DE102010010058A1 - Wiring system for vehicle, has energy storage, electric motor-generator-unit for alternating current and battery-charging unit made of external alternating current network for charging energy storage - Google Patents

Abstract

The wiring system has energy storage (2), an electric motor-generator-unit (4) for alternating current (8) and a battery-charging unit made of an external alternating current network for charging the energy storage. The battery-charging unit has an alternating current-direct current-converter (3), and a direct current-alternating current converter.

Description

The invention relates to a vehicle electrical system for a vehicle and in particular to a vehicle electrical system which has a charging unit for charging an energy store.

Electric vehicles are vehicles that are powered by electrical energy. These include in the following pure electric vehicles, but also those that have combinations with an internal combustion engine or a fuel cell. In a pure electric vehicle, the drive power is provided solely by an electric machine. An energy extraction from the fuel cell or the energy storage is generally used to provide drive power and to supply the vehicle electrical system.

The charging of the memory takes place by supplying electrical energy via a battery charger or a generator. When using a generator, kinetic energy provided by regenerative braking or the engine is converted into electrical energy. This process can also be carried out while driving, in electric vehicles with the aid of an onboard battery charger or in the form of an external off-board charger.

Due to the compact size, the relatively low weight and the very good efficiency are used as on-board battery charging unit essentially primarily clocked high-frequency charging units. In this case, such primary-clocked high-frequency charging units require some circuit complexity, which is also reflected in the weight and space requirements of such charging units. In addition, components for supplying the drive system (electric motor) or for feeding back energy into the battery by recuperation (regenerative braking) in electric or plug-in hybrid vehicles are provided, which like the on-board charging unit part of the power electronics of the vehicle are.

Object of the present invention is to reduce the scope, cost and space requirements of the power electronics of the vehicle.

The object is achieved by an arrangement according to claim 1. refinements and developments of the inventive concept are the subject of dependent claims.

The object is achieved in particular by a battery charging unit integrated into an electrical system of a vehicle, which also supplies an electric motor of the vehicle for the purpose of supplying energy to an energy storage device of the vehicle (recuperation) and for charging the energy storage device from an external one AC mains is used.

The invention will be explained in more detail with reference to the embodiments illustrated in the figures of the drawings, wherein like elements are provided with the same reference numerals. It shows:

1 an arrangement for recycling electrical energy;

2 the operating principle of a primary clocked high-frequency charging unit;

3 in a block diagram by way of example the interconnection of the battery charging unit 2 for charging a battery by a motor-generator unit operated as a generator;

4 in a block diagram by way of example the interconnection of the battery charging unit 2 for charging a battery from an external AC mains;

5 in a block diagram by way of example the interconnection of the battery charging unit 2 for operating a motor-generator unit as a motor powered by the battery;

6 a diagram of the energy flow in the supply of a motor-generator unit from a battery; and

7 in a diagram, the energy flow in the recovery of converted braking energy of a vehicle in the battery.

As an energy storage for electric vehicle applications, various types of batteries or batteries such as lead acid batteries, nickel-metal hydride, nickel-zinc or lithium-ion cells can be used. The electrical energy supplied during a charging process is used to increase the state of charge (SOC) of the accumulator. All accumulators or batteries are charged at an adapted voltage level with special characteristics, the charging process is carried out with direct current.

1 shows an arrangement for returning under certain operating conditions of the vehicle generated electrical energy in an energy storage. The vehicle 1 has an energy storage 2 , an AC-DC converter 3 , a motor-generator unit 4 , Drive wheels 5 and a reduction gear 6 on. The return of electrical energy in the energy storage 2 takes place by converting mechanical energy of the drive wheels 5 , This is the motor-generator unit 4 over the reduction gear 6 with the axle and thus the drive wheels 5 of the vehicle 1 connected. The mechanical energy 33 on the drive wheels 5 is through the motor-generator unit 4 converted into electrical energy, in the form of alternating current 8th is present.

This alternating current 8th is through the AC-DC converter 3 in direct current 9 converted, the energy storage 2 is supplied. This can be the mechanical energy 33 on the drive wheels 5 from an internal combustion engine or from the braking energy (recuperation) when braking the vehicle. For example, in a pure electric vehicle mechanical energy to the drive wheels 5 to provide the energy flow is reversed (arrows 9 . 8th . 33 vice versa as in 1 shown). Electrical energy from the energy storage 1 is supplied as a DC to a DC-AC converter, which converts it into an AC and thus the motor-generator unit 4 fed. This in turn gives the mechanical energy generated thereby via the reduction gear 6 to the drive wheels 5 from.

