Short-circuit ratio margin-based capacity configuration method and system for network construction type converter

Abstract

The invention discloses a short-circuit ratio margin-based capacity configuration method and system for a network construction type converter, and belongs to the technical field of new energy grid connection, and the method comprises the steps: constructing a network construction type converter system model, and obtaining a station critical short-circuit ratio; calculating the current short-circuit ratio of the station according to the alternating-current system short-circuit capacity and the grid-connected equipment capacity; setting a target short-circuit ratio margin of the station grid-connected system, calculating and comparing a current short-circuit ratio margin, and if the current short-circuit ratio margin is not less than the target short-circuit ratio margin, indicating that the stable requirement is met; otherwise, based on the target short-circuit ratio margin meter, calculating a corrected short-circuit ratio satisfying the short-circuit ratio margin; and based on the corrected short-circuit ratio, calculating the total capacity of the required network construction type converter. According to the method, the problem that quantitative capacity calculation is lacked for configuration of the network construction type converter for the network following type new energy station in the prior art is solved.

Description

Technical Field

[0001] The present invention belongs to the field of small disturbance stability analysis of renewable energy power generation, and specifically relates to a capacity configuration method and system for a grid-type converter based on short-circuit ratio margin. Background Art

[0002] Grid-following renewable energy adopts phase-locked synchronous grid connection, and the risk of subsynchronous oscillation occurs when the station is connected to the weak grid through long-distance lines and multi-stage transformers; while grid-building renewable energy is based on power synchronization control and is more adaptable under weak grids. It can be considered to configure a certain capacity in traditional renewable energy stations to improve the subsynchronous stability of small disturbances. At present, there is little research on the quantitative configuration of grid-building converters in traditional renewable energy stations.

[0003] The short circuit ratio (SCR) and its related indicators calculated from the short circuit capacity of the AC system and the capacity of the grid-connected equipment can reflect the relative strength of the grid-connected AC system of power electronic equipment such as converters. Currently, they have been used to assess the potential risks of subsynchronous oscillations caused by AC / DC interactions in weak AC systems. The short circuit ratio indicator is strongly correlated with the grid connection impedance of the converter and the converter capacity. As the grid-side connection impedance increases and the converter capacity increases, the short circuit ratio decreases and the subsynchronous oscillation risk increases.

[0004] Regarding the problem of configuring grid-connected converters, there are several existing studies:

[0005] 1. The patent with application number CN202410010304.X discloses a method and system for optimizing the location and configuration of a grid-type energy storage power station, which specifically includes: setting constraints for conventional units and energy storage power stations; under the constraints, establishing a joint optimization model of conventional units and energy storage power stations, including an inner optimization model and an outer optimization model; solving the inner optimization model to obtain the optimal operating cost, substituting the optimal operating cost into the outer optimization model, and using a particle swarm algorithm to solve the outer optimization model to obtain the optimized energy storage configuration capacity; setting a fixed number of iterations, when the current number of iterations is less than the fixed number of iterations, feeding back the solution result of the outer optimization model to the inner optimization model, updating the energy storage configuration capacity until the current number of iterations is equal to the fixed number of iterations, and obtaining the optimal energy storage configuration capacity; calculating the standard deviation of the inertia constant of the regional power grid according to the optimal energy storage configuration capacity, and when the standard deviation is the smallest, obtaining the optimal configuration position of the grid-type energy storage power station. However, this invention mainly optimizes the capacity configuration of the grid-type energy storage based on the system operating cost. After obtaining the capacity optimization configuration result, it optimizes the site selection based on the regional inertia constant. It ignores the relationship between the size of the grid-type energy storage capacity and the system stability, and cannot provide an optimized capacity configuration plan for weak power grid conditions.

