An improved variable speed integral nonlinear PI photovoltaic inverter control method and system

Abstract

The invention discloses an improved variable speed integral nonlinear PI photovoltaic inverter control method and system, which relates to the field of new energy power generation technology, including configuring a photovoltaic power generation unit and a front-stage chopper in a maximum power point tracking mode, so that the photovoltaic grid-connected system operates in a unit power factor mode and only provides active power to the distribution network, establishing a rotating coordinate system model of the inverter, and obtaining a control equation through Laplace transformation, performing feedforward compensation decoupling on the control equation, independently controlling the current of the d-axis and q-axis, calculating the DC bus voltage deviation and introducing a dead zone nonlinear link, using an improved variable speed integral PI controller to adjust the output of the dead zone link, and obtaining a reference input value of the d-axis current inner loop. The invention can adaptively adjust the integral coefficient according to the deviation, effectively reducing the frequent actions of the PI controller.

Description

Technical Field

[0001] The present invention relates to the technical field of renewable energy power generation, and in particular to an improved variable speed integral nonlinear PI photovoltaic inverter control method and system. Background Art

[0002] Grid-connected photovoltaic power generation systems mostly adopt a two-stage topology. The front stage is a unidirectional DC / DC chopper, and the rear stage is a DC / AC inverter. The power decoupling between the front and rear stages is achieved through the parallel capacitor of the DC bus, so that the power converters of the front and rear stages can be controlled independently. In order to make full use of solar energy resources, the front-stage DC / DC operates in the maximum power tracking control mode, and the rear-stage DC / AC operates in the unity power factor mode, that is, providing the distribution network with all the active power output by the photovoltaic unit. In order to ensure the accuracy of MPPT control and the stable operation of the grid-connected inverter, the DC bus voltage needs to be stable at its reference set value.

[0003] At present, the stable control of DC bus voltage is mainly achieved by adopting voltage and current dual closed-loop PI control for DC / AC grid-connected inverters; among them, the voltage outer loop realizes the zero-static error control of the DC bus voltage, and the current inner loop realizes the current regulation injected into the distribution network based on the dq rotating coordinate system; however, the integral coefficient in conventional PI control is a constant, and the integral increment remains unchanged during the entire regulation process. For scenarios where the DC bus is short-term and large due to large fluctuations in photovoltaic power, the fixed integral time constant will reduce the dynamic performance of the DC bus voltage regulation; in addition, conventional PI must be adjusted when the error is non-zero, which may cause oscillations caused by frequent actions.

[0004] In view of the deficiencies in the prior art, an object of the present invention is to provide a photovoltaic grid-connected inverter control method based on an improved variable speed integral nonlinear PI suitable for two-stage photovoltaic grid-connected power generation. Summary of the invention

[0005] In view of the above existing problems, the present invention provides an improved variable speed integral nonlinear PI photovoltaic inverter control method and system to solve the problem in the prior art that the DC bus may be short-term large due to large photovoltaic power fluctuations.

[0006] In order to solve the above technical problems, an improved variable speed integral nonlinear PI photovoltaic inverter control method is proposed, including:

[0007] The photovoltaic power generation unit and the front-stage chopper are configured in the maximum power point tracking mode, so that the photovoltaic grid-connected system operates in the unity power factor mode and only provides active power to the distribution network; the rotating coordinate system model of the inverter is established, and the control equation is obtained through Laplace transform, the control equation is decoupled by feedforward compensation, and the current of the d-axis and q-axis is independently controlled; the DC bus voltage deviation is calculated and the dead zone nonlinear link is introduced, and the output of the dead zone link is adjusted by using the improved variable speed integral PI controller to obtain the reference input value of the d-axis current inner loop.

[0008] As a preferred solution of the improved variable speed integral nonlinear PI photovoltaic inverter control method described in the present invention, the providing of active power to the distribution network includes configuring the photovoltaic power generation unit and the front-stage DC / DC chopper in the maximum power point tracking mode, and the rear-stage DC / AC inverter operates in the unity power factor mode.

