Multi-port fault ride-through and power reconstruction control method and system for solid-state transformer

Abstract

This invention relates to the field of solid-state transformer fault control technology, and particularly to a multi-port fault ride-through and power reconfiguration control method and system for solid-state transformers. The control method includes: real-time acquisition of voltage and current data from each port for fault detection, and broadcasting the real-time operating status as the faulty port ID; adjusting the phase shift angle of the dual active bridge converter chain associated with the faulty port to limit the current at the faulty port below a safe value; and performing adaptive power reconfiguration based on the dynamic power adjustability margin of the non-faulty ports, generating and issuing new power commands to each non-faulty port. This achieves direct and rapid power control, effectively suppressing the first peak of the fault current and improving the hardware security of the power system. Dynamic optimization decisions are made based on the real-time power system status to ensure the overall stability of the power system, enhance the resilience and survivability of the power system under complex fault conditions, and avoid cascading faults caused by improper power transfer.

Description

Technical Field

[0001] This invention relates to the field of solid-state transformer fault control technology, and in particular to a method and system for multi-port fault ride-through and power reconfiguration control of solid-state transformers. Background Technology

[0002] With the high proportion of renewable energy integration and the widespread adoption of DC loads, solid-state transformers with multi-port (high-voltage AC, low-voltage AC, and low-voltage DC) access capabilities have become key equipment for smart distribution networks and the energy internet. When any port fails, there are passive isolation solutions, current-limiting solutions, and power bypass solutions.

[0003] The mainstream passive isolation solution relies on fast mechanical circuit breakers or solid-state circuit breakers on the port side. When an overcurrent is detected, the connection between the faulty port and the internal DC bus is directly cut off.

[0004] Traditional current limiting schemes limit fault current by rapidly adjusting the duty cycle of pulse width modulation (PWM) or using droop control. However, solid-state transformers typically contain multiple energy buffers (such as submodule capacitors and DC bus capacitors). When a fault occurs, these capacitors discharge rapidly, generating a huge instantaneous short-circuit current. Traditional voltage-current dual-loop control has limited bandwidth and slow dynamic response (typically on the order of milliseconds), making it difficult to effectively suppress the first peak current before the capacitors have fully discharged, resulting in a protection blind zone.

[0005] Power bypass schemes are designs that attempt to transfer power to non-faulty ports during a fault. However, existing methods are mostly based on predefined fixed strategies, such as directly unloading renewable energy or connecting unloading resistors. This approach lacks flexibility and cannot be dynamically optimized based on the fault type (symmetrical / asymmetrical short circuit, open circuit) and depth, as well as the real-time load-bearing capacity of the non-faulty ports. This can easily lead to overload or voltage exceedance of the non-faulty ports, triggering a cascading failure.

[0006] In summary, existing technologies for fault handling of multi-port solid-state transformers have three major drawbacks: first, the speed and initiative of fault current suppression are insufficient; second, the fault isolation method is crude, sacrificing power supply continuity; and third, the power reconfiguration strategy is rigid and lacks system-level adaptive coordination capabilities. Summary of the Invention

[0007] The main objective of this invention is to provide a multi-port fault ride-through and power reconfiguration control method and system for solid-state transformers. The aim is to solve the problem of how to actively and quickly suppress the fault current when a single port of a solid-state transformer fails, and smoothly and safely reconfigure the power flow to the non-faulty port within milliseconds, thereby ensuring the uninterrupted operation of the power system.

[0008] To achieve the above objectives, the present invention proposes a multi-port fault ride-through and power reconfiguration control method for solid-state transformers, comprising the following steps: Real-time collection of voltage and current data from each port for fault detection, and broadcasting the real-time operating status as the port ID of the fault; Adjust the phase shift angle of the dual active bridge converter chain associated with the faulty port so that the current at the faulty port is limited to a safe value. After the power system has stabilized transiently, adaptive power reconfiguration is performed based on the dynamic power adjustability margin of the non-faulty ports, generating and issuing new power commands to each non-faulty port. Adjust the output power of each non-faulty port according to the new power command.

