Patent ID: 8488344

Claim:
An electrical power conversion apparatus for an electric railroad car, comprising: a converter for converting AC power produced between a line and a rail into DC power; a capacitor connected in parallel with the converter on the DC side thereof; a DC voltage measurement unit for measuring a voltage across the capacitor; an inverter including switching elements, connected in parallel with the capacitor, for converting DC power into AC power of an arbitrary frequency; and a control microprocessor into which DC voltage values each measured by the DC voltage measurement unit are inputted in a predetermined sampling period, for controlling the inverter, wherein the control microprocessor includes a voltage control unit for controlling a voltage amplitude of the AC power that the inverter outputs; a frequency control unit for controlling the frequency of the AC power that the inverter outputs; a DC voltage-value memory unit for storing the DC voltage values at predetermined sampling time-points going back from the latest; a DC voltage-value estimation unit for predicting a DC voltage estimate value at a predetermined time after a next sampling time-point using the DC voltage values at the predetermined sampling time-points going back from the latest, stored in the DC voltage-value memory unit; and a beat suppression unit into which the DC voltage estimate value predicted by the DC voltage-value estimation unit is inputted, for operating on either one or both of the voltage control unit and the frequency control unit so as to curb variation of the AC power that the inverter outputs, due to a ripple caused on the DC side of the inverter, and wherein the DC voltage-value estimation unit obtains a predetermined-order polynomial that approximates the DC voltage values stored in the DC voltage-value memory unit, and, using the polynomial, predicts a DC voltage estimate value at a predetermined time after the latest sampling time-point, and the beat suppression unit operates on the frequency control unit so that the frequency becomes smaller when the DC voltage estimate value predicted by the DC voltage-value estimation unit becomes larger, and the frequency becomes larger when the DC voltage estimate value becomes smaller.