Method, controller and computer program for operating a three-port series resonant converter, converter device and computer readable medium

Abstract

A method for operating a three-port series resonant converter (20) is described. The three-port series resonant converter (20) has a main feed bridge (22), at least one auxiliary feed bridge (24) and an output bridge (26). The main feed bridge (22) is electromagnetically coupled to the output bridge (26) via a first input coil (36) of the main feed bridge (22), the auxiliary feed bridge (24) is electromagnetically coupled to the output bridge (26) via a second input coil (46) of the auxiliary feed bridge (24), and the main feed bridge (22) and the auxiliary feed bridge (24) are configured such that their resonant frequencies are at least approximately the same. The method comprises: sending one or more control signals to one or more switches (32, 42) of the feed bridges (22, 24) based on a predetermined control scheme such that an input voltage (V LV,m , V LV,a ) applied to the feed bridges (22, 24) is converted into a total output voltage (V MV ) provided by the output bridge (26); sending a turn-off signal to at least some of the switches (32, 42) of at least one of the feed bridges (22, 24) such that an output voltage (v' p,m , v' p,a ) of the corresponding feed bridge (22, 24) is floating as soon as an output bridge current of the output bridge (26) is at least approximately zero.

Description

Technical Field

[0001] This invention relates to the field of electrical converters and the control of electrical converters. Specifically, this invention relates to a method, controller, and computer program for controlling a three-port series resonant converter; a converter apparatus including the controller and the three-port series resonant converter; and a computer-readable medium storing the computer program. Background Technology

[0002] Generally, electrical converters are used to convert input voltage to output voltage, such as from low voltage (LV) to medium voltage (MV) or vice versa. The LV range used in this specification is 120 V to 1500 V, while the MV range can refer to voltages greater than 1500 V. Resonant converters are a class of known electrical converters, such as two-port or three-port series resonant converters (SRC).

[0003] A two-port SRC has input and output bridges coupled to each other via transformers. A three-port SRC has a main input bridge, an auxiliary input bridge, and an output bridge, where each input bridge is coupled to the output bridge via a transformer. Both two-port and three-port SRCs can operate bidirectionally, such that in a first operating mode, the input voltage is supplied to the input bridge and the output voltage is supplied by the output bridge; and in a second operating mode, the input voltage is supplied to the output bridge and the output voltage is supplied by the input bridge.

[0004] One of the advantages of a two-port SRC is that it provides an operating mode called "half-cycle discontinuous conduction mode (HC-DCM)," in which the two-port SRC itself guarantees soft switching throughout the entire operating range, while also allowing for very simple open-loop control. In this operating mode, only one feed bridge in the two-port SRC is actively switched, while its output bridge operates as a passive diode rectifier.

[0005] A straightforward approach to operating a three-port SRC converter with two feed bridges is to apply the same modulation scheme typically used in conventional two-port SRCs. This involves actively switching the two feed bridges on the LV side at a fixed frequency and full duty cycle based on the corresponding control scheme, while the output bridge on the MV side operates as a passive diode rectifier. Specifically, for the power flow from the MV to the two LV-side feed bridges, this can be easily achieved by applying the same modulation strategy as in the two-port SRC case. However, when power flows from the two LV feed bridges to the MV output bridge, the modulation method used in conventional two-port SRCs causes a circulating current between the two power flow paths, resulting in a loss of soft-switching performance and reduced power flow controllability (except in certain special load scenarios). Summary of the Invention

[0006] The object of this invention is to provide a method, controller, and computer program for controlling a three-port SRC, which enables the three-port SRC to operate using HC-DCM, particularly when power flows from the LV feed bridge to the MV output bridge, and / or enables zero-current switching of the active bridge (preferably throughout the operating range), and controls the ratio of power flows between the feed bridges. Another object of this invention is to provide a converter device having a controller and a three-port SRC, and a computer-readable medium storing the computer program.

[0007] These objectives are achieved through the subject matter of the independent claims. Further exemplary embodiments will become clear from the dependent claims and the following description.

[0008] The first aspect relates to a method for operating a three-port series resonant converter. The three-port series resonant converter has a main feed bridge, at least one auxiliary feed bridge, and an output bridge. The main feed bridge is electromagnetically coupled to the output bridge via a first input coil of the main feed bridge, and the auxiliary feed bridge is electromagnetically coupled to the output bridge via a second input coil of the auxiliary feed bridge. The main feed bridge and the auxiliary feed bridge are configured such that their resonant frequencies are at least approximately the same. The method includes: sending one or more control signals to one or more switches of the feed bridges based on a predetermined control scheme, such that an input voltage applied to the feed bridges is transformed into a total output voltage provided by the output bridge; and sending a turn-off signal to at least some of the switches of at least one of the feed bridges, such that the output voltage of the corresponding feed bridge is floating once the output bridge current of the output bridge is at least approximately zero.

[0009] The second aspect relates to a controller for operating a three-port series resonant converter. The controller has a memory for storing one or more voltage and / or current values; and a processor communicatively coupled to the memory and configured to perform the methods described above and below based on the stored voltage and / or current values, respectively.

