A power conversion apparatus (700, 800) for controllably converting alternating current to direct current, the power conversion apparatus comprising: a plurality of AC sources galvanically isolated from one another; a plurality of bridge rectifier circuits (600, 810), including at least two controllable bridge rectifier circuits, wherein each bridge rectifier circuit (600; 810) has a number of phase legs, each phase leg comprising two arms, and respective AC-side terminals and DC- side terminals and each bridge rectifier circuit is connected to a corresponding one of the AC sources via its AC-side terminals, and wherein the DC-side terminals are connected so that the outputs of the bridge rectifier circuits are combined in series, and wherein the at least two controllable rectifier circuits have corresponding control terminals; and a control circuit configured to individually control each controllable bridge rectifier circuit via the corresponding control terminals to selectively operate in a regulator mode, whereby a non-zero voltage less than or equal to the maximum rectifier voltage is provided by the controllable bridge rectifier circuit, and a bypass mode, whereby switches of both arms of a same phase leg of the controllable bridge rectifier circuit are controlled to conduct simultaneously in order to provide a negligible voltage to its DC-side terminals and draws negligible current from its corresponding AC source, characterized in that the regulator mode for each of the at least two controllable bridge rectifier circuits comprises a voltage regulating mode and a full output mode, the full output mode corresponding to the mode where the maximum possible output voltage of the circuit is provided, and wherein the control circuit is configured to control the at least two controllable bridge rectifier circuits so that only one of the controllable bridge rectifier circuits is operating in voltage regulating mode at any given time, while each of the remaining controllable bridge rectifier circuits is operating in either bypass mode or full output mode. a plurality of AC sources galvanically isolated from one another; a plurality of bridge rectifier circuits (600, 810), including at least two controllable bridge rectifier circuits, wherein each bridge rectifier circuit (600; 810) has a number of phase legs, each phase leg comprising two arms, and respective AC-side terminals and DC- side terminals and each bridge rectifier circuit is connected to a corresponding one of the AC sources via its AC-side terminals, and wherein the DC-side terminals are connected so that the outputs of the bridge rectifier circuits are combined in series, and wherein the at least two controllable rectifier circuits have corresponding control terminals; and a control circuit configured to individually control each controllable bridge rectifier circuit via the corresponding control terminals to selectively operate in a regulator mode, whereby a non-zero voltage less than or equal to the maximum rectifier voltage is provided by the controllable bridge rectifier circuit, and a bypass mode, whereby switches of both arms of a same phase leg of the controllable bridge rectifier circuit are controlled to conduct simultaneously in order to provide a negligible voltage to its DC-side terminals and draws negligible current from its corresponding AC source, characterized in that the regulator mode for each of the at least two controllable bridge rectifier circuits comprises a voltage regulating mode and a full output mode, the full output mode corresponding to the mode where the maximum possible output voltage of the circuit is provided, and wherein the control circuit is configured to control the at least two controllable bridge rectifier circuits so that only one of the controllable bridge rectifier circuits is operating in voltage regulating mode at any given time, while each of the remaining controllable bridge rectifier circuits is operating in either bypass mode or full output mode.