DC bus overcurrent protection circuit and bidirectional converter

Abstract

The present disclosure provides a DC bus overcurrent protection circuit, coupled to a DC bus between a first DC terminal and a second DC terminal, wherein the DC bus includes a positive bus and a negative bus, and includes: a main protection branch, connected in series to the positive bus or the negative bus, and including a first protection switch and a second protection switch connected in series to a first node; a freewheeling switch branch, one end of which is connected to the positive bus and the other end of which is connected to the negative bus, and one of the two ends is coupled to the first node; a detection unit, coupled to the DC bus, for real-time sampling and judgment of the voltage or current on the DC bus to output an overcurrent detection signal; and a control unit, for controlling the main protection branch to perform a switch action according to the overcurrent detection signal provided by the detection unit. The embodiments of the present disclosure can improve the efficiency and reliability of overcurrent protection and reduce component loss.

Description

Technical Field

[0001] The present disclosure relates to the technical field of power supply circuits, and in particular to a direct current bus overcurrent protection circuit and a bidirectional converter. Background Art

[0002] In many DC power supply and inverter applications, short circuit and other faults may occur at the DC input port or output port, internal circuit or external load. In order to avoid the expansion of the fault and serious consequences, the abnormal current and energy caused by the fault must be removed from the system as soon as possible.

[0003] Fast fuses are a widely used overcurrent and short-circuit protection method, but the fault clearing current of this method when implementing fast protection is usually dozens of times larger than the rated current of the circuit, which can easily damage sensitive components. For overloads several times the rated current, the protection time of the fuse is often several seconds or even more than tens of seconds, which can easily cause heating damage to some circuits or components.

[0004] It should be noted that the information disclosed in the above background technology section is only used to enhance the understanding of the background of the present disclosure, and therefore may include information that does not constitute the prior art known to ordinary technicians in the field. Summary of the invention

[0005] The purpose of the present disclosure is to provide a DC bus overcurrent protection circuit and a bidirectional converter capable of realizing rapid overcurrent detection and circuit protection, so as to at least overcome to a certain extent the problem that the related technology is prone to damage components and reduce the service life of devices when performing circuit overcurrent detection and protection due to the limitations and defects of the related technology.

[0006] According to a first aspect of an embodiment of the present disclosure, a DC bus overcurrent protection circuit is provided, which is coupled to a DC bus between a first DC terminal and a second DC terminal, wherein the DC bus includes a positive bus and a negative bus, wherein the positive bus is connected between a first DC positive terminal and a second DC positive terminal, and the negative bus is connected between a first DC negative terminal and a second DC negative terminal, and includes: a main protection branch, which is connected in series to the positive bus or the negative bus, and includes a first protection switch and a second protection switch connected in series to a first node; a freewheeling switch branch, one end of which is connected to the positive bus and the other end of which is connected to the negative bus, and one of the two ends is connected to the first node; a detection unit, which is coupled to the DC bus and is used to perform real-time detection of a voltage or current on the DC bus and output an overcurrent detection signal used to characterize whether an overcurrent fault occurs in the circuit; and a control unit, which is coupled to the detection unit and controls the main protection branch to perform a switching action according to the overcurrent detection signal.

[0007] In an exemplary embodiment of the present disclosure, the overcurrent detection signal includes a first overcurrent signal indicating that an overcurrent has occurred at the first DC end and a second overcurrent signal indicating that an overcurrent has occurred at the second DC end; the control unit is used to control the second protection switch to disconnect according to the first overcurrent signal, and to control the first protection switch to disconnect according to the second overcurrent signal.

[0008] In an exemplary embodiment of the present disclosure, the detection unit is coupled to the first DC positive terminal and the first DC negative terminal to detect the voltage at the first DC end of the DC bus; or is coupled to the second DC positive terminal and the second DC negative terminal to detect the voltage at the second DC end of the DC bus.

[0009] In an exemplary embodiment of the present disclosure, the detection unit is coupled to the positive bus or the negative bus to detect the current of the DC bus.

[0010] In an exemplary embodiment of the present disclosure, the detection unit is coupled to two different detection positions on the positive bus, or is coupled to two different detection positions on the negative bus, to detect the voltage between the two detection positions.

[0011] In an exemplary embodiment of the present disclosure, the DC bus includes a filter inductor, and the two detection positions are respectively located before and after the filter inductor.

[0012] In an exemplary embodiment of the present disclosure, when the voltage difference before and after the filter inductor exceeds a preset positive threshold, the detection unit outputs the second overcurrent signal; or when the voltage difference before and after the filter inductor exceeds a preset negative threshold, the detection unit outputs the first overcurrent signal.

[0013] In an exemplary embodiment of the present disclosure, the first protection switch and the second protection switch are both IGBTs or MOSFETs.

[0014] In an exemplary embodiment of the present disclosure, the first protection switch and the second protection switch are connected in reverse series to the first node.

[0015] In an exemplary embodiment of the present disclosure, the control unit is coupled to the freewheeling switch branch, and is configured to control the freewheeling switch branch to be turned on in response to the overcurrent detection signal.

[0016] In an exemplary embodiment of the present disclosure, the freewheeling switch branch is implemented by a diode, a positive electrode of the diode is coupled to the negative bus, and a negative electrode of the diode is coupled to the positive bus.

[0017] In an exemplary embodiment of the present disclosure, it also includes: a starting current limiting circuit, which is connected in parallel to the main protection branch, with a first end coupled to the first DC end and a second end coupled to the second DC end.

[0018] In an exemplary embodiment of the present disclosure, the startup current limiting circuit includes an auxiliary switch and a current limiting resistor connected in series.