[0006] 2. The patent with application number CN202311736349.7 discloses a current limiting control system and method for a grid-type converter, including: step S1, analyzing the voltage source characteristics of the grid-type converter according to the maximum singular value index of the impedance matrix, and establishing a voltage source-equivalent internal reactance circuit model of the grid-type converter; step S2, using the generalized short-circuit ratio to quantify the small-disturbance stability of the hybrid grid system of the grid-type and grid-following converters, and obtaining the small-disturbance stability of the hybrid grid system of the grid-type and grid-following converters. Qualitative indicators; Step S3, according to the established voltage source-equivalent internal reactance circuit model, to correct the small disturbance stability index of the hybrid power grid system of the grid-forming and grid-following type converters, and obtain the analytical relationship between the capacity ratio of the grid-forming and grid-following type converters and the generalized short-circuit ratio; Step S4, according to the analytical relationship between the capacity ratio of the grid-forming and grid-following type converters and the generalized short-circuit ratio, obtain the estimation method of the capacity ratio of the grid-forming and grid-following type converters, and the recommended value of the capacity ratio of the grid-forming and grid-following type converters in typical scenarios. However, the invention estimates the capacity ratio of the grid-following type and grid-forming type converters based on the small disturbance stability index, but lacks clear quantitative standards for the capacity configuration method of the grid-forming type converter, especially when the power grid strength is low, and lacks consideration of the precise capacity configuration plan. Summary of the invention

[0007] In view of the shortcomings of existing research, the purpose of the present invention is to provide a capacity configuration method and system for a grid-connected converter based on a critical short-circuit ratio, which can better improve the sub-synchronous stability of new energy stations under weak power grids, and solve the problem in the prior art of lack of quantitative calculation capacity for configuring a grid-connected converter for grid-connected new energy stations.

[0008] The purpose of the present invention can be achieved through the following technical solutions:

[0009] In order to achieve the above object, the first aspect of the present invention proposes a network type variation based on short circuit ratio margin, including the following contents:

[0010] Construct a grid-connected converter system model and obtain the critical short-circuit ratio CSCR of the station;

[0011] Calculate the current short-circuit ratio SCR of the station based on the short-circuit capacity of the AC system and the capacity of the grid-connected equipment;

[0012] Set the target short-circuit ratio margin β0% of the station grid-connected system, calculate the current short-circuit ratio margin β% and compare them. If the current short-circuit ratio margin β% is not less than the target short-circuit ratio margin β0%, it indicates that the stability demand has been met; otherwise, based on the target short-circuit ratio margin β0%, calculate the corrected short-circuit ratio SCR′ that meets the short-circuit ratio margin;

[0013] Based on the corrected short-circuit ratio SCR′, calculate the total capacity of the required grid-connected converter

[0014] Preferably, the control strategy of the grid-connected converter in the system model is power outer loop control, and the voltage amplitude and phase angle are generated by the power outer loop.

[0015] Preferably, the control parameters of the grid-connected converter are acquired, and the critical short circuit ratio CSCR is obtained by analysis or black box testing.

[0016] Preferably, the current short-circuit ratio SCR is calculated by the short-circuit capacity of the AC system and the capacity of the grid-connected equipment. The calculation formula of the short-circuit ratio SCR of a single device is:

[0017]

[0018] The SCR calculation formula for multi-device station grid connection is:

[0019]

[0020] Among them, S PCC is the short-circuit capacity at the AC grid connection point, U g is the system rated voltage, Z g S is the sum of the transformer impedance and the tie line impedance of the converter connected to the grid. GFL is the capacity of a single grid-connected converter, and n is the number of grid-connected converters connected to the system.

[0021] Preferably, the current system short circuit ratio margin can be calculated from the relative relationship between the current short circuit ratio SCR and the critical short circuit ratio CSCR, and the formula is:

[0022]

[0023] Among them, β% is the current system short-circuit ratio margin, SCR is the current short-circuit ratio, and CSCR is the critical short-circuit ratio.

[0024] Preferably, the target short-circuit ratio margin β0% is set to 20%.

[0025] Preferably, the corrected short circuit ratio is calculated based on the target short circuit ratio margin, specifically:

[0026]

[0027] Among them, β0% is the target short-circuit ratio margin, SCR′ is the corrected short-circuit ratio, and CSCR is the critical short-circuit ratio.

