Multi-machine cooperative fault ride-through control method and system based on fault controllable boundary

Abstract

The invention provides a multi-machine cooperative fault ride-through control method and system based on a fault controllable boundary, and relates to the field of automation of a power transmission system, and the method comprises the steps: obtaining a multi-machine topological structure of wind and light power generation and the data of each unit, constructing a multi-machine fault controllable boundary model, and dividing the fault controllable boundary into a station-level boundary and a unit-level boundary; performing internally tangent projection mathematical transformation on data of each unit through a multi-unit fault controllable boundary model to obtain a decoupling minimum controllable domain of each unit; distributing reactive power instructions of each unit in a centralized manner according to the station-level boundary in response to the occurrence of a fault; and after responding to the occurrence of the fault, independently and adaptively adjusting the output of each unit according to the unit-level boundary and the decoupling minimum controllable domain. According to the method, a controllable boundary analysis model of a multi-machine interactive coupling and fault disturbance propagation process is constructed, a minimum controllable domain of a voltage distribution boundary is obtained, and multi-machine cooperative fault ride-through control of the wind and light power generation system is carried out based on a double-layer control architecture.

Description

Technical Field

[0001] This invention relates to the field of power transmission system automation technology, specifically to a multi-machine cooperative fault ride-through control method and system based on a fault controllable boundary. Background Technology

[0002] New energy power plants need to proactively utilize their controllable resources to provide transient voltage support. Existing fault transient voltage support control methods can be divided into two categories: single-unit control methods and multi-unit cooperative methods. Single-unit control methods treat the entire power plant as an equivalent unit, where each unit has the same low-voltage ride-through (LVRT) control parameters. In contrast, distributed cooperative methods employ techniques such as dynamic optimization control, model predictive control, and virtual bus (VB) control, avoiding the solution of high-dimensional controllable boundaries and not relying on grid-side fault equivalent information. However, the lack of a global perspective on boundary analysis fails to address the coupling problem of controllable boundaries between different units. When the controllable states of different units differ significantly, it may lead to safety risks of localized overvoltages.

[0003] Although previous studies have explored the sequential fault response characteristics of multi-machine systems under symmetrical fault conditions and proposed a pre-coordinated control approach, the controllable boundary exhibits stronger nonlinearity and complexity under asymmetrical fault conditions, requiring further research. In the context of large-scale wind and solar power systems connected to weak power grids, existing low-voltage control methods struggle to fully exploit the fault transient voltage support capability of wind and solar power systems while meeting safety control constraints, thus failing to ensure safe system operation. This results in unclear fault controllable boundaries and insufficient transient voltage support capability in the scenario of large-scale wind and solar power systems connected to weak power grids. Summary of the Invention

[0004] This invention addresses the problems existing in the prior art by providing a multi-machine collaborative fault ride-through control method and system based on the fault controllable boundary, which solves the problems of unclear fault controllable boundary and insufficient transient voltage support capability in the scenario of large-scale wind and solar power generation systems connected to weak power grids.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows: The multi-unit topology and data of each unit of wind and solar power generation are obtained, and a multi-unit fault controllable boundary model is constructed, dividing the fault controllable boundary into a station-level boundary and a unit-level boundary. By performing an internal projection mathematical transformation on the data of each unit using a multi-unit fault controllable boundary model, the decoupled minimum controllable domain of each unit is obtained. In response to a fault, the reactive power of each unit is centrally allocated according to the station-level boundary; In response to a fault, each unit independently and adaptively adjusts its output based on the unit-level boundary and the decoupled minimum controllable domain.

[0006] In some embodiments, the process of acquiring the multi-unit topology of wind and solar power generation and the data of each unit, and constructing a multi-unit fault controllable boundary model includes: Based on the typical topology of wind and solar power generation system, the equivalent impedance on the grid side is measured and the switching status and active power output of each unit in the power station are collected as data for each unit. A framework for constructing a multi-machine fault controllable boundary model is established by inputting the multi-machine topology of wind and solar power generation and the data of each unit into the framework of the multi-machine fault controllable boundary model to obtain the corresponding multi-machine fault controllable boundary model.

[0007] In some embodiments, the process of performing an internal projection mathematical transformation on the data of each unit using a multi-unit fault controllable boundary model to obtain the decoupled minimum controllable domain of each unit includes: Calculate the data of each unit, update the positive and negative sequence voltage control commands of each unit during fault ride-through according to the switching status of the units, calculate the droop control coefficient during fault ride-through according to the equivalent impedance of the grid side, and calculate the reactive power coordination ratio of each unit during fault ride-through and the upper limit of negative sequence reactive current that each unit can generate to maintain synchronous stability during fault ride-through according to the active power output. The positive and negative sequence voltage control commands, droop control coefficients, reactive power coordination ratios, and negative sequence reactive current upper limits during fault ride-through are transformed into the corresponding projection space by inscribed projection with the preset projection matrix. Based on the fault controllable boundary, the decoupled minimum controllable domain of each unit is divided in the projection space.

[0008] In some embodiments, the command to centrally allocate reactive power to each unit according to the station-level boundary is provided in response to a fault occurring. In response to the occurrence of a fault, the reactive power that each unit needs to output is calculated based on the preset grid voltage regulation requirements and the station-level boundary. The reactive power output of all units in the field is allocated based on the calculation results.

[0009] In some embodiments, in response to a fault, each unit independently and adaptively adjusts its output based on the unit-level boundary.

[0010] In response to the occurrence of a fault, each unit independently detects the voltage drop and enters the fault ride-through control mode, controlling the positive-sequence reactive component and the negative-sequence reactive component respectively, and generating control commands for the positive-sequence and negative-sequence reactive current components. The positive sequence active current component control command is calculated based on the positive sequence and negative sequence reactive current component control commands. The negative sequence active current component control command is set to 0; All control commands are input into the unit's internal current loop to adaptively adjust the output.

[0011] In some embodiments, the site-level boundary includes the minimum controllable domain of the voltage distribution boundary, which is independent of fault parameters, and the synchronous stability boundary equation. Unit-level boundaries include peak current boundaries and active power fluctuation boundaries, which are strongly correlated with fault parameters.

[0012] In some embodiments, the formula for the positive-sequence reactive component control strategy is: ; The formula for the negative-sequence reactive power component control strategy is: ; In the formula, This indicates the positive sequence voltage control commands for each unit during fault ride-through. This indicates the negative sequence voltage control command during fault ride-through for each unit. , These represent the positive and negative sequence virtual voltage values ​​within the controller at time t, respectively; Δt represents the hardware operation interval. This is the droop control coefficient. This represents the upper limit of negative sequence reactive current. This is the upper limit of positive sequence reactive current. Positive-sequence reactive current component control command. Negative sequence reactive current component control command.

