An ac-dc hybrid power grid system and a method for operating the same

Abstract

This disclosure relates to an AC / DC power grid system and its operation method. The AC / DC power grid system includes an AC power grid circuit and a DC power grid circuit. The AC power grid circuit is used to supply power to multiple AC zones; the DC power grid circuit includes a DC converter and multiple AC / DC converters; the input terminal of the DC converter is connected to at least one first DC bus; when at least one AC zone has insufficient power, the DC power grid circuit is used to receive the supply voltage provided by at least one first DC bus to supply power to the corresponding AC zone. When an AC zone faces a severe power shortage, the AC zone can directly draw power from the first DC bus through the DC power grid circuit. Furthermore, the DC power grid circuit provided in this disclosure does not require a large area of ​​land resources, thus achieving a low-cost solution to the problem of insufficient power supply capacity of AC zones during peak load periods.

Description

Technical Field

[0001] This disclosure relates to the field of power electronics technology, and in particular to an AC / DC power grid system and its operation method. Background Technology

[0002] In the current power system architecture, high-voltage direct current (HVDC) transmission is typically the main method for long-distance power transmission. The receiving end of an HVDC transmission system is generally connected to the local AC substation through a single converter station. However, as the load carried by the receiving-end AC substation continues to expand, the power supply capacity of the local AC substation is becoming increasingly strained, leading to a severe shortage of power supply capacity in the receiving-end power grid during peak load periods. Summary of the Invention

[0003] To solve the above-mentioned technical problems, or at least partially solve them, this disclosure provides an AC / DC power grid system and its operation method. When the AC zone faces a serious shortage of power supply capacity, the AC zone can directly draw power from the first DC bus through the DC power grid circuit. Furthermore, the DC power grid circuit set in this disclosure does not require a large area of ​​land resources, thus enabling a low-cost solution to the problem of insufficient power supply capacity of the AC zone during peak load periods.

[0004] This disclosure provides an AC / DC power grid system, which includes: an AC power grid circuit and a DC power grid circuit; The AC mains circuit is connected to multiple AC zones, and the AC mains circuit is used to supply power to the multiple AC zones. The DC grid circuit includes a DC converter and multiple AC-DC converters; the input terminal of the DC converter is connected to at least one first DC bus, the output terminal of the DC converter is connected to the DC side of multiple AC-DC converters, and the AC side of the multiple AC-DC converters is respectively connected to the corresponding AC zone. In the event of insufficient power in at least one AC zone, the DC grid circuit is used to receive the power supply voltage provided by at least one first DC bus to supply power to the corresponding AC zone.

[0005] Optionally, the DC grid circuit may also include a power collection node; Power aggregation nodes include energy storage devices and control circuits; The control circuit is connected to the energy storage device, which is connected to the output of the DC-DC converter and the DC side of multiple AC-DC converters. The energy storage device is used to store at least the supply voltage provided by the DC-DC converter; the control circuit is used to control the energy storage device to distribute the stored voltage to multiple AC-DC converters.

[0006] Optionally, the AC-DC converter is a bidirectional converter; The DC side of the AC-DC converter is connected to the energy storage device, and the AC side of the AC-DC converter is connected to the corresponding AC zone. An AC-DC converter is used to convert DC power supplied by an energy storage device into AC power, or to convert AC power supplied by an AC zone into DC power.

[0007] Optionally, the DC grid circuit may also include multiple DC circuit breakers; Multiple DC circuit breakers are connected to the input terminal of the DC converter, the output terminal of the DC converter, and the DC side of multiple AC-DC converters, respectively.

[0008] Optionally, the DC grid circuit may also include multiple AC circuit breakers; Multiple AC circuit breakers are connected to the AC side of multiple AC-DC converters.

[0009] This disclosure also provides an operation method for an AC / DC power grid system, which is applicable to any of the AC / DC power grid systems described above. AC / DC power grid systems include DC power grid circuits; DC grid circuits include DC converters and multiple AC-DC converters; The operation methods include: Acquire the first operating state of the DC-DC converter and the second operating states of multiple AC-DC converters; Based on the first operating state and multiple second operating states, the operating modes of the DC-DC converter and multiple AC-DC converters are controlled.

[0010] Optionally, based on a first operating state and multiple second operating states, the operating modes of the DC-DC converter and multiple AC-DC converters are controlled, including: When both the first operating state and the multiple second operating states are in normal operating conditions, the DC converter and one of the multiple AC-DC converters are controlled to operate in a voltage-fixed mode, while the DC converter and the other converters among the multiple AC-DC converters operate in a power-fixed mode.

