Direct-current micro-grid large signal stability analysis method and system

Abstract

The invention discloses a direct current micro-grid large signal stability analysis method and system. The method comprises the following steps: acquiring a first parameter of a target controller, and establishing a first equivalent model based on the first parameter; presetting a first improvement strategy, and improving the first equivalent model according to the first improvement strategy to obtain a first improved model; and carrying out stability analysis according to the first improved model. According to the method and the system for analyzing the stability of the large signal of the direct-current micro-grid, the dynamic behavior of the direct-current micro-grid under the disturbance of the large signal can be reflected more accurately by establishing the equivalent model and applying the improved strategy, so that a more accurate stability analysis result is provided. Compared with a traditional analysis method based on a small signal theory, the method can effectively avoid the problem that the stability criterion is too conservative, and can comprehensively consider the key parameters of the system, thereby accurately describing the stability boundary of the system.

Description

Technical Field

[0001] The present invention relates to the technical field of large-signal stability analysis of DC microgrids, and in particular to a method and system for large-signal stability analysis of DC microgrids. Background Art

[0002] DC Microgrid (DCMG) has become an important part of the new power system due to its advantages such as fewer energy conversion links, no reactive power loss, and no need to consider phase and frequency, and plays a key role in the integration and consumption of renewable energy.

[0003] However, the strong randomness of Distributed Energy Source (DES) and the negative resistance characteristics of Constant Power Load (CPL) pose challenges to the stable operation of DC microgrids. Regarding the stability problem of DC microgrids, there have been a large number of studies based on small-signal theory analysis. However, in actual operation, DES and CPL in DC microgrids usually exhibit large-signal disturbances, resulting in the invalidity of small-signal stability analysis.

[0004] Common large-signal nonlinear analysis methods include: Lyapunov direct method, Takagi-Sugeno fuzzy model (TS), and Mixed Potential Theory (MPT), etc. In existing research, when using MPT to analyze the large-signal stability of DC microgrids, there are still problems such as conservative stability criteria and inability to comprehensively cover key system parameters, making it difficult to accurately depict the stability boundary. Summary of the Invention

[0005] The purpose of this part is to outline some aspects of the embodiments of the present invention and briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this part, as well as in the abstract and title of the present application, to avoid obscuring the purpose of this part, the abstract, and the title, but such simplifications or omissions cannot be used to limit the scope of the present invention.

[0006] In view of the above existing problems, the present invention is proposed.

[0007] Therefore, the present invention provides a method and system for large-signal stability analysis of DC microgrids, which can solve the problems mentioned in the background art.

[0008] To solve the above technical problems, the present invention provides the following technical solutions:

[0009] In the first aspect, the present invention provides a method for large-signal stability analysis of DC microgrids, including:

[0010] Obtain the first parameter of the target controller, and establish a first equivalent model based on the first parameter;

[0011] Preset a first improvement strategy, and improve the first equivalent model according to the first improvement strategy to obtain a first improved model;

[0012] Perform stability analysis according to the first improved model.

[0013] As a preferred scheme of the large-signal stability analysis method for the DC microgrid of the present invention, wherein: the performing stability analysis according to the first improved model includes:

[0014] The stability analysis at least includes a stability criterion;

[0015] The stability criterion includes setting a first objective function;

[0016] Input the operating parameters of the first improved model into the first objective function to obtain a stability analysis result.

[0017] As a preferred scheme of the large-signal stability analysis method for the DC microgrid of the present invention, wherein: the improving the first equivalent model according to the first improvement strategy includes:

[0018] The first improvement strategy improves several partial models in the first equivalent model;

[0019] Determine the partial model to be improved in the first equivalent model;

[0020] Improve the partial model to be improved according to the first improvement strategy.

[0021] As a preferred scheme of the large-signal stability analysis method for the DC microgrid of the present invention, wherein: the first equivalent model at least includes a source converter equivalent circuit model and a load converter model.

[0022] As a preferred scheme of the large-signal stability analysis method for the DC microgrid of the present invention, wherein: the first equivalent model further includes:

[0023] The source converter adopts a voltage droop control and a voltage-current double-loop control structure, and the load converter adopts a voltage-current double-loop control structure.