[0009] As a preferred solution of the improved variable speed integral nonlinear PI photovoltaic inverter control method of the present invention, wherein: the establishment of the rotating coordinate system model of the inverter includes establishing a coordinate model of the DC / AC inverter based on the dp rotating coordinate system, and the formula is expressed as:

[0010]

[0011] Among them, e d is the d-axis component of the distribution network voltage, e q is the q-axis component of the distribution network voltage, u d is the d-axis component of the three-phase voltage at the inverter output side, u q is the q-axis component of the three-phase voltage at the inverter output side, ω is the fundamental angular frequency, i d is the d-axis component of the inverter grid-connected current, i q is the q-axis component of the inverter grid-connected current, Ri d and Ri q is the resistance and L is the inductance.

[0012] As a preferred solution of the improved variable speed integral nonlinear PI photovoltaic inverter control method of the present invention, wherein: the obtaining of the control equation includes establishing a rotating coordinate system model of the inverter, and obtaining the control equation through Laplace transform, wherein the Laplace transform formula is:

[0013]

[0014] Where s is the Laplace transform operator, E d (s) is e d The Laplace transform of E q (s) is e q The Laplace transform of U d(s) is u d The Laplace transform of U q (s) is u q The Plath transform, I d (s) is i d The Laplace transform of RI d (s) is the resistance Ri d The Laplace transform of RI q (s) is the resistance Ri q The Laplace transform of LI d (s) and LI q (s) is the Laplace transform of inductance, and ω is the fundamental angular frequency.

[0015] As a preferred solution of the improved variable speed integral nonlinear PI photovoltaic inverter control method described in the present invention, the feedforward compensation decoupling includes obtaining the control equation through Laplace transform, and performing feedforward compensation decoupling on the control equation to independently control the current of the d-axis and q-axis.

[0016] The decoupling formula is:

[0017]

[0018] Among them, s is the Laplace transform operator, U d (s) is u d The Laplace transform of U q 9s) is u q Plath transformation, R is the resistance, L is the inductance, I d (s) is i d The Laplace transform of q (s) is i q The Laplace transform of E d (s) is e d The Laplace transform of E q (s) is e q The Laplace transform of .

[0019] The independent control of the d-axis and q-axis currents includes controlling the currents respectively using two PI controllers after decoupling, wherein the reference input of the d-axis current control loop is determined by the voltage loop, the reference input of the q-axis current control loop is 0, and the PI controllers of the d-axis current loop and the q-axis current loop are set to the same parameters.

[0020] As a preferred solution of the improved variable speed integral nonlinear PI photovoltaic inverter control method described in the present invention, the dead zone nonlinear link includes calculating the deviation of the DC bus voltage based on the actual measured value of the DC bus voltage, and introducing the deviation into the dead zone nonlinear link.

[0021] The deviation formula for calculating the DC bus voltage is:

[0022] U err =U deref -U dc

[0023] Among them, U err is the DC bus voltage deviation, U deref is the expected value of the DC bus voltage, U dc is the actual measured value of the DC bus voltage.

[0024] The dead zone nonlinear link formula is:

[0025]

[0026] Among them, e is the output of the nonlinear link in the dead zone, U err is the DC bus voltage deviation, and δ is the dead zone threshold.

[0027] As a preferred solution of the improved variable speed integral nonlinear PI photovoltaic inverter control method described in the present invention, wherein: the obtaining of the reference input value of the d-axis current inner loop includes adjusting the output of the dead zone link using the improved variable speed integral PI controller to obtain the reference input of the d-axis current inner loop.

[0028] The improved variable speed integral PI control formula is:

[0029]

[0030] Among them, f(e(k)) is the weight coefficient of the speed change integral at time k, k is the sampling time, ξ is the setting parameter of the speed change integral, and e(k) is the output of the dead zone nonlinear link at time k.

