MMC capacitor state evaluation method and system based on voltage increment and health score
By using a voltage increment and health score evaluation method in the MMC system, the problems of misjudgment and long-term evaluation of submodule capacitor status are solved, achieving stable and accurate evaluation of capacitor performance and improving the reliability and safety of the system.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- SHANDONG UNIV
- Filing Date
- 2026-04-22
- Publication Date
- 2026-05-26
AI Technical Summary
Existing technologies in MMC systems cannot effectively identify misjudgments caused by initial voltage differences in submodule capacitors, nor can they continuously assess the health status of capacitors, and they are difficult to reflect long-term changes in capacitor performance.
An evaluation method based on voltage increment and health score is adopted. By calculating and sorting the capacitor voltage increment of the sub-module within the input window, and combining it with the health score mechanism, a reference sub-module is dynamically selected to realize the quantitative evaluation and anomaly identification of the capacitor status.
It avoids misjudgment caused by initial voltage differences between submodules, improves the stability and accuracy of anomaly identification, and can continuously reflect the degradation trend of capacitor performance, providing a basis for equipment maintenance decisions.
Smart Images
Figure CN122085035A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of power system condition monitoring technology, and in particular to a method and system for assessing the condition of MMC capacitors based on voltage increment and health score. Background Technology
[0002] The statements in this section are merely background information related to the present invention and do not necessarily constitute prior art.
[0003] Modular multilevel converters (MMCs) have been widely used in flexible DC transmission, new energy grid connection and large-capacity power conversion systems due to their advantages such as high modularity, high voltage level and good harmonic performance.
[0004] In MMC systems, numerous submodule capacitors serve as critical energy storage components, and their operating status directly impacts the stability, reliability, and system lifespan of the converter. However, during long-term operation, submodule capacitors may experience problems such as capacitance decay, increased equivalent series resistance, or performance degradation due to aging, temperature rise, voltage stress, and other factors. Failure to promptly identify abnormal capacitor conditions can lead to increased voltage fluctuations, decreased system control performance, and in severe cases, even converter failure.
[0005] Existing technology discloses a method for monitoring the health status of MMC capacitors based on an activation window. When all submodules in a bridge arm are activated simultaneously, the traditional capacitor voltage sorting algorithm temporarily fails, and this operating interval is defined as the activation window. At this time, the capacitor voltage change of abnormal submodules with degraded capacitors will be much greater than that of normal submodules due to the decrease in capacitor value. Therefore, the voltage difference between the reference submodule and the monitored submodule within the activation window is used to filter out abnormal submodules by comparing it with a threshold.
[0006] However, existing methods assume that the capacitor voltages of each submodule are basically the same before entering the input window. However, in actual operation, when the capacitor voltage sorting control algorithm fails consecutively under certain operating conditions or when consecutive input windows occur, the capacitor voltages of each submodule may have initial differences. This initial voltage difference will be incorrectly included in the input window voltage difference, leading to misjudgment or omission of abnormal submodules. Furthermore, existing methods typically only determine whether the capacitor exceeds a threshold, and cannot continuously assess the capacitor degradation trend, making it difficult to reflect long-term changes in the capacitor's health status. Summary of the Invention
[0007] To address the aforementioned issues, this invention proposes a method and system for evaluating the state of MMC capacitors based on voltage increment and health score. It utilizes the voltage increment of the sub-module itself within the input window as the criterion for capacitor state, avoiding misjudgments caused by the initial capacitor voltage difference between sub-modules. Simultaneously, a health score mechanism is introduced to achieve continuous quantitative evaluation of the health state of the sub-module capacitors.
[0008] In some implementations, the following technical solutions are adopted: A method for assessing the state of MMC capacitors based on voltage increment and health score includes: The time period during which all sub-modules within the bridge arm are simultaneously put into operation is defined as the operation window, and the start and end times of the operation window are determined respectively. Calculate the capacitor voltage increment of each submodule within the input window; Based on the sorting of the capacitor voltage increments of each submodule within the bridge arm, calculate the health score increment of each submodule within the current input window; after the end of each input window, cumulatively update the health score of each submodule based on the sorting results of the submodule voltage increments within the input window. Based on the health assessment of each submodule, an abnormal submodule is identified; Select a reference submodule, and calculate the capacitance parameters of the abnormal submodule based on the capacitor voltage increment and capacitance parameters of the reference submodule during the input window.