[0010] The third aspect relates to a converter device. The converter device has a three-port SRC and a controller, which is communicatively coupled to the three-port SRC and configured to operate the three-port SRC.

[0011] The fourth aspect relates to a computer program for operating a three-port SRC, wherein the computer program has computer-readable instructions that, when executed by the processor of the controller, perform the methods described above and below.

[0012] The fifth aspect relates to a computer-readable medium for storing the computer program. The computer-readable medium may be a floppy disk, hard disk, USB (Universal Serial Bus) storage device, RAM (Random Access Memory), ROM (Read-Only Memory), EPROM (Erasable Programmable Read-Only Memory), or flash memory. The computer-readable medium may also be a data communication network that allows the download of program code, such as the Internet. Generally, the computer-readable medium may be a non-transitory medium or a temporary medium.

[0013] It should be understood that, for the sake of brevity and to avoid unnecessary repetition, some features of the present invention are described with respect to only one aspect, but those skilled in the art can easily transfer these features to one or more other aspects.

[0014] The method for operating a three-port SRC presents a novel control strategy for three-port SRCs with at least two feed input ports (i.e., a main feed bridge and an auxiliary feed bridge). This new method enables the three-port SRC to establish a half-cycle discontinuous conduction mode (HC-DCM) similar to that of a two-port SRC. The proposed method uses the freewheeling state of the feed bridges to suppress circulating current between the two feed ports—circulating currents that form between the two feed bridges if the port power differs from a specific ratio defined by the circuit resonant elements of the three-port SRC. Using the proposed solution, soft-switching operation of the three-port SRC can be guaranteed while maintaining simple power flow controllability similar to that of conventional single-port or two-port series resonant converters.

[0015] Specifically, to eliminate coupling between the two converter paths and ensure that the voltage of the leakage inductance of the three-port SRC remains zero during the holdoff period, the output current of the output bridge is at least approximately zero during the holdoff period. Since the output voltage of the feed bridge supplied to the output bridge, which acts as a rectifier on the MV side, cannot float independently for the corresponding two different current paths, this can be achieved by turning off the signal to allow the AC output of the actively switched feed bridge to float during the holdoff time.

[0016] The output bridge current being "at least approximately zero" can mean that the output bridge current is zero, or that the deviation of the output bridge current from zero is less than 20% of the maximum output bridge current, for example, less than 5%, or less than 0.1%. The output bridge current can correspond to the sum of the first transformer current provided by the main feed bridge and the second transformer current provided by the auxiliary feed bridge.

[0017] The resonant frequencies of the main feed bridge and the auxiliary feed bridge are "at least approximately the same" in this context, which may mean that the resonant frequencies are the same, or that the deviation between the smaller resonant frequency and the larger resonant frequency is less than 20% of the larger resonant frequency, for example, less than 5%, for example, less than 0.1%.

[0018] The main feed bridge and / or auxiliary feed bridge can each be a full bridge with four switches or a half bridge with two switches. A three-port SRC can optionally have two or more auxiliary feed bridges. The output bridge can be used for active rectification of the output bridge current.

[0019] The main feed bridge is electromagnetically coupled to the output bridge via a first input coil, and the auxiliary feed bridge is electromagnetically coupled to the output bridge via a second input coil, which can be implemented using a three-port SRC with a single transformer. This single transformer can have a single output coil that is electrically coupled to the output bridge and inductively coupled to the first and second input coils. Alternatively, the three-port SRC can be equipped with a transformer for each feed bridge. In this case, the first output coil of the first transformer of the three-port series resonant converter can be electrically coupled to the output bridge and electromagnetically coupled to the first input coil, and the second output coil of the second transformer of the three-port series resonant converter can be electrically coupled to the output bridge and electromagnetically coupled to the second input coil of the auxiliary feed bridge.

[0020] According to one embodiment, the method includes: determining one or more time points when the output bridge current is at least approximately zero according to a predetermined control scheme; and sending a turn-off signal to a corresponding switch of the corresponding feed bridge at the determined time points. In this embodiment, when the output bridge current is zero can be predetermined according to the predetermined control scheme, and a fixed turn-off time can be provided at the determined time points, each time point being initiated by a corresponding turn-off signal. Therefore, it is assumed that the actual output bridge current corresponds to the output bridge current derived according to the predetermined control scheme. This allows for a fixed turn-off time without requiring any measurement of the output bridge current. This helps to keep the method and three-port SRC simple.

[0021] According to one embodiment, the method includes: determining a duration during which the output bridge current is at least approximately zero according to a predetermined control scheme; and sending one or more control signals based on the predetermined control scheme to activate one or more switches of the feed bridge to which a turn-off signal is sent, such that the corresponding output voltage no longer fluctuates after the duration following the sending of the turn-off signal. This duration may be referred to as the hold-off time. The duration can begin at each point in time determined according to the predetermined control scheme. The turn-off signal can always be sent at the beginning of the hold-off interval, and the control signal can always be sent at the end of the hold-off interval. This allows the turn-off time to be achieved without any measurement of the output bridge current. This helps to keep the method and the three-port SRC simple.

