Abstract: An uninterruptible power supply (UPS) system includes at least three UPSs configured to be connected in parallel to a common load. The system further includes control circuitry configured to support at least two redundant groups among the UPSs and to support at least two redundant subgroups among at least one of the redundant groups of UPSs. In this manner, a nested redundancy may be provided.

Abstract: A power supply apparatus includes first and second parallel-connected uninterruptible power supplies (UPSs), each including an AC/DC converter circuit and a DC/AC converter circuit having an input coupled to an output of the AC/DC converter circuit by a DC link, inputs of the AC/DC converter circuits of the first and second UPSs connected in common to an AC source and outputs of the DC/AC converter circuits of the first and second UPSs connected in common to a load. The first and second UPSs are configured to support a test mode wherein the first UPS is test loaded by transferring power from the output of the DC/AC converter circuit of the first UPS to the output of the DC/AC converter circuit of the second UPS. The first UPS may be configured to provide power to the load concurrent with test loading by the second UPS.

Abstract: An uninterruptible power supply (UPS) system includes at least three UPSs configured to be connected in parallel to a common load. The system further includes control circuitry configured to support at least two redundant groups among the UPSs and to support at least two redundant subgroups among at least one of the redundant groups of UPSs. In this manner, a nested redundancy may be provided.

Abstract: An uninterruptible power supply (UPS) system includes at least three UPSs configured to be connected in parallel to a common load. The system further includes control circuitry configured to support at least two redundant groups among the UPSs and to support at least two redundant subgroups among at least one of the redundant groups of UPSs. In this manner, a nested redundancy may be provided.

Abstract: In a power converter apparatus, such as an uninterruptible power supply, a phase reference signal is generated responsive to a DC voltage on a DC bus. A magnitude reference signal may be generated responsive to a phase current of an AC bus and/or the DC voltage on the DC bus. Power is transferred between the AC and DC busses responsive to the phase reference signal and the magnitude reference signal. Generation of the phase reference signal may include generating a DC voltage error signal responsive to the DC voltage on the DC bus, generating a phase offset signal responsive to the DC voltage error signal, and generating the phase reference signal responsive to the phase offset signal. Generation of the magnitude reference signal may include generating a volt-amperes reactive (VAR) error signal responsive to the phase current and generating the magnitude reference signal responsive to the VAR error signal.

Abstract: A power supply apparatus includes first and second parallel-connected uninterruptible power supplies (UPSs), each including an AC/DC converter circuit and a DC/AC converter circuit having an input coupled to an output of the AC/DC converter circuit by a DC link, inputs of the AC/DC converter circuits of the first and second UPSs connected in common to an AC source and outputs of the DC/AC converter circuits of the first and second UPSs connected in common to a load. The first and second UPSs are configured to support a test mode wherein the first UPS is test loaded by transferring power from the output of the DC/AC converter circuit of the first UPS to the output of the DC/AC converter circuit of the second UPS. The first UPS may be configured to provide power to the load concurrent with test loading by the second UPS.

Abstract: An uninterruptible power supply (UPS) system includes at least three UPSs configured to be connected in parallel to a common load. The system further includes control circuitry configured to support at least two redundant groups among the UPSs and to support at least two redundant subgroups among at least one of the redundant groups of UPSs. In this manner, a nested redundancy may be provided.

Abstract: A closed loop power converter circuit of a UPS or other power supply includes a pulse width modulator circuit in a forward path of the closed loop power circuit. A compensation circuit provides pulse width commands to the pulse width modulator at a first rate. A feedback circuit digitally filters samples of an output of the closed loop power converter at a second rate greater the first rate and that provides the filtered samples to the compensation circuit. In some embodiments, the compensation circuit may be operative to compensate for the phase lag associated with a low pass output filter.

Abstract: A power converter apparatus, such as a double-conversion or line-interactive UPS, includes first and second DC voltage busses and a polyphase DC to AC converter circuit coupled to the first and second DC voltage busses and operative to generate a polyphase AC output. The apparatus further includes a control circuit operatively associated with the polyphase DC to AC converter circuit and configured to shift a DC voltage range of the first and second DC voltage busses with respect to a reference voltage responsive to a relationship among phase components associated with the polyphase AC output. The components may include, for example, actual phase voltages or modulation commands (e.g., count values) from which the polyphase AC output is generated. The reference voltage may be a neutral voltage, e.g., a voltage of an actual neutral of a load receiving the AC output or a synthetic neutral voltage.

