DE102021119729A1 - Charging device in an electric vehicle - Google Patents

Abstract

The present invention relates to a charging device in an electric vehicle (1), which enables electricity from a photovoltaic system (6) to be used to charge a high-voltage battery (2) in the electric vehicle (1). of the type mentioned above while improving efficiency when using electricity from a photovoltaic system to charge a high-voltage battery (2) in the electric vehicle (1), it is proposed that the high-voltage battery (2) have its own Has input (8) for the photovoltaic feed.

Description

The present invention relates to a charging device in an electric vehicle, which makes it possible to use electricity from a photovoltaic system to charge a high-voltage battery in the electric vehicle.

It is known from the prior art to charge an electric vehicle with excess electricity from a photovoltaic system. However, this is always done via an external, stationary charging device that is fed by the photovoltaic system instead of electricity from the public grid.

Alternatively, photovoltaic modules are provided in, on or on the electric vehicle itself. An outer surface of the vehicle in question then serves as a carrier, or the photovoltaic modules form part of the outer surface of the electric vehicle.

The object of the present invention is to create a charging device of the type mentioned above while improving efficiency when using electricity from a photovoltaic system for charging a high-voltage battery in the electric vehicle.

This object is achieved by the features of claim 1 in that the charging device in the electric vehicle allows use of electricity from a photovoltaic system for charging a high-voltage battery in the electric vehicle by the high-voltage battery own Has input for a photovoltaic feed. This means that the photovoltaic feed-in is decoupled from a traction network and connected to the high-voltage battery.

The present invention is based on the knowledge that a photovoltaic feed-in via the HV traction network is generally only economical when the vehicle in question is in operation. The HV battery is then active and the LV vehicle electrical system is constantly supplied with energy. However, if the vehicle is parked and switched off, then active switches, which connect the high-voltage battery to the HV vehicle electrical system, must be kept closed continuously. In the case of HV battery systems, preference is given to using mechanical switches which are kept closed by the action of a magnetic force. The electrical work required for this depends on a maximum current of the HV vehicle electrical system signal carrier used. Since the switches of the traction network must be able to switch off very high currents, these switches are of correspondingly robust construction and require a comparatively large amount of electrical energy in order to be kept closed. For continuous charging using photovoltaics, this minimum amount of electrical work, which is only required to hold the magnetic switches, must be applied continuously, which has an extremely negative effect on the resulting efficiency of the PV feed-in. In unfavorable weather conditions, the electrical holding work of the switches can exceed the electrical work resulting from the PV system. The resulting energy balance at the HV battery is then even negative, so a net energy gain intended by the photovoltaic system becomes a loss. If the electrical energy of the vehicle's PV system is fed in via the HV on-board network, all consumers on the HV on-board network must also be kept awake, which results in increased energy consumption.

In order to prevent this, according to the state of the art, a control unit has to weigh up whether it makes sense at all to switch on the photovoltaic system, depending on the available power from solar radiation. Due to the power loss of the switches in the traction network, the profitable charging time is significantly reduced. In order not to fully use the capacity of the battery of the 12 V, 24 V or 48 V voltage level due to this holding work, the operation of galvanically isolated DC/DC converters is also necessary. This process is also subject to energy losses and further worsens the overall balance.

According to the invention, the high-voltage battery has its own input for a photovoltaic feed, so that a direct photovoltaic connection to a HV battery is realized while being decoupled from the traction network. This approach represents a simple way of connecting the PV feed-in directly to the HV battery with little additional equipment, without having to take the detour via the HV traction network. In this way, all other consumers on the HV traction network can remain offline.

Advantageous developments are the subject of the dependent claims. Accordingly, the charging device has a separate circuit branch that extends from the photovoltaic system via a control unit of the photovoltaic system with a downstream inverter to an additional HV plug that is adapted to the input. This circuit branch represents a bypass of the traction network in the case of pure charging by the photovoltaic system, via which feed-in takes place directly from the photovoltaic system to charge the high-voltage battery. This additional, separate charging line allows the high-voltage battery to be fed in from the photovoltaic system via the HV traction network be dispensed with, so that the photovoltaic feed-in when the vehicle is stationary is energetically attractive.

