A reliability evaluation method for a string-type energy storage coupled thermal power frequency modulation system

Abstract

The present disclosure provides a reliability evaluation method for a group string energy storage coupled thermal power frequency modulation system. By analyzing the topological characteristics and operation rules of the group string energy storage coupled thermal power frequency modulation system, the reliability parameters of the element level, subsystem level and system level are collected hierarchically. On this basis, the n-r redundancy model suitable for the group string parallel redundancy characteristics is constructed, and the coupling correction is carried out in combination with the frequency modulation depth and the frequency modulation depth increment caused by power transfer, so as to realize the accurate quantitative evaluation of the multi-dimensional comprehensive indexes such as the availability, frequency modulation capacity credibility and continuous frequency modulation capacity of the group string energy storage system and the thermal power frequency modulation system. The defects such as the underestimation of group string redundancy in the traditional method, the lack of frequency modulation working condition correlation, the neglect of subsystem coupling effect and the disconnection of evaluation index and frequency modulation function are effectively overcome.

Description

Technical Field

[0001] This disclosure relates to the intersection of power system frequency stability control and reliability assessment, and in particular to a reliability assessment method for a string energy storage coupled thermal power frequency regulation system. Background Technology

[0002] As the penetration rate of new energy power generation such as wind power and photovoltaics continues to increase, the grid inertia decreases and frequency fluctuations intensify, which places higher demands on the coordinated capability of frequency regulation services in terms of "rapid response-steady-state maintenance".

[0003] Thermal power units, as the traditional mainstay of frequency regulation, are limited by boiler thermal inertia and turbine response delay (typically 5-10 seconds), making it difficult to meet the millisecond-level rapid frequency regulation requirements. String energy storage, with its modular parallel design, offers advantages such as fast response speed (≤100ms), strong redundancy, and high regulation accuracy. When coupled with thermal power units to form a frequency regulation system, it can balance frequency regulation speed and continuity through a synergistic mode of "rapid energy storage compensation + steady-state thermal power regulation." However, existing reliability assessment methods have significant shortcomings for this type of string energy storage coupled with thermal power frequency regulation system: Insufficient string topology adaptability: String energy storage achieves capacity expansion by connecting multiple strings in parallel, and naturally has redundancy characteristics. However, traditional methods evaluate the reliability of a single module, without quantifying the role of string redundancy in improving system availability, resulting in conservative evaluation results. The impact of frequency regulation depth has been overlooked: The reliability of thermal power units is non-linearly related to the frequency regulation depth (actual regulation power / rated frequency regulation power) - deep frequency regulation will accelerate governor wear, boiler pressure fluctuations, and increase the risk of equipment failure, but existing methods have not established a quantitative relationship between the two. The coupling effect modeling is missing: In the string energy storage coupled thermal power frequency regulation system, there is a dynamic power transfer between the string energy storage (S1) and the thermal power unit (S2). When S1 is partially or completely shut down, the frequency regulation load it undertakes will be transferred to S2, which leads to an increase in the frequency regulation depth and a decrease in reliability of S2. Existing methods treat the two as independent systems for evaluation, which cannot reflect this coupling relationship. The indicators are disconnected from the frequency regulation function: Traditional evaluation indicators (such as system availability) only reflect "whether the system is out of service" and are not associated with functional indicators such as "whether the frequency regulation capacity meets the standard" and "whether the continuous frequency regulation duration meets the requirements", which cannot directly support the evaluation of frequency regulation service quality.

[0004] Therefore, a reliability assessment method that can adapt to string topology, quantify the influence of frequency modulation depth, and cover coupling effects is needed to accurately reflect the actual reliability level of coupled frequency modulation systems. Summary of the Invention

[0005] The first aspect of this disclosure provides a reliability assessment method for a string energy storage coupled thermal power frequency regulation system, comprising the following steps: Step S1: Determine the physical structure, functional division of labor and operating rules of the string energy storage coupled thermal power frequency regulation system to be evaluated. The system includes a string energy storage subsystem, a thermal power frequency regulation subsystem and a coupling control subsystem. Step S2: Collect reliability parameters at three levels: component level, subsystem level, and system level, and organize the collected parameters into a standardized parameter matrix; Step S3: Based on the topological characteristics of the string energy storage subsystem, which is composed of multiple independent energy storage strings connected in parallel, the availability of the subsystem is calculated using the redundancy model of taking r out of n, where n is the total number of strings and r is the redundancy threshold. Step S4: Based on the structural characteristics of the digital electro-hydraulic governor, turbine unit and boiler connected in series in the thermal power frequency regulation subsystem, and combined with the impact of frequency regulation depth on equipment reliability, calculate the basic availability of the subsystem; Step S5: Based on the impact of the availability change of the string energy storage subsystem on the frequency regulation load it undertakes, calculate the frequency regulation depth increment of the thermal power frequency regulation subsystem caused by power transfer, and correct the basic availability of the thermal power frequency regulation subsystem accordingly to obtain the availability of the coupled corrected thermal power frequency regulation subsystem. Step S6: Based on the structural characteristics of the communication system, controller and synchronization device connected in series in the coupled control subsystem, calculate the availability of the subsystem; Step S7: Integrate the availability of the string energy storage subsystem, the availability of the thermal power frequency regulation subsystem after coupling correction, and the availability of the coupling control subsystem to calculate the comprehensive reliability index of the string energy storage coupled thermal power frequency regulation system.

[0006] In conjunction with the first aspect, in step S1: The string energy storage subsystem consists of n independent energy storage strings connected in parallel. Each energy storage string includes an energy storage unit, a bidirectional power conversion system, and a local monitoring unit. The energy storage strings are connected in parallel through a combiner cabinet and are configured with a current sharing control strategy to suppress circulating current. The thermal power frequency regulation subsystem includes thermal power units, digital electro-hydraulic speed governors, boilers, and a coordinated control system. The dead zone of the digital electro-hydraulic speed governor is set to ±0.03 Hz. The coupling control subsystem includes a frequency regulation command receiver for receiving frequency regulation commands from the power grid dispatch center, a power distributor for allocating regulation power to the string energy storage subsystem and the thermal power frequency regulation subsystem according to the frequency deviation, and a synchronization device for synchronizing the power output of the two subsystems.

