Abstract: A system and method for estimating operating characteristics of an induction motor is disclosed. The system includes a motor control device that is electrically connectable between a motor and a power source. The motor control device includes a plurality of switching devices comprising at least one thyristor corresponding to a respective phase of the motor. The motor control device also includes a controller programmed to disconnect the power source from the motor for a predetermined time period following a first plurality of cycles of a mains phase voltage of the power source. The controller is further programmed to measure a back-emf voltage during the predetermined time period, estimate an operating characteristic of the motor from the measured back-emf voltage, and trigger the plurality of switching devices to reconnect the power source to the motor following estimation of the operating characteristic.

Abstract: A circuit for sensing a direct current includes a first resistance and a second resistance. A first portion of the direct current flows through the first resistance and a second portion of the direct current flows through the second resistance. The circuit further includes a current sensor having an opening, first and second conductors inductively coupled with the current sensor, and a switching circuit having a pair of switches structured to alternatingly switch in order that the second portion of the direct current alternatingly flows through the first and second conductors. The second portion of the direct current flowing through the first conductor passes through the opening of the current sensor in a first direction and the second portion of the direct current flowing through the second conductor passes through the opening of the current sensor in a second direction opposite to the first direction.

Abstract: A circuit for sensing a direct current includes a first resistance and a second resistance. A first portion of the direct current flows through the first resistance and a second portion of the direct current flows through the second resistance. The circuit further includes a current sensor having an opening, first and second conductors inductively coupled with the current sensor, and a switching circuit having a pair of switches structured to alternatingly switch in order that the second portion of the direct current alternatingly flows through the first and second conductors. The second portion of the direct current flowing through the first conductor passes through the opening of the current sensor in a first direction and the second portion of the direct current flowing through the second conductor passes through the opening of the current sensor in a second direction opposite to the first direction.

Abstract: A load control device to control current flow to an AC load includes a circuit having line-side switches and floating-neutral side switches, along with a controller connected to the circuit that is programmed to control the circuit so as to cause each of the line-side switches and each of the floating-neutral side switches to switch between an On condition or an Off condition to selectively operate the circuit in an active mode and a free-wheeling mode. A full phase voltage is provided to the AC load during the active mode and a zero voltage is provided to the AC load during the free-wheeling mode. The controller applies a modulating function to the circuit, so as to modulate a supply voltage to control a frequency and an average of a load voltage present across terminals of the AC load, thereby enabling variable frequency operation of the AC load.

Abstract: A power flow regulator includes a plurality of bi-directional DC-DC converters, each of said converters comprising a first input, a second input, a first output and a second output; and a capacitor electrically connected between the first and second inputs of each of said converters. Either the first output of each of said converters is electrically connected to a corresponding DC source and the second output of each of said converters is electrically connected to a common DC load, or the first output of each of said converters is electrically connected to a corresponding DC load and the second output of each of said converters is electrically connected to a common DC source.

Abstract: A protection apparatus is for a direct current electrical generating apparatus. The protection apparatus includes a first terminal; a second terminal; a third terminal; a fourth terminal; at least one current sensor structured to sense current flowing between the first and second terminals or between the third and fourth terminals; a voltage sensor structured to sense a voltage between the first terminal and the third terminal; at least one switch structured to interrupt the current flowing between the first and second terminals or between the third and fourth terminals; and a processor cooperating with the at least one current sensor, the voltage sensor and the at least one switch, and being structured to provide feed forward fault protection for the direct current electrical generating apparatus.

Abstract: A system for detecting islanding of a microgrid includes a number of power sources to output real power and controlled reactive power injection; a number of controllers each controlling one of the number of power sources; and an output from the microgrid powered by the number of power sources. A number of electrical switching apparatus electrically connect the output from the microgrid to a grid and electrically disconnect the output from the microgrid from the grid. A microgrid controller detects islanding of the microgrid with respect to the grid, and sends a number of commands to a number of the number of controllers in order to control reactive power injection by a number of the number of power sources. A communication channel is between the microgrid controller and the number of controllers. A number of microgrid loads are powered by the output from the microgrid.

Abstract: A load control device to control current flow to an AC load includes a circuit having line-side switches and floating-neutral side switches, along with a controller connected to the circuit that is programmed to control the circuit so as to cause each of the line-side switches and each of the floating-neutral side switches to switch between an On condition or an Off condition to selectively operate the circuit in an active mode and a free-wheeling mode. A full phase voltage is provided to the AC load during the active mode and a zero voltage is provided to the AC load during the free-wheeling mode. The controller applies a modulating function to the circuit, so as to modulate a supply voltage to control a frequency and an average of a load voltage present across terminals of the AC load, thereby enabling variable frequency operation of the AC load.

Abstract: A load control device includes an input and an output connectable to an AC source and an AC load, respectively, with one or more supply lines each corresponding to a phase in the load connecting the input and output. Line-side switches are connected between a line terminal and load terminal, and floating-neutral side switches are connected to the load terminal at one end and at a common neutral connection at another end. A controller determines a direction of current flow on each of the supply lines, determines a switching pattern for each of the line-side switches and each of the floating-neutral side switches based on the determined direction of current flow, and causes each of the line-side switches and floating-neutral side switches to operate in an On condition or an Off condition according to the determined switching pattern, such that a controlled uninterrupted current is provided to the AC load.

Abstract: A power management system includes an ultracapacitor and a charge shuttle including a power converter. The charge shuttle may be coupled with the ultracapacitor and may be configured to be coupled with a load. The charge shuttle can be configured to monitor one or more parameters of the load and the ultracapacitor, and to control energy flow between the load and the ultracapacitor based on or according to monitored parameters. The system may also include a battery or other rechargeable energy storage element.

