Coordination Control For Hybrid AC/DC Microgrids Connected With High-density Distributed Photovoltaic Sources

The briskly increase of the distributed renewable resource generation is changing the form of the future grids.On one hand,more and more distributed rooftop PV panels,PV generation of industrial park,small-scale PV plants of islands and remote areas are being installed;On the other hand,the variable frequency driving inductors,LED lights,DC charging piles of electric vehicles,and the DC loads such as laptops and mobile phones are becoming more and more popular.Both of the aspects make the hybrid AC/DC microgrid the ideal paradigm to integrate distributed generation and DC loads.Therefore,the hybrid AC/DC microgrid becomes one of the most important research directions.This thesis focuses on the coordination control of the hybrid AC/DC microgrid with high penetration of distributed PV sources,develops the decentralized control method of distributed PV sources,and unifies dc-bus voltage regulation and maximum power point tracking with the same control configuration.Also,this thesis proposes the typical topology of a bus-sectioned hybrid AC/DC microgrid and suggests its standardization oriented coordination control paradigm.Firstly,this thesis proposes the vdc2 feedback control method for two-stage photovoltaic gener-ation system.The two-stage topology has been widely used because its flexibility in PV integration voltage.However,the nonlinear characteristic of the dc-link voltage makes it hard to design the con-trol parameter and performance.This thesis establishes the systemic model of the whole two-stage PV generation system and execute the sensitive analysis by the method of the locus of eigenvalues.On this basis,a vdc2 feedback control method is suggested to linearize the system model of dc-link voltage control.By proper control parameter design,the transient performance of the system is improved.Secondly,this thesis proposes the V-dp/dv droop control for distributed PV sources.The pro-posed method unifies the dc-bus voltage regulation and maximum power point tracking in the sense of the same control configuration.There needs no transition of control configuration for different PV operation mode switching thus the seamless mode switching is achieved.When multiple PV sources operates in parallel,the power sharing among them is also achieved approximatively.Thirdly,this thesis develops the decentralized coordination control strategy of distributed PV sources.On the basis of V-dp/dv droop control strategy.The proposed method keeps the unifica-tion of dc-bus voltage regulation and maximum power point tracking as in V-dp/dv droop control,the autonomous and seamless mode switching is also achieved.The improvement compared with the V-dp/dv droop control is that by the proposed decentralized coordination control strategy,the accurate power sharing among multiple PV sources is achieved.Finally,this thesis defines the topology of a bus-sectioned hybrid AC/DC microgrid.Four different operation modes of the bus-sectioned hybrid AC/DC microgrid are suggested and the standardization oriented control paradigm is proposed.By using the proposed hierarchical con-trol paradigm,the stable operation and seamless switching among different operation modes are realized.Relying on the national 863 project,the proposed control paradigm is applied in the bus-sectioned hybrid AC/DC microgrid demonstration in Shaoxing,China.The test results in the demonstration project validates the verification and effectiveness of the proposed control paradigm.