[0022] According to one embodiment, the method includes: before sending a turn-off signal: receiving at least one current signal representing the output bridge current; once the output bridge current is at least approximately zero, sending a turn-off signal to a corresponding switch of the corresponding feed bridge; and sending one or more control signals based on a predetermined control scheme to activate one or more switches of the feed bridge to which the turn-off signal was sent, such that when the output bridge current is no longer approximately zero, the corresponding output voltage no longer fluctuates. The current signal can be continuously received and / or received during the operation of the three-port SRC, and can be monitored for current signals approaching and / or crossing zero. The current signal can be generated by a current sensor of the converter device and can be sent to a controller. The controller can monitor the current signal from the current sensor with respect to the zero-crossing point of the current sensor. Determining the suppression interval during the period when the output bridge current is at least approximately zero by measuring the output bridge current can help to determine the suppression interval very accurately. This can reduce losses during three-port SRC operation.

[0023] According to one embodiment, when a turn-off signal is sent to at least some switches of at least one of the feed bridges, causing the output voltage of the corresponding feed bridge to float, a turn-off signal is sent to either the main feed bridge or the auxiliary feed bridge, and another turn-off signal is sent to the other of the main feed bridge or the auxiliary feed bridge. The main feed bridge, the auxiliary feed bridge, and the turn-off signals are configured such that all switches of both feed bridges are turned off when the output bridge current of the output bridge is at least approximately zero. In the case where one or both feed bridges are half-bridges, all switches of the corresponding feed bridge can be turned off by the turn-off signal; in the case where one or both feed bridges are full-bridges, at least three switches of the corresponding feed bridge can be turned off by the turn-off signal.

[0024] Alternatively, according to another embodiment, when a turn-off signal is sent to at least some switches of at least one feed bridge, causing the output voltage of the corresponding feed bridge to float, a turn-off signal is sent to the main feed bridge or the auxiliary feed bridge, and the corresponding feed bridge and the turn-off signal are configured such that all switches of the corresponding feed bridge are turned off when the output bridge current of the output bridge is at least approximately zero.

[0025] In any case, the shutdown signal can be a single signal sent to each corresponding switch. Alternatively, the shutdown signal can represent a set of separate shutdown signals, with one shutdown signal corresponding to each corresponding switch.

[0026] These and other aspects of the invention will be apparent and illustrated by the embodiments described below. Attached Figure Description

[0027] The subject matter of the invention will be explained in more detail below with reference to the exemplary embodiments illustrated in the accompanying drawings.

[0028] Figure 1A circuit diagram illustrating an exemplary embodiment of a three-port SRC is shown;

[0029] Figure 2 It shows Figure 1 The equivalent circuit diagram of a three-port SRC;

[0030] Figure 3 It shows Figure 1 The equivalent circuit diagram of the three-port SRC in the first state;

[0031] Figure 4 It shows Figure 1 The equivalent circuit diagram of the three-port SRC in the second state;

[0032] Figure 5 It shows in Figure 1 Examples of voltage and current measurements taken at the three-port SRC;

[0033] Figure 6 It shows Figure 1 The equivalent circuit diagram of the three-port SRC in the third state; and

[0034] Figure 7 It shows the control Figure 1 A flowchart illustrating an exemplary embodiment of the three-port SRC method.

[0035] The reference numerals used in the accompanying drawings and their meanings are listed in a summary list of reference numerals. In principle, the same parts in the accompanying drawings are provided with the same reference numerals. Detailed Implementation

[0036] Figure 1 A circuit diagram illustrating an exemplary embodiment of a three-port series resonant converter (SRC) 20 is shown. The three-port SRC 20 has a main feed bridge 22, at least one auxiliary feed bridge 24, and an output bridge 26. Optionally, the three-port SRC 20 may have more than one auxiliary feed bridge 24.

[0037] The main feed bridge 22 has a first DC link 30, at least two (e.g., four) first switches 32, a first capacitor input 34, and a first input coil 36. Each first switch 32 can be a semiconductor switch. Each first switch 32 may include a dedicated first diode, which can be used as a freewheeling diode. The first input capacitor 34 has a first input capacitance C. LV,m .

[0038] The auxiliary feed bridge 24 has a second DC link 40, at least two (e.g., four) second switches 42, a second input capacitor 44, and a second input coil 46. Each second switch 42 can be a semiconductor switch. Each second switch 42 may include a dedicated second diode, which can be used as a freewheeling diode. The second input capacitor 44 has a second input capacitance C. LV,a .

[0039] Output bridge 26 has an output DC link 50, at least two (e.g., four) output switches 52, a first output capacitor 54, a second output capacitor 58, a first output inductor 56, and a second output inductor 60. Each output switch 52 may be a semiconductor switch. Each output switch 52 may include a dedicated output diode, which can be used as a freewheeling diode. The first output capacitor 54 has a first output capacitance C. MV,m The second output capacitor 58 has a second output capacitance C. MV,a .

[0040] Therefore, the main feed bridge 22 and the auxiliary feed bridge 24 can each be a full bridge with four switches 32, 42. Alternatively, the main feed bridge 22 and the auxiliary feed bridge 24 can each be a half bridge (not shown) with only two switches 32, 42.