[0009] In the above-mentioned multi-port fault ride-through and power reconfiguration control method for solid-state transformers, the fault detection includes: Overcurrent fault detection is performed based on the current data of each port, and voltage drop fault detection is performed based on the voltage data of each port. When the current data meets the preset overcurrent fault criterion and the voltage data meets the voltage drop fault criterion, the real-time operating status of the port is determined to be faulty; otherwise, the port is determined to be non-faulty.

[0010] In the above-mentioned multi-port fault ride-through and power reconfiguration control method for solid-state transformers, the fault detection further includes: Based on current and voltage data, the faulty ports are classified to obtain the fault type of the faulty ports; the fault types include first type fault, second type fault, and third type fault. The first type of fault is: the voltage drop depth is greater than a first preset value, and the port current continuously exceeds a first preset multiple of the rated current, and the current rise rate is greater than a preset threshold. The second type of fault is: the voltage drop depth is greater than or equal to the second preset value and less than or equal to the first preset value, and the port current continuously exceeds the second preset multiple of the rated current, and the current rise rate is lower than the preset threshold; wherein, the second preset multiple is less than the first preset multiple; The third type of fault is: the voltage drop depth is greater than or equal to the third preset value and less than or equal to the second preset value, and the port current has a momentary spike but does not continuously exceed the second preset multiple of its rated current.

[0011] In the above-mentioned multi-port fault ride-through and power reconfiguration control method for solid-state transformers, adjusting the phase shift angle of the dual active bridge converter chain associated with the faulty port includes the following steps: Lock the current phase shift angle command of the dual active bridge converter chain; Based on the fault type, retrieve a safety limit phase shift angle from a predefined lookup table; During the control cycle, the safety limit phase shift angle is overwritten with the current phase shift angle command of the dual active bridge converter chain, so that the active power of the dual active bridge converter chain is instantly latched to the power corresponding to the safety limit phase shift angle.

[0012] In the above-mentioned multi-port fault ride-through and power reconfiguration control method for solid-state transformers, for the first type of fault, the safety limit phase shift angle is a first value close to zero radians; for the second type of fault, the safety limit phase shift angle is a second value greater than the first value; and for the third type of fault, the safety limit phase shift angle is a third value greater than the second value.

[0013] In the above-mentioned multi-port fault ride-through and power reconfiguration control method for solid-state transformers, the transient stability of the power system is defined as the DC bus voltage being maintained within a first preset range of the rated value for several consecutive cycles, and the current at the fault port being below the safe value.

[0014] In the above-mentioned multi-port fault ride-through and power reconfiguration control method for solid-state transformers, the adaptive power reconfiguration includes the following steps: Calculate the power adjustability margin of the non-faulty ports; A power allocation optimization model is constructed, wherein the objective function of the power allocation optimization model is to minimize the total load shedding penalty cost, and the penalty coefficient of critical loads in the objective function is higher than that of non-critical loads; With the constraints that the adjusted power of each port does not exceed its own power adjustable margin and the DC bus voltage deviation is within a second preset range, an optimization algorithm is used to solve the power allocation optimization model and generate new power commands for each non-faulty port.

[0015] The above-mentioned multi-port fault ride-through and power reconfiguration control method for solid-state transformers uses heuristic rules for solution, including the following steps: The power loss of the faulty port is proportionally allocated to the non-faulty ports with adjustable margins. When the total adjustable margin is insufficient, non-critical loads are reduced or cut off in sequence according to a preset priority order until the high-voltage AC input power and the total power of the remaining ports are rebalanced. The non-critical loads include DC loads, interruptible AC loads and the power generation capacity of grid-connected power generation units. The priority of DC loads is greater than that of interruptible AC loads, and the priority of interruptible AC loads is greater than that of the power generation capacity of grid-connected power generation units.

