DE102013219293A1 - memory state - Google Patents

Abstract

Vehicle with a high-voltage electrical system, with a low-voltage electrical system, with a DC controller between the two on-board networks and a low-voltage energy storage (NVS) in the low-voltage electrical system and a high-voltage energy storage in the high-voltage electrical system, so that in a stance phase of the vehicle by the DC controller of the NVS with a predetermined current pulse is loadable and with a sensor assigned to the NVS, the current response to the current pulse can be measured.

Description

The invention relates to a vehicle with a high-voltage on-board electrical system, with a low-voltage on-board electrical system, with a DC controller between the two on-board networks and a low-voltage energy storage (NVS) in the low-voltage on-board electrical system and a high-voltage energy storage in the high-voltage on-board electrical system.

From the prior art vehicles with multi-voltage systems are known, see, for. Eg document DE10247523A1 , Thus, a DC-DC converter is suitable for transferring electrical power from a sub-board network having a first voltage level to a sub-board network having a second voltage level.

It is an object of the invention to provide an improved vehicle with a high-voltage vehicle electrical system, with a low-voltage on-board electrical system, with a DC-DC converter between the two on-board networks and a low-voltage energy storage (NVS) in the low-voltage on-board network and a high-voltage energy storage in the high-voltage vehicle electrical system.

This object is achieved by a vehicle according to claim 1. Advantageous embodiments and modifications of the invention will become apparent from the dependent claims.

According to the invention, in a stance phase of the vehicle, the NVS can load the NVS with a predefinable current pulse, and the voltage response to the current pulse can be measured with a battery sensor assigned to the NVS.

The DC-DC converter, also referred to as a DC-DC converter or DC / DC converter, is thus used to load the NVS in a specific operating phase of the vehicle, namely the stance phase, in order to determine information about the storage state of the NVS. The measurement of the voltage response relates to the measurement of the voltage at the end of the current pulse, which is of a defined period of time. The time duration is preferably of the order of 10 ⁰ -10 ² seconds.

According to a particularly preferred embodiment of the present invention, the vehicle comprises a charger for charging the high-voltage memory to an external power source, the vehicle during the stance phase to an external power source in a charging loadable and there is the current pulse through the DC chopper with fully loaded NVS.

This means that the defined load of the NVS takes place with a defined state of the NVS. The defined state is the fully loaded state of the NVS, i. H. the state of charge SoC is 100%.

The load is preferably carried out with the connection of selected consumers from the high-voltage vehicle electrical system and / or the low-voltage on-board electrical system.

This means that the current intensity of the current pulse can be purposefully increased in order to cause a higher voltage drop across the battery. In this way, according to a further embodiment, a plurality of current pulses can also be carried out with a respective voltage measurement in order, for. B. by connecting a respective different configuration of consumers current pulses of different current to form. Several current pulses form a current profile. The connection of the consumers is controlled by a control unit or by several control units. The self-adjusting current load can be monitored at least by the battery sensor. A regulation to an exact, specifiable target value is carried out by the DC-DC converter.

According to a further variant of the invention, the NVS can be discharged via the DC voltage regulator when fully charged until a discharge voltage value is reached, the charge quantity removed during the discharge from the full charge state until the discharge voltage value is reached can be determined by the battery sensor, when the discharge voltage value is reached NVS rechargeable and it can be determined by the battery sensor in the charge of the discharge voltage value until reaching a charge stop criterion charged amount of charge.

In particular, when the vehicle is in a charging process - alternatively at a sufficiently high state of charge of the high-voltage energy storage-, so can be carried out on the DC chopper capacity determination of the battery. For this purpose, the NVS is discharged at preferably fully charged NVS via the DC chopper until reaching a discharge voltage value with a time-varying current pulse constant current until reaching a voltage value (eg, 11.5 volts for a lead-acid battery). The constant amperage is ideally, but without limiting the general public between 20 and 50 A. This corresponds to a current strength, which also arises in a normal operating condition and is referred to as typical electrical system current range. According to a further embodiment variant of this typical electrical system current range can be determined via a self-learning function in the vehicle and used for the above current pulse. The amount of charge taken can be determined by the battery sensor over the detectable duration of the current pulse and the current intensity. This is called actual capacity. Optionally, the actual capacity can be related to a nominal capacity of the NVS (in the factory-new) state. After reaching the discharge voltage value, the battery is recharged via the DC chopper. Through current integration, the charged amount of charge can be determined by the battery sensor.

