DE102011006762A1 - Battery direct converter in ring configuration - Google Patents

Abstract

The invention relates to an electric drive system with an inverter for supplying an n-phase electric machine (11), where n ≥ 2, with a plurality of energy storage modules (2a, 2b, 2c, 2d) connected in series in a ring line (1). wherein each of the plurality of energy storage modules (2a, 2b, 2c, 2d) has a first terminal and a second terminal, an energy storage cell having at least one energy store (6a, 6b, 6c, 6d), and which between the first terminal and the second terminal is coupled, a ring switching device (5a, 5b, 5c, 5d), which is designed to connect the energy storage cell to the first terminal of the energy storage module (2a, 2b, 2c, 2d) switchable, and a first coupling device ( 21a-21c; 22a-22c; 23a-23c; 24a-24c) adapted to connect a node between the second terminal and the energy storage cell switchably with one of the phase lines (11a, 11b 11c) of the electric machine (11).

Description

The invention relates to a battery direct converter with energy storage modules, which are arranged in a ring configuration, for feeding an electric machine.

State of the art

It is becoming apparent that in the future, both in stationary applications, such as wind turbines, as well as in vehicles such as hybrid or electric vehicles, increasingly electronic systems will be used, which combine new energy storage technologies with electric drive technology. In order to meet the given requirements for a given application in terms of performance and energy, usually several battery cells are connected in series. Since the current provided by such a drive system must flow through all battery cells and a battery cell can only conduct a limited current, battery cells are often additionally connected in parallel in order to increase the maximum current.

The series connection of several battery cells in addition to a high total voltage involves the problem that the entire energy storage fails if a single battery cell fails, because then no battery power can flow. Such a failure of the energy storage can lead to a failure of the entire system. In a vehicle, failure of the traction battery can result in the vehicle "stalling". For other applications, such as. B. the rotor blade adjustment of wind turbines, it may be in unfavorable conditions such. B. strong wind, even come to safety-threatening situations. Therefore, a high reliability of the energy storage is always desirable, with "reliability" is the ability of a system to work for a given time error-free.

It is therefore possible to operate batteries with several battery module strings, which can be connected directly to phase lines of an electrical machine. The battery module strands in this case have a plurality of battery modules connected in series, each battery module having at least one battery cell and an associated controllable coupling unit, which makes it possible to interrupt the respective battery module string depending on control signals, or to bridge the respectively assigned at least one battery cell, or to switch the respectively assigned at least one battery cell into the respective battery module string. By suitable control of the coupling units, z. B. by means of pulse width modulation, suitable phase signals for controlling the electric machine can be provided, so that can be dispensed with a separate pulse inverter.

The publication US 5,642,275 For example, discloses a drive system for a three-phase electric machine with cascaded inverters, each associated with a single battery cell.

The publication US 6,577,087 B2 discloses a multi-stage drive system having a pulse inverter and a string of selectively bridgeable battery cells for supplying an electrical machine with stepped supply voltages.

The publication JP 2000-0341964 A also discloses a drive system with multi-stage switchable supply voltage.

Disclosure of the invention

According to one embodiment, the present invention provides an inverter for supplying an n-phase electric machine, where n ≥ 2, having a plurality of energy storage modules arranged in series in a loop, each of the plurality of energy storage modules having a first terminal and a second Connection, an energy storage cell which has at least one energy store, and which is coupled between the first terminal and the second terminal, a ring switching device which is adapted to switchably connect the energy storage cell with a first terminal of the energy storage module, and a first coupling device, which is configured to switchably connect a node between the second terminal and the energy storage cell to one of the phase lines of the electrical machine comprises.

According to a further embodiment, the present invention provides a system comprising an inverter according to the invention and an n-phase electric machine, wherein n ≥ 2, which is connected via n phase lines respectively to the first coupling means of the plurality of energy storage modules of the inverter.

According to a further embodiment, the present invention provides a method for operating a system according to the invention. The method includes the steps of opening one of the ring switching devices of the plurality of energy storage modules while simultaneously closing the remaining ring switching devices, and selectively driving the first coupling devices to connect the n phase lines to each of the plurality of energy storage modules.

