A method for power conversion includes coupling a first string to a second string via a first connecting node and a second connecting node to form at least one leg of a power converter. The first string is operatively coupled across a first bus and a second bus and comprises a first branch and a second branch coupled via a third connecting node. The first branch and the second branch include a plurality of controllable semiconductor switches. Furthermore, the second string comprises a first chain link and a second chain link coupled via an alternating current phase bus and includes a plurality of switching units. The first chain link and/or the second chain link are controlled to generate a negative voltage across at least one of the plurality of controllable semiconductor switches during a switch turn off process.

The present invention discloses a calculation method for a converter valve state and a valve current based on temporal features of a valve side current, the process is follows: collecting three-phase AC currents, DC currents on a valve side of a converter of a DC transmission system, and trigger pulses of converter valves; establishing a node current equation of the AC currents and valve currents; when detecting a rising edge of a trigger pulse of a converter valve, latching the number of the converter valve; according to the trigger pulses of the converter valves, and amplitude characteristics of the AC currents and characteristics of AC variations, to perform a conducting state and a blocking state judgment of valve states, and obtaining valve states; judging whether each phase has a bypass state; through summing the valve bypass states of the three phases to judge a number of bypass phases; supplementing bypass loop voltage equation; calculating the converter valve currents; when the calculated value of the valve currents is negative, the valve state is corrected to blocking state according to a one-way conductivity of the converter valves, otherwise do not correct; repeating the above steps again to calculate the valve current.

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.

Within a predetermined time range, record time information of status indication signals fed back by thyristor control units (TCU) of a converter valve. Perform, statistics and comparison of the pieces of time information using a bias statistics method. Mark, a thyristor level whose bias exceeds a preset value. And determine a probability of failure in the thyristor according to the marking result.

A voltage-regulated power converter module includes an electrical charge storage device and a semiconductor switch connected thereto and having a collector, a gate and an emitter, in which the collector-emitter path of the semiconductor switch is switched into a current path between first and second alternating-current terminals of the power converter module. The alternating-current terminals can be interconnected through a bypass switch. The voltage-regulated power converter module is intended to minimize the occurrence of damage in the event of a fault, and allow the multilevel power converter to continue operating without possibly having to use an extremely fast bypass switch for this purpose. To this end, the collector and the gate of the semiconductor switch are interconnected through a circuit configuration, which is configured in such a way that it becomes conductive above a predefined voltage threshold. A power converter is also provided.

A line commutated converter, LCC, for a high-voltage, direct current, HVDC, power converter comprises at least one bridge circuit for connection to at least one terminal of a DC system. Each bridge circuit comprises a plurality of arms, and each arm is associated with a respective phase of an AC system. Each arm comprises an upper and lower thyristor connected in series, an associated branch extending from between the upper and lower thyristors, and at least one capacitor module for each phase. The, or each capacitor module is operable to insert a capacitor into the respective arm of the bridge circuit.

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.

An arrangement for changing current return path in a bipole direct current power transmission system includes a converter station having an active and a passive converter connected in series between an active and a passive pole line via a first neutral bus, a metallic return transfer switch in an electrode line, a ground return transfer switch in a current redirecting path between the passive pole line and the neutral bus and a control unit which in case of change to the passive pole line for providing a return current path is configured to, upon control of power related to the active converter from steady-state to zero, close the ground return transfer switch and thereafter open the metallic return transfer switch, whereupon power related to the active converter may be controlled back to steady state.

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.

Methods and apparatus for controlling a voltage source converter to energise a DC link. A voltage order generating module generates a voltage order for controlling the voltage source converter to generate a DC voltage on the DC link. the voltage order is based on a time varying voltage reference signal. A voltage reference module, which may include a ramp generator generates the time varying voltage reference signal such that the rate of change of the voltage reference signal changes over time. The rate of change of the voltage reference signal may decrease over time, to become more gradual as the nominal operating voltage is reached to avoid over-voltages.