A power coordination method and system for a flexible direct current power distribution network

Abstract

The application discloses a power coordination method and system of a flexible DC power distribution network, belongs to the field of DC power distribution networks, and particularly relates to power control of a power distribution system, which comprises the following steps: identifying normally-operating submodules according to the operating states of each submodule of the flexible DC power distribution network; calculating the modulation depth adjustment value and the duty cycle of the normally-operating submodules according to an activated reserve capacity sequence, forming a dynamic adjustment scheme, and reallocating the power of the flexible DC power distribution network to generate a power coordination allocation result; updating the allocation proportion of the activated reserve capacity sequence according to the power coordination allocation result and load change requirements, evaluating the load bearing capacity of the normally-operating submodules, and generating a preventive adjustment value based on the load bearing capacity to realize the power coordination of the flexible DC power distribution network. The application realizes the power coordination allocation of the flexible DC power distribution network and improves the power supply reliability and power management efficiency of the DC power distribution network.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of direct current power distribution network, and in particular to a power coordination method and system for flexible direct current power distribution network. BACKGROUND

[0002] Flexible direct current power distribution network is the core of modern smart grid, which can efficiently integrate distributed new energy (such as photovoltaic and wind power) and provide high-quality power supply for sensitive loads. Its core component, modular multilevel converter, is responsible for precise power regulation to maintain system stability under dynamic load and fault conditions. However, in actual operation, the insulated gate bipolar transistor (IGBT) of the sub-module may be subjected to overvoltage stress due to sudden load changes or fault disturbances, which may cause overvoltage breakdown when exceeding the safety threshold, causing the sub-module to exit operation. If the system cannot respond quickly and intelligently, the power gap of the faulty sub-module will be transferred to the normal sub-module, increasing the risk of overload, and in severe cases, may cause global power imbalance, voltage collapse and power interruption.

[0003] Existing technologies usually adopt passive protection strategies based on fixed redundancy design or relatively simple power redistribution algorithms. However, these methods have obvious defects, lack real-time monitoring of sub-module operating state, and their coordination mechanism is rigid, slow to respond, and lacks proactive preventive adjustment capabilities, which cannot meet the high standards of dynamic response speed, power distribution balance and system operation robustness required by modern flexible direct current power distribution network. SUMMARY

[0004] The present application provides a power coordination method and system for flexible direct current power distribution network, which can realize power coordination of modular multilevel converters in flexible direct current power distribution network and improve system stability.

[0005] An embodiment of the present application provides a power coordination method for flexible direct current power distribution network, comprising:

[0006] Obtaining the operating state of each sub-module of the modular multilevel converter in the flexible direct current power distribution network, and identifying a plurality of normally operating sub-modules based on the operating state;

[0007] Generating an activated reserve capacity sequence for power coordination based on the power margin value of each normally operating sub-module;

[0008] According to the activated reserve capacity sequence, a modulation depth adjustment value and a duty cycle of each normal operation submodule are calculated to form a dynamic adjustment scheme, and power of the flexible DC power distribution network is re-distributed based on the dynamic adjustment scheme to generate a power coordination allocation result, and the allocation proportion of the activated reserve capacity sequence is updated according to the power coordination allocation result and load change demand to evaluate the load bearing capacity of each normal operation submodule, and voltage stability and power distribution balance margin of the modular multilevel converter are verified based on the load bearing capacity to generate a preventive adjustment value for preventing overvoltage breakdown, and power coordination of the flexible DC power distribution network is realized based on the preventive adjustment value.

[0009] The embodiments of the present application can exclude the interference of faulty or abnormal submodules in real time by obtaining submodule operation states and identifying normal operation submodules, and ensure that power coordination is only based on healthy units, thereby avoiding further problems caused by operating faulty modules. The activated reserve capacity sequence is generated based on the power margin value of the normal operation submodule, which allows the system to tap the potential capacity of the submodule, optimizes the allocation of standby resources, enhances the flexibility of power regulation, enables the system to quickly respond to load fluctuations, reduces the risk of power shortage or excess, and thereby suppresses voltage fluctuations. The modulation depth adjustment value and the duty cycle are calculated according to the reserve sequence to form a dynamic adjustment scheme, the power load between submodules is balanced by adjusting the modulation strategy to prevent over-modulation or under-modulation, and the converter is ensured to work in an efficient area, thereby directly improving the accuracy and dynamic stability of power distribution. The power is re-distributed based on the dynamic adjustment scheme and a power coordination allocation result is generated, which reduces the pressure on overloaded submodules and reduces thermal and electrical stress, thereby prolonging the service life of the equipment and maintaining stable operation of the system. The coordination reserve allocation proportion is updated according to the allocation result and the load change demand, so that the system can dynamically optimize the reserve utilization following the load change, improve the resilience and adaptability of the system, and avoid collapse caused by sudden load. Voltage stability and power distribution balance margin are verified based on the load bearing capacity, and a preventive adjustment value for preventing overvoltage breakdown is generated, which identifies potential overvoltage risks through forward-looking assessment, takes preventive measures such as adjusting the voltage reference value or limiting power flow, effectively suppresses the breakdown phenomenon, and improves the safety margin of the system. Power coordination is realized based on the preventive adjustment value, which integrates all adjustment measures to form a comprehensive optimization, ensuring that the system not only copes with the current state after coordination, but also prevents future disturbances, thereby achieving long-term stability. Compared with the prior art, the present application can realize power coordination of the modular multilevel converter in the flexible DC power distribution network and improve the stability of the system.

[0010] Further, the operation states of each submodule of the modular multilevel converter in the flexible DC power distribution network are obtained, and a plurality of normal operation submodules are identified based on the operation states, specifically:

[0011] Collecting a voltage signal from a collector electrode to an emitter electrode of an insulated gate bipolar transistor in each submodule of a modular multilevel converter in a flexible DC distribution network;

[0012] Comparing the voltage signal with a first preset threshold value, and determining a plurality of normally operating submodules when the voltage signal is lower than the first preset threshold value, wherein the first preset threshold value is set based on a breakdown voltage of the insulated gate bipolar transistor.

[0013] In this way, by obtaining the submodule operating state and identifying the normally operating submodules, the interference of faulty or abnormal submodules can be excluded in real time, and power coordination is ensured to be based only on healthy units, which directly improves the reliability and fault tolerance of the system.

[0014] Further, based on the power margin value of each normally operating submodule, an activated reserve capacity sequence for power coordination is generated, specifically:

[0015] The current output power of each normally operating submodule is determined, and the difference between the current output power and the rated power is calculated to determine the corresponding power margin value;

[0016] The normally operating submodule with a power margin value exceeding a second preset threshold value is determined as an activated reserve submodule, and the sum of the power margin values of all the activated reserve submodules is calculated as an activated reserve capacity threshold value;

[0017] The activated reserve submodules are sorted in descending order of the power margin values to obtain a sorting result, and the cumulative power margin value of a target submodule selected from the sorting result is calculated until the cumulative power margin value reaches a preset multiple of the activated reserve capacity threshold value. The identification, selection order and power margin value of the target submodule are combined to form the activated reserve capacity sequence.

[0018] In this way, the activated reserve capacity sequence is generated based on the power margin value of the normally operating submodule, which allows the system to tap the potential capacity of the submodule, optimizes the allocation of standby resources, enhances the flexibility of power regulation, enables the system to respond quickly to load fluctuations, reduces the risk of power shortage or excess, and thereby suppresses voltage fluctuations.

