Hybrid modeling control method and system of inverter

Abstract

The invention discloses a hybrid modeling control method and system for an inverter, and the method comprises the steps: carrying out the modeling of the grid connection of a control strategy of a grid-following type inverter, and constructing a first inverter grid-connected model; modeling is carried out on control strategy grid connection of the grid-forming type inverter, and a second inverter grid connection model is constructed; according to the first inverter grid-connected model and the second inverter grid-connected model, constructing a single-machine infinite bus model and a multi-bus power system model based on a power flow global characterization method; performing simulation verification on the single-machine infinite bus model and the multi-bus power system model to verify the power response characteristic of the grid-following inverter under the strong power grid and the frequency characteristic of the grid-constructing inverter under the weak power grid, and obtaining a simulation verification result; according to a simulation verification result, adjusting a control strategy of a network-following inverter and a network-constructing inverter; according to the invention, the coexistence scene of the grid-following type inverter and the grid-constructing type inverter can be effectively handled, and the stability of the power system is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of power systems, and in particular to a hybrid modeling control method and system for an inverter. Background Art

[0002] With the increasing penetration of renewable energy, inverter-based resources (such as photovoltaics and energy storage) have gradually become the core power source of power systems. The grid structure has also gradually shifted from being dominated by traditional synchronous generators to a structure supported by inverters. The hybrid operation of grid-following inverters (GFLI) and grid-forming inverters (GFMI) has become a key technical path to improve the stability and flexibility of power systems. Because GFLI relies on grid voltage for synchronization, while GFMI has the ability to independently establish grid voltage and frequency, the dynamic characteristics of the two differ significantly, resulting in severe challenges in the modeling and control of hybrid systems.

[0003] Currently, existing solutions primarily use state-space modeling or frequency-domain analysis to describe the behavior of a single inverter type. However, these solutions are limited in characterizing multi-inverter interactions and multi-physics coupling (such as electromagnetic-electromechanical-control loops). This makes it difficult to support global energy optimization and coordinated control of complex systems, and they are unable to cope with the coexistence of grid-following and grid-forming inverters, impacting power system stability. Summary of the Invention

[0004] In response to the problems existing in the prior art, an embodiment of the present invention provides a hybrid modeling control method and system for an inverter, which can effectively cope with the coexistence scenario of grid-following type and grid-forming type inverters and improve the stability of the power system.

[0005] In a first aspect, an embodiment of the present invention provides a hybrid modeling control method for an inverter, comprising: Modeling the control strategy of the grid-connected inverter and building the first inverter grid-connected model; Model the control strategy of the grid-connected inverter and build a grid-connected model for the second inverter; According to the first inverter grid-connected model and the second inverter grid-connected model, constructing a single-machine infinite bus model and a multi-bus power system model based on a power flow global characterization method; Performing simulation verification on the single-machine infinite bus model and the multi-bus power system model to verify the power response characteristics of the grid-following inverter under a strong power grid and the frequency characteristics of the grid-forming inverter under a weak power grid, and obtaining simulation verification results; According to the simulation verification result, the control strategies of the grid-following inverter and the grid-forming inverter are adjusted.

[0006] As an improvement to the above solution, the control strategy of the grid-connected inverter is modeled to construct a first inverter grid-connected model, including: The control strategy of the grid-connected inverter is equivalent to a power control unit based on a phase-locked loop, and a first inverter grid-connected model based on a single machine infinite bus is constructed.

[0007] As an improvement to the above solution, the control strategy of the grid-connected inverter is modeled to construct a second inverter grid-connected model, including: The control strategy of the grid-connected inverter is equivalent to the swing equation of the virtual synchronous generator, and a second inverter grid-connected model based on a single machine infinite bus is constructed.

[0008] As an improvement to the above solution, the single-machine infinite bus model and the multi-bus power system model are constructed based on the first inverter grid-connected model and the first inverter grid-connected model and the power flow global characterization method, including: The first inverter grid-connected model and the second inverter grid-connected model are coupled to construct a single-machine infinite bus model including control strategies of the grid-following inverter and the grid-forming inverter; The first inverter grid-connected model and the first inverter grid-connected model are embedded into a nine-bus system containing a synchronous generator to construct a multi-source coordinated multi-bus power system model including the synchronous generator, the grid-following inverter and the grid-building inverter.