[0011] Optionally, based on a first operating state and multiple second operating states, the operating modes of the DC-DC converter and multiple AC-DC converters are controlled, including: When at least one of the first operating state and multiple second operating states is an abnormal operating state, the DC-DC converter is controlled to operate in a voltage fixed mode, and multiple AC-DC converters in which all second operating states are normal operating states operate in a power fixed mode. Alternatively, one of the multiple AC-DC converters in which the second operating state is in normal operating state is operated in voltage fixed mode, while the other AC-DC converters in the second operating state and the DC converter are operated in power fixed mode. Alternatively, one of the multiple AC-DC converters in which the second operating state is in normal operating state may operate in a voltage-fixed mode, while the other AC-DC converters in the second operating state may operate in a power-fixed mode.

[0012] Optionally, the DC grid circuit may also include DC circuit breakers and AC circuit breakers; The execution method also includes: If the first operating state is an abnormal operating state, the control will disconnect the DC circuit breaker connected to the DC converter; And / or, if at least one of the multiple second operating states is an abnormal operating state, the control of the DC circuit breaker and the AC circuit breaker connected to the AC-DC converter in the abnormal operating state shall be disconnected.

[0013] Optionally, the DC grid circuit may also include a DC circuit breaker; The execution method also includes: If both the first and second operating states are abnormal operating states, the control will disconnect the DC circuit breaker connected to the DC converter, and the control will also disconnect the DC circuit breaker connected to the AC-DC converter.

[0014] This disclosure provides an AC / DC power grid system and its operation method. The AC / DC power grid system includes an AC power grid circuit and a DC power grid circuit. The AC power grid circuit is connected to multiple AC substations and supplies power to the multiple AC substations. The DC power grid circuit includes a DC-DC converter and multiple AC-DC converters. The input terminal of the DC-DC converter is connected to at least one first DC bus, and the output terminal of the DC-DC converter is connected to the DC side of the multiple AC-DC converters. The AC sides of the multiple AC-DC converters are respectively connected to the corresponding AC substations. When at least one AC substation has insufficient power, the DC power grid circuit receives the supply voltage provided by at least one first DC bus and supplies power to the corresponding AC substation. This disclosure connects the AC power grid circuit to multiple AC substations and the multiple AC-DC converters to the corresponding multiple AC substations. When at least one AC substation has insufficient power, the DC-DC converter draws power from at least one first DC bus and supplies it to the multiple AC-DC converters. The AC-DC converter corresponding to the AC substation with insufficient current converts the DC power supplied by the DC-DC converter into AC power, thereby supplying power to the AC substation with insufficient power. Therefore, when the AC zone faces a serious power supply shortage, this disclosure can directly draw power from the first DC bus through the DC grid circuit. Furthermore, the DC grid circuit set up in this disclosure does not require a large area of ​​land resources, thus enabling a low-cost solution to the problem of insufficient power supply capacity in the AC zone during peak load periods. Attached Figure Description

[0015] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments of this application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 This is a schematic diagram of the structure of an AC / DC power grid system provided in an embodiment of the present disclosure.

[0017] Figure 2 This is a schematic diagram of another AC / DC power grid system provided in the embodiments of this disclosure.

[0018] Figure 3 This is a schematic diagram of another AC / DC power grid system provided in the embodiments of this disclosure.

[0019] Figure 4 This is a schematic diagram of another AC / DC power grid system provided in the embodiments of this disclosure.

[0020] Figure 5 This is a flowchart illustrating an operation method for an AC / DC power grid system provided in an embodiment of the present disclosure. Detailed Implementation

[0021] The features and exemplary embodiments of various aspects of this application will now be described in detail. Numerous specific details are set forth in the following detailed description in order to provide a comprehensive understanding of this application. However, it will be apparent to those skilled in the art that this application can be implemented without some of these specific details. The following description of embodiments is merely intended to provide a better understanding of this application by illustrating examples thereof.

[0022] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The embodiments will now be described in detail with reference to the accompanying drawings.

[0023] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising..." does not exclude the presence of additional identical elements in the process, method, article, or apparatus that includes said element.

[0024] It should be understood that when describing the structure of a component, when referring to a layer or region as being "above" or "on top of" another layer or region, it can mean that it is directly above the other layer or region, or that it contains other layers or regions between it and the other layer or region. Furthermore, if the component is flipped over, that layer or region will be located "below" or "under" the other layer or region.

