A grid-connected off-grid control method and system for low-voltage power supply

Abstract

This invention discloses a grid-connected / off-grid control method and system for low-voltage power supply, applied in the field of power grid-connected / off-grid technology. The method includes: transforming and decomposing acquired main power source data and backup power source data to obtain a frequency deviation value; determining a frequency synchronization accuracy value based on the frequency deviation value; extracting the rotational speed sampling value from the backup power source data and the grid synchronization rotational speed value from the main power source data, and determining a slip ratio based on the rotational speed sampling value and the grid synchronization rotational speed value; inputting the frequency synchronization accuracy value and the slip ratio into a constructed grid-connected / off-grid control model to obtain a real-time phase compensation angle; sequentially performing phase lead compensation processing and torque conversion processing on the real-time phase compensation angle to obtain an electromagnetic torque correction amount; and obtaining a grid-connected / off-grid control strategy for low-voltage power supply based on the electromagnetic torque correction amount. The method provided by this invention can achieve stable grid-connected / off-grid control.

Description

Technical Field

[0001] This invention relates to the field of power grid connection and off-grid technology, and in particular to a grid connection and off-grid control method and system for low-voltage power supply. Background Technology

[0002] Low-voltage power supply is a key area for the stable operation of the power system. In particular, when the mains power is interrupted or fails, the rapid grid connection to power supply through backup power sources such as generator trucks is of great significance for ensuring people's livelihood and industrial production.

[0003] In existing technologies, when faced with deviations in the parameters of the main power supply and the backup power supply, the matching logic of fixed parameters is usually relied upon. This lacks the ability to adapt to dynamic changes and makes it difficult to achieve stable grid connection and off-grid switching, resulting in power quality fluctuations or even instability of the power system.

[0004] Therefore, how to achieve stable control of grid connection and off-grid operation has become a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0005] This invention provides a grid-connected and off-grid control method and system for low-voltage backup power supply, in order to solve the problem that the current method, when faced with the parameter deviation between the mains power and the backup power supply, usually relies on the matching logic of fixed parameters, which lacks the ability to adapt to dynamic changes, makes it difficult to achieve fast and stable grid-connected and off-grid switching, and leads to power quality fluctuations or even system instability.

[0006] To address the aforementioned technical problems, embodiments of the present invention provide a grid-connected / off-grid control method for low-voltage power supply, comprising:

[0007] The acquired main power supply data and backup power supply data are transformed and decomposed to obtain the frequency deviation value;

[0008] Based on the frequency deviation value, determine the frequency synchronization accuracy value;

[0009] Extract the speed sampling value from the backup power data and the grid synchronous speed value from the main power data, and determine the slip rate based on the speed sampling value and the grid synchronous speed value;

[0010] The frequency synchronization accuracy value and the slip rate are input into the constructed grid-connected and off-grid control model to obtain the real-time phase compensation angle. The construction process is configured to use sliding mode control to process the frequency synchronization accuracy value and the slip rate, and adjust the parameters of the grid-connected and off-grid control model based on an adaptive phase-locked loop to optimize the real-time phase compensation angle.

[0011] The real-time phase compensation angle is sequentially subjected to phase lead compensation processing and torque conversion processing to obtain the electromagnetic torque correction amount;

[0012] Based on the electromagnetic torque correction, a grid-connected and off-grid control strategy for low-voltage power supply is obtained.

[0013] As one preferred embodiment, the step of performing transformation and decomposition processing on the acquired main power supply data and backup power supply data to obtain the frequency deviation value includes:

[0014] The acquired main power data is standardized, and the fundamental component is extracted from the standardized main power data to obtain the main power fundamental voltage signal.

[0015] The main power supply fundamental voltage signal is processed by Fast Fourier Transform to obtain the main power supply frequency;

[0016] The acquired backup power data is standardized, and the fundamental component is extracted from the standardized backup power data to obtain the backup power fundamental voltage signal.

[0017] The backup power supply fundamental voltage signal is processed by Fast Fourier Transform to obtain the backup power supply frequency;

[0018] The frequency deviation value is obtained based on the main power supply frequency and the backup power supply frequency.

[0019] As one preferred embodiment, determining the frequency synchronization accuracy value based on the frequency deviation value includes:

[0020] The frequency deviation value is compared and analyzed with the preset deviation value to obtain the frequency exceeding the limit;

[0021] Based on the frequency over-limit, proportional-integral-derivative control processing is performed to obtain the excitation current regulation coefficient and the speed regulation coefficient.

[0022] The excitation circuit of the backup power supply is adjusted using the excitation current adjustment coefficient to obtain the excitation current correction value;

[0023] The speed of the backup power supply is processed according to the speed adjustment coefficient to obtain a speed correction value;

[0024] The frequency synchronization accuracy value is obtained based on the excitation current correction value and the rotational speed correction value.

