A dc distribution network ac / dc mmc submodule topology

Abstract

A DC distribution network AC / DC MMC submodule topology, comprising: a half-bridge submodule, a new type of submodule, a power module and a control module; the negative pole end of the half-bridge submodule is connected with the positive pole end of the new type of submodule, the positive pole end of the half-bridge submodule constitutes the positive pole end of the MMC submodule, and the negative pole end of the new type of submodule constitutes the negative pole end of the MMC submodule; the control module is powered by the power module, and control instructions are issued to the half-bridge submodule and the new type of submodule to suppress the DC side fault of the MMC topology; the power module is connected with the new type of submodule and the half-bridge submodule in parallel. The application realizes the suppression of the DC side fault of the MMC topology and eliminates the effect of the "black module".

Description

Technical Field

[0001] This invention relates to the field of power system distribution, and more specifically to an MMC submodule topology for DC distribution network AC / DC. Background Technology

[0002] As the global energy supply shifts towards cleaner, lower-carbon, and electrified power, the power distribution network landscape is rapidly changing. On the power supply side, the proportion of distributed renewable energy is continuously increasing, and the application of technologies such as distributed generation, energy storage, and integrated energy is promoting the cleaner and more diversified power sources in the distribution network. On the load side, the emergence of new load terminals such as data centers and electric vehicles will lead to deep competition among multiple stakeholders in the market environment, making the distribution network face more complex and interactive service demands. Meanwhile, compared to traditional AC distribution networks, DC distribution networks have the advantages of larger power supply capacity, higher power quality, lower line losses, higher power supply reliability, and direct DC power delivery to households.

[0003] AC / DC converters are used in DC distribution networks to convert high-voltage AC to low-voltage (or high-voltage) DC. They are core devices in medium- and high-voltage, high-power AC / DC systems used in renewable energy generation, power quality control, and energy storage system integration. AC / DC converter topologies mainly include Modular Multilevel Converter (MMC) and Cascade-Neutral Point Clamped (C-NPC) types. In applications above 5MW, the MMC topology is more commonly used due to transformer design considerations. Figure 1 The diagram shows the general structure of a three-phase MMC. This MMC model has 6 bridge arms, each containing n sub-modules. This avoids direct series connection of devices, reduces the requirements for power device consistency, and facilitates improvements in voltage level, transmission capacity, and redundancy configuration.

[0004] DC-side short-circuit faults remain one of the main problems faced by MMC (Multi-phase Converter) systems. In existing distribution network projects, MMC topologies mostly use half-bridge sub-modules. When a fault occurs on the DC side, the anti-parallel diodes can still provide a path for the fault current, resulting in an approximate three-phase short circuit in the system. Furthermore, the fault current cannot be interrupted by blocking the converter, seriously jeopardizing the safe and stable operation of the system.

[0005] The "black module" phenomenon is one of the main problems currently faced by MMC (Multi-Module Control). A "black module" refers to a situation where, after the entire converter valve is powered on, the operating information of individual sub-modules cannot be obtained by the control system. Under this condition, a "black module" may cause IGBT explosions, bypass switch malfunctions, and potentially lead to MMC bridge arm open circuits and power distribution network system tripping due to blockage. How to avoid the occurrence of "black modules" and eliminate their potential consequences is one of the important directions for improving MMC reliability. Summary of the Invention

[0006] To overcome the limitations of existing technologies that cannot interrupt fault currents by blocking the converter and thus avoid "black modules," this invention provides an MMC submodule topology for DC distribution network AC / DC converters, comprising:

[0007] The MMC submodule topology includes: a half-bridge submodule, a novel submodule, an energy harvesting module, and a control module;

[0008] The negative terminal of the half-bridge submodule is connected to the positive terminal of the novel submodule, the positive terminal of the half-bridge submodule constitutes the positive terminal of the MMC submodule, and the negative terminal of the novel submodule constitutes the negative terminal of the MMC submodule.

[0009] The control module is powered by the energy harvesting module and sends control commands to the half-bridge submodule and the new submodule to suppress DC-side faults in the MMC topology.