[0019] According to a second aspect of the present disclosure, a DC bus overcurrent protection circuit is provided, which is coupled to a DC bus between a first DC terminal and a second DC terminal, wherein the DC bus includes a positive bus and a negative bus, wherein the positive bus is connected between a first DC positive terminal and a second DC positive terminal, and the negative bus is connected between a first DC negative terminal and a second DC negative terminal, and comprises: a main protection branch, which is connected in series to the positive bus or the negative bus, and comprises at least one protection switch; a first freewheeling switch branch, one end of which is connected to the positive bus and the other end of which is connected to the negative bus. , one of the two ends is coupled to the first end of the main protection branch; a second freewheeling switch branch, one end is connected to the positive bus, the other end is connected to the negative bus, and one of the two ends is coupled to the second end of the main protection branch; a detection unit is coupled to the DC bus, used to perform real-time detection of the voltage or current on the DC bus, and output an overcurrent detection signal used to indicate whether an overcurrent fault occurs in the circuit; and a control unit is coupled to the detection unit, and controls the main protection branch to perform a switching action according to the overcurrent detection signal.

[0020] In an exemplary embodiment of the present disclosure, the overcurrent detection signal includes a first overcurrent signal indicating that an overcurrent has occurred at the first DC end and a second overcurrent signal indicating that an overcurrent has occurred at the second DC end; the control unit is used to control the conduction of the first freewheeling switch branch according to the first overcurrent signal, and to control the conduction of the second freewheeling switch branch according to the second overcurrent signal.

[0021] In an exemplary embodiment of the present disclosure, the detection unit is coupled to the first DC positive terminal and the first DC negative terminal to detect the voltage at the first DC end of the DC bus; or is coupled to the second DC positive terminal and the second DC negative terminal to detect the voltage at the second DC end of the DC bus.

[0022] In an exemplary embodiment of the present disclosure, the detection unit is coupled to the positive bus or the negative bus to detect the current of the DC bus.

[0023] In an exemplary embodiment of the present disclosure, the detection unit is coupled to two different detection positions on the positive bus, or is coupled to two different detection positions on the negative bus, to detect the voltage between the two detection positions.

[0024] In an exemplary embodiment of the present disclosure, the DC bus includes a filter inductor, and the two detection positions are respectively located before and after the filter inductor.

[0025] In an exemplary embodiment of the present disclosure, when the voltage difference before and after the filter inductor exceeds a preset positive threshold, the detection unit outputs the second overcurrent signal; or when the voltage difference before and after the filter inductor exceeds a preset negative threshold, the detection unit outputs the first overcurrent signal.

[0026] In an exemplary embodiment of the present disclosure, the main protection branch includes a first protection switch and a second protection switch connected in reverse series, and the first protection switch and the second protection switch are both IGBTs or both are MOSFETs.

[0027] In an exemplary embodiment of the present disclosure, the first freewheeling switch branch and the second freewheeling switch branch are both implemented by diodes, and the positive electrode of the diode is coupled to the negative bus, and the negative electrode is coupled to the positive bus.

[0028] In an exemplary embodiment of the present disclosure, it also includes: a starting current limiting circuit, which is connected in parallel to the main protection branch, with a first end coupled to the first DC end and a second end coupled to the second DC end.

[0029] In an exemplary embodiment of the present disclosure, the startup current limiting circuit includes an auxiliary switch and a current limiting resistor connected in series.

[0030] According to a third aspect of the present disclosure, a bidirectional converter is provided, wherein an input end or an output end of the bidirectional converter is provided with a DC bus overcurrent protection circuit as described in any one of the above items.

[0031] The DC bus overcurrent protection circuit provided by the embodiment of the present disclosure, by setting a main protection branch and a freewheeling switch branch on the DC bus, and detecting the voltage or current on the DC bus, can quickly cut off the current path between a DC end and another DC end when an overcurrent is detected at a DC end, effectively protect the DC end where no overcurrent or short circuit occurs, and quickly provide a freewheeling circuit for the DC end that is short-circuited or overcurrent, thereby realizing bidirectional rapid overcurrent protection and short-circuit protection; and the detection method is rapid and effective, so that the DC bus overcurrent protection circuit can act quickly, realize rapid separation of the faulty end, and avoid damage to components and equipment.

[0032] It is to be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the present disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The accompanying drawings herein are incorporated into the specification and constitute a part of the specification, illustrate embodiments consistent with the present disclosure, and together with the specification are used to explain the principles of the present disclosure. Obviously, the accompanying drawings described below are only some embodiments of the present disclosure, and for ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without creative work.

[0034] Figure 1A and Figure 1B Schematic diagram of a DC bus overcurrent protection circuit 100 according to a first embodiment and a second embodiment of the exemplary embodiments of the present disclosure.

[0035] Figure 2A and Figure 2B They are circuit connection diagrams of the detection unit 3 in two embodiments of the present disclosure respectively.

[0036] Figure 3A and Figure 3B They are circuit connection diagrams of the detection unit 3 in two other embodiments of the present disclosure.

[0037] Figure 4A and Figure 4B They are circuit connection diagrams of the detection unit 3 in two embodiments of the present disclosure respectively.

[0038] Figure 5 It is a circuit diagram of the main protection branch 1 in one embodiment of the present disclosure.

[0039] Figure 6 It is a circuit diagram of the main protection branch 1 in another embodiment of the present disclosure.

[0040] Figure 7 It is a schematic diagram of another embodiment of the DC bus overcurrent protection circuit 100 disclosed in the present invention.

[0041] Fig. 8A and Figure 8B is a schematic diagram of another DC bus overcurrent protection circuit 800 provided in the present disclosure.

[0042] Fig.9A and Fig. 9B They are circuit connection diagrams of the detection unit 84 in two embodiments of the present disclosure respectively.

[0043] Fig. 10A and Fig. 10B They are circuit connection diagrams of the detection unit 84 in two other embodiments of the present disclosure.

[0044] Fig.11A and Fig. 11B They are circuit connection diagrams of the detection unit 84 in two other embodiments of the present disclosure.

[0045] FIG. 12A to FIG. 12DIt is a schematic diagram of the form of the main protection branch 81 in the embodiment of the present disclosure.