[0025] As one preferred embodiment, determining the slip ratio based on the speed sampling value and the grid synchronous speed value includes:

[0026] The speed sampling value is processed by angular velocity conversion to obtain the mechanical angular velocity value of the backup power supply rotor;

[0027] The grid synchronous speed value is converted into an angular velocity value to obtain the grid synchronous angular velocity value.

[0028] The slip ratio is obtained based on the mechanical angular velocity value of the backup power supply rotor and the synchronous angular velocity value of the power grid.

[0029] As one preferred embodiment, the step of inputting the frequency synchronization accuracy value and the slip rate into the constructed grid-connected / off-grid control model to obtain the real-time phase compensation angle includes:

[0030] The initial phase correction angle is obtained by processing the frequency synchronization accuracy value and the slip rate using a sliding mode control law.

[0031] The phase offset is obtained by optimizing the fundamental voltage signal of the main power supply using an adaptive phase-locked loop.

[0032] The real-time phase compensation angle is determined based on the phase offset and the initial phase correction angle.

[0033] As one preferred embodiment, the step of sequentially performing phase lead compensation processing and torque conversion processing on the real-time phase compensation angle to obtain the electromagnetic torque correction amount includes:

[0034] The real-time phase compensation angle is processed by a dynamic lead compensation algorithm to obtain the lead compensation phase angle.

[0035] The advanced compensation phase angle is processed by power angle-torque relationship conversion to obtain the initial value of electromagnetic torque correction;

[0036] The initial value of the electromagnetic torque correction is corrected to obtain the electromagnetic torque correction amount.

[0037] As one preferred embodiment, the grid-connected and off-grid control strategy for low-voltage power supply based on the electromagnetic torque correction includes:

[0038] The electromagnetic torque correction amount is dynamically limited to obtain the safe torque correction amount;

[0039] The safety torque correction amount is input into the constructed multi-mode decision engine matrix to obtain the operating state decision vector;

[0040] Based on the operating state decision vector, a grid-connected and off-grid control strategy for low-voltage power supply is determined.

[0041] Another embodiment of the present invention provides a grid-connected and off-grid control system for low-voltage power supply, comprising:

[0042] The transformation module is used to transform and decompose the acquired main power supply data and backup power supply data to obtain the frequency deviation value.

[0043] The determining module is used to determine the frequency synchronization accuracy value based on the frequency deviation value;

[0044] The extraction module is used to extract the speed sampling value from the backup power data and the grid synchronous speed value from the main power data, and to determine the slip rate based on the speed sampling value and the grid synchronous speed value;

[0045] A construction module is used to input the frequency synchronization accuracy value and the slip rate into the constructed grid-connected and off-grid control model to obtain the real-time phase compensation angle. The construction process is configured to process the frequency synchronization accuracy value and the slip rate using sliding mode control, and adjust the parameters of the grid-connected and off-grid control model based on an adaptive phase-locked loop to optimize the real-time phase compensation angle.

[0046] The processing module is used to sequentially perform phase advance compensation processing and torque conversion processing on the real-time phase compensation angle to obtain the electromagnetic torque correction amount;

[0047] The control module is used to obtain a grid-connected and off-grid control strategy for low-voltage power supply based on the electromagnetic torque correction amount.

[0048] As one preferred embodiment, the step of performing transformation and decomposition processing on the acquired main power supply data and backup power supply data to obtain the frequency deviation value includes:

[0049] The acquired main power data is standardized, and the fundamental component is extracted from the standardized main power data to obtain the main power fundamental voltage signal.

[0050] The main power supply fundamental voltage signal is processed by Fast Fourier Transform to obtain the main power supply frequency;

[0051] The acquired backup power data is standardized, and the fundamental component is extracted from the standardized backup power data to obtain the backup power fundamental voltage signal.

[0052] The backup power supply fundamental voltage signal is processed by Fast Fourier Transform to obtain the backup power supply frequency;

[0053] The frequency deviation value is obtained based on the main power supply frequency and the backup power supply frequency.

[0054] As one preferred embodiment, the step of inputting the frequency synchronization accuracy value and the slip rate into the constructed grid-connected / off-grid control model to obtain the real-time phase compensation angle includes:

[0055] The initial phase correction angle is obtained by processing the frequency synchronization accuracy value and the slip rate using a sliding mode control law.

[0056] The phase offset is obtained by optimizing the fundamental voltage signal of the main power supply using an adaptive phase-locked loop.

[0057] The real-time phase compensation angle is determined based on the phase offset and the initial phase correction angle.