[0031] The reference input formula for obtaining the inner loop of the d-axis current is:

[0032]

[0033] Among them, i dref (k) is the reference input of the inner current loop at time k, k pu is the proportional coefficient of the voltage loop PI controller, k iu is the integral coefficient of the voltage loop PI controller, k is the sampling time, e(k) is the output of the dead zone nonlinear link at time k, T is the sampling period, f(e(k)) is the weight coefficient of the speed change integral at time k, and i is the variable index.

[0034] As a preferred solution of the improved variable speed integral nonlinear PI photovoltaic inverter control system described in the present invention, it is characterized by including a maximum power point tracking configuration module, an inverter rotating coordinate system model establishment module, a feedforward compensation decoupling control module, a dead zone nonlinear link module and an improved variable speed integral nonlinear PI controller module.

[0035] The maximum power point tracking configuration module is used to configure the photovoltaic power generation unit and the front-stage DC / DC chopper in the maximum power point tracking mode.

[0036] The inverter rotating coordinate system model building module is used to build a coordinate model of the DC / AC inverter based on the dp rotating coordinate system to describe the dynamic behavior of the inverter in the dq coordinate system.

[0037] The feedforward compensation decoupling control module is used to perform feedforward compensation decoupling on the control equation and independently control the current of the d-axis and the q-axis.

[0038] The dead zone nonlinear link module is used to calculate the voltage deviation based on the actual measurement value of the DC bus voltage, and introduce the dead zone nonlinear link to avoid excessively frequent control actions when the voltage deviation is small, thereby reducing system fluctuations and energy losses.

[0039] The improved variable speed integral nonlinear PI controller module is used to adjust the output of the dead zone link using the improved variable speed integral PI controller, obtain the reference input of the d-axis current inner loop, improve the performance of the controller, and improve the dynamic response and steady-state performance of the system.

[0040] A computer device comprises a memory and a processor, wherein the memory stores a computer program, and is characterized in that when the processor executes the computer program, the steps of a method for improving variable speed integral nonlinear PI photovoltaic inverter control are implemented.

[0041] A computer-readable storage medium having a computer program stored thereon, characterized in that when the computer program is executed by a processor, the steps of a method for improving variable speed integral nonlinear PI photovoltaic inverter control are implemented.

[0042] The beneficial effects of the present invention are as follows: the present invention can overcome the disadvantage that the traditional PI control cannot dynamically adjust the integral action strength, resulting in poor performance of the controlled system; compared with the conventional variable speed integral PI controller, the improved variable speed integral PI controller proposed by the present invention has fewer adjustment parameters and only needs to set a threshold parameter, which is more conducive to parameter setting; in order to reduce the frequent adjustment of the controller, a dead zone nonlinear term is introduced into the DC bus voltage deviation, which is conducive to reducing the frequent adjustment of the PI controller. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative work, among which:

[0044] Figure 1 An overall flow chart of an improved variable speed integral nonlinear PI photovoltaic inverter control method provided by an embodiment of the present invention.

[0045] Figure 2 An improved variable speed integral nonlinear PI control principle diagram of an improved variable speed integral nonlinear PI photovoltaic inverter control method provided by an embodiment of the present invention.

[0046] Figure 3 A topological structure diagram of a two-stage photovoltaic grid-connected system according to an improved variable speed integral nonlinear PI photovoltaic inverter control method provided by an embodiment of the present invention.

[0047] Figure 4 A system solution flow chart of an improved variable speed integral nonlinear PI photovoltaic inverter control system provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0048] In order to make the above-mentioned purposes, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the drawings of the specification. Obviously, the described embodiments are part of the embodiments of the present invention, but not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary persons in the art without creative work should fall within the scope of protection of the present invention.

[0049] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0050] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure or characteristic that may be included in at least one implementation of the present invention. The term "in one embodiment" that appears in different places in this specification does not necessarily refer to the same embodiment, nor is it an embodiment that is mutually exclusive with other embodiments, either individually or selectively.

