CN-121984367-A - Z-source inverter current switching control method and system of photovoltaic power generation system

CN121984367ACN 121984367 ACN121984367 ACN 121984367ACN-121984367-A

Abstract

The invention relates to a Z source inverter current switching control method and a Z source inverter current switching control system of a photovoltaic power generation system, wherein the Z source inverter current switching control method comprises the steps of establishing a current switching affine model based on a Z source inverter in the photovoltaic power generation system; the method comprises the steps of establishing a current error switching affine model according to the current switching affine model, establishing a plurality of subsystems of the Z source inverter based on the current switching affine model and the current error switching affine model, establishing a switching table according to the subsystems of the Z source inverter, and determining states of an upper switching tube and a lower switching tube in the Z source inverter of a next control period according to the switching table through a preset switching rule. The method has the advantages that the working state of the Z source inverter in the photovoltaic power generation system can be accurately described, the switching states of the Z source inverter in different control periods can be directly selected based on the switching rules, complex coordinate transformation and pulse width modulation processes are not needed, control parameters are not needed, and the method has strong robustness under the condition that circuit parameters are uncertain.

Inventors

GUO XIN
Qiao Jichen
CHENG GANG
Sai Ousuo Gribaki

Assignees

西安理工大学

Dates

Publication Date: 20260505
Application Date: 20260127

Claims (10)