[0025] It should be understood that the term "and / or" used in this article is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this article generally indicates that the preceding and following related objects have an "or" relationship.

[0026] In the embodiments of this application, the term "electrical connection" can refer to a direct electrical connection between two components, or it can refer to an electrical connection between two components via one or more other components.

[0027] In the embodiments of this application, the first node, the second node, and the third node are defined only for the convenience of describing the circuit structure, and the first node, the second node, and the third node are not actual circuit units.

[0028] Various modifications and variations can be made to this application without departing from its spirit or scope, which will be apparent to those skilled in the art. Therefore, this application is intended to cover modifications and variations falling within the scope of the corresponding claims (the claimed technical solutions) and their equivalents. It should be noted that the implementation methods provided in the embodiments of this application can be combined with each other without contradiction.

[0029] In the current power system architecture, high-voltage direct current (HVDC) transmission is typically the main method for long-distance power transmission. The receiving end of an HVDC transmission system is generally connected to the local AC substation through a single converter station. However, as the load carried by the receiving-end AC substation continues to expand, the power supply capacity of the local AC substation is becoming increasingly strained, leading to a severe shortage of power supply capacity in the receiving-end power grid during peak load periods.

[0030] In related technologies, it is common practice to build new AC substations in areas with high loads, thereby increasing the region's power receiving capacity by increasing the overall capacity of the AC substations. However, since urban load centers are usually located in areas with scarce land resources, building multiple AC substations would require even more land, resulting in extremely high construction costs. Therefore, how to provide a low-cost AC / DC power grid system that can solve the problem of insufficient power supply capacity of the receiving-end grid during peak load periods is a technical problem that urgently needs to be solved by those skilled in the art.

[0031] Therefore, this disclosure provides an AC / DC power grid system and its operation method. This disclosure connects to multiple AC substations via an AC power grid circuit and to the corresponding AC substations via multiple AC / DC converters. When all AC substations have sufficient power, they draw power from the AC power grid circuit. When at least one AC substation has insufficient power, the DC converters draw power from at least one first DC bus and supply it to the multiple AC / DC converters. The AC / DC converter corresponding to the AC substation with insufficient current converts the DC power supplied by the DC converter into AC power, thereby supplying power to the AC substation with insufficient power. Thus, when an AC substation faces a severe power shortage, this disclosure can directly draw power from the first DC bus via the DC converters in the DC power grid circuit and the AC / DC converters. Furthermore, the DC power grid circuit of this disclosure does not require a large area of ​​land, thus achieving a low-cost solution to the problem of insufficient power supply to AC substations during peak load periods.

[0032] The embodiments will now be described in detail with reference to the accompanying drawings.

[0033] Figure 1 This is a schematic diagram of the structure of an AC / DC power grid system provided in an embodiment of the present disclosure, such as... Figure 1 As shown, the AC / DC power grid system includes: AC power grid circuit 10 and DC power grid circuit 20.

[0034] The AC mains circuit 10 is connected to multiple AC zones 31 and is used to supply power to the multiple AC zones 31.

[0035] For example, consider multiple AC substations 31 as medium-voltage distribution areas, such as 10kV or 20kV. The AC grid circuit 10 includes an AC transformer, which is also connected to a high-voltage AC substation, such as a 500kV or 220kV high-voltage power supply area. The AC transformer converts the high-voltage AC power supplied by the high-voltage AC substation into the medium-voltage AC power required by the multiple AC substations 31; that is, the AC grid circuit 10 draws power from the high-voltage AC substation and supplies power to the multiple AC substations 31.

[0036] It should be noted that, Figure 1 Three communication partitions 31 are shown as an example only. The specific number of communication partitions 31 needs to be determined according to the actual situation, and no specific limit is made here.

[0037] The DC grid circuit 20 includes a DC converter 21 and multiple AC-DC converters 22. The input terminal of the DC converter 21 is connected to at least one first DC bus 32, and the output terminal of the DC converter 21 is connected to the DC side of multiple AC-DC converters 22. The AC side of each of the multiple AC-DC converters 22 is connected to a corresponding AC section 31.