[0007] In conjunction with the first aspect, in step S2: The component-level reliability parameters include: the failure rate, availability, and mean time to repair (MTBT) of each string in the string energy storage subsystem; the failure rate, availability, and MTBT of the battery management system; and the failure rate, availability, and MTBT of the cooling system. The failure rate, availability, and mean time to repair (MTBT) of the digital electro-hydraulic speed governor in the thermal power frequency regulation subsystem; the failure rate, availability, and MTBT of the steam turbine unit; and the failure rate, availability, and MTBT of the boiler. The failure rate, availability, and mean time to repair of the communication system, the failure rate, availability, and mean time to repair of the controller, and the failure rate, availability, and mean time to repair of the synchronization device in the coupling control subsystem. The subsystem-level reliability parameters include: the total number of strings, redundancy threshold, and rated frequency regulation power of the string energy storage subsystem; the rated frequency regulation power and maximum frequency regulation depth of the thermal power frequency regulation subsystem; and the command transmission delay and synchronization accuracy of the coupled control subsystem. The system-level reliability parameters include: the ratio of the rated frequency regulation power of the string energy storage subsystem to that of the thermal power frequency regulation subsystem, and the statistical period.

[0008] In conjunction with the first aspect, the availability of the string energy storage subsystem described in step S3 is calculated as follows: , in, For the availability of string energy storage subsystems, For battery management system availability, To improve the availability of the cooling system, The total number of strings, This is a redundancy threshold. The number of strings. For combinations, This represents the availability rate of a single string.

[0009] In conjunction with the first aspect, the calculation method for the basic availability rate of the thermal power frequency regulation subsystem mentioned in step S4 is as follows: , in, To ensure the basic availability of the thermal power frequency regulation subsystem, For the availability of digital electro-hydraulic speed controllers, For the availability of steam turbine units, For boiler availability, This is the frequency modulation depth influence coefficient. This represents the actual frequency modulation depth.

[0010] In conjunction with the first aspect, the availability of the thermal power frequency regulation subsystem after coupling correction in step S5 is calculated as follows: , in, To determine the availability of the thermal power frequency regulation subsystem after coupling correction. To ensure the basic availability of the thermal power frequency regulation subsystem, This represents the increment of the actual frequency regulation depth of the thermal power frequency regulation subsystem.

[0011] In conjunction with the first aspect, the calculation method for the availability of the coupled control subsystem in step S6 is as follows: , in To improve the availability of the coupled control subsystem, For the availability of the communication system, For controller availability, This refers to the availability of the synchronization device.

[0012] In conjunction with the first aspect, the comprehensive reliability indicators mentioned in step S7 include overall system availability, frequency modulation capacity reliability, and mean time between failures (MTBF). The overall availability of the system The calculation method is as follows: ; The reliability of the frequency modulation capacity The calculation method is as follows: ,in This refers to the rated frequency regulation power of the string energy storage subsystem. This refers to the rated frequency regulation power of the thermal power frequency regulation subsystem. The mean time between failures (MTBF) frequency modulation The calculation method is as follows: ,in For the failure rate of the string energy storage subsystem, The failure rate of the thermal power frequency regulation subsystem after coupling correction. The failure rate of the coupled control subsystem.

[0013] A second aspect of this disclosure provides an electronic device, comprising: One or more processors; A storage unit is used to store one or more programs that, when executed by one or more processors, enable the one or more processors to implement the method.

[0014] A third aspect of this disclosure provides a computer-readable storage medium having a computer program stored thereon that, when executed by a processor, implements the method.

[0015] Beneficial Effects: This disclosure provides a reliability assessment method for string energy storage coupled with thermal power frequency regulation systems. By analyzing the topological characteristics and operating rules of the string energy storage coupled with thermal power frequency regulation systems, it collects reliability parameters at the component level, subsystem level, and system level. Based on this, it constructs an n-of-r redundancy model adapted to the string parallel redundancy characteristics, and performs coupling correction by combining the frequency regulation depth and the frequency regulation depth increment caused by power transfer. This achieves accurate quantitative assessment of multi-dimensional comprehensive indicators such as availability, frequency regulation capacity reliability, and continuous frequency regulation capability of string energy storage systems and thermal power frequency regulation systems. It effectively overcomes the shortcomings of traditional methods, such as underestimation of string redundancy, lack of correlation of frequency regulation conditions, neglect of subsystem coupling effects, and disconnection between assessment indicators and frequency regulation functions. It provides a scientific decision-making basis for capacity configuration, operation and maintenance strategy optimization, and frequency regulation service quality assessment of coupled frequency regulation systems in high-proportion renewable energy grid-connected scenarios. Attached Figure Description

[0016] Figure 1 This is a flowchart illustrating a reliability assessment method for a string energy storage coupled thermal power frequency regulation system according to an embodiment of this disclosure; Figure 2 An electronic device according to an embodiment of this disclosure. Detailed Implementation

[0017] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with those disclosed herein.

[0018] The terminology used in this disclosure is for the purpose of describing particular embodiments only and is not intended to be limiting of the present disclosure. The singular forms “a,” “the,” and “the” as used in this disclosure and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used herein refers to and includes any and all possible combinations of one or more of the associated listed items.

