Energy recovery system and method for operating an energy recovery system

Abstract

Energy recovery system, especially for a vehicle, comprising: - at least one energy source (12) for converting kinetic energy into electrical energy, - at least one energy storage device (14), - at least one energy consumer (18), - a control unit (22) for selectively connecting the at least one energy source (12) with the at least one energy storage device (14) or the at least one energy consumer (18), wherein the at least one energy source (12) comprises at least one of the following systems: - a drive system of an electric vehicle with at least one traction electric motor, - a power steering system of a vehicle with at least one electric steering motor - a roll stabilization system of a vehicle with at least one stabilizing electric motor, wherein the control unit (22) is configured to connect the at least one energy source (12) to the at least one energy consumer (18) when the at least one energy source (12) is in a critical energy generation operating state that overloads the at least one energy storage device (14), and to connect the at least one energy source (12) to the at least one energy storage device (14) when the at least one energy source (12) is in a non-critical energy generation operating state that does not overload the at least one energy storage device (14), characterized by that at least one energy storage device (14) is a capacitor energy storage device (14), that the critical energy generation operating condition exists when at least one energy source (12) is in an intensive recovery operating condition, and that at least one energy source (12) is in the intensive recovery operating state if at least one of the following conditions is met: - the at least one energy source (12) comprises the at least one traction electric motor and a deceleration of the vehicle is above a threshold deceleration, - the at least one energy source (12) comprises the at least one steering electric motor and the extent of the steering interventions carried out to maintain a steering state is above a threshold extent and / or the frequency of the steering interventions carried out to maintain a steering state is above a threshold frequency, - the at least one energy source (12) comprises the at least one stabilizing electric motor and the extent of the roll control interventions carried out to maintain a roll state is above a threshold extent and / or the frequency of the roll control interventions carried out to maintain a roll state is above a threshold frequency.

Description

[0001] The present invention relates to an energy recovery system, for example used in a vehicle, with which kinetic energy can be converted into electrical energy and stored in an energy storage device, and to a method for operating an energy recovery system, for example in a vehicle.

[0002] To stabilize the on-board voltage in a vehicle's electrical system, such as that of an electric vehicle, which is generally generated or maintained by one or more battery energy storage devices, it is known to use capacitor energy storage devices, commonly referred to as SCAPs (supercapacitors), as buffer storage. Compared to battery energy storage devices, such capacitor energy storage devices can be charged relatively quickly and are capable of releasing large amounts of energy in a short time. This makes it possible, in particular, to absorb short-term peak loads on the on-board electrical system.

[0003] Such capacitor energy storage devices are generally designed for an operating voltage of, for example, around 18 V. The charging voltage applied to a capacitor energy storage device should not significantly exceed the operating voltage for which the capacitor energy storage device is designed, in order to avoid damage to the capacitor energy storage device due to overvoltage.

[0004] From DE 10 2019 125 877 A1, an energy recovery system according to the preamble of claim 1 is known. In this energy recovery system used in a vehicle, when a battery to be charged during regenerative braking is in a state that does not permit the absorption of the electrical energy provided during braking, the energy is directed to one or more electrical energy consumers.

[0005] WO 2008 / 147305A1 discloses an energy recovery system in a vehicle in which, for example during a prolonged downhill drive, when the electrical power or voltage supplied by a generator exceeds a threshold, the electrical energy supplied by the generator is dissipated in an electrical resistance.

[0006] The object of the present invention is to provide an energy recovery system and a method for operating an energy recovery system, with which an overload of a capacitor energy storage device can be reliably avoided with a structurally simple design.

[0007] According to a first aspect of the present invention, this problem is solved by an energy recovery system, in particular for a vehicle, according to claim 1. This energy recovery system comprises: - at least one energy source for converting kinetic energy into electrical energy, - at least one capacitor energy storage device, - at least one energy consumer, - a control unit for selectively connecting the at least one energy source to the at least one capacitor energy storage device or the at least one energy consumer,

[0008] In the energy recovery system constructed according to the invention, the control unit is designed to connect the at least one energy source to the at least one energy consumer when the at least one energy source is in a critical energy generation operating state that overloads the at least one capacitor energy storage device, and to connect the at least one energy source to the at least one capacitor energy storage device when the at least one energy source is in a non-critical energy generation operating state that does not overload the at least one capacitor energy storage device.

