Active power control methods, devices, equipment and media for grid-connected renewable energy power generation systems

Abstract

This invention discloses an active power control method, device, equipment, and medium for a grid-connected renewable energy power generation system, belonging to the field of renewable energy power generation systems. In this invention, when the renewable energy power generation system enters the LVRT (Low Voltage Reduction Test), the voltage drop and initial active power are determined. Then, based on the voltage drop, initial active power, and a preset first correspondence, the target recovery rate of active power is determined. Finally, the active power of the renewable energy power generation system is restored to the target value according to the target recovery rate. Since a fixed recovery rate is not used, but the target recovery rate is adaptively generated based on the voltage drop and initial active power when entering the LVRT, the efficiency of active power recovery after a fault in supporting the system frequency and the impact on the hardware of the renewable energy power generation system can be considered.

Description

Technical Field

[0001] This invention relates to the field of new energy power generation systems, and in particular to an active power control method, device, equipment and medium for grid-connected new energy power generation systems. Background Technology

[0002] For grid-connected renewable energy power generation systems, when the grid voltage drops significantly due to disturbances such as short-circuit faults or DC blocking, the renewable energy power generation system will enter the Low Voltage Ride Through (LVRT) operating state. During the LVRT period, the active power output of the renewable energy power generation system drops significantly. After the grid voltage recovers, the renewable energy power generation system needs to restore the active power to a higher target value. However, there is a lack of mature active power control methods in related technologies. Usually, a fixed rate of active power recovery is used, which may not be able to support the system frequency in time, and may also exceed the hardware physical limits of the renewable energy power generation system.

[0003] Therefore, how to provide a solution to the above-mentioned technical problems is a problem that needs to be solved by those skilled in the art. Summary of the Invention

[0004] The purpose of this invention is to provide an active power control method, device, equipment, and medium for grid-connected renewable energy power generation systems. In this invention, when the renewable energy power generation system enters the LVRT (Low Voltage Reduction Test), the voltage drop and initial active power are determined. Then, based on the voltage drop, initial active power, and a preset first correspondence, the target recovery rate of active power is determined. Finally, the active power of the renewable energy power generation system is restored to the target value according to the target recovery rate. Since a fixed recovery rate is not used, but the target recovery rate is adaptively generated based on the voltage drop and initial active power when entering the LVRT, the system frequency support efficiency of the grid connection point voltage and the impact on the hardware of the renewable energy power generation system can be taken into account.

[0005] To address the aforementioned technical problems, this invention provides an active power control method for a grid-connected renewable energy power generation system, applied to the controller of the renewable energy power generation system, comprising: When a new energy power generation system enters a low voltage ride-through state, the grid connection point voltage at the moment before entering the low voltage ride-through state is used as the initial voltage, and the active power at the moment before entering the low voltage ride-through state is used as the initial active power. The difference between the initial voltage and the grid connection point voltage under low voltage ride-through conditions is taken as the voltage drop. Based on the voltage drop, the initial active power, and the preset first correspondence, the target recovery rate of active power is determined; the first correspondence is the correspondence between the voltage drop, the initial active power, and the target recovery rate of active power. When the grid connection voltage of the new energy power generation system reaches the preset recovery threshold, the active power of the new energy power generation system is restored to the target value according to the target recovery rate.

[0006] On the other hand, determining the target recovery rate of active power based on the voltage drop, initial active power, and a preset first correspondence includes: Based on the voltage drop, initial active power, and the preset recovery rate formula, the target recovery rate of active power is determined. The recovery rate relationship includes: R=R min +(R max -R min ()( ) a ( ) b ; Where R is the target recovery rate, R min R is the minimum active power recovery rate for a new energy power generation system. max This represents the maximum active power recovery rate of the new energy power generation system. This is the initial active power normalization factor. This is the voltage sag normalization factor. =P0 / P n ; =ΔU / U0; P0 is the initial active power, P n The rated active power of the new energy power generation system is denoted as ΔU, the voltage drop is denoted as U0, and the initial voltage is denoted as a. Both a and b are sensitivity coefficients preset according to the physical characteristics of the new energy power generation system.

[0007] On the other hand, determining the target recovery rate of active power based on the voltage drop, initial active power, and a preset first correspondence includes: The target recovery rate corresponding to the voltage drop and the initial active power is determined from the preset recovery rate lookup table.

