Delay Compensation Design Of LCL Inverter Based On Active Damping

Nowadays,the demand for energy is increasing rapidly.How to obtain new sources of energy is the focus of scientific research in this century.Distributed generation technology is a new technology developed on the basis of it.It can transform new primary renewable energy into electric energy which is widely used in daily life and industry.Inverter is very important as a bridge for distributed generation system to access power grid.The output voltage of the inverter bridge contains switching harmonics,which need to be filtered by LCL filter.At the resonant frequency,the gain peak appears in the amplitude-frequency characteristic of the filter,and the phase mutation occurs in the phase-frequency characteristic.Under digital control,the method of damping spikes will introduce the inherent delay of the system,which will transform the feedback inner loop from resistance to vector-varying reactance.Under digital control,if the actual resonant frequency of the system is one sixth of the sampling frequency,the system will be unstable.Uncertainty of grid resistance will make the actual frequency of the inverter exceed one sixth of the sampling frequency.If the control delay is not compensated at this time,the system will have unstable hidden dangers.This paper will study how to solve the control delay by making a prototype.Therefore,this paper gives the design scheme of hardware module and software module of the experimental prototype and makes a detailed analysis,and puts forward a new sampling method and a new delay compensation scheme.The new sampling method is grid-connected current sampling in time,and the algorithm compensation is linear prediction plus zero-pole compensation.Finally,an experimental platform is built.The experimental platform adopts a single-phase full-bridge two-stage structure,digital bipolar SPWM modulation,capacitive current and grid-connected current double closed-loop feedback system.The simulation environment and experimental results verify the feasibility of the delay compensation strategy proposed in this paper.