Uncertain AC / DC micro-grid DC bus voltage control method containing time delay

Abstract

The invention relates to the technical field of voltage control, in particular to a time-delay-containing uncertain AC / DC micro-grid DC bus voltage control method, which comprises the following steps: acquiring load change and DC bus voltage fluctuation data, calculating a load current change rate, analyzing the correlation between voltage fluctuation and load change, and performing voltage adjustment. And time delay characteristics in a load state are identified, voltage fluctuation uncertainty factors are identified, and the time delay compensation amount is adjusted to restore the voltage stability. According to the invention, by adopting linear and nonlinear time-delay compensation strategies, the problem of accuracy of time-delay compensation under different load conditions is effectively solved, various load fluctuations and voltage changes can be dynamically adapted, the problem of uncertainty of voltage fluctuations is solved, and the prediction of voltage fluctuations is optimized by dynamically adjusting the weight of uncertainty factors. The over-reaction to sudden voltage change is reduced, the voltage stability is improved, and the operation stability and the voltage regulation precision of the micro-grid are remarkably improved.

Description

Technical Field

[0001] The present invention relates to the technical field of voltage control, in particular to a method for controlling the DC bus voltage of an AC-DC microgrid with time delay and uncertainty. Background Art

[0002] The technical field of voltage control includes the stabilization and regulation of voltage in a power system, especially its application in a microgrid system. A microgrid is a small, independent or grid-connected power system that includes multiple distributed energy devices such as solar energy, wind energy, and energy storage devices. In the technical field of voltage control, the core content is how to ensure that the voltage at each node in the power system is maintained within a specified range to ensure the stable operation of the power system and the normal operation of the load. With the gradual popularization of microgrids, voltage control technology faces new challenges such as time delay and uncertainty. How to effectively solve these problems and maintain voltage stability has become an important research direction in this field. Voltage control technology includes various control strategies, methods, and optimization means to adapt to the complex grid operation environment.

[0003] Among them, the method for controlling the DC bus voltage of an AC-DC microgrid with time delay and uncertainty refers to a technical solution for the problem of controlling the DC bus voltage of a microgrid. The patent theme covers how to stabilize the DC bus voltage in a microgrid through precise control in the presence of time delay and system uncertainty. The patent proposes a control strategy by modeling the microgrid system, analyzing the time delay characteristics and uncertainty factors existing in the system, and formulating corresponding control algorithms. This method optimizes the voltage regulation effect by introducing time delay compensation and uncertainty handling means during the control process to ensure that the microgrid can operate stably and maintain the voltage within a suitable range under various working conditions.

[0004] In the existing technology for microgrid voltage control, there are relatively fixed control algorithms and coping strategies, which cannot flexibly cope with the complexity of load fluctuations and voltage fluctuations. In the case of large load changes, traditional methods fail to accurately identify the time delay characteristics under different load states, resulting in inaccurate time delay compensation strategies and voltage fluctuations or instability. When facing the uncertainty of voltage fluctuations, the existing technology does not have an effective dynamic adjustment mechanism, resulting in overcompensation or slow response, causing the voltage to deviate from the set range at some moments and affecting the normal operation of load devices. When dealing with the time delay compensation problem under different loads, the existing technology adopts a single compensation method and cannot perform personalized adjustment according to the characteristics of light and heavy loads, resulting in poor efficiency and effect of the control strategy. These deficiencies lead to the inability of the microgrid to provide a stable and reliable voltage output when dealing with different working conditions, affecting the overall efficiency and operation safety of the system. Summary of the Invention

[0005] To address the complexity of the prior art in flexibly coping with load fluctuations and voltage fluctuations, in the case of large load changes, the traditional methods fail to accurately identify the time-delay characteristics under different load states, resulting in inaccurate time-delay compensation strategies and phenomena of voltage fluctuations or instability. In the face of the uncertainty of voltage fluctuations, the prior art lacks an effective dynamic adjustment mechanism, leading to overcompensation or slow response, causing the voltage to deviate from the set range at some moments and affecting the normal operation of load devices. When dealing with the time-delay compensation problem under different loads, the prior art adopts a single compensation method and cannot perform personalized adjustment according to the characteristics of light loads and heavy loads, resulting in poor efficiency and effectiveness of the control strategy. The deficiencies lead to the technical problem that the microgrid cannot provide a stable and reliable voltage output when coping with different working conditions, affecting the overall efficiency and operation safety of the system. Embodiments of the present invention provide a method for controlling the DC bus voltage of an AC-DC microgrid with time delay and uncertainty. The technical solution is as follows:

[0006] On the one hand, a method for controlling the DC bus voltage of an AC-DC microgrid with time delay and uncertainty is provided, and the method includes:

[0007] S1: Obtain the changes in the loads and the DC bus voltage fluctuation data in the AC-DC microgrid, calculate the rate of change of the load current, analyze the correlation between the voltage fluctuation and the load change, and perform voltage adjustment according to the relationship between the load change rate and the voltage fluctuation to obtain the load-voltage fluctuation correlation information;

[0008] S2: According to the load-voltage fluctuation correlation information, collect the voltage fluctuation and control time-delay data under different working conditions, identify the time-delay characteristics under different load states, and construct a time-delay compensation response model;

[0009] S3: Adopt the time-delay compensation response model, combine the DC bus voltage, the charge and discharge states of the energy storage device, the output power of wind and solar power generation, and the load power in the AC-DC microgrid to identify the uncertain factors of voltage fluctuation. When the voltage change trend deviates from the preset range, dynamically adjust the weights of the uncertain factors to generate a predicted value of voltage fluctuation uncertainty;

[0010] S4: Based on the predicted value of voltage fluctuation uncertainty, adjust the time-delay compensation amount in real time according to the load change, evaluate the impact of the load change on voltage stability, and avoid voltage fluctuations caused by overcompensation to obtain a record of the adjustment of the time-delay compensation amount.

