CN101857023B - Method for operating electric vehicle - Google Patents

Abstract

The invention relates to a method for operating an electric vehicle having at least one electric motor, at least one electric accumulator, and at least one power generating device, wherein from a defined state of charge (SOC) of the electric accumulator Activate the generator. In order to reduce the costs of electric vehicles and to save construction space, it is proposed to design the power generation device for the average power demand of the electric engine of the electric vehicle at a defined continuous speed on flat ground, and in terms of technology to reach the state of charge of the electric energy storage Activation of the generator before the lower operating limit of the switch-on charge (SOC1) which defines the energy reserve (R) of the electric energy storage in accordance with the technical lower operating limit (SOC2) , the energy reserve (R) is dimensioned such that a defined peak power can be met in quantity, size and/or duration, preferably for vehicle acceleration and/or hill climbing.

Description

Method for operating an electric vehicle

technical field

The invention relates to a method for operating an electric vehicle having at least one electric motor, at least one electric energy store, and at least one power generation device, wherein the power generation is activated starting from a defined state of charge of the electric energy store device.

Background technique

EP 1 225 074 A2 discloses a series hybrid vehicle with an electric motor, a generator and an internal combustion engine driving the generator. In this case, in the zero-emission zone, the motor vehicle is operated purely electrically with the internal combustion engine switched off. In this case, the electric energy store can be charged by the internal combustion engine not only immediately before entering the emission-free zone but also when leaving the emission-free zone.

WO 2005/082663 A1 discloses a portable generator set for an electric vehicle, which is configured to extend the travel length of the electric vehicle.

US 2009/015202A discloses a method for charge regulation in hybrid vehicles, where the nominal state of charge is defined as the average value of the charge range. Energy flow is regulated so as to maintain a nominal state of charge. By operating the electric motor of the hybrid vehicle, the state of charge is dropped from this target value and raised again by the electrical energy generated by the internal combustion engine.

WO 2008/128416A1 discloses an energy management for hybrid vehicles with a load forecasting system with which future load levels are calculated based on input parameters and by means of a self-learning system based on load requirements to determine optimal future output power, battery state of charge, and optimal vehicle speed. Based on this optimal future power estimate, the internal combustion engine, generator and electrical energy storage of the hybrid vehicle are coordinated.

In general, in known series hybrid vehicles, the internal combustion engine and the generator are designed such that the maximum power demand can be met.

Contents of the invention

The object of the invention is to meet temporary load requirements in electric vehicles with as little technical effort as possible.

According to the invention, this is achieved by designing the power generation unit for the average power demand of the electric motor at a defined continuous speed of the electric vehicle on level ground, and by technically achieving the state of charge of the electric energy storage Activation of the power generation device in the case of a defined cut-in state of charge prior to the lower operating limit, wherein the cut-in state of charge defines the energy reserve of the electric energy store according to the technical lower limit of operation, the size of which is determined in such a way that This enables a defined peak power to be met in terms of quantity, size and/or duration, preferably for vehicle acceleration and/or hill climbing. Preferably, the switch-on state of charge is set such that at least 10%, preferably at least 30%, of the capacity of the energy store is retained as an energy reserve. In this way, all operating ranges of the car can be met.

In a particularly advantageous embodiment variant of the invention, it is provided that the switch-on charging state is set during the self-learning process on the basis of the completed travel of the electric vehicle.

As an alternative or in addition, it can be provided that the switch-on state of charge is determined as a function of the driving destination and/or the planned driving route, wherein it is particularly advantageous to define different contact points for at least two driving segments of the planned driving route. pass charging status. As a result, the route characteristics can also be taken into account when defining the switch-on state of charge.

A very compact construction can be achieved by designing the power generation unit for the average power requirement of the electric motor at a defined nominal speed on level ground.

Description of drawings

The present invention will be further described below according to the accompanying drawings. The accompanying drawings show:

FIG. 1 shows the state of charge of the electric energy storage during operating hours; and

Figure 2 shows a layout of the power plant.

Detailed ways

FIG. 1 shows the state of charge SOC of an electrical energy store of an electrically driven motor vehicle above time t. In conventional electric vehicles, the electrical energy storage is discharged during driving operation up to the technically possible minimum state of charge, which represents the technical lower limit SOC2 of the driveability of the electric vehicle. After this state has been reached, the available driving power is directly dependent on the energy input of the generator (range extender) and is therefore limited.

According to the aforementioned method, the generator is not activated until the technical lower limit SOC2 of the electric energy store, but is activated in the range of the first intermediate state of charge—the switched-on state of charge SOC1 , The remaining energy reserve R is thus kept in the accumulator. By defining the switched-on state of charge SOC1 above the technical lower limit SOC2 , which after being reached triggers the charging process by the generator, the limitation of the acquired driving power can be extended to the system by a buffering effect via the energy reserve R limit. Therefore, temporary peak power such as acceleration or hill climbing can be satisfied without designing the power of the power generating device for the peak load, but only for the average power.

The dashed line 1 in FIG. 1 shows the driving operation of a conventional electrically driven electric vehicle, and 2 shows the driving operation according to the method described here. If the state of charge SOC reaches the switched-on state of charge SOC1 (point 3 ), the generator is switched on, wherein only the energy requirement exceeding the power of the generator is taken from the energy reserve R of the electric energy store.