[0051] The present invention is described in detail with reference to schematic diagrams. When describing the embodiments of the present invention, for the sake of convenience, the cross-sectional diagrams showing the device structure will not be partially enlarged according to the general scale, and the schematic diagrams are only examples, which should not limit the scope of protection of the present invention. In addition, in actual production, the three-dimensional dimensions of length, width and depth should be included.

[0052] At the same time, in the description of the present invention, it should be noted that the directions or positional relationships indicated by the terms "upper, lower, inner and outer" are based on the directions or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as limiting the present invention. In addition, the terms "first, second or third" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0053] In the present invention, unless otherwise clearly specified and limited, the terms "install, connect, connect" should be understood in a broad sense, for example: it can be a fixed connection, a detachable connection or an integral connection; it can also be a mechanical connection, an electrical connection or a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0054] Example 1, reference Figure 1-Figure 3 , which is the first embodiment of the present invention, provides an improved variable speed integral nonlinear PI photovoltaic inverter control method, comprising:

[0055] S1: The photovoltaic power generation unit and the front-stage chopper are configured in the maximum power point tracking mode, so that the photovoltaic grid-connected system operates in the unity power factor mode and only provides active power to the distribution network.

[0056] like Figure 2 The providing active power to the distribution network includes configuring the photovoltaic power generation unit and the front-stage DC / DC chopper in a maximum power point tracking mode, and the rear-stage DC / AC inverter operates in a unity power factor mode.

[0057] The current constraint condition of the unity power factor mode is:

[0058]

[0059] Among them, i inv is the input current, i dc is the current flowing through the DC bus capacitor, U dc is the DC bus terminal voltage, C dc is the capacitance, i pv is the output current of the photovoltaic panel, and t is the time.

[0060] The establishing of the rotating coordinate system model of the inverter includes establishing a coordinate model of the DC / AC inverter based on the dp rotating coordinate system, and the formula is expressed as:

[0061]

[0062] Among them, e d is the d-axis component of the distribution network voltage, e q is the q-axis component of the distribution network voltage, u d is the d-axis component of the three-phase voltage at the inverter output side, u q is the q-axis component of the three-phase voltage at the inverter output side, ω is the fundamental angular frequency, i d is the d-axis component of the inverter grid-connected current, i q is the q-axis component of the inverter grid-connected current, Ri d and Ri q is the resistance and L is the inductance.

[0063] S2: Establish a rotating coordinate system model of the inverter, obtain the control equation through Laplace transform, perform feedforward compensation decoupling on the control equation, and independently control the current of the d-axis and q-axis.

[0064] Further, the obtaining of the control equation includes establishing a rotating coordinate system model of the inverter and obtaining the control equation by Laplace transform, wherein the Laplace transform formula is:

[0065]

[0066] Where s is the Laplace transform operator, E d (s) is e d The Laplace transform of E q (s) is e q The Laplace transform of U d (s) is u d The Laplace transform of U q (s) is u q The Plath transform, I d (s) is i d The Laplace transform of RI d (s) is the resistance Ri d The Laplace transform of RI q (s) is the resistance Ri q The Laplace transform of LI d (s) and LI q (s) is the Laplace transform of inductance, and ω is the fundamental angular frequency.

[0067] Furthermore, the feedforward compensation decoupling includes obtaining a control equation through Laplace transformation, and performing feedforward compensation decoupling on the control equation to independently control the current of the d-axis and the q-axis.

[0068] The decoupling formula is:

[0069]

[0070] Among them, s is the Laplace transform operator, U d (s) is u d The Laplace transform of U q 9s) is u q Plath transformation, R is the resistance, L is the inductance, I d (s) is i d The Laplace transform of q (s) is i q The Laplace transform of E d (s) is e d The Laplace transform of E q (s) is e q The Laplace transform of .

[0071] The independent control of the current of the d-axis and the q-axis includes controlling the currents respectively by using two PI controllers after decoupling, wherein the reference input of the d-axis current control loop is determined by the voltage loop, the reference input of the q-axis current control loop is 0, and the PI controllers of the d-axis current loop and the q-axis current loop are set to the same parameters. S3: Calculate the DC bus voltage deviation and introduce a dead zone nonlinear link, use an improved variable speed integral PI controller to adjust the output of the dead zone link, and obtain the reference input value of the d-axis current inner loop.