[0028] Preferably, the total capacity of the required grid-connected converter is calculated based on the corrected short-circuit ratio, specifically:

[0029] Based on the corrected short-circuit ratio, the number of grid-connected converters N connected to the system is calculated, and the total capacity of the grid-connected converters required is calculated using the following formula:

[0030]

[0031] Among them, S GFM is the capacity of a single grid-connected converter. is the total capacity of the required grid-connected converter.

[0032] Preferably, the number N of grid-connected converters connected to the system is calculated based on the corrected short-circuit ratio, specifically:

[0033] The calculation formula for the short-circuit ratio of multiple grid-connected converters is:

[0034]

[0035] The formula for calculating the number N of grid-connected converters connected to the system is:

[0036]

[0037] Among them, SCR′ is the corrected short-circuit ratio, Zn is the grid-side line impedance, Un is the main grid-side voltage, and Z GFM is the transient reactance of the grid-type converter under the overcurrent constraint of a single grid-type converter, n is the number of grid-type converters connected to the system; where S GFM The capacity of a grid-type converter for a single access system.

[0038] The second aspect of the present invention provides a capacity configuration system for a grid-type converter based on a short-circuit ratio margin using the method described in the first aspect of the present invention, comprising: a critical short-circuit ratio acquisition module, which obtains the critical short-circuit ratio of a station by analytical calculation of specific control parameters provided by the equipment manufacturer or by performing a black box test, and is characterized in that:

[0039] Actual short-circuit ratio calculation module, the actual short-circuit ratio is calculated by the short-circuit capacity of the AC system and the capacity of the grid-connected equipment;

[0040] The actual stability margin compliance judgment module selects a suitable short-circuit ratio margin, calculates the current short-circuit ratio margin for comparison, and determines whether the actual stability margin meets the standard;

[0041] The actual short-circuit ratio correction module calculates the actual short-circuit ratio required after correction if the actual stability margin compliance judgment module determines that the compliance is not met;

[0042] The network capacity calculation module calculates the required total network capacity based on the corrected actual short-circuit ratio.

[0043] The third aspect of the present invention proposes an electronic device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor. When the computer program is loaded into the processor, the method for configuring the capacity of a grid-connected converter based on short-circuit ratio margin as described in the first aspect of the present invention is implemented.

[0044] The fourth aspect of the present invention proposes a computer-readable storage medium, which stores a computer program. When the computer program is executed by a processor, it implements the method for configuring the capacity of a grid-type converter based on short-circuit ratio margin as described in the first aspect of the present invention.

[0045] The present invention has the following beneficial effects:

[0046] 1. The present invention proposes a method and system for configuring the capacity of a grid-type converter based on a short-circuit ratio margin. By selecting a suitable short-circuit ratio margin to correct the actual short-circuit ratio, the grid-type capacity is quantitatively calculated, which solves the problem of quantitatively configuring the capacity of a grid-type converter in a new energy station in the prior art. Based on the proposed capacity calculation process, the grid-type configuration capacity under the required short-circuit ratio margin can be obtained, thereby improving the stability margin of the station grid-connected system under the sub-synchronous frequency band;

[0047] 2. Compared with other grid-connected converter configuration methods, the target short-circuit ratio margin is selected by selecting the set selection rules, which can more effectively and quantitatively improve the station stability margin and reduce the risk of subsynchronous oscillation. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 This is the main circuit topology of a grid-connected photovoltaic power station;

[0049] Figure 2 Time domain simulation waveform for grid-connected photovoltaic stations;

[0050] Figure 3 To configure the main circuit topology after the grid-type converter;

[0051] Figure 4 Time domain simulation waveform after quantitative configuration of grid-type converter;

[0052] Figure 5 It is the main circuit and control structure diagram of the grid-connected converter;

[0053] Figure 6 It is a flow chart of the present invention. DETAILED DESCRIPTION

[0054] In order to make the purpose, technical scheme and advantages of the present invention clearer, the technical scheme of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. The embodiments described in this application are only embodiments of a part of the present invention, rather than all embodiments. Based on the spirit of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work belong to the protection scope of the present invention.

[0055] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the accompanying drawings in the embodiments of the present invention.

