Distributed photovoltaic dynamic voltage control method based on feedback linearization

Abstract

A distributed photovoltaic dynamic voltage control method based on feedback linearization, the method comprising: establishing a nonlinear input-output model on the basis of voltage control, a nonlinear relationship between an operating voltage and output current of a photovoltaic array inside a distributed photovoltaic power generation system, and a nonlinear relationship between a direct-current bus voltage state and an output power (S21); performing linearized feedback on a nonlinear input and nonlinear output of the nonlinear input-output model, so as to obtain a feedback control model, an input and output of which are linearized (S22); and acquiring a current reference value of a response current and a voltage reference value of a direct-current bus voltage, and controlling the nonlinear input on the basis of the current reference value, the voltage reference value and the feedback control model (S23). The distributed photovoltaic dynamic voltage control method based on feedback linearization can accurately respond to a current required by a voltage deviation, thereby improving the distributed photovoltaic dynamic voltage control precision.

Description

A distributed photovoltaic dynamic voltage control method based on feedback linearization Technical Field

[0001] The present invention relates to the field of electric power technology, and in particular to a distributed photovoltaic dynamic voltage control method based on feedback linearization. Background Art

[0002] Traditional distributed photovoltaic (PV) operations primarily focus on maximizing power generation revenue. However, the recently released national standard, "Technical Requirements for Grid-Connected Photovoltaic Inverters," stipulates that distributed PV systems should possess dynamic voltage control capabilities during grid faults, providing dynamic reactive current support for transient high and low voltages. The existing distributed PV dynamic voltage control model superimposes the voltage deviation measured at the grid connection point on the inverter's current control command through proportional gain feedforward control, thereby providing voltage support through additional current injection. Because line impedance ratios in distribution networks are typically large, the active current component is also incorporated into the dynamic voltage control process of distributed PV systems to achieve more effective voltage control.

[0003] Existing technologies, from the perspective of unified control of different topologies of distributed photovoltaic systems, uniformly model photovoltaic systems with different topologies, or correct the target node voltage of the distributed photovoltaic power to achieve voltage regulation. However, the power-voltage relationship of dynamic voltage control is a relatively clear proportional relationship, resulting in a small effect of the overall photovoltaic system's accurate response to voltage deviation, making it difficult to improve the control accuracy of the distributed photovoltaic dynamic voltage.

[0004] Summary of the Invention

[0005] The purpose of the present invention is to address the deficiencies of the above-mentioned prior art and propose a distributed photovoltaic dynamic voltage control method based on feedback linearization, which can accurately respond to the current required for voltage deviation, thereby improving the control accuracy of distributed photovoltaic dynamic voltage.

[0006] The present invention provides a distributed photovoltaic dynamic voltage control method based on feedback linearization, comprising:

[0007] According to the nonlinear relationship between the photovoltaic array operating voltage and output current and the nonlinear relationship between the DC bus voltage state and output power in the distributed photovoltaic power generation system, a nonlinear input-output model is established based on voltage control.

[0008] Performing linearized feedback on the nonlinear input and nonlinear output of the nonlinear input-output model to obtain an input-output linearized feedback control model;

[0009] A current reference value of the response current and a voltage reference value of the DC bus voltage are obtained, and the nonlinear input is controlled according to the current reference value, the voltage reference value and the feedback control model.

[0010] The present invention establishes a nonlinear input-output model through the nonlinear relationship between the photovoltaic array operating voltage and the output current and the nonlinear relationship between the DC bus voltage state and the output power. Compared with the use of proportional gain feedforward, it can fully consider the influence of the nonlinear dynamic characteristics of the distributed photovoltaic state on the feedback control model, so that the distributed photovoltaic charging system can accurately respond to the demand for voltage deviation, thereby improving the control accuracy of the distributed photovoltaic dynamic voltage; and, the nonlinear input and nonlinear output are linearized and fed back to obtain the implicit linear relationship between the nonlinear input and the nonlinear output, thereby establishing an accurate feedback control model, further improving the control accuracy of the distributed photovoltaic power generation system according to the feedback control model.

