Apparatus with series connected switching devices and related methods

Abstract

Disclosed is an apparatus (100) comprising: a plurality of interconnected switching devices (1, 2), at least two of the plurality of interconnected switching devices being connected in series to form at least one series connection of switching devices (1, 2; 18, 19); and a plurality of switching device voltage balancing circuits VBC (3, 4) for balancing a voltage on a switching device in which at least one switching device is connected in series during and after switching the switching device from the first operating state to the second operating state. Each of the plurality of switching devices VBCs (3, 4) comprises an electrical energy storage EES module (6, 7) that can be controllably charged or discharged. Each of the plurality of switching devices VBCs (3, 4) corresponds to a respective switching device (1, 2) in which at least one switching device (1, 2) is connected in series. Each switching device is connected in series. The timing of switching the series-connected switching devices (1, 2) and / or the timing of charging and / or discharging the EES modules (6, 7) of respective ones of the switching device VBCs (3, 4) corresponding to the series-connected switching devices (1, 2) is controlled based on one or more values indicative of the voltage of each of the EES modules (6, 7), in this way, any difference between the voltages of the EES modules (6, 7) is reduced.

Description

Technical Field

[0001] The present invention relates to an apparatus comprising a plurality of switching devices (such as semiconductor-based switching devices) connected in series and a method thereof in such apparatus. Background Technology

[0002] In applications such as power transmission, it may be desirable to connect multiple switching devices (such as semiconductor-based switching devices) in series. One application (where multiple switching devices may be desired to be connected in series) is a modular multilevel converter (MMC). For example, in a cascaded half-bridge MMC, the half-bridge sub-modules of the MMC are connected in series.

[0003] Generally, series-connected semiconductor-based switching devices offer several advantages, such as (i) facilitating or allowing standardized solutions with variable semiconductor device voltages, (ii) facilitating or allowing the use of relatively inexpensive semiconductor devices for manufacturing high-power equipment, (iii) facilitating or allowing the production of reliable modules with potential redundancy that reduces equipment (e.g., converter) downtime, and (iv) simplifying any system used to protect the equipment, as the protection system can be slower and only needs to handle lower levels of energy compared to other connection types using semiconductor-based switching devices besides series connection. However, for series-connected semiconductor-based switching devices, it can be difficult to ensure that the voltage across the series-connected semiconductor-based switching devices is evenly distributed among the switching devices during switching transients. Summary of the Invention

[0004] When semiconductor-based switching devices are connected in series, voltage sharing between the devices may not occur naturally. Several solutions have been proposed in the art to address this situation, based on very fast dynamic feedback systems. However, such solutions are not considered practical or reliable for industrial applications. Furthermore, these solutions are often not easily scalable or not scalable at all.

[0005] The primary causes of voltage mismatch between series-connected semiconductor-based switching devices during switching transients (i.e., unequal voltages of the semiconductor-based switching devices during switching transients) are: (1) delays in switching commands for one or more semiconductor-based switching devices relative to another or a different semiconductor-based switching device; (2) different characteristic or parameter dispersion distributions between different semiconductor-based switching devices; and (3) dependent elements in a device or system that includes series-connected semiconductor-based switching devices. In practice, compensating for aspects (2) and (3) can be very complex. If left uncontrolled, the voltages on series-connected semiconductor-based switching devices can become unbalanced and divergent over time.

[0006] In view of the above, the present invention is concerned with providing means for promoting or allowing the reduction or even avoidance of the risk that the voltage on the series-connected switching devices becomes unbalanced and divergent over time in a device including series-connected switching devices.

[0007] To address this concern and at least one of other concerns, an apparatus and method according to the independent claim are provided. Preferred embodiments are defined by the dependent claims.

[0008] According to a first aspect of the invention, an apparatus is provided. The apparatus includes a plurality of interconnected switching devices, each of which is controllably switchable between operating states including at least an on state and a non-on state. At least two of the switching devices are connected in series to form at least one series connection of switching devices. The apparatus is connected or can be connected in a conductive path for conveying current in the conductive path via the at least one series connection of switching devices. The apparatus includes a plurality of switching device voltage balancing circuits (VBCs) for balancing the voltages on (or of) the at least one series-connected switching devices during and after switching the switching devices from a first operating state to a second operating state. Each of the plurality of switching device VBCs includes an electrical energy storage (EES) module capable of (e.g., controllably) charging or discharging. Each of the plurality of switching device VBCs corresponds to and is connected to a corresponding switching device in the at least one series connection of switching devices. The apparatus includes at least one control module. The at least one control module is configured to control the switching between operating states of each of the at least one series-connected switching devices, and to control the operation of the plurality of switching device VBCs at least with respect to charging or discharging the corresponding EES module. At least one control module is configured to: for each of the at least one series-connected switching devices: obtain one or more values ​​indicating the voltage of each of the EES modules; and based on the obtained values, control at least one of the following: (i) the timing of switching the series-connected switching devices between mutually related operating states, or (ii) the timing of charging and / or discharging the EES modules of the corresponding switching devices in the VBC of the series-connected switching devices, such that any difference between the voltages of the EES modules of the VBC is reduced, wherein the VBC is connected to the corresponding switching devices in the series-connected switching devices, such that any difference between the voltages of the series-connected switching devices is also reduced.

[0009] According to a second aspect of the invention, a method is provided in a device. The device includes a plurality of interconnected switching devices, each of which is controllably switchable between operating states including at least an on state and a non-on state. At least two of the switching devices are connected in series to form at least one series connection of switching devices. The device is connected or can be connected in a conductive path for conveying current in the conductive path via the at least one series connection of switching devices. The device includes a plurality of switching device VBCs for balancing the voltage across the at least one series-connected switching device during and after switching the switching devices from a first operating state to a second operating state. Each of the plurality of switching device VBCs includes an EES module capable of (e.g., controllably) charging or discharging. Each of the plurality of switching device VBCs corresponds to and is connected to a corresponding switching device of the at least one series-connected switching device.

[0010] The method according to a second aspect of the invention comprises: for each of at least one series-connected switching devices: obtaining one or more values ​​indicating the voltage of each of the EES modules; and based on the obtained values, controlling at least one of: (i) the timing of switching the series-connected switching devices between mutually related operating states, or (ii) the timing of charging and / or discharging the EES modules of the corresponding switching devices in the VBCs of the series-connected switching devices, such that any difference between the voltages of the EES modules of the VBCs is reduced, wherein the VBCs are connected to the corresponding switching devices in the series-connected switching devices, thereby reducing any difference between the voltages of the series-connected switching devices.

[0011] Although an energy storage module may be referred to herein as a capacitor, it will be understood that more than one capacitor and / or another type or other type of energy storage module besides capacitors may be used. Therefore, even though an energy storage module may be referred to herein as a capacitor, the disclosure herein may be applied in the same manner or similarly to other types of energy storage modules besides capacitors.

[0012] By controlling one or more of the aspects (i) and (ii) mentioned above, any difference between the voltages of the EES modules of the switching device VBC is reduced, and the voltages on (or of) at least one series-connected switching device can be balanced (e.g., such that the switching devices have equal or substantially equal voltages) during and after switching the switching device from a first operating state to a second operating state (e.g., from an on state to a non-on state). As mentioned, the switching device VBC is connected to the corresponding switching device connected in series, such that, through control, any difference between the voltages of the series-connected switching devices is reduced. For example, each of a plurality of switching device VBCs may be connected in parallel with a corresponding switching device connected in series with at least one switching device. Through control, possible delays in the switching command for one or more series-connected switching devices relative to another or other series-connected switching device due to voltage mismatch between the switching devices during the switching transient can be identified and compensated in the next switching instance. The control can be implemented as closed-loop control.

[0013] Each or any of a plurality of switching devices VBCs may include a resistive circuit system. The resistive circuit system may include at least one resistor. Each or any of the plurality of switching devices VBCs may be configured to selectively and controllably discharge current from its corresponding EES module through the resistive circuit system to reduce the voltage of the EES module. For each or any of the plurality of switching devices VBCs, when the voltage of the EES module of the switching device VBC exceeds a selected threshold voltage level, the switching device VBC may be controlled to discharge current from its corresponding EES module to at least one resistor in the resistive circuit system, such that the voltage of the EES module decreases below the selected threshold voltage level. For example, at least one control module may be configured to control the switching device VBC to discharge current from its corresponding EES module. For each switching device VBC, the selected threshold voltage level may, for example, be the same. By performing such control on the switching device VBC to discharge current from its corresponding EES module, it can be ensured that the voltage across each of the at least one switching device connected in series does not exceed a certain value. Therefore, by controlling the VBC of the switching device to discharge current from its corresponding EES module, the maximum voltage that each switching device connected in series with at least one switching device can withstand can be controlled or limited. The maximum voltage can be controlled by a selected threshold voltage level.

[0014] By controlling one or more of the aspects (i) and (ii) mentioned above, any difference between the voltages of the EES modules of the switching device VBC is reduced, and by controlling the switching device VBC to discharge current from its corresponding EES module, the voltages on (or on) the switching devices connected in series with at least one switching device can become equal or substantially equal during and after switching the switching device from a first operating state to a second operating state (e.g., from an on state to a non-on state). The control can be implemented as a closed-loop control.

[0015] It is possible to balance and / or limit the voltage across at least one series-connected switching device during and after switching the switching device from a first operating state to a second operating state, regardless of the cause of any voltage mismatch between the series-connected switching devices during the switching transient. Furthermore, the device can be readily extended in principle to any number of series-connected switching devices.

[0016] The EES module for each switching device VBC can 'contain' the switching transients of the corresponding switching device. In other words, the EES module for each switching device VBC can isolate the switching transients of each switching device from those of other switching devices. Therefore, in the presence of dependent elements in the equipment and different characteristic or parameter spreads between different switching devices, any voltage mismatch between switching devices connected in series after each switching instance can be reduced. By providing an EES module for each switching device VBC, the need for active compensation for the following can be eliminated or reduced to a very small extent: the dynamics of switching switching devices between different operating states, the delay in switching commands for one or more switching devices relative to another or other switching devices, the different characteristic or parameter spreads between different switching devices, and any dependent elements in the equipment. Instead, the voltage (e.g., average voltage) of the EES module for each switching device VBC can be actively controlled, which may be easier than active compensation.

