DC transformer and fault support method thereof

Abstract

The present application relates to a DC transformer and a fault support method thereof. The method comprises: obtaining the actual power consumption of a fault support module, the fault support module comprising a support resistor and a first controllable switch unit; obtaining the duty cycle of the first controllable switch unit according to the actual power consumption; controlling the opening or closing of the first controllable switch unit according to the duty cycle to control the switching on and off of the support resistor. By adopting this method, when the DC transformer is put into use in the distribution network, when part of the load on the low-voltage side is lost, the stability of the power demand on the input side is guaranteed by switching on and off the support resistor, providing a friendly operating environment for the new energy power generation system; at the same time, when the load on the low-voltage side is restored, the operation can be restored by switching out the support resistor, simplifying the control of the medium-voltage DC distribution system.

Description

Technical Field

[0001] The present application relates to the field of power electronics technology, and in particular to a DC transformer and a fault support method thereof. Background Art

[0002] With the proposal of the "dual carbon" goal, clean energy has become a key concern of power grid companies. In this context, clean energy such as photovoltaics and wind power has developed rapidly with its advantages of energy saving and environmental protection, flexible configuration, and small initial investment. However, the high penetration rate of distributed energy access will have a huge impact on the voltage quality of traditional AC distribution networks. In view of this, drawing on the application of DC technology at the transmission level, DC distribution networks have gradually attracted people's attention. In DC distribution networks, DC transformers are key commutation equipment for completing power transmission and voltage conversion.

[0003] When traditional DC transformers are applied to DC distribution networks, when a fault occurs in the DC grid or part of the load is lost, the new energy medium-voltage DC distribution network must perform a machine cut-off action to prevent the residual power on the medium-voltage side from increasing the voltage on the medium-voltage side and thus damaging the DC transformer. This is not friendly to the new energy power generation system. At the same time, when the fault on the low-voltage side is cleared, the cut-off new energy system needs to be restored, which prolongs the power outage time and increases the complexity of low-voltage side fault handling. Especially for instantaneous low-voltage DC faults, the above operations seriously reduce the power supply quality. Summary of the invention

[0004] Based on this, it is necessary to provide a DC transformer and a fault support method thereof to address the above technical problems, so that when the load on the low-voltage side changes, the power required on the input side of the DAB type DC transformer remains unchanged.

[0005] In order to achieve the above-mentioned purpose and other purposes, one aspect of the present application provides a DC transformer fault support method, wherein the DC transformer comprises a fault support module and a preset number of DC conversion units, wherein the input end of each of the DC conversion units is electrically connected to a new energy medium-voltage DC distribution network, and the output end of each of the DC conversion units is electrically connected in parallel to a low-voltage DC distribution network, and the method comprises:

[0006] Acquire actual power consumption of a fault support module, wherein the fault support module includes a support resistor and a first controllable switch unit;

[0007] Acquire a duty cycle of the first controllable switch unit according to the actual power consumption;

[0008] The first controllable switch unit is controlled to be turned on or off according to the duty cycle to control the input and output of the supporting resistor.

[0009] In the DC transformer fault support method in the above embodiment, the duty cycle is obtained by obtaining the actual power consumption and dividing the rated power to determine whether part of the load on the low-voltage side of the DC transformer is lost: if lost, the fault support module is controlled to be put into operation by controlling the opening of the first controllable switch unit, thereby ensuring the stability of the power demand on the input side and providing a friendly operating environment for the new energy power generation system; if not lost, the fault support module is controlled to be cut out by controlling the closing of the first controllable switch unit, thereby restoring the operation of the new energy system and simplifying the control of the medium-voltage DC power distribution system.

[0010] In one embodiment, obtaining the actual power consumption of the fault support module includes:

[0011] Get the input power P of the DC transformer in And the output power P of the DC transformer out ;

[0012] The actual power consumption P1 of the fault support module is calculated according to the following formula:

[0013] P1=P in -P out When part or all of the loads on the low-voltage side fail, the actual power consumption of the supporting resistor in the fault supporting module is obtained by calculating the difference between the input power and the output power of the DC transformer.