[0072] Furthermore, the dead zone nonlinear link includes calculating the deviation of the DC bus voltage based on the actual measured value of the DC bus voltage, and introducing the deviation into the dead zone nonlinear link.

[0073] The deviation formula for calculating the DC bus voltage is:

[0074] U err =U deref -U dc

[0075] Among them, U err is the DC bus voltage deviation, U deref is the expected value of the DC bus voltage, U dc is the actual measured value of the DC bus voltage.

[0076] The dead zone nonlinear link formula is:

[0077]

[0078] Among them, e is the output of the nonlinear link in the dead zone, U err is the DC bus voltage deviation, and δ is the dead zone threshold.

[0079] It should be noted that obtaining the reference input value of the d-axis current inner loop includes adjusting the output of the dead zone link by using an improved variable speed integral PI controller to obtain the reference input of the d-axis current inner loop.

[0080] like Figure 3 , the improved variable speed integral PI control formula is:

[0081]

[0082] Among them, f(e(k)) is the weight coefficient of the speed change integral at time k, k is the sampling time, ξ is the setting parameter of the speed change integral, and e(k) is the output of the dead zone nonlinear link at time k.

[0083] The reference input formula for obtaining the inner loop of the d-axis current is:

[0084]

[0085] Among them, i dref (k) is the reference input of the inner current loop at time k, k pu is the proportional coefficient of the voltage loop PI controller, k iu is the integral coefficient of the voltage loop PI controller, k is the sampling time, e(k) is the output of the dead zone nonlinear link at time k, T is the sampling period, f(e(k)) is the weight coefficient of the speed change integral at time k, and i is the variable index.

[0086] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

[0087] Example 2, reference Figure 4 , which is the second embodiment of the present invention, and this embodiment provides an improved variable speed integral nonlinear PI photovoltaic inverter control system, including a maximum power point tracking configuration module 100, an inverter rotating coordinate system model establishment module 200, a feedforward compensation decoupling control module 300, a dead zone nonlinear link module 400 and an improved variable speed integral nonlinear PI controller module 500.

[0088] The maximum power point tracking configuration module 100 is used to configure the photovoltaic power generation unit and the front-stage DC / DC chopper in a maximum power point tracking mode.

[0089] The inverter rotating coordinate system model building module 200 is used to build a coordinate model of the DC / AC inverter based on the dp rotating coordinate system to describe the dynamic behavior of the inverter in the dq coordinate system.

[0090] The feedforward compensation decoupling control module 300 is used to perform feedforward compensation decoupling on the control equation and independently control the current of the d-axis and the q-axis.

[0091] The dead zone nonlinear link module 400 is used to calculate the voltage deviation based on the actual measured value of the DC bus voltage, and introduce a dead zone nonlinear link to avoid too frequent control actions when the voltage deviation is small, thereby reducing system fluctuations and energy losses.

[0092] The improved variable speed integral nonlinear PI controller module 500 is used to adjust the output of the dead zone link using the improved variable speed integral PI controller, obtain the reference input of the d-axis current inner loop, improve the performance of the controller, and improve the dynamic response and steady-state performance of the system.

[0093] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

[0094] Embodiment 3, the third embodiment of the present invention, is different from the first two embodiments in that:

[0095] If the functions are implemented in the form of software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, 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. The computer software product is stored in a storage medium, including several 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 methods described in each embodiment of the present invention. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), disk or optical disk, and other media that can store program codes.

[0096] The logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as an ordered list of executable instructions for implementing logical functions, and can be embodied in any computer-readable medium for use by an instruction execution system, device or apparatus (such as a computer-based system, a system including a processor, or other system that can fetch instructions from an instruction execution system, device or apparatus and execute instructions), or in conjunction with such instruction execution systems, devices or apparatuses. For the purposes of this specification, "computer-readable medium" can be any device that can contain, store, communicate, propagate or transmit a program for use by an instruction execution system, device or apparatus, or in conjunction with such instruction execution systems, devices or apparatuses.