[0010] The energy harvesting module is connected in parallel with the novel submodule and the half-bridge submodule.

[0011] Preferably, the half-bridge submodule includes a first capacitor C1, a first switch module, and a second switch module;

[0012] The first switch module and the second switch module are connected in series and then connected in parallel with the first capacitor C1.

[0013] Preferably, the novel submodule includes a third switch module, a fourth switch module, a fifth switch module, and a second capacitor C2;

[0014] The third, fourth, and fifth switch modules are connected in series and then connected in parallel with the second capacitor C2.

[0015] Preferably, the first switch module, the second switch module, the third switch module, the fourth switch module, and the fifth switch module all include a switching transistor and a reverse diode connected in parallel with the switching transistor.

[0016] Preferably, the switching transistors of the first, second, third, and fifth switching modules are IGBTs, and the switching transistor of the fourth switching module is an IGCT.

[0017] Preferably, the energy harvesting module includes a first energy harvesting power supply P1 and a second energy harvesting power supply P2, and the control module includes a first control unit K1 and a second control unit K2;

[0018] The first control unit K1 is connected to the first power source P1 and the second power source P2 respectively;

[0019] The second control unit K2 is connected to the first power source P1 and the second power source P2 respectively;

[0020] The first control unit K1 and the second control unit K2 are electrically connected to the switching transistors of the first switch module, the second switch module, the third switch module, the fourth switch module and the fifth switch module, respectively;

[0021] The first power source P1 is connected in parallel with the first capacitor C1; the second power source P2 is connected in parallel with the second capacitor C2.

[0022] Preferably, the connection point of the first switch module and the second switch module is the positive terminal of the half-bridge submodule, and the connection point of the fourth switch module and the fifth switch module is the negative terminal of the novel submodule.

[0023] Preferably, a bypass switch B1 is connected in parallel between the positive terminal and the negative terminal of the MMC submodule;

[0024] The bypass switch B1 is electrically connected to the control module.

[0025] Preferably, the control strategy of the MMC submodule at startup includes:

[0026] The control module first sends an enable signal to the switch transistor of the fourth switch module, and then sends enable signals to the switch transistors of the first switch module, the second switch module, the third switch module, and the fifth switch module respectively. After startup, during normal operation, it sends a normally open signal to the switch transistor of the fourth switch module.

[0027] The control strategy of the MMC submodule during latch-up includes:

[0028] The control module first sends a lockout signal to the switching transistors of the first, second, third, and fifth switching modules, and then sends a lockout signal to the switching transistor of the fourth switching module to suppress DC-side faults.

[0029] Preferably, the power supply method of the MMC submodule includes: a first power source P1 draws power from a first capacitor C1 to supply power to the first control unit K1 and the second control unit K2, and a second power source P2 draws power from a second capacitor C2 to supply power to the first control unit K2 and the second control unit K2.

[0030] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0031] This invention discloses a DC distribution network AC / DC MMC submodule topology, comprising: a half-bridge submodule, a novel submodule, an energy harvesting module, and a control module; the negative terminal of the half-bridge submodule is connected to the positive terminal of the novel submodule, the positive terminal of the half-bridge submodule constitutes the positive terminal of the MMC submodule, and the negative terminal of the novel submodule constitutes the negative terminal of the MMC submodule; the control module is powered by the energy harvesting module and issues control commands to the half-bridge submodule and the novel submodule to suppress DC-side faults in the MMC topology; the energy harvesting module is connected in parallel with the novel submodule and the half-bridge submodule. The novel submodule of this invention can suppress DC-side faults in the MMC topology and can utilize the energy harvesting module to suppress and eliminate "black modules" (unauthorized modules). Attached Figure Description

[0032] Figure 1 This is a general structural diagram of a three-phase MMC in the prior art;

[0033] Figure 2 This is a topology diagram of the MMC submodule of the DC distribution network AC / DC according to the present invention. Detailed Implementation

[0034] To better understand the present invention, the following description, in conjunction with the accompanying drawings, will further illustrate the invention.

