This paper discusses automatic gain adjustment in fully-digital-controlled shunt active filters. This is the first step in cooperative control of the active filters based on voltage detection for harmonic damping throughout power distribution systems. In general, an optimal control gain is equal to the characteristic impedance of a distribution line. However, it is difficult to know circuit parameters of a real distribution line, that is, feeder connections, shunt capacitors and loads. Therefore, the main purpose of the gain adjustment is to make each active filter damp out harmonic propagation without considering the circuit parameters. Moreover, the gain adjustment can reduce the compensating currents and losses in each active filter. The two active filters with constant or automatic-adjustable gains are experimentally compared. Experiment results verify the effectiveness of the active filter with automatic gain adjustment.
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