DE102019002781A1 - A method of storing electrical energy in a high voltage power module for a vehicle and high voltage power module for storing electrical energy - Google Patents

Abstract

The invention relates to a method for storing electrical energy in a high-voltage power module (50) for a vehicle. The high-voltage power module (50) has a high-voltage battery (10), an asynchronous machine (ASM) and a synchronous machine (PSM). The high-voltage battery (10) is electrically disconnected from the high-voltage power module (50) of the vehicle during asynchronous machine (ASM) and synchronous machine (PSM) operation. A value of a predetermined parameter of the high-voltage power module (50) is detected and the value is compared with a predetermined threshold value. Depending on the comparison, the synchronous machine (PSM) is switched by means of a short-circuit unit (KZE) into a short circuit mode in which the synchronous machine (PSM) is electrically short-circuited. Thus, a DC link capacitor (16) of the synchronous machine (PSM) can be used to store the electrical energy.

Description

The invention relates to a method for storing electrical energy in a high-voltage power module for a vehicle. Moreover, the invention relates to a high-voltage power module for storing electrical energy.

When marketing electric vehicles, a range of the electric vehicle plays a major role, in particular for the customers. Many technical approaches are therefore trying to further increase the range of electric vehicles. One of these technical approaches is to recover part of the kinetic energy into electrical energy by means of recuperation when braking electric vehicles. However, in the worst case, unwanted voltage peaks can occur in a vehicle electrical system of an electric vehicle. Such a situation is often referred to as a load-dump case.

A load-dump case is understood to mean, in particular, the occurrence of a voltage spike in a high-voltage intermediate circuit. It can occur, for example, when a recuperation power of the electric machine is generated in regenerative operation and an envisaged energy feedback is unexpectedly no longer possible because, for example, a high-voltage battery was disconnected electrically from the electrical system. In the worst case, the recuperation power is not reduced, so that an electrical voltage in the high-voltage intermediate circuit increases. This voltage increase can then only be alleviated by any existing capacitors in the intermediate circuit of the high-voltage components. If, in the load-dump case, the electrical voltage in the DC link continues to rise above a defined threshold due to the electrically isolated high-voltage battery, a replacement reaction is usually initiated by means of the corresponding power electronics. This replacement reaction mostly aims to protect the high voltage components of the on-board electronics of the electric vehicle from damage.

The publication DE 10 2018 000 870 A1 describes a method and apparatus for reducing occurring electrical voltage spikes in a high voltage power module for a vehicle. In this case, a control device is provided with a characteristic curve and events are detected which each have at least one electrical voltage peak in the high-voltage power module. In addition, a plurality of the electrical voltage peak is counted by means of a counter. By means of a count of the electrical voltage spike and using the characteristic, a power reduction in the power module is initiated based on the count value.

The publication DE 10 2009 049 623 A1 describes a method for controlling the DC voltage of a supplied by a generator via an inverter DC link of a motor vehicle. Zero crossings of the generator current are detected. The induced voltage is estimated based on the zero crossings. An amount of charge to be fed into the intermediate circuit is regulated on the basis of an actual DC voltage of a predetermined desired DC voltage of the DC link. The inverter is controlled as a function of the zero crossings of the induced voltage and the amount of charge to be fed.

It is an object of the present invention to provide a method or a high-voltage power module, with which electrical energy can be stored in a load-dump case.

This object is achieved by the independent claims of this application. Meaningful developments and alternative embodiments are described in the subclaims, the description and the figures.

The invention provides a method for storing electrical energy in a high-voltage power module for a vehicle. The high-voltage power module has a high-voltage battery, an asynchronous machine for a first axis of the vehicle and a synchronous machine for a second axis of the vehicle. An asynchronous machine is in particular a three-phase machine in which a rotor advances or follows a rotating field of a stator. Thus, in an asynchronous machine, the respective rotating fields of the rotor and the associated magnetic field to each other are not in phase, so asynchronous to each other. In a synchronous machine, however, the rotor preferably runs synchronously with the rotating field of the stator. The procedure provides the following steps:

In a first step a), the high-voltage battery electrical is disconnected from the high-voltage power module of the vehicle during operation of the asynchronous machine and the synchronous machine. This electrical disconnection is done in particular by means of appropriate high-voltage contactors in or on the high-voltage battery. It should be noted that this step a) is not a desired process step, but represents a situation in which the high-voltage battery is electrically disconnected from the high-voltage power module for other reasons or must be. Thus, this electrical separation in step a), for example, due to another Power electronics are caused. Step a) can be regarded as an undesirable situation, but this is treated as meaningfully as possible within the scope of this invention.