[0008] On the other hand, determining the target recovery rate corresponding to the voltage drop and the initial active power from the preset recovery rate lookup table includes: The two-dimensional coordinate points formed by the initial active power and voltage drop are used as the target coordinate points. Determine whether the target coordinate point exists in the preset recovery rate lookup table; If it exists, the recovery rate corresponding to the target coordinate point will be used as the target recovery rate; If it does not exist, then determine the two adjacent coordinate points before and after the target coordinate point from the preset recovery rate lookup table; Based on two adjacent coordinate points and their corresponding recovery rates, the recovery rate corresponding to the target coordinate point is determined and used as the target recovery rate.

[0009] On the other hand, after determining the target recovery rate of active power based on the voltage drop, initial active power, and a preset first correspondence, before restoring the active power of the grid-connected new energy power generation system to the target value according to the target recovery rate when the grid connection point voltage of the new energy power generation system reaches the preset recovery threshold, the active power control method for the grid-connected new energy power generation system further includes: The maximum safe recovery rate of the new energy power generation system is determined; the maximum safe recovery rate is obtained by load simulation of the new energy power generation system. The smaller of the target recovery rate and the maximum safe recovery rate is taken as the new target recovery rate.

[0010] On the other hand, when the new energy power generation system enters the low voltage ride-through state, taking the grid connection point voltage at the moment before entering the low voltage ride-through state as the initial voltage and the active power at the moment before entering the low voltage ride-through state as the initial active power includes: When the grid connection point voltage of the new energy power generation system is lower than the low voltage ride-through initiation threshold, the new energy power generation system is determined to have entered the low voltage ride-through state. The grid connection point voltage at the moment before entering the low voltage ride-through state is taken as the initial voltage, and the active power at the moment before entering the low voltage ride-through state is taken as the initial active power. The new energy power generation system includes wind power generation system or photovoltaic power generation system.

[0011] On the other hand, when the grid connection voltage of the new energy power generation system reaches the preset recovery threshold, restoring the active power of the new energy power generation system to the target value according to the target recovery rate includes: When the grid connection voltage of the new energy power generation system reaches the preset recovery threshold, it is determined whether the target recovery rate is lower than the preset threshold. If it is lower, then the target recovery rate is used as the initial value and the maximum safe recovery rate of the preset new energy power generation system is used as the termination value to construct a smooth recovery rate sequence. The active power of the new energy power generation system is restored to the target value in sequence according to each recovery rate in the recovery rate sequence.

[0012] To address the aforementioned technical problems, this invention also provides an active power control device for a grid-connected renewable energy power generation system, applied to the controller of the renewable energy power generation system, comprising: The first determining module is used to take the grid connection point voltage at the moment before entering the low voltage ride-through state as the initial voltage and the active power at the moment before entering the low voltage ride-through state as the initial active power when the new energy power generation system enters the low voltage ride-through state. The second determining module is used to take the difference between the initial voltage and the grid connection point voltage under low voltage ride-through conditions as the voltage drop. The third determining module is used to determine the target recovery rate of active power based on the voltage drop, the initial active power, and a preset first correspondence; the first correspondence is the correspondence between the voltage drop, the initial active power, and the target recovery rate of active power. The control module is used to restore the active power of the new energy power generation system to the target value according to the target recovery rate when the grid connection point voltage of the new energy power generation system reaches the preset recovery threshold.

[0013] To address the aforementioned technical problems, the present invention also provides an active power control device for a grid-connected renewable energy power generation system, comprising: Memory, used to store computer programs; A processor is used to execute the computer program to implement the active power control method of the grid-connected new energy power generation system as described above.

[0014] To address the aforementioned technical problems, the present invention also provides a computer-readable storage medium storing a computer program, which, when executed by a processor, implements the steps of the active power control method for a grid-connected new energy power generation system as described above.

[0015] Beneficial Effects: This invention provides an active power control method for a grid-connected renewable energy power generation system. Considering that the voltage drop after the renewable energy power generation system enters the low voltage ride-through state and the initial active power before entering the low voltage ride-through state are both related to the voltage frequency deficit during the active power recovery process and the impact on the hardware of the renewable energy power generation system, this invention determines the voltage drop and the initial active power when the renewable energy power generation system enters the low voltage ride-through state. Then, based on the voltage drop, the initial active power, and a preset first correspondence, the target recovery rate of the active power is determined. Finally, the active power of the renewable energy power generation system is restored to the target value according to the target recovery rate. Since a fixed recovery rate is not used, but the target recovery rate is adaptively generated based on the voltage drop and the initial active power when entering the low voltage ride-through state, the system frequency support efficiency of the grid connection point voltage and the degree of impact on the hardware of the renewable energy power generation system can be taken into account.