[0097] More specific examples of computer-readable media (a non-exhaustive list) include the following: an electrical connection with one or more wires (electronic device), a portable computer disk case (magnetic device), a random access memory (RAM), a read-only memory (ROM), an erasable and programmable read-only memory (EPROM or flash memory), an optical fiber device, and a portable compact disk read-only memory (CDROM). In addition, the computer-readable medium may even be a paper or other suitable medium on which the program is printed, since the program may be obtained electronically, for example, by optically scanning the paper or other medium, followed by editing, deciphering or, if necessary, processing in another suitable manner, and then stored in a computer memory.

[0098] It should be understood that the various parts of the present invention can be implemented by hardware, software, firmware or a combination thereof. In the above-mentioned embodiments, a plurality of steps or methods can be implemented by software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented by hardware, as in another embodiment, it can be implemented by any one of the following technologies known in the art or their combination: a discrete logic circuit having a logic gate circuit for implementing a logic function for a data signal, a dedicated integrated circuit having a suitable combination of logic gate circuits, a programmable gate array (PGA), a field programmable gate array (FPGA), etc.

Claims

1. An improved variable speed integral nonlinear PI photovoltaic inverter control method, characterized in that: include, The photovoltaic power generation unit and the front-stage chopper are configured in the maximum power point tracking mode, so that the photovoltaic grid-connected system operates in the unity power factor mode and only provides active power to the distribution network; Establish the rotating coordinate system model of the inverter, obtain the control equation through Laplace transform, perform feedforward compensation decoupling on the control equation, and independently control the current of the d-axis and q-axis; The DC bus voltage deviation is calculated and a dead zone nonlinear link is introduced. The output of the dead zone link is adjusted using an improved variable speed integral PI controller to obtain the reference input value of the d-axis current inner loop.

2. The improved variable speed integral nonlinear PI photovoltaic inverter control method according to claim 1, characterized in that: Providing active power to the distribution network includes configuring the photovoltaic power generation unit and the front-stage DC / DC chopper in a maximum power point tracking mode, and the rear-stage DC / AC inverter operates in a unity power factor mode.

3. The improved variable speed integral nonlinear PI photovoltaic inverter control method according to claim 2, characterized in that: The establishing of the rotating coordinate system model of the inverter includes establishing a coordinate model of the DC / AC inverter based on the dp rotating coordinate system, and the formula is expressed as: Among them, e d is the d-axis component of the distribution network voltage, e q is the q-axis component of the distribution network voltage, u d is the d-axis component of the three-phase voltage at the inverter output side, u q is the q-axis component of the three-phase voltage at the inverter output side, ω is the fundamental angular frequency, i d is the d-axis component of the inverter grid-connected current, i q is the q-axis component of the inverter grid-connected current, Ri d and Ri q is the resistance and L is the inductance.

4. The improved variable speed integral nonlinear PI photovoltaic inverter control method according to claim 3, characterized in that: The obtaining of the control equation includes establishing a rotating coordinate system model of the inverter and obtaining the control equation by Laplace transform, wherein the Laplace transform formula is: Where s is the Laplace transform operator, E d ( s ) for e d The Laplace transform of E q ( s ) for e q The Laplace transform of U d ( s ) for u d The Laplace transform of U q ( s ) for u q The Plath transform, I d ( s ) for i d The Laplace transform of RI d ( s ) is the resistance Ri d The Laplace transform of RI q ( s ) is the resistance Ri q The Laplace transform of LI d ( s ) and LI q ( s ) is the Laplace transform of inductance, and ω is the fundamental angular frequency.