1. The Z source inverter current switching control method of the photovoltaic power generation system is characterized by comprising the following steps of: Establishing a current switching affine model based on a Z source inverter in the photovoltaic power generation system; Establishing a plurality of subsystems of the Z-source inverter based on the current switching affine model and the current error switching affine model; establishing a switching table according to a plurality of subsystems of the Z source inverter; And determining states of an upper switching tube and a lower switching tube in the Z-source inverter in the next control period according to the switching table through a preset switching rule.
2. The method of claim 1, wherein the establishing a current switching affine model based on the Z source inverter in the photovoltaic power generation system, and the establishing a current error switching affine model based on the current switching affine model, comprises: adopting a control method based on a switching model, taking alternating-current side three-phase current of a Z source inverter in the photovoltaic power generation system as a controlled system state, and establishing a current switching affine model according to the working principle of the Z source inverter in a through mode and a non-through mode; and based on the current switching affine model, obtaining a current error switching affine model of the Z source inverter by making a difference between an actual value and an expected value in the current switching affine model.
3. The method according to claim 2, wherein the current switching affine model satisfies the following formula: ; in the above formula: Representing the derivative of the state vector of the controlled system with respect to time t, R representing the AC side resistance value of the Z-source inverter, L representing the AC side inductance value of the Z-source inverter, The method comprises the steps of representing a state vector of a controlled system, i a (t), i b (t), i c (t) representing three-phase current of an alternating current side of a Z-source inverter at t moment, e a (t), e b (t), e c (t) representing three-phase voltage of alternating current measurement of the Z-source inverter at t moment, V c representing capacitance voltage value of the Z-source inverter, V pv representing output voltage of a photovoltaic side of the Z-source inverter, P k being a discrete switching function, wherein k=a, b, c, a, b and c represent a phase a, a phase b and a phase c of the alternating current side of the Z-source inverter respectively, S k =1 represents that an upper switching tube of a k-phase bridge arm of the Z-source inverter is conducted and a lower switching tube of the k-phase bridge arm of the Z-source inverter is disconnected, S k =0 represents that the upper switching tube of the k-phase bridge arm of the Z-source inverter is disconnected and the lower switching tube of the Z-source inverter is conducted, Z=1 represents that the Z=0 represents that the Z-source inverter is in a direct mode and Z=0 represents that the Z=0 is in a non-direct mode; representing a state matrix of the controlled system, wherein I represents an identity matrix; the switching affine term representing the controlled system.
4. A method according to claim 3, characterized in that the switching affine term of the controlled system satisfies the following formula: ; in the above formula: The switching affine term of the controlled system is represented by e a (t), e b (t), e c (T), the alternating current measured three-phase voltage of the Z source inverter at the T moment is represented by e a (t), e b (t), e c (T), the capacitance voltage value of the Z source inverter is represented by V c , the output voltage of the photovoltaic side of the Z source inverter is represented by V pv , the transposition of the matrix is represented by T, the inductance value of the alternating current side of the Z source inverter is represented by L, the discrete switching function is represented by P k , and k=a, b, c, a, b and c represent the a phase, the b phase and the c phase of the alternating current side of the Z source inverter respectively.
5. The method of claim 2, wherein the current error switches affine model to satisfy the following formula: ; In the above-mentioned method, the step of, Representing the derivative of the state error vector with respect to time t, Representing a state error vector, wherein: , , ; the actual value and the expected value of the a-phase current of the alternating-current side of the Z-source inverter at the t moment are represented to be different; the actual value and the expected value of the b-phase current of the alternating current side of the Z-source inverter at the t moment are represented to be different; The method comprises the steps of representing the difference between the actual value and the expected value of c-phase current of an alternating-current side of a Z-source inverter at the moment t, representing the actual value of three-phase current of the alternating-current side of the Z-source inverter at the moment t by i a (t), i b (t), i c (t), representing the expected value of three-phase current of the alternating-current side of the Z-source inverter at the moment t by i ar (t), i br (t), i cr (t), and representing the alternating-current measured three-phase voltage of the Z-source inverter at the moment t by e a (t), e b (t), e c (t); For switching affine terms, P k represents a discrete switching function, k=a, b, c, a, b, c represent a phase a, b phase, c phase on the ac side of the Z source inverter, in the discrete switching function, S k =1 represents that the upper switching tube of the k-phase bridge arm is on and the lower switching tube is off in the Z source inverter, S k =0 represents that the upper switching tube of the k-phase bridge arm is off and the lower switching tube is on in the Z source inverter, z=1 represents that the Z source inverter is in the pass-through mode, and z=0 represents that the Z source inverter is in the non-pass-through mode; representing the state matrix of the controlled system, and I represents the identity matrix.
6. The method of claim 5, wherein the switching affine term satisfies the following formula: ; In the above-mentioned method, the step of, For switching affine terms, e a (t), e b (t), e c (T) represents the ac measured three-phase voltage of the Z-source inverter at time T, V c represents the capacitance voltage value of the Z-source inverter, V pv represents the output voltage of the photovoltaic side of the Z-source inverter, T represents the transpose of the matrix, L represents the inductance value of the ac side of the Z-source inverter, Representing the product of the a-phase resistance value of the ac side of the Z-source inverter and its current desired value, Representing the product of the b-phase resistance value of the ac side of the Z-source inverter and its current desired value, P k represents a discrete switching function, and k=a, b, c, a, b, c represent a phase a, b, c, respectively, on the ac side of the Z source inverter.
7. The method of claim 1, wherein the establishing a plurality of subsystems of the Z-source inverter based on the current-switched affine model and the current-error-switched affine model comprises: Establishing corresponding relations between the switching states of different switching tubes in the Z source inverter and the Z source inverter according to the current switching affine model and the current error switching affine model; Forming periodic variation of output voltage of an alternating current side of the Z source inverter based on the switching states of different switching tubes in the Z source inverter; And dividing a Z-source inverter dynamic model corresponding to the switching states of the different switching tubes into a plurality of subsystems based on the alternating-current side output voltage period of the Z-source inverter.
8. The method of claim 1, wherein the establishing a switching table from the plurality of subsystems of the Z-source inverter comprises: dividing the acquired complete three-phase alternating voltage period into 6 sectors according to every 60-degree phase angle interval; And selecting a plurality of subsystems meeting the convex combination condition and the existence condition of the common Lyapunov function in each sector according to the magnitude relation of the three-phase voltage and the current error switching affine model to form a switching subsystem subset corresponding to the sector, and forming a complete switching table by all the sectors and the corresponding switching subsystem subset.
9. The method according to claim 1, wherein determining states of an upper switching tube and a lower switching tube inside the Z source inverter of a next control period according to the switching table by a preset switching rule comprises: acquiring a current error state vector and three-phase voltage, capacitor voltage, photovoltaic side output voltage and inductance value at the current moment; determining a current sector according to the three-phase voltage magnitude relation at the current moment, and acquiring a switching subsystem subset corresponding to the current sector according to the switching table; calculating a corresponding switching function value of each subsystem in the switching subsystem subset based on the current error switching affine model; comparing the switching function values corresponding to all subsystems in the switching subsystem subset, and selecting the subsystem with the smallest switching function value; The switching vector corresponding to the selected subsystem is used as the switching state output of the next control period and used for controlling the on and off of the upper and lower switching tubes of each phase bridge arm of the Z-source inverter; Wherein, the switching rule satisfies the following formula: ; In the above-mentioned method, the step of, Representing the selected subsystem, argmin represents a minimization function, Representing each subsystem in the currently selected handoff subset; p k represents a discrete switching function, and k=a, b, c, a, b, c represent a phase a, b phase c, respectively, on the ac side of the Z source inverter.
10. A Z source inverter current switching control system for a photovoltaic power generation system, comprising: The current error switching affine model construction module is used for establishing a current switching affine model based on a Z source inverter in the photovoltaic power generation system; A subsystem construction module for constructing a plurality of subsystems of the Z source inverter based on the current switching affine model and the current error switching affine model; The switching table construction module is used for establishing a switching table according to the plurality of subsystems of the Z-source inverter; And the determining module is used for determining the states of an upper switching tube and a lower switching tube in the Z-source inverter in the next control period according to the preset switching rule and the switching table.