[0038] For example, the DC converter 21 is connected to at least one first DC bus 32, which is connected to an external DC power source or to an external AC power source via an external AC-DC converter. The external DC power source includes, but is not limited to, photovoltaic power plants, wind power DC collection systems, and energy storage power plants; the external AC power source includes, but is not limited to, high-voltage AC power grids. The at least one first DC bus 32 can be a single first DC bus 32 connected to at least one of the aforementioned external DC power source or external AC power source. Alternatively, the at least one first DC bus 32 can be multiple first DC buses 32, each connected to the aforementioned external DC power source or external AC power source. The DC grid circuit 20, through the DC converter 21, converts the DC power provided by the at least one first DC bus 32 and supplies it to the DC side of the multiple AC-DC converters 22.

[0039] In the event of insufficient power in at least one AC partition 31, the DC grid circuit 20 is used to receive the power supply voltage provided by at least one first DC bus 32 to supply power to the corresponding AC partition 31.

[0040] For example, when at least one of the multiple AC zones 31 has insufficient power, the DC converter 21 in the DC grid circuit 20 draws power from the first DC bus 32 and supplies it to the AC DC converter 22 corresponding to the AC zone 31 with insufficient power. The AC DC converter 22 then converts the received DC voltage into AC voltage and supplies it to the AC zone 31 with insufficient power, thereby enabling the AC zone 31 to draw power from both the AC grid circuit 10 and the DC grid circuit 20 at the same time.

[0041] This disclosure connects to multiple AC substations 31 via an AC mains circuit 10 and to each of the corresponding AC substations 31 via multiple AC-DC converters 22. When all AC substations 31 have sufficient power, they draw power from the AC mains circuit 10. However, when at least one AC substation 31 has insufficient power, the DC converters 21 draw power from at least one first DC bus 32 and supply it to the multiple AC-DC converters 22. The AC-DC converter 22 corresponding to the AC substation with insufficient power converts the DC power supplied by the DC converter 21 into AC power, thereby providing power to the AC substation 31 with insufficient power. Therefore, when AC substation 31 faces a severe power supply shortage, this disclosure can directly draw power from the first DC bus 32 through the DC converter 21 and AC-DC converter 22 in the DC grid circuit 20. Furthermore, the DC grid circuit 20 configured in this disclosure can provide additional power to AC substation 31 through only the DC converter 21 and multiple AC-DC converters 22. Compared to increasing the overall capacity of the AC substation, the DC converter 21 and multiple AC-DC converters 22 require less land resources. Therefore, this disclosure can solve the problem of insufficient power supply capacity of AC substation 31 during peak load periods at a low cost.

[0042] In some embodiments, Figure 2 A schematic diagram of another AC / DC power grid system provided in this disclosure embodiment is shown below. Figure 2 As shown, the DC grid circuit 20 also includes a power collection node 23.

[0043] The power collection node 23 includes an energy storage device 231 and a control circuit 232.

[0044] The control circuit 232 is connected to the energy storage device 231, and the energy storage device 231 is connected to the output terminal of the DC converter 21 and the DC side of multiple AC-DC converters 22.

[0045] The energy storage device 231 is used to store at least the power supply voltage provided by the DC-DC converter 21; the control circuit 232 is used to control the energy storage device 231 to distribute the stored voltage to multiple AC-DC converters 22.

[0046] For example, when all AC zones 31 have sufficient power, each AC zone 31 does not need to draw power from the DC grid circuit 20. Therefore, the DC grid circuit 20 can store the electrical energy obtained from the first DC bus 32 in the energy storage device 231 in the power collection node 23. When at least one of the AC zones 31 experiences insufficient power, the corresponding AC-DC converter 22 can draw power from the energy storage device 231, or it can directly draw power from the first DC bus 32 through the DC converter 21 (connection path). Figure 2 (Not shown). However, in cases where, for example, the first DC bus 32 experiences a power supply anomaly, the AC-DC converter 22 cannot draw power from the first DC bus 32 through the DC converter 21. In this case, the AC-DC converter 22 can draw power from the energy storage device 231 to supply power to the AC partition 31 with insufficient power. Therefore, even if the power supply from the first DC bus 32 is also abnormal, this disclosure can still supply power to the AC partition 31 with insufficient power through the DC grid circuit 20 when the AC partition 31 faces a severe power shortage, thus improving the stability of the entire AC / DC grid system.

