Self-powered electric traction system with performance extender

Abstract

The present invention relates to an energy-autonomous electric traction system with a performance extender that can be implemented in light electric vehicles (LEVs) such as bicycles. This traction system comprises an electric machine (1) that generates positive and negative torque, a power module (2) for controlling it with positive or negative power, a subset of supercapacitors (3), which is the essential energy storage element, an optional energy storage system (4) designed to increase the vehicle's performance, and the electronics for interfacing it with the system (5). The system has the advantage of being autonomous by recovering energy during braking using the electric machine (1) and storing it in the supercapacitor pack (3). This energy can then be released during acceleration.Adding an additional source (4) increases the vehicle's assistance performance.

Description

Title of the invention: Energy-autonomous electric traction system with performance extender Technical field

[0001] The invention relates to a traction chain for VEL, that is to say for an intermediate locomotion vehicle. In the specific case where this vehicle is a bicycle equipped with a traction chain, we generally speak of an electrically assisted bicycle or VAE. Prior art

[0002] Most current human-powered light electric vehicles, such as VAE or intermediate vehicles, consist of a storage battery that transmits power to the drive wheel via a converter. The majority of these vehicles must be connected to the national electricity grid using a specific charger designed for this purpose in order to ensure their operation.

[0003] The disadvantages of these vehicles are of several types. The recharge time and the ease of access to a charging point can be considered problematic. The lifespan of the energy system and its recycling is a brake on the growth of this type of vehicle. In addition, the limited autonomy of the vehicle, as well as the absence of standards for the recharge and the design of these light vehicles complicates the use and interoperability of the systems.

[0004] One of the aims of this invention is to propose an energy-autonomous traction chain based on a long-life storage system in order to overcome the drawbacks linked to the autonomy and life span of the system.

[0005] Another aim is to integrate the possibility of connecting a plurality of energy storage systems to the traction chain in order to allow a higher level of performance but also to allow the adaptation of various storage system solutions on the same vehicle. Summary of the invention

[0006] The present invention relates to an energy-autonomous electric traction system with performance extender that can be implemented in the context of light electric vehicles (LEVs) such as a bicycle.

[0007] This traction system is composed of an electric machine (1) which must allow the production of a positive and negative torque, a power module (2) allowing it to be driven with positive or negative power, a sub-assembly of supercapacitors (3), which is the essential element for energy storage, an energy storage system (4) optional for use, aimed at increasing the performance of said vehicle, as well as the electronics allowing it to be interfaced with the system (5).

[0008] The system has the advantage of being able to be autonomous by recovering the braking energy thanks to the electric machine (1) to store it in the supercapacitor pack (3). This energy can be restored at start-up. The addition of an additional source (4) makes it possible to increase the assistance performance of the vehicle. Description of the drawings

[0009] The characteristics of the invention are described more precisely below with reference to the appended drawings, among which: - [Fig.l] is a simplified functional diagram allowing the identification of the different elements of the traction chain. - [Fig.2] is an electrical diagram of the converter used between the external energy source (4) and the supercapacitor-based energy storage system (3). Description of the invention

[0010] A light electric vehicle (LEV) or a bicycle is primarily made up of a frame, wheels, directional or not, an energy transmission system, mechanical or electrical, safety elements and comfort elements. The present invention consists of adding an electric machine (1), its power converter (2), an energy storage system based on supercapacitors intrinsically having a long service life (3) and finally an external energy source (4), typically a battery, connected to the supercapacitors via a second power converter (5). This assembly, the invention, is designated as a powertrain.

[0011] The electrical machine (1) is integral with at least one wheel of the VEL. Its rotor must be connected to this wheel by means of a possible mechanical reducer while its stator must be integral with the frame. The electrical machine (1) must allow mechanical power to be transmitted to the vehicle, or subtracted from it, depending on the vehicle's need for assistance or braking (two-quadrant operation). According to one embodiment, this electrical machine (1) may be a three-phase machine. The mechanical power produced (or generated) is transformed from the energy stored in the supercapacitor-based energy storage system (3) via the power converter (2).