[0017] For each of the at least one series-connected switching devices, obtaining one or more values ​​indicating the voltage of each of the EES modules may include obtaining one or more values ​​indicating the voltage of each of the EES modules at multiple different times. For example, the voltage of each of the EES modules may be obtained by receiving or retrieving one or more values ​​indicating the voltage of each of the EES modules from an entity (e.g., one or more voltage sensors configured to sense the voltage of the EES modules). Therefore, the one or more values ​​'indicating' the voltage of each of the EES modules may be one or more values ​​of the voltage of each of the EES modules, but may also be some values ​​from which the voltage of each of the EES modules can be derived or estimated.

[0018] This device can be used in various applications. For example, it can be used in or included in a converter configured to convert direct current (DC) power to alternating current (AC) power or vice versa. Multiple interconnected switching devices can be included, for example, in a modular multilevel converter (MMC). In a cascaded half-bridge or full-bridge MMC, the half-bridge or full-bridge submodules of the MMC are connected in series. Multiple interconnected switching devices can be included, for example, in a half-bridge or full-bridge submodule of the MMC.

[0019] In the context of this application, the non-conducting state of a switching device means a state in which no current is conducted through the switching device, or only to a very small extent. Therefore, a switching device can be switchable to prevent or substantially prevent current from being conducted through it.

[0020] Each or any of the switching devices may be of a type comprising two or more terminals. For example, each or any of the switching devices may include at least a first terminal and a second terminal, and may be arranged such that current flows in the current path between the first and second terminals of the switching device, at least when the switching device is in the ON state. Each of the plurality of switching devices VBC can be connected to the first and second terminals (if any) of the corresponding switching device.

[0021] The device may include, for example, one or more switching devices connected in series. For example, the device may include at least two switching devices connected in series, wherein at least two switching devices are connected in parallel.

[0022] At least one switching device connected in series may include a plurality of sub-switches connected in parallel. Each of the sub-switches may be controllably switched between operating states including at least an on state and a non-on state.

[0023] Each or any of the switching devices, sub-switching devices, or switching elements described herein may, for example, include or be constituted by at least one of the following: one or more field-effect transistors (FETs), one or more bipolar junction transistors (BJTs), or one or more insulated-gate bipolar transistors (IGBTs), or one or more of other types of semiconducting switches. One or more FETs may, for example, include one or more metal-oxide-semiconductor FETs (MOSFETs).

[0024] Each of the plurality of switching devices VBCs may include a first unidirectional conduction circuit system and a second unidirectional conduction circuit system, the second unidirectional conduction circuit system being connected in parallel with the first unidirectional conduction circuit system. The parallel connection of the first and second unidirectional conduction circuit systems may be connected in series with the EES module of the switching device VBC. The first and second unidirectional conduction circuit systems may be configured to conduct current in opposite directions. One of the first and second unidirectional conduction circuit systems may include at least one resistor.

[0025] As mentioned above, each or any of the plurality of switching devices VBC may include a resistive circuit system, which may include at least one resistor. The resistive circuit system may be identical to one of a first unidirectional conducting circuit system and a second unidirectional conducting circuit system that includes at least one resistor. The resistive circuit system may be referred to as one of the first unidirectional conducting circuit system and the second unidirectional conducting circuit system, or vice versa.

[0026] One of the first unidirectional conduction circuit system and the second unidirectional conduction circuit system can be configured to selectively and controllably allow current to be conducted through the first unidirectional conduction circuit system or the second unidirectional conduction circuit system, respectively.

[0027] One of the first and second unidirectional conduction circuit systems may include a series connection of at least one switching element and at least one resistor. Each of the at least one switching element can be controllably switched between operating states including at least an on state and a non-on state. The switching of the at least one switching element between operating states may be controlled, for example, by at least one control module, which may be appropriately configured for this purpose.

[0028] The first and second unidirectional conduction circuit systems can be arranged in relation to the EES module of the switching device VBC such that by switching at least one switching element between different operating states, the EES module of the switching device VBC can be selectively and controllably discharged via one of the first and second unidirectional conduction circuit systems and selectively and controllably charged via the other. Thus, the timing of charging and / or discharging the EES module of the switching device VBC can be, for example, controlled by at least one control module.

[0029] For each of the plurality of switching devices VBC, the resistive circuit system may include at least one resistor and a first diode connected in parallel with the at least one resistor. For each of the plurality of switching devices VBC, the resistive circuit system may further include a second diode, wherein the second diode is connected in series with the parallel connection of the at least one resistor and the first diode.

[0030] According to a third aspect of the invention, a computer program is provided. This computer program includes instructions that, when executed by one or more processors included in at least one control module, cause the at least one control module to perform the method according to a second aspect of the invention.

[0031] According to a fourth aspect of the invention, a processor-readable medium is provided. A computer program is loaded on the processor-readable medium, wherein the computer program includes instructions that, when executed by one or more processors included in at least one control module, cause the at least one control module to perform the method according to a second aspect of the invention.

[0032] At least one control module may include, for example, any suitable central processing unit (CPU), microcontroller, digital signal processor (DSP), application-specific integrated circuit (ASIC), field-programmable gate array (FPGA), etc., or any combination thereof. At least one control module may optionally be capable of executing software instructions stored in a computer program product (e.g., in the form of memory). The memory may, for example, be any combination of read-write memory (RAM) and read-only memory (ROM). The memory may include persistent storage devices, which may, for example, be magnetic memory, optical memory, solid-state memory, or remotely mounted memory, or any combination thereof.

[0033] Each or any of one or more processors may include, for example, a CPU, a microcontroller, a DSP, an ASIC, an FPGA, or any combination thereof.

[0034] Processor-readable media may include, for example, digital versatile optical discs (DVDs) or floppy disks or any other suitable type of processor-readable device or processor-readable (digital) media, such as, but not limited to, memory (such as, for example, non-volatile memory), hard disk drives, compact optical discs (CDs), flash memory, magnetic tape, universal serial bus (USB) memory devices, Zip drives, etc.

[0035] Further objects and advantages of the invention are described below with the aid of illustrative embodiments. It should be noted that the invention relates to all possible combinations of the features recited in the claims. Further features of the invention and the advantages achieved by utilizing the invention will become apparent when the appended claims and the description herein are examined. Those skilled in the art will recognize that different features of the invention can be combined to produce embodiments other than those described herein. Attached Figure Description

[0036] The following description will use the accompanying drawings to illustrate exemplary embodiments of the invention.

[0037] Figures 1 to 5 This is a schematic diagram of a device according to an embodiment of the present invention.

[0038] Figure 6 This is a schematic flowchart illustrating a method according to an embodiment of the present invention.

[0039] Figure 7 This is a schematic diagram of a device according to an embodiment of the present invention.

[0040] All accompanying drawings are schematic and not necessarily drawn to scale, and generally only show the parts necessary to illustrate embodiments of the invention, wherein other parts may be omitted or merely implied. Detailed Implementation

[0041] The invention will now be described below with reference to the accompanying drawings, which illustrate exemplary embodiments of the invention. However, the invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided by way of example so that this disclosure will convey the scope of the invention to those skilled in the art.

[0042] Figure 1This is a schematic diagram of a device 100 according to an embodiment of the present invention. Device 100 includes a plurality of interconnected switching devices, wherein at least two of the switching devices are connected in series to form at least one series-connected switching device. Each of the switching devices can switch between an operating state including at least an on state and a non-on state. Each or any of the switching devices may, for example, include or be composed of at least one of the following: one or more field-effect transistors (FETs), one or more bipolar junction transistors (BJTs), or one or more insulated-gate bipolar transistors (IGBTs), or one or more of other types of semiconducting switches. The one or more FETs may, for example, include one or more metal-oxide-semiconductor FETs (MOSFETs).

[0043] according to Figure 1 In the embodiments of the invention illustrated in the figures (and other embodiments illustrated in the figures), device 100 includes two switching devices 1, 2 connected in series to form a series connection of switching devices. However, it should be understood that the number of switching devices in the illustrated embodiments of the invention is based on example, and device 100 can in principle include any number of switching devices (e.g., three, four, five, six, eight, ten, twenty, fifty, one hundred, or more), and these switching devices are connected in series to form at least one series connection of switching devices. Therefore, switching devices in any embodiment of the invention can be connected in series to form several series connections of switching devices, such as, for example, two series connections of switching devices, wherein different series connections of switching devices are connected in parallel, for example (e.g., all series connections of switching devices can be connected in parallel). It will be understood that although references to “at least one switching device 1, 2 connected in series” or “switching device 1, 2 connected in series” may be used herein, this is for describing exemplary embodiments of the invention and will not be construed as limiting or implying that device 100 is limited to including only two switching devices.

[0044] Furthermore, although the switching device according to the illustrated embodiment of the present invention is composed of a single switching element, other configurations are possible. For example, at least one switching device connected in series may include a plurality of sub-switching devices (or switching elements) connected in parallel, wherein each of the sub-switching devices is controllably switchable between operating states including at least an on state and a non-on state. Each or any of the sub-switching devices may, for example, include or be composed of at least one of the following: one or more FETs (e.g., MOSFETs), one or more BJTs, or one or more IGBTs, or one or more of other types of semiconducting switches.

[0045] like Figure 1As illustrated, device 100 is connected in conductive path 5 for conveying current via at least one switching device 1, 2 connected in series in conductive path 5. In one or more embodiments of the invention, device 100 may be capable of being connected in conductive path 5. Conductive path 5 may be located at the first node and the second node (in... Figure 1 Between the first node and the second node (or in any other figure not shown), and the switching devices 1 and 2 can be connected between the first node and the second node. Device 100 can be connected or can be connected in the conductive path 5 for conveying current from the first node to the second node via at least one switching device 1 or 2 connected in series. The voltage between the first node and the second node can be referred to as the DC link voltage. The current conveyed in the conductive path 5 can be, for example, based on the load current i. load And thus, the result or estimate, such as Figure 1 As indicated in the document.

