Parallel-series hybrid vehicles

Controls and diagnostics for parallel-series hybrid vehicles. A typical set of control messages for hybrid vehicles is listed in Table 11.19. Although the variables are the same as those used in soft hybrids, the higher criticality of function implies that the calculated values, such as maximum source and sink currents, must be of even higher reliability if unexpected function fade or failure is to be avoided. 

The cost dependency on a minimized cell size for Ni-MH and VRLA batteries is shown in Fig. 11.21. In these cases, VRLA is limited by life and Ni-MH is limited by power. At the energy levels required for parallel-series hybrid vehicles, it can be shown that the watt-hour life cost of Ni-MH would have to exceed 33 times that of VRLA, which is not the case even today with prototype batteries. The initial cost consideration that tipped the favour to VRLA for soft hybrids is far less impressive with parallel or series hybrids, since it can be further demonstrated that, even on an initial cost basis, VRLA is about 60% of the cost of the equivalent Ni-MH battery for the parallel-series application, well outside of the bounds where trade-off to initial cost could be considered. 

General requirements. The attributes in Table 11.20 are typical for parallel hybrid applications, and the attributes in Table 11.21 are typical for series hybrid vehicles. 

High-voltage safety considerations require that the architecture of parallel- and series-hybrid vehicles include an integral BMM such that the battery can be controlled from within the pack. This assumes that the battery will be of an advanced design, such as Ni-MH, where safety requires fast, reliable, and self-contained communication with the contactor and charger. 

The control strategies for dual mode hybrid vehicles are a combination of those used for series and parallel hybrids. There are so many possible hardware arrangements and associated control strategies, it is not possible to summarize them in a simple manner as was the case for series and parallel hybrids. The objective of the dual mode operation is to use the... 

The fuel economy of series and parallel hybrid vehicles are compared in Table 3 for both the com-... 

Comparisons of the Fuel Economy for Series and Parallel Hybrid Vehicles (1) Fuel economy shown lor diesel engines is gasoline equivalent... 

A car company wants to design a battery for their hybrid vehicle. The battery requirement for this system is 300 V with a nominal capacity of 3.0 kW hr. Suppose they have a 5 A hr cell at 2.0 V. (a) How many cells will be required to make the required battery (b) How many cells will be in series and how many in parallel (Bhardwaj)... 

Hybrid thermal vehicles are more expensive than traditional vehicles, because they include more than one energy source on board. However, there are some components of traditional vehicles which are not required for hybrid vehicles and can be made some savings. For instance, in the series conhguration there is no need for the gear box because the electric drive regulates the motor speed electronically, transmission is simplihed and differential is useless if the motors are directly connected to the wheels. The starter can be eliminated in both series and parallel conhguration since electric machines do not need any specihc devices to start. Many hybrid vehicles are currently on the market and this sector is growing rapidly worldwide. 

Figure J6.4 Series hybrid (a) and parallel hybrid (b) for fuel-cell hybrid vehicle. Reproduced from [14].

FCVs are special as they have electrical power transmission, whereas a hybrid vehicle may be a combination of electrical and mechanical power transmission. Hybrid vehicles are further categorised as FCV with parallel hybrid power circuit and FCV with series hybrid power circuit as shown in Figs. 9.4 and 9.5, respectively. 

As shown in Fig. 9.4, in parallel hybrid power circuits the fuel cell delivers power to the motor and charges the battery when required. It also provides extra power to the motor for acceleration once the battery is fully charged. In the case of a series hybrid power circuit, all the power is delivered by battery so it needs to be large. The function of the fuel cell is only to charge the battery depending on driving conditions it can be of relatively low power. Such vehicles generally use alkaline fuel cells. 

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