[0009] As an improvement to the above solution, the single-machine infinite bus model and the multi-bus power system model are simulated and verified to verify the power response characteristics of the grid-following inverter under a strong grid and the frequency characteristics of the grid-forming inverter under a weak grid, and the simulation verification results are obtained, including: The single-machine infinite bus model is simulated and verified to verify the control strategy of the grid-following inverter in a strong grid and the grid-forming inverter in a simple scenario of interaction between a single machine and a grid, and a first verification result is obtained; Performing simulation verification on the multi-bus power system model to verify the control strategy of the grid-following inverter in the strong grid and the grid-forming inverter in a complex scenario of multi-machine collaboration and grid interaction, and obtaining a second verification result; According to the first verification result and the second verification result, the power response characteristics of the grid-following inverter under a strong grid and the frequency characteristics of the grid-forming inverter under a weak grid are determined to obtain simulation verification results.

[0010] As an improvement to the above solution, the control strategy of the grid-connected inverter is equivalent to a power control unit based on a phase-locked loop, and a first inverter grid-connected model based on a single machine infinite bus is constructed, including: The control strategy of the grid-connected inverter is equivalent to a power control unit based on a phase-locked loop, and the circuit topology of the grid-connected inverter is equivalent to a series filter of the grid-connected inverter, to obtain a first basic model; The first basic model is connected to the power grid through a common coupling point, and a first inverter grid-connected model based on a single-machine infinite bus is constructed using a global power flow characterization method.

[0011] As an improvement to the above solution, the control strategy of the grid-connected inverter is equivalent to the swing equation of the virtual synchronous generator, and a second inverter grid-connected model based on a single-machine infinite bus is constructed, including: The control strategy of the grid-type inverter is equivalent to the swing equation of the virtual synchronous generator, and the circuit topology of the grid-type inverter connected to the grid is equivalent to the grid-type inverter series filter, to obtain a second basic model; The second basic model is connected to the power grid through the common coupling point, and the second inverter grid-connected model based on a single machine infinite bus is constructed using the global power flow characterization method.

[0012] As an improvement to the above solution, the nine-bus system includes a nine-node test system.

[0013] In a second aspect, an embodiment of the present invention provides a hybrid modeling control system for an inverter, including: A first modeling module is used to model the control strategy of the grid-connected inverter and build a first inverter grid-connected model; The second modeling module is used to model the control strategy of the grid-connected inverter and build a second inverter grid-connected model; a third modeling module, configured to construct a single-machine infinite bus model and a multi-bus power system model based on the first inverter grid-connected model and the first inverter grid-connected model and a power flow global characterization method; A simulation verification module is used to simulate and verify the single-machine infinite bus model and the multi-bus power system model to verify the power response of the grid-following inverter under a strong grid and the frequency characteristics of the grid-forming inverter under a weak grid, and obtain simulation verification results; A control strategy adjustment module is used to adjust the control strategies of the grid-following inverter and the grid-forming inverter according to the simulation verification result.

[0014] As an improvement to the above solution, the first modeling module includes: The first inverter grid-connected model construction unit is used to make the control strategy of the grid-connected inverter equivalent to a power control unit based on a phase-locked loop, and to construct a first inverter grid-connected model based on a single machine infinite bus.

[0015] Compared with the prior art, the embodiment of the present invention provides a hybrid modeling control method and system for an inverter, which constructs a first inverter grid-connected model by modeling the control strategy of the grid-following inverter; models the control strategy of the grid-forming inverter, and constructs a second inverter grid-connected model; then, according to the first inverter grid-connected model and the first inverter grid-connected model, a single-machine infinite bus model and a multi-bus power system model are constructed based on the global flow characterization method; the single-machine infinite bus model and the multi-bus power system model are simulated and verified to verify the power response characteristics of the grid-following inverter under a strong power grid and the power response characteristics of the grid-forming inverter under a weak power grid. frequency characteristics to obtain simulation verification results; then, according to the simulation verification results, the control strategies of the grid-following inverter and the grid-forming inverter are adjusted; the embodiment of the present invention simplifies the complexity of the multi-physical field coupled power system through the physical causal logic of the global flow characterization method, and realizes the dynamic characteristic characterization in the scenario where the grid-following and grid-forming inverters coexist, which can effectively adapt to various scenarios such as the coexistence of the grid-following and grid-forming inverters, and can utilize the fast power response of the grid-following inverter under the strong power grid, and can utilize the virtual synchronous motor control of the grid-forming inverter to enhance the stability of the weak power grid, improve the adaptability of the inverter control strategy to the complex working conditions of the power grid, and improve the stability of the power system. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the technical solution of the present invention, the following is a brief introduction to the drawings used in the implementation methods. Obviously, the drawings described below are only some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0017] Figure 1 This is a flow chart of a hybrid modeling control method for an inverter provided by an embodiment of the present invention; Figure 2 1 is a schematic diagram of a circuit topology for connecting a grid-connected inverter to the grid according to an embodiment of the present invention; Figure 3 This is a schematic diagram of the circuit topology of the grid-connected grid-connected inverter provided by an embodiment of the present invention. Figure 4 1 is a schematic diagram of a first inverter grid-connected model for grid-connected inverters established based on the energy macroscopic representation method provided by an embodiment of the present invention; Figure 51 is a schematic diagram of a second inverter grid-connected model for grid-connected inverters established based on the energy macroscopic representation method provided by an embodiment of the present invention; Figure 6 Schematic diagram of a single-machine infinite busbar model provided by an embodiment of the present invention; Figure 7 is a schematic diagram of a multi-bus power system model provided by an embodiment of the present invention; Figure 8 Schematic diagram of the inverter modeling and verification process of the power system provided by an embodiment of the present invention; Figure 9 This is a structural block diagram of a hybrid modeling control system for an inverter provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0018] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0019] It is understood that the various numbers used in the embodiments of the present invention are merely for ease of description and are not intended to limit the scope of this application. The order of execution of each process does not necessarily imply a specific order of execution. The order of execution of each process should be determined by its function and inherent logic.

