Abstract: A ground fault detection system for locating a ground fault in a direct current (DC) power transfer system is provided. The system includes a ground fault detection component and a current sensor. The ground fault detection component includes a first switch and a first resistive element electrically coupled to each other in a series configuration. The ground fault detection component also includes a second switch and a second resistive element electrically coupled to each other in a series configuration. Furthermore, the current sensor is operatively coupled to a load and is configured to measure a fault current at the load upon switching at least one of the first switch or the second switch to a conducting state.

Abstract: A power system for a marine ship includes a plurality of protection zones, wherein at least two protection zones are coupled to each other via at least one bus-tie converter. Each of the protection zones includes a plurality of direct current (DC) buses; wherein DC buses which do not have same DC voltage are coupled to each other via at least one DC to DC converter. Furthermore, at least one energy source is coupled to at least one DC bus via a power electronic converter.

Abstract: A power system for a marine ship includes a plurality of protection zones, wherein at least two protection zones are coupled to each other via at least one bus-tie converter. Each of the protection zones includes a plurality of direct current (DC) buses and a plurality of power converters. The bus-tie converter includes at least two converter legs coupled by at least one inductor. Each converter leg includes a first branch connected with a snubber circuit. The first branch includes two outer switching devices and at least one inner switching device connected between the two outer switching devices. The first branch also includes a damping resistor coupled between the two outer switching devices to dissipate a fault current. The snubber circuit includes a combination of a diode, a resistor and a capacitor. A controller controls the operation of the plurality of power converters and the at least one bus-tie converter.

Abstract: An over-voltage protection system includes an electronic valve connected across two terminals of a circuit and an over-voltage detection circuit connected across one of the plurality of semiconductor devices for detecting an over-voltage across the circuit. The electronic valve includes a plurality of semiconductor devices connected in series. The over-voltage detection circuit includes a voltage divider circuit connected to a break-over diode in a way to provide a representative low voltage to the break-over diode and an optocoupler configured to receive a current from the break-over diode when the representative low voltage exceeds a threshold voltage of the break-over diode indicating an over-voltage condition. The representative low voltage provided to the break-over diode represents a voltage across the one semiconductor device.

Abstract: A gradient amplifier system, includes: a power stage comprising a plurality of bridge amplifiers, each operates at a first switching frequency; a gradient coil coupled to the power stage and configured to produce a magnetic field proportional to a coil current signal supplied by the power stage; a controller stage coupled to an input terminal of the power stage and configured to: generate a pulse width modulated gate signal based on the coil current signal and a reference current signal, wherein the pulse width modulated gate signal is generated at a second switching frequency when a slew rate associated with the reference current signal is below a threshold rate for at least a first time period; and apply the pulse width modulated gate signal to the power stage for changing an operating frequency of each of the plurality of bridge amplifiers from the first to the second switching frequency.

Abstract: A system and method for series connecting electronic power devices are disclosed. In one embodiment, a switching device system includes a first upper arm electrically coupled to a first lower arm and a second upper arm electrically coupled to a second lower arm. Each of the arms include a plurality of low voltage sub-modules connected in series and each plurality of low voltage sub-modules includes an auxiliary switching device, a series switching device, and a capacitor. Each plurality of low voltage sub-modules is configured to be sequentially switched using the auxiliary switching device and the series switching device separately in the upper arms and the respective lower arms to control change in voltage over time (dV/dt) while selectively blocking a desired high voltage. Further, a capacitor voltage balancing (sorting or rotating) algorithm may be used to actively balance voltage across each plurality of low voltage sub-modules.

Abstract: A power converter is presented. The power converter includes at least one leg, the at least one leg includes a first string, where the first string includes a plurality of diodes, a first connecting node, and a second connecting node, and where the first string is operatively coupled across a first bus and a second bus. Furthermore, the at least one leg includes a second string operatively coupled to the first string via the first connecting node and the second connecting node, where the second string includes a plurality of switching units.

Abstract: A method and a high-voltage DC (HVDC) power system are provided. The system includes a plurality of sending-end (SE) modules coupled in electrical series and divided into at least two groups that each operate independently with respect to an electrical ground and a plurality of receiving-end (RE) power converter modules electrically coupled to the plurality of SE modules, the plurality of RE power converter modules including a fast ground-fault detection and control device, the plurality of RE power converter modules including a receiving-end front-end DC-DC converter controller, and an output current damping control.

Abstract: A power transmission system includes a first unit for carrying out the steps of receiving high voltage direct current (HVDC) power from an HVDC power line, generating an alternating current (AC) component indicative of a status of the first unit, and adding the AC component to the HVDC power line. Further, the power transmission system includes a second unit for carrying out the steps of generating a direct current (DC) voltage to transfer the HVDC power on the HVDC power line, wherein the HVDC power line is coupled between the first unit and the second unit, detecting a presence or an absence of the added AC component in the HVDC power line, and determining the status of the first unit based on the added AC component.

Abstract: A power converter includes at least one leg with a first string including a plurality of controllable semiconductor switches, a first connecting node, and a second connecting node, wherein the first string is operatively coupled across a first bus and a second bus. The at least one leg also includes a second string operatively coupled to the first string via the first connecting node and the second connecting node, wherein the second string includes a plurality of switching units. The first string includes a first branch and a second branch, wherein the second branch is operatively coupled to the first branch via a third connecting node and the third connecting node is coupled to a ground connection.