In a further step b), a value of a predetermined parameter of the high-voltage power module is detected and this value is compared with a predetermined threshold value. The predetermined parameter may be, for example, the state of charge of the high-voltage battery, a voltage in the high-voltage power module, a recuperation power, a recuperation torque or a temperature of a capacitor in the high-voltage power module.

Depending on the comparison, in step c), the synchronous machine is switched to a short-circuit operation. In the short-circuit operation, the synchronous machine is electrically short-circuited. The synchronous machine is switched to use a DC link capacitor of the synchronous machine for storing the electric power. The situation after step a) can be called a load-dump case. In this situation, especially due to recuperation, electrical energy is gained in the high-voltage power module, which, however, can not be conducted into the high-voltage battery because it is electrically isolated from the remainder of the high-voltage power module. In this situation, the synchronous machine is preferably short-circuited. This is particularly possible because in the synchronous machine significantly lower short-circuit currents occur during short-circuiting compared to the asynchronous machine. In most cases, the synchronous machine has an intermediate circuit capacitor or other capacity for storing electrical energy. By short-circuiting the synchronous machine, existing energy storage capacities in the synchronous machine can be usefully used to save the electrical energy generated by the asynchronous machine.

Since the asynchronous machine generally generates a higher recuperation power in the load-dump case, it makes sense to short-circuit the synchronous machine in order to meaningfully use existing energy storage options. In this way, the electrical energy generated by the asynchronous machine can also be stored in the load-dump case.

The invention also provides a high voltage power module for storing electrical energy. The high-voltage power module has a high-voltage battery, which is electrically separable from the high-voltage power module. The high-voltage power module further includes an asynchronous machine and a synchronous machine having an intermediate circuit capacitor. The high-voltage power module further includes a short-circuit unit configured to detect a value of a predetermined parameter of the high-voltage power module in a state where the high-voltage battery is electrically disconnected from the high-voltage power module, and that value to a predetermined one Threshold to compare. Further, the short-circuit unit is configured to switch the synchronous machine to short-circuit operation depending on the comparison by short-circuiting the synchronous machine to use the DC link capacitor of the synchronous machine to store the electric power.

Using this high-voltage power module not only electrical energy can be stored, but also occurring electrical voltage peaks can be attenuated or smoothed. The advantages and examples described in connection with the method apply mutatis mutandis and analogously for the high-voltage power module according to the invention and vice versa.

The invention will now be explained in more detail with reference to the accompanying drawings. It should be noted that the figures and the accompanying description are merely intended to illustrate how the invention can be carried out. The examples and features mentioned in the description of the figures are not to be understood as limitations.

Further advantages, features and details of the invention will become apparent from the following description of preferred embodiments and from the drawings. The features and feature combinations mentioned above in the description as well as the features and feature combinations mentioned below in the description of the figures and / or in the figures alone can be used not only in the respectively specified combination but also in other combinations or in isolation, without the scope of To leave invention.

• 1 schematisch ein Hochvolt-Leistungsmodul, welches mehrere Komponenten aufweist;
• 2 beispielhaft eine Situation, welche einem Load-Dump Fall entspricht;
• 3 eine schematische Darstellung von Parametern für eine Kurzschlusseinheit.

Showing:

• 1 schematically a high-voltage power module having a plurality of components;
• 2 exemplarily a situation which corresponds to a load-dump case;
• 3 a schematic representation of parameters for a short-circuiting unit.

The situation in 1 represents a typical Rekuperationsbetrieb. To the components of 1 include a high-voltage battery 10 , an asynchronous machine ASM , a synchronous machine PSM , two motor inverters 12 for the two machines, two DC link capacitors 16 as well as two High-voltage contactors 14 , The sum of these components is a high-voltage power module 50 For example, during braking of the electric vehicle, an existing recuperation torque is converted into electrical current or electrical energy. 1 shows by way of example different current flows in the high-voltage power module 50 , A first current flow 11 is through the asynchronous machine ASM generated and a second current flow 12 is through the synchronous machine PSM generated. Often synchronous machines PSM permanently energized, which is why the synchronous machine with PSM referred to as. The first current flow 11 and the second current flow 12 result in the example of 1 a third current flow 13 leading to the high-voltage battery 10 is directed and this partially charged. Thus, during a braking operation of an electric vehicle, part of the braking energy can be converted into electrical energy, which is used to charge the high-voltage battery 10 can be used.

