Research On Power System Small Signal Stability With Distributed Small Hydropower

Small hydropower is the most widely distributed, abundant storage and lowdevelopment cost clean renewable energy in our country. China has supported thedevelopment of mall hydropower for a long time. By the end of2010, the total installedcapacity of small hydropower in our country is55120MW, while its annual powergeneration is160billion kWh, which account for30%respectively of china hydropowerinstalled capacity and annual generation. But the output of small hydropower isinfluenced by climate conditions greatly, which also has great fluctuation andrandomness. And the small hydropower’s characteristics of poor regulation performanceand seasonal output have a big influence on the safe and stable operation of powersystem, so it is very practical and significant to evaluate small signal stability of actualpower system timely and efficiently and master its characteristics of small signal stabilitydeeply.Closely combined with engineering practice, this paper evaluated small signalstability of actual power system with distributed small hydropower. Firstly, this paperdiscussed the development and utilization status of home and abroad small hydropowerbriefly, analyzed the influence on the stable operation of power system exerted by thegrid-connected small hydropower. In view of the historical changes of smallhydropower’s administrative jurisdiction and dispatching management, discussed thepractical engineering significance of the power system small signal stability under theinfluences of distributed small hydropower in-depth.This paper introduced the main current analysis methods for power system smallsignal stability, analyzed their main characteristics respectively. Studied and describedthe basic concepts and mathematical models of general dynamic system small signalstability. In accordance with practical needs of research, briefly described thesynchronous generator model, excitation system model and small hydropower equivalentmodel which were adopted in the small signal stability analysis, and also analyzed theirmodel characteristics respectively.Based on the above work and the background of Hunan power system, this paperstudied on the Hunan power system small signal stability with grid-connected distributedsmall hydropower systematically and comprehensively through the simulation tool ofPSASP. Set up the Hunan power grid model without considering small hydropowerdynamic characteristics, the Hunan power grid model with equivalent model of small hydropower and the Hunan power grid model with distributed grid-connected smallhydropower in detailed study area totally three models. Under the wet season with lightloads operating mode(small hydropower generators on full capacity operation with lightroads) and based on the massive simulation calculation, this paper analyzed the threeHunan power grid models comparatively from inter-area oscillation mode and internaloscillation mode two aspects. Studied on the influences on the Hunan power systemsmall signal stability exerted by the grid-connected distributed small hydropowersystematically. It can be concluded that small hydropower stations have a big influenceon the small signal stability of Hunan power system, the grid connected smallhydropower weakens the system damping and make the low frequency oscillation easy tooccur and surely be a big threat to the safe and stable operation of power system.The research in this paper comes from practical engineering subject, and theresearch results and conclusions have a great decision and reference value to powersystem operation dispatching.