[0014] In one embodiment, obtaining the duty cycle of the first controllable switch unit according to the actual power consumption includes:

[0015] Obtain the resistance value R of the voltage-supporting resistor and the voltage U of the medium-voltage DC side of the new energy source dc ;

[0016] The rated power consumption P2 of the fault support module is calculated according to the following formula:

[0017]

[0018] The duty cycle D is calculated according to the following formula:

[0019] The rated power consumption of the supporting resistor is calculated by the resistance value of the supporting resistor and the DC voltage on the medium voltage side, and the duty cycle is calculated by dividing the actual power consumption by the rated power consumption.

[0020] In one of the embodiments, controlling the first controllable switch unit to be turned on or off according to the duty cycle includes:

[0021] When the duty cycle does not reach the first preset value, the first controllable switch is turned on, so that the supporting resistor is turned on; and / or

[0022] When the duty cycle reaches a first preset value, the first controllable switch is turned off, so that the voltage-supporting resistor is cut out. Whether the duty cycle reaches the first preset value is used to determine whether the low-voltage side load is lost or restored.

[0023] A second aspect of the present application provides a DC transformer, including a fault support voltage module, a preset number of DC conversion units and a control module, wherein the input end of each of the DC conversion units is electrically connected to a new energy medium-voltage DC distribution network, and the output end of each of the DC conversion units is electrically connected in parallel to a low-voltage DC distribution network;

[0024] The control module is configured to:

[0025] Acquire the actual power consumption of the fault support module, wherein the fault support module includes a support resistor and a first controllable switch unit;

[0026] Obtaining a duty cycle of the first controllable switch unit according to the actual power consumption;

[0027] The first controllable switch unit is controlled to be turned on or off according to the duty cycle, thereby controlling the input and output of the supporting resistor.

[0028] In the DC transformer in the above embodiment, when the load on the low-voltage side changes by switching on or off the fault support module, the power required on the input side of the DAB type DC transformer remains unchanged, thereby improving the working environment of the new energy power generation system connected to the medium-voltage side. The control module obtains the actual power consumption and the rated power and divides them to obtain the duty cycle, thereby determining whether part of the load on the low-voltage side of the DC transformer is lost: if lost, the fault support module is controlled to be switched on by controlling the opening of the first controllable switch unit, thereby ensuring the stability of the power demand on the input side and providing a friendly operating environment for the new energy power generation system; if not lost, the fault support module is controlled to be switched off by controlling the closing of the first controllable switch unit, thereby restoring the operation of the new energy system and simplifying the control of the medium-voltage DC power distribution system.

[0029] In one embodiment, the control module is further configured to:

[0030] Get the input power P of the DC transformer in And the output power P of the DC transformer out ;

[0031] The actual power consumption P1 of the fault support module is calculated according to the following formula:

[0032] P1=P in -P out ;

[0033] Obtain the resistance value R of the voltage-supporting resistor and the voltage U of the medium-voltage DC side of the new energy source dc ;

[0034] The rated power consumption P2 of the fault support module is calculated according to the following formula:

[0035]

[0036] The duty cycle D is calculated according to the following formula:

[0037] The rated power consumption of the supporting resistor is calculated by the resistance value of the supporting resistor and the DC voltage on the medium voltage side, and the duty cycle is calculated by dividing the actual power consumption by the rated power consumption. The loss or recovery of the low voltage side load is determined by whether the duty cycle reaches the first preset value.

[0038] In one of the embodiments, the fault support voltage module includes a first controllable switch unit and a support voltage resistor;

[0039] The first controllable switch unit is configured as follows: the first port is electrically connected to the positive electrode of the new energy medium-voltage DC distribution network and the first DC conversion unit;

[0040] The supporting resistor is configured as follows: the first port is electrically connected to the second port of the first controllable switch unit, and the second port is electrically connected to the negative pole of the new energy medium-voltage DC distribution network. The first controllable switch unit is turned on or off to control the input or output of the supporting resistor, so as to ensure the stability of the input side power demand when a low-voltage side load fails.

