Optimal configuration method of grid-connected new energy considering power electronic transient support limit

Abstract

The application discloses a new energy grid-connected optimal configuration method considering power electronic transient support limits, belongs to the technical field of power system analysis, and comprises the following steps: step 1, evaluating the physical limits and control saturation limits of converter voltage, current, power and other electrical quantities to obtain a maximum working interval; and step 2, finding main factors influencing the transient stability of the converter by comprehensively considering the physical and control limits and comparison, wherein the optimal method proposed in the application considers the fundamental limiting factors influencing the transient support capability of the converter, solves the deficiency that the idealized results are caused by the fact that the converter support capability limits are not considered in the conventional new energy grid optimal configuration method, and makes the analysis results more consistent with the actual operation of the power grid.

Description

Technical Field

[0001] This invention relates to the field of power system analysis technology, specifically to a method for optimizing the grid connection of new energy sources considering the transient support limits of power electronics. Background Technology

[0002] Unlike traditional synchronous generator sets, new energy generator sets are connected to the grid through power electronic devices. Conventional power electronic devices usually need to feed power into the grid based on the grid voltage, which cannot provide the necessary support for the grid. Therefore, a high proportion of new energy access reduces the grid's inertia, damping, and voltage stability.

[0003] The aforementioned stability issues are essentially determined by the characteristics of power electronic control. Therefore, appropriate improvements to the control can enable the converter to provide certain grid support functions, such as droop control, virtual synchronous machine control, or various grid-type control. However, the essential factor restricting power electronic converter equipment is the overload capacity of the devices.

[0004] Power electronic equipment typically operates within a voltage and current tolerance range, which is related to the equipment's physical parameters and controller stability. To ensure the normal operation of power electronic equipment, voltage or current limiting saturation circuits are generally added to the converter's control loop to limit potential impacts during transient regulation and protect the converter equipment. However, this also limits the grid-connected converter's transient support performance to the power grid. Figure 1 The diagram illustrates the general topology and control principle of a renewable energy converter connected to the grid. Renewable energy power is fed into the inverter circuit via the DC side, and the inverted AC power is fed into the grid through the grid connection line. To protect the inverter, its hardware circuit protection includes voltage or current protection for both the DC and AC sides. The corresponding controllers include typical voltage and current controllers. Since the controller's adjustment signals ultimately serve as switching signals for the inverter circuit, controlling the inverter's output voltage or current, voltage or current limiting must be added to the controller to restrict its output within a reasonable range. This can be considered part of the software protection. The aforementioned circuit and controller limitations are factors to consider in the actual operation of renewable energy grid connection.

[0005] Due to differences in physical structure, the overload capacity of general power electronics is far lower than that of synchronous generators. Most current optimization problems for renewable energy sources are idealistic and primarily focus on steady-state conditions, assuming that renewable energy sources will always operate normally or provide the necessary functions. However, power electronic equipment is often more prone to instability or grid disconnection during transients. Therefore, assessing its transient support capabilities and optimizing its configuration are crucial for the safe and stable operation of the system. Current research in this area is insufficient. System planning needs to fully consider the transient support limits of converters to better reflect reality and ensure the safe and stable operation of renewable energy sources. Summary of the Invention

[0006] The purpose of this invention is to provide a method for optimizing the grid connection of new energy sources that takes into account the transient support limits of power electronics, so as to solve the problems mentioned in the background art.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] A method for optimizing grid-connected configuration of new energy sources considering the transient support limit of power electronics includes the following steps:

[0009] Step 1: Evaluate the physical limitations and control saturation limitations of electrical quantities such as voltage, current, and power of the converter to obtain the maximum operating range;

[0010] Step 2: By comprehensively considering and comparing physical and control limits, identify the main factors affecting the transient stability of the converter;

[0011] Step 3: Perform time-domain simulation calculations using different control stability constraints to analyze the key frequency and voltage indicators of the new energy power grid;

[0012] Step 4: Optimize the access ratio or location of new energy sources or converters based on comprehensive stability indicators.

[0013] As a further technical solution of the present invention: the physical limitations of the converter mainly include the short-time voltage withstand value u of the power electronic equipment. max Current withstand value i max and the maximum permissible overload power S for short time max These physical limitations should be necessary hardware protection parameters to ensure that the converter is not damaged.

