DC / DC converter, comprising

[0033] a) A first DC link, preferably including a first DC link capacitor;

[0034] b) A DC / AC converter, comprising a first plurality of N>1 converter bridges connected in parallel to a first DC link; each converter bridge comprising a plurality of switches, particularly semiconductor switches, each of the plurality of switches being switchable between an on state and a non-on state;

[0035] c) AC intermediate circuit, connected to the DC / AC converter and including

[0036] i) A transformer, preferably a medium-frequency transformer, having a primary side and a secondary side; wherein the primary side includes at least one primary winding;

[0037] d) The first plurality of N capacitors, where

[0038] e) For each converter bridge, different capacitors from the first plurality of capacitors are connected between the converter bridge and at least one primary winding;

[0039] f) A control unit configured to switch the inverter bridge switches between an on-state and an off-state at a switching frequency, or to switch the inverter bridge switches between an off-state and an on-state at a switching frequency, to provide AC current and / or voltage to the AC intermediate circuit.

[0040] g) Multiple N current sensing devices, wherein for each inverter bridge, different current sensing devices among the multiple current sensing devices are provided for monitoring the current through the converter bridge;

[0041] h) The control unit is configured to determine whether the current through one of the inverter bridges deviates from the expected value; and if the current through one of the inverter bridges deviates from the expected value, to adapt, in particular, to increase the switching frequency.

[0042] 3) A resonant DC / DC converter according to any of the foregoing embodiments, wherein the control system is configured to operate according to an adapted switching frequency. To adapt to the switching frequency.

[0043] 4) A resonant DC / DC converter according to any of the foregoing embodiments, wherein the control unit is configured to determine whether the current deviates from the expected value by determining whether the absolute value of the current through one of the inverter bridges of the inverter bridge is less than a given threshold.

[0044] 5) A resonant DC / DC converter according to any of the foregoing embodiments, wherein the control unit is configured to determine whether the current deviates from the expected value by determining whether the current through one of the inverter bridges is at least approximately zero, in particular less than 1 / 100, 1 / 1000 or 1 / 10000 of the rated current, nominal current and / or maximum current of the inverter bridge.

[0045] 6) A resonant DC / DC converter according to any of the foregoing embodiments, wherein the control unit is configured to deactivate the inverter bridges when it is determined that the current through one of the inverter bridges deviates from the expected value.

[0046] 7) A resonant DC / DC converter according to the foregoing embodiment, wherein for each converter bridge, different current sensing devices from a plurality of current sensing devices are provided between the converter bridge and at least one primary winding, particularly between the converter bridge and a capacitor connected between the converter bridge and at least one primary winding.

[0047] 8) A resonant DC / DC converter according to any of the foregoing embodiments, wherein the AC current sensor is used as a current sensing device for measuring the AC current output by the converter bridge.

[0048] 9) The resonant DC / DC converter according to any of the foregoing embodiments, further comprising:

[0049] a) An AC / DC converter is connected to the secondary side of an AC intermediate circuit.

[0050] b) A second DC link, preferably a second DC link capacitor, is connected to the output of the AC / DC converter.

[0051] 10) A resonant DC / DC converter according to any of the foregoing embodiments, wherein each of the converter bridges is an inverter half-bridge, the inverter half-bridge including a first input terminal and a second input terminal, and an inverter bridge output (alternatively, electrically connectable to the first input terminal or the second input terminal via a plurality of semiconductor switches), wherein for each inverter half-bridge, different capacitors of a first plurality of capacitors are connected in series with the inverter bridge output.

[0052] 11) A resonant DC / DC converter according to any one of the foregoing embodiments and having

[0053] a) A primary side of a transformer, including a plurality of M>1 primary windings, each of the plurality of primary windings having a first terminal and a second terminal;

[0054] b) A second plurality of M capacitors; and wherein

[0055] c) Each capacitor of a first plurality of N capacitors is connected between one converter bridge in the converter bridge and a common node (C);

[0056] d) Each capacitor of a second plurality of M capacitors is connected between the common node and the first terminal of a different primary winding among the plurality of primary windings.

[0057] 12) A resonant DC / DC converter according to any one of the foregoing embodiments and having

[0058] a) A primary side of a transformer, including a plurality of M>1 primary windings, each of the plurality of primary windings having a first terminal and a second terminal;

[0059] b) A second plurality of M capacitors; The DC / DC converter further includes

[0060] c) A plurality of O common nodes, O<N and O<M, and wherein

[0061] d) Each capacitor of a first plurality of N capacitors is connected between one converter bridge in the converter bridge and one of the common nodes;

[0062] e) Each capacitor of a second plurality of M capacitors is connected between one of the common nodes and the first terminal of a different primary winding among the plurality of primary windings.

[0063] 13) A resonant DC / DC converter according to any one of the foregoing embodiments, wherein M≠N, preferably M<N.

[0064] 14) A resonant DC / DC converter according to any one of the foregoing embodiments, and the primary side of the transformer includes a plurality of N primary windings, each of the plurality of primary windings having a first terminal and a second terminal; wherein the converter bridge and the primary windings are connected in pairs via different capacitors from a first plurality of capacitors, and the first plurality of capacitors are connected to the first terminals of the corresponding primary windings among the plurality of primary windings.

[0065] 15) A resonant DC / DC converter according to any one of the foregoing embodiments, wherein

[0066] a) Each converter bridge in the converter bridge is an inverter half-bridge, which includes a first input terminal and a second input terminal, and an inverter bridge output (which, alternatively, may be electrically connected to the first input terminal or the second input terminal via a plurality of semiconductor switches).

[0067] b) Each capacitor has a first terminal and a second terminal, and wherein

[0068] c) For each inverter half-bridge, the first terminal of each of the corresponding capacitors from the plurality of capacitors is connected to the corresponding inverter bridge output, and

[0069] d) The second terminals of all the capacitors in the first plurality of N capacitors are connected together at a common node.

[0070] 16) A resonant DC / DC converter according to any of the foregoing embodiments, wherein

[0071] a) Each converter bridge in the converter bridge is an inverter half-bridge, which includes a first input terminal and a second input terminal, and an inverter bridge output (which, alternatively, may be electrically connected to the first input terminal or the second input terminal via a plurality of semiconductor switches).