[0041] In one embodiment, the first DC conversion unit includes:

[0042] The medium voltage side capacitor is configured as follows: a first port is electrically connected to the first port of the first controllable switch unit, and a second port is connected to the next adjacent DC conversion unit;

[0043] A second controllable switch unit is configured to: electrically connect a first port to a first port of the medium voltage side capacitor;

[0044] A third controllable switch unit is configured such that: a first port is electrically connected to a second port of the second controllable switch unit, and a second port is electrically connected to a second port of the medium voltage side capacitor;

[0045] a fourth controllable switch unit, configured such that: a first port is electrically connected to the first port of the second controllable switch unit;

[0046] The fifth controllable switch unit is configured as follows: a first port is electrically connected to the second port of the fourth controllable switch unit, and a second port is electrically connected to the second port of the third controllable switch unit.

[0047] In one embodiment, the first DC conversion unit further includes:

[0048] a freewheeling inductor, configured such that: an input port is electrically connected to a second port of the second controllable switch unit;

[0049] The transformer is configured as follows: a first port is electrically connected to the output port of the freewheeling inductor, and a second port is electrically connected to the first port of the fifth controllable switch unit.

[0050] In one embodiment, the first DC conversion unit further includes:

[0051] A sixth controllable switch unit is configured as follows: a first port is electrically connected to the low-voltage DC distribution network;

[0052] a seventh controllable switch unit, configured as follows: a first port is electrically connected to the second port of the sixth controllable switch unit and the third port of the transformer, and a second port is electrically connected to the low-voltage DC distribution network;

[0053] an eighth controllable switch unit, configured such that: a first port is electrically connected to the first port of the sixth controllable switch unit;

[0054] a ninth controllable switch unit, configured as follows: a first port is electrically connected to the second port of the eighth controllable switch unit and the fourth port of the transformer, and a second port is electrically connected to the second port of the seventh controllable switch unit;

[0055] The low-voltage side capacitor is configured as follows: a first port is electrically connected to the first port of the eighth controllable switch unit, and a second port is electrically connected to the second port of the ninth controllable switch unit. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the conventional technology, the drawings required for use in the embodiments or the conventional technology descriptions are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0057] Figure 1 It is a flow chart of a DC transformer fault support method in one embodiment;

[0058] Figure 2 A schematic flow chart of a DC transformer fault support method in another embodiment;

[0059] Figure 3A schematic diagram of a flow chart of a DC transformer fault support method in another embodiment;

[0060] Figure 4 A schematic flow chart of a DC transformer fault support method in another embodiment;

[0061] Figure 5 FIG. 1 is a schematic diagram of the structure of a DC transformer in an embodiment.

[0062] Description of reference numerals:

[0063] 100. Fault support module; 1. First controllable switch unit; 2. Second controllable switch unit; 3. Third controllable switch unit; 4. Fourth controllable switch unit; 5. Fifth controllable switch unit; 6. Sixth controllable switch unit; 7. Seventh controllable switch unit; 8. Eighth controllable switch unit; 9. Ninth controllable switch unit; 10. Support resistor; 11. Medium voltage side capacitor; 12. Freewheeling inductor; 13. Transformer; 14. Low voltage side capacitor. DETAILED DESCRIPTION

[0064] In order to facilitate understanding of the present application, the present application will be described more fully below with reference to the relevant drawings. Embodiments of the present application are provided in the drawings. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present application more thorough and comprehensive.

[0065] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used herein in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0066] It can be understood that the terms "first", "second", etc. used in the present application can be used in this article to describe various elements, but these elements are not limited by these terms. These terms are only used to distinguish the first element from another element.

[0067] It should be noted that when an element is considered to be "connected" to another element, it can be directly connected to the other element, or connected to the other element through an intermediate element. In addition, the "connection" in the following embodiments should be understood as "electrical connection", "communication connection", etc. if there is transmission of electrical signals or data between the connected objects.

[0068] A DC transformer based on dual-active full-bridge (DAB) input series-output parallel connection, wherein: the two ends of the DC transformer input side are connected to the two poles of the medium-voltage DC bus, and the two ends of the output side are connected to the low-voltage DC bus; the DAB modules on the medium-voltage side are connected in series, and the DAB modules on the low-voltage side are connected in parallel. The above structure enables each DAB module to share the high voltage on the medium-voltage side and the large current on the low-voltage side, which is very suitable for the medium-low voltage DC conversion scenario of the DC distribution network. At the same time, the DAB type DC transformer adopts a modular design, and the DAB module can be replaced and expanded according to actual needs, which has high flexibility in design. The DAB module has a simple structure and simple control, and can realize bidirectional power flow and soft switching of some devices, showing excellent performance in the application of DC transformers. Due to its advantages of modular design, high power density, large transmission capacity and bidirectional power transmission, the DAB type DC transformer has been widely studied and applied in DC distribution networks.