[0014] As a further technical solution of the present invention: the saturation limitation in the converter control loop includes voltage and current limitations in the control loop. These limits vary slightly depending on the control type, but typically both the DC and AC control outputs are limited. The limitation in the controller is manifested as a limiting element; the controller output is limited after reaching the set limit value. Therefore, it is necessary to appropriately set the voltage and current limits in the power electronic control. The voltage limits on the DC and AC sides are respectively set to u. sd0 and u sa0 The current limiting on the DC side and the AC side are respectively set to i. sd0 and i sa0 .

[0015] As a further technical solution of the present invention: combining the specific converter circuit topology and control method, and referring to operating experience, the physical limitations and control stability limits of the converter are clarified, and the maximum operating range f(u) is initially determined. max )∩f(i max )∩f(S max )∩f(u sd0 )∩f(u sa0 )∩f(i sd0 )∩f(i sa0 The operating range is represented as the functional relationship f of the corresponding parameters.

[0016] As a further technical solution of the present invention: the transient influencing factor analysis mainly involves analyzing the main factors affecting the transient stability of the converter through two major aspects: physical and control limits. The physical limits can be determined by the factory parameters of power semiconductor devices, capacitors, inductors, and resistors, while the control stability limits are usually not fixed in range. Therefore, based on the preliminary classical control loop stability analysis method, the rationality of different voltage or current limit settings is further analyzed through simulation comparison of a single converter unit.

[0017] As a further technical solution of the present invention: the time-domain simulation calculation refers to establishing a single-machine system simulation model of the converter, setting different voltage and current limits in the control loop, and using the single variable method to study the influence of these main limiting factors on the transient stability characteristics of the converter itself.

[0018] As a further technical solution of the present invention: the single variable method refers to setting the initial value based on the aforementioned maximum operating range of the system, which means that the converter is operating normally and none of the components have reached saturation. Each time, while keeping other limits unchanged, a new voltage or current limit (1+λ)u is set by a step size λ (0<λ<1). sd0 、(1+λ)u sa0 、(1+λ)i sd0 or (1+λ)i sa0A simulation calculation is performed on the power grid model, incorporating load changes or faults to compare key frequency or voltage indicators. Control loop limits with good stability are obtained through parameter optimization methods, and the parameters are then corrected to u. sd1 u sa1 i sd1 i sa1 .

[0019] The frequency index refers to the frequency change rate α and the minimum frequency point β. The frequency change rate is the rate of change of frequency in a short period of time after the load changes, and is defined by equation (1). The minimum frequency point is the minimum value of frequency after the load changes, and is defined by equation (2).

[0020]

[0021] β=max|f t＞0 -f t＝0+ | (2)

[0022] Where t s It is the frequency sampling interval, t s Typical values ​​are 200-300ms.

[0023] The key voltage index refers to the change in voltage amplitude γ, which is defined by equation (3).

[0024]

[0025] Where t r It is the time to eliminate voltage disturbances, i.e., the system recovery time.

[0026] The key frequency and voltage indicators are strongly correlated with the system's inertia, damping, and short-circuit capacity, respectively. The smaller these three indicators are, the better the system stability.

[0027] The parameter optimization method involves comparing the relative magnitudes of the stability indices α, β, and γ in the simulation results corresponding to each limit. If all the stability indices show a decreasing trend, it indicates that λ > 0 can be maintained, and the range of the corresponding limit can be further optimized. If the stability indices change very little or show an increasing trend, the correction is stopped, and the latest value is taken as the optimization result.

[0028] As a further technical solution of the present invention: the new energy configuration optimization refers to optimizing the access ratio or location of new energy sources or converters by reasonably selecting voltage or current limits of converters, constrained by comprehensive stability indicators. Therefore, the above optimization can include three levels of optimization: physical and control constraint optimization, converter access ratio optimization, and converter access node optimization. The optimized system can be a power grid containing both traditional units and new energy sources, or it can be a 100% new energy power grid. Since the control types of converters are different, the influence laws of the limiting factors are also different, and they can be optimized and configured separately according to the control type of the converter.

[0029] As a further technical solution of the present invention: the simulation model can be an electromagnetic or electromechanical transient simulation, and an appropriate simulation platform is selected according to the simulation scale or scenario. Since electromagnetic transient simulation involves a large amount of computation, electromechanical transient simulation is generally chosen for large power grids; for smaller scenarios such as microgrids, electromagnetic transient simulation models can be selected. The main difference between the model and a conventional model is that the control loop includes a limiter, which facilitates simulation analysis on existing models.

