Single-phase voltage source AC/DC converter and interconnection system

A single-phase voltage source AC/DC converter, comprising:

• a single-phase voltage source AC/DC converting circuit which has internal equivalent impedance as seen from an AC terminal, for converting power from a DC voltage source connected to a DC terminal to single-phase AC power to output from the AC terminal or for converting single-phase AC power from a single-phase AC source connected to the AC terminal to DC power to output from the DC terminal in accordance with a pulse width of a gate signal generated based on a PWM command;
• a phase difference generating circuit, which has a phase delay single-phase AC generator for delaying a phase of a single-phase AC output voltage at the AC terminal and generating a delay single-phase alternating voltage, for generating a phase difference voltage corresponding to phase difference between the single-phase AC output voltage at the AC terminal and an internal electromotive voltage of the single-phase voltage source AC/DC converting circuit based on the delay single-phase alternating voltage;
• a superior voltage control circuit to which a first axis voltage command for amplitude of the single-phase AC output voltage at the AC terminal and a second axis voltage command for a single-phase AC frequency at the AC terminal are input for outputting a voltage command signal generated so that the amplitude of the single-phase AC output voltage at the AC terminal approaches the first axis voltage command and a frequency command signal generated so that the single-phase AC frequency at the AC terminal approaches the second axis voltage command based on the first axis voltage command, the second axis voltage command, the phase difference voltage from the phase difference generating circuit and the single-phase AC output voltage at the AC terminal;
• a frequency control circuit for determining an electrical angle of the internal electromotive voltage of the single-phase voltage source AC/DC converting circuit to generate a generated electrical angle based on a reference frequency of a single-phase AC output frequency at the AC terminal, the frequency command signal from the superior voltage control circuit, and an output signal from the phase difference generating circuit;
• a subordinate voltage control circuit for outputting a signal generated so that the amplitude, the frequency, and the phase of the single-phase AC output voltage approach a synthesized value of a reference voltage of the single-phase AC output voltage at the AC terminal, the voltage command signal, and the generated electrical angle as the PWM command based on the single-phase AC output voltage at the AC terminal, the generated electrical angle of the frequency control circuit, and the voltage command signal from the superior voltage control circuit;
• and
• a command value arithmetic circuit to which a DC voltage command value to specify a voltage at the DC terminal is set and which obtains the second axis voltage command by detecting a DC voltage detection value being the voltage at the DC terminal and calculating difference between the DC voltage command value and the DC voltage detection value.