FIG. 2 shows a layout of a power generating device (distance extender), where the power P is shown above the velocity v. For this configuration, the following precondition applies: Compared to purely electric operation, the electric vehicle should have no loss of driving power during operation with the range extender. The electric vehicle is designed for a defined driving performance (dynamics, gradeability, top speed, etc.). The power of the power generation device can be significantly smaller than the power of the engine of the electric vehicle. The power plant is designed in such a way that it satisfies the maximum speed of the electric vehicle on level ground and the additional energy consumers. The dynamic demand for the power exceeding the power generation system is met by means of a defined electrical reserve R of the electrical energy store (vehicle battery).

Calculations have shown that, for example, the driving dynamics can be met in the case of an electric vehicle with a total weight of 1450 kg and an electrical energy reserve R of approximately 2 kWh. Figure 2 shows the resistance curves 4, 5, 6, 7 for different ramps, wherein the energy requirements when using additional auxiliary units are shown with dashed curves 4', 5', 6', 7'. If one considers as an example a unit with an electric power of 15 kW (which corresponds to a wheel power of about 13 kW), it can be seen that the selected car (1475 kg fully occupied) can reach a constant speed of 100 km/h. If an electric energy reserve R of 2 kWh is used, this 100 km/h speed can be extended by 21 km even on a 2% incline with the range extender and the battery (see point 11). Alternatively, 22 accelerations from 100 km/h to 120 km/h can be performed. In contrast, a distance of more than 66 km can be traveled at 80 km/h and a 2% gradient or 28 accelerations from 80 km/h to 100 km/h can be performed (see point 12). On a 5% incline, the energy reserve R can be used to travel a distance of 9 km or to perform 19 accelerations from 100 km/h to 120 km/h, as indicated by point 13 . Reference numeral 14 designates an operating point at 80 km/h and a 5% gradient, in which energy reserve R can be used to travel 12 km or to perform 25 accelerations from 80 km/h to 100 km/h. Point 15 marks the operating point for a driving speed of 60 km/h, in which a distance of more than 22 km can be traveled or 34 accelerations from 60 km/h to 80 km/h can be performed. On an incline of 10% and a driving speed of 60 km/h, only a distance of approximately 6 km can be traveled with the energy reserve R or 28 accelerations from 60 km/h to 80 km/h can be carried out.

The switch-on state of charge SOC1 or the energy reserve R can be determined by the vehicle manufacturer on the basis of estimated usage characteristics of the electric vehicle. Alternatively, the switch-on state of charge SOC1 can also be flexibly determined during operation of the electric vehicle by means of a self-learning system. In this case, the past driving of the electric vehicle forms the basis for re-determining the switch-on state of charge SOC1 , so that the factory-default predefined settings can be readjusted downwards or upwards based on the actual road section. For example, in the case of a large number of vehicles accelerating and a steeper-than-average driving route, it may be expedient to provide a larger energy reserve R, so that the generator can be activated earlier in electric driving operation. On the other hand, when driving uniformly at an average speed on a flat street, it can be absolutely meaningful to reduce the electrical energy reserve R and to delay the activation of the power generation system, thereby saving fuel and preventing unnecessary emissions .

It is particularly advantageous to estimate the energy requirement for overcoming the approaching route section and to calculate the optimal energy based on the destination data entered into the navigation system and on the basis of information about the traffic flow and taking into account obstacles such as slopes, blockages, etc. The position of the switch-on state SOC1 that is decisive for activating the generator is stored and thus calculated. This optimization can be carried out with a trade-off between driving time or fuel consumption or emissions. In addition, different energy reserves R can be flexibly defined for certain driving distances. This is particularly advantageous when the essential road section properties (steepness, curvature, traffic flow) change during the course of the route.

Claims (7)

1. the method for operating electric vehicle, described electronlmobil has at least one electric engine, at least one electric energy accumulator, and at least one power generation assembly, wherein from the defined charge condition (SOC) of described electric energy accumulator, activate described power generation assembly, it is characterized in that, for described electronlmobil on level land in defined continuous speed situation the average power requirement of described electric engine design described power generation assembly, and in defined connection charge condition (SOC1) situation, described power generation assembly was activated before the technical lower work threshold of charge condition reaching described electric energy accumulator, wherein said connection charge condition (SOC1) defines the energy of reserve (R) of described electric energy accumulator according to described technical lower work threshold (SOC2), the size of described energy of reserve (R) is so measured, to make it possible to quantitatively, defined peak power is met in size and/or on time length.

2. the method for claim 1, is characterized in that, described peak power comprises automobile and accelerates and/or climbing.

3. method as claimed in claim 1 or 2, is characterized in that, so arrange described connection charge condition (SOC1), to make at least 10% in the capacity of described energy storage, be retained as energy of reserve (R).

4. method as claimed in claim 1 or 2, is characterized in that, so arrange described connection charge condition (SOC1), to make at least 30% in the capacity of described energy storage be retained as energy of reserve (R).

5. method as claimed in claim 1 or 2, is characterized in that, in the process of self study, arrange described connection charge condition (SOC1) based on the completed traveling of described electronlmobil.

6. method as claimed in claim 1 or 2, is characterized in that, according to travelling destination and/or the running route planned determines described connection charge condition (SOC1).

7. method as claimed in claim 1 or 2, is characterized in that, at least two running sections in the running route planned define different connection charge conditions (SOC1).