Direct current side protection method of power conversion system and related device

Abstract

The disclosure provides a direct current side protection method of a power conversion system and a related device, and relates to the technical field of power electronics. The direct current transmission device controls the first switch to be turned off when the output end electrical parameter of the direct current transmission device meets a preset fault condition and is maintained for a preset time length through the first control module. The preset time length is greater than the response time length of the power converter to the direct current side branch fault. That is, if the output end electrical parameter of the direct current transmission device meets the preset fault condition and is maintained at least until the response time length of the power converter to the direct current side branch fault, it is indicated that the response of the power converter fails to cut off the fault current path of the direct current transmission device. Therefore, the fault current path is cut off by controlling the first switch to be turned off. Otherwise, it is indicated that the response of the power converter has successfully cut off the fault branch, and the direct current transmission device can continue to maintain the operating state. In this way, accurate identification and isolation of the fault branch can be realized.

Description

Technical Field

[0001] This disclosure relates to the field of power electronics technology, and in particular to a DC-side protection method and related device for a power conversion system. Background Technology

[0002] In a power conversion system, when an abnormality is detected in any branch of the DC side of the downstream power converter, the power converter is usually used to disconnect all branches connected to its DC side, or other coarse protection strategies are adopted. These solutions will cause the corresponding upstream DC transmission equipment connected to each branch in the system to stop working, that is, even non-faulty branches will be mistakenly disconnected, thereby affecting the power generation efficiency and operational continuity of the entire system. Summary of the Invention

[0003] In view of the above problems, this disclosure provides a DC-side protection method and related device for a power conversion system to achieve accurate identification and isolation of faulty branches. The specific solution is as follows:

[0004] The first aspect of this disclosure provides a DC transmission device for use in a power conversion system, comprising: a power transmission circuit, a first switch, a first detection module, and a first control module; wherein...

[0005] The first side of the first switch serves as the input terminal of the DC transmission device, and the input terminal of the DC transmission device is used to connect at least one DC power supply.

[0006] The second side of the first switch is connected to the first side of the power transmission circuit;

[0007] The second side of the power transmission circuit serves as the output terminal of the DC transmission device, and the output terminal of the DC transmission device is used to connect to the corresponding DC-side interface of the power converter in the power conversion system.

[0008] The first detection module is configured to: sample the output electrical parameters of the DC transmission device and transmit them to the first control module;

[0009] The first control module is configured to: control the first switch to open when the output electrical parameters meet the preset fault conditions and continue for a preset duration; the preset duration is longer than the response time of the power converter to a DC-side branch fault.

[0010] In one possible implementation, the output terminal electrical parameter is the output terminal current, and the preset fault condition is: the output terminal current is reversed or greater than the preset current;

[0011] Alternatively, the output terminal electrical parameter is the output terminal voltage, and the preset fault condition is: the output terminal voltage is less than the preset voltage;

[0012] Alternatively, the output terminal electrical parameters include: output terminal current and output terminal voltage; the preset fault conditions include at least one of the following: the output terminal current is reversed or greater than the preset current, and the output terminal voltage is less than the preset voltage.

[0013] In one possible implementation, the first control module is also communicatively connected to the power converter, and the first control module is further configured to control the first switch to disconnect upon receiving a disconnection command sent by the power converter.

[0014] In one possible implementation, the first switch is a trip switch.

[0015] In one possible implementation, the DC transmission device further includes: a delayed power supply module;

[0016] The delayed power supply module is configured to provide power to the first control module; the power supply duration of the power supply meets the power supply requirements of the first control module for controlling the first switch to disconnect.

[0017] A second aspect of this disclosure provides a power conversion system, comprising: a power converter and at least one DC transmission device; the DC transmission device comprising: a power transmission circuit, a first switch, a first detection module, and a first control module; wherein...

[0018] The first side of the first switch serves as the input terminal of the DC transmission device, and the input terminal of the DC transmission device is used to connect at least one DC power supply.

[0019] The second side of the first switch is connected to the first side of the power transmission circuit;

[0020] The second side of the power transmission circuit serves as the output terminal of the DC transmission device, and the output terminal of the DC transmission device is connected to the corresponding DC side interface of the power converter via a branch cable.

[0021] The first detection module is configured to: sample the output electrical parameters of the DC transmission device and transmit them to the first control module;

[0022] The first control module is configured to: control the first switch to open when the output electrical parameters meet the preset fault conditions and continue for a preset duration; the preset duration is longer than the response time of the power converter to a DC-side branch fault.

[0023] In one possible implementation, the first control module is also communicatively connected to the power converter, and the first control module is further configured to control the first switch to disconnect upon receiving a disconnection command sent by the power converter.

[0024] In one possible implementation, the power converter includes: a second control module, a second detection module, a DC / AC conversion circuit, and at least one branch switching module; wherein,

[0025] The DC side of the DC / AC conversion circuit is connected to the second terminal of the branch switching module;

[0026] The first end of the branch switching module serves as the DC-side corresponding interface of the power converter.

[0027] The second detection module is configured to detect the branch current or first terminal voltage of each of the branch on / off modules and transmit it to the second control module;

[0028] The second control module is configured to: control the corresponding branch on / off module to disconnect when the presence of the branch current or the first terminal voltage meets the branch fault conditions.

