Study on Digital PI Control of Current Loop in Active Power Filter

With development of modern industry, more and more non-linear loads are used in power system, resulting in increasingly severe harmonic pollution. Harmonic becomes main factors affecting power quality. Active power filter, as the most effective method to eliminate harmonic, has been paid more and more attention recently. The current compensation performance of active power filter depends on the controller. At present, more and more active power filters have been controlled by digital controller, which has the advantage of flexible control strategy, powerful ability of signal processing. However, digital controller has inherent drawbacks, such as quantization error, signal delay caused by Zero-Order hold, sample and computation delay. With analyzing active power filter´s decreased performance caused by digital controller, this paper concentrates on two reasons: Zero-Order hold, sample and computation delay.