[0019] Further, according to the activated reserve capacity sequence, the modulation depth adjustment value and the duty cycle of each normally operating submodule are calculated to form a dynamic adjustment scheme, specifically:

[0020] Based on the power margin value of each normally operating submodule in the activated reserve capacity sequence, the proportion of the power increment that each normally operating submodule needs to bear to the rated power is calculated, and an initial modulation depth adjustment value is determined based on the proportion;

[0021] According to the initial modulation depth adjustment value, the on-time of each normal operation submodule in a switching cycle is calculated, and an initial duty cycle is determined based on the on-time and the switching cycle; and a voltage deviation value of a direct current side capacitor of each normal operation submodule is detected, and when the voltage deviation value exceeds a third preset threshold value, the initial duty cycle of the corresponding submodule is adjusted to obtain a corrected target duty cycle;

[0022] A first power difference value is determined based on the target duty cycle and the real-time output power of each normal operation submodule, a power distribution ratio is determined through a ratio of the first power difference value to a rated power, and the power distribution ratio and a voltage balance coefficient are combined as a duty cycle optimization parameter; the pulse width modulation signal of each normal operation submodule is adjusted through the duty cycle optimization parameter to determine the modulation depth adjustment value; the target duty cycles of the normal operation submodules are arranged in a position order to form a duty cycle adjustment sequence; and the modulation depth adjustment value and the duty cycle adjustment sequence are combined to determine the dynamic adjustment scheme, wherein the voltage balance coefficient is determined according to a ratio of a root mean square value of the capacitor voltage deviation to a rated voltage.

[0023] In this way, the modulation depth adjustment value and the duty cycle are calculated according to the reserve sequence to form the dynamic adjustment scheme, the power load between the submodules is balanced by adjusting the modulation strategy, over-modulation or under-modulation is prevented, the converter is ensured to work in the high-efficiency region, and the accuracy and dynamic stability of power distribution are directly improved.

[0024] Further, based on the dynamic adjustment scheme, the power of the flexible HVDC power distribution network is redistributed to generate a power coordination distribution result, specifically:

[0025] The target modulation depth value is obtained by adding the modulation depth adjustment value in the dynamic adjustment scheme to the current modulation depth reference value of each normal operation submodule;

[0026] According to the duty cycle adjustment sequence, the pulse width modulation signal corresponding to each normal operation submodule is generated, and the pulse width modulation signal is used to control the turn-on and turn-off of the corresponding insulated gate bipolar transistor; and the output voltage amplitude of the submodule is adjusted according to the target modulation depth value;

[0027] The active power and the reactive power actually output by each normal operation submodule are monitored to calculate a power deviation rate, and when the power deviation rate exceeds a fourth preset threshold value, a proportional integral control algorithm is used to fine-tune the target duty cycle of the corresponding submodule to make the actual power approach the target value; and the power data of each normal operation submodule is summarized to obtain the power coordination distribution result.

[0028] Thus, the power is redistributed based on the dynamic adjustment scheme and a power coordination allocation result is generated, which reduces the stress of the overloaded sub-modules, reduces thermal stress and electrical stress, thereby prolonging the service life of the equipment and maintaining stable operation of the system.

[0029] Further, the allocation proportion of the activated reserve capacity sequence is updated according to the power coordination allocation result and load change demand, so as to evaluate the load bearing capacity of each normal operation sub-module, specifically:

[0030] The allocation proportion of the activated reserve capacity sequence is updated according to the power coordination allocation result and load change demand;

[0031] The target power output value of each normal operation sub-module is extracted from the power coordination allocation result, and a second power difference value between the load power demand and the target power output value is calculated, and a load power demand change rate is determined based on the second power difference value;

[0032] The load power demand change rate is used to construct an initial population of a genetic algorithm, the allocation proportion is encoded as a chromosome, and a weighted sum of load matching degree and power balance degree is used as a fitness function, and the selection, crossover and mutation operations are iteratively optimized, and when the fitness value converges, the updated target allocation proportion is decoded;

[0033] According to the target allocation proportion, the maximum allocatable power, response time and overload risk index are calculated, and the load bearing capacity of each sub-module is determined based on the maximum allocatable power, the response time and the overload risk index.

[0034] Thus, the coordination reserve allocation proportion is updated according to the allocation result and the load change demand, so that the system can dynamically optimize the utilization of reserves following the load change, improve the resilience and adaptability of the system, and avoid collapse caused by sudden load.

[0035] Further, based on the load bearing capacity, the voltage stability and power allocation balance margin of the modular multilevel converter are verified to generate a preventive adjustment value for preventing overvoltage breakdown, specifically:

[0036] Based on the load bearing capacity, the real-time power output value of each normal operation sub-module is determined and is summarized to obtain a power summary value, and a satisfaction degree value is determined based on the power summary value;

[0037] According to the satisfaction degree value, the system operating state is judged, and based on the system operating state, the voltage data of the upper and lower bridge arms of the modular multilevel converter is collected, and the ratio of the absolute value of the voltage difference of the upper and lower bridge arms to the rated voltage is calculated as a voltage stability index;

[0038] Calculate the standard deviation between the actual power of each normally operating submodule and the average power of all submodules, and use the ratio of the standard deviation to the average power as the power distribution balance margin.

[0039] Based on the voltage stability index and the power distribution balance margin, the submodule with the highest voltage value is identified, the highest voltage value of the collector-emitter voltage of the corresponding submodule's insulated gate bipolar transistor is read, and the breakdown voltage of the insulated gate bipolar transistor and the highest voltage value are calculated as the voltage safety margin. Based on the voltage safety margin, the prevention adjustment value for potential overvoltage breakdown is obtained.

[0040] This approach verifies voltage stability and power distribution balance margin based on load-bearing capacity, and generates preventive adjustment values ​​to prevent overvoltage breakdown. By proactively assessing potential overvoltage risks and taking preventive measures such as adjusting voltage reference values ​​or limiting power flow, it effectively suppresses breakdown and improves the system's safety margin.

[0041] Furthermore, the power coordination of the flexible DC distribution network based on the preventive adjustment value specifically includes:

[0042] Based on the aforementioned prevention adjustment value, the target reserve allocation amount for the next control cycle of each of the aforementioned normal operation sub-modules is determined, and the modules are sorted from largest to smallest according to the target reserve allocation amount to generate a reserve update sequence;

[0043] The status parameters of all sub-modules of the modular multilevel converter are monitored to identify potential fault points based on the status parameters. If the number of potential fault points exceeds a preset threshold, it is determined that there is a new fault risk.

[0044] If a new fault risk exists, the reserve power of each of the normally operating sub-modules will be called sequentially according to the reserve update sequence for compensation until the output power of each sub-module reaches a stable operating state.

[0045] This power coordination based on preventative adjustment values ​​integrates all adjustment measures to form a comprehensive optimization, ensuring that the system, after coordination, can not only cope with the current state but also prevent future disturbances, thereby achieving long-term stability.

[0046] Another embodiment of the present invention provides a power coordination system for a flexible DC distribution network, comprising: an acquisition module, a generation module, and a coordination module;

[0047] The acquisition module is used to acquire the operating status of each sub-module of the modular multilevel converter in the flexible DC distribution network, and identify several normally operating sub-modules based on the operating status.

[0048] The generation module is used to generate an activation reserve capacity sequence for power coordination based on the power margin value of each of the normally operating sub-modules.

[0049] The coordination module is used to calculate the modulation depth adjustment value and duty cycle of each of the normally operating sub-modules according to the activated reserve capacity sequence to form a dynamic adjustment scheme. Based on the dynamic adjustment scheme, the power of the flexible DC distribution network is redistributed to generate a power coordination allocation result. The allocation ratio of the activated reserve capacity sequence is updated according to the power coordination allocation result and the load change demand to evaluate the load-bearing capacity of each of the normally operating sub-modules. Based on the load-bearing capacity, the voltage stability and power distribution balance margin of the modular multilevel converter are verified to generate a preventive adjustment value for preventing overvoltage breakdown. Based on the preventive adjustment value, the power coordination of the flexible DC distribution network is realized.

[0050] Furthermore, the coordination module includes:

[0051] An update unit is used to update the allocation ratio of the activated reserve capacity sequence based on the power coordination allocation result and load change requirements;

[0052] The extraction unit is used to extract the target power output value of each of the normal operation sub-modules from the power coordination and allocation result, calculate the second power difference between the load power demand and the target power output value, and determine the load power demand change rate based on the second power difference.