Due to the necessary voltage adaptation and insulation, the battery charging units used in this case usually have a transformer which transforms the mains voltage depending on the type of battery and the number of cells to a corresponding charging voltage level. Then the AC voltage is rectified and smoothed. The simplest battery charging units work with conventional, designed for 50 Hz power frequency transformers and are simple in their design and therefore very cost-effective. They are mainly offered with unregulated charging curves, so-called W or Wa charging characteristics. Since the charging current adjusts as a function of the accumulator voltage and the accumulator voltage increases with increasing charging time, the charging current decreases as the state of charge of the accumulator increases.

However, mains voltage fluctuations due to the lack of control of the output voltage affect the course of the charging curve very strong. If the mains voltage is too low during charging, the accumulator will not be fully charged. However, in the reverse case with increased charging voltage can also come to a very high charging voltage to the accumulator, which can lead to overcharging and damage to the battery. In addition to the very high weight of such battery charging units (50 Hz battery charging units), the charging efficiency is relatively low (<80%) and the heat losses are correspondingly high.

Due to their weight, size and low efficiency, these "50 Hz" chargers are rarely used in the automotive industry, especially in on-board technology, but are mainly used in bearing technology, preferably in lead-acid batteries. Also, the possible charging characteristics severely limits the universal use of charging technology for different battery types. A better match to the different types of accumulators allow controlled linear battery charging units. These also have a large transformer, which converts the mains voltage into charging voltage.

The control of the charging voltage via a controller that controls a rectifier. The easiest way to monitor the charging process is by switching off / or switching over the set voltage. By regulating this battery charging unit is much less dependent on fluctuations in the mains voltage. But even here there is a significant disadvantage is that such a battery charging unit has a large volume and high weight, so that this technology is only partially suitable for on-board use, especially for large charging power. In addition, the disadvantages of the low efficiency and the necessary reactive power compensation remain.

One solution to the problems described above is to use primary clocked battery charging units. In this case, the effect is exploited that higher powers can be transmitted at high frequencies and / or the transformer (as the component with the highest volume and weight) with the same transmitted power is much smaller executable. The linear transformer is replaced by a rectifier and an electronic switch (eg by a switch bridge) which converts the low frequency (50 Hz) alternating voltage from the mains into an alternating voltage at a much higher frequency (20 kHz 200 kHz). A high-frequency transformer (eg in the automotive sector) with much smaller dimensions compared to the 50 Hz model converts the high-frequency AC voltage to the required charging voltage level. Subsequently, the usual rectification process with subsequent screening via a balancing capacitor. Due to the conversion of the voltage from mains frequency to much higher frequencies, this charging technology is also referred to as HF technology (HF = high frequency). The transformer used in this charging technology is much more efficient and develops less heat loss. Therefore High-frequency charging units can also be made much smaller and lighter in weight yet high efficiency of up to 93%.

2 shows an embodiment of a primary clocked high-frequency charging unit 26 with a filter 10 , one of these downstream rectifiers 11 , a downstream PFC correction filter 12 , this downstream smoothing units 13 . 17 and 19 , subsequently an electronic high-frequency switch 14 , following a high frequency transformer 15 , following a charging switch 18 and finally a control unit 20 , Frequencies above 20 kHz are considered as high frequency. The operating principle of such a primary clocked battery charging unit is based on a conversion in two stages. The AC voltage (mains voltage) with 50 Hz is using the rectifier 11 rectified and the smoothing unit 13 smoothed, so that there is a DC voltage at this point.

Subsequently, the direct current through the electronic high-frequency switch 14 back into a high-frequency AC voltage, z. B. implemented with a frequency of 70 kHz or higher. This high frequency AC voltage is generated by the high frequency transformer 15 converted to the desired level of the charging voltage, then via the rectifier 16 rectified, so that there is again a DC voltage at this point. With the help of the downstream components smoothing unit 17 , Charging switch 18 and sieve chain 19 the DC voltage is smoothed. The control unit 20 controls the electronic high-frequency switch 14 (eg pulse width modulation), for example, to charge a rechargeable battery with the correct voltage and current even under fluctuating load.

Such primary switched high-frequency battery charging units are insensitive to fluctuations in the mains input voltage, allow high efficiency (in optimized cases up to 93%) and no reactive power compensation is required. A disadvantage is the uneven loading of the network by the electronic switch. Therefore, due to the switching operation with high frequencies consuming measures to improve the EMC behavior (noise emission) required, as in 2 through the filter 10 shown. In addition, due to the deformation of the mains current (current pulses), a relatively expensive power factor correction (eg by means of a power factor correction filter 12 like in the 2 represented by) required. Nevertheless, the presented RF charging technology is currently preferred due to the low weight, the low volume and the high energy efficiency in the realization of on-board charging units.