[0024] As a preferred scheme of the large-signal stability analysis method for the DC microgrid of the present invention, wherein: the source converter equivalent circuit model includes:

[0025] The source converter equivalent circuit model virtually equivalent the converter control system to an RLC circuit model;

[0026] The RLC circuit model after equivalence includes at least the mathematical model of the outer voltage loop control of the source converter and the mathematical model of the inner current loop control.

[0027] As a preferred solution of the large-signal stability analysis method for the DC microgrid described in the present invention, wherein: the model part to be improved is the load converter model.

[0028] In a second aspect, the present invention provides a large-signal stability analysis system for a DC microgrid, including:

[0029] A model establishment module, configured to obtain the first parameters of the target controller and establish a first equivalent model based on the first parameters;

[0030] A model improvement module, configured to preset a first improvement strategy and improve the first equivalent model according to the first improvement strategy to obtain a first improved model;

[0031] An analysis module, configured to perform stability analysis according to the first improved model.

[0032] In a third aspect, the present invention provides a computer device, including a memory and a processor, where the memory stores a computer program, and when the processor executes the computer program, the steps of the method described above are implemented.

[0033] In a fourth aspect, the present invention provides a computer-readable storage medium, on which a computer program is stored, and when the computer program is executed by a processor, the steps of the method described above are implemented.

[0034] Compared with the prior art, the beneficial effects of the present invention are as follows: The present invention proposes a large-signal stability analysis method and system for a DC microgrid, obtains the first parameters of the target controller, and establishes a first equivalent model based on the first parameters; presets a first improvement strategy, and improves the first equivalent model according to the first improvement strategy to obtain a first improved model; performs stability analysis according to the first improved model. The large-signal stability analysis method and system for the DC microgrid of the present invention can more accurately reflect the dynamic behavior of the DC microgrid under large-signal disturbances by establishing an equivalent model and applying an improvement strategy, thereby providing more accurate stability analysis results. Compared with the traditional analysis method based on small-signal theory, the method of the present invention can effectively avoid the problem that the stability criterion is too conservative, and can comprehensively consider the key parameters of the system, so as to accurately depict the stable boundary of the system. In addition, the present invention can also improve specific model parts, such as the load converter model, to further improve the accuracy and practicality of the analysis. Through these improvements, the present invention provides more reliable technical support for the stable operation of the DC microgrid, helps to improve the operation efficiency and reliability of the DC microgrid, and has important practical significance for promoting the integration and consumption of renewable energy.

[0035] In addition, the present invention separately establishes an equivalent circuit model of the source converter and an improved CPL model of the load converter, and obtains a more accurate large-signal stability criterion. The present invention can obtain a stability criterion including the control system, the main circuit parameters, and the improved CPL model, effectively reducing the conservativeness of the traditional method and obtaining a more accurate stability criterion. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings. Among them:

[0037] Figure 1 is a method flow chart of a large-signal stability analysis method and system for a DC microgrid provided by an embodiment of the present invention;

[0038] Figure 2 is a simplified DC microgrid diagram of a large-signal stability analysis method and system for a DC microgrid provided by an embodiment of the present invention;

[0039] Figure 3 is an equivalent circuit model diagram of a DC microgrid for a large-signal stability analysis method and system for a DC microgrid provided by an embodiment of the present invention;

[0040] Figure 4 is an equivalent circuit model diagram of the source converter after equivalence for a large-signal stability analysis method and system for a DC microgrid provided by an embodiment of the present invention;

[0041] Figure 5 is a CPL model diagram of a large-signal stability analysis method and system for a DC microgrid provided by an embodiment of the present invention;

[0042] Figure 6 is a voltage and current waveform diagram under large disturbances of a large-signal stability analysis method and system for a DC microgrid provided by an embodiment of the present invention;

[0043] Figure 7 is an internal structure diagram of a computer device of a large-signal stability analysis method and system for a DC microgrid provided by an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0044] To make the above objects, features, and advantages of the present invention more apparent and understandable, the following provides a detailed description of the specific embodiments of the present invention in conjunction with the accompanying drawings of the specification. Apparently, the described embodiments are only a part of the embodiments of the present invention, rather than all of them. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the scope of protection of the present invention.

