A new fast-converged estimation approach for Dynamic Voltage Restorer (DVR) to compensate voltage sags in waveform distortion conditions

• An estimation approach is developed.
• The approach detects symmetrical components of intended frequencies.
• The approach identifies symmetrical components of unbalanced voltages in a network.
• The approach is applicable in on-line and fast-responding applications.
• A control scheme well-suited to DVR, provides compensating voltages using the approach.

The on-line estimation of symmetrical components from network voltages and currents is widely used in the field of power quality monitoring and improvement of relevant disturbances, especially by CUstom Power Systems (CUPS). This paper proposes a new fast-converged estimation approach, which directly extracts amplitudes and phase angles of symmetrical components of desired frequencies from harmonic-distorted network voltages. The adequate convergence time and accuracy of this approach make it applicable in Dynamic Voltage Restorer (DVR) as an application in which the quickness of response is of the most important requirements. According to this objective, sensitivity analyses are prepared to assess the impacts of sag depth variations, phase angle jumps and frequency variations on the performance of the proposed algorithm. Further, in these analyses complete comparisons are made between the proposed approach and well-known algorithms such as KF, ADALINE and FFT using MATLAB/SIMULINK. The application of the proposed estimation approach in the DVR is realized by introducing a new control scheme. The proposed control scheme provides the compensation of different voltage sags through both pre-sag and in-phase strategies. Finally, simulation results, carried out in PSCAD/EMTDC environment, confirm the effectiveness of the suggested control scheme.