DC voltage control in renewable energy based multilevel power converter

A method for operating a renewable energy-based power converter including an input configured to be coupled to a renewable energy-based power source, a high-side DC bus, a low-side DC bus, and an output configured to be coupled to an AC grid, wherein the method comprises:

• receiving, at the input, input DC power from the renewable energy-based power source;
• providing, in a first mode of operation, the input DC power to the high-side DC bus and the low-side DC bus;
• converting, in the first mode of operation with an inverter portion, DC power from the high-side DC bus and the low-side DC bus into output AC power;
• providing, in the first mode of operation, DC power from the high-side DC bus and the low-side DC bus to an interface converter;
• converting, in the first mode of operation with the interface converter, DC power from the high-side DC bus and the low-side DC bus into regulated DC power having a regulated DC voltage level;
• converting, in the first mode of operation with a first auxiliary DC-DC converter, the regulated DC power into first output DC power;
• providing the first output DC power to a first DC load;
• and
• balancing, in the first mode of operation with the interface converter, a voltage level of the high-side DC bus with a voltage level of the low-side DC bus.

A renewable energy-based power converter comprising:

• an input configured to be coupled to a renewable energy-based power source and to receive input DC power having an input DC voltage level;
• a high-side DC bus;
• a low-side DC bus;
• a neutral point;
• a high-side capacitor coupled between the high-side DC bus and the neutral point;
• a low-side capacitor coupled between the low-side DC bus and the neutral point;
• an output configured to be coupled to an AC grid;
• an inverter portion coupled to the high-side DC bus and the low-side DC bus and configured to operate to convert DC power from the high-side DC bus and the low-side DC bus into output AC power and provide the output AC power to the output;
• and
• means for providing regulated DC power, derived from the input DC power, to at least one DC subsystem, for balancing a first voltage level on the high-side DC bus with a second voltage level on the low-side DC bus, and for pre-charging, prior to operating the inverter portion to convert DC power from the high-side DC bus and the low-side DC bus into output AC power, the high-side capacitor and the low-side capacitor.