Phase locking synchronous stable control method for new energy unit and related equipment

Abstract

The invention provides a new energy unit phase-locking synchronous stability control method and related equipment, and relates to the technical field of power system stability control, and the method comprises the steps: determining a phase-locking synchronous stability boundary of each output combination of a new energy unit and a thermal power unit in an amplitude limiting range when a fault of a new energy combined thermal power output system is removed; according to the actual new energy output, the actual current value and the actual thermal power output, a target phase locking synchronous stability boundary is matched; if it is determined that the new energy unit has a phase locking instability risk according to the target phase locking synchronous stability boundary, the actual current value of the new energy unit is reduced within the amplitude limiting value range; and after the actual current value is reduced to the lower limit value of the current limiting value range, if the new energy unit still has the phase locking instability risk, adjusting the operation condition of the new energy unit or the thermal power unit until the phase locking synchronization stability of the new energy unit meets the operation requirement. Therefore, the phase locking synchronization stability is improved by adjusting the self control of the unit.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of power system stability control, in particular to a new energy unit phase-locked synchronous stability control method and related equipment. BACKGROUND

[0002] With the accelerated access of large-scale photovoltaic power generation bases and offshore wind power projects, new energy combined thermal power transmission systems have become a typical operating mode in power systems. In this mode, new energy stations composed of multiple new energy units share the power transmission channel with thermal power units and operate in a joint transmission mode. In the traditional power system dominated by thermal power units, synchronous stability mainly depends on the mechanical inertia and damping characteristics of the synchronous generator rotor, while new energy units usually use grid synchronization control based on phase-locked loops, and their synchronous stability is directly affected by the voltage amplitude and phase angle at the grid connection point. When the system is disturbed, the voltage phase angle at the grid connection point of the new energy unit may change suddenly, and if the phase-locked loop cannot track the phase angle change in time, it may lead to phase-locked synchronous instability, and further cause unit disconnection, power oscillation and other cascading failures, threatening the safe operation of the system.

[0003] For the phase-locked synchronous stability problem of new energy units, existing research shows that under low short-circuit capacity conditions or after system disturbance, new energy units are prone to phase-locked synchronous instability. Therefore, existing technologies often use distributed phase modulation machines and other reactive power compensation devices to enhance system voltage support and alleviate phase-locked synchronous instability of new energy units. However, this type of technology mainly relies on external equipment and does not reveal the root cause of phase-locked synchronous instability of new energy units. It also fails to provide effective optimization methods for the impact of unit control strategies on synchronous stability, and cannot improve phase-locked synchronous stability by adjusting the unit's own control. SUMMARY

[0004] The purpose of the present application is to at least solve one of the above technical defects, in particular the technical defect that the existing technology cannot improve the phase-locked synchronous stability by adjusting the unit's own control.

[0005] In a first aspect, the present application provides a new energy unit phase-locked synchronous stability control method, the method comprising:

[0006] When the fault of the new energy combined thermal power transmission system is removed, determining the phase-locked synchronous stability boundary of each output combination of the new energy unit and the thermal power unit in a preset amplitude limiting value range;

[0007] According to the actual new energy output and actual current value of the new energy unit, and the actual thermal power output of the thermal power unit, matching a target phase-locked synchronous stability boundary in each phase-locked synchronous stability boundary;

[0008] If it is determined that the new energy unit has a risk of phase-locked instability based on the target phase-locked synchronization stability boundary, then the actual current value of the new energy unit shall be reduced within the limit range.

[0009] If the new energy unit still has the risk of phase-locked instability after the actual current value drops to the lower limit of the current limit range, the operating conditions of the new energy unit or the thermal power unit shall be adjusted until the phase-locked synchronization stability of the new energy unit meets the operating requirements.

[0010] In one embodiment, the step of determining the phase-locked synchronization stability boundary for each output combination of the new energy unit and the thermal power unit within a preset limit range includes:

[0011] Obtain the first functional relationship and the second functional relationship. The first functional relationship is used to represent the correspondence between the d-axis component of the output current of the new energy power station and the output phase angle of the phase-locked loop. The second functional relationship is used to represent the correspondence between the d-axis component of the actual injected current of the new energy node and the output phase angle of the phase-locked loop. Both the first functional relationship and the second functional relationship are determined based on the characteristic equation of the phase-locked loop of the new energy unit.

[0012] Within the amplitude limit range, the phase-locked synchronization stability boundary corresponding to each output combination is obtained based on the first curve and the second curve corresponding to each output combination. The first curve is generated based on the first functional relationship, and the second curve is generated based on the second functional relationship.

[0013] In one embodiment, the step of obtaining the phase-locked synchronization stability boundary corresponding to each output combination based on the first curve and the second curve corresponding to each output combination within the amplitude limiting range includes:

[0014] For each power output combination, the phase-locked loop (PLL) output phase angle corresponding to the intersection of the first curve and the second curve before and during fault clearing is calculated to obtain the steady-state phase angle of the first PLL and the steady-state phase angle of the second PLL. Based on the second curve and the limiting value range corresponding to the power output combination, multiple PLL output phase angles to be evaluated are determined. When there is a critical phase angle among the PLL output phase angles to be evaluated, the phase-locked synchronization stability boundary corresponding to the power output combination is obtained by combining the steady-state phase angles of the first PLL and the steady-state phase angles of the second PLL. The critical phase angle of the PLL is used to indicate that the new energy unit is in a critical stable state of phase-locked loop.

[0015] In one embodiment, the characteristic equation of the phase-locked loop of the new energy unit is:

[0016]

[0017] in, The first derivative of the phase angle output by the phase-locked loop. The second derivative of the phase angle output by the phase-locked loop. The phase-locked loop inertial time constant is... The damping coefficient is... The actual d-axis component of the injected current at the new energy node. The d-axis component of the output current of the new energy power station.

[0018] In one embodiment, the expression for the first functional relationship is:

[0019]

[0020]

[0021] The expression for the second functional relationship is:

[0022]

[0023] in, The d-axis component of the output current of the new energy power station. Contributing to the development of new energy power plants Contributing reactive power to new energy power plants As an auxiliary variable, it represents voltage-related combination terms. For the self-impedance of new energy nodes, and Weighting coefficients for parameters of new energy combined with thermal power transmission system. This refers to the voltage amplitude within the thermal power unit. The voltage amplitude at the infinite power supply node. The power angle of the thermal power unit. The phase angle is output by the phase-locked loop. The d-axis component of the actual injected current is used to power new energy nodes.

[0024] In one embodiment, the step of determining the risk of phase-locked instability in a new energy unit based on the target phase-locked synchronization stability boundary includes:

[0025] If the actual current value of the new energy unit exceeds the boundary current limit value corresponding to the target phase-locked synchronization stability boundary, then the new energy unit is determined to have a risk of phase-locked instability.

[0026] In one embodiment, the step of reducing the actual current value of the renewable energy unit within a limiting range includes:

[0027] Within the limit range, the actual current value of the new energy unit is gradually reduced according to the preset limit adjustment step size, or the lower limit of the limit range is used as the reduced actual current value of the new energy unit.

[0028] Secondly, this application provides a phase-locked synchronization and stability control device for new energy generating units, the device comprising:

[0029] The phase-locked synchronization stability boundary determination module is used to determine the phase-locked synchronization stability boundary of each output combination of new energy units and thermal power units within a preset limit range when the fault of the new energy combined thermal power transmission system is cleared.

[0030] The phase-locked synchronization stability boundary matching module is used to match the target phase-locked synchronization stability boundary in each phase-locked synchronization stability boundary based on the actual new energy output and actual current value of the new energy unit and the actual thermal power output of the thermal power unit.

[0031] The actual current value reduction module is used to reduce the actual current value of the new energy unit within a limited range if it is determined that the new energy unit has a risk of phase-locked instability based on the target phase-locked synchronization stability boundary.

[0032] The operating condition adjustment module is used to adjust the operating conditions of the new energy unit or thermal power unit if the risk of phase-locked instability still exists after the actual current value drops to the lower limit of the current limit range, until the phase-locked synchronization stability of the new energy unit meets the operating requirements.