[0029] In one possible implementation, the second control module is further configured to send a disconnection command to the DC transmission equipment connected to the corresponding DC-side interface when the presence of the branch current or the first terminal voltage is detected to meet the branch fault condition.

[0030] In one possible implementation, the branch switching module includes a second switch and a fuse connected in series.

[0031] A third aspect of this disclosure provides a DC-side protection method for a power conversion system, comprising:

[0032] The DC transmission device in the power conversion system acquires the output electrical parameters of the DC transmission device;

[0033] If the output electrical parameters meet the preset fault conditions and remain for a preset duration, the DC transmission device controls the first switch in the DC transmission device to open; the first side of the first switch serves as the input terminal of the DC transmission device, and the second side of the first switch is connected to the power transmission circuit in the DC transmission device; the preset duration is longer than the response time of the power converter connected to the output terminal of the DC transmission device on the DC side of the power conversion system for a DC side branch fault.

[0034] In one possible implementation, the output terminal electrical parameter is the output terminal current, and the preset fault condition is: the output terminal current is reversed or greater than the preset current;

[0035] Alternatively, the output terminal electrical parameter is the output terminal voltage, and the preset fault condition is: the output terminal voltage is less than the preset voltage;

[0036] Alternatively, the output terminal electrical parameters include: output terminal current and output terminal voltage; the preset fault conditions include at least one of the following: the output terminal current is reversed or greater than the preset current, and the output terminal voltage is less than the preset voltage.

[0037] In one possible implementation, the DC-side protection method further includes:

[0038] The power converter detects the branch current or first terminal voltage of each internal branch switching module; the first terminal of the branch switching module serves as the DC-side corresponding interface of the power converter, and the second terminal of the branch switching module is connected to the DC-side of the internal DC / AC conversion circuit of the power converter.

[0039] If the branch current or the first terminal voltage meets the branch fault condition, the power converter controls the corresponding branch on / off module to disconnect.

[0040] In one possible implementation, the DC-side protection method further includes:

[0041] If the branch current or the first terminal voltage meets the branch fault condition, the power converter sends a disconnection command to the DC transmission device connected to the corresponding DC side interface.

[0042] The DC transmission device controls the first switch to open according to the cut-off command.

[0043] This disclosure provides a controller for performing a DC-side protection method for a power conversion system as described in the third aspect or any implementation thereof.

[0044] The DC transmission device provided in this disclosure samples the output electrical parameters of the DC transmission device through a first detection module and transmits them to a first control module for judgment. If the output electrical parameters meet a preset fault condition and remain at that condition for a preset duration, the first control module controls a first switch to open. This preset duration is longer than the response time of the power converter to a DC-side branch fault. That is, after the output electrical parameters of the DC transmission device meet the preset fault condition, and after the power converter's response time to the DC-side branch fault has elapsed, if the output electrical parameters still meet the preset fault condition, it indicates that the power converter's response has failed to cut off the fault current path of the DC transmission device. The DC transmission device needs to disconnect all connected photovoltaic strings; therefore, the fault current path is cut off by controlling the first switch to open. If, before the preset duration ends, the output electrical parameters of the DC transmission device no longer meet the preset fault condition, it indicates that the power converter's response has successfully cut off the faulty branch, and the DC transmission device can continue to operate. This enables accurate identification and isolation of faulty branches, improving the system's power generation efficiency and operational continuity. Attached Figure Description

[0045] The features, advantages, and aspects of the embodiments of this disclosure will become more apparent from the accompanying drawings and the following detailed description. Throughout the drawings, the same or similar reference numerals denote the same or similar elements. It should be understood that the drawings are schematic, and elements and actual parts are not necessarily drawn to scale.

[0046] Figure 1 A schematic diagram of the structure of the power conversion system provided in the embodiments of this disclosure and its state in a no-communication scenario;

[0047] Figure 2 A schematic diagram illustrating the structure of the power conversion system provided in this embodiment of the disclosure and its state in a communication scenario;

[0048] Figure 3 Another structure of the power conversion system provided in this disclosure and a schematic diagram of its state in a communication scenario;

[0049] Figure 4 A first flowchart of a DC-side protection method for a power conversion system provided in an embodiment of this disclosure;

[0050] Figure 5 A second flowchart of a DC-side protection method for a power conversion system provided in this disclosure embodiment;

[0051] Figure 6 A third flowchart of a DC-side protection method for a power conversion system provided in an embodiment of this disclosure. Detailed Implementation

[0052] The embodiments of this disclosure are described below with reference to the accompanying drawings. The terminology used in the Description of Embodiments section of this disclosure is for illustrative purposes only and is not intended to limit the scope of this disclosure.

[0053] The embodiments of this disclosure are described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this disclosure, and not all of them. Based on the embodiments of this disclosure, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this disclosure. Those skilled in the art will understand that with the development of technology and the emergence of new scenarios, the technical solutions provided by the embodiments of this disclosure are also applicable to similar technical problems.

[0054] The terms “first,” “second,” etc., used in this disclosure are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such terms are interchangeable where appropriate; this is merely a way of distinguishing objects with the same attributes in the description of embodiments of this disclosure. Furthermore, the terms “comprising” and “having,” and any variations thereof, are intended to cover non-exclusive inclusion, so that a process, method, system, product, or apparatus that comprises a series of units is not necessarily limited to those units, but may include other units not expressly listed or inherent to those processes, methods, products, or apparatuses.