[0016] The aforementioned multi-port fault ride-through and power reconfiguration control method for solid-state transformers also includes using a ramp function with a rate-of-change limit to track new power commands.

[0017] The second aspect of the present invention discloses a multi-port fault ride-through and power reconfiguration control system for solid-state transformers, which is applied to the above-mentioned multi-port fault ride-through and power reconfiguration control method for solid-state transformers, including: a central coordination controller, a DAB controller, and a port local controller. The central coordination controller is used to collect voltage and current data from each port in real time for fault detection and broadcast the real-time operating status as the port ID of the fault. The DAB controller is used to adjust the phase shift angle of the dual active bridge converter chain associated with the faulty port so that the current at the faulty port is limited to a safe value. The central coordination controller is also used to perform adaptive power reconfiguration based on the dynamic power adjustability margin of non-faulty ports after the power system has stabilized transiently, and to generate and issue new power commands to each non-faulty port. The port local controller is used to adjust the transmission power of non-faulty ports according to new power commands.

[0018] The technical solution provided by this invention may include the following beneficial effects: In this application, the phase shift angle of the associated dual active bridge converter chain is adjusted at the faulty port to achieve direct and rapid power control. This improves the fault response speed from milliseconds to microseconds, effectively suppressing the first peak of the fault current and fundamentally protecting semiconductor devices, thus enhancing the hardware safety of the power system. Based on effective current limiting, "flexible isolation" of the faulty port is achieved, maintaining a controllable low-power connection to allow for recovery of some critical loads or faults, rather than physical disconnection.

[0019] Furthermore, adaptive power reconfiguration based on the dynamic power adjustability margin of non-faulty ports enables dynamic optimization decisions based on the real-time power system status, achieving optimized power redistribution, ensuring global stability of the power system, enhancing the resilience and survivability of the power system under complex fault conditions, and avoiding cascading failures caused by improper power transfer. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0021] Figure 1 This is a control schematic diagram of the multi-port fault ride-through and power reconfiguration control system for the solid-state transformer of the present invention; Figure 2This is a flowchart illustrating the steps of the multi-port fault ride-through and power reconfiguration control method for solid-state transformers according to the present invention. Detailed Implementation

[0022] 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 a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0023] It should be noted that all directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of the present invention are only used to explain the relative positional relationship and movement of each component in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indication will also change accordingly.

[0024] In this invention, unless otherwise explicitly specified and limited, the terms "connection," "fixed," etc., should be interpreted broadly. For example, "fixed" can mean a fixed connection, a detachable connection, or an integral part; it can mean a mechanical connection or an electrical connection; it can mean a direct connection or an indirect connection through an intermediate medium; it can mean the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0025] Furthermore, in this invention, descriptions involving "first," "second," etc., are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the word "and / or" throughout the text means including three parallel solutions; taking "A and / or B" as an example, it includes solution A, solution B, or a solution that simultaneously satisfies A and B. Furthermore, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.

[0026] The following is combined Figure 1The multi-port fault ride-through and power reconfiguration control system for a solid-state transformer, as shown in this embodiment, describes a multi-port fault ride-through and power reconfiguration control method for a solid-state transformer according to an embodiment of the present invention. The control system includes a central coordination controller 101, DAB controllers 102 distributed in each DAB unit (connecting the high-voltage side module and the low-voltage DC bus), and port local controllers 103. The port local controllers 103 are used to control the power interface converters of the ports themselves, such as inverters, DC / DC converters, and other output converters. The central coordination controller 101 is capable of fault diagnosis and fault classification, as well as adaptive power reconfiguration. The DAB controllers 102 are capable of controlling the phase shift angle of the dual active bridge converter chain associated with the faulty port, thereby limiting the transmission power of the faulty port. The port local controllers 103 are capable of adjusting the output of the inverters / DC / DC converters to which the non-faulty ports belong, based on the new power command after adaptive power reconfiguration, thereby adjusting the transmission power of the non-faulty ports.

