A direct current power distribution system with direct current bus architecture reconfiguration capability

Abstract

The application relates to a direct current power distribution system with a direct current bus architecture reconstruction capability, comprising a plurality of alternating current power sources, a plurality of corresponding AC / DC energy routers, a plurality of corresponding direct current bus switching switches, positive / zero / negative direct current buses, a power frequency isolation transformer and a plurality of DC / DC charging modules constituting a direct current load. The working state of the system can be transformed among two unipolar direct current bus architectures and a true bipolar bus architecture. Compared with the prior art, the application has the advantages of flexibly meeting the needs according to the changes of load access and the like.

Description

Technical Field

[0001] This invention relates to the technical field of DC power distribution, and in particular to a DC power distribution system with DC bus architecture reconfiguration capability. Background Technology

[0002] Low-voltage DC distribution systems are characterized by easy connection to DC loads such as electric vehicles, low line loss, and long distribution distances. Multiple AC power sources can be fed into the DC bus via converters / inverters, enabling interconnection and mutual support. Low-voltage DC distribution systems mainly have two system structures: unipolar and bipolar DC bus. Unipolar DC distribution systems are simple in structure but can only provide one DC voltage bus from positive to negative. Bipolar DC distribution systems, on the other hand, have three buses: positive, negative, and zero. The voltages of the positive and negative DC buses can be independently adjusted, providing three voltage levels: positive to negative, positive to zero, and zero to negative. Based on the load-carrying capacity of the zero pole, bipolar DC distribution systems can be further divided into true bipolar DC systems and pseudo-bipolar DC systems. In pseudo-bipolar DC systems, the load can only be connected to the positive and negative buses; the zero pole cannot carry a load. In true bipolar DC systems, the load can be connected to any two DC buses according to its voltage requirements, thus offering better flexibility and redundancy.

[0003] Currently, low-voltage DC power distribution systems mostly adopt unipolar or bipolar DC bus architectures, which cannot be reconfigured according to load or power supply requirements. Unipolar DC power distribution systems often use one or more converters connected in parallel on the DC side, while to form a true bipolar DC power distribution system, two converters are generally connected in series on the DC side.

[0004] Publications CN 111555617 A, CN 112491272 A, and CN 109861546 A all proposed AC / DC energy routers with DC output capabilities, making further explorations and research for the development of DC power distribution systems.

[0005] Patent CN 111555617 A proposes a high-power modular pseudo-bipolar DC / DC converter, consisting of a phase a converter, a phase b converter, and a phase c converter connected in parallel. It offers advantages such as higher transmission efficiency, smaller footprint, high turns ratio, and modularity. However, the load cannot be connected to the zero pole; it can only be connected to the positive and negative poles, which is not advantageous for scenarios requiring multi-level switching. Patent CN 112491272 A proposes a bipolar bidirectional DC-DC transformer, including four insulated-gate bipolar transistors (IGBTs), two inductors, and four capacitors. The high-voltage positive terminal (+HV) of this bipolar bidirectional DC-DC transformer is connected to the collector of the first IGBT Q1 and one end of the first capacitor C1. The high-voltage positive terminal (-HV) of this bipolar bidirectional DC-DC transformer is connected to the emitter of the third IGBT Q3 and one end of the second capacitor C2. However, when considering multiple transformers, the patent does not mention a suitable method to handle the switching between unipolar and true bipolar switching after multiple transformers are connected in series and parallel. Patent CN109861546A proposes an AC / DC power router with true bipolar DC output capability. It achieves voltage balancing between the positive and negative DC outputs by controlling the switching transistors of a full-bridge / three-level combined converter, and ensures normal operation of the DC output on the non-faulty poles even in the event of a unipolar fault. However, when considering the interconnection and mutual support of multiple transformers in a unipolar DC system to achieve power flow, there are no corresponding measures to realize the reconfiguration between unipolar and true bipolar distribution systems, and it cannot flexibly meet the needs of changes in load access.

