Abstract: A power conversion system includes a first converter effectively connected in series to a second converter. Each converter has a plurality of output levels. A phase-shifted transformer is coupled to the converters. The phase-shifted transformer has a delta-wound winding and an open star winding. The first converter is coupled to the open star winding and the second converter is coupled to the delta winding. The open star winding is configured for direct connection to either of a load or the open star winding of a second phase-shifted transformer, having a delta winding connected to a third converter. One or more DC voltage sources are each connected to the first and second converters by a respective DC link capacitor. Each DC voltage source is connected to a common power grid by an isolated multiphase transformer winding.

Abstract: A power converter includes a first phase leg including a first di/dt reactor and a first control section, the first di/dt reactor and the first control section being coupled between an active line and a neutral line. The power converter also includes a first current crowbar coupled between the active line and the neutral and a controller coupled to the first di/dt reactor, the control section and the first current crowbar and configured to activate the current crowbar based on a voltage across the first di/dt reactor.

Abstract: Systems and methods for converting power are presented. The power conversion includes conducting load current through a first current path of multiple current paths in a power conversion unit using switches, diodes, or a combination thereof. The power conversion also includes blocking one or more additional current paths of the multiple current paths in the power conversion unit using one or more of the switches, one or more of the diodes, or a combination thereof. Furthermore, the power conversion includes reducing potential voltage stress on the one or more switches by using one or more voltage stress reduction switches to reduce a voltage that is blocked by the one or more blocking switches or diodes by connecting an end of each of the one or more switches opposite to a blocking edge to an intermediate voltage node.

Abstract: Systems and methods for power conversion are disclosed. The systems and methods use generation of a plurality of power levels approximately equal to multiples of one or more power supply voltage levels along with generation of one or more intermediate power levels between levels of the plurality of power levels via spanning reactor inductors. Furthermore, the method includes generating an output signal using the generated plurality of power levels and the one or more intermediate levels.

Abstract: Systems and methods for converting power are presented. The power conversion includes conducting load current through a first current path of multiple current paths in a power conversion unit using switches, diodes, or a combination thereof. The power conversion also includes blocking one or more additional current paths of the multiple current paths in the power conversion unit using one or more of the switches, one or more of the diodes, or a combination thereof. Furthermore, the power conversion includes reducing potential voltage stress on the one or more switches by using one or more voltage stress reduction switches to reduce a voltage that is blocked by the one or more blocking switches or diodes by connecting an end of each of the one or more switches opposite to a blocking edge to an intermediate voltage node.

Abstract: A load commutated inverter (LCI) drive system for a synchronous electrical machine is provided. The system may include a first supply bridge and a second supply bridge, each of which may include an alternating current to direct current (AC-to-DC) source side converter, a DC link circuit, and a DC-to-AC load side inverter. The system may include a controller for selectively controlling at least one of the first supply bridge and the second supply bridge by selective firings of silicon controlled rectifiers (SCRs). The electrical power outputted from the first supply bridge and the second supply bridge may be combined by an output delta-wye electric power transformer and supplied to the electrical machine. The LCI drive system may further include one or more input electric power transformers configured to supply an input electric power to the first supply bridge and the second supply bridge.

Abstract: A power conversion system includes a first converter effectively connected in series to a second converter. Each converter has a plurality of output levels. A phase-shifted transformer is coupled to the converters. The phase-shifted transformer has a delta-wound winding and an open star winding. The first converter is coupled to the open star winding and the second converter is coupled to the delta winding. The open star winding is configured for direct connection to either of a load or the open star winding of a second phase-shifted transformer, having a delta winding connected to a third converter. One or more DC voltage sources are each connected to the first and second converters by a respective DC link capacitor. Each DC voltage source is connected to a common power grid by an isolated multiphase transformer winding.

Abstract: A load commutated inverter (LCI) drive system for a synchronous electrical machine is provided. The system may include a first supply bridge and a second supply bridge, each of which may include an alternating current to direct current (AC-to-DC) source side converter, a DC link circuit, and a DC-to-AC load side inverter. The system may include a controller for selectively controlling at least one of the first supply bridge and the second supply bridge by selective firings of SCRs. The electrical power outputted from the first supply bridge and the second supply bridge may be combined by an output delta-wye electric power transformer and supplied to the electrical machine. The LCI drive system may further include one or more input electric power transformers configured to supply an input electric power to the first supply bridge and the second supply bridge.

Abstract: Systems and methods for suppressing resonances in power converters are provided. A power converter (100) includes an input stage (101) configured to receive alternating current (AC), an output stage (102) configured to output alternating current (AC), a first direct current (DC) bus (106) coupling the input stage (101) to the output stage (102), a second DC bus (108) coupling the input stage (101) to the output stage (102), a first capacitor leg (110) coupling the first DC bus (106) to the second DC bus (108) and a second capacitor leg (112) coupling the first DC bus (106) to the second DC bus (108). The first DC bus (106), the second DC bus (108), the first capacitor leg (110), and the second capacitor leg (112) form a current loop (130) having an effective inductance, and at least one resistor (140,142) configured to suppress a resonance of the power converter (100), wherein the resonance is based at least in part on the effective inductance of the current loop.