[0072] b) Each capacitor has a first terminal and a second terminal, and wherein

[0073] c) For each inverter half-bridge, the first terminal of each of the corresponding capacitors from the plurality of capacitors is connected to the corresponding inverter bridge output, and

[0074] d) The second terminal of each of the first plurality of N capacitors is connected to a different primary winding.

[0075] 17) A resonant DC / DC converter according to any of the foregoing embodiments, wherein the second terminals of all the plurality of primary windings are connected together.

[0076] 18) A resonant DC / DC converter according to any of the foregoing embodiments, wherein

[0077] a) The first DC link has a positive terminal and a negative terminal.

[0078] b) The first input terminals of all inverter half-bridges are connected to the positive terminals, and

[0079] c) The second input terminal of all inverter half-bridges is connected to the negative terminal.

[0080] 19) A resonant DC / DC converter according to any of the foregoing embodiments, wherein the first DC link further has a neutral terminal, and the second terminals of all the plurality of primary windings are connected to the neutral terminal.

[0081] 20) A resonant DC / DC converter according to any of the foregoing embodiments, wherein the converter is a resonant converter and each of the plurality of capacitors is a capacitor.

[0082] 21) The resonant DC / DC converter according to any of the foregoing embodiments further includes

[0083] a) Second DC link, preferably a second DC link capacitor

[0084] b) A second plurality of N'>1 converter bridges connected in parallel with the second DC link;

[0085] c) The secondary side of the transformer includes at least one secondary winding;

[0086] d) The converter also includes a second plurality of N' capacitors, wherein

[0087] e) For each of the second plurality of N'>1 converter bridges, different capacitors from the second plurality of capacitors are connected between the converter bridge and at least one secondary winding.

[0088] 22) A resonant DC / DC converter according to any of the foregoing embodiments, wherein

[0089] a) Each of the first N>1 converter bridges is an inverter bridge;

[0090] b) The secondary side of the transformer includes at least one secondary winding; the converter also includes:

[0091] c) A second DC link, preferably a second DC link capacitor;

[0092] d) A second plurality of N'>1 rectifier bridges connected in parallel with the second DC link;

[0093] e) A third set of N' capacitors, of which

[0094] f) For each rectifier bridge, different capacitors from the third plurality of capacitors are connected between the rectifier bridge and at least one secondary winding.

[0095] 23) A resonant DC / DC converter according to any of the foregoing embodiments, wherein it has

[0096] a) The secondary side of the transformer includes multiple M'>1 secondary windings, each of the multiple secondary windings having a first terminal and a second terminal;

[0097] b) A fourth set of M' capacitors; and among them

[0098] c) Each of the third N' capacitors is connected between one of the converter bridges and another common node in the converter bridge;

[0099] d) Each of the fourth plurality of M' capacitors is connected between another common node and the first terminal of a different secondary winding in the plurality of secondary windings.

[0100] 24) The resonant DC / DC converter according to any of the foregoing embodiments further includes

[0101] a) Second DC link, preferably a second DC link capacitor

[0102] b) A second plurality of N'>1 converter bridges connected in parallel with the second DC link; and

[0103] c) The secondary side of the transformer includes a plurality of N' secondary windings, each of the plurality of secondary windings having a first terminal and a second terminal; wherein the converter bridge and the secondary windings are connected in pairs via different capacitors from a third plurality of capacitors, the third plurality of capacitors being connected to the first terminal of the respective secondary winding of the plurality of secondary windings.

[0104] 25) A resonant DC / DC converter according to any of the foregoing embodiments, wherein the converter bridge in the first plurality of N>1 converter bridges is an active bridge configured to operate in at least a substantially synchronous manner, and if present, the converter bridge in the second plurality of converter bridges is also an active bridge configured to operate in at least a substantially synchronous manner.

[0105] 26) A method for controlling a resonant DC / DC converter, the converter comprising...

[0106] a) First DC link (10), preferably including a first DC link capacitor;

[0107] b) A first plurality of N>1 converter bridges are connected in parallel to a first DC link and adapted to operate at a switching frequency f res Switch;

[0108] c) A transformer, preferably a medium-frequency transformer (2141), having a primary side and a secondary side; wherein the primary side includes at least one primary winding;

[0109] d) The first plurality of N capacitors, where

[0110] e) For each converter bridge, different capacitors from the first plurality of capacitors are connected between the converter bridge and at least one primary winding; the method includes the following steps:

[0111] f) For each converter bridge, monitor the current through the inverter bridge;

[0112] g) Determine whether the current through the first inverter bridge deviates from the expected value;

[0113] h) If the current through the first inverter bridge deviates from the expected value, then adapt, in particular, increase the switching frequency.

[0114] 27) A method for controlling a resonant DC / DC converter, the converter comprising...

[0115] a) First DC link 10, preferably including a first DC link capacitor;

[0116] b) A DC / AC converter, including a first plurality of N>1 converter bridges connected in parallel to a first DC link; each converter bridge includes a plurality of semiconductor switches, each of the plurality of semiconductor switches being able to switch between an on state and a non-on state;

[0117] c) The AC intermediate circuit connected to the DC / AC converter, including

[0118] i) A transformer, preferably a medium-frequency transformer, having a primary side and a secondary side; wherein the primary side includes at least one primary winding;

[0119] d) The first plurality of N capacitors, where

[0120] e) For each converter bridge, different capacitors from the first plurality of capacitors are connected between the converter bridge and at least one primary winding;

[0121] f) The control unit is configured to operate at a switching frequency f res The semiconductor switches of the inverter bridge switch between on and off states, or at a switching frequency f. res The method involves switching the semiconductor switches of the inverter bridge between a non-conducting state and a conducting state to provide AC current and / or voltage to an AC intermediate circuit; the method includes the following steps:

[0122] g) For each converter bridge, monitor the current through the inverter bridge;

[0123] h) Determine whether the current through the first inverter bridge deviates from the expected value;

[0124] i) If the current through the first inverter bridge deviates from the expected value, then adapt, in particular, increase the switching frequency.