[0058] Compared with the prior art, the beneficial effects of the embodiments of the present invention are at least one of the following:

[0059] This invention obtains a frequency deviation value by transforming and decomposing the acquired main power supply data and backup power supply data; determines a frequency synchronization accuracy value based on the frequency deviation value; extracts the speed sampling value from the backup power supply data and the grid synchronization speed value from the main power supply data, and determines the slip rate based on the speed sampling value and the grid synchronization speed value; inputs the frequency synchronization accuracy value and the slip rate into a constructed grid-connected / off-grid control model to obtain a real-time phase compensation angle. The construction process is configured to use sliding mode control to process the frequency synchronization accuracy value and the slip rate, and adjust the parameters of the grid-connected / off-grid control model based on an adaptive phase-locked loop to optimize the real-time phase compensation angle; sequentially performs phase lead compensation processing and torque conversion processing on the real-time phase compensation angle to obtain an electromagnetic torque correction amount; and obtains a grid-connected / off-grid control strategy for low-voltage power supply based on the electromagnetic torque correction amount.

[0060] Compared with existing technologies, this invention processes the acquired data to obtain a frequency synchronization accuracy value, quantifies the synchronization quality for rapid determination of the synchronization state, and calculates the slip rate by acquiring rotational speed characteristics, directly reflecting the phase difference trend between power sources and providing a dynamic basis for phase compensation. The acquired frequency synchronization accuracy value and slip rate are then fused into multi-parameter control. In this step, the robustness of sliding mode control combined with the adaptability of the adaptive phase-locked loop enables the system to quickly track the phase difference under complex operating conditions, avoiding the lag or overshoot problems of traditional control, thus obtaining a real-time phase compensation angle. The real-time phase compensation angle is corrected, and the output phase of the backup power supply is adjusted in advance to offset control delays, ensuring that the phase difference approaches zero at the moment of grid connection. Phase control is then converted into torque control, bridging electrical and mechanical quantities, allowing the abstract phase synchronization target to be realized through actual actuators, thereby achieving stable control during grid connection and off-grid operation. Attached Figure Description

[0061] Figure 1 This is a schematic flowchart of a grid-connected and off-grid control method for low-voltage power supply in one embodiment of the present invention;

[0062] Figure 2 This is a schematic diagram of the grid-connected and off-grid control system for low-voltage power supply in one embodiment of the present invention.

[0063] Figure label:

[0064] Among them, 11. Transformation module; 12. Determination module; 13. Extraction module; 14. Construction module; 15. Processing module; 16. Control module. Detailed Implementation

[0065] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The purpose of providing these embodiments is to make the disclosure of the present invention more thorough and comprehensive. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0066] In the description of this invention, the terms "first," "second," "third," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first," "second," "third," etc., may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0067] In the description of this invention, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium; and they can refer to communication within two components. The terms "vertical," "horizontal," "left," "right," "upper," "lower," and similar expressions used herein are for illustrative purposes only and do not indicate or imply that the device or component referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as limiting the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items. Those skilled in the art will understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0068] In the description of this invention, it should be noted that, unless otherwise defined, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art. The terminology used in this specification is for the purpose of describing specific embodiments only and is not intended to limit the invention. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0069] Low-voltage power supply is a key area for the stable operation of the power system. In particular, when the mains power is interrupted or fails, the rapid grid connection to power supply through backup power sources such as generator trucks is of great significance for ensuring people's livelihood and industrial production.

[0070] In existing technologies, when faced with deviations in the parameters of the main power supply and the backup power supply, the matching logic of fixed parameters is usually relied upon. This lacks the ability to adapt to dynamic changes and makes it difficult to achieve stable grid connection and off-grid switching, resulting in power quality fluctuations or even instability of the power system.

[0071] Therefore, how to achieve stable control of grid connection and off-grid operation has become a technical problem that urgently needs to be solved by those skilled in the art.

[0072] Therefore, one embodiment of the present invention provides a grid-connected and off-grid control method for low-voltage power supply. For details, please refer to [link to relevant documentation]. Figure 1 , Figure 1 The diagram shown is a schematic flowchart of a grid-connected / off-grid control method for low-voltage power supply in one embodiment of the present invention. The method includes:

[0073] S1: Perform transformation and decomposition processing on the acquired main power supply data and backup power supply data to obtain the frequency deviation value;

[0074] S2: Determine the frequency synchronization accuracy value based on the frequency deviation value;

[0075] S3: Extract the speed sampling value from the backup power data and the grid synchronous speed value from the main power data, and determine the slip rate based on the speed sampling value and the grid synchronous speed value;

[0076] S4: Input the frequency synchronization accuracy value and the slip rate into the constructed grid-connected / off-grid control model to obtain the real-time phase compensation angle. The construction process is configured to use sliding mode control to process the frequency synchronization accuracy value and the slip rate, and adjust the parameters of the grid-connected / off-grid control model based on an adaptive phase-locked loop to optimize the real-time phase compensation angle.

[0077] S5: Perform phase advance compensation processing and torque conversion processing on the real-time phase compensation angle in sequence to obtain the electromagnetic torque correction amount;

[0078] S6: Based on the electromagnetic torque correction, a grid-connected and off-grid control strategy for low-voltage power supply is obtained.

