Active voltage regulator based on novel synchronization method for unbalance and fluctuation compensation

Requirements on the power quality of AC sources are becoming more stringent as more voltage-sensitive equipments are being used. Among the power quality deterioration issues, voltage unbalance and voltage fluctuations are two serious ones. An active voltage regulator, which is used as a part of unified power quality conditioner (UPQC), is proposed to compensate for the voltage unbalance and fluctuations in this paper. It is composed of a voltage source inverter (VSI) coupled in series with the supply through transformers. The adopted topology guarantees that the energy can flow bi-directionally, thus it can regulate the load voltage to the expected value during long-drawn supply voltage fluctuation. Another aspect covered in this paper is the synchronization problem or the technique to get the phase angle of the reference signal, which is essential in voltage regulation. A software synchronization based on a new fundamental positive sequence (FPS) component extraction method is presented and proven in the paper. The active voltage regulator with the proposed topology and the synchronization method features in no hardware synchronization requirement, accurate and fast phase tracking and high dynamic performance. Experimental results performed on the prototype testify the validity of the proposed active voltage regulator in voltage unbalance and fluctuation compensation.