[0033] Thirdly, this application provides a storage medium storing computer-readable instructions, which, when executed by one or more processors, cause the one or more processors to perform the steps of any of the new energy unit phase-locked synchronization and stability control methods described in the above embodiments.

[0034] Fourthly, this application provides a computer device, including: one or more processors, and a memory;

[0035] The memory stores computer-readable instructions, which, when executed by one or more processors, perform the steps of any of the new energy unit phase-locked synchronization and stability control methods described in the above embodiments.

[0036] As can be seen from the above technical solutions, the embodiments of this application have the following advantages:

[0037] The phase-locked synchronization stability control method and related equipment for new energy generating units provided in this application analyze the output combination of new energy generating units and thermal power units after fault clearance, combined with a preset limit value range, to construct phase-locked synchronization stability boundaries and clarify the corresponding synchronization stability safety ranges for various output combinations, thereby achieving a quantitative assessment of the phase-locked synchronization stability of new energy generating units. Furthermore, based on the current output of new energy and the current value of thermal power, corresponding stability boundaries are matched. If a risk of phase-locked instability is determined, control adjustments are prioritized by reducing the current output of the new energy generating units; if stability requirements cannot be met within the current limiting range, the operating conditions of the new energy or thermal power units are further adjusted in conjunction, achieving overall output optimization configuration of the new energy combined thermal power transmission system. This method does not rely on external reactive power compensation equipment, but actively improves the phase-locked synchronization stability of the new energy combined thermal power transmission system through dynamic adjustment of the control parameters of the new energy generating units and coordinated cooperation with the output of the thermal power units. This fundamentally reduces the risk of new energy generating units disconnecting from the grid and power oscillation, enhances the response capability of the new energy combined thermal power transmission system to disturbances, and ensures the safe grid connection and stable operation of new energy power plants in complex operating environments. Attached Figure Description

[0038] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0039] Figure 1 A schematic flowchart of the phase-locked synchronization and stability control method for new energy generating units provided in the embodiments of this application;

[0040] Figure 2 This is a block diagram of a phase-locked loop control for a new energy unit provided in an embodiment of this application;

[0041] Figure 3 Example diagram of a new energy and thermal power combined transmission system provided in the embodiments of this application;

[0042] Figure 4 Example diagram of equivalent circuit of new energy and thermal power combined transmission system provided in the embodiments of this application;

[0043] Figure 5 Provided for the embodiments of this application , and One example of a function relationship curve;

[0044] Figure 6 Provided for the embodiments of this application , and Example graph of function relationship curve (2);

[0045] Figure 7 Different embodiments provided for this application Down , and Example graph of function relationship curve;

[0046] Figure 8 Different embodiments provided for this application Example diagram of the stable boundary of the locked phase synchronization;

[0047] Figure 9 Example diagram of the phase-locked loop stability improvement strategy scheme for new energy power stations provided in the embodiments of this application;

[0048] Figure 10 A flowchart illustrating the phase-locked loop (PLL) stabilization enhancement strategy provided in this application embodiment;

[0049] Figure 11 The simulation results for Case 1 provided in the embodiments of this application;

[0050] Figure 12 The simulation results for Case 2 provided in the embodiments of this application;

[0051] Figure 13 This is a schematic diagram of the structure of the phase-locked synchronization and stability control device for new energy generating units provided in the embodiments of this application;

[0052] Figure 14 This is a schematic diagram of the internal structure of a computer device provided in an embodiment of this application. Detailed Implementation

[0053] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0054] This application provides a phase-locked synchronous stability control method for new energy generating units. The following embodiments illustrate this method using a computer device as an example. It is understood that the computer device refers to a data processing device capable of collecting, analyzing, judging, and issuing control commands to operating data of new energy generating units and thermal power units. It includes at least a processor, memory, and a communication module, used to execute the method provided in this application. The computer device can be integrated into a power dispatch automation system, a new energy power station main control system, or a thermal power plant coordination control system. It can also be centrally deployed in a power grid dispatch control center or regional energy management platform, or it can be a dedicated embedded device or industrial controller with remote data access and edge computing capabilities. Specifically, the computer device can be a single server, a server cluster, an embedded processing terminal with an industrial-grade communication interface, or a multi-node collaborative processing system interconnected via a network. It can achieve real-time perception and synchronous stability assessment of the multi-source output status in a combined new energy and thermal power transmission system, and dynamically adjust the unit operating conditions according to the control strategy. Figure 1 As shown, the method includes:

[0055] S101: When the fault of the new energy combined with thermal power transmission system is cleared, the phase-locked synchronization stability boundary of each output combination of the new energy unit and the thermal power unit is determined within the preset limit value range.

[0056] Among them, the new energy combined with thermal power transmission system refers to a power generation system structure in which multiple new energy power generation units (such as photovoltaic or wind turbines) and traditional thermal power units are jointly connected to the grid through a shared transmission channel. It is mainly used to meet the power transmission and grid stability requirements under the background of large-scale new energy access. Phase-locked loop (PLL) synchronization stability boundary refers to the parameter boundary conditions under specific output combination conditions, which allow new energy units to maintain synchronization when operating in grid-connected mode based on PLL control. It is usually determined by a combination of factors such as voltage phase angle, amplitude, and current limit. The preset limit range refers to the upper and lower limits of operating parameters such as current and voltage set according to the operating requirements and equipment safety characteristics of the new energy combined with thermal power transmission system, aiming to prevent overload or instability of new energy units. Output combination refers to the active power output configuration of new energy units and thermal power units at a specific moment, used to characterize the overall load distribution and power structure of the current system.

[0057] Specifically, the computer equipment receives the fault clearing signal, and once it detects that a fault has been cleared in a grid-connected branch or node in the new energy combined thermal power transmission system, it immediately triggers the phase-locked synchronization stability analysis task.

[0058] Subsequently, the computer equipment can access preset limit range parameters in local memory and, based on the current system operating status after fault clearance, collect multiple historical output combinations of new energy units and thermal power units and their corresponding operational stability labels, such as whether instability has occurred or whether power fluctuations have occurred. By calling the stability boundary determination model (which can be a boundary recognition algorithm based on physical modeling or neural network modeling), boundary traversal calculations are performed on all output combinations within the limit range to determine the phase-locked synchronization stability boundary corresponding to different output combinations under the current operating conditions, and the boundary is stored in a boundary mapping table in the form of a two-dimensional or multi-dimensional feature space.

[0059] Furthermore, computer equipment can simulate the dynamic response of the phase-locked loop (PLL), including the phase angle abrupt change process under system disturbances, the tracking error change of the PLL, and the coupling relationship between current output and voltage disturbance, to determine whether the corresponding output combination is prone to phase-locked instability. During the calculation process, numerical simulation, amplitude-frequency response analysis, and time-domain integration methods can be used to improve the accuracy of stability boundary determination.

[0060] Therefore, by determining the phase-locked synchronization stability boundaries of various output combinations of renewable energy units and thermal power units within a preset limit range, it is possible to achieve quantitative assessment and boundary modeling of the synchronization stability of the renewable energy-thermal power transmission system using computer equipment. This provides a clear basis for output control during the dynamic adjustment process of the renewable energy-thermal power transmission system after fault clearance. This not only avoids the risk of renewable energy units disconnecting from the grid due to phase-locked instability during disturbance response, but also allows the renewable energy-thermal power transmission system to adaptively optimize operating conditions without relying on external auxiliary equipment such as synchronous condensers. This improves the system's robustness to disturbances and the stability of renewable energy grid connection, thereby achieving safe, stable, and efficient operation of the renewable energy-renewable energy-thermal power transmission system under large-scale integration.

[0061] S102: Based on the actual new energy output and actual current value of the new energy unit, and the actual thermal power output of the thermal power unit, match the target phase-locked synchronization stability boundary in each phase-locked synchronization stability boundary.

[0062] Among them, actual renewable energy output refers to the current active power output value collected in real time by computer equipment from renewable energy units (such as photovoltaic and wind power), reflecting the current operating status of renewable energy units. Actual current value refers to the real-time current measurement value generated when renewable energy units inject power into the grid, usually collected by sensors or power quality monitoring devices at the grid connection point, reflecting the power injection intensity of renewable energy units and the electrical coupling of the system. Actual thermal power output refers to the active power output value currently provided by thermal power units, provided by the dispatching system or power plant control system, indicating the proportion of thermal power units in the combined power transmission system. Target phase-locked synchronization stability boundary refers to a set of boundary parameters that best matches the real-time operating status of the renewable energy combined thermal power transmission system, used to determine whether the current operating point is within the phase-locked synchronization stability range.