[0056] Embodiment 1 of the present invention proposes a method for configuring the capacity of a grid-type converter based on a short-circuit ratio margin. Referring to a photovoltaic power station in Tibet, a total of 32 grid-type converters are set up with a rated capacity of 1260kW. Through a box-type transformer with a capacity of 1250kW, three 35kV collector lines are collected to a 110kV booster station, and one overhead line is sent to a 110kVkV substation. The total installed capacity is 40MW. The station topology is as follows: Figure 1 As shown. The line impedance Zg is 0.01mH. Set the simulation time to 3s, the simulation step to 1 / 32000s, the initial state is 10% rated power delivery, and it switches to rated power delivery at 3s. The three-phase voltage V abc The simulation waveforms of active power P and reactive power Q are shown in Figure 2 Under this grid strength, the grid-type converter station cannot deliver rated power under the constraint of small disturbance subsynchronous oscillation, and the delivery capacity is insufficient, resulting in power loss. It is necessary to configure the grid-type converter quantitatively. The station topology after configuring the grid-type converter is as follows: Figure 1 As shown, Figure 6 The following are shown:

[0057] Construct a grid-connected converter system model and obtain the critical short-circuit ratio CSCR of the station.

[0058] Preferably, if Figure 5 As shown, the control strategy of the grid-type converter in the system model is power outer loop control, and the voltage amplitude and phase angle are generated by the power outer loop.

[0059] Preferably, the control parameters of the grid-connected converter are acquired, and the critical short circuit ratio CSCR is obtained by analysis or black box testing.

[0060] Specifically, the critical short circuit ratio CSCR of the station measured in this embodiment is 1.417.

[0061] The current short circuit ratio SCR of the station is calculated based on the short circuit capacity of the AC system and the capacity of the grid-connected equipment. Preferably, the short circuit ratio SCR is calculated based on the short circuit capacity of the AC system and the capacity of the grid-connected equipment, and the calculation formula for the short circuit ratio SCR of a single device is:

[0062]

[0063] The SCR calculation formula for multi-device station grid connection is:

[0064]

[0065] Among them, S PCC is the short-circuit capacity at the AC grid connection point, U g is the system rated voltage, Z g is the sum of the transformer impedance and the tie line impedance of the converter connected to the grid, S GFL is the capacity of a single grid-connected converter, and n is the number of grid-connected converters connected to the system.

[0066] Specifically, the station short circuit ratio SCR calculated in this embodiment is 1.19.

[0067] Preferably, the current system short circuit ratio margin can be calculated from the relative relationship between the current short circuit ratio SCR and the critical short circuit ratio CSCR, and the formula is:

[0068]

[0069] Among them, β% is the current system short-circuit ratio margin, SCR is the current short-circuit ratio, and CSCR is the critical short-circuit ratio.

[0070] Specifically, the β% calculated in this embodiment is -19%.

[0071] Set the target short-circuit ratio margin β0% of the station grid-connected system, calculate the current short-circuit ratio margin β% and compare them. If the current short-circuit ratio margin β% is not less than the target short-circuit ratio margin β0%, it indicates that the stability requirement has been met; otherwise, based on the target short-circuit ratio margin β0%, calculate the corrected short-circuit ratio SCR′ that meets the short-circuit ratio margin.

[0072] Preferably, the target short-circuit ratio margin β0% is set to 20%.

[0073] Preferably, the corrected short circuit ratio is calculated based on the target short circuit ratio margin, specifically:

[0074]

[0075] Among them, β0% is the target short-circuit ratio margin, SCR′ is the corrected short-circuit ratio, and CSCR is the critical short-circuit ratio.

[0076] Specifically, the calculated short-circuit ratio SCR′ after the calculated network-type access correction should be 1.77.

[0077] Based on the corrected short-circuit ratio SCR′, calculate the total capacity of the required grid-connected converter

[0078] Preferably, the total capacity of the required grid-connected converter is calculated based on the corrected short-circuit ratio, specifically:

[0079] Based on the corrected short-circuit ratio, the number of grid-connected converters N connected to the system is calculated, and the total capacity of the grid-connected converters required is calculated using the following formula:

[0080]

[0081] Among them, S GFM is the capacity of a single grid-connected converter. is the total capacity of the required grid-connected converter.