2 corresponds in particular to the situation which exists after step a). 2 thus corresponds in particular to the load-dump case. In this case, the high-voltage contactors 14 which the high-voltage battery 10 with the rest of the high-voltage power module 50 connect, open. Thus, the high-voltage battery 10 electrically from the high-voltage power module 50 separated. This means in particular that the third current flow 13 no longer the high-voltage battery 10 can charge. Because in the situation of 2 Nevertheless, electrical energy is generated due to recuperation, a voltage UDC a DC link 18 in the high-voltage power module 50 increase. Because in the situation of 2 the asynchronous machine ASM has a much greater contribution to the recovery of electrical energy is in the synchronous machine PSM an active short circuit AKS induced.

This active short circuit AKS in particular, includes all three phases U . V . W the synchronous machine PSM short. Resulting short-circuit currents IAK do not get into the DC link capacitor 16 , This happens especially when the voltage in the high-voltage intermediate circuit 18 exceeds the predetermined threshold. This threshold value is chosen in particular such that in a normal operation on the voltage levels occurring in the high-voltage intermediate circuit 18 the high-voltage power module 50 do not lead to a replacement reaction in which, for example, clocked switches of the asynchronous machine are opened. The initiation of the active short circuit can not only from the voltage UDC of the DC link 18 be dependent, but of other parameters. The DC link 18 in the high-voltage power module 50 includes in particular the asynchronous machine ASM and existing DC link capacitors 16 the synchronous machine, but not the high-voltage battery 10 ,

A further embodiment provides that after the electrical disconnection of the high-voltage battery 10 a clocked switching element of the asynchronous machine ASM is switched to an open state. The clocked switching element may be formed in particular as an IGBT transistor.

The transistors of the high-voltage vehicle electrical system, in this case, for example, IGBTs, are transferred or commanded into the open state by a pulse-width-modulated drive, PWM for short. The period of time between violation of the voltage limit and opening of the transistors, ie the IGBTs, is in the microsecond range (μs range). As soon as the transistors or IGBTs are opened, the recuperation power is immediately limited. The residual energy in the motor windings, in particular in the coils, leads to a further increase in the intermediate circuit voltage. In the worst case, thus, the height of the DC link voltage UDC penetrate into an area where high-voltage components are damaged. Since the high-voltage component damage depends on the voltage level, different aging conditions result. In the synchronous machine PSM This gives the possibility of over the active short circuit AKS the phases U . V and W the power entry in the DC link 18 to prevent.

A further embodiment provides that in the case of a three-phase alternating current for the synchronous machine PSM all three phases U . V . W be shorted. This ensures safe short-circuiting and the DC link capacitor 16 the synchronous machine PSM is the storage of the asynchronous machine ASM Generated electrical energy available.

The method according to the invention is preferably used in a braking operation of the vehicle. This means that in particular the high-voltage battery 10 during a braking operation of the vehicle from the intermediate circuit 18 the high-voltage power module 50 is electrically disconnected. In this case, the predetermined parameter as a state of charge SOC the high-voltage battery 10 , as tension UDC in the intermediate circuit 18 the high-voltage power module 50 , a recuperation moment MRK , a recuperation service PRK and / or as temperature T of the DC link capacitor 16 the synchronous machine PSM or the DC link capacitor 16 the asynchronous machine ASM To be defined. This can be the initiation of the active short circuit AKS be controlled flexibly and situationally.

