A bipole power transmission scheme includes a first converter station that is positioned, in-use, remote from a second converter station. First and second transmission conduits and a return conduit interconnect, in-use, the first converter station with the second converter station and thereby permit the transfer of power between the first and second converter stations. The first converter station includes a first power converter, a second power converter, and a converter station controller.

A bipole power transmission scheme includes a first converter station that is positioned, in-use, remote from a second converter station. First and second transmission conduits and a return conduit interconnect, in-use, the first converter station with the second converter station and thereby permit the transfer of power between the first and second converter stations. The first converter station includes a first power converter, a second power converter, and a converter station controller.

A power converter connected between a direct current power supply and a load, the power converter including a switching unit energizing the load based on inputted control signal, a voltage detector detecting a voltage of the direct current power supply, and a protection operation portion detecting a steep elevation of the voltage and performing protection operation to stop a switching operation by the switching unit, wherein the protection operation portion includes an addition circuit adding a predetermined voltage to the voltage detected by the voltage detector and a delay time generator connected to an output of the addition circuit, and wherein the protection operation is performed when a difference between the voltage detected by the voltage detector and an output voltage of the delay time generator reaches a certain value.

A power converter connected between a direct current power supply and a load, the power converter including a switching unit energizing the load based on inputted control signal, a voltage detector detecting a voltage of the direct current power supply, and a protection operation portion detecting a steep elevation of the voltage and performing protection operation to stop a switching operation by the switching unit, wherein the protection operation portion includes an addition circuit adding a predetermined voltage to the voltage detected by the voltage detector and a delay time generator connected to an output of the addition circuit, and wherein the protection operation is performed when a difference between the voltage detected by the voltage detector and an output voltage of the delay time generator reaches a certain value.

A method for connecting an energy generation installation to a medium-voltage grid includes determining a calibration factor for adjusting first voltage values to second voltage values by a controller of the energy generation installation. During an idle state of a medium-voltage transformer, the first voltage values are detected at a capacitive voltage divider, arranged on the medium-voltage side of the medium-voltage transformer, and the second voltage values are detected by a voltage detection means, arranged on the low-voltage side of the medium-voltage transformer. The method further includes closing a circuit breaker arranged on the medium-voltage side of the medium-voltage transformer by the controller of the energy generation installation, when voltage values determined at the capacitive voltage divider exceed a first threshold value after the calibration factor has been applied.

A method for connecting an energy generation installation to a medium-voltage grid includes determining a calibration factor for adjusting first voltage values to second voltage values by a controller of the energy generation installation. During an idle state of a medium-voltage transformer, the first voltage values are detected at a capacitive voltage divider, arranged on the medium-voltage side of the medium-voltage transformer, and the second voltage values are detected by a voltage detection means, arranged on the low-voltage side of the medium-voltage transformer. The method further includes closing a circuit breaker arranged on the medium-voltage side of the medium-voltage transformer by the controller of the energy generation installation, when voltage values determined at the capacitive voltage divider exceed a first threshold value after the calibration factor has been applied.

A power converter connected between a direct current power supply and a load, the power converter including a switching unit energizing the load based on inputted control signal, a voltage detector detecting a voltage of the direct current power supply, and a protection operation portion detecting a steep elevation of the voltage and performing protection operation to stop a switching operation by the switching unit, wherein the protection operation portion includes an addition circuit adding a predetermined voltage to the voltage detected by the voltage detector and a delay time generator connected to an output of the addition circuit, and wherein the protection operation is performed when a difference between the voltage detected by the voltage detector and an output voltage of the delay time generator reaches a certain value.

A power converter connected between a direct current power supply and a load, the power converter including a switching unit energizing the load based on inputted control signal, a voltage detector detecting a voltage of the direct current power supply, and a protection operation portion detecting a steep elevation of the voltage and performing protection operation to stop a switching operation by the switching unit, wherein the protection operation portion includes an addition circuit adding a predetermined voltage to the voltage detected by the voltage detector and a delay time generator connected to an output of the addition circuit, and wherein the protection operation is performed when a difference between the voltage detected by the voltage detector and an output voltage of the delay time generator reaches a certain value.

An advantageous method of converting solar energy from a photovoltaic array into alternating current for feeding into the electricity grid is described based on the use of an inventive rotary machine. The inventive rotary machine has a rotor and a set of stator coils which are excited in a first mode by a polyphase current derived from the solar array and simultaneously in a second, orthogonal mode by a polyphase voltage derived from the electricity grid.

An advantageous method of converting solar energy from a photovoltaic array into alternating current for feeding into the electricity grid is described based on the use of an inventive rotary machine. The inventive rotary machine has a rotor and a set of stator coils which are excited in a first mode by a polyphase current derived from the solar array and simultaneously in a second, orthogonal mode by a polyphase voltage derived from the electricity grid.