[0019] Figure 1 This is a flowchart of a reliability assessment method for a string energy storage coupled thermal power frequency regulation system according to an embodiment of the present disclosure, including: Step S1: Determine the physical structure, functional division of labor and operating rules of the string energy storage coupled thermal power frequency regulation system to be evaluated. The system includes a string energy storage subsystem, a thermal power frequency regulation subsystem and a coupling control subsystem. In step S1: The string energy storage subsystem consists of n independent energy storage strings connected in parallel. Each energy storage string includes an energy storage unit, a bidirectional power conversion system, and a local monitoring unit. The energy storage strings are connected in parallel through a combiner cabinet and are configured with a current sharing control strategy to suppress circulating current. The thermal power frequency regulation subsystem includes thermal power units, digital electro-hydraulic speed governors, boilers, and a coordinated control system. The dead zone of the digital electro-hydraulic speed governor is set to ±0.03 Hz. The coupling control subsystem includes a frequency regulation command receiver for receiving frequency regulation commands from the power grid dispatch center, a power distributor for allocating regulation power to the string energy storage subsystem and the thermal power frequency regulation subsystem according to the frequency deviation, and a synchronization device for synchronizing the power output of the two subsystems.

[0020] In this embodiment, step S1 is first executed to determine the physical structure, functional division of labor and operating rules of the string energy storage coupled thermal power frequency regulation system to be evaluated. The system includes a string energy storage subsystem, a thermal power frequency regulation subsystem and a coupling control subsystem.

[0021] Specifically, the system to be evaluated includes a string energy storage subsystem, a thermal power frequency regulation subsystem, and a coupling control subsystem. The string energy storage subsystem consists of n independent energy storage strings connected in parallel. Each energy storage string includes an energy storage unit, a bidirectional power conversion system, and a local monitoring unit. The energy storage strings are connected in parallel via combiner cabinets and are configured with a current sharing control strategy to suppress circulating current. In this embodiment, the energy storage unit uses lithium battery clusters, the bidirectional power conversion system realizes AC / DC conversion and power regulation, and the local monitoring unit is used to collect real-time operating parameters such as voltage, current, and state of charge of each string.

[0022] The thermal power frequency regulation subsystem includes the thermal power unit, digital electro-hydraulic governor, boiler, and coordinated control system. The digital electro-hydraulic governor controls the steam valve opening to regulate power output, with a deadband set at ±0.03 Hz to ensure regulation sensitivity under small frequency deviations. The coordinated control system enables coordinated frequency regulation between the boiler and turbine, ensuring stable operation of the thermal power unit.

[0023] The coupling control subsystem includes a frequency regulation command receiver, a power distributor, and a synchronization device. The frequency regulation command receiver receives frequency regulation commands from the power grid dispatch center. The power distributor allocates regulating power to the string energy storage subsystem and the thermal power frequency regulation subsystem based on the grid frequency deviation. The synchronization device synchronizes the power output of the two subsystems to avoid power surges. In this embodiment, the coupling control subsystem uses the IEC 61850 communication protocol to ensure that the command transmission delay does not exceed 50 milliseconds.

[0024] Based on the above system topology analysis, the operating rules of this string energy storage coupled thermal power frequency regulation system are further clarified: a three-level frequency regulation strategy is defined according to the grid frequency deviation, specifying the power division of the string energy storage subsystem and the thermal power frequency regulation subsystem in different frequency deviation segments to ensure the efficiency and stability of their coordinated frequency regulation. After step S1 is completed, proceed to step S2.

[0025] Step S2: Collect reliability parameters at three levels: component level, subsystem level, and system level, and organize the collected parameters into a standardized parameter matrix; In step S2: The component-level reliability parameters include: the failure rate, availability, and mean time to repair (MTBT) of each string in the string energy storage subsystem; the failure rate, availability, and MTBT of the battery management system; and the failure rate, availability, and MTBT of the cooling system. The failure rate, availability, and mean time to repair (MTBT) of the digital electro-hydraulic speed governor in the thermal power frequency regulation subsystem; the failure rate, availability, and MTBT of the steam turbine unit; and the failure rate, availability, and MTBT of the boiler. The failure rate, availability, and mean time to repair of the communication system, the failure rate, availability, and mean time to repair of the controller, and the failure rate, availability, and mean time to repair of the synchronization device in the coupling control subsystem. The subsystem-level reliability parameters include: the total number of strings, redundancy threshold, and rated frequency regulation power of the string energy storage subsystem; the rated frequency regulation power and maximum frequency regulation depth of the thermal power frequency regulation subsystem; and the command transmission delay and synchronization accuracy of the coupled control subsystem. The system-level reliability parameters include: the ratio of the rated frequency regulation power of the string energy storage subsystem to that of the thermal power frequency regulation subsystem, and the statistical period.

[0026] In this embodiment, step S2 is then executed, where reliability parameters are collected at three levels: component level, subsystem level, and system level, and the collected parameters are organized into a standardized parameter matrix.

[0027] Specifically, component-level reliability parameter acquisition covers all core components of the three subsystems. For the string energy storage subsystem, the failure rate, availability, and mean time to repair (MTBT) of each string, the failure rate, availability, and MTBT of the battery management system, and the failure rate, availability, and MTBT of the cooling system are collected. For the thermal power frequency regulation subsystem, the failure rate, availability, and MTBT of the digital electro-hydraulic governor, the turbine unit, and the boiler are collected. For the coupled control subsystem, the failure rate, availability, and MTBT of the communication system, the controller, and the synchronization device are collected. In this embodiment, some basic data of the above-mentioned component-level parameters are extracted from the equipment's factory technical documents, such as the design failure rate and rated average repair time of the digital electro-hydraulic speed controller. Some parameters are obtained through statistical calculations of on-site operation and maintenance records. Specifically, the availability of a single string is calculated by dividing the difference between the total running time and the total downtime during the statistical period by the total running time during the statistical period.