[0046] Device 100 includes multiple switching device voltage balancing circuits (VBCs), each of the multiple switching device VBCs corresponding to and connected to at least one corresponding switching device connected in series. Due to... Figure 1 The embodiment of the invention illustrated in the figure (and other embodiments of the invention illustrated in the figures) device 100 includes two switching devices 1, 2 connected in series to form a series connection of switching devices, therefore Figure 1 The device 100 illustrated includes two switching devices VBCs 3 and 4, corresponding to different switching devices in switching devices 1 and 2. For example... Figure 1 As illustrated in the figure, according to the illustrated embodiment, switching device VBC 3 corresponds to switching device 1, and switching device VBC 4 corresponds to switching device 2. However, if device 100 will include more than two switching devices (as also described above), device 100 will also include more than two switching devices VBC.

[0047] As described above and will be further described below, switching devices VBC 3, 4 are used to balance the voltage on (or the voltage of) at least one of the switching devices 1, 2 connected in series during and after switching devices 1, 2 from a first operating state to a second operating state.

[0048] Typically, each of the multiple switching devices VBC can be connected in parallel with a corresponding switching device that is connected in series with at least one switching device. According to Figure 1 In the embodiment of the present invention illustrated in the figure, switching device VBC 3 is connected in parallel with switching device 1, and switching device VBC 4 is connected in parallel with switching device 2.

[0049] Each of the switching devices VBC 3 and 4 includes an electrical energy storage (EES) module 6 and 7 that can be charged or discharged.

[0050] according to Figure 1 In the embodiments of the invention illustrated herein, each of the switching devices VBC 3, 4 may include a resistive circuit system, which may include at least one resistor. Figure 1 As illustrated, the switching device VBC 3 includes a resistive circuit system 11, which includes a resistor 13, and the switching device VBC 4 includes a resistive circuit system 10, which includes a resistor 12.

[0051] Each of the multiple switching devices VBC 3, 4 can be configured to selectively and controllably discharge current from its corresponding EES module 6, 7 through resistive circuit systems 10, 11 to reduce the voltage of EES modules 6, 7.

[0052] according to Figure 1 In the embodiments of the invention illustrated herein, each of the switching devices VBC 3, 4 (such as their resistive circuit systems 10, 11) may further include at least one switching element, which may be connected in series with at least one resistor 12, 13. Figure 1 As illustrated, the resistive circuit system 11 of the switching device VBC 3 includes a switching element 15 connected in series with the resistor 13, and the resistive circuit system 10 of the switching device VBC 4 includes a switching element 14 connected in series with the resistor 12.

[0053] Each of the switching elements 14 and 15 is controllably switchable between operating states including at least an on state and a non-on state. Each or any of the switching elements 14 and 15 may include or be constituted by at least one of the following: one or more FETs (e.g., MOSFETs), one or more BJTs, or one or more IGBTs, or one or more of other types of semiconducting switches.

[0054] according to Figure 1 In the embodiment of the invention illustrated, each of the plurality of switching devices VBC 3, 4 includes a first unidirectional conducting circuit system 8, 9 connected in parallel with corresponding ones in resistive circuit system 10 and resistive circuit system 11. Resistive circuit system 10 and resistive circuit system 11 may be referred to as second unidirectional conducting circuit system 10 and second unidirectional conducting circuit system 11. Figure 1As illustrated, switching device VBC 3 includes a first unidirectional conducting circuit system 9 connected in parallel with resistive circuit system 11, and switching device VBC 4 includes a first unidirectional conducting circuit system 8 connected in parallel with resistive circuit system 10. For each of the plurality of switching devices VBC 3, 4, the parallel connection of the first unidirectional conducting circuit systems 8, 9 and the second unidirectional conducting circuit systems 10, 11 is connected in series with the EES modules 6, 7 of switching devices VBC 3, 4, and wherein the first unidirectional conducting circuit systems 8, 9 and the second unidirectional conducting circuit systems 10, 11 (or resistive circuit systems 10 and 11) are configured to conduct current in opposite directions. Figure 1 As illustrated in the figure, for this purpose, the first unidirectional conduction circuit system 8, 9 and the second unidirectional conduction circuit system 10, 11 may include corresponding diodes, wherein the diodes of the first unidirectional conduction circuit system 8, 9 and the diodes of the second unidirectional conduction circuit system 10, 11 may be connected in anti-parallel relative to each other.

[0055] according to Figure 1 In the embodiment of the invention illustrated herein, for each of the plurality of switching devices VBC 3, 4, the second unidirectional conduction circuit system 10, 11 (or resistive circuit systems 10 and 11) is configured to selectively and controllably allow current conduction through. Figure 1 As illustrated, this can be achieved by providing switching elements 14 and 15 respectively in the second unidirectional conduction circuit systems 10 and 11.

[0056] Further based on Figure 1 The embodiments of the invention illustrated herein, and as indicated above, for each of the plurality of switching devices VBC 3, 4, the second unidirectional conductive circuit system 10, 11 (or resistive circuit systems 10 and 11) includes a series connection of switching elements 14, 15 and resistors 12, 13. As mentioned, each of the switching elements 14, 15 is controllably switchable between operating states including at least an on state and a non-on state.

[0057] As mentioned, each of the switching devices 1 and 2 can switch between operating states including at least an on state and a non-on state. For example, each of the switching devices 1 and 2 may include at least a first terminal, a second terminal, and a third terminal, and is arranged such that current can flow in a current path between the first terminal and the second terminal, and further such that the third terminal controls the conductivity of the current path between the first terminal and the second terminal based on the voltage at the third terminal relative to the voltage at the second terminal. Each of the switching devices 1 and 2 may be arranged such that if the voltage at the third terminal relative to the second terminal is within a predefined switching device threshold voltage range, current flows unimpeded from the first terminal to the second terminal in the current path between the first terminal and the second terminal. For example, if each or any of the switching devices 1 and 2 includes a FET, the predefined switching device threshold voltage range may be defined by the threshold voltage of the FET. Alternatively or supplementarily, if each or any of the switching devices 1 and 2 includes a BJT, the predefined switching device threshold voltage range may be defined by the threshold voltage of the BJT. As an alternative or supplement, if each or any of the switching devices 1 and 2 includes an IGBT, the predefined threshold voltage range of the switching device can be defined by the threshold voltage of the IGBT.

[0058] Therefore, each of the switching devices 1 and 2 can be switchable between operating states including at least an on state and a non-on state, for example by providing a voltage pulse that changes the voltage at the third terminal of the switching device relative to the voltage at the second terminal. Generally, each of the switching devices 1 and 2 can be switchable between operating states, for example by being provided with a switching command to switch to a non-on state (this switching command may be referred to as a shutdown switching command) or a switching command to switch to an on state (this switching command may be referred to as an on switching command). The switching commands (multiple) may include, for example, the voltage pulse as described above. In the following, the terms shutdown switching command and on switching command may be used in connection with describing the switching of the switching devices 1 and 2 between different operating states (such as switching to a non-on state or an on state) without loss of generality.

[0059] Figure 1 The capacitor (by its capacitance c) connected in parallel with switching devices 1 and 2 as shown in the figure. dc The indicator can be referred to as the (main) DC link capacitor.

[0060] according to Figure 1In the embodiments of the invention illustrated herein, the charging and discharging of each of the EES modules 6 and 7 is controlled by the following: the switching instances of switching devices 1 and 2 (i.e., which operating state switching devices 1 and 2 switch to), the current in the conductive path 5, and the direction of current conduction through switching devices VBC 3 and 4 (which can be controlled by the switching instances of switching elements 14 and 15 (i.e., which operating state switching elements 14 and 15 switch to)).

[0061] Different voltage rises and falls during the turn-off and turn-on events of switching devices 1 and 2 may result in unequal voltages on switching devices 1 and 2. This may be unrelated to the cause of the different voltage rise / fall instances. The different turn-on and turn-off instances of switching devices 1 and 2 can be controlled by controlling the timing of the switching commands provided to them. The effects of different switching instances of switching devices 1 and 2 on the voltages of EES module 6 and EES module 7 are described below.

[0062] When a turn-off switching command is given to both switching devices 1 and 2, the two switching devices 1 and 2 can turn off at slightly different times (i.e., reach a non-conducting state). Assuming that switching device 1 turns off before switching device 2, and the current in conductive path 5 is positive, the voltage of EES module 6 will conduct current until switching device 2 has also been turned off. The time delay between the voltage rise instances of the two switching devices 1 and 2, together with the current in conductive path 5 at the time of switching, defines the difference between the voltage V1 of EES module 6 and the voltage V2 of EES module 7 at the end of the turn-off. The time delay can be defined by the time difference between two instants t1 and t2. Specifically, the difference between the voltage V1 of EES module 6 and the voltage V2 of EES module 7 after turn-off is influenced by V1, V2, and the current i in conductive path 5. c The following relationships between them should be managed:

[0063]

[0064] In this relation, it is assumed that i c The capacitance values ​​are greater than or equal to t1 and t2 > t1. Each of EES module 6 and EES module 7 is a capacitor, and the capacitance of EES module 6 and EES module 7 are the same and equal to c. However, it should be understood that the above relationships are intended to describe the principles of one or more embodiments of the present invention and do not require that the capacitance of EES module 6 and EES module 7 be the same. Simulations performed by the inventors have shown that a difference of up to at least 20% between the capacitance of EES module 6 and EES module 7 is acceptable.

[0065] Current i in conductive path 5 cThis can be achieved, for example, directly by means of one or more current sensors configured to sense the current in the conductive path 5. Figure 1 (not shown in the image) is used for sensing. Alternatively or supplemented, the current i in conductive path 5 is... c Can be based on being configured to sense Figure 1 The load current i indicated in the middle load One or more current sensors ( Figure 1 (Not shown in the image) is derived or estimated from the load current i. load It can represent the current of an electrical load or device that is connected to or can be connected to device 100.