[0011] As a further solution of the present invention, the load and voltage fluctuation correlation information includes the load change rate, the voltage fluctuation amplitude, and the correlation coefficient between the load and the voltage fluctuation. The time-delay compensation response model includes a linear time-delay compensation response model, a non-linear time-delay compensation response model, and the relationship between the time-delay compensation amount and the load fluctuation. The predicted value of voltage fluctuation uncertainty includes the voltage fluctuation uncertainty amount, the adjusted weight of the uncertainty factor, and the predicted voltage fluctuation amplitude.

[0012] As a further solution of the present invention, the steps for obtaining the load and voltage fluctuation correlation information are specifically as follows:

[0013] S101: Obtain the load change and DC bus voltage fluctuation data in the AC-DC microgrid, extract the power, frequency, and current information of the load, analyze the change of the load current over time, identify the change amplitude of the load current, and obtain the load current change rate;

[0014] S102: Compare the load current change rate with the voltage fluctuation data, analyze the correlation between the load change and the voltage fluctuation, and adjust the voltage through the load current change rate to obtain the load and voltage fluctuation correlation information.

[0015] As a further solution of the present invention, the steps for obtaining the time-delay compensation response model are specifically as follows:

[0016] S201: According to the load and voltage fluctuation correlation information, collect the voltage fluctuation data of the AC-DC microgrid under different working conditions, obtain the corresponding control time-delay data, monitor and record the voltage fluctuation under the load state, extract the time-delay characteristics under different load states, and obtain the voltage fluctuation and control time-delay data;

[0017] S202: According to the voltage fluctuation and time-delay data, analyze and identify the time-delay characteristics under different load states. For the light load state, adjust the voltage response through linear time-delay compensation, and for the heavy load state, adopt a non-linear compensation method to cope with the time-delay effect to obtain the time-delay characteristic analysis result;

[0018] S203: Based on the time-delay characteristic analysis result, combined with the real-time load fluctuation and voltage state of the AC-DC microgrid, calculate the voltage stability index according to the linear compensation under light load and the non-linear compensation under heavy load, and construct a time-delay compensation response model.

[0019] As a further solution of the present invention, the formula for calculating the voltage stability index is as follows:

[0020]

[0021] Wherein, V stability represents the voltage stability index, Vload Represents the real-time load voltage, V ref Represents the reference voltage, I load,i Represents the current value at the i-th load point, I ref,i Represents the i-th reference current value, P load Represents the load power, P ref Represents the reference power, α is the compensation factor, and n is the number of load points.

[0022] As a further solution of the present invention, the steps for obtaining the predicted value of voltage fluctuation uncertainty are specifically as follows:

[0023] S301: Based on the time-delay compensation response model, combined with the DC bus voltage in the AC-DC microgrid, the charge and discharge states of energy storage devices, the output power of wind and solar power generation, and the load power, monitor and record the changes of each factor to obtain the key data change record;

[0024] S302: Based on the key data change record, analyze the voltage change trend and identify the uncertainty factors in the voltage fluctuation. When the voltage change trend deviates from the preset range, adjust the weight of the uncertainty factors, refer to the charge and discharge states of energy storage devices and the fluctuations of wind and solar power generation, optimize the weight allocation method, and output the predicted value of voltage fluctuation uncertainty.

[0025] As a further solution of the present invention, the steps for obtaining the time-delay compensation amount adjustment record are specifically as follows:

[0026] S401: According to the predicted value of voltage fluctuation uncertainty, monitor the load change situation in real time, and adjust the time-delay compensation amount according to the amplitude of the load change. During the adjustment process, refer to the change of voltage fluctuation uncertainty, and adjust the time-delay compensation in real time dynamically to obtain the time-delay compensation amount adjustment record;

[0027] S402: According to the time-delay compensation amount adjustment record, evaluate the impact of load change on voltage stability. By comparing the voltage fluctuation conditions before and after the load change, analyze the impact of load change on voltage stability, and judge whether the time-delay compensation is excessive to obtain the load impact evaluation result;

[0028] S403: Use the load impact evaluation result to adjust the time-delay compensation amount, avoid voltage fluctuations caused by time-delay compensation, and record each adjustment to obtain the time-delay compensation amount adjustment record.

[0029] As a further solution of the present invention, when analyzing the impact of load change on voltage stability, the formula is used:

[0030]

[0031] Among them, ΔU represents the voltage fluctuation amplitude, V a(t) represents the voltage value at the a-th moment, V a-1 (t) represents the voltage value at the (a - 1)-th moment, N represents the total number of voltage sampling points, ΔL represents the load change amount, K1 and K2 are adjustment coefficients, P load represents the power value of the real-time load.

[0032] As a further solution of the present invention, the method further includes step S5:

[0033] S5: Adjust the record using the time-delay compensation amount, evaluate the voltage stability, judge whether the real-time voltage is within the stable range. When the voltage fluctuation exceeds the set range, adjust the time-delay compensation amount and the voltage regulation to restore the voltage stability, and obtain the voltage stability evaluation result;

[0034] The voltage stability evaluation result includes a voltage stability determination result, a voltage adjustment measure, and a voltage stable recovery time.

[0035] As a further solution of the present invention, the steps for obtaining the voltage stability evaluation result are specifically as follows:

[0036] S501: Based on the record of the time-delay compensation amount adjustment, evaluate the stability of the real-time voltage, monitor the voltage fluctuation in real time, compare it with the set stable range, judge whether the voltage exceeds the preset range, record the fluctuation situation during the voltage change process, and obtain the basic data for voltage stability evaluation;

[0037] S502: Use the basic data for voltage stability evaluation. When the voltage fluctuation exceeds the set range, adjust the time-delay compensation amount according to the real-time data, combine the voltage fluctuation trend and the real-time compensation amount, iteratively adjust the voltage regulation method, perform voltage regulation operations and record the adjustment process to obtain voltage fluctuation recovery information;

[0038] S503: Call the voltage fluctuation recovery information, evaluate the impact of voltage recovery according to the adjusted time-delay compensation amount and voltage regulation operations, and judge whether the voltage is stable within the set range to obtain the voltage stability evaluation result.