Advantages of the invention

An idea of the invention is to provide a battery powered drive system which can provide a stepped supply voltage to an n-phase electric machine. For this purpose, energy storage modules are arranged in a ring, which can be separated at arbitrary points via switching devices in a chain of energy storage modules. As a result, energy storage cells, which are arranged in the energy storage modules, can be variably connected in the chain for supplying energy to phase lines of the electrical machine.

This topology also allows a uniform load on all energy storage cells or all energy storage modules, so that to achieve a respective supply voltage value, the individual energy storage cells can be charged different current by appropriate connection and disconnection. This can be achieved on average over time a uniform average load of all energy storage cells.

In addition, the system is robust to a failure or failure of a single energy storage cell or energy storage module because each of the energy storage cells can either be permanently switched to the end of the power supply chain via the ring switching devices where it does not bother or benefit, or through one of the phase lines be bridged by means of the first coupling devices. In both cases, the drive system with the other energy storage modules can still be operated safely, so that the reliability of the entire system is very high.

The number of energy storage cells required for the production of any three-phase systems is very low in the system according to the invention, whereby a space-saving and cost-effective design is possible.

Further features and advantages of embodiments of the invention will become apparent from the following description with reference to the accompanying drawings.

Brief description of the drawings

Show it:

1 a schematic representation of an embodiment of a system according to the invention;

1a a schematic representation of an energy storage module of the system in 1 in greater detail in accordance with another embodiment of the invention;

2 a schematic representation of another embodiment of a system according to the invention;

3 a schematic representation of another embodiment of a system according to the invention; and

4 a schematic representation of a method for operating a system according to the invention according to another embodiment.

1 shows an electric drive system 10 for supplying an electrical machine 11 with a supply voltage. The electric machine 11 is an n-phase machine with n ≥ 2. The electric drive system 10 therefore includes n phase lines 11a ... 11n of which in 1 exemplified two phase lines 11a and 11n are shown. To supply the electrical machine with electricity is a loop 1 provided in which a number m energy storage modules 2a ... 2m are connected in series, of which in 1 exemplary three energy storage modules 2a . 2 B . 2m are shown. The number of energy storage modules 2a ... 2m is arbitrary. The energy storage modules 2a ... 2m are each via supply connections 3a ... 3n with the n phase lines 11a ... 11n connected. For example, the phase line 11a via one supply connection each 3a with each of the energy storage modules 2a . 2 B . 2m connected. Here is the number of supply connections 3a ... 3n from the number of phase lines 11a ... 11n dependent.

In 1a is in more detail the structure of an energy storage module 2 shown. The energy storage modules 2a ... 2m of the 1 can do like that in 2 shown energy storage module 2 be constructed. The energy storage module 2 includes a first port 4a and a second connection 4b , Furthermore, the energy storage module comprises 2 an energy storage cell 6 , The energy storage cell 6 may include at least one energy storage, such as a battery. It may be provided that in the energy storage cell 6 several energy storage devices can be connected in series or in parallel. The number and arrangement of energy storage in the energy storage cell 6 can adapt to the requirements of the drive system 10 judge.

The energy storage module 2 further comprises a switching device 5 which the first connection 4a of the energy storage module 2 Switchable with the energy storage cell 6 combines. The switching device 5 Can also be used as ring switching device 5 be designated as they are in the open state the ring passing through the loop 1 about all energy storage modules 2 is formed, interrupts. The energy storage module 2 also includes a node 7 which is between the second port 4b and the energy storage cell 6 is arranged. With the node 7 is a coupling device 8th connected to the supply connections 3a ... 3n of the energy storage module 2 with the node 7 combines. The coupling device 8th For example, it may include switching devices that connect each of the phase lines 11a ... 11n via the supply connections 3a ... 3n separately and independently switchable with the node 7 can connect.

