Studies On The Coordination Of Large Scale Wind Generation And The Incorporated Power Grid

Large scale wind power concentrated integrating to power grid is an effective way for the wind energy exploiture. Since the fluctuant, almost uncontrollable and low forecasting precision characteristic of wind power, the controlability of power generation has been weakened, and which is the ultimate reason of the worse effects on power grid security caused by the wind power. If the worse effects of wind power on power grid has not been accurately evaluated, the power grid operater normally would overestimate the risk, and then the incorporation of wind power is to be restricted at a lower level. So the development of wind power is limited in certain extent. With the construction of some 1000MW-class wind farms in China, the contradiction between the large-scale integrated wind power and the security of power grid will be further emerged. How to meet the needs of wind power development and ensure power grid security is an urgent task to be studied with both important theoretical and practical significance.After a sound review of the fast development of wind power and effects on its integrated power grid, the conception of coordination between the wind power and the power grid is proposed in this paper. The contradiction would be mitigated by exploring the wind power characteristics and accurately assessing the wind power effects on the grid. The potential of the existing power grid for accepting wind power could be maximized.The mathematics model characteristics in different time scales of DFIG has been analyzed, which would provide the model foundation for further study of the coordination between the source and the power grid.The fluctuant characteristic of large-scale wind power is analyzed based on the probability statistics of historical measured operation data of the wind farm. The spatio-temporal distribution characteristic of large-scale wind farms is recognized and the clustering effect is revealed, which provides the foundation for further study of the coordination between the source and the grid.The Multi-Scenario Calculation Method on wind power accepted capability of the grid is proposed. By analysis of the limitation and disadvantage of existing calculation method, a new calculation model for acceptance capability is built with two influence coefficients defined to reflect the different effects of wind power and the grid.The transient characteristics of the DFIG during the short circuit process has been analyzed based on the electromagnetic transient model. The characteristics of short-time asynchronous operation during abnormal disconnection process of DFIG is revealed. The voltage level of the integrated grid would be badly influenced when the DFIG operated asynchronously, which has been proved authentic by analysis on the measured disconnection event of a certain wind farm.The measured data of short circuit tests in wind farm has been analyzed in this paper, and the trip logic of crowbar protective relay is obtained. The voltage and current characteristics of the stator, rotor and the converter during abnormal disconnection process are revealed, for the reason that the crowbar trips more faster than the switch of stator circuit does. Besides, the validity of the bulit electromagnetic transient model of DFIG and the correctness of the analysis on the transient characteristics during the voltage dipping process, are verified by postmortem simulation of the tests.Safe faults area has been researched determined by the Low Voltage Ride Through requirement of the technical rule for connecting wind farm into power grid. Voltage dipping extent of wind farm during different faults has been analyzed, together with the effects on voltage distribution by the clustering system of wind farm.The steady state and transient simulation models of DFIG are developed with the popular power system analysis softwares, such as PSASP/UPI and PSCAD/EMTDC.