[0069] When a DAB type DC transformer is put into the DC distribution network, when a fault occurs in the low voltage DC grid or part of the load is lost, the new energy medium voltage DC distribution network must cut off the machine to prevent the residual power on the medium voltage side from increasing the voltage on the medium voltage side and destroying the DAB type DC transformer. This is not friendly to the new energy power generation system. At the same time, when the fault on the low voltage side is cleared, the cut-off new energy system needs to be restored, which prolongs the power outage time and increases the complexity of low voltage side fault handling. Especially for instantaneous low voltage DC faults, the above operation seriously reduces the power supply quality.

[0070] Based on this, please refer to Figure 1 In one embodiment of the present application, a DC transformer fault support method is provided, wherein the DC transformer comprises a fault support module and a preset number of DC conversion units, wherein the input end of each of the DC conversion units is electrically connected to a new energy medium-voltage DC distribution network, and the output end of each of the DC conversion units is electrically connected in parallel to a low-voltage DC distribution network, and the method comprises:

[0071] S10: Acquire actual power consumption of a fault-supporting voltage module, where the fault-supporting voltage module includes a supporting voltage resistor and a first controllable switch unit.

[0072] Specifically, when part or all of the load on the low-voltage side fails, the actual functional power consumption of the fault supporting module is calculated by the difference between the input power and the output power of the DC transformer. In the fault supporting module, the first controllable switch unit can put the supporting resistor into operation to ensure that the input side power remains unchanged when the low-voltage side load is lost; when the low-voltage side load is restored, the supporting resistor is cut out in time to reduce the complexity of system control.

[0073] S20: Obtaining a duty cycle of the first controllable switch unit according to the actual power consumption.

[0074] Specifically, the actual power consumption is divided by the rated power consumption to obtain the duty ratio.

[0075] S30: Controlling the first controllable switch unit to be turned on or off according to the duty cycle, so as to control the switching on and off of the supporting resistor.

[0076] In the DC transformer fault support method in the above embodiment, the duty cycle is obtained by obtaining the actual power consumption and dividing the rated power to determine whether part of the load on the low-voltage side of the DC transformer is lost: if lost, the fault support module is controlled to be put into operation by controlling the opening of the first controllable switch unit, thereby ensuring the stability of the power demand on the input side and providing a friendly operating environment for the new energy power generation system; if not lost, the fault support module is controlled to be cut out by controlling the closing of the first controllable switch unit, thereby restoring the operation of the new energy system and simplifying the control of the medium-voltage DC power distribution system.

[0077] As an example, see Figure 2 , the obtaining of the actual power consumption of the fault support module includes:

[0078] S11: Obtaining the input power P of the DC transformer in And the output power P of the DC transformer out ;

[0079] S12: Calculate the actual power consumption P1 of the fault support module according to the following formula:

[0080] P1=P in -P out When part or all of the loads on the low-voltage side fail, the actual power consumption of the supporting resistor in the fault supporting module is obtained by calculating the difference between the input power and the output power of the DC transformer.

[0081] As an example, see Figure 3 , obtaining the duty cycle of the first controllable switch unit according to the actual power consumption includes:

[0082] S21: Obtain the resistance value R of the voltage-supporting resistor and the voltage U of the medium-voltage DC side of the new energy source dc ;

[0083] S22: Calculate the rated power consumption P2 of the fault support module according to the following formula:

[0084]

[0085] S23: Calculate the duty cycle D according to the following formula:

[0086] The rated power consumption of the supporting resistor is calculated by the resistance value of the supporting resistor and the DC voltage on the medium voltage side, and the duty cycle is calculated by dividing the actual power consumption by the rated power consumption.