Abstract: An uninterruptible power supply apparatus includes a first bidirectional power converter circuit having first and second ports and a second bidirectional power converter circuit having first and second ports. The apparatus further includes a DC link that couples the second port of the first bidirectional power converter circuit to the first port of the second bidirectional power converter circuit. A first load port is coupled to the second port of the second bidirectional power converter circuit and a second load port is coupled to the first port of the first bidirectional power converter circuit. The apparatus further includes a control circuit that is configured to control the first and second bidirectional power converter circuits such that each of the first and second bidirectional power converter circuits can generate and/or condition AC power at each of the first and second load ports.

Abstract: A closed loop power converter circuit of a UPS or other power supply includes a pulse width modulator circuit in a forward path of the closed loop power circuit. A compensation circuit provides pulse width commands to the pulse width modulator at a first rate. A feedback circuit digitally filters samples of an output of the closed loop power converter at a second rate greater the first rate and that provides the filtered samples to the compensation circuit. In some embodiments, the compensation circuit may be operative to compensate for the phase lag associated with a low pass output filter. For example, the compensation circuit may include a high pass IIR filter, operating at the first rate, that compensates for a pole associated with the low pass output filter, while the feedback circuit includes a low pass filter, operating at the second rate, that compensates for a frequency response peak associated with the high pass filter.

Abstract: Twelve-pulse rectifiers include a first controller that controls a first six-pulse rectifier, a second controller that controls a second six-pulse rectifier and a data network that couples the first controller and the second controller to exchange data therebetween. The first and second controllers preferably have a common architecture and preferably operate independently. Each controller preferably controls its associated six-pulse rectifier as a function of the current and/or voltage output of the associated six-pulse rectifier, preferably using conventional feedback control techniques. Moreover, the first controller also preferably controls the first six-pulse rectifier as a function of a second current at the second six-pulse rectifier output, and the second controller preferably controls the second six-pulse rectifier as a function of a first current at the first six-pulse rectifier output.

Abstract: Uninterruptible power supplies (UPSs), power conversion apparatus and power conversion methods are provided which may improve phase regulation of polyphase AC voltages in the presence of load imbalances. According to one embodiment, a UPS includes a DC voltage generating circuit that produces a DC voltage. A space vector domain controlled inverter couples the DC voltage generating circuit to an AC load, and produces a polyphase AC output voltage at the load by sensing a plurality of voltages at the load, transforming the plurality of sensed voltages according to a space vector (d-q) transformation to produce an output space vector, generating an error space vector from the output space vector and a reference space vector, and selectively coupling the DC voltage generating circuit to the load responsive to the error space vector. In this manner, a voltage control loop is closed in the d-q domain, which may improve per-phase regulation of the polyphase AC output.

Abstract: A parallel redundant power supply system which does not use any inter-unit signaling is obtained by using the AC output power level of a power system to coordinate load sharing. The necessary information for load sharing is derived solely from each power system's output power level in such a manner that the output of a power system is inherently phase locked to the output of other power systems to which it is connected in parallel. Each parallel connected power system designed in accordance with the invention includes means for generating an AC output voltage from a DC input power source, means for sampling either a DC input voltage from the DC input power source or the AC output voltage from the AC output voltage generating means to provide power level samples, and means for determining the AC output power of the AC output voltage generating means from the power level samples.

Abstract: A parallel redundant power supply system which does not use any inter-unit signaling is obtained by deriving all information necessary for a robust selective trip regime from the output signals of each respective power system. Each respective power system monitors its own power output and keeps a running average of its own performance to determine whether it is operating properly, rather than comparing itself to other units. The trip function is created by sampling the AC output voltage of the power system and multiplying an instantaneous difference in voltage (compared with a previous cycle) with the instantaneous difference in current (also compared with a previous cycle) of the power system's AC output power. If the two transients are in opposite directions, then the multiplicative product will be negative and indicative of a good power system. On the other hand, if the two transients are in the same direction, then the multiplicative product will be positive and indicative of a failed unit.

Abstract: An uninterruptible power supply including a transformer having a first input winding normally coupling an inverter AC source with a critical AC load, which transformer also includes a second input winding operable to supply power from a bypass source to the load in the event of malfunction of the inverter circuit. The inverter is of the four-quadrant pulse-width-modulated type, thereby to permit recharging of the battery which serves as the DC source to the inverter. An inductance is provided for varying the phase relationship between a utility voltage source and the inverter voltage to produce minimum real inverter current and the "break-even" operating conduction, and a step-up device is provided for increasing the utility voltage to further minimize the break-even inverter current required during normal operation, and to maximize the through-put efficiency.