Abstract
This paper mainly concentrates on design of improved controller and its implementation based on single phase synchronous reference frame theory (SRFT) for Dynamic Voltage Restorer (DVR) compensating voltage sag particularly for nonlinear load. In case of single phase distribution line with nonlinear load, the complexity of controller’s design becomes more serious issue. The present single phase and/or three phase theories applicable to DVR shows poor response to restore voltage sag in case of nonlinear load due to presence of harmonics. Hence restoration of voltage sag in single phase nonlinear load connected system has been a serious concern. Therefore, new controller for DVR has been proposed incorporating effective design concept for fundamental component extraction in case of nonlinear load. The single phase SRFT based main controller for DVR works on two separate closed path viz. feed forward path for quick transient response and feedback path for reducing the steady state error. Moreover, pre-sag mitigation strategy of DVR has been adapted through these two aforementioned paths. Complete design of proposed controller is based on phasor analysis. It also consist of proportional integral (PI) controller to reduce the error in the DC-link voltage during compensation time. The controller performance has been verified in MATLAB Simulink for both types (linear and nonlinear) of load. The results obtained indicates that the proposed controller is effective in its performance.
Highlights
In distribution system power electronics based custom power devices plays a major role in present modern industries for upgrading the power quality during production process
This paper mainly concentrates on design of improved controller and its implementation based on single phase synchronous reference frame theory (SRFT) for Dynamic Voltage Restorer (DVR) compensating voltage sag for nonlinear load
When LG phase fault occurs in one line, the other load experiences voltage sag at point of common coupling (PCC)
Summary
In distribution system power electronics based custom power devices plays a major role in present modern industries for upgrading the power quality during production process. Power quality issue has major impact on sensitive industrial and utility end loads in distribution line. The conventional theories which are generally used in compensation of unbalance voltage sag with the utilization of custom power devices gives inefficient performance in case of nonlinear load. Occurring single phase short circuit faults have become one of the most important problem which results in voltage sag facing industrial customers. Disturbances due to short circuit of line, sudden change in the load and starting of inductive type load [3] has effect on voltage waveform causing problems related with the operation of sensitive electrical devices. A typical single-phase DVR consist of H-bridge voltage source inverter (VSI) structure with self-supporting DC-link connected in series with coupling transformer. The system is represented with Vs as a source voltage, VL as load voltage and Vt as terminal voltage at point of common coupling (PCC), is Supply power
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