[0016] The present invention also provides an active power control device, equipment and computer-readable storage medium for a grid-connected new energy power generation system, which has the same beneficial effects as the active power control method for the grid-connected new energy power generation system described above. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention, the relevant technologies and the accompanying drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 A schematic diagram of the first process of the active power control method for a grid-connected new energy power generation system provided by the present invention; Figure 2 This is a schematic diagram of a wind power generation system. Figure 3 A schematic diagram of the second process of the active power control method for a grid-connected new energy power generation system provided by the present invention; Figure 4 A schematic diagram of the active power control device for a grid-connected new energy power generation system provided by the present invention; Figure 5 A schematic diagram of the active power control equipment for the grid-connected new energy power generation system provided by the present invention. Detailed Implementation

[0019] The core of this invention is to provide an active power control method, device, equipment, and medium for a grid-connected renewable energy power generation system. In this invention, when the renewable energy power generation system enters the LVRT (Low Voltage Reduction Test), the voltage drop and initial active power are determined. Then, based on the voltage drop, initial active power, and a preset first correspondence, the target recovery rate of active power is determined. Finally, the active power of the renewable energy power generation system is restored to the target value according to the target recovery rate. Since a fixed recovery rate is not used, but the target recovery rate is adaptively generated based on the voltage drop and initial active power when entering the LVRT, the system frequency support efficiency of the grid connection point voltage and the impact on the hardware of the renewable energy power generation system can be taken into account.

[0020] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] Please refer to Figure 1 , Figure 1 This is a first flowchart illustrating the active power control method for a grid-connected renewable energy power generation system provided by the present invention. The active power control method for the grid-connected renewable energy power generation system is applied to the controller of the renewable energy power generation system and includes: S101: When a new energy power generation system enters the low voltage ride-through state, the grid connection point voltage at the moment before entering the low voltage ride-through state is used as the initial voltage, and the active power at the moment before entering the low voltage ride-through state is used as the initial active power. Specifically, for a better explanation of the embodiments of the present invention, please refer to... Figure 2 , Figure 2 This is a schematic diagram of a wind power generation system. Taking a wind power generation system as an example, when a wind power generation system recovers active power at a high rate, it will cause a high mechanical load on the transmission chain shaft system, resulting in high losses on the transmission chain shaft system, and may even lead to direct damage. In addition to the transmission chain shaft system, a wind power generation system also includes a fan (there is inertia between the fan and the transmission chain shaft system), a generator, a controller, a converter, and a transformer.

[0022] Specifically, considering the technical problems mentioned above, in order to balance the grid frequency recovery requirements and equipment hardware safety constraints during the recovery of active power in a grid-connected renewable energy power generation system after the low-voltage ride-through state, the scheme in this embodiment of the invention is proposed. Considering that traditional fixed-rate recovery strategies cannot dynamically adjust according to the severity of the fault and the initial state of the equipment, they are prone to insufficient frequency support or equipment overload. This embodiment of the invention aims to achieve adaptive optimization of the recovery process by real-time acquisition of grid connection point voltage and active power, recording the initial voltage and initial active power when entering the low-voltage ride-through state, calculating the voltage drop, and determining the target recovery rate based on the correspondence between the voltage drop and the initial active power. Therefore, this step first uses the grid connection point voltage at the moment before entering the low-voltage ride-through state as the initial voltage and the active power at the moment before entering the low-voltage ride-through state as the initial active power, and uses these as the data basis for subsequent steps.

[0023] S102: The difference between the initial voltage and the grid connection point voltage under low voltage ride-through condition is taken as the voltage drop. Specifically, considering that the voltage drop is related to the voltage frequency deficit during the active power recovery process and the hardware impact on the new energy power generation system, and that the voltage drop can be determined by the initial voltage and the grid connection point voltage under the low voltage ride-through state, the difference between the initial voltage and the grid connection point voltage under the low voltage ride-through state can be used as the voltage drop in this step, and it can be used as the data basis for subsequent steps.

[0024] The grid connection point voltage under low voltage ride-through conditions can be of various types. For example, the lowest voltage value during a fault or the voltage value at the moment the fault is cleared can be selected as the grid connection point voltage under low voltage ride-through conditions. This embodiment of the invention does not limit the specific voltage value.

[0025] S103: Determine the target recovery rate of active power based on the voltage drop, the initial active power, and the preset first correspondence; the first correspondence is the correspondence between the voltage drop, the initial active power, and the target recovery rate of active power. Specifically, considering the pre-set correspondence between voltage sag and initial active power and the target recovery rate of active power, the corresponding target recovery rate can be determined efficiently and accurately based on the voltage sag and initial active power. Therefore, this step can determine the target recovery rate of active power based on the voltage sag, initial active power, and the pre-set first correspondence; the first correspondence is the correspondence between voltage sag, initial active power, and the target recovery rate of active power.

