Three-level inverter linear periodic time-varying model considering neutral point dynamics

Abstract

The invention belongs to the technical field of power systems, and particularly discloses a three-level inverter linear periodic time-varying model considering neutral point dynamics. According to the method, the non-differentiable terms in the original nonlinear model of the three-level inverter are divided into a plurality of linear segments by adopting a segmented linearization processing mode, linearization processing is carried out in each segment, and the non-differentiable terms of non-differentiable parts (such as neutral point voltage and neutral point current) are eliminated; the local analysis of the obtained linear period time-varying model of the three-level inverter is ensured, and the problem of difficulty in overall linearization is avoided. The three-level inverter linear period time-varying model is generated in combination with the steady-state track, the small disturbance characteristic of the three-level inverter can be comprehensively reflected, particularly, the neutral point dynamic characteristic of the three-level inverter under small disturbance can be accurately described, the behavior of the three-level inverter under small disturbance can be effectively described, and the three-level inverter can be applied to the field of small disturbance. The method can be applied to small-interference stability analysis of a three-level inverter-containing power system.

Description

Technical Field

[0001] The present application belongs to the technical field of power systems, and more specifically, relates to a linear periodic time-varying model of a three-level inverter considering neutral point dynamics. Background Art

[0002] At present, new energy sources such as wind power and photovoltaic power generation have been rapidly developed. With the continuous increase in the capacity of new energy units, higher requirements are placed on the power level of inverters. Three-level inverters are widely used in wind power and photovoltaic power generation because they are suitable for high voltage, large capacity, high efficiency and low harmonic content. However, as the proportion of new energy in the power grid continues to increase, the power system has gradually shown a trend of power electronics, its stability characteristics have changed, and electromagnetic oscillation accidents have occurred frequently in actual systems.

[0003] The small disturbance model of power electronic equipment is the basis for studying the stability of power systems with small disturbances. Establishing an accurate small disturbance model is of great significance for studying the stability mechanism of the system. At present, the two-level wind turbine model is generally used to model the small disturbance of new energy three-level grid-connected inverters. There is no relevant research on the small disturbance model of three-level inverters considering the dynamics of the neutral point. It cannot accurately reflect the internal characteristics of the three-level inverter, resulting in some oscillation modes that cannot be identified, making the stability analysis of the power system not comprehensive enough. Summary of the invention

[0004] In view of the defects of the prior art, the purpose of this application is to provide a linear periodic time-varying model of a three-level inverter taking into account the dynamics of the neutral point, aiming to solve the problem that the two-level wind turbine model equivalent used in the prior art cannot accurately reflect the internal characteristics of the three-level inverter, resulting in certain oscillation modes being unable to be identified, making the stability analysis of the power system not comprehensive enough.

[0005] To achieve the above objectives, in a first aspect, the present application provides a linear periodic time-varying model of a three-level inverter considering the dynamics of a neutral point, comprising: A building block for constructing the original nonlinear model of the three-level inverter taking into account the neutral point dynamics; A first processing module is used to perform piecewise processing on non-differentiable items in the original nonlinear model of the three-level inverter to obtain a nonlinear model of the three-level inverter; The second processing module is used to perform piecewise linearization processing on the nonlinear model of the three-level inverter to obtain a linear periodic time-varying model of the three-level inverter considering the dynamics of the neutral point.

[0006] In some embodiments, the original nonlinear model of the three-level inverter includes: External circuit dynamic module, power outer loop controller, current inner loop controller, phase-locked loop controller, internal circuit dynamic module and neutral point potential balance controller; The external circuit dynamic module is used to send the output current and grid connection point voltage of the three-level inverter to the phase-locked loop controller, the power outer loop controller and the current inner loop controller, and send the output current, power factor angle and output current amplitude to the internal circuit dynamic module; The phase-locked loop controller is used to determine the phase-locked angle according to the output current and the grid-connected point voltage, and send the phase-locked angle to the inner circuit dynamic module, the current inner loop controller and the power outer loop controller respectively; The power outer loop controller is used to generate a reference current according to the phase-locking angle, the grid-connected point voltage and the output current, and send the reference current to the current inner loop controller; The current inner loop controller is used to generate a modulation wave according to the phase-locking angle, the reference current and the output current, and send the modulation wave to the inner circuit dynamic module; The internal circuit dynamic module is used to determine the neutral point current and neutral point voltage of the three-level inverter according to the output value of the neutral point potential balance controller, the phase-locking angle, the output current and the modulation wave; The neutral point potential balance controller is used to determine the output value according to the neutral point voltage.