[0011] Furthermore, the establishment of a nonlinear input-output model based on voltage control includes:

[0012] A nonlinear input-output model of the distributed photovoltaic power generation system is established based on a preset state transfer function, with the inverter current components and the DC bus voltage as state variables, the inverter voltage components as input variables, the current components of the response voltage and the energy stored on the DC bus capacitor as output variables, and a preset state transfer function. The distributed photovoltaic power generation system includes: a photovoltaic array, an inverter and a DC bus.

[0013] The present invention uses specific parameters within the distributed photovoltaic power generation system to accurately characterize the nonlinear relationship between the photovoltaic array operating voltage and output current and the nonlinear relationship between the DC bus voltage state and the output power, thereby improving the control accuracy of the distributed photovoltaic dynamic voltage.

[0014] Furthermore, controlling the nonlinear input according to the current reference value, the voltage reference value and the feedback control model includes:

[0015] The current reference value is obtained according to the voltage measurement amplitude deviation and the dynamic voltage response coefficient, and the branch bus voltage rated value is used as the voltage reference value, the current reference value is used as a first reference instruction for the first output variable, and 1 / 2 of the square of the voltage reference value is used as a second reference instruction for the second output variable;

[0016] The nonlinear input is controlled according to a control law obtained from the first reference instruction, the second reference instruction, the first output variable, and the second output variable.

[0017] Furthermore, the control law obtained according to the first reference instruction, the second reference instruction, the first output variable, and the second output variable controls the nonlinear input, including:

[0018] using a difference between the first output variable and the first reference instruction as a first tracking error variable, and using a difference between the second output variable and the second reference instruction as a second tracking error variable;

[0019] A control law is established according to a first full-state order of the first tracking error variable and a second full-state order of the second tracking error variable, and the nonlinear input is controlled according to the control law.

[0020] The existing technology uses a method to characterize the control law through input and feedback quantities. However, due to the large difference between the input quantity and the output quantity obtained after being affected by various factors in the photovoltaic system, the accuracy of the photovoltaic system reduced by the obtained control law is low. Compared with the existing technology, the present invention establishes a control law based on the full-order state orders corresponding to the tracking error variables obtained according to the output variable and the reference instruction. It can accurately characterize the relationship between the reference instruction and the output variable. On the basis of fully considering the influence of the nonlinear dynamic characteristics of the distributed photovoltaic state on the feedback control model, it can further improve the control accuracy of the distributed photovoltaic dynamic voltage.

[0021] Furthermore, before establishing the control law according to the first full-state order of the first tracking error variable and the second full-state order of the second tracking error variable, the method includes: obtaining the first full-state order and the second full-state order, specifically:

[0022] A first full-state order of the second order of the first tracking error variable is obtained according to the first relative degree of the first output variable, and a second full-state order of the third order of the second tracking error variable is obtained according to the second relative degree of the second output variable.

[0023] Furthermore, performing linearized feedback on the nonlinear input and nonlinear output of the nonlinear input-output model to obtain an input-output linearized feedback control model includes:

[0024] Obtaining multiple continuous Lie derivatives for each of the N output variables according to the output function of the nonlinear input-output model until at least one of the derived input variables appears in the Lie derivative results; wherein N is a positive integer;

[0025] The system parameters of the distributed photovoltaic power generation system are obtained to form a first non-singular matrix in the state space, and a feedback control model with input-output linearization is obtained based on a second matrix composed of the first matrix and Lie derivative results of all output variables.

[0026] Furthermore, the multiple continuous Lie derivatives are obtained for each of the N output variables, specifically:

[0027] Multiple continuous Lie derivatives are obtained for the first first output variable and the second second output variable, respectively, to obtain a first Lie derivative result of the first output variable with a relative degree of 1 and a second Lie derivative result of the second output variable with a relative degree of 2, in sequence; wherein the second matrix includes: the first Lie derivative result and the second Lie derivative result.