[0125] 28) According to any of the method variations, wherein the switching frequency f res Adapted to the already adapted switching frequency

[0126] 29) A method according to any of the method variants, wherein determining whether the current through one of the inverter bridges deviates from a expected value is performed by determining whether the current, in particular the absolute value of the current, is less than a given threshold.

[0127] 30) The method according to any of the method variants, wherein determining whether the current through one of the inverter bridges deviates from the expected value is performed by determining whether the current is at least approximately zero, in particular less than 1 / 100, 1 / 1000 or 1 / 10000 of the rated current, nominal current and / or maximum current of the inverter bridge.

[0128] 31) The method according to any of the method variants further includes the step of: deactivating the first inverter bridge when it is determined that the current through the first inverter bridge deviates from the expected value.

[0129] 32) A method for controlling a resonant DC / DC converter according to one of the method variations further comprising the following steps:

[0130] a) Provide multiple N current sensing devices;

[0131] b) For each converter bridge, the current through the inverter bridge is measured by different current sensing devices from a plurality of current sensing devices provided between the converter bridge and at least one primary winding, particularly between the converter bridge and a capacitor connected between the converter bridge and at least one primary winding.

[0132] 33) A method for controlling a resonant DC / DC converter according to one of the method variations, wherein the converter further comprises:

[0133] a) An AC / DC converter connected to the secondary side of an AC intermediate circuit.

[0134] b) A second DC link, preferably a second DC link capacitor, is connected to the output of the AC / DC converter.

[0135] 34) A method for controlling a resonant DC / DC converter according to one of the method variations, wherein each converter bridge in the converter bridge is an inverter half-bridge, the inverter half-bridge including a first input terminal and a second input terminal, an inverter bridge output (alternately, electrically connectable to the first input terminal or the second input terminal via a plurality of semiconductor switches), wherein for each inverter half-bridge, different capacitors of a first plurality of capacitors are connected in series with the inverter bridge output.

[0136] A method for controlling a resonant DC / DC converter according to one of the method variants, comprising

[0137] a) a primary side of a transformer, comprising a plurality of more than M primary windings, each of the plurality of primary windings having a first terminal and a second terminal;

[0138] b) a second plurality of M capacitors; and wherein

[0139] c) each capacitor of a first plurality of N capacitors is connected between one converter bridge in a converter bridge and a common node (C);

[0140] d) each capacitor of a second plurality of M capacitors is connected between the common node and the first terminal of a different one of the plurality of primary windings.

[0141] A method for controlling a resonant DC / DC converter according to one of the method variants, comprising

[0142] a) a primary side of a transformer, comprising a plurality of more than M primary windings, each of the plurality of primary windings having a first terminal and a second terminal;

[0143] b) a second plurality of M capacitors; the DC / DC converter further comprises

[0144] c) a plurality of O common nodes, O < N and O < M, and wherein

[0145] d) each capacitor of a first plurality of N capacitors is connected between one converter bridge in a converter bridge and one of the common nodes;

[0146] e) each capacitor of a second plurality of M capacitors is connected between one of the common nodes and the first terminal of a different one of the plurality of primary windings.

[0147] A method for controlling a resonant DC / DC converter according to one of the method variants, wherein M ≠ N, preferably M < N.

[0148] A method for controlling a resonant DC / DC converter according to one of the method variants, wherein the primary side of the transformer comprises a plurality of N primary windings, each of the plurality of primary windings having a first terminal and a second terminal; wherein the converter bridge and the primary windings are connected in pairs via different capacitors from a first plurality of capacitors, the first plurality of capacitors being connected to the first terminal of the respective primary windings in the plurality of primary windings.

[0149] A method for controlling a resonant DC / DC converter according to one of the method variants, wherein

[0150] a) Each converter bridge in the converter bridge is an inverter half-bridge, which includes a first input terminal and a second input terminal, and an inverter bridge output (which, alternatively, may be electrically connected to the first input terminal or the second input terminal via a plurality of semiconductor switches).

[0151] b) Each capacitor has a first terminal and a second terminal, and wherein

[0152] c) For each inverter half-bridge, the first terminal of each of the corresponding capacitors from the plurality of capacitors is connected to the corresponding inverter bridge output, and

[0153] d) The second terminals of all the capacitors in the first plurality of N capacitors are connected together at a common node.

[0154] 40) A method for controlling a resonant DC / DC converter according to one of the method variations, wherein

[0155] a) Each converter bridge in the converter bridge is an inverter half-bridge, which includes a first input terminal and a second input terminal, and an inverter bridge output (optionally, electrically connectable to either the first or second input terminal via multiple semiconductor switches).

[0156] b) Each capacitor has a first terminal and a second terminal, and wherein

[0157] c) For each inverter half-bridge, the first terminal of each of the corresponding capacitors from the plurality of capacitors is connected to the corresponding inverter bridge output, and

[0158] d) The second terminal of each of the first plurality of N capacitors is connected to a different primary winding.

[0159] 41) A method for controlling a resonant DC / DC converter according to one of the method variants, wherein the second terminals of all plurality of primary windings are connected together.

[0160] 42) A method for controlling a resonant DC / DC converter according to one of the method variations, wherein

[0161] a) The first DC link has a positive terminal and a negative terminal.

[0162] b) The first input terminals of all inverter half-bridges are connected to the positive terminals, and

[0163] c) The second input terminal of all inverter half-bridges is connected to the negative terminal.

[0164] 43) A method for controlling a resonant DC / DC converter according to one of the method variants, wherein the first DC link also has a neutral terminal, and the second terminals of all the plurality of primary windings are connected to the neutral terminal.

[0165] 44) A method for controlling a resonant DC / DC converter according to one of the method variants, wherein the converter is a resonant converter and each of a plurality of capacitors is a capacitor.

[0166] 45) A method for controlling a resonant DC / DC converter according to one of the method variations, wherein the converter further comprises:

[0167] a) Second DC link, preferably a second DC link capacitor

[0168] b) A second plurality of N'>1 converter bridges connected in parallel with the second DC link;

[0169] c) The secondary side of the transformer includes at least one secondary winding;

[0170] d) The converter also includes a third N' capacitors, wherein

[0171] e) For each of the second plurality of N'>1 converter bridges, a different capacitor from the third plurality of capacitors is connected between the converter bridge and at least one secondary winding.