[0045] Embodiment 1

[0046] Referring to Figures 1-7 , which is the first embodiment of the present invention. This embodiment provides a method and system for analyzing the large-signal stability of a DC microgrid, including:

[0047] In the existing related technologies, there are some problems. For example, traditional methods for analyzing the stability of DC microgrids often ignore the influence of nonlinear elements in the system, resulting in a deviation between the analysis results and the actual operating conditions. In addition, due to the diversity of the topological structure and operating mode of DC microgrids, existing analysis methods are difficult to adapt to various different application scenarios and lack flexibility and universality. Moreover, for the response analysis of large-signal disturbances, traditional methods often cannot accurately predict the dynamic behavior of the system under extreme conditions, which may pose potential safety hazards in practical applications.

[0048] This application provides a method that can effectively solve the above-mentioned problems. Next, multiple embodiments will be used to elaborate in detail on how to implement this method for analyzing the large-signal stability of a DC microgrid;

[0049] Figure 1 Figure 1 shows a flowchart of a method for analyzing the large-signal stability of a DC microgrid, including:

[0050] S101, obtaining the first parameters of the target controller and establishing a first equivalent model based on the first parameters;

[0051] In an optional embodiment, the target controller is a controller for controlling the target DC microgrid, and its first parameters include key control parameters such as the gain and time constant of the controller. By obtaining these parameters, an equivalent model that matches the actual behavior of the controller can be constructed. This equivalent model can simulate the dynamic response of the controller in the DC microgrid, thereby providing a more accurate basis for stability analysis.

[0052] In an optional embodiment, after establishing the equivalent model, the dynamic behavior of the DC microgrid under large-signal disturbances is further analyzed to evaluate the stability and security of the system. By this method, potential problems of the DC microgrid under extreme conditions can be effectively predicted and solved, improving the reliability and adaptability of the system.

[0053] In an alternative embodiment, the first equivalent model is equivalent according to the target DC microgrid plus the target controller, thus ensuring the accuracy and practicability of the model. This equivalent model not only considers the electrical characteristics of the DC microgrid, but also synthesizes the control strategy and response characteristics of the controller. In this way, the behavior of the DC microgrid under various operating conditions can be more comprehensively simulated, providing a more comprehensive perspective for stability analysis.

[0054] In an alternative embodiment, the large-signal stability analysis method for the DC microgrid further includes modeling the load characteristics of the DC microgrid. By accurately simulating the dynamic changes of the load, the prediction accuracy of the equivalent model can be further improved. The establishment of the load model takes into account different types of loads, such as constant power loads, constant current loads, and constant impedance loads, etc., as well as their distribution in the DC microgrid. Such a load model can reflect the impact of the actual load on the stability of the DC microgrid, providing a more reliable reference basis for system design and operation.

[0055] In the embodiment of the present application, the first equivalent model at least includes a source converter equivalent circuit model and a load converter model.

[0056] In an alternative embodiment, the first equivalent model may further include equivalent models of other relevant components, such as energy storage units, loads, and distributed energy, etc. Such a comprehensive model can more comprehensively reflect the complexity and dynamic characteristics of the DC microgrid, providing more detailed data support for stability analysis.

[0057] Exemplarily, based on the connection between the control system and the RLC circuit, the source converter equivalent circuit model represents the control system with a circuit of equivalent resistance, inductance, and capacitance, solving the defect that the hybrid potential theory is insensitive to the control system.

[0058] In the embodiment of the present application, the first equivalent model further includes:

[0059] The source converter adopts a voltage droop control and a voltage-current double-loop control structure, and the load converter adopts a voltage-current double-loop control structure.

[0060] In the embodiment of the present application, the source converter equivalent circuit model includes:

[0061] The source converter equivalent circuit model virtually equivalent the converter control system to an RLC circuit model;

[0062] The equivalent RLC circuit model at least includes a source converter voltage outer-loop control mathematical model and a current inner-loop control mathematical model.

[0063] In an alternative embodiment, the method equivalent to the RLC circuit model can be further refined by introducing non-linear elements to simulate the dynamic behavior of the converter at different operating points. For example, the non-linear characteristics of the converter can be represented by a non-linear resistor whose resistance value varies with the current.

[0064] In an alternative embodiment, in order to more accurately simulate the dynamic response of the converter, the equivalent circuit model can also include a non-linear inductor whose inductance varies with the magnitude of the current.