[0055] In power conversion systems, DC-side protection mechanisms primarily rely on the power converter's monitoring of input voltage, current, and other parameters to identify abnormal conditions such as short circuits or overcurrents. Taking a distributed power conversion system as an example, a short circuit or other fault in any of the upstream DC transmission devices or its branch cable connecting to the downstream power converter may trigger all DC transmission devices to disconnect their internal input-side trip switches, causing all DC transmission devices to stop operating. Furthermore, the automatic control of these trip switches can only disconnect; their reclosing requires manual intervention to restart, impacting the overall system's power generation efficiency and operational continuity. In addition, some power conversion systems lack reliable communication connections between the DC transmission devices and the power converter; in scenarios without communication support, the system's fault response capability is further limited.

[0056] In other words, related technologies have significant technical problems in fault location, isolation, and recovery on the DC side, especially in scenarios without communication support, lacking an efficient protection mechanism that can both ensure system safety and maintain normal operation. This technical bottleneck limits the adaptability and reliability of power conversion systems in complex operating environments. Therefore, this disclosure provides a DC transmission device to achieve accurate identification and isolation of faulty branches. The specific solution is as follows:

[0057] Figure 1 The first DC transmission device 10 is shown as an example. This DC transmission device 10 includes: a power transmission circuit 101, a first switch QS0, a first detection module 102, and a first control module 100; wherein:

[0058] The first side of the first switch QS0 serves as the input terminal of the DC transmission device 10. The input terminal of the DC transmission device 10 is used to connect at least one DC power source. In practical applications, the input terminal of the DC transmission device 10 can connect to two or more DC power sources; this is not limited here and depends on the specific application environment. The DC power source can be a photovoltaic string or a battery cluster. A photovoltaic string includes one photovoltaic module or at least two photovoltaic modules connected in series, and a battery cluster includes one battery pack or at least two battery packs connected in series.

[0059] The second side of the first switch QS0 is connected to the first side of the power transmission circuit 101, and the second side of the power transmission circuit 101 is connected to the output terminal of the DC transmission device 10. The output terminal of the DC transmission device 10 is used to connect to the corresponding DC-side interface of the power converter 20. Specifically, the output terminal of the DC transmission device 10 can be connected to the corresponding DC-side interface of the power converter 20 through a branch cable.

[0060] In practical applications, the power transmission circuit 101 can be a DC / DC converter circuit. For example, when the DC power source is a photovoltaic string, the power transmission circuit 101 can be a unidirectional DC / DC converter circuit, and the DC transmission device 10 is an intelligent combiner box that can realize the MPPT (Maximum Power Point Tracking) function for each connected photovoltaic string. When the DC power source is a photovoltaic string, the power transmission circuit 101 can be a bidirectional DC / DC converter circuit to realize bidirectional conversion of electrical energy. The specific topology of the power transmission circuit 101 can be determined according to the actual application environment and is not limited here. Figure 1 In this system, each DC transmission device 10 and the power converter 20 together constitute a distributed power conversion system. In practical applications, Figure 1 The devices shown can also be integrated into the same device, such as a string power converter.

[0061] The first detection module 102 is configured to sample the output electrical parameters of the DC transmission device 10 and transmit them to the first control module 100. The output electrical parameters may refer to at least one of the output voltage and output current, which is not limited here. For details, please refer to the following description.

[0062] The first control module 100 is configured to: control the first switch QS0 to open when the output electrical parameters meet the preset fault conditions and are maintained for a preset duration; the preset duration is longer than the response time of the power converter 20 to a DC-side branch fault.

[0063] In practical applications, the power conversion system may include a power converter 20 and multiple DC transmission devices 10 connected to its DC side; each DC transmission device 10 has an independent first switch QS0, which can be driven by an internal first control module 100 and has a fast response capability.

[0064] Furthermore, the first detection module 102 and the first control module 100 built into the DC transmission equipment 10 can respond to abnormal conditions on itself and the connected branch cables. Specifically, when the first control module 100 detects an abnormality through the first detection module 102, it will initiate a tripping judgment process.

[0065] In this process, the first control module 100 first sets a delay time, namely the aforementioned preset duration, which is longer than the response time of the power converter 20 to a DC-side branch fault. That is, after detecting a DC-side branch fault, the power converter 20 executes the corresponding second switch (such as...). Figure 1 The time required for the disconnection operation of QS1, QS2, or QS3 (as shown). For example, if the response time of the power converter 20 to a DC-side branch fault is approximately 500 milliseconds, the preset duration of the DC transmission device 10 can be set to 600 to 1000 milliseconds; this depends on the specific application environment and is not limited here.

[0066] During this delay, the first control module 100 of each DC transmission device 10 continuously monitors whether the power converter 20 has performed a disconnection operation on the faulty branch. Specifically, this can be achieved by judging whether the corresponding output electrical parameters still meet the preset fault conditions.

