Short-circuit current suppression circuit for flying capacitor converter and energy storage system having the same

Abstract

The present invention discloses a flying capacitor converter and a short-circuit current suppression circuit and an energy storage system for the flying capacitor converter. The flying capacitor converter includes a controller, and the high-voltage side of the flying capacitor converter is connected to a first power supply, and the low-voltage side of the flying capacitor converter is connected to a second power supply. The short-circuit current suppression circuit includes: at least one current detection component connected to the low-voltage side and / or the high-voltage side of the flying capacitor converter; and at least one switch component connected in series to the high-voltage side and / or the low-voltage side of the flying capacitor converter, wherein when the current detection component detects a short circuit, the controller controls the switch component to disconnect the connection between the flying capacitor converter and the first power supply and / or the flying capacitor converter and the second power supply. The present invention can quickly suppress the short-circuit current of the flying capacitor converter, reduce the short-circuit capacity of the converter itself, and improve the short-circuit reliability of the energy storage system composed of multiple flying capacitor converters.

Description

Technical Field

[0001] The present invention relates to a short-circuit current suppression circuit, and in particular to a short-circuit current suppression circuit for a flying capacitor converter, a flying capacitor converter having the short-circuit current suppression circuit, and an energy storage system having the flying capacitor converter. Background Art

[0002] At present, flying capacitor converters have begun to be used in energy storage systems, such as Figure 1 As shown, multiple flying capacitor converters (eg Figure 1 One end of the converter (converter #1, converter #2, ..., converter #n, etc.) is connected to the DC grid or DC common bus, and the other end is connected to an energy storage element, such as a super capacitor or a battery (for example Figure 1 There are n batteries shown in the figure (Battery-1, Battery-2, ..., Battery-n, etc.).

[0003] In actual applications, multiple flying capacitor converters are connected to the DC common bus to charge and discharge multiple energy storage elements respectively. When one of the converters is short-circuited, the short-circuit current that a single converter can provide is only a few hundred amperes. However, since multiple converters are connected in parallel, each converter will provide a short-circuit current to the short-circuit point, and the value of the short-circuit current depends on the number of converters in parallel. When the number of converters in parallel increases, a large short-circuit current will be formed. This short-circuit current will cause overcurrent and overheating damage to some devices. If the short-circuit current cannot be eliminated in time, it will cause a larger short-circuit accident or fire.

[0004] For example, in Figure 1 When a short circuit occurs inside one of the flying capacitor converters, for example, a short circuit occurs between points ab of converter #2 (such as Figure 1 As shown by the arrow between points a and b), the system will have the following problems:

[0005] (1) The diodes D1 / D2 inside the faulty converter cannot shut off the short-circuit current from the energy storage element;

[0006] (2) Short circuit of the DC common bus causes short circuit of other converters, leading to failure of the entire system;

[0007] (3) The short-circuit currents of other converters will flow to the short-circuit point of the faulty converter #2. For example, when the short-circuit current of each converter is 100A, if 100 converters are connected in parallel, the total short-circuit current flowing through the short-circuit point is 10kA. However, the excessive total short-circuit current will cause the fuse of the faulty converter to fail to disconnect effectively.

[0008] (4) Excessive total short-circuit current will cause overheating and damage to the mechanical components of the faulty converter that has a short circuit;

[0009] (5) Too large a total short-circuit current will make it difficult to select devices that meet the short-circuit capacity when designing the converter, or it will be necessary to select large-capacity devices, resulting in an increase in converter cost;

[0010] (6) The total short-circuit current will not flow through the fuses located on the DC common bus, such as fuse Fuse_a / Fuse_b, and will not trigger the total fuse Fuse_a / Fuse_b protection.

[0011] Therefore, there is an urgent need for a short-circuit current suppression circuit for a flying capacitor converter, so as to quickly suppress the short-circuit current of a single converter. Summary of the invention

[0012] The object of the present invention is to provide a flying capacitor converter and a short-circuit current suppression circuit and an energy storage system used therefor, which can quickly suppress the short-circuit current of a single converter.

[0013] In order to achieve the above-mentioned purpose, the present invention provides a short-circuit current suppression circuit for a flying capacitor converter, wherein the flying capacitor converter includes at least one power switch and a controller, and the high-voltage side of the flying capacitor converter is connected to a first power supply, and the low-voltage side of the flying capacitor converter is connected to a second power supply, wherein the short-circuit current suppression circuit includes: at least one current detection component connected to the low-voltage side and / or the high-voltage side of the flying capacitor converter; and at least one switch component connected in series to the high-voltage side and / or the low-voltage side of the flying capacitor converter, wherein when the current detection component detects a short circuit, the controller controls the switch component to disconnect the connection between the flying capacitor converter and the first power supply and / or the connection between the flying capacitor converter and the second power supply.