[0007] In some embodiments, the first processing module is further configured to: The non-differentiable items in the neutral point current and neutral point voltage are processed piecewise to obtain a nonlinear model of the three-level inverter.

[0008] In some embodiments, the neutral point potential balance controller adopts a proportional-integral controller.

[0009] In some embodiments, the second processing module is further configured to: Determine the steady-state trajectory of a nonlinear model of a three-level inverter as it operates to a steady-state condition.

[0010] In some embodiments, the three-level inverter is a neutral point clamped three-level inverter or a T-type three-level inverter.

[0011] In a second aspect, the present application provides a method for constructing a linear periodic time-varying model of a three-level inverter considering the dynamics of a neutral point, comprising: Construct the original nonlinear model of three-level inverter considering the neutral point dynamics; The non-differentiable items in the original nonlinear model of the three-level inverter are processed piecewise to obtain the nonlinear model of the three-level inverter. The nonlinear model of the three-level inverter is piecewise linearized to obtain a linear periodic time-varying model of the three-level inverter considering the neutral point dynamics.

[0012] In a third aspect, the present application provides an electronic device comprising: at least one memory for storing programs; and at least one processor for executing the programs stored in the memory. When the programs stored in the memory are executed, the processor is used to execute the method described in the first aspect or any embodiments of the first aspect.

[0013] In a fourth aspect, the present application provides a computer-readable storage medium, which stores a computer program. When the computer program runs on a processor, the processor executes the method described in the first aspect or any embodiments of the first aspect.

[0014] In a fifth aspect, the present application provides a computer program product. When the computer program product runs on a processor, the processor executes the method described in the first aspect or any embodiments of the first aspect.

[0015] In general, the above technical solutions conceived by this application have the following beneficial effects compared with the prior art: The linear periodic time-varying model of the three-level inverter considering the neutral point dynamics provided in the present application adopts a segmented linearization processing method to divide the non-differentiable items in the original nonlinear model of the three-level inverter into multiple linear segments, and performs linearization processing in each segment to eliminate the non-differentiable items of the non-differentiable part (such as the neutral point voltage and the neutral point current), thereby ensuring that the obtained linear periodic time-varying model of the three-level inverter can be analyzed locally and avoiding the problem of overall linearization difficulties. The linear periodic time-varying model of the three-level inverter is generated in combination with the steady-state trajectory, which can fully reflect the small disturbance characteristics of the three-level inverter, especially, it can accurately describe the dynamic characteristics of the neutral point of the three-level inverter under small disturbances, effectively characterize the behavior of the three-level inverter under small disturbances, and can be applied to the small disturbance stability analysis of the power system containing the three-level inverter. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is one of the structural schematic diagrams of a linear periodic time-varying model of a three-level inverter considering the dynamics of the neutral point provided in an embodiment of the present application; Figure 2 This is the second structural schematic diagram of a linear periodic time-varying model of a three-level inverter considering the neutral point dynamics provided in an embodiment of the present application; Figure 3 It is a schematic diagram comparing the time domain responses of the neutral point dynamics of the linear periodic time-varying model of the three-level inverter provided by the embodiment of the present application and the original nonlinear model of the three-level inverter under small disturbances; Figure 4 It is a flow chart of a method for constructing a linear periodic time-varying model of a three-level inverter considering the dynamics of a neutral point provided in an embodiment of the present application; Figure 5It is a schematic diagram of the structure of an electronic device provided in an embodiment of the present application. DETAILED DESCRIPTION

[0017] In order to make the purpose, technical solution and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0018] The term "and / or" in this article is a description of the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. The symbol " / " in this article indicates that the associated objects are in an or relationship, for example, A / B means A or B.

[0019] The terms "first" and "second" in the specification and claims herein are used to distinguish different objects rather than to describe a specific order of the objects. For example, a first processing module and a second processing module are used to distinguish different processing modules rather than to describe a specific order of the processing modules.