[0027] like Figure 2 As shown, the multi-port fault ride-through and power reconfiguration control method for solid-state transformers according to an embodiment of the present invention includes the following steps: Step S1: Collect voltage and current data of each port in real time for fault detection, and broadcast the real-time operating status as the port ID of the fault; optionally, sample the voltage and current of each port at a frequency higher than 50KHz. Step S2: Adjust the phase shift angle of the dual active bridge converter chain associated with the faulty port so that the current at the faulty port is limited to a safe value. Step S3: After the power system has stabilized transiently, adaptive power reconfiguration is performed based on the dynamic power adjustability margin of the non-faulty ports, and new power commands are generated and issued to each non-faulty port. Step S4: Adjust the output power of each non-faulty port according to the new power command.

[0028] In this application, the phase shift angle of the associated dual active bridge converter chain is adjusted at the faulty port to achieve direct and rapid power control. This improves the fault response speed from milliseconds to microseconds, effectively suppressing the first peak of the fault current and fundamentally protecting semiconductor devices, thus enhancing the hardware safety of the power system. Based on effective current limiting, "flexible isolation" of the faulty port is achieved, maintaining a controllable low-power connection to allow for recovery of some critical loads or faults, rather than physical disconnection.

[0029] Furthermore, adaptive power reconfiguration based on the dynamic power adjustability margin of non-faulty ports enables dynamic optimization decisions based on the real-time power system status, achieving optimized power redistribution, ensuring global stability of the power system, enhancing the resilience and survivability of the power system under complex fault conditions, and avoiding cascading failures caused by improper power transfer.

[0030] In the above-mentioned multi-port fault ride-through and power reconfiguration control method for solid-state transformers, the fault detection is as follows: overcurrent fault judgment is performed based on the current data of each port and voltage drop fault judgment is performed based on the voltage data of each port; when the current data meets the preset overcurrent fault criterion and the voltage data meets the voltage drop fault criterion, the real-time operating state of the port is determined to be faulty; otherwise, the port is determined to be non-faulty.

[0031] In this embodiment, each port is assessed for both overcurrent faults and voltage dip faults based on current data. Only when both current and voltage data meet the preset overcurrent fault criteria and voltage dip fault criteria is the port's real-time operating state determined to be faulty. This improves the accuracy of fault diagnosis, prevents erroneous actions, and ultimately enhances the stability of the power system. For example, in some real-world scenarios, when a motor or capacitive load starts, the starting current is 5-7 times the rated current for a very short time. However, the power supply capacity is sufficient, and the voltage does not experience a significant drop. If the fault is assessed solely based on the port's current, it might be mistakenly interpreted as a port fault, limiting the port's transmission power and causing the equipment to malfunction.

[0032] Specifically, in some optional embodiments, if the current value exceeds the maximum rated current that the port converter can continuously carry for several switching cycles, it is considered an overcurrent fault, and the current data meets the preset overcurrent fault criterion. That is, for several consecutive switching cycles, I port (t)>k 1 *I rated , k 1 =1.5-2.0 . I port (t) This is the real-time current value. k 1 is the first rated multiple. I rated This is the maximum rated current that the port converter is allowed to carry continuously. If the voltage sag exceeds the rated value (calculated using the positive sequence component for AC ports), a voltage sag fault is identified, and the voltage data meets the voltage sag fault criterion. |U port (t)-U ref | / U ref>k 2, U port (t) This is the real-time voltage value. U ref This is the target voltage reference value for the port under normal operating conditions. k 2 is the rated value; for example, k 2 =0.2 .

[0033] Furthermore, in some optional embodiments, the fault detection further includes: Based on the current and voltage data, the faulty ports are classified to obtain the fault type of the faulty ports; the fault type includes first type fault, second type fault and third type fault.

[0034] The first type of fault is: the voltage drop depth is greater than the first preset value, and the port current continuously exceeds the first preset multiple of the rated current, and the current rise rate is greater than the preset threshold. For example, when the voltage drop depth is >50%, and the current rises sharply, exceeding 3 times the rated maximum current that the port converter can pass for a long time, it is identified as the first type of fault, which belongs to the serious short circuit fault type.