[0053] An iterative unit is used to construct an initial population for a genetic algorithm using the load power demand change rate, encode the allocation ratio as a chromosome, use the weighted sum of load matching degree and power balance degree as the fitness function, iteratively optimize through selection, crossover and mutation operations, and decode the updated target allocation ratio when the fitness value converges.

[0054] The determining unit is used to calculate the maximum allocable power, response time, and overload risk index according to the target allocation ratio, so as to determine the load-bearing capacity of each submodule based on the maximum allocable power, the response time, and the overload risk index. Attached Figure Description

[0055] To more clearly illustrate the technical solution of this application, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0056] Figure 1 This is a flowchart illustrating one embodiment of the power coordination method for flexible DC distribution networks provided in this application;

[0057] Figure 2 This is a flowchart illustrating one embodiment of steps S201 to S203 provided in this application;

[0058] Figure 3 This is a flowchart illustrating one embodiment of steps S301 to S303 provided in this application;

[0059] Figure 4 This is a flowchart illustrating one embodiment of steps S401 to S403 provided in this application;

[0060] Figure 5 This is a flowchart illustrating one embodiment of steps S501 to S504 provided in this application;

[0061] Figure 6 This is a flowchart illustrating one embodiment of steps S601 to S604 provided in this application;

[0062] Figure 7 This is a schematic diagram of one embodiment of the power coordination system for the flexible DC distribution network provided in this application. Detailed Implementation

[0063] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions of this application will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0064] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0065] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined.

[0066] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0067] In the description of the embodiments in this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.

[0068] In the description of the embodiments of this application, the term "multiple" refers to two or more (including two), similarly, "multiple sets" refers to two or more (including two sets), and "multiple pieces" refers to two or more (including two pieces).

[0069] In the description of the embodiments of this application, unless otherwise expressly specified and limited, technical terms such as "installation," "connection," "joining," and "fixing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; 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 refer to the internal communication of two components or the interaction between two components. For those skilled in the art, the specific meaning of the above terms in the embodiments of this application can be understood according to the specific circumstances.

[0070] Flexible DC distribution networks are the core of modern smart grids, playing a crucial role in efficiently integrating distributed renewable energy sources such as photovoltaics and wind power, and ensuring high-quality power supply to sensitive loads. Their core relies on modular multilevel converters to precisely regulate power, ensuring system stability under dynamic loads and fault scenarios. However, in actual operation, sub-module insulated gate bipolar transistors (IGBTs) are prone to breakdown due to sudden load changes or fault disturbances, leading to sub-module failure. If the system does not respond quickly and intelligently, a chain reaction can occur: the power deficit of the faulty sub-module is transferred to the normal sub-module, drastically increasing its overload risk, and in severe cases, causing global power imbalance, voltage collapse, and power outages. Existing technologies mostly employ fixed redundancy passive protection or simple power redistribution algorithms, which are insufficient to meet the high requirements of modern flexible DC distribution networks for dynamic response, power balance, and operational robustness.

[0071] See Figure 1 To achieve power coordination of modular multilevel converters in flexible DC distribution networks, an embodiment of the present invention provides a power coordination method for flexible DC distribution networks, including steps S101 to S103.

[0072] Step S101: Obtain the operating status of each sub-module of the modular multilevel converter in the flexible DC distribution network, and identify several normally operating sub-modules based on the operating status;

[0073] In some embodiments, step S101 includes: acquiring the collector-to-emitter voltage signal of the insulated gate bipolar transistor (IGBT) in each sub-module of the modular multilevel converter in a flexible DC distribution network; comparing the voltage signal with a first preset threshold; and determining a plurality of normally operating sub-modules when the voltage signal is lower than the first preset threshold, wherein the first preset threshold is set based on the breakdown voltage of the IGBT. Specifically, firstly, the collector-to-emitter voltage signal of the IGBT in each sub-module is acquired in real time through a distributed voltage acquisition terminal deployed on the modular multilevel converter. Subsequently, the acquired real-time voltage signal is compared with a first preset threshold. The setting of the first preset threshold is crucial. It is not a fixed value, but is scientifically determined based on the rated breakdown voltage and safe operating range of the selected IGBT device. For example, for an IGBT with a rated voltage of 1700V, the first preset threshold can be set to a specific safe percentage (such as 80%) of its rated withstand voltage. When the detected collector-emitter voltage is lower than the first preset threshold, it indicates that the submodule is currently operating within a safe voltage range, and thus can be judged as a normally operating submodule.

[0074] It should be noted that each submodule in the modular multilevel converter is equipped with an independent differential amplifier circuit, which is directly connected to the collector and emitter pins of the IGBT. By using a high-precision analog-to-digital converter to convert the analog voltage signal into a digital signal at a sampling frequency of no less than a thousand times per second, it is possible to capture transient voltage fluctuations that may indicate a fault.

[0075] It should be noted that when the voltage signal exceeds the first preset threshold, it will be marked as a potentially faulty submodule, and these need to be eliminated in the future to avoid affecting the normal operation of the submodule.

[0076] By acquiring the operating status of submodules and identifying normally operating submodules, interference from faulty or abnormal submodules can be eliminated in real time, ensuring that power coordination is performed only based on healthy units. This directly improves the reliability and fault tolerance of the system.

[0077] Step S102: Based on the power margin values ​​of each of the normally operating submodules, generate an active reserve capacity sequence for power coordination;

[0078] Please refer to Figure 2 In some embodiments, step S102 includes steps S201 to S203:

[0079] Step S201: Determine the current output power of each of the normally operating submodules, and calculate the difference between the current output power and the rated power to determine the corresponding power margin value;

[0080] In some embodiments, firstly, the operating data of each submodule, including the instantaneous values ​​of voltage and current at the output terminal, are acquired in real time through a distributed voltage acquisition terminal of the modular multilevel converter. The acquired voltage and current signals are then processed by a power calculation unit (such as a digital signal processor or application-specific integrated circuit), and the average active power over one power frequency cycle is obtained through integration, which is used as the current output power. Then, the rated power of each submodule (pre-stored in the system parameter database) is read to calculate the difference between the current output power and the rated power, thus obtaining the power margin value.

[0081] It should be noted that the power margin value reflects the available capacity of the submodule. A positive value indicates that the submodule has redundant power available for coordination and reserve. For example, if a submodule has a rated power of 100kW and a current output power of 75kW, then the power margin value is 25kW.

[0082] Step S202: Determine the normally operating submodules whose power margin values ​​exceed the second preset threshold as activatable reserve submodules, and calculate the sum of the power margin values ​​of all activatable reserve submodules as the activation reserve capacity threshold.

[0083] In some embodiments, firstly, a second preset threshold is set, and the power margin value of each normally operating submodule is compared with the second preset threshold. If the power margin value exceeds the second preset threshold, the submodule is marked as an activatable reserve submodule. Subsequently, the power margin values ​​of all activatable reserve submodules are summed, and their sum is calculated as the activation reserve capacity threshold. This threshold represents the total available reserve power capacity of the system, used to determine whether there is sufficient coordination capability. For example, assuming there are 10 normally operating submodules, and the power margin values ​​of 5 of them exceed the threshold (e.g., 20kW, 15kW, 10kW, etc.), then the activation reserve capacity threshold is the sum of these margins (e.g., 55kW).

[0084] It should be noted that the second preset threshold can be dynamically adjusted according to the load characteristics of the distribution network, for example, it can be set to 5%-10% of the rated power, and this application does not impose any restrictions.

[0085] Step S203: Sort the activatable reserve sub-modules in descending order of power margin value to obtain a sorting result, and calculate the cumulative power margin value of the target sub-modules selected sequentially from the sorting result until the cumulative power margin value reaches a preset multiple of the activation reserve capacity threshold. Combine the identifier, selection order and power margin value of the target sub-modules to form the activation reserve capacity sequence.