[0079] In step S1, the transformation and decomposition processing of the acquired main power supply data and backup power supply data to obtain the frequency deviation value includes:

[0080] The acquired main power supply data is standardized, and the fundamental component is extracted from the standardized main power supply data to obtain the main power supply fundamental voltage signal. The main power supply fundamental voltage signal is then subjected to a Fast Fourier Transform (FFT) to obtain the main power supply frequency. Similarly, the acquired backup power supply data is standardized, and the fundamental component is extracted from the standardized backup power supply data to obtain the backup power supply fundamental voltage signal. The backup power supply fundamental voltage signal is then subjected to a FFT to obtain the backup power supply frequency. Based on the main power supply frequency and the backup power supply frequency, the frequency deviation value is obtained.

[0081] Specifically, the main power supply data and backup power supply data are standardized separately. The original data of different power supplies may differ due to different sampling equipment or transmission paths. Standardization can ensure the fairness of subsequent analysis and ensure that the backup power supply data is comparable to the main power supply data.

[0082] The fundamental component of the standardized main power supply data is extracted to obtain the fundamental voltage signal of the main power supply. The fundamental component of the standardized backup power supply data is also extracted to obtain the fundamental voltage signal of the backup power supply. The fundamental component is extracted from the standardized main power supply data and the standardized backup power supply data respectively. This is mainly because the frequency characteristics of the power system are mainly determined by the fundamental wave. Extracting the fundamental wave is a prerequisite for accurate frequency measurement. The 50Hz / 60Hz fundamental voltage signal is separated from the standardized data to filter out harmonic interference.

[0083] After the fundamental frequency is extracted, a Fast Fourier Transform (FFT) is performed on the fundamental voltage signal of the main power supply. The FFT can convert the fundamental frequency signal in the time domain into a frequency domain representation, identify the frequency components of the signal, and obtain the main power supply frequency. Similarly, a FFT is performed on the fundamental voltage signal of the backup power supply. The FFT can convert the fundamental frequency signal in the time domain into a frequency domain representation, identify the frequency components of the signal, and obtain the backup power supply frequency.

[0084] By comparing the frequency values ​​of the main power supply and the backup power supply, the difference between the two can be quantified. Specifically, the frequency deviation is a key indicator for measuring power quality during power switching. The smaller the deviation, the smaller the impact of switching on the load.

[0085] It should be noted that the main power source is the primary source of power supply during normal operation of the power system, undertaking the daily power supply task and providing continuous and stable power to the load. It is generally supplied by the power grid, i.e., the mains power. On the other hand, the backup power source is an emergency power supply device that automatically starts operating when the main power source fails or is interrupted. It is used to ensure the continuous power supply to critical loads and avoid losses due to power outages. Examples include backup generators such as diesel / gas generators and battery energy storage systems such as lithium batteries. The two work together through standardized data monitoring, fundamental frequency analysis, and frequency synchronization technologies to jointly build a reliable power security system.

[0086] In step S2, based on the frequency deviation value, the frequency synchronization accuracy value is determined, specifically including:

[0087] The frequency deviation value is compared and analyzed with the preset deviation value to obtain the frequency over-limit; based on the frequency over-limit, proportional-integral-derivative control processing is performed to obtain the excitation current adjustment coefficient and the speed adjustment coefficient; the excitation current adjustment coefficient is used to adjust the excitation circuit of the backup power supply to obtain the excitation current correction value; the speed of the backup power supply is processed according to the speed adjustment coefficient to obtain the speed correction value; based on the excitation current correction value and the speed correction value, the frequency synchronization accuracy value is obtained.

[0088] Specifically, the frequency deviation value is compared with the preset deviation value to obtain the frequency over-limit. The frequency deviation value is the frequency difference between the main power supply and the backup power supply, and the preset deviation value is the maximum frequency deviation threshold allowed by the system, which can be determined by the specific main power supply and backup power supply. In this step, the frequency over-limit is used to quantify the severity of the frequency deviation and identify the range that needs to be adjusted. If the over-limit is less than a certain value, it means that the frequency is within the allowable range and no adjustment is required.

[0089] In this embodiment, a proportional-integral-derivative (PID) controller is used to process the frequency over-limit, obtaining the excitation current regulation coefficient and the speed regulation coefficient. The excitation current regulation coefficient is used to adjust the magnetic field strength of the backup power supply, and the speed regulation coefficient is used to adjust the prime mover speed of the backup power supply. The proportional term (P) in the PID controller immediately responds to the current error, providing regulation proportional to the over-limit. The integral term (I) eliminates steady-state error and accumulates historical errors to compensate for system static deviations. The derivative term (D) predicts the error change trend, providing proactive regulation to suppress system oscillations. The optimal regulation parameters are dynamically calculated using the PID controller.