[0035] The second type of fault is defined as follows: the voltage drop depth is greater than or equal to the second preset value and less than or equal to the first preset value, the port current continuously exceeds the second preset multiple of the rated current, and the current rise rate is lower than the preset threshold; wherein, the second preset multiple is less than the first preset multiple; for example, when 20%≤voltage drop depth≤50%, the current value exceeds 1.5 times the rated maximum current that the port converter can pass for a long time, and the current rise rate is low, it is identified as the second type of fault, which belongs to the general short circuit fault type.

[0036] The third type of fault is: the voltage drop depth is greater than or equal to the third preset value and less than or equal to the second preset value, and the port current has a momentary spike but does not continuously exceed the second preset multiple of its rated current. For example, when 10% ≤ voltage drop depth ≤ 20%, and the port current has a momentary spike but does not continuously exceed 1.5 times its rated current, it belongs to a voltage temporary fault.

[0037] In this embodiment, fault classification facilitates the determination of the corresponding safety limit phase shift angle based on the fault type. It also helps in subsequent adaptive power reconfiguration by identifying the corresponding input parameters and constraints based on different fault types. For example, for ports with a first-type fault, no transmission power is reserved for that port during reconfiguration; all power is shared or offloaded by other ports. For ports with a second-type or third-type fault, a certain power channel (e.g., 10% of the rated power) is reserved for that port during reconfiguration, and the power lost by that port is allocated to non-faulty ports.

[0038] In some optional implementations, adjusting the phase shift angle of the dual active bridge converter chain associated with the faulty port includes the following steps: Step S21: Lock the current phase shift command of the dual active bridge converter chain; Step S22: Based on the fault type, retrieve a safety limit phase shift angle from a predefined lookup table; Step S23: During the control cycle, the safety limit phase shift angle is overwritten with the current phase shift angle command of the dual active bridge converter chain, so that the active power of the dual active bridge converter chain is instantly latched to the power corresponding to the safety limit phase shift angle.

[0039] For example, the instantaneous effective power of a dual active bridge converter P dab The approximate formula is: P dab (φ)=(n·U 1 ·U 2 ) / (2·π·f s ·L)·φ·(1-|φ| / π) ; in, n For the variable ratio, U 1. U 2 represents the voltage on both sides. f s For switching frequency, L For equivalent inductance, f This represents the phase shift angle between the square waves of the two full-bridge circuits. According to the approximate formula for the instantaneous effective power of a dual active bridge converter, the instantaneous effective power... P dab With phase angle f It exhibits a strong nonlinear positive correlation.

[0040] In this embodiment, when a fault occurs, the current power or voltage outer loop is immediately frozen, thereby locking the current phase shift angle command of the dual active bridge converter chain. Based on the fault type, a safe limit phase shift angle is retrieved from a predefined lookup table. f limWithin a control period (e.g., 10 μs), the safety limit phase shift angle is adjusted. f lim The current phase shift angle command overlays the dual active bridge converter chain, causing the active power of the dual active bridge converter chain to be instantly latched to the safe limit phase shift angle. f lim The corresponding power. The entire operation is a pure hardware logic or high-speed digital signal processing (DSP) instruction, with a response delay of less than 10μs, which is much faster than the capacitor discharge speed, effectively clamping the current rise, thereby suppressing the first peak of the fault current.

[0041] More specifically, for the first type of fault, the safety limit phase shift angle is a first value close to zero radians; for example, for the first type of fault, the safety limit phase shift angle is... f lim Set to a minimum value close to 0 (e.g., 0.05 rad) to make the instantaneous effective power P dab The theoretical value drops sharply to near zero, thus preventing further energy injection from the DC bus to the faulty port at the source. Similarly, for the second type of fault, the safety limit phase shift angle is a second value greater than the first value; for the third type of fault, the safety limit phase shift angle is a third value greater than the second value. When the safety limit phase shift angle is the second or third value, the faulty port can maintain a certain transmission power and is not completely disconnected.