Furthermore, it makes sense if the charging time forms a charging stop criterion in order to terminate charging when a charging time has been reached, and / or if the charging current forms a charging stop criterion in order to terminate charging when a charging current is undershot, and / or if a terminal change on the vehicle forms a charge stop criterion to end the charge.

A terminal change is about switching the terminal 15 or disconnecting the charging cable.

According to a further embodiment of the invention, a disconnect switch is located between the low-voltage loads and the NVS, the disconnect switch can be opened and closed during a stance phase of the vehicle, the voltage at the NVS can be determined before closing the switch, and the duration of the opening of the switch can be determined.

This means that in a stance phase, the voltage of the NVS with the circuit not open (the so-called open circuit voltage) is measurable and the minimum time is determined within which the NVS was not connected. If the time duration exceeds a predefinable value, the measured no-load voltage can be used as the open-circuit voltage for determining the state of charge of the NVS. For a lead-acid battery, the time to be exceeded is about three to five hours.

Furthermore, it makes sense if the vehicle includes a control unit, and the controller controls the DC chopper, the battery sensor and the circuit breaker and monitors.

The control unit detects a stance phase or a charging phase of the vehicle as well as a charging status of the vehicle (eg charging connection for charging process is established / not established). In the stance phase, the vehicle is in an idle state. In a charging phase, the vehicle is also in the state and it is additionally loaded at the established charging connection.

It controls and monitors the DC chopper and loads to load the NVS and the battery sensor to measure the voltage levels. Measured values are stored by the control unit and transferred to an energy management system of the vehicle. If there is an optional disconnector, the control unit also controls and monitors it.

In addition, it is particularly useful if from the given current strength of the current pulse of the load and the voltage response an ohmic internal resistance of the NVS can be determined on a control unit of the vehicle, a first map is stored, the first map a relationship between the determined internal resistance and the state of charge reflects the given current, and the controller from the first map a state of charge of the NVS based on the current and the internal resistance determined.

The determined internal resistance correlates in particular with the power output capability of the memory, since in the first food alone the ohmic internal resistance determines the voltage of the NVS under load. An increasing internal resistance stands for a worsening memory state or SoH (state-of-health).

The first map is a characteristic of the type of battery used characteristic. The determination of such a map is not part of this document and usually takes place during the development of the vehicle.

Furthermore, a second map can be stored on the control unit of the vehicle, which represents a relationship between the determined no-load voltage and the state of charge, wherein the controller determines from the second map a state of charge of the NVS based on the measured open circuit voltage.

This is particularly useful if the measured open circuit voltage can be considered as open circuit voltage.

The second map is a characteristic of the type of battery used characteristic. The determination of such a map is not part of this document and usually takes place during the development of the vehicle.

In addition to the variants described, the battery temperature can also be determined during a measurement by the battery sensor. An advantage arises when the first and the second map contain the temperature as a parameter.

The invention is based on the following considerations:
It is assumed that vehicles with an electrified powertrain. This applies to hybrid and plug-in hybrid vehicles as well as electric vehicles with a low-voltage on-board electrical system (eg rated voltage position at 12 volts), which is supplied via a DC / DC converter from the high-voltage on-board electrical system. The well-known for conventional vehicles from the prior art method for determining the memory state of an energy storage in the electrical system is only partially suitable for an energy storage in the low-voltage electrical system (NV energy storage or NVS) of a vehicle with a HV electrical system.

It is proposed to perform a reduction of the power output of the DC / DC converter situationally (that is, limited in time to a few minutes) in order to bring about specifically defined or specific load situations on the NVS. By detecting the voltage at the NVS which is set in the respective defined load state, the internal resistance and, to a limited extent, the storage state can be determined with regard to its state of charge (SoC) and its state of health (SoH).