[0065] It should be noted that in this way, the equivalent circuit model can more accurately reflect the dynamic characteristics of the converter in actual operation, thereby improving the accuracy of the large-signal stability analysis of the DC microgrid.

[0066] In an alternative embodiment, the mathematical models of the outer voltage loop control and the inner current loop control of the source converter can be implemented by a digital signal processor (DSP) to ensure the fast response and high-precision execution of the control algorithm.

[0067] In an alternative embodiment, the mathematical model of the outer voltage loop control can adopt a proportional-integral-derivative (PID) controller to achieve precise regulation of the output voltage. The mathematical model of the inner current loop control can adopt a proportional controller (P controller) or a proportional-integral (PI) controller to quickly track the current command and suppress current fluctuations. Through this control strategy, the dynamic performance and stability of the DC microgrid can be effectively improved.

[0068] In an alternative embodiment, the mathematical models of the outer voltage loop control and the inner current loop control of the source converter can also be implemented by software to adapt to different control requirements and optimization algorithms. For example, advanced control algorithms such as fuzzy logic control or neural network control can be adopted to further improve the adaptability and robustness of the system.

[0069] In an alternative embodiment, in order to implement a more advanced control strategy, the system can also integrate an adaptive control mechanism to dynamically adjust the control parameters according to the real-time operating conditions to optimize the overall performance. Through these methods, the stability and efficiency of the DC microgrid can be further improved to ensure good operation under various load and environmental changes.

[0070] Exemplarily, the equivalent circuit model of the source converter can be implemented through the following specific steps:

[0071] For the mathematical model of the outer voltage loop control of the source converter, it can be simulated by a parallel branch of R and L, and its dual mathematical model is:

[0072]

[0073] Among them, v busset and i sref are respectively the set value of the output voltage of the source converter and the reference value of the current inner loop. R v and L v are respectively the virtual equivalent inductance and resistance corresponding to the proportional and integral coefficients of the voltage outer loop. V doop is the droop control voltage, and v bus is the output voltage of the source converter.

[0074] For the mathematical model of the current inner loop control, it can be simulated by an R-C series branch, and its dual mathematical model is:

[0075]

[0076] Among them, u 0 is the output voltage of the converter bridge arm, R i and C i are respectively the virtual equivalent resistance and capacitance corresponding to the proportional and integral coefficients of the current inner loop. i s is the inductor current of the source converter.

[0077] The relationship between the converter control system and the RLC circuit is as follows:

[0078]

[0079] Among them, R v and L v are respectively the virtual equivalent inductance and resistance corresponding to the proportional and integral coefficients of the voltage outer loop. R i and C i are respectively the virtual equivalent resistance and capacitance corresponding to the proportional and integral coefficients of the current inner loop. k vp and k vi are respectively the proportional and integral coefficients of the voltage outer loop of the source converter. k ip and k ii are respectively the proportional and integral coefficients of the current inner loop of the source converter. k is the voltage amplification coefficient.

[0080] In the embodiment of the present application, the previous load converter model uses an ideal CPL model;

[0081] It should be noted that obtaining the first parameter of the target controller and establishing the first equivalent model based on the first parameter can provide a more accurate starting point for the stability analysis of the DC microgrid. In this way, it can be ensured that each link in the analysis process is based on the actual controller parameters, thereby improving the accuracy and reliability of the entire analysis process. In addition, the establishment of the first equivalent model also takes into account various non-ideal factors that may exist in the DC microgrid, such as line losses, nonlinear characteristics of switching elements, etc., making the model closer to the actual operating conditions.

[0082] S102, preset the first improvement strategy, and improve the first equivalent model according to the first improvement strategy to obtain the first improved model;

[0083] In an alternative embodiment, the first improvement strategy may be a dynamic adjustment strategy based on load changes. This strategy dynamically adjusts the controller parameters by real-time monitoring the load change situation in the DC microgrid to adapt to the impact brought by load fluctuations. For example, when it is detected that the load suddenly increases, the system will automatically increase the voltage amplification factor k to maintain the stable operation of the DC microgrid. Similarly, if the load decreases, the system will correspondingly decrease the k value to avoid overvoltage.

[0084] It should be noted that in this way, the first improved model can more flexibly cope with various situations that may occur in actual operation, thereby further improving the stability and reliability of the DC microgrid.

