The present application provides a method for pre-charging a cascade converter and a cascade converter. The cascade converter includes a main transformer, multiple power units, a control unit and a precharge unit. Power units connected with the precharge unit are a first power unit group, and other power units are a second power unit group. The control unit controls first switch set in the precharge unit to be turned on, and low-voltage AC power supply in the precharge unit performs pre-charging for a bus capacitor through an inverter circuit in the first power unit group. When a voltage of the bus capacitor reaches a first voltage threshold, the control unit controls a rectifier circuit in the first power unit group to work to magnetize the main transformer, thereby performing pre-charging for bus capacitors in the second power unit group.

An apparatus includes a mechanical switch and a solid-state switch, such as a diamond switch or antiparallel-connected thyristor pair, coupled in series between an AC source and the load, such as a substation input transformer. The control circuit may be configured to connect the AC power source to the load by closing the mechanical switch and turning on the solid-state switch thereafter. The control circuit may be configured to interrupt a connection of the AC source to the load by turning off the solid-state switch and closing the mechanical switch thereafter. Operations of the switches may be coordinated with a fuse coupled in series with the solid-state switch to address different types of fault conditions.

The present application provides a method for pre-charging a cascade converter and a cascade converter. The cascade converter includes a main transformer, multiple power units, a control unit and a precharge unit. Power units connected with the precharge unit are a first power unit group, and other power units are a second power unit group. The control unit controls first switch set in the precharge unit to be turned on, and low-voltage AC power supply in the precharge unit performs pre-charging for a bus capacitor through an inverter circuit in the first power unit group. When a voltage of the bus capacitor reaches a first voltage threshold, the control unit controls a rectifier circuit in the first power unit group to work to magnetize the main transformer, thereby performing pre-charging for bus capacitors in the second power unit group.

The present application provides a method for pre-charging a cascade converter and a cascade converter. The cascade converter includes a main transformer, multiple power units, a control unit and a precharge unit. Power units connected with the precharge unit are a first power unit group, and other power units are a second power unit group. The control unit controls first switch set in the precharge unit to be turned on, and low-voltage AC power supply in the precharge unit performs pre-charging for a bus capacitor through an inverter circuit in the first power unit group. When a voltage of the bus capacitor reaches a first voltage threshold, the control unit controls a rectifier circuit in the first power unit group to work to magnetize the main transformer, thereby performing pre-charging for bus capacitors in the second power unit group.

An electrical power distribution network includes: a plurality of electrical power control apparatuses, each of which include one or more signal conversion components receiving electrical power in the form of a first signal and generating a corresponding second signal, a controller that controls operation of the signal conversion components, electrical power generation components acting as sources of electrical power to at least some of the electrical power control apparatuses, and electrical power consumption components acting as sinks of electrical power from at least some of the electrical power control apparatuses. The electrical power control apparatuses operate autonomously but are interconnected so that the electrical power control apparatuses collectively maintain the voltages and frequencies of electrical power signals flowing through the electrical power distribution network at target values to compensate for variations in the sinks and/or sources of electrical power.

An electrical power distribution network includes: a plurality of electrical power control apparatuses, each of which include one or more signal conversion components receiving electrical power in the form of a first signal and generating a corresponding second signal, a controller that controls operation of the signal conversion components, electrical power generation components acting as sources of electrical power to at least some of the electrical power control apparatuses, and electrical power consumption components acting as sinks of electrical power from at least some of the electrical power control apparatuses. The electrical power control apparatuses operate autonomously but are interconnected so that the electrical power control apparatuses collectively maintain the voltages and frequencies of electrical power signals flowing through the electrical power distribution network at target values to compensate for variations in the sinks and/or sources of electrical power.

A power converter apparatus is provided to include a switching circuit, and a filter circuit. The switching circuit generates an AC voltage by switching a DC voltage at a predetermining switching frequency, and the filter circuit converts the AC voltage from the switching circuit into the DC voltage by low-pass filtering the AC voltage. The filter circuit induces first and second bypass capacitors, and an inductor. The first bypass capacitor bypasses noise of a first frequency component of the AC voltage from the switching circuit, and the second bypass capacitor bypasses noise of a second frequency component of the AC voltage from the switching circuit, which is lower than the first frequency component. The inductor is inserted between the first and second bypass capacitors, and the inductance thereof is set so that a resonance frequency of the filter circuit is lower than the switching frequency by insertion of the inductor.

An electrical converter with at least two output phases includes a rectifier and a thyristor-based inverter interconnected by a DC link with an inductor, wherein the thyristor-based inverter includes a half-bridge with at least two half-bridge arms for each output phase of the electrical converter and each arm being provided by a thyristor. A method for switching the electrical converter includes: cyclically switching the thyristors of the inverter, such that at least one time instant, two thyristors of different half-bridge arms are switched on simultaneously, such that a pulse number, which determines at how many time instants thyristors of the inverter are switched during one stator voltage period, is lower than the number of half-bridge arms of the inverter.

An electrical converter with at least two output phases includes a rectifier and a thyristor-based inverter interconnected by a DC link with an inductor, wherein the thyristor-based inverter includes a half-bridge with at least two half-bridge arms for each output phase of the electrical converter and each arm being provided by a thyristor. A method for switching the electrical converter includes: cyclically switching the thyristors of the inverter, such that at least one time instant, two thyristors of different half-bridge arms are switched on simultaneously, such that a pulse number, which determines at how many time instants thyristors of the inverter are switched during one stator voltage period, is lower than the number of half-bridge arms of the inverter.

An electrical power distribution network is disclosed, the network can include: a plurality of electrical power control apparatuses, each of the electrical power control apparatuses including: one or more signal conversion components receiving electrical power in the form of a corresponding first signal having a corresponding first fundamental frequency and a corresponding first characteristic voltage, and generating a corresponding second signal having a corresponding second fundamental frequency and a corresponding second characteristic voltage; and a controller that controls operation of the signal conversion components to determine an output voltage and an output frequency of an output signal of the electrical power control apparatus; electrical power generation components acting as sources of electrical power to at least some of the electrical power control apparatuses; and electrical power consumption components acting as sinks of electrical power from at least some of the electrical power control apparatuses.