[0172] 46) A method for controlling a resonant DC / DC converter according to one of the method variations, wherein

[0173] a) Each of the first N>1 converter bridges is an inverter bridge;

[0174] b) The secondary side of the transformer includes at least one secondary winding; the converter also includes:

[0175] c) A second DC link, preferably a second DC link capacitor;

[0176] d) A second plurality of N'>1 rectifier bridges connected in parallel with the second DC link;

[0177] e) A third set of N' capacitors, of which

[0178] f) For each rectifier bridge, different capacitors from the third plurality of capacitors are connected between the rectifier bridge and at least one secondary winding.

[0179] 47) A method for controlling a resonant DC / DC converter according to one of the method variations, having

[0180] a) The secondary side of the transformer includes multiple M'>1 secondary windings, each of the multiple secondary windings having a first terminal and a second terminal;

[0181] b) A fourth set of M' capacitors; and among them

[0182] c) Each of the third N' capacitors is connected between one of the converter bridges and another common node in the converter bridge;

[0183] d) Each of the fourth plurality of M' capacitors is connected between another common node and the first terminal of a different secondary winding in the plurality of secondary windings.

[0184] 48) A method for controlling a resonant DC / DC converter according to one of the method variations, wherein the converter further comprises:

[0185] a) Second DC link, preferably a second DC link capacitor

[0186] b) A second plurality of N'>1 converter bridges connected in parallel with the second DC link; and

[0187] c) The secondary side of the transformer includes a plurality of N' secondary windings, each of the plurality of secondary windings having a first terminal and a second terminal; wherein the converter bridge and the secondary windings are connected in pairs via capacitors different from a third plurality of capacitors, the third plurality of capacitors being connected to the first terminal of the corresponding secondary winding of the plurality of secondary windings.

[0188] 49) A method for controlling a resonant DC / DC converter according to one of the method variations, wherein the converter bridges in a first plurality of N>1 converter bridges are active bridges configured to operate in at least substantially synchronous manner, and, if present, the converter bridges in a second plurality of converter bridges are also active bridges configured to operate in at least substantially synchronous manner.

[0189] 50) A control unit for controlling a resonant DC / DC converter, particularly according to one of the embodiments, according to one of the variations of the method.

[0190] 51) A data processing system comprising means for performing a method according to one of the method variants.

[0191] 52) A computer program product comprising instructions which, when executed by a data processing system, cause the data processing system to perform a method according to one of the method variants.

[0192] Referring to the accompanying drawings and exemplary embodiments described below, the aspects described above, as well as other aspects of the invention, will become clear and elucidated. Attached Figure Description

[0193] The subject matter of the present invention will be explained in more detail below with reference to exemplary embodiments shown in the accompanying drawings.

[0194] Figure 1 A basic, general-purpose, prior art resonant DC / DC converter is shown.

[0195] Figure 2 A schematic diagram of an exemplary resonant DC / DC converter according to an embodiment of the present invention is shown.

[0196] Figure 3 A schematic diagram of an exemplary resonant DC / DC converter according to another embodiment of the present invention is shown.

[0197] Figure 4 An exemplary physical winding configuration of a DC / DC converter according to another embodiment of the present invention is shown.

[0198] In principle, the same reference numerals in the figures represent the same features or elements. Detailed Implementation

[0199] Figure 1 a) A basic prior art resonant DC / DC converter 1 is shown, which can be considered a potential starting point for the present invention. A DC / AC converter 12 is configured to convert a DC voltage and / or current from a DC source into an intermediate frequency (i.e., preferably in the frequency range between 500 Hz and 500 kHz) AC voltage and / or current. The DC source preferably includes a DC link capacitor connected to the input of the DC source. The AC voltage and / or current is fed into an AC intermediate circuit 14, which includes a transformer, particularly an intermediate frequency transformer (MFT), comprising a primary side and a secondary side, and providing current insulation between the sides. The transformer is characterized in particular by a coupling inductor L. m and L m’ and stray inductance L s One or more of its primary-side windings are connected to the DC / AC converter via capacitors as impedance elements, said capacitors having a capacitance C. res1 The capacitor, together with the stray inductor, is part of a resonant circuit formed by an AC intermediate circuit. It can store electrical energy and is characterized by a resonant frequency, which in turn depends on L. s and C res1The value of . Therefore, the capacitor is often referred to as a resonant capacitor. The transformer transforms the voltage and / or current on its primary side to the voltage and / or current on its secondary side in a known manner. The secondary side voltage and / or current is then converted into DC voltage and / or current by the AC / DC converter 16, particularly the rectifier, at the output of the AC / DC converter 16. In particular, the DC / AC converter 12 may include a plurality of semiconductor switches arranged in relation to Figure 1 The half-bridge configuration shown in b) corresponds to the half-bridge configuration, or is arranged in a manner similar to... Figure 1 The full-bridge configuration shown in c) corresponds to the full-bridge configuration. Similarly, the AC / DC converter 16 may in particular include a plurality of semiconductor switches arranged in a manner consistent with... Figure 1 The half-bridge configuration shown in b) corresponds to the half-bridge configuration, or is arranged in a manner similar to... Figure 1 c) shows a full-bridge configuration corresponding to the full-bridge configuration described above. As an alternative to a variant including an active bridge as described above and allowing bidirectional power flow, the AC / DC converter 16 can be implemented without semiconductor switches and including only diodes arranged in a half-bridge or full-bridge configuration, particularly without transistors and thyristors, if only unidirectional power flow is required. A resonant DC / DC converter is exemplarily described in PCT patent application WO 2018 / 141092 A1, the entire contents of which are incorporated herein by reference.

