Bidirectional asymmetric feeding type non-isolated dc transformer and control method thereof
By designing a bidirectional asymmetrical feeder type non-isolated DC transformer, the problem of the lack of reverse power transmission capability in the new energy all-DC collection and transmission system was solved, realizing black start and emergency power support, and improving system flexibility and energy transmission efficiency.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- CHINA THREE GORGES CORPORATION
- Filing Date
- 2026-04-24
- Publication Date
- 2026-07-21
AI Technical Summary
The new energy all-DC collection and transmission system does not have the ability to reverse power transmission, which makes it impossible to complete the black start and emergency power support of the new energy base.
Design a bidirectional asymmetric feeding type non-isolated DC transformer. By setting up a reverse power transmission circuit and a non-reverse power transmission circuit in the DC transformer and connecting them in parallel to the branch, reverse power transmission capability is achieved. Furthermore, the power transmission path is optimized through control methods to reduce high-frequency switching operations.
It improves the system's flexibility, enabling it to perform black start and emergency power support for large-scale new energy bases, reduces device losses, and improves energy transmission efficiency.
Smart Images
Figure CN122437379A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of DC power transmission technology, specifically to a bidirectional asymmetrical feeding type non-isolated DC transformer and its control method. Background Technology
[0002] my country's large-scale new energy bases are mainly distributed in the "Three Norths" (Northeast, North, and Northwest China) and Tibet, located at the end of the main power grid. These local power grids are weak, lack absorption capacity, and are unsupported by large power grids. In this scenario, the technical and economic feasibility of transmitting large-scale photovoltaic power generation bases to load centers via AC aggregation + DC systems is poor. To achieve the goal of transmitting power from large-scale photovoltaic power generation bases to eastern load centers, it is necessary to solve the problems of efficient, economical, stable aggregation of photovoltaic power and long-distance transmission. A new energy all-DC aggregation and transmission system is a feasible solution for efficient power transmission. Compared with traditional AC power generation, the all-DC system is not affected by reactive power, avoids frequency and power angle stability issues, and significantly improves transmission efficiency and increases transmission distance. However, the new energy all-DC aggregation and transmission system also has a series of problems. For example, due to its lack of reverse power transmission capability, it cannot complete the black start and emergency power support for large-scale new energy bases. Summary of the Invention
[0003] In view of this, the present invention provides a bidirectional asymmetrical feeding type non-isolated DC transformer and its control method to solve the problem that the new energy all-DC collection and transmission system does not have the ability to send back power.
[0004] In a first aspect, the present invention provides a bidirectional asymmetrically fed non-isolated DC transformer, wherein the DC transformer is disposed between a low-voltage side DC bus and a high-voltage side DC bus, and the DC transformer includes: n reversible circuits, each reversible circuit including: a first diode valve branch, a second diode valve branch, a first bridging branch, a second bridging branch, and a first grounding branch, wherein... The anode of the first diode valve branch is connected to the low-voltage side DC bus, the cathode of the first diode valve branch is connected to the anode of the second diode valve branch, and the cathode of the second diode valve branch is connected to the high-voltage side DC bus. The positive terminal of the first grounding branch is connected to the connection point between the first diode valve branch and the second diode valve branch, and the negative terminal of the first grounding branch is connected to the system ground. The positive terminal of the first bridging branch is connected to the cathode of the first diode valve branch, the negative terminal of the first bridging branch is connected to the anode of the first diode valve branch, the positive terminal of the second bridging branch is connected to the cathode of the second diode valve branch, and the negative terminal of the second bridging branch is connected to the anode of the second diode valve branch.
[0005] The present invention provides a bidirectional asymmetrical feeding type non-isolated DC transformer. By connecting a first bridging branch in parallel across the two ends of the first diode valve branch and a second bridging branch in parallel across the two ends of the second diode valve branch, the overall topology of the bidirectional asymmetrical feeding type non-isolated DC transformer has the ability to reverse power transmission. It can complete the black start and emergency power support of large-scale new energy bases and improve the system flexibility.