[0030] As a further technical solution of the present invention: the comprehensive stability index is to assign weights to different indicators, where a is the weight of indicator α, b is the weight of indicator β, and c is the weight of indicator γ, and a+b+c=1. When frequency stability is the primary consideration, a+b>0.7 is selected; when voltage stability is the primary consideration, a+b<0.7 is selected; and when both voltage and frequency stability are considered, a+b=0.5. Furthermore, since inertia mainly affects indicator α, a>b is generally preferred. The comprehensive evaluation index after considering all weights is expressed as shown in equation (4).

[0031] ξ=a·α+b·β+c·γ (4)

[0032] Furthermore, the three-layer optimization in step S5 all employ the aforementioned optimization method. The control limits after sequentially undergoing the three-layer optimization are respectively u sdi u sai i sdi or i sai (i = 2, 3, 4), the corresponding converter operating range is f(u sdi ), f(u) sai ), f(i sdi ) or f(i sai (i = 2, 3, 4). Finally, considering the access ratio and access nodes, the optimal control loop limit value u' of the converter can be obtained. sd 、u' sa 、i' sd 、i' sa and the operating interval f(u') sd ), f(u'sa ), f(i' sd ), f(i' sa ), as shown in equation (5) and equation (6) respectively.

[0033]

[0034]

[0035] As a further technical solution of the present invention: the control limiting parameters after the optimization process are the minimum values ​​of the limits of each control parameter; the converter operating range is the intersection of the operating ranges. That is, the set of physical limit parameters of the converter is P = (u max i max ,S max ), control loop limit parameter set C = (u' sd ,u' sa ,i' sd ,i' sa The operating range F of the converter is expressed as shown in equation (7).

[0036] F=(f(u max )∩f(i max )∩f(S max ))∩(f(u′ sd )∩f(u′ sa )∩f(i′ sd )∩f(i′ sa (7)

[0037] The optimized parameters P, C, and F are the limiting parameters for optimizing the configuration of new energy sources considering the transient support limit of power electronic equipment, which can provide a feasible solution for the configuration of new energy sources in actual power grids.

[0038] Compared with the prior art, the beneficial effects of the present invention are:

[0039] 1. The optimization method proposed in this invention takes into account the fundamental limiting factors affecting the transient support capability of the converter, and solves the problem of the idealized results caused by the failure to consider the limiting of the converter support capability in conventional new energy power grid optimization analysis, so that the analysis results are more consistent with the actual operation of the power grid.

[0040] 2. The optimization method proposed in this invention can be used for converters of all control types. It can conduct a detailed study on the transient support limit of the converter. By selecting appropriate parameters, the transient support performance of power electronic equipment can be improved, thereby enhancing the overall operational stability of the new energy power grid.

[0041] 3. The optimization method proposed in this invention comprehensively considers key indicators of voltage and frequency, and can simultaneously optimize the voltage and frequency stability of the power grid by optimizing the proportion and location of new energy access. Furthermore, this optimization method can be extended to the optimization analysis of other application scenarios by considering other influencing factors. Attached Figure Description

[0042] Figure 1 This is a general topology and control principle diagram of a new energy converter connected to the grid;

[0043] Figure 2 This is a flowchart of the new energy grid connection configuration considering the transient support limit of power electronics proposed in this invention;

[0044] Figure 3 This is a detailed process diagram of the third and fourth steps in the optimized configuration process proposed in this invention;

[0045] Figure 4 This is a flowchart illustrating the fifth step of the optimized configuration process proposed in this invention.

[0046] Figure 1 In the middle: 101-DC side, 102-inverter circuit, 103-grid connection line, 104-grid, 201-controller, 202-voltage controller, 203-current controller, 204-voltage limiting, 205-current limiting. Detailed Implementation

[0047] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0048] Example 1: A method for optimizing the grid connection of new energy sources considering the transient support limit of power electronics. The specific method is as follows:

[0049] First, the physical and control saturation limits of electrical quantities such as voltage, current, and power of the converter are evaluated to obtain the maximum operating range. Then, by comprehensively considering and comparing physical and control limits, the main factors affecting the transient stability of the converter are identified. Second, time-domain simulation calculations are performed using different control stability limits to analyze the key frequency and voltage indicators of the new energy grid. Finally, the connection ratio or location of new energy sources or converters is optimized based on the comprehensive stability indicators.