[0042] In this embodiment, by presetting corresponding safety limit phase shift angles for different types of faults, it is easier to quickly confirm the safety limit phase shift angles, reduce calculation steps, achieve rapid response, and perform current limiting control on the faulty port.

[0043] Specifically, in step S3, the power system is considered transiently stable when the DC bus voltage remains within a first preset range of its rated value for several consecutive cycles, and the current at the fault port is below a safe value. For example, if the DC bus voltage remains within ±2% of its rated value for several consecutive cycles, and the current at the fault port is reliably limited to below a safe value through current limiting control, then the power system is considered transiently stable.

[0044] Furthermore, the adaptive power reconstruction includes the following steps: Calculate the power adjustability margin of the non-faulty port; for example, the formula for calculating the power adjustability margin of the non-faulty low-voltage DC port is as follows: ; For the power adjustable margin of the low-voltage DC port, The maximum allowable power at the low-voltage DC port. This represents the current actual operating power of the low-voltage DC port.

[0045] The formula for calculating the power adjustability margin of a non-faulty low-voltage AC port is as follows: ; For the power adjustment margin of the low-voltage AC port, The rated apparent power of the low-voltage AC port. The power factor for the low-voltage AC port. This represents the current actual operating active power of the low-voltage AC port.

[0046] The formula for calculating the power adjustability margin (downward adjustment) at the input port of renewable energy sources (such as photovoltaics) is as follows: ; Power adjustability margin at the input port of renewable energy; This represents the current actual power generation capacity of the renewable energy port.

[0047] A power allocation optimization model is constructed, where the objective function is to minimize the total load shedding penalty cost, with critical loads having a higher penalty coefficient than non-critical loads in the objective function. Critical loads refer to loads essential for maintaining the system's basic functions or safety, and their specific definition depends on the application scenario. Examples include system controllers, communication equipment, and security equipment. Similarly, non-critical loads are predefined, with their specific definition depending on the application scenario. For example, non-critical loads include DC loads, interruptible AC loads, and the power output of grid-connected generation units. By setting a higher penalty coefficient for critical loads in the objective function than for non-critical loads, priority is given to ensuring the protection of critical loads.

[0048] With the constraints that the adjusted power of each port does not exceed its own power adjustable margin and the DC bus voltage deviation is within a second preset range, an optimization algorithm is used to solve the power allocation optimization model and generate new power commands for each non-faulty port.

[0049] For example, there are N non-faulty ports, and the power regulation of port i is: The power allocation optimization model is as follows: ; ; ; ; Where C represents the cost of minimizing the total load shedding penalty. This is the unit power reduction penalty factor for port i, where i is the index of the non-faulty port. It is the power reduction amount at port i. It is the power loss at the faulty port. and These are the power adjustability margins for downward and upward adjustments of port i, respectively; This represents the actual DC bus voltage after adjustment for all non-faulty ports; This is the rated reference value for the DC bus voltage. Furthermore, the power allocation optimization model can be solved using linear programming or heuristic rules.

[0050] As a further example, solving the power allocation optimization model using heuristic rules includes the following steps: The power loss of the faulty port is proportionally allocated to the non-faulty ports with adjustable margins; for example, if the high-voltage AC input power is... The power loss at the faulty port is Its specific value is the original transmission power of the faulty port minus the transmission power retained after current limiting adjustment. The goal of power reconfiguration is to make the high-voltage AC input power equal to... Rebalance with the total power of the remaining ports. According to the formula: ; For the power adjustability margin of port i, This provides a total power adjustment margin. In this way, the power loss from a faulty port is allocated to a non-faulty port with an adjustable margin.