[0028] Preferably, the nonlinear input-output model can be expressed as:

[0029] in, is the time derivative of the state variable, x is the state variable, u is the input variable, y is the output variable, f(·) is the state transfer function, g(·) is the input function, and h(·) is the output function; I d is the d-axis component of the inverter current, I q is the q-axis component of the inverter current, V dc is the DC bus voltage, V id is the d-axis component of the inverter voltage, V iq is the q-axis component of the inverter voltage; the output variables include: the first output variable y1 = I d , corresponding to the current component in the dynamic voltage response, and the second output variable reflecting the energy stored on the DC bus capacitor of the photovoltaic power generation system

[0030] Preferably, the state transfer function can be expressed as:

[0031] Among them, V gd is the d-axis component of the grid-connected point voltage, V gq is the q-axis component of the grid-connected point voltage, P dc is the photovoltaic DC side power, ω is the system frequency, R and L are the resistance and inductance of the photovoltaic grid-connected line respectively, and C is the DC bus capacitance.

[0032] Preferably, the control law can be expressed as:

[0033] Among them, a 11 ,…,a 23 is the dynamic response characteristic coefficient obtained according to the transient characteristic requirements of dynamic voltage control; and are the second-order derivative and first-order derivative of the first tracking error variable ε1 with respect to time; and They are respectively the third-order derivative, second-order derivative and first-order derivative of the second tracking error variable ε2 with respect to time. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] FIG1 is a schematic diagram of a module for implementing a distributed photovoltaic dynamic voltage control method provided in this embodiment;

[0035] FIG2 is a flow chart of a distributed photovoltaic dynamic voltage control method based on feedback linearization according to an embodiment of the present invention;

[0036] FIG3 is a schematic structural diagram of a two-stage photovoltaic power generation system provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0037] 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.

[0038] Example 1

[0039] 1 , which is a module diagram of the distributed photovoltaic dynamic voltage control method provided in this embodiment, including: a controller 11 and a distributed photovoltaic power generation system 12 ; wherein the controller 11 includes: a dynamic voltage control module 101 and a feedback linearization module 102 .

[0040] Specifically, the dynamic voltage control module 101 sends an inverter control command to the distributed photovoltaic power generation system 12. After the distributed photovoltaic power generation system 12 receives the inverter control command, which fully considers the nonlinear dynamic characteristics of the distributed photovoltaic state, it responds to the corresponding demand by injecting additional current or power to provide voltage support, and provides feedback to the controller 11 based on the measured grid-connected point voltage of the distributed photovoltaic power generation system 12. After receiving the grid-connected point voltage, the feedback linearization module 101 of the controller 11 first performs a feedback linearization operation and transmits the obtained accurate feedback control model to the dynamic voltage control module 101; the dynamic voltage control module 101 then performs dynamic voltage control on the distributed photovoltaic power generation system 12 according to the feedback control model, and controls the distributed photovoltaic power generation system 12 in the form of issuing inverter control commands.

[0041] 2 is a flow chart of a distributed photovoltaic dynamic voltage control method based on feedback linearization according to an embodiment of the present invention, which includes steps S21 to S23, specifically:

[0042] Step S21 : establishing a nonlinear input-output model based on voltage control according to the nonlinear relationship between the photovoltaic array operating voltage and the output current and the nonlinear relationship between the DC bus voltage state and the output power within the distributed photovoltaic power generation system.

[0043] Specifically, a nonlinear input-output model of the distributed photovoltaic power generation system is established based on a preset state transfer function, using the inverter current components and the DC bus voltage as state variables, the inverter voltage components as input variables, the current components of the response voltage, and the energy stored in the DC bus capacitor as output variables. The distributed photovoltaic power generation system includes a photovoltaic array, an inverter, and a DC bus. It is worth noting that the output power is the output power on the AC side.

[0044] The present invention uses specific parameters within the distributed photovoltaic power generation system to accurately characterize the nonlinear relationship between the photovoltaic array operating voltage and output current and the nonlinear relationship between the DC bus voltage state and the output power, thereby improving the control accuracy of the distributed photovoltaic dynamic voltage.