Together with the coupling devices 8th form energy storage modules 2 which is in a loop 1 according to the topology 1 are connected in series, an inverter, which is one of the energy storage cells 6 supplied DC voltage via an active control of the coupling devices 8th can convert into an AC voltage for an electrical machine. The granularity of the implementation of the digital drive signals for the coupling devices 8th the energy storage modules 2 in an analog output AC voltage depends, inter alia, on the number of energy storage modules used 2 or the energy storage cells used 6 as well as the clock rate of the control of the coupling devices 8th from.

2 shows a schematic representation of an embodiment of a drive system 20 , The drive system 20 corresponds to the configuration of in 1 shown drive system 10 , The drive system 20 serves as an example for three-phase current generation for a three-phase electrical machine 11 with three phase lines 11a . 11b . 11c , which can also be called U, V and W. The drive system 20 includes four energy storage modules by way of example 2a . 2 B . 2c . 2d , which in the ring line 1 are connected in series. Each of the energy storage modules 2a . 2 B . 2c . 2d includes a ring switching device 5a . 5b . 5c . 5d , an energy storage cell 6a . 6b . 6c . 6d and coupling means for coupling the energy storage modules 2a . 2 B . 2c . 2d with the respective phase lines 11a . 11b . 11c ,

The coupling devices in this case each comprise three switching devices per energy storage module, which encircle the loop 1 in the respective power supply module with one of the three phase lines 11a . 11b . 11c connect switchable. For example, the energy storage module comprises 2a the switching devices 21a . 21b and 21c , wherein the switching device 21a the phase line 11a switchable with the ring line 1 in the energy storage module 2a connects, the switching device 21b the phase line 11b switchable with the ring line 1 in the energy storage module 2a connects and the switching device 21c the phase line 11c switchable with the ring line 1 in the energy storage module 2a combines. Analog have the energy storage modules 2 B . 2c . 2d each switching devices 22a . 22b . 22c . 23a . 23b . 23c such as 24a . 24b and 24c on.

The ring switching devices 5a . 5b . 5c . 5d serve to interrupt the loop 1 at a suitable location, so that in each case a chain of power supply modules 2a . 2 B . 2c . 2d arises. The switching devices of the coupling devices of the energy storage modules 2a . 2 B . 2c . 2d can be controlled so that per phase line 11a . 11b . 11c in each case only one switching device is closed. This results in each of the phase lines 11a . 11b . 11c a supply voltage from the respective closed switching device of the coupling devices and the point of interruption of the loop 1 through the respective ring switching device 5a . 5b . 5c . 5d is dependent. For example, is due to the phase line 11a with open ring switching device 5c and closed switching device 21a a supply voltage to that of the sum of the energy storage cells 6a . 6b and 6c provided voltage minus that through the energy storage cells 6d provided voltage corresponds.

At the output voltage of the system 20 is only the difference between the supply voltages of the individual phase lines 11a . 11b . 11c relevant. This can be done with the system 20 a seven-level setting of the output voltage as the difference between each two phase line 11a . 11b . 11c possible because of the respective opened ring switching device 5a . 5b . 5c . 5d assigned energy storage cell 6a . 6b . 6c respectively. 6d can not be used for the output voltage difference. In general, it is possible to provide a (2m-1) -stepped output voltage when using m energy storage modules with energy storage cells of the same voltage.

By timely switching the switching devices of the coupling devices of the energy storage modules can approach the output voltage of a sine wave voltage. In this case, for example, intermediate values between the stages of the output voltage can be realized via corresponding switching back and forth between two switching settings of the switching devices, so that an intermediate value of the output voltage is applied to the respective phase lines in the time average.

3 shows a schematic representation of a drive system 30 which is different from the one in 2 shown drive system 20 only differs in that one of the power supply modules, exemplified in 3 shown the power supply module 2d , with an additional Coupling device is equipped. The additional coupling device connects a node between the ring switching device 5d and the energy storage cell 6d of the power supply module 2d with the phase lines 11a . 11b . 11c , For example, switching devices can be used 34a . 34b and 34c be provided, which in each case one of the phase lines 11a . 11b respectively. 11c with the ring line 1 in the power supply module 2d connect. It is of course also possible, the coupling device in another of the power supply modules 2a . 2 B or 2c to arrange.