[0013] This invention proposes a multi-machine cooperative fault ride-through control system based on a fault-controllable boundary, comprising: The acquisition unit is configured to acquire the multi-unit topology and data of each unit of wind and solar power generation, and to construct a multi-unit fault controllable boundary model, dividing the fault controllable boundary into a station-level boundary and a unit-level boundary. The decoupling unit is configured to perform an internal projection mathematical transformation on the data of each unit through a multi-machine fault controllable boundary model to obtain the decoupling minimum controllable domain of each unit. A centralized control unit is configured to, in response to a failure, centrally allocate reactive power to each unit according to the station-level boundary. An independent control unit is configured to independently and adaptively adjust the output of each unit based on the unit-level boundary and the decoupled minimum controllable domain in response to a fault.

[0014] This invention proposes a computer device, comprising: At least one processor; and a memory storing a computer program executable on the processor, wherein the processor executes the program to perform the steps of the multi-machine cooperative fault-crossing control method based on fault-controllable boundaries.

[0015] This invention proposes a computer-readable storage medium storing a computer program, which, when executed by a processor, performs the steps of the multi-machine cooperative fault-crossing control method based on a fault-controllable boundary.

[0016] Compared with the prior art, the present invention has the following beneficial effects: This invention proposes a multi-unit cooperative fault ride-through control method and system based on a controllable fault boundary. The method includes: acquiring the multi-unit topology and data of each unit in a wind and solar power generation system, and constructing a multi-unit fault controllable boundary model, dividing the fault controllable boundary into a station-level boundary and a unit-level boundary; performing an internal projection mathematical transformation on the data of each unit through the multi-unit fault controllable boundary model to obtain the decoupled minimum controllable domain of each unit; responding to the failure before it occurs, centrally allocating reactive power commands to each unit according to the station-level boundary; and responding to the failure after it occurs, independently and adaptively adjusting the output of each unit according to the unit-level boundary and the decoupled minimum controllable domain.

[0017] This invention constructs a controllable boundary analysis model that considers multi-machine interaction coupling and fault disturbance propagation processes, obtaining the minimum controllable domain of the voltage distribution boundary and its corresponding optimal control trajectory. Based on a two-layer control architecture, multi-machine collaborative fault ride-through control of wind and solar power generation systems is implemented, requiring no real-time communication and independent of grid-side fault equivalent parameters, demonstrating good engineering practicality. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention 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 the present invention. For those skilled in the art, other embodiments can be obtained based on these drawings without creative effort.

[0019] Figure 1 The flowchart of the multi-machine cooperative fault-crossing control method based on the fault controllable boundary provided by the present invention is shown.

[0020] Figure 2 The block diagram of the multi-machine cooperative fault-crossing control system based on the fault controllable boundary provided by the present invention.

[0021] Figure 3 A schematic diagram of the structure of an embodiment of the computer device provided by the present invention.

[0022] Figure 4 This is a schematic diagram of an embodiment of the computer-readable storage medium provided by the present invention.

[0023] Figure 5 The embodiment of the multi-machine cooperative fault ride-through control method based on fault controllable boundary provided by the present invention is a generalized new energy power station grid-connected system topology. Figure 6 The single-machine fault control system architecture is provided in the embodiment of the multi-machine cooperative fault ride-through control method based on fault controllable boundary provided by the present invention. Figure 7 The phasor relationship diagram of the GE, IR and SR terms in the boundary equation of the multi-machine cooperative fault ride-through control method based on the fault controllable boundary provided by the present invention; Figure 8 Phasor trajectory diagrams of voltage distribution boundaries of multiple units in an embodiment of the multi-machine cooperative fault ride-through control method based on fault controllable boundaries provided by the present invention; Figure 9 A control flow diagram of the centralized-distributed two-level cooperative fault transient voltage support control strategy in an embodiment of the multi-machine cooperative fault ride-through control method based on a controllable fault boundary provided by the present invention. Figure 10 In an embodiment of the multi-machine cooperative fault-crossing control method based on controllable fault boundaries provided by the present invention, controllable boundary diagrams of units 2 and 3 of unit 1 under different output conditions are provided. Figure 11 A geometrical comparison diagram on the plane between the proposed theory and existing theories in the embodiments of the multi-machine cooperative fault-crossing control method based on fault controllable boundaries provided by the present invention.

[0024] Figure 12 This is a diagram illustrating the optimal control trajectory within the fault-controllable region in an embodiment of the multi-machine cooperative fault-crossing control method based on a fault-controllable boundary provided by the present invention.

[0025] Figure 13 The three-phase voltage amplitude diagrams at the grid connection points of units 1 to 3 at 0.38kV and 35kV under three control strategies in the embodiment of the multi-machine cooperative fault ride-through control method based on the fault controllable boundary provided by the present invention.

[0026] Figure 14 The above are the positive and negative sequence voltage amplitude diagrams of the grid connection point of units 1 to 3 under three control strategies in the embodiment of the multi-machine cooperative fault ride-through control method based on the fault controllable boundary provided by the present invention.

[0027] Figure 15The relationship between the output characteristics of unit 2 and the corresponding controllable boundary under the control strategy proposed in the embodiment of the multi-machine cooperative fault-crossing control method based on the controllable fault boundary provided by the present invention. Detailed Implementation

[0028] The present invention will be further described below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solutions of the present invention and should not be construed as limiting the scope of protection of the present invention. It should be noted that the following detailed descriptions are exemplary and intended to provide further explanation of this application.

[0029] It should be noted that all uses of "first" and "second" in the embodiments of the present invention are for the purpose of distinguishing two entities with the same name but different names or different parameters. It is clear that "first" and "second" are only for the convenience of description and should not be construed as limiting the embodiments of the present invention. Subsequent embodiments will not explain this in detail.

[0030] This invention proposes a multi-machine cooperative fault ride-through control method based on a fault-controllable boundary. Please refer to [link / reference]. Figure 1 and Figure 5 ,include: S1. Obtain the multi-unit topology and data of each unit of wind and solar power generation, and construct a multi-unit fault controllable boundary model, dividing the fault controllable boundary into a station-level boundary and a unit-level boundary; S2. By performing an internal projection mathematical transformation on the data of each unit through a multi-unit fault controllable boundary model, the decoupled minimum controllable domain of each unit is obtained. S3. In response to the failure, the reactive power command of each unit is centrally allocated according to the station-level boundary before the fault occurs; S4. In response to a fault, each unit independently and adaptively adjusts its output based on the unit-level boundary and the decoupled minimum controllable domain.

[0031] This invention applies to the site coordination controller and unit controller of a wind and solar power generation system. A typical topology of a wind and solar power generation system is as follows: Figure 5 As shown. During the normal operation phase of the wind and solar power system without major disturbances, the site-level coordinated controller is activated once when the unit switching status changes or every 5 minutes. After the coordinated controller is activated, it uses an online impedance estimator to measure the current equivalent impedance on the grid side, and the variable is defined as... In addition, the collaborative controller also collects the current switching status of each unit within the station, and the variable is defined as follows: And the current active power output, the variable is defined as follows: The safety constraints on converter peak current and active power second harmonic oscillation were considered. In each execution cycle, the unit controller ensures that the generated fault ride-through current control command value does not exceed the aforementioned safety constraints. The safety constraints on converter negative sequence synchronous stability were also considered. In each execution cycle, the unit controller ensures that the generated fault ride-through current control command value does not exceed the safety limits.