[0020] In embodiments of the present invention, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. The terms "include", "comprises", or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article, or device comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or elements inherent to such process, method, article, or device. In the absence of further restrictions, the elements defined by the statement "includes..." do not exclude the presence of additional identical elements in the process, method, article, or device comprising the elements. The term "plurality or several" refers to two or more.

[0021] The following is an explanation of some terminology concepts involved in the embodiments of the present invention.

[0022] See also Figure 1 , Figure 11 is a flow chart of a hybrid modeling control method for an inverter provided by an embodiment of the present invention. The hybrid modeling control method for an inverter specifically includes: S11: Modeling the control strategy of the grid-connected inverter and building a first inverter grid-connected model; S12: Modeling the control strategy of the grid-connected inverter and building a grid-connected model of the second inverter; S13: constructing a single-machine infinite bus model and a multi-bus power system model based on the first inverter grid-connected model and the second inverter grid-connected model based on a power flow global characterization method; S14: performing simulation verification on the single-machine infinite bus model and the multi-bus power system model to verify the power response characteristics of the grid-following inverter under a strong grid and the frequency characteristics of the grid-forming inverter under a weak grid, and obtaining simulation verification results; S15: According to the simulation verification result, the control strategies of the grid-following inverter and the grid-forming inverter are adjusted.

[0023] It should be noted that the hybrid modeling control method of the inverter described in the embodiment of the present invention can be executed by computing devices such as servers and computers. The embodiment of the present invention integrates the control strategies of the grid-following inverter and the grid-forming inverter with the grid side through the global flow characterization method, and constructs a unified dynamic model from the single-machine infinite bus model to the multi-bus power system model. The physical causal logic of the global flow characterization method simplifies the complexity of the power system coupled with multiple physical fields, and realizes the dynamic characteristic characterization in the scenario where the grid-following and grid-forming inverters coexist. It can effectively cope with various scenarios such as the coexistence of the grid-following and grid-forming inverters, and can utilize the fast power response of the grid-following inverter under the strong power grid, and can also utilize the virtual synchronous motor control of the grid-forming inverter to enhance the stability of the weak power grid, improve the adaptability of the inverter control strategy to the complex working conditions of the power grid, and improve the stability of the power system.

[0024] Grid-following inverters and grid-building inverters are two different types of inverter-based resources (IBRs). Grid-following inverters use a phase-locked loop (PLL) control strategy to follow the grid frequency and phase; grid-building inverters use a virtual synchronous generator (VSG) control strategy to actively adjust active and reactive power to maintain grid stability. It is understood that IBRs typically generate a controllable three-phase AC voltage from a DC-side power source (such as a photovoltaic array or energy storage battery) via a full-bridge inverter circuit. The AC side requires a filter to suppress switching harmonics. Typical circuit topologies include L-type, LC-type, and LCL-type filters. This embodiment of the present invention considers a simplified model of a voltage source converter (VSC) connected in series with an L-type filter, enabling power interaction with the grid through a point of common coupling (PCC).

[0025] In an optional embodiment, S11: modeling the control strategy of the grid-connected inverter to construct a first inverter grid-connected model, including: The control strategy of the grid-connected inverter is equivalent to a power control unit based on a phase-locked loop, and a first inverter grid-connected model based on a single machine infinite bus is constructed.

[0026] Specifically, the control strategy of the grid-connected inverter is equivalent to a power control unit based on a phase-locked loop, and a first inverter grid-connected model based on a single-machine infinite bus is constructed, including: The control strategy of the grid-connected inverter is equivalent to a power control unit based on a phase-locked loop, and the circuit topology of the grid-connected inverter is equivalent to a series filter of the grid-connected inverter, to obtain a first basic model; The first basic model is connected to the power grid through a common coupling point, and a first inverter grid-connected model based on a single-machine infinite bus is constructed using a global power flow characterization method.