[0006] In summary, existing technologies lack corresponding measures to achieve reconfiguration between unipolar and true bipolar power distribution systems, and cannot flexibly meet needs based on changes in load access. Summary of the Invention

[0007] The purpose of this invention is to overcome the defects of the prior art by providing a DC power distribution system with DC bus architecture reconfiguration capability, which can realize the reconfiguration between unipolar and true bipolar power distribution systems and flexibly meet the needs according to the changes in load access.

[0008] The objective of this invention can be achieved through the following technical solutions:

[0009] A DC power distribution system with DC bus architecture reconfiguration capability is characterized in that the system includes multiple AC power sources, and AC / DC energy routers and DC bus switching switches corresponding to each AC power source, and also includes a DC bus and DC loads, wherein...

[0010] The output of the AC power supply is connected to the AC / DC power router;

[0011] The DC voltage output level of the AC / DC power router is unipolar Vdc, unipolar 2Vdc, or true bipolar ±Vdc.

[0012] The DC bus has three lines: a positive bus, a neutral bus, and a negative bus. The voltage between the positive bus and the neutral bus is Vdc, the voltage between the negative bus and the neutral bus is Vdc, and the voltage between the positive bus and the negative bus is 2Vdc.

[0013] The positive and negative terminals of the AC / DC power router output are connected to the DC bus switching switches. These switches are divided into a positive switch, a zero-level switch, and a negative switch. The positive switch connects to the positive bus, the zero-level switch connects to the neutral bus, and the negative switch connects to the negative bus.

[0014] DC loads include low-power loads and high-power loads;

[0015] When a low-power charging command is received, the DC voltage level output by the AC / DC power router is unipolar Vdc, and a unipolar DC bus architecture is adopted. At this time, the positive terminals of all AC / DC power router outputs are connected to the positive switch, and the negative terminals are connected to the 0-level switch. The low-power load is connected to the positive bus and the neutral bus. Alternatively, the positive terminals of all AC / DC power router outputs are connected to the 0-level switch, and the negative terminals are connected to the negative switch. The low-power load is connected to the negative bus and the neutral bus. At this time, the high-power load does not work, and the AC power supply is connected in parallel to the DC bus.

[0016] When receiving a simultaneous charging command of varying power levels, the AC / DC power router outputs a unipolar DC voltage level (Vdc) and employs a true bipolar bus architecture. This allows some AC / DC power routers to connect their positive output to a positive switch and their negative output to a level 0 switch, while other AC / DC power routers connect their positive output to a level 0 switch and their negative output to a negative switch.

[0017] When the nth AC power source is connected to the DC power distribution system, if the load rate of the AC power source connected to the positive bus and the neutral bus is greater than the load rate of the AC power source connected to the negative bus and the neutral bus, then connect the positive terminal of the AC / DC power router corresponding to the nth AC power source to the positive switch and the negative terminal to the 0-level switch. Conversely, connect the positive terminal of the AC / DC power router corresponding to the nth AC power source to the 0-level switch and the negative terminal to the negative switch. At this time, high-power loads are connected to the positive bus and the negative bus, and low-power loads are connected to the positive bus and the neutral bus or the negative bus and the neutral bus.

[0018] When a high-power simultaneous charging command is received, the DC voltage level output by the AC / DC power router is unipolar 2Vdc. A different unipolar DC bus architecture is adopted. At this time, the positive terminals of all AC / DC power router outputs are connected to the positive switch, and the negative terminals are connected to the negative switch. The AC power supply is connected in parallel to the DC bus. High-power loads are connected to the positive and negative buses, and low-power loads do not work.

[0019] The two unipolar DC bus architectures and the true bipolar bus architecture mentioned above can all be converted into each other.

[0020] Furthermore, the AC / DC power router is a high-frequency isolated power electronic transformer.

[0021] Furthermore, the AC / DC power router is an AC / DC conversion circuit isolated by a power frequency transformer.

[0022] Furthermore, the DC bus switching switch is a single-pole double-throw switch.

[0023] Furthermore, the DC bus switching switch is either a mechanical switch or an electronic switch.