[0020] In the embodiments of the present application, words such as "exemplary" or "for example" are used to indicate examples, illustrations or descriptions. Any embodiment or design described as "exemplary" or "for example" in the embodiments of the present application should not be interpreted as being more preferred or more advantageous than other embodiments or designs. Specifically, the use of words such as "exemplary" or "for example" is intended to present related concepts in a specific way.

[0021] In the description of the embodiments of the present application, unless otherwise specified, “plurality” means two or more than two.

[0022] The embodiments of the present application are described below in conjunction with the drawings in the embodiments of the present application.

[0023] See also Figure 1 An embodiment of the present application provides a linear periodic time-varying model of a three-level inverter considering the dynamics of a neutral point, including: a construction module 110, a first processing module 120 and a second processing module 130.

[0024] A construction module 110 is used to construct an original nonlinear model of a three-level inverter considering the neutral point dynamics; A first processing module 120 is used to perform piecewise processing on non-differentiable items in the original nonlinear model of the three-level inverter to obtain a nonlinear model of the three-level inverter; The second processing module 130 is used to perform piecewise linearization processing on the nonlinear model of the three-level inverter to obtain a linear periodic time-varying model of the three-level inverter that takes into account the dynamics of the neutral point.

[0025] In the embodiment of the present application, the three-level inverter linear periodic time-varying model may specifically include a construction module 110 , a first processing module 120 and a second processing module 130 .

[0026] The dynamic balance of the neutral point of the three-level inverter is a key issue in its operation, which directly affects the output voltage quality, device stress and system reliability. Based on this, in the embodiment of the present application, the original nonlinear model corresponding to the three-level inverter considering the neutral point dynamics (i.e., the original nonlinear model of the three-level inverter) is established by building module 110.

[0027] Furthermore, in some embodiments, the three-level inverter is a neutral point clamped three-level inverter or a T-type three-level inverter.

[0028] In the embodiment of the present application, the three-level inverter may be a neutral point clamped three-level inverter or a T-type three-level inverter.

[0029] In addition, since the neutral point current is affected by the control logic of the switching devices, there are non-differentiable points in the power system, making it difficult to linearize the original nonlinear model of the three-level inverter considering the neutral point dynamics. The neutral point potential of the three-level inverter exhibits a time-varying characteristic of 3-fold frequency pulsation under steady-state conditions, which also puts forward requirements for the small disturbance model of the three-level inverter.

[0030] Based on this, in the embodiment of the present application, the non-differentiable terms in the original non-linear model corresponding to the three-level inverter established above are processed piecewise in combination with the first processing module 120 to construct a non-linear model of the three-level inverter.

[0031] The nonlinear model of the three-level inverter obtained above is linearized in combination with the second processing module 130 to obtain a linear periodic time-varying model of the three-level inverter that takes into account the dynamics of the neutral point.

[0032] The linear periodic time-varying model of the three-level inverter considering the neutral point dynamics provided in the embodiment of the present application adopts a segmented linearization processing method to divide the non-differentiable items in the original nonlinear model of the three-level inverter into multiple linear segments, and performs linearization processing in each segment to eliminate the non-differentiable items of the non-differentiable part (such as the neutral point voltage and the neutral point current), thereby ensuring that the obtained linear periodic time-varying model of the three-level inverter can be analyzed locally and avoiding the problem of overall linearization difficulties. The linear periodic time-varying model of the three-level inverter is generated in combination with the steady-state trajectory, which can fully reflect the small disturbance characteristics of the three-level inverter, especially, it can accurately describe the dynamic characteristics of the neutral point of the three-level inverter under small disturbances, effectively characterize the behavior of the three-level inverter under small disturbances, and can be applied to the small disturbance stability analysis of the power system containing the three-level inverter.

