Systems and Methods for Variable Speed Drives

Systems and methods for driving downhole equipment using a variable speed drive that has a switching mechanism between a first, constant-voltage capacitor bank and a second capacitor bank to control the voltage on the second capacitor bank, thereby enabling generation of a six-step output waveform while maintaining low input harmonics. In one embodiment, a variable speed drive has a converter section, an inverter section, two capacitor banks and a chopper. The converter section is controlled by a controller to convert AC power to DC power and charges the first capacitor bank to a substantially constant voltage. A chopper selectively couples the first capacitor bank to the second capacitor bank and thereby controls the voltage on the second capacitor bank. The inverter section can then produce a six-step output waveform at the voltage of the second capacitor bank. The variable speed drive can operate alternately in a pulse width modulation mode.