The photovoltaic feed-in is now docked directly to the other HV connector of the battery, so that the control units of the HV vehicle electrical system no longer have to be kept active in the event of a photovoltaic charging process.

Advantageously, the high-voltage battery in the high-voltage junction box, HVJB for short, has at least one, preferably two, additional switches. Due to the lower current, these switches can be dimensioned smaller than the normal HV switches for the traction network. As an alternative to switches, relays could be used to protect the connector.

In a development of the invention, the battery management system, BMS for short, is designed to switch the photovoltaic feed on the high-voltage battery on and off via the at least one additional switch. The at least one switch for the photovoltaic charging is advantageously arranged logically behind switches of the traction network of the battery. This makes it possible for the battery to be charged via a photovoltaic system without affecting the HV traction network and its components, e.g. with regard to waking hours, etc.

In order for the injection to happen, the BMS needs to be “awake” all the time to keep switches closed and also to monitor the HV battery. The currents, temperatures and cell voltages in the battery are also monitored during charging. The BMS advantageously switches the photovoltaic feed on and off in coordination with the control device for the photovoltaic system. In an alternative embodiment, these processes are controlled via a central vehicle control VCU. In any case, it must be ensured for switching on that the inverter is designed to adapt the voltage level at its output to the voltage level of the high-voltage battery. For this purpose, the inverter is connected to the battery management system to exchange this data or current measured values of the voltage on the high-voltage battery. For switching off, the inverter must also ensure that no more current flows, so that the switches are not switched under load. Only after the switch has been opened can the BMS be switched from a wake mode to a more economical sleep mode.

The BMS also determines the energy throughput through the photovoltaic system in order to monitor the warranty conditions of the photovoltaic system. Monitoring by the BMS is crucial in order to ensure reliable feed-in at all times. In case of failure, the BMS will open the switches to protect the HV battery.

• 1: ein Flussdiagramm eines Elektro-Fahrzeugs mit einer Erweiterung gemäß eines Ausführungsbeispiels der Erfindung;
• 2: ein Flussdiagramm eines Elektro-Fahrzeugs nach dem Stand der Technik in einer Darstellung gemäß 1 und
• 3: ein detaillierteres Blockschaltdiagramm unter Andeutung abschaltbarer Bereiche.

Further features and advantages of embodiments according to the invention are explained in more detail below with reference to exemplary embodiments using the drawing. It shows in a schematic representation:

• 1 : a flow chart of an electric vehicle with an extension according to an embodiment of the invention;
• 2 FIG. 1: a flowchart of an electric vehicle according to the prior art in an illustration according to FIG 1 and
• 3 : a more detailed block diagram indicating areas that can be switched off.

The same reference symbols are always used for the same elements or method steps throughout the various figures. Without restricting the invention, only one application of exemplary embodiments of the invention using battery modules for electrically powered road vehicles is shown and described below. However, it is obvious to the person skilled in the art that an adaptation to mixed forms, such as hybrid vehicles, as well as to electrically powered aircraft or ships, and on the other hand to stationary applications for power supply is also possible in the same way.

Several technical approaches are currently being discussed to equip electric vehicles with photovoltaic systems and thereby charge the vehicle's high-voltage battery regularly and in an environmentally friendly manner. These concepts provide for the electrical energy generated by the photovoltaic systems to be fed in via a HV traction network. As long as the vehicle in question is in operation, the HV battery is active anyway and an LV vehicle electrical system is constantly supplied with energy. However, if the vehicle is parked and switched off, then active switches that connect the battery system to the HV on-board network must be kept closed continuously. In the case of battery systems, preference is given to using mechanical switches which are kept closed by the action of a magnetic force. The electrical work required for this depends on the maximum current of the HV on-board signal carrier used. Since the switches of the traction network have to be able to switch off very high currents, they are built to be correspondingly robust and require a comparatively large amount of energy to be kept closed. For continuous charging using photovoltaics, the minimum The amount of electrical work required to hold the magnetic switches must be applied continuously, which has an extremely negative impact on the resulting PV feed-in efficiency.

2 shows a flowchart of an electric vehicle 1 that is fundamentally known from the prior art. In it, a high-voltage battery 2 with a battery management system BMS and a higher-level vehicle controller VCU form the core for a regulated supply of an electric motor 3 with electrical Energy through a HV traction network 4, shown here in simplified form, for driving the vehicle 1. During regenerative braking, electrical energy can also be returned to the high-voltage battery 2 via the electric motor 3, which is then operated as a generator.