[0033] Furthermore, in some embodiments, the original nonlinear model of the three-level inverter includes: External circuit dynamic module, power outer loop controller, current inner loop controller, phase-locked loop controller, internal circuit dynamic module and neutral point potential balance controller; The external circuit dynamic module is used to send the output current and grid connection point voltage of the three-level inverter to the phase-locked loop controller, the power outer loop controller and the current inner loop controller, and send the output current, power factor angle and output current amplitude to the internal circuit dynamic module; The phase-locked loop controller is used to determine the phase-locked angle according to the output current and the grid-connected point voltage, and send the phase-locked angle to the inner circuit dynamic module, the current inner loop controller and the power outer loop controller respectively; The power outer loop controller is used to generate a reference current according to the phase-locking angle, the grid-connected point voltage and the output current, and send the reference current to the current inner loop controller; The current inner loop controller is used to generate a modulation wave according to the phase-locking angle, the reference current and the output current, and send the modulation wave to the inner circuit dynamic module; The internal circuit dynamic module is used to determine the neutral point current and neutral point voltage of the three-level inverter according to the output value of the neutral point potential balance controller, the phase-locking angle, the output current and the modulation wave; The neutral point potential balance controller is used to determine the output value according to the neutral point voltage.

[0034] In the embodiment of the present application, the constructed original nonlinear model of the three-level inverter may include an external circuit dynamic module, a power outer loop controller, a current inner loop controller, a phase-locked loop controller, an internal circuit dynamic module, a neutral point potential balance controller, etc., as shown in FIG. Figure 2 shown.

[0035] Among them, the external circuit dynamic module reflects the output current of the three-level inverter , internal potential , grid connection point voltage Specifically, the external circuit dynamic module is used to convert the output current of the three-level inverter and grid voltage Send to the phase-locked loop controller power outer loop controller and current inner loop controller, the output current , power factor angle and output current The amplitude is sent to the inner circuit dynamic module; the power outer loop controller is used to , grid connection point voltage and output current Generate a reference current and send the reference current to the current inner loop controller, so that the current inner loop controller can generate a reference current according to the reference current and the phase-locked angle. and output current , generating the modulated wave Specifically, the power outer loop controller is used to perform Park transformation on the grid connection point voltage and output current to obtain a reference current; the phase-locked loop controller is used to and grid voltage , the output phase-lock angle The power outer loop reference module is used to output the reference value of the active power and reactive power output of the three-level inverter. for Three-phase modulation wave, output current include Three-phase output current , .

[0036] The internal circuit dynamic module can be used to adjust the output value of the neutral point potential balance controller , Phase-locking angle , output current and modulation wave , determine the neutral point current of the three-level inverter and neutral point voltage .

[0037] Specifically, the internal circuit dynamic module includes the DC side voltage dynamics and the neutral point voltage dynamics, the neutral point current of the three-level inverter It can be expressed as:

[0038] In the formula, the absolute value of the three-phase modulation wave is a continuous non-differentiable term, is the output current i abc The amplitude of is the power factor angle, which can be obtained by measurement.

[0039] Neutral point voltage The expression is:

[0040] In the formula, Represents the neutral point voltage The derivative of (the voltage difference between the two capacitors), and is the capacitance value of the two capacitors connected in series on the DC side.

[0041] The neutral point potential balance controller is used to , determine the output value , the output value It is a three-phase modulated wave.

[0042] Furthermore, in some embodiments, the neutral point potential balance controller adopts a proportional-integral controller.

[0043] In the embodiment of the present application, the neutral point potential balance controller may adopt a proportional-integral controller.

[0044] The neutral point potential balance controller is specifically used to balance the neutral point voltage , which can be expressed as:

[0045] In the formula, is the proportional gain coefficient of the neutral point potential balance controller (i.e. proportional-integral controller), is the integral adjustment coefficient of the neutral point potential balance controller, is the output of the proportional link, is the input of the integration phase, is the voltage on the DC side of the three-level inverter.

[0046] The above formulas together constitute the original nonlinear model of the three-level inverter in the embodiment of the present application.

[0047] Furthermore, in some embodiments, the first processing module 120 is further configured to: The non-differentiable terms in the neutral point current and neutral point voltage are piecewise linearized to obtain a nonlinear model of the three-level inverter.

[0048] In the embodiment of the present application, after obtaining the original nonlinear model of the three-level inverter, the non-differentiable items in the original nonlinear model of the three-level inverter are processed piecewise, and the following are obtained:

[0049] In the formula, For the non-differentiable terms Values ​​after piecewise linearization.

[0050] The non-differentiable terms in the neutral point current and neutral point voltage are processed piecewise to obtain the nonlinear model of the three-level inverter, whose main features include:

[0051] Furthermore, in some embodiments, the second processing module 130 is further configured to: Determine the steady-state trajectory of a nonlinear model of a three-level inverter as it operates to a steady-state condition.