[0063] Specifically, the computer equipment first receives real-time power output data from both the new energy units and the thermal power units. The power output and current values ​​of the new energy units are obtained through measurement devices at the grid connection point or data acquisition units at the station control level, while the thermal power output can be obtained from the thermal power control system or the regional dispatch platform. The acquisition frequency can be set from 1 second to tens of seconds to ensure both real-time performance and stability of the system response.

[0064] Subsequently, the computer equipment combines the actual renewable energy output and actual current values ​​of the renewable energy units with the actual thermal power output of the thermal power units to form an operating state vector. It then retrieves a pre-built set of phase-locked loop (PLL) synchronization stability boundaries from the local database. This set can be structured in a multi-dimensional space, containing stability classification results under different output combinations. The computer equipment can use vector similarity matching, nearest neighbor search, or other multi-dimensional mapping methods to quickly locate the set of stability boundaries closest to the current operating state—the target PLL synchronization stability boundaries. Rule-based determination methods can also be used, and machine learning models (such as KNN classifiers, decision trees, and support vector machines) can be introduced for boundary classification to improve matching accuracy and processing efficiency.

[0065] It is understandable that by matching the target phase-locked synchronization stability boundary, computer equipment can accurately determine whether the current output combination is in a stable operating state during the operation of the combined renewable energy and thermal power transmission system, thereby identifying potential phase-locked synchronization instability risks of renewable energy units in advance. This not only avoids unit disconnection and system oscillation caused by lagging control strategies, but also provides the combined renewable energy and thermal power transmission system with a basis for targeted adjustment of operating parameters. In addition, this matching process can dynamically adapt to different operating scenarios, improve the recognition and response capabilities of the combined renewable energy and thermal power transmission system to disturbance conditions, thereby effectively ensuring the safety and stability of renewable energy unit grid-connected operation and enhancing the overall operational resilience of the combined renewable energy and thermal power transmission system.

[0066] S103: If it is determined that the new energy unit has a risk of phase-locked instability based on the target phase-locked synchronization stability boundary, then reduce the actual current value of the new energy unit within the limit range.

[0067] Among them, the risk of phase-locked loop instability refers to the possibility that when a new energy unit is connected to the grid based on a phase-locked loop (PLL), its current, voltage or phase angle operation status deviates from the stable range of the target boundary, and it may be unable to stably track the grid phase angle and thus lose synchronization.

[0068] Specifically, the computer equipment can compare the current operating parameters of the combined renewable energy and thermal power transmission system with the target phase-locked synchronization stability boundary to determine whether the current operating point falls into the unstable region of the boundary. If the calculation results indicate that the current renewable energy unit has a risk of phase-locked instability, the computer equipment will activate the phase-locked stability active intervention mechanism.

[0069] Next, the computer equipment, based on a preset limit range, prioritizes the assessment of the acceptable current adjustment range under the current system architecture. By invoking internal limit control logic, the computer equipment determines the target value for current adjustment and constructs a current reduction curve or a stepped reduction strategy to minimize disturbances to other systems caused by sudden current drops. This process can be combined with unit response characteristics (such as response time, current change rate, etc.) to optimize the control scheme, ensuring that the reduction behavior is both effective and smooth.

[0070] Subsequently, the computer equipment issues control commands to the corresponding renewable energy units, instructing them to perform current limiting operations according to the calculated target current value. This current limiting process can be achieved by controlling the inverter's current loop setpoint and the voltage and current dual closed-loop parameters. To ensure the stability of the renewable energy combined with thermal power transmission system, the computer equipment continues to monitor current changes in real time after the commands are issued, comparing them with the target stability boundary until it is confirmed that the renewable energy unit's operating point has returned to the stable range.

[0071] It is understandable that by reducing the actual current value of renewable energy units, it is possible to effectively adjust their operating state back to the safe range of the phase-locked loop (PLL) synchronization stability boundary when disturbances occur in the renewable energy-coal power transmission system and the renewable energy units face the risk of phase-locked loop instability. This operation does not rely on external compensation equipment; it directly mitigates the risk by adjusting the output current of the renewable energy units themselves. This not only reduces system hazards such as grid instability and frequency fluctuations caused by PLL tracking failures, but also improves the robustness and adaptability of the renewable energy-coal power transmission system under complex operating conditions, significantly enhancing the safety and stability after large-scale grid integration of renewable energy.

[0072] S104: If the new energy unit still has the risk of phase-locked instability after the actual current value drops to the lower limit of the current limit range, the operating conditions of the new energy unit or the thermal power unit shall be adjusted until the phase-locked synchronization stability of the new energy unit meets the operating requirements.

[0073] Among them, operating conditions refer to the current operating status parameters of new energy units and thermal power units, including but not limited to active power output, reactive power output, voltage setpoint, excitation current, grid connection point voltage level, etc., which are key factors that determine the power flow of the system and the grid support capacity.

[0074] Specifically, once the output current of the new energy unit has dropped to the lower limit of the current limit, the computer equipment continuously assesses the stability of the unit's phase-locked loop (PLL) and determines whether there is still a risk of instability based on the target PLL synchronization stability boundary. If it is confirmed that the PLL still cannot stably track the voltage phase angle, the computer equipment triggers the operating condition linkage adjustment mechanism.

[0075] Next, the computer equipment analyzes the available operating condition adjustment paths. For new energy units, adjustment schemes may include increasing the reactive current setpoint, modifying the inverter voltage reference point, current loop bandwidth, or changing the grid connection point voltage target. For thermal power units, these may include increasing or decreasing output, optimizing active and reactive power distribution, and adjusting the excitation system response characteristics. In actual operation, the computer equipment will combine the unit response characteristics, grid topology, and power flow constraints to select the optimal or suboptimal adjustment strategy, forming a set of command parameters. Subsequently, the computer equipment issues control commands to the target new energy unit or thermal power unit, instructing the relevant equipment to perform operating condition adjustment operations. To ensure that the adjustment process does not cause new system disturbances, the computer equipment can introduce a dynamic process control mechanism. That is, in multi-step execution, after each adjustment step, the phase-locked loop stability is reassessed, and a decision is made on whether to continue subsequent operations, until the phase-locked loop synchronization state is restored to within the stability boundary, meaning that the new energy unit does not have the risk of phase-locked loop instability. The absence of phase-locked loop instability risk is one of the components of the new energy unit's phase-locked loop synchronization stability meeting the operating requirements.

[0076] Finally, when the phase-locked loop response of the new energy unit is detected to be stable and the voltage phase angle tracking accuracy meets the preset tolerance, the computer equipment will record the current operating condition as a stable state, end the control process, and update the operating data.

[0077] It is understandable that when the output current of a renewable energy unit has dropped to the lower limit of the current limit, its control capability is close to its limit. If the risk of phase-locked loop instability still exists, current regulation alone cannot restore stability. At this point, computer equipment can continue to optimize the voltage support path and output structure at the overall system level by adjusting the operating conditions of renewable energy or thermal power units, thereby improving the voltage stability and phase angle tracking capability of the renewable energy unit's phase-locked loop control. This not only avoids the renewable energy unit being forced to disconnect from the grid due to phase-locked loop instability, but also improves the system's coordinated regulation capability and anti-disturbance capability, thus achieving safe and stable operation of the renewable energy combined with thermal power system under strong disturbance conditions, demonstrating high reliability and practical value.