[0086] In some embodiments, firstly, the activatable reserve submodules are sorted from largest to smallest according to their power margin values, forming a sorting result. Then, target submodules are selected sequentially from the sorting result, and the cumulative power margin value of the selected target submodules is calculated in real time. When the cumulative power margin reaches a preset multiple of the activation reserve capacity threshold (e.g., 1.2 times or 1.5 times, which is set according to the system redundancy design requirements), the selection stops. Finally, the identifier (e.g., submodule number), selection order (e.g., priority number), and power margin information of each target submodule are combined to form an activation reserve capacity sequence. For example, if the activation reserve capacity threshold is 55kW and the preset multiple is 1.2, the cumulative target is 66kW; the submodules with the largest power margin (e.g., 20kW, 15kW, 10kW, etc.) are selected from the sorting list until the cumulative value reaches 66kW, and the information of these submodules is recorded.

[0087] It should be noted that the activation reserve capacity sequence defines the order and allocation ratio of reserve power, ensuring that reserves can be activated quickly and orderly in the event of a fault.

[0088] This method generates an active reserve capacity sequence based on the power margin values ​​of normally operating submodules. This allows the system to tap into the potential capabilities of submodules, optimize the allocation of backup resources, enhance the flexibility of power regulation, enable the system to respond quickly to load fluctuations, reduce the risk of power shortage or excess, and thus suppress voltage fluctuations.

[0089] Step S103: Based on the activated reserve capacity sequence, calculate the modulation depth adjustment value and duty cycle of each of the normal operation sub-modules to form a dynamic adjustment scheme. Based on the dynamic adjustment scheme, redistribute the power of the flexible DC distribution network to generate a power coordination allocation result. Update the allocation ratio of the activated reserve capacity sequence according to the power coordination allocation result and load change requirements to evaluate the load-bearing capacity of each of the normal operation sub-modules. Based on the load-bearing capacity, verify the voltage stability and power distribution balance margin of the modular multilevel converter to generate a preventive adjustment value for preventing overvoltage breakdown. Based on the preventive adjustment value, realize the power coordination of the flexible DC distribution network.

[0090] Please refer to Figure 3In some embodiments, the step of calculating the modulation depth adjustment value and duty cycle of each of the normal operation submodules based on the activated reserve capacity sequence to form a dynamic adjustment scheme includes steps S301 to S303:

[0091] Step S301: Based on the power margin value of each normal operation submodule in the activated reserve capacity sequence, calculate the proportion of the power increment to be borne by each normal operation submodule to the rated power, and determine the initial modulation depth adjustment value based on the proportion;

[0092] In some embodiments, firstly, the power margin value and corresponding position number of each normally operating submodule are extracted from the activated reserve capacity sequence. The power margin value is defined as the difference between the submodule's rated power and its current output power, reflecting the submodule's additional power capacity. Then, based on the total power gap generated after a faulty submodule exits, the power gap is allocated according to the power margin ratio of each normally operating submodule to determine the proportion of the power increment each submodule needs to bear relative to its rated power. This allocation follows a power margin priority principle, where submodules with larger power margins bear a higher proportion of the power increment to ensure reasonable power allocation. Finally, the current modulation depth reference value of the modular multilevel converter (typically set between 0.8 and 0.95) is read, and the power increment ratio is multiplied by the modulation depth reference value to obtain the initial modulation depth adjustment value for each submodule. This step ensures that the modulation depth adjustment of the submodule matches its real-time power handling capacity, laying the foundation for subsequent dynamic adjustments.

[0093] Step S302: Calculate the conduction time of each normal operation submodule within one switching cycle based on the initial modulation depth adjustment value, determine the initial duty cycle based on the conduction time and the switching cycle, and detect the voltage deviation value of the DC side capacitor of each normal operation submodule. When the voltage deviation value exceeds the third preset threshold, adjust the initial duty cycle of the corresponding submodule to obtain the corrected target duty cycle.

[0094] In some embodiments, firstly, based on the initial modulation depth adjustment value, the conduction time of each normally operating submodule within one switching cycle is calculated. Dividing the conduction time by the switching cycle yields the initial duty cycle. For example, at a switching frequency of 10kHz, the switching cycle is 100 microseconds. If the conduction time is 60 microseconds, the initial duty cycle is 0.6. Simultaneously, the system collects capacitor voltage data using a high-precision voltage sensor to monitor the voltage deviation of the DC-side capacitors of each submodule in real time. When the voltage deviation of a submodule exceeds a third preset threshold (e.g., 5% of the rated voltage), the system corrects the initial duty cycle to obtain the corrected target duty cycle.

[0095] It should be noted that the conduction time is related to the modulation depth adjustment value, which determines the energy transfer window of the submodule during the switching cycle.

[0096] It should be noted that during the initial duty cycle correction process, generally speaking, for submodules with high voltage, the duty cycle is appropriately reduced to extend the discharge time; for submodules with low voltage, the duty cycle is increased to extend the charging time. This closed-loop adjustment mechanism helps to balance the capacitor voltage, resulting in the corrected target duty cycle, thereby effectively suppressing voltage fluctuations and circulating currents, and improving system stability.

[0097] Step S303: Based on the target duty cycle and the real-time output power of each of the normal operation sub-modules, a first power difference is determined. The power allocation ratio is determined by the ratio of the first power difference to the rated power. The power allocation ratio and the voltage balance coefficient are combined into a duty cycle optimization parameter. The pulse width modulation signal of each of the normal operation sub-modules is adjusted by the duty cycle optimization parameter to determine the modulation depth adjustment value. The target duty cycle is arranged according to the positional order of each of the normal operation sub-modules to form a duty cycle adjustment sequence. The modulation depth adjustment value and the duty cycle adjustment sequence are combined to determine the dynamic adjustment scheme. The voltage balance coefficient is determined based on the ratio of the root mean square value of the capacitor voltage deviation to the rated voltage.

[0098] In some embodiments, firstly, a first power difference between submodules is calculated based on the target duty cycle and the real-time output power of each normally operating submodule, where the first power difference reflects the degree of imbalance in the actual output power of each submodule. Then, a power allocation ratio is determined by the ratio of the first power difference to the rated power, where this ratio quantifies the magnitude of power reallocation required. Simultaneously, a voltage balance coefficient (e.g., 0.65) is determined based on the ratio of the root mean square value of the capacitor voltage deviation of all submodules to the rated voltage to characterize the overall voltage balance level. Subsequently, the power allocation ratio and the voltage balance coefficient are combined into a duty cycle optimization parameter to adjust the pulse width modulation (PWM) signal of each submodule; then, the amplitude and pulse width of the PWM wave are recalculated to generate the adjusted drive signal. Subsequently, based on the difference between the adjusted PWM signal and the original signal, a modulation depth adjustment value is determined to reflect the change in output voltage amplitude. Simultaneously, according to the physical position of the submodules in the converter arm (e.g., from top to bottom or from left to right), the target duty cycle of each submodule is arranged to form a duty cycle adjustment sequence. This ensures that the duty cycle differences between adjacent submodules are reasonable and avoids localized stress concentration. Finally, the modulation depth adjustment value and the duty cycle adjustment sequence are combined to form a dynamic adjustment scheme.

[0099] This dynamic adjustment scheme is formed by calculating the modulation depth adjustment value and duty cycle based on the reserve sequence. By adjusting the modulation strategy, the power load between submodules is balanced, over-modulation or under-modulation is prevented, and the converter is ensured to operate in the high-efficiency region, which directly improves the accuracy and dynamic stability of power distribution.

[0100] Please refer to Figure 4 In some embodiments, the step of redistributing power in the flexible DC distribution network based on the dynamic adjustment scheme to generate a power coordination allocation result includes steps S401 to S403:

[0101] Step S401: Based on the modulation depth adjustment value in the dynamic adjustment scheme, add the current modulation depth reference value of each normal operation submodule to obtain the target modulation depth value;

[0102] In some embodiments, the modulation depth adjustment value of each normally operating submodule is first extracted from the dynamic adjustment scheme. Then, the modulation depth adjustment value is algebraically added to the current modulation depth reference value to obtain the target modulation depth value for each submodule. This ensures that the output voltage capability of the submodule can be dynamically increased according to power demand.