In this case, such a battery charging unit 26 be divided into several functional groups. Such a subdivision initially results in two functional groups (see also 2 ). The one function group sees a first DC-DC converter 29 with filter 10 , the rectifier 11 , the power factor correction filter 12 and the smoothing unit 13 in front. The other functional group is a DC-DC converter 29 (eg DC chopper, chopper, etc.) with the high frequency switch 14 , the high-frequency transformer 15 , the rectifier 16 , the smoothing units 17 . 19 , the charging switch 18 and the control unit 20 ,

In this case, the DC-DC converter 29 again divided into two sub-function groups. Of these, a sub-functional group is a DC-AC converter 30 that the high frequency switch 14 and the high-frequency transformer 15 having. The other sub-function group is as a second AC-DC converter 31 executed and has the rectifier 16 , the smoothing units 17 and 19 , the charging switch 18 and the control unit 20 on.

According to the invention, it is therefore advantageously possible, by means of an appropriate interconnection, to supply one or more functional and sub-functional groups of a battery charging unit to supply the drive system of an electric vehicle (electric motor), to feed kinetic energy back into a battery and to charge the battery via an external power connection use. This leads to an efficient use of individual functional groups (converter) of the battery charging unit by multiple use, both during a charging process when the vehicle is stationary, as well as in the operation of the vehicle (drive), when the electric motor is powered from the battery or the braking energy in the Battery (regenerative braking, recuperation) is fed back. This results in further significant advantages in terms of cost, weight and installation volume.

3 shows an example of an interconnection of the second AC-DC converter 31 the battery charging unit 26 to 2 to charge a battery 2 via a motor-generator unit operated as a generator 4 , The battery charging unit 26 indicates the first AC to DC converter 28 , the second AC-DC converter 31 and the DC-AC converter 30 on (see also 2 ). The battery 2 is via a switching device 32 to the second AC-DC converter 31 switched, in turn, via the switching device 32 on the motor-generator unit operated as a generator 4 is switched on.

The one from the motor generator unit 4 provided AC power is through the second AC-DC converter 31 converted into direct current, that of the battery 2 is fed to the store. The generator-driven motor-generator unit 4 For example, the AC-converted kinetic energy can be obtained by coupling with the drive system of a vehicle. In this case, the kinetic energy can be generated by means of an internal combustion engine or be released during a braking process (recuperation). The first AC-DC converter 28 and the DC-AC converter 30 the battery charging unit 26 are not used in this embodiment.

4 shows by way of example the interconnection of the first and second AC-DC converter 28 and 31 and the DC-AC converter 30 for charging the battery 2 from an external AC mains having, for example, a voltage of 220 V at 50 Hz. The battery 2 is about the switching device 32 to the second AC-DC converter 31 switched, in turn, via the switching device 32 to the DC-AC converter 30 is switched on. The DC-AC converter 30 is about the switching device 32 to the first AC-DC converter 28 switched on, the over the switching device 32 is switched to the AC mains. Thus, the arrangement acts in this constellation as a battery charging unit 26 with connection to the AC mains. All functional groups of the battery charging unit 26 , the first and second AC-DC converters 28 . 31 and the DC-AC converter 30 are used.

5 shows the constellation in which the DC-AC converter 30 for operating the motor-generator unit 4 as from the battery 2 powered motor is used. The motor-generator unit 4 is about the switching device 32 to the DC-AC converter 30 switched on and this is in turn on the switching device 32 on the battery 2 switched. The one from the battery 2 discharged DC is through the DC-AC converter 30 converted into alternating current, which then in the motor-driven motor-generator unit 4 is fed. The motor-generator unit 4 will be used in this constellation to drive a vehicle (electric or hybrid vehicle). Advantageously, eliminates a dedicated, so only for this one constellation designed DC-AC converter, as it is usually installed. The first and second AC-DC converters 28 and 31 are not used in this embodiment.

It is therefore according to the invention, therefore, the possibility of multiple use of functional groups of the power electronics of a hybrid vehicle and by extension of the battery charging unit with additional modules (for example, an inverter) to a functional extension as a plug-in hybrid vehicle with on-board battery charging unit create. This includes, for example, the possibility of stationary charging of a battery and also allows a favorable optimization in terms of cost, weight and volume required for accommodation in a vehicle.