2 represents the load-dump case where the vehicle is in recuperation mode. In this case, the electric currents flow I1 and I2 in the DC link capacitors 16 the two machines. As a result, the voltage increases UDC in the intermediate circuit 18 the high-voltage power module 50 and reaches a threshold, which may be predetermined by the software or hardware. At the asynchronous machine ASM It is often envisaged that when this threshold value of voltage is exceeded, a replacement reaction is triggered in which the power transistors are transferred from a clocked state to an open state. At the same time the recuperation moment becomes MRK or the recuperation power PRK canceled, as a magnetic field in the stator and rotor of an electrical machine of the asynchronous machine ASM is resolved. A residual inductive energy of the electric motor and the electrical high-voltage cable set can via freewheeling diodes of the power electronics in the DC link capacitors 16 the high-voltage power module 50 reach. This increases the tension UDC in the high-voltage power module 50 continue on. This energy input through the asynchronous machine ASM can not be stopped directly. Regarding the asynchronous machine ASM is an active short circuit AKS extremely unfavorable, because with the asynchronous machine ASM the occurring short-circuit currents are significantly greater than in comparison to the synchronous machine PSM , For this reason, the active short circuit AKS preferably exclusively in the synchronous machine PSM carried out.

In the synchronous machine PSM is also like the asynchronous machine ASM due to the recuperation torque MRK gained electrical energy. In contrast to the asynchronous machine ASM can the synchronous machine PSM definitely be shorted. This can be an energy input of the electric motor of the synchronous machine PSM be stopped very quickly. For example, after a predetermined value with respect to the voltage UDC of the DC link 18 the high-voltage power module 50 is achieved, the power transistors of the synchronous machine PSM be switched to the open state and shortly thereafter the active short circuit AKS be initiated. The term "shortly thereafter" means "up to 50 microseconds". The due to the active short circuit AKS generated short-circuit current is in the synchronous machine PSM many times less than the asynchronous machine ASM and thus can be initiated safely. In case of active short circuit AKS become the three phases U . V and W the electric machine of the synchronous machine PSM bridged in the power electronics via the power transistors. After initiating the active short circuit AKS no electrical energy is left in the DC link capacitor 16 as well as in the high-voltage power module 50 transported.

As 2 By way of example, the currents occurring due to the active short circuit indicate circulating between the electrical machine of the synchronous motor PSM and the motor inverter 12 in the "circle". As a result, no voltage due to the electric machine of the synchronous motor in the high-voltage power module 50 arrives. Thus, the synchronous machine delivers PSM no additional contribution to an increase in electrical voltage UDC the high-voltage power module 50 , However, this can be the DC link capacitor 16 the synchronous machine PSM be used meaningfully. For example, in a 4x4 vehicle variant in the load-dump case, the electrical energy generated by the asynchronous machine ASM is generated, with the aid of the DC link capacitor 16 the synchronous machine PSM at least partially stored. Is for example the asynchronous machine ASM associated with a front axle of the vehicle and the synchronous machine PSM assigned to a rear axle of the vehicle, so can with the help of the active short circuit AKS In a load-dump case, the electrical energy gained from the front axle is stored more efficiently.

If, for example, based on the rear axle, the predetermined threshold for the voltage to switch selected very low, for example, for example, 430 volts, so from 430 volts, the active short circuit AKS initiated. Due to the freewheeling DC link capacitor 16 the synchronous machine PSM There is an additional, very large storage capacity available "free of charge". With the help of this additional capacitance of the DC link capacitor 16 the synchronous machine PSM can a much greater recuperation performance PRK that from the asynchronous machine ASM is achievable, stored. As a result, previously existing barriers or restrictions can be overcome during the Rekuperationsbetriebs. By using the DC link capacity 16 the synchronous machine PSM can be a much larger part of the asynchronous machine ASM recovered electrical energy can be stored. In this case, a maximum voltage of 500 volts (DC) is preferably not exceeded. Without the targeted initiation of the active short circuit AKS must be at the asynchronous machine ASM In the load-dump case, a very large safety margin in terms of voltage levels are met, but this means that the maximum Rekuperationsleistung can not be achieved.

This means that by means of the targeted initiation of the active short circuit AKS the storage capacity or storage capacity in the Case of load-dump case can be increased significantly. Thus, the high-voltage battery 10 be charged much more efficiently in the load-dump case. Thus, a total range of the electric vehicle can be increased. Thus, the solution presented here can help to increase the range of electric vehicles and thus generate greater acceptance of electric vehicles to customers. Is the predetermined threshold regarding the voltage in the high voltage power module 50 Intelligently selected, this creates de facto "free" an additional energy storage capacity. This additional energy storage capacity can be used to power the asynchronous machine ASM in terms of their generated Rekuperationsleistung PRK does not have to be limited. As a result, the braking energy of the electric vehicle can be better utilized. This can lead to a greater range of the electric vehicle and a greater efficiency for the electric vehicle. In case of 2 represents the right DC link capacitor 16 the additional energy storage option. This can be done using the active short circuit AKS be used as described above meaningful.