[0078] In the above embodiments, after fault clearance, the output combinations of new energy units and thermal power units are analyzed in conjunction with preset limiting value ranges to construct phase-locked synchronization stability boundaries, clarify the corresponding synchronization stability safety ranges for various output combinations, thereby achieving a quantitative assessment of the phase-locked synchronization stability of new energy units. Furthermore, based on the current output of new energy units, current values, and thermal power units, corresponding stability boundaries are matched. If a risk of phase-locked instability is determined, control adjustments are prioritized by reducing the current output of the new energy units. If stability requirements cannot be met within the current limiting range, the operating conditions of either the new energy or thermal power units are further adjusted in conjunction to achieve optimized overall system output configuration. This method does not rely on external reactive power compensation equipment but actively improves the phase-locked synchronization stability of the system through dynamic adjustment of the control parameters of new energy units and coordinated coordination with the output of thermal power units. This fundamentally reduces the risk of new energy units disconnecting from the grid and power oscillations, enhances the system's response to disturbances, and ensures the safe grid connection and stable operation of new energy power plants in complex operating environments.

[0079] In one embodiment, the step of determining the phase-locked synchronization stability boundary for each output combination of the new energy unit and the thermal power unit within a preset limit range includes:

[0080] Obtain the first functional relationship and the second functional relationship. The first functional relationship is used to represent the correspondence between the d-axis component of the output current of the new energy power station and the output phase angle of the phase-locked loop. The second functional relationship is used to represent the correspondence between the d-axis component of the actual injected current of the new energy node and the output phase angle of the phase-locked loop. Both the first functional relationship and the second functional relationship are determined based on the characteristic equation of the phase-locked loop of the new energy unit.

[0081] Within the amplitude limit range, the phase-locked synchronization stability boundary corresponding to each output combination is obtained based on the first curve and the second curve corresponding to each output combination. The first curve is generated based on the first functional relationship, and the second curve is generated based on the second functional relationship.

[0082] The first functional relationship refers to the function established based on the mathematical model of the phase-locked loop (PLL) of the new energy unit, used to describe the quantitative mapping relationship between the d-axis component of the output current of the new energy power station and the output phase angle of the PLL. The second functional relationship refers to the functional model established based on the relationship between the d-axis component of the injected current of the new energy node and the phase angle of the PLL in actual operation, used to reflect the interactive characteristics of unit response and system feedback under the dynamic coupling conditions of the power grid. The first curve and the second curve are two-dimensional graphs generated by the above two types of functional relationships, used to reflect the changing trend of the output phase angle of the PLL under different current conditions.

[0083] Specifically, the computer equipment acquires characteristic parameters of the new energy unit, such as control parameters, internal control structure of the phase-locked loop (PLL), sampling delay, and filtering bandwidth, and constructs a state-space model of the system based on the characteristic differential equations of the PLL. According to this model, the computer equipment generates the first functional relationship between the d-axis component of the output current of the new energy power station and the output phase angle of the PLL through analytical or simulation methods.

[0084] Secondly, computer equipment collects real-time operational data from the renewable energy grid connection points, including the d-axis component of the inverter injected current, the rate of change of voltage phase angle, and the frequency disturbance response. This data is then combined with historical disturbance samples to perform regression modeling or multi-parameter fitting, thereby obtaining a second functional relationship that reflects the system's coupling characteristics. This functional relationship demonstrates the sensitivity and dynamic adjustment capability of renewable energy nodes to grid voltage disturbances.

[0085] After modeling the two functional relationships, the computer equipment selects several typical output combinations within a preset current limit range, such as distribution points of new energy power in the 10%~100% range. Each output combination is then input into the first and second functional relationships to generate a first curve and a second curve. For each set of curves, the computer equipment can extract the overlapping area or critical deviation position using graphical intersection solving, difference analysis, or stable region identification algorithms, thereby determining the corresponding phase-locked loop synchronization stability boundary.

[0086] It is understandable that since the stability of phase-locked loop (PLL) synchronization is directly affected by the phase angle response relationship between the renewable energy unit and the power grid, constructing the internal control response characteristics (first functional relationship) and the external grid connection point response characteristics (second functional relationship) of the renewable energy unit, and generating curves reflecting their interaction, is the scientific basis for constructing the stability boundary. Through this method, computer equipment can predict the critical operating conditions of PLL instability under different output combinations, enabling refined control strategy scheduling. This not only avoids the problem of relying on external equipment for redundant voltage support, but also allows for the adaptive construction of a stability judgment model based on the unit's own operating data, improving the initiative and accuracy of renewable energy unit control, thereby significantly enhancing the system's PLL synchronization capability under low inertia and multi-source coupling conditions.

[0087] In one embodiment, the step of obtaining the phase-locked synchronization stability boundary corresponding to each output combination based on the first curve and the second curve corresponding to each output combination within the amplitude limiting range includes:

[0088] For each power output combination, the phase-locked loop (PLL) output phase angle corresponding to the intersection of the first curve and the second curve before and during fault clearing is calculated to obtain the steady-state phase angle of the first PLL and the steady-state phase angle of the second PLL. Based on the second curve and the limiting value range corresponding to the power output combination, multiple PLL output phase angles to be evaluated are determined. When there is a critical phase angle among the PLL output phase angles to be evaluated, the phase-locked synchronization stability boundary corresponding to the power output combination is obtained by combining the steady-state phase angles of the first PLL and the steady-state phase angles of the second PLL. The critical phase angle of the PLL is used to indicate that the new energy unit is in a critical stable state of phase-locked loop.

[0089] The first phase-locked loop (PLL) steady-state phase angle refers to the stable phase angle maintained by the PLL of the renewable energy unit before a fault occurs in a combined renewable energy and thermal power transmission system, reflecting the normal synchronization state between the unit and the grid. The second phase-locked loop (PLL) steady-state phase angle refers to the new steady-state PLL output phase angle that the renewable energy unit tends to under new electrical topology and power flow conditions after the fault is cleared. The critical phase angle of the PLL refers to the critical value between the stable and unstable boundaries of the renewable energy unit's PLL output phase angle, indicating that the system is at its weakest point in synchronization stability. The PLL output phase angle to be evaluated refers to a series of PLL phase angle points selected based on the second curve within the limiting range for evaluating the synchronization stability state.

[0090] Specifically, the computer equipment, based on a preset power output combination, acquires the first and second functional relationships corresponding to each power output group in the pre-fault state and at the fault clearing time, and uses these functional relationships to generate the corresponding first and second curves. Subsequently, the computer equipment uses an intersection point solving algorithm (such as Newton's iteration method or interpolation approximation method) to find the intersection point of the two curves. The phase angle at this intersection point is the steady-state output value of the phase-locked loop (PLL) of the new energy unit. By performing the above steps before and after the fault clearing, the steady-state phase angles of the first and second PLLs corresponding to the power output combination can be obtained.

[0091] Next, within the amplitude limit, the computer equipment selects multiple phase angles of the phase-locked loop (PLL) to be evaluated based on the second curve generated by the second functional relationship, at set angular intervals or feature points. For example, several step phase angle points can be selected within ±15° to the left and right of the steady-state phase angle for simulation evaluation. For each phase angle point to be evaluated, the computer equipment executes a synchronization stability discrimination algorithm to determine whether it belongs to the critical phase angle of the PLL, that is, whether the new energy unit is in a critical stable state at this angle, such as increased phase drift or a significantly longer PLL oscillation period.

[0092] After completing the stability identification of all angles to be evaluated, if there are one or more critical phase angles of the phase-locked loop, the computer device combines the steady-state phase angles of the first phase-locked loop and the second phase-locked loop corresponding to the power output combination, comprehensively judges the phase angle change path, the degree of deviation and the system feedback response, and calculates and outputs the phase-locked synchronization stability boundary corresponding to the power output combination based on stability discrimination criteria, such as the Lyapunov stability criterion or the eigenvalue discrimination method.

[0093] It is understandable that the phase-locked synchronization stability capability of renewable energy units exhibits dynamic changes before and after fault disturbances. Judging phase-locked capability solely based on a single steady-state point or limit curve may not accurately reflect its critical state during transient processes. By separately calculating the steady-state phase angles before and after the fault, and evaluating whether multiple phase angle points within the limit value represent critical states, a more comprehensive and detailed description of the phase-locked dynamic behavior of renewable energy units can be achieved. Furthermore, by combining the dynamic migration paths described by the two steady-state phase angles, the phase-locked synchronization stability boundary can be calculated. This not only improves the accuracy of boundary judgment and dynamic adaptability but also enables rapid identification of potential instability risks after grid disturbances occur. This, in turn, guides the real-time adjustment of renewable energy output control strategies, effectively enhancing the security and operational stability of renewable energy integration in the power system.