6 illustrates, by means of an embodiment, the use of the DC-AC converter 30 the battery charging unit 26 (see. 5 ) in the supply of an electrical machine of a vehicle, for example a motor-generator unit, from an energy store (battery). The vehicle 1 therefore has the energy storage 2 , the motor generator unit 4 , the drive wheels 5 , the reduction gearbox 6 and the battery charging unit 26 on. While driving the vehicle 1 DC current flows from the energy storage 2 to the battery charging unit 26 and is via their DC-AC converter 30 (please refer 5 in AC 24 changed. With this alternating current is the motor-generator unit 4 fed the kinetic energy generated thereby 7 over the reduction gear 6 to the drive wheels 5 surrenders and drives them. This eliminates a dedicated DC-AC converter for driving the vehicle 1 ,

At one of the 4 corresponding interconnection can then the energy storage 2 of the vehicle 1 in the state of the vehicle 1 be downloaded from the network. In this case, the (mains) AC voltage 25 into the battery charging unit 26 fed and for charging the energy storage 2 in the (charging) direct current 22 changed (cf. 4 ).

7 illustrates the use of the AC-DC converter based on an embodiment 31 the battery charging unit 26 to regenerate converted braking energy into the energy storage of a vehicle (recuperation). The return of electrical energy in the energy storage 2 takes place by converting the kinetic energy to the drive wheels 5 , This is the motor-generator unit 4 over the reduction gear 6 with the axle or the drive wheels 5 of the vehicle 1 mechanically coupled. The braking energy 33 the drive wheels 5 is powered by the motor-generator unit operated as a generator 4 into electrical energy, in the form of an alternating current 27 changed. This alternating current 27 is through the second AC-DC converter 31 (see. 3 ) of the battery charging unit 26 in a direct current 23 converted, the energy storage 2 (Battery of the vehicle) is supplied.

Multiple use of converters (eg, AC to DC converters for recuperation and DC to AC converters to power a motor-generator unit for propulsion and use both when charging from an external AC grid) in the on-board Battery charging unit, the cost of the entire electronics of an electric or hybrid vehicle are significantly reduced and the volume and / or weight of the vehicle electronics significantly reduced.

Claims (7)

On-board network for a vehicle ( 1 ) with an energy store ( 2 ), an electric motor-generator unit ( 4 ) for alternating current ( 8th . 27 ) and one for charging the energy store ( 2 ) battery charging unit formed from an external AC power network ( 26 ), a first AC-DC converter ( 28 ), a DC-AC converter ( 30 ) and a second AC-DC converter ( 31 ), as well as with a switching device ( 32 ), which is designed to charge the energy store ( 2 ) from the AC mains this to the second AC-DC converter ( 31 ), this in turn to the DC-AC converter ( 30 ), this in turn to the first AC-DC converter ( 28 ) and this aufzuschalten on the AC mains, for charging the energy storage ( 2 ) by the generator-operated motor-generator unit ( 4 ) the energy store ( 2 ) to the second AC-DC converter ( 31 ) and this in turn to the motor-generator unit ( 4 ) and to operate the motor-generator unit ( 4 ) as the energy store ( 2 ) motor fed this to the DC-AC converter ( 30 ) and this in turn on the energy storage ( 2 ) aufzuschalten. The vehicle electrical system according to claim 1, wherein the DC-AC converter ( 30 ) a controllable switch ( 14 ) and a transformer ( 15 ) having. The vehicle electrical system according to claim 2, wherein the DC-AC converter ( 30 ) in a frequency range of 20 kHz to 200 kHz. Vehicle electrical system according to Claim 1, 2 or 3, in which the first AC-DC converter ( 28 ) a filter ( 10 ), a downstream rectifier ( 11 ), a downstream power factor correction filter ( 12 ) and a downstream smoothing unit ( 13 ) having. Vehicle electrical system according to one of the preceding claims, in which the second AC-DC converter ( 31 ) a rectifier ( 16 ), a downstream smoothing unit ( 17 ), one of these downstream charging switch ( 18 ) and a downstream smoothing unit ( 19 ) having. Vehicle electrical system according to one of the preceding claims, in which the charging unit ( 26 ) a control unit formed in this way ( 20 ), that of the loading unit ( 26 ) one for charging the energy storage ( 2 ) required power is provided. Vehicle electrical system according to one of the preceding claims, in which the motor-generator unit ( 4 ) via a reduction gear ( 6 ) with drive wheels ( 5 ) of the vehicle ( 1 ) is mechanically coupled and designed to operate as a generator on the drive wheels ( 5 ) kinetic energy ( 33 ) to convert into electrical energy and when operating as from the energy storage ( 2 ) motor fed alternating current into kinetic energy ( 7 ) for the drive wheels ( 5 ) implement.

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