[0009] In this energy recovery system, the at least one capacitor energy storage device can be dimensioned such that, in a predominantly occurring energy generation operating state of the at least one energy source, which is considered non-critical and cannot, in principle, lead to an overload and thus damage to the capacitor energy storage device, it can be used to absorb or store electrical energy generated by the at least one energy source. Since, in energy generation operating states that are potentially critical or damaging to the at least one capacitor energy storage device, it is decoupled from the at least one energy source and the energy released by the source is directed towards the at least one energy consumer, it is not necessary to dimension the at least one capacitor energy storage device to also absorb peak loads.This contributes to a compact and cost-efficient design of the energy recovery system, in particular the at least one capacitor energy storage device.

[0010] Although in principle the at least one energy source can comprise any system area, particularly in a vehicle, which is capable of converting kinetic energy into electrical energy, in the energy recovery system constructed according to the invention the at least one energy source comprises at least one of the following systems: - a drive system of an electric vehicle with at least one traction electric motor, - a power steering system of a vehicle with at least one electric steering motor - a roll stabilization system of a vehicle with at least one stabilizing electric motor.

[0011] To provide a comparatively large storage capacity of the at least one capacitor energy storage device at a sufficiently high operating voltage, the at least one capacitor energy storage device can comprise a plurality of capacitor cells connected in series.

[0012] At least one energy consumer can comprise at least one of the following systems: - at least one load resistor, - at least one resistance heater for transferring heat to a heat transfer medium, - at least one latent heat storage system, - at least one electrically operated system area powered by a vehicle's on-board voltage system.

[0013] In this context, it should also be noted that, in principle, any system present in a vehicle that requires electrical energy for its operation can be used as an energy consumer. Designing an energy consumer for generating or storing heat is particularly advantageous, as such systems are generally less susceptible to damage from short-term overloads.

[0014] A critical energy generation operating condition, which can potentially also lead to damage to a capacitor energy storage system, exists when at least one energy source is in an intensive recovery operating condition.

[0015] Additionally, a critical energy generation operating condition may exist if a charging voltage generated by at least one energy source exceeds a threshold charging voltage.

[0016] At least one energy source is in the intensive recovery operating state if at least one of the following conditions is met: - which includes at least one energy source, at least one traction electric motor, and a deceleration of the vehicle is above a threshold deceleration, - the at least one energy source includes the at least one steering electric motor and the extent of the steering interventions carried out to maintain a steering state is above a threshold extent and / or the frequency of the steering interventions carried out to maintain a steering state is above a threshold frequency, - the at least one energy source includes the at least one stabilizing electric motor and the extent of the roll control interventions carried out to maintain a roll state is above a threshold extent and / or the frequency of the roll control interventions carried out to maintain a roll state is above a threshold frequency.

[0017] Such an intensive energy recovery operating state of the at least one energy source can therefore be a state in which it is generally known that, under this operating state, phases can occur with a high probability in which the potential danger of overloading a capacitor energy storage device can arise. As long as such an intensive energy recovery operating state exists, for example, because a vehicle is braking intensively or because a power steering system or a roll stabilization system is intensively active due to poor road conditions in order to maintain a defined, predetermined driving state, it is advantageous to keep the at least one capacitor energy storage device decoupled from the at least one energy source in order to fundamentally eliminate the risk of it being overloaded.

[0018] In order to enable charging of the at least one capacitor energy storage device after the transition to a state in which the at least one energy source is connected to the at least one energy consumer, in order to avoid overloading the at least one capacitor energy storage device, the control unit can be configured to disconnect the connection of the at least one energy source from the at least one energy consumer and to connect the at least one energy source to the at least one capacitor energy storage device if at least one of the following conditions is met: - at least one energy source is in a non-critical energy generation operating state, - A predetermined period of time has elapsed since entering the critical energy generation operating state, - a charging current generated by at least one energy source is below a threshold charging current.

[0019] According to a further aspect of the present invention, the aforementioned problem is solved by a method according to claim 6 for operating an energy recovery system, preferably an energy recovery system constructed according to the invention, the energy recovery system comprising: - at least one energy source for converting kinetic energy into electrical energy, - at least one capacitor energy storage device, - at least one energy consumer.