[0006] In one optional embodiment, the DC transformer further includes: m non-reverse transmission circuits, each non-reverse transmission circuit including: a third diode valve branch, a fourth diode valve branch, and a second grounding branch, wherein, The anode of the third diode valve branch is connected to the low-voltage side DC bus, the cathode of the third diode valve branch is connected to the anode of the fourth diode valve branch, and the cathode of the fourth diode valve branch is connected to the high-voltage side DC bus. The positive terminal of the second grounding branch is connected to the connection point of the third diode valve branch and the fourth diode valve branch, and the negative terminal of the second grounding branch is connected to the system ground.
[0007] By setting up a non-reverse-feeding circuit, it is given priority to undertake the main power transmission task during forward power transmission, thereby reducing the switching frequency of the reverse-feeding circuit and effectively reducing device losses caused by high-frequency switching.
[0008] In one alternative implementation, m≥1, n≥1, m+n≥3.
[0009] In one alternative implementation, each diode valve branch is composed of multiple diodes connected in series with their positive and negative terminals connected end to end.
[0010] In one alternative implementation, each grounding branch consists of a first reactor and a first half-bridge module cascade valve connected in series, wherein the first half-bridge module cascade valve is formed by cascading multiple half-bridge modules.
[0011] In one alternative implementation, each jumper branch consists of a second reactor and a second half-bridge module cascade valve connected in series, wherein the second half-bridge module cascade valve is formed by cascading multiple half-bridge modules.
[0012] In one alternative implementation, the capacity of the jumper branch is less than the capacity of the grounding branch.
[0013] Secondly, the present invention provides a control method for a bidirectional asymmetrically fed non-isolated DC transformer, the control method comprising: When power is transmitted from the high-voltage side to the low-voltage side, the half-bridge modules in all the first crossover branches, all the second crossover branches, and all the first grounding branches are switched on and off according to the transmitted power.
[0014] This invention provides a control method for a bidirectional asymmetrically fed non-isolated DC transformer. By connecting a first bridging branch in parallel across the first diode valve branch and a second bridging branch in parallel across the second diode valve branch, the overall topology of the bidirectional asymmetrically fed non-isolated DC transformer acquires reverse power transmission capability, enabling it to complete black start and emergency power support for large-scale new energy bases, thus improving system flexibility.
[0015] In an optional implementation, the control method further includes: When power is transmitted from the low-voltage side to the high-voltage side, the half-bridge modules in all the first grounding branches and all the half-bridge modules in all the second grounding branches are switched on and off, and the half-bridge modules in all the first bridging branches and all the half-bridge modules in all the second bridging branches are locked out.
[0016] By setting up a non-reverse-feeding circuit, it is given priority to undertake the main power transmission task during forward power transmission, thereby reducing the switching frequency of the reverse-feeding circuit and effectively reducing device losses caused by high-frequency switching. Attached Figure Description
[0017] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.
[0018] Figure 1 This is a topology diagram of a bidirectional asymmetric fed non-isolated DC transformer according to an embodiment of the present invention; Figure 2 This is another bidirectional asymmetric feeding type non-isolated DC transformer topology diagram according to an embodiment of the present invention; Figure 3 This is a flowchart illustrating a control method for another bidirectional asymmetrically fed non-isolated DC transformer according to an embodiment of the present invention. Detailed Implementation
[0019] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0020] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.
[0021] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can also refer to the internal connection of two components; and they can refer to a wireless connection or a wired connection. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.
[0022] Furthermore, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.
[0023] Because the AC collection + DC system for transmitting load centers is technically and economically unsound, a photovoltaic all-DC collection and transmission system is used as an alternative. However, the photovoltaic all-DC collection and transmission system also has a series of problems. For example, because it does not have the ability to reverse power transmission, it cannot complete the black start and emergency power support of large-scale new energy bases.
