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The squirrel-cage induction machine (IM) has been widely employed in microgrid. Accurate electrical parameters are necessary for the field-oriented control of the IM to achieve excellent performance. In this paper, a new offline identification scheme is presented based on the vector constructing method. The IM parameters are estimated using the recursive least squares (RLS) algorithm, which is applied to the continuous-time model of the IM at standstill. A single-phase ac test is used to make the machine standstill. The main feature of the proposed scheme is that the stator voltage, stator current and their derivatives, which are normally needed for the RLS algorithm, are constructed by the vector constructing method. The constructing rules are elaborated, which indicate that the phase shift and the amplitude ratio between the fundamental components of the voltage and the current have to be unchanged. This feature can avoid the analog or digital differentiators and greatly increase the noise immunity. Furthermore, the digital low-pass filter is not required for the proposed scheme, which can reduce the complexity of the identification scheme. Simulation and experimental results have been presented to demonstrate the validity and the feasibility of the proposed scheme.
Date of Publication: Feb. 2012