Abstract: A motor for a synchronous electric machine includes a first inverter configured to provide alternating current power at a first plurality of phases. Also included is a second inverter configured to provide alternating current power at a second plurality of phases. Further included is a first stator winding and a second stator winding each in operable communication with the first inverter and the second inverter and configured to operate synchronously at a first phase, a second phase and a third phase. Yet further included is a first interphase transformer for receiving one of the first plurality of phases and one of the second plurality of phases for communicating a pair of simultaneous, matching voltage outputs to the first stator winding and the second stator winding for reducing a stress imposed on a rotor.

Abstract: The present subject matter is directed to systems and methods for interfacing variable speed generators to a power distribution grid. A plurality of doubly-fed induction generators (DFIG) are provided and coupled to a common shaft of a prime mover. Each of the plurality of DFIGs provides an electrical power output having an output frequency based on a rotational speed of the common shaft. A converter coupled to each DFIG provides variable excitation signals to its respective DFIG sufficient to adjust its output frequency to conform to a power grid frequency requirement.

Abstract: A motor for a synchronous electric machine includes a first inverter configured to provide alternating current power at a first plurality of phases. Also included is a second inverter configured to provide alternating current power at a second plurality of phases. Further included is a first stator winding and a second stator winding each in operable communication with the first inverter and the second inverter and configured to operate synchronously at a first phase, a second phase and a third phase. Yet further included is a first interphase transformer for receiving one of the first plurality of phases and one of the second plurality of phases for communicating a pair of simultaneous, matching voltage outputs to the first stator winding and the second stator winding for reducing a stress imposed on a rotor.

Abstract: A method of assembling a testing apparatus for a full-power converter assembly includes coupling an electric power supply apparatus to an electric power grid. The method also includes coupling a direct current (DC) generation apparatus to the electric power supply apparatus. The method further includes coupling an electric power grid simulation device to the DC generation apparatus. The method also includes coupling a full-power converter assembly test connection to the electric power grid simulation device.

Abstract: A device includes a controller that receives current values generated by at least four parallel load commutated inverters (LCIs). The controller includes a source firing generator that generates independent source firing commands for each of the at least four parallel LCIs based on the received current values and transmits each of the independent source firing commands to a respective one of the at least four parallel LCIs, wherein the source firing commands are configured to set input phase angle values of the four parallel LCIs.

Abstract: A power converter includes a first phase leg including a first di/dt reactor and a first control section, the first di/dt reactor and the first control section being coupled between an active line and a neutral line. The power converter also includes a first current crowbar coupled between the active line and the neutral and a controller coupled to the first di/dt reactor, the control section and the first current crowbar and configured to activate the current crowbar based on a voltage across the first di/dt reactor.

Abstract: A method of assembling a testing apparatus for a full-power converter assembly includes coupling an electric power supply apparatus to an electric power grid. The method also includes coupling a direct current (DC) generation apparatus to the electric power supply apparatus. The method further includes coupling an electric power grid simulation device to the DC generation apparatus. The method also includes coupling a full-power converter assembly test connection to the electric power grid simulation device.

Abstract: A line side crowbar circuit for an energy converter is disclosed. In one aspect there is a power unit that includes an energy converter; a transformer configured to transfer electrical energy generated from the energy converter to an electrical grid; and a crowbar coupled to the energy converter and the transformer that is configured to prevent an overvoltage event from damaging electrical components associated with the energy converter and the transformer.

Abstract: A method for coupling an energy storage system to a variable energy supply system includes providing an energy storage system including at least one Vanadium redox battery and at least one battery charge controller. The method also includes electrically coupling the at least one battery charge controller to the variable energy supply system such that the at least one battery is configured to supply a substantially consistent energy output during fluctuating energy loads of the energy supply system.

Abstract: A method for coupling an energy storage system to a variable energy supply system includes providing an energy storage system including at least one Vanadium redox battery and at least one battery charge controller. The method also includes electrically coupling the at least one battery charge controller to the variable energy supply system such that the at least one battery is configured to supply a substantially consistent energy output during fluctuating energy loads of the energy supply system.

Abstract: A method for controlling a pitch control system of a wind turbine includes providing a charged backup battery configured to supply no energy to a DC link when full AC input power is available, wherein the DC link includes a DC link capacitor. The method further includes using energy stored in the DC link capacitor to operate a pitch control system during a loss or dip of AC input power, and maintaining charge on the DC link capacitor using the charged backup battery as voltage across the DC link capacitor drops during the operation of the pitch control system.