EP1344304A2

EP1344304A2 - Converter with integrated link-circuit capacitors

Info

Publication number: EP1344304A2
Application number: EP01270943A
Authority: EP
Inventors: Thomas Paesler; Kurt Reutlinger
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2000-12-13
Filing date: 2001-12-08
Publication date: 2003-09-17
Also published as: WO2002049196A2; WO2002049196A3; DE10062075A1; JP2004516781A

Abstract

The invention relates to a converter, in particular a DC-AC converter, connected to a voltage link circuit, comprising a charge store. Said converter comprises a half-bridge, or a bridge circuit, forming a module, arranged in a housing. The charge store is divided into several link circuit capacitors, of which one, several or all form integrated components of the module.

Description

Converter with integrated DC link capacitors

The invention relates to a converter according to the preamble of the main claim. This is preferably a DC-AC converter.

State of the art

In converter technology, it is already known to use intermediate circuit converters with a voltage intermediate circuit. The intermediate voltage circuit can also be formed by a direct voltage network, which contains, for example, the on-board electrical system battery of a motor vehicle. The voltage intermediate circuit also has an intermediate circuit capacitor, using which pulse currents are generated or the alternating current is taken over. Such pulse currents occur in all clocked converter bridges. In the case of two-stage converters, a Umrichtexbrücke consists of one or more half bridges, which alternately connect the output to either the positive or the negative DC link potential. For this purpose, a half bridge has one or more high-side switches for the connection to the positive intermediate circuit potential and one or more low-side switches for the connection to the negative DC link potential. A high-side switch and a low-side switch together form a half bridge.

In order to obtain a compact structure, it is already known to combine the two switches of a half bridge in one housing, in a so-called module. It is also already known to combine all three half bridges of a three-phase converter in one module.

In such converters, the connecting lines between the intermediate circuit capacitor and the converter bridge are loaded by the rapid current changes that occur. If the high-side switch of a half-bridge is switched on and the low-side switch is switched off, then the output of a half-bridge is at the positive intermediate circuit potential and the output current is taken from the intermediate circuit. If the half bridge switches, the output is at the negative intermediate circuit potential and the current in the intermediate circuit, which flows from the intermediate circuit capacitor to the converter bridge, must drop to the value zero. The resulting large change in the current dl / dt leads to an overvoltage on the connecting line between the intermediate circuit capacitor and the semiconductor switches of the half-bridge. This overvoltage can assume considerable values to which the semiconductor switches are to be dimensioned.

In order not to overload the semi-conductor switches with regard to their dielectric strength, it is already known to slow down the switching processes and thereby to reduce the current changes dl / dt that occur. On however, such a procedure leads to considerable losses in the semiconductor switches.

Furthermore, efforts are made to keep the inductance between the intermediate circuit capacitor and the converter bridge as small as possible. For this purpose, it is known to use so-called busbar assemblies, on the basis of which the connecting lines between the semiconductor switches and the intermediate circuit capacitor are designed to be low-inductance. Furthermore, it is already known for this purpose to position the intermediate circuit capacitor spatially in the area of the converter bridge. However, this is only possible to a certain extent, since the intermediate circuit capacitor itself has large dimensions.

From DE 197 09 298 C2 starter systems for an internal combustion engine are known which have a DC voltage intermediate circuit inverter. This includes a DC-AC converter, a short-term energy storage and an on-board network

DC converter. The components mentioned are controlled by a control device. This specifies the amplitude, the phase and the frequency of the three-phase current to be supplied to the starter of the vehicle. The control device specifies the amount of current, the direction of current and the amount of the voltage step-up or step-down to the DC-DC converter. Furthermore, the control device specifies to a consumer control device what amount of current it can draw from the short-term energy store and, if appropriate, what voltage difference is to be overcome. During the starting process, the starter motor requires energy from the short-term energy storage. To During the starting process, it works as a generator and supplies energy to the intermediate circuit via the converter. The DC voltage converter on the electrical system side is designed as a bidirectional converter, in order to be able to transfer electrical energy from the on-board electrical system battery to the DC link for the starting process or its preparation, and to transfer energy from the DC link to the low voltage side during generator operation of the starter motor, in order to transfer consumers there To feed the on-board electrical system and to charge the on-board electrical system battery.

Advantages of the invention

In contrast, a converter according to the invention has the

The advantage of being parasitic due to the division of the charge storage of the intermediate circuit into several intermediate circuit capacitors and the integration of one, several or all of these intermediate circuit capacitors into the half-bridge or bridge module

Line inductances can be kept small.

If one or more of the DC link capacitors are integrated into the module and an additional external DC link capacitor is used, then this can be done

Capacity be dimensioned smaller than in the prior art.

