The present invention discloses an LCC and MMC series-connected HVDC system with DC fault ride-through capacity, comprising rectifier and inverter linked by DC transmission line; Both the positive pole and the negative pole of the rectifier and the inverter consist of line-commutated converter and modular converter in series-connection; the modular converter adopts one MMC or several parallel-connected MMCs. The present invention has the advantage of low cost, low power loss and high reliability of the LCC, as well as flexible control, low harmonics and AC voltage support of the MMC. Further, the present invention is able to deal with DC fault by itself, hence additional DC fault clearing equipment is not needed. As a result, the present invention is suitable for the field of long-distance large-capacity power transmission and has broad development potential.

A high voltage direct current (HVDC) transmission system is provided. The high voltage direct current (HVDC) transmission system includes a rectifier converting alternating current (AC) power into DC power; an inverter converting the DC power into the AC power; DC transmission lines W1 and W2 transmitting the DC power obtained from the rectifier through conversion to the inverter; a first active power measurement unit measuring first active power input to the rectifier; a second active power measurement unit measuring second active power output from the inverter; and a first control unit controlling the operations of the rectifier and the inverter based on the first active power measured and the second active power measured, wherein the first control unit senses oscillation generated in the HVDC transmission system and generates a control signal for damping the sensed oscillation to control one or more of the rectifier and the inverter.

A converter scheme (30) comprises a plurality of poles and a plurality of converters (32), the plurality of poles (60,62,64) including at least one positive pole (60), at least one negative pole (62) and a neutral pole (64), the plurality of converters (32) including at least one first converter (32a) and at least one second converter (32b), the or each first converter (32a) connected to the neutral pole (64) and the or the respective positive pole (60), the or each first converter (32a) operable to control a converter voltage across the neutral pole (64) and the corresponding positive pole (60), the or each second converter (32b) connected to the neutral pole (64) and the or the respective negative pole (62), the or each second converter (32b) operable to control a converter voltage across the neutral pole (64) and the corresponding negative pole (62), wherein the converter scheme (30) includes a controller (36) programmed to perform a voltage control mode when there is an imbalance between power or current levels of the positive and negative poles (60,62) and when the neutral pole (64) is at a non-zero potential, the controller (36) programmed to perform the voltage control mode to operate each converter (32a,32b) to control the corresponding converter voltage so that a pole-to-ground voltage of the corresponding positive or negative pole (60,62) is equal to or lower than a voltage rating of the corresponding positive or negative pole (60,62).

A current flow control assembly, for controlling current flow in an electrical network of interconnected electrical elements, having: current flow controllers, each current flow controller connectable to at least one of the interconnected electrical elements, and being configured to control current flow in at least one of the interconnected electrical elements within a current flow control range; a control unit in communication with each of the current flow controllers, wherein the control unit is configured to: select at least one of the current flow controllers with a flow control range that corresponds to one or more current flow control requirements of the electrical network; and operate the selected current flow controller to control current flow in at least one of the interconnected electrical elements to control current flow in the electrical network in accordance with the current flow control requirement of the electrical network.

A wind power converter device is provided. The wind power converter device includes grid side converters, generator side converters and a DC bus module. Each of the grid side converters includes grid side outputs electrically coupled to a grid and a first and a second DC inputs. Each two of the neighboring grid side converters are connected in series at the second and the first DC inputs. Each of the generator side converters includes generator side inputs electrically coupled to a generator device and a first and a second DC outputs. Each two of the neighboring generator side converters are coupled in series at the second and the first DC outputs. The DC bus module is electrically coupled between the grid side converters and the generator side converters.

An assembly having a multilevel power converter, which has at least one phase module, wherein the phase module has a plurality of modules, each with a first electrical module terminal and a second electrical module terminal. The plurality of modules includes modules of a first type, which are able to output a voltage of only one polarity or zero voltage at their first electrical module terminal and their second electrical module terminal. The plurality of modules includes modules of a second type, which are able to output a voltage of one polarity, a voltage of opposite polarity or zero voltage at their first electrical module terminal and their second electrical module terminal. Depending on the polarity of a voltage across the modules of the second type, a voltage limiting device limits the voltage.

The disclosure discloses a commutation failure prediction method, device and storage medium based on energy accumulation features of inverter. The method includes the following steps: collecting instantaneous values of three-phase valve side current and calculating the derivatives of the three-phase valve side current according to the instantaneous values of three-phase valve side current; the derivative includes positive, negative and zero states; according to the derivatives of the three-phase valve side current, determining the locations of incoming valve and ongoing valve; based on the valve side current of the incoming valve and ongoing valve, calculating energy accumulation features of the 12-pulse inverter; predicting whether the commutation failure from the incoming valve to the ongoing valve will happen according to the states of the derivatives of the three-phase valve side current and the energy accumulation features of the 12-pulse inverter.

A converter arrangement has a line-commutated converter with an AC voltage terminal to be connected to an AC voltage grid via at least one phase line. The converter arrangement has at least one switching module branch that is arranged in series in the at least one phase line and that includes a series connection of switching modules at whose terminals bipolar voltages that sum to give a branch voltage are in each case able to be generated. A bypass branch is arranged in a parallel connection to the switching module branch. At least one switching device is arranged in the bypass branch. The switching device includes activatable semiconductor switches that are connected in antiparallel. There is also described a method for starting up the converter arrangement.

The disclosure relates to a line commutated converter, LCC, for a high-voltage direct current, HVDC, power converter. The LCC comprises at least one bridge circuit for connection to at least one terminal of a DC system. Each bridge circuit comprises at least two arms, and each arm is associated with a phase of an AC system. Each arm comprises one or more upper thyristor valves and one or more lower thyristor valves connected in series, and a branch extending from between the upper and lower thyristor valves. Each arm further comprises a parallel capacitor module comprising at least one parallel capacitor being connected in parallel between at least one pair of branches comprising a first branch and a second branch wherein during commutation of a flow of current in the first branch to a flow of current in the second branch, the at least one parallel capacitor is configured to discharge current in to the second branch in the same direction as the flow of current in the second branch.

A converter arrangement has a line-commutated converter with an AC voltage terminal to be connected to an AC voltage grid via at least one phase line. The converter arrangement has at least one switching module branch that is arranged in series in the at least one phase line and that includes a series connection of switching modules at whose terminals bipolar voltages that sum to give a branch voltage are in each case able to be generated. A bypass branch is arranged in a parallel connection to the switching module branch. At least one switching device is arranged in the bypass branch. The switching device includes activatable semiconductor switches that are connected in antiparallel. There is also described a method for starting up the converter arrangement.