[0039] The beneficial effects brought by the technical solution provided by the embodiments of the present invention at least include:

[0040] By obtaining the load change and DC bus voltage fluctuation data in real time, deeply analyzing the relationship between the load current change rate and voltage fluctuation, the voltage can be accurately adjusted to ensure the stable operation of the system. By identifying the time-delay characteristics under different load states, linear and non-linear time-delay compensation strategies are respectively adopted to effectively solve the accuracy problem of time-delay compensation under different load conditions. The introduction of the time-delay compensation response model enables the dynamic adaptation to various load fluctuations and voltage changes under the complex working conditions of the microgrid. This precise compensation strategy not only solves the uncertainty problem of voltage fluctuation, but also optimizes the prediction of voltage fluctuation by dynamically adjusting the weights of uncertainty factors, reduces the overreaction to sudden voltage changes, and improves the voltage stability. By real-time adjusting the predicted value of voltage fluctuation uncertainty, the voltage instability caused by overcompensation can be effectively avoided, ensuring the continuous and stable operation of power, making the dynamic adaptation to uncertainty factors more flexible, being able to respond to challenges in various power grid environments timely and accurately, and significantly improving the operation stability and voltage regulation accuracy of the microgrid. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 is a schematic diagram of the working process of the present invention; DETAILED DESCRIPTION OF THE EMBODIMENTS

[0042] The technical solutions in the present invention will be described below with reference to the drawings.

[0043] In the embodiments of the present invention, words such as "exemplarily" and "for example" are used to represent examples, illustrations or explanations. Any embodiment or design solution described as "example" in the present invention should not be construed as being more preferred or having more advantages than other embodiments or design solutions. Exactly speaking, the use of the word "example" is intended to present concepts in a specific way. In addition, in the embodiments of the present invention, the meaning expressed by "and / or" can be both, or either one of the two.

[0044] To make the technical problems, technical solutions and advantages to be solved by the present invention clearer, the following will be described in detail with reference to the drawings and specific embodiments.

[0045] Please refer to Figure 1 , the embodiments of the present invention provide a DC bus voltage control method for an AC-DC microgrid with time delay, and the processing flow of this method can include the following steps:

[0046] S1: Obtain the load change and DC bus voltage fluctuation data in the AC-DC microgrid, calculate the rate of change of the load current, analyze the correlation between the voltage fluctuation and the load change, and adjust the voltage according to the relationship between the load change rate and the voltage fluctuation to obtain the load-voltage fluctuation association information;

[0047] S2: According to the correlation information between the load and voltage fluctuations, collect the voltage fluctuation and control time-delay data under different working conditions, identify the time-delay characteristics under different load states. For the light load state, apply linear time-delay compensation; for the heavy load, adopt a non-linear compensation method. Based on the real-time load fluctuations and voltage status, construct a time-delay compensation response model;

[0048] S3: Use the time-delay compensation response model, combined with the DC bus voltage in the AC-DC microgrid, the charge and discharge status of the energy storage device, the output power of wind and solar power generation, and the load power, to identify the uncertain factors of voltage fluctuations. When the voltage change trend deviates from the preset range, dynamically adjust the weights of the uncertain factors to generate a predicted value of voltage fluctuation uncertainty;

[0049] S4: Based on the predicted value of voltage fluctuation uncertainty, adjust the time-delay compensation amount in real time according to the load change, evaluate the impact of the load change on voltage stability, avoid voltage fluctuations caused by over-compensation, and obtain a record of the adjustment of the time-delay compensation amount;

[0050] S5: Use the record of the adjustment of the time-delay compensation amount to evaluate the voltage stability, judge whether the real-time voltage is within the stable range. When the voltage fluctuation exceeds the set range, adjust the time-delay compensation amount and the voltage regulation to restore the voltage stability, and obtain the voltage stability evaluation result;

[0051] The correlation information between the load and voltage fluctuations includes the load change rate, voltage fluctuation amplitude, and correlation coefficient between the load and voltage fluctuations. The time-delay compensation response model includes a linear time-delay compensation response model, a non-linear time-delay compensation response model, and the relationship between the time-delay compensation amount and load fluctuations. The predicted value of voltage fluctuation uncertainty includes the voltage fluctuation uncertainty amount, the adjusted weights of the uncertain factors, and the predicted voltage fluctuation amplitude. The record of the adjustment of the time-delay compensation amount includes the change of the time-delay compensation amount, the impact of the load change on the compensation amount, and the voltage stability evaluation result.

[0052] The specific steps for obtaining the correlation information between the load and voltage fluctuations are as follows:

[0053] S101: Obtain the load change and DC bus voltage fluctuation data in the AC-DC microgrid, extract the power, frequency, and current information of the load, and identify the change amplitude of the load current by analyzing the change of the load current over time to obtain the load current change rate;

[0054] When obtaining the data of load changes and DC bus voltage fluctuations in an AC / DC microgrid, the operating states of each load in the microgrid are monitored by installing current, voltage, and power sensors. The sensors record the power, frequency, and current data of the loads in real time. The data can be used to analyze the changing trend of load current over time. Through data acquisition equipment, the current value (such as 10 A), power (such as 2 kW), and frequency (such as 50 Hz) of the load at a certain moment can be recorded. In the following time, data is continuously collected to obtain the change of load current over time. For easy analysis, data processing software can be used to sort the current data at each moment in chronological order to form a curve of current change over time. In an actual scenario, it is set that the current gradually increases or decreases within a certain period of time. By comparing the current data at different time points and calculating the difference between the maximum and minimum values, the change amplitude of the load current can be obtained. By calculating the change rate of the current, the fluctuation of the current can be further analyzed to help identify the changing trend of the load current. If the change amplitude of the current is 0.7 A within 10 seconds, it indicates that the load current has fluctuated to a certain extent during this period. By analyzing the change rate of the current, the impact of the load on the grid stability can be inferred and data support can be provided for subsequent adjustments to obtain the change rate of the load current.

