New rotating transformation for efficient DSP control of active power-line conditioners

This paper presents a new rotating transformation for the control of APLC (active power line conditioners). APLC is a power electronic inverter which is designed to suppress power line distortion caused by nonlinear loads. Existing control methods for the APLC such as the popular instantaneous power transformation, are based on measurements of both power line voltage and current to estimate the required compensation for the power line distortion. These methods are quite sensitive to the power line voltage distortion that can introduce control errors. This paper presents a new simple transformation method for the APLC which determines the correct power line compensation using the line current measurement only. This method simplifies the existing control processing and reduces the power line measurement requirements. The accuracy of the new method is not affected by the power line voltage distortion and therefore, it is reliable for all power line conditions. A 10 kVA prototype APLC has been developed to verify the accuracy and efficiency of the new method.