Research On The Dumping Mechanism Of Typical Wind Generators And The Forced Oscillation Suppression Method

The power system stability is proved to be the key factor that affects the power system’s reliability and economy. The large scale integration of wind farm will provide the system more complicated stable condition. Recently, the mechanism of the new stable problems led by wind farm have not been deeply studied yet by the academia as well as the industry, while their importance and urgency are salience. The stable mechanism research of power system integrated with wind farm will provide theoretical support to power system operation and controlling.Compared to the conventional energy, wind generators have many differences. First, as the output power of wind farm fluctuates randomly, meanwhile the controlling purpose of wind generators is to gain wind power in the maximum degree, the outcome of wind farm is not completely controllable, which will cause power flow transferring randomly. Second, as an asynchronous generator, the operating characteristics and rotational inertia are totally different from conventional synchronous generators, therefore lager scale integration of wind farm will affect the whole system’s inertia as well as dumping evidently. Third, the conventional generators has the self-synchronous characteristic, which is not inherent by asynchronous wind generators. Forth, as the capacity of single wind generator is much less than that of synchronous, the wind farm’s normally composed by hundreds of wind generators, so the fault and wind fluctuation will cause wind generators’ random chain reaction, which provides the system many uncertain discrete issues.According to recent research, the dumping offered by wind farm will be affected by the connecting point, penetration rate, operating condition and exciting parameters. But how the above factors influence the damping is still needed to study. The common method of wind farm stability analyzing is to replace the synchronous generators with wind generators of the same capacity, then to calculate the eigenvalues to tell if the wind farm will improve system stability. Obviously, this method is universal but not clarified in terms of physical meaning.First of all, the dumping mechanism of DFIG is discussed in this paper. According to the decouple characteristic of DFIG, a conclusion is gained that the dumping from DFIG is caused by its electromagnetic dynamics. Furthermore, the DFIG can be seen as the dumping source of power system, and its dumping will be distributed to power angle oscillation mode in a specific way.Second, the complex dumping torque theory is established, which clarified how the DFIG’s dumping is distributed to power angle oscillation. Meanwhile, how exciting parameters affect the complex torque is discussed.Third, according to forced oscillation theory, the mechanism of power angle oscillation caused by wind fluctuation is studied. Furthermore, the magnitude of forced oscillation is affected by dumping torque is gained as a conclusion.