This makes it possible to take energy management measures in the event of a critical storage state in order to be able to operate the vehicle electrical system in a voltage-stable and fail-safe manner. In this way, the risk of failure of the NVS can be reduced in a vehicle with HV electrical system.

In detail, it is assumed that state-of-the-art technology enables conventional vehicles to determine the condition of the NVS in the 12 V electrical system based on the detection of load situations by means of an intelligent battery sensor (IBS) and the detection of idle conditions by means of the IBS.

It may be at an engine start of the conventional vehicle to determine the performance of the NVS, d. H. the starter battery, the resulting from the engine start measurable high current load of the starter battery are used to determine the capacity of the battery or the internal resistance of the battery over the resulting adjustable voltage at the battery terminals. This procedure is called start evaluation.

In order to determine the state of charge of the NVS, a measurement of the quiescent voltage is carried out by the IBS in phases in which the memory is charged only negligibly (for example, only by quiescent current). The value of the quiescent voltage represents the acid density in the electrolyte of the battery according to the Nernst equation and gives approximately the state of charge of the battery, since at rest, the state of charge of the battery (SoC) with the rest voltage (U ₀ ) correlated in the known manner. With a lead-acid battery as NVS an approximately linear behavior results. In order to obtain as meaningful measurement results as possible, it is necessary that the battery is not or only negligibly loaded for a long period of time before the measurement of the quiescent voltage takes place. This method is called resting voltage measurement.

The state of charge of the battery, after determining the state of charge via a quiescent voltage measurement by integration of the discharged current and the charged current z. B. be updated during the driving of the vehicle by an updating balance.

In order to check the plausibility of this balanced state of charge, the current load resulting from the operation of the vehicle, for instance at terminal 15 (eg entertainment functions, etc.), can be used to determine the performance or the internal resistance by detecting the resulting measurable voltage at the battery terminals to determine the battery. The internal resistance, for example, in a lead-acid battery shows a weak dependence on the state of charge of the battery and is influenced by the battery temperature (also measurable with the IBS) and the discharge rate (non-linear). This procedure is referred to as SoC plausibility.

The above-described from the prior art known determination of the state of charge of an NV energy storage in the 12 V electrical system is not useful in a vehicle with HV electrical system.

In such vehicles, the 12 V electrical system is supported by the supply of the 12 V electrical system via a DC / DC converter from the HV electrical system when activating the terminal 15 via the converter. Thus, the load of the battery caused by the engine start is too low to be able to draw conclusions about the condition of the NVS via the start evaluation as introduced in the document. Under certain circumstances, the engine is even started via the HV electrical system.

For the same reason, the method of SoC plausibility check as introduced in the document is just as inapplicable.

Furthermore, as a result of a regularly occurring in such a vehicle balancing of cells of the HV memory during the rest periods of the vehicle and the recurrent current load on the battery no meaningful resting voltage measurement as introduced in the document is reliably feasible.

Thus, a determinability of the NVS in vehicles with high-voltage vehicle electrical system is not given, in particular not by transferring the methods that are known in the art for conventional vehicles with only a low-voltage electrical system. It can lead to unwanted and sudden malfunctions of the NVS.

It is proposed to carry out a memory state determination (possibly with fully charged battery, that is to say at SoC = 100%) during a standstill and / or charging phase of the vehicle by the DC / DC converter and / or by consumers. The memory state determination consists in the defined load of the NVS by the DC / DC converter and in a determination of the voltage response according to a predeterminable current profile. Thus, the internal resistance of the NVS can be determined. By a simultaneous simultaneous activation of multiple consumers, an internal resistance determination is possible even at an increased current load. This results in an internal resistance value which enables a performance determination under high current loads with optimized accuracy.

In addition, after the determination of the internal resistance by a circuit breaker, the NVS can be disconnected from the electrical system and a quiescent voltage measurement can be measured before the request for the switch closure (eg for a cell symmetrization of the HV memory). Depending on the duration of the switch opening, the quiescent voltage measurement can be discarded or used for a SoC determination.

Additionally or alternatively, in the event of an imminent prolonged service life known to the vehicle, the battery can be discharged via the DC / DC converter with defined current to a minimum voltage value and can be charged in a defined manner in the case of a charging device connected to an external power supply of the vehicle to determine available capacity.