In order to comply with applicable safety regulations, a high-voltage battery 2 must be equipped with at least two mechanically separable high-voltage switching units 5 for reasons of redundancy, which are able to electrically isolate the battery voltage from the rest of the vehicle electrical system. Electrical work must therefore be performed to hold the high-voltage switching unit 5 of the battery system. The energy flow through this high-voltage switching unit 5 must be decoupled from the HV network and therefore takes place from a low-voltage or LV vehicle electrical system with a voltage level of only 12 V to 24 V assumed in this example. To the capacity of a 24 V -Battery in this LV on-board network not to be fully stressed by the holding work are additionally - without graphic representation in 2 - Provided galvanically isolated DC/DC controllers for supplying the LV vehicle electrical system and thus above all the high-voltage switching unit 5 . This process also incurs electrical losses that add to the losses of the HV switch holding operation.

Regulation and control of the high-voltage supply between the high-voltage battery 2 and the electric motor 3 as a so-called traction circuit 4 within the electric vehicle 1 therefore also requires the operation of a low-voltage or LV vehicle electrical system. While driving, the high-voltage battery 2 provides the necessary energy for the propulsion of the vehicle 1 via the electric motor 3 and the operation of the LV vehicle electrical system described above.

If the sun shines strong enough, the BMS of a vehicle 1 equipped with a photovoltaic system 6 receives a signal from a control unit Ctrl of the photovoltaic system 6 integrated, for example, on the roof of this vehicle 1. The BMS transmits a current voltage level to the PV control unit Ctrl, so that a subsequent inverter Inv upconverts the electrical energy provided by the photovoltaic system 6 to this voltage level. Then the PV feed-in is switched on by the BMS via switches in the HV traction network 4, in 2 simplified as a summation point. The high-voltage battery 2 of the vehicle 1 is then additionally charged by the photovoltaic system 6 while driving via the HV traction network 4 . The BMS assumes the monitoring of the PV feed-in within this charging device 7 in order to reliably prevent overcharging, for example.

If the vehicle 1 after 2 but now stands still and is switched off, but the sun is shining and the available charging capacity of the photovoltaic system 6 would be large enough, then the HV battery 2 must continue to be charged via the HV traction network 4 . For this purpose, all components from the VCU to the high-voltage switching unit 5 within the HV traction network 4 that have previously been put into an energy-saving sleep state must then be activated or “woken up”. This gives rise to the problem that electrical work is required via the LV vehicle electrical system to hold the HV switches in the HV traction network 4 . In total, approximately 100 W of auxiliary consumer loads occur within the charging device 7 when charging the vehicle 1 in the idle state.

This is where the present invention comes in, the aim of which is to create a charging device 7 that improves efficiency when using electricity from a photovoltaic system to charge a high-voltage battery in the electric vehicle. This goal is achieved in that the auxiliary consumer load indicated above is significantly reduced. For this purpose, a charging device in the electric vehicle 1 that enables the use of electricity from a photovoltaic system 6 to charge the high-voltage battery 2 in the electric vehicle is connected to the high-voltage battery 2 via a dedicated input 8 . While known approaches with reference to 2 When the vehicle 1 is at a standstill, all components of the HV traction network 4 also need to be woken up. This saves the auxiliary consumer load from the HV on-board network estimated above at approx. 100 W when the vehicle is at rest during PV charging, and this makes PV charging possible even at lower charging capacities with a positive power balance. If the vehicle in question has been parked and the sun is shining, according to this concept for a charging device 7 it is no longer necessary to wake up the entire HV traction network 4, which would have a standby consumption of approx. 100 W, but the high-voltage battery 2 is charged directly via its own input 8 connected to the photovoltaic system 6 . The additional consumption of 100 W is saved by direct charging when stationary.