If all DC link capacitors are integrated in the module, an additional external DC link capacitor can be omitted. Furthermore, the overvoltages occurring at the semiconductor switches during the switching process can be kept small by the invention. Furthermore, high switching speeds with low switching losses are made possible in the semiconductor switches, since the inductance between the switching elements and the intermediate circuit capacitance is minimized because of the spatial proximity. The busbar used in known inverters between the intermediate circuit capacitor and the semiconductor switches can be reduced in size or eliminated entirely.

Preferably, two or more capacitors, which extend parallel to the complete half bridge, are integrated into the module per half bridge. This reduces the interference radiation from the converter bridge.

drawing

The invention is illustrated in the drawing and explained in more detail in the following description. 1 shows a representation of a half-bridge according to an exemplary embodiment for the invention, FIG. 2 shows a simplified module representation of the half-bridge according to FIG. 1, FIG. 3 shows an equivalent circuit diagram of the half-bridge module, FIG. 4 shows a first exemplary embodiment for a converter, and FIG. 5 shows a second exemplary embodiment for a Converter and Figure 6 shows a third embodiment of a converter, only the components necessary for understanding the invention are shown in the figures. description

FIG. 1 shows an illustration of a half bridge according to an exemplary embodiment of the invention. The half bridge is realized in the form of a module M arranged in a housing. In addition to a high-side switch Tl, a low-side switch T2 and inverse diodes Dl and D2, capacitors C _H s, C _LS , C _K ι and C _{ZK2 are also} integrated in this module M. The capacitors C _H s and C _LS are each arranged in parallel with an inverse diode and a switch. They serve to mitigate the negative effects of the current stall behavior of the inverse diodes during the switching processes. A current stall means a very rapid change in current, which leads to corresponding overvoltages caused by the parasitic inductances. The two other capacitors C _ZK ι and C _ZK 2 _/ which are each arranged parallel to the entire half bridge and thus directly on the

DC link voltage are used as block capacitors for the DC link. At the same time, they are intended to filter out high-frequency current components, which leads to an improvement in electromagnetic compatibility (EMC). Furthermore, these two capacitors C _ZK1 and C _Z κ ₂ also take over the task of a conventional intermediate _circuit capacitor in whole or in part.

Two or more capacitors of different capacitance are preferably connected in parallel as block capacitors. Since capacitors of different capacitance have different frequency responses, broadband filtering of the high-frequency current components is possible. Consequently, the capacitors C _Hs and C _LS shown in FIG. 1 mitigate the overvoltages due to the reverse current stall of the inverse and reverse diodes and the capacitors C _Z κι and Czκ ₂ improve the electromagnetic compatibility, the latter capacitors. also take over the task of a conventional intermediate circuit capacitor in whole or in part.

FIG. 2 shows a simplified schematic module representation of the half-bridge according to FIG. 1. The intermediate _circuit capacitors C _ZK ι and C _ZK2 are described by the capacitor C _zκ . In series with this capacitor, an ohmic resistance R _{D is} shown, which represents the internal resistance or damping resistance of the capacitor. The inductance L _{zκ of} the connection connection forms a resonant circuit together with the capacitor C ₂ κ.

The inductance of the connecting line to the intermediate _circuit and the permissible overvoltage at the semiconductor _{switches T1} and T2 are important for the size of the capacitor C _zκ required in the module M.

FIG. 3 shows an equivalent circuit diagram of the

Half-bridge module. This shows that the half-bridge module is a damped series resonant circuit11.

The voltage U _Ven tii at the semiconductor switches is composed of the capacitor voltage U _c plus the voltage drop U _R at the damping resistor nd R _D. In order not to destroy the semiconductor switches, the voltage is the load current can be assumed to be constant. The starting values of the energy storage are therefore:

Uc (0) = U _zκ I _L (0) = I _LaS t-

To calculate the minimum capacitance _value C _zκ , _m in for the capacitor C _zκ , in which it is ensured that the maximum permitted voltage at the semiconductor switches is not exceeded, it is assumed that there is an infinitely high switching speed, that is to say that the switch connected Switch off the load current in an infinitely short time. In real conditions, however, this switching time is finite. The current rise in the capacitor is given by this switching time.

The voltage at the semiconductor _switches rises from U ₂ κ before the switching process to U _zκ + R * I _{L s} t after the switching process. The current drop after the switching process is:

branch

The voltage increase after the switching process is:

In the range of resonant vibrations up to the aperiodic limit case (0 <D <1) the minimum capacitance _value C _{zκ is calculated} , min ie follows: In the range of resonant vibrations up to the aperiodic limit case (0 <D <1) the minimum capacitance _value C _zκ , _m i _{n is} calculated as follows:

The overvoltage in this area is only determined by the capacitor C _z and not by the

Damping resistance R _D. Low-damped capacitors cause vibrations between the inductors and the capacitors. With low damping, the resonant vibrations of two switching processes can overlap, which results in larger overvoltages. With large damping resistances (D>1; corresponds to the non-resonant case), the overvoltage depends on the ohmic voltage drops. As a favorable damping factor

D = RD - ΛJCZK I LZK

a numerical value of 0.5 can be considered.