[0055] S102: Compare the load current change rate with the voltage fluctuation data, analyze the correlation between load changes and voltage fluctuations, and adjust the voltage according to the load current change rate to obtain the associated information of the load and voltage fluctuations;

[0056] Compare the rate of change of load current with the voltage fluctuation data, aiming to deeply analyze the relationship between the change of load current and voltage fluctuation. In a microgrid, voltage fluctuation will affect the stability, and the change of load current is one of the reasons for voltage fluctuation. Therefore, voltage fluctuation can be monitored simultaneously and relevant data can be recorded. By collecting voltage data in real time (setting 220V, 221V, etc.), the voltage fluctuation range can be obtained, and the amplitude of voltage fluctuation can be analyzed. When the amplitude of voltage data fluctuates by 3V within a certain period of time, it indicates that there is a certain voltage fluctuation. Using the aforementioned rate of change of load current, compare through a data analysis tool to analyze the correlation between the rate of change of load current and the amplitude of voltage fluctuation. In this process, explore the impact of load current fluctuation on voltage through correlation analysis. If the rate of current change is high (setting 0.07A / s) and the amplitude of voltage fluctuation is large (such as 3V), it can be inferred that current fluctuation is the key factor causing voltage fluctuation. According to this analysis result, an automatic adjustment method can be adopted to reduce voltage fluctuation by controlling the rate of change of load current. When it is detected that the change of load current is too large, the rate of current change can be optimized by switching loads or adjusting the power factor to reduce the impact of voltage fluctuation on the microgrid. This adjustment process realizes the benign adjustment between the grid load and voltage fluctuation through real-time data feedback and control algorithms, improves the overall stability of the grid, and obtains the correlation information between the load and voltage fluctuation.

[0057] The steps for obtaining the time-delay compensation response model are specifically as follows:

[0058] S201: According to the correlation information between the load and voltage fluctuation, collect the voltage fluctuation data of the AC-DC microgrid under different working conditions, and obtain the corresponding control time-delay data. Monitor and record the voltage fluctuation under the load state, extract the time-delay characteristics under different load states, and obtain the voltage fluctuation and control time-delay data;

[0059] According to the correlation information between the load and voltage fluctuations, collect the voltage fluctuation data of the AC-DC microgrid under different working conditions, and obtain the corresponding control time-delay data. Through multi-dimensional data acquisition equipment, monitor and record the voltage fluctuation conditions of the power grid under the load state in real time, and further extract the time-delay characteristics under different load states. When the load changes, the voltage fluctuation will also change accordingly, but its response does not occur immediately, which leads to the time-delay phenomenon of voltage fluctuation. For different load states (such as light load and heavy load), the voltage fluctuation and control time-delay of the power grid show different characteristics. In practical applications, by installing high-precision voltage sensors and time-delay measurement devices, the amplitude, frequency, and response time of voltage fluctuations can be accurately recorded. Under the light load state, the voltage fluctuation is small, but its control time-delay is long; while under the heavy load state, the voltage fluctuation is more significant, and the time-delay response is more complex. Through the analysis of the data, the voltage fluctuation and control time-delay data under different load conditions can be obtained, providing a reference for subsequent compensation adjustment to further understand the response characteristics of the power grid under different loads and obtain the voltage fluctuation and control time-delay data.

[0060] S202: Analyze and identify the time-delay characteristics under different load states based on the voltage fluctuation and time-delay data. For the light load state, adjust the voltage response through linear time-delay compensation, and for the heavy load state, adopt a non-linear compensation method to cope with the time-delay effect to obtain the analysis results of the time-delay characteristics.

[0061] Further analyze and identify the time-delay characteristics under different load states. For the light load state, adopt a linear time-delay compensation method to adjust the voltage response to make it more stable; for the heavy load state, due to the increase in the power grid load, the time-delay effect is more complex, so a non-linear time-delay compensation method is adopted to cope with the impact of time-delay on voltage fluctuation. In practical applications, under light load, the change in voltage fluctuation is relatively gentle, and the control time-delay is relatively short. The linear time-delay compensation method can effectively adjust the voltage response to restore the voltage fluctuation to the normal range. Suppose in a certain light load condition, the voltage fluctuation is ±0.5V and the control time-delay is 200ms. The linear compensation method eliminates this part of the fluctuation by directly adjusting the voltage output signal. While under the heavy load state, due to the increase in load, the voltage fluctuation amplitude increases, and the time-delay response is more complex. The non-linear time-delay compensation method needs to dynamically adjust the voltage response through a more flexible algorithm. When the voltage fluctuation reaches ±2V and the time-delay is 500ms, the non-linear compensation will combine the load characteristics and adjust the phase relationship between the current and voltage to achieve the purpose of balancing the voltage fluctuation. By analyzing the time-delay characteristics, the performance of the time-delay effect under different load states can be obtained, and a suitable compensation strategy can be formulated to ensure the stability of the power grid operation and obtain the analysis results of the time-delay characteristics.