[0027] Among them, the circuit topology diagram of the grid-connected inverter is as follows: Figure 2 As shown, in the embodiment of the present invention, a proportional-integral controller based on a phase-locked loop (i.e., a control strategy based on a phase-locked loop) in a grid-following inverter is used to form its power control unit. The control strategy of the phase-locked loop (i.e., the power control unit) is specifically expressed as follows: (1); in, 、 Respectively represent the proportional coefficient and integral coefficient of the phase-locked loop, which are used to adjust the dynamic response speed and stability of the phase-locked loop PLL; represents the three-phase voltage at the connection point between the grid-following inverter and the grid (i.e., the three-phase voltage at the common coupling point); C(s) represents the transfer function of the phase-locked loop; s represents the Laplace complex frequency variable, represents the real part, j represents the imaginary part, represents the angular frequency, Indicates the output phase of the phase-locked loop.

[0028] It can be understood that the above formula (1) is the control strategy of the grid-following inverter.

[0029] In an optional embodiment, S12: modeling the control strategy of the grid-connected inverter to build a second inverter grid-connected model, including: The control strategy of the grid-connected inverter is equivalent to the swing equation of the virtual synchronous generator, and a second inverter grid-connected model based on a single machine infinite bus is constructed.

[0030] Specifically, the control strategy of the grid-connected inverter is equivalent to the swing equation of the virtual synchronous generator, and a second inverter grid-connected model based on a single-machine infinite bus is constructed, including: The control strategy of the grid-type inverter is equivalent to the swing equation of the virtual synchronous generator, and the circuit topology of the grid-type inverter connected to the grid is equivalent to the grid-type inverter series filter, to obtain a second basic model; The second basic model is connected to the power grid through the common coupling point, and the second inverter grid-connected model based on a single machine infinite bus is constructed using the global power flow characterization method.

[0031] Among them, the circuit topology diagram of the grid-connected grid-connected inverter is as follows: Figure 3 As shown, in this embodiment of the present invention, the grid-type inverter imitates the swing equation of a traditional synchronous generator, and the control strategy of the grid-type inverter is equivalent to a virtual synchronous generator. In addition to the active power control loop, it is used to simulate the excitation system. The swing equation of the virtual synchronous generator is as follows: (2); in, represents the equivalent moment of inertia of the virtual synchronous generator; represents the virtual angular velocity of the virtual synchronous generator; Indicates the actual angular velocity of the power grid; Indicates the reference active power of the virtual synchronous generator; It represents the active power actually output by the virtual synchronous generator; D represents the damping coefficient; represents the virtual rotor angular velocity of the virtual synchronous generator, and t represents time.

[0032] The equivalent excitation of the virtual synchronous generator is as follows: (3); in, represents the equivalent excitation voltage of the virtual synchronous generator; Indicates the initial excitation voltage reference value of the virtual synchronous generator; Indicates the reactive power regulation coefficient of the virtual synchronous generator; represents the voltage regulation coefficient of the virtual synchronous generator; Indicates the system rated voltage of the virtual synchronous generator (i.e. the voltage expected to be output); Indicates the voltage at the point of common coupling; represents the reference reactive power of the virtual synchronous generator; Represents the reactive power actually output by the virtual synchronous generator.

[0033] It can be understood that the above formulas (2) and (3) are the control strategies of the grid-connected inverter.

[0034] By combining the grid-connected inverter, grid-connected inverter and single-machine infinite bus (SMIB) with the global power flow characterization method, the corresponding first inverter grid-connected model (i.e., the GFLI-SMIB model under the single-machine infinite bus system, such as Figure 4 As shown), the second inverter grid-connected model (i.e., the GFMI-SMIB model under the single-machine infinite system SMIB system, as shown Figure 5 shown).

[0035] When the inverter GFLI / GFMI adopts the single-machine infinite bus (SMIB) scheme, the global power flow representation method (i.e., energy macroscopic representation, EMR) of the GFLI / GFMI-SMIB model is as follows: Figure 4 、 Figure 5 shown.

[0036] On the grid side, each phase of the inverter GFLI / GFMI is connected to an ideal voltage source through a series RL branch. According to Kirchhoff's voltage law, the model of the grid impedance block is expressed as follows: (4); in, Indicates the voltage at the point of common coupling; Indicates the grid voltage; Indicates the equivalent inductance on the grid side; Indicates the equivalent resistance on the grid side; Indicates the common coupling point current.