[0035] This invention provides an MMC submodule topology for DC distribution network AC / DC, such as... Figure 2 As shown, it includes: a half-bridge submodule, a new type of submodule, an energy harvesting module, and a control module;

[0036] The negative terminal of the half-bridge submodule is connected to the positive terminal of the novel submodule, the positive terminal of the half-bridge submodule constitutes the positive terminal of the MMC submodule, and the negative terminal of the novel submodule constitutes the negative terminal of the MMC submodule.

[0037] The control module is powered by the energy harvesting module and sends control commands to the half-bridge submodule and the new submodule to suppress DC-side faults in the MMC topology.

[0038] The energy harvesting module is connected in parallel with the novel submodule and the half-bridge submodule.

[0039] The half-bridge module includes a first capacitor C1, a first switch module, and a second switch module. The first switch module and the second switch module are connected in series and then connected in parallel with the first capacitor C1.

[0040] The novel submodule includes a third switch module, a fourth switch module, a fifth switch module, and a second capacitor C2. The third switch module, the fourth switch module, and the fifth switch module are connected in series and then connected in parallel with the second capacitor C2.

[0041] The first, second, third, fourth, and fifth switch modules all include a switching transistor and a reverse diode connected in parallel with the switching transistor, such as... Figure 2 As shown, the first switching module includes a switching transistor S1 and a diode D1, the second switching module includes a switching transistor S2 and a diode D2, the third switching module includes a switching transistor S3 and a diode D3, the fourth switching module includes a switching transistor S4 and a diode D4, and the fifth switching module includes a switching transistor S5 and a diode D5.

[0042] In the MMC submodule topology, during DC faults, the switching transistor S4 needs to withstand overvoltages exceeding the rated voltage of the first capacitor C1 and the second capacitor C2. Therefore, considering the economics and practicality of DC distribution network applications, S1, S2, S3, and S5 are low-voltage IGBTs, while S4 is a high-voltage IGCT. By using a high-voltage IGCT, S4 assumes the role of reverse withstand voltage and fault clearing after a DC system fault.

[0043] During normal startup, the control module first sends an enable signal to the IGCT and then to the IGBT. During normal operation, the IGCT needs to be kept open. During the interlocking process, the IGBT needs to be interlocked and turned off first, and then the IGCT needs to be turned off. When all interlocks are performed, the fault can be cleared by utilizing the high voltage performance of the IGCT to naturally block the fault.

[0044] The power extraction module includes a first power extraction power supply P1 and a second power extraction power supply P2;

[0045] The control module includes a first control unit K1 and a second control unit K2;

[0046] The first control unit K1 is connected to the first power source P1 and the second power source P2 respectively;

[0047] The second control unit K2 is connected to the first power source P1 and the second power source P2 respectively;

[0048] The first control unit K1 and the second control unit K2 are electrically connected to the switching transistors of the first switch module, the second switch module, the third switch module, the fourth switch module and the fifth switch module, respectively;

[0049] The first power source P1 is connected in parallel with the first capacitor C1; the second power source P2 is connected in parallel with the second capacitor C2.

[0050] The second, third, and fourth switch modules are connected in parallel with a bypass switch B1, which is electrically connected to the control module. The bypass switch B1 disconnects the current to the MMC submodule when a component in the MMC submodule fails.

[0051] The submodule includes two independent capacitors C1 and C2, and is designed with two completely independent power sources P1 and P2. Power sources P1 and P2 independently draw power from C1 and C2 and independently supply power to control boards K1 and K2. Power sources P1 and P2 are respectively connected to control units K1 and K2 to power control units K1 and K2, achieving redundant configuration. The topology used in this invention is not the traditional MMC half-bridge or full-bridge topology; it utilizes the hybrid selection of IGCT and IGBT and their coordination logic during operation to suppress DC-side faults in the MMC topology.

[0052] For ease of description, the various parts of the above device are described separately as modules or units based on their functions. Of course, in implementing this application, the functions of each module or unit can be implemented in one or more software or hardware components.

