A measurement data based method for identifying wind turbine generators which cause sub-synchronous oscillations (SSOs) in a complex power system, comprising following steps of:
- (1) obtaining a set of measurement data when the SSOs occur in the power system;
- reducing noise by applying a filtering algorithm;
- identifying an SSO frequency by using a signal processing method;
- wherein the identified SSO frequency is denoted as fs;
- (2) designing a parallel band-pass filter to ensure that only a signal at frequency fs passes through to earth and signals at other frequencies are suppressed;
- (3) for a power system with n wind turbine generators, installing the parallel band-pass filter designed in the step (2) on an interface between each of the wind turbine generators and the power system;
- wherein subsequently, dynamic interactions between the wind turbine generators and the power system at the SSO frequency fs are suppressed and filtered out;
- whilst those at other frequencies are not affected;
- (4) measuring a response from each of the wind turbine generators by adding a disturbance signal on a side of a wind turbine generator near the band-pass filter;
- (5) from the measurement data of the response of an i-th wind turbine generator, identifying an oscillation frequency, fij, and residuing Rij by applying a signal processing method;
- wherein in notations above for fij and Rij, subscript i refers to the i-th wind turbine generator and the subscript j refers to the j-th SSO frequency identified;
- afterwards, comparing fij and fs;
- recording the fij and Rij if a following condition is met:
- 1.05*fs≥fij≥0.95*fs;
- wherein finally, if no fij which can meet the above condition, it is concluded that the i-th wind turbine generator is not the wind turbine generator which causes the SSOs in the power system;
- (6) measuring the response from the power system by adding a disturbance signal on the side of the power system near the band-pass filter for the i-th wind turbine generator;
- (7) from the measurement data of the response, identifying an oscillation frequency faij and a residue Raij by using the signal processing method;
- wherein in notations of faij and Raij, subscript a indicates that the measurement data is about the power system, subscript i refers to the i-th wind turbine generator and subscript j refers to the j-th oscillation frequency and residue;
- afterwards, comparing faij and fs;
- recording faij and Raij if a following condition is met:
- 1.05*fs≥faij≥0.95*fs and
- (8) Computing Zi=|√{square root over (RijRaij)}|, i=1, 2, L n based on recorded results in the step (5) and (7);
- wherein if Zk is the largest among Zi, i=1, 2, L n, the i-th wind turbine generator is identified to be the wind turbine generator causing the SSOs in the power system.