[0103] It should be noted that the current modulation depth reference value of each submodule is obtained by the system in real time and is usually set between 0.8 and 0.95 to balance the output voltage and adjustment margin.

[0104] Step S402: Based on the duty cycle adjustment sequence, generate pulse width modulation signals corresponding to each of the normal operation sub-modules, and use the pulse width modulation signals to control the on and off of the corresponding insulated gate bipolar transistors, while adjusting the output voltage amplitude of the sub-modules according to the target modulation depth value;

[0105] In some embodiments, the pulse width modulation (PWM) signal for each normally operating submodule is first generated by combining the target modulation depth value and the duty cycle adjustment sequence in the dynamic adjustment scheme. Then, the duty cycle value is used as the amplitude of the modulation wave and compared with a high-frequency triangular carrier wave to generate a square wave signal with a specific duty cycle, i.e., a PWM signal. This signal is amplified by the drive circuit and controls the gate of the corresponding insulated-gate bipolar transistor (IGBT) to precisely adjust its turn-on and turn-off timing. Simultaneously, the target modulation depth value is used to adjust the output voltage amplitude of the submodule, specifically by adjusting the amplitude of the modulation wave.

[0106] It should be noted that the higher the target modulation depth value, the greater the output voltage amplitude, thereby ensuring that the submodule can handle additional load requirements during power redistribution.

[0107] Step S403: Monitor the actual active power and reactive power output of each of the normally operating sub-modules to calculate the power deviation rate. When the power deviation rate exceeds the fourth preset threshold, use a proportional-integral control algorithm to fine-tune the target duty cycle of the corresponding sub-module to make the actual power approach the target value, and summarize the power data of each of the normally operating sub-modules to obtain the power coordination and allocation result.

[0108] In some embodiments, firstly, instantaneous voltage and current values ​​are acquired using a high-precision power analyzer to monitor the actual active and reactive power output of each normally operating submodule in real time. Then, the actual power (including active and reactive power) is compared with the target power value to calculate the power deviation rate (i.e., the percentage of deviation to target power). When the power deviation rate exceeds a fourth preset threshold (e.g., 5%), a proportional-integral control algorithm is initiated for fine-tuning. The proportional term responds quickly to the magnitude of the deviation, while the integral term accumulates historical deviations to eliminate steady-state errors, thereby adjusting the target duty cycle of the corresponding submodule. For example, if the actual power is lower than the target value, the duty cycle is increased to extend the conduction time; conversely, the duty cycle is decreased. After multiple iterations, the actual power gradually approaches the target value. Finally, the system summarizes the power output data of all submodules, including submodule number, target power, actual power, deviation rate, and adjusted duty cycle, forming a structured power coordination and allocation result.

[0109] This dynamic adjustment scheme redistributes power and generates a coordinated power allocation result, reducing the pressure on overloaded submodules, lowering thermal and electrical stresses, thereby extending equipment life and maintaining stable system operation.

[0110] Please refer to Figure 5 In some embodiments, updating the allocation ratio of the activated reserve capacity sequence based on the power coordination allocation result and load change requirements to assess the load-bearing capacity of each of the normally operating submodules includes steps S501 to S504:

[0111] Step S501: Update the allocation ratio of the activated reserve capacity sequence according to the power coordination allocation result and load change requirements;

[0112] In some embodiments, since the power coordination allocation result reflects the actual power output status of each normally operating submodule after dynamic adjustment in the previous control cycle, the system first calculates the difference between the current total load demand power and the actual total output power of all normally operating submodules. This difference directly reflects whether the system has a power deficit or surplus. Subsequently, the system divides this power difference by the data sampling time interval to accurately calculate the rate of change of load power demand. This rate of change is a key indicator for judging the severity of dynamic load changes and provides important input for subsequent optimization algorithms. Finally, based on this rate of change, the system initiates the allocation ratio update process, aiming to make the allocation of coordinated reserve capacity more adaptable to actual load fluctuations.

[0113] Step S502: Extract the target power output value of each of the normal operation sub-modules from the power coordination and allocation results, calculate the second power difference between the load power demand and the target power output value, and determine the load power demand change rate based on the second power difference;

[0114] In some embodiments, the system reads the target power output value set for each normally operating submodule from the stored power coordination and allocation results. Simultaneously, it continuously acquires the real-time power demand at the load end of the distribution network at the current moment, and calculates a second power difference by comparing the total load power demand with the sum of the target power output values ​​of all submodules. Then, based on this second power difference, it divides it by the sampling time interval to obtain a more instructive rate of change in load power demand, which is used to construct subsequent optimization algorithms.

[0115] It should be noted that the target power output value is the expected stable output power of each submodule after considering the failure of the submodule and the redistribution of power.

[0116] Step S503: The initial population of the genetic algorithm is constructed using the load power demand change rate. The allocation ratio is encoded as a chromosome. The fitness function is the weighted sum of load matching degree and power balance degree. The algorithm is iteratively optimized through selection, crossover and mutation operations. When the fitness value converges, the updated target allocation ratio is decoded.

[0117] In some embodiments, firstly, the load power demand change rate is used as heuristic information to generate the initial population for the genetic algorithm. Each individual (chromosome) in the population represents a possible coordinated reserve allocation scheme, and each gene position on the chromosome corresponds to the reserve allocation weight of a normally functioning submodule. Then, the fitness function is based on a weighted sum of load matching and power balance. Next, the system iteratively evolves the population by simulating selection, crossover, and mutation operations in biological evolution. In the selection operation, individuals with higher fitness are more likely to be retained; the crossover operation exchanges some genes from different chromosomes to generate new schemes; the mutation operation randomly changes the values ​​of individual gene positions to increase population diversity. When the optimal fitness value of the population no longer significantly increases over several generations, the algorithm is considered to have converged. At this point, decoding the optimal individual chromosome yields an updated, optimized target allocation ratio.

[0118] It should be noted that the design of the fitness function is the core of the optimization. It consists of a weighted sum of two key indicators: one is the "load matching degree", which measures the degree of matching between the total output power of the submodule and the load demand under the allocation scheme. The higher the matching degree, the better. The other is the "power balance degree", which evaluates the uniformity of power distribution among the submodules under the scheme, avoiding some submodules from being overloaded while other submodules are lightly loaded. The higher the balance degree, the better.

[0119] Step S504: Calculate the maximum allocable power, response time, and overload risk index according to the target allocation ratio, so as to determine the load-bearing capacity of each submodule based on the maximum allocable power, the response time, and the overload risk index.

[0120] In some embodiments, after obtaining the optimized target allocation ratio, the system needs to quantitatively evaluate the load-bearing capacity of each submodule in the current state. This is mainly achieved through three indicators: maximum allocable power, response time, and overload risk index. The maximum allocable power is calculated based on the submodule's rated power and its current target output power, determining its theoretical power margin. The response time is evaluated by assessing the time required from receiving the adjustment command to the output power reaching the new set value; this time depends on the controller's processing speed, the response characteristics of the drive circuit, and the switching speed of the power devices themselves. The overload risk index is predicted by combining the ratio of maximum allocable power to rated power with the submodule's historical operating data (such as mean time between failures). Finally, these three indicators for each submodule are summarized to form a load-bearing capacity evaluation table.

[0121] It should be noted that if the overload risk index of a certain submodule exceeds the preset safety threshold, the system will automatically reduce its weight in subsequent power allocation, thereby improving system reliability while ensuring that each submodule operates within a safe range.

[0122] This method updates the coordination reserve allocation ratio based on the allocation results and load change requirements, enabling the system to dynamically optimize reserve utilization in response to load changes. This improves the system's resilience and adaptability, and prevents crashes caused by sudden loads.