[0047] Furthermore, when two or more AC zones 31 experience power shortages, the control circuit 232 can determine the importance of the AC zones 31 with insufficient power. For example, each AC zone 31 can be assigned a different weight based on its importance. By comparing and ranking the weights of the AC zones 31 with insufficient power, the circuit provides the most power to the AC zone 31 ranked first and provides less power to the AC zone 31 ranked last. For example, the AC zone 31 ranked first may include, but is not limited to, transportation hubs and communication hubs, while the AC zone 31 ranked last may include, but is not limited to, residential areas, small commercial areas, rural areas, and remote areas. Therefore, this disclosure can actively allocate the power obtained from the first DC bus 32 or the power stored in the energy storage device 231 through the power aggregation node 23, thereby enabling the AC zone 31 with higher power demand to obtain more power and realizing controllable scheduling of power allocation.

[0048] In some embodiments, the AC-DC converter 22 is a bidirectional converter; the DC side of the AC-DC converter 22 is connected to the energy storage device 231, and the AC side of the AC-DC converter 22 is connected to the corresponding AC partition 31.

[0049] The AC-DC converter 22 is used to convert the DC power provided by the energy storage device 231 into AC power, or to convert the AC power provided by the AC partition 31 into DC power.

[0050] For example, when at least one of the multiple AC zones 31 experiences a power shortage, the AC-DC converter 22 corresponding to the AC zone 31 with insufficient power can draw power from the energy storage device 231, thereby converting the DC power provided by the energy storage device 231 into AC power and supplying it to the corresponding AC zone 31. Alternatively, the AC-DC converter 22 can also draw power from the first DC bus 32 via the DC converter 21, thereby converting the DC power provided by the first DC bus 32 into AC power and supplying it to the corresponding AC zone 31.

[0051] When all AC partitions 31 have sufficient power, after the AC partitions 31 draw power from the AC grid circuit 10, the AC power in the AC partitions 31 can be converted into DC power by the corresponding AC-DC converter 22 and supplied to the energy storage device 231. This not only enables the charging of the energy storage device 231, but also avoids wasting the power supplied to the AC partitions 31.

[0052] In some embodiments, Figure 3 A schematic diagram of another AC / DC power grid system provided in this disclosure embodiment is shown below. Figure 3 As shown, the DC grid circuit 20 also includes multiple DC circuit breakers 24.

[0053] Multiple DC circuit breakers 24 are respectively connected to the input terminal of DC converter 21, the output terminal of DC converter 21, and the DC side of multiple AC-DC converters 22.

[0054] For example, in the event of an abnormality in DC converter 21, such as a short circuit fault, the DC circuit breaker 24 connected to the output terminal of DC converter 21 can be disconnected to protect multiple AC-DC converters 22 and prevent abnormal current or voltage from damaging the multiple AC-DC converters 22.

[0055] If an abnormality occurs in the first DC bus 32 connected to the DC converter 21, such as an abnormally large output current or voltage, the DC circuit breaker 24 connected to the input terminal of the DC converter 21 can be disconnected to protect the multiple AC-DC converters 22 and the DC converter 21, thereby preventing damage to the DC converter 21 and the multiple AC-DC converters 22 caused by abnormal current or voltage.

[0056] In the event of an abnormality in the AC section 31 connected to the AC-DC converter 22, or an abnormality in the AC-DC converter 22 itself, the DC circuit breaker 24 connected to the DC side of the abnormal AC-DC converter 22 can be disconnected to protect the other multiple AC-DC converters 22 and the DC converter 21, thereby preventing damage to the DC converter 21 and multiple AC-DC converters 22 caused by abnormal current or voltage.

[0057] In some embodiments, Figure 4 For another schematic diagram of an AC / DC power grid system provided in this disclosure, see [link to schematic diagram]. Figure 3 and Figure 4 The DC grid circuit 20 also includes multiple AC circuit breakers 25.

[0058] Multiple AC circuit breakers 25 are respectively connected to the AC side of multiple AC-DC converters 22.

[0059] For example, in the event of an abnormality in the AC partition 31 connected to the AC-DC converter 22, the AC circuit breaker 25 connected to the AC side of the abnormal AC-DC converter 22 can be disconnected to protect multiple AC-DC converters 22 and DC converters 21, thereby preventing abnormal current or voltage from damaging DC converters 21 and multiple AC-DC converters 22.

[0060] This disclosure also provides an operation method for an AC / DC power grid system, which is applied to the AC / DC power grid system provided in any of the above embodiments.

[0061] An AC / DC power grid system includes a DC power grid circuit; the DC power grid circuit includes a DC converter and multiple AC / DC converters.

[0062] Figure 5 This is a flowchart illustrating an operation method for an AC / DC power grid system provided in an embodiment of the present disclosure, as shown below. Figure 5 As shown, the operation method includes: S110: Obtain the first operating state of the DC converter and the second operating state of multiple AC-DC converters.

