Each of n uninterruptible power supplies connected in parallel includes m uninterruptible power supply modules connected in parallel between an input terminal and an output terminal. In each uninterruptible power supply module, a controller controls an inverter so that the current value of AC power supplied from the inverter to a load matches a first instruction value. The nm controllers are connected to one another to constitute an integrated controller. When a failure is detected in one of the m uninterruptible power supply modules in any one of the n uninterruptible power supplies, the integrated controller disconnects the failed uninterruptible power supply module and changes the first instruction value to a second instruction value so as to equalize the current values of AC power output from the inverters of the remaining normal uninterruptible power supply modules.

According to one aspect, embodiments of the invention provide a UPS comprising a plurality of inputs, a PFC converter configured to convert 3-phase input power into DC power, an inverter coupled to a positive DC bus and a negative DC bus and configured to convert the DC power received from the positive DC bus and the negative DC bus into output AC power, a first output configured to provide a first portion of the output AC power from the inverter to a load, a second output configured to provide a second portion of the output AC power from the inverter to the load, a third output configured to be selectively coupled to a neutral line via the inverter, and a controller configured to operate the inverter to generate current between the load and the neutral line via the third output and the inverter.

An uninterruptible power supply apparatus includes a switch, a first inductor, a direct current controlling unit, a first bridge arm, a second bridge arm and a third bridge arm. When the switch switches the first inductor coupled to an alternative current (AC) power, the AC power converts into a bus voltage via the first inductor, the first bridge arm and the second bridge arm, and converts into an output power via the second bridge arm and the third bridge arm. When the switch switches the first inductor coupled to a DC power, the DC power converts into the bus voltage via the DC controlling unit and the first inductor, and converts into the output power via the second bridge arm and the third bridge arm.

Systems and methods of controlling uninterruptible power supplies of electrical power systems are described. According to one aspect, an electrical power system can include a generator having a stator and a rotor, a power converter coupled to a rotor bus of the rotor, and a control system comprising one or more control devices, the one or more control devices configured to operate the power converter to provide an AC signal for a rotor bus. The system can also include an uninterruptible power supply (UPS). The UPS can include a power storage element configured to receive and store electrical power, and configured to power the control system during a power failure, and, a health check circuit configured to verify a health status of the power storage element, and including a health check disable component configured to disable the health check circuit during the power failure.

A control system and hardware with a controllable input relay provides two different modes of operationuninterruptable power supply (UPS) and mixed energy-AC support. For each operation mode, regulation of the DC-Link and neutral point balancing is guaranteed even for non-linear unsymmetrical AC loads. Moreover, in the mixed energy-AC support mode, unity power factor operation of AC input source, seamless zero current crossing, and very low total harmonic distortion (THD) is provided by the applied non-linear control algorithm. The system has a higher efficiency in comparison to other AC-DC-AC converters with smaller size and weight because of the elimination of the typical balancing circuit.

A UPS circuit, comprising a rectification phase leg (PL1) for rectification, which is used for converting a received alternating current into a direct current; inversion phase legs (PL21, PL22, PL23) for inversion, which are used for inverting the direct current output by the rectification phase leg into an alternating current; a failure detection device (D) which is used for detecting whether an inversion phase leg has failed; a redundant inversion phase leg (PL2a), with an input end thereof being connected to an output end of the rectification phase leg; and a control device which is used for receiving a signal sent by the failure detection device and is also used for enabling the redundant inversion phase leg to replace the inversion phase leg which has failed when a failure occurs.

A power converter includes an AC power input line, an AC power output line, a neutral line, a first capacitor connected to the AC power input line and the neutral line, a first inductor connected to the AC power input line, a first bus, a second bus, a second capacitor connected to the first bus and the second bus, a first half-bridge circuit connected to the first bus, the second bus and the first inductor, a second half-bridge circuit connected in series with the first half-bridge circuit and connected to the AC power output line, a third half-bridge circuit connected in series with the first half-bridge circuit, a second inductor connected to the third half-bridge circuit and the neutral line, and a controller.

A three arm rectifier and inverter circuit is provided. The three arm rectifier and inverter circuit includes an input end, a rectifier circuit and an inverter circuit. The input end is utilized for inputting an input voltage and an input current. The rectifier circuit includes a low frequency switching arm. The low frequency switching arm is coupled to the input end for receiving the input voltage and the input current and generating a trigger signal. The inverter circuit includes a full bridge switch. The full bridge switch is coupled to the low frequency switching arm for receiving the trigger signal and adjusting an output voltage.

In an uninterruptible power supply apparatus, AC current, which includes a feedback component having a value corresponding to deviation between terminal-to-terminal voltage of a capacitor and reference voltage, and a feed forward component obtained by multiplying load current by a gain, is passed into a converter such that the terminal-to-terminal voltage of the capacitor becomes the reference voltage. The gain is set to a first gain in an inverter power feed mode and a bypass power feed mode, and the gain is set to a second gain smaller than the first gain in a switching period of switching between the inverter power feed mode and the bypass power feed mode, to prevent the terminal-to-terminal voltage of the capacitor from exceeding an upper limit voltage in a lap power feed mode.

A power system including a rectifier and an inverter. The rectifier has a plurality of phase input terminals and a plurality of rectifier output terminals that provide respective rectified outputs, rectifier circuitry that rectifies the signals on the phase input terminals to generate respective rectified outputs on the rectifier output terminals, a rectifier neutral to receive a power source neutral, and capacitors connected between the rectifier neutral and the rectifier output terminals. The inverter includes a respective plurality of inverter input terminals respectively connected to the rectifier output terminals, a plurality of inverter output terminals, and an inverter neutral. The rectifier neutral and the inverter neutral are coupled by a conductor to form a same neutral.