[0123] Please refer to Figure 6 In some embodiments, the step of verifying the voltage stability and power distribution balancing margin of the modular multilevel converter based on the load-bearing capacity to generate preventive adjustment values ​​for overvoltage breakdown includes steps S601 to S604:

[0124] Step S601: Based on the load-bearing capacity, determine the real-time power output value of each of the normally operating sub-modules and summarize it to obtain a power summary value, and determine the satisfaction level value based on the power summary value;

[0125] In some embodiments, firstly, the real-time power output values ​​of each normally operating submodule are read from an established load-bearing capacity assessment table. Then, the real-time power output values ​​of all normally operating submodules are summarized to obtain the total output power of the current system, i.e., the power summary value. Next, the power summary value is compared with the preset load power demand, and the ratio is calculated as a satisfaction level value. This satisfaction level value is a key performance indicator: a ratio of 1 indicates a balance between power supply and demand; a ratio greater than 1 indicates that the system has power redundancy and a certain buffering capacity; a ratio less than 1 indicates a current power supply gap, requiring immediate activation of a supplementary mechanism. By determining the overall operating status based on the different value ranges of the satisfaction level value, a basis for subsequent stability verification can be provided.

[0126] Step S602: Determine the system operating status based on the satisfaction level value, collect voltage data of the upper and lower arms of the modular multilevel converter based on the system operating status, and calculate the ratio of the absolute value of the voltage difference between the upper and lower arms to the rated voltage as a voltage stability index.

[0127] In some embodiments, after obtaining the satisfaction level value and making a preliminary judgment on the system operating status, it is necessary to further evaluate the voltage stability inside the converter. Specifically, high-precision differential voltage probes are used to synchronously collect the voltage to ground or critical node voltage of the upper and lower arms of the modular multilevel converter. Then, the collected voltage data is filtered, the difference between the upper and lower arm voltages is calculated, and the absolute value of this difference is taken. Simultaneously, to eliminate the influence of the system voltage level and to make the indicator universal, the absolute value of the voltage difference is divided by the system's rated DC voltage, thereby obtaining a normalized voltage stability index.

[0128] It should be noted that the voltage stability index directly reflects the voltage balance between the upper and lower arms of the converter. If this index value is too high, it indicates a significant voltage imbalance between the arms, which may cause problems such as increased common-mode voltage and electromagnetic interference, threatening the stable operation of the system. Therefore, controlling this index within a preset reasonable range is crucial to ensuring voltage stability.

[0129] Step S603: Calculate the standard deviation between the actual power of each normally operating submodule and the average power of all submodules, and use the ratio of the standard deviation to the average power as the power distribution balance margin.

[0130] In some embodiments, the average actual output power of all normally operating submodules is first calculated. Then, the deviation of each submodule's actual power from this average is calculated, and the standard deviation of these deviations is further calculated, reflecting the dispersion of load distribution among the submodules. Finally, to quantify the relative severity of this imbalance, the calculated standard deviation is again divided by the average power to obtain the power distribution balance margin.

[0131] It should be noted that the smaller the power distribution balance margin, the closer the load of each submodule is, the more balanced the power distribution, and the better the system's redundancy and lifespan expectation. Conversely, if the margin value is too large, it indicates that there is a risk that some submodules are overloaded while others are underloaded, and the system needs to be optimized and adjusted accordingly.

[0132] Step S604: Based on the voltage stability index and the power distribution balance margin, identify the sub-module with the highest voltage value, read the highest voltage value of the collector-emitter voltage of the corresponding sub-module's insulated gate bipolar transistor, calculate the voltage safety margin by comparing the breakdown voltage of the insulated gate bipolar transistor with the highest voltage value, and obtain the prevention adjustment value for potential overvoltage breakdown based on the voltage safety margin.

[0133] In some embodiments, after confirming that the overall system is under control by considering the aforementioned voltage stability indicators and power distribution balance margin, it is necessary to focus on the submodule experiencing the greatest voltage stress. Specifically, by real-time scanning and comparing the collector-emitter voltage of the insulated gate bipolar transistors (IGBTs) in all normally operating submodules, the highest voltage value and its corresponding submodule are identified. Subsequently, the rated breakdown voltage of the IGBT of that model is retrieved from the device database, and the difference between the breakdown voltage and the measured highest voltage is calculated as the voltage safety margin of the critical submodule, directly reflecting how much safety margin the device has before overvoltage breakdown. Finally, based on engineering safety principles, the voltage safety margin is multiplied by a preset safety factor (this factor is typically set between 0.7 and 0.8 according to the reliability requirements of the power grid), and the resulting product is used as the final preventative adjustment value.

[0134] It should be noted that this preventive adjustment value will be used in the next control cycle to pre-adjust the voltage output reference value or modulation depth of the relevant sub-modules, actively increase the safety margin, thereby effectively preventing the occurrence of overvoltage breakdown faults and realizing the transformation from passive response to active defense.

[0135] This approach verifies voltage stability and power distribution balance margin based on load-bearing capacity, and generates preventive adjustment values ​​to prevent overvoltage breakdown. By proactively assessing potential overvoltage risks and taking preventive measures such as adjusting voltage reference values ​​or limiting power flow, it effectively suppresses breakdown and improves the system's safety margin.

[0136] In some embodiments, the power coordination of the flexible DC distribution network based on the preventive adjustment value specifically involves: determining the target reserve allocation amount for the next control cycle of each of the normally operating sub-modules according to the preventive adjustment value, and sorting the target reserve allocation amounts from largest to smallest to generate a reserve update sequence; monitoring the status parameters of all sub-modules of the modular multilevel converter to determine potential fault points based on the status parameters; if the number of potential fault points exceeds a preset threshold, it is determined that there is a new fault risk; if there is a new fault risk, the reserve power of each of the normally operating sub-modules is called sequentially according to the reserve update sequence for compensation until the output power of each sub-module reaches a stable operating state. Specifically, firstly, the reserve capacity of each normally operating submodule is dynamically allocated based on the preventive adjustment value. This involves multiplying the preventive adjustment value by the proportion of each submodule's carrying capacity to the total carrying capacity to obtain the individual reserve adjustment amount. This individual reserve adjustment amount is then added to the current reserve capacity to generate the target reserve allocation amount for the next control cycle. Subsequently, each submodule is sorted from largest to smallest according to the target reserve allocation amount, forming a reserve update sequence. This sequence clarifies the priority of reserve power utilization, ensuring that submodules with larger allocation amounts are activated first, thereby optimizing resource utilization and avoiding local overload. Next, the status parameters of all submodules of the modular multilevel converter, including temperature, voltage fluctuations, current characteristics, and switching status, are monitored in real time to determine whether there are any new fault risks. If there is a risk of failure, the reserve power of each normally operating submodule is called in sequence according to the priority order of the reserve update sequence for compensation. The calling process adopts a gradual principle. After each submodule is called, the power balance status of the system is monitored in real time. If the power demand is met, the calling stops; otherwise, the next priority submodule is called. At the same time, the stability is evaluated by observing the fluctuation amplitude and frequency of the output power. When the fluctuation amplitude is less than 2% of the rated power and the duration exceeds 100 milliseconds, the system is considered to have reached a stable operating state, thereby completing the closed-loop control of power coordination and realizing a continuously adaptive intelligent coordination mode.

[0137] It should be noted that if the temperature of a submodule exceeds a preset threshold, the standard deviation of voltage fluctuation exceeds the allowable range, or an abnormal spike in current occurs, it will be marked as a potential fault point; when the number of potential fault points exceeds the system's fault tolerance capability (such as a preset number threshold), it is determined that there is a new fault risk.

[0138] This power coordination based on preventative adjustment values ​​integrates all adjustment measures to form a comprehensive optimization, ensuring that the system, after coordination, can not only cope with the current state but also prevent future disturbances, thereby achieving long-term stability.

