Modelling and improvement of open-UPQC performance in voltage sag compensation by contribution of shunt units

Abstract

Voltage and current deficiencies in distribution network (DN) necessitate the improvement of power quality (PQ). Custom power devices (CPDs) compensate for these deficiencies. Recently, in presence of communication infrastructure in smart distribution network, open unified power quality conditioner (OUPQC) is attracted the attention of DN researchers and operators. OUPQC is utilized in DN to improve voltage and current deficiencies by operation of series unit (SEU) and shunt unit (SHU), respectively. In this paper, an accurate modelling of OUPQC and its integration in backward/forward sweep load flow (BFSLF) is proposed. In addition, it is confirmed that SEU performance which is responsible for voltage sag compensation, is limited. Hence, an operational method of the OUPQC is proposed to improve the performance of SEU. In the proposed method, SHUs contribute in voltage sag compensation by modifying their reactive power injection. The proposed method, determines the reactive power injection of SHUs and make the SEU possible to compensate the voltage sag by quadrature injection of series voltage (e.g. reactive power injection). The proposed method is utilized in two DNs: IEEE 69-bus and practical 95-bus Iranian DN. Results confirms that the performance of OUPQC in healthy and especially in voltage sag condition is deeply improved. The proposed method can be utilized in designing the operational algorithm of OUPQC.