[0024] To address the aforementioned problems, this application provides a bidirectional asymmetrically fed non-isolated DC transformer. For example... Figure 1As shown, a DC transformer is positioned between the low-voltage side DC bus and the high-voltage side DC bus. The DC transformer includes n reversible circuits 1, each comprising: a first diode valve branch 11, a second diode valve branch 12, a first bridging branch 13, a second bridging branch 14, and a first grounding branch 15. The anode of the first diode valve branch 11 is connected to the low-voltage side DC bus, the cathode of the first diode valve branch 11 is connected to the anode of the second diode valve branch 12, and the cathode of the second diode valve branch 12 is connected to the high-voltage side DC bus. The positive terminal of the first grounding branch 15 is connected to the junction of the first diode valve branch 11 and the second diode valve branch 12, and the negative terminal of the first grounding branch 15 is connected to system ground. The positive terminal of the first bridging branch 13 is connected to the cathode of the first diode valve branch 11, and the negative terminal of the first bridging branch 13 is connected to the anode of the first diode valve branch 11. The positive terminal of the second bridging branch 14 is connected to the cathode of the second diode valve branch 12, and the negative terminal of the second bridging branch 14 is connected to the anode of the second diode valve branch 12. Wherein, n≥1.
[0025] Specifically, during forward power transmission (i.e., from the low-voltage side to the high-voltage side), the switching control is applied to all half-bridge modules in the first grounding branch 15. The number of half-bridge modules in all first bridging branches 13 and all second bridging branches 14 is adjusted according to power transmission requirements to achieve voltage transformation and power transmission. At this time, the half-bridge modules in all first bridging branches 13 and all second bridging branches 14 can be selectively locked or switched on as needed. Typically, to reduce losses, all half-bridge modules in all first bridging branches 13 and all second bridging branches 14 can be locked. During reverse power transmission (i.e., from the high-voltage side to the low-voltage side), the switching control is applied to all half-bridge modules in all first bridging branches 13, all second bridging branches 14, and all first grounding branches 15. By connecting the half-bridge modules in the first bridging branch 13 and all the second bridging branches 14, a path for reverse power transmission is provided. At the same time, the half-bridge module in the first grounding branch 15 of the reverse power transmission circuit participates in the regulation, realizing power transmission from the high-voltage side to the low-voltage side and improving system flexibility.
[0026] The present invention provides a bidirectional asymmetrical feeding type non-isolated DC transformer. By connecting a first bridging branch in parallel across the two ends of the first diode valve branch and a second bridging branch in parallel across the two ends of the second diode valve branch, the overall topology of the bidirectional asymmetrical feeding type non-isolated DC transformer has the ability to reverse power transmission. It can complete the black start and emergency power support of large-scale new energy bases and improve the system flexibility.
[0027] In one alternative implementation, such as Figure 2As shown, the DC transformer also includes m non-reverse transmission circuits 2. Each non-reverse transmission circuit 2 includes a third diode valve branch 21, a fourth diode valve branch 22, and a second grounding branch 23. The anode of the third diode valve branch 21 is connected to the low-voltage side DC bus, the cathode of the third diode valve branch 21 is connected to the anode of the fourth diode valve branch 22, and the cathode of the fourth diode valve branch 22 is connected to the high-voltage side DC bus. The positive terminal of the second grounding branch 23 is connected to the junction of the third diode valve branch 21 and the fourth diode valve branch 22, and the negative terminal of the second grounding branch 23 is connected to system ground. Where m ≥ 1, m + n ≥ 3.
[0028] Specifically, during forward power transmission (from the low-voltage side to the high-voltage side), the switching control of the half-bridge modules in all first grounding branches 15 and all second grounding branches 23 is performed. The number of half-bridge modules engaged in all first bridging branches 13 and all second bridging branches 14 is adjusted according to power transmission requirements to achieve voltage transformation and power transmission. At this time, the half-bridge modules in all first bridging branches 13 and all second bridging branches 14 can be selectively locked or switched on as needed. Typically, to reduce losses, all half-bridge modules in all first bridging branches 13 and all second bridging branches 14 are locked. During reverse power transmission (from the high-voltage side to the low-voltage side), all half-bridge modules in the second grounding branch 23 are locked out, preventing them from participating in operation. The switching control of the half-bridge modules in all first bridging branches 13, all second bridging branches 14, and all first grounding branches 15 is then performed. By setting up a non-reverse-feeding circuit 2, it is given priority to undertake the main power transmission task during forward power transmission, thereby reducing the switching frequency of the reverse-feeding circuit 1 and effectively reducing device losses caused by high-frequency switching.
