Bidirectional power conversion with fault-handling capability

A power conversion system includes a unipolar bidirectional power converter with DC terminals and a first controller, and a bipolar bidirectional power converter with DC terminals connected in series with the DC terminals of the unipolar bidirectional power converter and a second controller. The first controller is operable to cause only a positive-valued DC voltage across the DC terminals. The second controller is operable to cause a positive-valued or negative-valued DC voltage across the DC terminals of the bipolar bidirectional power converter so that a total voltage of the power conversion system is the sum of the positive-valued or negative-valued DC voltage across the DC terminals of the bipolar bidirectional power converter and the positive-valued DC voltage across the DC terminals of the unipolar bidirectional power converter.