[0046] Fig.13 It is a schematic diagram of another embodiment of the DC bus overcurrent protection circuit 800 disclosed in the present invention.

[0047] Fig.14A and Fig. 14B is a schematic diagram of a bidirectional converter provided by the present disclosure. DETAILED DESCRIPTION

[0048] 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 being limited to the examples set forth herein; on the contrary, these embodiments are provided so that the present disclosure will be more comprehensive and complete, and the concepts of the example embodiments are fully conveyed to those skilled in the art. The described features, structures, or characteristics may be combined in one or more embodiments in any suitable manner. In the following description, many specific details are provided to provide a full understanding of the embodiments of the present disclosure. However, those skilled in the art will appreciate that the technical solutions of the present disclosure may be practiced while omitting one or more of the specific details, or other methods, components, devices, steps, etc. may be adopted. In other cases, known technical solutions are not shown or described in detail to avoid obscuring various aspects of the present disclosure.

[0049] In addition, the accompanying drawings are only schematic diagrams of the present disclosure, and the same reference numerals in the drawings represent the same or similar parts, so their repeated description will be omitted. Some of the block diagrams shown in the accompanying drawings are functional entities, which do not necessarily correspond to physically or logically independent entities. These functional entities can be implemented in software form, or implemented in one or more hardware modules or integrated circuits, or implemented in different networks and / or processor devices and / or micro control unit devices.

[0050] The exemplary embodiments of the present disclosure are described in detail below with reference to the accompanying drawings.

[0051] Figure 1A and Figure 1B It is a schematic diagram of a DC bus overcurrent protection circuit of the first embodiment and the second embodiment in the exemplary embodiments of the present disclosure.

[0052] refer to Figure 1A and Figure 1BThe DC bus overcurrent protection circuit 100 is coupled to a DC bus between a first DC terminal A and a second DC terminal B, wherein the DC bus includes a positive bus Bus+ connected between a first DC positive terminal A+ and a second DC positive terminal B+, and a negative bus Bus- connected between a first DC negative terminal A- and a second DC negative terminal B-, and the DC bus overcurrent protection circuit 100 may include:

[0053] Main protection branch 1, connected in series to the positive bus Bus+( Figure 1A ) or negative bus Bus-( Figure 1B ), comprising a first protection switch 11 and a second protection switch 12 connected in series to a first node N1;

[0054] A freewheeling switch branch 2, one end of which is connected to the positive bus Bus+, the other end of which is connected to the negative bus Bus-, and one end of which is coupled to the first node N1;

[0055] The detection unit 3 is coupled to the DC bus and is used to detect the voltage V bus Or the current I bus Performing real-time detection to output an overcurrent detection signal used to indicate whether an overcurrent fault occurs in the circuit;

[0056] The control unit 4 is coupled to the detection unit 3 and is used for controlling the main protection branch 1 to perform a switching action according to the overcurrent detection signal.

[0057] It is worth mentioning that in normal operation, the main protection branch 1 is in the on state, the first protection switch 11 and the second protection switch 12 are closed by default; and the freewheeling switch branch 2 is in the off state by default.

[0058] In an exemplary embodiment of the present disclosure, the overcurrent detection signal includes a first overcurrent signal S indicating that an overcurrent fault occurs at the first DC terminal A. A and a second overcurrent signal S indicating that an overcurrent fault occurs at the second DC terminal B B The detection unit 3 is used to detect the voltage V on the DC bus according to the real-time sampling bus Or the current I bus Determine and output the first overcurrent signal S A Or the second overcurrent signal S B .

[0059] When receiving the first overcurrent signal S A When the second overcurrent signal S is received, the control unit 4 controls the second protection switch 12 to be disconnected to protect the circuit of the second DC terminal B; BWhen the overcurrent detection signal is on, the control unit 4 controls the first protection switch 11 to be disconnected to protect the circuit of the first DC terminal A. At the same time, if the freewheeling switch branch 2 is a controllable switch branch, the control unit 4 is also coupled to the freewheeling switch branch 2 to respond to the overcurrent detection signal (whether the first overcurrent signal S A Or the second overcurrent signal S B ) controls the freewheeling switch branch 2 to be turned on, so as to provide a freewheeling circuit for the overcurrent DC end while cutting off the DC bus connection of the overcurrent DC end.

[0060] Figure 2A and Figure 2B They are circuit connection diagrams of the detection unit 3 in two embodiments of the present disclosure respectively.

[0061] exist Figure 2A and Figure 2B In the illustrated embodiment, the detection unit 3 is coupled to the positive and negative busbars of the first DC terminal A or the positive and negative busbars of the second DC terminal B to detect the busbar voltage and output an overcurrent detection signal when the busbar voltage change (e.g., the voltage change amplitude or the voltage change speed) is greater than a preset voltage threshold. For example, when the busbar voltage between the positive and negative busbars of the first DC terminal drops significantly and exceeds the preset voltage threshold, the first overcurrent signal S A When the bus voltage between the positive and negative busbars of the second DC terminal drops significantly and exceeds the preset voltage threshold, a second overcurrent signal S can be output. B .

[0062] In the embodiment of the present disclosure, the detection unit 3 can implement voltage measurement between the positive and negative bus bars through the operational amplifier 31 .

[0063] exist Figure 2A In the illustrated embodiment, the detection unit 3 is coupled to the first DC positive terminal A+ and the first DC negative terminal A- of the first DC terminal A, and detects the voltage V between the positive bus Bus+ and the negative bus Bus-. bus The positive and negative input terminals of the operational amplifier 31 are coupled to the positive and negative terminals A+ and A− of the first DC terminal A respectively.

[0064] exist Figure 2B In the embodiment shown, the detection unit 3 is coupled to the second DC positive terminal B+ and the second DC negative terminal B- of the second DC terminal B, and detects the voltage V between the positive bus Bus+ and the negative bus Bus-. bus The positive and negative input terminals of the operational amplifier 31 are coupled to the positive and negative terminals B+ and B− of the second DC terminal B respectively.

