Patent ID: 6844690
Filing Date: 2005-01-18
Classification: H02M

Abstract:
1. A method of compensating for dc offset in a three phase ac current signal, comprising the steps of: providing a sample of the ac current signal; generating a rotating vector (r) from the sample; extracting a dc offset from the sample; removing the dc offset from the ac current signal; and generating a Park vector representing a total measured current vector (iT) from the sample using the formula: iT=(⅔)(Ia+(a)(Ib)+(a2)(Ic)); where a=exp(j2π/3), Ia equals the amplitude of the phase current A (Ia=I sin(wt)), Ib equals the amplitude of the phase current B (Ib=I sin(wt+π/3)) and Ic equals the amplitude of the phase current C (Ic=I sin(wt+2π/3)) and w=frequency and t=time; wherein the three phases of the ac current signal comprise a phase current A, a phase current B, and a phase current C.