Abstract: Two single phase uninterruptible power supplies are coupled together and controlled such that the two-phase output voltage is matched in frequency and phase with the electrical power provided by the electric utility. The phase difference between the electric utility power lines is measured and stored as a reference signal. When electrical power from the electric utility is lost, the stored reference signal is used to control a master and slave UPS to deliver two-phase power having the same frequency and phase.

Abstract: An AC to DC power converter comprises an imput filter for filtering the alternating current input and an output filter for filtering and smoothing the direct current power output to a load. The output alternating current of the input filter is rectified and electronically switched by buck and boost switching circuits at a frequency much higher than the frequency of the alternating line current input. The rectified line current is sensed and provided to a control circuit which controls the operation of the buck and boost switching such that the power line current will follow a predetermined reference voltage waveform.

Abstract: An AC to DC power converter comprises an input filter for filtering the alternating current input and an output filter for filtering and smoothing the direct current power output to a load. The output alternating current of the input filter is rectified and electronically switched by buck and boost switching circuits at a frequency much higher than the frequency of the alternating line current input. The rectified line current is sensed and provided to a control circuit which controls the operation of the buck and boost switching such that the power line current will follow a predetermined reference voltage waveform.

Abstract: A line isolated current detector for detecting low frequency peak to peak currents on a high frequency chopped line with a first series diode and resistor detecting positive waves and a second series diode and resistor detecting negative waves. First and second capacitors across the first and second resistors, respectively, temporarily store positive and negative detected waves. A third series diode and resistor connected in parallel across the first series diode and resistor and a fourth series diode and resistor connected in parallel across the second series diode and resistor allows faster charging and slower discharging of the capacitors. This allow the capacitors to charge waveforms quick enough to use a high frequency current transformer sensing a high frequency chopped line and discharge waveform slow enough to reconstruct the low frequency waveform before high frequency chopping to allow accurate current measurements of direct current or low frequency currents using a current transformer.

Abstract: An AC to DC power converter comprises an input filter for filtering the alternating current input and an output filter for filtering and smoothing the direct current power output to a load. The output alternating current of the input filter is rectified and electronically switched at a frequency much higher than the frequency of the alternating line current input. The rectified line current is sensed and provided to an integrator circuit whose output provides one control signal input of a pulse width modulator circuit. The pulse width modulator circuit drives the electronic switching an at the same time, provides an output to a discharge circuit for discharging the integrator circuit.

Abstract: An AC to DC power converter comprises an input filter for filtering the alternating current input and an output filter for filtering and smoothing the direct current power output to a load. The output alternating current of the input filter is rectified and electronically switched at a frequency much higher than the frequency of the alternating line current input. The rectified line current is sensed and provided to an integrator circuit whose output provides one control signal input of a pulse width modulator circuit. The pulse width modulator circuit drives the electronic switching and at the same time, provides an output to a discharge circuit for discharging the integrator circuit.