[0065] Figure 3A and Figure 3B They are respectively circuit connection diagrams of the detection unit 3 in another embodiment of the present disclosure.

[0066] exist Figure 3A In the embodiment shown, the detection unit 3 is coupled to the positive bus Bus+ to detect the current I bus Taking the current flowing from the first DC positive terminal A+ to the second DC positive terminal B+ as an example, when the bus current is detected to be positive and the absolute value exceeds the preset current threshold, the second overcurrent signal S is output. B Or, when the bus current is negative and the absolute value exceeds the preset current threshold, the first overcurrent signal S is output A Similarly, the detection unit 3 can also be coupled to the negative bus Bus-, such as Figure 3B shown.

[0067] exist Figure 3A and Figure 3B In the illustrated embodiment, the positive input terminal of the operational amplifier 31 may be coupled to the positive bus or the negative bus, and the negative input terminal may be grounded, so as to determine the current direction and the absolute value of the current.

[0068] It should be noted that the above-mentioned determination of the positive and negative of the detection voltage or current is based on a certain direction as a reference. If the reference direction is changed, the positive and negative determination will also change accordingly. The present disclosure does not limit this relative relationship.

[0069] Figure 4A and Figure 4B They are circuit connection diagrams of the detection unit 3 in two embodiments of the present disclosure respectively.

[0070] refer to Figure 4A and Figure 4B In some embodiments, the first DC terminal A can be a DC bus connection port or a load port, and is provided with common-mode and differential-mode filter inductors Lo, filter capacitors, and positive and negative input fuses F1 and F2; the second DC terminal B can be used to connect a power converter, an energy storage element, and other DC power supplies or loads, etc.

[0071] At this time, the detection unit 3 can also be coupled to two different positions on the positive bus Bus+ or two different positions on the negative bus Bus- to detect the voltage between the two different positions.

[0072] exist Figure 4A In the illustrated embodiment, the main protection branch 1 is coupled to the positive bus Bus+, and the detection unit 3 is coupled to points a and b on the positive bus Bus+, so as to detect the voltage difference between points a and b to determine whether there is overcurrent. For example, the detection unit 3 can be coupled to two points before and after the filter inductor Lo to detect the voltage difference before and after the filter inductor Lo; or, the detection unit 3 can be coupled before and after the fuse F1 and the filter inductor Lo to detect the voltage difference between the two points. It should be noted that the present disclosure does not impose any special restrictions on the selection of two points on the bus, and the coupling position of the detection unit can be the same as or different from the coupling position of the main protection branch 1.

[0073] When the voltage difference before and after the filter inductor exceeds the preset positive threshold, the detection unit 3 outputs a second overcurrent signal S B The control unit 4 controls the first protection switch (i.e. Figure 4A or the voltage difference before and after the filter inductor exceeds the preset negative threshold, the detection unit 3 outputs a first overcurrent signal S A , the control unit 4 controls the second protection switch (ie Figure 4A When Q2 is disconnected, the overcurrent protection circuit performs protection, so that the dangerous energy at port A or port B is separated from the line fault on the other side.

[0074] exist Figure 4B In the illustrated embodiment, when the main protection branch 1 is coupled to the negative bus Bus-, the detection unit 3 is coupled to the fuse F2 and the filter inductor Lo on the negative bus Bus- (points a and b) to detect the voltage difference before and after the filter inductor Lo.

[0075] Figure 4A and Figure 4B In the figure, the equivalent circuit between point a and point b is a series circuit of resistor Rs and inductor Ls. Rs includes the line resistance of the filter inductor and the DC resistance of the fuse, and Ls includes the equivalent differential mode inductance of the filter inductor and the line distributed inductance.

[0076] The voltage V on the above equivalent circuit ab It complies with the following formula:

[0077]

[0078] From formula (1), we can know that the voltage V ab It consists of two parts. When a fault such as a short circuit just occurs, the current value is small but the current rises quickly, and the voltage is mainly manifested as the voltage drop on the inductor Ls; when the current value is large, the inductor tends to saturation, and the voltage is mainly manifested as the voltage of the resistor Rs. Therefore, using the voltage drop of these two points as an important basis for judging whether the line is overcurrent and short circuit has the advantages of easy detection and strong anti-interference ability.

[0079] Figure 5 and Figure 6 They are circuit diagrams of the main protection branch 1 in two embodiments of the present disclosure.

[0080] exist Figure 5 and Figure 6 In the illustrated embodiment, the first protection switch and the second protection switch are both IGBTs or MOSFETs. At this time, the first protection switch Q1 and the second protection switch Q2 both have a first end, a second end and a control end, and the first protection switch Q1 and the second protection switch Q2 are connected in reverse series.

[0081] exist Figure 5 In the illustrated embodiment, when the main protection branch 1 is located on the positive bus Bus+, the second end of the first protection switch Q1 and the second end of the second protection switch Q2 are connected to the first node N1 to form a reverse series structure.

[0082] exist Figure 6 In the illustrated embodiment, when the main protection branch 1 is located on the negative bus Bus-, the first end of the first protection switch Q1 and the first end of the first protection switch Q2 are connected to the first node N1 to form a reverse series structure.

[0083] In the above embodiment, the freewheeling switch branch 2 can be implemented by a controllable switch (in this case, it needs to be coupled to the control unit 4), or by one or more diodes, or can include other electronic components. The present disclosure does not limit the detailed circuit form of the freewheeling switch branch 2. Figure 5 and Figure 6 In the illustrated embodiment, the freewheeling switch branch 2 may be, for example, a diode D1. Wherein, no matter the main protection branch 1 is connected in series to the positive bus or the negative bus, the diode is connected in such a way that the positive electrode is coupled to the negative bus Bus- and the negative electrode is coupled to the positive bus Bus+, so as to provide a freewheeling loop for the second DC terminal B when the first protection switch Q1 is disconnected, or to provide a freewheeling loop for the first DC terminal A when the second protection switch Q2 is disconnected.

