Rectifier arrangement

A rectifier arrangement (20) for rectifying an AC voltage into a DC voltage has a first connection (21), a second connection (22), a third connection (23) and a fourth connection (24), which rectifier arrangement (20) has an intermediate circuit (50) with a first line (51), a second line (52) and a node point (53), which node point (53) is connected to the first line (51) via at least one first capacitor (61) and to the second line (52) via at least one second capacitor (62), which first connection (21), second connection (22) and third connection (23) are each connected to a star point (40) via an associated circuit arrangement (31, 32, 33), which fourth connection (24) is likewise connected to the star point (40), and which star point (40) is connected to the node point (53) via a controllable switch (45).

CROSS REFERENCE TO RELATED APPLICATION

This application claims priority under 35 USC 119 to German Patent Appl. No. 10 2019 106 484.8 filed on Mar. 14, 2020, the entire disclosure of which is incorporated herein by reference.

BACKGROUND

Field of the Invention

The invention relates to a rectifier arrangement.

Related Art

EP 2 226 926 A1 discloses an inverter that is able to generate different output voltages from a split DC voltage source using switches.

US 2014/0375121 A1 discloses a converter having a single-phase two-stage rectifier.

US 2016/0315540 A1 discloses a bidirectional AC-to-DC converter having two series-connected capacitors by way of which a potential reference is able to be produced on the DC voltage side.

U.S. Pat. No. 5,430,639 A discloses an AC-to-DC converter having a DC current intermediate circuit with chokes that are influenced using switches.

An object of the invention is to provide a novel rectifier arrangement and a novel vehicle having such a rectifier arrangement.

SUMMARY

A rectifier arrangement for rectifying an AC voltage into a DC voltage has a first connection, a second connection, a third connection and a fourth connection. The rectifier arrangement further has an intermediate circuit with a first line, a second line and a node point. The node point is connected to the first line via at least one first capacitor and to the second line via at least one second capacitor. The first, second and third connections are connected to a star point via an associated circuit arrangement. The fourth connection likewise is connected to the star point, and the star point is connected to the node point via a controllable switch. The switch allows a selective connection between the star point and the node point or a disconnection so that different properties of the rectifier arrangement are able to be achieved.

The circuit arrangements may be designed to allow a current between the circuit arrangement, on the one hand, and the first line and/or the second line, on the other hand. The circuit arrangements may thereby feed the intermediate circuit.

The rectifier arrangement may have a control device designed to influence the controllable switch and to permit automatic switching of the controllable switch.

The control device may be designed to switch the controllable switch either into the on state or into the off state during the entire rectification procedure on a connected supply grid. It is not necessary to switch over the switch during the rectification procedure as long as the connected supply grid remains unchanged.

The control device may be designed to generate a first value that is dependent on the supply grid that is connected to the connections, and further may be designed to influence the controllable switch depending on the first value. This makes it possible to influence the controllable switch depending on the connected supply grid.

The control device may be designed to generate the first value by checking whether the fourth connection is connected to a neutral conductor. It has proven to be advantageous to switch the controllable switch depending on whether a neutral conductor is present.

The control device may measure the potential at the fourth connection and to determine whether a neutral conductor is connected to the fourth connection on the basis of the temporal profile of the potential at the fourth connection. Since significantly lower potential fluctuations occur on a neutral conductor than on a phase connection or external conductor, it is able to be determined whether a neutral conductor or an external conductor is connected by measuring the potential at the fourth connection.

The control device may be designed to switch the controllable switch into the on state under the condition that the fourth connection is connected to a neutral conductor. In tests, this led to a reduction in leakage currents and to an increase in safety.

The control device may be designed to switch the controllable switch into the off state if the fourth connection is not connected to a neutral conductor. If no neutral conductor is connected, opening the controllable switch led to a reduction in the leakage currents in tests.

The rectifier arrangement may have a grid filter that allows a leakage current. Using such a grid filter improves the EMC properties of the entire circuit, and the optimization by virtue of suitably setting the controllable switch has a positive effect.

