A converter station for the transmission of electrical power has a diode rectifier with a DC terminal and an AC terminal. At least one transformer is connected to the AC terminal. In order to render the converter station as compact as possible, the diode rectifier is arranged in an insulating material.

A multi-level power converter includes switching cells, each comprising switching devices and an energy storage element. The switching cells include switching cells of a first type and switching cells of a second type. The converter includes, for each phase, a first arm of serial connected switching cells and a second arm of serial connected switching cells, which first arm and second arm are connected in parallel. The first arm includes more switching cells of the first type than switching cells of the second type and the second arm includes more switching cells of the second type than switching cells of the first type. The switching cells of the first type have lower conduction loss than the switching cells of the second type. The converter is arranged so that a larger current flows through the first arm than the second arm.

A multi-level power converter includes switching cells, each comprising switching devices and an energy storage element. The switching cells include switching cells of a first type and switching cells of a second type. The converter includes, for each phase, a first arm of serial connected switching cells and a second arm of serial connected switching cells, which first arm and second arm are connected in parallel. The first arm includes more switching cells of the first type than switching cells of the second type and the second arm includes more switching cells of the second type than switching cells of the first type. The switching cells of the first type have lower conduction loss than the switching cells of the second type. The converter is arranged so that a larger current flows through the first arm than the second arm.

A zero-sequence current suppression method and device, a converter and a wind turbine are provided. The converter comprises N converter units connected in parallel, N being a positive integer greater than or equal to 2. The zero-sequence current suppression method comprises: obtaining a zero-sequence current in each of N1 converter units among the N converter units; synchronizing pulse width modulation PWM control signals of all rectifiers in the N converter units and synchronizing PWM control signals of all inverters in the N converter units, to suppress high-frequency components of zero-sequence currents in the N converter units; and performing PI regulation by using the zero-sequence currents of the N1 converter units and zero-sequence current reference values of the N1 converter units, to suppress low frequency components of the zero-sequence currents in the N converter units.

A method for operating a hybrid rectifier includes an AC input, a DC output and a thyristor rectifier arranged in a first path, and a transistor rectifier arranged in a second, parallel path. The method includes when a DC voltage at the DC output of the hybrid rectifier is below a voltage threshold value, operating the hybrid rectifier in a first operating state in which the transistor rectifier is isolated from the DC output and connected to the AC input and the thyristor rectifier is connected both to the AC input and to the DC output. When the DC voltage at the DC output of the hybrid rectifier reaches or exceeds the voltage threshold value, operating the hybrid rectifier in a second operating state in which the thyristor rectifier and the transistor rectifier are each connected to the AC input and to the DC output.

A method for operating a hybrid rectifier includes an AC input, a DC output and a thyristor rectifier arranged in a first path, and a transistor rectifier arranged in a second, parallel path. The method includes when a DC voltage at the DC output of the hybrid rectifier is below a voltage threshold value, operating the hybrid rectifier in a first operating state in which the transistor rectifier is isolated from the DC output and connected to the AC input and the thyristor rectifier is connected both to the AC input and to the DC output. When the DC voltage at the DC output of the hybrid rectifier reaches or exceeds the voltage threshold value, operating the hybrid rectifier in a second operating state in which the thyristor rectifier and the transistor rectifier are each connected to the AC input and to the DC output.

A power converter and an UPS including the same are provided. The power converter includes a first and second switching modules, and a first and second power conversion modules. Each of the first and second power conversion modules includes two bridge arms. The first switching module is configured to cause an input terminal of the first power conversion module to be selectively electrically connected to a DC power supply or a first phase of an AC power supply, the second switching module is configured to cause an input terminal of the second power conversion module to be selectively electrically connected to the DC power supply or a second phase of the AC power supply, and the first and the second power conversion modules are configured to cause the two bridge arms to independently perform AC-DC conversion, or configured to cause the two bridge arms to cooperatively perform DC-DC conversion.

A power converter and an UPS including the same are provided. The power converter includes a first and second switching modules, and a first and second power conversion modules. Each of the first and second power conversion modules includes two bridge arms. The first switching module is configured to cause an input terminal of the first power conversion module to be selectively electrically connected to a DC power supply or a first phase of an AC power supply, the second switching module is configured to cause an input terminal of the second power conversion module to be selectively electrically connected to the DC power supply or a second phase of the AC power supply, and the first and the second power conversion modules are configured to cause the two bridge arms to independently perform AC-DC conversion, or configured to cause the two bridge arms to cooperatively perform DC-DC conversion.

A three phase rectifier includes n converter modules in each phase A, B, and C, wherein the AC inputs of the n converter modules of each phase are connected together in parallel, and the DC outputs of respective first to n.sup.th converter modules of phases A, B, and C are connected together in parallel as first to n.sup.th sub-combinations of DC outputs. The first to n.sup.th sub-combinations of DC outputs may be connected together in selected modes to produce a range of total output DC voltage, wherein the range of total output DC voltage is substantially free of double line frequency ripple and the converter modules are implemented without electrolytic output capacitors. The three phase rectifier is suitable for use in high power applications such as electric vehicle fast chargers.

A three phase rectifier includes n converter modules in each phase A, B, and C, wherein the AC inputs of the n converter modules of each phase are connected together in parallel, and the DC outputs of respective first to n.sup.th converter modules of phases A, B, and C are connected together in parallel as first to n.sup.th sub-combinations of DC outputs. The first to n.sup.th sub-combinations of DC outputs may be connected together in selected modes to produce a range of total output DC voltage, wherein the range of total output DC voltage is substantially free of double line frequency ripple and the converter modules are implemented without electrolytic output capacitors. The three phase rectifier is suitable for use in high power applications such as electric vehicle fast chargers.