5. The improved variable speed integral nonlinear PI photovoltaic inverter control method according to claim 4, characterized in that: The feedforward compensation decoupling includes obtaining a control equation through Laplace transformation, and performing feedforward compensation decoupling on the control equation to independently control the current of the d-axis and the q-axis; The decoupling formula is: Among them, s is the Laplace transform operator, U d ( s ) for u d The Laplace transform of U q ( s ) for u q Plath transformation, R is the resistance, L is the inductance, I d ( s ) for i d The Laplace transform of q ( s ) for i q The Laplace transform of E d ( s ) for e d The Laplace transform of E q ( s ) for e q The Laplace transform of The independent control of the d-axis and q-axis currents includes controlling the currents respectively using two PI controllers after decoupling, wherein the reference input of the d-axis current control loop is determined by the voltage loop, the reference input of the q-axis current control loop is 0, and the PI controllers of the d-axis current loop and the q-axis current loop are set to the same parameters.

6. The improved variable speed integral nonlinear PI photovoltaic inverter control method according to claim 5, characterized in that: The dead zone nonlinear link includes calculating the deviation of the DC bus voltage based on the actual measured value of the DC bus voltage, and introducing the deviation into the dead zone nonlinear link; The deviation formula for calculating the DC bus voltage is: IN err =U deref -IN dc Among them, U err is the DC bus voltage deviation, U deref is the expected value of the DC bus voltage, U dc is the actual measured value of the DC bus voltage; The dead zone nonlinear link formula is: Among them, e is the output of the nonlinear link in the dead zone, U err is the DC bus voltage deviation, and δ is the dead zone threshold.

7. The improved variable speed integral nonlinear PI photovoltaic inverter control method according to claim 6, characterized in that: The obtaining of the reference input value of the d-axis current inner loop includes adjusting the output of the dead zone link by using an improved variable speed integral PI controller to obtain the reference input of the d-axis current inner loop; The improved speed-changing integral PI control formula is: Among them, f(e(k)) is the weight coefficient of the speed change integral at time k, k is the sampling time, ξ is the setting parameter of the speed change integral, and e(k) is the output of the dead zone nonlinear link at time k; The reference input formula for obtaining the inner loop of the d-axis current is: Among them, i dref ( k ) is the reference input of the inner current loop at time k, pu is the proportional coefficient of the voltage loop PI controller, k iu is the integral coefficient of the voltage loop PI controller, k is the sampling time, e(k) is the output of the dead zone nonlinear link at time k, T is the sampling period, f(e(k)) is the weight coefficient of the speed change integral at time k, and i is the variable index.

8. A system using an improved variable speed integral nonlinear PI photovoltaic inverter control method as claimed in any one of claims 1 to 7, characterized in that: It includes a maximum power point tracking configuration module, an inverter rotating coordinate system model building module, a feedforward compensation decoupling control module, a dead zone nonlinear link module, and an improved variable speed integral nonlinear PI controller module; The maximum power point tracking configuration module is used to configure the photovoltaic power generation unit and the front-stage DC / DC chopper in the maximum power point tracking mode; The inverter rotating coordinate system model building module is used to build a coordinate model of the DC / AC inverter based on the dp rotating coordinate system to describe the dynamic behavior of the inverter in the dq coordinate system; The feedforward compensation decoupling control module is used to perform feedforward compensation decoupling on the control equation and independently control the current of the d-axis and the q-axis; The dead zone nonlinear link module is used to calculate the voltage deviation based on the actual measured value of the DC bus voltage, and introduce the dead zone nonlinear link to avoid too frequent control actions when the voltage deviation is small, thereby reducing system fluctuations and energy losses; The improved variable speed integral nonlinear PI controller module is used to adjust the output of the dead zone link using the improved variable speed integral PI controller, obtain the reference input of the d-axis current inner loop, improve the performance of the controller, and improve the dynamic response and steady-state performance of the system.

9. A computer device comprising a memory and a processor, wherein the memory stores a computer program, wherein: When the processor executes the computer program, the steps of an improved variable speed integral nonlinear PI photovoltaic inverter control method according to any one of claims 1 to 7 are implemented.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of an improved variable speed integral nonlinear PI photovoltaic inverter control method according to any one of claims 1 to 7 are implemented.

Images