Power conversion apparatus, power conversion method, motor system, and two-phase induction motor

#One or more exemplary embodiments disclosed herein relate generally to a power conversion apparatus and a power conversion method, and particularly to a technique of converting single-phase AC power into two-phase AC power and a two-phase induction motor driven by two-phase AC power obtained by converting single-phase AC power using such a technique.

#Conventionally, power conversion apparatuses including a matrix converter have been in practical use (see Patent Literature (PTL) 1 and PTL 2, for example).

#FIG. 24 is a circuit diagram of a matrix converter 200 disclosed in PTL 1. To drive a three-phase motor 203 using a single-phase AC power supply 201, the matrix converter 200 directly converts an input AC voltage supplied from the single-phase AC power supply 201 into a three-phase output AC voltage using bidirectional switches 202a to 202f, and supplies the output AC voltage of each phase to a winding of a corresponding phase of the three-phase motor 203.

#These and other advantages and features will become apparent from the following description thereof taken in conjunction with the accompanying drawings, by way of non-limiting examples of embodiments disclosed herein.

#FIG. 1A is a block diagram illustrating an example of a functional configuration of a motor system including a power conversion apparatus according to Embodiment 1.

#FIG. 1B is a block diagram illustrating another example of a motor system according to Embodiment 1.

#A power conversion apparatus according to an exemplary embodiment disclosed herein is a power conversion apparatus which converts an input voltage which is a single-phase AC voltage into output voltages forming a two-phase AC voltage, the power conversion apparatus including: a pair of input terminals to which the input voltage is applied; a pair of first output terminals which output one of the output voltages as a first-phase output voltage; a pair of second output terminals which output the other of the output voltages as a second-phase output voltage; four first bidirectional switches each corresponding to a different combination of one of the paired input terminals and one of the paired first output terminals to switch connection and disconnection between the corresponding input terminal and first output terminal according to a corresponding one of first control signals; four second bidirectional switches each corresponding to a different combination of one of the paired input terminals and one of the paired second output terminals to switch connection and disconnection between the corresponding input terminal and second output terminal according to a corresponding one of second control signals; a target voltage designating unit configured to designate a first target voltage representing, using one of AC voltages forming a two-phase AC voltage, consecutive target values of the first-phase output voltage and a second target voltage representing, using the other of the AC voltages forming the two-phase AC voltage, consecutive target values of the second-phase output voltage; a control signal generating unit configured to (i) generate the first control signals to cyclically connect and disconnect the pair of the input terminals and the pair of the first output terminals via the first bidirectional switches at a duty cycle corresponding to a ratio of an instantaneous absolute value of the first target voltage to an instantaneous absolute value of the input voltage during a time period in which the instantaneous absolute value of the input voltage is greater than the instantaneous absolute value of the first target voltage, and (ii) generate the second control signals to cyclically connect and disconnect the pair of the input terminals and the pair of the second output terminals via the second bidirectional switches at a duty cycle corresponding to a ratio of an instantaneous absolute value of the second target voltage to the instantaneous absolute value of the input voltage during a time period in which the instantaneous absolute value of the input voltage is greater than the instantaneous absolute value of the second target voltage; and a driver which supplies the generated first control signals to the first bidirectional switches and the generated second control signals to the second bidirectional switches.

#With such a configuration, the single-phase AC voltage can be converted into the two-phase AC voltage through the switching control by the bidirectional switches. As a result, the two-phase AC voltage can be generated from the single-phase AC voltage with high efficiency without using a capacitor having a possibility of undermining the long-term reliability of the apparatus.

#The target voltage designating unit may be configured to designate the first target voltage and the second target voltage using AC voltages forming a two-phase sinusoidal AC voltage which have: an amplitude 1/√2 times smaller than an amplitude of the input voltage; a frequency identical to a frequency of the input voltage; and phase differences of +45 degrees and −45 degrees relative to the input voltage.