A robust control strategy for mitigating the effects caused by random loads on the grid impedances

The interaction between the loads and grid impedances can cause deleterious effects on the dynamic model of shunt active power filters (SAPF). These effects may lead to instabilities on the control system, specially if the loads vary randomically. These side effects could be minimized if SAP F employs a robust control strategy which controller gains are adjusted by adaptation. To overcome these side effects, this paper proposes a non-standard control strategy in which the power grid currents are indirectly regulated. This strategy do not use harmonic detection which reduces the number of current sensors. The reference currents of system are generated by the dc-link voltage controller and is based on the active power balance of SAPF system. The current control strategy is implemented by an adaptive pole placement control strategy integrated to a variable structure control scheme V S - APPC. In this scheme, the internal model principle IMP of reference currents is used for achieving the zero steady state tracking error. Experimental results are shown for determining the effectiveness of SAPF proposed control system.