Research On Control Strategy For Unified Power Quality Controller (UPQC)

With the wide application of power electronic devices and nonlinear loads, power quality problems arising in power are increasing. For example:harmonic pollution, reactive problems, three-phase unbalance, voltage fluctuation, voltage sag, and so on. Therefore, to solve the grid power quality research has been growing attention. Unified Power Quality Controller (Unified Power Quality Controller UPQC), it can compensate load reactive current and harmonic current, while suppressing power voltage fluctuations, voltage flicker and voltage of each phase imbalance, Unified Power Quality Controller will provide an effective way to solve the above problem. Based on the actual conditions to improve Power quality, in-depth study UPQC theory and topology,the real-time detection and control strategies compensation component of UPQC.At first, the topology and the function of UPQC are explained in this paper based on the analysis of active power filter (APF), and the control strategy of a hybrid UPQC (UPQC combined with passive filter) in detailed analysis. And finally select the three-phase three-wire UPQC as the object of this paper. Then, the detecting method and controlling strategy, which are the important parts affecting the compensation effect of the UPQC, are discussed and investigated in detail in the paper. In the basis of the current compensation detecting method on active power filter (APF), and combined with compensation thought of UPQC, the paper deduces the p-q method and ip-iq method based on the theory instantaneous reactive power theory. Since ip-iq method and p-q method in the process of compensation diction for various kinds of restrictions, this paper presents an effective detecting method: improved p-q method. Based on the analysis of space vector pulse width modulation and current hysteresis loop controlling method, series of UPQC adopts space vector controlling strategy and parallel of UPQC adopts current hysteresis controlling strategy based on space vector pulse width modulation. Simulation with MATLAB has been carried in this Compensation and control strategy put forward by this paper, the results of simulation indicate that the detect method and control strategy is valid and feasible.