Abstract: Aspects of the disclosure include a power system comprising at least one three-wire active harmonic filter (AHF) configured to be coupled to, and provide compensation current to, a three-phase load, at least one four-wire AHF configured to be coupled to, and provide compensation current to, the three-phase load, and a controller configured to determine a total compensation current to provide to the three-phase load, the total compensation current including a zero component and a non-zero component, determine an output capacity of the at least one three-wire AHF and the at least one four-wire AHF, calculate a current-compensation ratio based on the output capacity of the at least one three-wire AHF and the at least one four-wire AHF, and control the at least one four-wire AHF to provide at least a portion of the non-zero component of the total compensation current to the three-phase load based on the current-compensation ratio.

Abstract: Aspects of the disclosure include a power system comprising at least one three-wire active harmonic filter (AHF) configured to be coupled to, and provide compensation current to, a three-phase load, at least one four-wire AHF configured to be coupled to, and provide compensation current to, the three-phase load, and a controller configured to determine a total compensation current to provide to the three-phase load, the total compensation current including a zero component and a non-zero component, determine an output capacity of the at least one three-wire AHF and the at least one four-wire AHF, calculate a current-compensation ratio based on the output capacity of the at least one three-wire AHF and the at least one four-wire AHF, and control the at least one four-wire AHF to provide at least a portion of the non-zero component of the total compensation current to the three-phase load based on the current-compensation ratio.

Abstract: According to one aspect of the disclosure, a power filter is provided including a first input configured to receive measurements of electrical characteristics of source power lines from a power source, a second input configured to receive measurements of electrical characteristics of load power lines to a load, an output configured to couple to output power lines to provide output current compensation signals, a power converter coupled to the power output and configured to receive input power, receive input control signals and provide the output current compensation signals based on the input control signals, and a controller configured to provide the control signals to the power converter, wherein the controller receives an indication of a neutral current limit, and the controller is configured to adjust the control signals based on the indication of the neutral current limit to limit current on a neutral of the output power line.

Abstract: According to one aspect of the disclosure, a power filter is provided including a first input configured to receive measurements of electrical characteristics of source power lines from a power source, a second input configured to receive measurements of electrical characteristics of load power lines to a load, an output configured to couple to output power lines to provide output current compensation signals, a power converter coupled to the power output and configured to receive input power, receive input control signals and provide the output current compensation signals based on the input control signals, and a controller configured to provide the control signals to the power converter, wherein the controller receives an indication of a neutral current limit, and the controller is configured to adjust the control signals based on the indication of the neutral current limit to limit current on a neutral of the output power line.

Abstract: Aspects of the present disclosure are directed to a power filter comprising a first input configured to receive measurements of electrical characteristics of source power lines from a power source, a second input configured to receive measurements of electrical characteristics of load power lines to a load, an output configured to couple to output power lines to provide output current compensation signals, a power converter coupled to the power output and configured to receive input power, receive input control signals and provide the output current compensation signals based on the input control signals, and control circuitry coupled to the first input, the second input and the power converter and configured to provide the control signals to the power converter, wherein the control circuitry is configured to detect a connection status of a neutral connection to the load, wherein the connection status includes one of connected and disconnected.

Abstract: A method for pulse width modulated pulse synchronization in a parallel UPS system uses the locally measured critical bus voltage to detect a zero crossing and adjust the PWM pulse to coincide with the zero crossing. No communication between the units is required to perform synchronization, and no “master” and “slave” relationship exists to thereby increase the total system reliability.

Abstract: A method of increasing the reliability of an uninterruptible power supply (UPS) providing AC power to a load, comprising determining the magnitude and duration of an actual undervoltage event in a power output of the UPS; providing a predetermined undervoltage standard establishing at least a range of undervoltage events of acceptable magnitude and duration for the load; comparing the magnitude and duration of the actual undervoltage event with the predetermined standard; and causing the load to be transferred to an alternate source of AC power when the comparison of the actual undervoltage event with the predetermined standard reveals that the actual undervoltage event is not acceptable.

Abstract: A serial communications bus is utilized to send key action data between parallel UPS units. The communications bus is used to transmit data at the zero crossing of the critical bus voltage. Each UPS unit then takes action based upon the event data received at the next zero crossing of the critical bus voltage.

Abstract: A method for pulse width modulated pulse synchronization in a parallel UPS system uses the locally measured critical bus voltage to detect a zero crossing and adjust the PWM pulse to coincide with the zero crossing. No communication between the units is required to perform synchronization, and no “master” and “slave” relationship exists to thereby increase the total system reliability.

Abstract: An uninterruptible power supply is disclosed that includes a digital controller comprising a plurality of microprocessors. These microprocessors are programmed and arranged to provide various control features heretofore unavailable using analog controllers of the prior art.

Abstract: An uninterruptible power supply is disclosed that includes a digital controller comprising a plurality of microprocessors. These microprocessors are programmed and arranged to provide various control features heretofore unavailable using analog controllers of the prior art.