[0024] Furthermore, a power frequency isolation transformer is connected between the AC power supply and the AC / DC power router. The input of the power frequency isolation transformer is connected to the output of the AC power supply, and the output of the power frequency isolation transformer is connected to the input of the AC / DC power router.

[0025] Furthermore, the high-voltage side of the power frequency transformer adopts a delta connection, while the low-voltage side uses three independent single-phase windings. The three single-phase windings on the low-voltage side are independent of each other and do not connect to provide phase-to-phase isolation for the three-phase H-bridge converter.

[0026] Furthermore, the AC power supply is a three-phase AC power supply with a voltage level of 380V, 10kV, or 35kV.

[0027] Furthermore, the DC load includes a DC / DC charging module and a DC load. The DC load is connected to the DC bus through the DC / DC charging module, which consists of multiple DC / DC charging converters.

[0028] Furthermore, the DC load can be a single DC load or a distributed DC load.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] (1) The DC power distribution system of the present invention has three DC buses: a positive bus, a negative bus, and a zero bus. The DC output of each AC / DC energy router in the power distribution system can be selected to connect to different buses through its output switch, namely, positive bus and negative bus, or positive bus and zero bus, or zero bus and negative bus, so as to provide flexible power supply and bus voltage supply methods to meet the needs of different DC loads, realize that multiple AC / DC energy routers can be connected in series or in parallel to the DC power distribution bus, and switch between the unipolar and true bipolar architecture of the DC bus.

[0031] (2) When the DC outputs of multiple AC / DC power routers are connected in parallel to the same two DC buses, a unipolar DC bus architecture can be formed, providing a single bus voltage (which can be Vdc or 2Vdc). The multiple AC / DC power routers of this invention can be connected in parallel to supply power to the load on this bus, improving the power supply capacity and flexibility of this bus. At the same time, multiple AC / DC power routers can also perform bidirectional energy exchange, enabling power flow interconnection and mutual assistance among multiple AC sources.

[0032] (3) When the DC outputs of the two AC / DC energy routers of the present invention are connected in series (i.e., the output of one group is connected to the positive bus and the zero bus, and the output of the other group is connected to the zero bus and the negative bus), a true bipolar DC bus architecture can be formed, which can provide both Vdc and 2Vdc DC bus voltages at the same time, and can meet the access requirements of different voltage loads. For example, low-voltage and low-power electric vehicle charging loads can be connected to the Vdc DC bus, and high-voltage and high-power electric vehicle charging loads can be connected to the 2Vdc DC bus.

[0033] (4) The power distribution system of the present invention can flexibly reconfigure the DC output terminal connection mode of the AC / DC power router according to the dynamic changes of load access to meet load requirements. For example, if the load between the positive bus and the neutral bus increases and more power supply is required, the output of the AC / DC power router originally connected to the neutral bus and the negative bus can be switched to the positive bus and the neutral bus. When there is a demand for high-voltage, high-power DC load access, the original unipolar DC bus architecture can be reconfigured into a true bipolar architecture, and a higher level of DC bus voltage can be output through the series connection of the AC / DC power router, thereby reducing line current and reducing line losses. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of the unipolar Vdc DC bus architecture of the present invention;

[0035] Figure 2 This is a schematic diagram of the true bipolar DC bus architecture of the present invention;

[0036] Figure 3This is a schematic diagram of the unipolar 2Vdc DC bus architecture of the present invention. Detailed Implementation

[0037] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0038] This invention proposes a DC power distribution system with DC bus architecture reconfiguration capability. The system can operate in three modes depending on the load: charging only low-power loads (unipolar Vdc DC bus architecture), charging both high and low-power loads simultaneously (true bipolar DC bus architecture), and charging only high-power loads (unipolar 2Vdc DC bus architecture). The system's structural diagrams for each mode are shown below. Figure 1 , 2 As shown in Figure 3.