[0066] Besides the voltage difference between EES module 6 and EES module 7, after each turn-off of switching devices 1 and 2, the energy of the stray inductor (from...) Figure 1 l in σ (This indicates that) buffering will also occur in EES modules 6 and 7. This energy buffering occurs after all switching devices 1 and 2 have been turned off. Therefore, from l σ Energy transfer to EES modules 6 and 7 can generate a common-mode voltage rise (the voltage rise is equal in all EES modules 6 and 7). In fact, EES modules 6 and 7, together with any dependent inductance in conductive path 5, can form a natural boost converter. Therefore, in the absence of a resistive current path in switching devices VBC12, 13, the uncontrolled voltage on EES modules 6 and 7 can increase after each turn-off (assuming low losses in EES modules 6 and 7, which is a reasonable assumption).

[0067] Similar to the shutdown scenario, different activation instances will cause a voltage difference between the voltage of EES module 6 and the voltage of EES module 7. For example, if switching device 1 is activated before switching device 2, the voltage difference between the voltage of EES module 6 and the voltage of EES module 7 is governed by the following relationship:

[0068]

[0069] Again, it has been assumed that i c >0 and t2>t1, each of EES module 6 and EES module 7 is a capacitor, and the capacitance of EES module 6 and EES module 7 are the same and equal to c.

[0070] In both cases, the voltages of EES module 6 and EES module 7 will increase. When off, the voltage of EES module 6 increases, and when on, the voltage of EES module 7 increases. Therefore, as long as the current in conductive path 5 is positive, the voltages of both EES module 6 and EES module 7 will increase until at least one of them carries the full voltage of conductive path 5 (e.g., the DC link voltage). In practice, the situation may be even more complex. The on and off delays are not necessarily the same. Moreover, these values ​​will change over time and may differ from one system to another.

[0071] One or more embodiments of the present invention address these problems and facilitate or allow balancing of the voltage on (or of) at least one switch device 1, 2 connected in series during and after switching devices 1, 2 from a first operating state to a second operating state.

[0072] Device 100 includes at least one control module. According to... Figure 1 The embodiment of the invention illustrated in the figure includes a control module 50. Typically, the control module 50 (and / or any other control module that may be included in device 100) is capable of being connected to at least one series-connected switching device and a plurality of switching device VBCs for controlling their operation. The connections between the control module(s) 50 and the at least one series-connected switching device and the plurality of switching device VBCs can be implemented or realized, for example, through any suitable wired and / or wireless communication device (e.g., any suitable wired and / or wireless communication device known in the art), thereby allowing the transmission of control messages, commands, instructions, etc., between the control module 50 and the at least one series-connected switching device and the plurality of switching device VBCs.

[0073] The control module 50 is configured to control the switching between operating states of each of at least one series-connected switching devices 1, 2, and to control the operation of multiple switching devices VBC 3, 4 at least with respect to charging or discharging the corresponding EES modules 6, 7.

[0074] according to Figure 1 The embodiment of the invention illustrated herein has one switching device 1 and 2 connected in series. However, device 100 may provide more than one switching device connected in series, such as... Figure 2 As shown in the diagram.

[0075] Control module 50 is configured to obtain one or more values ​​indicating the voltage of each of the EES modules 6 and 7, for the series connection of switching devices 1 and 2. Obtaining one or more values ​​indicating the voltage of each of the EES modules 6 and 7 may include obtaining one or more values ​​indicating the voltage of each of the EES modules 6 and 7 at multiple different times. For example, this can be achieved by obtaining values ​​from an entity (e.g., one or more voltage sensors configured to sense the voltage of the EES modules 6 and 7). Figure 1 (not shown) Receive or retrieve one or more values ​​of the voltage of each of the EES modules 6 and 7 to obtain one or more values ​​of the voltage of each of the EES modules 6 and 7.

[0076] Control module 50 is further configured to, for the series connection of switching devices 1 and 2, control at least one of the following based on the obtained value:

[0077] (i) The timing for switching devices 1 and 2 connected in series between their related operating states; or

[0078] (ii) The timing for charging and / or discharging the corresponding EES modules 6 and 7 in the switching devices VBC 3 and 4 that are connected in series with the switching devices 1 and 2.

[0079] This reduces any difference between the voltages of the EES modules 6 and 7 of the switching devices VBC 3 and 4.

[0080] Switching devices VBC 3 and 4 are connected to corresponding switching devices 1 and 2 connected in series, so that any voltage difference between the series-connected switching devices 1 and 2 is also reduced. For example... Figure 1 As shown in the diagram, each of the multiple switching devices VBC 3, 4 can be connected in series with the corresponding switching devices 1, 2, which are then connected in parallel.

[0081] By controlling one or more of the aspects (i) and (ii) mentioned above, any difference between the voltages of the EES modules 6 and 7 of switching devices VBC 3 and 4 is reduced, and during and after switching devices 1 and 2 are switched from a first operating state to a second operating state (e.g., from an on state to a non-on state), the voltages on (or of) the series-connected switching devices 1 and 2 can become balanced (e.g., such that switching devices 1 and 2 have equal or substantially equal voltages). The control can be implemented as a closed-loop control. Through this control, it can be ensured that the voltages of the EES modules 6 and 7 of switching devices VBC 3 and 4 converge to a certain voltage value.

[0082] The control module 50 can be further configured to, for each of the plurality of switching devices VBCs 3, 4, discharge current from its corresponding EES module 6, 7 to resistors 12, 13 of the resistive circuit system 10, 11 when the voltage of the EES module 6, 7 of the switching devices VBCs 3, 4 exceeds a selected threshold voltage level, thereby reducing the voltage of the EES module 6, 7 below the selected threshold voltage level. Through this possible additional control, it can be ensured that the voltage on each of the switching devices 1, 2 connected in series does not exceed a certain value. Therefore, by means of this additional control, the maximum voltage that each of the switching devices 1, 2 connected in series can withstand can be controlled or limited. The maximum voltage is controlled by the selected threshold voltage level. Thus, it can be ensured that the total voltage of the EES modules 6, 7 does not exceed the selected voltage value. The possible additional control can be implemented as closed-loop control.

[0083] according to Figure 1 In the embodiment of the invention illustrated, the control module 50 is configured to control the switching of each of the switching elements 14, 15 between operating states. Control of each of the plurality of switching devices VBC 3, 4 to discharge current from its corresponding EES modules 6, 7 to resistors 12, 13 of the resistive circuit systems 10, 11 can be achieved by controlling the switching of each of the switching elements 14, 15 between operating states.

[0084] For each of the multiple switching devices VBC 3, 4, the switching elements 14, 15, resistors 12, 13, and the diode connected in series with resistors 12, 13 can be considered as the 'active' part of the switching devices VBC 3, 4, which controls the current path in the switching devices VBC 3, 4.

[0085] The diodes in the first unidirectional conduction circuit systems 8 and 9 may only need to conduct current in the conduction path 5 for a relatively short period of time, and therefore these diodes can be sized to be much smaller than the diodes in switching devices 1 and 2. Furthermore, switching elements 14 and 15 can be switched only to dissipate some energy from EES modules 6 and 7. Therefore, switching elements 14 and 15 can be sized to be much smaller than switching devices 1 and 2. This is in Figure 1 The middle has a ratio through switching elements 14 and 15. Figure 1 The smaller size of the switching devices 1 and 2 in the diagram is used for indication.

[0086] As mentioned, for the series connection of switching devices 1 and 2, the timing of switching between their related operating states can be controlled based on the obtained values. More specifically, after each switching event or instance of switching devices 1 and 2, the on and off delays can be manipulated to proceed to the next switching event or instance. Specifically, after each switching event or instance, the time-dependent relationship between V1, V2, and the current i in the conductive path 5 can be solved. c The above relationship defines two equations, and the result can be used to compensate for voltage differences in the next switching event or instance.

[0087] Therefore, control module 50 can be configured to control the switching devices 1 and 2 connected in series to switch from a first operating state to a second operating state before controlling the timing of switching between the series-connected switching devices 1 and 2 between their respective operating states. Control module 50 can also be configured to control the timing of switching between the series-connected switching devices 1 and 2 between their respective operating states based on any time difference between the moments when the series-connected switching devices 1 and 2 reach the second operating state after being controlled to switch from the first operating state to the second operating state, such that any difference between the voltages of the EES modules 6 and 7 of the switching devices VBC 3 and 4 is reduced.

[0088] The time difference mentioned above can be determined based on: (i) any difference between the voltages of the EES modules 6 and 7 of the switching devices VBC 3 and 4 corresponding to these switching devices when they are in the second operating state after being controlled to switch from the first operating state to the second operating state; and (ii) the current i in the conductive path 5 during the switching of the switching devices 1 and 2, which are connected in series, from the first operating state to the second operating state. c More specifically, the time difference mentioned above can be determined based on the following relationship: (i) any difference between the voltages of the EES modules 6 and 7 corresponding to the series-connected switching devices VBC 3 and 4 when the switching devices are in the second operating state after being controlled to switch from the first operating state to the second operating state, and (ii) the current i in the conductive path 5 during the time it takes for the series-connected switching devices 1 and 2 to switch from the first operating state to the second operating state. c Integral over time. The current i in conductive path 5 during the transition from a first operating state to a second operating state of switching devices 1 and 2 connected in series. c Integration over time may involve solving for the current i in the conductive path 5, given V1, V2, and V1. c The two equations defined by the above relationship can be solved for each switching event or instance.

[0089] As mentioned, the current i in conductive path 5 c This can be achieved, for example, directly by means of one or more current sensors configured to sense the current in the conductive path 5. Figure 1 (not shown in the image) is used for sensing. Alternatively or supplemented, the current i in conductive path 5 is... c Can be based on being configured to sense Figure 1 The load current i indicated in the middle load One or more current sensors ( Figure 1 (Not shown in the image) is derived or estimated from the load current i. load It can represent the current of an electrical load or device that is connected to or can be connected to device 100.