[0067] by Figure 1Taking the illustrated scenario as an example, suppose the branch cable connecting the first DC transmission device 10 to the power converter 20 fails. At this time, other DC transmission devices 10 respectively send reverse current to the fault location through the parallel connection points of the branch switching modules 202 in the power converter 20. In this case, the first DC transmission device 10 and its branch cable together constitute the fault branch. The output current of the DC transmission device 10 in this fault branch is excessive, for example, greater than the preset current under normal conditions, which can be determined as meeting the preset fault conditions. At this time, the current on the branch cable to the right of the fault location reverses, and the current on the corresponding branch switching module 202 also reverses. Other DC transmission devices 10 and their branch cables are respectively considered as non-faulty branches. For example, the second DC transmission device 10 and its branch cables are considered as a non-faulty branch, the third DC transmission device 10 and its branch cables are also considered as a non-faulty branch, and so on. At this time, although these branches are all non-faulty branches, because they backflow current to the fault location, the output current of the corresponding DC transmission device 10 in these non-faulty branches is also too large, for example, greater than the preset current under normal conditions, and can also be judged as meeting the preset fault conditions. At the same time, the current on the branch cables in these non-faulty branches and the current on the connected branch switching module 202 are also too large.

[0068] If the DC transmission device 10 detects that the power converter 20 has successfully disconnected the faulty branch before the preset time expires, for example, if the DC transmission device 10 in the non-faulty branch detects that its output current is no longer greater than the preset current under normal conditions, but is within the normal range, then its first control module 100 will not control the first switch QS0 to open, thereby preventing the non-faulty branch from being mistakenly disconnected. Specifically, such as... Figure 1 As shown, the second control module 200 in the power converter 20 can disconnect the faulty branch by controlling the second switch QS1 or the fuse FUSE1 in the corresponding branch switching module 202 to disconnect.

[0069] If, at the end of the preset time, the DC transmission device 10 still does not detect a response from the power converter 20, for example, if the DC transmission device 10 in the aforementioned faulty branch detects that its output current is still outside the normal range, it indicates that the corresponding branch switching module 202 in the power converter 20 has failed to cut off the fault current path of the DC transmission device 10. The DC transmission device 10 needs to cut off the fault current path by controlling the first switch QS0 to open. This situation arises because the fault location still affects the DC transmission device 10. For example, if the branch cable connected to the DC transmission device 10 has a short circuit due to insulation problems, even if the corresponding branch switching module 202 in the power converter 20 is disconnected, it only allows the power converter 20 to complete fault isolation, but the DC transmission device 10 has not yet achieved fault isolation. In this case, controlling the first switch QS0 to open can cut off the fault current path and prevent the fault from escalating.

[0070] Through the above process, after the power converter 20 completes the disconnection operation, the non-faulty branch can continue to operate without manual intervention, and the system will automatically restore its operating state to ensure the continuous power generation capacity of the system.

[0071] The DC transmission device 10 provided in this embodiment introduces a tripping mechanism with delay characteristics. Even in scenarios where there is no communication support between the DC transmission device 10 and the power converter 20 (hereinafter referred to as a no-communication scenario), it can achieve accurate identification and isolation of faulty branches and automatic recovery of non-faulty branches through effective delay protection, thereby improving the power generation efficiency and operational continuity of the system.

[0072] In practical applications, the output electrical parameters of the aforementioned DC transmission equipment can refer to at least one of output current and output voltage. For example, if the output electrical parameter is output current, then the output current being reversed or greater than a preset current can be determined as meeting the preset fault condition. Alternatively, if the output electrical parameter is output voltage, then the output voltage being less than a preset voltage can be determined as meeting the preset fault condition. Or, if the output electrical parameter includes both output current and output voltage, then meeting at least one of the following conditions—output current being reversed or greater than a preset current, and output voltage being less than a preset voltage—can be determined as meeting the preset fault condition.

[0073] The specific settings of the output terminal electrical parameters are not limited, as long as the preset fault conditions can characterize abnormal conditions such as short circuit, insulation, reverse connection, and loose connection. For details, please refer to relevant technologies, which will not be elaborated here.

[0074] The DC transmission device provided in the above embodiments can realize the isolation of faulty branches and the automatic recovery of non-faulty branches in the absence of communication; while in the scenario where there is communication support between the DC transmission device and the power converter (hereinafter referred to as the communication scenario), the power converter can also directly control the DC transmission device to cut off the fault current path through communication.

[0075] Therefore, this embodiment provides another DC transmission device, based on the above embodiments, such as... Figure 2 As shown, its first control module 100 is also communicatively connected to the power converter 20, and the first control module 100 is also configured to control the first switch QS0 to open when it receives a cut-off command sent by the power converter 20.

[0076] Specifically, in scenarios involving communication:

[0077] The power converter 20 and the DC transmission device 10 communicate via a communication bus, such as RS485 or a PLC (Power Line Carrier). When the power converter 20 detects an abnormality in the current or voltage of a DC input, its internal second control module 200 can determine the specific location of the fault. Once the specific faulty branch is identified, the power converter 20 sends a disconnection command to the corresponding DC transmission device 10, such as a command to trip the corresponding first switch QS0. Upon receiving the disconnection command, the first switch QS0 of the DC transmission device 10 immediately activates, disconnecting the DC input and preventing the fault from escalating. Simultaneously, the power converter 20 can upload the fault information to the monitoring system for further processing by maintenance personnel. During this process, non-faulty branches can continue to operate normally without affecting the overall power generation capacity of the system.