[0026] S104: When the grid connection voltage of the new energy power generation system reaches the preset recovery threshold, the active power of the new energy power generation system is restored to the target value according to the target recovery rate.

[0027] Specifically, after determining the target recovery rate, when the grid connection point voltage of the new energy power generation system reaches the preset recovery threshold, the active power of the new energy power generation system can be restored to the target value according to the target recovery rate. The grid connection point voltage reaching the preset recovery threshold indicates that the grid fault has been cleared, which is reflected in the recovery and rise of the grid connection point voltage. The embodiments of the present invention can dynamically adjust the recovery rate according to the specific operating conditions of each low voltage ride-through, maximize the frequency support capability while ensuring equipment safety, and avoid the limitations of fixed rate strategies.

[0028] This invention provides an active power control method for a grid-connected renewable energy power generation system. Considering that the voltage drop after the renewable energy power generation system enters the low voltage ride-through state and the initial active power before entering the low voltage ride-through state are both related to the voltage frequency deficit during the active power recovery process and the impact on the hardware of the renewable energy power generation system, this invention determines the voltage drop and the initial active power when the renewable energy power generation system enters the low voltage ride-through state. Then, based on the voltage drop, the initial active power, and a preset first correspondence, the target recovery rate of the active power is determined. Finally, the active power of the renewable energy power generation system is restored to the target value according to the target recovery rate. Since a fixed recovery rate is not used, but the target recovery rate is adaptively generated based on the voltage drop and the initial active power when entering the low voltage ride-through state, the system frequency support efficiency of the grid connection point voltage and the degree of impact on the hardware of the renewable energy power generation system can be taken into account.

[0029] Based on the above embodiments: As an optional embodiment, the target recovery rate of active power is determined based on the voltage drop, the initial active power, and a preset first correspondence, including: Based on the voltage drop, initial active power, and the preset recovery rate formula, the target recovery rate of active power is determined. The relationships between recovery rates include: R=R min +(R max -R min ()( ) a ( ) b ; Where R is the target recovery rate, R min R is the minimum active power recovery rate for a new energy power generation system. max This represents the maximum active power recovery rate of the new energy power generation system. This is the initial active power normalization factor. This is the voltage sag normalization factor. =P0 / P n ; =ΔU / U0; P0 is the initial active power, P n The rated active power of the new energy power generation system is denoted as ΔU, the voltage drop is denoted as U0, and the initial voltage is denoted as a. Both a and b are sensitivity coefficients preset according to the physical characteristics of the new energy power generation system.

[0030] Specifically, considering the nonlinear characteristics of the impact of voltage dips and initial active power on the recovery rate, and the need to balance the simplicity of mathematical expression with the feasibility of engineering implementation, this embodiment of the invention sets up this recovery rate relationship scheme. This relationship, by introducing a sensitivity coefficient, can accurately describe the variation law of the recovery rate under different operating conditions, avoiding the shortcomings of simple linear relationships that cannot accurately reflect the actual physical process. It provides an accurate mathematical model to calculate the target recovery rate, enabling the recovery process to not only quickly respond to the grid frequency demand but also automatically adjust according to the equipment status, improving the accuracy and adaptability of control.

[0031] Specifically, the recovery rate relationship is expressed using an initial active power normalization factor. and voltage drop normalization factor Characterizes the current fault condition. Among them, The larger the value, the higher the output power before the fault. The larger the value, the deeper the voltage drop. Both reflect the strength of the system's active power recovery demand after a fault. Therefore, when and When the value is large, the theoretical recovery rate R also increases accordingly, so as to improve the ability of active power recovery to support the system frequency after a fault.

[0032] The larger the voltage drop and the higher the initial active power, the greater the active power deficit caused by the fault and the stronger the system frequency support requirement. Therefore, the corresponding theoretical target recovery rate is higher. Thus, the support efficiency of active power recovery after the fault for the system frequency and the safety constraints on the hardware of the new energy power generation system can be taken into account.

[0033] Of course, in addition to this specific form, the recovery rate relationship can also take other forms, and the embodiments of the present invention are not limited here.

[0034] As an optional embodiment, the target recovery rate of active power is determined based on the voltage drop, the initial active power, and a preset first correspondence, including: The target recovery rate corresponding to the voltage drop and the initial active power is determined from the preset recovery rate lookup table.

[0035] Specifically, considering that complex mathematical calculations may increase the controller's burden in some new energy power generation systems, and that actual operating data is often obtained through experiments or simulations, this embodiment of the invention provides a lookup table scheme. This scheme avoids the complexity of real-time calculations and is particularly suitable for embedded control systems with limited computing resources, while accurately reflecting the nonlinear characteristics of actual equipment. This scheme simplifies the controller's computational burden, improves the real-time performance and reliability of the control system, and is particularly suitable for upgrading old equipment or low-cost controller applications.

