CN-122026296-A - Polynomial fuzzy modeling method and device for multi-source direct-current micro-grid

CN122026296ACN 122026296 ACN122026296 ACN 122026296ACN-122026296-A

Abstract

The application provides a polynomial fuzzy modeling method and device for a multisource direct-current micro-grid, and relates to the technical field of direct-current micro-grid modeling and control. The method comprises the steps of constructing a state vector of a target system, constructing a unit state equation by using the state vector, wherein the unit state equation comprises a first state equation and a second state equation corresponding to the constant power load unit, a third state equation corresponding to the photovoltaic unit, a fourth state equation corresponding to the energy storage converter unit and a fifth state equation corresponding to the direct current bus unit, obtaining a nonlinear state space equation of a single constant power load unit based on the unit state equation, and constructing a global fuzzy model of the target system based on the nonlinear state space equation. The application can improve the accuracy and reliability of the model.

Inventors

LI XIAOMIAO
ZHANG JIAHAO
BAO ZHIYONG
MA JIE
LIANG JIFENG
WANG LEIBAO

Assignees

燕山大学
国网河北省电力有限公司电力科学研究院

Dates

Publication Date: 20260512
Application Date: 20260414

Claims (10)

1. The polynomial fuzzy modeling method for the multisource direct-current micro-grid is characterized by comprising the following steps of: Constructing a state vector of a target system, wherein the state vector comprises an inductance current of a constant power load unit, a capacitance voltage of the constant power load unit, an inductance current of a photovoltaic unit, an inductance current of an energy storage converter unit and a voltage of a direct current bus unit; Constructing a unit state equation by using the state vector, wherein the unit state equation comprises a first state equation and a second state equation corresponding to the constant power load unit, a third state equation corresponding to the photovoltaic unit, a fourth state equation corresponding to the energy storage converter unit and a fifth state equation corresponding to the direct current bus unit; Based on the unit state equation, a nonlinear state space equation of a single constant-power load unit is obtained, and based on the nonlinear state space equation, a global fuzzy model of the target system is constructed.
2. The method of polynomial fuzzy modeling of a multi-source dc micro-grid of claim 1, wherein said constructing a unit state equation using said state vector comprises: According to a structural topological diagram of the target system, topological structures of the constant power load unit, the photovoltaic unit and the energy storage converter unit are respectively determined, wherein the topological structure of the constant power load unit comprises a first switch tube, a first diode and an LC filter connected with the first diode, the topological structure of the photovoltaic unit comprises a first inductor, a second switch tube and a second diode, and the topological structure of the energy storage converter unit comprises a second inductor, a third switch tube and a fourth switch tube; based on the topological structure of the constant power load unit, a kirchhoff voltage law and a kirchhoff current law are adopted to obtain a first switch differential equation and a second switch differential equation of the constant power load unit, and the first state equation and the second state equation are determined based on the first switch differential equation, the second switch differential equation and a first preset switch state variable; Based on the topological structure of the photovoltaic unit, a third switch differential equation and a fourth switch Guan Weifen equation of the photovoltaic unit are obtained by adopting the kirchhoff voltage law and the kirchhoff current law, and the third state equation is determined based on the third switch differential equation, the fourth switch Guan Weifen equation and a second preset switch state variable; Based on the topological structure of the energy storage converter unit, a fifth switch differential equation and a sixth switch Guan Weifen equation of the energy storage converter unit are obtained by adopting the kirchhoff voltage law and the kirchhoff current law, and the fourth state equation is determined based on the fifth switch differential equation, the sixth switch Guan Weifen equation and a third preset switch state variable; Determining charging and discharging currents of the direct current bus unit based on the inductance current of the constant power load unit, the inductance current of the photovoltaic unit, the inductance current of the energy storage converter unit, the first preset switch state variable, the second preset switch state variable and the third preset switch state variable; and calculating the charge and discharge current of the direct current bus unit based on the capacitance volt-ampere characteristic to obtain a differential equation of the direct current bus unit, and determining the fifth state equation based on the differential equation of the direct current bus unit.
3. The method of polynomial fuzzy modeling of a multi-source dc micro-grid of claim 2, wherein the determining the first and second state equations based on the first, second, and first preset switch state variables comprises: inputting the first switch differential equation, the second switch differential equation and a first preset switch state variable into a first formula to obtain the first state equation and the second state equation, wherein the first formula is as follows: Wherein, the Is the first derivative of the state variable of the inductor current of the constant power load unit, Is the first derivative of the state variable of the capacitive current of the constant power load unit, As a state variable of the inductor current of the constant power load unit, As a state variable of the capacitive current of the constant power load unit, As a state variable of the voltage of the dc bus unit, For said first preset switch state variable, For the inductance of the constant power load unit, For the power of the constant power load unit, For the capacitance of the constant power load unit, 、、 And And the nonlinear coefficients are the nonlinear coefficients corresponding to the switching states of the constant power load units.
