HiL for Battery Management Systems

HiL for Battery Management Systems

In addition to the electronics dedicated to the vehicle propulsion, the hybrid, and electric powertrain systems also consist of other systems used for vehicle energy management.

One of these, always present in electric vehicles is the BMS (Battery Management System).

BMS are electronic control circuits that monitor and regulate the charge and discharge of batteries. The characteristics of the battery to monitor include the detection of the battery type, voltages, temperature, capacity, state of charge, power consumption, remaining operating time, charge cycles, and some other features.

The primary task of a BMS is to consistently run the high voltage battery in an optimal range.

Downstream of the sensor analysis, the action undertaken by the BMS to do this is to balance the impedance of the cells to optimize the charge exchange by acting on single or groups of cells through specific electronic units called CMC (Cell Management Controller).

Due to the safety-critical nature of its components, it is imperative to pre-test a BMS.

Hardware-in-the-Loop (HiL) simulation is a cost-effective and efficient tool for this. Testing the BMS on a HiL test bench requires an electronic unit to simulate cell voltages and a real-time scalable battery model.

The HiL systems involved in the test of this control unit are essentially divided into two types: Low Voltage HiL and Power HiL.

The power hil system

The PHiL system has the characteristics of being able to simulate the battery pack bringing with it the power of the same. Compared to the adoption of a real battery pack The advantage is that of being able to decide, by the model implemented, the electrical characteristics, i.e. voltage, current, and therefore power in real-time, to give the possibility to study the behavior of the control unit (BMS) at various charge levels or battery health states, also including the electronics included in the BMS for the high voltage interfaces.

the low voltage HiL system

A second approach is to propose an LV HIL which involves adopting procedures that bypass the sensing of high voltage signals by acting directly downstream of the conditioning electronics. This irreparably involves the modification of the control unit under test or of some specific agreements with the HW and SW manufacturers of the control unit to supply a control unit already suitable for LV environments. In addition to the overall dimensions, the cost of a PHiL system can easily exceed by a few orders of magnitude compared to an LV environment.

In general, for both a PHiL and an LV HIL to obtain a significant HIL environment for the validation of SOC (Status of Charge) and SoH (State of Health) algorithms it is important to have a reliable model of the single cell, that can describe its static and dynamic behaviors concerning its technology and other external factors.

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