Research On Control Algorithms Of Three-phase Voltage Source Inverter

Three-phase voltage inverter is an important device for electric energy conversion in new energy power generation technology.Effective and reasonable control algorithm is one of the key technologies to improve the performance of the inverter.Since the three-phase voltage inverter is a type of time-varying,coupled,non-linear system,it is difficult to meet people's requirements for the inverter's performance indicators using the linear control PI algorithm commonly used in the industry.Therefore,the study of a reasonable control algorithm is An important part of inverter research.This article takes three-phase voltage inverters as research objects,and studies its modeling analysis and control algorithms.The main contents include: According to the working principle and structural characteristics of the three-phase voltage-type inverter,a mathematical model in a stationary coordinate system is established.The average switching model of the switching average operator is used to analyze and discuss such a discrete system into a continuous system model.The frequency-domain mathematical model considering the delay of the inverter is also discussed,and the transfer function model from the modulated wave input to the inverter output is obtained.The dq coordinate transformation is used to change the AC quantity model in the three-phase stationary coordinate system into the DC quantity model in the dq coordinate system.For the coupling relationship between the d-axis and q-axis variables,the decoupling principle is used to change the variables The feedback model is used to obtain the mathematical model of the three-phase voltage inverter in the dq coordinate system.Using the engineering design method,the current inner loop is designed according to a typical type I system,and the voltage outer loop is designed according to a typical type II system.The control parameters of the controller are obtained.A DSP28335 microprocessor is used as the controller to build a three-phase voltage-type inverter closed-loop system.The effectiveness of the dual-loop PI control algorithm based on dq decoupling is verified.The finite control model predictive control algorithm is applied to a three-phase voltage inverter system.The discrete mathematical model and prediction model are established.The advantages and disadvantages of the penalty function method and multi-step method of the improved finite control model predictive control are analyzed.A derivative method is proposed to optimize the objective function.The advantages of this method are discussed.The simulation experiments verify the rationality and effectiveness of this method.In order to overcome the drawbacks of the power electronics switching frequency is not fixed when using the penalty function method,multi-step method and derivative method,a triangular carrier frequency determination method based on virtual space vector is proposed.First,the basic space vector and the composition of the virtual space vector are introduced,and the limitations of traversing all the virtual space vectors when selecting the traditional optimal vector are analyzed.A method for online calculation of alternative virtual vectors is discussed.In order to achieve the fixed frequency control in the full sense,the triangular carrier fixed frequency method is used to achieve the fixed frequency control.Finally,simulation experiments verify the effectiveness of the method.