[0087] As an example, see Figure 4 , the controlling the first controllable switch unit to be turned on or off according to the duty cycle includes:

[0088] S31: when the duty cycle does not reach the first preset value, the first controllable switch is turned on, so that the supporting resistor is turned on; and / or

[0089] S32: When the duty cycle reaches a first preset value, the first controllable switch is turned off, so that the voltage-supporting resistor is cut out. The loss or recovery of the low-voltage side load is determined by whether the duty cycle reaches the first preset value.

[0090] Specifically, when the duty cycle does not reach the first preset value, part or all of the load on the low-voltage side fails. At this time, in order to ensure that the power on the input side remains unchanged, the first controllable switch unit is controlled to be turned on, so that the supporting resistor is put into operation; when the duty cycle reaches the first preset value, it means that the load on the low-voltage side is restored, and the first controllable switch is controlled to be turned off, so that the supporting resistor is cut out and the operation can be restored, which simplifies the control of the medium-voltage DC power distribution system.

[0091] It should be understood that although Figure 1-Figure 4 The steps in the flowchart are shown in sequence as indicated by the arrows, but these steps are not necessarily executed in the order indicated by the arrows. Unless otherwise specified in this document, there is no strict order restriction for the execution of these steps, and these steps can be executed in other orders. Moreover, Figure 1-Figure 4 At least part of the steps may include multiple steps or multiple stages. These steps or stages are not necessarily performed at the same time, but can be performed at different times. The execution order of these steps or stages is not necessarily sequential, but can be performed in turn or alternately with other steps or at least part of the steps or stages in other steps.

[0092] In one embodiment of the present application, please refer to Figure 5 , a DC transformer is provided, comprising a fault support voltage module 100, a preset number of DC conversion units and a control module, wherein the input end of each of the DC conversion units is electrically connected to a new energy medium-voltage DC distribution network, and the output end of each of the DC conversion units is electrically connected in parallel to a low-voltage DC distribution network;

[0093] The control module is configured to:

[0094] Acquire the actual power consumption of the fault support module 100, wherein the fault support module 100 comprises a support resistor 10 and a first controllable switch unit 1;

[0095] Obtaining a duty cycle of the first controllable switch unit 1 according to the actual power consumption;

[0096] The first controllable switch unit 1 is controlled to be turned on or off according to the duty cycle, thereby controlling the input and output of the supporting resistor 10 .

[0097] In the DC transformer in the above embodiment, when the load on the low-voltage side changes by switching on or off the fault support module 100, the power required on the input side of the DAB type DC transformer remains unchanged, thereby improving the working environment of the new energy power generation system connected to the medium-voltage side. The control module obtains the actual power consumption and the rated power and divides them to obtain the duty cycle, thereby determining whether part of the load on the low-voltage side of the DC transformer is lost: if lost, the fault support module 100 is controlled to be switched on by controlling the opening of the first controllable switch unit 1, thereby ensuring the stability of the power demand on the input side and providing a friendly operating environment for the new energy power generation system; if not lost, the fault support module 100 is controlled to be switched off by controlling the closing of the first controllable switch unit 1, thereby restoring the operation of the new energy system and simplifying the control of the medium-voltage DC power distribution system.

[0098] Because of the use of DAB type DC transformer, its structure allows each DAB module to share the high voltage on the medium voltage side and the large current on the low voltage side, which is very suitable for the medium and low voltage DC conversion scenario of the DC distribution network. At the same time, the DAB type DC transformer adopts a modular design, and the DAB module can be replaced and expanded according to actual needs. It has high flexibility in design. The DAB module has a simple structure and simple control, and can realize bidirectional power flow and soft switching of some devices, showing excellent performance in the application of DC transformers.

[0099] In one embodiment, the control module is further configured to:

[0100] Get the input power P of the DC transformer in And the output power P of the DC transformer out ;

[0101] The actual power consumption P1 of the fault support module 100 is calculated according to the following formula:

[0102] P1=P in -P out ;

[0103] Obtain the resistance R of the voltage-supporting resistor 10 and the voltage U of the medium-voltage DC side of the new energy source dc ;

[0104] The rated power consumption P2 of the fault support module 100 is calculated according to the following formula:

[0105]

[0106] The duty cycle D is calculated according to the following formula:

[0107] The rated power consumption of the supporting resistor 10 is calculated by the resistance value of the supporting resistor 10 and the DC voltage on the medium voltage side, and the duty cycle is calculated by dividing the actual power consumption by the rated power consumption. The loss or recovery of the low voltage side load is determined by whether the duty cycle reaches the first preset value.