[0200] Figure 2 A schematic diagram of an exemplary resonant DC / DC converter according to an embodiment of the present invention is shown. The converter includes a first DC link 10, a DC / AC converter 212 including a plurality of semiconductor switches S1, S2, S3, ..., S6, an AC intermediate circuit 214, an AC / DC converter 216, and a second DC link 18. The DC / AC converter includes a common node C of a plurality of active half-bridges connected to a single first DC link 10 and the primary winding of an intermediate frequency transformer 2141, with each output of the active half-bridges connected via a first plurality of (N=3) capacitors C. resA1 C resA2 and C resA3 Individual capacitors are connected, and the transformer specifically provides current insulation between the primary and secondary sides of the transformer. The primary winding is connected to a common node C, where capacitor C... resA1 C resA2 and C resA3 All are connected. Preferably, the first plurality of capacitors C resAAll capacitors in the series have the same capacitance. For background information purposes only, a voltage source connected to the first DC link 10, a resistive load connected to the second DC link 18, and a magnetoresistive network 19 indicating the transformer core and stray flux are also shown. A control unit is also shown, configured to provide switching signals for periodically switching the inverter bridge between an on and off state at a predetermined first switching frequency, or between an off and on state at a predetermined first switching frequency, and to monitor the currents i1, i2, i3 of each of the plurality of active half-bridges connected to the first DC link 10 via current sensors 17.

[0201] Figure 3 A schematic diagram of an exemplary resonant DC / DC converter according to another embodiment of the present invention is shown. The converter includes a first DC link 10, a DC / AC converter 212 including a plurality of semiconductor switches S1, S2, S3, ..., S6, an AC intermediate circuit 214', an AC / DC converter 216, and a second DC link 18. The converter includes a plurality of active half-bridges and a common node C of the primary coil of an intermediate frequency transformer 2141'. The plurality of active half-bridges are connected to a single first DC link 10, and each output of the active half-bridges is via a first plurality of (N=3) capacitors C. resA1 C resA2 and C resA3 Individual capacitors are connected, and the transformer specifically provides current insulation between the primary and secondary sides. The primary coil comprises multiple M = 2 parallel windings N. 1,wire1 and N 1,wire2 That is, windings connected in parallel, each winding consisting of a conductor, wherein each conductor or winding is connected via a second (M=2) capacitor C. resB1 and C resB2 Individual capacitors are connected to a common node C. The common node C is provided as a single-point coupling, where capacitor C... resA ...and capacitor C resB ...all are connected, allowing for independent optimization of the semiconductor switching and transformer lines. Preferably, the first plurality of capacitors C resA ...all the capacitors have the same capacitance. Similarly, the second plurality of capacitors C... resB ...the capacitances of all the capacitors are the same as each other, but not necessarily the same as the first multiple capacitors C. resAThe capacitances are the same. For background information purposes only, a voltage source connected to the first DC link 10, a resistive load connected to the second DC link 18, and a magnetoresistive network 19 indicating the transformer core and stray flux are also shown. A control unit is also shown, configured to provide switching signals for periodically switching the inverter bridge between an on and off state at a predetermined first switching frequency, or periodically switching the inverter bridge between an off and on state at a predetermined first switching frequency, and to monitor the currents i1, i2, i3 of each of the plurality of active half-bridges connected to the first DC link 10 via current sensors 17.

[0202] exist Figure 2 and Figure 3 In the embodiment shown, capacitor C resA1 C resA2 ... and C resB1 C resB2 (If it exists) Replace Figure 1 a) Resonant capacitor C res1 And together they serve as resonant capacitors for the AC intermediate circuits 214 and 214'. The capacitor C resA ...and C resB ...(if present) can therefore be considered as separate resonant capacitors, where each individual capacitor in the capacitors serves as a partial resonant capacitor. Due to the presence of these partial resonant capacitors, the current through each active half-bridge or arm is not defined by power module parasitic effects, non-uniform temperature distribution, and / or semiconductor switching characteristics (not perfectly equal for all chips), but by the resonant circuit (defined by transformer stray flux (approximately equal for all parallel wires)) and the separate resonant capacitors (with a limited maximum deviation from the reference capacitance, e.g., 5%) within a defined range. This makes the current distribution uniform and stable without additional measures or effort.

[0203] Furthermore, connecting the parallel half-bridge via a separate resonant capacitor also located at the common node C and between multiple M=2 parallel windings can prevent circulating currents in the transformer windings, which would otherwise result in significant losses and / or a substantial reduction in converter performance during MFT.

[0204] Therefore, a converter bridge employing low-cost discrete off-the-shelf components for relatively low current can be used, and via a discrete resonant capacitor (C resA1 C resA2 C resA3 ...C resAiThey are connected to a common point, specifically common node C, from which the primary winding of the intermediate frequency transformer (MFT) is connected. In the case where the primary winding consists of parallel lines, the disconnecting resonant capacitor C... res Other components (C) resB1 C resB2 ...C resBi This also allows for current balance in the transformer lines, and the effective capacitance is given by the following formula.

[0205]

[0206] If multiple converter bridges employ low-current power semiconductors, gate drivers can be implemented at very low cost, for example, through bootstrap designs that eliminate the associated cost factor of requiring additional gate drivers. The potential reduction in system reliability due to the significantly increased number of components and gate drivers can be addressed through switching frequency adaptation according to the present invention.

[0207] The generation of circulating current, particularly in a configuration of two windings connected in parallel without impedance elements and each winding comprising multiple turns, can be understood as follows: each turn is exposed to a stray magnetic field, for example, in a winding window formed by the transformer core. Parallel Litz wires forming separate windings connected at the transformer's input and output terminals create a loop exposed to the stray magnetic field. The stray magnetic field varies with the operating frequency of the MFT, thereby generating a voltage that drives the circulating current in this loop. The circulating current increases the nominal current in the MFT, which may result in one Litz wire carrying more than half of the nominal current, while a parallel Litz wire correspondingly carries less than half. If the circulating current is large enough, a single Litz wire can carry more than the total nominal current, thus a parallel Litz wire carries a negative (180° phase shift) current. In this way, not only is the total available copper cross-section effectively reduced by 50%, but additional losses are also introduced, and the maximum output power of the MFT is reduced by two times or more.

[0208] The following discussion addresses the impact of the loss of one or more discrete resonant capacitors, for example, due to a converter bridge arm failure, on the converter's resonant frequency. All converter-side capacitors C resA1 Cres A2 and C resA3 The sum is called C resA All primary winding side capacitors C resB1 and C resB2 The sum is called C resB See equations (1) and (2). Resonant capacitance C res Defined in equation (3), and as shown in equation (4), it depends on the transformer stray inductance L. s and the selected switching frequency f of the half-bridgeP This frequency is preferably slightly lower than the resonant frequency f. res In order to operate with minimal switching losses, especially by using soft switching.

