A high voltage direct current (HVDC) transmission system is provided. The high voltage direct current (HVDC) transmission system includes: an integrated measurement panel; and an HVDC transmission device, wherein the HVDC transmission device is configured to: receive, from the integrated measurement panel, compensation values for compensating for the voltage values output through the first to Nth potential transformers, compensate for the voltage values output through the first to Nth potential transformers by using the received compensation values, and measure the actual voltage values by using the compensated voltage values.

An electric power conversion circuit includes: a first leg including first and third switches; a second leg including second and fourth switches; a third leg including fifth and seventh switches; a fourth leg including sixth and eighth switches; a first reactor connected between a first node, in which the first and second legs are connected to each other, and a fifth node, in which the third and fourth legs are connected to each other; a second reactor connected between a second node to which the first and second legs are connected and a sixth node to which the third and fourth legs are connected; a first port terminal connected to the first node; a second port terminal connected to the sixth node; a third port terminal connected to a midpoint of each of the first and third legs; and a fourth port terminal connected to a midpoint of each of the second and fourth legs.

A power calculation apparatus includes a power measurement unit configured to measure alternating-current electric power input to a converter unit to obtain measured power, power consumption estimation units configured to estimate power consumption on motor axes of corresponding motors, respectively, using parameters concerning the motors, to obtain estimated power for each motor axis, and a power consumption calculation unit configured to distribute the measured power obtained by measurement according to a ratio in accordance with the estimated power obtained by estimation to calculate power consumption for each motor axis.

Power conversion systems, methods and precharge systems are disclosed to charge a DC bus capacitor, including thyristors and reverse diodes coupled in AC circuit paths between AC input lines and a rectifier, a precharge resistor coupled in one or more of the AC circuit paths, and a controller to turn all the thyristors off to allow the DC bus capacitor to charge through the precharge resistor, and to turn all the thyristors on when the DC bus voltage reaches a non-zero threshold value.

A power converting apparatus includes a diode bridge that converts first AC power supplied from a power supply into DC power, a main circuit capacitor that smooths the DC power, one or more capacitors that reduces a noise component included in the first AC power, and a path switch. The path switch switches a charging path for the main circuit capacitor so that current output from the AC power supply flows into the main circuit capacitor via the capacitor(s) from when supply of the first AC power starts until a voltage of the main circuit capacitor reaches a predetermined voltage, and that the current output from the AC power supply flows into the main circuit capacitor without bypassing the capacitor(s) after the voltage of the main circuit capacitor reaches the predetermined voltage.

A control apparatus configured to control a chain link voltage source converter, the control apparatus comprising; two converter controllers, each converter controller configured to receive a measure of the output voltage and/or current from the converter and determine a control signal therefrom for controlling the voltage source converter, each converter controller including at least one integrator element configured to perform an integration operation and output an integrator term in said determination of the control signal, a selector configured to select which one of the converter controllers provides its control signal to the converter; wherein each integrator element is configured to have two modes, a first mode in which the integrator element determines the integrator term and a second mode in which the integrator term is provided by a corresponding integrator element in the other converter controller.

A control apparatus configured to control a chain link voltage source converter, the control apparatus comprising; two converter controllers, each converter controller configured to receive a measure of the output voltage and/or current from the converter and determine a control signal therefrom for controlling the voltage source converter, each converter controller including at least one integrator element configured to perform an integration operation and output an integrator term in said determination of the control signal, a selector configured to select which one of the converter controllers provides its control signal to the converter; wherein each integrator element is configured to have two modes, a first mode in which the integrator element determines the integrator term and a second mode in which the integrator term is provided by a corresponding integrator element in the other converter controller.

A motor driving device and an air conditioner including the same are disclosed. The disclosed motor driving device includes a multi-level converter to receive AC power, thereby outputting multi-level power, the multi-level converter including plural diodes and plural switching elements, plural capacitors for storing the multi-level power from the multi-level converter, and a gate drive signal generator to generate gate drive signals for the switching elements of the multi-level converter. The gate drive signal generator includes a gate drive power source to supply a gate drive voltage, a gate driver to generate the gate drive signals, using the gate drive voltage, a gate capacitor connected to both terminals of the gate driver, and a gate switching element connected between one end of the gate capacitor and one end of one of the plural capacitors. Accordingly, gate drive signals for the multi-level converter can be generated.

The present invention relates to a method for simultaneous operation of a plurality of chopper circuits of a wind turbine power converter, the method comprising the steps of operating a controllable switching member of a first chopper circuit in accordance with a first switching pattern, and operating a controllable switching member of a second chopper circuit in accordance with a second switching pattern, wherein the first switching pattern is different from the second switching pattern during a first time period. In order to reduce switching losses the first switching pattern may involve that the controllable switching member of the first chopper circuit is clamped during the first time period. Additional chopper circuits may be provided in parallel to the first and second chopper circuits. The present invention further relates to a power dissipation chopper being operated in accordance with the before mentioned method.

Precharging systems and methods are presented for precharging a DC bus circuit in a power conversion system, in which precharging current is connected through a precharging resistance coupled between only a single AC input line and the DC bus circuit when the DC bus voltage is less than a non-zero threshold, and a controller individually activates controllable rectifier switching devices when the DC bus voltages greater than or equal to the threshold using DC gating or pulse width modulation to selectively provide a bypass path around the precharging resistance for normal load currents in the power conversion system.