FIG. 4 shows a first exemplary embodiment of a converter. Several half bridges are provided, each of which is implemented as a module. The connection between the modules and an additional, external DC link capacitor C _zκ, e _x e _rn via a low-inductance busbar B. The capacity of the additional external DC link capacitor C _zκ, χtern _e art is reduced by the sum of the capacitances of the integrated in the modules capacitors compared to the prior.

FIG. 5 shows a second exemplary embodiment of a converter. Several half bridges are also provided in this case, each of which is implemented as a module. In this _exemplary embodiment, it is assumed that the sum of the capacitance _{values of the} capacitors C _zκ or C _ZK ι and C _ZK2 integrated in the half-bridge _{modules is} sufficient for the intermediate _circuit , so that an additional, external intermediate _circuit capacitor can be dispensed with. This can be the case in particular when the switching times are offset. In this exemplary embodiment, a low-inductance connection via a busbar B is only provided between the half-bridge modules. The converter can be connected to the DC link via a conventional connecting line or via a busbar. The line inductance can also be used as a filter inductance or can also be used.

In the exemplary embodiment shown in FIG. 5, only a low-inductance busbar B between the half-bridge modules is necessary. The inductance between the half-bridge modules should be as small as possible, since the overvoltages occurring at the modules or semiconductor switches are directly proportional to this inductance. FIG. 6 shows a third exemplary embodiment for a converter. With this, all partial bridges are part of a single module. This solution eliminates the need for a bus bar, since the half-bridges are interconnected with each other in a very low-inductance manner. The module can be connected to the DC link by means of a busbar. The inductance of this busbar can also be used as the inductance of an output filter. An advantage of this solution is that high-frequency interference is limited to the module, which has advantages in terms of electromagnetic compatibility.

After all, the invention divides a conventional intermediate circuit capacitor into several intermediate circuit capacitors of smaller capacitance, some or all of which are an integral part of a half-bridge or bridge module. This leads to a reduction in overvoltages that occur, an improvement in electromagnetic compatibility, high switching speeds with low switching losses in the semiconductor switches and a reduction or elimination of a busbar provided in the prior art.

Claims

Expectations

1. converter which is connected to a voltage intermediate _{circuit having a charge store} , the converter containing a half-bridge or bridge circuit and the half-bridge or bridge circuit being part of a module arranged in a housing, characterized in that the charge _{store has a} plurality of intermediate capacitors (C _zκ , C _ZK1 , C _zκ2 / C2; _Kιex tern), one, several or all of which are also an integral part of the module (M).

2. Converter according to claim 1, characterized in that the half-bridge circuit has one or more high-side switches (Tl) and one or more low-side switches (T2).

3. Converter according to claim 1 or 2, characterized in that it is a three-phase converter with three half bridges, which are all part of a single module.

, Converter according to claim 2 or 3, characterized in that each high-side switch and each low-side switch is provided with an inverse diode (D1, D2) connected in parallel therewith.

5. Converter according to claim 4, characterized in that each inverse diode, a capacitor (C _H s, C _L s) is connected in parallel.

6. Converter according to claim 4 or 5, characterized in that the module has an intermediate _circuit capacitor (C _zκ , C _Z κι) which extends over the entire half bridge and is arranged parallel _thereto .

7. Converter according to claim 6, characterized in that a second intermediate _circuit capacitor (C _ZK2 ) is arranged parallel to the intermediate _circuit capacitor (C _ZK ι).

8. Converter according to claim 7, characterized in that the two _{DC link} capacitors (C _{ZK1 /} have different capacities.

9. Converter according to one of the preceding claims, characterized in that it has a plurality of half-bridge modules which are connected to one another via a low-inductance busbar.

10. Converter according to claim 9, characterized in that the connection of the half-bridge modules to the intermediate circuit via a conventional connecting line or via a busbar.

11. Converter according to claim 10, characterized in that the inductance of the connecting line serves as a filter inductance.

12. Converter according to one of claims 9-11, characterized in that the half-bridge modules on the low-inductance busbar are connected to an external DC link capacitor (C _z , external).

13. Converter according to one of claims 1-8, characterized in that it has several half bridges, which are all part of a single module.

14. Converter according to claim 13, characterized in that the module is connected via a busbar to the intermediate circuit.

15. Converter according to claim 14, characterized in that the inductance of the busbar also serves as the inductance of an output filter.