[0009] As a further solution, a health score corresponding to the capacitor voltage increment with different rankings is pre-set, and the health score increment of each submodule within the bridge arm is calculated according to the sorting of the capacitor voltage increments of each submodule.
[0010] As a further solution, a forgetting factor is introduced. After each input window ends, the health score of each submodule is cumulatively updated based on the submodule voltage increment ranking results within the input window.
[0011] As a further measure, the cumulative update of the health score specifically includes: The updated health score of the current submodule is equal to the product of the current health score of the submodule and the forgetting factor, plus the health score increment of the submodule within the current input window.
[0012] As a further solution, abnormal sub-modules are identified based on the health assessment of each sub-module, specifically as follows: A health threshold is set. If the health score of a submodule is lower than the health threshold, it is determined to be an abnormal submodule.
[0013] As a further solution, once a submodule is determined to be abnormal, it is removed from the capacitor voltage increment sorting process.
[0014] As a further solution, the submodule with the highest current health score is adaptively selected as the reference submodule.
[0015] In other embodiments, the following technical solutions are adopted: A system for assessing the condition of MMC capacitors based on voltage increment and health score, comprising: The input window determination module is used to define the time period during which all sub-modules within the bridge arm are simultaneously put into operation as the input window, and to determine the start and end times of the input window respectively. The capacitor voltage increment calculation module is used to calculate the capacitor voltage increment of each sub-module within the input window. The health score update module is used to calculate the health score increment of each submodule within the current input window based on the sorting of the capacitor voltage increments of each submodule within the bridge arm; after the end of each input window, the health score of each submodule is cumulatively updated based on the sorting results of the submodule voltage increments within the input window. An abnormal submodule identification module is used to identify abnormal submodules based on the health assessment of each submodule. The capacitor parameter calculation module is used to select a reference submodule and calculate the capacitor parameters of the abnormal submodule based on the capacitor voltage increment and capacitor parameters of the reference submodule during the input window.
[0016] In other embodiments, the following technical solutions are adopted: A terminal device includes a processor and a memory, the processor being used to implement instructions; the memory being used to store multiple instructions adapted to be loaded and executed by the processor to perform the above-described method for assessing the MMC capacitor status based on voltage increment and health score.
[0017] In other embodiments, the following technical solutions are adopted: A computer-readable storage medium storing a plurality of instructions adapted for loading and execution by a processor of a terminal device of the above-described method for assessing the MMC capacitor status based on voltage increment and health score.
[0018] Compared with the prior art, the beneficial effects of the present invention are: (1) The present invention uses the voltage increment of the sub-module itself as the criterion, and does not depend on the voltage difference between sub-modules, thus avoiding the misjudgment problem caused by the initial voltage difference.
[0019] By dynamically selecting the submodule with the highest health score as the reference submodule, systematic biases in monitoring results caused by aging or measurement errors of the fixed reference submodule can be avoided.
[0020] (2) By accumulating the evaluation of voltage characteristics within multiple input windows, this invention can effectively suppress the impact of single window noise and short-term operating condition changes, thereby improving the stability of anomaly identification.
[0021] The health scoring mechanism can continuously and quantitatively assess the health status of capacitors, thereby reflecting the trend of capacitor performance degradation and providing a basis for equipment maintenance decisions.
[0022] Other features and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description
[0023] Figure 1 This is a schematic diagram of the MMC topology; Figure 2 Here is a flowchart of the MMC capacitor voltage equalization algorithm; Figure 3 This is a schematic diagram of the input window; Figure 4 This is a schematic diagram illustrating the voltage increment of the submodule capacitor within the input window in an embodiment of the present invention; Figure 5 This is a schematic diagram illustrating the judgment of the abnormal submodule and the selection of the reference submodule in an embodiment of the present invention; Figure 6 This is a flowchart of the MMC capacitor status assessment method based on voltage increment and health score in an embodiment of the present invention. Detailed Implementation
[0024] It should be noted that the following detailed description is illustrative and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.
[0025] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.
[0026] Example 1 In one or more embodiments, a method for assessing the state of MMC capacitors based on voltage increment and health score is disclosed. By analyzing the voltage change characteristics of submodule capacitors within the input window and combining it with a health score mechanism, the operating state of the capacitors is quantitatively assessed, thereby enabling rapid identification of abnormal capacitors and improving the reliability and safety of MMC system operation.