[0050] like Figure 2As shown, the above optimization process can be summarized into five main stages: physical limit assessment S1, controller limit assessment S2, transient influencing factor analysis S3, time-domain simulation calculation S4, and new energy configuration optimization S5.

[0051] Physical and control parameters x of each stage i The corresponding operating interval is denoted as the functional relationship f(x) of each parameter. i ), operating interval f(x) i The term f(x) represents the converter's ability to output electromagnetic power during transient processes (typically on the order of milliseconds), specifically including but not limited to the range of instantaneous active and reactive power. When considering transient limits, the support requirements for the power grid are usually taken into account, i.e., an upper limit is set for equipment protection. Therefore, this invention specifies a clear upper limit for the operating range, namely f(x). i )<ε i (ε i >0).

[0052] Since the tolerance range corresponding to some physical parameters usually has a specific time range, time t should also be f(x) i The independent variable is f(x), therefore the range function can be expressed as f(x) i ,t).

[0053] The physical limitation assessment S1 step mainly involves determining the rated parameters of the power electronic converter equipment, such as voltage, current, and power, as well as the short-time maximum voltage withstand value u. max Current withstand value i max and the maximum permissible overload power S for short time max These physical limitations are necessary hardware protection limits to ensure that the converter is not damaged. Furthermore, the converter typically has a defined tolerance time under these limitations.

[0054] The operating range of the physical limit assessment S1 stage, determined by the voltage, current, and power tolerance ranges, is f(u) max ,t),f(i max ,t),f(S max ,t).

[0055] The controller limit assessment S2 stage refers to determining the voltage limit u in the control stage. s and current limiting i s The voltage limiting in the converter control loop depends on the control type, and both the DC and AC control outputs generally have voltage limiting. The voltage limiting on the DC and AC sides are respectively set to u. sd0 and u sa0 The current limiting on the DC side and the AC side are respectively set to i. sd0 and i sa0 .

[0056] Limiting in a control loop refers to adding a limiting element to the controller. Once the set limit is reached, the controller output saturates and becomes constant. Setting a limiting value ensures stable operation of the converter. The limiting in the controller typically restricts the converter output continuously; therefore, it is expressed as a function of the corresponding parameters and is independent of time.

[0057] The operating ranges determined by the DC / AC voltage limiting and DC / AC current limiting in the S2 stage of the controller limit evaluation are f(u) sd0 ), f(u) sa0 ), f(i sd0 ), f(i sa0 ).

[0058] In the controller limit assessment S2 stage, the control stability limits of the converter can generally be determined based on the specific converter circuit topology and operating requirements, and the range of values ​​for each limit can be initially determined.

[0059] The transient influencing factor analysis in step S3 mainly combines the physical constraints obtained from step S1 and the control stability constraints obtained from step S2 to analyze the main factors affecting the transient stability of the converter. The physical constraints can be determined by the factory parameters of power semiconductor devices, capacitors, inductors, and resistors, and the protection parameters of the components themselves should be set accordingly in the simulation. max i max S max Since the range of control stability limits is usually not fixed, the impact of different voltage or current limits on transient characteristics is analyzed by comparing the simulation of a single converter unit based on the preliminary control loop stability analysis.

[0060] The operating range f(u) of the converter is determined through the S3 stage. max ,t),f(i max ,t),f(S max ,t),f(u sd0 ), f(u) sa0 ), f(i sd0 ), f(i sa0 A preliminary verification was conducted, and the rationality of the above limit settings was analyzed based on the preliminary simulation results.

[0061] The S4 stage of time-domain simulation calculation refers to establishing a simulation model of the converter single-machine system. By setting different voltage and current limits in the control loop, and using the single variable method, the influence of these main limiting factors on the transient stability characteristics of the converter itself is studied.

[0062] The single variable method refers to setting u in the S3 stage based on the maximum range of restrictions obtained from the previous system analysis. sd0 u sa0i sd0 i sa0 The initial value indicates that the converter is operating normally and none of its components have reached saturation. Each time a new voltage or current limit is set while keeping other limits constant, a simulation calculation is performed on the power grid model. Load changes or faults are then introduced into the model to compare key frequency or voltage indicators.

[0063] The key frequency indicators are: the rate of change of frequency α and the minimum frequency β. The rate of change of frequency is the rate of change of frequency in a short period of time after the load changes, and is defined by equation (1); the minimum frequency is the maximum frequency after the load changes, and is defined by equation (2).

