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Small-Signal Stability Analysis Of Microgrid Control And Strategy For Microgrid Energy Management

Posted on:2012-06-03Degree:DoctorType:Dissertation
Country:ChinaCandidate:L SuFull Text:PDF
GTID:1102330335454040Subject:Power system and its automation
Abstract/Summary:PDF Full Text Request
Many institutions and universities in our country are working on microgrid in the situation of the increasing penetration of distributed generation(DG), the strong policy support and the implementation of smart grid. Microgrid can not only solve the problem of large scale DG coupling but also play full advantages of DG, improve power supply reliability and bring more benefits to users. Since the key technology of microgrid is control, it is necessary to conduct a comprehensive study on DG control, microgird control and microgrid energy management.The main content of this dissertation are as follows:1.The control of Inverter interfaced DG is flexible and inertialess. DG inverter employs active power and voltage magnitude (PV control) to carry out DG (microturbine) determining power by heat when grid-connected operation. Inverter employs droop control (P-f control and Q-V control) to carry out plug and use when islanding operation. Each DG shares load only according to the local measurement at the situation of load variation and the demands of load for voltage and frequency are met. The minimum and maximum output limits are added in P/f droop control for the safety of energy storage used to improve the dynamic performance. The proposed method can control microgrid flexible switch between grid-connected operation and islanding operation. The output of DG can be limited to its allowable scope and prevent the damage of DC energy storage.2.Ideal inverter model and state-less impedance model of network and loads are currently used to analyze the small signal stability of microgrid, which will cause important dynamics to be omitted. For capturing the dynamics of microgrid and large power inverters more accurately, the complete small-signal model of microgrid based on inverter-interfaced distributed generation is developed when microgrid is gird-connected or islanding. This integrated model consists of two sub-models:the small signal sub-model of network and load considering dynamics and the complete sub-model of DG inverters. The eigenvalues of state matrix of small signal model of microgrid can be used to investigate small signal stability directly and compare the dynamic performance of each contol method. A sensitivity analysis is furtherly implemented which helps to identify the origin of dominate low frequency eigenvalues. This model can optimize parameters and improve the small signal stability of microgrid.3.The functions, tasks and operation flow of energy management system are planned for microgrid after comparing the respective characteristics belong to DG and traditional power. The mathematical formulation on economical dispatching and optimal operation is presented in detail. The control strategy combined central control and local control is put forward for lab microgrid operation and can switch microgrid between grid-connected operation and islanding operation flexibly and seamlessly, follow the load variation and keep system stable.4. Supervisory control platform of lab microgrid is developed using configuration software iFix and embedded with optimal operation and control software. This platform gives the support to have a deep research on microgrid and lays the foundation for teaching and experiment.
Keywords/Search Tags:inverter-interfaced distributed generation, distributed generation control, microgrid control, small-siganl stability analysis, microgrid engergy mangagement
PDF Full Text Request
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