[0027] The following sections introduce the topology and operating principle of MMC, the capacitor voltage equalization control of MMC, the failure phenomenon of capacitor voltage equalization control during the input window, existing MMC capacitor state evaluation methods based on the input window, and the MMC capacitor state evaluation method proposed in this embodiment of the invention.
[0028] The topology of MMC is as follows Figure 1 As shown, each phase consists of two bridge arms, upper and lower. Each bridge arm is composed of... N One half-bridge or full-bridge submodule and one bridge arm inductor The components are connected in series. This embodiment focuses on an MMC composed of half-bridge submodules. Each half-bridge module consists of two insulated-gate bipolar transistors S1 and S2 with complementary switching signals, and two anti-parallel diodes D1 and D2. and a capacitor composition.
[0029] This indicates three phases, and j indicates the upper or lower bridge arm. ; i represents the bridge arm submodule number, ; express Phase j-arm current, express The switching state of the i-th submodule of the phase j-arm bridge arm. express The capacitor voltage of the i-th submodule of phase j bridge arm.
[0030] Based on the submodule's switching state and the direction of the bridge arm current, the submodule can be divided into three operating states, each with two operating modes, as shown in Table 1. When S1 is on and S2 is off, the submodule is in the active state, and its output voltage is the capacitor voltage, with the capacitor in a charging or discharging state. When S1 is off and S2 is on, the submodule is in the bypass state, and the SM output voltage is 0, while the capacitor voltage remains unchanged. When both S1 and S2 are off, the submodule is in the latched state, which is typically only activated during fault conditions.
[0031] Table 1 Submodule Working Status
[0032] Submodule output voltage and sub-module capacitors It can be expressed by equations (1) and (2) respectively: (1) (2) Each bridge arm of an MMC has numerous submodules. Balancing the capacitor voltages among these submodules is a crucial control objective for ensuring the safe and stable operation of the MMC. This is typically achieved using a sorting-based capacitor voltage balancing algorithm, as shown in the flowchart below. Figure 2 As shown.
[0033] Obtain the number of submodules that should be deployed in the bridge arm during each control cycle. Then, based on the bridge arm current The direction of the control prioritizes the capacitor voltages of the bridge arm submodules according to positive or negative order. When the bridge arm current is positive, submodules with lower capacitor voltages are activated first to charge and increase their voltage; when the bridge arm current is negative, submodules with higher capacitor voltages are activated first to discharge and decrease their voltage. After selecting the specific submodule to activate, a specific drive pulse sequence is generated and sent to the corresponding submodule. This control method achieves better voltage balance among the submodule capacitors in the same bridge arm.
[0034] The time period during which all sub-modules within the bridge arm are simultaneously put into operation is defined as the operation window, such as... Figure 3 As shown. During this period, all submodules in the bridge arm are in the active state to meet the needs of MMC operation control, and there are no redundant submodules available for selection for activation or bypass. Therefore, the capacitor voltage equalization control that relies on the rotational activation of submodules fails during the activation window, and the change in the capacitor voltage of each submodule is determined only by the bridge arm current and its own capacitance parameters.
[0035] The existing method for assessing the state of MMC capacitors based on voltage difference is as follows: During the operation of a modular multilevel converter, when all submodules within an arm are in operation, the arm current flows through all submodule capacitors, and the capacitor voltages change due to charging and discharging under the same arm current. Ideally, if the capacitor parameters of each submodule are consistent, and their initial voltages are at the same level before entering the operation window, then the voltage change trends of each submodule capacitor should be consistent within the operation window, and the voltage difference between them should be close to zero.
[0036] Based on the above assumptions, the existing MMC capacitor state monitoring method based on the input window selects a submodule within the bridge arm as a reference submodule and compares the capacitor voltage difference between the monitoring submodule and the reference submodule in real time within the input window. Let the capacitor voltages of the monitoring submodule and the reference submodule be respectively... and The capacitances are respectively and .
[0037] Let the input window interval be According to equation (2), the capacitor voltage of the submodule during the input window can be expressed as: (3) in, This refers to the capacitor voltage when the submodule enters the input window. .
[0038] Assume that before entering the input window, the capacitor voltages of both the reference submodule and the monitored submodule are... Within the input window, the capacitor voltages of the reference submodule and the monitored submodule undergo charging and discharging changes. The voltage difference between the two can be expressed as: (4) If the capacitor parameters of the monitored submodule are the same as those of the reference submodule, then the change in its capacitor voltage is synchronized with that of the reference submodule, and the aforementioned voltage difference is 0.