[0063] S120: Based on the first operating state and multiple second operating states, control the operating modes of the DC converter and multiple AC-DC converters.

[0064] For example, the first operating state of the DC converter and the second operating states of multiple AC-DC converters are acquired respectively. The first operating state is used to indicate whether the DC converter is working normally, and the second operating state is used to indicate whether the AC-DC converter is working normally.

[0065] In some embodiments, S120 includes: when both the first operating state and the plurality of second operating states are in normal operating states, controlling one of the DC converters and the plurality of AC-DC converters to operate in a voltage fixed mode, and the DC converter and the other converters of the plurality of AC-DC converters to operate in a power fixed mode.

[0066] For example, the voltage-fixed mode includes a first control mode for the DC-DC converter and a second control mode for the AC-DC converter. In the first control mode, the DC voltage on the DC side of the DC-DC converter remains fixed. In the second control mode, the DC voltage on the DC side of the AC-DC converter remains fixed, and the reactive power on the AC side also remains fixed.

[0067] The fixed-power modes include the third control mode of the DC-DC converter and the fourth control mode of the AC-DC converter. In the third control mode, the active power on the DC side of the DC-DC converter remains constant. In the fourth control mode, both the active power on the DC side and the reactive power on the AC side of the AC-DC converter remain constant.

[0068] When the DC converter and multiple AC-DC converters are all operating normally, the DC converter and one of the multiple AC-DC converters operate in voltage-fixed mode, while the DC converter and the other converters in the multiple AC-DC converters operate in power-fixed mode.

[0069] For example, the DC converter operates in the first control mode, while multiple AC-DC converters operate in the fourth control mode.

[0070] For example, one of the multiple AC-DC converters operates in the second control mode, while the other AC-DC converters operate in the fourth control mode, and the DC converter operates in the third control mode.

[0071] In some embodiments, S120 includes: when at least one of the first operating state and a plurality of second operating states is an abnormal operating state, controlling the DC converter to operate in a voltage fixed mode, and all of the plurality of AC-DC converters, whose second operating states are all normal operating states, operate in a power fixed mode.

[0072] For example, if at least one of a plurality of AC-DC converters is operating abnormally, while the other plurality of AC-DC converters and DC converters are operating normally, the abnormally operating AC-DC converter does not work, the DC converter operates in the first control mode, and the plurality of normally operating AC-DC converters all operate in the fourth control mode.

[0073] In some embodiments, S120 includes: when at least one of the first operating state and a plurality of second operating states is an abnormal operating state, controlling one of the plurality of AC-DC converters in which all second operating states are in normal operating states to operate in a voltage fixed mode, and controlling the other AC-DC converters in the second operating states and the DC converters to operate in a power fixed mode.

[0074] For example, if at least one of a plurality of AC-DC converters is operating abnormally, while the other plurality of AC-DC converters and DC converters are operating normally, the abnormally operating AC-DC converter does not work, one of the plurality of normally operating AC-DC converters operates in a second control mode, the DC converter operates in a third control mode, and the other plurality of normally operating AC-DC converters operate in a fourth control mode.

[0075] In some embodiments, S120 includes: controlling one of a plurality of AC-DC converters, all of which are in normal operating state in the second operating state, to operate in a voltage fixed mode, and the other AC-DC converters in normal operating state in the second operating state to operate in a power fixed mode.

[0076] For example, when a DC-DC converter is malfunctioning and multiple AC-DC converters are operating normally, the malfunctioning DC-DC converter does not work, one of the multiple normally operating AC-DC converters operates in the second control mode, and the other multiple normally operating AC-DC converters operate in the fourth control mode.

[0077] In some embodiments, the DC grid circuit further includes a DC circuit breaker and an AC circuit breaker.

[0078] The operating method also includes: in the case that the first operating state is an abnormal operating state, controlling the DC circuit breaker connected to the DC converter to disconnect.

[0079] And / or, if at least one of the multiple second operating states is an abnormal operating state, the control of the DC circuit breaker and the AC circuit breaker connected to the AC-DC converter in the abnormal operating state shall be disconnected.

[0080] For example, the multiple AC-DC converters include a first AC-DC converter, a second AC-DC converter, and a third AC-DC converter. Abnormal operating modes may include, for example, a converter failure or a converter being under maintenance.