[0052] In the embodiment of the present application, the second processing module 130 runs the constructed three-level inverter nonlinear model to a steady state to obtain a steady-state trajectory , are the variables, and the subscript “0” is the corresponding steady-state trajectory.

[0053] The following processing method is used to perform piecewise linearization on the nonlinear model of the three-level inverter: right The trajectory is linearized near the zero point, and we have:

[0054] In the formula, " represents the small disturbance of each variable, represent The steady-state trajectory of represent A small disturbance of represent A small disturbance of represent The steady-state trajectory of represent A small disturbance of represent The steady-state trajectory of represent A small disturbance of represent The steady-state trajectory of represent steady-state trajectory.

[0055] right Perform piecewise linearization processing. x 0 Nearby and , is a minimum value close to zero, at this time , that is, the two disturbances are opposite in sign but equal in magnitude. In the numerical integration environment, according to the impulse law, it is considered that near the zero point arrive The impact of disturbances in the interval on the system ,therefore The zero-crossing linearization of is achieved by:

[0056] In the formula, for A small disturbance of for steady-state trajectory.

[0057] The main features of the established linear periodic time-varying model of the three-level inverter include:

[0058] In the formula, " represents the small disturbance of each variable, represent Small disturbance amount.

[0059] In the specific implementation, after obtaining the original nonlinear model of the three-level inverter, the three-phase grid voltage balance power system is considered in this embodiment. It can be expressed as:

[0060] because The cycle is ,and The cycle is , so for Due to the periodicity, The zero crossing point in the integration interval is and ,right Perform piecewise linearization, and we have:

[0061] in, , and For ( ) is obtained after piecewise linearization, For the modulation wave The amplitude A small disturbance of for The steady-state trajectory of for The steady-state trajectory of for The steady-state trajectory of for The steady-state trajectory of for The steady-state trajectory of for The steady-state trajectory of for A small disturbance of for A small disturbance of for Small disturbance amount.

[0062] Steady-state trajectory of a nonlinear model of a three-level inverter , as shown below:

[0063] The steady-state trajectory of the nonlinear model of the three-level inverter is linearized, and a linear periodic time-varying model of the three-level inverter considering the neutral point dynamics is constructed. Its main features include:

[0064] Based on the Matlab / Simulink simulation software platform, a linear periodic time-varying model of a three-level inverter is established. When the system runs at rated state for 2s, a disturbance is given to the system (the voltage reference value is reduced by 5%) to obtain the time domain dynamic response of the proposed three-level linear periodic time-varying model. The time domain dynamic response and steady-state trajectory of the linear periodic time-varying model (LTP Model) of the three-level inverter are superimposed, and the dynamic process of the neutral point voltage of the original nonlinear model of the three-level inverter is compared. Figure 3 As shown, it can be seen that after being disturbed, the neutral point voltage of the inverter oscillates and decays rapidly, and the system returns to stability after 0.5 seconds. Comparing the simulation results of the original nonlinear model of the three-level inverter with the calculation results of the proposed linear periodic time-varying model of the three-level inverter, it can be seen that the linear periodic time-varying model of the three-level inverter proposed in the embodiment of the present application can accurately reflect the neutral point dynamics in the original nonlinear model under small disturbances.

[0065] The following describes a method for constructing a linear periodic time-varying model of a three-level inverter considering neutral point dynamics provided in the present application. The method for constructing a linear periodic time-varying model of a three-level inverter considering neutral point dynamics described below can be executed by the linear periodic time-varying model of a three-level inverter considering neutral point dynamics described above.

[0066] See also Figure 4 , an embodiment of the present application provides a method for constructing a linear periodic time-varying model of a three-level inverter considering the dynamics of a neutral point, including: step 410, step 420 and step 430.

[0067] Step 410 constructs an original nonlinear model of a three-level inverter considering the neutral point dynamics; Step 420 performs piecewise linearization processing on the non-differentiable terms in the original nonlinear model of the three-level inverter to obtain the nonlinear model of the three-level inverter; Step 430 performs piecewise linearization processing on the nonlinear model of the three-level inverter to obtain a linear periodic time-varying model of the three-level inverter that takes into account the dynamics of the neutral point.