[0064]

[0065] β=max|f t＞0 -f t＝0+ | (2)

[0066] Where t s It is the frequency sampling interval, t s Typical values ​​are 200-300ms.

[0067] The key voltage index refers to the change in voltage amplitude γ, defined by equation (3), such as the change in voltage amplitude at the fault point. The key frequency and voltage indices are strongly correlated with the system's inertia, damping, and short-circuit capacity, respectively, and therefore can be used to judge the transient stability of the system.

[0068]

[0069] Where t r It is the time to eliminate voltage disturbances, i.e., the system recovery time.

[0070] The key to frequency and voltage stability metrics lies in the magnitude of each value. Smaller α and β values ​​indicate better system frequency stability; smaller γ values ​​indicate better system voltage stability.

[0071] The simulation model of a single-machine system can be an electromagnetic or electromechanical transient simulation. However, since the computational load of a single-machine system is not large, electromagnetic transient simulation is usually used. Based on the new limit values ​​obtained, the simulation results are used to optimize the controller limit values.

[0072] Through steps S3 and S4, the physical and control limiting factors that significantly affect the converter can be further identified, allowing for the correction and optimization of the aforementioned maximum operating range. The resulting optimized operating range can then be used for renewable energy configuration optimization in step S5.

[0073] The S5 stage of new energy configuration optimization refers to optimizing the access ratio or location of new energy sources or converters by selecting different physical or control constraints of converters through multiple simulation calculations within the main restricted operating range, based on the constraints of key frequency or voltage stability indicators and building upon the S1-S4 stages.

[0074] New energy power grid simulation models can be electromagnetic or electromechanical transient simulations, with the appropriate simulation platform selected based on the simulation scale or scenario. Since electromagnetic transient simulations involve significant computational loads, electromechanical transient simulations are generally chosen for large power grids; electromagnetic transient simulation models can be selected for smaller-scale scenarios such as microgrids.

[0075] The main difference between the new energy power grid simulation model and the ordinary model is that the control loop limiter is considered in the control loop, which also makes it easier to perform simulation analysis on the existing model.

[0076] Figure 3 This describes the specific processes of steps S3 and S4 in the optimized configuration process provided in this patent implementation example. Steps S3 and S4 are closely related, analyzing factors affecting transient stability through simulation calculations, and have an overlapping relationship in the process. Step S3 includes step S3.1 of establishing a single-machine model of the converter and step S3.2 of analyzing the impact of different limiting factors on operation. Step S4 includes step S4.1 of setting voltage / current saturation limits, step S4.2 of comparing transient stability indicators through time-domain simulation, step S4.3 of analyzing the influence of physical and control loop limits, and step S4.4 of optimizing the converter operating range.

[0077] The influencing factors analysis and time-domain simulation analysis of stages S3 and S4 are based on the maximum operating range f(u) initially determined in stages S1 and S2. max ,t),f(i max ,t),f(S max ,t),f(u sd0 ), f(u) sa0 ), f(i sd0 ), f(i sa0 ).

[0078] The S3.1 step of establishing a single-machine model of the converter refers to establishing an electromagnetic or electromechanical transient simulation model of the single-machine system, and being able to set a limiting element in the control loop to limit the controller output, which can be used for the time-domain simulation in the subsequent S4.2 step.

[0079] The S3.2 step, analyzing the impact of different limiting factors on operation, involves further analyzing the effects of different voltage or current limits on the transient characteristics of the converter through simulation comparison of the initial control loop stability analysis, and determining the control loop limit value u. sd0 u sa0 isd0 i sa0 The initial value is deemed reasonable; if the initial value is not set reasonably, it is corrected and the updated value is used as the initial value.

[0080] Setting the voltage / current saturation limit S4.1 refers to adding a limiting element to the control loop to limit the output of the converter. In this invention, the main consideration is the converter's ability to support the voltage and frequency of the power grid. Therefore, this limit generally refers to the upper limit to constrain the converter to operate within the normal range.

[0081] The time-domain simulation comparison of transient stability indices (S4.2) involves performing simulation calculations using single-machine models with different voltage / current limits. The transient stability indices of voltage and frequency are used as evaluation criteria, with a new voltage or current limit (1+λ)u set each time. sd0 、(1+λ)u sa0 、(1+λ)i sd0 or (1+λ)i sa0 (where 0 < λ < 1), and keeping other limits unchanged, perform a simulation calculation on the power grid model.

