A Robust Inductive Current Proportional Feedback-Grid Voltage Prediction Feedforward Control For Single-Phase Grid-tied Converter

As energy issues become more severe,distributed power generation technologies that utilize new energy sources has attracted more and more attention in the world.Single-phase grid-connected inverter is widely used in distributed power generation system with small unit capacity as the energy conversion bridge between distributed power and users and power grid.In order to realize the current loop control of single-phase grid-connected inverter,various control strategies have been developed,such as PI control,hysteresis control,current prediction control,etc.Based on the idea of deadbeat control in current predictive control,this paper proposes a proportional-grid voltage prediction feed-forward control method for single-phase grid-connected inverter.The control method can be designed directly in the static coordinate system without phase-locking loop,and the algorithm is simple and requires little computation.The main research contents of this paper are as follows:1)The state average mathematical model of single-phase grid-connected inverter is derived in the static coordinate system,and the principle and design process of traditional deadbeat predictive control are introduced.Based on that,an improved deadbeat predictive control strategy is proposed,i.e.proportional-grid voltage prediction feed-forward control,which differs from the traditional deadbeat control in that the backward Euler approximation is used to discretize the control object,and the control law derived therefrom is simpler;2)The closed-loop control performance of the proportional-grid voltage prediction feedforward control is discussed.The closed-loop mathematical model is modified considering the influence of the inductor current sampling filter.The influence of the first-order filtering on the performance of the closed-loop system is analyzed and verified by simulation;3)The Hopfield neural network is used to predict the grid voltage,and the grid voltage feedforward value and reference current value of the future time are obtained.Moreover,the prediction function of Hopfield neural network is used to compensate the grid voltage sampling filter delay.The design process of Hopfield neural network and the error of the prediction results are quantified,and finally verified by simulation;4)Based on TMS320F28377 chip,the proportional-grid voltage prediction feedforward control system of single-phase grid-connected inverter is designed.The control performance of the control algorithm is verified by experiments,and the key factors in the control such as proportional coefficient,filtering delay,whether or not the Hopfield neural network predicts verify the impact on control performance.