There is provided a switching valve for a voltage source converter. The switching valve comprises a plurality of modules, each module including at least one switching element and at least one energy storage device, the or each switching element and the or each energy storage device in each module arranged to be combinable to selectively provide a voltage source, the switching valve including a controller configured to selectively control the switching of the switching elements to select one or more of the modules to contribute a or a respective voltage to a switching valve voltage, wherein the controller is configured to selectively carry out a module selection by: assigning each module with a respective address in an address queue; in a respective one of a plurality of sampling events, selecting one or more voltage contributing modules in order of its assigned address in the address queue; and between different sampling events, changing the order of selecting the or each voltage contributing module based on its assigned address in the address queue.

This application provides an isolation transformer. The isolation transformer is applicable to a power converter, the power converter further includes a first power conversion module and a second power conversion module, the isolation transformer includes a high-voltage winding, a low-voltage winding, and a solid insulation housing. The high-voltage winding has a solid insulation layer and the solid insulation housing has an opening surface, the opening surface faces the second power conversion module, the solid insulation housing covers the low-voltage winding and the high-voltage winding that has the solid insulation layer, a conducting layer or a semi-conducting layer is disposed on the solid insulation housing, and the conducting layer or the semi-conducting layer of the solid insulation housing is grounded. In this application, a volume of the isolation transformer can be reduced, power density of the power converter can be improved, and low costs and high applicability can be ensured.

This application provides an isolation transformer. The isolation transformer is applicable to a power converter, the power converter further includes a first power conversion module and a second power conversion module, the isolation transformer includes a high-voltage winding, a low-voltage winding, and a solid insulation housing. The high-voltage winding has a solid insulation layer and the solid insulation housing has an opening surface, the opening surface faces the second power conversion module, the solid insulation housing covers the low-voltage winding and the high-voltage winding that has the solid insulation layer, a conducting layer or a semi-conducting layer is disposed on the solid insulation housing, and the conducting layer or the semi-conducting layer of the solid insulation housing is grounded. In this application, a volume of the isolation transformer can be reduced, power density of the power converter can be improved, and low costs and high applicability can be ensured.

In the field of high voltage direct current (HVDC) power transmission networks, there is a need for improvements to allow a single power converter to control individual AC network voltages carried by multiple AC transmission conduits to multiple AC network elements, such as respective wind parks.

A power transmission network (10; 100) comprises a power converter (12) which has first and second DC converter terminals (14, 16) that are for connection, in use, to a DC network. The power converter (12) also includes an AC converter terminal (22) which is electrically connected to a plurality of AC transmission conduits (24.sub.1, 24.sub.2, 24.sub.n), each of which is for connection, in use, to a respective AC network element (26.sub.1, 26.sub.2, 26.sub.n) that is configured to operate at a respective individual AC network voltage. The power converter (12) further includes a primary converter controller (34) which is programmed, in use, to control the transfer of power through the power converter (12) and thereby between the DC network and the plurality of AC network elements (26.sub.1, 26.sub.2, 26.sub.n). The primary converter controller (34) is further programmed, in use, to control each individual AC network voltage by establishing a virtual voltage which is representative of the plurality of AC network voltages and altering a single AC converter voltage produced by the power converter (12) at the AC converter terminal (22) to adjust the virtual voltage and thereby adjust each individual AC network voltage.

There is provided a switching valve for a voltage source converter. The switching valve comprises a plurality of modules, each module including at least one switching element and at least one energy storage device, the or each switching element and the or each energy storage device in each module arranged to be combinable to selectively provide a voltage source, the switching valve including a controller configured to selectively control the switching of the switching elements to select one or more of the modules to contribute a or a respective voltage to a switching valve voltage, wherein the controller is configured to selectively carry out a module selection by: assigning each module with a respective address in an address queue; in a respective one of a plurality of sampling events, selecting one or more voltage contributing modules in order of its assigned address in the address queue; and between different sampling events, changing the order of selecting the or each voltage contributing module based on its assigned address in the address queue.

An adapter device, including an AC connection including first AC contact and second AC contact; a DC connection including first DC contact and second DC contact; a first bridge branch including first switching device and second switching device, the first switching device and second switching device connected in series at a first bridge point, the first bridge point connected to first AC contact; a second bridge branch including third switching device and fourth switching device, third switching device and fourth switching device connected in series at a second bridge point, the second bridge point connected to second AC contact; and mode-setting device configured to predetermine a direction of power flow between AC connection and/or DC connection, first bridge branch and second bridge branch connected in parallel to the first DC contact and second DC contact, and different types of switching devices used as switching devices of a bridge branch.

A multilevel power converter, or inverter, for converting a direct current electrical power to an alternating current electrical power includes one or more 2-level converters each including gallium nitride (GaN) transistors configured to switch two input lines to a three-phase output line. The multilevel power converter may be used in a motor drive circuit, which may provide a 3-phase AC supply. Two power converters, which may be 2-level or 3-level power converters, may be alternately switched to provide the AC power to an AC motor by an output stage including bi-directional switching transistors configured to switch a corresponding three-phase output lines from the multilevel power converters. The multilevel power converters switch input lines from a neutral-point clamped input stage including capacitors connected in series across input terminals having a DC voltage therebetween to energize a midpoint terminal with an intermediate voltage half of the voltage between the input terminals.

In a power converter, a DC bus is supplied with a DC power from a voltage conversion circuit for regulating a voltage of a power output from a DC power supply, a voltage of the DC power being regulated by the voltage conversion circuit. An inverter converts a DC power on the DC bus into an AC power and supplies the AC power as converted to a power system. A controller controls the inverter. When it is necessary to suppress an output, the controller suppresses the AC power supplied by the inverter to increase a voltage on the DC bus.

An electric power conversion apparatus includes: a heat-generating element; a case having a cooling wall portion on which the heat-generating element is held and accommodating the heat-generating element; a flow passage cover having an opening formed therein and covering a surface of the cooling wall portion on the opposite side to the heat-generating element; a standing portion standing from the cooling wall portion and inserted in the opening; a flow-passage side wall portion formed in one of the cooling wall portion and the flow passage cover to protrude toward the other; a coolant flow passage surrounded by the cooling wall portion, the flow passage cover and the flow-passage side wall portion; and a sealant that seals both a gap between the cooling wall portion and the flow passage cover at a periphery of the coolant flow passage and a gap between the standing portion and the flow passage cover.

A circuit for minimizing energy provided to a ground fault includes a source, a multiple switches, an output filter, and a controller. The switches include a first side pair of switches and a second side pair of switches configured to provide an output signal based on the source. The output filter includes one or more energy storage elements coupled to the first side pair of switches or the second side pair of switches. The controller is configured to receive a ground fault signal that indicates a fault has occurred and configured to generate a switch signal for the switches for a minimum energy state of the output filter and in response to the ground fault signal.