[0020] The method according to the invention comprises the following measures: a) Recording an energy generation operating state of at least one energy source, b) Determine whether the energy generation operating state is a critical energy generation operating state that overloads the at least one capacitor energy storage device or a non-critical energy generation operating state that does not overload the at least one capacitor energy storage device. c) Connecting the at least one energy source with the at least one energy consumer, if in measure b) it is determined that the energy generation operating state is a critical energy generation operating state, and connecting the at least one energy source with the at least one capacitor energy storage device, if in measure b) it is determined that the energy generation operating state is a non-critical energy generation operating state.

[0021] Measure b) stipulates that the energy generation operating state is a critical energy generation operating state if at least one energy source is in an intensive recovery operating state.

[0022] Furthermore, it can be determined that the energy generation operating state is a critical energy generation operating state if a charging voltage generated by the at least one energy source is above a threshold charging voltage.

[0023] Measure b) stipulates that at least one energy source is in an intensive recovery operating state if at least one of the following conditions is met: - which includes at least one energy source, at least one traction electric motor in an electric vehicle, and a deceleration of the vehicle is above a threshold deceleration, - the at least one energy source includes at least one steering electric motor in a power steering system of a vehicle and the extent of the steering interventions carried out to maintain a steering state is above a threshold extent and / or the frequency of the steering interventions carried out to maintain a steering state is above a threshold frequency, - the at least one energy source includes at least one stabilizing electric motor in a roll stabilization system of a vehicle and the extent of the roll interventions carried out to maintain a roll state is above a threshold extent and / or the frequency of the roll interventions carried out to maintain a roll state is above a threshold frequency.

[0024] To ensure sufficient charging of the at least one capacitor energy storage device, it is further proposed that when, in measure c), the at least one energy source is connected to the at least one energy consumer, the connection of the at least one energy source to the at least one energy consumer is again removed and the at least one energy source is connected to the at least one capacitor energy storage device if at least one of the following conditions is met: - in a subsequent implementation of measure b) of the repeatedly implemented measures a) to c), it is determined that the energy generation operating state is a non-critical energy generation operating state, - A predetermined period of time has elapsed since entering the critical energy generation operating state and connecting at least one energy source to at least one energy consumer, - a charging current generated by at least one energy source is below a threshold charging current.

[0025] It should be noted that, where it is stated in connection with the present invention that at least one of several conditions must be met in order to recognize the existence of a certain state or to take certain measures, this does not mean that each of the stated conditions is monitored for its existence. Each individual condition, or only some of the stated conditions, can be monitored for their presence or absence without actually considering the other conditions, in order to draw the necessary conclusions or to be able to take the necessary measures.

[0026] The present invention is described below with reference to the enclosed Fig. 1. A detailed description is provided, showing in principle an energy recovery system, for example in a vehicle.

[0027] In Fig. In 1, such an energy recovery system is generally designated by 10. The energy recovery system 10, used, for example, in a vehicle, particularly an electric vehicle, comprises one or more energy sources 12 capable of converting kinetic energy into electrical energy. Such an energy source 12 can, for example, comprise one or more traction electric motors of an electric vehicle, which, during braking, convert the kinetic energy released when the vehicle decelerates into electrical energy in a generator operation. Alternatively or additionally, such an energy source 12 can comprise one or more steering electric motors in a power steering system of a vehicle.These steering electric motors, which assist the steering operation, can convert kinetic energy, resulting from external forces acting on the steered wheels of a vehicle, into electrical energy in generator mode. Such forces can occur, for example, when a vehicle is driven on uneven roads and the steering electric motors are used to keep the steered wheels in the steering position specified by the driver. Alternatively or additionally, such an energy source 12 can comprise one or more stabilizing electric motors of a vehicle's roll stabilization system. Such a roll stabilization system serves to keep the vehicle body in a stable position, particularly when cornering or driving on uneven terrain.