[0039] When the capacitance of a submodule degrades, causing its value to decrease, the rate of change of its capacitor voltage will differ from that of the reference submodule under the same bridge arm current. This results in a gradual accumulation and increase in the voltage difference between the two submodules over time. Therefore, within the operating window, if the voltage difference between a submodule and the reference submodule is significantly greater than that of other submodules, it can be determined that the submodule has abnormal capacitor parameters or is at risk of aging.
[0040] The above method calculates the capacitor voltage difference between the monitored submodule and the reference submodule within the input window and compares it with a preset threshold. When the voltage difference is less than the threshold, the submodule's capacitor state is considered normal; when the voltage difference exceeds the threshold, the submodule is identified as abnormal. This method enables online monitoring and anomaly identification of the submodule's capacitor state. Finally, the capacitor value of the selected abnormal submodules is estimated based on the capacitor parameter calculation principle of the input window voltage increment.
[0041] Based on the above analysis, it can be seen that the effectiveness of existing capacitor state monitoring methods based on input windows in identifying abnormal sub-modules and estimating parameters depends to some extent on the following implicit preconditions: First, this method assumes that the capacitor voltages of each submodule have been sufficiently balanced through capacitor voltage balancing control before entering the input window, meaning that the initial capacitor voltage difference between submodules can be ignored. Under this assumption, the separation characteristics of submodule capacitor voltages during the input window are mainly caused by differences in capacitor parameters, thus providing a basis for anomaly identification. However, in actual MMC operation, factors such as continuous input windows and rapid changes in operating conditions may prevent the complete elimination of initial capacitor voltage differences between submodules. The residual deviation will be added to the voltage difference calculation within the input window, thus affecting the accuracy of anomaly submodule identification.
[0042] Secondly, this method assumes that the selected reference submodule's capacitance parameters are always in a healthy state, and that its voltage measurement accuracy is higher than or at least no worse than that of other submodules. Under long-term operation or complex operating conditions, if the reference submodule itself experiences slight degradation, or if its voltage sampling has a systematic deviation, the relevant error will be transmitted to the anomaly identification and capacitance parameter estimation process through the voltage difference ratio, thus causing a systematic shift in the monitoring results.
[0043] Given that the aforementioned preconditions are difficult to meet consistently, existing input window-based methods still face several specific problems in engineering applications: First, existing methods mainly rely on the capacitor voltage difference within a single input window to determine abnormal sub-modules. When the input window duration is short or the voltage change amplitude is close to the measurement noise level, the monitoring results are easily affected by noise interference and short-term operating condition fluctuations, thereby increasing the risk of misjudgment or missed judgment.
[0044] Second, existing methods typically employ threshold-based instantaneous decision mechanisms, focusing on the immediate identification of abnormal sub-modules. This makes it difficult to reflect the long-term degradation trend of capacitor performance and is not conducive to conducting long-term health status assessments and trend analyses.
[0045] During the operation of a modular multilevel converter, when all submodules within a bridge arm are in the active state, the bridge arm current flows through the capacitors of all submodules, and the capacitor voltages of the submodules change due to charging and discharging under the same bridge arm current. In this fully active state, the capacitor voltage change of the i-th submodule can be expressed as: As can be seen from the above relationship, within the same input window, each submodule experiences the same bridge arm current integral, and the change in capacitor voltage is only related to the capacitor parameters of the submodule.
[0046] When a capacitor in a submodule ages, its capacitance value will deviate from its nominal value, exhibiting degradation. Therefore, under the same bridge arm current conditions: submodules with smaller capacitance values will experience larger voltage fluctuations, while submodules with larger capacitance values will experience smaller voltage fluctuations. Thus, the magnitude of the capacitor voltage increment obtained within the input window directly reflects the relative status of the submodule's capacitance parameters.
[0047] Based on this, this embodiment proposes an MMC capacitor status assessment method based on voltage increment and health score. The voltage increment of a submodule within the input window is used as the health criterion, and the voltage increments of all submodules are ranked: submodules with significantly larger voltage increments correspond to smaller capacitor values, indicating aging or abnormality risks; submodules with smaller and more stable voltage increments correspond to healthier capacitor states. Through cumulative assessment of voltage increment characteristics within multiple input windows, the influence of measurement noise and short-term operating disturbances can be effectively suppressed, achieving reliable screening of abnormal submodules. Finally, the capacitor values of the screened abnormal submodules are calculated based on the capacitor parameter calculation principle of the input window voltage increment.