[0032] This invention subdivides the controllable fault boundary into plant-level and unit-level. The plant-level boundary considers the overall stability and power balance of the entire power plant, while the unit-level boundary focuses on the operating limits and fault isolation capabilities of individual units. By decoupling the mutual influence of units in a complex system, the decoupled minimum controllable domain of each unit is obtained, which is the minimum power range that each unit can independently adjust without affecting other units. Before a fault occurs, reactive power commands for each unit are centrally allocated according to the plant-level boundary to optimize overall power generation efficiency and reserve sufficient fault response capabilities. Once a fault occurs, the system quickly switches to the unit-level boundary and decoupled minimum controllable domain mode. Each unit independently and adaptively adjusts its output according to its own state and boundary conditions to minimize the impact of the fault and quickly restore stable operation.

[0033] Assume a wind and solar power plant comprises 10 wind turbine generators and 50 photovoltaic power generation units, with a total installed capacity of 100MW. After constructing a multi-unit fault controllable boundary model, it is found that the unit-level boundary for a certain wind turbine generator is ±5MW, and the minimum decoupling controllable domain is ±2MW. When a fault occurs near this unit, it can independently adjust its output within ±2MW without affecting other units, thus responding quickly and stabilizing the system.

[0034] In some embodiments, the process of acquiring the multi-unit topology of wind and solar power generation and the data of each unit, and constructing a multi-unit fault controllable boundary model includes: Based on the typical topology of wind and solar power generation system, the equivalent impedance on the grid side is measured and the switching status and active power output of each unit in the power station are collected as data for each unit. A framework for constructing a multi-machine fault controllable boundary model is established by inputting the multi-machine topology of wind and solar power generation and the data of each unit into the framework of the multi-machine fault controllable boundary model to obtain the corresponding multi-machine fault controllable boundary model.

[0035] Specifically, this invention collects the on / off status of each generating unit within the power station, i.e., whether the unit is in operation or shutdown, and the active power output data of each unit reflects its real-time power generation capacity. Based on the input topology and unit data, it simulates the system's response characteristics under various fault conditions. It can determine under what fault conditions the system can maintain stable operation by adjusting unit output, and the role and adjustment range of each unit in fault response.

[0036] For example, in a wind and solar power plant containing 10 wind turbine generators and 50 photovoltaic power generation units, the equivalent impedance on the grid side was measured to be 0.5 ohms. Simultaneously, the switching status and active power output data of each generator were collected. After inputting this data into a pre-constructed multi-generator fault controllable boundary model framework, the model output shows that in the event of a three-phase short-circuit fault, the system can control the impact of the fault within the plant by adjusting the output of some generators, ensuring the stability of overall power generation efficiency.

[0037] In some embodiments, the process of performing an internal projection mathematical transformation on the data of each unit using a multi-unit fault controllable boundary model to obtain the decoupled minimum controllable domain of each unit includes: Calculate the data of each unit, update the positive and negative sequence voltage control commands of each unit during fault ride-through according to the switching status of the units, calculate the droop control coefficient during fault ride-through according to the equivalent impedance of the grid side, and calculate the reactive power coordination ratio of each unit during fault ride-through and the upper limit of negative sequence reactive current that each unit can generate to maintain synchronous stability during fault ride-through according to the active power output. The positive and negative sequence voltage control commands, droop control coefficients, reactive power coordination ratios, and negative sequence reactive current upper limits during fault ride-through are transformed into the corresponding projection space by inscribed projection with the preset projection matrix. Based on the fault controllable boundary, the decoupled minimum controllable domain of each unit is divided in the projection space.

[0038] The co-controller executes the following formula based on the unit switching status of each unit, thereby updating the positive and negative sequence voltage control commands for each unit during fault ride-through. , : ; In the formula, This indicates the positive sequence voltage control commands for each unit during fault ride-through. This indicates the negative sequence voltage control command during fault ride-through of each unit. This represents the negative sequence voltage at each node of the system when the fault just occurred. Since there is no negative sequence component in the system during normal operation, the negative sequence voltage is equal everywhere. and The upper and lower limits of the phase voltage allowed by the power system during normal operation are typically 1.1 pu and 0.9 pu, respectively, according to existing standards. R represents the impedance of the k-th segment of the i-th collector line within the wind-solar power generation system. R represents the total number of generating units on the i-th collector line, and M represents the number of generating units on the additional lines on the i-th collector line. This represents the sum of the rated output currents from the j-th to the R-th generator unit. This represents the sum of the rated output currents of units j through R in the additional branch. 'a' represents the unit node where the additional node connects to the busbar.

[0039] The collaborative controller uses the collected equivalent impedance from the power grid side. The droop control coefficient during fault ride is calculated for each wind and solar power generating unit. The calculation method is shown in the following formula: .

[0040] In the formula, SCR represents the grid-connected short-circuit ratio of the wind and solar power generation system, and λ represents the margin coefficient for maintaining control stability of the droop control of the wind and solar power generation unit under different SCRs, which is usually taken as 3~10.

[0041] Based on the ratio of the current active power output of each unit to its total capacity, the reactive power coordination ratio during fault ride-through of each unit is calculated using the following formula: .

[0042] Based on the reactive power coordination ratio calculated by the collaborative controller during fault ride-through, the upper limit of negative sequence reactive current that each unit can generate to maintain synchronous stability during fault ride-through is further calculated. As shown in the formula... .

[0043] The calculated results are transmitted to each unit in the wind and solar power system via the IEC104 communication protocol. The coordination controller process ends, and the coordination controller temporarily shuts down, awaiting the next startup. The small-disturbance stability of each unit in the wind and solar power system under various fault conditions is considered. Combined with the equivalent impedance value of the grid side obtained through online estimation, the virtual node control parameters of each unit are calculated. A mathematical expression for reactive power coordination ratio is defined for the first time. This expression measures the relationship between the current controllable transient reactive power capacity of each unit. It is calculated based on the difference between the rated capacity and the square of the current active power output of each unit. The negative-sequence synchronization stability of each unit in the wind and solar power system is considered, and the upper limit of the negative-sequence reactive current component that each unit can stably output is derived.

[0044] This invention dynamically updates the positive and negative sequence voltage control commands (i.e., instantaneous values) during fault ride-through based on the unit's switching status. By combining this with the equivalent impedance on the grid side, the droop control coefficient during fault ride-through is accurately calculated, thus determining the unit's power distribution characteristics during a fault.

[0045] Furthermore, based on the active power output data of the generating units, the reactive power coordination ratio during fault ride-through is calculated to provide active power, allocate reactive power, and maintain the system voltage level. Subsequently, these key parameters—positive and negative sequence voltage control commands, droop control coefficient, reactive power coordination ratio, and negative sequence reactive current upper limit—are internally projected onto a preset projection matrix. This transformation from the original data space to the corresponding projection space reflects the correlation and differences between the data. Finally, in the projection space, the decoupled minimum controllable domain of each generating unit is precisely divided according to the fault controllable boundary.

[0046] In some embodiments, the command to centrally allocate reactive power to each unit according to the station-level boundary is provided in response to a fault occurring. In response to the occurrence of a fault, the reactive power that each unit needs to output is calculated based on the preset grid voltage regulation requirements and the station-level boundary. The reactive power output of all units in the field is allocated based on the calculation results.