[0041] The main feed bridge 22 is electromagnetically coupled to the output bridge 26 via a first input coil 36 and a first output inductor 56. The first output inductor 56 may be provided by a first output coil. The first input coil 36 and the first output coil may form the first transformer 38 of the three-port SRC 20, or may be components of the first transformer 38. The auxiliary feed bridge 24 is electromagnetically coupled to the output bridge 26 via a second input coil 46 and a second output inductor 60 of the output bridge 26. The second output inductor 60 may be provided by a second output coil. The second input coil 46 and the second output coil may form the second transformer 48 of the three-port SRC 20, or may be components of the second transformer 48. Alternatively, the three-port SRC 20 may have only one transformer (not shown) with only one output inductor, for example, a single output coil, to which both input coils 36 and 46 may be electromagnetically coupled.

[0042] The main feed bridge 22 and the auxiliary feed bridge 24 are configured such that their resonant frequencies are at least approximately the same, as described below. Figure 2 The explanation given.

[0043] The three-port SRC 22 is configured to receive the first input voltage V via the main feed bridge 22. LV,m Used to receive the second input voltage V via the auxiliary feed bridge 24 LV,aAnd used at the output of output bridge 26 according to the input voltage V LV,m and V LV,a Generate total output voltage V MV In this context, output bridge 26 can be used to actively rectify the output bridge current provided by output bridge 26.

[0044] Therefore, the three-port SRC 22 can be controlled by a controller (not shown) based on a predetermined control scheme. The controller has a memory (not shown) for storing one or more voltage and / or current values, and a processor (not shown) communicatively coupled to the memory, which is configured to perform the actions described above and related to the stored voltage and / or current values, respectively. Figure 7 The method is explained in detail. The controller can be communicatively coupled to switches 32, 42, and 52 of bridges 22, 24, and 26, and can be configured to provide one or more control signals to activate switches 32, 42, and 52 individually or collectively, and to provide one or more shutdown signals to deactivate (i.e., shut down) switches 32, 42, and 52 individually or collectively.

[0045] Essentially, the three-port SRC 20 can operate in reverse, allowing the total input voltage to be supplied to the output bridge 20, and the three-port SRC 20 to convert the total input voltage into individual output voltages supplied by the main feed bridge 22 and the auxiliary feed bridge 24, respectively. However, in this case, the conventional methods used for operating a two-port SRC (not shown) can be used for this alternative power flow direction. Therefore, this description focuses on the power flow from feed bridges 22, 24 to the output bridge 26.

[0046] The three-port SRC 20 and the controller communicatively coupled to the three-port SRC 20 can form a converter device, or can be part of the converter device.

[0047] Figure 2 It shows Figure 1 The equivalent circuit diagram of the three-port SRC is shown below. The first DC link 30 and the first switch 32 of the main feed bridge 22 are represented by the first ideal voltage source 62. The second DC link 40 and the second switch 42 of the auxiliary feed bridge 24 are represented by the second ideal voltage source 72.

[0048] The first input capacitor 34 and the first output capacitor 54 can be represented by a first alternative capacitor 64. Thus, the first input capacitor C... LV,m and the first output capacitor C MV,m They can be combined into the first resonant capacitor C r,m The second input capacitor 44 and the second output capacitor 58 can be represented by a second alternative capacitor 74. Thus, the second input capacitor C... LV,a Second output capacitor CMV,a They can be combined into a second resonant capacitor C r,a .

[0049] The first transformer 38 can be represented by the first alternative inductor 66, and can be represented by the first leakage inductance L. σ,m Modeling. The second transformer 48 can be represented by a second alternative inductor 76, and can be represented by a second leakage inductance L. σ,a Modeling.

[0050] The first alternative resistor 68 can represent the conduction losses of the first switch 32, the first diode, the first transformer 38, and the output switch 52, which can be ignored in the following text. The second alternative resistor 78 can represent the conduction losses of the second switch 42, the second diode, the second transformer 58, and the output switch 52, which can be ignored in the following text.

[0051] Output switch 52 is represented by its output diode, which in Figure 2 They are labeled D1, D2, D3 and D4 respectively.

[0052] The first resonant frequency ω of the main feed bridge 22 m It can be given as

[0053] .

[0054] The second resonant frequency ω of the auxiliary feed bridge 24 a It can be given as

[0055] .

[0056] Leakage inductance L σ,m L σ,a and resonant capacitor C r,m C r,a Chosen such that the first resonant frequency ω m Second resonant frequency ω a At least approximately the same.

[0057] The first ideal voltage source 62 can provide a first output voltage v' p,m First output voltage v' p,m This can generate the first transformer current i' p,m This current can cause a first capacitor voltage v across the first alternative capacitor 64. C,m This results in a voltage vfirst on the first primary capacitor between the two parallel lines of the main feed bridge 22. p,C,m And causing a first inductor voltage v across the first alternative inductor 66. L,mIn this context, it should be noted that all quantities marked with an apostrophe “'” are scaled to the turns ratio of their respective transformers for the three-port SRC 20. Specifically, in this specification, quantities on the LV side are scaled to quantities on the MV side to enhance computability, as is known in the art.