[0048] Combination Figure 6 The MMC capacitor status assessment method based on voltage increment and health score in this embodiment specifically includes the following process: S101: Define the time period during which all sub-modules within the bridge arm are simultaneously put into operation as the input window, and determine the start and end times of the input window respectively.
[0049] Specifically, the start and end times of the input window can be determined using existing technologies. For example, when the number of sub-modules input in the bridge arm is equal to the total number of sub-modules N, the delay factor starts counting. When the delay factor exceeds a preset threshold, it is considered to enter a valid input window, and this time is taken as the start point of the input window. When a bridge arm current commutation occurs or a sub-module exits the fully input state within the input window, the input window is determined to end.
[0050] Alternatively, adjustments can be made according to actual needs. For example, when the number of sub-modules engaged equals the total number of bridge arm sub-modules for a continuous control cycle exceeding a preset delay factor threshold, the system is considered to have entered an effective engagement window. The time when the number of sub-modules engaged for the first time equals the total number of bridge arm sub-modules is taken as the starting point of the engagement window, so as to make full use of the voltage change information in the early stage of the window.
[0051] S102: Calculate the capacitor voltage increment of each sub-module within the input window.
[0052] Specifically, in combination Figure 4 Let the input window interval be... Calculate the capacitor voltage increment of each submodule. .in, , They are respectively The capacitor voltage of the i-th submodule of phase j-arm at the start and end times of the input window; for The capacitor voltage increment of the i-th submodule of phase j bridge arm during the input window.
[0053] S103: Based on the sorting of the capacitor voltage increments of each submodule within the bridge arm, calculate the health score increment of each submodule within the current input window; the health score is accumulated from 0, and after the end of each input window, the health score of each submodule is cumulatively updated based on the sorting results of the submodule voltage increments within the input window.
[0054] Unlike existing technologies that determine anomalies based on the magnitude of the voltage difference within a single input window, the method proposed in this embodiment introduces a ranking-based health score update mechanism to cumulatively evaluate the relative performance of sub-modules across multiple input windows. This mechanism does not rely on the absolute magnitude of the voltage difference but reflects the relative degradation degree between sub-modules through the ranking results, thereby significantly reducing the impact of measurement noise and short-term operating condition fluctuations on the single determination result.
[0055] Specifically, the health score of submodule i is defined as follows: The initial scores were all 0.
[0056] Sort the capacitor voltage increments of all submodules within the bridge arm in ascending order, and denote the sorting rank as . ( This indicates that the voltage increment is minimal. (This indicates the maximum voltage increment).
[0057] Based on the ranking results, calculate the score increment for each submodule within the current input window. After each input window ends, the health score of each submodule is updated based on the submodule voltage increment ranking results within the input window.
[0058] As an example, Table 2 provides the corresponding health score update rules for different rankings; for instance: For top-ranked (healthy) sub-modules: Rank 1: +3 points; Rank 2: +2 points; Rank 3: +1 point. For bottom-ranked (deteriorated) sub-modules: Rank N: 3 points; ranked N 1: 2 points; ranked N 2: 1 point.
[0059] Table 2 Health Score Update Rules
[0060] Of course, the above rules are just examples, and those skilled in the art can formulate specific ranking and score increment correspondences according to actual needs.
[0061] As a further implementation, considering the slow evolution of the capacitance degradation process, a forgetting factor is introduced. ∈(0,1), the submodule health score is updated recursively. While retaining historical information, the health score can gradually reflect the changes in the capacitor health status, thus realizing continuous tracking of the submodule health status.
[0062] The forgetting factor depends on the degree of reliance on current information and is determined based on human experience. If you want historical information to have a greater determining weight, choose a larger number, such as 0.9; if you want current information to have a greater determining weight, choose a smaller number, such as 0.6.
[0063] In this embodiment, the update format for health scores is uniformly as follows: ; in, for The updated health score of the i-th submodule of the phase j bridge arm. for The health score of the i-th submodule of the bridge arm before the update. This represents the score increment for the submodule within the current input window.
[0064] S104: Identify abnormal submodules based on health assessment of each submodule.