[0062] S203: Based on the time-delay feature analysis results, combined with the real-time load fluctuations and voltage status of the AC-DC microgrid, calculate the voltage stability index according to the linear compensation under light load and the non-linear compensation under heavy load, and construct a time-delay compensation response model;

[0063] The formula for calculating the voltage stability index is as follows:

[0064]

[0065] Among them, V stability represents the voltage stability index, V load represents the real-time load voltage, V ref represents the reference voltage, I load,i represents the current value of the i-th load point, I ref,i represents the i-th reference current value, P load represents the load power, P ref represents the reference power, α is the compensation factor, and n is the number of load points;

[0066] Meaning of parameters and derivation process of formula calculation:

[0067] V stability is the voltage stability index, indicating the degree of voltage deviation from the reference voltage;

[0068] V load is the real-time load voltage, indicating the current voltage of the AC-DC microgrid;

[0069] V ref is the reference voltage, which is a set standard voltage value based on a predetermined load condition;

[0070] I load,i is the current value of the i-th load point, measured by monitoring the current sensor;

[0071] I ref,i is the i-th reference current value, which is a preset standard current value according to the current sensor and load characteristics;

[0072] P load is the load power, indicating the power consumed by the actual load;

[0073] P ref is the reference power, which is the ideal load power value during normal operation;

[0074] α is the compensation factor, adjusted according to the load characteristics and voltage stability requirements;

[0075] Parameter acquisition and quantization process:

[0076] V load and V refis the real-time data obtained through the on-line monitoring system, where V load is directly measured by a voltage sensor, and V ref is set during the design of the power system;

[0077] I load,i and I ref,i are measured by a current sensor. Specifically, the load current I load,i is the real-time current at each load point, and the reference current I ref,i is the expected current value calculated based on the rated power and voltage of the electrical equipment;

[0078] P load and P ref are provided by the load power measurement device. The load power P load is the power value calculated by combining the real-time voltage and current data, while the reference power P ref is the preset target power;

[0079] α is a constant that is dynamically adjusted according to the change of the load state, determined during debugging and fine-tuned during actual operation to ensure voltage stability even when the load fluctuates greatly;

[0080] Set the monitoring data to be displayed as follows:

[0081] V load = 220V, V ref = 230V;

[0082] Current measurement: I load,1 = 10A, I ref,1 = 12A, I load,2 = 15A, I ref,2 = 14A;

[0083] Load power: P load = 2200W, P ref = 2000W;

[0084] Compensation factor: α = 0.05

[0085] Calculate the voltage deviation part:

[0086] V load - V ref = 220 - 230 = -10;

[0087] Absolute value:

[0088] |V load - V ref | = 10;

[0089] Calculate the current deviation part:

[0090]

[0091] Calculate the sum of squares:

[0092] (-0.167) 2 +(0.071) 2 = 0.0279 + 0.0050 = 0.0329;

[0093] Find the square root:

[0094]

[0095] Calculate the part of the voltage stability index:

[0096]

[0097] Calculate the part of the power difference:

[0098] P load -P ref = 2200 - 2000 = 200;

[0099] |P load -P ref | = 200;

[0100] Calculate the voltage stability:

[0101] V stability = 55.1·(1 + 0.05·200) = 606.1;

[0102] The result represents the value of the voltage stability index. A high stability value indicates that a relatively stable voltage level can be maintained under the current load and voltage conditions, with a small deviation.

[0103] The specific steps for obtaining the predicted value of voltage fluctuation uncertainty are as follows:

[0104] S301: Based on the time-delay compensation response model, combine the DC bus voltage, the charge and discharge states of energy storage devices, the output power of wind and solar power generation, and the load power in the AC-DC microgrid, monitor and record the changes of each factor, and obtain the key data change record;

[0105] Combined with the DC bus voltage, the charge and discharge status of energy storage devices, the output power of wind and solar power generation, and the load power in the AC-DC microgrid, the changes of these factors are monitored and recorded in real time to obtain the change records of key data. Through the integrated data acquisition device, the changes of key factors during the operation of the power grid can be continuously tracked and recorded. The DC bus voltage is a key indicator of the power grid stability. The charge and discharge status of energy storage devices directly affects the balance of the power grid load. The output power of wind and solar power generation fluctuates with climate conditions and time, and the load power is closely related to the power demands of individual users in the power grid. By monitoring the real-time data, the change records of each factor at different time periods can be obtained. Suppose at a certain moment, the DC bus voltage is 300V, the energy storage device is in the discharge state, the output power of wind power generation is 50kW, the output of photovoltaic power generation is 30kW, and the load power is 70kW. The changes of each factor can be stored by the data recording device and used for subsequent analysis. The data provides a basis for analyzing the overall operation of the power grid and data support for further identifying the uncertain factors in voltage fluctuations, and obtains the change records of key data.

[0106] S302: Based on the change records of key data, analyze the voltage change trend and identify the uncertain factors in voltage fluctuations. When the voltage change trend deviates from the preset range, adjust the weights of the uncertain factors, refer to the charge and discharge status of energy storage devices and the fluctuations of wind and solar power generation, optimize the weight allocation method, and output the predicted value of voltage fluctuation uncertainty;

[0107] Further analyze the voltage change trend and identify the uncertain factors in voltage fluctuations. When the voltage change trend deviates from the preset range, the weights of the uncertain factors need to be adjusted. The uncertainty of voltage fluctuations comes from the combined action of multiple factors, such as the charge and discharge fluctuations of energy storage devices, the instability of the output power of wind and solar power generation, and the changes in load demands, etc. When analyzing the voltage change trend, by calculating the change rate and amplitude of real-time voltage data, the normal range of voltage fluctuations is identified. If the voltage change trend exceeds the preset range, intervention is required. The weights of each uncertain factor can be adjusted. When the power fluctuation of wind and solar power generation is large, the weight of the fluctuation of wind and solar power generation on voltage fluctuation needs to be increased; if the charge and discharge status of the energy storage device is abnormal, the influence weight of the energy storage device needs to be reduced. The weight distribution of each factor should also be optimized with reference to the charge and discharge status of the energy storage device and the fluctuations of wind and solar power generation. When the energy storage device is in the charging state, its influence on the power grid voltage is small, while in the discharge state, the influence of the energy storage is large. The weight distribution needs to be adjusted to make it more in line with the actual operation of the power grid, and output the predicted value of voltage fluctuation uncertainty.

