Research On Several Issues About Microgrid Generntion Technology

As an effective supplement to the traditional centralized power generation, the distributed generation helps to promote the usage of the clean energy and renewable energy into the electricity production, alone with improving local reliability of electricity power supply.Microgrid is capable to coordinate and synthesize the operation of different types of distributed generation, Microgrid can be adopted as a feasible management method to ensure the coordinated interaction between the power grid and the distributed generations. But the effective operation coordination management methods between Microgrid and the distributed grid, the effective operation coordination and integration of the distributed generations within Microgrid, the methods to enhance the power supply reliability within Microgrid, Microgrid fault protection methods, the reasonable configuration and control of the power storage units of Microgrid’s master power source are urgent to be researched and solved.This thesis focuses on the effective operation coordination of the distributed generations within Microgrid, the methods to enhance the power supply reliability within Microgrid, Microgrid fault protection methods and the reasonable configuration and control of the power storage units of the master power sources within Microgrid.First to introduce the control design of the three-phase-four-leg interfacing inverter of the master power sources, and to adopt a method to enhance the power supply reliability within Microgrid by equipping with PQ power source to Microgrid, then to propose a software method to limit the output current of the master power source and a Microgrid partitioned fault protection method, finally to propose a master-and-slave control method to suitably manage the hybrid power storage units of the master power sources within Microgrid, the more detailed chief research work of this thesis is as followed by:1) The chapter I firstly introduces the developing background and state quo of the the distributed generation, Microgrid and control structure, then Microgrid’s impacts on the fault protection of the distributed grid, the fault protection methods within Microgrid and the usage of the power storage units are briefly reviewed, at last the focus of this thesis’ research work and the arrangement of the chapters are introduced.2) The chapter Ⅱ firstly introduces the three-phase-four-leg voltage control method based on four-orthogonal-space matrix transformation and adds a virtual impedance, consisting of high pass filter and band pass filter, to the mater power source’s output voltage control loop in order to decoupling the control of the master power source’s output power. Then the selection of the relevant coefficients of the droop control block is introduced and the real power forward feed is adopted to the droop control block in order to set the dampening coefficients of the roots of Microgrid’s real power small-signal-disturb model. Finally the synchronization method of the master power source is introduced and the time simulation is built to confirm the feasibility of the above control design.3) The chapter III firstly introduces the necessity of the reliability enhancement of Microgrid’s power supply and adopts the injection of compensation power by PQ power source to Microgrid to enhance Microgrid power supply reliability. The control method of PQ power source is introduced and the small-signal-disturb stability is analyzed. Finally the time simulation is built to confirm the feasibility of the proposed method to enhance Microgrid power supply reliability.4) The chapter IV firstly adopts a software current limitting method to the master power source in order to ensure the stable running of the master power source under the condition of Microgrid’s line fault without causing an over-current phenomenon to the inverter’s switching legs. Then the difficulty of Microgrid line fault protection is briefly analyzed and a Microgrid partitioned line fault protection method based on the communication network is adopted to satisfy the flexible operation mode of Microgrid. Finally the time simulation is built to confirm the feasibility of the proposed Microgrid partitioned line fault protection method.5) The chapter V firstly compares the characteristics of several common small-scale power storage units. Then the hybrid power storage system is adopted as the DC side power storage units of the master power source and the master-and-slave control method is proposed to control the hybrid power storage system which selects the banks of super-capacitors as the master storage unit and the banks of lead-acid batteries as the slave storage unit, in order to avoid the frequent charge and discharge of the banks of lead-acid batteries. Finally the time simulation is built to confirm the feasibility of the proposed master-and-slave control method.6) The chapter VI summarizes this thesis’s research achievements and point out the future research focus.