[0036] In one specific example, the controller pre-constructs a recovery rate lookup table. This table is a two-dimensional table, with the horizontal axis representing the normalized value of the initial active power P0 (range 0-1) and the vertical axis representing the normalized value of the voltage sag ΔU (range 0-1). The table stores the optimal recovery rate value for the corresponding coordinate point. These data are obtained through offline simulation or field experiments, fully considering the mechanical load constraints of the equipment and the grid frequency support requirements. During actual operation, when the new energy power generation system enters the low voltage ride-through state and calculates the normalized... (Normalized value of initial active power P0) and After obtaining the normalized value of the voltage drop ΔU, the controller locates the corresponding target recovery rate in the lookup table based on these two parameter values.

[0037] As an optional embodiment, the target recovery rate corresponding to the voltage drop and the initial active power is determined from a preset recovery rate lookup table, including: The two-dimensional coordinate points formed by the initial active power and voltage drop are used as the target coordinate points. Determine if the target coordinate point exists in the preset recovery rate lookup table; If it exists, the recovery rate corresponding to the target coordinate point will be used as the target recovery rate; If it does not exist, then determine the two adjacent coordinate points before and after the target coordinate point from the preset recovery rate lookup table; Based on two adjacent coordinate points and their corresponding recovery rates, the recovery rate corresponding to the target coordinate point is determined and used as the target recovery rate.

[0038] Specifically, considering that actual operating parameters often cannot accurately match discrete points in the lookup table, and that the continuity and accuracy of control need to be guaranteed, a coordinate point judgment and interpolation scheme is set up in this embodiment of the invention. This scheme solves the matching problem between discrete data and continuous operating conditions, avoids control discontinuity or accuracy reduction caused by parameter mismatch, improves the accuracy and adaptability of the lookup table method, ensures smooth and continuous recovery rate control under any operating condition, and avoids jumps and instability in the control process.

[0039] The determination of the recovery rate corresponding to the target coordinate point based on two adjacent coordinate points and their corresponding recovery rates, and using this as the target recovery rate, can be implemented in various ways. For example, the recovery rate corresponding to the target coordinate point can be determined by interpolation based on two adjacent coordinate points and their corresponding recovery rates, and used as the target recovery rate. This embodiment of the invention does not limit this approach. In one specific instance, the controller uses the normalized initial active power... and voltage drop Two-dimensional coordinate points ( , The target coordinate point is used as the reference point. The controller first determines whether the target coordinate point exists precisely in the preset recovery rate lookup table. For example, when... =0.325, When the value is 0.275, there may be no exact match in the query table.

[0040] At this point, the controller determines the two adjacent coordinate points before and after the target coordinate point from the lookup table. Specifically, it finds the two adjacent coordinate points in the horizontal axis direction. =0.3 and Find two points with a value of 0.4 along the vertical axis. =0.2 and Two points with a value of 0.3 are used to form four adjacent coordinate points. The controller reads the recovery rate values ​​R1, R2, R3, and R4 corresponding to these four points, and then uses bilinear interpolation to calculate the recovery rate corresponding to the target coordinate point. The interpolation calculation process is as follows: First, in... Perform linear interpolation in the direction and calculate When =0.2, The speed R at =0.325 a =R1+(R2-R1)×(0.325-0.3) / (0.4-0.3); Calculate similarly. The speed R at =0.3 β Then Linear interpolation is performed in the direction to obtain the final target recovery rate R=R a +(R β -R a (0.275 - 0.2) / (0.3 - 0.2). This calculation process is efficiently completed in the floating-point unit of the controller, ensuring real-time performance.

[0041] As an optional embodiment, after determining the target recovery rate of active power based on the voltage drop, initial active power, and a preset first correspondence, before restoring the active power of the grid-connected new energy power generation system to the target value according to the target recovery rate when the grid connection point voltage of the new energy power generation system reaches the preset recovery threshold, the active power control method for the grid-connected new energy power generation system further includes: The maximum safe recovery rate of the preset new energy power generation system is determined; the maximum safe recovery rate is obtained by load simulation of the new energy power generation system. The smaller of the target recovery rate and the maximum safe recovery rate is taken as the new target recovery rate.