[0078] like Figure 2 As shown, it is also assumed that the branch cable connecting the first DC transmission device 10 to the power converter 20 is faulty. For the power converter 20, the current flow direction of the faulty branch is different from that of the non-faulty branch, which can be used to determine the faulty branch. That is, the current of the faulty branch flows from the power converter 20 to the DC transmission device 10. After transmitting the cut-off command to the first control module 100 of the first DC transmission device 10 through communication, the first switch QS0 is controlled to open. At the same time, the second switch QS1 or the fuse FUSE1 in the corresponding branch on / off module 202 in the power converter 20 is also disconnected.

[0079] In other words, in a communication scenario, this embodiment uses the power converter 20 to accurately identify the faulty branch and disconnect the specific DC transmission device 10 via a disconnect command. In a non-communication scenario, a tripping mechanism with reasonable delay characteristics is introduced to ensure that only the faulty branch is disconnected, while non-faulty branches automatically resume normal operation after the power converter 20 completes the disconnection operation. Regardless of the scenario, only the faulty branch can be disconnected, allowing other DC transmission devices 10 to continue operating.

[0080] Furthermore, regardless of the scenario, this embodiment can achieve a multi-level protection mechanism based on the coordinated operation of the DC transmission device 10 and the power converter 20: First, multiple branch switching modules 202 are set on the DC side of the power converter 20, with the second switch (such as...) among them... Figure 1 (as shown in QS1, QS2, or QS3) or fuses (such as Figure 1 The FUSE1, FUSE2, or FUSE3 shown in the diagram implements the first level of fast protection, while the aforementioned communication or time-delay tripping mechanism is set in the DC transmission equipment 10 to implement the second level of precise protection. This multi-level protection mechanism can provide more comprehensive protection capabilities under different fault scenarios.

[0081] Based on the above embodiments, such as Figure 3 (in) Figure 2 As shown in the example (based on the structure shown), the DC transmission device 10 may further include: a delayed power supply module 103; the delayed power supply module 103 is configured to provide power to the first control module 100; the power supply duration of the power supply meets the power supply requirements of the first control module 100 for controlling the first switch QS0 to disconnect.

[0082] That is, the first control module 100 can draw power from the power supply, and the power supply capacity of the power supply is sufficient to support the first control module 100 to disconnect the first switch QS0 when it detects that the output electrical parameters meet the preset fault conditions and continue for a preset time, so as to ensure that the fault protection can be completed.

[0083] In practical applications, the first control module 100 can also draw power from any side of the power transmission circuit 101, such as from the first side of the power transmission circuit 101. In the event of a fault in the DC transmission device 10 or its connected branch cable, disconnecting the first switch QS0 will cause the first control module 100 to lose power. Therefore, this power supply can provide backup power so that the first control module 100 can continue to operate after the first switch QS0 is disconnected.

[0084] Furthermore, this embodiment does not limit the specific implementation of the first switch QS0. For example, it can be a trip switch, which may include a trip unit and a linkage switch, etc. For details, please refer to relevant technologies, which will not be elaborated here. Specifically, the trip unit can be an electromagnetic trip unit, an electronic trip unit, or a thermomagnetic trip unit, etc., which is not limited here, as long as the first switch QS0 can have the function of disconnection, and can be configured according to the actual application scenario.

[0085] Another embodiment of this disclosure also provides a power conversion system, such as Figures 1 to 3 As shown, it includes: a power converter 20 and at least one DC transmission device 10; the DC transmission device 10 includes: a power transmission circuit 101, a first switch QS0, a first detection module 102, and a first control module 100; wherein:

[0086] The first side of the first switch QS0 serves as the input terminal of the DC transmission device 10, which is used to connect at least one DC power source. The DC power source can be a photovoltaic string or a battery cluster, which is not limited here.

[0087] The second side of the first switch QS0 is connected to the first side of the power transmission circuit 101; the second side of the power transmission circuit 101 serves as the output terminal of the DC transmission device 10, and the output terminal of the DC transmission device 10 is connected to the corresponding DC side interface of the power converter 20 via a branch cable.

[0088] The first detection module 102 is configured to sample the output electrical parameters of the DC transmission device 10 and transmit them to the first control module 100; the first control module 100 is configured to control the first switch QS0 to open when the output electrical parameters meet the preset fault conditions and continue for a preset duration; the preset duration is longer than the response time of the power converter 20 to the DC side branch fault.

[0089] The other structures and working principles of the junction box 10 can be found in the above embodiments, and will not be repeated here.

[0090] The power conversion system provided in this embodiment introduces a tripping mechanism with delay characteristics in the DC transmission device 10. Even in the absence of communication, it can achieve accurate identification and isolation of faulty branches and automatic recovery of non-faulty branches through effective delay protection, thereby improving the power generation efficiency and operational continuity of the system.

[0091] In practical applications, the first control module 100 can also be communicatively connected to the power converter 20. The first control module 100 is further configured to control the first switch QS0 to open upon receiving a disconnection command from the power converter 20. Therefore, in communication scenarios, the power converter 20 can accurately identify faulty branches and disconnect specific DC transmission devices 10 via disconnection commands, allowing other DC transmission devices 10 to continue operating.

