According to one aspect, embodiments of the invention provide a power supply system comprising a power factor correction circuit coupled to an input and configured to draw input current from the input, an inverter coupled to an output and configured to provide output current to the output, a bus coupled to the power factor correction circuit and the inverter, and a switching circuit, the switching circuit configured to direct power from the power factor correction circuit to the inverter in a first mode of operation and from the bus to the inverter in a second mode of operation, wherein the switching circuit includes a neutral clamp circuit coupled to the power factor correction circuit and the inverter, the neutral clamp circuit configured to control a level of the input current drawn by the power factor correction circuit and a level of the output current provided by the inverter.

A circuit for selecting between a primary power source and a back-up power source is provided in one embodiment. The circuit includes a first port configured to be coupled to a primary power source, a second port configured to be coupled to a back-up power source, a third port configured to be coupled to provide power to a load. The circuit also includes first and second power field effect transistors (FET) coupled between the second port and the third port, a third power FET coupled between the first port and the third port, and a dual ideal diode-OR controller coupled between the second and third power FETs to selectively turn on and off the second and third power FETs. The circuit further includes an opto-isolator coupled to a control input of the first power FET and a controller, coupled to the opto-isolator, that selectively turns on and off the opto-isolator.

When a power outage occurs, an uninterruptable power supplies may lose all grid connections including a neutral connection which may be connected to ground. To avoid the loss of a ground connection to the power circuits of the UPS, a switch unit may be used to selectively connect a neutral conductor of the circuit to a ground terminal. The switch unit may comprise a power relay, a fast switch device (FSD), and a controller. The power relay and FSD may be connected in series between the neutral conductor of the circuit and a ground terminal. The controller may be configured to: close the FSD when the voltage between ground and neutral (Vng) goes above a first threshold, open the FSD when the voltage between any grid connection and neutral (Vg) goes above a second threshold, and close the FSD when Vg is below the second threshold.

A control system and methods for a multilevel power converter are provided. The converter includes a rectifier coupled to a DC link having a midpoint coupled to electrical ground that divides the DC link into two halves. The control system is configured to generate a reference current command for controlling an output of the rectifier, the reference current command generated based on a difference between a desired and measured DC link voltage value. The system is also configured to determine a zero-sequence current component of input current supplied to the multilevel power converter, wherein the zero-sequence current component is associated with non-linearities in said multilevel power converter that cause ground current injection into the input current by the rectifier. The system is further configured to subtract the determined zero-sequence current component from the reference current command to reduce the ground current injected into the input current by the rectifier.

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.

According to one aspect, embodiments of the invention provide a power supply system comprising an input, an output, a neutral point, a converter configured to convert input AC power into converted DC power, the converter including a first converter switch, a positive DC bus configured to receive the converted DC power, a negative DC bus configured to receive the converted DC power, an inverter configured to convert DC power from the positive and negative DC busses into output AC power, the inverter including a first inverter switch, and a clamp circuit coupled to the positive DC bus and coupled across at least one of the first converter switch and the first inverter switch, the clamp circuit configured, during switching operation, to clamp a voltage across the first converter switch and/or the first inverter switch to a voltage level of the positive DC bus or the negative DC bus.

The present specification relates to a power supply device and a power supply system which enable uninterruptible power supply, wherein a circuit breaker is provided in a power bus to which a plurality of power supply devices are connected, so as to switch on/off the connected power supply devices, and thus the UPS function can be performed among the plurality of power supply devices by opening or closing the circuit breaker according to various situations occurring in the system to control power reception and supply.

An uninterruptible power supply adapted to be connected between an AC line and a load, comprising a battery system, an inverter, and a transformer, and a controller. The battery system stores battery power. The inverter is operatively connected to the battery system. The transformer is operatively connected to the AC line, the load, and an inverter winding operatively connected to the inverter. The controller controls the inverter to supply power to the primary winding using battery power stored in the battery system based on a cost value indicative of reduction of life of the battery system.

A power supply system includes an input terminal that receives electrical energy from an alternating current source and an output terminal connected to a load. Current and voltage measuring devices measure current and voltage values of the electrical energy received from the alternating current source. Three phase conductors and a neutral conductor connect the input terminal to the output terminal. A power converter includes a direct current terminal and an alternating current terminal that is coupled to the load. The power converter outputs alternating voltage. A DC link connects the direct current terminal to a chargeable electrical energy storage system. A control unit controls the alternating voltage output by the power converter onto the alternating current terminal, which is connected to the phase conductors in parallel with the alternating current source. The control unit uses the current and voltage values to control the alternating voltage output by the power converter.

A three-phase UPS control method and apparatus, and a three-phase uninterruptible power supply resolve a problem that after a zero wire is lost, when a current control method is applied to a three-phase UPS using a three-level topology, a 0-axis direct-current modulated wave results in that positive and negative buses are unbalanced. The method includes: determining that a zero wire of a three-phase uninterruptible power supply is lost; using an alternating current whose frequency is a harmonic frequency of mains as a 0-axis reference current; and generating a 0-axis modulated wave according to a difference between the 0-axis reference current and a 0-axis sampling current, to control a rectifier in the three-phase uninterruptible power supply to convert a received alternating current to a direct current.