[0094] In one embodiment, the characteristic equation of the phase-locked loop of the new energy unit is:

[0095]

[0096] in, The first derivative of the phase angle output by the phase-locked loop. The second derivative of the phase angle output by the phase-locked loop. The phase-locked loop inertial time constant is... The damping coefficient is... The actual d-axis component of the injected current at the new energy node. The d-axis component of the output current of the new energy power station.

[0097] In this embodiment, the phase-locked loop (PLL) used in the new energy unit is used to track the grid voltage phase in real time, achieving synchronous operation with the grid. The characteristic equation of the new energy unit's PLL is essentially a second-order differential control system model, reflecting the PLL's response to current disturbances in the new energy unit. The left side represents the inertia and damping terms of the system response, and the right side represents the balance between the input control signal and the external current disturbance.

[0098] Based on the characteristic equations of the phase-locked loop (PLL) of renewable energy units, the phase angle dynamic behavior of the PLL is incorporated into the second-order dynamic system framework between current input disturbances and control objectives for modeling. This not only realistically reflects the transient synchronization response characteristics of renewable energy units under grid disturbances but also provides a mathematical foundation for the accurate calculation of the subsequent PLL synchronization stability boundary. By introducing inertial time constants and damping parameters, the differences in control response among different renewable energy units (such as wind power and photovoltaics) can be distinguished, providing a quantifiable and adjustable basis for stability assessment.

[0099] Furthermore, by incorporating this characteristic equation into the phase-locked loop (PLL) synchronization evaluation algorithm, computer equipment can accurately acquire the changing trend of the phase-locked angle and critical response behavior of new energy units at any given time, leveraging the nonlinear dynamic relationship it expresses. This improves the sensitivity and accuracy of phase-locked loop critical point identification, ultimately enabling real-time monitoring and control of the synchronization capability of new energy systems under complex grid disturbance conditions. Consequently, this helps prevent new energy PLL systems from falling into oscillation or unlocking states, significantly enhancing the ability of new energy units to overcome grid faults and maintain stable grid connection.

[0100] In one embodiment, the expression for the first functional relationship is:

[0101]

[0102]

[0103] The expression for the second functional relationship is:

[0104]

[0105] in, The d-axis component of the output current of the new energy power station. Contributing to the development of new energy power plants Contributing reactive power to new energy power plants As an auxiliary variable, it represents voltage-related combination terms. For the self-impedance of new energy nodes, and Weighting coefficients for parameters of new energy combined with thermal power transmission system. This refers to the voltage amplitude within the thermal power unit. The voltage amplitude at the infinite power supply node. The power angle of the thermal power unit. The phase angle is output by the phase-locked loop. The d-axis component of the actual injected current is used to power new energy nodes.

[0106] In this embodiment, to achieve accurate calculation of the stable boundary of phase-locked loop (PLL) synchronization for new energy power units, the computer equipment constructs a first functional relationship and a second functional relationship based on the characteristics of the PLL of the new energy power units. The first functional relationship describes the relationship between the d-axis output current and the PLL output phase angle under the condition that the active and reactive power of the new energy power station are known. This function formally introduces auxiliary variables, including the internal potential of the thermal power unit, the infinite power node voltage, system coefficients, and phase angle differences, to comprehensively reflect the influence of the relative phase and amplitude between voltage sources on the current output. The second functional relationship characterizes the nonlinear correspondence between the actual injected current of the new energy node and the PLL phase angle, reflecting the dynamic response of current injection behavior affected by the grid voltage phase difference. This expression directly incorporates the self-impedance of the new energy node into the calculation, further enhancing the engineering interpretability and applicability of the model.

[0107] In summary, the first and second functional relationships respectively demonstrate the regularity of the target output current and the actual injected current in the phase-locked system as a function of phase angle under different physical constraints, laying a mathematical foundation for constructing a synchronous stability boundary through intersection analysis.

[0108] Based on the first and second functional relationships, the computer equipment can construct two nonlinear function curves reflecting the difference between the control target and the actual response of the new energy unit, using the phase angle of the phase-locked loop (PLL) output as the variable axis. It can then extract the steady-state characteristic phase angle of the new energy system under different operating states (such as before a fault and during fault clearing) by analyzing the intersection points of these curves within a defined current output range. Through systematic analysis of the intersection characteristics, phase angle monotonicity, extreme point locations, and possible multiple solutions of these two types of function curves within a defined current output range, the computer equipment can further identify the critical stability point of the PLL and determine the phase-locked synchronization stability boundary for each output combination accordingly.

[0109] Therefore, by modeling the quantitative relationship between the output of new energy power plants and the electrical parameters of the power grid in the form of explicit functions, the accuracy and real-time performance of phase-locked synchronization state assessment can be significantly improved, freeing the acquisition of stability boundaries from the reliance on traditional empirical rules or numerical iterative simulations. At the same time, based on the changing trend of the intersection of the first and second curves, the adaptability of the new energy system to sudden power grid disturbances can be dynamically determined, thereby realizing the controllable, measurable, and adjustable operation of the new energy system under weak power grid conditions, and improving the overall operational stability and security of the system.

[0110] In one embodiment, the step of determining the risk of phase-locked instability in a new energy unit based on the target phase-locked synchronization stability boundary includes:

[0111] If the actual current value of the new energy unit exceeds the boundary current limit value corresponding to the target phase-locked synchronization stability boundary, then the new energy unit is determined to have a risk of phase-locked instability.

[0112] Specifically, the computer equipment extracts the actual current value of the new energy unit based on the real-time collected injected current. This current value can be obtained by sampling at the inverter output terminal, and the d-axis component is extracted using the d / q-axis component decomposition method to ensure that the physical quantity used for subsequent comparison with boundary values ​​remains consistent.

[0113] Next, based on the target phase-locked loop (PLL) synchronization stability boundary, the boundary current limiting value corresponding to the current output combination is extracted. This value is derived in advance by computer equipment based on system structure, power flow conditions, and PLL stability equations, and has dynamic adjustment capabilities, which can be refreshed in real time according to operating conditions.

[0114] Based on this, the computer equipment performs a threshold judgment operation, which compares the current actual current value with the target boundary current limit value. If the judgment result shows that the actual current value is greater than the target boundary current limit value, then by executing stability assessment logic, it is determined that the new energy unit has a risk of phase-locked instability, and this result is output to the dispatch center as a risk warning signal of the control system.

[0115] Because the phase-locked loop (PLL) control of renewable energy units relies on high-precision tracking of the grid phase, when the injected current exceeds the maximum current threshold limited by the system's allowable synchronous stability boundary, the dynamic response performance of the PLL may degrade, leading to synchronous instability. Computer equipment can quickly determine whether the actual current exceeds the limit based on current operating data, using this as the basis for assessing the risk of PLL instability, avoiding the lag problem of relying solely on frequency or voltage anomalies for instability detection. This execution method significantly improves the real-time performance, accuracy, and system stability of renewable energy PLL control, ensuring a higher operational safety margin for renewable energy units during sudden disturbances.

[0116] In one embodiment, the step of reducing the actual current value of the renewable energy unit within a limiting range includes:

[0117] Within the limit range, the actual current value of the new energy unit is gradually reduced according to the preset limit adjustment step size, or the lower limit of the limit range is used as the reduced actual current value of the new energy unit.

[0118] Among them, the limiting adjustment step size refers to the current reduction amplitude in each round of adjustment during the current regulation process. It has a preset value and is used to achieve fine control step by step.

[0119] Specifically, the computer equipment can retrieve the current limit range and adjustment step size corresponding to the current operating scenario from a preset parameter library. Then, through a loop logic program, the computer equipment gradually reduces the current output of the renewable energy unit according to the adjustment step size. Within each control cycle, the computer equipment sends a new current command value to the renewable energy inverter, which is one step smaller than the previous cycle value, ensuring that the adjusted current value always remains within the limit range to avoid over-adjustment or exceeding the limit.