[0065] Existing methods mainly rely on the voltage difference of a single input window for anomaly detection. However, the voltage change within a single window is small and easily affected by measurement noise and short-term operating disturbances, thus reducing the reliability of anomaly identification.
[0066] To address the aforementioned issues, this embodiment employs a cumulative evaluation mechanism with multiple input windows to improve the reliability of anomaly identification.
[0067] Specifically, set health thresholds. When the health score of a certain submodule i... Below this health threshold When this happens, it is determined to be an abnormal submodule.
[0068] Initially, all submodules have a health score of 0. As the input window accumulates, the scores of submodules with healthy capacitors continuously increase, while the scores of submodules with unhealthy capacitors continuously decrease. The health threshold is selected based on human experience. As an example, if you want more reliable monitoring results, you can choose a smaller threshold, such as -20; if you want to detect abnormal submodules faster, you can choose a larger threshold, such as -8.
[0069] S105: Select a reference submodule, and calculate the capacitance parameters of the abnormal submodule based on the capacitor voltage increment and capacitance parameters of the reference submodule during the input window.
[0070] Existing methods typically select a fixed submodule as the reference submodule. When the reference submodule itself undergoes slight aging or has measurement errors, it will cause a systematic shift in all monitoring results, thereby reducing monitoring accuracy.
[0071] To address the aforementioned issues, this embodiment dynamically selects a reference submodule to avoid system deviations caused by fixing the reference submodule.
[0072] Specifically, the submodule with the highest health score is adaptively selected as the reference submodule. Furthermore, when a submodule is determined to be abnormal, it is removed from the sorting process to avoid interfering with the sorting results of other submodules, thereby accelerating the identification of subsequent abnormal submodules.
[0073] Figure 5 Taking ten sub-modules per bridge arm as an example, this paper demonstrates the changes in the health score of the upper bridge arm sub-modules in phase a within the deployment window, as well as the process of identifying abnormal sub-modules and selecting reference sub-modules based on the relationship between the health score and the health threshold. Compared with the strategy of fixing the reference sub-module in traditional methods, the method in this embodiment can effectively avoid systematic shifts caused by slight degradation of the reference sub-module or measurement errors, and improve the reliability of abnormal sub-module identification and subsequent parameter estimation.
[0074] After identifying the abnormal submodule, the capacitance parameters of the abnormal submodule are determined using the following method: Let the capacitor voltage increments of the abnormal submodule and the reference submodule during the input window be respectively... and The capacitances are respectively and Since the abnormal submodule and the reference submodule experience the exact same bridge arm current during the input window, the ratio of their capacitor voltage increments satisfies: (5) in, , These represent the capacitor voltage increment and capacitance of the reference submodule during the input window, respectively. , These represent the capacitor voltage increment and capacitance of the abnormal submodule during the input window, respectively.
[0075] This allows for online quantitative identification of the capacitance parameters of abnormal submodules without introducing additional sensors or affecting the normal operation of the system.
[0076] Example 2 In one or more embodiments, a MMC capacitor status assessment system based on voltage increment and health score is disclosed, specifically including: The input window determination module is used to define the time period during which all sub-modules within the bridge arm are simultaneously put into operation as the input window, and to determine the start and end times of the input window respectively. The capacitor voltage increment calculation module is used to calculate the capacitor voltage increment of each sub-module within the input window. The health score update module is used to calculate the health score increment of each submodule within the current input window based on the sorting of the capacitor voltage increments of each submodule within the bridge arm; after the end of each input window, the health score of each submodule is cumulatively updated based on the sorting results of the submodule voltage increments within the input window. An abnormal submodule identification module is used to identify abnormal submodules based on the health assessment of each submodule. The capacitor parameter calculation module is used to select a reference submodule and calculate the capacitor parameters of the abnormal submodule based on the capacitor voltage increment and capacitor parameters of the reference submodule during the input window.
[0077] It should be noted that the specific implementation methods of the above modules are exactly the same as those in Example 1, and will not be described in detail again.
[0078] Example 3 In one or more embodiments, a terminal device is disclosed, comprising a processor and a memory, wherein the processor is used to implement instructions; and the memory is used to store multiple instructions adapted to be loaded by the processor and executed by the processor to perform the MMC capacitor state assessment method based on voltage increment and health score as described in Embodiment 1.
[0079] It should be understood that in this embodiment, the processor can be a central processing unit (CPU), or it can be other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The general-purpose processor can be a microprocessor or any conventional processor, etc.