[0037] To calculate the voltage at the point of common coupling (PCC), the power control unit uses the control strategy in the basic model corresponding to the inverter GFLI / GFMI, taking the grid voltage source as input. The specific representation of the grid voltage source as input is as follows: (5); in, Indicates the filter inductance on the inverter side; Indicates the filter resistor on the inverter side; Indicates the inverter output voltage.

[0038] In an optional embodiment, S13: constructing a single-machine infinite bus model and a multi-bus power system model based on the first inverter grid-connected model and the first inverter grid-connected model based on a power flow global characterization method, including: The first inverter grid-connected model and the second inverter grid-connected model are coupled to construct a single-machine infinite bus model including control strategies of the grid-following inverter and the grid-forming inverter; The first inverter grid-connected model and the first inverter grid-connected model are embedded into a nine-bus system containing a synchronous generator to construct a multi-source coordinated multi-bus power system model including the synchronous generator, the grid-following inverter and the grid-building inverter.

[0039] The nine-bus system includes a nine-node test system, such as an IEEE nine-node test system or an improved IEEE nine-node test system.

[0040] In the embodiment of the present invention, in a hybrid power system, the power control unit adopts the control strategies of GFLI and GFMI at the same time, and couples the GFLI-SMIB model under the single-machine infinite bus system SMIB system and the GFMI-SMIB model under the single-machine infinite bus system SMIB system, so as to obtain a single-machine infinite bus model suitable for simple scenarios in the hybrid power system, such as Figure 6 shown.

[0041] Furthermore, the embodiment of the present invention uses an improved IEEE nine-bus system (also known as an IEEE nine-node test system) for simulation to construct a multi-bus power system model, such as Figure 7 The system includes three power sources: a synchronous generator, a grid-connected inverter GFMI, and a grid-following inverter GFLI. The voltage calculation method for the point of common coupling (PCC) is the same as that for the single-machine infinite bus (SMIB) system. Specifically, the voltage between lines m and n can be expressed as: (6); in, Indicates the inductance between lines m and n; Indicates the resistance between lines m and n; represents the inductance of line n; represents the resistance of circuit n; Indicates the simulated grid voltage; Indicates the bus voltage corresponding to line m, that is, the bus voltage connected to the power source associated with line m (such as load, synchronous generator, grid-connected inverter GFMI, grid-connected inverter GFLI).

[0042] Among them, the bus voltage Voltage across the three adjacent busbars / points of common coupling (PCC) 、 、 The calculations are as follows: (7); in, Indicates bus voltage; 、 、 Respectively represent the inductance of lines i, j, and k associated with the three adjacent busbars / points of common coupling PCC; 、 、 Respectively represent the resistance of lines i, j, and k associated with three adjacent busbars / points of common coupling PCC; 、 、 Respectively represent the voltages of the lines related to the three adjacent busbars / common coupling points PCC.

[0043] Assume that the load in the improved IEEE nine-bus system is a resistance-inductance (RL) load. is the bus voltage to which the load is connected, the mathematical model of the load is as follows: (8); in, Indicates the load equivalent inductance; Indicates the load equivalent resistance; Indicates the load current.

[0044] In an optional embodiment, S14: performing simulation verification on the single-machine infinite bus model and the multi-bus power system model to verify the power response characteristics of the grid-following inverter under a strong grid and the frequency characteristics of the grid-forming inverter under a weak grid, and obtaining simulation verification results, including: The single-machine infinite bus model is simulated and verified to verify the control strategy of the grid-following inverter in a strong grid and the grid-forming inverter in a simple scenario of interaction between a single machine and a grid, and a first verification result is obtained; Performing simulation verification on the multi-bus power system model to verify the control strategy of the grid-following inverter in the strong grid and the grid-forming inverter in a complex scenario of multi-machine collaboration and grid interaction, and obtaining a second verification result; According to the first verification result and the second verification result, the power response characteristics of the grid-following inverter under a strong grid and the frequency characteristics of the grid-forming inverter under a weak grid are determined to obtain simulation verification results.

[0045] In the embodiment of the present invention, dynamic simulation verification is performed on a single machine infinite bus model in a simple scenario and a multi-bus power system model in a complex scenario, such as using MATLAB or Simulink simulation, to verify the effectiveness of the control strategies of the two inverters. Figure 8 As shown, the specific process is as follows: Decomposition and modeling are performed on power systems containing inverter-type power sources to break down complex power systems into analyzable submodules, laying the foundation for subsequent simulation and verification. Specifically, the inverter type of the inverter-type power source in the power system is determined. For inverter-type power sources with grid-following inverters (GFLI), the energy macro-representation (EMR) modeling is based on a control strategy using a phase-locked loop (PLL) to track the grid phase and PI to control current and power. For inverter-type power sources with grid-forming inverters (GFMI), the energy macro-representation (EMR) modeling is based on a control strategy using virtual synchronous generators (VSG) to regulate voltage using virtual excitation.