[0042] Specifically, considering that the physical limits of the hardware of the new energy power generation system (such as the fatigue strength of the mechanical transmission system or the thermal stress limitations of power electronic devices) may be more stringent than the theoretically calculated recovery rate, a maximum safe recovery rate limiting scheme is set in this embodiment of the invention. To avoid the impact of an excessively high recovery rate on the hardware of the new energy power generation system, this embodiment of the invention can also determine the maximum safe recovery rate based on the load simulation results, and limit the theoretical target recovery rate with the maximum safe recovery rate, and finally restore the active power of the new energy power generation system to the target value according to the limited target recovery rate. This scheme, as a safety protection mechanism, ensures that the control commands never exceed the actual bearing capacity of the equipment, preventing equipment damage or shortened lifespan due to overload. While making full use of the equipment's potential, it provides a final safety guarantee, ensuring that the control system can operate safely under various extreme conditions, improving the system's reliability and service life.

[0043] In one specific example, the simulation process for determining the maximum safe recovery rate can be flexibly set. For example, it can be: establishing a dual-mass block model of the wind turbine transmission chain, simulating the transient torque impact of the main shaft and gearbox under different recovery rates, analyzing the accumulation of fatigue damage, and determining the maximum allowable recovery rate under the premise of ensuring the preset design life. This embodiment of the invention does not limit the specific details.

[0044] In addition, the maximum active power recovery rate R max This is not the same as the maximum safe recovery rate, where R max The theoretical upper limit parameter in the recovery rate formula is used to limit the calculation range of the theoretical target recovery rate; the maximum safe recovery rate is a safe upper limit determined based on the hardware safety constraints of the new energy power generation system, used to limit the final executed recovery rate from exceeding the equipment's tolerance range. Therefore, the target recovery rate is used to reflect the system's frequency support requirements after a fault, while the maximum safe recovery rate is used to reflect the equipment's safety constraints, and the final executed recovery rate is the smaller of the two.

[0045] As an optional embodiment, when the new energy power generation system enters the low voltage ride-through state, the grid connection point voltage at the moment before entering the low voltage ride-through state is used as the initial voltage, and the active power at the moment before entering the low voltage ride-through state is used as the initial active power, including: When the grid connection point voltage of the new energy power generation system is lower than the low voltage ride-through initiation threshold, the new energy power generation system is determined to have entered the low voltage ride-through state. The grid connection point voltage at the moment before entering the low voltage ride-through state is taken as the initial voltage, and the active power at the moment before entering the low voltage ride-through state is taken as the initial active power. New energy power generation systems include wind power generation systems or photovoltaic power generation systems.

[0046] Specifically, considering the differences in low-voltage ride-through characteristics and hardware constraints among different types of new energy power generation systems (such as wind power systems and photovoltaic power generation systems), a low-voltage ride-through state judgment and system type differentiation scheme is proposed in this embodiment of the invention. This scheme can accurately identify when the system enters the low-voltage ride-through state and adopt corresponding control strategies for different system types, improving the accuracy of state recognition, avoiding control failures caused by misjudgments, and providing a unified control framework for different types of new energy power generation systems, thereby enhancing the universality and engineering applicability of the scheme.

[0047] The low voltage ride-through threshold can be set flexibly and independently, for example, it can be 0.88 times the rated voltage, etc., and this embodiment of the invention does not limit it.

[0048] Specifically, the controller identifies the type of new energy power generation system through system configuration parameters. For wind power systems, the characteristic is rotational inertia, with the main constraint being the fatigue load of the mechanical transmission system; for photovoltaic power systems, the characteristic is the absence of rotating parts, with the main constraint being the thermal stress limitation of power electronic devices (such as Insulated Gate Bipolar Transistors, IGBTs). In practical implementation, the controller automatically adjusts control parameters according to the system type: for wind power systems, R is based on mechanical load. mech Due to the (maximum safe recovery rate) limitation, photovoltaic power generation systems employ R based on the thermal time constant. mech Limitations. For example, the R of a 1.5MW wind turbine generator set. mech It is 60% of the rated power / second, while the R of a photovoltaic power generation system of the same capacity is... mech The value is 80% of the rated power per second, reflecting the different physical characteristics of the two systems.

[0049] As an optional embodiment, when the grid connection point voltage of the new energy power generation system reaches a preset recovery threshold, restoring the active power of the new energy power generation system to the target value according to the target recovery rate includes: S201: When the grid connection point voltage of the new energy power generation system reaches the preset recovery threshold, determine whether the target recovery rate is lower than the preset threshold. S202: If it is lower than the target recovery rate, then a smooth recovery rate sequence is constructed with the target recovery rate as the initial value and the preset maximum safe recovery rate of the new energy power generation system as the termination value. S203: The active power of the new energy power generation system is restored to the target value in sequence according to each recovery rate in the recovery rate sequence.

