Brief view on control of grid-interfacing AC-DC-AC converter and active filter under unbalanced and distorted voltage conditions

Purpose - The purpose of this paper is to consider both sides of a back-to-back AC-DC-AC interface. Design/methodology/approach - The paper presents a mathematical 'analysis, simulation, laboratory test in scaled model. Findings - The two main findings comprised concept of control methods for grid AC-DC-AC converter applied in renewable energy sources with variable speed operation under distorted grid. Active filtering functionality in case of non-linear current of a parallel load. Second, a control algorithm dedicated for two-level AC-DC converter applied in industrial networks with high-order harmonics compensation working under hard conditions balanced and unbalanced voltage dips. Research limitations/implications - The paper shows preliminary results for AC-DC-AC converter and active filter (AF) during voltage dips and for harmonics compensation. Control methods and/or topology should be improved and tested in scale and after at high-power system. Practical implications - Power quality supplied/received to/from the grid can be increased. In case of low-cost system only AF can be applied to existing non-linear receivers. Moreover, in case of full AC-DC-AC converter energy saving and production is possible. Originality/value - Presented control methods give satisfactory results. Paper presents laboratory results for grid and machine side two different power circuits during steady states and transients. Moreover, active filtering operation during voltage dips is presented.