[0084] Specifically, Figure 4A or Figure 5 For example, when a short circuit overcurrent occurs at the second DC terminal B, the control unit 4 controls the first protection switch Q1 to be turned off, thereby cutting off the connection between the first DC terminal A and the second DC terminal B. It should be noted that Figure 4A , Figure 4B , Figure 5 , Figure 6 Q1 and Q2 in the circuit can use the same drive or different drives. When the same drive is used, Q1 and Q2 are turned off at the same time. At this time, the diode D1 and the anti-parallel diode of the switch tube Q2 can provide a freewheeling circuit for the second DC terminal B to avoid damage to subsequent circuits and devices. Of course, when Q1 and Q2 do not use the same drive, only Q1 can be turned off without turning off Q2. At this time, the diode D1 and the switch tube Q2 and / or the anti-parallel diode of the switch tube Q2 can provide a freewheeling circuit for the second DC terminal B.

[0085] Figure 7 It is a schematic diagram of another embodiment of the DC bus overcurrent protection circuit 100 disclosed in the present invention.

[0086] exist Figure 7 In the illustrated embodiment, the DC bus overcurrent protection circuit further includes:

[0087] The startup current limiting circuit 5 is connected in parallel to both ends of the main protection branch 1. In an exemplary embodiment of the present disclosure, the startup current limiting circuit 5 includes an auxiliary switch 51 and a current limiting resistor 52 connected in series. When the circuit is powered on for the first time, the auxiliary switch 51 is closed first. Due to the effect of the current limiting resistor 52, the current in the circuit rises slowly, which can effectively prevent the device from being damaged by excessive current at the moment of power-on. After the circuit is started, the first protection switch 11 and the second protection switch 12 on the main protection branch are closed, and the auxiliary switch 51 is turned off. At this time, a passage is formed by the main protection branch and the overcurrent protection function is played.

[0088] The T-type DC bus overcurrent protection circuit 100 provided in the embodiment of the present disclosure can be used as the main power switch or load switch of the converter or power module, and a resistor and switch series circuit are connected in parallel to achieve surge current suppression during startup. In addition, the circuit composed of the diode D1, the anti-parallel diode of the switch tube of the main protection branch, and the fuses F1 and F2 can achieve reverse polarity input protection for the input DC power port (for example, the first DC terminal A), avoiding damage to subsequent circuits and devices.

[0089] Fig. 8A and Figure 8B is a schematic diagram of another DC bus overcurrent protection circuit 800 provided in the present disclosure.

[0090] refer to Fig. 8A and Figure 8B , the DC bus overcurrent protection circuit 800 is similar to the circuit shown in FIG1 , and is also coupled to the DC bus between the first DC terminal A and the second DC terminal B. The DC bus includes a positive bus Bus+ connected between the first DC positive terminal A+ and the second DC positive terminal B+, and a negative bus Bus- connected between the first DC negative terminal A- and the second DC negative terminal B-. The DC bus overcurrent protection circuit 800 includes:

[0091] The main protection branch 81 is connected in series to the positive bus Bus+( Fig. 8A ) or negative bus Bus-( Figure 8B ) includes at least one protection switch;

[0092] A first freewheeling switch branch 82, one end of which is connected to the positive bus Bus+, the other end of which is connected to the negative bus Bus-, and one end of which is coupled to the first end of the main protection branch 81;

[0093] A second freewheeling switch branch 83, one end of which is connected to the positive bus Bus+, the other end of which is connected to the negative bus Bus-, and one end of which is coupled to the second end of the main protection branch 81;

[0094] The detection unit 84 is coupled to the DC bus and is used to detect the voltage V BusOr the current I Bus Performing real-time detection to output an overcurrent detection signal used to indicate whether an overcurrent fault occurs in the circuit;

[0095] The control unit 85 is coupled to the detection unit 84 and is used to control the main protection branch 81 to perform a switching action according to the over-current detection signal.

[0096] In an exemplary embodiment of the present disclosure, the overcurrent detection signal includes a first overcurrent signal S indicating that an overcurrent occurs at the first DC terminal A. A and a second overcurrent signal S indicating that an overcurrent occurs at the second DC terminal B B .

[0097] In some embodiments, when the freewheeling switch branch 82 and / or 83 is implemented by a controllable switch, the control unit 85 is coupled to the first freewheeling switch branch 82 and / or the second freewheeling switch branch 83, and controls the freewheeling switch branch 82 to control the freewheeling switch branch 83 according to the first overcurrent signal S A The first freewheeling switch branch 82 is controlled to be turned on according to the second overcurrent signal S B The second freewheeling switch branch 83 is controlled to be turned on. A Or the second overcurrent signal S B ) when the control unit 85 has controlled the main protection branch 81 to be disconnected. When the control unit 85 detects the first overcurrent signal S A When the first freewheeling switch branch 82 is controlled to be turned on, the electrical connection between the first DC terminal A and the second DC terminal B is cut off and a freewheeling circuit is provided for the first DC terminal A where overcurrent occurs. B When the second freewheeling switch branch 83 is controlled to be turned on, the electrical connection between the first DC terminal A and the second DC terminal B is cut off and a freewheeling loop is provided for the second DC terminal B where overcurrent occurs.

[0098] Fig.9A and Fig. 9B They are circuit connection diagrams of the detection unit 84 in two embodiments of the present disclosure respectively.

[0099] exist Fig.9A and Fig. 9B In the illustrated embodiment, the detection unit 84 is coupled only to the positive and negative busbars of the DC terminal on one side to detect the busbar voltage and output an overcurrent signal when the busbar voltage changes by more than a preset voltage threshold. For example, when the busbar voltage between the positive and negative busbars of the first DC port on the left side changes by more than the preset voltage threshold, the first overcurrent signal S A When the bus voltage between the positive and negative busbars of the second DC port changes beyond the preset voltage threshold, a second overcurrent signal S can be output B .