[0050] Specifically, for a better explanation of the embodiments of the present invention, please refer to... Figure 3 , Figure 3This is a second flowchart illustrating the active power control method for a new energy power generation system provided by the present invention; furthermore, it may include step S204: if it is not lower than the target value, restore the active power of the new energy power generation system to the target value according to the target recovery rate.

[0051] Specifically, considering that a sudden start to the recovery process at a low target recovery rate may impact the equipment, but gradually increasing the recovery rate after active power recovery begins will not cause further impact on the hardware of the new energy power generation system, this embodiment of the invention sets up a smooth recovery rate sequence scheme. This scheme, by constructing a smooth rate sequence from low to high, achieves a gradual start-up of the recovery process, reducing mechanical or electrical impact on the equipment while also enabling rapid active power recovery, thereby instantly replenishing the voltage frequency at the grid connection point.

[0052] Please refer to Figure 4 , Figure 4 This is a schematic diagram of the active power control device for a grid-connected renewable energy power generation system provided by the present invention. The active power control device is applied to the controller of the renewable energy power generation system and includes: The first determining module 41 is used to take the grid connection point voltage at the moment before entering the low voltage ride-through state as the initial voltage and the active power at the moment before entering the low voltage ride-through state as the initial active power when the new energy power generation system enters the low voltage ride-through state. The second determining module 42 is used to take the difference between the initial voltage and the grid connection point voltage under the low voltage ride-through state as the voltage drop amount. The third determining module 43 is used to determine the target recovery rate of active power based on the voltage drop, the initial active power and the preset first correspondence; the first correspondence is the correspondence between the voltage drop and the initial active power and the target recovery rate of active power. The control module 44 is used to restore the active power of the new energy power generation system to the target value according to the target recovery rate when the grid connection point voltage of the new energy power generation system reaches the preset recovery threshold.

[0053] For an introduction to the active power control device of the grid-connected new energy power generation system provided in the embodiments of the present invention, please refer to the aforementioned embodiments of the active power control method of the grid-connected new energy power generation system. The embodiments of the present invention will not be repeated here.

[0054] Please refer to Figure 5 , Figure 5 This is a schematic diagram of the active power control device for a grid-connected renewable energy power generation system provided by the present invention. The active power control device for the grid-connected renewable energy power generation system includes: Memory 51 is used to store computer programs; The processor 52 is used to execute computer programs to implement the steps of the active power control method for the grid-connected new energy power generation system as described in the foregoing embodiments.

[0055] For an introduction to the active power control equipment of the grid-connected new energy power generation system provided in the embodiments of the present invention, please refer to the aforementioned embodiments of the active power control method of the grid-connected new energy power generation system. The embodiments of the present invention will not be repeated here.

[0056] The present invention also provides a computer-readable storage medium storing a computer program, which, when executed by a processor, implements the steps of the active power control method for the grid-connected new energy power generation system as described in the foregoing embodiments.

[0057] For a description of the computer-readable storage medium provided in the embodiments of the present invention, please refer to the aforementioned embodiments of the active power control method for grid-connected new energy power generation systems. The embodiments of the present invention will not be repeated here.

[0058] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatuses disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the descriptions are relatively simple; relevant parts can be referred to the method section. It should also be noted that in this specification, 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. Without further limitations, an element defined by the phrase "comprising a..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element.

[0059] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. 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 the invention. Therefore, the invention 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. An active power control method for a grid-connected new energy power generation system, characterized in that, Controllers used in new energy power generation systems include: When a new energy power generation system enters a low voltage ride-through state, the grid connection point voltage at the moment before entering the low voltage ride-through state is used as the initial voltage, and the active power at the moment before entering the low voltage ride-through state is used as the initial active power. The difference between the initial voltage and the grid connection point voltage under low voltage ride-through conditions is taken as the voltage drop. Based on the voltage drop, the initial active power, and the preset first correspondence, the target recovery rate of active power is determined; the first correspondence is the correspondence between the voltage drop, the initial active power, and the target recovery rate of active power. When the grid connection voltage of the new energy power generation system reaches the preset recovery threshold, the active power of the new energy power generation system is restored to the target value according to the target recovery rate.

2. The active power control method for a grid-connected new energy power generation system according to claim 1, characterized in that, The step of determining the target recovery rate of active power based on the voltage drop, the initial active power, and a preset first correspondence includes: Based on the voltage drop, initial active power, and the preset recovery rate formula, the target recovery rate of active power is determined. The recovery rate relationship includes: R=R min +(R max -R min )( ) a ( ) b ; Where R is the target recovery rate, R min R is the minimum active power recovery rate for a new energy power generation system. max This represents the maximum active power recovery rate of the new energy power generation system. This is the initial active power normalization factor. This is the voltage sag normalization factor. =P0 / P n ; =ΔU / U0; P0 is the initial active power, P n The rated active power of the new energy power generation system is denoted as ΔU, the voltage drop is denoted as U0, and the initial voltage is denoted as a. Both a and b are sensitivity coefficients preset according to the physical characteristics of the new energy power generation system.

