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dc.contributorDepartment of Electrical Engineeringen_US
dc.contributor.advisorChan, K. W. (EE)en_US
dc.creatorZhai, Yueting-
dc.publisherHong Kong Polytechnic Universityen_US
dc.rightsAll rights reserveden_US
dc.titleStudy of secondary control strategies of microgrids with high voltage qualityen_US
dcterms.abstractIn recent years, renewable energy power generation system, represented by solar photovoltaic power generation, storage battery and wind power generation, has developed rapidly. In this trend, microgrid and distributed energy have received great attention.en_US
dcterms.abstractAccording to the current research, renewable energy will affect the operation of distribution network after grid connected operation. This dissertation introduces the characteristics of microgrid technology and analyzes the uneasiness of operation and control of microgrid caused by the randomness of distributed power supply and its adverse effect on the electrical energy quality.en_US
dcterms.abstractThe particularity of the electrical power quality of the microgrid is determined by the operation and control approaches of the microgrid. The power quality control strategies of microgrid has the following requirements: (1) reactive voltage control, (2) frequency stability, (3) unbalanced control, (4) harmonic suppression. Therefore, this thesis proposes a hierarchical control method of microgrid to study and improve the power quality of microgrid.en_US
dcterms.abstractThe manifestations of the above microgrid power quality issues are different, but the solutions depend on the balanced control of energy. The hierarchical control strategy is an important way to realize the energy balance and make sure the stable operation of the microgrid.en_US
dcterms.abstractThe deviation of voltage and frequency in microgrid are two important indexes of power quality. The traditional droop control method of distributed power inverters will cause the voltage and frequency deviation. In primary control of microgrid, most of the distributed power supplies use power electronic interface, and the load and network structure are variable, which increases the difficulty in stability control of voltage and frequency of microgrid.en_US
dcterms.abstractHow to ensure the microgrid to satisfy the voltage and frequency stability indexes in the island operation mode is the key to reliable operation of the grid. To compensate for the influence of voltage and frequency deviation of microgrid, the control strategy of microgrid based on secondary control is established. This control approach uses the primary control signal to regulate the output voltage amplitude and frequency of the inverter again to make the voltage and frequency deviation at PCC within a certain range. In addition, the smooth synchronization progress between microgrid and main grid can be achieved by adopting the grid-connected control method of the microgrid based on the secondary control. Finally, realizing smooth switching from the island mode to the grid-connected mode and avoiding the issue of impulse current occurring in grid-connection process.en_US
dcterms.extentviii, 50 pages : color illustrationsen_US
dcterms.isPartOfPolyU Electronic Thesesen_US
dcterms.educationalLevelAll Masteren_US
dcterms.LCSHMicrogrids (Smart power grids) -- Automatic controlen_US
dcterms.LCSHElectric power systems -- Controlen_US
dcterms.LCSHHong Kong Polytechnic University -- Dissertationsen_US
dcterms.accessRightsrestricted accessen_US

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