Hereinafter, a preferred embodiment of the invention will be described with reference to the accompanying drawings. This results in further details, preferred embodiments and further developments of the invention. In detail shows schematically

1 Vehicle electrical system for a vehicle with two voltage levels and a DC chopper

The 1 shows a schematic section of an electrical system of a hybrid, plug-in hybrid or electric vehicle with an AC-DC adjuster (also referred to as a charger, 1 ) for charging a high-voltage memory (HV memory, 3 ) on an external AC mains (not shown). For high-voltage storage are high-voltage consumers ( 2 ) connected in parallel.

A DC-DC converter, also referred to as a DC-DC converter or DC / DC converter ( 4 ), bi-directionally transfers power as an electrical interface between a high-voltage vehicle electrical system in which the high-voltage storage is integrated, and a low-voltage on-board electrical system into which a low-voltage accumulator (NVS, 6 ) is integrated.

The NVS is preferably designed as a lead-acid battery, the HV memory as a lithium-ion battery. NVS are low-voltage consumers ( 5 ) is connected in parallel and the NVS is assigned a battery sensor for measuring battery current and battery voltage.

Optionally there is a circuit breaker ( 7 ) between the NVS and the low-voltage consumers.

At least one controller controls and monitors the charger, DC chopper, consumers, battery sensor and optional disconnect switch.

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 10247523 A1 [0002]

Claims (9)

Vehicle with a high-voltage electrical system, with a low-voltage onboard power, with a DC controller between the two on-board networks and a low-voltage energy storage (NVS) in the low-voltage electrical system and a high-voltage energy storage in the high-voltage electrical system, characterized - in a stance phase of the vehicle by the DC controller of the NVS with a predetermined current pulse loadable and - the current response to the current pulse can be measured with a battery sensor assigned to the NVS. A vehicle according to claim 1, characterized in that - the vehicle comprises a charger for charging the high-voltage accumulator to an external power source, - during the stance phase, the vehicle at an external power source in a charging is loadable, and - the current pulse through the DC chopper when fully loaded NVS he follows. Vehicle according to one of claims 1 or 2, characterized in that - the load takes place with the connection of selected consumers from the high-voltage vehicle electrical system and / or the low-voltage vehicle electrical system. Vehicle according to one of the preceding claims, characterized in that - the NVS can be discharged via the DC converter when fully charged until reaching a discharge voltage value, - the amount of charge taken during the discharge from the full state of charge to reaching the discharge voltage value can be determined by the battery sensor, can be charged upon reaching the discharge voltage value of the NVS, and - the amount of charge charged in the charge from the discharge voltage value until a charge stop criterion has been reached can be determined by the battery sensor. Vehicle according to one of claims 1 or 2, characterized in that - the charging time forms a charge stop criterion to terminate the charge upon reaching a charging time, - the charging current forms a charge stop criterion to end the charge when falling below a charging current, and that - a terminal change on the vehicle forms a charge stop criterion to end the charge. Vehicle according to one of the preceding claims, characterized in that - between the low-voltage consumers and the NVS a disconnect switch ( 7 - is located, and - the circuit breaker during a stance phase of the vehicle is openable, and - before closing the switch, the open circuit voltage at the NVS is determined, and - the duration of the opening of the switch can be determined. Vehicle according to one of the preceding claims, characterized in that - the vehicle comprises a control unit, and - the control unit controls the DC chopper, the battery sensor and the circuit breaker and monitors. Vehicle according to one of the preceding claims, characterized in that - an ohmic internal resistance of the NVS can be determined from the given current strength of the current pulse of the load and the voltage response, - a first characteristic field is stored on a control device of the vehicle, - the first characteristic field has a relationship between the determined internal resistance and the state of charge at the given current reflects, and - the controller determines from the first map a state of charge of the NVS based on the current and the internal resistance. Vehicle according to claim 6, characterized in that - on the control unit of the vehicle, a second map is stored, - the second map represents a relationship between the determined open circuit voltage and the state of charge, and - the controller from the second map a state of charge of the NVS based on measured open circuit voltage.

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