[0039] The system proposed in this invention includes multiple AC power sources, corresponding multiple AC / DC energy routers, corresponding multiple DC bus switching switches, positive / zero / negative DC buses, power frequency isolation transformers, and a DC load (such as an electric vehicle charging pile) composed of multiple DC / DC charging modules. The AC / DC energy routers can be in the form of high-frequency isolated power electronic transformers or AC / DC conversion circuits isolated by power frequency transformers, both of which can realize the interconnection and voltage / current control of AC power sources and the DC grid. The output of the AC / DC energy routers achieves connection switching between different DC buses through switching switches, forming a DC power distribution system with DC bus architecture reconfiguration capabilities.

[0040] The AC / DC power router uses a three-phase AC power supply, with voltage levels of 380V, 10kV, or 35kV, which can be different from the distribution network voltage levels.

[0041] Multiple AC / DC power routers can be in the form of high-frequency isolated power electronic transformers or AC / DC conversion circuits isolated by power frequency transformers. The DC voltage level output by the AC / DC power router can be unipolar Vdc, unipolar 2Vdc, or true bipolar ±Vdc.

[0042] The power distribution system has three DC buses: a positive bus, a neutral bus, and a negative bus. The voltage between the positive bus and the neutral bus is Vdc, the voltage between the negative bus and the neutral bus is Vdc, and the voltage between the positive bus and the negative bus is 2Vdc. DC loads (such as electric vehicle charging piles) or DC power sources (such as distributed photovoltaics) can be connected to different DC buses according to their required voltage.

[0043] Each AC / DC power router outputs a positive and negative terminal, which are connected to corresponding DC bus switching switches. These switches are single-pole double-throw switches. The positive DC bus switch can be connected to either the positive or neutral DC bus, and the negative DC bus switch can be connected to either the neutral or negative DC bus. The DC bus switching switches can be either mechanical or electronic.

[0044] Each AC / DC power router has three possible connection methods for its positive and negative DC bus switching switches: the first is connecting the positive DC bus and the neutral DC bus; the second is connecting the neutral DC bus and the negative DC bus; and the third is connecting the positive DC bus and the negative DC bus. The output DC voltage level of the AC / DC power router is consistent with the voltage level of the selected connected DC bus.

[0045] The high-voltage side of the power frequency transformer adopts a delta connection, while the low-voltage side uses three independent single-phase windings. The three independent single-phase windings on the low-voltage side provide phase-to-phase isolation for the three-phase H-bridge converter, forming a DC power distribution system with multiple voltage level outputs.

[0046] Based on the connection status of DC loads and DC distributed power sources, this invention allows for flexible switching of the output DC bus of the AC / DC energy router via a switching switch. The AC / DC energy router outputting Vdc can switch between the positive bus, neutral bus, and neutral bus / negative bus. The switching operation enables the reconfiguration of the DC bus architecture between unipolar and true bipolar configurations, meeting the different charging voltage requirements of electric vehicles and achieving flexible charging of electric vehicles and interconnection and mutual support between multiple AC power sources. The DC outputs of multiple AC / DC energy routers can be connected in parallel to form a low-voltage DC bus (positive bus and neutral bus or neutral bus and negative bus), and the DC outputs of multiple AC / DC energy routers can be connected in series to form a high-voltage DC bus (positive bus and negative bus).

[0047] A DC / DC charging module composed of multiple DC / DC charging converters is connected to a low-voltage DC bus or a high-voltage DC bus on one side, and a DC load (such as an electric vehicle charging pile) or a DC power source (such as distributed photovoltaic) on the other side. The energy flow direction is bidirectional, and it can flow from the DC bus to the DC load or DC power source, or from the DC load or DC power source to the DC bus.

[0048] Taking n AC power sources as an example, the positive (+) terminals of the n switching cabinets are always connected, the negative (-) terminals are always connected, and the zero (0) terminal is also always connected. In the first case, when a low-power charging command is received, the DC voltage output by the AC / DC power router is unipolar Vdc, using a unipolar DC bus architecture. The switching connections in this case are as follows: Figure 1As shown. Switches a1 to an and b1 to bn are connected to the positive and negative poles (or the negative and negative poles) respectively. At this time, n AC sources are connected in parallel to the DC bus, forming a unipolar DC bus topology. The DC load is connected to the positive and zero bus (or the zero and negative bus). Multiple AC sources operate in parallel through an AC / DC energy router to provide energy to the DC load. The DC bus voltage is Vdc, enabling parallel interconnection and mutual support among multiple AC power sources. Furthermore, when one pole of the line fails, the other poles can still operate, improving the system's power supply reliability. At this time, DC / DC charging modules 1, 2, and 3 perform low-to-medium power charging at a voltage level of Vdc, while DC / DC charging modules 4 and 5, which perform high-power charging, do not operate.