[0046] Understandably, the GFLI grid-following inverter uses a phase-locked loop (PLL) to synchronize the inverter with the grid frequency and phase, ensuring grid-connected current and power are compatible with the grid. PI control rapidly adjusts output current or active and reactive power to track grid demand. The GFMI grid-forming inverter simulates the "inertia + frequency / voltage regulation" characteristics of a synchronous generator, giving the inverter voltage support and frequency response capabilities. The virtual excitation stage dynamically adjusts the output voltage amplitude to adapt to grid or load voltage requirements.

[0047] The grid impedance, load, and line of the power system are coupled with the model obtained after the above modeling according to the actual electrical connection; specifically, according to the research scenario requirements, coupling models of different grid model levels are constructed, such as the model of a simple scenario of a single-machine infinite SMIB or the model of a complex scenario of an IEEE nine-bus system, and dynamic simulation verification is performed, such as using MATLAB / Simulink to simulate the dynamic process of the grid (such as load switching, short-circuit faults, power supply fluctuations, etc.).

[0048] Based on the inverter type (GFLI / GFMI), we focus on the performance indicators of simple and complex grid scenarios: GFLI performance evaluation results: Fast power response under strong grid conditions. For example, in a verification scenario, the speed with which GFLI tracks grid commands (e.g., current / power response time and overshoot after a sudden change in power command) was evaluated when the grid short-circuit capacity was large (strong grid).

[0049] GFMI performance evaluation results: Frequency stability in weak grid conditions. For example, the verification scenario examined GFMI's ability to simulate the inertia and damping characteristics of synchronous machines (e.g., GFMI frequency regulation speed and frequency steady-state error after grid frequency fluctuations) when the grid short-circuit capacity is low (weak grid).

[0050] It is understandable that for dynamic simulations in simple scenarios and complex scenarios, the above GFLI performance evaluation results and GFMI performance evaluation results can be obtained as the first verification results in the corresponding simple scenarios and the second verification results in the corresponding complex scenarios.

[0051] By summarizing the above GFLI / GFMI performance evaluation results, simulation verification results can be obtained and output.

[0052] Furthermore, based on the frequency stability of GFMI under weak power grid and the fast power response of GFLI under strong power grid, the advantages and disadvantages of the control strategies are analyzed and the control strategies of GFMI and GFLI are adjusted.

[0053] For example, for the grid-forming inverter GFMI, the virtual inertia and damping coefficient are dynamically adjusted to optimize the frequency stability of the grid-forming inverter GFMI under weak power grids; for the grid-following inverter GFLI, the phase-locked loop and feedforward compensation are enhanced to optimize the fast power response speed of the grid-following inverter GFLI under strong power grids; for example, in complex scenarios, it is necessary to take into account the characteristics of GFMI and GFLI for zoning control and interactive supplementation. For example, GFMI is deployed preferentially in weak power grid areas (such as remote busbars) to stabilize local frequency through virtual inertia and voltage support; GFLI is deployed in strong power grid areas (such as main grid-side busbars) to achieve power dispatch and absorb new energy through fast power response; GFMI and GFLI exchange frequency and power information through "virtual interconnection lines". When GFLI power responds quickly, GFMI dynamically adjusts the inertia compensation system inertia to avoid frequency shocks caused by large-scale power fluctuations of GFLI under strong power grids. Through "differentiated optimization + collaborative compensation", the frequency of GFMI in weak power grids is more stable and the power response of GFLI in strong power grids is faster. At the same time, the cross-scenario adaptation problem is solved, and the overall stability and responsiveness of the multi-source power system are improved.

[0054] See also Figure 9 , Figure 91 is a block diagram of a hybrid modeling control system for an inverter provided by an embodiment of the present invention. The hybrid modeling control system for the inverter includes: A first modeling module 11 is used to model the control strategy of the grid-connected inverter and build a first inverter grid-connected model; The second modeling module 12 is used to model the control strategy of the grid-connected inverter and build a second inverter grid-connected model; A third modeling module 13 is configured to construct a single-machine infinite bus model and a multi-bus power system model based on the first inverter grid-connected model and the first inverter grid-connected model and a power flow global characterization method; A simulation verification module 14 is used to simulate and verify the single-machine infinite bus model and the multi-bus power system model to verify the power response of the grid-following inverter under a strong grid and the frequency characteristics of the grid-forming inverter under a weak grid, and obtain simulation verification results; The control strategy adjustment module 15 is used to adjust the control strategies of the grid-following inverter and the grid-forming inverter according to the simulation verification result.