[0092] Based on the above embodiments, such as Figures 1 to 3 As shown, the power converter 20 in the power conversion system includes: a second control module 200, a second detection module 203, a DC / AC conversion circuit 201, and at least one branch switching module 202; wherein:

[0093] The AC side of the DC / AC conversion circuit 201 serves as the AC side of the power converter 20. In practical applications, a corresponding AC switch QSac can also be installed between the two. The DC side of the DC / AC conversion circuit 201 is connected to the second end of the branch switching module 202, and the first end of the branch switching module 202 serves as the corresponding DC side interface of the power converter 20.

[0094] In practical applications, the branch circuit switching module 202 may include a second switch and a fuse connected in series, such as... Figure 1 or Figure 2 As shown, the first branch switching module 202 includes a second switch QS1 and a fuse FUSE1 connected in series, the second branch switching module 202 includes a second switch QS2 and a fuse FUSE2 connected in series, and the third branch switching module 202 includes a second switch QS3 and a fuse FUSE3 connected in series. The situation is similar when the power converter 20 has more DC-side interfaces, and will not be described in detail.

[0095] The second detection module 203 is configured to detect the branch current or first terminal voltage of each branch switching module 202 and transmit it to the second control module 200. The second control module 200 is configured to control the corresponding branch switching module 202 to disconnect when it detects that the branch current or first terminal voltage meets the branch fault condition. When the second detection module 203 detects the branch current of each branch switching module 202, if the branch current is reversed or greater than a preset current, it can be determined that the branch fault condition is met. When the second detection module 203 detects the first terminal voltage of each branch switching module 202, if the first terminal voltage is less than a preset voltage, it can be determined that the branch fault condition is met. When the second detection module 203 detects the branch current and first terminal voltage of each branch switching module 202, if the branch current is reversed or greater than a preset current, and / or the first terminal voltage is less than a preset voltage, it can be determined that the branch fault condition is met. The specific values ​​of the preset current and preset voltage are not limited and can be found in related technologies, which will not be elaborated here.

[0096] In both communication-free and communication-enabled scenarios, the power converter 20 can identify faulty branches using any of the methods described above. Combined with the delayed tripping mechanism of the DC transmission equipment 10 in communication-free scenarios, multi-level protection can be achieved in such scenarios.

[0097] Furthermore, in communication scenarios, the second control module 200 is also configured to send a disconnection command to the DC transmission equipment 10 connected to the corresponding DC-side interface when a branch current or the first terminal voltage is detected to meet the branch fault conditions. This enables multi-level protection in communication scenarios.

[0098] In other words, regardless of the scenario, this embodiment can achieve a multi-level protection mechanism based on the coordinated operation of the DC transmission device 10 and the power converter 20: First, multiple branch switching modules 202 are set on the DC side of the power converter 20, and the second switch or fuse among them achieves the first level of fast protection. Meanwhile, the aforementioned communication or time-delay tripping mechanism is set in the DC transmission device 10 to achieve the second level of precise protection. This multi-level protection mechanism can provide more comprehensive protection capabilities under different fault scenarios.

[0099] Furthermore, in related technologies, power restoration typically requires manual intervention or a lengthy restart process after a short-circuit fault. However, in this embodiment, after the power converter 20 completes the disconnection operation, the DC transmission equipment 10 in the non-faulty branch can automatically return to normal operation without external commands or manual reset. This automatic recovery mechanism not only improves system availability but also significantly reduces operation and maintenance costs and system downtime.

[0100] This embodiment also provides another method for DC-side protection of a power conversion system, such as... Figure 4 As shown, it includes:

[0101] S11. The DC transmission equipment in the power conversion system acquires the output electrical parameters of the DC transmission equipment.

[0102] As mentioned earlier, the output terminal electrical parameters can refer to at least one of the output terminal voltage and output terminal current. This is not limited here and depends on the specific application environment.

[0103] If the output electrical parameters meet the preset fault conditions and remain for the preset duration, then execute S12.

[0104] S12, The first switch in the DC transmission equipment is turned off.

[0105] Specifically, if the output terminal electrical parameter is the output terminal current, then the preset fault condition is: the output terminal current is reversed or greater than the preset current; if the output terminal electrical parameter is the output terminal voltage, then the preset fault condition is: the output terminal voltage is less than the preset voltage; if the output terminal electrical parameter includes both the output terminal current and the output terminal voltage, then the preset fault condition includes: the output terminal current is reversed or greater than the preset current, and / or, the output terminal voltage is less than the preset voltage.

[0106] The preset duration is longer than the response time of the power converter in the power conversion system to a DC-side branch fault.

[0107] The structure and working principle of the DC transmission device can be found in the above embodiments, and will not be repeated here.

[0108] The DC-side protection method for the power conversion system provided in this embodiment introduces a tripping mechanism with delay characteristics into the DC transmission equipment. Even in the absence of communication, it can achieve accurate identification and isolation of faulty branches and automatic recovery of non-faulty branches through effective delay protection, thereby improving the power generation efficiency and operational continuity of the system.

[0109] Based on the above embodiments, the DC-side protection method may further include Figure 5 As shown:

[0110] S01, The power converter detects the branch current or first terminal voltage of each branch switching module inside.