[0047] The multi-unit cooperative fault ride-through control strategy proposed in this invention adopts a control strategy whereby the station-level cooperative controller centrally coordinates the fault before it occurs, and each unit independently performs fault ride-through without communication after the fault. The station-level cooperative controller and the unit-level controller interact via the IEC104 communication protocol. The station-level cooperative controller initiates communication whenever the unit's switching status changes or every 5 minutes, thus the communication hardware cost is not high. After completing the above centralized cooperative operation, the station-level cooperative controller stops operating and communication. It only restarts when the unit's switching status changes again or after a 5-minute interval. This significantly reduces the hardware cost of the control strategy and improves its engineering practicality.

[0048] This invention uses the station-level boundary as a constraint on the overall stable operation of the system, reflecting the maximum power fluctuation range that the station can withstand under different operating conditions. In practical implementation, specific requirements for grid voltage regulation are obtained, including key indicators such as voltage fluctuation range and power factor limits. Based on these requirements and the station-level boundary, the reactive power output value that each unit needs to output before a fault occurs is determined, ensuring that the allocation result meets grid demand. Based on the above calculation results, the system will allocate reactive power output across all units in the station to jointly maintain power balance and voltage stability between the station and the grid.

[0049] For example, in a wind and solar power plant comprising multiple wind turbines and photovoltaic (PV) units, assuming the grid requires voltage fluctuations to be no more than ±5% of the rated value and the power factor to be maintained above 0.95, according to the site-level boundary analysis, the maximum reactive power fluctuation that the site can withstand under full-load conditions is ±20 Mvar. Based on this, calculations show that each wind turbine needs to output 5 Mvar of reactive power, while the PV units need to adjust their reactive power output according to sunlight conditions, collectively ensuring that the total reactive power output of the site meets the grid requirements, thereby effectively preventing faults and ensuring stable system operation.

[0050] In some embodiments, in response to a fault, each unit independently and adaptively adjusts its output based on the unit-level boundary.

[0051] In response to the occurrence of a fault, each unit independently detects the voltage drop and enters the fault ride-through control mode, controlling the positive-sequence reactive component and the negative-sequence reactive component respectively, and generating control commands for the positive-sequence and negative-sequence reactive current components. The positive sequence active current component control command is calculated based on the positive sequence and negative sequence reactive current component control commands. The negative sequence active current component control command is set to 0; All control commands are input into the unit's internal current loop to adaptively adjust the output.

[0052] After a system disturbance occurs, each unit in the wind and solar power system independently detects voltage dips and enters fault ride-through control mode. Specific detection methods can be found in current national standards for wind farms and photovoltaic power plants. The units are controlled according to the following control strategy. The mathematical expression of the control strategy for the positive-sequence reactive power component is: .

[0053] For the negative-order reactive power components, the mathematical expression of the control strategy is: .

[0054] In the formula, , These represent the positive and negative sequence virtual voltage values ​​within the controller at time t, respectively. Δt represents the hardware operation interval.

[0055] Each unit will generate control commands for the positive and negative sequence reactive current components. and Substitute the instantaneous value into the following inequality for judgment. If the following inequality is satisfied, then issue the positive-sequence active current component control command. Set to 0. Conversely, if the following inequality does not meet the requirements, then the positive-sequence active current component control command... Calculate using the following formula.

[0056] .

[0057] When the above inequality does not meet the requirements, the positive sequence active current component control command is calculated according to the following formula: .

[0058] Conversely, if the above inequality is detected to be false, the control process is stopped, and the control commands for the positive and negative sequence reactive current components are changed. and The value of the previous operation step is fixed and remains unchanged, while the positive sequence active current command is simultaneously... It is set to zero and no longer changes.

[0059] The generated negative-sequence reactive current component command is then substituted into the following inequality for judgment: .

[0060] If the inequality is satisfied, proceed to step 11); otherwise, execute the following equation: .

[0061] The negative-sequence active current component control command is set to 0. The positive and negative-sequence active and reactive current component control commands are then input to the unit's current inner loop. The multi-unit cooperative fault ride-through control process of the wind-solar power generation system of this invention is now complete.

[0062] The coordinated controller will allocate fault ride-through droop control voltage commands and coefficients to each unit based on the electrical distance and current operating status of each unit within the wind and solar power system. This ensures that the entire wind and solar power system can raise the fault voltage to the maximum extent during fault ride-through, and that the voltage of the non-faulty phases at each node does not exceed the limit. This analysis process mainly considers the influencing factors of multi-unit interactive coupling and fault disturbance propagation laws, establishing a controllable fault boundary for multiple units. Furthermore, through mathematical methods of internal projection decoupling, a decoupling minimum controllable domain analysis model for the units is established. Based on this analysis model, the calculation formulas for the positive and negative sequence voltages of each unit can be further obtained.

[0063] A unit-level fault ride-through control strategy based on positive and negative sequence virtual nodes is introduced to dynamically control the positive and negative sequence reactive power output of each unit in real time, thereby dynamically improving the fault voltage support capability of the wind and solar power generation system. In the virtual node control strategy, through defined reactive power coordination ratio parameters, the positive and negative sequence reactive power output of each unit can be dynamically coordinated even without communication. This prioritizes units with low active power output and large controllable reactive power capacity to output reactive power to support fault voltage, thus efficiently allocating the controllable resources of the entire wind and solar power generation system.

[0064] When this invention detects a voltage dip, indicating the need to enter fault ride-through control mode, each generating unit immediately activates an independent fault response mechanism. This involves separately controlling the positive-sequence reactive power component and the negative-sequence reactive power component. The positive-sequence reactive power component compensates for grid voltage dips, improving system voltage levels; the negative-sequence reactive power component suppresses unbalanced currents caused by faults, reducing the impact on the generating units. Based on the control commands for the positive-sequence and negative-sequence reactive current components, a control command for the positive-sequence active current component is calculated to ensure that the generating units provide reactive power support, adjust active power output, and maintain stable operation. The negative-sequence active current component, which has an adverse effect on unit operation, typically has its control command set to 0. Based on real-time commands, the unit's output is quickly and accurately adjusted to achieve adaptive fault ride-through.

[0065] For example, in a wind and solar power plant, after a fault occurred, a wind turbine detected a voltage drop to 80% of its rated value and immediately entered fault ride-through control mode. Through independent calculations, the unit generated a positive-sequence reactive current component control command of 10A and a negative-sequence reactive current component control command of 5A, which in turn resulted in a positive-sequence active current component control command of 20A, while the negative-sequence active current component control command was set to 0. After inputting these commands into the inner current loop, the unit quickly adjusted its output and successfully maintained stable operation.

[0066] In some embodiments, the site-level boundary includes the minimum controllable domain of the voltage distribution boundary, which is independent of fault parameters, and the synchronous stability boundary equation. Unit-level boundaries include peak current boundaries and active power fluctuation boundaries, which are strongly correlated with fault parameters.