[0028] The energy recovery system 10 further comprises one or more capacitor energy storage devices 14. Such a capacitor energy storage device 14 can comprise several capacitor cells 16 connected in series. Electrical energy generated by the energy source 12 during energy recovery operation can be fed into the capacitor energy storage device 14 in the form of a charging voltage applied to the device and a charging current flowing when the voltage is applied, in order to electrically charge the device or the capacitor cells 16 contained therein and thereby store energy that can be fed into, for example, a vehicle's electrical system when required.

[0029] The energy recovery system 10 further comprises one or more energy consumers 18. In the Fig.In the embodiment shown in Figure 1, such an energy consumer 18 can comprise a resistance heater, for example in the form of a load resistor or a heating conductor, which generates heat when an electrical voltage is applied and an electric current is passed through it. This heat can be transferred to air L in the area of ​​a heat exchanger 20, which, for example, comprises a plurality of cooling fins, so that electrical energy generated by the energy source 12 in the energy recovery system 10 is dissipated in the form of heat energy. For example, the heat absorbed in the air L can be used to heat the interior of a vehicle if this air L is introduced into the interior.

[0030] In an alternative design of such an energy consumer 18, it can, for example, be designed as a latent heat storage device in which a phase transition is brought about by heating in a phase change material based, for example, on salt or paraffin, and energy can thereby be stored, which can subsequently be released, for example, to heat the air to be introduced into a vehicle interior.

[0031] In a further alternative embodiment, such an energy consumer 18 can comprise one or more electrically operated system areas present in a vehicle, which are generally operated from the on-board voltage system supplied by a battery, but can be supplied from the energy recovery system if electrical energy is available in the energy recovery system.

[0032] The energy recovery system 10 further comprises a control unit 22, which is designed to selectively direct the electrical energy present in the energy recovery system 10 or generated by the energy source 12 to either the capacitor energy storage device 14 or the energy consumer 18, which means that the electrical voltage generated by the energy source 12 is selectively applied to either the capacitor energy storage device 14 or the energy consumer 18.

[0033] The decision as to whether the electrical voltage generated by the energy source 12 is applied to the capacitor energy storage device 14 or the energy consumer 18 is made in the control unit 22 depending on whether the energy source 12 is in an energy generation operating state which, due to the comparatively high voltage generated, can lead to an overload of the capacitor energy storage device 14 and is therefore generally to be considered critical, or in an energy generation operating state in which the electrical voltage generated by the energy source 12 is in such a range that it does not lead to an overload of the capacitor energy storage device 14 and is therefore to be considered non-critical.For example, if the capacitor energy storage device 14 is designed for an operating voltage of 18 V, a threshold charging voltage set in the control unit 22 as a decision criterion can be in the range of this operating voltage of approximately 18 V.

[0034] If the electrical voltage generated by the energy source 12 during energy recovery operation is below this threshold charging voltage, the control unit 22 connects the capacitor energy storage device 14 to the energy source 12, so that the electrical voltage generated by the latter is applied to the capacitor energy storage device 14 and it is charged to store energy. If the electrical voltage generated by the energy source 12 and detected by a voltmeter 24 is above the threshold charging voltage, the control unit 22 decouples the capacitor energy storage device 14 from the energy source 12 and applies the voltage generated by the latter to the energy consumer 18 in order to dissipate the electrical energy generated in the energy recovery system in the manner described above or to use it in other areas of a vehicle.

[0035] According to the principles of the present invention, the feeding of electrical energy into the capacitor energy storage device 14 is prevented when the energy source(s) 12 are in an intensive energy recovery operating state. This can be a state in which, without detecting the charging voltage, for example by the voltmeter 24 and transmitting the corresponding information to the control unit 22, or detecting a charging current by an ammeter 26 and transmitting the corresponding information to the control unit 22, there is a fundamental possibility that a critical operating state with regard to the charge level is present and that an overload of the capacitor energy storage device 14 could occur. This can be, for example, an intensive braking process of a vehicle if it is electrically powered and one or more of the traction motors are used in generator mode to brake the vehicle.Even in a state where, for example, when the vehicle is moving on an uneven road, there are intense external influences on a power steering system or a roll stabilization system, and the steering electric motors or stabilization electric motors provided therein are operated intensively to keep the steering state or the roll state stable, excessively high voltages can be generated by the electric motors operating in phases in generator mode, which can lead to an overload of the capacitor energy storage 14.

