Novel Direct Current-Space-Vector Control for shunt active power filters based on three-Level inverters

The permanently growing number of electric drives with non-sinusoidal line currents has given increased interest in active power filters (APF), to avoid grid problems caused by harmonic distortions. In this paper, a novel direct current-space-vector control scheme (DCSVC) is presented for a three-level, neutral- point-clamped voltage-source inverter, which is employed as an active power filter. The proposed method works in the time domain, generating the equivalent ohmic conductance indirectly by means of the dc-link voltage control of the APF. Based on the Fast Fourier Transform (FFT) the compensation of the reactive fundamental current can be cancelled, confining the operation to only harmonic compensation and thus saving the APF´s apparent power. The novel direct current-space-vector controller, operating in synchronously rotating coordinates is implemented in a field programmed gate array (FPGA), realizing the switching states from switching tables. The proposed control reduces the average switching frequency and thus, the switching power loss significantly, compared with a previous direct current-space-vector control, operating in stationary coordinates. Simulation and experimental results validate the feasibility and highly dynamic performance of the proposed control, both for harmonic and total non-active current compensation.