[0081] As an example, when the first operating state of the DC-DC converter is an abnormal operating state, the DC circuit breaker connected to the DC-DC converter is disconnected, thereby isolating the DC-DC converter from the first, second, and third AC-DC converters. The corresponding DC and AC circuit breakers of the first, second, and third AC-DC converters remain connected. The first, second, and third AC-DC converters form a three-terminal network operating mode. One of the first, second, and third AC-DC converters operates in the second control mode, while the other two operate in the fourth control mode.

[0082] As another example, if the second operating state of the first AC-DC converter is an abnormal operating state, the DC circuit breaker and AC circuit breaker connected to the first AC-DC converter are both disconnected, thereby isolating the first AC-DC converter from the DC converter, the second AC-DC converter, and the third AC-DC converter. The DC circuit breaker corresponding to the DC converter remains on, and the DC circuit breakers and AC circuit breakers corresponding to the second and third AC-DC converters also remain on. The DC converter, the second AC-DC converter, and the third AC-DC converter form a three-terminal network operating mode. When the DC converter is operating in the first control mode, both the second and third AC-DC converters operate in the fourth control mode. When one of the second and third AC-DC converters is operating in the second control mode, the DC converter operates in the third control mode, and the other of the second and third AC-DC converters operates in the fourth control mode.

[0083] As another example, if the first operating state of the DC-DC converter is an abnormal operating state, and for example, the second operating state of the first AC-DC converter is an abnormal operating state, the DC circuit breaker connected to the DC-DC converter, as well as the DC circuit breaker and AC circuit breaker connected to the first AC-DC converter, are all disconnected. This isolates the DC-DC converter and the first AC-DC converter from the second AC-DC converter and the third AC-DC converter, while the corresponding DC circuit breakers and AC circuit breakers of the second AC-DC converter and the third AC-DC converter remain connected. The second AC-DC converter and the third AC-DC converter form a dual-end operating mode, with one of the second AC-DC converter and the third AC-DC converter operating in the second control mode, and the other operating in the fourth control mode.

[0084] As another example, if both the first and second AC-DC converters are in an abnormal operating state in their second operating state, the DC circuit breakers and AC circuit breakers connected to the first and second AC-DC converters are disconnected, thus isolating the first and second AC-DC converters from the DC converter and the third AC-DC converter. The DC circuit breakers corresponding to the DC converters remain conducting, and the DC circuit breakers and AC circuit breakers corresponding to the third AC-DC converter also remain conducting. The DC converter and the third AC-DC converter form a dual-end operating mode. When the DC converter is operating in the first control mode, the third AC-DC converter operates in the fourth control mode. Alternatively, when the third AC-DC converter is operating in the second control mode, the DC converter operates in the third control mode.

[0085] As another example, when the DC converter, the first AC-DC converter, the second AC-DC converter, and the third AC-DC converter are all in abnormal operating states, the DC circuit breaker and the AC circuit breaker connected to the DC converter, the first AC-DC converter, the second AC-DC converter, and the third AC-DC converter are all disconnected.

[0086] For example, Table 1 is a schematic table illustrating the control modes adopted by the DC-DC converter, the first AC-DC converter, the second AC-DC converter, and the third AC-DC converter in the embodiments of this disclosure, wherein Udc is the first control mode, UdcQ is the second control mode, P is the third control mode, and PQ is the fourth control mode. Please refer to Table 1 below: Table 1:

[0087] It should be noted that the multiple AC-DC converters, including the first AC-DC converter, the second AC-DC converter, and the third AC-DC converter, are only examples. The specific number of multiple AC-DC converters needs to be determined according to the actual situation, and no specific limit is made here.

[0088] In some embodiments, the DC grid circuit further includes a DC circuit breaker; The operating method also includes: when both the first operating state and the second operating state are abnormal operating states, controlling the DC circuit breaker connected to the DC converter to disconnect, and controlling all DC circuit breakers connected to the AC-DC converter to disconnect.

[0089] For example, when the DC converter and multiple AC-DC converters are all in abnormal operating states, the DC circuit breakers controlling the DC converter and the multiple AC-DC converters connected to it are all disconnected. At this time, the multiple AC-DC converters operate in reactive power regulation mode, and each of the multiple AC-DC converters is used to provide a certain voltage support to its corresponding AC zone, thereby maintaining the voltage stability of each AC zone for a period of time.