[0090] By solving the current i in V1, V2 and conductive path 5 c The two equations defined by the above relationship (which can be solved for each switching event or instance) can predict turn-on and turn-off delays. Following such predictions, a compensation algorithm can be applied. Such a compensation algorithm may involve the following:

[0091] (A) After each switching event or instance, obtain (e.g., sense) the voltages V1 and V2 of the EES modules 6 and 7 of the switching devices VBC 3 and 4;

[0092] (B) Each time the voltage of the EES modules 6 and 7 of the switching devices VBC 3 and 4 is obtained (in step A), the difference ΔV between the voltages of the EES modules 6 and 7 of the switching devices VBC 3 and 4 is determined as ΔV = V1 - V2.

[0093] (C) Compare ΔV = V1 - V2 before and after the switching event or instance;

[0094] (D) Determine any time difference(s) between the switching events or instances of different switching devices 1 and 2; and

[0095] (E) Use the determined time difference(s) to change the turn-on / turn-off delay of switching devices 1 and 2 for the next switching event or instance.

[0096] As mentioned, for the series connection of switching devices 1 and 2, the timing of charging and / or discharging of the corresponding EES modules 6 and 7 in the switching devices VBCs 3 and 4 corresponding to the series connection of switching devices 1 and 2 can be controlled (e.g., by control module 50). More specifically, as an alternative or supplement to manipulating the turn-on and turn-off delays after each switching event or instance of switching devices 1 and 2 as described herein for the next switching event or instance, any difference between the voltages of the EES modules 6 and 7 of the switching devices VBCs 3 and 4 can be reduced by shortening the voltage of these switching devices VBCs with the lowest voltage (while the current i in the conductive path 5 is also at its lowest). c The voltage pulses of the EES module (positive) are used for compensation. This ensures that the voltages of the EES modules 6 and 7 of the switching devices VBC 3 and 4 are closer to each other.

[0097] according to Figure 1 The embodiment of the invention illustrated herein, for each of a plurality of switching devices VBC 3, 4, the EES modules 6, 7 of the switching devices VBC 3, 4 are arranged in relation to the corresponding switching devices 1, 2 of the switching devices VBC 3, 4 such that by switching at least one switching device 1, 2 between different operating states, the EES modules 6, 7 of the switching devices VBC 3, 4 can be selectively charged or discharged.

[0098] Before (e.g., by control module 50) controlling the timing of charging and / or discharging the EES modules 6 and 7 of the corresponding EES modules 3 and 4 of the VBCs of the series-connected switching devices 1 and 2, the series-connected switching devices 1 and 2 can be controlled to switch from a first operating state to a second operating state. Then, it can be determined which of the EES modules 6 and 7 of the VBCs 3 and 4 of the series-connected switching devices 1 and 2 has the lowest voltage level when the series-connected switching devices 1 and 2 are in the second operating state after being controlled to switch from the first operating state to the second operating state. Subsequently, it can be determined which of the following EES modules has the lowest voltage level when the series-connected switching devices 1 and 2 are in the second operating state after being controlled to switch from the first operating state to the second operating state: (ii) the difference between the lowest voltage level and the voltage of the EES modules of the other VBCs of these switching devices. Operations (I) and (II) mentioned above can be implemented, for example, by control module 50.

[0099] Then, by controlling the timing of switching the series-connected switching devices 1 and 2 between related operating states based on the differences determined by operation (II) mentioned above (e.g., by control module 50), the timing of charging and / or discharging the corresponding EES modules 6 and 7 in the switching devices VBCs 3 and 4 corresponding to the series-connected switching devices 1 and 2 can be controlled, thereby reducing any difference between the voltages of the corresponding EES modules 6 and 7 in the switching devices VBCs 3 and 4. Thus, any difference between the voltages of the series-connected switching devices 1 and 2 can be reduced.

[0100] As an alternative to or supplement to operations (I) and (II) mentioned above, it can be determined that: (III) when the series-connected switching devices 1 and 2 are in the second operating state after being controlled to switch from the first operating state to the second operating state, the average voltage of each voltage of the EES modules 6 and 7 corresponding to the switching devices VBC 3 and 4 of the series-connected switching devices 1 and 2 is determined. Subsequently, for each of the switching devices VBC 3 and 4 corresponding to the series-connected switching devices 1 and 2, it can be determined that: (IV) the difference between the voltage of the EES modules 6 and 7 of the switching devices VBC 3 and 4 and the average voltage (determined by operation (III)). Operations (III) and (IV) mentioned above can be implemented, for example, by the control module 50.

[0101] Then, by controlling the timing of switching the series-connected switching devices 1 and 2 between related operating states based on the difference determined by the aforementioned operation (IV) (e.g., by control module 50), the timing of charging and / or discharging the corresponding EES modules 6 and 7 in the switching devices VBCs 3 and 4 corresponding to the series-connected switching devices 1 and 2 can be controlled, thereby reducing any difference between the voltages of the corresponding EES modules 6 and 7 in the switching devices VBCs 3 and 4. Thus, any difference between the voltages of the series-connected switching devices 1 and 2 can be reduced.

[0102] Operations (III) and (IV) mentioned above may, for example, make the following necessary:

[0103] (A1) Obtain (e.g., sense or measure) the voltages V1 and V2 of the corresponding EES modules 6 and 7 in the switching devices VBC 3 and 4 (possibly, the obtained values ​​of the voltages may be filtered, for example, using a selected time constant);

[0104] (A2) Determine the average voltage (e.g., based on...) Figure 1 The embodiment of the present invention illustrated in the figure, V 平均 = (V1+V2) / 2);

[0105] (A3) Determine the difference between the voltage of EES modules 6 and 7 and the average voltage (e.g., based on...). Figure 1 In the embodiment of the invention illustrated in the figure, the difference e1 = V1 – V 平均 And e2 = V2 – V 平均 );as well as

[0106] (A4) Based on the determined difference (from step A3), proportional control action may be used to shorten or lengthen the upcoming discharge of the EES modules 6 and 7 of the corresponding switching devices VBC3 and 4.

[0107] Figure 2 This is a schematic diagram of a device 100 according to an embodiment of the present invention. Figure 2 The device 100 shown in the figure and Figure 1 The device 100 shown in the figure is similar, and Figure 1 and Figure 2 The same reference numerals in the accompanying drawings indicate the same or similar parts or elements having the same or similar functions. Figure 1 Compared to the device 100 shown in the figure (which includes a switching device 1 and 2 connected in series), Figure 2 The device 100 illustrated includes two switching devices connected in series, wherein the two switching devices are connected in parallel. Figure 2 As illustrated, device 100 includes first switching devices 1 and 2 connected in series and second switching devices 18 and 19 connected in series, wherein the first switching devices 1 and 2 connected in series and the second switching devices 18 and 19 connected in series are connected in parallel. It will be understood that... Figure 2 The device 100 illustrated may include two or more switching devices connected in series, such as, for example, three, four, five, six, eight, ten, twelve or more switching devices connected in series. Each series connection of switching devices does not necessarily include two switching devices, but in principle may include any number of switching devices.

[0108] like Figure 2 As illustrated, device 100 includes multiple switching devices VBCs 3, 4, 16, and 17, each of which corresponds to and is connected to corresponding switching devices 1, 2, 18, and 19 connected in series with two other switching devices. Figure 2 As shown in the diagram, switching devices VBC 3, 4, 16 and 17 correspond to switching devices 1, 2, 18 and 19, respectively. Figure 2 The switching devices VBC 3 and 4 of the device 100 shown in the figure can be connected with Figure 1 The illustrations shown in the figure and referenced above are as follows. Figure 1The switching devices VBC 3 and 4 of the described device 100 are configured in the same or similar manner and may have the same or similar functions.

[0109] As mentioned above (refer to the previous text) Figure 1 The described target Figure 1 The control achieved by the series connection of switching devices 1 and 2 in the device 100 shown in the figure can be combined with... Figure 2 The switching devices 1 and 2 of the device 100 illustrated herein are connected in series in the same or similar manner. This type of control can also be implemented with... Figure 2 The switching devices 18 and 19 of the device 100 illustrated are implemented in the same or similar manner, connected in series. For example, the control module 50 may be configured to control the switching of each of the series-connected switching devices 18 and 19 between operating states, and to control the switching devices VBC 16 and 17 at least with respect to the corresponding EES module ( Figure 2 (The operation of charging or discharging is not indicated by the reference numerals in the accompanying drawings.)

[0110] Figure 3 This is a schematic diagram of a device 100 according to an embodiment of the present invention. Figure 3 The device 100 shown in the figure and Figure 1 The device 100 shown in the figure is similar, and Figure 1 and Figure 3 The same reference numerals in the accompanying drawings indicate the same or similar parts or elements having the same or similar functions. Figure 1 Compared to device 100 shown in the figure, Figure 3 Each of the switching devices 1 and 2 in the illustrated device 100 includes a plurality of sub-switching devices connected in parallel. Each of the sub-switching devices is controllably switchable between operating states including at least an on state and a non-on state. Figure 3 As illustrated, switching device 1 includes two sub-switching devices 22 and 23 connected in parallel, and switching device 2 includes two sub-switching devices 20 and 21 connected in parallel. It will be understood that the number of sub-switching devices in each of switching devices 1 and 2 is determined by example, and either switching device 1 or 2 may, in principle, include any number of sub-switching devices connected in parallel, and each of the sub-switching devices can be controllably switched between operating states including at least an on state and a non-on state. Figure 4 This is a schematic diagram of a device 100 according to an embodiment of the present invention. Figure 4 The device 100 shown in the figure and Figure 1 The device 100 shown in the figure is similar, and Figure 1 and Figure 4 The same reference numerals in the figures indicate the same or similar parts or elements having the same or similar functions.

[0111] Typically, at least one of a plurality of switching devices VBCs can be connected to or is capable of being connected to an electrical device, wherein at least one switching device VBC can be configured to selectively supply electrical energy from the EES module of at least one switching device VBC to the electrical device.

[0112] according to Figure 4 In the embodiment of the invention illustrated in the figure, each of the switching devices VBCs 3 and 4 is connected to electrical devices 31 and 32. Figure 4 As illustrated, switching device VBC 3 is connected to electrical device 31, and switching device VBC 4 is connected to electrical device 32. Further, according to... Figure 4 In the embodiment of the invention illustrated in the figure, switching devices VBCs 3 and 4 can be connected to electrical devices 31 and 32 respectively via converters 33 and 34. Each or any of converters 33 and 34 may, for example, comprise a DC-DC converter or be composed of a DC-DC converter. Converters 33 and 34 may be omitted, and therefore switching devices VBCs 3 and 4 can be directly connected to electrical devices 31 and 32 respectively.