[0111] As mentioned above, the first end of the branch switching module serves as the DC-side corresponding interface of the power converter, and the second end of the branch switching module is connected to the DC-side of the DC / AC conversion circuit inside the power converter. The structure and working principle of the power converter can be found in the above embodiments, and will not be repeated here.

[0112] If a branch current or the first terminal voltage meets the branch fault condition, then execute S02.

[0113] S02, the power converter controls the corresponding branch on / off module to disconnect.

[0114] As mentioned earlier, the first level of rapid protection can be achieved by disconnecting the second switch or fuse of the corresponding branch switching module in the power converter; then, the second level of precise protection is achieved by the time-delay tripping mechanism of the aforementioned DC transmission equipment. This multi-level protection mechanism can provide more comprehensive protection capabilities under different fault scenarios.

[0115] In addition, this DC-side protection method may also include Figure 6 As shown:

[0116] If a branch current or the first terminal voltage meets the branch fault condition, then execute S03.

[0117] S03. The power converter sends a disconnect command to the DC transmission equipment connected to the corresponding DC side interface.

[0118] This allows the corresponding DC transmission equipment to directly control the first switch to disconnect according to the disconnection command, thus achieving a second level of precise protection in communication scenarios.

[0119] The DC-side protection method provided in this embodiment, in scenarios without communication, can introduce a reasonably configured time-delay tripping mechanism into the DC transmission equipment. This ensures that the fault current path is disconnected only when the power converter fails to disconnect it, while non-faulty branches have automatic recovery capabilities, thus improving the system's operational continuity. In scenarios with communication, the faulty branch can be accurately located and isolated directly through communication.

[0120] In other words, this embodiment employs different protection strategies in scenarios with and without communication to ensure that only the faulty branch is isolated when a fault occurs on the DC side, thereby minimizing the impact on the overall system power generation efficiency.

[0121] Moreover, this embodiment can achieve multi-level protection mechanisms in both scenarios, and has significant advantages in terms of fault isolation accuracy, system operating efficiency and protection mechanism adaptability.

[0122] Based on the above embodiments, this embodiment provides a controller for executing the DC-side protection method of the power conversion system as described in any of the above embodiments. The specific process and principle of this DC-side protection method can be found in the above embodiments, and will not be repeated here.

[0123] The controller provided in this disclosure may include software to implement the DC-side protection method for the power conversion system described above. Alternatively, the controller provided in this disclosure may include hardware to implement the DC-side protection method for the power conversion system described above. Or, the controller provided in this disclosure may include both software and hardware, using a combination of software and hardware to execute the DC-side protection method for the power conversion system described above.

[0124] In practical applications, the controller can specifically be the first control module inside the DC transmission equipment in the power conversion system described in the above embodiments, to realize the detection and response on the DC transmission equipment side in the above embodiments. Alternatively, the controller can also be a controller independent of the DC transmission equipment, such as a system controller; or, the controller can also be a control board in a string power converter; in both cases, the controller is equivalent to including the first control module and the second control module described in the above embodiments, to realize the detection and response on the DC transmission equipment side and the power converter side in the above embodiments; it depends on the specific application environment, and all are within the protection scope of this disclosure.

[0125] The controller provided in this embodiment, in scenarios without communication, can introduce a reasonably configured delayed tripping mechanism into the DC transmission equipment. This ensures that the fault current path is disconnected only when the power converter fails to disconnect it, while non-faulty branches have automatic recovery capabilities, thus improving system operational continuity. In scenarios with communication, the faulty branch can be accurately located and isolated directly through communication. In both scenarios, it ensures that only the faulty branch is isolated when a fault occurs on the DC side, thereby minimizing the impact on the overall system power generation efficiency. Moreover, this embodiment can implement multi-level protection mechanisms in both scenarios, exhibiting significant advantages in fault isolation accuracy, system operating efficiency, and adaptability of protection mechanisms.

[0126] Similar or identical parts between the various embodiments in this disclosure can be referred to mutually. Each embodiment focuses on describing the differences from other embodiments. In particular, for system or system embodiments, since they are basically similar to method embodiments, the description is relatively simple, and relevant parts can be referred to the description of the method embodiments. The systems and system embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units, that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of this embodiment solution according to actual needs. Those skilled in the art can understand and implement this without creative effort.

[0127] Those skilled in the art will also recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of both. To clearly illustrate the interchangeability of hardware and software, the components and steps of the various examples have been generally described in terms of functionality in the foregoing description. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this disclosure.

[0128] The above description of the disclosed embodiments shows that the features described in the various embodiments of this disclosure can be substituted for or combined with each other, enabling those skilled in the art to implement or use this disclosure. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of this disclosure. Therefore, this disclosure is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A DC transmission device, applied in a power conversion system, characterized in that, include: The power transmission circuit, the first switch, the first detection module, and the first control module; wherein, The first side of the first switch serves as the input terminal of the DC transmission device, and the input terminal of the DC transmission device is used to connect at least one DC power supply. The second side of the first switch is connected to the first side of the power transmission circuit; The second side of the power transmission circuit serves as the output terminal of the DC transmission device, and the output terminal of the DC transmission device is used to connect to the corresponding DC-side interface of the power converter in the power conversion system. The first detection module is configured to: sample the output electrical parameters of the DC transmission device and transmit them to the first control module; The first control module is configured to: control the first switch to open when the output electrical parameters meet the preset fault conditions and continue for a preset duration; the preset duration is longer than the response time of the power converter to a DC-side branch fault.