[0055] In an optional embodiment, the first modeling module 11 includes: The first inverter grid-connected model construction unit is used to make the control strategy of the grid-connected inverter equivalent to a power control unit based on a phase-locked loop, and to construct a first inverter grid-connected model based on a single machine infinite bus.

[0056] As an improvement of the above solution, the second modeling module 12 includes: The second inverter grid-connected model construction unit is used to equate the control strategy of the grid-connected inverter to the swing equation of the virtual synchronous generator, and to construct the second inverter grid-connected model based on a single-machine infinite bus.

[0057] In an optional embodiment, the third modeling module 13 includes: a single-machine infinite bus model construction unit, configured to couple the first inverter grid-connected model and the first inverter grid-connected model to construct a single-machine infinite bus model including control strategies for the grid-following inverter and the grid-forming inverter; A multi-bus power system model construction unit is used to embed the first inverter grid-connected model and the first inverter grid-connected model into a nine-bus system containing a synchronous generator, and construct a multi-bus power system model with multi-source coordination including the synchronous generator, the grid-following inverter and the grid-forming inverter.

[0058] In an optional embodiment, the simulation verification module 14 includes: A first verification unit is used to simulate and verify the single-machine infinite bus model to verify the control strategy of the grid-following inverter in the strong grid and the grid-forming inverter in a simple scenario of interaction between the single machine and the grid, and obtain a first verification result; A second verification unit is used to simulate and verify the multi-bus power system model to verify the control strategy of the grid-following inverter in the strong grid and the grid-forming inverter in a complex scenario of multi-machine collaboration and interaction with the grid, and obtain a second verification result; The simulation verification result obtaining unit is used to determine the power response characteristics of the grid-following inverter under a strong grid and the frequency characteristics of the grid-forming inverter under a weak grid based on the first verification result and the second verification result, and obtain the simulation verification result.

[0059] In an optional embodiment, the first inverter grid-connected model building unit includes: A first basic model construction subunit is configured to equate the control strategy of the grid-connected inverter to a power control unit based on a phase-locked loop, and equate the grid-connected circuit topology of the grid-connected inverter to a series filter of the grid-connected inverter, thereby obtaining a first basic model; The first grid-connected model construction subunit is used to connect the first basic model to the power grid through the common coupling point, and use the power flow global characterization method to construct a first inverter grid-connected model based on a single machine infinite bus.

[0060] In an optional embodiment, the second inverter grid-connected model building unit includes: A second basic model construction subunit is used to equate the control strategy of the grid-type inverter to the swing equation of the virtual synchronous generator, and equate the grid-connected circuit topology of the grid-type inverter to the grid-type inverter series filter, to obtain a second basic model; The second grid-connected model construction subunit is used to connect the second basic model to the power grid through the common coupling point, and use the power flow global characterization method to construct a second inverter grid-connected model based on a single machine infinite bus.

[0061] In an optional embodiment, the nine-bus system includes a nine-node test system.

[0062] It should be noted that the working process of each module in the hybrid modeling control system of the inverter described in the embodiment of the present invention can refer to the working process of the hybrid modeling control method of the inverter described in the above embodiment, and the technical effect achieved is also the same as the hybrid modeling control method of the inverter described in the above embodiment, which will not be repeated here.

[0063] It should be noted that the system embodiment described above is merely illustrative, wherein the units described as separate components may or may not be physically separate, and the components displayed as units may or may not be physical units, that is, they may be located in one place, or they may be distributed across multiple network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the present embodiment. In addition, in the drawings of the system embodiment provided by the present invention, the connection relationship between the modules indicates that there is a communication connection between them, which can be specifically implemented as one or more communication buses or signal lines. A person of ordinary skill in the art can understand and implement the present invention without inventive work.

[0064] The above is a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, various improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A hybrid modeling control method for an inverter, characterized in that: include: Modeling the control strategy of the grid-connected inverter and building the first inverter grid-connected model; Model the control strategy of the grid-connected inverter and build a grid-connected model for the second inverter; According to the first inverter grid-connected model and the second inverter grid-connected model, constructing a single-machine infinite bus model and a multi-bus power system model based on a power flow global characterization method; Performing simulation verification on the single-machine infinite bus model and the multi-bus power system model to verify the power response characteristics of the grid-following inverter under a strong power grid and the frequency characteristics of the grid-forming inverter under a weak power grid, and obtaining simulation verification results; According to the simulation verification result, the control strategies of the grid-following inverter and the grid-forming inverter are adjusted.

