Patent ID: 7132816

Claim:
A field oriented control (FOC) system for a polyphase brushless wound field synchronous machine that has a main stator, an exciter stator and a rotor assembly comprising a direct current (DC) main rotor wiring supplied by a rotating rectifier assembly that rectifies alternating current (AC) generated by an exciter rotor winding and that uses an estimated rotor position signal {circumflex over (θ)} for control of the machine, the system comprising: a first Clarke transformation that receives electrical potentials for each phase of a polyphase excitation of frequency F exc for the exciter stator and transforms them to an α-axis excitation potential v exc — α and a β-axis excitation potential v exc — β in a two-phase α-β stationary reference frame an exciter excitation electrical potential space vector with fundamental frequency F exc ; a first phase locked loop (PLL) that receives the two excitation potentials v exc — α and v exc — β outputs a signal that is representative of an estimated position {circumflex over (θ)} exc of the exciter excitation space vector; a harmonic filter tuned to at least one desired harmonic of the excitation frequency F exc that receives the signal that is representative of the estimated position {circumflex over (θ)} exc and passes the desired harmonic of {circumflex over (θ)} exc ; a second Clarke transformation that receives the exciter stator current signals representative of current on each phase of the polyphase exciter excitation and transforms them to digital α-axis and β-axis exciter current signals i exc — α and i exc — β in a two-phase stationary α-β reference frame for the exciter excitation space vector; a Park transformation that receives the digital α-axis and β-axis exciter current signals i exc — α and uses the desired harmonic of {circumflex over (θ)} exc to transform them to a d-axis exciter signal i exc — d and q-axis exciter signal i exc — q in a rotating d-q reference frame of the exciter excitation space vector harmonic; and a second PLL that receives the signals i exc — d and i exc — q and outputs the estimated rotor position signal {circumflex over (θ)}.