[0067] For example, in a wind and solar power plant containing multiple wind turbine generators, site-level boundary analysis shows that the minimum controllable range of the voltage distribution boundary is ±10% of the site's rated voltage. The synchronization stability boundary equation indicates that after a fault, the phase difference between generators needs to be controlled within ±30° to restore synchronization. For unit-level boundaries, the peak current boundary of a wind turbine generator is set to twice its rated current, while the active power fluctuation boundary is limited to ±20% of its rated power.

[0068] In some embodiments, the formula for the positive-sequence reactive component control strategy is: ; The formula for the negative-sequence reactive power component control strategy is: ; In the formula, This indicates the positive sequence voltage control commands for each unit during fault ride-through. This indicates the negative sequence voltage control command during fault ride-through for each unit. , These represent the positive and negative sequence virtual voltage values ​​within the controller at time t, respectively. Δt represents the hardware operating interval. This is the droop control coefficient. This represents the upper limit of negative sequence reactive current. This is the upper limit of positive sequence reactive current. Positive-sequence reactive current component control command. Negative sequence reactive current component control command.

[0069] By independently controlling the positive and negative sequence voltages, the positive sequence voltage control command and the negative sequence voltage control command enable the unit to simultaneously cope with voltage dips and imbalance faults, thereby improving the flexibility and adaptability of fault ride-through.

[0070] By dynamically adjusting the virtual voltage values, the controller can quickly respond to voltage changes, achieving both accuracy and stability in closed-loop control.

[0071] The hardware operation interval needs to be selected based on the dynamic characteristics of the unit and the trade-off between hardware performance, with a typical value of 1-10ms.

[0072] The droop control coefficient enables the proportional distribution of reactive power among generating units within the power station, avoiding reactive power competition.

[0073] The upper limit of negative sequence reactive current and the upper limit of positive sequence reactive current are set differently according to the unit capacity, heat dissipation capacity and other factors.

[0074] The positive-sequence reactive current component control command and the negative-sequence reactive current component control command directly control the positive and negative sequence reactive current output of the unit, realize the dynamic adjustment of fault ride-through, and enable the unit to accurately compensate for the positive-sequence voltage drop of the grid, effectively suppress the negative-sequence component of the grid, and improve power quality.

[0075] This invention proposes a multi-machine cooperative fault ride-through control system based on a fault-controllable boundary. Please refer to [link / reference]. Figure 2 ,include: The acquisition unit 100 is configured to acquire the multi-unit topology and data of each unit of wind and solar power generation, and to construct a multi-unit fault controllable boundary model, dividing the fault controllable boundary into a station-level boundary and a unit-level boundary. Decoupling unit 200 is configured to perform an internal projection mathematical transformation on the data of each unit through a multi-machine fault controllable boundary model to obtain the decoupling minimum controllable domain of each unit. The centralized control unit 300 is configured to, in response to a failure, centrally allocate reactive power to each unit according to the station-level boundary command. Independent control unit 400 is configured to independently and adaptively adjust the output of each unit according to the unit-level boundary and the decoupled minimum controllable domain in response to a fault.

[0076] In one specific embodiment, please refer to Figures 5-15 This includes the following steps: Figure 5 , Figure 6 A generalized topology for a renewable energy power plant's grid connection system and a fault control structure for the unit's grid-connected converter are presented. The power plant contains R busbars, each of which may contain additional branches. These additional branches connect to the main branch before the a-th unit. Considering the large capacity and high voltage level of the power plant, it can be equivalent to an inductive power grid. The control structure for the unit's grid-connected converter during faults includes an LVRT module, a phase-locked loop (PLL) module, and a current inner loop module. The LVRT module is responsible for generating positive and negative sequence active and reactive current commands during faults.

[0077] Figure 5 Subscript Indicates the equivalent quantity on the power grid side, subscript Represents the PCC point variable. Subscript This indicates the j-th unit on the i-th aggregation line, with the subscript... This represents the j-th unit on the additional branch inserted at node a on the i-th aggregation line. This indicates the step-up transformers for the 1st and Rth junction lines. R represents the number of junction lines, N represents the number of generators on junction line 1, and M represents the number of generators on the additional branch line. denoted by , where 'p' represents the transition resistance at the fault point and 'p' represents the location of the fault.

[0078] Figure 6 middle, , , , These represent the amplitude and phase of the positive and negative sequence voltages at point PCC, respectively. 、 、 、 These are positive and negative sequence active and reactive current commands, respectively. , These represent the positive and negative phases of the PLL output, respectively. , These are the filter's inductance, resistance, and capacitance parameters, respectively.

[0079] For the For a grid-connected converter, the voltage and output current at the PCC point can be decomposed into positive and negative sequence components: ; ; First, we will take a single busbar with an additional branch as an example for the derivation. Based on the grid-side voltage phase, we establish a unified reference coordinate system for this busbar, and use Kirchhoff's laws to write the voltage distribution characteristics of the i-th converter: ; ; In the formula, and The equivalent voltage, resistance, reactance, and phase difference between positive and negative sequence voltages on the grid side after a fault occur can all be expressed by the fault sequence network diagram and Thevenin's equivalent theorem.

[0080] Based on the above formula, it is further extended to a station with R converging lines. The voltage distribution characteristics of any node ij are as follows: ; ; ; ; In the formula, This represents the phase difference between the positive and negative sequence voltage phasors on the grid side. Represents phase abc, with values ​​of 0, 2 / 3π, and 2 / 3π.

[0081] The above equation represents the controllable boundary of the substation voltage distribution after multi-machine interactive coupling. The boundary equation can be decomposed into grid excitation (GE), self-response (SR), interactive-response (IR), and a composite response (MR) term resulting from the product of SR and IR. The SR term depends only on the converter's own output, while the IR term depends on the outputs of other converters. Both IR and MR terms are greater than zero, increasing the value on the right side of the equation. Therefore, the multi-machine interactive coupling characteristic imposes certain limitations on the maximum controllability of each unit. Furthermore, the controllable boundary of voltage distribution also needs to consider the influence of fault disturbance propagation laws. Within the entire substation, considering factors such as the need to filter third harmonics, isolate zero-sequence paths, and manufacturer differences, the transformer connection (TC) model may have different configurations, such as YNy0 and Dyn11. Different types of TCs will reshape the amplitude of the asymmetrical three-phase voltage, thus affecting the controllable boundary of voltage distribution. After taking into account the disturbance propagation law, a correction angle quantity GTC needs to be added to the controllable boundary of the voltage distribution. The boundary expression is as follows: .

[0082] Finally, during fault periods, the controllable boundaries of synchronization stability, peak current, and active power fluctuations should also be considered for renewable energy power plants. Existing literature has already provided relatively complete analytical conclusions on this matter, and the boundary equations are listed below: ; ; ; .

[0083] The above equations together constitute the fault controllable boundary analysis model for multi-machine systems.

