Applying a Control Strategy Consisting of TCCF in Four-Leg Shunt Active Filter in Order to Improve Power Quality

In this paper, a control scheme is proposed to compensate nonlinear and unbalanced loads currents and mitigate neutral current in a weak distribution network utilizing a four-leg converter. Two separate Complex Coefficient-Filters (CCF) have been used to extract the fundamental frequency positive sequence component of the load current and the converter to compensate for and control the dc- link voltage. Also, due to the presence of unbalance and harmonics the voltage of the weak grid, a CCF-based Phase Locked Loop (PLL) has been used for proper synchronization with grid voltage. Owing to absence of a low-pass filter in the CCF structure does not reduce the system dynamics and increases the speed and accuracy of estimation of the frequency and phase angle of the grid voltage. The Triple-CCF (TCCF) control strategy proposed in this article is compared with the same case, Triple-Reduced Order Generalized Integrator (TROGI). Simulation results show the performance and efficiency of the four-leg active filter control strategy based on TCCF.