[0068] The method for constructing a linear periodic time-varying model of a three-level inverter considering the neutral point dynamics provided in the embodiment of the present application adopts a segmented linearization processing method to divide the non-differentiable items in the original nonlinear model of the three-level inverter into multiple linear segments, and performs linearization processing in each segment to eliminate the non-differentiable items of the non-differentiable part (such as the neutral point voltage and the neutral point current), thereby ensuring that the obtained linear periodic time-varying model of the three-level inverter can be analyzed locally and avoiding the problem of overall linearization difficulties. The linear periodic time-varying model of the three-level inverter is generated in combination with the steady-state trajectory, which can fully reflect the small disturbance characteristics of the three-level inverter, especially, it can accurately describe the dynamic characteristics of the neutral point of the three-level inverter under small disturbances, effectively characterize the behavior of the three-level inverter under small disturbances, and can be applied to the small disturbance stability analysis of the power system containing the three-level inverter.

[0069] It can be understood that the detailed functional implementation of each of the above-mentioned units / modules can be found in the introduction of the aforementioned method embodiment, and will not be repeated here.

[0070] It should be understood that the above-mentioned device is used to execute the method in the above-mentioned embodiment. The implementation principle and technical effect of the corresponding program module in the device are similar to those described in the above-mentioned method. The working process of the device can refer to the corresponding process in the above-mentioned method, which will not be repeated here.

[0071] Based on the method in the above embodiment, the present application embodiment provides an electronic device, see Figure 5 The electronic device may include: a processor (Processor) 510, a communication interface (Communications Interface) 520, a memory (Memory) 530 and a communication bus 540, wherein the processor 510, the communication interface 520, and the memory 530 communicate with each other through the communication bus 540. The processor 510 may call the logic instructions in the memory 530 to execute the method in the above embodiment.

[0072] In addition, the logic instructions in the above-mentioned memory 530 can be implemented in the form of software functional units and can be stored in a computer-readable storage medium when sold or used as an independent product. Based on this understanding, the technical solution of the present application, or the part that contributes to the prior art, or the part of the technical solution, can be embodied in the form of a software product, which is stored in a storage medium and includes a number of instructions for a computer device (which can be a personal computer, a server, or a network device, etc.) to perform all or part of the steps of the method described in each embodiment of the present application.

[0073] Based on the method in the above embodiment, an embodiment of the present application provides a computer-readable storage medium, which stores a computer program. When the computer program runs on a processor, the processor executes the method in the above embodiment.

[0074] Based on the method in the above embodiment, an embodiment of the present application provides a computer program product. When the computer program product runs on a processor, the processor executes the method in the above embodiment.

[0075] It is understandable that the processor in the embodiment of the present application may be a central processing unit (CPU), or other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field programmable gate arrays (FPGA) or other programmable logic devices, transistor logic devices, hardware components or any combination thereof. The general-purpose processor may be a microprocessor or any conventional processor.

[0076] The method steps in the embodiments of the present application can be implemented by hardware or by a processor executing software instructions. The software instructions can be composed of corresponding software modules, and the software modules can be stored in random access memory (RAM), flash memory, read-only memory (ROM), programmable read-only memory (PROM), erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), registers, hard disks, mobile hard disks, CD-ROMs, or any other form of storage medium known in the art. An exemplary storage medium is coupled to the processor so that the processor can read information from the storage medium and write information to the storage medium. Of course, the storage medium can also be a component of the processor. The processor and the storage medium can be located in an ASIC.

[0077] In the above embodiments, it can be implemented in whole or in part by software, hardware, firmware or any combination thereof. When implemented by software, it can be implemented in whole or in part in the form of a computer program product. The computer program product includes one or more computer instructions. When the computer program instructions are loaded and executed on a computer, the process or function described in the embodiment of the present application is generated in whole or in part. The computer may be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The computer instructions may be stored in a computer-readable storage medium or transmitted through the computer-readable storage medium. The computer instructions may be transmitted from a website site, computer, server or data center to another website site, computer, server or data center by wired (e.g., coaxial cable, optical fiber, digital subscriber line (DSL)) or wireless (e.g., infrared, wireless, microwave, etc.) means. The computer-readable storage medium may be any available medium that a computer can access or a data storage device such as a server or data center that includes one or more available media integrated. The available medium may be a magnetic medium (e.g., a floppy disk, a hard disk, a tape), an optical medium (e.g., a DVD), or a semiconductor medium (e.g., a solid-state drive (SSD)), etc.

