Improved Trans-Z-source inverter based dynamic voltage restorer

Abstract

ABSTRACT This paper presents an improved Trans-Z-source inverter-based DVR to enhance the quality of power and to compensate the voltage abnormalities seen in the industrial and consumer premises. The proposed improved impedance structure of the inverter performs buck/boost inversion in a single stage with improved voltage gain featuring minimal component count. Constant maximum boost control logic for the inverter switches is implemented in this paper to minimise the size, cost of the passive components, accomplishment of maximum voltage boost for the given modulation index which in turn relieves the stress of the dc voltage source. Closed loop operation of DVR is carried out using synchronous reference frame control with PI controller to regulate the load terminal voltage at the point of common coupling (PCC). The voltage injected by the proposed inverter structure is able to mitigate balanced and unbalanced with dynamically occurring multiple voltage sag and swell conditions. It features fault ride through capability at the event of fault and ensures harmonic mitigation capability in the presence of non-linear loads. Simulation model developed using Matlab/Simulink is presented to validate the performance of improved Trans-Z-Source inverter based DVR and to indicate the effectiveness of the proposed modulation strategy for the inverter. The FFT spectral analysis obtained for the inverter output voltage is well below the IEEE harmonic limits.