[0029] In one alternative implementation, each diode valve branch is composed of multiple diodes connected in series with their positive and negative terminals connected end to end.
[0030] Specifically, such as Figure 2 As shown, in all reversible circuits 1, the first diode valve branch 11 and the second diode valve branch 12 are composed of multiple diodes connected in series with their positive and negative terminals connected end to end. Similarly, in all non-reversible circuits 2, the third diode valve branch 21 and the fourth diode valve branch 22 are also composed of multiple diodes connected in series with their positive and negative terminals connected end to end.
[0031] In one alternative implementation, each grounding branch consists of a first reactor and a first half-bridge module cascade valve connected in series, wherein the first half-bridge module cascade valve is formed by cascading multiple half-bridge modules.
[0032] Specifically, such as Figure 2As shown, the first grounding branch 15 in all reversible circuits 1 and the second grounding branch 23 in all non-reversible circuits 2 are composed of a first reactor and a first half-bridge module cascade valve connected in series.
[0033] In one alternative implementation, each jumper branch consists of a second reactor and a second half-bridge module cascade valve connected in series, wherein the second half-bridge module cascade valve is formed by cascading multiple half-bridge modules.
[0034] Specifically, such as Figure 2 As shown, in all reversible circuits 1, the first bridging branch 13 and the second bridging branch 14 are composed of a second reactor and a second half-bridge module cascaded valve connected in series. Similarly, in all non-reversible circuits 2, the third diode valve branch 21 and the fourth diode valve branch 22 are also composed of a second reactor and a second half-bridge module cascaded valve connected in series. In this embodiment of the invention, the power module is configured as a half-bridge, eliminating the need for AC transformers and other equipment, thus reducing equipment costs and system complexity.
[0035] Furthermore, the capacity of the bridging branch is less than that of the grounding branch. The number of half-bridge modules in the second half-bridge cascade valve is less than that in the first half-bridge cascade valve. The power of the half-bridge modules in the second half-bridge cascade valve may also be less than that in the first half-bridge cascade valve.
[0036] The bidirectional asymmetrical feeder non-isolated DC transformer proposed in this application has a simple overall structure, high maturity in high-voltage applications, and is easy to implement and maintain in engineering projects. It has low equipment losses and an overall efficiency of over 99%, which improves energy transmission efficiency. By adding cross-connecting branches, the overall topology has reverse power transmission capability, which can complete the black start and emergency power support of large-scale new energy bases.
[0037] This invention provides a control method for a bidirectional asymmetrically fed non-isolated DC transformer, such as... Figure 3 As shown, the control method includes the following steps: Step S1: When power is transmitted from the high-voltage side to the low-voltage side, the half-bridge modules in all the first bridging branches, all the second bridging branches, and all the first grounding branches are switched on and off according to the transmitted power.
[0038] Step S2: When power is transmitted from the low-voltage side to the high-voltage side, control the switching of half-bridge modules in all first grounding branches and all second grounding branches, and control the blocking of half-bridge modules in all first bridging branches and all second bridging branches.
[0039] Specifically, when power is transmitted in the forward direction (i.e., from the low-voltage side to the high-voltage side), the switching control of the half-bridge modules in all first grounding branches 15 and all second grounding branches 23 is performed, and the number of half-bridge modules engaged in all first bridging branches 13 and all second bridging branches 14 is adjusted to achieve voltage transformation and power transmission. To reduce losses, the half-bridge modules in all first bridging branches 13 and all second bridging branches 14 can be locked out at this time. When power is transmitted in the reverse direction (i.e., from the high-voltage side to the low-voltage side), all half-bridge modules in the second grounding branches 23 are locked out, preventing them from participating in operation, and the switching control of the half-bridge modules in all first bridging branches 13, all second bridging branches 14, and all first grounding branches 15 is performed.
