Research On Phasor Detection Techniques Based On Orthogonal Decoupling In Hilbert Space And Its Application In Microgrid

The global requirement for sustainable energy provision will become increasingly important over the next years as the environmental effects of fossil fuels become apparent.Distributed Generation(DG)based on Renewable Energy Technologies(solar,wind,hydro and biomass)is becoming a more important energy option in the future generation system.However,the power grid will be subject to some adverse impacts regarding the increased penetration level of DG and the excessive usage of single-phase,asymmetric,and non-linear loads,such as voltage unbalance,voltage distortion,frequency jumping,and so on.These problems will make it difficult to keep the microgrid inverter synchronized with the grid voltages,which will reduce the operation performance of the microgrid inverter.In order to detect the phasor information such as amplitudes,phases,and frequency of the non-ideal voltages efficiently and reliably,so as to improve the performance of the microgrid inverters under non-ideal voltage conditions,this paper proposes a phasor detection technique based on the orthogonal decoupling principle in Hilbert space.By vector analysis of the phase detector’s error,a decoupling control law can be designed for each voltage phasor to realize the decoupling detection.Then,the overall detection speed of the phasor detection system can be improved by setting the settling time of all the voltage phasor control laws as the same value.According to the need for detecting the zero-sequence components of non-ideal voltages,this paper designs the voltage phasor detection techniques based on the orthogonal decoupling principle in Hilbert space through Tan-Sun coordinate transformation and three-dimensional space coordinate transformation,respectively.The control law of the detection techniques is designed to detect the unbalance phasor,DC-offset phasor,and higher-harmonic phasor of three-phase non-ideal voltages,so as to improve the effectiveness of the voltage phasor detection system in various power electronic systems and various non-ideal voltage conditions.In addition,this paper takes three-phase four-wire islanded microgrid system as an example to verify the detection effect of the phasor detection of the inverter output voltages based on three-dimensional space coordinate transformation,and the corresponding control strategy to be adopted.Finally,this paper set up a hardware experimental platform of the voltage phasor detection system,and the performance of the phasor detection techniques designed based on the above two coordinate transformations for detecting the non-ideal voltage phasors is verified experimentally,so as to verify the feasibility and correctness of the detection method applied in the actual systems.