[0113] Switching device VBC 3 can be configured to selectively supply electrical energy from the EES module 6 of switching device VBC 3 to electrical device 31 (possibly via converter 33). Similarly, switching device VBC 4 can be configured to selectively supply electrical energy from the EES module 7 of switching device VBC 4 to electrical device 32 (possibly via converter 34).

[0114] according to Figure 4 In the embodiment of the invention illustrated herein, the energy in the EES modules 6 and 7 of the switching devices VBC 3, 4 can be used to power electrical devices 31, 32 as needed or as desired. Such functionality can be incorporated into any embodiment of the invention.

[0115] Figure 5 This is a schematic diagram of a device 100 according to an embodiment of the present invention. Figure 5 The device 100 shown in the figure and Figure 1 The device 100 shown in the figure is similar, and Figure 1 and Figure 5 The same reference numerals in the figures indicate the same or similar parts or elements having the same or similar functions.

[0116] Typically, each of a plurality of switching devices VBCs may be connected in parallel with a buffer circuit system, which may include a series connection of: (i) a parallel connection of a unidirectional conduction circuit system and a resistive current path, and (ii) at least one EES module. The buffer circuit system may be arranged between the switching device VBC and at least one switching device corresponding to the switching device VBC connected in series.

[0117] Figure 5 The device 100 shown in the figure and Figure 1 The device 100 shown in the figure differs in that each of the plurality of switching devices VBC 3, 4 is connected in parallel with a buffer circuit system 41, 42, which includes a series connection of the following: (i) a parallel connection of unidirectional conduction circuit systems 43, 44 and resistive current paths 45, 46, and (ii) at least one EES module 47, 48.

[0118] like Figure 5 As illustrated, switching device VBC 3 is connected in parallel with buffer circuit system 41, which includes a series connection of (i) a parallel connection of unidirectional conduction circuit system 43 and resistive current path 45, and (ii) at least one EES module 47. Furthermore, switching device VBC 4 is connected in parallel with buffer circuit system 42, which includes a series connection of (i) a parallel connection of unidirectional conduction circuit system 44 and resistive current path 46, and (ii) at least one EES module 48. Each of the unidirectional conduction circuit systems 43 and 44 may, for example, include one or more diodes or be implemented by means of one or more diodes, such as... Figure 5 As illustrated in the diagram. Each or any of the resistive current paths 45 and 46 may, for example, include one or more resistors, such as... Figure 5 As shown in the diagram.

[0119] according to Figure 5 In the embodiment of the present invention illustrated herein, for each of the plurality of switching devices VBC 3, 4, the corresponding buffer circuit system 41, 42 may be arranged between the switching device VBC 3, 4 and at least one switching device 1, 2 corresponding to the switching device VBC 3, 4 connected in series.

[0120] like Figure 5 The diagrams shown in the image and the references above are also included. Figure 5 The described buffer circuit system may be incorporated into or implemented in any embodiment of the invention.

[0121] Figure 6This is a schematic flowchart of method 600 according to an embodiment of the present invention. Method 600 is implemented in a device comprising a plurality of interconnected switching devices, each of which is controllably switchable between operating states including at least an on state and a non-on state. At least two of the switching devices are connected in series to form at least one series connection of switching devices. The device is connected or can be connected in a conductive path for conveying current in the conductive path via the at least one series connection of switching devices. The device includes a plurality of switching device VBCs for balancing the voltage across the at least one series connection of switching devices during and after switching the switching devices from a first operating state to a second operating state. Each of the plurality of switching device VBCs includes an EES module that can be (e.g., controllably) charged or discharged. Each of the plurality of switching device VBCs corresponds to and is connected to a corresponding switching device of the at least one series connection of switching devices.

[0122] Method 200 includes: for each of at least one series-connected switching devices: at 201, obtaining one or more values ​​indicating the voltage of each of the EES modules; and at 202, based on the obtained values, controlling at least one of: (i) the timing of switching the series-connected switching devices between mutually related operating states, or (ii) the timing of charging and / or discharging the EES modules of the corresponding switching devices in the VBC of the series-connected switching devices, such that any difference between the voltages of the EES modules of the VBC is reduced, wherein the VBC is connected to the corresponding switching devices in the series-connected switching devices, thereby reducing any difference between the voltages of the series-connected switching devices.

[0123] Then, method 200 can be completed.

[0124] However, method 200 can be repeated multiple times to balance the voltages on at least one series-connected switching device during and after switching the switching device from a first operating state to a second operating state for a period of time. Method 200 can be repeated until any difference between the voltages of the series-connected switching devices does not exceed a threshold difference.

[0125] Will understand, as Figure 1-5 The configuration of switching devices VBC 3 and 4 shown in the figure is based on an example, and variations are possible. Figure 7 The figure shows an example of different configurations of switching devices VBC 3, 4, which is a schematic diagram of device 100 according to an embodiment of the present invention. Figure 7 The device 100 shown in the figure and Figure 1The device 100 shown in the figure is similar, and Figure 1 and Figure 7 The same reference numerals in the figures indicate the same or similar parts or elements having the same or similar functions.

[0126] according to Figure 7 The embodiment of the invention illustrated herein, for each of the plurality of switching devices VBC 3, 4, has resistive circuit systems 10, 11 connected in parallel with EES modules 6, 7. Figure 7 As illustrated, for switching device VBC 3, resistive circuit system 11 is connected in parallel with EES module 6, and for switching device VBC 4, resistive circuit system 10 is connected in parallel with EES module 7. For each of the multiple switching devices VBC 3, 4, resistive circuit systems 10, 11 can be connected to first unidirectional conductive circuit systems 8, 9, such as... Figure 7 As shown in the diagram.

[0127] As Figure 1 The diagram in the figure and according to the reference Figure 1 Like the aforementioned device 100, in Figure 7 In the device 100 illustrated, the switching elements 14 and 15 of the switching devices VBC 3 and 4 can be used in the same or similar manner to control the energy of the corresponding EES modules 6 and 7. Although the discharge paths of EES modules 6 and 7 are... Figure 1 The device 100 shown in the figure and Figure 7 The devices 100 shown in the diagram are different, but the charging paths of EES modules 6 and 7 are... Figure 1 The device 100 shown in the figure and Figure 7 The device 100 shown in the figure is the same. Figure 7 The configuration of switching devices VBC 3 and 4 shown in the figure can be used Figure 2-5 In any of the devices 100 shown in the figures, the configuration of the switching devices VBC 3, 4 shown in the figures is used instead. Figure 1 The functions and operation of the device 100 illustrated in the figure and described above are for Figure 7 The device 100 shown in the figure is also applicable.

[0128] In summary, an apparatus is disclosed comprising: a plurality of interconnected switching devices, at least two of which are connected in series to form at least one series connection; and a plurality of switching device VBCs for balancing the voltages across the at least one series-connected switching devices during and after switching the switching devices from a first operating state to a second operating state. Each of the plurality of switching device VBCs includes an EES module capable of controllable charging or discharging. Each of the plurality of switching device VBCs corresponds to a corresponding switching device in the at least one series connection. For each series connection, the timing of switching the series-connected switching devices between mutually related operating states and / or the timing of charging and / or discharging the corresponding EES modules in the switching device VBCs corresponding to the series-connected switching devices are controlled based on one or more values ​​indicative of the voltage of each EES module, such that any difference between the voltages of the EES modules is reduced.

[0129] Although the invention has been illustrated in the accompanying drawings and foregoing description, such illustrations are to be considered illustrative or exemplary rather than limiting; 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 in practicing the claimed invention by studying the drawings, the disclosure, and the appended claims. In the appended claims, the word "comprising" does not exclude other elements or steps, and the indefinite articles "a" or "an" do not exclude multiple. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that combinations of these measures cannot be advantageously used. Any reference numerals in the claims should not be construed as limiting the scope.

[0130] Various aspects of the invention can be understood from the following enumerated example embodiments (EEE):

[0131] EEE 1. An apparatus comprising:

[0132] A plurality of interconnected switching devices, each of which is controllably switchable between an operating state including at least an on state and a non-on state, wherein at least two of the switching devices are connected in series to form at least one switching device series connection, wherein the device is connected or can be connected in a conductive path for conveying current in the conductive path via the at least one switching device series connection;

[0133] A plurality of switching device voltage balancing circuits VBC for balancing the voltage on the at least one switching device connected in series during and after switching the switching device from a first operating state to a second operating state, wherein each of the plurality of switching device VBCs includes an energy storage EES module that can be controlled to be charged or discharged, and wherein each of the plurality of switching device VBCs corresponds to and is connected to a corresponding switching device connected in series with the at least one switching device.

[0134] At least one control module is configured to control the switching of each of the at least one series-connected switching devices between operating states, and to control the VBC of the plurality of switching devices at least with respect to charging or discharging the corresponding EES module.

[0135] Wherein, the at least one control module is configured to: connect each of the at least one series-connected switching devices in series:

[0136] Obtain one or more values ​​indicating the voltage of each of the EES modules; and based on the obtained values, control at least one of the following: (i) the timing of switching between interconnected switching devices in related operating states, or (ii) the timing of charging and / or discharging the EES modules of the corresponding devices in the VBC of the switching devices connected in series, such that any difference between the voltages of the EES modules in the VBC of the switching devices is reduced, wherein the VBC of the switching devices is connected to the corresponding devices in series, such that any difference between the voltages of the interconnected switching devices is also reduced.

[0137] EEE 2. The device according to EEE 1, wherein each of the plurality of switching devices VBC includes a resistive circuit system comprising at least one resistor, wherein each of the plurality of switching devices VBC can be configured to selectively and controllably discharge current from its corresponding EES module through the resistive circuit system to reduce the voltage of the EES module.