[0084] The aforementioned controllable boundary equations for voltage distribution are related to fault parameters, which are difficult to obtain. Furthermore, the equations have numerous variables, making it challenging to solve high-order multidimensional optimization problems in real-time. To obtain a practical theoretical form that can guide LVRT control strategy design, the phasor trajectory of the voltage distribution boundary is analyzed in the complex domain plane. Based on the geometric relationship of the trajectory, the minimum controllable domain intersection of various fault conditions projected onto the geometric plane is analyzed, establishing a multi-machine decoupled voltage distribution boundary analysis model, and subsequently deriving the optimal control trajectory. A complex domain is constructed, where the real part of the coordinate axes represents the reactive component and the imaginary part represents the active component. The following phasors are defined in the complex domain: .

[0085] Substituting the above equation into the aforementioned controllable boundary equation, we can obtain the voltage distribution boundary in the complex domain: .

[0086] In the complex number plane, the phasor trajectory relationships of the GE, SR, and IR terms of unit ij. Figure 7 As shown. In Figure 7 In the expression, the positive and negative sequence voltage phasors of unit ij are represented as the sum of the GE, SR, and IR phasors, and... , The phases all vary within the range of 0 to 2π. Clearly, when... , , When all three phases are in phase, the combined phase voltage amplitude is at its maximum. Further derivation of the combined phase voltage phasor trajectory for multiple units is then performed. This assumes two units with equal electrical distance. and and units with greater electrical distances The phase voltage phasor trajectories of the three generating units are as follows: Figure 8 As shown in the figure, the blue, red, and black solid arrows represent the positive and negative sequence voltage phasors and the synthesized phase voltage phasor of the node, respectively. Figure 8 The unit was drawn and The geometrical positional relationships of the five typical voltage controllable boundaries that may occur, including the unit The three-phase voltage boundaries of ABC and the unit The voltage boundary of phase a after TC transformation, and the unit The voltage boundary of phase a. The geometric positions and trajectories of the above five nodes indicate that the voltage distribution boundary phasor trajectory is an ellipse, and the position of the minimum controllable region in the complex domain plane should be at the major axis of the ellipse, such as... Figure 8 The yellow dots indicate this. At this point, the magnitudes of each phasor in the boundary equation should be at their maximum and remain in phase. In contrast, the position of the existing theory in the complex domain plane can be visually represented by pink dots. Because it only considers the safety constraints of a single node phase voltage, the boundary equations given by the existing theory for each unit are completely identical, depending only on the relationship between the three-phase voltage and output current of the corresponding node. This cannot cover all possible operating states. Based on the above analysis, the minimum controllable domain equation is mathematically derived below. The controllable boundary equation is decomposed one by one and substituted into... Figure 8 The constraints corresponding to the yellow dots are defined, and inequality scaling is applied. For the SR term, the derivation yields: ; The other terms can be derived similarly: ; To maximize the efficiency of raising the fault phase voltage within a limited controllable capacity, it is necessary to analyze the optimal control trajectory within the controllable region. Based on the functional relationship between the phase voltage amplitude and the positive and negative sequence voltages, partial derivatives with respect to the positive and negative sequence voltage components can be obtained as follows: ; Setting the two partial derivatives in the above equation to be equal, we get: ; It can be seen that when ≥ When the positive order partial derivative is greater than the negative order partial derivative, the positive order priority principle should be adopted; otherwise, when... ≤ Negative time order takes precedence. Considering that this holds true in virtually any situation... ≥ Therefore, the system has maximum and minimum limits on phase voltage during normal operation. and (Typically 1.1 pu and 0.9 pu), the positive and negative sequence voltage command values ​​of each unit under the optimal control trajectory can be calculated as shown in the following formula, where the negative sequence command changes dynamically with the positive sequence voltage.

[0087] ; Based on the above theories, this invention proposes a multi-unit cooperative fault ride-through control strategy for wind and solar power systems, based on a controllable fault boundary. The strategy is grounded in a pre-fault centralized coordination and distributed coordination approach. Within the constructed controllable boundary, the minimum controllable domain of the voltage distribution boundary and the synchronous stability boundary equation are independent of fault parameters and only related to the output of each unit, belonging to the station-level boundary, allowing for centralized coordination before a fault occurs. In contrast, the current peak boundary and active power fluctuation boundary are strongly correlated with fault parameters and mainly depend on the unit's own output, belonging to the unit-level boundary, allowing for adaptive coordinated control after a fault occurs.

[0088] For voltage distribution boundaries, the coordinated controller can calculate the LVRT voltage command for each unit using the following formula. First, define the reactive power coordination ratio as a variable, which depends on the current active power output and rated capacity of each unit. The calculation formula is as follows: .

[0089] For the synchronous stability boundary, combined with the reactive power coordination ratio, the upper limit of the negative sequence reactive current that each unit can generate can be obtained, as expressed below: .

[0090] To achieve adaptive coordination at the unit-level boundary, a VB control strategy is introduced. Its principle is based on the assumption that the converter passes through a manually set virtual impedance. Connected to a virtual node, and achieving fast voltage command tracking through droop and feedback mechanisms, the control equations are as follows: For the positive-sequence reactive power component, the mathematical expression of the control strategy is: .

[0091] For the negative-order reactive power components, the mathematical expression of the control strategy is: .

[0092] The complete flowchart of the multi-machine cooperative low-voltage ride-through control provided by this invention is as follows: Figure 9 As shown. This invention is a control scheme that includes a cooperative controller in which the above-mentioned process execution code is embedded, and also includes the code for a newly developed fault ride-through module, which is embedded in the controller of each wind and solar power generation unit.

[0093] To further illustrate the performance of the present invention, a detailed description is provided in conjunction with an embodiment. Referring to a wind and solar power generation system, a system is constructed as follows... Figure 5 The research example shown is illustrated in Table 1. Specific system parameters are also shown in Table 1.

[0094] Table 1 Figure 5 Parameters of the wind and solar power generation system shown To demonstrate the impact of multi-machine interactive coupling on the controllable boundary, the influence of the output variation of unit 1 on the controllable boundaries of units 2 and 3 is shown on a geometric plane using positive and negative sequence reactive current components as the horizontal and vertical axes. In output condition 1, the three units... 、 、 、 Set to: 1) Unit 1: 0.1 pu, 0 pu, 0.04 pu, 0.23 pu; 2) Unit 2: 0.05 pu, 0 pu, 0.03 pu, 0.11 pu; 3) Unit 3: 0.01pu, 0pu, 0.17pu, 0.22pu.

[0095] Output condition 2 involves changing the output of unit 1 to 0.45 pu, 0 pu, 0.64 pu, and 0.43 pu. Under these two output conditions, Figure 10 The controllable boundary changes of units 2 and 3 are given. Figure 10 In the diagram, the boundary line DVO represents the active power fluctuation boundary. These represent the peak current boundaries of phases a, b, and c, respectively. These represent the voltage boundaries of phases a, b, and c, respectively. It is a multi-machine voltage distribution boundary that takes into account the interaction and coupling of multiple machines and the law of disturbance propagation. SS represents the synchronous, stable and controllable boundary line. PSRC represents the positive sequence reactive current and NSRC represents the negative sequence reactive current. Figure 10 This indicates that increasing the output of unit 1 will cause the voltage controllable boundary line of units 2 and 3 to shift inward, thereby reducing the controllable area of ​​units 2 and 3. This is consistent with the theoretical analysis and proves that the multi-machine interaction coupling in a multi-machine system will affect the controllable boundary of each unit.