[0028] The subsystem-level reliability parameters collected include: the total number of strings, redundancy threshold, and rated frequency regulation power of the string energy storage subsystem; the rated frequency regulation power and maximum frequency regulation depth of the thermal power frequency regulation subsystem; and the command transmission delay and synchronization accuracy of the coupled control subsystem. In this embodiment, the string energy storage subsystem contains 6 independent energy storage strings, i.e., the total number of strings n is 6, and the redundancy threshold r is set to 4, meaning that at least 4 strings are normal to maintain the rated frequency regulation power output; the thermal power frequency regulation subsystem uses a 300MW thermal power unit with a rated frequency regulation power of 300MW and a maximum frequency regulation depth set to 70% of the unit's rated capacity; the command transmission delay of the coupled control subsystem does not exceed 50 milliseconds, and the synchronization accuracy is better than 0.01 Hz.

[0029] System-level reliability parameter acquisition includes: the ratio of the rated frequency regulation power of the string energy storage subsystem to that of the thermal power frequency regulation subsystem, and the statistical period. In this embodiment, based on the system's rated parameters determined in step S1, the ratio k of the rated frequency regulation power of the string energy storage subsystem to that of the thermal power frequency regulation subsystem is set to 0.3, and the statistical period is set to 1 year, i.e., the parameter statistics are based on the past 12 consecutive months of on-site operation and maintenance data.

[0030] After the above parameters are collected, all collected parameters are organized into a standardized parameter matrix according to the format of level-subsystem-parameter name-value-unit-data source to ensure the convenience and accuracy of parameter retrieval in subsequent modeling steps. After step S2 is completed, proceed to step S3.

[0031] Step S3: Based on the topological characteristics of the string energy storage subsystem, which is composed of multiple independent energy storage strings connected in parallel, the availability of the subsystem is calculated using the redundancy model of taking r out of n, where n is the total number of strings and r is the redundancy threshold. The availability of the string energy storage subsystem described in step S3 is calculated as follows: , in, For the availability of string energy storage subsystems, For battery management system availability, To improve the availability of the cooling system, The total number of strings, This is a redundancy threshold. The number of strings. For combinations, This represents the availability rate of a single string.

[0032] In this embodiment, step S3 is then executed. Based on the topological characteristics of the string energy storage subsystem, which is composed of multiple independent energy storage strings connected in parallel, the availability of the subsystem is calculated using the n-r redundancy model, where n is the total number of strings and r is the redundancy threshold.

[0033] Specifically, the reliable operation of the string energy storage subsystem depends on the simultaneous fulfillment of two conditions: the normal operation of the string array and the normal operation of the auxiliary system. The auxiliary system includes a battery management system and a cooling system. The battery management system is responsible for the status monitoring and protection control of each string, while the cooling system ensures that each string operates within a suitable temperature range. The string array adopts a redundancy design of r out of n, meaning that at least r strings out of the n independent energy storage strings are functioning normally to maintain the subsystem's rated frequency regulation power output. Since a failure in any component of the string array, battery management system, or cooling system will lead to the failure of the string energy storage subsystem, these three components form a series structure in terms of reliability logic. The overall availability of the subsystem is the product of the string array redundancy availability, the battery management system availability, and the cooling system availability.

[0034] In this embodiment, the physical meaning of the availability formula of the string energy storage subsystem is: the redundancy availability of the string array is the sum of the probabilities of all possible states from the redundancy threshold r to the total number of strings n. The probability of each state is the number of combinations C(n,j) multiplied by the probability of j strings working normally and then multiplied by the probability of the remaining (nj) strings failing.

[0035] In this embodiment, based on the parameter matrix collected in step S2, the total number of strings n is set to 6, and the redundancy threshold r is set to 4, meaning that at least 4 strings are normal to ensure the rated frequency regulation power output of the string energy storage subsystem. From the parameter matrix in step S2, the availability rate of a single string is extracted as 0.998, the battery management system availability rate as 0.9995, and the cooling system availability rate as 0.9998. Substituting these parameters into the formula, the calculated redundancy availability rate of the string array is approximately 0.9992, multiplied by... and Then, the availability of the string energy storage subsystem was obtained. The value is approximately 0.9995. This result quantifies the role of series-parallel redundancy in improving the reliability of the energy storage subsystem, and more accurately reflects the actual topology characteristics compared to the traditional method of evaluating by a single module.

[0036] After step S3 is completed, proceed to step S4.

[0037] Step S4: Based on the structural characteristics of the digital electro-hydraulic governor, turbine unit and boiler connected in series in the thermal power frequency regulation subsystem, and combined with the impact of frequency regulation depth on equipment reliability, calculate the basic availability of the subsystem; The basic availability rate of the thermal power frequency regulation subsystem mentioned in step S4 is calculated as follows: , in, To ensure the basic availability of the thermal power frequency regulation subsystem, For the availability of digital electro-hydraulic speed controllers, For the availability of steam turbine units, For boiler availability, This is the frequency modulation depth influence coefficient. This represents the actual frequency modulation depth.

[0038] In this embodiment, step S4 is then executed, and the basic availability of the subsystem is calculated based on the structural characteristics of the digital electro-hydraulic governor, turbine unit and boiler connected in series in the thermal power frequency regulation subsystem, combined with the impact of frequency regulation depth on equipment reliability.

[0039] Specifically, the reliable operation of the thermal power frequency regulation subsystem depends on the simultaneous normal operation of the digital electro-hydraulic governor, the turbine unit, and the boiler. The digital electro-hydraulic governor controls the steam valve opening to regulate power output; the turbine unit serves as the power conversion and output execution link; and the boiler provides the steam power required to drive the turbine unit. Since a failure of any of these three core devices will cause the thermal power frequency regulation subsystem to lose its frequency regulation capability, they form a series structure in terms of reliability logic. The basic availability rate of the subsystem is the product of the availability rates of the three components. However, the reliability of thermal power equipment is not static but decreases with the increase of actual frequency regulation depth. The physical reason is that under deep frequency regulation conditions, frequent governor operation exacerbates mechanical wear, and drastic fluctuations in boiler load lead to frequent pressure changes, accelerating equipment aging and increasing the failure rate. Therefore, this step introduces a frequency regulation depth influence coefficient α on the basis of the series structure to correct the basic availability rate.