[0139] This application embodiment, by acquiring the operating status of submodules and identifying normally operating submodules, can eliminate interference from faulty or abnormal submodules in real time, ensuring that power coordination is only based on healthy units and avoiding further problems caused by operating faulty modules. An activation reserve capacity sequence is generated based on the power margin value of normally operating submodules. This allows the system to tap the potential capabilities of submodules, optimize the allocation of backup resources, enhance the flexibility of power regulation, and enable the system to respond quickly to load fluctuations, reducing the risk of power shortages or excesses, thereby suppressing voltage fluctuations. The modulation depth adjustment value and duty cycle are calculated based on the reserve sequence to form a dynamic adjustment scheme. By adjusting the modulation strategy, the power load among submodules is balanced, preventing over-modulation or under-modulation, ensuring the converter operates in the high-efficiency region, and directly improving the accuracy and dynamic stability of power allocation. Power is redistributed based on the dynamic adjustment scheme, generating power coordination allocation results, reducing the pressure on overloaded submodules, lowering thermal and electrical stresses, thereby extending equipment life and maintaining stable system operation. The coordination reserve allocation ratio is updated according to the allocation results and load change requirements, enabling the system to dynamically optimize reserve utilization in response to load changes, improving system resilience and adaptability, and preventing collapse due to sudden loads. Based on load-bearing capacity, voltage stability and power distribution balance margin are verified, and preventative adjustment values ​​to prevent overvoltage breakdown are generated. This proactive assessment identifies potential overvoltage risks and takes preventative measures such as adjusting voltage reference values ​​or limiting power flow, effectively suppressing breakdown and improving system safety margins. Power coordination is achieved based on these preventative adjustment values, integrating all adjustment measures to form a comprehensive optimization. This ensures that the coordinated system can not only cope with the current state but also prevent future disturbances, thereby achieving long-term stability. Compared with existing technologies, this application can realize power coordination of modular multilevel converters in flexible DC distribution networks, improving system stability.

[0140] like Figure 7 As shown, based on the above method embodiments, corresponding apparatus embodiments are provided;

[0141] One embodiment of the present invention provides a power coordination system for a flexible DC distribution network, comprising: an acquisition module 100, a generation module 200, and a coordination module 300;

[0142] The acquisition module 100 is used to acquire the operating status of each sub-module of the modular multilevel converter in the flexible DC distribution network, and identify several normally operating sub-modules based on the operating status.

[0143] The generation module 200 is used to generate an activation reserve capacity sequence for power coordination based on the power margin value of each of the normal operation submodules.

[0144] The coordination module 300 is used to calculate the modulation depth adjustment value and duty cycle of each of the normal operation sub-modules according to the activated reserve capacity sequence to form a dynamic adjustment scheme. Based on the dynamic adjustment scheme, the power of the flexible DC distribution network is redistributed to generate a power coordination allocation result. The allocation ratio of the activated reserve capacity sequence is updated according to the power coordination allocation result and the load change demand to evaluate the load-bearing capacity of each of the normal operation sub-modules. Based on the load-bearing capacity, the voltage stability and power distribution balance margin of the modular multilevel converter are verified to generate a preventive adjustment value for preventing overvoltage breakdown. Based on the preventive adjustment value, the power coordination of the flexible DC distribution network is realized.

[0145] Further, the coordination module 300 includes: an update unit, configured to update the allocation ratio of the activated reserve capacity sequence according to the power coordination allocation result and load change requirements; an extraction unit, configured to extract the target power output value of each of the normally operating sub-modules from the power coordination allocation result, calculate a second power difference between the load power requirement and the target power output value, and determine the load power requirement change rate based on the second power difference; an iteration unit, configured to construct an initial population of a genetic algorithm using the load power requirement change rate, encode the allocation ratio as chromosomes, use the weighted sum of load matching degree and power balance degree as the fitness function, iteratively optimize through selection, crossover and mutation operations, and decode the updated target allocation ratio when the fitness value converges; and a determination unit, configured to calculate the maximum allocable power, response time and overload risk index according to the target allocation ratio, and determine the load-bearing capacity of each sub-module based on the maximum allocable power, the response time and the overload risk index.

[0146] It is understood that the above-described device embodiments correspond to the method embodiments of the present invention, and can realize the power coordination method for flexible DC distribution networks provided by any of the above-described method embodiments of the present invention.

[0147] It should be noted that the device embodiments described above are merely illustrative, and some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs. Furthermore, in the accompanying drawings of the device embodiments provided by this invention, the connection relationships between modules indicate that they have communication connections, which can specifically be implemented as one or more communication buses or signal lines. Those skilled in the art can understand and implement this without any creative effort.

[0148] Based on the above embodiments of the power coordination method for flexible DC distribution networks, another embodiment of the present invention provides a terminal device, which includes a processor, a memory, and a computer program stored in the memory and configured to be executed by the processor. When the processor executes the computer program, it implements the power coordination method for flexible DC distribution networks according to any embodiment of the present invention.

[0149] For example, in this embodiment, the computer program can be divided into one or more modules, which are stored in the memory and executed by the processor to complete the present invention. The one or more modules may be a series of computer program instruction segments capable of performing a specific function, which describe the execution process of the computer program in the terminal device.

[0150] The terminal device may be a desktop computer, laptop, handheld computer, or cloud server, etc. The terminal device may include, but is not limited to, a processor and a memory.

[0151] The processor can be a Central Processing Unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. A general-purpose processor can be a microprocessor or any conventional processor. The processor is the control center of the terminal device, connecting all parts of the terminal device via various interfaces and lines.

[0152] Based on the above-described method embodiments, another embodiment of the present invention provides a computer-readable storage medium including a stored computer program, wherein, when the computer program is executed, it controls the device where the computer-readable storage medium is located to execute the power coordination method for flexible DC distribution networks described in any of the above-described method embodiments of the present invention.

[0153] The modules / units integrated in the device / terminal equipment, if implemented as software functional units and sold or used as independent products, can be stored in a computer-readable storage medium. Based on this understanding, all or part of the processes in the above embodiments of the present invention can also be implemented by a computer program instructing related hardware. The computer program can be stored in a computer-readable storage medium, and when executed by a processor, it can implement the steps of the various method embodiments described above. The computer program includes computer program code, which can be in the form of source code, object code, executable files, or certain intermediate forms. The computer-readable medium can include: any entity or device capable of carrying the computer program code, a recording medium, a USB flash drive, a portable hard drive, a magnetic disk, an optical disk, a computer memory, a read-only memory (ROM), a random access memory (RAM), an electrical carrier signal, a telecommunication signal, and a software distribution medium, etc.

[0154] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A power coordination method for a flexible DC distribution network, characterized in that, include: The operating status of each sub-module of the modular multilevel converter in the flexible DC distribution network is obtained, and several normally operating sub-modules are identified based on the operating status. Based on the power margin values ​​of each of the normally operating submodules, an active reserve capacity sequence for power coordination is generated; Based on the activated reserve capacity sequence, the modulation depth adjustment value and duty cycle of each of the normally operating submodules are calculated to form a dynamic adjustment scheme. Based on the dynamic adjustment scheme, the power of the flexible DC distribution network is redistributed to generate a power coordination allocation result. The allocation ratio of the activated reserve capacity sequence is updated according to the power coordination allocation result and load change requirements to evaluate the load-bearing capacity of each of the normally operating submodules. Based on the load-bearing capacity, the voltage stability and power distribution balance margin of the modular multilevel converter are verified to generate a preventive adjustment value to prevent overvoltage breakdown. Power coordination of the flexible DC distribution network is achieved based on the preventive adjustment value. The dynamic adjustment scheme is updated according to the power coordination allocation result and load change requirements. The allocation ratio of the activated reserve capacity sequence is used to evaluate the load-bearing capacity of each of the normally operating sub-modules. Specifically, the allocation ratio of the activated reserve capacity sequence is updated according to the power coordination allocation result and the load change demand; the target power output value of each of the normally operating sub-modules is extracted from the power coordination allocation result, and a second power difference between the load power demand and the target power output value is calculated, and the load power demand change rate is determined based on the second power difference; the initial population of the genetic algorithm is constructed using the load power demand change rate, the allocation ratio is encoded as chromosomes, and the fitness function is obtained by using the weighted sum of load matching degree and power balance degree as the fitness function. Iterative optimization is performed through selection, crossover and mutation operations. When the fitness value converges, the updated target allocation ratio is decoded. Based on the target allocation ratio, the maximum allocable power, response time, and overload risk index are calculated to determine the load-bearing capacity of each submodule.