[0014] In one embodiment of the present invention, each of the switch components includes two switch elements connected in reverse series and is connected to the controller of the flying capacitor converter.

[0015] In one embodiment of the present invention, each of the switch components further comprises at least one mechanical switch connected in series with the two switch elements connected in reverse series.

[0016] In one embodiment of the present invention, when the current detection component detects a short circuit, it is determined whether the short circuit occurs inside or outside the flying capacitor converter according to the detected current direction.

[0017] In one embodiment of the present invention, when the current detection component detects a short circuit, the controller controls the switch element to be disconnected.

[0018] In one embodiment of the present invention, when a short circuit occurs inside the flying capacitor converter, the controller further controls the mechanical switch connected in series with the switch element to be disconnected.

[0019] In order to achieve the above object, the present invention further provides a flying capacitor converter, which is characterized in that it includes the short-circuit current suppression circuit as described above.

[0020] In one embodiment of the present invention, the flying capacitor converter is a three-level flying capacitor converter, including a first power switch, a second power switch, a third power switch, a fourth power switch, a flying capacitor and an output capacitor connected in series in sequence, the first power switch and the fourth power switch are connected to the high voltage side; the flying capacitor is connected across the second power switch and the third power switch; the connection point of the second power switch and the third power switch is coupled to the low voltage side through an inductor.

[0021] In one embodiment of the present invention, the flying capacitor converter is a multi-level flying capacitor converter, including a plurality of power switches connected in series in sequence, and a plurality of flying capacitors.

[0022] In an embodiment of the present invention, the power switch and the switch element include at least one of Si MOSFET, SiC MOSFET, GaN FET or IGBT.

[0023] In order to achieve the above-mentioned purpose, the present invention further provides an energy storage system, which includes: a plurality of flying capacitor converters as described above; a power supply, whose positive end is connected to the positive input end of the high voltage side of each flying capacitor converter, and whose negative end is connected to the negative input end of the high voltage side of each flying capacitor converter; and a plurality of energy storage elements, each of which is correspondingly connected between the positive output end and the negative output end of the low voltage side of each flying capacitor converter.

[0024] In yet another embodiment of the present invention, the power source is a DC grid or a DC common bus, and the multiple energy storage elements are batteries or supercapacitors.

[0025] The present invention can quickly suppress the short-circuit current of the flying capacitor converter, reduce the short-circuit capacity requirements of the converter's internal components, and improve the short-circuit reliability of an energy storage system composed of multiple flying capacitor converters. When a converter in the energy storage system fails, the present invention can bypass the failed converter to ensure stable operation of the system.

[0026] Additional aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The above and other features and advantages of the present invention will become more apparent by describing in detail exemplary embodiments thereof with reference to the attached drawings.

[0028] Figure 1 A schematic diagram of a circuit structure of a flying capacitor converter in the prior art applied to an energy storage system;

[0029] Figure 2 A schematic structural diagram of a flying capacitor converter and a short-circuit current suppression circuit for a flying capacitor converter according to a preferred embodiment of the present invention;

[0030] Figure 3 For the present invention Figure 2 The flying capacitor converter shown is a structural schematic diagram of an energy storage system. DETAILED DESCRIPTION

[0031] Example embodiments will now be described more fully with reference to the accompanying drawings. However, example embodiments can be implemented in a variety of forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that the present invention will be comprehensive and complete and fully convey the concepts of the example embodiments to those skilled in the art. The same reference numerals in the figures represent the same or similar structures, and thus their detailed description will be omitted.

[0032] When introducing the elements / components / etc. described and / or illustrated herein, the terms "a", "an", "the", "said", and "at least one" are used to indicate the presence of one or more elements / components / etc. The terms "comprises", "includes", and "have" are used to indicate an open-ended inclusive meaning and mean that additional elements / components / etc. may be present in addition to the listed elements / components / etc. Relative terms may be used in the embodiments, such as "upper" or "lower" to describe the relative relationship of one component of the icon to another component. It is understood that if the device of the icon is turned over so that it is upside down, the component described on the "upper" side will become the component on the "lower" side. In addition, the terms "first", "second", etc. in the claims are used only as labels and are not numerical limitations on their objects.