[0040] In this embodiment, the physical meaning of the basic availability rate of the thermal power frequency regulation subsystem is: the probability that the thermal power frequency regulation subsystem can provide normal frequency regulation service after considering the influence of actual frequency regulation operating conditions. From the standardized parameter matrix in step S2, the availability rate of the digital electro-hydraulic governor is extracted as 0.9992, the turbine unit availability rate as 0.9950, and the boiler availability rate as 0.9940. The frequency regulation depth influence coefficient α characterizes the degree of influence of the actual frequency regulation depth on the reliability of thermal power equipment. Its value increases linearly with the increase of the actual frequency regulation depth, reflecting the deteriorating effect of deep frequency regulation on equipment reliability.

[0041] In this embodiment, based on the rated frequency regulation power of the thermal power frequency regulation subsystem determined in step S2 and the power allocation involved in step S5, the actual frequency regulation depth is taken as 60% of the rated frequency regulation power, and the frequency regulation depth influence coefficient α is calibrated to 0.08 based on the equipment's historical operating data. Substituting the above parameters into the formula, the product of the availability rate of the digital electro-hydraulic governor, the availability rate of the turbine unit, and the availability rate of the boiler is 0.9992 × 0.9950 × 0.9940 ≈ 0.9882, with a correction term. =0.952, and multiplying the two yields a basic availability rate of approximately 0.9408 for the thermal power frequency regulation subsystem. This result reflects the significant impact of actual frequency regulation conditions on the reliability of thermal power equipment and is more accurate than a static assessment that does not consider the frequency regulation depth.

[0042] After step S4 is completed, proceed to step S5.

[0043] Step S5: Based on the impact of the availability change of the string energy storage subsystem on the frequency regulation load it undertakes, calculate the frequency regulation depth increment of the thermal power frequency regulation subsystem caused by power transfer, and correct the basic availability of the thermal power frequency regulation subsystem accordingly to obtain the availability of the coupled corrected thermal power frequency regulation subsystem. The availability of the thermal power frequency regulation subsystem after coupling correction in step S5 is calculated as follows: , in, To determine the availability of the thermal power frequency regulation subsystem after coupling correction. To ensure the basic availability of the thermal power frequency regulation subsystem, This represents the increment of the actual frequency regulation depth of the thermal power frequency regulation subsystem.

[0044] In this embodiment, step S5 is then executed, which calculates the frequency regulation depth increment of the thermal power frequency regulation subsystem caused by power transfer based on the impact of the availability change of the string energy storage subsystem on the frequency regulation load it undertakes, and corrects the basic availability of the thermal power frequency regulation subsystem accordingly to obtain the availability of the thermal power frequency regulation subsystem after coupling correction.

[0045] Specifically, in a string energy storage coupled thermal power frequency regulation system, the string energy storage subsystem and the thermal power frequency regulation subsystem collaboratively undertake frequency regulation tasks according to the physical structure, functional division of labor, and operating rules determined in step S1. When the availability of the string energy storage subsystem decreases, for example, due to the failure of some strings causing it to shut down, its actual output frequency regulation power decreases accordingly. The frequency regulation load that should have been borne by the string energy storage subsystem cannot be fully covered, and the uncovered power deficit needs to be transferred to the thermal power frequency regulation subsystem, with the thermal power unit undertaking the additional regulation task. The direct consequence of this power transfer is an increase in the actual frequency regulation depth of the thermal power frequency regulation subsystem, which further accelerates the wear and aging of thermal power equipment, leading to a decrease in its reliability. This step establishes a coupling regulation effect correction model to quantify the impact of this power transfer effect on the reliability of the thermal power frequency regulation subsystem, thereby realizing a dynamic reliability correlation between the string energy storage subsystem and the thermal power frequency regulation subsystem.

[0046] In this embodiment, the core logic of the coupling correction is as follows: when the availability of the string energy storage subsystem decreases, its unavailability rate is the probability that the energy storage cannot bear the original frequency regulation load. This probability is multiplied by the ratio of the rated frequency regulation power to obtain the proportion of frequency regulation load that needs to be transferred to the thermal power side. This proportion is converted into the increment of the actual frequency regulation depth of the thermal power frequency regulation subsystem. According to the calculation results of steps S2 and S3, the availability of the string energy storage subsystem is approximately 0.9995, that is, its unavailability rate is 0.0005; the ratio k of the rated frequency regulation power is determined by step S2 as the ratio of the rated frequency regulation power of the string energy storage subsystem to that of the thermal power frequency regulation subsystem, and the value is 0.3. Thus, the power transfer ratio caused by the insufficient availability of the string energy storage subsystem is calculated to be 0.0005 multiplied by 0.3, which is approximately equal to 0.00015. That is, the actual frequency regulation depth of the thermal power frequency regulation subsystem is increased by approximately 0.015 percentage points on top of the 60% used in step S4.

[0047] Based on the aforementioned power transfer ratio, the basic availability rate of the thermal power frequency regulation subsystem obtained in step S4 is corrected. The correction method is as follows: the basic availability rate of the thermal power frequency regulation subsystem is multiplied by a correction factor. This correction factor reflects the deteriorating effect of the actual frequency regulation depth increment on reliability, and its value decreases as the actual frequency regulation depth increment increases. Since the availability rate of the string energy storage subsystem in this embodiment is extremely high, reaching 0.9995, its outage probability is extremely small. Therefore, the frequency regulation load increment transferred to the thermal power side is extremely limited, and the correction magnitude for the availability rate of the thermal power frequency regulation subsystem is also very small. Calculations show that the availability rate of the thermal power frequency regulation subsystem after coupling correction is approximately 0.9407, which is only slightly different from the basic availability rate of 0.9408 obtained in step S4. The results show that under the string configuration and high availability of energy storage, the negative impact of coupling effect on the reliability of thermal power is negligible. However, if the availability of the string energy storage subsystem is low, the power transfer effect will significantly increase the frequency regulation depth of thermal power, thereby having a non-negligible deterioration effect on the reliability of thermal power. The modified model in this step can accurately capture this coupling relationship.