[0051] When the total adjustable margin is insufficient, non-critical loads are reduced or cut off in sequence according to a preset priority order until the high-voltage AC input power and the total power of the remaining ports are rebalanced. The non-critical loads include DC loads, interruptible AC loads and the power generation capacity of grid-connected power generation units. The priority of DC loads is greater than that of interruptible AC loads, and the priority of interruptible AC loads is greater than that of the power generation capacity of grid-connected power generation units.

[0052] Preferably, the multi-port fault ride-through and power reconfiguration control method for solid-state transformers further includes using a ramp function with a rate-of-change limit to track new power commands. This avoids secondary oscillations caused by sudden power changes.

[0053] The present invention also discloses a multi-port fault ride-through and power reconfiguration control system for a solid-state transformer, which is applied to the multi-port fault ride-through and power reconfiguration control method for solid-state transformers described in any of the above claims, including: a central coordination controller, a DAB controller, and a port local controller. The central coordination controller is used to collect voltage and current data from each port in real time for fault detection and broadcast the real-time operating status as the port ID of the fault. The DAB controller is used to adjust the phase shift angle of the dual active bridge converter chain associated with the faulty port so that the current at the faulty port is limited to a safe value. The central coordination controller is also used to perform adaptive power reconfiguration based on the dynamic power adjustability margin of non-faulty ports after the power system has stabilized transiently, and to generate and issue new power commands to each non-faulty port. The port local controller is used to adjust the transmission power of non-faulty ports according to new power commands.

[0054] The multi-port fault ride-through and power reconfiguration control system for solid-state transformers provided in this invention adjusts the phase shift angle of the associated dual active bridge converter chain at the faulty port, achieving direct and rapid power control. This improves the fault response speed from milliseconds to microseconds, effectively suppressing the first peak of the fault current and fundamentally protecting semiconductor devices, thus enhancing the hardware security of the power system. Based on effective current limiting, it achieves "flexible isolation" of the faulty port, maintaining a controllable low-power connection to allow for recovery of some important loads or faults, rather than physical disconnection.

[0055] Furthermore, adaptive power reconfiguration based on the dynamic power adjustability margin of non-faulty ports enables dynamic optimization decisions based on the real-time power system status, achieving optimized power redistribution, ensuring global stability of the power system, enhancing the resilience and survivability of the power system under complex fault conditions, and avoiding cascading failures caused by improper power transfer.

[0056] The above description is only a preferred embodiment of the present invention and does not limit the patent scope of the present invention. All equivalent structural transformations made under the concept of the present invention using the contents of the present invention specification and drawings, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A method for multi-port fault ride-through and power reconfiguration control of a solid state transformer, characterized in that: Includes the following steps: Real-time collection of voltage and current data from each port for fault detection, and broadcasting the real-time operating status as the port ID of the fault; Adjust the phase shift angle of the dual active bridge converter chain associated with the faulty port so that the current at the faulty port is limited to a safe value. After the power system has stabilized transiently, adaptive power reconfiguration is performed based on the dynamic power adjustability margin of the non-faulty ports, generating and issuing new power commands to each non-faulty port. Adjust the output power of each non-faulty port according to the new power command.

2. The multi-port fault ride through and power reconfiguration control method of a solid state transformer according to claim 1, characterized in that: The fault detection includes: Overcurrent fault detection is performed based on the current data of each port, and voltage drop fault detection is performed based on the voltage data of each port. When the current data meets the preset overcurrent fault criterion and the voltage data meets the voltage drop fault criterion, the real-time operating status of the port is determined to be faulty; otherwise, the port is determined to be non-faulty.

3. The multi-port fault ride through and power reconfiguration control method of a solid state transformer according to claim 1, characterized in that: The fault detection also includes: Based on current and voltage data, the faulty ports are classified to obtain the fault type of the faulty ports; the fault types include Class I fault, Class II fault, and Class III fault. The first type of fault is: the voltage drop depth is greater than a first preset value, and the port current continuously exceeds a first preset multiple of the rated current, and the current rise rate is greater than a preset threshold. The second type of fault is: the voltage drop depth is greater than or equal to the second preset value and less than or equal to the first preset value, and the port current continuously exceeds the second preset multiple of the rated current, and the current rise rate is lower than the preset threshold; wherein, the second preset multiple is less than the first preset multiple; The third type of fault is: the voltage drop depth is greater than or equal to the third preset value and less than or equal to the second preset value, and the port current has a momentary spike but does not continuously exceed the second preset multiple of its rated current.