[0090] The excitation circuit of the backup power supply is adjusted using the excitation current adjustment coefficient. The adjustment process is based on the excitation current of the original excitation circuit of the backup power supply and the excitation current adjustment coefficient to obtain the excitation current correction value. Then, the original speed of the backup power supply is adjusted by the speed adjustment coefficient to obtain the speed correction value. Finally, the excitation current correction value and the speed correction value are used to determine the frequency synchronization accuracy value. The frequency synchronization accuracy value is used to quantify the closeness between the frequency of the backup power supply and the main power supply. The closer the value is to 1, the higher the synchronization accuracy.

[0091] In this embodiment, excitation regulation is used for rapid response and provides short-term frequency support, while speed regulation is slow but fundamental, achieving long-term frequency stability. Through the division of labor and cooperation between excitation regulation and speed regulation, high-precision synchronization between the backup power supply and the main power supply is achieved. Its core lies in the synergy between rapid response and steady-state regulation, ensuring the stability and power quality of the power system during the switching process.

[0092] In step S3, the slip ratio is determined based on the speed sampling value and the grid synchronous speed value. Specifically, this includes: performing angular velocity conversion processing on the speed sampling value to obtain the mechanical angular velocity value of the backup power supply rotor; performing angular velocity conversion processing on the grid synchronous speed value to obtain the grid synchronous angular velocity value; and obtaining the slip ratio based on the mechanical angular velocity value of the backup power supply rotor and the grid synchronous angular velocity value.

[0093] Specifically, slip ratio represents the relative deviation between the backup power supply rotor speed and the grid synchronization speed. By continuously monitoring the slip ratio, it is possible to determine whether the backup power supply is stably synchronized and prevent out-of-synchronization faults.

[0094] Meanwhile, by converting angular velocity and calculating slip rate, a bridge was established between rotating machinery and the electromagnetic system of the power grid. Its core is to unify mechanical motion and electromagnetic motion to the same physical quantity dimension for comparison. By quantifying the speed difference between the backup power supply and the power grid, the two are synchronized in frequency and phase, thus achieving smooth grid connection.

[0095] In step S4, the step of inputting the frequency synchronization accuracy value and the slip rate into the constructed grid-connected / off-grid control model to obtain the real-time phase compensation angle specifically includes:

[0096] The frequency synchronization accuracy value and the slip rate are processed using a sliding mode control law to obtain an initial phase correction angle; the fundamental voltage signal of the main power supply is optimized using an adaptive phase-locked loop to obtain a phase offset; and the real-time phase compensation angle is determined based on the phase offset and the initial phase correction angle.

[0097] Sliding mode control is a nonlinear control method. Its core idea is to force the system state to move along a predetermined trajectory by designing a suitable "sliding mode", which has strong robustness to external disturbances and parameter perturbations.

[0098] The sliding mode control law uses a nonlinear feedback mechanism to convert the deviation signals of frequency synchronization accuracy and slip rate into control quantities and calculates the initial phase correction angle. This correction angle is used to compensate for the phase deviation caused by the difference in frequency and speed, so that the output voltage phase of the backup power supply gradually approaches the phase of the main grid.

[0099] In this step, the robustness of sliding mode control is utilized to quickly suppress phase deviations caused by frequency and speed fluctuations, thereby enhancing the system's anti-interference capability.

[0100] An adaptive phase-locked loop (APLL) is a closed-loop control system that can automatically track the phase and frequency of an input signal, and is especially suitable for scenarios where the grid voltage has harmonics or fluctuations.

[0101] Specifically, the APLL dynamically adjusts its internal parameters by sampling the phase and frequency of the main power supply fundamental voltage in real time, thereby achieving precise tracking of the fundamental signal phase and outputting the phase offset. The phase offset is the difference between the actual phase of the main power grid and the ideal reference phase. The adaptive phase-locked loop can accurately capture the real-time phase changes of the main power grid, especially when there are voltage distortions or frequency fluctuations in the grid, it can still maintain high tracking accuracy.

[0102] By combining the obtained phase offset with the initial phase correction angle through proportional weighting or linear superposition, a real-time phase compensation angle is obtained. This compensation angle is used to directly adjust the output voltage phase of the backup power supply to match the phase of the main grid. The specific method can be determined based on historical experience.

[0103] This step simultaneously considers the frequency / speed deviation of the backup power supply itself (i.e., the initial correction angle) and the phase fluctuation on the grid side (i.e., the offset), thus achieving bidirectional dynamic compensation.

[0104] Specifically, the construction process of the grid-connected and off-grid control model is configured to use sliding mode control to process the frequency synchronization accuracy value and the slip rate, and adjust the parameters of the grid-connected and off-grid control model based on an adaptive phase-locked loop to optimize the real-time phase compensation angle.

[0105] Power systems face challenges such as nonlinearity in generator rotor motion equations, sudden load changes, line parameter perturbations, and grid faults. The advantage of sliding mode control lies in its ability to force the system state to evolve along a preset "sliding surface," making it naturally immune to model errors and external disturbances. It does not require precise knowledge of system parameters, making it particularly suitable for the complex environment of power systems. Adaptive phase-locked loops, based on the coarse frequency / phase adjustment provided by sliding mode control, optimize parameters through dynamic parameter adjustment.

