Research On Control Of Static Synchronous Compensator In Distribution Network Based On P-DPC Theory

Distribution Static Synchronous Compensator(D-STATCOM) is an important “DFACTS” device, which can be an effective solution to power quality problems such as voltage fluctuation and flicker, three-phase voltage imbalance and harmonics pollution. According to the guidelines set in the<Distribution Network Construction and Transformation Action Plan(2015-2020years)>, which is issued by National Energy Administration recently, comprehensive voltage qualification rate reaches 98.65%, and the percent of line losses is reduced to 6% by then, believing that the D-STATCOM can play its role to achieve the goals. This thesis mainly focuses on a STATCOM based on three-level neutral-point clamped converter, compensation current detection, control strategies under balanced and unbalanced grid voltage, three-phase unbalanced load compensation are deeply studied in this paper.Firstly, operational principle of three-level STATCOM is briefly described and mathematical models are also established, then PI feed-forward decoupling double closed loop control strategy is presented. In the meanwhile, taking the random asymmetry of distribution network voltage into account, the influence of grid voltage unbalance on STATCOM and the countermeasure are discussed. Even though double closed loop has a series of defects-dynamic decoupling performance unsatisfactorily, poor adaptive performance and PI parameter tuning with difficulty, its dominant position is still impregnable. An attempt to introduce predictive direct power control(P-DPC) strategy into the control of D-STATCOM is made, after background information of P-DPC theory the whole content is separated into four aspects: model parameter adaptive identification, harmonic characteristic under non-ideal condition, unbalanced control strategy and three-phase unbalanced load compensation.Main parameters of D-STATCOM apparatus are well designed once theory analysis accomplished, then simulation model is established to testify the accuracy, the results indicated that P-DPC strategy has excellent compensation effect. In order to further verify the correctness and superiority of the theory, a D-STATCOM experimental prototype is developed. After implementation of a series of experiments, the experiment results match with the simulation results, and achieve the expected effect.