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Teknikimobil.com – On this occasion, technicianmobil will discuss the general design of hybrid electric vehicles which are generally divided into three. The three parts are series hybrid, parallel hybrid, and series-parallel hybrid. Let’s discuss them one by one.
Lummi Photography
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Basically there are two general designs for a hybrid car, namely the first is a series hybrid. A series hybrid is characterized by the engine being coupled to a generator, powering the generator which recharges the battery and/or supplies electrical energy to the electric motor. The motor, in turn, provides torque to the wheels. The second type is a parallel hybrid vehicle. Parallel hybrids are driven by an engine or electric motor or both. The electric motor works as a generator to recharge the battery during regenerative braking or when the engine produces more power than is needed to propel the vehicle. Despite having the advantageous features of series and parallel HEV (Hybrid Electric Vehicle), series-parallel HEV is relatively more complicated and expensive. However, this system design has been used in some modern HEVs because of the advanced control and manufacturing technology that can be applied.
Hybrid Series
Series HEVs, as shown in the figure below, have an electromechanical circuit power source. The electric powertrain only provides propulsion power to the drive wheels, and the engine generator installation unit (Genset) recharges the energy storage system (ESS/energy storage system) which provides energy to the electric powertrain. Therefore, in general, hybrid series vehicles are electric vehicles with a generator to supply electrical energy when the vehicle battery does not have sufficient energy to start the vehicle.
Rear-wheel-drive series hybrid electric vehicle layout. Source: Edited from Liu, W.
Due to their simplicity of control, these types of hybrid vehicles can find practical use, especially heavy/medium-duty delivery trucks and shuttle buses. In this type of system, the main function of the Generator is to extend the range of the electric vehicle beyond what is possible on batteries alone. This type of HEV can optimize energy sources globally, but the implementation costs are high.
Parallel Hybrid
Next is the parallel hybrid.
Rear-wheel-drive parallel hybrid electric vehicle layout.
Unlike a series HEV, a parallel HEV combines the power output of an ICE (Internal Combustion Engine) with the power output of an electric motor/generator. There are several potential points connecting these two power sources to the drivetrain depending on component availability. In a parallel HEV configuration, as shown in the figure above, the electric powertrain system is connected to the conventional powertrain system via a clutch that allows the vehicle to be driven by the electric motor or engine separately or simultaneously. The maximum power rating of an electric powertrain is usually less than that of a conventional engine-based powertrain in a parallel hybrid vehicle. The principle of measuring an electric powertrain is that the electric motor and ESS can provide the power required for a particular drive cycle. In addition, a conventional powertrain must be capable of providing sufficiently flexible torque that can be combined smoothly and efficiently with the torque from the electric motor to meet the torque requirements for propelling the vehicle. Machines may be turned on and off frequently in response to the system’s containment strategy.
Series-Parallel Hybrid
Lastly is the series-parallel hybrid arrangement, which is a combination of a series hybrid arrangement and a parallel hybrid arrangement. In the series-parallel configuration the electric motor, electric generator, internal combustion engine and vehicle wheels can be connected together via one or more sets of planetary gears or other devices. The image below shows a series-parallel configuration where the power provided by the engine is split and distributed to the wheels via two paths, namely series and parallel. The series path leads through the electric generator connected to the ESS to the electric motor to the wheels. In this path, the mechanical power of the engine is converted into electricity via a generator, and the electrical power can partially flow to the ESS or completely to the wheels via the electric driveline.
Layout Rear-wheel-drive series–parallel hybrid.
In parallel path , the engine is connected via a ring gear to a conventional drivetrain. On this path, the mechanical power of the engine is partially or completely transmitted mechanically to the wheels, and the part that is not sent to the wheels will be converted into electrical power via an electric motor to charge the battery. If all the engine’s mechanical power cannot meet the vehicle’s demand, the drivetrain’s electric motor will supply additional torque to the wheels. Series-parallel hybrid electrical conjunctions act at all times as a combination of parallel circuits and configurations. This allows the electric motor drivetrain to adjust engine load to achieve optimal fuel economy. The percentage of power flowing through parallel circuits and paths determines the performance of a series-parallel hybrid vehicle. Although power flow can be regulated by controlling the speed of the planetary gears, a sophisticated control system is required to control the power flow to achieve the best fuel efficiency.
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The above comparison of series and parallel configurations leads to the conclusion that, in city driving conditions, series hybrid behavior is better, but in highway driving conditions, parallel hybrid action is very likely to be used. Therefore, the series-parallel configuration combines the positive aspects of the series configuration – the independence of engine operation from driving conditions – with the advantages of the efficient parallel configuration – an efficient mechanical drivetrain. The complexity of control tasks for series-parallel configurations is the main point of difference compared to series or parallel systems.[]