[0106] In step S5, the phase lead compensation processing and torque conversion processing are performed sequentially on the real-time phase compensation angle to obtain the electromagnetic torque correction amount, specifically including:

[0107] The real-time phase compensation angle is processed by a dynamic lead compensation algorithm to obtain a lead compensation phase angle; the lead compensation phase angle is then processed by a power angle-torque relationship conversion to obtain an initial value for electromagnetic torque correction; the initial value for electromagnetic torque correction is then corrected to obtain the electromagnetic torque correction amount.

[0108] Power systems suffer from mechanical inertia (such as generator rotors) and control delays (such as governor response time), causing phase adjustment actions to lag behind commands. A dynamic lead compensation algorithm is used to perform phase lead compensation processing on the real-time phase compensation angle, resulting in a lead compensation phase angle. Lead compensation generates a phase lead by predicting phase change trends in advance, offsetting system delays and improving response speed. Furthermore, during rapid grid connection or sudden load changes, the system may experience phase oscillations due to inertia; lead compensation introduces a phase lead, enabling the system to reach a stable state more quickly.

[0109] The advanced compensation phase angle is converted into a power angle-torque relationship to obtain the initial value of the electromagnetic torque correction. The conversion is based on the generator's power angle characteristic equation, which transforms the abstract phase control quantity into an executable electromagnetic torque command. It should be noted that the actual control of the generator is achieved by adjusting the torque; therefore, it is necessary to establish a mapping relationship between phase and torque.

[0110] The initial value of the electromagnetic torque correction is corrected to obtain the electromagnetic torque correction amount. During the correction process, dynamic damping terms, such as additional torque feedback, can be introduced to suppress system oscillations and thus ensure a smooth control process.

[0111] This process addresses system delay issues through phase lead compensation, maps physical quantities through power angle-torque conversion, improves control accuracy through correction and optimization, and ultimately transforms abstract phase control into executable torque commands, ensuring the stability and power quality of the backup power supply during grid connection / off-grid processes.

[0112] In step S6, based on the electromagnetic torque correction, a grid-connected and off-grid control strategy for low-voltage power supply is obtained, specifically including:

[0113] The electromagnetic torque correction is dynamically limited to obtain a safe torque correction; the safe torque correction is input into the constructed multi-mode decision engine matrix to obtain an operating state decision vector; based on the operating state decision vector, a grid-connected and off-grid control strategy for low-voltage power supply is determined.

[0114] The electromagnetic torque correction amount is dynamically limited using a dynamic limiting algorithm to obtain a safe torque correction amount. In this step, the electromagnetic torque correction amount is the theoretical adjustment amount obtained in the previous step through phase compensation and torque conversion, and the safe torque correction amount is the torque adjustment command that limits the equipment to a safe operating range. Preferably, the dynamic limiting algorithm can be a limiter with hysteresis or an adaptive saturation function, depending on the specific operating environment of the main power supply and the backup power supply.

[0115] Limiting can prevent the backup power supply from overloading and shutting down due to excessive torque adjustment.

[0116] The safety torque correction and real-time operating parameters of the power supply are input into the constructed multi-mode decision engine matrix to obtain the operating state decision vector. The multi-mode decision engine matrix is ​​a predefined multi-mode rule base, such as "grid-connected priority mode", "off-grid isolated mode" and "load graded shelving mode". The system operating parameters include voltage amplitude, frequency deviation, power supply status and load priority. The operating state decision vector is a multi-dimensional vector containing information such as mode selection, parameter configuration and execution priority.

[0117] Based on the operating state decision vector, a grid-connected and off-grid control strategy for low-voltage power supply is determined.

[0118] In this step, dynamic limiting ensures that torque regulation is within a safe range, and a multi-mode decision engine matrix expands a single control quantity into a global strategy. Finally, a control scheme that meets the low-voltage power supply requirements is generated based on the operating state decision vector.

[0119] Another embodiment of the present invention provides a grid-connected and off-grid control system for low-voltage power supply. For details, please refer to [link to relevant documentation]. Figure 2 , Figure 2 The diagram shown is a structural schematic of a grid-connected and off-grid control system for low-voltage power supply in one embodiment of the present invention. The system includes:

[0120] The transformation module 11 is used to perform transformation and decomposition processing on the acquired main power supply data and backup power supply data to obtain the frequency deviation value.