[0085] In an alternative embodiment, the first improvement strategy may also be a control strategy based on system state feedback. This strategy uses the real-time state information of the DC microgrid, such as voltage, current, etc., to dynamically adjust the controller parameters to achieve precise control of the system's dynamic behavior. For example, when the system detects a voltage drop, the controller will automatically increase the output voltage to maintain the stable operation of the DC microgrid. On the contrary, if the voltage is too high, the controller will reduce the output voltage to prevent overvoltage.

[0086] It should be noted that this feedback-based control strategy can effectively improve the adaptability and robustness of the DC microgrid in the face of large-signal disturbances.

[0087] In an alternative embodiment, the first improvement strategy may also be to directly improve the target effect of some content in the first equivalent model. For example, improve the CPL model for the load converter.

[0088] In the embodiment of the present application, the improving the first equivalent model according to the first improvement strategy includes:

[0089] The first improvement strategy improves several partial models in the first equivalent model;

[0090] Determine the part of the first equivalent model to be improved;

[0091] Improve the part of the model to be improved according to the first improvement strategy.

[0092] In the embodiment of the present application, the part of the model to be improved is a load converter model.

[0093] Exemplarily, the improved CPL model of the load converter uses a controlled current source type:

[0094]

[0095] Replace P CPL / v bus , fully considering the dynamics of the load converter, which is closer to the actual load converter.

[0096] It should be noted that by presetting the first improvement strategy and improving the first equivalent model according to the first improvement strategy to obtain the first improved model, the adaptability and stability of the DC microgrid in the face of various operating conditions can be significantly improved. Through this improvement, the system can more flexibly cope with unstable factors such as load fluctuations and power disturbances, thereby ensuring the efficient and safe operation of the DC microgrid. In addition, the improved model can also provide a more accurate simulation environment for subsequent stability analysis, providing strong support for system design and optimization.

[0097] S103, perform stability analysis according to the first improved model.

[0098] In the embodiment of the present application, the performing stability analysis according to the first improved model includes:

[0099] The stability analysis at least includes stability criteria;

[0100] The stability criteria include setting a first objective function;

[0101] Input the operating parameters of the first improved model into the first objective function to obtain the stability analysis result.

[0102] In an alternative embodiment, the stability criterion can be a stability criterion based on Lyapunov theory, which can evaluate the dynamic behavior of the DC microgrid under large-signal disturbances. By constructing a suitable Lyapunov function, it can ensure that the system remains stable when subjected to large-signal disturbances. In addition, this criterion can also provide a quantitative index for evaluating the stability margin of the system under different operating conditions. In practical applications, such a stability criterion can help engineers quickly identify potential unstable factors and adopt corresponding control strategies to enhance the stability of the system.

[0103] In an alternative embodiment, the stability criterion can also be a criterion based on Popov hyperstability theory. This theory provides a method for analyzing the stability of nonlinear systems, and is particularly applicable to systems with nonlinear characteristics such as DC microgrids. By constructing the Popov function, the stability of the system under various operating conditions can be analyzed, especially when the system is subject to external disturbances or parameter variations. This criterion can not only determine whether the system is stable, but also give the boundary conditions of the system stability, providing a theoretical basis for system design and parameter adjustment. In the stability analysis of DC microgrids, this criterion helps engineers to deeply understand the dynamic behavior of the system, so as to design more robust control strategies.

[0104] In an alternative embodiment, the stability criterion can also be the application of the third stability theory of the hybrid potential theory to obtain the large-signal stability criterion of the DC microgrid.

[0105] In the embodiment of the present application, for the modeling of the system, the hybrid potential function P(i, v) can be constructed as:

[0106]

[0107] where i = i 1 , …, i r is the current flowing through the inductor, and v = v r+1 , …, v r+s is the voltage of the capacitor branch.

[0108] In the embodiment of the present application, by applying the third stability theory of the hybrid potential theory, the large-signal stability criterion of the DC microgrid can be obtained as:

[0109]

[0110] This formula gives the large-signal stability criterion of the DC microgrid including system parameters such as the control system, the main circuit, and the improved CPL model.

[0111] In an alternative embodiment, for the obtained improved circuit model, the specific relationship is as follows:

[0112]

[0113] where L d is the constructed virtual inductor, and its value approaches 0 infinitely.