[0100] In the embodiment of the present disclosure, the detection unit 84 can implement voltage measurement between the positive and negative bus bars through the operational amplifier 841 .

[0101] exist Fig.9A In the illustrated embodiment, the detection unit 84 is coupled to the first DC positive terminal A+ and the first DC negative terminal A− of the first DC terminal A, and detects the voltage between the positive bus Bus+ and the negative bus Bus−.

[0102] The positive and negative input terminals of the operational amplifier 841 are coupled to the positive and negative terminals of the first DC terminal A respectively.

[0103] exist Fig. 9B In the illustrated embodiment, the detection unit 84 is coupled to the second DC positive terminal B+ and the second DC negative terminal B- of the second DC terminal B, and detects the voltage between the positive bus Bus+ and the negative bus Bus-. The positive and negative input terminals of the comparator 841 are coupled to the positive and negative terminals of the second DC terminal B, respectively.

[0104] Fig. 10A and Fig. 10B They are respectively circuit connection diagrams of the detection unit 84 in another embodiment of the present disclosure.

[0105] exist Fig. 10A In the illustrated embodiment, the detection unit 84 is coupled to the positive bus Bus+ to detect the current I bus Taking the current flowing from the first DC positive terminal A+ to the second DC positive terminal B+ as an example, when the bus current is positive and the absolute value exceeds the preset current threshold, the second overcurrent signal S is output. B Or, when the bus current is negative and the absolute value exceeds the preset current threshold, the first overcurrent signal S is output A Similarly, the detection unit 84 can also be coupled to the negative bus Bus-, such as Fig. 10B shown.

[0106] exist Fig. 10A and Fig. 10B In the illustrated embodiment, the positive input terminal of the comparator 841 may be coupled to the positive bus or the negative bus, and the negative input terminal may be grounded, so as to determine the current direction and the absolute value of the current.

[0107] It should be noted that the above-mentioned determination of the positive and negative of the detection voltage or current is based on a certain direction as a reference. If the reference direction is changed, the positive and negative determination will also change accordingly. The present disclosure does not limit this relative relationship.

[0108] Fig.11A and Fig. 11B They are circuit connection diagrams of the detection unit 84 in two other embodiments of the present disclosure.

[0109] In some embodiments, the first DC terminal A can be a DC bus connection port or a load port, and is provided with common-mode and differential-mode filter inductors Lo, filter capacitors C1, C2, and positive and negative input fuses F1 and F2; the second DC terminal B can be used to connect a power converter, an energy storage element, and other DC power supplies or loads, etc.

[0110] At this time, the detection unit 84 can also be coupled to two different positions on the positive bus Bus+ or two different positions on the negative bus Bus- to detect the voltage between the two different positions.

[0111] exist Fig.11A In the illustrated embodiment, when the main protection branch 81 is coupled to the positive bus Bus+, the detection unit 84 is coupled to the fuse F1 and the filter inductor Lo on the positive bus Bus+ (points a and b) to detect the voltage difference before and after the filter inductor Lo.

[0112] When the voltage difference before and after the filter inductor exceeds the preset positive threshold, the detection unit 84 outputs a second overcurrent signal S B Or when the voltage difference before and after the filter inductor exceeds the preset negative threshold, the detection unit 84 outputs a first overcurrent signal S A .

[0113] exist Fig. 11B In the illustrated embodiment, when the main protection branch 81 is coupled to the negative bus Bus-, the detection unit 84 is coupled to the fuse F2 and the filter inductor Lo on the negative bus Bus- (points a and b) to detect the voltage difference before and after the filter inductor Lo.

[0114] FIG. 12A to FIG. 12D It is a schematic diagram of the form of the main protection branch 81 in the embodiment of the present disclosure.

[0115] In the embodiments of the present disclosure, there is no limitation on the types of the protection switches, and any main protection branch 1 formed by switches having a switching function is within the protection scope of the present disclosure.

[0116] refer to Fig. 12A , the main protection branch 81 can be implemented by only one protection switch 811, and the present disclosure does not limit the connection position and number of other passive components such as resistors in the main protection branch 81 (there may be no other passive components). Fig. 12B The main protection branch 81 may also include a first protection switch 811 and a second protection switch 812 connected in series. The main protection branch 81 may also include more controllable switch elements. As long as the main protection branch 1 is composed of controllable protection switches with switching functions, it is within the protection scope of the present disclosure.

[0117] refer to Fig. 12C and Fig.12DIf the first protection switch 811 and the second protection switch 812 are both IGBTs or MOSFETs, when the main protection branch 81 includes a first protection switch Q1 and a second protection switch Q2 connected in series, the first protection switch Q1 and the second protection switch Q2 both have a first end, a second end and a control end, and the first protection switch Q1 and the second protection switch Q2 are connected in reverse series.

[0118] exist Fig. 12C In the illustrated embodiment, when the main protection branch 81 is located on the positive bus Bus+, the second end of the first protection switch Q1 and the second end of the second protection switch Q2 are connected to the first node N1 to form a reverse series structure.

[0119] exist Fig.12D In the illustrated embodiment, when the main protection branch 81 is located on the negative bus Bus-, the second end of the first protection switch Q1 and the second end of the second protection switch Q2 are connected to the first node N1 to form a reverse series structure.

[0120] exist Fig. 12C and Fig.12D In the embodiment, the positions of the first protection switch Q1 and the second protection switch Q2 are interchangeable. It should be noted that when an overcurrent occurs at the first DC terminal A or the second DC terminal B, it is necessary to turn off the forward-conducting protection switch of the two switches or both protection switches.