The controllable switch may be an electromechanical switch. Such switches, when open, have a high insulation effect, and fast switching is not necessary.

The controllable switch may be a relay. Relays are well-suited in terms of both electrical and mechanical properties.

In one embodiment, a vehicle, such as an electric vehicle or hybrid vehicle, has a corresponding rectifier arrangement. High-performance rectifier arrangements are required in vehicles, and the above-described rectifier arrangement has comparatively low leakage currents in spite of high power.

The vehicle may have a plug connector for connecting a charging cable for the vehicle, and there is at least temporarily galvanic coupling between the connections on the plug connector and the rectifier arrangement. According to one embodiment, the vehicle has a traction battery, and there is at least temporarily galvanic coupling between the connections on the plug connector and the traction battery. In such embodiments, the leakage currents in the rectifier arrangement also have an effect outside the vehicle since there is no galvanic isolation there.

Further details and advantageous refinements of the invention will emerge from the exemplary embodiments described below and illustrated in the drawings, which embodiments should in no way be understood as restricting the invention, and also from the dependent claims.

DETAILED DESCRIPTION

FIG. 1shows a rectifier arrangement20for rectifying an AC voltage into a DC voltage. The rectifier arrangement20has a first connection21, a second connection22, a third connection23and a fourth connection24. The rectifier arrangement20has an intermediate circuit50with a first line51, a second line52and a node point53. The node point53is connected to the first line51via a first capacitor61and to the second line52via at least one second capacitor62. The capacitors61,62are preferably intermediate circuit capacitors for storing energy in the intermediate circuit50and for smoothing the DC voltage on the lines51,52, and have a capacitance suitable for the respective application case. In the exemplary embodiment, the intermediate circuit is designed as a DC voltage intermediate circuit. The first connection21, the second connection22and the third connection23are each connected to a star point40via an associated circuit arrangement31,32,33, and the fourth connection24is likewise connected to the star point40. The star point40is connected to the node point53via a controllable switch45. The rectifier arrangement20preferably additionally has a fifth connection25via which a protective conductor PE of the supply grid is able to be connected. A protective conductor sign69is provided symbolically at the fifth connection25, this being able to be used in the rectifier arrangement20and likewise being provided there with the reference sign69. The supply grid may also be referred to as grid connection.

The circuit arrangements31,32,33are each designed to allow a current between the circuit arrangement31,32,33, on the one hand, and the first line51or second line52, on the other hand. In order to charge the capacitors61,62, a current preferably flows from the circuit arrangements31,32,33to the first line51, and a current preferably flows from the second line52to the circuit arrangements31,32,33. This leads to a higher potential in the first line51than in the second line52. It is optionally also possible to generate a higher potential on the second line52than on the line51.

The rectifier arrangement20has a control device41that is designed to influence the controllable switch45, that is to say in particular to switch it into the on state or into the off state. The control device41is preferably designed to switch the controllable switch45either into the on state or into the off state during the entire rectification on a predefined supply grid. After it has been established, that is to say after the rectifier arrangement20has been connected to the supply grid10, whether the controllable switch45should be in the on state or in the off state, the controllable switch45is switched accordingly, and the rectification takes place in this set state until the supply grid10is disconnected from the rectifier arrangement20or the rectification procedure is ended.

The control device41is preferably designed to generate a first value VAL1, which first value VAL1is dependent on the supply grid10that is connected to the connections21to24, and the control device41is designed to influence the controllable switch45depending on the first value VAL1.

The control device41is preferably designed to generate the first value VAL1by checking whether the fourth connection24is connected to a neutral conductor.

The control device41is preferably designed to measure the potential at the fourth connection24and to determine whether a neutral conductor14is connected to the fourth connection24on the basis of the temporal profile of the potential at the fourth connection24. If for example the potential at the fourth connection24is constant, this means that a neutral conductor14is connected to the fourth connection. If on the other hand the potential has a sinusoidal profile, this means that a phase, such as for example the HOT2phase of a split-phase type US grid, is connected to the fourth connection24.