[0114] In an alternative embodiment, the DC microgrid large-signal analysis method can obtain the detailed expression of i bus :

[0115]

[0116] where, i bus is the DC bus current, k ip,L is the proportional coefficient of the current inner loop of the load converter, v bus is the output voltage of the source converter, i Lref is the reference value of the current inner loop of the load converter, R L is the equivalent resistance of the load converter, v out is the output voltage of the load converter, g(t)=k ii,L v bus ∫(i Lref -i L )dt - f(t) is the time-varying term.

[0117] It should be noted that both the physical dynamics and control dynamics of the source and load converters are considered simultaneously. The stability criterion covers the system parameters comprehensively and has low conservativeness. The effectiveness of its equivalent circuit model is verified by simulation. This model considers both the control system dynamics and the main circuit dynamics, and its voltage response waveform is basically the same as that of the switching model.

[0118] It should be noted that based on the mapping relationship between the converter control equation and the RLC circuit, the control system is virtually represented by the RLC circuit; an improved CPL model considering the dynamics of the load converter. Based on this model, the large-signal stability criterion and its stability boundary of the DC microgrid are derived by MPT. The simulation results show that the proposed equivalent circuit model and stability criterion can accurately reflect the influence of control parameters on stability, effectively reduce the conservativeness, and obtain a more accurate stability boundary.

[0119] In summary, the present invention proposes a method for analyzing the large-signal stability of a DC microgrid, obtaining the first parameter of the target controller, and establishing a first equivalent model based on the first parameter; presetting a first improvement strategy, improving the first equivalent model according to the first improvement strategy to obtain a first improved model; and performing stability analysis according to the first improved model. The method and system for analyzing the large-signal stability of the DC microgrid of the present invention can more accurately reflect the dynamic behavior of the DC microgrid under large-signal disturbances by establishing an equivalent model and applying an improvement strategy, thereby providing a more accurate stability analysis result. Compared with the traditional analysis method based on small-signal theory, the method of the present invention can effectively avoid the problem that the stability criterion is too conservative, and can comprehensively consider the key parameters of the system, so as to accurately depict the stability boundary of the system. In addition, the present invention can also improve specific model parts, such as the load converter model, further improving the accuracy and practicality of the analysis. Through these improvements, the present invention provides more reliable technical support for the stable operation of the DC microgrid, helps to improve the operation efficiency and reliability of the DC microgrid, and has important practical significance for promoting the integration and consumption of renewable energy.

[0120] In addition, the present invention separately establishes an equivalent circuit model of the source converter and an improved CPL model of the load converter, and obtains a more accurate large-signal stability criterion. The present invention can obtain a stability criterion including the control system, the main circuit parameters, and the improved CPL model, effectively reducing the conservativeness of the traditional method and obtaining a more accurate stability criterion.

[0121] Embodiment 2

[0122] In a preferred embodiment, Figure 2 is a simplified DC microgrid diagram of the present invention. It mainly includes the ESS power supply voltage (v s ), the output voltage of the source converter (v bus ), the filter inductor of the source converter (L s ), the equivalent resistance of the source converter (R s ), the filter capacitor of the source converter (C dc ), the filter inductor of the load converter (L L ), the equivalent resistance of the load converter (R L ), the filter capacitor of the load converter (C L ), the output voltage of the load converter (v out ), and the resistive load (R load ).

[0123] Figure 3 is the equivalent circuit model diagram of the DC microgrid of the present invention. Using Figure 3 the equivalent circuit model of the DC microgrid shown, a stability criterion including the control system, the main circuit parameters, and the improved CPL model can be obtained, effectively reducing the conservativeness of the traditional method and obtaining a more accurate stability criterion.

[0124] Figure 4 is the improved equivalent circuit model diagram of the source converter of the present invention. Since there is an equivalent connection in the mathematical model of the typical PI controller and the RLC circuit in terms of physical essence, the present invention virtually equivalent the converter control system to the RLC circuit, established an equivalent circuit model of the source converter including the control system and the main circuit parameters, and improved it. The improved circuit model is Figure 4 . The following relationships exist in the figure:

[0125]

[0126] Among them, L d is the constructed virtual inductor, and its value approaches 0 infinitely.