[0045] It is worth noting that the distributed photovoltaic power generation system can adopt a two-stage photovoltaic power generation system and a monopole photovoltaic power generation system, and can adopt a distributed photovoltaic power generation system composed of a two-stage photovoltaic power generation system and a monopole photovoltaic power generation system; wherein, the two-stage photovoltaic power generation system includes: a photovoltaic array, a boost circuit, a DC bus, an inverter, and a filter circuit five parts connected in sequence, while the monopole photovoltaic power generation system can make corresponding simplifications to the model description part, the main difference being that the boost circuit part is reduced. Preferably, the present invention adopts a two-stage photovoltaic power generation system to construct a more realistic application scenario. See Figure 3, which is a structural schematic diagram of the two-stage photovoltaic power generation system provided by an embodiment of the present invention.

[0046] It is worth noting that, for the sake of convenience, it is assumed that the time constant of the inner loop of voltage and current control in the photovoltaic power generation system can be ignored in the problem under study, and it is considered that the inverter of the photovoltaic power generation system can directly accept voltage instructions.

[0047] As a preferred embodiment, the nonlinear input-output model can be expressed as:

[0048] in, is the time derivative of the state variable, x is the state variable, u is the input variable, y is the output variable, f(·) is the state transfer function, g(·) is the input function, and h(·) is the output function; I d is the d-axis component of the inverter current, I q is the q-axis component of the inverter current, V dcis the DC bus voltage, V id is the d-axis component of the inverter voltage, V iq is the q-axis component of the inverter voltage; the output variables include: the first output variable y1 = I d , corresponding to the current component in the dynamic voltage response, and the second output variable reflecting the energy stored on the DC bus capacitor of the photovoltaic power generation system

[0049] As a preferred embodiment, the state transfer function can be expressed as:

[0050] Among them, V gd is the d-axis component of the grid-connected point voltage, V gq is the q-axis component of the grid-connected point voltage, P dc is the photovoltaic DC side power, ω is the system frequency, R and L are the resistance and inductance of the photovoltaic grid-connected line respectively, and C is the DC bus capacitance.

[0051] Preferably, the input function is composed of only the reciprocal elements of the inductance of the photovoltaic grid-connected line as non-zero elements.

[0052] As a preferred embodiment, the input function can be expressed as:

[0053] Step S22: performing linearized feedback on the nonlinear input and nonlinear output of the nonlinear input-output model to obtain an input-output linearized feedback control model.

[0054] It is worth noting that the feedback control model of the distributed photovoltaic power generation system is processed using the feedback linearization method. Specifically, the output function is continuously differentiated until at least one input variable appears in the result.

[0055] Specifically, according to the output function of the nonlinear input-output model, multiple continuous Lie derivatives are obtained for N output variables until at least one derivatived input variable appears in the Lie derivative results; wherein N is a positive integer; the system parameters of the distributed photovoltaic power generation system are obtained to form a first non-singular matrix in the state space domain, and a feedback control model of input-output linearization is obtained based on a second matrix composed of the first matrix and the Lie derivative results of all output variables.

[0056] Among them, multiple continuous Lie derivatives are obtained for the N output variables respectively, specifically: multiple continuous Lie derivatives are obtained for the first first output variable and the second second output variable respectively, and the first Lie derivative result of the first output variable with a relative degree of 1 and the second Lie derivative result of the second output variable with a relative degree of 2 are obtained in sequence; wherein, the second matrix includes: the first Lie derivative result and the second Lie derivative result.

[0057] It is worth noting that the output variable includes two values, including: the first output variable y1=I d , corresponding to the current component in the dynamic voltage response, and the second output variable reflecting the energy stored on the DC bus capacitor of the photovoltaic power generation system Therefore, when taking continuous derivatives of output variables, it is necessary to take derivatives of the first output variable and the second output variable separately.

[0058] As a preferred embodiment, the Lie derivative result can be expressed as:

[0059] Among them, r i is the output variable y i The relative degree, r i and y i The subscript i in the output variable indicates the serial number, u j The subscript j represents the serial number of the input variable; L f h is the Lie derivative operator, defined as The higher-order Lie derivative is expressed as r is the relative degree, g i is the input variable.