[0121] The determining module 12 is used to determine the frequency synchronization accuracy value based on the frequency deviation value;

[0122] Extraction module 13 is used to extract the speed sampling value from the backup power data and the grid synchronous speed value from the main power data, and determine the slip rate based on the speed sampling value and the grid synchronous speed value;

[0123] The construction module 14 is used to input the frequency synchronization accuracy value and the slip rate into the constructed grid-connected and off-grid control model to obtain the real-time phase compensation angle. The construction process is configured to process the frequency synchronization accuracy value and the slip rate using sliding mode control, and adjust the parameters of the grid-connected and off-grid control model based on an adaptive phase-locked loop to optimize the real-time phase compensation angle.

[0124] Processing module 15 is used to sequentially perform phase advance compensation processing and torque conversion processing on the real-time phase compensation angle to obtain the electromagnetic torque correction amount;

[0125] Control module 16 is used to obtain grid-connected and off-grid control strategies for low-voltage power supply based on the electromagnetic torque correction amount.

[0126] Compared with the prior art, the beneficial effects of the embodiments of the present invention are at least one of the following:

[0127] This invention obtains a frequency deviation value by transforming and decomposing the acquired main power supply data and backup power supply data; determines a frequency synchronization accuracy value based on the frequency deviation value; extracts the speed sampling value from the backup power supply data and the grid synchronization speed value from the main power supply data, and determines the slip rate based on the speed sampling value and the grid synchronization speed value; inputs the frequency synchronization accuracy value and the slip rate into a constructed grid-connected / off-grid control model to obtain a real-time phase compensation angle. The construction process is configured to use sliding mode control to process the frequency synchronization accuracy value and the slip rate, and adjust the parameters of the grid-connected / off-grid control model based on an adaptive phase-locked loop to optimize the real-time phase compensation angle; sequentially performs phase lead compensation processing and torque conversion processing on the real-time phase compensation angle to obtain an electromagnetic torque correction amount; and obtains a grid-connected / off-grid control strategy for low-voltage power supply based on the electromagnetic torque correction amount.

[0128] Compared with existing technologies, this invention processes the acquired data to obtain a frequency synchronization accuracy value, quantifies the synchronization quality for rapid determination of the synchronization state, and calculates the slip rate by acquiring rotational speed characteristics, directly reflecting the phase difference trend between power sources and providing a dynamic basis for phase compensation. The acquired frequency synchronization accuracy value and slip rate are then fused into multi-parameter control. In this step, the robustness of sliding mode control combined with the adaptability of the adaptive phase-locked loop enables the system to quickly track the phase difference even under complex operating conditions, avoiding the lag or overshoot problems of traditional control, thus obtaining a real-time phase compensation angle. The real-time phase compensation angle is then corrected, and the output phase of the backup power supply is adjusted in advance to offset control delays, ensuring that the phase difference approaches zero at the moment of grid connection. Phase control is then converted into torque control, bridging electrical and mechanical quantities, allowing the abstract phase synchronization target to be realized through actual actuators, thereby achieving stable control during grid connection and off-grid operation.

[0129] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A grid-connected and off-grid control method for low-voltage power supply, characterized in that, include: The acquired main power supply data and backup power supply data are transformed and decomposed to obtain the frequency deviation value; Based on the frequency deviation value, determine the frequency synchronization accuracy value; Extract the speed sampling value from the backup power data and the grid synchronous speed value from the main power data, and determine the slip rate based on the speed sampling value and the grid synchronous speed value; The frequency synchronization accuracy value and the slip rate are input into the constructed grid-connected and off-grid control model to obtain the real-time phase compensation angle. The construction process is configured to use sliding mode control to process the frequency synchronization accuracy value and the slip rate, and adjust the parameters of the grid-connected and off-grid control model based on an adaptive phase-locked loop to optimize the real-time phase compensation angle. The real-time phase compensation angle is sequentially subjected to phase lead compensation processing and torque conversion processing to obtain the electromagnetic torque correction amount; Based on the electromagnetic torque correction, a grid-connected and off-grid control strategy for low-voltage power supply is obtained.

2. The grid-connected and off-grid control method for low-voltage power supply as described in claim 1, characterized in that, The process of transforming and decomposing the acquired main power supply data and backup power supply data to obtain the frequency deviation value includes: The acquired main power data is standardized, and the fundamental component is extracted from the standardized main power data to obtain the main power fundamental voltage signal. The main power supply fundamental voltage signal is processed by Fast Fourier Transform to obtain the main power supply frequency; The acquired backup power data is standardized, and the fundamental component is extracted from the standardized backup power data to obtain the backup power fundamental voltage signal. The backup power supply fundamental voltage signal is processed by Fast Fourier Transform to obtain the backup power supply frequency; The frequency deviation value is obtained based on the main power supply frequency and the backup power supply frequency.