The switching devices 34a . 34b and 34c can be similar to the coupling devices in 2 be controlled. They offer the advantage that even the energy storage cell 6d in forming the difference between the supply voltages of two phase lines 11a . 11b . 11c can be taken into account when the ring switching device 5d the opened ring switching device is. That way, with the system 30 a (2m + 1) -stepped output voltage setting, here for example nine-stage, compared to only (2m - 1) -step with the system 20 in 2 be achieved.

In the systems 10 . 20 and 30 of the 1 . 2 respectively. 3 In general, it is also possible to control the ring switching devices and the coupling devices for charging the energy storage cells from a three-phase network.

4 shows a schematic representation of a method 40 for operating an electric drive system one of 1 . 2 or 3 , In a first step 41 one of the ring switching devices of the energy storage modules is opened while the others are each closed to the loop 1 at one point to interrupt and provide a chain of power modules. In a second step 42 Then, the coupling devices can be controlled to produce a desired output voltage for the electric machine to the phase lines.

In one step 43 can be checked whether the setting of the ring switching devices to be changed. This can be done depending on the setting of the drive system. For example, it can be provided that always the same ring switching device should be opened, for example in the system 30 of the 3 when the maximum output voltage is needed, which only when opening the ring switching device 5d can be achieved. In this case, the method returns to the checking step 43 back to the beginning of the procedure.

However, it can also be provided, for example, to change the open ring switching device at periodic intervals. This can be advantageous in order to keep the current load of the energy storage cells the same for each of the energy storage cells in the time average. This is done in one step 44 Checking whether the system is still in the normal operating state, that is, whether all energy storage cells or energy storage modules work properly. Should this be the case, in one step 45 the in step 41 to be opened ring switching device to be changed. It may be possible to set a fixed order of the Ringschalteinrichtungswechsels in step 45 be maintained in order to achieve a uniform load on the energy storage cells over a longer period of time. The period with which the ring switching device is changed, can be much longer than a switching period of the coupling devices of the energy storage modules for generating a sine wave of the output voltage.

In certain chain formations, that is, when certain ring switching devices are opened, it is still possible to obtain the same supply voltages on the phase lines with different settings of the coupling devices of the energy storage modules. This is possible if the output voltage to be set is less than the maximum possible output voltage, with the selection of the three closed switching devices for the three phase lines remaining the same in relation to one another, but shifted along the chain between the ends. By uniform choice of the different equivalent settings of the coupling devices in step 42 It is thus possible to balance the current load of the individual energy storage cells in the time average.

Should in the step 44 However, it can be determined that one of the energy storage cells or one of the energy storage modules is not in a normal operating state, that is, for example, defective, disturbed or failed, can be provided in one step 46 between two alternative emergency modes. The selection may depend, for example, on the desired output voltage.

It can, for example, in step 47 be provided to give up the change of the ring switching devices. In this case, the one ring switching device, which is located in the energy storage module with the defective energy storage cell, permanently as the in step 41 to be opened ring switching device to be selected. In this case, the defective energy storage cell is permanently at the negative pole, which means that it is never integrated into the supply chain. For the special case that the energy storage cell 6d in the system 30 in 3 In the event of failure, it is still necessary to ensure that the additional switching devices 34a . 34b . 34c be driven accordingly to the energy storage cell 6d reliably keep out of the energy supply chain.

Alternatively, for example, in step 48 be provided to bridge the defective energy storage cell in the chain. For this purpose, it may be provided that the defective energy storage cell associated ring switching device in addition to that for the interruption of the loop 1 open to opening ring switching device and to bridge the defective energy storage cell using two coupling devices via one of the phase lines. For example, if the energy storage cell 5c is defective, can the ring switching device 5c additionally be opened. So that the circuit is closed again, a bridging of the energy storage cell 5c over one of the phase lines 11a . 11b . 11c respectively. For example, the switching devices 24a and 23a be permanently closed. In this case, the current flows from the (intact) energy storage cell 6d over the switching device 24a , the phase line 11a and the switching device 23a to ring switching device 5b , whereby the opened ring switching device 5c and the defective energy storage cell 6c have been bridged. The phase line 11a However, in this case can not be controlled for a change in the output voltage, because except the switching devices 24a and 23a no further switching device to the phase line 11a more may be closed. The maximum output voltage is thus lower when bridging a defective energy storage cell via the corresponding voltage of the energy storage cell. If several energy storage cells should be defective at the same time, bridging via coupling devices and phase lines can only take place if directly adjacent energy storage cells fail.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• US 5642275 [0005]
• US 6577087 B2 [0006]
• JP 2000-0341964A [0007]

