Patent ID: 9654019
Date: 2017-05-16
CPC Classifications: H02M,Y02B

Claim:
1. A method for controlling a direct power converter, said direct power converter comprising: a first power supply line; a second power supply line which is applied with a potential lower than said first power supply line is applied; a converter including an input side connected with a single-phase AC power supply and an output side connected with said first power supply line and said second power supply line, and performing single-phase full-wave rectification; a charge and discharge circuit located between said first power supply line and said second power supply line; and an inverter that converts a DC voltage between said first power supply line and said second power supply line into an AC voltage, said charge and discharge circuit comprising a buffer circuit including a capacitor and a first switch connected in series with said capacitor at a side close to said first power supply line between said first power supply line and said second power supply line, and providing and receiving power between said first power supply line and said second power supply line, and a boost circuit that boosts a rectified voltage from said converter to charge said capacitor, said buffer circuit providing power to said first power supply line and said second power supply line in a first period in which a cosine value to a value of twice a phase angle of an AC waveform output from said single-phase AC power supply is positive when the AC waveform is regarded as a sine value of the phase angle, and receiving power from said first power supply line and said second power supply line in a second period in which said cosine value is negative, said method comprising steps of: rendering said first switch conductive at a discharge duty to discharge said capacitor in said first period, and is rendered non-conductive in said second period; rendering said converter conductive at a rectifying duty; and rendering both a sum, in said first period, of a product of said rectified voltage and said rectified duty and a product of a both-end voltage of said capacitor and said discharge duty and a product, in said second period, of said rectified voltage and said rectifying duty to take a product of a crest value of an AC voltage of said single-phase AC power supply, a first value, and a second value, wherein said first value is half a value obtained by subtracting, from one, a product of a positive constant less than one and said cosine value, and said second value is a value obtained by dividing a virtual crest value, which is √{square root over (2)}-times an effective value of a first current input to the converter by a second current input to said inverter.