Electrical Energy System



The main energy storage unit is a Lithium Ion Battery which has sufficient capacity for a range of 100 km. It powers the traction motors and is inserted and released from the bottom side of the vehicle. Two DC/DC converters connect the 340V high-voltage system with the 24V low voltage system, which supply the steering and braking actuators as well as the onboard computer systems.

The fourth vehicle module is the energy unit. The main energy storage unit is a Lithium Ion Battery which has sufficient capacity for a range of 100 km. It powers the traction motors and is inserted and released from the bottom side of the vehicle. Two DC/DC converters connect the 340V high-voltage system with the 24V low voltage system, which supply the steering and braking actuators as well as the onboard computer systems.

The ROMO Lithium Ion Battery

The electrical architecture consists of a high-voltage (HV) battery as the main power source. This is connected directly to the inverters of the four traction motors, and also to two DC/DC converters to supply the low voltage (LV) system. A direct connection with a high voltage DC power supply allows on-board electrical system investigations as well as fast charging of the vehicle. The states of the electrical system are controlled by the BNCU (on-Board Network Control Unit), one of the components of the hierarchical controller architecture.

The air-cooled battery unit consists of 90 pouch type cells divided into nine stacks, providing a nominal capacity of 13 kWh at 342V. Simulations show that the ROMO can travel approximately 100 km within the usable SOC range. To ensure operational safety, the HV electrical system is designed in accordance to the ECE R100 regulations for electric and hybrid vehicles.

Development of operating strategies to optimising the energy management requires high-fidelity models of the energy sources and the sinks. In the case of the HV system, these are the Li-Ion battery pack and the in-wheel drive motors respectively. The information from systematic battery cell testing was used to configure and parameterise a real-time capable battery model. With this a model based state observation concept was developed to predict the states within the battery, including state of charge (SOC) and power availability.

Schematic of the ROMO electrical system


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