[0060] As a preferred embodiment, corresponding Lie derivative results are obtained for all output variables. Since the relative degrees of the output variables are 1 and 2 respectively, two Lie derivative results can be obtained. Therefore, the matrix form of all Lie derivative results can be expressed as:

[0061] Where E(x) is the first non-singular matrix of system parameters in the neighborhood of the state space, u is the input variable, and L f h1(·) and is the first-order Lie derivative of the first output variable with respect to the state transfer function and the second-order Lie derivative of the second output variable with respect to the state transfer function, and are the first derivative of the first output variable with respect to time and the second derivative of the second output variable with respect to time, respectively.

[0062] It is worth noting that the Lie derivative results include the first-order Lie derivative of the first output variable with respect to the state transfer function and the second-order Lie derivative of the second output variable with respect to the state transfer function.

[0063] An equivalent third input variable is introduced into the matrix form of all Lie derivative results, and the input variable is represented by the third input variable. The input variable expression is written as:

[0064] Where v is the third input variable.

[0065] According to the matrix form of all Lie derivative results and the input variable expressions, the third input variable can be expressed as:

[0066] At this point, the feedback control model with input and output linearization is obtained.

[0067] Step S23: Acquire a current reference value of the response current and a voltage reference value of the DC bus voltage, and control the nonlinear input according to the current reference value, the voltage reference value, and the feedback control model.

[0068] The nonlinear input is controlled according to the current reference value, the voltage reference value and the feedback control model, including: obtaining the current reference value according to the voltage measurement amplitude deviation and the dynamic voltage response coefficient, and using the branch bus voltage rated value as the voltage reference value, using the current reference value as a first reference instruction for the first output variable, and using 1 / 2 of the square of the voltage reference value as a second reference instruction for the second output variable; and controlling the nonlinear input according to a control law obtained from the first reference instruction, the second reference instruction, the first output variable and the second output variable.

[0069] Specifically, the nonlinear input is controlled according to a control law obtained based on the first reference instruction, the second reference instruction, the first output variable, and the second output variable, including: taking the difference between the first output variable and the first reference instruction as a first tracking error variable, and taking the difference between the second output variable and the second reference instruction as a second tracking error variable; establishing a control law based on a first full-state order of the first tracking error variable and a second full-state order of the second tracking error variable, and controlling the nonlinear input according to the control law.

[0070] The existing technology uses a method to characterize the control law through input and feedback quantities. However, due to the large difference between the input quantity and the output quantity obtained after being affected by various factors in the photovoltaic system, the accuracy of the photovoltaic system reduced by the obtained control law is low. Compared with the existing technology, the present invention establishes a control law based on the full-order state orders corresponding to the tracking error variables obtained according to the output variable and the reference instruction. It can accurately characterize the relationship between the reference instruction and the output variable. On the basis of fully considering the influence of the nonlinear dynamic characteristics of the distributed photovoltaic state on the feedback control model, it can further improve the control accuracy of the distributed photovoltaic dynamic voltage.

[0071] As a preferred embodiment, the current reference value can be expressed as: I ref =KΔV g ,

[0072] Among them, I ref is the current reference value of the response current, ΔV g is the voltage measurement amplitude deviation at the grid connection point, and K is the dynamic voltage response coefficient.

[0073] It is worth noting that, in order to ensure the stability of the internal state of the photovoltaic power generation system during the response process, the DC bus voltage needs to be kept near the rated value. The voltage reference value can be expressed as: V dc,ref =V dcN ,

[0074] Among them, V dc,ref Voltage reference value of DC bus voltage, V dcN is the rated value of the DC bus voltage.

[0075] Therefore, according to the voltage measurement of the grid connection point and the rated parameters of the DC bus voltage, the tracking target of the output variable can be obtained, including the first reference instruction and the second reference instruction corresponding to the current reference value and the voltage reference value respectively.

[0076] As a preferred embodiment, the first reference instruction and the second reference instruction can be respectively expressed as:

[0077] Among them, y 1,ref and y 1,ref They are respectively a first reference instruction for the first output variable y1 and a second reference instruction for the second output variable y2.

[0078] As a preferred embodiment, the first tracking error variable and the second tracking error variable can be respectively expressed as: ε1=y1-y 1,ref ,ε2=y2-y 2,ref .