[0138] The at least one control module is configured to, for each of the plurality of switching devices VBCs, discharge current from its corresponding EES module to the at least one resistor in the resistive circuit system when the voltage of the EES module of the switching device VBC exceeds a selected threshold voltage level, thereby reducing the voltage of the EES module to below the selected threshold voltage level.

[0139] EEE 3. The device according to EEE 2, wherein the selected threshold voltage level is the same for each switching device VBC.

[0140] EEE 4. The device according to any one of EEE 1 to 3, wherein each of the plurality of switching devices VBC is connected in parallel with a corresponding switching device that is connected in series with the at least one switching device.

[0141] EEE 5. The device according to any one of EEE 1 to 4, wherein each of the plurality of switching devices VBC further includes a first unidirectional conduction circuit system and a second unidirectional conduction circuit system connected in parallel with the first unidirectional conduction circuit system, wherein the parallel connection of the first unidirectional conduction circuit system and the second unidirectional conduction circuit system is connected in series with the EES module of the switching device VBC, and wherein the first unidirectional conduction circuit system and the second unidirectional conduction circuit system are configured to conduct current in opposite directions, and wherein one of the first unidirectional conduction circuit system and the second unidirectional conduction circuit system includes at least one resistor.

[0142] EEE 6. The device according to EEE 5, wherein one of the first unidirectional conduction circuit system and the second unidirectional conduction circuit system is configured to selectively and controllably allow current to be conducted through the first unidirectional conduction circuit system or the second unidirectional conduction circuit system, respectively.

[0143] EEE 7. The device according to EEE 5 or EEE 6, wherein the first unidirectional conductive circuit system and the second unidirectional conductive circuit system include a series connection of at least one switching element and at least one resistor, wherein each of the at least one switching element is controllably switchable between an operating state including at least an on state and an off state, wherein the at least one control module is configured to control the switching of the at least one switching element between operating states.

[0144] EEE 8. The device according to EEE 7, wherein the first unidirectional conduction circuit system and the second unidirectional conduction circuit system are arranged in relation to the EES module of the switching device VBC such that by switching the at least one switching element between different operating states, the EES module of the switching device VBC can be selectively and controllably discharged via one of the first unidirectional conduction circuit systems and selectively and controllably charged via the other of the first unidirectional conduction circuit system and the second unidirectional conduction circuit system, thereby the timing of charging and / or discharging the EES module of the switching device VBC is controllable by the at least one control module.

[0145] EEE 9. The device according to any one of EEE 1 to 8, comprising at least two switching devices connected in series, the at least two switching devices being connected in parallel.

[0146] EEE 10. The device according to any one of EEE 1 to 9, wherein the at least one switching device connected in series comprises a plurality of sub-switching devices connected in parallel, each of the sub-switching devices being controllably switchable between an operating state including at least an on state and an off state.

[0147] EEE 11. The device according to any one of EEE 1 to 10, wherein the at least one control module is configured to: control the switching device to switch from a first operating state to a second operating state in the operating states before controlling the timing of switching the switching device connected in series between the switching devices in the interrelated operating states;

[0148] The at least one control module is configured to: control the timing of switching the series-connected switching devices between related operating states based on any time difference between the moment when the series-connected switching devices reach the second operating state after being controlled to switch from the first operating state to the second operating state, so that any difference between the voltages of the EES modules of the switching device VBC is reduced.

[0149] The time difference is determined based on: (i) any difference between the voltages of the EES modules of the switching devices VBCs of the switching devices connected in series when the switching devices have been controlled to switch from the first operating state to the second operating state, and (ii) the current in the conductive path during the switching of the switching devices connected in series from the first operating state to the second operating state.

[0150] EEE 12. The device according to EEE 11, wherein the time difference is determined based on the relationship between: (i) any difference between the voltages of the EES modules of the switching devices VBCs of the switching devices connected in series when the switching devices have been controlled to switch from the first operating state to the second operating state, and (ii) the integral of the current in the conductive path over time during the switching of the switching devices connected in series from the first operating state to the second operating state.

[0151] EEE 13. The device according to any one of EEE 1 to 12, wherein, for each of the plurality of switching devices VBC, the EES module of the switching device VBC is arranged in relation to the switching device corresponding to the switching device VBC such that by switching the at least one switching device between different operating states, the EES module of the switching device VBC can be selectively charged or discharged.

[0152] The at least one control module is configured to: before controlling the timing of discharging the EES module of the corresponding device in the VBC of the switching device connected in series with the switching device:

[0153] The control switching devices connected in series switch the switching devices from the first operating state to the second operating state of the operating state;

[0154] Determine: When the series-connected switching devices are in the second operating state after being controlled to switch from the first operating state to the second operating state, which(s) of the EES modules in the VBC of the series-connected switching devices have the lowest voltage level; and

[0155] Determine: When at least two of the switching devices connected in series have been controlled to switch from a first operating state to a second operating state and are in the second operating state, the minimum voltage level of the EES module corresponding to the VBC of the other switching devices(a) of these switching devices is between the voltage(a) and the voltage(a).

[0156] The at least one control module is configured to: control the timing of switching between interconnected switching devices in a series connection between interrelated operating states based on the determined (multiple) differences, and control the timing of charging and / or discharging the EES modules of the corresponding devices in the VBC of the series-connected switching devices, such that any difference between the voltages of the corresponding EES modules in the VBC of the switching devices is reduced, thereby reducing any difference between the voltages of the series-connected switching devices.

[0157] EEE 14. The device according to any one of EEE 1 to 12, wherein, for each of the plurality of switching devices VBC, the EES module of the switching device VBC is arranged in relation to the switching device corresponding to the switching device VBC such that by switching the at least one switching device between different operating states, the EES module of the switching device VBC can be selectively charged or discharged.

[0158] The at least one control module is configured to: before controlling the timing of discharging the EES module of the corresponding device in the VBC of the switching device connected in series with the switching device:

[0159] The control switching devices connected in series switch the switching devices from the first operating state to the second operating state of the operating state;

[0160] Determine: the average voltage of each voltage in the EES module corresponding to the VBC of the series-connected switching devices when the switching devices are in the second operating state after being controlled to switch from the first operating state to the second operating state; and

[0161] For each of the switching devices VBCs corresponding to the switching devices connected in series, determine the difference between the voltage of the EES module of the switching device VBC and the average voltage.

[0162] The at least one control module is configured to: control the timing of switching between interconnected switching devices in a series connection between related operating states based on the determined difference, and control the timing of charging and / or discharging the EES modules of the corresponding devices in the VBC of the series-connected switching devices, so that any difference between the voltages of the corresponding EES modules in the VBC of the switching devices is reduced, thereby reducing any difference between the voltages of the series-connected switching devices.

[0163] EEE 15. The device according to any one of EEE 1 to 14, wherein at least one of the plurality of switching devices VBCs is connected to or is connectable to an electrical device, wherein the at least one switching device VBC is configured to selectively supply electrical energy from the EES module of the at least one switching device VBC to the electrical device.

[0164] EEE 16. The device according to any one of EEE 1 to 15, wherein each of the plurality of switching devices VBC is connected in parallel with a buffer circuit system comprising a series connection of (i) a parallel connection of a unidirectional conduction circuit system and a resistive current path, and (ii) at least one EES module.

[0165] EEE 17. The device according to EEE 16, wherein the buffer circuit system is arranged between the switching device VBC and the at least one switching device corresponding to the switching device VBC connected in series.

[0166] EEE 18. A method in a device comprising a plurality of interconnected switching devices, each of the plurality of interconnected switching devices being controllably switchable between an operating state including at least an on state and a non-on state, wherein at least two of the switching devices are connected in series to form at least one switching device series connection, wherein the device is connected or is capable of being connected in a conductive path for delivering current in the conductive path via the at least one switching device series connection, the device further comprising a plurality of switching device voltage balancing circuits VBC, the plurality of switching device VBCs being used to balance the voltages on the at least one switching device series connection during and after switching the switching devices from a first operating state to a second operating state, wherein each of the plurality of switching device VBCs includes an electrical energy storage EES module that can be controllably charged or discharged, wherein each of the plurality of switching device VBCs corresponds to and is connected to a corresponding switching device of the at least one switching device series connection, the method comprising: for each of the at least one switching device series connection, a series connection is made:

[0167] Obtain one or more values ​​indicating the voltage of each in the EES module; and

[0168] Based on the obtained values, control at least one of the following: (i) the timing of switching between interconnected switching devices in related operating states, or (ii) the timing of charging and / or discharging the EES modules of the corresponding devices in the VBC of the series-connected switching devices, such that any difference between the voltages of the EES modules of the VBC is reduced, wherein the VBC is connected to the corresponding interconnected switching devices, thereby reducing any difference between the voltages of the interconnected switching devices.

[0169] EEE 19. A computer program comprising instructions which, when executed by one or more processors included in at least one control module, cause the at least one control module to perform the method according to EEE 18.

Claims

1. An apparatus (100), comprising: A plurality of interconnected switching devices (1, 2), each of which is controllably switchable between an operating state including at least an on state and an off state, wherein at least two of the switching devices are connected in series to form at least one series connection of switching devices (1, 2; 18, 19), wherein the device is connected or can be connected in a conductive path (5) for conveying current in the conductive path via the at least one series connection of switching devices; Multiple switching device voltage balancing circuits VBC (3, 4; 16, 17) are used to balance the voltage on the at least one switching device connected in series during and after switching the switching device from a first operating state to a second operating state, wherein each of the multiple switching device VBCs includes an electrical energy storage module (6, 7) capable of being controlled to charge or discharge, and wherein each of the multiple switching device VBCs corresponds to and is connected to a corresponding switching device connected in series with the at least one switching device; At least one control module (50) is configured to control the switching of each of the at least one switching devices connected in series between the operating states, and to control the VBC of the plurality of switching devices at least with respect to charging or discharging the corresponding EES module; Wherein, the at least one control module is configured to: connect each of the at least one series-connected switching devices in series: Obtain one or more values ​​indicating the voltage of each of the EES modules; and Based on the obtained values, control at least one of the following: (i) the timing of switching the series-connected switching devices between the related operating states, or (ii) the timing of charging and / or discharging the EES modules of the corresponding devices in the VBC of the series-connected switching devices, such that any difference between the voltages of the EES modules of the VBC is reduced, wherein the VBC is connected to the corresponding series-connected switching devices, such that any difference between the voltages of the series-connected switching devices is also reduced; Each of the plurality of switching devices VBC includes a resistive circuit system (10, 11), the resistive circuit system including at least one resistor (12, 13) and a first diode connected in parallel with the at least one resistor, wherein each of the plurality of switching devices VBC is configured to selectively and controllably discharge current from its corresponding EES module through the resistive circuit system to reduce the voltage of the EES module; The at least one control module is configured to, for each of the plurality of switching devices VBCs, when the voltage of the EES module of the switching device VBC exceeds a selected threshold voltage level, control the switching device VBC to discharge current from its corresponding EES module to the at least one resistor of the resistive circuit system, such that the voltage of the EES module is reduced to below the selected threshold voltage level.