[0120] In some implementations, to improve response efficiency, when it is determined that multiple consecutive adjustments still cannot make the phase-locked loop synchronization stability meet the requirements, the computer equipment can directly use the lower limit of the limiting range as the target current output value of the new energy unit, thereby quickly adjusting the system to a relatively safe and stable state.

[0121] Throughout the adjustment process, the computer equipment can monitor the changing trend of the phase angle of the phase-locked loop output in real time, evaluate the degree of improvement of the phase-locked stability by each round of current adjustment, and decide whether to continue the adjustment based on the evaluation results, so as to ensure the effectiveness of the adjustment action and the adaptability of the closed-loop control.

[0122] It is understandable that the phase-locked loop (PLL) stability of renewable energy units is highly dependent on their output current level under disturbance conditions. Failure to adjust in a timely manner could lead to the PLL losing its synchronization control capability. Therefore, using a preset limiting adjustment step size to gradually reduce the actual current value of the renewable energy unit enables flexible control, balancing adjustment speed and system stability. When the system is in an emergency, directly using the lower limit of the limiting range as the target current value can quickly pull the renewable energy unit back to a stable range, preventing the PLL from entering an uncontrollable and unstable state. This improves the accuracy and timeliness of current regulation, enhances the robustness of PLL control and system security, and provides a more reliable technical guarantee for grid operation, especially under conditions of high-penetration renewable energy integration.

[0123] To facilitate understanding of the scheme in this application, specific examples are provided below.

[0124] The block diagram of the phase-locked loop control of the new energy unit is as follows:Figure 2 As shown in the figure , , These are the instantaneous values ​​of the three-phase voltage of the new energy unit. , These are the d-axis and q-axis components of the unit terminal voltage, respectively. For the phase-locked loop proportional gain, For phase-locked loop integral gain, To synchronize the angular velocity of the rotating shaft, This is the phase angle output of the phase-locked loop with a stationary coordinate system as the reference.

[0125] Depend on Figure 2 The phase angle motion equation of the phase-locked loop output can be written as shown in equation (1).

[0126] (1)

[0127] Transforming equation (1) from the s-domain to the time domain yields the following:

[0128] (2)

[0129] in For the phase angle of the synchronous rotating shaft, Let be the phase angle of the phase-locked loop output when the synchronous rotating axis is used as the reference axis. From equation (2), it can be seen that... The equations of motion are subject to The impact of this requires constructing a new energy node voltage expression based on the system's equivalent circuit.

[0130] Figure 3 The equivalent circuit of the new energy and thermal power combined transmission system shown is as follows: Figure 4 As shown in Table 1, the system parameter settings are shown in Table 2, and the equivalent circuit parameters are shown in Table 2.

[0131] Table 1. Parameters of the combined new energy and thermal power transmission system:

[0132]

[0133] Table 2. Equivalent model parameters for the bundled transmission system of new energy and thermal power:

[0134]

[0135] according to Figure 4 It can be seen that the output voltage of the new energy power station It is the combined effect of the voltage generated at node W by the current injected at nodes S, G, and W, denoted as […]. , , The voltage components generated at node W by the infinite power source, thermal power unit, and new energy source are shown in equation (3). This represents the self-impedance of the new energy node. According to the principle of linear network superposition, the voltage at the new energy node is... The sum of the effects of the three is shown in equation (4).

[0136] (3)

[0137] (4)

[0138] New energy power generation adopts grid voltage orientation, and the d-axis component of the terminal voltage. equal q-axis components The value is 0. Taking the d-axis of the terminal voltage as the real axis reference direction, the dq decomposition of the terminal voltage of the new energy power station in equation (4) yields the expressions for the d-axis and q-axis components of the terminal voltage of the new energy power station:

[0139] (5)

[0140] in , These represent the power angle of the thermal power unit and the voltage phase angle of the new energy terminal, respectively. Substituting into equation (2), we can obtain,

[0141] (6)

[0142] Equation (6) can be simplified to,

[0143] (7)

[0144] parameter , , The expression is shown in equation (8).

[0145] (8)

[0146] Depend on Figure 2 Therefore, the new energy phase-locked loop adopts d-axis voltage-oriented control, and the new energy unit achieves phase-locked synchronization. According to equations (5) and (8), we can... use and This indicates that the unit's phase-locked synchronization is stable when it meets the following conditions. ,in and The physical meaning is as follows.

[0147] (9)

[0148] The d-axis component of the output current of the new energy power station is expressed as in equation (10), and it is affected by the active power output of the new energy power station. and terminal voltage The impact.

[0149] (10)

[0150] Combining equations (5) and (10), we can obtain expression,

[0151] (11)

[0152] For equation (11) Solving for the problem yields the following results:

[0153] (12)

[0154] The mathematical expression can be represented as,

[0155] (13)

[0156] Since the time scale of the phase-locked loop output phase angle movement is much smaller than that of the synchronous motor power angle movement, the power angle of the thermal power unit can be considered constant during the phase-locked loop output phase angle movement. When the system structure and the output of new energy sources are determined, equation (13) reflects... and The functional relationship between them, such as Figure 5 As shown by the blue solid line. When When it increases, This decreases accordingly, thus leading to Increase; if Increase to Id will exceed the output current limit for new energy power plants. ,at this time Restricted to .

[0157] From equation (8) As can be seen from the expression, The q-axis voltage component generated at the new energy node W by injecting current into the thermal power unit node G and the infinite power supply node S is related to... The ratio between them, in its physical sense, represents the d-axis component of the output current of the infinite power source and the new energy absorbed by the thermal power unit. Equation (8) clarifies the system structure and output conditions when they are determined. and The functional relationship between them, such as Figure 5 As shown by the solid black line. This is the steady-state solution for the phase angle output by the phase-locked loop.

[0158] When the actual injected current d-axis component of the new energy node The d-axis component of the output current of the new energy power station is greater than that of the new energy power station. At that time, it can be seen from equation (9) that ,at this time ,according to Figure 2 The control block diagram shows that at this time Decelerate; similarly, when Less than At that time, it can be seen from equation (9) that ,at this time ,according to Figure 2 The control block diagram shows that at this time accelerate.

[0159] set up Figure 3 A three-phase short-circuit fault occurred at the nearest bus L on Line 1-II of the medium-speed line. After 0.1 seconds, Line 1-II was disconnected. The steady-state solution of the phase angle output by the phase-locked loop before the fault disturbance was set as follows: The power angle of the thermal power unit is During a system failure, the voltage at the renewable energy power station drops, entering a low-voltage ride-through state. The low-voltage ride-through control is set to reduce the active power of the renewable energy to 0. Substituting this into equation (13) yields... Self-impedance of new energy nodes during faults Infinity, from equation (8) we can obtain Reduced to 0. Due to During the fault, the phase angle of the phase-locked loop output is... Nothing will change, that is .

[0160] When the system fault is cleared, the voltage at the renewable energy power station recovers, the generating units exit the low-voltage ride-through state, and active power is restored. During fault clearing, the power angle of the thermal power unit accelerates to [a certain value]. Current , The relation becomes,

[0161] (14)

[0162] Due to the acceleration of the synchronous machine's power angle, fault clearing is affected. and The phases are no longer equal, causing a change in the phase angle of the phase-locked loop output. At this time, and about The characteristic curves are shown below. Figure 6 The red area Greater than 0, for It has an accelerating effect; in the green area Less than 0, for It has a decelerating effect. The steady-state phase angle of the phase-locked loop at the moment of fault clearing; The critical phase angle of the phase-locked loop is determined by... and The intersection point is determined.

[0163] At the time of system fault clearing, if If the deceleration zone (green zone) is smaller than the acceleration zone (red zone), it will cause phase-locked synchronization instability in new energy units.

[0164] Depend on Figure 6 It can be seen that, The deceleration region is subject to the current limiting value of the new energy unit. The impact can be mitigated during the fault recovery phase. To improve The deceleration region effectively improves the phase-locked synchronization stability of new energy units. Different Down Acceleration and deceleration regions, such as Figure 7 As shown.

[0165] Based on equation (14), the phase-locked synchronization stability boundary corresponding to different output combinations of new energy and synchronous machine under different current limit values ​​of new energy units can be calculated. Setting the current limit value for new energy units... , The value range is 1.05≤ ≤1.3, make Stability boundaries of phase-locked loop synchronization at different levels, such as Figure 8 As shown.