[0096] To demonstrate the difference between the proposed theory and existing theories, taking Unit 2 as an example, the controllable regions of both theories are shown on the geometric plane, such as... Figure 11 As shown. Figure 11 In this study, existing theories do not consider the effects of interactive coupling and disturbance propagation, calculating the controllable region as the sum of the blue, yellow, and pink regions, which is significantly larger than the actual controllable region of the unit. The optimal control point coordinates calculated by existing theories are (1.08, 0.13), while the actual optimal control point coordinates should be (0.66, 0.55), showing a significant deviation. Therefore, under the guidance of existing theories, the positive-sequence reactive power output of each unit is too large, and the negative-sequence reactive power is too small, which may lead to overvoltage in some non-faulty phases of certain nodes. This will be quantitatively demonstrated in the next section.

[0097] To demonstrate the effectiveness of the proposed optimal control trajectory, within the controllable region defined by the proposed theory, the amplitude of the fault phase voltage (phase b) corresponding to different control point coordinates is shown, such as... Figure 12 As shown. From Figure 12 As can be seen from the contour lines, within the controllable region, the trajectory indicated by the red arrow represents the fastest rising path on the fault phase voltage amplitude plane, with a final voltage amplitude of 1.1 pu, precisely corresponding to the upper limit of voltage safety, thus verifying the accuracy of the proposed theoretical calculations. Therefore, under the condition of limited controllable capacity, the fault phase voltage can be raised with maximum efficiency along the proposed control trajectory. In contrast, existing methods mostly passively allocate reactive power commands based on the ratio of positive and negative sequence voltage drops at the fault point, rather than achieving a solution that optimally supports transient voltage. In summary, the innovation and correctness of the proposed theory have been proven.

[0098] To demonstrate the advantages of the proposed control strategy, this section compares it with traditional engineering field methods and existing literature methods. Under the fault conditions described in 4.1, the performance of the three methods is as follows: Figures 13-15 As shown. Among them, Figure 13 The three-phase voltage amplitudes (a, b, c) at 0.38kV and 35kV at the grid connection points of the three units are given. Figure 14 The positive and negative sequence voltage amplitudes at the grid connection points of the three units are given. Figure 11 The relationships between the output three-phase current amplitude, active power fluctuation amplitude, and negative sequence reactive current value of Unit 2 under the proposed method and the corresponding three types of controllable boundaries are presented. Table 1 comprehensively compares the transient voltage support performance of the proposed method and existing literature methods under different fault conditions. Figure 13It can be seen that traditional engineering methods do not consider the controllable boundaries of each unit, and only use a fixed parameter K=1.5 for droop control, which cannot effectively raise the voltage of the fault phase. The controllable boundary analysis of existing literature methods is incomplete, ignoring the influence of multi-machine interaction coupling and disturbance propagation laws, resulting in excessive positive-sequence reactive power output of each unit. The voltage amplitudes of the 35kV side c-phase of unit 1 and unit 3 reached 1.17pu and 1.21pu, respectively, exceeding the limit by 6.4% and 10.0%; unit 2 has the farthest electrical distance from the fault point, and the impact is the most severe, with the voltage amplitude of the 0.38kV side b-phase reaching 1.13pu, exceeding the limit by 2.7%, and the voltage amplitude of the 35kV side c-phase reaching 1.24pu, exceeding the limit by 12.7%. In contrast, the proposed method is based on more complete controllable boundary modeling, rationally plans the transient reactive power output of each unit, and effectively suppresses local overvoltage. Meanwhile, by using the optimal control trajectory, the fault phase voltage amplitudes of the three units were increased to 0.19 pu, 0.43 pu, and 0.39 pu, respectively, representing improvements of 35.7%, 48.3%, and 50.0% compared to traditional engineering methods, and improvements of 5.6%, 7.5%, and 8.3% compared to methods in existing literature. These results demonstrate that the proposed method not only avoids the risk of local overvoltage but also enhances the fault transient voltage support capability under conditions of limited controllable capacity.

[0099] from Figure 14 It is evident that the proposed method slightly reduces the positive sequence voltage rise compared to existing methods, but significantly suppresses the negative sequence voltage, thus effectively ensuring that the phase voltage of each node in the station does not exceed the limit. Figure 15 The proposed method further demonstrates its real-time detection mechanism for active power fluctuation amplitude, phase current amplitude, and negative sequence current upper limit. Dynamic adjustment terminates when any indicator reaches the safety boundary, and the current command value from the previous calculation cycle is locked. In this example, the phase a current of unit 2 reaches the current peak safety boundary 75ms after the fault occurs, the dynamic adjustment process stops, and the positive and negative sequence current output components remain constant, ensuring that the unit-level boundaries do not exceed limits.

[0100] Table 1, through a comparison of the fault phase voltage amplitude results under various asymmetrical fault conditions, further demonstrates that the proposed method possesses stronger fault transient voltage support capability compared to existing methods. Under conditions of limited controllable capacity, the fault phase voltage amplitude is improved by an average of 11.0%.

[0101] Based on the same inventive concept, according to another aspect of the present invention, such as Figure 3 As shown, an embodiment of the present invention also provides a computer device 30, which includes a processor 310 and a memory 320. The memory 320 stores a computer program 321 that can be run on the processor. When the processor 310 executes the program, it performs the steps of the method described above.

[0102] Based on the same inventive concept, according to another aspect of the present invention, such as Figure 4 As shown, embodiments of the present invention also provide a computer-readable storage medium 40, which stores a computer program 410 that, when executed by a processor, performs the methods described above.

[0103] Embodiments of the present invention may also include a corresponding computer device. The computer device includes a memory, at least one processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes any of the methods described above when executing the program.

[0104] The memory, as a non-volatile computer-readable storage medium, can be used to store non-volatile software programs, non-volatile computer-executable programs, and modules, such as program instructions / modules in the embodiments of this application. The processor executes various functional applications and data processing of the device by running the non-volatile software programs, instructions, and modules stored in the memory, thereby implementing the above-described method.

[0105] The memory may include a program storage area and a data storage area. The program storage area may store the operating system and applications required for at least one function; the data storage area may store data created based on the use of the device. Furthermore, the memory may include high-speed random access memory and non-volatile memory, such as at least one disk storage device, flash memory device, or other non-volatile solid-state storage device. In embodiments, the memory may optionally include memory remotely located relative to the processor, which can be connected to the local module via a network. Examples of such networks include, but are not limited to, the Internet, corporate intranets, local area networks, mobile communication networks, and combinations thereof.

[0106] Finally, it should be noted that those skilled in the art will understand that all or part of the processes in the above embodiments can be implemented by a computer program instructing related hardware. The program can be stored in a computer-readable storage medium, and when executed, it can include the processes of the embodiments of the methods described above. The storage medium for the program can be a magnetic disk, optical disk, read-only memory (ROM), or random access memory (RAM), etc. The above computer program embodiments can achieve the same or similar effects as any of the corresponding foregoing method embodiments.