[0036] Such intensive energy recuperation operating conditions can be detected, for example, by sensors 28 assigned to these various system areas. For instance, these sensors 28 can include one or more acceleration sensors that detect the occurrence of excessively strong deceleration and initiate a corresponding signal in the control unit 22. In the context of a power steering system, the sensors 28 can include sensors that detect the steering inputs generated in the power steering system and, in particular, feed information representing the extent and frequency of these steering inputs into the control unit 22.If the frequency is excessively high and / or the steering operation is excessively extensive, this can be used as a decision criterion to indicate that the vehicle is in such an intensive recuperation operating state and therefore, as long as this state exists, the capacitor energy storage 14 must be decoupled from the energy source(s) 12.

[0037] In order to return to a state in which the electrical energy generated in the energy recovery system 10 can be used to charge the capacitor energy storage system 14 or generally to power system areas of a vehicle from the capacitor energy storage system 14, after entering such a critical energy generation operating state that could potentially lead to an overload of the capacitor energy storage system 14, in which the capacitor energy storage system 14 is decoupled from the energy source 12, the control unit 22 can, for example, when it is detected that such an intensive recovery operating state no longer exists, for example because the deceleration of a vehicle has fallen below a critical level again or there is excessive influence on a power steering system orSince a roll stabilization system is no longer present, the control unit 22 terminates the coupling of the energy consumer 18 with the energy source 12 and accordingly re-establishes the coupling of the capacitor energy storage device 14 with the energy source 12. Since it can generally be assumed that such critical energy generation operating states leading to an overload of the capacitor energy storage device 14 only last a relatively short time, a predetermined time interval can be used as a further or alternative decision criterion for coupling the capacitor energy storage device 14 to the energy source 12. The elapsed time of this interval since the onset of the critical energy generation operating state, and therefore since the coupling of the energy consumer 18 with the energy source 12, leads to a switchover in order to re-couple the capacitor energy storage device 14 with the energy source 12.An alternative decision criterion could be, for example, the charging current detected by the current sensing device 26. If this current falls below a threshold charging current again after entering the critical energy generation operating state, it can be assumed that the risk of overloading the capacitor energy storage device 14 no longer exists, so that it can be coupled with the energy source 12 again.

[0038] By selectively coupling either the capacitor energy storage device 14 or the energy consumer 18 with the energy source 12, it becomes possible to eliminate the risk of overload and thus damage to the capacitor energy storage device 14 with a comparatively simple design. Therefore, it can generally be designed for an operating voltage that is not exceeded, or not significantly exceeded, in a normal, non-critical energy generation operating state of the energy source 12. Designing the capacitor energy storage device 14 to handle short-term load peaks can thus be avoided, which contributes to a reduction in the size and construction costs of the capacitor energy storage device 14.