[0121] Specifically, Fig.11A or Fig. 12C For example, when a short circuit overcurrent occurs at the second DC terminal B, the control unit 4 controls the first protection switch Q1 to disconnect, and cuts off the connection between the first DC terminal A and the second DC terminal B. It should be noted that Q1 and Q2 in the figure can use the same drive or different drives. When the same drive is used, Q1 and Q2 are turned off at the same time; when Q1 and Q2 do not use the same drive, only Q1 can be turned off, and Q2 is not turned off. At this time, the second freewheeling switch branch 83 can provide a freewheeling circuit for the second DC terminal B.

[0122] In the above embodiment, the first freewheeling switch branch 82 and the second freewheeling switch branch 83 can be implemented by a controllable switch (in this case, a coupling control unit 85 is required), or by one or more diodes, and may also include other electronic components. The present disclosure does not control the detailed circuit form of the freewheeling switch branch.

[0123] When the first freewheeling switch branch 82 and the second freewheeling switch branch 83 are realized by one or more diodes, no matter the main protection branch 81 is connected in series to the positive bus or the negative bus, the diodes are connected in such a way that the positive pole is coupled to the negative bus Bus- and the negative pole is coupled to the positive bus Bus+, so as to provide a freewheeling circuit for the first DC terminal A or the second DC terminal B which is overcurrent or short-circuited when the main protection branch 81 is disconnected.

[0124] The above-mentioned various main protection branches and freewheeling switch branches can be freely combined with various connection methods of the aforementioned detection circuits to form more embodiments within the protection scope of the present disclosure.

[0125] Fig.13 It is a schematic diagram of another embodiment of the DC bus overcurrent protection circuit 800 disclosed in the present invention.

[0126] exist Fig.13 In the illustrated embodiment, the DC bus overcurrent protection circuit further includes:

[0127] The startup current limiting circuit 86 is connected in parallel to the main protection branch 81, with a first end coupled to the first DC terminal A and a second end coupled to the second DC terminal B. In an exemplary embodiment of the present disclosure, the startup current limiting circuit 5 includes an auxiliary switch 861 and a current limiting resistor 862 connected in series. When the circuit is powered on for the first time, the auxiliary switch 861 is closed first. Due to the effect of the current limiting resistor 862, the current in the circuit rises slowly, which can effectively prevent the device from being damaged by excessive current at the moment of power-on. After the circuit is started, the main protection branch 81 is closed again, and the auxiliary switch 861 is turned off. At this time, the main protection branch 81 forms a passage and plays the role of overcurrent protection.

[0128] Fig.14A and Fig. 14B Schematic diagram of a DC bus overcurrent protection circuit for two two-port circuits provided by the present disclosure. Fig.14A and Fig. 14B As shown, the bidirectional converter 1400 can be a combination application of two two-port circuits with T-shaped (circuit 100) or π-shaped (circuit 800) switching circuits. The two two-port circuits can be connected in series at the first DC terminal A and the second DC terminal B to realize a DC circuit 1400 with three wires connected to the positive pole, the negative pole and the neutral line. Among them, two identical overcurrent protection circuits can be used in the two-port circuit, such as Fig.14A As shown; two different overcurrent protection circuits can also be used, such as Fig. 14B shown.

[0129] The π-type DC bus overcurrent protection circuit 800 provided in the embodiment of the present disclosure can be used as the main power switch or load switch of the converter or power module, and a resistor and switch series circuit are connected in parallel to achieve surge current suppression during startup. In addition, the diode 83 or 83 can achieve reverse polarity input protection of the DC power port to avoid damage to subsequent circuits and devices.

[0130] The input end or the output end of the bidirectional converter 1400 is provided with a DC bus overcurrent protection circuit as described in any one of the above items.

[0131] The DC bus overcurrent protection circuit provided by the embodiment of the present disclosure, by setting a main protection branch and a freewheeling switch branch on the DC bus, and detecting the voltage or current on the DC bus, can quickly cut off the current path between the faulty DC terminal and another DC terminal when an overcurrent is detected at a DC terminal, effectively protect the DC terminal where no overcurrent or short circuit occurs, and quickly provide a freewheeling circuit for the DC terminal that is short-circuited or overcurrent, thereby realizing bidirectional rapid overcurrent protection and short-circuit protection; and the detection method is rapid and effective, so that the DC bus overcurrent protection circuit can act quickly, realize rapid separation of the faulty terminal, and avoid damage to components and equipment.

[0132] Those skilled in the art will readily appreciate other embodiments of the present disclosure after considering the specification and practicing the invention disclosed herein. This application is intended to cover any variations, uses, or adaptations of the present disclosure that follow the general principles of the present disclosure and include common knowledge or customary techniques in the art that are not disclosed in the present disclosure. The specification and examples are to be considered exemplary only, and the true scope and concept of the present disclosure are indicated by the claims.

Claims

1. A DC bus overcurrent protection circuit, coupled to a DC bus between a first DC terminal and a second DC terminal, wherein the DC bus comprises a positive bus and a negative bus, wherein the positive bus is connected between a first DC positive terminal and a second DC positive terminal, and the negative bus is connected between a first DC negative terminal and a second DC negative terminal, wherein: include: A main protection branch, connected in series to the positive bus or the negative bus, comprising a first protection switch and a second protection switch connected in series to a first node; A freewheeling switch branch, one end of which is connected to the positive bus, the other end of which is connected to the negative bus, and one end of which is connected to the first node; A detection unit, coupled to the DC bus, for detecting the voltage or current on the DC bus in real time and outputting an overcurrent detection signal for indicating whether an overcurrent fault occurs in the circuit; as well as A control unit, coupled to the detection unit, and controlling the main protection branch to perform a switching action according to the overcurrent detection signal; Wherein, the overcurrent detection signal includes a first overcurrent signal indicating that an overcurrent occurs at the first DC end and a second overcurrent signal indicating that an overcurrent occurs at the second DC end; the control unit is used to control the second protection switch to disconnect according to the first overcurrent signal, and control the first protection switch to disconnect according to the second overcurrent signal.