The control device41is preferably designed to switch the controllable switch45into the on state under the condition that the fourth connection24is connected to a neutral conductor. When a neutral conductor14is present, this is preferably connected to the node point53via the switch45.

The control device41is preferably designed to switch the controllable switch45into the off state under the condition that the fourth connection24is not connected to a neutral conductor.

As an alternative, the first value VAL1may be generated via a user input by the user defining the grid to which the rectifier arrangement20is connected.

The potential at the connection24may also be measured using a measurement device42, and it may be determined whether the fourth connection24is connected to a neutral conductor depending on the potential.

In larger overall devices, such as for example the charging infrastructure for an electric or hybrid vehicle, there are possibly already electronics that determine which supply grid10is connected to the vehicle. With corresponding knowledge, this information may be used to directly determine the first value VAL1. According to one preferred embodiment, the voltages at all of the active connections21to24are measured in order to reliably determine the connected supply grid.

If different plugs for connecting the supply grid10to the connections21to24are used for different grid connections10, the information may also be provided via a signal for identifying the plug that is used.

Mode of Operation

There are different grid connections, and the rectifier arrangement20preferably functions with a number of grid connection variants that is as high as possible.

FIG. 2shows for example the conventional Central European supply grid10, which is designed as a TN system with three phases L1, L2and L3that are available at associated connections11,12,13, and with a star point14′ as neutral conductor. The three phases L1, L2and L3are supplied by the AC voltage sources17that have a respective phase difference of 120°. In the embodiment that is shown, the neutral conductor (N)14′ is earthed and thus likewise serves as a protective conductor (PE). This is referred to as PEN conductor. Many other grid connections, but not all of them, also have a neutral conductor. In an intermediate station18, for example a home or a charging station, the PEN connection14′ is normally split into a neutral conductor connection (N) 14 and a protective conductor connection (PE)15. The connections11,12,13,14,15may be connected directly to the connections21,22,23,24,25in order to operate the rectifier arrangement20. For this purpose, a plug connector16, via which the connections21to25are connected directly or indirectly to the supply grid10, is for example provided in a vehicle. The connections21to24, which are responsible for actually channeling currents, are also referred to as active connections21to24.

If such a neutral conductor14is present and connected to the fourth connection24, it is advantageous to connect the star point40ofFIG. 1to the node point53via the switch45. The node point53is thereby set to the potential of the neutral conductor14, and the voltage at the capacitors61,62, which is for example 800 V between the lines51and52, is kept at +/−400 V with respect to the potential on the neutral conductor N. As a result, in the case of an insulation fault, the maximum voltage is kept comparatively low with respect to the potential on the neutral conductor N, and this improves safety. Without the connection of the neutral conductor14to the node point, on the other hand, the voltage on the first line51could for example be +600 V with respect to the neutral conductor, and the voltage on the second line52could be −200 V.

A further advantage is that the leakage currents that flow through the capacitors63and64to the protective conductor PE become lower due to the connection of the node point53to the fourth connection24. The current at the capacitors63,64drops.

In contrast to a supply grid10with a neutral conductor, the US supply grid called split phase has for example a first phase connection and a second phase connection, wherein the phase of the second phase connection is phase-shifted by 180° with respect to the phase of the first phase connection. The first phase connection is also referred to as HOT1, and the second phase connection is also referred to as HOT2. A neutral conductor may be provided, but it is not always provided. A protective conductor PE is often provided. In the case of a supply grid without a neutral conductor, the first phase connection HOT1may be connected to one of the connections21,22,23or, in order to reduce the currents through the circuit arrangements31,32,33, to all three connections21,22,23, and the second phase connection HOT2may be connected to the fourth connection24. What is connected to the fourth connection24is thus not a neutral conductor, but rather the phase connection HOT2that has a phase difference of 180° from HOT1. Tests using a charging device for an electric vehicle revealed that the leakage currents with a connection of the star point40to the node point53via the switch45are greater than without this connection. Specifically, with a connection or a switch45in the on state, leakage currents of the order of magnitude of 100 mA occurred. In the case of a switch45in the off state, the leakage currents on the other hand were considerably less than 10 mA. Fault current circuits have for example limit values of 10 mA or 3.5 mA depending on the respective supply grid10. It is therefore advantageous to switch the switch45into the off state when a neutral conductor is not connected to the fourth connection24.