[0033] The flying capacitor converter of the present invention includes a controller, and its high-voltage side is connected to the first power supply, and the low-voltage side is connected to the second power supply. The flying capacitor converter of the present invention also includes a short-circuit current suppression circuit, which includes at least one current detection component and at least one switch component. The at least one current detection component is connected to the low-voltage side and / or high-voltage side of the flying capacitor converter. The at least one switch component is connected in series to the high-voltage side and / or low-voltage side of the flying capacitor converter. Wherein, when the current detection component detects a short circuit, the controller of the flying capacitor converter can control the switch component to disconnect the connection between the flying capacitor converter and the first power supply and / or the flying capacitor converter and the second power supply. In this way, the present invention can effectively suppress the short-circuit current of the flying capacitor converter, and by controlling the switch component to disconnect, the faulty converter can be bypassed.

[0034] like Figure 2 As shown, it shows the structure of a flying capacitor converter and its short-circuit current suppression circuit of a preferred embodiment of the present invention. Figure 2 In the preferred embodiment shown, the flying capacitor converter 200 includes four switch elements 21 connected in series, for example, including switch elements S1 / D1, S2 / D2, S3 / D3, S4 / D4. Taking the switch element S1 / D1 as an example, it is composed of a controllable switch S1 and a diode D1, wherein the diode D1 can be the body diode of the controllable switch S1 or an external diode. The flying capacitor converter 200 also includes a controller (not shown in the figure), which is connected to these switch elements S1 / D1, S2 / D2, S3 / D3, S4 / D4 and controls the operation of the aforementioned switch elements. The flying capacitor converter 200 also includes an input capacitor C1, a flying capacitor C2 and an output capacitor C3, wherein the input capacitor C1 is connected to the high voltage side (HV side), that is, connected between the node a and the node b on the input side of the four switch elements 21; the flying capacitor C2 is connected across the two ends of the middle two switch elements 21 (i.e., S2 / D2 and S3 / D3); the output capacitor C3 is connected to the low voltage side (LV side) through an inductor L1, that is, connected between the node c and the node d on the output side of the two switch elements 21 (i.e., S3 / D3 and S4 / D4) on the low voltage side. In this way, a flying capacitor three-level converter can be formed. Of course, it can be understood that in other embodiments, the circuit of the flying capacitor converter can also be a multi-level circuit topology known to other technicians in this field, such as a flying capacitor four-level converter, which is not a limitation of the present invention.

[0035] exist Figure 2In the preferred embodiment shown, the flying capacitor converter 200 of the present invention also includes a short-circuit current suppression circuit, which includes current detection components CS1 and CS2, which are respectively connected to the high-voltage side and the low-voltage side of the flying capacitor converter 200, and can be used to detect the current of the high-voltage side and the low-voltage side respectively. The short-circuit current suppression circuit also includes a switch component 23 connected in series to the high-voltage side and the low-voltage side of the flying capacitor converter 200, each of which may include two switch elements 231 connected in series with each other in reverse and connected to the controller of the flying capacitor converter 200, for example, including switch elements S5 / D5, S6 / D6 located on the high-voltage side and switch elements S7 / D7, S8 / D8 located on the low-voltage side. Taking the switch element S5 / D5 located on the high-voltage side as an example, it is composed of a controllable switch S5 and a diode D5. The controller of the flying capacitor converter 200 is also connected to these switch elements S5 / D5, S6 / D6, S7 / D7, and S8 / D8 respectively. When the driving signal applied to these switching elements S5 / D5, S6 / D6, S7 / D7, S8 / D8 is at a high level, these switching elements S5 / D5, S6 / D6, S7 / D7, S8 / D8 are in an on state; when the applied driving signal is at a low level, these switching elements S5 / D5, S6 / D6, S7 / D7, S8 / D8 are disconnected.

[0036] Preferably, the switch element 21 and the switch element 231 in the switch assembly 23 include at least one of Si MOSFET, SiC MOSFET, GaN FET or IGBT.

[0037] Preferably, each of the switch components 23 further includes a mechanical switch 232, which is connected in series with the two reversely connected switch elements 231 on the high voltage side and the low voltage side. For example, the mechanical switch K1, the current detection component CS1 and the switch elements S5 / D5, S6 / D6 are arranged on the positive bus on the high voltage side; the mechanical switch K4 and the switch elements S5 / D5, S6 / D6 are arranged on the negative bus on the low voltage side, and the current detection component CS2 is arranged on the positive bus on the low voltage side.