Claims (9)

Inverter for supplying an n-phase electric machine ( 11 ), where n ≥ 2, with a plurality of energy storage modules ( 2 ), which are connected in series in a loop ( 1 ), each of the plurality of energy storage modules ( 2 ): a first port ( 4a ) and a second port ( 4b ); an energy storage cell ( 6 ), which at least one energy store ( 6a . 6b . 6c . 6d ), and which between the first port ( 4a ) and the second port ( 4b ) is coupled; a ring switching device ( 5 ), which is adapted to the energy storage cell ( 6 ) with the first connection ( 4a ) of the energy storage module ( 2 ) switchable to connect; and a first coupling device ( 8th ), which is designed to be a node ( 7 ) between the second port ( 4b ) and the energy storage cell ( 6 ) switchable with one of the phase lines ( 11a . 11b . 11c ) of the electric machine ( 11 ) connect to. Inverter according to claim 1, wherein the first coupling devices ( 8th ) for each phase line ( 11a . 11b . 11c ) of the electric machine ( 11 ) a controllable semiconductor switch ( 21a . 21b . 21c ; 22a . 22b . 22c ; 23a . 23b . 23c ; 24a . 24b . 24c ) having. Inverter according to one of claims 1 or 2, wherein the energy storage cell ( 6 ) a plurality of series or parallel connected batteries ( 6a . 6b . 6c . 6d ) having. Inverter according to one of the preceding claims, wherein one of the plurality of energy storage modules ( 2d ) further comprises: a second coupling device ( 34a . 34b . 34c ), which is adapted to a node between the ring switching device ( 5d ) and the energy storage cell ( 6d ) switchable with one of the phase lines ( 11a . 11b . 11c ) of the electric machine ( 11 ) connect to. System ( 10 ; 20 ; 30 ), comprising: an inverter according to one of the preceding claims; and an n-phase electric machine ( 11 ), where n ≥ 2, which are over n phase lines ( 11a . 11b . 11c ) each with the first coupling devices ( 8th ) of the plurality of energy storage modules ( 2 ) of the inverter is connected. Procedure ( 40 ) for operating a system ( 10 ; 20 ; 30 ) according to claim 5, comprising the steps of: opening one of the ring switching devices ( 5 ) of the plurality of energy storage modules ( 2 ) while simultaneously closing the remaining ring switching devices ( 5 ); and selectively driving the first coupling devices ( 8th ) for connecting the n phase lines ( 11a . 11b . 11c ) each with one of the plurality of energy storage modules ( 2 ). Procedure ( 40 ) according to claim 6, wherein in the step of opening one of the ring switching devices ( 5 ) the opened ring switching device ( 5 ) periodically between all ring switching devices ( 5 ) of the plurality of energy storage modules ( 2 ) is changed. Procedure ( 40 ) according to claim 6, further comprising the steps of: detecting a defect of an energy storage cell ( 6 ) one of the plurality of energy storage modules ( 2 ); and permanent opening of the ring switching device ( 5 ) of the energy storage module ( 2 ), in whose energy storage cell ( 6 ) a defect is detected. Procedure ( 40 ) according to claim 6, further comprising the steps of: detecting a defect of an energy storage cell ( 6 ) one of the plurality of energy storage modules ( 2 ); and permanent bridging of the defective energy storage cell ( 6 ) via one of the phase lines ( 11a . 11b . 11c ) by driving the first coupling device ( 8th ) of the energy storage module ( 2 ) with the defective energy storage cell ( 6 ) and the first coupling device ( 8th ) of the energy storage module ( 2 ) with the defective energy storage cell ( 6 ) adjacent energy storage module ( 2 ).

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