[0080] Memory may include read-only memory and random access memory, and provides instructions and data to the processor. A portion of memory may also include non-volatile random access memory. For example, memory may also store information about the device type.
[0081] In the implementation process, each step of the above method can be completed by the integrated logic circuits in the processor hardware or by software instructions.
[0082] Example 4 In one or more embodiments, a computer-readable storage medium is disclosed, wherein a plurality of instructions are stored, the instructions being adapted to be loaded by a processor of a terminal device and executed by the MMC capacitor state assessment method based on voltage increment and health score as described in Embodiment 1.
[0083] While the specific embodiments of the present invention have been described above in conjunction with the accompanying drawings, this is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art without creative effort based on the technical solutions of the present invention are still within the scope of protection of the present invention.
Claims
1. A method for assessing the state of MMC capacitors based on voltage increment and health score, characterized in that, include: The time period during which all sub-modules within the bridge arm are simultaneously put into operation is defined as the operation window, and the start and end times of the operation window are determined respectively. Calculate the capacitor voltage increment of each submodule within the input window; Based on the sorting of the capacitor voltage increments of each submodule within the bridge arm, calculate the health score increment of each submodule within the current input window; after the end of each input window, cumulatively update the health score of each submodule based on the sorting results of the submodule voltage increments within the input window. Based on the health assessment of each submodule, an abnormal submodule is identified; Select a reference submodule, and calculate the capacitance parameters of the abnormal submodule based on the capacitor voltage increment and capacitance parameters of the reference submodule during the input window.
2. The method for assessing the state of MMC capacitors based on voltage increment and health score as described in claim 1, characterized in that, The health scores corresponding to the capacitor voltage increments of different rankings are preset. Based on the sorting of the capacitor voltage increments of each submodule in the bridge arm, the health score increment of each submodule in the current input window is calculated.
3. The method for assessing the state of MMC capacitors based on voltage increment and health score as described in claim 1, characterized in that, A forgetting factor is introduced, and the health score of each submodule is cumulatively updated based on the submodule voltage increment sorting results within the input window after each input window ends.
4. The method for assessing the state of MMC capacitors based on voltage increment and health score as described in claim 3, characterized in that, The cumulative update of the health score is specifically as follows: The updated health score of the current submodule is equal to the product of the current health score of the submodule and the forgetting factor, plus the health score increment of the submodule within the current input window.
5. The method for assessing the state of MMC capacitors based on voltage increment and health score as described in claim 1, characterized in that, Based on the health assessment of each submodule, an abnormal submodule is identified, specifically: A health threshold is set. If the health score of a submodule is lower than the health threshold, it is determined to be an abnormal submodule.
6. The method for assessing the state of MMC capacitors based on voltage increment and health score as described in claim 5, characterized in that, Once a submodule is determined to be abnormal, it is removed from the capacitor voltage increment sorting process.
7. The method for assessing the state of MMC capacitors based on voltage increment and health score as described in claim 1, characterized in that, The submodule with the highest current health score is adaptively selected as the reference submodule.
8. A system for assessing the state of MMC capacitors based on voltage increment and health score, characterized in that, include: The input window determination module is used to define the time period during which all sub-modules within the bridge arm are simultaneously put into operation as the input window, and to determine the start and end times of the input window respectively. The capacitor voltage increment calculation module is used to calculate the capacitor voltage increment of each sub-module within the input window. The health score update module is used to calculate the health score increment of each submodule within the current input window based on the sorting of the capacitor voltage increments of each submodule within the bridge arm; after the end of each input window, the health score of each submodule is cumulatively updated based on the sorting results of the submodule voltage increments within the input window. An abnormal submodule identification module is used to identify abnormal submodules based on the health assessment of each submodule. The capacitor parameter calculation module is used to select a reference submodule and calculate the capacitor parameters of the abnormal submodule based on the capacitor voltage increment and capacitor parameters of the reference submodule during the input window.
9. A terminal device comprising a processor and a memory, the processor for implementing instructions; the memory for storing multiple instructions, characterized in that, The instructions are adapted to be loaded by a processor and executed as described in any one of claims 1-7, the method for assessing the MMC capacitor status based on voltage increment and health score.
10. A computer-readable storage medium storing a plurality of instructions, characterized in that, The instructions are adapted to be loaded by the processor of the terminal device and executed by the MMC capacitor status assessment method based on voltage increment and health score as described in any one of claims 1-7.