[0079] As a preferred embodiment, the control law can be expressed as:

[0080] Among them, a 11 ,…,a 23 is the dynamic response characteristic coefficient obtained according to the transient characteristic requirements of dynamic voltage control; and are the second-order derivative and first-order derivative of the first tracking error variable ε1 with respect to time; and They are respectively the third-order derivative, second-order derivative and first-order derivative of the second tracking error variable ε2 with respect to time.

[0081] It is worth noting that the control instruction obtained according to the control rate is still expressed in the form of input variable v. The input variable expression is converted into the form of input variable u through the formula to obtain a nonlinear control instruction directly issued to the photovoltaic power generation system.

[0082] Before establishing the control law based on the first full-state order of the first tracking error variable and the second full-state order of the second tracking error variable, the method includes: obtaining the first full-state order and the second full-state order, specifically: obtaining the first full-state order of the second order of the first tracking error variable based on the first relative degree of the first output variable, and obtaining the second full-state order of the third order of the second tracking error variable based on the second relative degree of the second output variable.

[0083] The present invention establishes a nonlinear input-output model through the nonlinear relationship between the photovoltaic array operating voltage and the output current and the nonlinear relationship between the DC bus voltage state and the output power. Compared with the use of proportional gain feedforward, it can fully consider the influence of the nonlinear dynamic characteristics of the distributed photovoltaic state on the feedback control model, so that the distributed photovoltaic charging system can accurately respond to the demand for voltage deviation, thereby improving the control accuracy of the distributed photovoltaic dynamic voltage; and, the nonlinear input and nonlinear output are linearized and fed back to obtain the implicit linear relationship between the nonlinear input and the nonlinear output, thereby establishing an accurate feedback control model, further improving the control accuracy of the distributed photovoltaic power generation system according to the feedback control model.

[0084] Those skilled in the art will appreciate that the embodiments of the present application may also provide computer program products. Therefore, the present application may adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment in combination with software and hardware. Moreover, the present application may adopt the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to magnetic disk storage, CD-ROM, optical storage, etc.) that contain computer-usable program code.

[0085] The present application is described with reference to the flow chart and / or block diagram of the method, device (system), and computer program product according to the embodiment of the present application. It should be understood that each flow process and / or box in the flow chart and / or block diagram and the combination of the flow process and / or box in the flow chart and / or block diagram can be realized by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processing machine or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device produce a device for realizing the function specified in one flow chart flow or multiple flows and / or one box or multiple boxes of the block diagram.

[0086] These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce a product including an instruction device that implements the functions specified in one or more processes in the flowchart and / or one or more boxes in the block diagram.

[0087] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, so that the instructions executed on the computer or other programmable device provide steps for implementing the functions specified in one or more processes in the flowchart and / or one or more boxes in the block diagram.

[0088] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A distributed photovoltaic dynamic voltage control method based on feedback linearization, It is characterized in that include: According to the nonlinear relationship between the working voltage and output current of the photovoltaic array in the distributed photovoltaic power generation system and the nonlinear relationship between the DC bus voltage state and the output power, a nonlinear input-output model is established based on voltage control. Performing linearized feedback on the nonlinear input and nonlinear output of the nonlinear input-output model to obtain an input-output linearized feedback control model; A current reference value of the response current and a voltage reference value of the DC bus voltage are obtained, and the nonlinear input is controlled according to the current reference value, the voltage reference value and the feedback control model.

2. The distributed photovoltaic dynamic voltage control method based on feedback linearization according to claim 1, It is characterized in that The nonlinear input-output model is established based on voltage control, including: Taking the inverter current components and the DC bus voltage as state variables, the inverter voltage components as input variables, the current components of the response voltage and the energy stored on the DC bus capacitor as output variables, and at the same time according to a preset state transfer function, a nonlinear input-output model of the distributed photovoltaic power generation system is established; wherein the distributed photovoltaic power generation system includes: a photovoltaic array, an inverter and a DC bus.