[0209] If n out of N converter bridges fail, and correspondingly n discrete capacitors (each with a capacitance C) fail... resAi If the effective resonant capacitance C is lost, then... res Fail According to equation (5), the resonant frequency changes, and according to equation (6), the resonant frequency changes. For example, Figure 3 In the embodiment shown, the control scheme according to the present invention will adjust the switching frequency of the remaining bridge arm according to (6):

[0210]

[0211] C resB =∑C resB，i (2)

[0212]

[0213]

[0214]

[0215]

[0216]

[0217] For the case where there is no primary winding-side disconnect capacitor (C) res =C resA No C resB ,like Figure 2 In the embodiment shown, the equation for the new resonant frequency simplifies to equation (7). It can be deduced that if approximately 1 / 6 of the parallel half-bridge is lost, the resonant frequency will increase by approximately 10%. Therefore, the controller must adjust the switching frequency of the remaining bridge arms accordingly.

[0218] If the converter bridge fails when its switch is in the non-conducting state, its output current becomes zero, and this will be detected. If the converter bridge fails when its switch is in the conducting state, a circuit breaker must disconnect the affected converter, and its monitored output current also becomes zero. Therefore, the method according to the invention operates independently in the event of a converter bridge failure.

[0219] Figure 4An exemplary physical winding configuration of a DC / DC converter according to another embodiment of the invention is shown. It can be seen that the spatial relationship between the parallel lines 2143' and 2144' remains constant throughout the entire winding; that is, no transposition occurs. In the prior art, such transposition is provided, for example, by parallel lines that are intertwined or otherwise wound or interlaced. However, such transposition requires additional manufacturing work, particularly for foil windings, resulting in an increase in effective conductor length, exhibiting limited efficiency in MFTs with only a few turns, and potentially leading to high-voltage insulation challenges, such as due to geometric inhomogeneities near the transposition location.

[0220] In all the embodiments shown, the secondary side of the DC / DC converter (such as...) Figure 2 and Figure 3 (As shown on the right-hand side) can alternatively be implemented in a manner similar to the primary side.

[0221] The advantages of this invention are:

[0222] High redundancy leads to high reliability.

[0223] • Achieve reliable, low-cost inverters based on readily available discrete power devices.

[0224] • High modularity and scalability due to passive current sharing between parallel bridge arms.

[0225] No additional components are required. As proposed, the resonant capacitor is separated to maintain the total capacitor / inductor size, especially the total / sum capacitance or inductance remains unchanged.

[0226] • Allows for low-cost implementation of resonant DC / DC converter units by simply adding more half-bridges to employ and / or enable off-the-shelf power semiconductor switches for high-current applications.

[0227] • Allows the use of wide-bandgap semiconductor switches for high-current applications to realize resonant DC / DC converter units at low cost, which would otherwise become increasingly difficult due to the fast switching speed and smaller chip size (compared to non-wide-bandgap semiconductor switches).

[0228] There is no theoretical limit to the number (N or N') of parallel converter bridges (i.e., power semiconductor switches).

[0229] Simple, robust, and requires no active current balancing control.

[0230] • As the maximum current that a single MFT can handle increases, the maximum and / or nominal power of each MFT can increase. This is key to building cost-effective MFTs. In higher power (and therefore larger) MFTs, the insulation workload, particularly the volume required for sufficient insulation, decreases relatively. Another way to provide higher power with higher current is to parallel the entire resonant converter or dual active bridge converter unit in the SST, or even the entire SST and therefore the required number of MFTs. However, this does not increase the power level of a single MFT.

[0231] • The circulating current in the parallel transformer windings, which consist of parallel lines, can be effectively suppressed because the isolated resonant capacitor or isolated energy transfer inductor will block the current. This can also be achieved using the more common Litz wire with a smaller cross-section, which may be cheaper and can be manufactured with less effort and resources.

[0232] • A very general concept for handling DC / DC resonant converters of hundreds of amperes; not only for units in SSTs connected to MV grids, but also for high-power low-voltage applications, such as those required in various EV fast charger topologies.

[0233] Unless otherwise stated, a control unit (also referred to as a control system or controller) can be any (first) device, apparatus, system, unit, etc., configured to manage, command, direct, or regulate another (second) device, apparatus, sensor, unit, etc., which may be part of a higher-level or superior (third) device, apparatus, sensor, unit, etc. The control unit may apply open-loop or closed-loop control, where the latter may take into account feedback from sensors.

[0234] The control unit may include and / or be at least partially implemented on a “computer,” “processor,” “processing device,” “central processing unit (CPU),” or “computing device,” terms that are not limited to these devices literally but should refer to data processing systems in general, including microcontrollers, microcomputers, programmable logic controllers (PLCs), application-specific integrated circuits (ASICs), and other programmable circuits, wherein these terms are used interchangeably herein. In the embodiments described herein, memory may include, but is not limited to, computer-readable media such as random access memory (RAM) and computer-readable non-volatile media such as flash memory. Alternatively, floppy disks, optical discs—read-only memory (CD-ROM), magneto-optical discs (MOD), digital versatile optical discs (DVDs), USB flash drives, and / or flash memory cards (e.g., CF, SD, miniSD, microSD) may also be used. Furthermore, in the embodiments described herein, input channels may include, but are not limited to, computer peripherals associated with sensors or sensing devices or having an operator interface such as a mouse and keyboard. Additionally, in exemplary embodiments, additional output channels may include, but are not limited to, operator interface displays.

[0235] Furthermore, as used herein, the terms “software” and “firmware” are interchangeable and include any computer program that can be stored in memory for execution by a computer, workstation, client, and / or server as defined above.