4. The multi-port fault ride-through and power reconfiguration control method for solid-state transformers according to claim 3, characterized in that: Adjusting the phase shift angle of the dual active bridge converter chain associated with the faulty port includes the following steps: Lock the current phase shift angle command of the dual active bridge converter chain; Based on the fault type, retrieve a safety limit phase shift angle from a predefined lookup table; During the control cycle, the safety limit phase shift angle is overwritten with the current phase shift angle command of the dual active bridge converter chain, so that the active power of the dual active bridge converter chain is instantly latched to the power corresponding to the safety limit phase shift angle.

5. The multi-port fault ride-through and power reconfiguration control method for solid-state transformers according to claim 4, characterized in that: For the first type of fault, the safety limit phase shift angle is a first value close to zero radians; for the second type of fault, the safety limit phase shift angle is a second value greater than the first value; for the third type of fault, the safety limit phase shift angle is a third value greater than the second value.

6. The multi-port fault ride-through and power reconfiguration control method for solid-state transformers according to claim 1, characterized in that: Transient stability of a power system is defined as the DC bus voltage remaining within a first preset range of its rated value for several consecutive cycles, and the current at the fault port being below a safe value.

7. The multi-port fault ride-through and power reconfiguration control method for solid-state transformers according to claim 1, characterized in that: The adaptive power reconstruction includes the following steps: Calculate the power adjustability margin of non-faulty ports; A power allocation optimization model is constructed, wherein the objective function of the power allocation optimization model is to minimize the total load shedding penalty cost, and the penalty coefficient of critical loads in the objective function is higher than that of non-critical loads; With the constraints that the adjusted power of each port does not exceed its own power adjustable margin and the DC bus voltage deviation is within a second preset range, an optimization algorithm is used to solve the power allocation optimization model and generate new power commands for each non-faulty port.

8. The multi-port fault ride-through and power reconfiguration control method for solid-state transformers according to claim 7, characterized in that: The solution is obtained using heuristic rules, including the following steps: The power loss of the faulty port is proportionally allocated to the non-faulty ports with adjustable margins. When the total adjustable margin is insufficient, non-critical loads are reduced or cut off in sequence according to a preset priority order until the high-voltage AC input power and the total power of the remaining ports are rebalanced. The non-critical loads include DC loads, interruptible AC loads and the power generation capacity of grid-connected power generation units. The priority of DC loads is greater than that of interruptible AC loads, and the priority of interruptible AC loads is greater than that of the power generation capacity of grid-connected power generation units.

9. The multi-port fault ride-through and power reconfiguration control method for solid-state transformers according to claim 1, characterized in that: It also includes using a ramp function with a rate-of-change limit to track new power commands.

10. A multi-port fault ride-through and power reconfiguration control system for solid-state transformers, characterized in that: The multi-port fault ride-through and power reconfiguration control method for solid-state transformers as described in any one of claims 1-9 includes: a central coordination controller, a DAB controller, and a port local controller; The central coordination controller is used to collect voltage and current data from each port in real time for fault detection and broadcast the real-time operating status as the port ID of the fault. The DAB controller is used to adjust the phase shift angle of the dual active bridge converter chain associated with the faulty port so that the current at the faulty port is limited to a safe value. The central coordination controller is also used to perform adaptive power reconfiguration based on the dynamic power adjustability margin of non-faulty ports after the power system has stabilized transiently, and to generate and issue new power commands to each non-faulty port. The port local controller is used to adjust the transmission power of non-faulty ports according to new power commands.

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