[0082] Preferably, the number N of grid-connected converters connected to the system is calculated based on the corrected short-circuit ratio, specifically:

[0083] The calculation formula for the short-circuit ratio of multiple grid-connected converters is:

[0084]

[0085] The formula for calculating the number N of grid-connected converters connected to the system is:

[0086]

[0087] Among them, SCR′ is the corrected short-circuit ratio, Zn is the grid-side line impedance, Un is the main grid-side voltage, and Z GFM is the transient reactance of the grid-type converter under the overcurrent constraint of a single grid-type converter, n is the number of grid-type converters connected to the system; where S GFM The capacity of a grid-type converter for a single access system.

[0088] Specifically, the capacity of a single grid-connected converter in this embodiment is 1.25MW. Figure 3 As shown. The equivalent output impedance under short-circuit fault is 0.16mH after test. After calculation and rounding, the required capacity is 8 1.25MW grid-type converters. The corrected calculated short-circuit ratio is 1.78, which meets the requirements. At this time, the capacity of grid-type converters in the station accounts for 20%. Time domain simulation is performed, and the simulation waveform is shown in Figure 4 , verifying the effectiveness of capacity configuration. Embodiment 2 of the present invention proposes a capacity configuration system for a grid-type converter based on short-circuit ratio margin using the method described in Embodiment 1 of the present invention, comprising: a critical short-circuit ratio acquisition module, which obtains the critical short-circuit ratio of the station through analytical calculation of specific control parameters provided by the equipment manufacturer or black box testing, characterized in that;

[0089] Actual short-circuit ratio calculation module, the actual short-circuit ratio is calculated by the short-circuit capacity of the AC system and the capacity of the grid-connected equipment;

[0090] The actual stability margin compliance judgment module selects a suitable short-circuit ratio margin, calculates the current short-circuit ratio margin for comparison, and determines whether the actual stability margin meets the standard;

[0091] The actual short-circuit ratio correction module calculates the actual short-circuit ratio required after correction if the actual stability margin compliance judgment module determines that the compliance is not met;

[0092] The network capacity calculation module calculates the required total network capacity based on the corrected actual short-circuit ratio.

[0093] Embodiment 3 of the present invention proposes an electronic device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor. When the computer program is loaded into the processor, the method for configuring the capacity of a grid-type converter based on short-circuit ratio margin described in Embodiment 1 of the present invention is implemented.

[0094] Embodiment 4 of the present invention proposes a computer-readable storage medium, which stores a computer program. When the computer program is executed by a processor, it implements the method for configuring the capacity of a grid-type converter based on short-circuit ratio margin described in Embodiment 1 of the present invention.

[0095] The above descriptions are only some specific implementation methods of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical solutions and inventive concepts of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A capacity configuration method for a grid-connected converter based on short-circuit ratio margin, characterized in that: It includes the following: Construct a grid-connected converter system model and obtain the critical short-circuit ratio CSCR of the station; Calculate the current short-circuit ratio SCR of the station based on the short-circuit capacity of the AC system and the capacity of the grid-connected equipment; Set the target short-circuit ratio margin β0% of the station grid-connected system, calculate the current short-circuit ratio margin β% and compare them. If the current short-circuit ratio margin β% is not less than the target short-circuit ratio margin β0%, it indicates that the stability demand has been met; otherwise, based on the target short-circuit ratio margin β0%, calculate the corrected short-circuit ratio SCR′ that meets the short-circuit ratio margin; Based on the corrected short-circuit ratio SCR′, calculate the total capacity of the required grid-connected converter 2. A method for configuring the capacity of a grid-connected converter based on short-circuit ratio margin according to claim 1, characterized in that: The control strategy of the grid-connected converter in the system model is power outer loop control, and the voltage amplitude and phase angle are generated by the power outer loop.

3. The method for configuring the capacity of a grid-connected converter based on short-circuit ratio margin according to claim 1, characterized in that: The control parameters of the grid-connected converter are obtained, and the critical short circuit ratio CSCR is obtained through analysis or black box testing.