[0236] As used herein, the term "non-transitory computer-readable medium" is intended to mean any tangible computer-based device implemented using any technical method for short-term and / or long-term storage of information, such as computer-readable instructions, data structures, program modules and submodules, or other data in any device. Therefore, the methods described herein can be encoded as executable instructions embodied in a tangible, non-transitory computer-readable medium, including but not limited to storage devices and / or memory devices. Such instructions, when executed by a computer as defined above, cause the computer to perform at least a portion of the methods described herein. Furthermore, as used herein, the term "non-transitory computer-readable medium" can include all tangible computer-readable media, including but not limited to non-transitory computer storage devices, including but not limited to volatile and non-volatile media and removable and non-removable media, such as firmware, physical and virtual storage, CD-ROMs, DVDs, and any other digital resources (such as networks or the Internet), as well as undeveloped digital means, with the sole exception of transient propagation signals.

[0237] Unless otherwise stated, the term "connection" as used throughout this patent application, particularly the connection between any two entities (including nodes, points, terminals, elements, devices, etc., or combinations thereof), refers to a conductive connection, especially a connection established by wires, cables, busbars, conductive tracks, traces, or lines, such as (printed) circuit boards, solder, etc. A conductive connection is preferably at least substantially direct, particularly without any discrete components, particularly resistors, capacitors, inductors, or other passive or active components or devices connected between the connected entities. A conductive connection thus has at least substantially negligible resistance, capacitance, and inductance, preferably at least substantially zero resistance, capacitance, and inductance. In particular, the resistance, capacitance, and inductance of a conductive connection are essentially entirely parasitic. Furthermore, the resistance, capacitance, and inductance of a conductive connection are much smaller (preferably 1 / 100, 1 / 1000, or 1 / 10000) than the resistance, capacitance, and impedance of the resistors, capacitors, or inductors included in the circuit or network connected and / or including the conductive connection.

[0238] Unless otherwise specified, electrical connections or wiring connections are the same as those defined above.

[0239] Unless otherwise stated, if two entities (in particular including nodes, points, terminals, elements, devices, etc. or combinations thereof) are referred to as a connection, electrical connection, or (electrically) connected together, then a connection exists between the two entities as defined above.

[0240] Unless otherwise stated, if a first entity and a second entity (in particular including a first node, point, terminal, element, device, and a second node, point, terminal, element, device, etc., or combinations thereof) are said to be connected via a third entity (in particular including a third node, point, terminal, element, device, or such a third entity existing between them), the connection described above exists between the first entity and the third entity, and between the third entity and the second entity. However, the connection described above does not exist, particularly the absence of at least substantially direct connection between the first entity and the second entity. If explicitly specified, the third element can also be a connection, particularly a conductor, wire, cable, busbar, etc. In this case, it can be assumed that the connection described above does not exist except for the specified connection.

[0241] Unless otherwise indicated, it is assumed throughout this patent application that the statement a≈b means |a - b| / (|a|+|b|)<10, preferably |a - b| / (|a|+|b|)<100, where a and b can represent any variable described and / or defined anywhere in this patent application or known to those skilled in the art. Further, the statement that a is at least approximately equal to or at least approximately the same as b means a≈b, preferably a = b. Further, unless otherwise indicated, it is assumed throughout this patent application that the statement a>>b or a is significantly greater than or much greater than b means a>10b, preferably a>100b; the statement a<<b or a is significantly less than or much less than b means 10a<b, preferably 100a<b. Further, the statement that two values a and b are substantially deviated from each other or significantly different means that a≈b does not hold, particularly a>>b or a<<b.

[0242] Unless otherwise indicated, N, M, O, N’, M’, O’ are used in this patent application to represent integers.

[0243] This description and the drawings that illustrate aspects and embodiments of the invention should not be regarded as limiting the claims that define the protected invention. In other words, although the invention has been illustrated and described in detail in the drawings and the foregoing description, such illustration and description are considered to be illustrative or exemplary and not restrictive. Various mechanical, compositional, structural, electrical, and operational changes may be made without departing from the spirit and scope of this specification and the claims. In some instances, well-known circuits, structures, and techniques have not been shown in detail so as not to obscure the invention. Accordingly, it should be understood that modifications and changes may be made by those of ordinary skill within the scope of the appended claims. In particular, the invention encompasses other embodiments having any combination of features from different and / or separate embodiments described above and below. Embodiments in accordance with the invention may particularly include further and / or additional features, elements, aspects, etc. not shown in the drawings or described above.

[0244] This disclosure also separately covers all other features shown in the figures, even though they may not be described in the preceding or following description. Further, separate alternatives of the embodiments described in the drawings and the specification and separate alternatives of their features may be excluded from the subject matter of the invention or the disclosed subject matter. This disclosure includes the subject matter consisting of the features defined in the claims or exemplary embodiments and the subject matter including such features.

[0245] Furthermore, in the claims, the word "comprising" does not exclude other or additional features, elements, steps, etc., and the indefinite article "a" or "an" does not exclude a plurality. A single unit or step can perform the function of several features listed in the claims. The fact that certain measures are listed in mutually different dependent claims does not indicate that a combination of these measures cannot be used advantageously. As mentioned above, the terms "substantially," "approximately," "approximately," etc., related to attributes, characteristics, or values ​​also specifically and accurately include the attributes, characteristics, or values, respectively. In the context of a given numerical value or range, the terms "approximately" or "approximately" refer to, for example, values ​​or ranges within 20%, 10%, 5%, or 2% of a given value or range, and in particular, also include the exact value or range. Components described as coupled or connected may be electrically or mechanically directly coupled, or they may be indirectly coupled via one or more intermediate components. Any reference numerals in the claims should not be construed as limiting the scope.

Claims

1. A resonant DC / DC converter, comprising: a) First DC link (10); b) A DC / AC converter (212) comprising a first plurality of N>1 converter bridges connected in parallel to the first DC link; each converter bridge comprising a plurality of switches, each of the plurality of switches being switchable between an on state and a non-on state; c) An AC intermediate circuit (214, 214') is connected to the DC / AC converter and includes... i) A transformer (2141, 2141') having a primary side and a secondary side; wherein the primary side comprises a plurality of M>1 windings; d) A first plurality of N capacitors, wherein each of the first plurality of N capacitors is connected between one of the converter bridges and a common node (C) in the converter bridge; e) A second plurality of M capacitor bridges, wherein each capacitor in the second plurality of M capacitor bridges is connected between the common node (C) and a different primary winding among the plurality of primary windings; f) A control unit configured to switch the converter bridge switch at a switching frequency between the on state and the off state, or to switch the converter bridge switch at the switching frequency between the off state and the on state, to provide AC current and / or voltage to the AC intermediate circuit. g) A plurality of N current sensing devices (17), wherein for each converter bridge, different current sensing devices among the plurality of current sensing devices are provided for monitoring the current through the converter bridge; h) The control unit is configured to determine whether the current through one of the converter bridges deviates from the expected value; and if the current through one of the converter bridges deviates from the expected value, to adapt the switching frequency.