[0049] In the second scenario, when receiving simultaneous charging commands of varying power levels, the AC / DC power router outputs a unipolar Vdc DC voltage, employing a true bipolar bus architecture. In this case, the switching switches a1 and b1 of AC power supply #1 are connected to the + and 0 poles respectively, and the switching switches a2 and b2 of AC power supply #2 are connected to the 0 and - poles respectively. This results in a true bipolar bus topology, achieving a reconfiguration of the DC bus architecture. This topology can operate in a high-power charging mode with a voltage level of 2Vdc. When AC power supply #n is connected, it will be connected in parallel with the AC power supply group with the highest load rate. For example, if the load rate of the AC power supply group connected to the + and 0 poles is greater than that of the AC power supply group connected to the - and 0 poles, then AC power supply #n will be connected to the + and 0 poles to alleviate the pressure on that side of the power supply group. The wiring diagram in this case is as follows: Figure 2 As shown. At this time, DC / DC charging module 4 and DC / DC charging module 5 perform high-power charging at a voltage level of 2Vdc, while DC / DC charging module 1, DC / DC charging module 2 and DC / DC charging module 3 can still perform medium- and low-power charging at a voltage level of Vdc, meeting the needs of different charging power and realizing flexible charging of electric vehicles.

[0050] In the third scenario, when receiving a high-power simultaneous charging command, the AC / DC power router outputs a unipolar 2Vdc DC voltage and employs a different unipolar DC bus architecture. The wiring in this case is as follows: Figure 3As shown. Switches a1 to an and b1 to bn are connected to the positive and negative poles respectively. At this time, n AC sources are connected in parallel to the DC bus, forming a unipolar DC bus topology. Multiple AC sources operate in parallel through an AC / DC energy router to provide energy to the DC load. The system operates in a unipolar DC bus architecture, with a DC bus voltage of 2Vdc. This satisfies the high-power charging requirements of the vehicle while achieving parallel interconnection and mutual support between multiple AC power sources. At this time, DC / DC charging modules 4 and 5 perform high-power charging at a voltage level of 2Vdc, while DC / DC charging modules 1, 2, and 3 are not operational.

[0051] This invention provides a DC power distribution system with DC bus architecture reconfiguration capability, enabling a DC power distribution system with multiple AC / DC energy routers to flexibly switch between unipolar DC bus architecture and true bipolar DC bus architecture according to the needs of DC load and power supply, thereby meeting the requirements of different load access.

[0052] The preferred embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make numerous modifications and variations based on the concept of the present invention without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning, or limited experimentation on the basis of existing technology should be within the scope of protection defined by the claims.

