Constant voltage constant frequency inverter and method for controlling the same

A constant voltage constant frequency inverter comprising:

• main circuit means for converting a DC input voltage to an AC output voltage which has a frequency;
• voltage control means for controlling the output voltage of said main circuit means;
• frequency control means for controlling the frequency of the output voltage of said main circuit means so that the frequency is maintained at a reference frequency;
• input voltage detecting means for detecting the DC voltage inputted to said main circuit means;
• and
• adjusting means for reducing a cross current flowing through said main circuit means by adjusting the reference frequency in accordance with an output of said input voltage detecting means, said adjusting means including comparing means for comparing the detected DC voltage with a predetermined value, and voltage adjuster means for controlling said frequency control means so that the reference frequency is increased by an amount corresponding to the difference between the detected DC voltage and the predetermined value when the detected DC voltage exceeds the predetermined value.

A method for controlling a constant voltage constant frequency inverter having a main circuit for converting a DC input voltage to an AC output voltage which has a frequency, said method comprising the steps of:

• controlling the frequency of the output voltage of said main circuit so that the frequency is maintained at a reference frequency;
• detecting the output voltage of said main circuit;
• detecting an output current of said main circuit;
• computing effective power outputted from or inputted to said main circuit based on the output voltage and the output current of said main circuit;
• and
• adjusting the reference frequency in accordance with the effective power to reduce a cross current flowing through said main circuit, said step of adjusting including the steps of increasing the reference frequency when the effective power is flowing into the main circuit and decreasing the reference frequency when the effective power is flowing out of said main circuit.

A method for controlling a constant voltage constant frequency inverter having a main circuit for converting a DC input voltage to an AC output voltage which has a frequency, said method comprising the steps of:

• controlling the frequency of the output voltage of said main circuit so that the frequency is maintained at a reference frequency;
• detecting the DC voltage inputted to said main circuit;
• and
• adjusting the reference frequency in accordance with the detected DC voltage to reduce a cross current flowing through said main circuit, said step of adjusting including the steps of comparing the detected DC voltage with a predetermined value, and increasing the reference frequency by an amount corresponding to the difference between the detected DC voltage and the predetermined value when the detected DC voltage exceeds the predetermined value.