[0166] in accordance with Figure 8 A strategy for improving the stability of phase-locked synchronization of new energy sources can be proposed, such as... Figure 9 and Figure 10 As shown. The specific process is as follows:

[0167] 1) The dispatch center calculates different current limiting values ​​for new energy units offline or in near real-time based on the output combination of new energy and synchronous machines in the combined power transmission system. Lock the phase synchronization stability boundary and generate a policy table, which is similar to... Figure 7 The results are shown below;

[0168] 2) The dispatch center adjusts the real-time output of the new energy units and the synchronous machine. , and the actual current limit of new energy sources Determine whether there is a risk of phase-locked instability in the new energy unit. If there is no risk of phase-locked instability, set the combined power transmission system to operate in the current mode.

[0169] 3) If the assessment results in 2) indicate that the new energy generating units have a risk of phase-locked instability, then set a current limiting value for the new energy generating units. Reduce and reassess. If the risk of phase-locked instability in new energy units can be effectively avoided, then the current limiting command for new energy units will be implemented. The data is transmitted to the new energy power station to regulate the current limiting value of the generating units.

[0170] 4) If the rate limiting value set in 3) It is difficult to satisfy 1.05≤ If the current limit is ≤1.3, the new energy unit will experience phase-locked instability under the current output combination, and this cannot be avoided by changing the current limit value. The system operating conditions need to be adjusted.

[0171] by Figure 3 Taking the typical structure of the combined renewable energy and thermal power transmission system shown as an example, a corresponding calculation example structure is built in PSCAD / EMTDC. The renewable energy type selected is the wind power model, and the renewable energy power station capacity is S. W =2000MVA, thermal power plant capacity S G =2400MVA. The thermal power unit output is set at 2500MW, the new energy unit output at 1500MW, and the current limit for the new energy power station is 1.1pu. A comparative analysis is conducted for the following two operating conditions.

[0172] 1) Case 1: Current limiting value of renewable energy power plants Keep 1.1 pu unchanged

[0173] 2) Case 2: Current limiting value of renewable energy power plants during normal operation The power consumption is 1.1 PU. After the fault is cleared, the power consumption is adjusted according to the control instructions. Reduced to 1.05 pu.

[0174] set up Figure 3 A three-phase short-circuit fault occurred at the nearest busbar L of Line 1-II in the middle line at 7s. After 0.1s, Line 1-II was disconnected. The simulation results of Case 1 and Case 2 are as follows: Figure 11 and Figure 12 As shown.

[0175] Comparing the simulation results of Case 1 and Case 2, we can see that:

[0176] 1) When the current limit of new energy sources is When the current reference value of the new energy unit is kept constant at 1.1 pu, after the fault is cleared, the current reference value of the new energy unit reaches the limit, and the phase angle angular velocity of the phase-locked loop output continues to increase until it reaches the limit. At this time, the new energy unit experiences phase-locked synchronization instability; the voltage and output of the new energy unit and the synchronous generator both experience severe oscillations.

[0177] 2) Current limiting value of new energy sources during normal operation The power consumption is 1.1 PU. After the fault is cleared, the power consumption is adjusted according to the control instructions. The current was reduced to 1.05 pu. After the fault was cleared, the reference current values ​​of the new energy units did not reach the limit, and the phase angle and angular velocity of the phase-locked loop output recovered. At this time, the new energy units did not have phase-locked synchronization stability problems. Due to the low voltage level of the new energy units, the low voltage ride-through control of the units continued to operate.

[0178] The following describes the phase-locked synchronization and stability control device for new energy generating units provided in the embodiments of this application. The phase-locked synchronization and stability control device for new energy generating units described below can be referred to in correspondence with the phase-locked synchronization and stability control method for new energy generating units described above. Figure 13 As shown, this application provides a phase-locked synchronization and stability control device for new energy generating units, the device comprising:

[0179] The phase-locked synchronization stability boundary determination module 201 is used to determine the phase-locked synchronization stability boundary of each output combination of the new energy unit and the thermal power unit within a preset limit range when the fault of the new energy combined thermal power transmission system is cleared.

[0180] The phase-locked synchronization stability boundary matching module 202 is used to match the target phase-locked synchronization stability boundary in each phase-locked synchronization stability boundary according to the actual new energy output and actual current value of the new energy unit and the actual thermal power output of the thermal power unit.

[0181] The actual current value reduction module 203 is used to reduce the actual current value of the new energy unit within a limit range if it is determined that the new energy unit has a risk of phase-locked instability based on the target phase-locked synchronization stability boundary.

[0182] The operating condition adjustment module 204 is used to adjust the operating conditions of the new energy unit or thermal power unit if the new energy unit still has the risk of phase-locked instability after the actual current value drops to the lower limit of the current limit range, until the phase-locked synchronization stability of the new energy unit meets the operating requirements.

[0183] In one embodiment, the phase-locked loop synchronization stability boundary determination module 201 includes:

[0184] The function relationship acquisition unit is used to acquire the first function relationship and the second function relationship. The first function relationship is used to represent the correspondence between the d-axis component of the output current of the new energy power station and the output phase angle of the phase-locked loop. The second function relationship is used to represent the correspondence between the d-axis component of the actual injected current of the new energy node and the output phase angle of the phase-locked loop. Both the first function relationship and the second function relationship are determined based on the characteristic equation of the phase-locked loop of the new energy unit.

[0185] The phase-locked synchronization stability boundary determination unit is used to obtain the phase-locked synchronization stability boundary corresponding to each output combination within the amplitude limit range, based on the first curve and the second curve corresponding to each output combination. The first curve is generated based on the first functional relationship, and the second curve is generated based on the second functional relationship.

[0186] In one embodiment, the phase-locked loop synchronization stability boundary determination unit includes:

[0187] The phase-locked loop (PLL) synchronization stability boundary determination subunit is used to solve for the PLL output phase angle corresponding to the intersection of the first curve and the second curve before and during fault clearing for each output combination, respectively, to obtain the steady-state phase angle of the first PLL and the steady-state phase angle of the second PLL. Based on the second curve and the limiting value range corresponding to the output combination, multiple PLL output phase angles to be evaluated are determined. When there is a critical phase angle among the output phase angles of each PLL to be evaluated, the phase-locked loop synchronization stability boundary corresponding to the output combination is obtained by combining the steady-state phase angles of the first PLL and the steady-state phase angles of the second PLL. The critical phase angle of the PLL is used to indicate that the new energy unit is in a critical stable state of phase-locked loop.

[0188] In one embodiment, the characteristic equation of the phase-locked loop of the new energy unit is:

[0189]

[0190] in, The first derivative of the phase angle output by the phase-locked loop. The second derivative of the phase angle output by the phase-locked loop. The phase-locked loop inertial time constant is... The damping coefficient is... The actual d-axis component of the injected current at the new energy node. The d-axis component of the output current of the new energy power station.

[0191] In one embodiment, the expression for the first functional relationship is:

[0192]

[0193]

[0194] The expression for the second functional relationship is:

[0195]

[0196] in, The d-axis component of the output current of the new energy power station. Contributing to the development of new energy power plants Contributing reactive power to new energy power plants As an auxiliary variable, it represents voltage-related combination terms. For the self-impedance of new energy nodes, and Weighting coefficients for parameters of new energy combined with thermal power transmission system. This refers to the voltage amplitude within the thermal power unit. The voltage amplitude at the infinite power supply node. The power angle of the thermal power unit. The phase angle is output by the phase-locked loop. The d-axis component of the actual injected current is used to power new energy nodes.

[0197] In one embodiment, the actual current value reduction module 203 includes:

[0198] The phase-locked instability risk determination unit is used to determine that the new energy unit has a phase-locked instability risk if the actual current value of the new energy unit exceeds the boundary current limit value corresponding to the target phase-locked synchronization stability boundary.

[0199] In one embodiment, the actual current value reduction module 203 includes:

[0200] The actual current value reduction unit is used to gradually reduce the actual current value of the new energy unit within the limit range according to the preset limit adjustment step size, or to use the lower limit of the limit range as the reduced actual current value of the new energy unit.

