control theory&cr; drops&cr; harmonic analysis&cr; voltage control&cr; ac power supplies&cr; closed-loop operations&cr; control schemes&cr; control strategies&cr; fundamental components&cr; harmonic cancellations&cr; low frequencies&cr; modulation techniques&cr; non-linear loads&cr; operating conditions&cr; operating principles&cr; output voltages&cr; pre distortions&cr; simulation results&cr; switching patterns&cr; voltage drops&cr; industrial electronics&cr