[0040] By connecting a first bridging branch 13 in parallel across the first diode valve branch 11 and a second bridging branch 14 in parallel across the second diode valve branch 12, the overall topology of the bidirectional asymmetrical feed-in non-isolated DC transformer acquires reverse power transmission capability, enabling black start and emergency power support for large-scale new energy bases. By setting up a non-reverse-feed circuit 2, it is prioritized for main power transmission during forward power transmission, thereby reducing the switching frequency of the reverse-feed circuit 1 and effectively reducing device losses caused by high-frequency switching.
[0041] Although embodiments of the invention have been described in conjunction with the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of the invention, and such modifications and variations all fall within the scope defined by the appended claims.
Claims
1. A bidirectional asymmetrically fed non-isolated DC transformer, characterized in that, The DC transformer is located between the low-voltage side DC bus and the high-voltage side DC bus. The DC transformer includes n reversible circuits, each of which includes: a first diode valve branch, a second diode valve branch, a first bridging branch, a second bridging branch, and a first grounding branch. The anode of the first diode valve branch is connected to the low-voltage side DC bus, the cathode of the first diode valve branch is connected to the anode of the second diode valve branch, and the cathode of the second diode valve branch is connected to the high-voltage side DC bus. The positive terminal of the first grounding branch is connected to the connection point between the first diode valve branch and the second diode valve branch, and the negative terminal of the first grounding branch is connected to the system ground. The positive terminal of the first bridging branch is connected to the cathode of the first diode valve branch, the negative terminal of the first bridging branch is connected to the anode of the first diode valve branch, the positive terminal of the second bridging branch is connected to the cathode of the second diode valve branch, and the negative terminal of the second bridging branch is connected to the anode of the second diode valve branch.
2. The bidirectional asymmetrically fed non-isolated DC transformer according to claim 1, characterized in that, The DC transformer further includes m non-reverse transmission circuits, each non-reverse transmission circuit comprising: a third diode valve branch, a fourth diode valve branch, and a second grounding branch, wherein... The anode of the third diode valve branch is connected to the low-voltage side DC bus, the cathode of the third diode valve branch is connected to the anode of the fourth diode valve branch, and the cathode of the fourth diode valve branch is connected to the high-voltage side DC bus. The positive terminal of the second grounding branch is connected to the connection point of the third diode valve branch and the fourth diode valve branch, and the negative terminal of the second grounding branch is connected to the system ground.
3. The bidirectional asymmetrically fed non-isolated DC transformer according to claim 2, characterized in that, m≥1, n≥1, m+n≥3.
4. The bidirectional asymmetrically fed non-isolated DC transformer according to claim 2, characterized in that, Each diode valve branch is composed of multiple diodes connected in series with their positive and negative terminals connected end to end.
5. The bidirectional asymmetrically fed non-isolated DC transformer according to claim 2, characterized in that, Each grounding branch consists of a first reactor and a first half-bridge module cascade valve connected in series, wherein the first half-bridge module cascade valve is formed by multiple half-bridge modules cascaded together.
6. The bidirectional asymmetrically fed non-isolated DC transformer according to claim 5, characterized in that, Each jumper branch consists of a second reactor and a second half-bridge module cascade valve connected in series, and the second half-bridge module cascade valve is formed by multiple half-bridge modules cascading together.
7. The bidirectional asymmetrical feed type non-isolated DC transformer according to claim 6, characterized in that, The capacity of the jumper branch is less than the capacity of the grounding branch.
8. A control method for a bidirectional asymmetrically fed non-isolated DC transformer, characterized in that, The control method includes: When power is transmitted from the high-voltage side to the low-voltage side, the half-bridge modules in all the first crossover branches, all the second crossover branches, and all the first grounding branches are switched on and off according to the transmitted power.
9. The control method for a bidirectional asymmetrically fed non-isolated DC transformer according to claim 8, characterized in that, The control method further includes: When power is transmitted from the low-voltage side to the high-voltage side, the half-bridge modules in all the first grounding branches and all the half-bridge modules in all the second grounding branches are switched on and off, and the half-bridge modules in all the first bridging branches and all the half-bridge modules in all the second bridging branches are locked out.