[0082] In the simulation results corresponding to each limit, compare the relative magnitudes of the stability indices α, β, and γ. If all stability indices show a decreasing trend, it indicates that λ > 0 can be maintained, and the corresponding limit range can be further optimized. If the stability indices change very little or show an increasing trend, then stop the correction, and the limit value is u. sd1 u sa1 i sd1 or i sa1 The corresponding converter operating range is f(u) sd1 ), f(u) sa1 ), f(i sd1 ) or f(i sa1 The process of optimizing parameters or ranges corresponds to step S4.3, which yields a control limit range that ensures the transient stability of the converter. The maximum operating range obtained in steps S1 and S2 is then corrected and optimized, corresponding to step S4.4. Steps S3.1 to S3.2 and S4.1 to S4.4 ultimately yield the operating range that ensures the transient stability of the converter. This range serves as the input condition for optimizing the new energy configuration in step S5.

[0083] Figure 4This describes the specific process of step S5 in the optimized configuration process provided in this patent implementation example. Step S5 optimizes the entire new energy power grid based on the results of the above four steps. Step S5 includes: establishing a new energy power grid model with converters (S5.1); setting physical and control constraints for converters (S5.2); comparing transient stability indicators using time-domain simulation (S5.3); setting the converter access ratio (S5.4); comparing transient stability indicators using time-domain simulation (S5.5); setting converter access nodes (S5.6); and comparing transient stability indicators using time-domain simulation (S5.7). Finally, the optimized results of the new energy access ratio and access location in the new energy power grid are obtained.

[0084] Step S5.1 of establishing a new energy power grid model with converters refers to establishing a new energy power grid that includes different types of converters. This new energy power grid can be a grid that includes both traditional generating units and new energy sources, or it can be a 100% new energy power grid. Since the control types of converters are different, the influence patterns of limiting factors also differ. Therefore, they can be optimized and configured separately according to their control types.

[0085] The optimization of the S5 stage can include three levels of optimization: namely, physical and control constraint optimization, converter access ratio optimization, and converter access node optimization. In fact, it uses a single variable method to optimize the grid-connected converter from the above three levels.

[0086] In the S5 stage, indices α and β refer to the frequency stability of the entire system, while index γ refers to the voltage stability at the converter connection point. When it is necessary to selectively determine frequency stability or voltage stability, weights need to be assigned to different indices: a is the weight of index α, b is the weight of index β, and c is the weight of index γ, satisfying a + b + c = 1.

[0087] For weighted stability indicators, when frequency stability is the primary consideration, a+b>0.7 is chosen; when voltage stability is the primary consideration, a+b<0.7 is chosen; and when both voltage and frequency stability are considered, a+b=0.5. Furthermore, since inertia primarily affects indicator α, a>b is generally preferred. The comprehensive evaluation index after considering all weights is expressed as shown in equation (4).

[0088] ξ=a·α+b·β+c·γ (4)

[0089] For the three-layer optimization in the S5 stage, the following optimization method is adopted: For each limit value, the simulation results are compared with the stability index ξ. If ξ is decreasing, it means that λ>0 (0<λ<1) can be maintained, and the interval of the corresponding limit value can be optimized. If the stability index changes very little or shows an increasing trend, the correction is stopped, and finally the new limit value and the corresponding operating interval are obtained.

[0090] Sections S5.2 and S5.3 are essentially optimizations based on physical and control constraints, similar to section S4. Simulation optimization is performed by setting different physical or control constraints for the converter, and stability indicators under different parameters are analyzed. The control limit value of the converter, u, is obtained. sd2 u sa2 i sd2 or i sa2 The corresponding converter operating range is f(u) sd2 ), f(u) sa2 ), f(i sd2 ) or f(i sa2 ).

[0091] Steps S5.4 and S5.5 are essentially optimizations of the grid connection ratio. When the simulated grid model includes both traditional generating units and new energy sources, simulation optimization is performed separately by setting the connection ratio of each converter. The simulation results for each limit are compared with the comprehensive stability index ξ to obtain the maximum connection ratio of converters under the grid stability limit constraint. When the simulated grid model only includes new energy sources, simulation optimization can be performed separately by setting the connection ratio of different types of converters. The simulation results at different ratios are recorded, and the connection ratio of converters with specific control under the grid stability limit constraint is obtained by comparing the comprehensive transient stability index.

