Researches On Distributed Coordinated Control Methods Of Power Sharing For Networked AC/DC Hybrid Microgrids

The Energy Internet(EI),which is becoming an inevitable development trend and direction for the future energy network,has risen to a national energy strategy of China and become a hot research topic in academia in the world wide.As an important part of EI,the microgrid is of great significance to the large-scale inte-gration and application of the renewable energy sources.In the context of Energy Internet,the coordinated energy management and control issues of(interconnected)microgrids which is an important part of El are mainly focused and researched in this thesis,and the improvement of power quality is also studied.Firstly,distribut-ed control issues of the reactive,harmonic and imbalance power sharing and power quality improvement is investigated for microgrids containing unbalanced and non-linear loads.Secondly,this thesis proposes a hybrid microgrid structure containing single-/three-phase distributed renewable energy generation systems(DREGS)and its power balance management control strategy.Thirdly,the energy coordination and distributed control of the AC/DC hybrid microgrid and the microgrid clusters are studied,respectively.Based on the above mentioned,hierarchical coordinated power control and power quality improvement is further investigated for networked hybrid microgrids,in which unbalanced microgrids containing both single-/three-phase DGs and loads are considered.Finally,numerical simulation and experimental results are provided to demonstrate the correctness and effectiveness of the proposed methods.The main contributions and salient features are summarised as follows:(1)For issues of power sharing and power quality improvement in a microgrid with unbalanced and nonlinear loads,harmonic and imbalance droop controllers and a distributed multi-agent consensus approach adaptively regulating both the fundamental positive and negative and the harmonic virtual impedances,respectively are developed,respectively.The theoretical analysis and experi-mental results show that the method can effectively overcome the influence of line impedance mismatch and ensure accurate power sharing among DGs,and better improve the voltage quality at PCC.(2)For the practical applications of the fast proliferation of single-/three-phase DGs and loads,a single phase/three-phase hybrid microgrid architecture with autonomous energy management capability based on PSU system intercon-nection is proposed for the first time,and the control strategy of PSU system based on adaptive Backstepping-sliding mode control and droop control is de-signed.This method addresses the issue that the interphase power of the hybrid microgrid cannot be transferred and co distributed,and the power supply flexibility,reliability and renewable energy efficiency of the microgrid system are enhanced.(3)For the coordinated power management and control issues of interlinked AC/DC microgrids,an energy management and control strategy for IC,con-sisting of primary outer-loop dual-droop controller and inner-loop data-driven model-free adaptive voltage controller,is proposed.This method solves the cooperative power sharing control problem of the hybrid microgrid,and makes IC have the ability to participate in voltage and frequency regulation like DGs.Also,it shows that ICs have good robustness of data driven control to the un-certainty and unmodeled dynamics of the hybrid microgrid system.(4)For active power sharing among a cluster of AC and DC microgrids intercon-nected by a set of ICs,an event-triggered communication-based distributed multi-agent coordinated power sharing control approach is proposed.Then,the stability determination theorem and its proof are provided with the con-sideration of communication delays.Meanwhile,reactive power support for ac MGs is studied utilizing the available power ratings of ICs.Theoretical and experimental results show that microgrid clusters share load accurately and dramatically reduce communications,with high flexibility and reliability.(5)For the networked AC and DC microgrids containing single-/three-phase MGs,a hierarchical power management and dynamic power flow routing coordinat-ed control approach is proposed for power sharing between MGs and differ-ent phases,respectively,based on structure-decentralized distributed event-triggered PI controllers.Meanwhile,the voltage quality improvement method is studied based on the coordination of DGs and ICs.Three objectives can be achieved with this method:power mutual support among MGs,power balancing between phases and improved voltage quality.