Detection Of Dynamic Voltage Restorer And Control Strategy

With the development of science and technology and industrial automation level, many of the power quality sensitive loads are applied to the production and living, so the user a higher power quality requirements.The voltage sag rate is the highest in the various power quality problems in the power system according to the statistics from national scholars and Power Department. So the voltage sag is much higher concerned than other problems of power quality.Voltage sag reasons are analysed simply and several methods of inhibiting voltage sag are proposed in this paper on the basis of discussing power quality problem and meeting the requirements from contemporary power system. The DVR(Dynamic Voltage Restorer)main circuit is determined by analysing other DVR Working Principles and other circuits, following actual situation of low voltage distribution network.Single-phase short circuit rate is the highest in the various system faults and it can be caused the network voltage asymmetry. So the DC voltage influence by network voltage asymmetry is analysised detail in this paper and the DVR detection algorithm is proposed in the situation of network voltage asymmetry. DVR compensatory ability is affected largely by voltage sag detection algorithm, systematic voltage sag and harmonic can be detected well by Based on instantaneous reactive power theory dq transformation, but it is only applicable to the case of three-phase symmetric not to three-phase Unbalance caused by systematic short circuit. Positive and negative sequence voltage in the dq coordinate transformation The method of improvement phase-locked loop based on double dq decoupling decoupling is present in this paper, Positive and negative sequence by setting the baseline reference voltage, the lifting of the coupling between the output voltage accurately extract the positive and negative sequence voltage component, and the phase deviation introduced into the transformation matrix.output phase Amplitude and phase waveform is improved. The DC voltage is pumped caused by inverter absorbs continued active power from the power when DVR works in asymmetric voltage for long time, energy storage components and power devices will be damaged in severe. composite control is presented this paper for the problem, where the phase shift control is used to reduce absorbing active power from the inverter, so DC voltage pump is suppressed. Network voltage disturbances are inhibited well by using two closed loop control strategy, so the load stability is improved greatly. The simulation results show the feasibility and effectiveness of the method can meet the asymmetryin the case of grid voltage requirements of the DVR.