Systems and methods for providing ride-through for interruptions in the
power supplied to drives that are used to control equipment such as
downhole submersible pumps. In one embodiment, a variable speed drive
includes converter and inverter sections, a capacitor bank and a control
system. The drive shuts down the converter section upon detecting a
disruption in the AC input power and continues to generate output power
by drawing on the energy stored in the capacitor bank. When the AC input
power returns (or begins to return) to normal, the drive resumes
operation of the converter section in a controlled manner (e.g., by
presetting the firing angle of the SCR's in the converter to match the
voltage across the capacitor bank.) The drive thereby limits the current
that recharges the capacitor bank and prevents sudden inrushes of current
that could damage the drive.