[0058] Similarly, the second ideal voltage source 72 can provide a second output voltage v' p,a Second output voltage v' p,a It can generate a second transformer current i' p,a This current can cause a second capacitor voltage v across the second alternative capacitor 74. C,a This results in a voltage v in the second primary capacitor between the two parallel lines of the auxiliary feed bridge 24. p,C,a And this results in a second inductor voltage v across the second alternative inductor 76. L,a .

[0059] These voltages generate voltage v in output bridge 26. s Transformer current i' p,m and i' p,a The output bridge current of the three-port SRC 20 can be obtained by summing these values. In other words, the output bridge current of the three-port SRC 20 may correspond to the transformer current i'. p,m and i' p,a sum.

[0060] Figure 3 It shows Figure 1 The equivalent circuit diagram of the three-port SRC 20 in the first state. The first state represents the effective interval of the positive half-cycle of the predetermined control scheme for operating the three-port SRC 20. During the effective interval, diodes D1 and D4 (see...) Figure 2 ) is turned on, and the total output voltage V MV It is applied to the two feed bridges 22 and 24. The two transformer currents i' p,m and i' p,a They can be determined independently of each other and by the resonant elements (i.e., the alternative capacitors 64 and 74 and the alternative inductors 66 and 76).

[0061] During the effective period, the output bridge current is neither zero nor approximately zero, as defined in this specification, and will be related to... Figure 5 Further explanation.

[0062] Figure 4 It shows Figure 1 The equivalent circuit diagram of the three-port SRC 20 in the second state. The second state represents the suppression interval, where the output bridge 26 acts as a diode rectifier and is in the blocking state. Due to the parallel connection of the resonant elements of the two feed bridges 22 and 24, the resulting voltage vs It cannot float independently, and circulating current may occur between the two feed bridges 22 and 24. Specifically, the transformer current i' p,m 、i' p,a It may not be at least approximately zero during the release interval, as regarding Figure 5 Further explanation.

[0063] Transformer current i' p,m 、i' p,a A value that is not zero or will not at least approximate zero during the release interval implies that a non-soft handover will occur at the end of the release interval, which could lead to high losses. Therefore, this second state should be avoided, especially the circulating current during the release interval.

[0064] However, there is only one case, namely the transformer current i' p,m 、i' p,a During the release interval, it is zero or at least approximately zero, as explained below; for all other cases, the principle regarding... Figure 6 and Figure 7 The operating method of the three-port SRC 20 is explained.

[0065] In fact, if the transformer current i' p,m 、i' p,a To maintain a value of zero or at least approximately zero over the release time interval, the following conditions must be ensured:

[0066] .

[0067] That is, for the two feed bridges 22 and 24, the output voltage v' p,m v' p,a One of them and the corresponding capacitor voltage v C,m v C,a The sum must be equal. This takes into account the LV-side DC link voltage V'. LV,m and V' LV,a If they are equal, the condition becomes:

[0068] .

[0069] Due to the capacitor voltage v C,m v C,a Defined by its corresponding power flow, the above equation means:

[0070] .

[0071] P m The power flowing through the main feed bridge 22 is indicated by P. a The power flowing through the auxiliary feed bridge 24 is indicated.

[0072] Simplifying this expression results in:

[0073] .

[0074] This is also referred to below as "natural load".

[0075] Therefore, when the power flow and resonant elements of feed bridges 22 and 24 result in a natural load being given, there is no problem, and the three-port SRC 20 can be operated using a conventional control scheme. In all other cases, the following can be used: Figure 6 and Figure 7 A new method for interpretation is used to implement soft handover operations.

[0076] Figure 5 It shows in Figure 1 Examples of voltage and current measurements taken at the three-port SRC 20. The left graph shows the case when the natural load is given, while the right graph shows the case when the natural load is not given.

[0077] The first row of the graph shows the first output voltage v' in the main feed bridge 22. p,m The voltage of the first capacitor is v C,m and the first transformer current i' p,m The second row of the graph shows the second output voltage v' in the auxiliary feed bridge 24. p,a The voltage of the second capacitor is v C,a Second transformer current i' p,a The third row of the graph shows the obtained voltage v. s and the transformer current i' corresponding to the output bridge 26 p,m and i' p,a The sum of the output bridge currents.

[0078] As can be seen from the first two rows of charts on the left, the transformer current i' p,m and i' p,a At the corresponding output voltage v' p,m and v' p,a The voltage rises from zero at each rising edge, where the output voltage v' p,m and v' p,a The rising edge of the signal marks the switching operation performed according to a predetermined control scheme. Similarly, the transformer current i' p,m ,i' p,a At the corresponding output voltage v' p,m ,v' p,a It starts decreasing from zero at each falling edge. However, at the output voltage v' p,m ,v' p,a The corresponding transformer current i' is shortly before the rising or falling edge. p,m ,i'p,a It is zero or at least approximately zero. Transformer current i' p,m ,i' p,a The period during which the value is zero or at least close to zero is the aforementioned repression interval, while the period between repression intervals is the effective interval.

