Abstract:
Cost and shortage of fuel oil is one of the major problems for the customers. Parallel
Hybrid Electric Vehicle (PHEV) has ability to overcome these difficulties and minimize
the fuel cost because such electric vehicles contain number of batteries that help to
minimize the use of conventional fuel sources. The aim of the thesis is to introduce a
battery cell balancing strategy that uses the battery in efficient way to maximize the drive
of electric vehicle.
Battery management system (BMS) is an imperative feature for the al range of electrical
vehicle and electrical energy storage system as it accomplish lot of features. Battery cell
balancing hinders electric vehicle performance, due to the mismatch in the state of charge
(SoC) difference among the cells. In many cases, such mismatch even leads to the failure
of the whole battery pack. In order to avoid this disaster, many cell balancing strategies
has been proposed such as resistive shuttling, capacitor shuttling, transformer/inductor
based and converter based. Shuttling capacitor has many advantage over the resistive one
due to its high efficiency and less energy dissipation while transferring charge from
higher SoC cell to the lower SoC cell. However, after the certain SoC difference of the
cells, this capacitor shuttling technique lot of time to eliminate this SoC difference which
eventually increases the time to balance the battery pack. Keeping this problem in mind, a
hybrid strategy is proposed in this thesis which uses two technique to work after one
another. When the SoC difference goes higher than a certain number (4%), double tiered
shuttling capacitor (DTSC) will be used to lower the difference till it reaches to the SoC
difference of 4%. From here, the passive balancing (resistor shuttling) will take the
control and remove the SoC difference using the resistor to dissipate extra energy in the
form of heat. This lead to a new regulator strategy for balancing the SoC of the cells. In
addition to this, such system is cost effective, less heat dissipation as compared to
individual resistive shuttling method for large SoC difference. In this way, we can use the
complete capacity of the battery pack.