[0127] Figure 5This is the CPL model diagram of the present invention. For a DC microgrid containing a CPL, the usual modeling method is to simplify the load converter into an ideal controlled current source, and its current response dynamics can be described as i bus =P CPL / v bus , where PCPL is the constant power load power value. G udc,L (s)=k vp,L +k vi,L / s, G in,L (s)=k ip,L +k ii,L / s, k vp,L and k ii,L are the proportional and integral coefficients of the current inner loop of the load converter respectively. The mathematical model of the load converter is as follows:

[0128]

[0129] The control system model of the load converter is as follows:

[0130]

[0131] where v outref , i Lref are the output voltage reference value and the current inner loop reference value of the load converter respectively, and d L is the duty ratio of the load converter.

[0132] Solving the first differential equation in the mathematical model formula of the load converter gives:

[0133]

[0134] where, is the time-varying term, C is a constant. Combining the above formula with the control system model formula of the load converter gives:

[0135]

[0136] where, g(t)=k ii,L v bus ∫(i Lref -i L )dt - f(t) is the time-varying term.

[0137] Ignoring the energy loss of the load converter, according to the law of conservation of energy, there is:

[0138] i bus v bus =v out i L

[0139] Combining the above two formulas can obtain i busThe detailed expression is as follows:

[0140]

[0141] Figure 6 is the voltage and current waveform diagram under large disturbances of the present invention. When a large disturbance occurs in the system, the bus voltage will fluctuate accordingly. If the change rate of the output current of the source converter with respect to the bus voltage is faster than the change rate of the output current of the load converter with respect to the bus voltage, the system will tend to be stable. However, the dynamic response of the actual load converter is significantly slower than that of the ideal CPL model, as Figure 6 shown. When a large disturbance occurs in the system, it is very likely that the change rate of the output current of the source converter with respect to the bus voltage is faster than that of the actual load converter and slower than that of the ideal CPL model. This means that, compared with the actual load converter, the ideal CPL model will cause the absolute value of μ2 in Equation and Equation to be greater than the actual value, thus introducing conservatism. Therefore, the present invention proposes an improved CPL equivalent model, that is, using the controlled current source Equation to replace P CPL / v bus , as Figure 5 shown.

[0142] Embodiment 3

[0143] This embodiment also provides a large-signal stability analysis system for a DC microgrid, including:

[0144] A model establishment module, configured to obtain the first parameters of the target controller and establish a first equivalent model based on the first parameters;

[0145] A model improvement module, configured to preset a first improvement strategy and improve the first equivalent model according to the first improvement strategy to obtain a first improved model;

[0146] An analysis module, configured to perform stability analysis according to the first improved model.

[0147] The above-mentioned unit modules can be embedded in the processor of the computer device in hardware form or independent of it, or stored in the memory of the computer device in software form, so that the processor can call and execute the operations corresponding to the above-mentioned modules.

[0148] This embodiment also provides a computer device, which can be a terminal, and its internal structure diagram can be as Figure 7As shown in the figure. The computer device includes a processor, a memory, a communication interface, a display screen, and an input device connected through a system bus. Among them, the processor of the computer device is used to provide computing and control capabilities. The memory of the computer device includes a non-volatile storage medium and an internal memory. The non-volatile storage medium stores an operating system and computer programs. The internal memory provides an environment for the operation of the operating system and computer programs in the non-volatile storage medium. The communication interface of the computer device is used to communicate with an external terminal in a wired or wireless manner, and the wireless manner can be implemented through WIFI, a carrier network, NFC (Near Field Communication), or other technologies. When the computer program is executed by the processor, it realizes a method for analyzing the large-signal stability of a DC microgrid. The display screen of the computer device can be a liquid crystal display screen or an electronic ink display screen, and the input device of the computer device can be a touch layer covered on the display screen, or a button, a trackball, or a touchpad provided on the computer device housing, or an external keyboard, touchpad, or mouse, etc.

[0149] This embodiment also provides a computer-readable storage medium, on which a computer program is stored. When the computer program is executed by a processor, the following steps are implemented:

[0150] Obtain the first parameter of the target controller, and establish a first equivalent model based on the first parameter;

[0151] Preset a first improvement strategy, and improve the first equivalent model according to the first improvement strategy to obtain a first improved model;

[0152] Perform stability analysis according to the first improved model.