Claims

1. A DC power distribution system with DC bus architecture reconfiguration capability, characterized in that, The system includes multiple AC power sources, as well as AC / DC power routers and DC bus switching switches corresponding to each AC power source. It also includes DC buses and DC loads. The output of the AC power supply is connected to the AC / DC power router; The DC voltage output level of the AC / DC power router is unipolar Vdc, unipolar 2Vdc, or true bipolar ±Vdc. The DC bus has three lines: a positive bus, a neutral bus, and a negative bus. The voltage between the positive bus and the neutral bus is Vdc, the voltage between the negative bus and the neutral bus is Vdc, and the voltage between the positive bus and the negative bus is 2Vdc. The positive and negative terminals of the AC / DC power router output are connected to the DC bus switching switches. These switches are divided into a positive switch, a zero-level switch, and a negative switch. The positive switch connects to the positive bus, the zero-level switch connects to the neutral bus, and the negative switch connects to the negative bus. DC loads include low-power loads and high-power loads; When a low-power charging command is received, the DC voltage level output by the AC / DC power router is unipolar Vdc, and a unipolar DC bus architecture is adopted. At this time, the positive terminals of all AC / DC power router outputs are connected to the positive switch, and the negative terminals are connected to the 0-level switch. The low-power load is connected to the positive bus and the neutral bus. Alternatively, the positive terminals of all AC / DC power router outputs are connected to the 0-level switch, and the negative terminals are connected to the negative switch. The low-power load is connected to the negative bus and the neutral bus. At this time, the high-power load does not work, and the AC power supply is connected in parallel to the DC bus. When receiving a simultaneous charging command of varying power levels, the AC / DC power router outputs a unipolar DC voltage level (Vdc) and employs a true bipolar bus architecture. This allows some AC / DC power routers to connect their positive output to a positive switch and their negative output to a level 0 switch, while other AC / DC power routers connect their positive output to a level 0 switch and their negative output to a negative switch. When the nth AC power source is connected to the DC power distribution system, if the load rate of the AC power source connected to the positive bus and the neutral bus is greater than the load rate of the AC power source connected to the negative bus and the neutral bus, then connect the positive terminal of the AC / DC power router corresponding to the nth AC power source to the positive switch and the negative terminal to the 0-level switch. Conversely, connect the positive terminal of the AC / DC power router corresponding to the nth AC power source to the 0-level switch and the negative terminal to the negative switch. At this time, high-power loads are connected to the positive bus and the negative bus, and low-power loads are connected to the positive bus and the neutral bus or the negative bus and the neutral bus. When a high-power simultaneous charging command is received, the DC voltage level output by the AC / DC power router is unipolar 2Vdc. A different unipolar DC bus architecture is adopted. At this time, the positive terminals of all AC / DC power router outputs are connected to the positive switch, and the negative terminals are connected to the negative switch. The AC power supply is connected in parallel to the DC bus. High-power loads are connected to the positive and negative buses, and low-power loads do not work. The two unipolar DC bus architectures and the true bipolar bus architecture mentioned above can all be converted into each other.

2. A DC power distribution system with DC bus architecture reconfiguration capability according to claim 1, characterized in that, AC / DC power routers are high-frequency isolated power electronic transformers.

3. A DC power distribution system with DC bus architecture reconfiguration capability according to claim 1, characterized in that, An AC / DC power router is an AC / DC conversion circuit isolated by a power frequency transformer.

4. A DC power distribution system with DC bus architecture reconfiguration capability according to claim 1, characterized in that, The DC bus switching switch is a single-pole double-throw switch.

5. A DC power distribution system with DC bus architecture reconfiguration capability according to claim 1, characterized in that, The DC bus switching switch can be either a mechanical switch or an electronic switch.

6. A DC power distribution system with DC bus architecture reconfiguration capability according to claim 1, characterized in that, A power frequency isolation transformer is connected between the AC power supply and the AC / DC power router. The input of the power frequency isolation transformer is connected to the output of the AC power supply, and the output of the power frequency isolation transformer is connected to the input of the AC / DC power router.

7. A DC power distribution system with DC bus architecture reconfiguration capability according to claim 6, characterized in that, The high-voltage side of the power frequency transformer adopts a delta connection, while the low-voltage side uses three independent single-phase windings. The three independent single-phase windings on the low-voltage side provide phase-to-phase isolation for the three-phase H-bridge converter.

8. A DC power distribution system with DC bus architecture reconfiguration capability according to claim 1, characterized in that, The AC power supply is a three-phase AC power supply with a voltage level of 380V, 10kV, or 35kV.

9. A DC power distribution system with DC bus architecture reconfiguration capability according to claim 1, characterized in that, The DC load includes a DC / DC charging module and a DC load. The DC load is connected to the DC bus through the DC / DC charging module, which consists of multiple DC / DC charging converters.

10. A DC power distribution system with DC bus architecture reconfiguration capability according to claim 9, characterized in that, The DC load can be a standalone DC load or a distributed DC load.

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