The active short circuit is in particular by means of a short-circuit unit KZE realized. 3 clearly shows that the short-circuit unit KZE depending on several parameters the active short circuit AKS can control or regulate. These parameters include the state of charge of the battery SOC , the voltage UDC the high-voltage power module 50 , the recuperation power PRK , the recuperation moment MRK as well as the temperature of the DC link capacitor 16 , All these parameters can be obtained from the short circuit unit KZE for determining an optimal switching point of the synchronous machine PSM be taken into account. The switching point of the synchronous machine PSM is in particular that point where the active short circuit AKS is initiated. This switching point can be determined by means of a corresponding logic or a neural network. This allows the short-circuit unit KZE the switching point for the active short circuit AKS determine flexibly and appropriate to the situation. By means of the variable switching point concerning the active short circuit AKS Energy recovery can be further optimized in the load-dump case.

LIST OF REFERENCE NUMBERS

10

High-voltage battery

12

motor inverter

14

High-voltage contactors

16

Link capacitor

18

DC

50

High voltage power module

AKS

active short circuit

ASM

asynchronous

11, 12, 13

Current flows in the high-voltage power module

KZE

Short-circuit unit

MRK

recuperation

PRK

Rekuperationsleistung

PSM

synchronous machine

SOC

SOC

T

temperature

AND MANY MORE

Phases of the three-phase alternating current

UDC

Voltage in the high-voltage power module

IAK

Short circuit current

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

• DE 102018000870 A1 [0004]
• DE 102009049623 A1 [0005]

Claims (6)

Method for storing electrical energy in a high-voltage power module (50) for a vehicle, wherein the high-voltage power module (50) comprises a high-voltage battery (10), an asynchronous machine (ASM) for a first axle of the vehicle and a synchronous machine (PSM) for a second axle of the vehicle, characterized by : a) electrically disconnecting the high voltage battery (10) from the high voltage power module (50) of the vehicle during asynchronous machine (ASM) and synchronous machine (PSM) operation, b) sensing a value of a predetermined parameter of the high-voltage power module (50) and comparing the value with a predetermined threshold value, c) switching the synchronous machine (PSM) into a short-circuit operation in which the synchronous machine (PSM) is electrically short-circuited, depending on the comparison, to use a DC link capacitor (16) of the synchronous machine (PSM) to store the electrical energy. Method according to Claim 1 , wherein after the electrical disconnection of the high-voltage battery (10), a clocked switching element of the asynchronous machine (ASM) is switched to an open state. Method according to one of the preceding claims, wherein in a three-phase alternating current for the synchronous machine (PSM) all three phases (U, V, W) are short-circuited. Method according to one of the preceding claims, wherein the high-voltage battery (10) is electrically disconnected from the high-voltage power module (50) during a braking operation of the vehicle. Method according to one of the preceding claims, wherein the predetermined parameter as the state of charge (SOC) of the high-voltage battery, a voltage (UZK) in the high-voltage power module (50), a recuperation (MRK), a Rekuperationsleistung (PRK) and / or as a temperature (T) of the intermediate circuit capacitor (16) of the synchronous machine (PSM) or of an intermediate circuit capacitor (16) of the asynchronous machine (ASM) is defined. High-voltage power module (50) for storing electrical energy, with a high-voltage battery (10) which is electrically separable from the high-voltage power module (50), an asynchronous machine (ASM), - A synchronous machine (PSM) having a link capacitor (16), and a short circuit unit (KZE), which is designed to detect a value of a predetermined parameter of the high-voltage power module (50) in a state in which the high-voltage battery (10) is electrically disconnected from the high-voltage power module (50) and to compare this value with a predetermined threshold value; and * to switch the synchronous machine (PSM) into a short-circuit operation in response to the comparison in which the synchronous machine (PSM) is short-circuited to use the DC link capacitor (16) of the synchronous machine (PSM) to store the electrical energy.

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