Standstill Time-Domain Response Parameter Estimation of the Large Synchronous Condenser in Arbitrary Rotor Position

The necessity to align the rotor with the <inline-formula> <tex-math notation="LaTeX">$d$ </tex-math></inline-formula>-<inline-formula> <tex-math notation="LaTeX">$q$ </tex-math></inline-formula> magnetic axes is the main obstacle for the wide application of synchronous machine standstill parameter tests, especially for the high-power units. This paper presents an arbitrary rotor position parameter estimation method for standstill time-domain response (SSTRs) tests and applied on a 300 MVar, 20 kV large synchronous condenser, a DC step voltage signal is selected as the input signal. Firstly, a frequency-domain Dalton-Cameron transformation is demonstrated and used to simultaneously obtain both axes’ operational inductances in an arbitrary rotor position, thus eliminating the need for the rotor prepositioning process. Then, a novel analytical parameter estimation method combined with an I/T transformation is proposed, all the parameters of both axes are determined without extra tests, the mutual leakage flux between the field winding and the <inline-formula> <tex-math notation="LaTeX">$d$ </tex-math></inline-formula>-axis damper winding is also taken in account. To validate the proposed method, this test is carried out and its parameter estimation results are compared against that of the three-phase sudden short-circuit test and the traditional SSTR test. Estimation results are given in the form of I-type and T-type circuits, the maximum relative error no more than 6% and 10%, respectively.