Regenerative braking

REGENERATIVE BRAKING

Index

1.Introduction           

2.History        

3.What is Regenerative Braking?  

4.Switching of Regenerative Braking System      

5.Types of regenerative braking    

i.Series Regenerative Braking     

ii.Parallel Regenerative Braking  

6. Conclusion

Introduction

Nowadays, electric vehicles (EVs) have gained a great deal of publicity for alternatives to conventional combustion engines (ICEs). The creation of hybrids and EVs has become mostly popular.

The global fossil fuels reserves are finite. Instead, the use of electricity, produced by renewable energy sources and stored chemically in some medium like hydrogen or batteries is a, long term, environmentally friendly, cost-effective, zero-emission solution for endless automotive power supply.

History

In 1908, C.J. Paulson invented a smart car with a regenerative braking system. AMC (American Motors Corporation) further improved the "Energy Regenerative Braking" system in 1967. In the 2000s, the electronic control system used BMW, which used an alternator during braking to regenerate energy. They were mild regenerative braking devices.

Tesla motors in 2008 released first ever completely electric Roadster which was capable of running 254 km on single charge. This was the time when there was big revolution in Automobile industry.

In Electric Vehicles, the source for energy is only battery and these batteries face problem like less charging and recharging cycles also they have poor driving range so to overcome this problem there is invention of concept called regenerative braking.

What is Regenerative Braking?

In battery-operated EV, the battery is the only source of energy and these batteries are faced with problems such as fewer charging and recharging cycles and poor response in driving range. In addition to this issue, engineers are trying to develop various types of methods/technologies to improve performance, increase power or produce energy that is lost due to external factors. One of which is regenerative breaking. It is used from consumer cars to Formula 1 cars to improve performance.The most common form of regenerative brake involves an electric motor functioning as an electric generator. In electric railways, the electricity generated is fed back into the traction power supply. 

The Kinetic Energy of the car during braking is used to rotate the engine in the opposite direction. As a result, the very same engine used for propulsion now serves as a battery, which feeds the generator. A battery with power supply. Once we apply force to the accelerator or brake, the car will be obstructed and the engine will operate in the opposite direction. When running in invalidate direction, the engine works because the generator charges the battery as shown in the figure.

Braking power/ braking energy used by the front and rear wheels are related to the braking forces on the front and rear wheels.

The braking torque requirement for the front and rear axles are often calculated from the subsequent equation given that the normal force, F, at each of the axles and the tire radius, rtire, is known during a braking event.

Switching of Regenerative Braking System

The armature current flows through the positive side to negative side of the battery. The diode is linked in parallel with every MOSFETs  and those diodes are often used as freewheeling diodes such that PWM are often useful to modify devices, thus the efficiency of the system is perfect.

Driving Mode

When we apply brakes , when it is in motion the system switches to braking mode. The braking mode isconverted in two sorts of conduct stages. During the first stage of breaking the back EMF and battery which matches serial . In this type Q2, Q3 are switched on and Q1,Q4 are switched  , so on change the direction of armature current easily

 

Initial Braking Mode

To change the direction of armature current, in the first stage of initial braking mode the back-emf and therefore the battery goes within the series connected as shown in figure 5b. In this mode of initial braking, Q2 and Q3 are switched on and Q1 and Q4 are transitioned in order that armaturecurrent can change its direction automatically. When armature current increases and changes the direction itself, the state of MOSFETs will come back automatically to its position as shown in figure 5c and the battery will get charged automatically. This is how regenerative braking gets implemented.

Regenerative Braking Mode

Advantages of regenerative braking

Implementing Regenerative braking in a vehicle provides us many advantages as- 

1: It increases the driving range of a vehicle. 

2: It helps us to reduce the battery size of vehicle. 

3: As battery size gets reduced, thus weight of vehicle is reduced so there will be increase in performance of vehicle.

Types of regenerative braking

1.Series Regenerative Braking

It is based on a combination of a friction-based adjustable braking system witha regenerative braking system that transfers energy to electrical motors and batteries under an integrated control strategy.The deceleration achieved  is at a significant rate. When  brake torque applied is the maximum that could be applied without wheel lock-up is divided among four wheels.

Serial Regenerative Braking at full brake input

Serial regenerative braking at maximum brake input provides the necessary braking torque, and the non-driven axle (rear) starts to split in order to ensure proper brake torque distribution. If the application of the rear friction brakes along with the regenerative braking does not fulfill the required brake torque, the front friction brake may begin to operate. As a result, vehicles are brought to rest within the required stopping space.

2.Parallel Regenerative Braking

It is based on a combination of a friction-based adjustable braking system with a regenerative braking system that transfers energy to electrical motors and batteries under an integrated control strategy. The second type is a parallel braking system  in which the friction-based braking system and the regenerative braking system are controlled in tandem without integrated power, which means that neither the friction braking force nor the regenerative braking force can be easily modified. The benefit of the parallel regenerative braking system  is that it does not require a complex control system and the existing friction-based braking system can be used without alteration. However, the energy recovered by the regenerative braking system will be small and the driving capacity of the vehicle can be adversely affected.

Parallel Regenerative Braking at full brake pedal input

In Conclusion

Regenerative braking is one of the most critical systems in the generation of electric vehicles. Regenerative braking has the potential to save up to 8-25% of waste energy. The regenerative braking system, strengthened by the advanced technology of power electronic components,is an ultracapacitor, DC-DC converter. Further research and advancement in the efficiency of electronic components and technological progress will contribute to sustainable transport and increased energy efficiency in our transport vehicles.

 

Authors:

Pranjal Sarode
Anirudh Sharma
Ayush Kagne 
Niranjan Dhokarikar 
Rachit Singh