[0108] The specific steps for obtaining the adjustment record of the time-delay compensation amount are as follows:

[0109] S401: Monitor the load change situation in real time according to the predicted value of voltage fluctuation uncertainty, and adjust the time-delay compensation amount according to the amplitude of the load change. During the adjustment process, refer to the change of voltage fluctuation uncertainty, dynamically adjust the time-delay compensation in real time, and obtain the adjustment record of the time-delay compensation amount.

[0110] According to the predicted value of voltage fluctuation uncertainty, monitor the load change situation in real time, and adjust the time-delay compensation amount according to the amplitude of the load change. In practical applications, the change of voltage fluctuation is closely related to the fluctuation of the load. By monitoring the load change in real time, the fluctuation of the power grid load can be captured, and the time-delay compensation can be adjusted accordingly. When the load changes, if the change amplitude of the load power is large, it will be determined whether to adjust the time-delay compensation amount according to the predicted value of voltage fluctuation uncertainty. If the uncertainty of voltage fluctuation is high, the adjustment of the time-delay compensation amount needs to be more sensitive and real-time to avoid overcompensation or slow response. Suppose at a certain moment, the load power increases from 50kW to 70kW. Identify the change through real-time monitoring, and adjust the time-delay compensation amount according to the predicted voltage fluctuation uncertainty. When the load change amplitude is large, the time-delay compensation amount needs to be increased accordingly to respond to the voltage change faster and reduce the fluctuation of the power grid. During the adjustment process, the impact of the load change on the voltage fluctuation will be dynamically monitored in real time, and the compensation amount will be continuously adjusted to ensure the stable operation of the power grid, provide data support for subsequent analysis and optimization, and obtain the adjustment record of the time-delay compensation amount.

[0111] S402: Evaluate the impact of the load change on the voltage stability according to the adjustment record of the time-delay compensation amount. By comparing the voltage fluctuation situations before and after the load change, analyze the impact of the load change on the voltage stability, judge whether the time-delay compensation is excessive, and obtain the load impact evaluation result.

[0112] Analyze the impact of the load change on the voltage stability, using the formula:

[0113]

[0114] where, ΔU represents the voltage fluctuation amplitude, V a V(t) represents the voltage value at the ath moment, V a-1 V(t - 1) represents the voltage value at the (a - 1)th moment, N represents the total number of voltage sampling points, ΔL represents the load change amount, K1 and K2 are adjustment coefficients, P load represents the power value of the real-time load;

[0115] Parameter meaning and formula calculation derivation process:

[0116] V a V(t) represents the voltage value at the ath moment at time t, and the voltage value is obtained by sampling the voltage sensor;

[0117] V a-1(t) represents the voltage value at the previous moment t, that is, the voltage value at the (a - 1)-th moment in the previous moment;

[0118] N represents the total number of voltage sampling points, which is determined according to the monitored time period and sampling frequency. Sampling is performed once per second, and the monitoring time is 10 seconds, so N = 10;

[0119] ΔL represents the load change amount, which is obtained by monitoring the power change amount of the load device, and a power meter is used to quantify the load change;

[0120] K1 and K2 are adjustment coefficients, which are determined through simulation and experiments based on the requirements of power stability. The common range is K1 = 0.5 and K2 = 0.3, and these two values are adjusted according to the load fluctuation characteristics of the power;

[0121] P load represents the power value of the current load, which is measured in real time by a power meter;

[0122] Formula calculation process

[0123] The following parameters are set:

[0124] The monitored time period is 10 seconds, the sampling frequency is 1 time per second, and N = 10 is obtained.

[0125] The voltage sampling data is: V1(t) = 220V, V2(t) = 221V, V3(t) = 219V, V4(t) = 220V, V 10 (t) = 220V;

[0126] The voltage difference between two consecutive moments is:

[0127] |V a (t) - V a-1 (t)| = |V2(t) - V1(t)| = |221 - 220| = 1;

[0128] |V3(t) - V2(t)| = |219 - 221| = 2;

[0129] Similarly, calculate the voltage difference:

[0130] Since the difference is calculated and accumulated for each voltage change, the total sum is obtained:

[0131]

[0132] Substitute into the formula:

[0133]

[0134] where ΔL = 3 is the load change amount, and the load power is set as P load = 1000;

[0135] Further calculation:

[0136]

[0137] The result represents the voltage fluctuation amplitude caused by the load change. According to the calculation, the impact of the load change on the voltage is approximately 0.87V. This indicates that during this time period, the voltage is significantly affected by the load change. The result directly reflects the response ability to the load change and serves as the basis for subsequent evaluation of voltage stability.

[0138] S403: Utilize the evaluation result of the load impact to adjust the time-delay compensation amount, avoid voltage fluctuations caused by time-delay compensation, and record each adjustment to obtain the adjustment record of the time-delay compensation amount;

[0139] Adjust the time-delay compensation amount to avoid voltage fluctuations caused by time-delay compensation. During this process, based on the evaluation result of the impact of the load change on voltage stability, dynamically adjust the time-delay compensation amount to avoid voltage fluctuations caused by overcompensation. If the evaluation result indicates overcompensation of the time-delay compensation, the time-delay compensation amount will be correspondingly reduced to ensure that the voltage fluctuation is controlled within a reasonable range. When the voltage fluctuation amplitude caused by the load change is large, if the time-delay compensation is excessive and leads to more severe voltage fluctuations, the amplitude of the time-delay compensation amount will be reduced to balance the power grid. The process of adjusting the time-delay compensation amount each time will be recorded for subsequent optimization and analysis. In this way, continuously adjust and optimize the time-delay compensation strategy to ensure the stable operation of the power grid and obtain the adjustment record of the time-delay compensation amount.