[0153] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not restrictive. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the spirit and scope of the technical solutions of the present invention, and they should all be covered within the scope of the claims of the present invention.

[0154] Those skilled in the art should understand that the embodiments of the present application can be provided as a method, a system, or a computer program product. Therefore, the present application can adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present application can adopt the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code. The solutions in the embodiments of the present application can be implemented in various computer languages. For example, object-oriented programming languages such as Java and interpreted scripting languages such as JavaScript.

[0155] This application is described with reference to the flowcharts and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the present application. It should be understood that each flow and / or block in the flowchart and / or block diagram, and the combination of flows and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to the processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing device to generate a machine, such that the instructions executed by the processor of the computer or other programmable data processing device produce a means for implementing the functions specified in one Figure 1 flow or multiple flows and / or blocks Figure 1 or multiple blocks.

[0156] These computer program instructions can also be stored in a computer-readable memory that can direct a computer or other programmable data processing device to work in a specific manner, such that the instructions stored in the computer-readable memory produce a manufactured article including an instruction means that implements the functions specified in one Figure 1 flow or multiple flows and / or blocks Figure 1 or multiple blocks.

[0157] These computer program instructions can also be loaded onto a computer or other programmable data processing device, such that a series of operational steps are executed on the computer or other programmable device to generate a computer-implemented process, and thus the instructions executed on the computer or other programmable device provide steps for implementing the functions specified in one Figure 1 flow or multiple flows and / or blocks Figure 1 or multiple blocks.

[0158] Although the preferred embodiments of the present application have been described, those skilled in the art can make additional changes and modifications once they learn the basic creative concepts. Therefore, the appended claims are intended to be construed to include the preferred embodiments as well as all changes and modifications falling within the scope of the present application.

[0159] Obviously, those skilled in the art can make various changes and variations to the present application without departing from the spirit and scope of the present application. Thus, if these modifications and variations of the present application fall within the scope of the claims of the present application and their equivalent technologies, the present application is also intended to include these changes and variations.

Claims

1. A DC microgrid large signal stability analysis method, characterized in that: include: Acquire a first parameter of the target controller, and establish a first equivalent model based on the first parameter; Preset a first improvement strategy, and improve the first equivalent model according to the first improvement strategy to obtain a first improved model; According to the first improved model, stability analysis is performed.

2. The DC microgrid large signal stability analysis method according to claim 1, characterized in that: The performing stability analysis according to the first improved model comprises: The stability analysis includes at least a stability criterion; The stability criterion includes setting a first objective function; The operating parameters of the first improved model are input into the first objective function to obtain a stability analysis result.

3. The DC microgrid large signal stability analysis method according to claim 2, characterized in that: Improving the first equivalent model according to the first improvement strategy includes: The first improvement strategy improves several partial models in the first equivalent model; Determine a part model of the first equivalent model to be improved; The part of the model to be improved is improved according to the first improvement strategy.

4. The DC microgrid large signal stability analysis method according to claim 3, characterized in that: The first equivalent model at least includes a source converter equivalent circuit model and a load converter model.

5. The DC microgrid large signal stability analysis method according to claim 4, characterized in that: The first equivalent model also includes: The source converter adopts voltage-type droop control and voltage-current dual-loop control structure, and the load converter adopts voltage-current dual-loop control structure.

6. The DC microgrid large signal stability analysis method according to claim 5, characterized in that: The source converter equivalent circuit model includes: The source converter equivalent circuit model virtually converts the converter control system into an RLC circuit model; The equivalent RLC circuit model at least includes a source converter voltage outer loop control mathematical model and a current inner loop control mathematical model.

7. The DC microgrid large signal stability analysis method according to claim 6, characterized in that: The part of the model to be improved is the load converter model.

8. A DC microgrid large signal stability analysis system, characterized in that: include: A model building module, used for acquiring a first parameter of a target controller and building a first equivalent model based on the first parameter; A model improvement module, used for presetting a first improvement strategy, improving the first equivalent model according to the first improvement strategy, and obtaining a first improved model; An analysis module is used to perform stability analysis based on the first improved model.

9. A computer device comprising a memory and a processor, wherein the memory stores a computer program, wherein: When the processor executes the computer program, the steps of the method according to any one of claims 1 to 7 are implemented.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the method according to any one of claims 1 to 7 are implemented.

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