[0090] The above are merely specific embodiments of this disclosure, enabling those skilled in the art to understand or implement this disclosure. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this disclosure. Therefore, this disclosure is not to be limited to these embodiments, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. An AC / DC grid system, characterized by include: An AC mains circuit is connected to multiple AC zones, the AC mains circuit being used to supply power to the multiple AC zones; A DC power grid circuit includes a DC converter and multiple AC-DC converters; the input terminal of the DC converter is connected to at least one first DC bus, the output terminal of the DC converter is connected to the DC side of the multiple AC-DC converters, and the AC side of the multiple AC-DC converters is respectively connected to the corresponding AC partition. In the event that at least one of the AC zones is underpowered, the DC grid circuit is used to receive the power supply voltage provided by at least one of the first DC buses to supply power to the corresponding AC zone.

2. The AC / DC grid system of claim 1, wherein The DC grid circuit also includes a power collection node; The power aggregation node includes an energy storage device and a control circuit. The control circuit is connected to the energy storage device, and the energy storage device is connected to the output terminal of the DC converter and the DC side of the plurality of AC-DC converters; The energy storage device is used to store at least the power supply voltage provided by the DC-DC converter; the control circuit is used to control the energy storage device to distribute the stored voltage to multiple AC-DC converters.

3. The AC / DC grid system of claim 2, wherein, The AC-DC converter is a bidirectional converter; The DC side of the AC-DC converter is connected to the energy storage device, and the AC side of the AC-DC converter is connected to the corresponding AC partition. The AC-DC converter is used to convert the DC power provided by the energy storage device into AC power, or to convert the AC power provided by the AC partition into DC power.

4. The AC / DC grid system of claim 1, wherein, The DC power grid circuit also includes multiple DC circuit breakers; The plurality of DC circuit breakers are respectively connected to the input terminal of the DC converter, the output terminal of the DC converter, and the DC side of the plurality of AC-DC converters.

5. The AC / DC grid system according to claim 1 or 4, characterized in that, The DC power grid circuit also includes multiple AC circuit breakers; The plurality of AC circuit breakers are respectively connected to the AC side of the plurality of AC-DC converters.

6. A method for operating an AC / DC power grid system, characterized in that, Applied to the AC / DC power grid system as described in any one of claims 1-5; The AC / DC power grid system includes a DC power grid circuit; The DC power grid circuit includes a DC converter and multiple AC-DC converters; The operating method includes: Obtain the first operating state of the DC converter and the second operating state of the plurality of AC-DC converters; Based on the first operating state and multiple second operating states, the operating modes of the DC converter and the multiple AC-DC converters are controlled.

7. The operating method according to claim 6, characterized in that, The control of the operating modes of the DC converter and the plurality of AC-DC converters based on the first operating state and multiple second operating states includes: When both the first operating state and the multiple second operating states are in normal operating state, the DC converter and one of the multiple AC-DC converters are controlled to operate in voltage fixed mode, and the DC converter and the other converters of the multiple AC-DC converters are controlled to operate in power fixed mode.

8. The operating method according to claim 6, characterized in that, The control of the operating modes of the DC converter and the plurality of AC-DC converters based on the first operating state and multiple second operating states includes: If at least one of the first operating state and the plurality of second operating states is an abnormal operating state. The DC-DC converter is controlled to operate in a fixed voltage mode, and all of the AC-DC converters in the second operating state are in normal operation mode, and all of them are operating in a fixed power mode. Alternatively, one of the multiple AC-DC converters whose second operating state is the normal operating state may be controlled to operate in the voltage fixed mode, while the other AC-DC converters in the second operating state and the DC converter operate in the power fixed mode. Alternatively, one of the AC-DC converters whose second operating state is the normal operating state may be controlled to operate in the voltage fixed mode, while the other AC-DC converters whose second operating state is the normal operating state may operate in the power fixed mode.

9. The operating method according to claim 6, characterized in that, The DC power grid circuit also includes a DC circuit breaker and an AC circuit breaker; The operating method further includes: If the first operating state is an abnormal operating state, the DC circuit breaker connected to the DC converter is controlled to disconnect. And / or, if at least one of the multiple second operating states is an abnormal operating state, the control to disconnect both the DC circuit breaker and the AC circuit breaker connected to the AC-DC converter in the second operating state that is in the abnormal operating state.

10. The operating method according to claim 6, characterized in that, The DC power grid circuit also includes a DC circuit breaker; The operating method further includes: If both the first operating state and the second operating state are abnormal operating states, the DC circuit breaker connected to the DC converter is disconnected, and the DC circuit breaker connected to the AC-DC converter is also disconnected.

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