[0140] The specific steps for obtaining the voltage stability evaluation result are as follows:

[0141] S501: Based on the adjustment record of the time-delay compensation amount, evaluate the stability of the real-time voltage, monitor the voltage fluctuation in real time, compare it with the set stable range, determine whether the voltage exceeds the preset range, record the fluctuation situation during the voltage change process, and obtain the basic data for voltage stability evaluation;

[0142] Evaluate the stability of the real-time voltage. By monitoring voltage fluctuations in real time and comparing them with a preset stable range, it is possible to effectively determine whether the voltage exceeds the set stable range. It will continuously track voltage changes and compare the measured real-time voltage value with the set stable range (such as ±2V). If the voltage exceeds this range, it will immediately record the fluctuations during the voltage change process, including the amplitude, frequency, and duration of the voltage fluctuations, etc. Through recording, basic data on voltage stability can be obtained, and the data provides a basis for subsequent adjustment and optimization. At a certain moment, the voltage fluctuation amplitude is ±2.5V, exceeding the set range, then this fluctuation will be marked and recorded as the basic data for voltage stability assessment. The data will help determine whether the voltage stability is ensured and whether it is necessary to further adjust the time-delay compensation amount to restore voltage stability, and obtain the basic data for voltage stability assessment.

[0143] S502: Adopt the basic data for voltage stability assessment. When the voltage fluctuation exceeds the set range, adjust the time-delay compensation amount according to real-time data, combine the voltage fluctuation trend and real-time compensation amount, iteratively adjust the voltage regulation method, perform voltage regulation operations and record the adjustment process to obtain voltage fluctuation recovery information;

[0144] When the voltage fluctuation exceeds the set range, the time-delay compensation amount will be adjusted according to real-time data. Through the analysis of the real-time voltage fluctuation trend and the dynamic adjustment of the time-delay compensation amount, the voltage regulation method can be iteratively adjusted. When the voltage fluctuation exceeds the preset range (such as ±2V), the time-delay compensation amount will be adjusted according to real-time voltage data. Set the current time-delay compensation amount to 0.5A, and if the voltage fluctuation amplitude exceeds the set range, the time-delay compensation amount will be automatically increased to 1A in order to control the voltage fluctuation. During the adjustment process, the voltage regulation operation will be iteratively optimized by combining the voltage fluctuation trend and real-time compensation amount to ensure that the voltage fluctuation is effectively controlled. Each time an adjustment is made, the detailed data of the adjustment process will be recorded, including the change in the compensation amount, the execution time of the adjustment operation, and the key data during the voltage recovery process, to generate voltage fluctuation recovery information.

[0145] S503: Call the voltage fluctuation recovery information, evaluate the impact of voltage recovery according to the adjusted time-delay compensation amount and voltage regulation operation, and determine whether the voltage is stable within the set range to obtain the voltage stability assessment result;

[0146] The impact of voltage recovery can be evaluated, and it can be determined whether the voltage is stable within the set range. By analyzing the adjusted time-delay compensation amount and voltage regulation operation, the effect of voltage recovery can be evaluated, and it can be determined whether the voltage returns to the preset stable range. It is set that after adjusting the time-delay compensation amount and voltage regulation operation, when the voltage recovers to the range of ±1.5V, it will be confirmed that the voltage has recovered to the set range. If the voltage fluctuation still exceeds the set range, the time-delay compensation amount will be continuously adjusted, and the regulation effect will be re-evaluated. Through the dynamic evaluation and adjustment process, a voltage stability evaluation result is generated.

[0147] As described above, it is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention can easily think of changes or substitutions, which should all be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims described.

Claims

1. A DC bus voltage control method for an uncertain AC-DC microgrid with time delay, characterized in that It includes the following steps: S1: Obtain the load change and DC bus voltage fluctuation data in the AC-DC microgrid, calculate the rate of change of the load current, analyze the correlation between the voltage fluctuation and the load change, and perform voltage adjustment according to the relationship between the load change rate and the voltage fluctuation to obtain the load-voltage fluctuation correlation information; S2: According to the load-voltage fluctuation correlation information, collect the voltage fluctuation and control time-delay data under different working conditions, identify the time-delay characteristics under different load states, and construct a time-delay compensation response model; S3: Use the time-delay compensation response model, combine the DC bus voltage, the charge and discharge state of the energy storage device, the output power of wind and solar power generation, and the load power in the AC-DC microgrid to identify the uncertain factors of the voltage fluctuation. When the voltage change trend deviates from the preset range, dynamically adjust the weights of the uncertain factors to generate a predicted value of the voltage fluctuation uncertainty; S4: Based on the predicted value of the voltage fluctuation uncertainty, adjust the time-delay compensation amount in real time according to the load change, evaluate the impact of the load change on the voltage stability, avoid voltage fluctuations caused by over-compensation, and obtain the adjustment record of the time-delay compensation amount.

2. The method for controlling the DC bus voltage of an AC-DC microgrid with time delay and uncertainty according to claim 1, characterized in that, The load-voltage fluctuation correlation information includes the load change rate, the voltage fluctuation amplitude, and the correlation coefficient between the load and the voltage fluctuation. The time-delay compensation response model includes a linear time-delay compensation response model, a non-linear time-delay compensation response model, and the relationship between the time-delay compensation amount and the load fluctuation. The predicted value of the voltage fluctuation uncertainty includes the voltage fluctuation uncertainty amount, the adjusted weight of the uncertain factor, and the predicted voltage fluctuation amplitude.