[0092] The S5.4 and S5.5 stages employ a similar parameter optimization method to the S5.2 and S5.3 stages to obtain the converter's control limit value u. sd3 u sa3 i sd3 or i sa3 The corresponding converter operating range is f(u) sd3 ), f(u) sa3 ), f(i sd3 ) or f(i sa3 ).

[0093] Steps S5.6 and S5.7 are essentially about optimizing the connection location. By setting the connection node of the converter and performing simulation optimization, the comprehensive transient stability index of the simulation results under different connection locations is compared to obtain the converter connection location that is most conducive to grid stability.

[0094] After optimization in steps S5.6 and S5.7, the control limit value of the converter is obtained as u. sd4 u sa4 i sd4 or i sa4 The corresponding converter operating range is f(u) sd4 ), f(u) sa4 ), f(i sd4 ) or f(i sa4 ).

[0095] By optimizing the S5 stage, the optimal control loop limit value u' of the converter can be obtained after considering the access ratio and access nodes. sd 、u' sa 、i' sd 、i' sa and the operating interval f(u') sd ), f(u' sa ), f(i' sd ), f(i' sa ), which can be expressed as shown in equation (5) and equation (6) respectively.

[0096]

[0097]

[0098] Through optimization in steps S3-S5, the optimized configuration parameters and operating range of the converter, taking into account the converter's physical support, control limits, connection ratio, and connection nodes, can be obtained. The set of physical limit parameters for the converter is P = (u max i max ,S max ), control loop limit parameter set C = (u' sd ,u' sa ,i' sd ,i' sa The operating range F of the converter is expressed as shown in equation (7).

[0099] F=(f(u max )∩f(i max )∩f(S max ))∩(f(u′ sd )∩f(u′ sa )∩f(i′ sd )∩f(i′ sa (7)

[0100] The optimized parameters P, C, and F represent the optimal configuration scheme for new energy sources that takes into account the transient support limits of power electronic equipment. This scheme can provide maximum support to the power grid while ensuring the normal operation of the converter. The optimization results can provide a feasible solution for the configuration of new energy sources in the actual power grid.

[0101] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0102] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for optimizing grid-connected configuration of new energy sources considering the transient support limit of power electronics, characterized in that, Includes the following steps: Step 1: Evaluate the physical and control saturation limits of the converter voltage, current, and power to obtain the maximum operating range; Step 2: By comprehensively considering and comparing physical and control limits, identify the main factors affecting the transient stability of the converter; Step 3: Perform time-domain simulation calculations using different control stability constraints to analyze the key frequency and voltage indicators of the new energy power grid; And step 4, optimize the access ratio and location of new energy sources or converters based on comprehensive stability indicators; The time-domain simulation calculation refers to establishing a simulation model of the converter single-machine system, setting different voltage and current limits in the control loop, and using the single variable method to study the influence of these limiting factors on the transient stability characteristics of the converter itself. The single-variable method refers to setting the initial value based on the system's maximum operating range. At this point, the converter is operating normally and none of the components have reached saturation. Each time, while keeping other limits constant, the method uses a step size... λ Set a new voltage or current limit (1+ λ ) u sd0 、(1+ λ ) u sa0 、(1+ λ ) i sd0 or (1+ λ ) i sa0 ,0< λ <1. Perform a simulation calculation on the power grid model, setting load changes or faults in the model to compare key frequency or voltage indicators. Obtain control loop limits with good stability indicators through parameter optimization methods, and then correct the parameters. u sd1 , u sa1 , i sd1 , i sa1 ; Frequency index refers to the rate of change of frequency. α and the lowest frequency point β The frequency change rate is the rate of change of frequency within a short period of time after a load change, and is defined by equation (1); the minimum frequency point is the maximum frequency after a load change, and is defined by equation (2). ； ； in t s It is the frequency sampling interval. t s The value is 200-300ms; Voltage index refers to the change in voltage amplitude. γ The definition adopts equation (3); ； in t r It is the time to eliminate voltage disturbances, i.e., the system recovery time; The key frequency and voltage parameters are strongly correlated with the system's inertia, damping, and short-circuit capacity, respectively. The smaller these three parameters are, the better the system stability. The parameter optimization method compares the stability indicators in the simulation results corresponding to each limit value. α , β and γ If the relative magnitude of the values, such as the aforementioned stability indicators, all show a decreasing trend, then maintain... λ If the value is greater than 0, continue to optimize the corresponding limit range; if the stability index changes very little or shows an increasing trend, stop the correction and take the latest value as the optimization result.