[0201] In one embodiment, this application also provides a storage medium storing computer-readable instructions, which, when executed by one or more processors, cause the one or more processors to perform the steps of the new energy unit phase-locked synchronization and stability control method as described in any of the above embodiments.

[0202] In one embodiment, this application also provides a computer device storing computer-readable instructions, which, when executed by one or more processors, cause the one or more processors to perform the steps of the new energy unit phase-locked synchronization and stability control method as described in any of the above embodiments.

[0203] Indicatively, such as Figure 14 As shown, Figure 14 This is a schematic diagram of the internal structure of a computer device 300 provided in an embodiment of this application. The computer device 300 can be provided as a server. (Refer to...) Figure 14 The computer device 300 includes a processing component 302, which further includes one or more processors, and memory resources represented by memory 301 for storing instructions, such as application programs, that can be executed by the processing component 302. The application programs stored in memory 301 may include one or more modules, each corresponding to a set of instructions. Furthermore, the processing component 302 is configured to execute instructions to perform the new energy unit phase-locked synchronization stability control method of any of the above embodiments.

[0204] The computer device 300 may also include a power supply component 303 configured to perform power management of the computer device 300, a wired or wireless network interface 304 configured to connect the computer device 300 to a network, and an input / output (I / O) interface 305. The computer device 300 may operate on an operating system stored in memory 301, such as Windows Server™, Mac OS X™, Unix™, Linux™, Free BSD™, or similar.

[0205] Those skilled in the art will understand that Figure 14 The structure shown is merely a block diagram of a portion of the structure related to the present application and does not constitute a limitation on the computer device to which the present application is applied. Specific computer devices may include more or fewer components than those shown in the figure, or combine certain components, or have different component arrangements.

[0206] Finally, it should be noted that in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element. In this document, "a," "an," "the," "the," and "its" may also include plural forms unless the context clearly indicates otherwise. "Multiple" refers to at least two, such as 2, 3, 5, or 8, etc. "And / or" includes any and all combinations of the related listed items.

[0207] The various embodiments in this specification are described in a progressive manner. Each embodiment focuses on the differences from other embodiments. The various embodiments can be combined as needed, and the same or similar parts can be referred to each other.

[0208] The above description of the disclosed embodiments enables those skilled in the art to make or use this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for phase-locked synchronous stable control of a new energy generating unit, characterized in that, The method includes: When the fault of the new energy combined with thermal power transmission system is cleared, the phase-locked synchronization stability boundary of each output combination of new energy units and thermal power units is determined within the preset limit value range. Based on the actual new energy output and actual current value of the new energy unit, and the actual thermal power output of the thermal power unit, the target phase-locked synchronization stability boundary is matched in each of the phase-locked synchronization stability boundaries. If, based on the target phase-locked synchronization stability boundary, it is determined that the new energy unit has a risk of phase-locked instability, then the actual current value of the new energy unit is reduced within the limit range. If the new energy unit still has a risk of phase-locked instability after the actual current value drops to the lower limit of the current limiting range, the operating conditions of the new energy unit or the thermal power unit shall be adjusted until the phase-locked synchronization stability of the new energy unit meets the operating requirements.

2. The new energy unit phase-locked synchronization and stability control method according to claim 1, characterized in that, The step of determining the phase-locked synchronization stability boundary for each output combination of new energy units and thermal power units within a preset limit range includes: Obtain a first functional relationship and a second functional relationship. The first functional relationship is used to represent the correspondence between the d-axis component of the output current of the new energy power station and the output phase angle of the phase-locked loop. The second functional relationship is used to represent the correspondence between the d-axis component of the actual injected current of the new energy node and the output phase angle of the phase-locked loop. Both the first functional relationship and the second functional relationship are determined based on the characteristic equation of the phase-locked loop of the new energy unit. Within the specified amplitude range, the phase-locked synchronization stability boundary corresponding to each output combination is obtained based on the first curve and the second curve corresponding to each output combination. The first curve is generated based on the first functional relationship, and the second curve is generated based on the second functional relationship.

3. The new energy unit phase-locked synchronization and stability control method according to claim 2, characterized in that, The step of obtaining the phase-locked synchronization stability boundary corresponding to each output combination within the amplitude limiting range, based on the first curve and the second curve corresponding to each output combination, includes: For each output combination, the phase-locked loop (PLL) output phase angle corresponding to the intersection of the first curve and the second curve before and during fault clearing is calculated to obtain the first PLL steady-state phase angle and the second PLL steady-state phase angle. Based on the second curve corresponding to the output combination and the amplitude limiting range, multiple PLL output phase angles to be evaluated are determined. When there is a critical phase angle among the PLL output phase angles to be evaluated, the phase-locked loop synchronization stability boundary corresponding to the output combination is obtained by combining the first PLL steady-state phase angle and the second PLL steady-state phase angle. The critical phase angle is used to indicate that the new energy unit is in a critical stable state of phase-locked loop.

4. The new energy unit phase-locked synchronization and stability control method according to claim 2, characterized in that, The characteristic equation of the phase-locked loop of the new energy unit is: in, The first derivative of the phase angle output by the phase-locked loop. The second derivative of the phase angle output by the phase-locked loop. The phase-locked loop inertial time constant is... The damping coefficient is... The actual d-axis component of the injected current at the new energy node. The d-axis component of the output current of the new energy power station.

5. The new energy unit phase-locked synchronization and stability control method according to claim 2, characterized in that, The expression for the first functional relationship is: The expression for the second functional relationship is: in, The d-axis component of the output current of the new energy power station. Contributing to the development of new energy power plants Contributing reactive power to new energy power plants As an auxiliary variable, it represents voltage-related combination terms. For the self-impedance of new energy nodes, and Weighting coefficients for parameters of new energy combined with thermal power transmission system. This refers to the voltage amplitude within the thermal power unit. The voltage amplitude at the infinite power supply node. The power angle of the thermal power unit. The phase angle is output by the phase-locked loop. The d-axis component of the actual injected current is used to power new energy nodes.

6. The new energy unit phase-locked synchronization and stability control method according to any one of claims 1 to 5, characterized in that, The step of determining the risk of phase-locked instability of the new energy unit based on the target phase-locked synchronization stability boundary includes: If the actual current value of the new energy unit exceeds the boundary current limit value corresponding to the target phase-locked synchronization stability boundary, then the new energy unit is determined to have a risk of phase-locked instability.

7. The new energy unit phase-locked synchronization and stability control method according to any one of claims 1 to 5, characterized in that, The step of reducing the actual current value of the new energy unit within the specified limit range includes: Within the specified limit range, the actual current value of the new energy generator is gradually reduced according to a preset limit adjustment step size, or the lower limit of the limit range is used as the reduced actual current value of the new energy generator.

8. A phase-locked synchronous stability control device for new energy generating units, characterized in that, The device includes: The phase-locked synchronization stability boundary determination module is used to determine the phase-locked synchronization stability boundary of each output combination of new energy units and thermal power units within a preset limit range when the fault of the new energy combined thermal power transmission system is cleared. The phase-locked synchronization stability boundary matching module is used to match the target phase-locked synchronization stability boundary in each of the phase-locked synchronization stability boundaries based on the actual new energy output and actual current value of the new energy unit and the actual thermal power output of the thermal power unit. The actual current value reduction module is used to reduce the actual current value of the new energy unit within the limit value range if it is determined that the new energy unit has a risk of phase-locked instability based on the target phase-locked synchronization stability boundary. The operating condition adjustment module is used to adjust the operating conditions of the new energy unit or the thermal power unit if the new energy unit still has a risk of phase-locked instability after the actual current value drops to the lower limit of the current limiting value range, until the phase-locked synchronization stability of the new energy unit meets the operating requirements.

9. A storage medium, characterized in that: The storage medium stores computer-readable instructions, which, when executed by one or more processors, cause the one or more processors to perform the steps of the phase-locked synchronization and stability control method for new energy generating units as described in any one of claims 1 to 7.

10. A computer device, characterized in that, include: One or more processors, and memory; The memory stores computer-readable instructions, which, when executed by the one or more processors, perform the steps of the phase-locked synchronization and stability control method for new energy generating units as described in any one of claims 1 to 7.

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