Abstract: A hybrid DC contactor includes contacts that provide a first current path between a DC power source and a load, an electromagnetic coil to position the contacts, a semiconductor switch in parallel with contacts that, when turned on, provides a second parallel current path that diverts current away from the contacts when the main contacts are being opened in either direction. A controller is provided to terminate power to the electromagnetic coil to open the contacts, detect an arc voltage across the contacts as the contacts open, provide a gate signal to the semiconductor switch to pulse the switch on for a pre-determined period of time to route current to the semiconductor switch, measure a current through the contacts and, if current is present through the contacts, then provide another gate signal to the semiconductor switch to pulse the switch on again so as to route current thereto.

Abstract: A system and method for selectively connecting photovoltaic (PV) arrays of a PV power system in series and parallel arrangements is disclosed. A DC-to-AC power inverter in the PV power system is electrically coupled to a plurality of PV arrays to receive a DC output therefrom and invert the DC output to an AC output, with the DC-to-AC power inverter including a DC link that receives the DC output from the plurality of PV arrays. A contactor arrangement is positioned between the plurality of PV arrays and the DC-to-AC power inverter, with the contactor arrangement including a plurality of contactors that are switchable between an on state and an off state to selectively connect the plurality of PV arrays to the DC-to-AC power inverter in a specified arrangement, so as to control a level of DC voltage received by the DC-to-AC power inverter from the plurality of PV arrays.

Abstract: A photovoltaic (PV) power system is disclosed that includes hybrid DC contactors corresponding to each of a plurality of PV strings, with each hybrid DC contactor having main contacts, a solid state switching unit positioned in parallel with the main contacts, and sensors configured to measure a voltage and current on respective PV strings. A controller is provided in the PV power system that is configured to receive voltage and current data on the PV strings, detect a fault condition on a respective PV string based on the voltage and current data, cause the main contacts of a respective hybrid DC contactor to remain closed on each PV string for which a fault condition is detected, and cause the main contacts of a respective hybrid DC contactor to open on each PV string for which no fault condition is detected, so as to clear the fault condition.

Abstract: A photovoltaic (PV) power system is disclosed that includes hybrid DC contactors corresponding to each of a plurality of PV strings, with each hybrid DC contactor having main contacts, a solid state switching unit positioned in parallel with the main contacts, and sensors configured to measure a voltage and current on respective PV strings. A controller is provided in the PV power system that is configured to receive voltage and current data on the PV strings, detect a fault condition on a respective PV string based on the voltage and current data, cause the main contacts of a respective hybrid DC contactor to remain closed on each PV string for which a fault condition is detected, and cause the main contacts of a respective hybrid DC contactor to open on each PV string for which no fault condition is detected, so as to clear the fault condition.

Abstract: A hybrid DC contactor includes contacts that provide a first current path between a DC power source and a load, an electromagnetic coil to position the contacts, a semiconductor switch in parallel with contacts that, when turned on, provides a second parallel current path that diverts current away from the contacts when the main contacts are being opened in either direction. A controller is provided to terminate power to the electromagnetic coil to open the contacts, detect an arc voltage across the contacts as the contacts open, provide a gate signal to the semiconductor switch to pulse the switch on for a pre-determined period of time to route current to the semiconductor switch, measure a current through the contacts and, if current is present through the contacts, then provide another gate signal to the semiconductor switch to pulse the switch on again so as to route current thereto.

Abstract: An area electric power system includes a number of direct current power sources, and a number of inverters operatively associated with the number of direct current power sources. Each of the number of inverters is structured to provide real power and controlled reactive power injection to detect islanding. An output is powered by the number of inverters. A number of electrical switching apparatus are structured to electrically connect the number of inverters to and electrically disconnect the number of inverters from a utility grid. A number of devices are structured to detect islanding with respect to the utility grid responsive to a number of changes of alternating current frequency or voltage of the output.

Abstract: A power flow regulator includes a plurality of bi-directional DC-DC converters, each of said converters comprising a first input, a second input, a first output and a second output; and a capacitor electrically connected between the first and second inputs of each of said converters. Either the first output of each of said converters is electrically connected to a corresponding DC source and the second output of each of said converters is electrically connected to a common DC load, or the first output of each of said converters is electrically connected to a corresponding DC load and the second output of each of said converters is electrically connected to a common DC source.

Abstract: A protection apparatus is for a direct current electrical generating apparatus. The protection apparatus includes a first terminal; a second terminal; a third terminal; a fourth terminal; at least one current sensor structured to sense current flowing between the first and second terminals or between the third and fourth terminals; a voltage sensor structured to sense a voltage between the first terminal and the third terminal; at least one switch structured to interrupt the current flowing between the first and second terminals or between the third and fourth terminals; and a processor cooperating with the at least one current sensor, the voltage sensor and the at least one switch, and being structured to provide feed forward fault protection for the direct current electrical generating apparatus.

Abstract: A power conversion system includes a number of photovoltaic arrays, a number of inverters, a transformer, and processor. The processor is structured to control the number of inverters and operate the power conversion system to provide maximum efficiency of power conversion by the number of photovoltaic arrays, the number of inverters and the transformer, and to maximize power output from the number of photovoltaic arrays.

Abstract: An area electric power system includes a number of direct current power sources, and a number of inverters operatively associated with the number of direct current power sources. Each of the number of inverters is structured to provide real power and controlled reactive power injection to detect islanding. An output is powered by the number of inverters. A number of electrical switching apparatus are structured to electrically connect the number of inverters to and electrically disconnect the number of inverters from a utility grid. A number of devices are structured to detect islanding with respect to the utility grid responsive to a number of changes of alternating current frequency or voltage of the output.