Abstract: An apparatus and methods to reduce current transient during power mode transfer in uninterruptible power supply (UPS). The disclosure provides a zero-cross detection based phase width modulated (PWM) element (E3). The element (E3) is configured to delay activation of a PWM modulator, by delaying a PWM start command for a first delay time (Tdz), wherein the first delay time is the time between receiving a static switch command to the time when a positive sequence component of a phase load current crosses zero. The element (E3) is further configured to delay the activation of the PWM modulator for a second delay time (Tdi) after the end of the first delay time (Tdz), by delaying the PWM start command for the second delay time, wherein the second delay time is based on a power factor of load connected to the UPS.

Abstract: The present disclosure discloses a UPS system configured in parallel configuration. The UPS system comprises a plurality of slave UPS units, a master UPS unit comprising a controller configured to identify number of operative slave UPS units from the plurality of slave UPS units when at least one slave UPS unit from the plurality of slave UPS units is inoperative and change operating voltage of the master UPS unit based on the identified number of operative slave UPS units. The UPS system further comprises at least one slave UPS unit from the plurality of slave UPS units comprising a controller configured to monitor the operating voltage of the master UPS unit to detect the change in the operating voltage, determine the number of operative slave UPS units, calculate a slave current for supplying to the load, and initiate the slave UPS unit to supply the slave current to the load.

Abstract: An apparatus and methods to reduce current transient during power mode transfer in uninterruptible power supply (UPS). The disclosure provides a zero-cross detection based phase width modulated (PWM) element (E3). The element (E3) is configured to delay activation of a PWM modulator, by delaying a PWM start command for a first delay time (Tdz), wherein the first delay time is the time between receiving a static switch command to the time when a positive sequence component of a phase load current crosses zero. The element (E3) is further configured to delay the activation of the PWM modulator for a second delay time (Tdi) after the end of the first delay time (Tdz), by delaying the PWM start command for the second delay time, wherein the second delay time is based on a power factor of load connected to the UPS.

Abstract: The present disclosure discloses a UPS system configured in parallel configuration. The UPS system comprises a plurality of slave UPS units, a master UPS unit comprising a controller configured to identify number of operative slave UPS units from the plurality of slave UPS units when at least one slave UPS unit from the plurality of slave UPS units is inoperative and change operating voltage of the master UPS unit based on the identified number of operative slave UPS units. The UPS system further comprises at least one slave UPS unit from the plurality of slave UPS units comprising a controller configured to monitor the operating voltage of the master UPS unit to detect the change in the operating voltage, determine the number of operative slave UPS units, calculate a slave current for supplying to the load, and initiate the slave UPS unit to supply the slave current to the load.