2. The hybrid modeling control method for an inverter according to claim 1, wherein: The control strategy for the grid-connected inverter is modeled to construct a first inverter grid-connected model, including: The control strategy of the grid-connected inverter is equivalent to a power control unit based on a phase-locked loop, and a first inverter grid-connected model based on a single machine infinite bus is constructed.

3. The hybrid modeling control method for an inverter according to claim 1, wherein: The control strategy of the grid-connected inverter is modeled to construct a second inverter grid-connected model, including: The control strategy of the grid-connected inverter is equivalent to the swing equation of the virtual synchronous generator, and a second inverter grid-connected model based on a single machine infinite bus is constructed.

4. The hybrid modeling control method for an inverter according to claim 1, wherein: The step of constructing a single-machine infinite bus model and a multi-bus power system model based on the power flow global characterization method according to the first inverter grid-connected model and the second inverter grid-connected model includes: The first inverter grid-connected model and the second inverter grid-connected model are coupled to construct a single-machine infinite bus model including control strategies of the grid-following inverter and the grid-forming inverter; The first inverter grid-connected model and the first inverter grid-connected model are embedded into a nine-bus system containing a synchronous generator to construct a multi-source coordinated multi-bus power system model including the synchronous generator, the grid-following inverter and the grid-building inverter.

5. The hybrid modeling control method for an inverter according to claim 1, wherein: The simulation verification of the single-machine infinite bus model and the multi-bus power system model is performed to verify the power response characteristics of the grid-following inverter under a strong grid and the frequency characteristics of the grid-forming inverter under a weak grid, and the simulation verification results are obtained, including: The single-machine infinite bus model is simulated and verified to verify the control strategy of the grid-following inverter in a strong grid and the grid-forming inverter in a simple scenario of interaction between a single machine and a grid, and a first verification result is obtained; Performing simulation verification on the multi-bus power system model to verify the control strategy of the grid-following inverter in the strong grid and the grid-forming inverter in a complex scenario of multi-machine collaboration and grid interaction, and obtaining a second verification result; According to the first verification result and the second verification result, the power response characteristics of the grid-following inverter under a strong grid and the frequency characteristics of the grid-forming inverter under a weak grid are determined to obtain simulation verification results.

6. The hybrid modeling control method for an inverter according to claim 2, wherein: The control strategy of the grid-connected inverter is equivalent to a power control unit based on a phase-locked loop, and a first inverter grid-connected model based on a single machine infinite bus is constructed, including: The control strategy of the grid-connected inverter is equivalent to a power control unit based on a phase-locked loop, and the circuit topology of the grid-connected inverter is equivalent to a series filter of the grid-connected inverter, to obtain a first basic model; The first basic model is connected to the power grid through a common coupling point, and a first inverter grid-connected model based on a single-machine infinite bus is constructed using a global power flow characterization method.

7. The hybrid modeling control method for an inverter according to claim 3, wherein: The control strategy of the grid-connected inverter is equivalent to the swing equation of the virtual synchronous generator, and a second inverter grid-connected model based on a single-machine infinite bus is constructed, including: The control strategy of the grid-type inverter is equivalent to the swing equation of the virtual synchronous generator, and the circuit topology of the grid-type inverter connected to the grid is equivalent to the grid-type inverter series filter, to obtain a second basic model; The second basic model is connected to the power grid through the common coupling point, and the second inverter grid-connected model based on a single machine infinite bus is constructed using the global power flow characterization method.

8. The hybrid modeling control method for an inverter according to claim 4, wherein: The nine-bus system includes a nine-node test system.

9. A hybrid modeling control system for an inverter, characterized in that: include: A first modeling module is used to model the control strategy of the grid-connected inverter and build a first inverter grid-connected model; The second modeling module is used to model the control strategy of the grid-connected inverter and build a second inverter grid-connected model; a third modeling module, configured to construct a single-machine infinite bus model and a multi-bus power system model based on the first inverter grid-connected model and the first inverter grid-connected model and a power flow global characterization method; A simulation verification module is used to simulate and verify the single-machine infinite bus model and the multi-bus power system model to verify the power response of the grid-following inverter under a strong grid and the frequency characteristics of the grid-forming inverter under a weak grid, and obtain simulation verification results; A control strategy adjustment module is used to adjust the control strategies of the grid-following inverter and the grid-forming inverter according to the simulation verification result.

10. The hybrid modeling control system of the inverter according to claim 9, characterized in that: The first modeling module includes: The first inverter grid-connected model construction unit is used to make the control strategy of the grid-connected inverter equivalent to a power control unit based on a phase-locked loop, and to construct a first inverter grid-connected model based on a single machine infinite bus.

Images