4. The method of polynomial fuzzy modeling of a multi-source dc micro-grid of claim 2, wherein the determining the charge-discharge current of the dc bus unit based on the inductor current of the constant power load unit, the inductor current of the photovoltaic unit, the inductor current of the energy storage converter unit, the first preset switch state variable, the second preset switch state variable, and the third preset switch state variable comprises: Inputting the inductance current of the constant-power load unit, the inductance current of the photovoltaic unit, the inductance current of the energy storage converter unit, the first preset switch state variable, the second preset switch state variable and the third preset switch state variable into a second formula, and calculating to obtain the charging and discharging current of the direct-current bus unit, wherein the second formula is as follows: Wherein, the For the charge and discharge current of the DC bus unit, For the inductor current of the energy storage converter cell, For the inductive current of the photovoltaic unit, For the inductor current of the constant power load unit, For said first preset switch state variable, For said second preset switch state variable, And a switch state variable is preset for the third.
5. The method of polynomial fuzzy modeling of a multi-source dc micro-grid of claim 2, wherein the determining the fifth state equation based on differential equations of the dc bus unit comprises: Converting the differential equation of the direct current bus unit into a state equation to obtain a fifth state equation, wherein the fifth state equation is as follows: Wherein, the Is the first derivative of the state variable of the voltage of the dc bus unit, As a state variable of the inductor current of the constant power load unit, As a state variable of the inductance current of the photovoltaic unit, As a state variable of the inductor current of the energy storage converter cell, For said first preset switch state variable, For said second preset switch state variable, For said third preset switch state variable, And the supporting capacitor is used for the direct current bus unit.
6. The polynomial fuzzy modeling method of a multi-source direct current micro grid according to claim 1, wherein the obtaining a nonlinear state space equation of a single constant power load unit based on the unit state equation comprises: determining a system matrix and an input matrix by using the unit state equation; Determining a constant vector matrix by using the output voltage of the photovoltaic unit, the inductance of the photovoltaic unit, the input voltage of the energy storage converter unit and the inductance of the energy storage converter unit; and determining a nonlinear state space equation of a single constant power load unit by using the system matrix, the input matrix and the constant vector matrix.
7. The method of polynomial fuzzy modeling of a multi-source dc micro-grid of claim 6, wherein said determining a nonlinear state space equation for a single constant power load cell using said system matrix, said input matrix, and said constant vector matrix comprises: inputting the system matrix, the input matrix and the constant vector matrix into a third formula to obtain a nonlinear state space equation of a single constant power load unit, wherein the third formula is as follows: Wherein, the Is the first derivative of the system state vector, For the matrix of the system to be described, For the input matrix to be used, For the matrix of constant-value vectors, In order to control the input vector(s), Is a system state vector.
8. The method for polynomial fuzzy modeling of a multi-source dc micro-grid of claim 1, wherein the constructing a global fuzzy model of the target system based on the nonlinear state space equation comprises: under the constraint condition of the capacitance voltage of a constant power load unit, calculating the vertex value of a nonlinear term at a boundary, wherein the vertex value comprises an upper vertex value and a lower vertex value, and the nonlinear term is the nonlinear term of the capacitance voltage of the constant power load unit; Constructing a membership function by using the upper vertex value and the lower vertex value, wherein the membership function comprises a first membership function and a second membership function; Under the constraint of a preset fuzzy rule, calculating a rule activation weight corresponding to the preset fuzzy rule by using the upper vertex value, the lower vertex value and the membership function; and constructing a global fuzzy model of the target system by utilizing the nonlinear state space equation and the rule activation weight.
9. The method of polynomial fuzzy modeling of a multi-source dc micro-grid of claim 8, wherein said constructing a global fuzzy model of the target system using the nonlinear state space equation and the rule activation weights comprises: Inputting the nonlinear state space equation and the rule activation weight into a fourth formula, and constructing a global fuzzy model of the target system, wherein the fourth formula is as follows: Wherein, the Is the first derivative of the system state vector, Is the first The system matrix under the preset fuzzy rule is set, In order to input the matrix of the data, Is a matrix of vectors of constant values, In order to control the input vector(s), As a system state vector of the system, For the total number of constant power load units, Is the first The rule activation weights of the preset fuzzy rules, For the preset blur sequence number of rule.
10. A polynomial fuzzy modeling apparatus for a multi-source dc micro-grid, comprising: The vector construction module is used for constructing a state vector of the target system, and the state vector comprises an inductance current of a constant power load unit, a capacitance voltage of the constant power load unit, an inductance current of a photovoltaic unit, an inductance current of an energy storage converter unit and a voltage of a direct current bus unit; The state equation construction module is used for constructing a unit state equation by utilizing the state vector, wherein the unit state equation comprises a first state equation and a second state equation corresponding to the constant power load unit, a third state equation corresponding to the photovoltaic unit, a fourth state equation corresponding to the energy storage converter unit and a fifth state equation corresponding to the direct current bus unit; and the fuzzy model construction module is used for obtaining a nonlinear state space equation of a single constant-power load unit based on the unit state equation and constructing a global fuzzy model of the target system based on the nonlinear state space equation.

