Rectifying circuit and method for an unbalanced two phase DC grid
The present invention relates to a rectifying method and circuit using a magnetically coupled double flyback converter. The main circuit can consist of only one transformer, two switches, two low frequency diodes, two high frequency diodes and two capacitors, so that power is inherently distributed according to the demand on the two DC phases and a sinusoidal grid current can be obtained without sophisticated control.
1. A rectifying circuit for providing an interface between an alternating current supply grid and a direct current grid, said circuit comprising:
a transformer having a first and second primary windings and first and second secondary windings;
a first half-wave rectifier for outputting positive half-waves of an AC signal supplied from said AC supply grid;
a second half-wave rectifier for outputting negative half-waves of said AC signal;
a first controlled switch for continuously switching on and off supply of said positive half-waves to said first primary winding during each of said positive half-waves;
a second controlled switch for continuously switching on and off supply of said negative half-waves to said second primary winding during each of said negative half-waves;
a first rectifier circuit connected to said first secondary winding of said transformer for generating a first DC output voltage based on a discharge current of said transformer during a switched-off state of said first and second controlled switches; and
a second rectifier circuit connected to said second secondary winding of said transformer for generating a second DC output voltage based on a discharge current of said transformer during said switched-off state of said first and second controlled switches.
2. The circuit according to claim 1 , wherein said first and second primary windings are both connected with one end to a neutral line of said AC grid, and wherein said first and second secondary windings are both connected with one end to ground potential of said DC grid.
3. The circuit according to claim 2 , wherein said neutral line is directly connected to said ground potential.
4. The circuit according to claim 1 , wherein said first and second rectifier circuits each comprise one diode and one capacitor only.
5. The circuit according to claim 1 , wherein said first and second half-wave rectifiers each comprise one diode only.
6. The circuit according to claim 1 , further comprising a first filter capacitor connected in parallel to the output of said first half-wave rectifier and a second filter capacitor connected in parallel to the output of said second half-wave rectifier.
7. The circuit according to claim 1 , wherein said circuit is adapted to generate said first and second DC voltages with same absolute values.
8. The circuit according to claim 1 , wherein a switching frequency of said first and second controlled switches is selected in the 10 or 100 kHz range.
9. A method of providing an interface between an alternating current supply grid and a direct current grid, said method comprising the steps of:
rectifying an AC signal supplied from said AC supply grid to generate positive half-waves of said AC signal;
rectifying said AC signal to generate negative half-waves of said AC signal;
continuously switching on and off supply of said positive half-waves to a first primary winding of a transformer during each of said positive half-waves;
continuously switching on and off supply of said negative half-waves to a second primary winding of said transformer during each of said negative half-waves;
generating a first DC output voltage based on a discharge current in a first secondary winding of said transformer during a switched-off supply state of said positive and negative half-waves; and
generating a second DC output voltage based on a discharge current in a second secondary winding of said transformer during a switched-off supply state of said positive and negative half-waves.