Stationary-frame generalized integrators for current control of active power filters with zero steady-state error for current harmonics of concern under unbalanced and distorted operating conditions

The paper proposes the concepts of integrators for sinusoidal signals. A proportional-integral (PI) current controller using stationary-frame generalized integrators is applied for current control of active power filters. Zero steady-state error for the concerned current harmonics is realized, with reduced computation, under unbalanced utility or load conditions. Designing of the PI constants, digital realization of the generalized integrators, as well as compensation of the computation delay are studied. Extensive test results from a 10-kW prototype are demonstrated.