[0108] In one embodiment, the fault support module 100 includes a first controllable switch unit 1 and a support resistor 10;

[0109] The first controllable switch unit 1 is configured as follows: the first port is electrically connected to the positive electrode of the new energy medium-voltage DC distribution network and the first DC conversion unit;

[0110] The supporting resistor 10 is configured as follows: the first port is electrically connected to the second port of the first controllable switch unit 1, and the second port is electrically connected to the negative pole of the new energy medium-voltage DC distribution network. The first controllable switch unit 1 is turned on or off to control the input or output of the supporting resistor 10, so as to ensure the stability of the input side power demand when a low-voltage side load fails.

[0111] In one embodiment, the first DC conversion unit includes:

[0112] The medium voltage side capacitor 11 is configured as follows: a first port is electrically connected to the first port of the first controllable switch unit 1, and a second port is connected to the next adjacent DC conversion unit;

[0113] The second controllable switch unit 2 is configured as follows: a first port is electrically connected to a first port of the medium voltage side capacitor 11;

[0114] The third controllable switch unit 3 is configured as follows: a first port is electrically connected to the second port of the second controllable switch unit 2, and a second port is electrically connected to the second port of the medium voltage side capacitor 11;

[0115] The fourth controllable switch unit 4 is configured as follows: a first port is electrically connected to the first port of the second controllable switch unit 2;

[0116] The fifth controllable switch unit 5 is configured as follows: a first port is electrically connected to the second port of the fourth controllable switch unit 4 , and a second port is electrically connected to the second port of the third controllable switch unit 3 .

[0117] In one embodiment, the first DC conversion unit further includes:

[0118] The freewheeling inductor 12 is configured as follows: an input port is electrically connected to the second port of the second controllable switch unit 2;

[0119] The transformer 13 is configured as follows: a first port is electrically connected to the output port of the freewheeling inductor 12 , and a second port is electrically connected to the first port of the fifth controllable switch unit 5 .

[0120] In one embodiment, the first DC conversion unit further includes:

[0121] The sixth controllable switch unit 6 is configured as follows: a first port is electrically connected to the low-voltage DC distribution network;

[0122] The seventh controllable switch unit 7 is configured as follows: a first port is electrically connected to the second port of the sixth controllable switch unit 6 and the third port of the transformer 13, and a second port is electrically connected to the low-voltage DC distribution network;

[0123] The eighth controllable switch unit 8 is configured as follows: a first port is electrically connected to the first port of the sixth controllable switch unit 6;

[0124] The ninth controllable switch unit 9 is configured as follows: a first port is electrically connected to the second port of the eighth controllable switch unit 8 and the fourth port of the transformer 13, and a second port is electrically connected to the second port of the seventh controllable switch unit 7;

[0125] The low-voltage side capacitor 14 is configured as follows: a first port is electrically connected to the first port of the eighth controllable switch unit 8 , and a second port is electrically connected to the second port of the ninth controllable switch unit 9 .

[0126] In the description of this specification, the description with reference to the terms "some embodiments", "other embodiments", "ideal embodiments", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic descriptions of the above terms do not necessarily refer to the same embodiment or example.

[0127] The technical features of the above embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0128] The above-mentioned embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application shall be subject to the attached claims.

Claims

1. A DC transformer fault support method, characterized in that: The DC transformer includes a fault support module and a preset number of DC conversion units, the input end of each DC conversion unit is electrically connected to a new energy medium-voltage DC distribution network, and the output end of each DC conversion unit is electrically connected in parallel to a low-voltage DC distribution network. The method includes: Get the input power P of the DC transformer in And the output power P of the DC transformer out ; Calculate the actual power consumption P1 of the fault support module according to the following formula: P1 = P in -P out ; The fault support pressure module includes a support pressure resistor and a first controllable switch unit; Obtain the resistance value R of the voltage-supporting resistor and the voltage U of the medium-voltage DC side of the new energy source dc ; The rated power consumption P2 of the fault support module is calculated according to the following formula: The duty cycle D is calculated according to the following formula: Where P R Equal to P1; The first controllable switch unit is controlled to be turned on or off according to the duty cycle to control the input and output of the supporting resistor.