[0078] It should be understood that the various numerical numbers involved in the embodiments of the present application are only used for the convenience of description and are not used to limit the scope of the embodiments of the present application.

[0079] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present application shall be included in the scope of protection of the present application.

Claims

1. A linear periodic time-varying model of a three-level inverter considering the dynamics of the neutral point, characterized in that: include: A building block for constructing the original nonlinear model of the three-level inverter taking into account the neutral point dynamics; A first processing module, configured to perform piecewise processing on the non-differentiable terms in the original nonlinear model of the three-level inverter to obtain a nonlinear model of the three-level inverter; The second processing module is used to perform piecewise linearization processing on the three-level inverter nonlinear model to obtain a three-level inverter linear periodic time-varying model that takes into account the neutral point dynamics.

2. The linear periodic time-varying model of a three-level inverter considering neutral point dynamics according to claim 1, characterized in that: The original nonlinear model of the three-level inverter includes: External circuit dynamic module, power outer loop controller, current inner loop controller, phase-locked loop controller, internal circuit dynamic module and neutral point potential balance controller; The external circuit dynamic module is used to send the output current and grid connection point voltage of the three-level inverter to the phase-locked loop controller, the power outer loop controller and the current inner loop controller, and send the output current, power factor angle and the amplitude of the output current to the internal circuit dynamic module; The phase-locked loop controller is used to determine a phase-locked angle according to the output current and the grid-connected point voltage, and send the phase-locked angle to the inner circuit dynamic module, the current inner loop controller and the power outer loop controller respectively; The power outer loop controller is used to generate a reference current according to the phase-locked angle, the grid-connected point voltage and the output current, and send the reference current to the current inner loop controller; The current inner loop controller is used to generate a modulation wave according to the phase-locked angle, the reference current and the output current, and send the modulation wave to the inner circuit dynamic module; The internal circuit dynamic module is used to determine the neutral point current and neutral point voltage of the three-level inverter according to the output value of the neutral point potential balance controller, the phase lock angle, the output current and the modulation wave; The neutral point potential balance controller is used to determine the output value according to the neutral point voltage.

3. The linear periodic time-varying model of a three-level inverter considering neutral point dynamics as claimed in claim 2, characterized in that: The first processing module is also used for: The non-differentiable items in the neutral point current and the neutral point voltage are processed in a piecewise manner to obtain the nonlinear model of the three-level inverter.

4. The linear periodic time-varying model of a three-level inverter considering neutral point dynamics according to claim 2, characterized in that: The neutral point potential balance controller adopts a proportional integral controller.

5. The linear periodic time-varying model of a three-level inverter considering neutral point dynamics according to claim 1, characterized in that: The second processing module is also used for: The steady-state trajectory of the three-level inverter nonlinear model when it runs to a steady-state state is determined.

6. The linear periodic time-varying model of a three-level inverter considering the neutral point dynamics according to any one of claims 1 to 5, characterized in that: The three-level inverter is a neutral point clamped three-level inverter or a T-type three-level inverter.

7. A method for constructing a linear periodic time-varying model of a three-level inverter considering the neutral point dynamics according to any one of claims 1 to 6, characterized in that: include: Construct the original nonlinear model of three-level inverter considering the neutral point dynamics; Performing piecewise processing on the non-differentiable items in the original nonlinear model of the three-level inverter to obtain a nonlinear model of the three-level inverter; The three-level inverter nonlinear model is subjected to piecewise linearization processing to obtain a three-level inverter linear periodic time-varying model that takes into account the neutral point dynamics.

8. An electronic device, characterized in that: include: at least one memory for storing a computer program; At least one processor is used to execute the program stored in the memory, and when the program stored in the memory is executed, the processor is used to execute the method according to claim 7.

9. A computer-readable storage medium storing a computer program, characterized in that: When the computer program is executed on a processor, the processor is caused to execute the method as claimed in claim 7.

10. A computer program product, characterized in that When the computer program product is run on a processor, the processor is caused to perform the method as claimed in claim 7.

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