2. The resonant DC / DC converter according to claim 1, wherein the first DC link (10) includes a first DC link capacitor.

3. The resonant DC / DC converter according to claim 1, wherein the transformer (2141, 2141') is an intermediate frequency transformer.

4. The resonant DC / DC converter of claim 1, wherein, with exactly N capacitors connected between the N converter bridges and at least one primary winding: the initial switching frequency applied when all N converter bridges are active and / or operating normally. f res The control unit is configured to operate according to an adapted switching frequency. To adapt to the switching frequency.

5. The resonant DC / DC converter of claim 1, wherein the control unit is configured to determine whether the current deviates from an expected value by determining whether the current through one of the converter bridges is less than a given threshold.

6. The resonant DC / DC converter of claim 1, wherein the control unit is configured to determine whether the current deviates from a expected value by determining whether the current through one of the converter bridges is at least approximately zero.

7. The resonant DC / DC converter of claim 1, wherein the control unit is configured to deactivate the converter bridges if it determines that the current through one of the converter bridges deviates from a expected value.

8. The resonant DC / DC converter of claim 1, wherein for each converter bridge, different current sensing devices from the plurality of current sensing devices are provided between the converter bridge and at least one primary winding.

9. The resonant DC / DC converter of claim 1, wherein an AC current sensor is used as a current sensing device for measuring the AC current output from the converter bridge.

10. The resonant DC / DC converter according to claim 1, wherein the switch is a semiconductor switch.

11. The resonant DC / DC converter of claim 1, wherein adapting the switching frequency is increasing the switching frequency.

12. The resonant DC / DC converter of claim 5, wherein the control unit is configured to determine whether the current deviates from a desired value by determining whether the absolute value of the current through one of the converter bridges is less than a given threshold.

13. The resonant DC / DC converter of claim 6, wherein the control unit is configured to determine whether the current deviates from an expected value by determining whether the current through one of the converter bridges is less than 1 / 100, 1 / 1000, or 1 / 10000 of the rated current, nominal current, and / or maximum current of the converter bridge.

14. The resonant DC / DC converter of claim 8, wherein for each converter bridge, different current sensing devices from the plurality of current sensing devices are provided between the converter bridge and the capacitor connected between the converter bridge and the at least one primary winding.

15. A method for controlling a resonant DC / DC converter, the converter comprising: a) First DC link (10); b) A DC / AC converter (212) including a first plurality of N>1 converter bridges connected in parallel to the first DC link; each converter bridge includes a plurality of semiconductor switches, each of the plurality of semiconductor switches being switchable between an on state and a non-on state; c) An AC intermediate circuit (214, 214') is connected to the DC / AC converter and includes... i) A transformer (2141, 2141') having a primary side and a secondary side; wherein the primary side comprises a plurality of M>1 windings; d) A first plurality of N capacitors, wherein each of the first plurality of N capacitors is connected between one of the converter bridges and a common node (C) in the converter bridge; e) A second plurality of M capacitor bridges, wherein each capacitor in the second plurality of M capacitor bridges is connected between the common node (C) and a different primary winding among the plurality of primary windings; f) The control unit is configured to operate at a switching frequency. f res The semiconductor switch of the converter bridge switches between the on state and the off state, or at the switching frequency. f res The method involves switching the semiconductor switches of the converter bridge between the non-conducting state and the conducting state to provide AC current and / or voltage to the AC intermediate circuit; the method includes the following steps: g) For each converter bridge, monitor the current through the converter bridge; h) Determine whether the current through the first converter bridge deviates from the expected value; i) If the current through the first converter bridge deviates from the expected value, then the switching frequency is adapted.

16. The method of claim 15, wherein the first DC link (10) includes a first DC link capacitor.

17. The method of claim 15, wherein the transformer (2141, 2141') is a medium frequency transformer.

18. The method of claim 15, wherein, when exactly N capacitors are connected between the N converter bridges and at least one primary winding: the initial switching frequency applied when all N converter bridges are active and / or operating normally. f res The switching frequency f res Adapted to the already adapted switching frequency .

19. The method of claim 15, wherein determining whether the current through one of the converter bridges deviates from an expected value is performed by determining whether the current is less than a given threshold.

20. The method of claim 15, wherein determining whether the current through one of the converter bridges deviates from the expected value is performed by determining whether the current is at least approximately zero.

21. The method of claim 15, further comprising the step of: When it is determined that the current through the first converter bridge deviates from the expected value, the first converter bridge is deactivated.

22. The method of claim 15, further comprising the step of: a) Provide multiple N current sensing devices (17); b) For each converter bridge, the current through the converter bridge is measured by different current sensing devices from the plurality of current sensing devices provided between the converter bridge and the plurality of primary windings.

23. The method of claim 15, wherein adapting the switching frequency is increasing the switching frequency.

24. The method of claim 19, wherein determining whether the current through one of the converter bridges deviates from a expected value is performed by determining whether the absolute value of the current is less than a given threshold.

25. The method of claim 20, wherein determining whether the current through one of the converter bridges deviates from the expected value is performed by determining whether the current is less than 1 / 100, 1 / 1000, or 1 / 10000 of the rated current, nominal current, and / or maximum current of the converter bridge.

26. The method of claim 22, wherein for each converter bridge, the current through the converter bridge is measured by different current sensing devices from the plurality of current sensing devices, the different current sensing devices from the plurality of current sensing devices being provided between the converter bridge and the capacitor connected between the converter bridge and the plurality of primary windings.

27. A control unit for controlling a resonant DC / DC converter according to any one of claims 1 to 14 using the method of any one of claims 15 to 26.

28. A computer program product comprising instructions that, when executed by a data processing system, cause the data processing system to perform the method according to any one of claims 15 to 26.

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