Power inverters operating as active power filters must offer a wide bandwidth, as they supply currents with steep variations, necessary for harmonic and reactive power compensation. Four quadrant inverters, driven by current mode PWM modulators, can perform as transconductance switch mode power amplifiers being, consequently, best suited for this application. An extra feedback loop is needed to obtain a switching mode power operational amplifier, which further allows AC voltage regulation. The abruptness of voltages and currents depend on maximum bandwidths. Therefore, it is important to quantify the relationship of power and small signal bandwidth with the PWM switching frequency. The author shows and discusses the relationships of the output current and voltage slew-rate, of the small signal and maximum power modulation bandwidths and of the maximum instantaneous output error voltage, with the output filter cut-off frequency, the duty-cycle and the switching frequency of the DC-AC converter used as the active power filter. The major conclusion points to small signal bandwidths roughly one fifth of the switching frequency, and to maximum power bandwidth approximately one seventh of the switching frequency.
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