Synchronization detecting circuit and automatic synchronous parallelization apparatus

An automatic synchronous parallelization apparatus comprising:

• a synchronization detecting circuit comprising:
• a detection unit that detects a value relating to a frequency difference between an external single-phase AC voltage source that is a parallelization target of a single-phase voltage-type DC-to-AC converting device performing an autonomous parallel operation based on a 1st-axis voltage command value, which is used for adjusting an amplitude of an output single-phase AC voltage, and a 2nd-axis voltage command value, which is used for adjusting a frequency, and the single-phase voltage-type DC-to-AC converting device and a value relating to an effective value of a voltage of the external single-phase AC voltage source;
• a voltage amplitude command value generating circuit that generates the 1st-axis voltage command value for which the effective value of the single-phase AC voltage of the single-phase voltage-type DC-to-AC converting device approaches an effective value of a voltage of the external single-phase AC voltage source by using the value relating to the effective value of the voltage that is detected by the synchronization detecting circuit and inputs the 1st-axis voltage command value to the single-phase voltage-type DC-to-AC converting device;
• and
• a frequency command value generating circuit that generates the 2nd-axis voltage command value for which the frequency of the single-phase AC voltage of the single-phase voltage-type DC-to-AC converting device becomes a frequency that is shifted from the frequency of the external single-phase AC voltage source by an arbitrary frequency by using the value relating to the frequency difference that is detected by the synchronization detecting circuit and inputs the 2nd-axis voltage command value to the single-phase voltage-type DC-to-AC converting device,
• wherein the voltage amplitude command value generating circuit comprises:
• a voltage system subtractor that subtracts the value relating to the effective value of the single-phase AC voltage by the single-phase voltage-type DC-to-AC converting device from the effective value of the voltage of the external single-phase AC voltage source that is detected by the synchronization detecting circuit;
• a voltage system integrator that integrates a value acquired through subtraction of the voltage system subtractor;
• and
• a voltage system adder that generates the 1st-axis voltage command value by adding an initial value of the single-phase AC voltage of the single-phase voltage-type DC-to-AC converting device prior to start of automatic parallelization control with the external single-phase AC voltage source and the value acquired through integration of the voltage system integrator.