Energy recovery device in a variable-frequency drive
A variable-frequency drive that includes a DC power supply bus with a positive line and a negative line, and an inverter module powered by the DC bus for supplying a variable voltage to an electric load. The inverter includes a first DC/DC converter including output terminals connected in series on the positive line of the DC bus, a second DC/DC converter including input terminals connected between the positive line and the negative line of the DC bus, a filtering capacitor connected in parallel to the input terminals of the first converter and to the first output terminals of the second converter, and an electric power storage module connected in parallel to the second output terminals of the second converter.
1. A variable speed drive comprising:
a DC power supply bus comprising a positive line and a negative line;
an inverter module supplied by the DC bus so as to provide a variable voltage to an electric load;
a first DC/DC converter comprising input terminals and output terminals, the output terminals of the first converter being connected in series on the positive line of the DC bus;
a second DC/DC converter comprising input terminals, first output terminals, and second output terminals, the input terminals of the second converter being connected between the positive line and the negative line of the DC bus;
a filtering capacitor connected in parallel to the input terminals of the first converter and to the first output terminals of the second converter; and
an electrical energy storage module connected in parallel to the second output terminals of the second converter.
2. The variable speed drive as claimed in claim 1 , wherein the electrical energy storage module comprises one or more super-capacitors.
3. The variable speed drive as claimed in claim 1 , wherein the electrical energy storage module comprises one or more super-capacitors in series with a filtering inductor.
4. The variable speed drive as claimed in claim 1 , further comprising a filtering assembly linked between the positive line and the negative line of the DC bus, the filtering assembly comprising two capacitors linked in series, wherein one of the two capacitors of the filtering assembly is the filtering capacitor.
5. The variable speed drive as claimed in claim 1 , wherein the first DC/DC converter is a non-isolated monodirectional converter that comprises an active switch and a passive switch.
6. The variable speed drive as claimed in claim 5 , wherein the passive switch of the first converter comprises a diode connected between the output terminals of the first converter, and wherein an assembly formed by the active switch and the passive switch linked in series is connected in parallel to the input terminals of the first converter.
7. The variable speed drive as claimed in claim 1 , wherein the second converter comprises a non-isolated bidirectional converter that comprises a switching cell comprising four active switches linked in series between the positive line and the negative line of the DC bus, the cell further comprising a central mid-point between the second and the third active switch, a high mid-point between the third and the fourth active switch, and a low mid-point between the first and the second active switch.
8. The variable speed drive as claimed in claim 7 , wherein the positive line of the DC bus and the central mid-point form the first output terminals of the second converter, and wherein the high mid-point and the low mid-point form the second output terminals of the second converter.
9. The variable speed drive as claimed in claim 8 , wherein the second converter further comprises two voltage control diodes mounted in series between the positive line of the DC bus and the central mid-point, and a load capacitor linked in series between the low mid-point and a mid-point of the two voltage control diodes.