[0048] Step S6: Based on the structural characteristics of the communication system, controller and synchronization device connected in series in the coupled control subsystem, calculate the availability of the subsystem; The availability of the coupled control subsystem mentioned in step S6 is calculated as follows: , in To improve the availability of the coupled control subsystem, For the availability of the communication system, For controller availability, This refers to the availability of the synchronization device.

[0049] In this embodiment, step S6 is then executed to calculate the availability of the subsystem based on the structural characteristics of the communication system, controller and synchronization device connected in series in the coupled control subsystem.

[0050] Specifically, the coupling control subsystem is the central link in the coordinated operation of the string energy storage subsystem and the thermal power frequency regulation subsystem. Its functional integrity directly determines whether the entire string energy storage coupled thermal power frequency regulation system can normally receive and execute frequency regulation commands issued by the power grid dispatch center. The reliable operation of the coupling control subsystem depends on the simultaneous normal operation of the communication system, controller, and synchronization device. The communication system includes a frequency regulation command receiver, responsible for reliably transmitting frequency regulation commands from the power grid dispatch center to the local control terminal. The controller includes a power divider, used to calculate the power distribution scheme in real time based on the frequency deviation and issue regulation commands to the string energy storage subsystem and the thermal power frequency regulation subsystem. The synchronization device ensures that the power output of the two subsystems remains synchronized at the grid connection node, avoiding power surges that could disturb the power grid. Since a failure of any of these three functional modules will cause the coupling control subsystem to fail, thereby causing the entire string energy storage coupled thermal power frequency regulation system to lose its frequency regulation capability, the three modules form a series structure in terms of reliability logic, and the subsystem availability rate is the product of the availability rates of the three modules.

[0051] In this embodiment, the availability rates of the communication system, controller, and synchronization device are extracted from the parameter matrix in step S2. The communication system uses the IEC61850 communication protocol, and its availability rate is 0.9999 based on field maintenance records. The controller is a redundant dual-machine hot standby controller, with a single-machine availability rate of 0.9995. Since any failure of the primary machine in the dual-machine hot standby architecture allows seamless switching to the standby machine, its overall availability rate, calculated based on parallel redundancy, is approximately 0.99999975. However, to simplify the calculation and be conservative, this embodiment directly uses the equivalent availability rate of 0.9998. The availability rate of the synchronization device is determined to be 0.9992 based on the equipment's factory technical documentation and field operation data. Multiplying these three values ​​together, the availability rate of the coupled control subsystem is approximately 0.9989.

[0052] The calculation results show that the availability of the coupled control subsystem is mainly constrained by the availability of the synchronization device, while the communication system, due to its mature technology and extremely low failure rate, has the least impact on the availability of the entire subsystem. After step S6 is completed, proceed to step S7.

[0053] Step S7: Integrate the availability of the string energy storage subsystem, the availability of the thermal power frequency regulation subsystem after coupling correction, and the availability of the coupling control subsystem to calculate the comprehensive reliability index of the string energy storage coupled thermal power frequency regulation system.

[0054] The comprehensive reliability indicators mentioned in step S7 include overall system availability, frequency modulation capacity reliability, and mean time between failures (MTBF). The overall availability of the system is calculated as follows: ; The reliability of the frequency modulation capacity The calculation method is as follows: ,in This refers to the rated frequency regulation power of the string energy storage subsystem. This refers to the rated frequency regulation power of the thermal power frequency regulation subsystem. The mean time between failures (MTBF) frequency modulation The calculation method is as follows: ,in For the failure rate of the string energy storage subsystem, The failure rate of the thermal power frequency regulation subsystem after coupling correction. The failure rate of the coupled control subsystem.

[0055] In this embodiment, step S7 is executed last to integrate the availability of the string energy storage subsystem, the availability of the coupled and corrected thermal power frequency regulation subsystem, and the availability of the coupled control subsystem to calculate the comprehensive reliability index of the string energy storage coupled thermal power frequency regulation system.

[0056] Specifically, the comprehensive reliability indicators include three dimensions: overall system availability, frequency regulation capacity reliability, and mean time between failures (MTBF). These dimensions characterize the reliability level of the string energy storage coupled with thermal power frequency regulation system from different perspectives. Overall system availability reflects the comprehensive probability that the string energy storage coupled with thermal power frequency regulation system can provide normal frequency regulation services. Its physical meaning is: the coupled control subsystem must be functioning normally to ensure the effective transmission and execution of frequency regulation commands; simultaneously, at least one subsystem in both the string energy storage subsystem and the thermal power frequency regulation subsystem must be able to output normal frequency regulation power. Only when both conditions are met is the system as a whole available. Since the coupled control subsystem is a common link preceding the two power subsystems, logically, the three constitute a "coupled control subsystem in series (string energy storage subsystem in parallel with thermal power frequency regulation subsystem)" structure. Therefore, the overall system availability is the coupling control subsystem availability multiplied by the combined availability of the string energy storage subsystem and the thermal power frequency regulation subsystem.