In the specific process, the photovoltaic control unit Crtl wakes up the VCU so that it transfers the BMS from sleep mode to active operation. The BMS then receives the message from the PV control unit Crtl that the HV battery 2 should be charged and then transmits the current voltage level for the inverter Inv. The PV feed is then connected via the described separate circuit branch from the photovoltaic system 6 to the high-voltage battery 2 via a switch 9 and monitored by the BMS. The switch 9 is designed to be opened and closed by the BMS. The BMS also monitors the currents, cell voltages and temperatures in the high-voltage battery 2. If an error occurs, the BMS switches off the PV feed-in by immediately opening the switch 9. Alternatively, the BMS will transmit a signal to the control device Crtl of the photovoltaic system 6 to terminate the feed as soon as the high-voltage battery 2 is fully charged. The BMS then opens the switches 9 as soon as there is no longer any load and all the control devices mentioned above can be switched back to sleep mode.

3 now shows, in a modified and partly more detailed representation, an entire energy supply of an electric drive with an extension according to FIG 1 . If electrical energy from the PV system of the vehicle is fed into the battery 2 via a separate input 8 in the HV level instead of via the HV on-board network, it is no longer necessary to keep all consumers from the HV on-board network awake. Only components of the photovoltaic system 6 located within the dashed line via the respective maximum power point tracker MPPT and a DC voltage controller within a module control unit MCU or Crtl and part of the BMS must be active. The BMS is supplied via a 12V low-voltage network NV, which is also switched to active.

Within the BMS, a significantly smaller and therefore more economical contactor is provided as a safety switch in a separate branch. This results in an overall significantly reduced energy consumption.

With the charging device 7 described above, the high-voltage battery 2 is charged with greater efficiency by the photovoltaic device 6 at its own input 8, and charging via the photovoltaic system 6 of the electric vehicle 1 through a separate circuit branch is worthwhile in terms of energy and ecologically even at lower charging capacities, such as those provided in the shade or under cloudy skies.

Reference List

1

electric vehicle

2

high-voltage battery

3

electric motor

4

HV traction network

5

High-voltage switching unit in the HV traction network 4

6

Photovoltaic system

7

loading device

8th

separate input of the separate circuit branch from the photovoltaic system 6 to the high-voltage battery 2

9

Switch within the PV charging branch

B

Bus (LIN/CAN)

BMS

battery management system

Ctrl

Photovoltaic system control device 6

f

fuse

HV

high-voltage level

HVJB

High Voltage Connector Box

inventory

adjustable inverter

MCU

module control unit

MPPT

Maximum powerpoint tracker

NV

low voltage level

OBC

On board charger

S

contactor

Sht

measuring shunt

VCU

central vehicle control

Claims (10)

Charging device in an electric vehicle (1), which enables electricity from a photovoltaic system (6) to be used to charge a high-voltage battery (2) in the electric vehicle (1), characterized in that the charging device (7 ) is connected to the high-voltage battery (2) via its own input (8). Charging device according to the preceding claim, characterized in that the charging device (7) has a separate circuit has a branch that extends from the photovoltaic system (6) via a control unit (Crtl) of the photovoltaic system (6) with a downstream inverter (Inv) to an additional HV plug that is adapted to the input (8). Charging device according to the preceding claim, characterized in that the high-voltage battery (2) has at least one, preferably two, further switches (9) in a high-voltage junction box. Charging device according to one of the preceding claims, characterized in that the battery management system (BMS) is designed to switch the photovoltaic feed on the high-voltage battery (2) on and off via the at least one additional switch (9). Charging device according to the preceding claim, characterized in that the battery management system (BMS) is designed to switch the photovoltaic feed on and off in coordination with the control unit (Crtl) for the photovoltaic system. Loading device according to one of Claims 1 - 4 , characterized in that a central vehicle control unit (VCU) is designed to switch the photovoltaic feed on and off in coordination with the control unit (Crtl) for the photovoltaic system. Charging device according to one of the preceding claims, characterized in that the inverter (Inv) is designed to adapt a voltage level at its output to a voltage level of the high-voltage battery (2). Charging device according to the preceding claim, characterized in that the inverter (Inv) is connected to the battery management system (BMS) for data exchange. Charging device according to one of the preceding claims, characterized in that the photovoltaic system (6) is connected to the high-voltage battery (2) via a switch (9) and is monitored by the BMS. Charging device according to the preceding claim, characterized in that the switch (9) is designed to be opened and closed by the battery management system (BMS).

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