Multi-module bidirectional zero voltage switching DC-DC converter

A multi-module bipolar bidirectional power converter operable with one or more of its modules comprising:

• a gating controller connected to control gating for any one or more power converter modules;
• a bipolar low side DC bus having a positive rail, a negative rail and a neutral point;
• a bipolar high side DC bus having a positive rail, a negative rail and a neutral point;
• at least a first and second ones of the power converter modules, comprising:
• a first low voltage switch having a first side connected to the positive rail of the bipolar low side DC bus;
• a second low voltage switch having a first side connected to the negative rail of the bipolar low side DC bus;
• the first and second low voltage switches having second sides that are connected together;
• an inductor interposed between the low side DC bus neutral point and the second sides of the first and second low voltage switches;
• a low side winding of a transformer having a first leg connected to the inductor and having a second leg connected to the neutral point of the low side DC bus;
• a first high voltage switch having a first side connected to the positive rail of the bipolar high side DC bus;
• a second high voltage switch having a first side connected to the negative rail of the bipolar high side DC bus;
• the first and second high voltage switches having second sides that are connected together;
• and
• a high side winding of the transformer having a first leg connected to the second sides of the first and second high voltage switching devices and having a second leg connected a neutral point of the high side DC bus.

A method for bidirectional conversion of power comprising the steps of:

• converting power through a plurality of interconnected power conversion modules operated in succession;
• employing a phase shifting gating pattern so that each module is operated with a phase shift relative to a prior module of the succession and a phase shift relative to a subsequent module in the succession;
• determining a load level for the plurality of conversion modules;
• comparing the determined load level against a predetermined low-load condition at which the plurality of conversion modules will not operate with zero voltage switching (ZVS);
• and
• changing the gating pattern so that only a single one of the conversion modules operates during the low load condition, whereby the converter continues to operate with ZVS.