Abstract: In one embodiment, a system includes a gradient coil driver configured to supply electrical signals to a gradient coil of a magnetic resonance imaging system. The gradient coil driver includes an electronic circuit. The electronic circuit includes a first H-bridge circuit electrically coupled to a power source. The first H-bridge includes a plurality of metal-oxide-semiconductor field-effect transistor (MOSFET) switches; and a plurality of diodes electrically coupled in parallel with each MOSFET switch. Each diode of the plurality of diodes is configured to conduct current to cause zero voltage potential across a source and a drain of one of the plurality of MOSFET switches. The first H-bridge also includes a load configured to regulate currents flowing through each of the plurality of diodes and each MOSFET switch of the plurality of MOSFET switches.

Abstract: A ground fault detection system for locating a ground fault in a direct current (DC) power transfer system is provided. The system includes a ground fault detection component and a current sensor. The ground fault detection component includes a first switch and a first resistive element electrically coupled to each other in a series configuration. The ground fault detection component also includes a second switch and a second resistive element electrically coupled to each other in a series configuration. Furthermore, the current sensor is operatively coupled to a load and is configured to measure a fault current at the load upon switching at least one of the first switch or the second switch to a conducting state.

Abstract: An over-voltage protection system includes an electronic valve connected across two terminals of a circuit and an over-voltage detection circuit connected across one of the plurality of semiconductor devices for detecting an over-voltage across the circuit. The electronic valve includes a plurality of semiconductor devices connected in series. The over-voltage detection circuit includes a voltage divider circuit connected to a break-over diode in a way to provide a representative low voltage to the break-over diode and an optocoupler configured to receive a current from the break-over diode when the representative low voltage exceeds a threshold voltage of the break-over diode indicating an over-voltage condition. The representative low voltage provided to the break-over diode represents a voltage across the one semiconductor device.

Abstract: A system for driving an electric machine is provided. The system includes a power converter coupled to an input source and the electric machine. The power converter includes a leg that includes a first and second string. The first string includes plurality of controllable semiconductor switches, a first and second connecting node. The first string is operatively coupled across a first and second bus. The second string is operatively coupled to the first string via the first and second connecting node. The second string comprises plurality of switching modules. The switching modules include fully controllable semiconductor switches and energy storage devices. The system further includes a system controller configured to provide activation commands to the controllable semiconductor switches and the switching modules such that energy stored in the energy storage device is provided to the electric machine when the machine is switched on for operation.

Abstract: A system and method for series connecting electronic power devices are disclosed. In one embodiment, a switching device system includes a first upper arm electrically coupled to a first lower arm and a second upper arm electrically coupled to a second lower arm. Each of the arms include a plurality of low voltage sub-modules connected in series and each plurality of low voltage sub-modules includes an auxiliary switching device, a series switching device, and a capacitor. Each plurality of low voltage sub-modules is configured to be sequentially switched using the auxiliary switching device and the series switching device separately in the upper arms and the respective lower arms to control change in voltage over time (dV/dt) while selectively blocking a desired high voltage. Further, a capacitor voltage balancing (sorting or rotating) algorithm may be used to actively balance voltage across each plurality of low voltage sub-modules.

Abstract: A power system for a marine ship includes a plurality of protection zones, wherein at least two protection zones are coupled to each other via at least one bus-tie converter. Each of the protection zones includes a plurality of direct current (DC) buses and a plurality of power converters. The bus-tie converter includes at least two converter legs coupled by at least one inductor. Each converter leg includes a first branch connected with a snubber circuit. The first branch includes two outer switching devices and at least one inner switching device connected between the two outer switching devices. The first branch also includes a damping resistor coupled between the two outer switching devices to dissipate a fault current. The snubber circuit includes a combination of a diode, a resistor and a capacitor. A controller controls the operation of the plurality of power converters and the at least one bus-tie converter.

Abstract: A power converter includes at least one leg including a first string that includes controllable semiconductor switches, a first connecting node, and a second connecting node and that is operatively coupled across a first bus and a second bus. A second string is operatively coupled to the first string via the first connecting node and the second connecting node. The second string includes a plurality of switching modules wherein each of the plurality of switching modules includes a plurality of fully controllable semiconductor switches and at least one energy storage device. The power converter includes a system controller to control activation of the controllable semiconductor switches and switching modules such that a controlled electrical variable is maintained at a first predetermined reference voltage value and the average internal stored energy of the energy storage devices is maintained at a second predetermined reference value.

Abstract: A power system for a marine ship includes a plurality of protection zones, wherein at least two protection zones are coupled to each other via at least one bus-tie converter. Each of the protection zones includes a plurality of direct current (DC) buses; wherein DC buses which do not have same DC voltage are coupled to each other via at least one DC to DC converter. Furthermore, at least one energy source is coupled to at least one DC bus via a power electronic converter.

Abstract: A high-voltage DC (HVDC) power system and a method of controlling and protecting the HVDC power system includes a plurality of sending-end (SE) modules coupled in electrical series and a plurality of receiving-end (RE) power converter modules electrically coupled to said plurality of SE modules, the RE modules coupled in a switchyard configuration, the switchyard configuration including a plurality of load branches coupled together in electrical series, each load branch including a branch bypass switch configured to bypass load current around an associated load branch, and a branch protection system.

Abstract: A power converter is presented. The power converter includes at least one leg, the at least one leg includes a first string, where the first string includes a plurality of diodes, a first connecting node, and a second connecting node, and where the first string is operatively coupled across a first bus and a second bus. Furthermore, the at least one leg includes a second string operatively coupled to the first string via the first connecting node and the second connecting node, where the second string includes a plurality of switching units.