2. The power coordination method for flexible DC distribution networks according to claim 1, characterized in that, The process involves acquiring the operating status of each sub-module of the modular multilevel converter in the flexible DC distribution network, and identifying several normally operating sub-modules based on the operating status. Specifically: Collect the collector-emitter voltage signal of the insulated gate bipolar transistor in each sub-module of the modular multilevel converter in the flexible DC distribution network; The voltage signal is compared with a first preset threshold. When the voltage signal is lower than the first preset threshold, several normal operating sub-modules are determined. The first preset threshold is set based on the breakdown voltage of the insulated gate bipolar transistor.

3. The power coordination method for flexible DC distribution networks according to claim 1, characterized in that, The generation of an activation reserve capacity sequence for power coordination based on the power margin values ​​of each of the normally operating submodules is specifically as follows: Determine the current output power of each of the normally operating submodules, and calculate the difference between the current output power and the rated power to determine the corresponding power margin value; The normally operating submodule whose power margin value exceeds the second preset threshold is identified as an activatable reserve submodule, and the sum of the power margin values ​​of all the activatable reserve submodules is calculated as the activation reserve capacity threshold. The activatable reserve sub-modules are sorted from largest to smallest according to the power margin value to obtain the sorting result. The cumulative power margin value of the target sub-modules selected sequentially from the sorting result is calculated until the cumulative power margin value reaches a preset multiple of the activation reserve capacity threshold. The identifier, selection order and power margin value of the target sub-modules are combined to form the activation reserve capacity sequence.

4. The power coordination method for flexible DC distribution networks according to claim 1, characterized in that, The step involves calculating the modulation depth adjustment value and duty cycle of each of the normally operating sub-modules based on the activated reserve capacity sequence to form a dynamic adjustment scheme, specifically as follows: Based on the power margin value of each normal operation submodule in the activated reserve capacity sequence, calculate the proportion of the power increment to be borne by each normal operation submodule to the rated power, and determine the initial modulation depth adjustment value based on the proportion; Based on the initial modulation depth adjustment value, the conduction time of each normal operation submodule within one switching cycle is calculated, and the initial duty cycle is determined based on the conduction time and the switching cycle. The voltage deviation value of the DC side capacitor of each normal operation submodule is detected. When the voltage deviation value exceeds the third preset threshold, the initial duty cycle of the corresponding submodule is adjusted to obtain the corrected target duty cycle. A first power difference is determined based on the target duty cycle and the real-time output power of each of the normal operation submodules. A power allocation ratio is determined by the ratio of the first power difference to the rated power. The power allocation ratio and the voltage balance coefficient are combined to form a duty cycle optimization parameter. The pulse width modulation signal of each of the normal operation submodules is adjusted by the duty cycle optimization parameter to determine the modulation depth adjustment value. The target duty cycles are arranged in the positional order of each of the normal operation submodules to form a duty cycle adjustment sequence. The modulation depth adjustment value and the duty cycle adjustment sequence are combined to determine the dynamic adjustment scheme. The voltage balance coefficient is determined based on the ratio of the root mean square value of the capacitor voltage deviation to the rated voltage.

5. The power coordination method for flexible DC distribution networks according to claim 4, characterized in that, The process of redistributing power in the flexible DC distribution network based on the dynamic adjustment scheme to generate a power coordination allocation result is as follows: The target modulation depth value is obtained by adding the modulation depth adjustment value in the dynamic adjustment scheme to the current modulation depth reference value of each normal operating submodule. According to the duty cycle adjustment sequence, a pulse width modulation signal corresponding to each normal operation submodule is generated, and the pulse width modulation signal is used to control the on and off of the corresponding insulated gate bipolar transistor. At the same time, the output voltage amplitude of the submodule is adjusted according to the target modulation depth value. The active and reactive power output of each normally operating submodule is monitored to calculate the power deviation rate. When the power deviation rate exceeds the fourth preset threshold, the target duty cycle of the corresponding submodule is finely adjusted using a proportional-integral control algorithm to make the actual power approach the target value. The power data of each normally operating submodule are then summarized to obtain the power coordination and allocation result.

6. The power coordination method for flexible DC distribution networks according to claim 1, characterized in that, Based on the load-bearing capacity, the voltage stability and power distribution balancing margin of the modular multilevel converter are verified to generate preventive adjustment values ​​for overvoltage breakdown, specifically: Based on the load-bearing capacity, the real-time power output value of each of the normally operating sub-modules is determined and summarized to obtain a power summary value, and a satisfaction level value is determined based on the power summary value. The system operating status is determined based on the satisfaction level value. Based on the system operating status, the voltage data of the upper and lower arms of the modular multilevel converter are collected, and the ratio of the absolute value of the voltage difference between the upper and lower arms to the rated voltage is calculated as a voltage stability index. Calculate the standard deviation between the actual power of each normally operating submodule and the average power of all submodules, and use the ratio of the standard deviation to the average power as the power distribution balance margin. Based on the voltage stability index and the power distribution balance margin, the submodule with the highest voltage value is identified, the highest value of the collector-emitter voltage of the corresponding submodule's insulated gate bipolar transistor is read, and the voltage safety margin is calculated based on the breakdown voltage of the insulated gate bipolar transistor and the highest voltage value. Based on the voltage safety margin, the prevention adjustment value for potential overvoltage breakdown is obtained.

7. The power coordination method for flexible DC distribution networks according to claim 1, characterized in that, The power coordination of the flexible DC distribution network based on the aforementioned preventive adjustment value specifically includes: Based on the aforementioned prevention adjustment value, the target reserve allocation amount for the next control cycle of each of the aforementioned normal operation sub-modules is determined, and the modules are sorted from largest to smallest according to the target reserve allocation amount to generate a reserve update sequence; The status parameters of all sub-modules of the modular multilevel converter are monitored to identify potential fault points based on the status parameters. If the number of potential fault points exceeds a preset threshold, it is determined that there is a new fault risk. If a new fault risk exists, the reserve power of each of the normally operating sub-modules will be called sequentially according to the reserve update sequence for compensation until the output power of each sub-module reaches a stable operating state.

8. A power coordination system for a flexible DC distribution network, characterized in that, include: Acquisition module, generation module, and coordination module; The acquisition module is used to acquire the operating status of each sub-module of the modular multilevel converter in the flexible DC distribution network, and identify several normally operating sub-modules based on the operating status. The generation module is used to generate an activation reserve capacity sequence for power coordination based on the power margin value of each of the normally operating sub-modules. The coordination module is used to calculate the modulation depth adjustment value and duty cycle of each of the normal operation sub-modules according to the activated reserve capacity sequence to form a dynamic adjustment scheme. Based on the dynamic adjustment scheme, the power of the flexible DC distribution network is redistributed to generate a power coordination allocation result. The allocation ratio of the activated reserve capacity sequence is updated according to the power coordination allocation result and the load change demand to evaluate the load-bearing capacity of each of the normal operation sub-modules. Based on the load-bearing capacity, the voltage stability and power distribution balance margin of the modular multilevel converter are verified to generate a preventive adjustment value for preventing overvoltage breakdown. Based on the preventive adjustment value, the power coordination of the flexible DC distribution network is realized. Specifically, the allocation ratio of the activated reserve capacity sequence is updated based on the power coordination allocation result and load change requirements to evaluate the load-bearing capacity of each of the normally operating sub-modules. This involves: updating the allocation ratio of the activated reserve capacity sequence based on the power coordination allocation result and load change requirements; extracting the target power output value of each of the normally operating sub-modules from the power coordination allocation result, calculating the second power difference between the load power requirement and the target power output value, and determining the load power requirement change rate based on the second power difference; constructing the initial population of a genetic algorithm using the load power requirement change rate, encoding the allocation ratio as chromosomes, using the weighted sum of load matching degree and power balance degree as the fitness function, iteratively optimizing through selection, crossover, and mutation operations, and decoding the updated target allocation ratio when the fitness value converges. Based on the target allocation ratio, the maximum allocable power, response time, and overload risk index are calculated to determine the load-bearing capacity of each submodule.

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