Voltage Supply Device having an Intermediate Circuit, A Power Converter and Braking Chopper

Abstract

A voltage supply device includes at least one intermediate circuit that has at least one intermediate circuit capacitor, at least one power converter, wherein the power converter is connected to the connections of the intermediate circuit such that the power converter can be supplied with electrical energy from the intermediate circuit capacitor, and includes at least one braking chopper that is connected to the connections of the intermediate circuit capacitor such that electrical energy from the intermediate circuit capacitor can be converted into thermal energy by the braking chopper, where the power converter is equipped with at least one semiconductor switch that is clocked at a higher rate, in particular based on SiC, while the braking chopper is equipped with at least one semiconductor switch that is clocked at a lower rate, in particular based on Si.

Claims

1.-9. (canceled)

10. A voltage supply device comprising: at least one intermediate circuit comprising at least one intermediate circuit capacitor; at least one power converter which is connected to connections of the at least one intermediate circuit such that at least one of (i) the power converter is supplied with electrical energy from the intermediate circuit capacitor (ii) the power converter feeds electrical energy into the at least one intermediate circuit; and at least one braking chopper which is connected to the connections of the at least one intermediate circuit capacitor such that electrical energy of the at least one intermediate circuit capacitor is convertible into thermal energy by the at least one braking chopper; wherein the power converter includes at least one semiconductor switch which is clocked at a relatively high rate, and the braking chopper includes a semiconductor switch which is clocked at a relatively low rate.

11. The voltage supply device as claimed in claim 10, wherein the power converter includes at least one semiconductor switch which is clocked at a relatively high rate and is based on SiC, and the braking chopper includes at least one semiconductor switch which is clocked at a relatively low rate and is based on Si.

12. The voltage supply device as claimed in claim 10, wherein the power converter includes at least one SiC MOSFET.

13. The voltage supply device as claimed in claim 11, wherein the power converter includes at least one SiC MOSFET.

14. The voltage supply device as claimed in claim 10, wherein the braking chopper includes at least one Si insulated-gate bipolar transistor.

15. The voltage supply device as claimed in claim 10, wherein at least one power converter is formed as a pulse width modulator.

16. The voltage supply device as claimed in claim 10, wherein at least one power converter is formed as an H bridge.

17. The voltage supply device as claimed in claim 10, wherein all power converters of the voltage supply device exclusively include semiconductor switches which are clocked at a relatively high rate and which are based on SiC.

18. The voltage supply device as claimed in claim 10, wherein all braking choppers of the voltage supply device exclusively include semiconductor switches which are clocked at a low rate and are based on Si.

19. The voltage supply device as claimed in claim 10, wherein the voltage supply device powers a railroad.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The invention will now be explained in more detail with reference to preferred exemplary embodiments. The drawings are exemplary and are intended to illustrate the inventive idea but not to restrict it in any way or even represent it conclusively, in which:

[0030] FIG. 1 shows a voltage supply device in accordance with the invention in a DC vehicle;

[0031] FIG. 2 shows a braking chopper in accordance with the invention with Si IGBT;

[0032] FIG. 3 shows a graphical plot of the current profile and voltage profile plotted against the time for the braking chopper of FIG. 2;

[0033] FIG. 4 shows a braking chopper with a SiC MOSFET in accordance with the invention; and

[0034] FIG. 5 shows a graphical plot of the current profile and voltage profile plotted against the time for the braking chopper from FIG. 4.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

[0035] FIG. 1 shows a voltage supply device in accordance with the invention that is connected to a power grid N, here a DC power grid. On the grid side, the voltage supply device comprises a line choke L and an intermediate circuit with an intermediate circuit capacitor Czk. In a vehicle that is supplied with an alternating voltage, the intermediate circuit is fed via an H bridge instead of the line choke, where the transformer that is usually mounted upstream would again constitute an inductor.

[0036] Viewed from the power grid N, the voltage supply device has an input impedance Zin. Two power converters S, e.g., pulse width inverters and/or H bridges, are connected to the terminals of the intermediate circuit capacitor Czk here. It would also be possible to connect further power converters as indicated by the dots. Furthermore, at least one braking chopper B is connected to the terminals of the intermediate circuit capacitor Czk. Other braking choppers B could also be connected.

[0037] The braking chopper B from FIG. 1 is illustrated in FIG. 2. The braking chopper B is connected in parallel with the intermediate circuit capacitor Czk, and the voltage Uzk,Si is present at the intermediate circuit capacitor Czk. The braking chopper B comprises a semiconductor switch H-Si that is based on Si and through which the current I-Si flows. The control signal for the semiconductor switch H-Si is illustrated to the left of the semiconductor switch H-Si as a rectangular function plotted over time. Furthermore, the braking chopper B has a resistor R and a free-wheel diode D parallel thereto.

[0038] In FIG. 3, the current profile and voltage profile are illustrated plotted against the time t for the braking chopper B from FIG. 2. The current profile shows the periodic profile of the current I-Si, resulting from the control signal, through the semiconductor switch H-Si. This results in the triangular profile of the voltage Uzk,Si in the intermediate circuit. The distance between the highest and the lowest voltage values denotes the voltage ripple U-Ri,Si (see double arrow) owing to the current I-Si.

[0039] If a semiconductor switch H-SiC that is based on SiC, such as a SiC MOSFET, were also to be installed in the braking chopper B, as in the power converters S, the rest of the circuit remains fundamentally as in FIG. 2, see FIG. 4. However, the control signal for the semiconductor switch H-SiC, which is again a square-wave function, could have a higher frequency than for the semiconductor switch H-Si which is based on Si in FIG. 2.

[0040] Correspondingly, the current I-SiC through the semiconductor switch H-SiC and the voltage Uzk,SiC in the intermediate circuit or at the intermediate circuit capacitor Czk would change correspondingly, see FIG. 5. In the figure, the current profile and voltage profile are illustrated again plotted against the time t for the braking chopper B from FIG. 4.

[0041] The current profile shows the periodic stepped profile of the current I-SiC, resulting from the control signal, through the semiconductor switch H-SiC. The current I-SiC has a higher frequency than the current I-Si in FIG. 3. Correspondingly, the triangular profile of the voltage Uzk,SiC in the intermediate circuit has a higher frequency than that of the voltage Uzk,Si in FIG. 3. The distance between the highest and the lowest voltage values denotes the voltage ripple U-Ri,SiC owing to the current I-SiC. Although the voltage ripple is lower than that in FIG. 3, the advantages which can be achieved thereby do not outweigh the disadvantage of higher procurement costs of the SiC semiconductor switch H-SiC.

[0042] Thus, while there have been shown, described and pointed out fundamental novel features of the invention as applied to a preferred embodiment thereof, it will be understood that various omissions and substitutions and changes in the form and details of the methods described and the devices illustrated, and in their operation, may be made by those skilled in the art without departing from the spirit of the invention. For example, it is expressly intended that all combinations of those elements and/or method steps which perform substantially the same function in substantially the same way to achieve the same results are within the scope of the invention. Moreover, it should be recognized that structures and/or elements and/or method steps shown and/or described in connection with any disclosed form or embodiment of the invention may be incorporated in any other disclosed or described or suggested form or embodiment as a general matter of design choice. It is the intention, therefore, to be limited only as indicated by the scope of the claims appended hereto.