3. The method for controlling the DC bus voltage of an AC-DC microgrid with time delay and uncertainty according to claim 1, characterized in that The specific steps for obtaining the load-voltage fluctuation correlation information are as follows: S101: Obtain the load change and DC bus voltage fluctuation data in the AC-DC microgrid, extract the power, frequency, and current information of the load, analyze the change of the load current over time, identify the change amplitude of the load current, and obtain the load current change rate; S102: Compare the load current change rate with the voltage fluctuation data, analyze the correlation between the load change and the voltage fluctuation, and adjust the voltage through the load current change rate to obtain the load-voltage fluctuation correlation information.

4. The method for controlling the DC bus voltage of an AC-DC microgrid with time delay and uncertainty according to claim 3, characterized in that The specific steps for obtaining the time-delay compensation response model are as follows: S201: According to the load-voltage fluctuation correlation information, collect the voltage fluctuation data of the AC-DC microgrid under different working conditions, and obtain the corresponding control time-delay data. Monitor and record the voltage fluctuation under the load state, extract the time-delay characteristics under different load states, and obtain the voltage fluctuation and control time-delay data; S202: According to the voltage fluctuation and time-delay data, analyze and identify the time-delay characteristics under different load states. For the light load state, adjust the voltage response through linear time-delay compensation, and for the heavy load state, adopt a non-linear compensation method to cope with the time-delay effect to obtain the time-delay characteristic analysis result; S203: Based on the time-delay characteristic analysis result, combine the real-time load fluctuation and voltage state of the AC-DC microgrid, and calculate the voltage stability index according to the linear compensation under light load and the non-linear compensation under heavy load to construct a time-delay compensation response model.

5. The time-delay-containing uncertain AC-DC microgrid DC bus voltage control method according to claim 4, characterized in that, The formula for calculating the voltage stability index is as follows: Among them, V stability represents the voltage stability index, V load represents the real-time load voltage, V ref represents the reference voltage, I load,i represents the current value at the i-th load point, I ref,i represents the i-th reference current value, P load represents the load power, P ref represents the reference power, α is the compensation factor, and n is the number of load points.

6. The time-delay-containing uncertainty AC-DC microgrid DC bus voltage control method according to claim 4, characterized in that The specific steps for obtaining the predicted value of voltage fluctuation uncertainty are as follows: S301: Based on the time-delay compensation response model, in combination with the DC bus voltage in the AC-DC microgrid, the charge and discharge states of energy storage devices, the output power of wind and solar power generation, and the load power, monitor and record the changes of each factor to obtain a record of key data changes; S302: Based on the record of key data changes, analyze the voltage change trend and identify the uncertainty factors in voltage fluctuations. When the voltage change trend deviates from the preset range, adjust the weights of the uncertainty factors, and optimize the weight allocation method with reference to the charge and discharge states of energy storage devices and the fluctuations of wind and solar power generation, and output the predicted value of voltage fluctuation uncertainty.

7. The method for controlling the DC bus voltage of an AC-DC microgrid with time delay and uncertainty according to claim 6, wherein The specific steps for obtaining the record of time-delay compensation amount adjustment are as follows: S401: According to the predicted value of voltage fluctuation uncertainty, monitor the load change situation in real time, and adjust the time-delay compensation amount according to the amplitude of the load change. During the adjustment process, refer to the change of voltage fluctuation uncertainty and dynamically adjust the time-delay compensation in real time to obtain a record of time-delay compensation amount adjustment; S402: According to the record of time-delay compensation amount adjustment, evaluate the impact of load change on voltage stability. By comparing the voltage fluctuation conditions before and after the load change, analyze the impact of load change on voltage stability, and judge whether the time-delay compensation is excessive to obtain the load impact evaluation result; S403: Use the load impact evaluation result to adjust the time-delay compensation amount, avoid voltage fluctuations caused by time-delay compensation, and record each adjustment to obtain a record of time-delay compensation amount adjustment.

8. The time-delay-containing uncertainty AC-DC microgrid DC bus voltage control method according to claim 7, wherein The analysis of the impact of load change on voltage stability uses the formula: Among them, ΔU represents the voltage fluctuation amplitude, V a (t) represents the voltage value at the a-th moment, V a-1 (t) represents the voltage value at the (a - 1)-th moment, N represents the total number of voltage sampling points, ΔL represents the load change amount, K1 and K2 are adjustment coefficients, P load represents the power value of the real-time load.

9. The method for controlling the DC bus voltage of an AC / DC microgrid with time delay and uncertainty according to claim 1, wherein, The method also includes step S5: S5: Use the record of time-delay compensation amount adjustment to evaluate voltage stability, judge whether the real-time voltage is within the stable range. When the voltage fluctuation exceeds the set range, adjust the time-delay compensation amount and voltage regulation to restore the voltage stability to obtain the voltage stability evaluation result; The voltage stability evaluation result includes the voltage stability determination result, voltage adjustment measures, and voltage stable recovery time.

10. The time-delay-containing uncertain AC-DC microgrid DC bus voltage control method according to claim 9, characterized in that, The specific steps for obtaining the voltage stability evaluation result are as follows: S501: Based on the record of time-delay compensation amount adjustment, evaluate the stability of the real-time voltage, monitor the voltage fluctuation in real time, and compare it with the set stable range to judge whether the voltage exceeds the preset range, record the fluctuation situation during the voltage change process, and obtain the basic data for voltage stability evaluation; S502: Use the basic data for voltage stability evaluation. When the voltage fluctuation exceeds the set range, adjust the time-delay compensation amount according to the real-time data, combine the voltage fluctuation trend and the real-time compensation amount, iteratively adjust the voltage regulation method, perform voltage regulation operations and record the adjustment process to obtain voltage fluctuation recovery information; S503: Call the voltage fluctuation recovery information, and evaluate the impact of voltage recovery according to the adjusted time-delay compensation amount and voltage regulation operation to judge whether the voltage is stable within the set range to obtain the voltage stability evaluation result.

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