2. The DC bus overcurrent protection circuit according to claim 1, characterized in that: The detection unit is coupled to the first DC positive terminal and the first DC negative terminal to detect the voltage of the first DC terminal on the DC bus; or is coupled to the second DC positive terminal and the second DC negative terminal to detect the voltage of the second DC terminal on the DC bus.

3. The DC bus overcurrent protection circuit according to claim 1, characterized in that: The detection unit is coupled to the positive bus or the negative bus to detect the current of the DC bus.

4. The DC bus overcurrent protection circuit according to claim 1, characterized in that: The detection unit is coupled to two different detection positions on the positive bus, or is coupled to two different detection positions on the negative bus, to detect the voltage between the two detection positions.

5. The DC bus overcurrent protection circuit according to claim 4, characterized in that: The DC bus includes a filter inductor, and the two detection positions are respectively located before and after the filter inductor.

6. The DC bus overcurrent protection circuit according to claim 5, characterized in that: When the voltage difference before and after the filter inductor exceeds a preset positive threshold, the detection unit outputs the second overcurrent signal; or when the voltage difference before and after the filter inductor exceeds a preset negative threshold, the detection unit outputs the first overcurrent signal.

7. The DC bus overcurrent protection circuit according to claim 1, characterized in that: The first protection switch and the second protection switch are both IGBTs or MOSFETs.

8. The DC bus overcurrent protection circuit according to claim 7, characterized in that: The first protection switch and the second protection switch are connected in reverse series to the first node.

9. The DC bus overcurrent protection circuit according to claim 1, characterized in that: The control unit is coupled to the freewheeling switch branch, and is used for controlling the freewheeling switch branch to be turned on in response to the overcurrent detection signal.

10. The DC bus overcurrent protection circuit according to claim 1, characterized in that: The freewheeling switch branch is implemented by a diode, the positive electrode of the diode is coupled to the negative bus, and the negative electrode of the diode is coupled to the positive bus.

11. The DC bus overcurrent protection circuit according to claim 1, characterized in that: Also includes: The starting current limiting circuit is connected in parallel to the main protection branch, with a first end coupled to the first DC end and a second end coupled to the second DC end.

12. The DC bus overcurrent protection circuit according to claim 11, characterized in that: The startup current limiting circuit includes an auxiliary switch and a current limiting resistor connected in series.

13. A DC bus overcurrent protection circuit, coupled to a DC bus between a first DC terminal and a second DC terminal, wherein the DC bus comprises a positive bus and a negative bus, wherein the positive bus is connected between a first DC positive terminal and a second DC positive terminal, and the negative bus is connected between a first DC negative terminal and a second DC negative terminal, wherein: include: A main protection branch, connected in series to the positive bus or the negative bus, comprising at least one protection switch; A first freewheeling switch branch, one end of which is connected to the positive bus, the other end of which is connected to the negative bus, and one end of which is coupled to the first end of the main protection branch; A second freewheeling switch branch, one end of which is connected to the positive bus, the other end of which is connected to the negative bus, and one end of which is coupled to the second end of the main protection branch; A detection unit, coupled to the DC bus, for detecting the voltage or current on the DC bus in real time and outputting an overcurrent detection signal for indicating whether an overcurrent fault occurs in the circuit; as well as A control unit, coupled to the detection unit, and controlling the main protection branch to perform a switching action according to the overcurrent detection signal. When the control unit receives the overcurrent detection signal, the control unit controls the main protection branch to be turned off; Wherein, the overcurrent detection signal includes a first overcurrent signal indicating that an overcurrent occurs at the first DC end and a second overcurrent signal indicating that an overcurrent occurs at the second DC end; the control unit is used to control the conduction of the first freewheeling switch branch according to the first overcurrent signal, and to control the conduction of the second freewheeling switch branch according to the second overcurrent signal.

14. The DC bus overcurrent protection circuit according to claim 13, characterized in that: The detection unit is coupled to the first DC positive terminal and the first DC negative terminal to detect the voltage of the first DC terminal on the DC bus; or is coupled to the second DC positive terminal and the second DC negative terminal to detect the voltage of the second DC terminal on the DC bus.

15. The DC bus overcurrent protection circuit according to claim 13, characterized in that: The detection unit is coupled to the positive bus or the negative bus to detect the current of the DC bus.

16. The DC bus overcurrent protection circuit according to claim 13, characterized in that: The detection unit is coupled to two different detection positions on the positive bus, or is coupled to two different detection positions on the negative bus, to detect the voltage between the two detection positions.

17. The DC bus overcurrent protection circuit according to claim 13, characterized in that: The DC bus includes a filter inductor, and the two detection positions are respectively located before and after the filter inductor.

18. The DC bus overcurrent protection circuit according to claim 17, characterized in that: When the voltage difference before and after the filter inductor exceeds a preset positive threshold, the detection unit outputs the second overcurrent signal; or when the voltage difference before and after the filter inductor exceeds a preset negative threshold, the detection unit outputs the first overcurrent signal.

19. The DC bus overcurrent protection circuit according to claim 13, characterized in that: The main protection branch includes a first protection switch and a second protection switch connected in reverse series, and both the first protection switch and the second protection switch are IGBTs or MOSFETs.

20. The DC bus overcurrent protection circuit according to claim 13, characterized in that: The first freewheeling switch branch and the second freewheeling switch branch are both implemented by diodes, and the positive electrode of the diode is coupled to the negative bus, and the negative electrode of the diode is coupled to the positive bus.

21. The DC bus overcurrent protection circuit according to claim 13, characterized in that: Also includes: The starting current limiting circuit is connected in parallel to the main protection branch, with a first end coupled to the first DC end and a second end coupled to the second DC end.

22. The DC bus overcurrent protection circuit according to claim 21, characterized in that: The startup current limiting circuit includes an auxiliary switch and a current limiting resistor connected in series.

23. A bidirectional converter, characterized in that: The input end or the output end of the bidirectional converter is provided with a DC bus overcurrent protection circuit as described in any one of claims 1 to 22.

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