FIGS. 12A to 12J show the second compensation current signal (isig″) obtained by adding the second compensation signal (icomp′) as in Equation 11 to the current signal (isig) according to the first angular error ({tilde over (θ)}r) and the injection angle (?i) when the torque command has a predetermined value (1 pu) according to an embodiment of the present disclosure.
In FIGS. 12A to 12J, the first portion 12-1 is a portion where the second compensation current signal (isig″) makes zero up-crossing and becomes a convergence point of the angle estimator 180. However, a second portion 12-2 is a portion where the second compensation current signal (isig″) makes zero down-crossing and cannot be a convergence point of the angle estimator 180.
Thus, by applying any injection angle corresponding to the first portion 12-1, it is possible to estimate the position of the rotor while removing the first angular error. For example, an intermediate value in the injection angle range corresponding to the first portion 12-1 may be representatively applied, and the intermediate value may be stored in advance.
That is, the injection angle may be determined within a range where the first angular error is 0 and the second compensation current signal becomes 0 while having a positive slope on the basis of the first angular error.
FIGS. 12A to 12J show the results of a specific torque command, and the above process may be repeatedly performed to all available torque commands to determine a suitable injection angle for every torque command.
