Efficient Reference Compensation Current Control Strategy of Shunt Active Power Filter for Improvement of Power Quality(2/3)

With the widespread use of nonlinear loads in the power system, the problems associated withharmonics have been of great concerns. These disturbances may not only introduce the additional power lossin the transmission, but also reduce the usage life of the power system equipments. Therefore, improving thepower quality has become an important issue for both utilities and customers.A new theory and a conceptual design for the three-phase shunt active power filter (APF) controlstrategy under imbalanced and distorted supply voltages are present in this project. Conventionally, thecompensation currents injected by the APF are determined according to reference frametransformation-based approaches, where the load instantaneous real and reactive powers are calculated in thenew reference frame. The APF injection currents are then computed to maintain the balanced and sinusoidalsource currents, as well as the least active power consumption by the APF. However, it is necessary that theline-to-neutral value of the fundamental source voltage and phase angle at each phase must be obtained sothat the reference compensation currents can be accurately determined in this technique. To provide accuratecompensation currents, an effective approach will be analyzed and proposed in this project.Since those power quality analyzer based on the traditional Fourier series time-varying approachesonly take the harmonics into account, it is not able to effectively analyze the interharmonic components dueto the power converters in recent years. Hence, several commonly used methods will be reviewed andcompared in this project, and a novel improved method will also be proposed to implement. In addition, thedeveloped harmonic/interharmonic analysis algorithm in this project will be implemented with the dedicatedhardware to form a virtual monitoring system and make the actual measurement to verify and correct theanalysis method.From above, the main tasks of this project can be summarized, which include: (1) Review andcompare the recent analysis methods for the harmonics and the related power quality signal processingmethods; (2) Find out the deficiencies of the traditional designs and propose a method to remedy; (3) Designand implement the APF reference compensation current control strategy according to the proposed designingrules; (4) Make the measurements and analysis for the actual harmonic sources with the developed APFcontroller; (5) Establish and design the related database for the power quality signal measurements ofnonlinear loads.