Patent ID: 8044672

Claim:
A method for measuring D-Q impedance of a component of a plurality of polyphase power grid components connected to a grid node in a polyphase power grid, said component being at least one electrical device, said plurality of components including a generator, as one component of said plurality of polyphase power grid components, coupled to said polyphase power grid, said generator, having a speed input to regulate generator no-load speed and a field input to regulate field excitation of said generator, with said no-load speed and field excitation being used to cause said generator connected to said grid node on said polyphase power grid to induce suppressed-carrier stimulus current into said grid node to produce response signals, said measuring being performed by circuitry to measure said response signals of suppressed-carrier form existing within a bus voltage at said grid node and a branch current of said component being measured, said method comprising: applying each test frequency signal of a first frequency sweep over a frequency band of interest to said speed input of said generator while measuring said response signals in said bus voltage in real and imaginary form to generate a first set of voltage values; applying each test frequency signal of a second frequency sweep over said frequency band of interest to said speed input of said generator while measuring said response signals in said branch current in real and imaginary form to generate a first set of current values; processing said first set of voltage values and said first set of current values to form a first set of two equations of four simultaneous equations; applying each test frequency signal of a third frequency sweep over said frequency band of interest to said field input of said generator while measuring said response signals in said bus voltage in real and imaginary form to generate a second set of voltage values; applying each test frequency signal of a fourth frequency sweep over said frequency band of interest to said field input of said generator while measuring said response signals in said bus current in real and imaginary form to generate a second set of current values; processing said second set of voltage values and said second set of current values to form a second set of two equations of said four simultaneous equations; and resolving said four simultaneous equations to determine said D-Q impedance parameters Zqq, Zqd, Zdq and Zdd of said measured component.