2. The DC transmission device according to claim 1, characterized in that, The output terminal electrical parameter is the output terminal current, and the preset fault condition is: the output terminal current is reversed or greater than the preset current. Alternatively, the output terminal electrical parameter is the output terminal voltage, and the preset fault condition is: the output terminal voltage is less than the preset voltage; Alternatively, the output electrical parameters may include: output current and output voltage; The preset fault conditions include at least one of the following: the output current is reversed or greater than the preset current, and the output voltage is less than the preset voltage.

3. The DC transmission device according to claim 1, characterized in that, The first control module is also communicatively connected to the power converter, and the first control module is further configured to control the first switch to open upon receiving a cut-off command sent by the power converter.

4. The DC transmission device according to any one of claims 1 to 3, characterized in that, The first switch is a trip switch.

5. The DC transmission device according to any one of claims 1 to 3, characterized in that, The DC transmission device further includes: a delayed power supply module; The delayed power supply module is configured to provide power to the first control module; the power supply duration of the power supply meets the power supply requirements of the first control module for controlling the first switch to disconnect.

6. A power conversion system, characterized in that, include: A power converter and at least one DC transmission device; The DC transmission device includes: a power transmission circuit, a first switch, a first detection module, and a first control module; wherein... The first side of the first switch serves as the input terminal of the DC transmission device, and the input terminal of the DC transmission device is used to connect at least one DC power supply. The second side of the first switch is connected to the first side of the power transmission circuit; The second side of the power transmission circuit serves as the output terminal of the DC transmission device, and the output terminal of the DC transmission device is connected to the corresponding DC side interface of the power converter via a branch cable. The first detection module is configured to: sample the output electrical parameters of the DC transmission device and transmit them to the first control module; The first control module is configured to: control the first switch to open when the output electrical parameters meet the preset fault conditions and continue for a preset duration; the preset duration is longer than the response time of the power converter to a DC-side branch fault.

7. The power conversion system according to claim 6, characterized in that, The first control module is also communicatively connected to the power converter, and the first control module is further configured to control the first switch to open upon receiving a cut-off command sent by the power converter.

8. The power conversion system according to claim 6, characterized in that, The power converter includes: a second control module, a second detection module, a DC / AC conversion circuit, and at least one branch on / off module; wherein... The DC side of the DC / AC conversion circuit is connected to the second terminal of the branch switching module; The first end of the branch switching module serves as the DC-side corresponding interface of the power converter. The second detection module is configured to detect the branch current or first terminal voltage of each of the branch on / off modules and transmit it to the second control module; The second control module is configured to: control the corresponding branch on / off module to disconnect when the presence of the branch current or the first terminal voltage meets the branch fault conditions.

9. The power conversion system according to claim 8, characterized in that, The second control module is further configured to send a disconnection command to the DC transmission equipment connected to the corresponding DC side interface when the presence of the branch current or the first terminal voltage is detected to meet the branch fault conditions.

10. The power conversion system according to claim 8, characterized in that, The branch circuit switching module includes a second switch and a fuse connected in series.

11. A DC-side protection method for a power conversion system, characterized in that, include: The DC transmission device in the power conversion system acquires the output electrical parameters of the DC transmission device; If the output electrical parameters meet the preset fault conditions and remain for a preset duration, the DC transmission device controls the first switch in the DC transmission device to open; the first side of the first switch serves as the input terminal of the DC transmission device, and the second side of the first switch is connected to the power transmission circuit in the DC transmission device; the preset duration is greater than the response time of the power converter connected to the output terminal of the DC transmission device on the DC side of the power conversion system for a DC side branch fault.

12. The DC-side protection method for a power conversion system according to claim 11, characterized in that, The output terminal electrical parameter is the output terminal current, and the preset fault condition is: the output terminal current is reversed or greater than the preset current. Alternatively, the output terminal electrical parameter is the output terminal voltage, and the preset fault condition is: the output terminal voltage is less than the preset voltage; Alternatively, the output electrical parameters may include: output current and output voltage; The preset fault conditions include at least one of the following: the output current is reversed or greater than the preset current, and the output voltage is less than the preset voltage.

13. The DC-side protection method for a power conversion system according to claim 11 or 12, characterized in that, The DC-side protection method further includes: The power converter detects the branch current or first terminal voltage of each internal branch switching module; the first terminal of the branch switching module serves as the DC-side corresponding interface of the power converter, and the second terminal of the branch switching module is connected to the DC-side of the internal DC / AC conversion circuit of the power converter. If the branch current or the first terminal voltage meets the branch fault condition, the power converter controls the corresponding branch on / off module to disconnect.

14. The DC-side protection method for a power conversion system according to claim 13, characterized in that, The DC-side protection method further includes: If the branch current or the first terminal voltage meets the branch fault condition, the power converter sends a disconnection command to the DC transmission device connected to the corresponding DC side interface. The DC transmission device controls the first switch to open according to the cut-off command.

15. A controller, characterized in that, A method for implementing DC-side protection of a power conversion system as described in any one of claims 11 to 14.

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