[0038] Preferably, a mechanical switch K2 may be provided on the negative busbar on the high voltage side, and a mechanical switch K3 may be provided on the positive busbar on the low voltage side. More preferably, a fuse 24 may be provided on the positive busbar and the negative busbar on the high voltage side, and on the positive busbar and the negative busbar on the low voltage side, respectively, such as fuses Fuse1 to Fuse4. Furthermore, the controller of the flying capacitor converter 200 may also be connected to the control of the mechanical switches K1 to K4.

[0039] exist Figure 2In the preferred embodiment shown, the high voltage side of the flying capacitor converter 200 of the present invention can be connected to a first power source, and the low voltage side can be connected to a second power source.

[0040] In the present invention, when the current detection component detects a short circuit, it can be determined whether the short circuit occurs inside or outside the flying capacitor converter according to the direction of the detected current. In addition, when the current detection component detects a short circuit, the controller of the flying capacitor converter can control the switch element to disconnect. Preferably, when the short circuit occurs inside the flying capacitor converter, the controller of the flying capacitor converter also controls the mechanical switch connected in series with the switch element to disconnect.

[0041] For example, in Figure 2 In the example, when the flying capacitor converter 200 operates normally, both the high voltage side and the low voltage side are connected to a power supply or an energy storage element. When a short circuit fault occurs, the current detection components CS1 and CS2 will detect a short circuit current of a certain value and make a quick judgment, thereby turning off the driving of the switch elements S5 / D5, S6 / D6, S7 / D7, and S8 / D8.

[0042] Specifically, the current detection components CS1 and CS2 inside the converter 200 can determine the direction of the short-circuit current, and further distinguish whether it is an internal short circuit or an external short circuit.

[0043] If a short-circuit fault occurs outside the converter, such as a short circuit between the positive and negative poles on the high-voltage side, the current detection component CS1 will detect an increase in current. When the detected current reaches a certain overcurrent protection threshold, the converter can generate an overcurrent protection signal through a fast hardware comparison circuit, turn off the drive signals of the switch elements S5 / D5, S6 / D6, S7 / D7, and S8 / D8 to disconnect from the high-voltage side, thereby quickly cutting off the short-circuit current from the internal capacitor of the converter and from the energy storage element on the low-voltage side. In this way, the short-circuit loop can be cut off before the fuse protection, thereby avoiding overcurrent damage to fuse Fuse1, fuse Fuse2, mechanical switch K1, and mechanical switch K2.

[0044] If a short circuit fault occurs inside the converter, for example, between nodes a and b, the current detection component CS1 will detect an increase in current. When the detected current reaches a certain overcurrent protection threshold, the converter can generate an overcurrent protection signal through a fast hardware comparison circuit, and the converter controller will first quickly turn off the drive signals of the switch elements S5 / D5, S6 / D6, S7 / D7, and S8 / D8 to cut off the short circuit loop; then the controller of converter #2 will issue an instruction to disconnect the mechanical switches K1, K2, K3, and K4, and cut off the faulty converter, so that the short circuit fault is limited to the inside of the converter, thereby ensuring the stable operation of other converters in the system.

[0045] like Figure 3 As shown, it shows the structure of the flying capacitor converter with short-circuit current suppression circuit of the present invention applied to the energy storage system. The energy storage system of the present invention includes a power supply 100, a plurality of flying capacitor converters 200 and a plurality of energy storage elements 300. The flying capacitor converter 200 includes, for example, converter #1, converter #2, ..., converter #n and other n converters, and its structure can be, for example, as shown in Figure 2 The power source 100 may be, for example, a DC grid or a DC common bus, the positive end of which is connected to the positive input end of the high voltage side of each flying capacitor converter 200, and the negative end of which is connected to the negative input end of the high voltage side of each flying capacitor converter 200. Each energy storage element 300 is correspondingly connected between the positive output end and the negative output end of the low voltage side of each flying capacitor converter 200, and may be, for example, a battery.