2. The device according to claim 1, wherein, The selected threshold voltage level is the same for each switching device VBC.

3. The device according to any one of claims 1 to 2, wherein, Each of the plurality of switching devices VBCs is connected in parallel to a corresponding switching device that is connected in series with the at least one switching device.

4. The device according to any one of claims 1 to 3, wherein, Each of the plurality of switching devices VBCs further includes a first unidirectional conduction circuit system (8, 9) and a second unidirectional conduction circuit system (10, 11) connected in parallel with the first unidirectional conduction circuit system, wherein the parallel connection of the first unidirectional conduction circuit system and the second unidirectional conduction circuit system is connected in series with the EES module of the switching device VBC, and wherein the first unidirectional conduction circuit system and the second unidirectional conduction circuit system are configured to conduct current in opposite directions, and wherein one of the first unidirectional conduction circuit system and the second unidirectional conduction circuit system includes at least one resistor (12, 13).

5. The device according to claim 4, wherein, One of the first unidirectional conduction circuit system and the second unidirectional conduction circuit system is configured to selectively and controllably allow current to be conducted through the first unidirectional conduction circuit system or the second unidirectional conduction circuit system, respectively.

6. The device according to claim 4 or 5, wherein, The first unidirectional conduction circuit system and the second unidirectional conduction circuit system include a series connection of at least one switching element (14, 15) and at least one resistor (12, 13), wherein each of the at least one switching element is controllably switchable between an operating state including at least an on state and a non-on state, wherein the at least one control module is configured to control the switching of the at least one switching element between the operating states.

7. The device according to claim 6, wherein, The first unidirectional conduction circuit system and the second unidirectional conduction circuit system are arranged in relation to the EES module of the switching device VBC such that by switching the at least one switching element between different operating states, the EES module of the switching device VBC can be selectively and controllably discharged via one of the first unidirectional conduction circuit systems and selectively and controllably charged via the other of the first unidirectional conduction circuit system and the second unidirectional conduction circuit system, thereby the timing of charging and / or discharging the EES module of the switching device VBC can be controlled by the at least one control module.

8. The device according to any one of claims 1 to 7, comprising at least two switching devices connected in series (1, 2; 18, 19), wherein the at least two switching devices are connected in series and in parallel.

9. The device according to any one of claims 1 to 8, wherein, The at least one switching device (1, 2) connected in series includes a plurality of sub-switching devices (20, 21, 22, 23) connected in parallel, each of the sub-switching devices being controllably switchable between operating states including at least an on state and an off state.

10. The device according to any one of claims 1 to 9, wherein, The at least one control module is configured to: control the switching device to switch from a first operating state to a second operating state before controlling the timing of switching the switching devices connected in series between the interrelated operating states. The at least one control module is configured to: control the timing of switching the series-connected switching devices between the related operating states based on any time difference between the moment when the series-connected switching devices reach the second operating state after being controlled to switch from the first operating state to the second operating state, so that any difference between the voltages of the EES modules of the VBC of the switching devices is reduced. The time difference is determined based on: (i) any difference between the voltages of the EES modules of the VBCs of the switching devices connected in series with the switching devices when the switching devices are in the second operating state after being controlled to switch from the first operating state to the second operating state; and (ii) the current in the conductive path during the switching of the switching devices connected in series with the switching devices from the first operating state to the second operating state.

11. The device of claim 10, wherein the time difference is determined based on the relationship between: (i) any difference between the voltages of the EES modules of the VBCs of the switching devices connected in series with the switching devices when the switching devices have been controlled to switch from the first operating state to the second operating state, and (ii) the integral of the current in the conductive path over time during the switching of the switching devices connected in series with the switching devices from the first operating state to the second operating state.

12. The device according to any one of claims 1 to 11, wherein, For each of the plurality of switching devices VBCs, the EES module of the switching device VBC is arranged in relation to the switching device corresponding to the switching device VBC such that by switching the at least one switching device between different operating states, the EES module of the switching device VBC can selectively charge or discharge. The at least one control module is configured to: discharge the EES module of the corresponding device in the VBC of the switching device connected in series with the switching device before: The switching devices connected in series with the switching devices are controlled to switch from a first operating state to a second operating state. When the series-connected switching devices are in the second operating state after being controlled to switch from the first operating state to the second operating state, determine which EES module in the EES module of the VBC of the series-connected switching devices has the lowest voltage level; and When at least two of the switching devices connected in series have been controlled to switch from the first operating state to the second operating state and then be in the second operating state, determine the difference between the lowest voltage level and the voltage of the EES module corresponding to the VBC of the other switching devices. The at least one control module is configured to: control the timing of switching the series-connected switching devices between the related operating states based on a determined difference, and control the timing of charging and / or discharging the EES modules of the corresponding devices in the VBC of the series-connected switching devices, such that any difference between the voltages of the corresponding EES modules in the VBC of the switching devices is reduced, thereby reducing any difference between the voltages of the series-connected switching devices.

13. The device according to any one of claims 1 to 11, wherein, For each of the plurality of switching devices VBCs, the EES module of the switching device VBC is arranged in relation to the switching device corresponding to the switching device VBC such that by switching the at least one switching device between different operating states, the EES module of the switching device VBC can selectively charge or discharge. The at least one control module is configured to: discharge the EES module of the corresponding device in the VBC of the switching device connected in series with the switching device before: The switching devices connected in series with the switching devices are controlled to switch from a first operating state to a second operating state. When the series-connected switching devices are in the second operating state after being controlled to switch from the first operating state to the second operating state, the average voltage of the EES module of the switching device VBC corresponding to the series-connected switching devices is determined; and For each of the switching devices VBCs corresponding to the switching devices connected in series with the switching devices, determine the difference between the voltage of the EES module of the switching device VBC and the average voltage. The at least one control module is configured to: control the timing of switching the series-connected switching devices between the related operating states based on a determined difference, and control the timing of charging and / or discharging the EES modules of the corresponding devices in the VBC of the series-connected switching devices, such that any difference between the voltages of the corresponding EES modules in the VBC of the switching devices is reduced, thereby reducing any difference between the voltages of the series-connected switching devices.

14. The device according to any one of claims 1 to 13, wherein, At least one of the plurality of switching devices VBCs is connected to or is capable of being connected to the electrical devices (31, 32), wherein the at least one switching device VBC is configured to selectively supply electrical energy from the EES module of the at least one switching device VBC to the electrical devices.

15. The device according to any one of claims 1 to 14, wherein, Each of the plurality of switching devices VBC is connected in parallel with a buffer circuit system (41, 42), the buffer circuit system comprising the following series connections: (i) a parallel connection of a unidirectional conduction circuit system (43, 44) and a resistive current path (45, 46), and (ii) at least one EES module (47, 48).

16. The device according to claim 15, wherein, The buffer circuit system is arranged between the switching device VBC and the at least one switching device corresponding to the switching device VBC connected in series.

17. The device according to any one of claims 1 to 16, wherein, For each of the plurality of switching devices VBC, the resistive circuit system further includes a second diode, wherein the second diode is connected in series with the parallel connection of the at least one resistor and the first diode.

18. A method (200) performed in a device, said device comprising a plurality of interconnected switching devices, each of said plurality of interconnected switching devices being controllably switchable between an operating state including at least an on state and a non-on state, wherein, At least two of the switching devices are connected in series to form at least one series connection of switching devices, wherein the device is connected or can be connected in a conductive path for delivering current in the conductive path via the at least one series connection of switching devices, the device further comprising a plurality of switching device voltage balancing circuits VBC, the plurality of switching device VBCs being used to balance the voltage on the at least one series connection of switching devices during and after switching the switching devices from a first operating state to a second operating state, wherein each of the plurality of switching device VBCs includes an electrical energy storage (EES) module capable of controllable charging or discharging, wherein each of the plurality of switching device VBCs corresponds to and is connected to a corresponding switching device in the at least one series connection of switching devices, the method comprising: for each of the at least one series connection of switching devices connected in series: (201) Obtain one or more values ​​of voltage indicating each of the EES modules; and Based on the obtained values, control (202) at least one of the following: (i) the timing of switching the series-connected switching devices between the mutually related operating states, or (ii) the timing of charging and / or discharging the EES modules of corresponding devices in the VBC of the series-connected switching devices, such that any difference between the voltages of the EES modules of the VBC is reduced, wherein the VBC is connected to the corresponding series-connected switching devices, thereby reducing any difference between the voltages of the series-connected switching devices; wherein each of the plurality of VBCs includes a resistive circuit system, the resistive circuit system including at least one resistor and a first diode connected in parallel with the at least one resistor, wherein each of the plurality of VBCs is configured to selectively and controllably discharge current from its corresponding EES module through the resistive circuit system to reduce the voltage of the EES module; Wherein, for each of the at least one series-connected switching devices, the method further includes: For each of the plurality of switching devices VBCs, when the voltage of the EES module of the switching device VBC exceeds a selected threshold voltage level, the switching device VBC is controlled to discharge current from its corresponding EES module to at least one resistor of the resistive circuit system, such that the voltage of the EES module decreases below the selected threshold voltage level.

19. A computer program comprising instructions that, when executed by one or more processors included in at least one control module, cause the at least one control module to perform the method according to claim 18.

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