Description

Z-source inverter current switching control method and system of photovoltaic power generation system Technical Field The invention belongs to the technical field of photovoltaic power generation in new energy technology, and particularly relates to a Z-source inverter current switching control method and system of a photovoltaic power generation system. Background The Z source inverter in the photovoltaic power generation system can realize buck-boost conversion and allow bridge arm direct connection due to the unique impedance network structure, and has important application in the fields of new energy grid connection and the like. However, the conventional Z-source inverter control method, particularly the voltage modulation-based pulse width modulation strategy, has significant drawbacks in terms of dynamic performance, model accuracy and control robustness. Disclosure of Invention The invention aims to provide a Z-source inverter switching control method based on a current switching affine model, which aims to overcome the defects that in the prior art, the model description is inaccurate, the control performance is limited and a complex pulse width modulation algorithm is relied on. In order to achieve the purpose, the technical scheme adopted by the invention is to provide a Z source inverter current switching control method of a photovoltaic power generation system, which comprises the following steps: Establishing a current switching affine model based on a Z source inverter in the photovoltaic power generation system; Establishing a plurality of subsystems of the Z-source inverter based on the current switching affine model and the current error switching affine model; establishing a switching table according to a plurality of subsystems of the Z source inverter; And determining states of an upper switching tube and a lower switching tube in the Z-source inverter in the next control period according to the switching table through a preset switching rule. Preferably, the establishing a current switching affine model based on the Z source inverter in the photovoltaic power generation system includes: adopting a control method based on a switching model, taking alternating-current side three-phase current of a Z source inverter in the photovoltaic power generation system as a controlled system state, and establishing a current switching affine model according to the working principle of the Z source inverter in a through mode and a non-through mode; and based on the current switching affine model, obtaining a current error switching affine model of the Z source inverter by making a difference between an actual value and an expected value in the current switching affine model. Preferably, the current switching affine model satisfies the following formula: in the above formula: Representing the derivative of the state vector of the controlled system with respect to time t, R representing the AC side resistance value of the Z-source inverter, L representing the AC side inductance value of the Z-source inverter, The method comprises the steps of representing a state vector of a controlled system, i a(t), ib(t), ic (t) representing three-phase current of an alternating current side of a Z-source inverter at t moment, e a(t), eb(t), ec (t) representing three-phase voltage of alternating current measurement of the Z-source inverter at t moment, V c representing capacitance voltage value of the Z-source inverter, V pv representing output voltage of a photovoltaic side of the Z-source inverter, P k being a discrete switching function, wherein k=a, b, c, a, b and c represent a phase a, a phase b and a phase c of the alternating current side of the Z-source inverter respectively, S k =1 represents that an upper switching tube of a k-phase bridge arm of the Z-source inverter is conducted and a lower switching tube of the k-phase bridge arm of the Z-source inverter is disconnected, S k =0 represents that the upper switching tube of the k-phase bridge arm of the Z-source inverter is disconnected and the lower switching tube of the Z-source inverter is conducted, Z=1 represents that the Z=0 represents that the Z-source inverter is in a direct mode and Z=0 represents that the Z=0 is in a non-direct mode; representing a state matrix of the controlled system, wherein I represents an identity matrix; the switching affine term representing the controlled system. Preferably, the switching affine term of the controlled system satisfies the following formula: in the above formula: The switching affine term of the controlled system is represented by e a(t), eb(t), ec (T), the alternating current measured three-phase voltage of the Z source inverter at the T moment is represented by e a(t), eb(t), ec (T), the capacitance voltage value of the Z source inverter is represented by V c, the output voltage of the photovoltaic side of the Z source inverter is represented by V pv, the transposition of the matrix is represented by