[0012] The power converter (2) controls the electric machine (1) and makes it possible to manage the power flows by converting the direct voltage of the supercapacitor-based energy storage system (3) into an alternating voltage allowing the speed or torque control of the electric machine (1). The power converter (2) is also the element which integrates the energy management system. This energy management system recovers the energy from the vehicle as soon as the command brake is activated by imposing a negative power flow allowing the supercapacitor-based energy storage system (3) to be recharged. The user (the driver) of the vehicle has a command allowing a positive power flow to be activated and thus the supercapacitor-based energy storage system (3) to be discharged. In order to facilitate energy management, an indicator of the amount of energy remaining is present on the VEL.

[0013] The supercapacitor-based energy storage system (3) is an assembly of several supercapacitors (7) making it possible to obtain an assembly with a higher voltage than a unit cell and with increased power capacities making it possible to support the high powers involved in light electric vehicles. According to one embodiment, the maximum voltage of the supercapacitor-based energy storage system (3) must be as high as possible in order to simplify the electrical machine (1). The energy stored in the supercapacitor-based energy system (3) is of the order of a few thousand joules to a few tens of thousands of joules. This modest quantity of energy means that the energy storage system (3) will only be able to provide positive power, and therefore assistance, continuously to the power controller (2) for a few tens of seconds.The negative power generated by the power controller (2) in other operating phases must allow recharging. The energy storage system based on supercapacitors (3) is therefore energy autonomous and therefore does not need to be recharged on the public electricity network.

[0014] The energy flows from the supercapacitor-based energy storage system (3) are transmitted to the power converter (2) of the electrical machine (1) via electrical conductors (6). These electrical conductors (6) are also connected to the power converter (5).

[0015] The power converter (5) is at the interface between the supercapacitor-based energy storage system (3) and the external energy storage system (4). The purpose of the power converter (5) is to promote power transfers between the two systems, which are both continuous systems. The role of the power converter (5) is to ensure that the supercapacitor-based energy storage system (3) operates over an optimal operating range. According to one embodiment, this operating range may be selected at around 80% of the state of charge.

[0016] The nature of the storage system based on supercapacitors (3) whose voltage is highly dependent on the state of charge implies for the converter (5) a particular structure making it possible to manage step-down and step-up operations on the same typology. [Fig.2] describes such a converter composed of a subset of step-up switches (12,13) ​​and a subset of switches step-down (10,11) around an inductance (14). The control system (15) of the switches then allows operation in step-up, step-down, with positive or negative power. The power converter (5) is sufficiently flexible to be able to accept various external energy storage systems (4) as long as the latter has the characteristic of being a current-reversible safety low-voltage generator. According to one embodiment, the control system (15) can also return energy from the storage system (3) to the storage system (4) via the power converter (5) in order to promote the performance of the vehicle.

[0017] The energy managed by the power converter (5) comes from an external energy storage system (4). According to one embodiment, this external energy storage system (4) can be a battery. The energy management of the external storage system (4) is linked to the control capabilities of the control system (15) of the power converter (5). According to embodiments, voltage control of the energy storage system based on supercapacitors (3) or even constant power discharge control of the external energy storage system (4) have been proposed.

[0018] The presence of the power converter (5) and an external energy storage system (4) allows energy to be added to the system and therefore to promote and prolong the performance of the vehicle. That is to say, the vehicle will be able to accelerate more quickly, and possibly reach a higher travel speed.

Claims

Claims

1. Energy-autonomous electric traction system for a light electric vehicle, comprising a traction chain characterized by the assembly of: a. an electric machine operating on two quadrants to assist the vehicle and the driver's effort b. a supercapacitor system, main energy storage system for powering the electric machine c. at least one control allowing the driver to manage his energy. all allowing the driver to benefit from an energy-autonomous traction system and a system with a long service life.

2. Electric traction system according to claim 1 characterized in that an external energy storage system can be connected to the electric traction system for the purpose of providing vehicle performance extension functions allowing the driver to benefit from additional assistance.

3. Electric traction system according to claim 2 characterized in that the external energy storage system is connected to the supercapacitor system via a power converter capable of operating at positive or negative power.

4. Electric traction system according to claim 1 characterized in that the supercapacitor system is connected to the electric machine via a power converter allowing operation at positive power and at negative power of the electric machine.

5. Light electric vehicle, characterized in that it comprises an electric traction system according to one of claims 1 to 4.

6. Electrically assisted bicycle, characterized in that it comprises an electric traction system according to one of claims 1 to 4.

Images