3. The grid-connected and off-grid control method for low-voltage power supply as described in claim 1, characterized in that, Determining the frequency synchronization accuracy value based on the frequency deviation value includes: The frequency deviation value is compared and analyzed with the preset deviation value to obtain the frequency exceeding the limit; Based on the frequency over-limit, proportional-integral-derivative control processing is performed to obtain the excitation current regulation coefficient and the speed regulation coefficient. The excitation circuit of the backup power supply is adjusted using the excitation current adjustment coefficient to obtain the excitation current correction value; The speed of the backup power supply is processed according to the speed adjustment coefficient to obtain a speed correction value; The frequency synchronization accuracy value is obtained based on the excitation current correction value and the rotational speed correction value.

4. The grid-connected and off-grid control method for low-voltage power supply as described in claim 1, characterized in that, The determination of slip rate based on the speed sampling value and the grid synchronous speed value includes: The speed sampling value is processed by angular velocity conversion to obtain the mechanical angular velocity value of the backup power supply rotor; The grid synchronous speed value is converted into an angular velocity value to obtain the grid synchronous angular velocity value. The slip ratio is obtained based on the mechanical angular velocity value of the backup power supply rotor and the synchronous angular velocity value of the power grid.

5. The grid-connected and off-grid control method for low-voltage power supply as described in claim 2, characterized in that, The step of inputting the frequency synchronization accuracy value and the slip rate into the constructed grid-connected / off-grid control model to obtain the real-time phase compensation angle includes: The initial phase correction angle is obtained by processing the frequency synchronization accuracy value and the slip rate using a sliding mode control law. The phase offset is obtained by optimizing the fundamental voltage signal of the main power supply using an adaptive phase-locked loop. The real-time phase compensation angle is determined based on the phase offset and the initial phase correction angle.

6. The grid-connected and off-grid control method for low-voltage power supply as described in claim 1, characterized in that, The process of sequentially performing phase lead compensation and torque conversion processing on the real-time phase compensation angle to obtain the electromagnetic torque correction amount includes: The real-time phase compensation angle is processed by a dynamic lead compensation algorithm to obtain the lead compensation phase angle. The advanced compensation phase angle is processed by power angle-torque relationship conversion to obtain the initial value of electromagnetic torque correction; The initial value of the electromagnetic torque correction is corrected to obtain the electromagnetic torque correction amount.

7. The grid-connected and off-grid control method for low-voltage power supply as described in claim 1, characterized in that, The grid-connected and off-grid control strategy for low-voltage power supply based on the electromagnetic torque correction includes: The electromagnetic torque correction amount is dynamically limited to obtain the safe torque correction amount; The safety torque correction amount is input into the constructed multi-mode decision engine matrix to obtain the operating state decision vector; Based on the operating state decision vector, a grid-connected and off-grid control strategy for low-voltage power supply is determined.

8. A grid-connected and off-grid control system for low-voltage power supply, characterized in that, include: The transformation module is used to transform and decompose the acquired main power supply data and backup power supply data to obtain the frequency deviation value. The determining module is used to determine the frequency synchronization accuracy value based on the frequency deviation value; The extraction module is used to extract the speed sampling value from the backup power data and the grid synchronous speed value from the main power data, and determine the slip rate based on the speed sampling value and the grid synchronous speed value; A construction module is used to input the frequency synchronization accuracy value and the slip rate into the constructed grid-connected and off-grid control model to obtain the real-time phase compensation angle. The construction process is configured to process the frequency synchronization accuracy value and the slip rate using sliding mode control, and adjust the parameters of the grid-connected and off-grid control model based on an adaptive phase-locked loop to optimize the real-time phase compensation angle. The processing module is used to sequentially perform phase advance compensation processing and torque conversion processing on the real-time phase compensation angle to obtain the electromagnetic torque correction amount; The control module is used to obtain a grid-connected and off-grid control strategy for low-voltage power supply based on the electromagnetic torque correction amount.

9. The grid-connected and off-grid control system for low-voltage power supply as described in claim 8, characterized in that, The process of transforming and decomposing the acquired main power supply data and backup power supply data to obtain the frequency deviation value includes: The acquired main power data is standardized, and the fundamental component is extracted from the standardized main power data to obtain the main power fundamental voltage signal. The main power supply fundamental voltage signal is processed by Fast Fourier Transform to obtain the main power supply frequency; The acquired backup power data is standardized, and the fundamental component is extracted from the standardized backup power data to obtain the backup power fundamental voltage signal. The backup power supply fundamental voltage signal is processed by Fast Fourier Transform to obtain the backup power supply frequency; The frequency deviation value is obtained based on the main power supply frequency and the backup power supply frequency.

10. The grid-connected and off-grid control system for low-voltage power supply as described in claim 9, characterized in that, The step of inputting the frequency synchronization accuracy value and the slip rate into the constructed grid-connected / off-grid control model to obtain the real-time phase compensation angle includes: The initial phase correction angle is obtained by processing the frequency synchronization accuracy value and the slip rate using a sliding mode control law. The phase offset is obtained by optimizing the fundamental voltage signal of the main power supply using an adaptive phase-locked loop. The real-time phase compensation angle is determined based on the phase offset and the initial phase correction angle.

Images