3. The distributed photovoltaic dynamic voltage control method based on feedback linearization according to claim 1, It is characterized in that The controlling the nonlinear input according to the current reference value, the voltage reference value and the feedback control model comprises: According to the voltage measurement amplitude deviation and the dynamic voltage response coefficient, the current reference value is obtained, and the branch bus voltage rated value is used as the voltage reference value, the current reference value is used as the first reference instruction of the first output variable, and 1 / 2 of the square of the voltage reference value is used as the second reference instruction of the second output variable; According to the first reference instruction, the second reference instruction, the first output variable and the The control law obtained by the two output variables controls the nonlinear input.

4. The distributed photovoltaic dynamic voltage control method based on feedback linearization as claimed in claim 3, It is characterized in that The control law obtained according to the first reference instruction, the second reference instruction, the first output variable and the second output variable controls the nonlinear input, including: using a difference between the first output variable and the first reference instruction as a first tracking error variable, and using a difference between the second output variable and the second reference instruction as a second tracking error variable; A control law is established according to a first full-state order of the first tracking error variable and a second full-state order of the second tracking error variable, and the nonlinear input is controlled according to the control law.

5. The distributed photovoltaic dynamic voltage control method based on feedback linearization as claimed in claim 4, It is characterized in that Before establishing a control law according to the first full-state order of the first tracking error variable and the second full-state order of the second tracking error variable, the method includes: obtaining the first full-state order and the second full-state order, specifically: According to the first relative degree of the first output variable, a first full-state order of the second order of the first tracking error variable is obtained, and according to the second relative degree of the second output variable, a second full-state order of the third order of the second tracking error variable is obtained.

6. The distributed photovoltaic dynamic voltage control method based on feedback linearization according to claim 1, It is characterized in that The step of performing linearized feedback on the nonlinear input and nonlinear output of the nonlinear input-output model to obtain an input-output linearized feedback control model comprises: According to the output function of the nonlinear input-output model, multiple continuous Lie derivatives are obtained for N output variables respectively until at least one input variable to be derived appears in the Lie derivative result; wherein N is a positive integer; The system parameters of the distributed photovoltaic power generation system are obtained to form a non-singular first matrix in the state space, and a feedback control model of input-output linearization is obtained according to a second matrix composed of the first matrix and Lie derivative results of all output variables.

7. The distributed photovoltaic dynamic voltage control method based on feedback linearization according to claim 6, It is characterized in that The method of obtaining multiple continuous Lie derivatives for N output variables is as follows: Multiple continuous Lie derivatives are obtained for the first first output variable and the second second output variable, respectively, to obtain the first Lie derivative result with a relative degree of 1 for the first output variable and the second Lie derivative result with a relative degree of 2 for the second output variable in turn; wherein the second matrix includes: the first Lie derivative result and the second Lie derivative result.

8. The distributed photovoltaic dynamic voltage control method based on feedback linearization as claimed in claim 2, It is characterized in that The nonlinear input-output model can be expressed as: in, is the time derivative of the state variable, x is the state variable, u is the input variable, y is the output variable, f(·) is the state transfer function, g(·) is the input function, and h(·) is the output function; I d is the d-axis component of the inverter current, I q is the q-axis component of the inverter current, V dc is the DC bus voltage, V id is the d-axis component of the inverter voltage, V iq is the q-axis component of the inverter voltage; the output variables include: the first output variable y 1 =I d , corresponding to the current component in the dynamic voltage response, and the second output variable reflecting the energy stored on the DC bus capacitor of the photovoltaic power generation system 9. The distributed photovoltaic dynamic voltage control method based on feedback linearization according to claim 2, It is characterized in that The state transfer function can be expressed as: Among them, V gd is the d-axis component of the grid-connected point voltage, V gq is the q-axis component of the grid-connected point voltage, P dc is the photovoltaic DC side power, ω is the system frequency, R and L are the resistance and inductance of the photovoltaic grid-connected line respectively, and C is the DC bus capacitance.

10. The distributed photovoltaic dynamic voltage control method based on feedback linearization according to claim 3, It is characterized in that The control law can be expressed as: Among them, a 11 ,…,a 23 is the dynamic response characteristic coefficient obtained according to the transient characteristic requirements of dynamic voltage control; and are the first tracking error variables ε 1 Second and first derivatives with respect to time; and are the second tracking error variables ε 2 The third, second, and first derivatives with respect to time.

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