[0053] Those skilled in the art will understand that embodiments of this application can be provided as methods, systems, or computer program products. Therefore, this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application can take the form of a computer program product embodied on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0054] This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart... Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0055] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0056] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0057] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Those skilled in the art can still make modifications or equivalent substitutions to the specific implementation of the present invention by referring to the above embodiments. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention are within the protection scope of the present invention pending approval.

Claims

1. A DC distribution network AC / DC MMC submodule topology, characterized in that, The MMC submodule topology includes: a half-bridge submodule, a novel submodule, an energy harvesting module, and a control module; The negative terminal of the half-bridge submodule is connected to the positive terminal of the novel submodule, the positive terminal of the half-bridge submodule constitutes the positive terminal of the MMC submodule, and the negative terminal of the novel submodule constitutes the negative terminal of the MMC submodule. The control module is powered by the energy harvesting module and sends control commands to the half-bridge submodule and the new submodule to suppress DC-side faults in the MMC topology. The energy harvesting module is connected in parallel with the novel submodule and the half-bridge submodule; The half-bridge submodule includes a first capacitor C1, a first switch module, and a second switch module; The first switch module and the second switch module are connected in series and then connected in parallel with the first capacitor C1; The first switch module, the second switch module, the third switch module, the fourth switch module, and the fifth switch module all include a switching transistor and a reverse diode connected in parallel with the switching transistor; The first, second, third, and fifth switch modules use IGBTs as their switching transistors, while the fourth switch module uses an IGCT.

2. The MMC submodule topology of a DC distribution network AC / DC according to claim 1, characterized in that, The novel submodule includes a third switch module, a fourth switch module, a fifth switch module, and a second capacitor C2; The third, fourth, and fifth switch modules are connected in series and then connected in parallel with the second capacitor C2.

3. The MMC submodule topology of a DC distribution network AC / DC according to claim 1, characterized in that, The energy harvesting module includes a first energy harvesting power supply P1 and a second energy harvesting power supply P2, and the control module includes a first control unit K1 and a second control unit K2. The first control unit K1 is connected to the first power source P1 and the second power source P2 respectively; The second control unit K2 is connected to the first power source P1 and the second power source P2 respectively; The first control unit K1 and the second control unit K2 are electrically connected to the switching transistors of the first switch module, the second switch module, the third switch module, the fourth switch module and the fifth switch module, respectively; The first power source P1 is connected in parallel with the first capacitor C1; the second power source P2 is connected in parallel with the second capacitor C2.

4. The MMC submodule topology of a DC distribution network AC / DC according to claim 2, characterized in that, The connection point of the first and second switch modules is the positive terminal of the half-bridge submodule, and the connection point of the fourth and fifth switch modules is the negative terminal of the novel submodule.

5. The MMC submodule topology of a DC distribution network AC / DC according to claim 1, characterized in that, It also includes a bypass switch B1 connected in parallel between the positive terminal and the negative terminal of the MMC submodule; The bypass switch B1 is electrically connected to the control module.

6. The MMC submodule topology of a DC distribution network AC / DC according to claim 1, characterized in that... The control strategy for the MMC submodule at startup includes: The control module first sends an enable signal to the switch transistor of the fourth switch module, and then sends enable signals to the switch transistors of the first switch module, the second switch module, the third switch module, and the fifth switch module respectively. After startup, during normal operation, it sends a normally open signal to the switch transistor of the fourth switch module. The control strategy of the MMC submodule during latch-up includes: The control module first sends a lockout signal to the switching transistors of the first, second, third, and fifth switching modules, and then sends a lockout signal to the switching transistor of the fourth switching module to suppress DC-side faults.

7. The MMC submodule topology of a DC distribution network AC / DC according to claim 3, characterized in that, The power supply method of the MMC submodule includes: the first power source P1 draws energy from the first capacitor C1 to supply the first control unit K1 and the second control unit K2, and the second power source P2 draws energy from the second capacitor C2 to supply the first control unit K2 and the second control unit K2.

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