[0079] Therefore, under natural load conditions, all currents i' p,m 、i' p,a and i' p,m +i' p,a The values ​​are all zero during the release interval, and soft switching can be performed during the release interval.

[0080] Conversely, when the natural load is not given, as shown in the diagram on the right, the transformer current i' p,m 、i' p,a During the suppression interval (i.e., during the output bridge current i') p,m +i' p,a The period (when zero) is neither zero nor approximately zero, because of the fact that... Figure 4 This is due to the circulating current. In this situation, a soft handover cannot be achieved without further measures. At least one of these measures is provided by the operating method of the three-port SRC 20, as explained below.

[0081] Figure 6 It shows Figure 1 The equivalent circuit diagram of the three-port SRC 20 in the third state. In the first state, at least one of the feed bridges 22 and 24 (e.g., auxiliary feed bridge 24) is controlled such that the corresponding output voltage v' p,m v' p,a float.

[0082] Specifically, in order to eliminate the coupling between the two feed bridges 22 and 24 during the suppression interval, the inductor voltage v can be ensured. L,m and v L,a It remains zero during the suppression interval. This is due to the resulting voltage v of output bridge 26. s Since it is not possible to float the two feed bridges 22 and 24 independently, this can be achieved by causing at least one AC output of the actively switched feed bridges 22 and 24 on the LV side to float during the suppression time. This can be achieved by turning off all four switches of one (or both) of the feed bridges 22 and 24 when the three-port SRC 20 enters the suppression interval where the output bridge current is zero.

[0083] Since there is no closed current path, no circulating current will flow. This can be achieved by setting a fixed on-time for the corresponding feed bridges 22 and 24, or by adjusting the turn-off time relative to the transformer current i'. p,m and i'p,a The zero-crossing synchronization triggers the turn-off of the corresponding feed bridges 22 and 24. In this case, the transformer current i' can be measured. p,m and i' p,a The zero crossing point, such as regarding Figure 7 A detailed explanation.

[0084] If only one of the two feed bridges 22 and 24 is turned off during the suppression interval, it must be ensured that the floating potential generated by the deactivated feed bridge 22 and 24 remains within its DC link voltage range; otherwise, it will act as a diode rectifier, driven on by the other of the two feed bridges 22 and 24, as well as the two substitute capacitors 64 and 74. This can be achieved from... Figure 6 As seen in the diagram, the auxiliary feed bridge 24 is exemplarily deactivated, while the main feed bridge 22 remains active during the release interval. This is considering the positive half-cycle (i.e., v'). p,m =+V' LV,m The output voltage v' generated by the auxiliary feed bridge 22 p,a lead to

[0085] .

[0086] The output voltage must be maintained at ±V' LV,a Within this range, so that the freewheeling diode of the auxiliary feed bridge 24 remains off. Therefore, due to V' LV,m =V' LV,a This applies, therefore leading to the following situation:

[0087] .

[0088] If the main feed bridge 22 is deactivated while the auxiliary feed bridge 24 remains active, then the opposite is true. Therefore, if only one of the two feed bridges 22, 24 is deactivated, the feed bridges 22, 24 that must float are always feed bridges whose output power share is less than the ideal ratio given by the ratio of the reactance elements in the above equation (1).

[0089] Figure 7 It shows the control Figure 1 A flowchart illustrating an exemplary embodiment of the method of the three-port SRC 20.

[0090] In step S2, based on a predetermined control scheme, one or more control signals are sent to one or more switches 32, 42 of the feed bridges 22, 24, causing the input voltage V applied to the feed bridges 22, 24 to... LV,m V LV,aThe voltage is converted to the output bridge voltage provided by output bridge 26. This step can be performed continuously while operating the three-port SRC 20. The predetermined control scheme can be based on, for example, pulse width modulation (PWM) or model predictive control (MPC).

[0091] In step S4, it can be determined that the output bridge current of output bridge 26 is at least approximately zero.

[0092] In step S6, a turn-off signal can be sent to at least some switches 32, 42 of at least one feed bridge 22, 24, causing the output voltage v' of the corresponding feed bridge 22, 24 to be turned off. p,m and v' p,a float.

[0093] In step 4 above, one or more time points when the output bridge current is at least approximately zero can be determined according to a predetermined control scheme to determine whether the output bridge current of output bridge 26 is at least approximately zero. In this case, in step S6, a turn-off signal can be sent to the corresponding switches 32 and 42 of the corresponding feed bridges 22 and 24 at the determined time points. In this embodiment, when the output bridge current is zero can be predetermined according to the predetermined control scheme, and a fixed turn-off time can be provided at the determined time points, with each turn-off time initiated by a corresponding turn-off signal. Therefore, in this embodiment, it is assumed that the actual output bridge current corresponds to the output bridge current derived according to the predetermined control scheme.