[0057] In this embodiment, the availability rate of the string energy storage subsystem obtained in step S3 is approximately 0.9995, the availability rate of the coupled-corrected thermal power frequency regulation subsystem obtained in step S5 is approximately 0.9407, and the availability rate of the coupled control subsystem obtained in step S6 is approximately 0.9989. Substituting these values ​​into the overall system availability calculation formula, the combined availability rate of the string energy storage subsystem and the thermal power frequency regulation subsystem is 1 minus the product of the unavailability rates of the string energy storage subsystem and the thermal power frequency regulation subsystem, i.e., 1 - (1 - 0.9995) × (1 - 0.9407), which is approximately 0.99997. This combined availability rate is then multiplied by the availability rate of the coupled control subsystem, 0.9989, to obtain an overall system availability rate of approximately 0.99887. The results show that although the availability of the thermal power frequency regulation subsystem itself is only about 0.94, the overall availability of the string energy storage coupled thermal power frequency regulation system is significantly improved due to the high availability of the string energy storage subsystem and its parallel redundancy with the thermal power frequency regulation subsystem, which fully demonstrates the advantages of string energy storage coupled thermal power frequency regulation in terms of reliability.

[0058] The physical meaning of frequency regulation capacity reliability (CR) is: the sum of the available frequency regulation power of the string energy storage subsystem (calculated based on its availability rate) and the available frequency regulation power of the thermal power frequency regulation subsystem (calculated based on its coupling correction availability rate), divided by the sum of the rated frequency regulation power of the two subsystems. This indicator is directly related to the "capacity compliance" requirement of frequency regulation services and reflects the system's ability to meet grid dispatch requirements.

[0059] In this embodiment, the rated frequency regulation power of the string energy storage subsystem is 90MW, and the rated frequency regulation power of the thermal power frequency regulation subsystem is 300MW. The ratio of the rated frequency regulation power k= / =0.3. The available frequency regulation power of the string energy storage subsystem is calculated by multiplying the rated frequency regulation power of the string energy storage subsystem by its availability rate, i.e., 90MW × 0.9995 ≈ 89.955MW; the available frequency regulation power of the thermal power frequency regulation subsystem is calculated by multiplying the rated frequency regulation power of the thermal power frequency regulation subsystem by the coupling-corrected availability rate, i.e., 300MW × 0.9407 ≈ 282.21MW; the sum of the two is 372.165MW, which, divided by the sum of the rated frequency regulation power of the two subsystems (390MW), yields the frequency regulation capacity reliability. The value is approximately 0.954. This result means that, constrained by the availability of the thermal power frequency regulation subsystem, the available frequency regulation power of the string energy storage coupled thermal power frequency regulation system is approximately 95.4% of the sum of the rated frequency regulation power of the two subsystems. This indicator can provide a direct quantitative basis for power grid dispatch to evaluate the frequency regulation service capability of the string energy storage coupled thermal power frequency regulation system.

[0060] Mean Time Between Failures (MTBF) The ability of a string energy storage system coupled with a thermal power plant to continuously and reliably provide frequency regulation services is used to quantify this capability. Its physical meaning is the average continuous operating time between two system failures. This indicator is directly related to the "continuous capability" requirement of the frequency regulation service. Calculating the average fault-free frequency regulation time requires converting the availability rate of each subsystem into a failure rate. In this embodiment, the availability rate of the string energy storage subsystem is 0.9995, and its average repair time, based on the maintenance statistics from step S2, is 8 hours. Therefore, its failure rate is derived. =(1-0.9995) / 8≈6.25×10 -5 Frequency regulation subsystem availability after coupling correction (times / hour); The value is 0.9407, and the average repair time is 24 hours. The resulting failure rate is... =(1-0.9407) / 24≈0.00247 times / hour; Availability of the coupled control subsystem The value is 0.9989, and the average repair time is 4 hours. The resulting failure rate is... =(1-0.9989) / 4≈2.75×10 -4 The system's total failure rate is approximately 0.0028075 times per hour. Taking the reciprocal gives the mean time between failures (MTBF). The result indicates that, due to the low availability of the thermal power frequency regulation subsystem, the continuous fault-free frequency regulation time of the string energy storage coupled thermal power frequency regulation system is approximately 356 hours, or about 15 days. This indicator can provide a reference for optimizing operation and maintenance strategies. For example, it is recommended to regularly perform preventive maintenance on the digital electro-hydraulic speed governor of the thermal power frequency regulation subsystem to reduce its failure rate and extend the system's mean time between failures.

[0061] At this point, step S7 is complete, and the entire evaluation process is finished. All the evaluation results are compiled into an evaluation report, which includes the parameter matrix established in step S2, the reliability indicators of each subsystem from steps S3 to S6, the comprehensive reliability indicators of the system in step S7, and corresponding conclusions and recommendations. This report guides the capacity configuration optimization, operation and maintenance strategy formulation, and frequency regulation service quality evaluation of this string energy storage coupled thermal power frequency regulation system.

[0062] Electronic device 200 can be a desktop computer, laptop, handheld computer, cloud server, or other electronic device. Electronic device 200 may include, but is not limited to, processor 201 and memory 202. Those skilled in the art will understand that... Figure 2 This is merely an example of electronic device 200 and does not constitute a limitation on electronic device 200. It may include more or fewer components than shown, or combine certain components, or different components. For example, electronic device may also include input / output devices, network access devices, buses, etc.

[0063] The processor 201 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.

[0064] The memory 202 can be an internal storage unit of the electronic device 200, such as a hard disk or RAM of the electronic device 200. The memory 202 can also be an external storage device of the electronic device 200, such as a plug-in hard disk, Smart Media Card (SMC), Secure Digital (SD) card, or Flash Card equipped on the electronic device 200. Furthermore, the memory 202 can include both internal and external storage units of the electronic device 200. The memory 202 is used to store the computer program 203 and other programs and data required by the electronic device. The memory 202 can also be used to temporarily store data that has been output or will be output.

[0065] The above embodiments are only used to illustrate the technical solutions of this disclosure, and are not intended to limit it. Although this disclosure has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this disclosure, and should all be included within the protection scope of this disclosure.

