An interface arrangement is configured to couple an alternating current, AC, power system with a direct current, DC, power system, or vice versa. The interface arrangement includes a plurality of series-connected converter modules. Each converter module includes at least one multi-level converter cell configured to provide a voltage contribution to at least a portion of an AC waveform for example based on voltage of the DC power system. Each converter module includes at least one converter valve, electrically connected to the multi-level converter cells and including at least two anti-parallel thyristors. The converter valves are switchable between conducting states with a selected current conduction direction and a non-conducting state so as to selectively control polarity of any voltage contribution provided by the at least one multi-level converter cell. The converter valves can also serve as fault protection, e.g. to divert overcurrents.

A bipolar DC power transmission scheme including first and second DC poles, each including a respective DC power transmission medium extending between first and second ends; a plurality of converters wherein each end of the transmission medium of each of the poles is operatively connected to at least one of the converters to form a rectifier and an inverter at opposite ends of the DC power transmission media; and a controller to operate at least one converter of one of the rectifier and inverter in a control mode and at least one converter of the other of the rectifier and inverter in a second control mode in response to a fault occurring on either of the poles. Additionally, the first control mode decreases and the second control mode increases the operating DC voltage of the or each corresponding converter from a normal operating voltage value.

A power transmission network including: a variable power source; an AC transmission link for AC power transmission from the variable power source to at least one source side converter; at least one source side converter including: an AC connecting point operably connected to the AC transmission link; and a DC connecting point for connection to a DC transmission link; and a control system configured to operate the source side converter or at least one of the source side converters in a frequency damping mode to control an AC voltage at its AC connecting point and thereby damp at least one frequency component at its AC connecting point and/or in the AC transmission link.

A line commutated converter (LCC) for a high voltage direct current power converter, the LCC comprising at least one LCC bridge circuit for connection to at least one terminal of a DC system, each bridge circuit comprising a plurality of arms, each associated with a respective phase of an AC system, each arm comprising: an upper thyristor valve or valves, and lower thyristor valve or valves connected in series; an associated branch extending from between the upper and lower thyristors; and at least one thyristor-based capacitor module for each phase, each module comprising a plurality of module thyristors, the or each capacitor module operable to insert a main capacitor into the respective arm of the bridge circuit by firing at least one or more of said module thyristors.

The invention relates to the field of electrical engineering. An electricity supply system for a transport vehicle contains an electric network (1) with negative and positive wires, to which are connected an accumulator battery (2) and an electric starter (3); a capacitor bank (4); a bidirectional converter (5), which is connected between the capacitor bank and the electric network; a regulator (6); and a temperature sensor (11). Voltage from the capacitor bank is fed to an input (10) of the regulator, an additional input (12) of the regulator is connected to the temperature sensor, and outputs of the regulator are connected to control inputs (7, 8, 9) of the bidirectional converter, which bidirectional converter, in accordance with a signal at the control inputs, is capable of changing the parameters of its own volt-ampere characteristics at the outputs on the side of the electric network. The regulator is carried out in a way that the maximum current flowing from the bidirectional converter to the electric network is a decreasing function of the temperature-sensor temperature. The invention extends the service life of an electric starter and enhances the reliability of an electricity supply system.

A power transmission network, for interconnecting a variable power source and a AC electrical network including: a DC transmission link for power transmission between a network side converter and a source side converter; a AC transmission link for power transmission from the respective variable power source to a source side converter; a source side converter including: a DC connecting point operably connected to the respective transmission link; and an AC connecting point operably connected to the respective transmission link; a network side converter including: an AC connecting point for connection to the respective electrical network; and a DC connecting point operably connected to the respective transmission link; and a control system, where a network side converter is designated as a first converter, and the control system is configured to operate each first converter as a DC slack bus to vary a DC voltage at its DC connecting point.

In a power conversion device in a configuration in which a plurality of power converter cells has serially connected outputs and includes a converter and an inverter as components, when a load is light, the cells also operate with a light load, and efficiency is reduced. A power conversion device has a plurality of power converter cells. The outputs of the cells are connected in series. The device has a controller that controls the cells. The cells each have a converter that converts an externally inputted power supply voltage and generates a DC link voltage and an inverter that converts the DC link voltage into an alternating current voltage and outputs the current. The controller stops a converter in some of the cells depending on power supply electric power or load electric power. The inverter continues to operate using a link capacitor as a power supply.

The present invention discloses a power conversion system and a method for pre-charging DC-Bus capacitors therein. The power conversion system comprises a plurality of power modules, each including a power input end; a charging input end; a power output end; at least one power conversion unit, each of the power conversion unit including at least one DC-Bus capacitor and being electrically connected to the power input end and the power output end; and a pre-charging unit electrically connected to the charging input end for receiving direct current and electrically connected to the DC-Bus capacitor for pre-charging the DC-Bus capacitor. The power input ends of the plurality of power modules are connected in series and then electrically connected to an AC power source, and the power output ends of the plurality of power modules are connected in parallel.

A device for extinction angle control of a high voltage direct current (HVDC) system, includes: a converter reactive power calculator calculating a reactive power variation amount of a converter included in the HVDC system, depending on firing angle control of the converter; an alternating current (AC) system short circuit level calculator calculating a short circuit level of an AC system by applying the reactive power variation amount to a short circuit level formula of the AC system connected to the HVDC system; an extinction angle variation value calculator calculating an extinction angle variation value of the converter, corresponding to the short circuit level; and an extinction angle controller controlling an extinction angle of the converter, depending on an extinction angle control value reflecting the extinction angle variation value.

The present invention discloses a DC converter valve state detection method based on temporal features of converter terminal currents, including the following steps: collecting three-phase AC currents on a converter valve-side of a DC transmission system; defining a current when the currents of two commutating valves are equal as a base value, greater than the base value as a valve conducting current, and less than the base value as a valve blocking current; constructing a valve conducting state by a relative relationship among amplitudes of the three-phase AC currents, and calculating a time interval of each valve conducting state; comparing time intervals of 6 valve conducting states with a time interval of a valve conducting state in normal operation, and determining whether the 6 valve states are normal according to the result of comparison and locating all abnormal valves. The present invention can reliably detect valve states and locate abnormal valves through sequence detection. This method can be applied to actual fault phase judgment and commutation failure judgment, providing a good support for accurate judgment of DC control and protection.