Description

Polynomial fuzzy modeling method and device for multi-source direct-current micro-grid Technical Field The application relates to the technical field of direct current micro-grid modeling and control, in particular to a polynomial fuzzy modeling method and a device for a multi-source direct current micro-grid. Background As a high-efficiency and flexible distributed energy integration scheme, the direct-current micro-grid is widely applied in the fields of ship power systems, data center power supply, electric vehicle charging stations, renewable energy grid connection and the like in recent years. Compared with an alternating-current micro-grid, the direct-current micro-grid has the remarkable advantages of being few in energy conversion links, simple to control, natural in direct-current load adaptation, high in electric energy quality and the like. A typical dc microgrid system generally comprises a photovoltaic unit, an energy storage unit and various types of power electronic loads. In a direct current micro grid system, a constant power load (Constant Power Load, CPL) is a special load type, the power of which is kept constant, and the load has a negative impedance characteristic that when the voltage of a load terminal increases, the current decreases instead, and when the voltage decreases, the current increases. The negative impedance characteristic forms a serious threat to the stability of the direct-current micro-grid, and is mainly expressed as stability problems such as bus voltage oscillation, voltage collapse risk, multi-CPL coupling effect and the like. In the field of direct current micro-grids, the existing Constant Power Load (CPL) modeling method also faces contradiction between accuracy and complexity. The modeling method commonly used at present comprises the steps of small-signal linearization modeling, namely carrying out Taylor expansion on a nonlinear equation near a steady-state working point, and reserving a first-order term to obtain a linearization model. The method is simple in model, can directly apply linear system theory, is only suitable for small disturbance analysis near a working point, cannot describe dynamic behavior under large disturbance, is limited in precision, needs to be re-linearized when the working point changes, is not suitable for a wide-range operation scene, and is accurate in switching model, namely, a piecewise linear differential equation is established based on the actual switching state of a power electronic device. The method has the highest precision, can completely describe the nonlinear characteristics of the system, but has the advantages of complex calculation, small simulation step length, large calculation amount, huge model, inconvenient controller design and serious simulation time consumption, and T-S fuzzy modeling, namely, the nonlinear system is represented as a fuzzy weighted sum of a plurality of linear subsystems. The method provides a global model, is effective in the whole definition domain, is convenient for the design of the controller, and can apply a parallel distribution compensation method. However, membership functions are strong in experience, generally adopting functions such as triangle, gaussian and the like, lacking theoretical basis, uncontrollable approximation error and incapability of guaranteeing accurate approximation to an original nonlinear system. Currently, CPL characteristics are aimed atThe precise fuzzy modeling method of the system is imperfect, the existing research is concentrated on a single type unit, the fuzzy modeling research on a multi-source hybrid system is insufficient, and the whole analysis and the coordination control are difficult to carry out. Disclosure of Invention The application provides a polynomial fuzzy modeling method and a device for a multi-source direct-current micro-grid, which are used for solving the problem that the precision of the conventional direct-current micro-grid constant-power load system is low in a high-precision scene. In a first aspect, the present application provides a polynomial fuzzy modeling method for a multi-source direct current micro-grid, including: Constructing a state vector of a target system, wherein the state vector comprises an inductance current of a constant power load unit, a capacitance voltage of the constant power load unit, an inductance current of a photovoltaic unit, an inductance current of an energy storage converter unit and a voltage of a direct current bus unit; Constructing a unit state equation by using the state vector, wherein the unit state equation comprises a first state equation and a second state equation corresponding to the constant power load unit, a third state equation corresponding to the photovoltaic unit, a fourth state equation corresponding to the energy storage converter unit and a fifth state equation corresponding to the direct current bus unit; Based on the unit state equation, a nonlinear state space equatio