| Because of many advantages, distributed generations have achieved rapid developmentin recent years, and been widely used around the world. Along with the development ofcapacity, the randomness and intermittent of new energy generation, such as photovoltaicpower and wind power generation, have more and more negative effect on the grid.Therefore, It is necessary to conduct a study on that.Microgrid usually consists of such distributed powers as wind power generation, solarpower generation, micro gas turbine, energy storing device, which are connected by powerelectronics converters. On account of the randomness and intermittent of distributedgenerations and the randomness of loads, there are many small interfering events during theoperation of microgrid. Therefore, It is significant to study the small-signal stability ofmicrogrid.First, the small-signal stability of single-machine infinite-bus system of two-stagephotovoltaic power generation was studied in this paper. The small-signal model ofphotovoltaic power generation system was built, including voltage stabilizing capacitor,Boost circuit, L filter, MPPT controller and controller for grid-connected inverter. Itssmall-signal stability was analyzed by means of eigenvalues analysis. Through thecalculation of participation factors, the internal correlation degree between oscillation modeand state variable was analyzed. The controller’s parameters were adjusted by eigenvaluelocus method. Additionally, the simulation model of photovoltaic power generation systembased on PSCAD/EMTDC was built. The small-signal analysis and the simulation resultsshowed that reasonable adjusting of the controller’s parameters can improve the small-signalstability of the system.Second, the small-signal stability of single-machine infinite-bus system ofpermanent-magnet synchronous wind generation was studied in this paper. The small-signalmodel of permanent-magnet synchronous wind generation system was built, including windturbine, permanent-magnet synchronous wind generator, controller for AC/DC inverter, Lfilter, controller for DC/AC inverter, DC-link capacitor. Its small-signal stability wasanalyzed by means of eigenvalues analysis. The simulation model of photovoltaic powergeneration system based on PSCAD/EMTDC was built. From the simulations, it comes tothe conclusion that the small-signal model and analysis are right.Last, the small-signal stability of a3node microgrid was studied in this paper, whichconsists of photovoltaic power generation, wind power generation, energy storage battery,resistance-inductance load, induction motor. The interface inverters of photovoltaic and windpower generation use voltage and current double loop control while the interface inverter ofenergy storage battery use P-f&Q-V droop control. Complete small-signal model of themicrogrid is obtained, and detailed derivation of the model is given. The small-signalstability of a case was analyzed by means of eigenvalues analysis. Through the calculation ofparticipation factors, the internal correlation degree between oscillation mode and statevariable was analyzed. The controller’s parameters were adjusted by eigenvalue locusmethod. Additionally, the simulation model of photovoltaic power generation system based on PSCAD/EMTDC was built. |
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