Claims

1. A reliability assessment method for a string energy storage coupled thermal power frequency regulation system, characterized in that, Includes the following steps: Step S1: Determine the physical structure, functional division of labor and operating rules of the string energy storage coupled thermal power frequency regulation system to be evaluated. The system includes a string energy storage subsystem, a thermal power frequency regulation subsystem and a coupling control subsystem. Step S2: Collect reliability parameters at three levels: component level, subsystem level, and system level, and organize the collected parameters into a standardized parameter matrix; Step S3: Based on the topological characteristics of the string energy storage subsystem, which is composed of multiple independent energy storage strings connected in parallel, the availability of the subsystem is calculated using the redundancy model of taking r out of n, where n is the total number of strings and r is the redundancy threshold. Step S4: Based on the structural characteristics of the digital electro-hydraulic governor, turbine unit and boiler connected in series in the thermal power frequency regulation subsystem, and combined with the impact of frequency regulation depth on equipment reliability, calculate the basic availability of the subsystem; Step S5: Based on the impact of the availability change of the string energy storage subsystem on the frequency regulation load it undertakes, calculate the frequency regulation depth increment of the thermal power frequency regulation subsystem caused by power transfer, and correct the basic availability of the thermal power frequency regulation subsystem accordingly to obtain the availability of the coupled corrected thermal power frequency regulation subsystem. Step S6: Based on the structural characteristics of the communication system, controller and synchronization device connected in series in the coupled control subsystem, calculate the availability of the subsystem; Step S7: Integrate the availability of the string energy storage subsystem, the availability of the thermal power frequency regulation subsystem after coupling correction, and the availability of the coupling control subsystem to calculate the comprehensive reliability index of the string energy storage coupled thermal power frequency regulation system.

2. The method according to claim 1, characterized in that, In step S1: The string energy storage subsystem consists of n independent energy storage strings connected in parallel. Each energy storage string includes an energy storage unit, a bidirectional power conversion system, and a local monitoring unit. The energy storage strings are connected in parallel through a combiner cabinet and are configured with a current sharing control strategy to suppress circulating current. The thermal power frequency regulation subsystem includes thermal power units, digital electro-hydraulic speed governors, boilers, and a coordinated control system. The dead zone of the digital electro-hydraulic speed governor is set to ±0.03 Hz. The coupling control subsystem includes a frequency regulation command receiver for receiving frequency regulation commands from the power grid dispatch center, a power distributor for allocating regulation power to the string energy storage subsystem and the thermal power frequency regulation subsystem according to the frequency deviation, and a synchronization device for synchronizing the power output of the two subsystems.

3. The method according to claim 2, characterized in that, In step S2: The component-level reliability parameters include: the failure rate, availability, and mean time to repair (MTBT) of each string in the string energy storage subsystem; the failure rate, availability, and MTBT of the battery management system; and the failure rate, availability, and MTBT of the cooling system. The failure rate, availability, and mean time to repair (MTBT) of the digital electro-hydraulic speed governor in the thermal power frequency regulation subsystem; the failure rate, availability, and MTBT of the steam turbine unit; and the failure rate, availability, and MTBT of the boiler. The failure rate, availability, and mean time to repair of the communication system, the failure rate, availability, and mean time to repair of the controller, and the failure rate, availability, and mean time to repair of the synchronization device in the coupling control subsystem. The subsystem-level reliability parameters include: the total number of strings, redundancy threshold, and rated frequency regulation power of the string energy storage subsystem; the rated frequency regulation power and maximum frequency regulation depth of the thermal power frequency regulation subsystem; and the command transmission delay and synchronization accuracy of the coupled control subsystem. The system-level reliability parameters include: the ratio of the rated frequency regulation power of the string energy storage subsystem to that of the thermal power frequency regulation subsystem, and the statistical period.

4. The method according to claim 3, characterized in that, The availability of the string energy storage subsystem described in step S3 is calculated as follows: ， in, For the availability of string energy storage subsystems, For battery management system availability, To improve the availability of the cooling system, The total number of strings, This is a redundancy threshold. The number of strings. For combinations, This represents the availability rate of a single string.

5. The method according to claim 4, characterized in that, The basic availability rate of the thermal power frequency regulation subsystem mentioned in step S4 is calculated as follows: ， in, To ensure the basic availability of the thermal power frequency regulation subsystem, For the availability of digital electro-hydraulic speed controllers, For the availability of steam turbine units, For boiler availability, This is the frequency modulation depth influence coefficient. This represents the actual frequency modulation depth.

6. The method according to claim 5, characterized in that, The availability of the thermal power frequency regulation subsystem after coupling correction in step S5 is calculated as follows: ， in, To determine the availability of the thermal power frequency regulation subsystem after coupling correction. To ensure the basic availability of the thermal power frequency regulation subsystem, This represents the increment of the actual frequency regulation depth of the thermal power frequency regulation subsystem.

7. The method according to claim 6, characterized in that, The availability of the coupled control subsystem mentioned in step S6 is calculated as follows: ， in To improve the availability of the coupled control subsystem, For the availability of the communication system, For controller availability, This refers to the availability of the synchronization device.

8. The method according to claim 7, characterized in that, The comprehensive reliability indicators mentioned in step S7 include overall system availability, frequency modulation capacity reliability, and mean time between failures (MTBF). The overall availability of the system The calculation method is as follows: ; The reliability of the frequency modulation capacity The calculation method is as follows: ,in This refers to the rated frequency regulation power of the string energy storage subsystem. This refers to the rated frequency regulation power of the thermal power frequency regulation subsystem. The mean time between failures (MTBF) frequency modulation The calculation method is as follows: ,in For the failure rate of the string energy storage subsystem, The failure rate of the thermal power frequency regulation subsystem after coupling correction. The failure rate of the coupled control subsystem.

9. An electronic device, characterized in that, include: One or more processors; A storage unit for storing one or more programs that, when executed by one or more processors, enable the one or more processors to implement the method of claim 1.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by a processor, it implements the method as described in claim 1.

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