Virtual lab on power systems management: the Hybrid Electric Vehicle A. Escolà, A. Dòria-Cerezo,...

Virtual lab on power systems management: the Hybrid Electric Vehicle

A. Escolà, A. Dòria-Cerezo, R. Costa-Castelló

Virtual lab on power systems management: A. Escolà, A. Dòria-Cerezo, R. Costa-Castellóthe Hybrid Electric Vehicle IOC- Universitat Politècnica de Catalunya

8th IFAC Symposium on Advances in Control Education Kumamoto, October 21-23,2009 1

Institut d’Organització i Control de Sistemes IndustrialsUniversitat Politècnica de Catalunya



Outline

•Introduction•HEV model• The DC bus• Electric machines• Power converters• Storage elements• Electrical loads• ICE model and fuel consumption• Mechanical transmission and vehicle modelling

•Power management•Standard speed profiles•HEV virtual lab description•Conclusions



Introduction

The increase in industrial activity, and the improvementof population living standards makes that the EuropeanUnion (EU) increases year by year its energy consumption.

Different strategies are developed to search for alternative energies and to rationalize and optimize the energy consumption.

Temporary energy storage elements can be applied to manage the energy consumption of several systems, such as an Hybrid Electric Vehicle.



Introduction

In order to disseminate the existing problems in keygeneration, processing and energy management virtual laboratories (VL) can serve as platforms for testing and learning different systems and concepts related with them.

Virtual laboratories:•allow students to construct their own mental model•are cheaper than the hands-on laboratories•allow to compare different scenarios and configurations



HEV model

HEV can be classified in two large families, depending on the topology:

•Series: mechanical decoupling between ICE and the wheels, which allows to regulate the ICE speed independently of the velocity of the vehicle.

•Parellel: only one electrical machine is required.



HEV model

To simplify the model implementation, a generic system able to describe the behaviour of both HEV configurations and conventional vehicle, has been developed.



HEV model: The DC bus

All electrical components are connected through a DC bus. All elements connected in the DC bus share the same voltage, Vbat, which in the model is fixed by the batteries in order to assure causality.

This connection is modelled using the Kirchhoff law:



HEV model: Electric machines

Permanent magnet motors, induction motors, and recently switched reluctance machines, are considered the most likely candidates for the propulsion system for an HEV.

Since the dynamics of the electrical machines are faster that the vehicle ones, they are reduced to a simple static relationships:



HEV model: Power converters

Power converters are switched electronic devices which allow to regulate the electrical power flow in the system. In the proposed scheme the power converter allows to control the energy flow to the electrical machines and the ultra-capacitors by means of the n control signal.

The simplified static model for the power converter (neglecting the losses) is:



HEV model: Storage elements

Batteries and ultra-capacitors are included in the HEV as energy storage elements. Only the energy in the ultra-capacitor is managed, while the energy stored in the batteries comes from the power balance of the system.

Battery:

Ultracapacitor:



HEV model: Electrical loads

Current vehicles contain a number of comfort components such as air conditioning system, illumination, or music.

In the proposed model the effect of these components is modeled as resistive load with a certain power consumption:



HEV model: ICE model and fuel consumption

The ICE has been considered as an ideal torque source.

The fuel consumption of the ICE, is also obtained as afunction of the mechanical speed and power.

Depending on the HEV topology, the ICE speed corresponds to the mechanical transmission or the electrical generator.



HEV model: Mechanical transmission and vehicle modelling

The vehicle is modelled as a mass under the action of some external forces.

Considering a gear box, g, and the wheel radius, r:

Damping force, Fa:

Fb is the break force.



Power management

The power management is based on to determine Kp, the ratio of the delivered power by the ICE in front of the required by the vehicle.

The power management of this IVL takes into account:• Regenerative breaking policy.• State of charge of the battery.• Vehicle speed and acceleration.



Standard speed profiles

In order to compare different energy management algorithms and HEV topologies a set of standard speed profiles have been designed. These profiles take into account urban, road or highway driving, or a mixed case.

The default driving cycle included in the interactive virtual lab is the mixed cycle so-called New European Driving Cycle (NEDC).



HEV virtual lab description

Presented Interactive Virtual Lab has been entirely developed using Easy Java Simulations, EJS. EJS is a free and open-source interactive tool developed to build Interactive Virtual Lab in a very simple and straightforward manner.

The laboratory is decomposed in three almost independent parts:1. Model: Variables and relations between these variables. This

includes the differential and algebraic equations.2. View: The view corresponds to the virtual laboratory outputs.

These outputs are constituted by different windows which contain generic graphics and representations of the systems.

3. Control: This part contains the actions that a user can perform on the simulation.




The main window of the virtual lab contains:•Start, Stop and Reset buttons.•Configuration menu, which allows to choose the configuration of the HEV (series, parallel or conventional).•Speed profile, with a pointer with the position in the profile.•Dynamic bars with the battery and ultracapacitor levels.•Load selector.




Additional windows have been introduced in order to tune and analyze the energy management algorithms (for example the braking police).

The evolution of most relevant parameters can be observed in several graphical windows.

Simulations obtained with different configurations or parameters, can be compared.

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8th IFAC Symposium on Advances in Control Education Kumamoto, October 21-23,2009



Conclusions

This tool has been developed using the EJS software, which lets you create dynamic models with a graphical interface.

Future developments includes: a pollution model, a power management tool,… and the use of EJS with other kind of energy systems such as wind turbines, flywheel energy storage system,...

An interactive virtual laboratory which allows to simulate an energy management system (an hybrid electric vehicle) is presented.

This IVL has been developed as a pedagogical tool to introduceengineering students in concepts and main ideas behind HEV.

The use and evaluation of the IVL in courses will give a necessary feedback to improve the presented tool.

Virtual lab on power systems management: the Hybrid Electric Vehicle A. Escolà, A. Dòria-Cerezo,...

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