2. The method for optimizing grid connection of new energy sources considering the transient support limit of power electronics as described in claim 1, characterized in that, The physical limitations of the converter include the short-time voltage tolerance of the power electronic equipment. u max Current withstand value i max and short-term maximum permissible overload power S max .

3. The method for optimizing grid connection of new energy sources considering the transient support limit of power electronics as described in claim 2, characterized in that, The saturation limiting in the converter control loop includes voltage and current limiting. This limiting depends on the control type; the limiting in the controller is a limiting element. The controller output is limited after reaching the set limit. The voltage limits on the DC and AC sides are respectively set to... u sd0 and u sa0 The current limiting on the DC side and AC side are respectively taken as follows: i sd0 and i sa0 .

4. The method for optimizing grid connection of new energy sources considering the transient support limit of power electronics as described in claim 3, characterized in that, Based on the specific converter circuit topology and control method, the physical limitations and control stability limits of the converter are clarified, and the maximum operating range is initially determined. f ( u max )∩ f ( i max )∩ f ( S max )∩ f ( u sd0 )∩ f ( u sa0 )∩ f ( i sd0 )∩ f ( i sa0 The working interval is represented as a functional relationship of the corresponding parameters. f .

5. The method for optimizing grid connection of new energy sources considering the transient support limit of power electronics as described in claim 4, characterized in that, Transient influencing factor analysis involves analyzing the main factors affecting the transient stability of a converter from both physical and control perspectives. The physical limits are determined by the factory parameters of power semiconductor devices, capacitors, inductors, and resistors. The range of control stability limits is not fixed. Therefore, based on the preliminary classical control stability analysis method, the rationality of different voltage or current limit settings is further analyzed through simulation comparison of a single converter unit.

6. The method for optimizing grid connection of new energy sources considering the transient support limit of power electronics as described in claim 5, characterized in that, The aforementioned new energy grid connection optimization configuration refers to optimizing the access ratio and location of new energy sources or converters by selecting voltage or current limits of converters, constrained by comprehensive stability indicators. This includes three levels of optimization: physical and control constraint optimization, converter access ratio optimization, and converter access node optimization. For the optimized system, which includes a grid containing both traditional units and new energy sources, the influence of limiting factors differs due to the different control types of converters. Therefore, optimization configuration needs to be carried out separately according to the control type of the converters.

7. The method for optimizing grid connection of new energy sources considering the transient support limit of power electronics as described in claim 6, characterized in that, The comprehensive stability index assigns weights to different indicators. a As an indicator α The weight, b As an indicator β The weight, c As an indicator γ The weights, and satisfying a + b + c =1, when frequency stability is the primary consideration, select a + b >0.7; When voltage stability is the primary consideration, select a + b <0.7; while considering both voltage and frequency stability a + b =0.5, and since inertia mainly affects the index α ,therefore a > b The comprehensive evaluation index after considering all weights is expressed as shown in equation (4); ； The three-layer optimization all employs an optimal selection method, and the control limits after sequentially undergoing the three-layer optimization are as follows: u sdi , u sai , i sdi or i sai , i =2, 3, or 4, corresponding to the converter operating range is: f ( u sdi ), f ( u sai ), f ( i sdi )or f ( i sai ), i =2, 3, or 4; ultimately, the limit values ​​for the converter optimization control loop considering the access ratio and access nodes are obtained. u ' sd , u ' sa , i ' sd , i ' sa and work area f ( u ' sd ), f ( u ' sa ), f ( i ' sd ), f ( i ' sa ), as shown in equation (5) and equation (6) respectively; ； 。 8. The method for optimizing grid connection of new energy sources considering the transient support limit of power electronics as described in claim 7, characterized in that, After optimization, the control limit parameters are the minimum values ​​of each control parameter limit; the converter operating range is the intersection of all operating ranges; that is, the set of physical limit parameters of the converter is... P =( u max , i max , S max ), set of limit parameters for control loop C =( u ' sd , u ' sa , i ' sd , i ' sa The operating range of the converter F It is represented as shown in equation (7); ； Parameters obtained after optimization P , C and F These are the limiting parameters for optimizing the configuration of new energy sources, taking into account the transient support limits of power electronic equipment.

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