3. The active power control method for a grid-connected new energy power generation system according to claim 1, characterized in that, The step of determining the target recovery rate of active power based on the voltage drop, the initial active power, and a preset first correspondence includes: The target recovery rate corresponding to the voltage drop and the initial active power is determined from the preset recovery rate lookup table.

4. The active power control method for a grid-connected new energy power generation system according to claim 3, characterized in that, Determining the target recovery rate corresponding to the voltage drop and initial active power from a preset recovery rate lookup table includes: The two-dimensional coordinate points formed by the initial active power and voltage drop are used as the target coordinate points. Determine whether the target coordinate point exists in the preset recovery rate lookup table; If it exists, the recovery rate corresponding to the target coordinate point will be used as the target recovery rate; If it does not exist, then determine the two adjacent coordinate points before and after the target coordinate point from the preset recovery rate lookup table; Based on two adjacent coordinate points and their corresponding recovery rates, the recovery rate corresponding to the target coordinate point is determined and used as the target recovery rate.

5. The active power control method for a grid-connected new energy power generation system according to claim 1, characterized in that, After determining the target recovery rate of active power based on the voltage drop, initial active power, and a preset first correspondence, before restoring the active power of the grid-connected new energy power generation system to the target value according to the target recovery rate when the grid connection point voltage of the new energy power generation system reaches the preset recovery threshold, the active power control method for the grid-connected new energy power generation system further includes: The maximum safe recovery rate of the new energy power generation system is determined; the maximum safe recovery rate is obtained by load simulation of the new energy power generation system. The smaller of the target recovery rate and the maximum safe recovery rate is taken as the new target recovery rate.

6. The active power control method for a grid-connected new energy power generation system according to claim 1, characterized in that, The provision that when a new energy power generation system enters a low-voltage ride-through state, the grid connection point voltage at the moment preceding the entry into the low-voltage ride-through state is used as the initial voltage, and the active power at the moment preceding the entry into the low-voltage ride-through state is used as the initial active power, includes: When the grid connection point voltage of the new energy power generation system is lower than the low voltage ride-through initiation threshold, the new energy power generation system is determined to have entered the low voltage ride-through state. The grid connection point voltage at the moment before entering the low voltage ride-through state is taken as the initial voltage, and the active power at the moment before entering the low voltage ride-through state is taken as the initial active power. The new energy power generation system includes wind power generation system or photovoltaic power generation system.

7. The active power control method for a grid-connected new energy power generation system according to any one of claims 1 to 6, characterized in that, When the grid connection voltage of the new energy power generation system reaches a preset recovery threshold, restoring the active power of the new energy power generation system to the target value according to the target recovery rate includes: When the grid connection voltage of the new energy power generation system reaches the preset recovery threshold, it is determined whether the target recovery rate is lower than the preset threshold. If it is lower, then the target recovery rate is used as the initial value and the maximum safe recovery rate of the preset new energy power generation system is used as the termination value to construct a smooth recovery rate sequence. The active power of the new energy power generation system is restored to the target value in sequence according to each recovery rate in the recovery rate sequence.

8. An active power control device for a grid-connected new energy power generation system, characterized in that, Controllers used in new energy power generation systems include: The first determining module is used to take the grid connection point voltage at the moment before entering the low voltage ride-through state as the initial voltage and the active power at the moment before entering the low voltage ride-through state as the initial active power when the new energy power generation system enters the low voltage ride-through state. The second determining module is used to take the difference between the initial voltage and the grid connection point voltage under low voltage ride-through conditions as the voltage drop. The third determining module is used to determine the target recovery rate of active power based on the voltage drop, the initial active power, and a preset first correspondence; the first correspondence is the correspondence between the voltage drop, the initial active power, and the target recovery rate of active power. The control module is used to restore the active power of the new energy power generation system to the target value according to the target recovery rate when the grid connection point voltage of the new energy power generation system reaches the preset recovery threshold.

9. An active power control device for a grid-connected new energy power generation system, characterized in that, include: Memory, used to store computer programs; A processor is configured to execute the computer program to implement the steps of the active power control method for a grid-connected renewable energy power generation system as described in any one of claims 1 to 7.

10. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores a computer program, which, when executed by a processor, implements the steps of the active power control method for the grid-connected new energy power generation system as described in any one of claims 1 to 7.

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