[0094] Furthermore, in this embodiment, the duration during which the output bridge current is at least approximately zero can be determined according to a predetermined control scheme. Then, one or more control signals can be sent based on the predetermined control scheme to activate one or more switches 32, 42 in the feed bridges 22, 24 to which the turn-off signal is sent, such that after the turn-off signal has been sent for the specified duration, the corresponding output voltage v'... p,m and v' p,a The floating stops. This corresponds to continuing the method in step S2. This duration can be referred to as the release time. This duration can begin at each time point determined in step S4 according to the predetermined control scheme. The shutdown signal can always be sent at the beginning of the release interval, and the control signal can always be sent at the end of the release interval.

[0095] Alternatively, in step S4, at least one current signal representing the output bridge current can be received. In this case, once the output bridge current is at least approximately zero, in step S6, a turn-off signal can be sent to the corresponding switches 32, 42 of the corresponding feed bridges 22, 24. Then, one or more control signals can be sent based on a predetermined control scheme to activate one or more switches 32, 42 of the feed bridges 22, 24 to which the turn-off signal was sent, such that when the output bridge current is no longer approximately zero, the corresponding output voltage v' p,m v' p,a No longer floating. This corresponds to continuing the method in step S2. The current signal can be continuously received and / or received during the operation of the three-port SRC 20, and can be monitored for current signal approaching and / or crossing zero. The current signal can be generated by the current sensor of the converter device and can be sent to the controller. The controller can monitor the current signal from the current sensor with respect to the zero-crossing point of the current sensor.

[0096] Regardless of which of the two embodiments above is used, when a turn-off signal is sent to at least some switches 32, 42 of at least one feed bridge 22, 24, the output voltage v' of the corresponding feed bridge 22, 24 is reduced. p,m v' p,a When floating, a turn-off signal can be sent to either the main feed bridge 22 or the auxiliary feed bridge 24, and another turn-off signal can be sent to the other of the main feed bridge 22 or the auxiliary feed bridge 24. The main feed bridge 22, the auxiliary feed bridge 24, and the turn-off signals can be configured such that all switches 32 and 42 of both feed bridges are turned off when the output bridge current of the output bridge 26 is at least approximately zero. If one or both of the feed bridges 22 and 24 are half-bridges, all switches 32 and 42 of the corresponding feed bridges 22 and 24 can be turned off by the turn-off signal; while if one or both of the feed bridges 22 and 24 are full-bridges, at least three switches 32 and 42 of the corresponding feed bridges 22 and 24 can be turned off by the turn-off signal.

[0097] Alternatively, when a turn-off signal is sent to at least some switches 32, 42 of at least one feed bridge 22, 24, causing the output voltage of the corresponding feed bridge 22, 24 to float, a turn-off signal can be sent to the main feed bridge 22 or the auxiliary feed bridge 24, and the corresponding feed bridge 22, 24 and the turn-off signal are configured such that all switches 32, 42 of the corresponding feed bridge 22, 24 are turned off when the output bridge current of the output bridge 26 is at least approximately zero.

[0098] The method for controlling the three-port SRC 20 can be embodied as a computer program for operating the three-port SRC 20. This computer program has computer-readable instructions that, when executed by a processor of a controller for controlling the three-port SRC 20, perform the method for controlling the three-port SRC 20 as described above. The computer program can be stored on a computer-readable medium. This computer-readable medium can be a floppy disk, hard disk, USB (Universal Serial Bus) storage device, RAM (Random Access Memory), ROM (Read-Only Memory), EPROM (Erasable Programmable Read-Only Memory), or flash memory. The computer-readable medium can also be a data communication network that allows downloading program code, such as the Internet. Generally, the computer-readable medium can be a non-transitory medium or a transient medium.

[0099] While the invention has been detailed and described in the accompanying drawings and foregoing description, such descriptions should be considered illustrative or exemplary, not restrictive; the invention is not limited to the disclosed embodiments. Other variations of the disclosed embodiments can be understood and implemented by those skilled in the art through study of the drawings, the disclosure, and the appended claims. The word "comprising" in the claims does not exclude other elements or steps, and the indefinite articles "a" or "an" do not exclude multiple. A single processor, controller, or other unit can perform the functions of several items set forth in the claims. The fact that certain measures are set forth in mutually different dependent claims does not indicate that a combination of these measures cannot be fully utilized. Any reference signs in the claims should not be construed as limiting the scope. List of reference numerals Three-port series resonant converter 20 Main feeder bridge 22 Auxiliary feed bridge 24 Output bridge 26 First DC Link 30 First switch 32 First capacitor 34 First input coil 36 First Transformer 38 Second DC link 40 Second switch 42 Second capacitor 44 Second input coil 46 Second transformer 48 Output DC link 50 Output switch 52 First output capacitor 54 First output inductor 56 Second output capacitor 58 Second output inductor 60 First Ideal Voltage Source 62 First replacement capacitor 64 First Alternate Inductor 66 First replacement resistor 68 Second ideal voltage source 72 Second replacement capacitor 74 Second alternative inductor 76 Second replacement resistor 88 Diodes D1, D2, D3, and D4 (first to fourth) First input voltage V LV,m Second input voltage V LV,a Total output voltage V MV First input capacitor C LV,m Second input capacitor C LV,a First output capacitor C MV,m Second output capacitor C MV,a First leakage inductance L σ,m Second leakage inductance L σ,a First resonant capacitor C r,m Second resonant capacitor C r,a First resistor R s,m Second resistor R s,a First output voltage v' p,m Second output voltage v' p,a First transformer current i' p,m The second transformer current i' p,a The voltage of the first capacitor is v C,m The voltage of the second capacitor is v C,a The voltage of the first primary capacitor is v. p,C,m The voltage v of the second primary capacitor p,C,a The voltage of the first inductor is v L,m The voltage of the second inductor is v L,a The obtained voltage v s Steps 2 to 8 (S2–S8)

