Abstract: A power supply unit includes: a plurality of secondary batteries connected in series; limiting resistors connected to individual electrodes of the plurality of secondary batteries; a voltage detection circuit detecting inter-terminal voltages of each of the plurality of secondary batteries based on potentials obtained from the plurality of secondary batteries through the limiting resistors; a control circuit specifying one of the secondary batteries to be discharged based on the inter-terminal voltages of the plurality of secondary batteries detected by the voltage detection circuit and sending a discharge instruction; and a discharge circuit allowing the specified secondary battery to discharge through the limiting resistors in response to the instruction from the control circuit.

Abstract: A digital signal transfer device generates from a modulating section (100) a modulated signal responsive to a digital input signal and transfers this to a demodulating section (200) through a pulse transformer (6). The demodulating section (200) generates from the modulated signal an output signal in which the digital input signal waveform is restored.

Abstract: A control apparatus for a power converter having a plurality of semiconductor switching devices that converts DC power into AC power and outputs three levels of voltages, including a command voltage generator configured to output a command voltage vector that represents a voltage to be output from the power converter, an integrator configured to calculate a difference integral vector by integrating a difference between the command voltage vector and an output voltage vector that represents a voltage command for the power converter, a difference vector calculator configured to calculate difference vectors by subtracting the command voltage vector from each of the possible output voltage vectors, a vector selector configured to select one of the possible output voltage vectors which corresponds to one of the difference vectors making the largest angle with the difference integral vector as the output voltage vector only if the difference integral vector exceeds a predetermined value, and a gate signal generator

Abstract: The controller for a power converter of the present invention, connects a transformer in series with the AC system, and has devices which find the voltage drop portion generated by the impedance of this transformer when introducing a voltage in series by an inverter into the above-mentioned AC system via this transformer, and control the output of the above-mentioned inverter to compensate this voltage drop portion.