4. A method for configuring the capacity of a grid-connected converter based on short-circuit ratio margin according to claim 3, characterized in that: The current short-circuit ratio SCR is calculated by the short-circuit capacity of the AC system and the capacity of the grid-connected equipment. The calculation formula of the short-circuit ratio SCR of a single device is: The SCR calculation formula for multi-device station grid connection is: Among them, S PCC is the short-circuit capacity at the AC grid connection point, U g is the system rated voltage, Z g S is the sum of the transformer impedance and the tie line impedance of the converter connected to the grid. GFL is the capacity of a single grid-connected converter, and n is the number of grid-connected converters connected to the system.

5. A method for configuring the capacity of a grid-connected converter based on short-circuit ratio margin according to claim 4, characterized in that: The current system short circuit ratio margin can be calculated from the relative relationship between the current short circuit ratio SCR and the critical short circuit ratio CSCR, and the formula is: Among them, β% is the current system short-circuit ratio margin, SCR is the current short-circuit ratio, and CSCR is the critical short-circuit ratio.

6. The method for configuring the capacity of a grid-connected converter based on short-circuit ratio margin according to claim 1, characterized in that: The target short-circuit ratio margin β0% is set to 20%.

7. A method for configuring the capacity of a grid-connected converter based on short-circuit ratio margin according to claim 6, characterized in that: The corrected short circuit ratio is calculated based on the target short circuit ratio margin, specifically: Among them, β0% is the target short-circuit ratio margin, SCR′ is the corrected short-circuit ratio, and CSCR is the critical short-circuit ratio.

8. A method for configuring the capacity of a grid-connected converter based on short-circuit ratio margin according to claim 7, characterized in that: The total capacity of the required grid-connected converter is calculated based on the corrected short-circuit ratio, specifically: Based on the corrected short-circuit ratio, the number of grid-connected converters N connected to the system is calculated, and the total capacity of the grid-connected converters required is calculated using the following formula: Among them, S GFM is the capacity of a single grid-connected converter. is the total capacity of the required grid-connected converter.

9. A method for configuring the capacity of a grid-connected converter based on short-circuit ratio margin according to claim 8, characterized in that: The number N of grid-connected converters connected to the system is calculated based on the corrected short-circuit ratio, specifically: The calculation formula for the short-circuit ratio of multiple grid-connected converters is: The formula for calculating the number N of grid-connected converters connected to the system is: Among them, SCR′ is the corrected short-circuit ratio, Zn is the grid-side line impedance, Un is the main grid-side voltage, and Z GFM is the transient reactance of the grid-type converter under the overcurrent constraint of a single grid-type converter, n is the number of grid-type converters connected to the system; where S GFM The capacity of a grid-type converter for a single access system.

10. A capacity configuration system for a grid-connected converter based on short-circuit ratio margin using the method according to any one of claims 1 to 9, comprising: The critical short-circuit ratio acquisition module obtains the critical short-circuit ratio of the station through analytical calculation of specific control parameters provided by the equipment manufacturer or black box testing. It is characterized by: Actual short-circuit ratio calculation module, the actual short-circuit ratio is calculated by the short-circuit capacity of the AC system and the capacity of the grid-connected equipment; The actual stability margin compliance judgment module selects a suitable short-circuit ratio margin, calculates the current short-circuit ratio margin for comparison, and determines whether the actual stability margin meets the standard; The actual short-circuit ratio correction module calculates the actual short-circuit ratio required after correction if the actual stability margin compliance judgment module determines that the compliance is not met; The network capacity calculation module calculates the required total network capacity based on the corrected actual short-circuit ratio.

11. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that: When the computer program is loaded into a processor, the method for configuring the capacity of a grid-connected converter based on short-circuit ratio margin according to any one of claims 1 to 9 is implemented.

12. A computer-readable storage medium storing a computer program, characterized in that: When the computer program is executed by a processor, a capacity configuration method for a grid-type converter based on a short-circuit ratio margin is implemented according to any one of claims 1 to 9.

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