[0107] Those skilled in the art will also understand that the various exemplary logic blocks, modules, circuits, and algorithm steps described in conjunction with the disclosure herein can be implemented as electronic hardware, computer software, or a combination of both. To clearly illustrate this interchangeability between hardware and software, the functionality of various illustrative components, blocks, modules, circuits, and steps has been generally described. Whether this functionality is implemented as software or as hardware depends on the specific application and the design constraints imposed on the system as a whole. Those skilled in the art can implement the functionality in various ways for each specific application, but such implementation decisions should not be construed as departing from the scope of the embodiments disclosed herein.

[0108] The above are exemplary embodiments disclosed in this invention. However, it should be noted that various changes and modifications can be made without departing from the scope of the embodiments of this invention as defined by the claims. The functions, steps, and / or actions of the methods according to the disclosed embodiments described herein do not need to be performed in any particular order. The sequence numbers of the disclosed embodiments of this invention are for descriptive purposes only and do not represent the superiority or inferiority of the embodiments. Furthermore, although the elements disclosed in the embodiments of this invention may be described or claimed individually, they may be understood as multiple unless the limitation is singular.

[0109] It should be understood that, as used herein, the singular form "one" is intended to include the plural form as well, unless the context clearly supports an exception. It should also be understood that, as used herein, "and / or" refers to any and all possible combinations of one or more of the associated listed items.

[0110] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the invention (including the claims) is limited to these examples. Within the framework of the invention, technical features of the above embodiments or different embodiments can be combined, and many other variations of different aspects of the invention exist, which are not provided in the details for the sake of brevity. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the invention should be included within the protection scope of the invention.

Claims

1. A multi-machine cooperative fault-crossing control method based on a controllable fault boundary, characterized in that, include: The multi-unit topology and data of each unit of wind and solar power generation are obtained, and a multi-unit fault controllable boundary model is constructed, dividing the fault controllable boundary into a station-level boundary and a unit-level boundary. By performing an internal projection mathematical transformation on the data of each unit using a multi-unit fault controllable boundary model, the decoupled minimum controllable domain of each unit is obtained. In response to a fault, the reactive power of each unit is centrally allocated according to the station-level boundary; In response to a fault, each unit independently and adaptively adjusts its output based on the unit-level boundary and the decoupled minimum controllable domain.

2. The multi-machine cooperative fault ride-through control method based on a controllable fault boundary as described in claim 1, characterized in that, The process of acquiring the multi-unit topology and data of each unit in wind and solar power generation, and constructing a multi-unit fault controllable boundary model includes: Based on the typical topology of wind and solar power generation system, the equivalent impedance on the grid side is measured and the switching status and active power output of each unit in the power station are collected as data for each unit. A framework for constructing a multi-machine fault controllable boundary model is established by inputting the multi-machine topology of wind and solar power generation and the data of each unit into the framework of the multi-machine fault controllable boundary model to obtain the corresponding multi-machine fault controllable boundary model.

3. The multi-machine cooperative fault-crossing control method based on a controllable fault boundary as described in claim 2, characterized in that, The process of performing an internal projection mathematical transformation on the data of each unit using a multi-unit fault controllable boundary model to obtain the decoupled minimum controllable domain of each unit includes: Calculate the data of each unit, update the positive and negative sequence voltage control commands of each unit during fault ride according to the switching status of the units, calculate the droop control coefficient during fault ride according to the equivalent impedance of the grid side, and calculate the reactive power coordination ratio of each unit during fault ride and the upper limit of negative sequence reactive current that each unit can generate to maintain synchronous stability during fault ride according to the active power output. The positive and negative sequence voltage control commands, droop control coefficients, reactive power coordination ratios, and negative sequence reactive current upper limits during fault ride-through are transformed into the corresponding projection space by inscribed projection with the preset projection matrix. Based on the fault controllable boundary, the decoupled minimum controllable domain of each unit is divided in the projection space.

4. The multi-machine cooperative fault ride-through control method based on a controllable fault boundary as described in claim 1, characterized in that, The response is to centrally allocate reactive power to each unit according to the station-level boundary before the fault occurs; In response to the occurrence of a fault, the reactive power that each unit needs to output is calculated based on the preset grid voltage regulation requirements and the station-level boundary. The reactive power output of all units in the field is allocated based on the calculation results.

5. The multi-machine cooperative fault ride-through control method based on a controllable fault boundary as described in claim 1, characterized in that, In response to a fault, each unit independently and adaptively adjusts its output based on the unit-level boundary. In response to the occurrence of a fault, each unit independently detects the voltage drop and enters the fault ride-through control mode, controlling the positive-sequence reactive component and the negative-sequence reactive component respectively, and generating control commands for the positive-sequence and negative-sequence reactive current components. The positive sequence active current component control command is calculated based on the positive sequence and negative sequence reactive current component control commands. The negative sequence active current component control command is set to 0; All control commands are input into the unit's internal current loop to adaptively adjust the output.

6. The multi-machine cooperative fault ride-through control method based on a controllable fault boundary as described in claim 1, characterized in that, The site-level boundary includes the minimum controllable domain of the voltage distribution boundary, which is independent of fault parameters, and the synchronous stability boundary equation. Unit-level boundaries include peak current boundaries and active power fluctuation boundaries, which are strongly correlated with fault parameters.

7. The multi-machine cooperative fault ride-through control method based on a controllable fault boundary as described in claim 5, characterized in that, The formula for the positive-sequence reactive component control strategy is as follows: ； The formula for the negative-sequence reactive power component control strategy is: ； In the formula, This indicates the positive sequence voltage control commands for each unit during fault ride-through. This indicates the negative sequence voltage control command during fault ride-through for each unit. , These represent the positive and negative sequence virtual voltage values ​​within the controller at time t, respectively; Δt represents the hardware operation interval. This is the droop control coefficient. This represents the upper limit of negative sequence reactive current. This is the upper limit of positive sequence reactive current. Positive sequence reactive current component control command. Negative sequence reactive current component control command.

8. A multi-machine cooperative fault ride-through control system based on a controllable fault boundary, characterized in that, include: The acquisition unit is configured to acquire the multi-unit topology and data of each unit of wind and solar power generation, and to construct a multi-unit fault controllable boundary model, dividing the fault controllable boundary into a station-level boundary and a unit-level boundary. The decoupling unit is configured to perform an internal projection mathematical transformation on the data of each unit through a multi-machine fault controllable boundary model to obtain the decoupling minimum controllable domain of each unit. A centralized control unit is configured to, in response to a failure, centrally allocate reactive power to each unit according to the station-level boundary. An independent control unit is configured to independently and adaptively adjust the output of each unit based on the unit-level boundary and the decoupled minimum controllable domain in response to a fault.

9. A computer device, comprising: At least one processor; And a memory storing a computer program executable on the processor, characterized in that, when the processor executes the program, it performs the steps of the multi-machine cooperative fault-crossing control method based on a fault-controllable boundary as described in any one of claims 1 to 7.

10. A computer-readable storage medium storing a computer program, characterized in that, When the computer program is executed by the processor, it performs the steps of the multi-machine cooperative fault-crossing control method based on fault-controllable boundaries as described in any one of claims 1 to 7.

Images