Claims

1. A method for operating a three-port series resonant converter (20), the three-port series resonant converter (20) having a main feed bridge (22), at least one auxiliary feed bridge (24), and an output bridge (26), wherein the main feed bridge (22) is electromagnetically coupled to the output bridge (26) via a first input coil (36) of the main feed bridge (22), the auxiliary feed bridge (24) is electromagnetically coupled to the output bridge (26) via a second input coil (46) of the auxiliary feed bridge (24), and the main feed bridge (22) and the auxiliary feed bridge (24) are configured such that their resonant frequencies are at least approximately the same, the method comprising: -Based on a predetermined control scheme, one or more control signals are sent to one or more switches (32, 42) of the feed bridge (22, 24) to cause the input voltage (V) applied to the feed bridge (22, 24) to be increased. LV,m V LV,a The voltage is transformed into a total output voltage (V) provided by the output bridge (26). MV ); - Send a turn-off signal to some of the switches (32, 42) of at least one of the feed bridges (22, 24) such that once the output bridge current of the output bridge (26) is at least approximately zero, the output voltage (v') of the corresponding feed bridge (22, 24) is... p,m ,v' p,a () is floating.

2. The method according to claim 1, comprising: According to the predetermined control scheme, one or more time points are determined when the output bridge current is at least approximately zero. as well as The shutdown signal is sent to the corresponding switch (32, 42) of the corresponding feed bridge (22, 24) at a determined time point.

3. The method according to claim 2, comprising: The duration during which the output bridge current is at least approximately zero is determined according to the predetermined control scheme; as well as Based on the predetermined control scheme, one or more control signals are sent to activate one or more switches (32, 42) of the feed bridge (22, 24) to which the turn-off signal is sent, such that after the specified duration has elapsed following the sending of the turn-off signal, the corresponding output voltage (v') p,m ,v' p,a It is no longer floating.

4. The method according to claim 1, further comprising, before sending the shutdown signal: - Receive at least one current signal representing the output bridge current; - Once the output bridge current is at least approximately zero, the shutdown signal is sent to the corresponding switch (32, 42) of the corresponding feed bridge (22, 24); as well as - Based on the predetermined control scheme, one or more control signals are sent to activate one or more switches (32, 42) of the feed bridge (22, 24) to which the shutdown signal is sent, such that when the output bridge current is no longer approximately zero, the corresponding output voltage (v') p,m ,v' p,a It is no longer floating.

5. The method according to any one of the preceding claims, wherein when the turn-off signal is sent to at least some of the switches (32, 42) of at least one of the feed bridges (22, 24), the output voltage (v') of the corresponding feed bridge (22, 24) is such that... p,m ,v' p,a When ) is floating, Send the shutdown signal to the main feed bridge (22) or the auxiliary feed bridge (24). Send another shutdown signal to the other of the main feed bridge (22) or the auxiliary feed bridge (24), and The main feed bridge (22), the auxiliary feed bridge (24), and the shutdown signal are configured such that the switches (32, 42) of the two feed bridges (22, 24) are turned off when the output bridge current of the output bridge (26) is at least approximately zero.

6. The method according to any one of claims 1 to 4, wherein when the turn-off signal is sent to at least some of the switches (32, 42) of at least one of the feed bridges (22, 24), the output voltage (v') of the corresponding feed bridge (22, 24) is such that... p,m ,v' p,a When ) is floating, Send the shutdown signal to the main feed bridge (22) or the auxiliary feed bridge (24), and The corresponding feed bridge (22, 24) and the shutdown signal are configured such that the switches (32, 42) of the corresponding feed bridge (22, 24) are turned off when the output bridge current of the output bridge (26) is at least approximately zero.

7. A controller for operating a three-port series resonant converter (20), the controller comprising: A memory used to store one or more voltage values ​​and / or current values; as well as The processor is communicatively coupled to the memory and configured to perform the method according to any one of the preceding claims based on the stored voltage value and / or current value, respectively.

8. A converter device, comprising: Three-port series resonant converter (20); as well as The controller according to claim 7 is communicatively coupled to the three-port series resonant converter (20) and configured to operate the three-port series resonant converter (20).

9. A computer program for operating a three-port series resonant converter (20), the computer program comprising computer-readable instructions that, when executed by a processor of a controller according to claim 7, perform the method according to any one of claims 1 to 6.

10. A computer-readable medium on which a computer program according to claim 9 is stored.

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