2. The DC transformer fault support method according to claim 1, characterized in that: The controlling the first controllable switch unit to be turned on or off according to the duty cycle comprises: When the duty cycle does not reach the first preset value, the first controllable switch is turned on, so that the supporting resistor is turned on; and / or When the duty cycle reaches a first preset value, the first controllable switch is turned off, thereby cutting out the supporting resistor.

3. A DC transformer, characterized in that: It includes a fault support voltage module, a preset number of DC conversion units and a control module, the input end of each DC conversion unit is electrically connected to the new energy medium-voltage DC distribution network, and the output end of each DC conversion unit is electrically connected in parallel to the low-voltage DC distribution network; The control module is configured to: Get the input power P of the DC transformer in And the output power P of the DC transformer out ; The actual power consumption P1 of the fault support module is calculated according to the following formula: P1 = P in -P out ; The fault support pressure module includes a support pressure resistor and a first controllable switch unit; Obtain the resistance value R of the voltage-supporting resistor and the voltage U of the medium-voltage DC side of the new energy source dc ; The rated power consumption P2 of the fault support module is calculated according to the following formula: The duty cycle D is calculated according to the following formula: Where P R Equal to P1; The first controllable switch unit is controlled to be turned on or off according to the duty cycle, thereby controlling the input and output of the supporting resistor.

4. The DC transformer according to claim 3, characterized in that: The fault support voltage module includes a first controllable switch unit and a support voltage resistor; The first controllable switch unit is configured as follows: the first port is electrically connected to the positive electrode of the new energy medium-voltage DC distribution network and the first DC conversion unit; The supporting resistor is configured as follows: a first port is electrically connected to the second port of the first controllable switch unit, and a second port is electrically connected to the negative pole of the new energy medium-voltage DC distribution network.

5. The DC transformer according to claim 4, characterized in that: The first DC conversion unit comprises: The medium voltage side capacitor is configured as follows: a first port is electrically connected to the first port of the first controllable switch unit, and a second port is connected to the next adjacent DC conversion unit; A second controllable switch unit is configured to: electrically connect a first port to a first port of the medium voltage side capacitor; A third controllable switch unit is configured such that: a first port is electrically connected to a second port of the second controllable switch unit, and a second port is electrically connected to a second port of the medium voltage side capacitor; a fourth controllable switch unit, configured such that: a first port is electrically connected to the first port of the second controllable switch unit; The fifth controllable switch unit is configured as follows: a first port is electrically connected to the second port of the fourth controllable switch unit, and a second port is electrically connected to the second port of the third controllable switch unit.

6. The DC transformer according to claim 5, characterized in that: The first DC conversion unit also includes: a freewheeling inductor, configured such that: an input port is electrically connected to a second port of the second controllable switch unit; The transformer is configured as follows: a first port is electrically connected to the output port of the freewheeling inductor, and a second port is electrically connected to the first port of the fifth controllable switch unit.

7. The DC transformer according to claim 6, characterized in that: The first DC conversion unit also includes: A sixth controllable switch unit is configured as follows: a first port is electrically connected to the low-voltage DC distribution network; a seventh controllable switch unit, configured as follows: a first port is electrically connected to the second port of the sixth controllable switch unit and the third port of the transformer, and a second port is electrically connected to the low-voltage DC distribution network; an eighth controllable switch unit, configured such that: a first port is electrically connected to the first port of the sixth controllable switch unit; a ninth controllable switch unit, configured as follows: a first port is electrically connected to the second port of the eighth controllable switch unit and the fourth port of the transformer, and a second port is electrically connected to the second port of the seventh controllable switch unit; The low-voltage side capacitor is configured as follows: a first port is electrically connected to the first port of the eighth controllable switch unit, and a second port is electrically connected to the second port of the ninth controllable switch unit.

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