In the case of a switch45switched into the off state, the potential at the node point53is not fixed at a potential predefined by the fourth connection24, but rather it may fluctuate. This is referred to as free floating.

The controllable switch45may be an electromechanical switch. A relay also may be used for the controllable switch45. Electromechanical switches have the advantage that they have a very low resistance in the on state and have a high insulation resistance in the off state. Since the controllable switch45does not normally change its state during the charging procedure, fast switching times are also not necessary.

FIG. 3schematically shows a vehicle19in which the rectifier arrangement20ofFIG. 1is arranged. The first line51and the second line52are connected to a DC-to-DC voltage converter (DC-to-DC converter)55to supply same with energy from the intermediate circuit50. The DC-to-DC voltage converter55may be a Buck converter.

Lines56,57and an EMC filter63are provided at the output of the DC-to-DC voltage converter55. The EMC filter63has an X-capacitor161that is connected between the lines56,57, a Y-capacitor162between the line57and the connection25(protective conductor PE) and a Y-capacitor163between the line56and the connection25. The lines56,57are then in each case connected to lines156and157, respectively, via an inductor164and165, respectively. There is then provision of an X-capacitor166that is connected between the lines156,157, a Y-capacitor167between the line157and the connection25(protective conductor PE) and a Y-capacitor168between the line156and the connection25. The EMC filter63may also be designed to be multi-stage.

The Y-capacitors reduce interference voltages that occur with respect to the potential on the protective conductor connection25. They usually have a lower capacitance than the capacitors61,62ofFIG. 1. Interference voltages are reduced by a leakage current flowing between the protective conductor connection25and the line56or57. The X-capacitors attenuate the push-pull interference voltage between the connections56and57. Leakage currents from or to the protective conductor PE arise via the EMC filter63.

The lines156,157are connected to a load58, in particular a vehicle battery (traction battery) for a vehicle with an electric drive, or for example a heating device. No transformer is provided in the illustrated part of the vehicle19in the exemplary embodiment. Vehicles with a charging device for a traction battery usually have a transformer, and this leads to galvanic isolation between the external grid and the components on that side of the transformer within the vehicle. This results in leakage currents on the side of the transformer within the vehicle not having any effect on the side of the transformer outside the vehicle. This may also result in such leakage currents not tripping a grid safety mechanism. In the exemplary embodiment that is shown, on the other hand, a transformer and galvanic isolation are not present, and it is therefore advantageous to reduce the leakage currents by appropriately switching the switch45.

FIG. 4shows, by way of example, an embodiment of the circuit arrangement31that may be used in the same form for the switching arrangements32,33. The switching arrangement is designed as a Vienna rectifier.

The first connection21is connected to a node point102via a coil101. The node point102is connected to a point104via a diode103, and the point104is connected to the first line51via a diode105. The node point102is connected to a point107via a diode106, and the point107is connected to the second line52via a diode108. A switch110is provided between the points107and104. The switch110is designed as a MOSFET in the exemplary embodiment, but other electronic switches, such as IGBTs, are also for example possible. The point107is connected to a point113via a diode112, and the point113is connected to the point104via a diode111. The point113is connected to the star point40. The cathodes of the diodes103,105,106,108,111,112are in each case connected on the side toward the first line51, and the anodes are in each case connected on the side toward the second line52. The operation of the Vienna rectifier is described for example in EP 0 660 498 A2.

A further embodiment of the switching arrangements31,32,33is for example a totem pole connection, such that the rectifier arrangement operates as a totem pole rectifier.

Variations and modifications are of course possible within the scope of the present invention.

In real embodiments, further components are preferably present, for example EMC filters, power factor controller, and/or insulation supervision circuits.