Claims

[1] Energy recovery system, especially for a vehicle, comprising: - at least one energy source (12) for converting kinetic energy into electrical energy, - at least one energy storage device (14), - at least one energy consumer (18), - a control unit (22) for selectively connecting the at least one energy source (12) with the at least one energy storage device (14) or the at least one energy consumer (18), wherein the at least one energy source (12) comprises at least one of the following systems: - a drive system of an electric vehicle with at least one traction electric motor, - a power steering system of a vehicle with at least one electric steering motor - a roll stabilization system of a vehicle with at least one stabilizing electric motor, wherein the control unit (22) is configured to connect the at least one energy source (12) to the at least one energy consumer (18) when the at least one energy source (12) is in a critical energy generation operating state that overloads the at least one energy storage device (14), and to connect the at least one energy source (12) to the at least one energy storage device (14) when the at least one energy source (12) is in a non-critical energy generation operating state that does not overload the at least one energy storage device (14), characterized by , that at least one energy storage device (14) is a capacitor energy storage device (14), that the critical energy generation operating condition exists when at least one energy source (12) is in an intensive recovery operating condition, and that at least one energy source (12) is in the intensive recovery operating state if at least one of the following conditions is met: - the at least one energy source (12) comprises the at least one traction electric motor and a deceleration of the vehicle is above a threshold deceleration, - the at least one energy source (12) comprises the at least one steering electric motor and the extent of the steering interventions carried out to maintain a steering state is above a threshold extent and / or the frequency of the steering interventions carried out to maintain a steering state is above a threshold frequency, - the at least one energy source (12) comprises the at least one stabilizing electric motor and the extent of the roll control interventions carried out to maintain a roll state is above a threshold extent and / or the frequency of the roll control interventions carried out to maintain a roll state is above a threshold frequency. [2] Energy recovery system according to claim 1, characterized by , that the at least one capacitor energy storage device (14) comprises a plurality of capacitor cells (16) connected in series with each other. [3] Energy recovery system according to one of claims 1 or 2, characterized by , that the at least one energy consumer (18) comprises at least one of the following systems: - at least one load resistor, - at least one resistance heater for transferring heat to a heat transfer medium, - at least one latent heat storage system, - at least one electrically operated system area powered by a vehicle's on-board voltage system. [4] Energy recovery system according to one of claims 1-3, characterized by , that the critical energy generation operating condition is present when a charging voltage generated by the at least one energy source (12) is above a threshold charging voltage. [5] Energy recovery system according to one of claims 1-4, characterized by , that the control unit (22) is configured to disconnect the connection of the at least one energy source (12) with the at least one energy consumer (18) and to connect the at least one energy source (12) with the at least one capacitor energy storage device (14) when at least one of the following conditions is met: - at least one energy source (12) is in a non-critical energy generation operating state, - A predetermined period of time has elapsed since entering the critical energy generation operating state, - a charging current generated by at least one energy source (12) is below a threshold charging current. [6] Method for operating an energy recovery system, preferably according to one of the preceding claims, the energy recovery system comprising: - at least one energy source (12) for converting kinetic energy into electrical energy, - at least one capacitor energy storage device (14), - at least one energy consumer (18), the procedure includes the following measures: a) Recording an energy generation operating state of at least one energy source, b) Determine whether the energy generation operating state is a critical energy generation operating state that overloads the at least one capacitor energy storage device (14) or a non-critical energy generation operating state that does not overload the at least one capacitor energy storage device (14), c) Connecting the at least one energy source (12) to the at least one energy consumer (18) if, in measure b), it is determined that the energy generation operating state is a critical energy generation operating state, and connecting the at least one energy source (12) to the at least one capacitor energy storage device (14) if, in measure b), it is determined that the energy generation operating state is a non-critical energy generation operating state, where, in measure b), it is determined that the energy generation operating state is a critical energy generation operating state if at least one energy source (12) is in an intensive recovery operating state, where in measure b) it is determined that at least one energy source (12) is in the intensive recovery operating state if at least one of the following conditions is met: - the at least one energy source (12) comprises at least one traction electric motor in an electric vehicle and a deceleration of the vehicle is above a threshold deceleration, - the at least one energy source (12) comprises at least one steering electric motor in a power steering system of a vehicle and the extent of the steering interventions carried out to maintain a steering state is above a threshold extent and / or the frequency of the steering interventions carried out to maintain a steering state is above a threshold frequency, - the at least one energy source (12) comprises at least one stabilizing electric motor in a roll stabilization system of a vehicle and the extent of the roll interventions carried out to maintain a roll state is above a threshold extent and / or the frequency of the roll interventions carried out to maintain a roll state is above a threshold frequency. [7] Method according to claim 6, characterized by, that in measure b) it is determined that the energy generation operating state is a critical energy generation operating state if a charging voltage generated by the at least one energy source (12) is above a threshold charging voltage. [8] Method according to one of claims 6 or 7, characterized by , that if, in measure c), the at least one energy source (12) is connected to the at least one energy consumer (18), the connection of the at least one energy source (12) to the at least one energy consumer (18) is again removed and the at least one energy source (12) is connected to the at least one capacitor energy storage device (14), if at least one of the following conditions is met: - in a subsequent implementation of measure b) of the repeatedly implemented measures a) to c), it is determined that the energy generation operating state is a non-critical energy generation operating state, - a predetermined period of time has elapsed since entering the critical energy generation operating state and connecting the at least one energy source (12) to the at least one energy consumer (18), - a charging current generated by at least one energy source (12) is below a threshold charging current.

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