[0046] The following will be combined Figure 3 , further illustrating the advantages of the energy storage system of the present invention:

[0047] (1) For example, when a short circuit fault occurs between node a and node b of converter #2, the controller of converter #2 will turn off the drive signals of switch elements S5 / D5, S6 / D6, S7 / D7, and S8 / D8 after detecting the short circuit current, and disconnect the connection with the high voltage side, thereby preventing converter #2 from causing short circuits of other parallel converters;

[0048] (2) For example, after a short circuit occurs inside converter #2, the controller of converter #2 will first quickly turn off the drive signals of switch elements S5 / D5, S6 / D6, S7 / D7, and S8 / D8 to cut off the short circuit loop; then the controller of converter #2 will issue an instruction to disconnect mechanical switches K1, K2, K3, and K4 to cut off the faulty converter (i.e., converter #2), so that the short circuit fault is limited to converter #2, thereby ensuring the stable operation of other converters in the system;

[0049] (3) The converter of the present invention adds switch elements S5 / D5, S6 / D6, S7 / D7, and S8 / D8, which reduces the short-circuit capacity of the fuse of the converter itself, which is beneficial to reducing device costs.

[0050] The flying capacitor converter of the present invention can quickly suppress the short-circuit current of the flying capacitor converter through the short-circuit current suppression circuit therein, reduce the short-circuit capacity of the internal components of the converter, and improve the short-circuit reliability of the energy storage system composed of multiple flying capacitor converters. When a converter in the energy storage system fails, the present invention can bypass the faulty converter to ensure stable operation of the system.

[0051] The flying capacitor converter of the present invention can be widely used in rail transportation, electric power, new energy power generation, distributed energy storage, high-power transmission and other fields.

[0052] The exemplary embodiments of the present invention are specifically shown and described above. It should be understood that the present invention is not limited to the disclosed embodiments, but rather is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.

Claims

1. A short-circuit current suppression circuit for a flying capacitor converter, wherein the flying capacitor converter comprises at least one power switch and a controller, wherein the high voltage side of the flying capacitor converter is connected to a first power supply, and the low voltage side of the flying capacitor converter is connected to a second power supply, wherein: The short-circuit current suppression circuit comprises: At least one current detection component connected to the low voltage side and / or the high voltage side of the flying capacitor converter; At least one switch component is connected in series to the high voltage side and / or the low voltage side of the flying capacitor converter, each of the switch components includes two switch elements connected in reverse series and connected to the controller of the flying capacitor converter, each of the switch components also includes at least one mechanical switch, and is connected in series with the two switch elements connected in reverse series, wherein when the current detection component detects a short circuit, the controller controls the switch component to disconnect the connection between the flying capacitor converter and the first power supply and / or between the flying capacitor converter and the second power supply.

2. The short-circuit current suppression circuit according to claim 1, characterized in that: When the current detection component detects a short circuit, it determines whether the short circuit occurs inside or outside the flying capacitor converter according to the detected current direction.

3. The short-circuit current suppression circuit according to claim 1, characterized in that: When the current detection component detects a short circuit, the controller controls the switch element to be turned off.

4. The short-circuit current suppression circuit according to claim 2, characterized in that: When a short circuit occurs inside the flying capacitor converter, the controller further controls the mechanical switch connected in series with the switch element to be disconnected.

5. The short-circuit current suppression circuit according to claim 1, characterized in that: The flying capacitor converter is a three-level flying capacitor converter, comprising a first power switch, a second power switch, a third power switch, a fourth power switch, and a flying capacitor connected in series in sequence, wherein the first power switch and the fourth power switch are connected to the high voltage side; the flying capacitor is connected across the second power switch and the third power switch; and the connection point of the second power switch and the third power switch is coupled to the low voltage side through an inductor.

6. The short-circuit current suppression circuit according to claim 1, characterized in that: The flying capacitor converter is a multi-level flying capacitor converter, comprising a plurality of power switches connected in series in sequence and a plurality of flying capacitors.

7. The short-circuit current suppression circuit according to any one of claims 1 to 6, characterized in that: The power switch and the switching element include at least one of Si MOSFET, SiC MOSFET, GaN FET or IGBT.

8. A flying capacitor converter, characterized in that: The invention comprises a short-circuit current suppression circuit as claimed in any one of claims 1 to 7.

9. An energy storage system, characterized in that: include: A plurality of flying capacitor converters as claimed in claim 8; A power supply, whose positive end is connected to the positive input end of the high voltage side of each of the flying capacitor converters, and whose negative end is connected to the negative input end of the high voltage side of each of the flying capacitor converters; A plurality of energy storage elements, each of which is correspondingly connected between the positive output terminal and the negative output terminal of the low voltage side of each flying capacitor converter.

10. The energy storage system according to claim 9, characterized in that: The power source is a DC grid or a DC common bus, and the multiple energy storage elements are batteries or super capacitors.

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