EMR 12 Madrid June 2012 Joint Summer School EMR 12 Energetic Macroscopic Representation «Modelling and EMR of a Hybrid Elevator» Dr. Philippe Barrade LEI, Ecole Polytechnique Fédérale de Lausanne, Suisse philippe.barrade@epfl.ch
- Outline - 2 Introduction Modelling and Representation Objectives Representation Inversed Based Control Objectives Independent control loops Strategies Back to the system Links from Strategies to the accumulator sizing Conclusion
EMR 12 Madrid June 2012 Joint Summer School EMR 12 Energetic Macroscopic Representation «Introduction»
- Variable frequency drive - 4 Most of elevators are moved with Induction Machines (or PMSM for the most recent) Needs in Variable frequency feeding From a constant frequency grid Needs in variable frequency drives Generally non-reversible» Energy can never be recovered (dissipation in braking resistors)
- Solutions for allowing an efficiency increase - 5 Solutions for the recovering of energy Non-Reversible 3 a) Reversible front-end b) Local accumulator c)
- Solutions for allowing an efficiency increase - 6 Solutions for the recovering of energy Reversible front-end Solve the problem of energy recovering Does not solve the problem of power fluctuations on the grid» It is reinforced Local accumulator Solve the problem of energy recovering Depends on the size of the accumulator Depends on the control Can solve the problem of power fluctuations on the grid Depends on the size of the accumulator Depends on the control
EMR 12 Madrid June 2012 Joint Summer School EMR 12 Energetic Macroscopic Representation «Modelling and Representation»
- Structure and objectives - 8 Structure Objectives Identify how the accumulator impacts on the system from an energetic point of view Identify all the possibilities to control the system
- Consideration on modelling and representation- 9 If the representation is made just by a scheme analysis The pulley is a coupling element The car+passengers and the counterweight are 2 independent accumulation elements The state variables of the 2 accumulation elements are merged threw a coupling element to the environment (gravity) If the representation is made from the modelling The car+passengers and the counterweight are merged in only one accumulation element This accumulation element represents the total energy of the elevator Kinetic (sum of masses) Potential (difference of masses)
- Representation - Representation obtained after modelling 10 The car+passengers and the counterweight have been merged in one single accumulation element
- Synthesis - 11 Insertion of an accumulator Add a new degree of freedom It interacts with the system at the same level than the braking resistors It is pure energy accumulation, offers the reversibility
EMR 12 Madrid June 2012 Joint Summer School EMR 12 Energetic Macroscopic Representation «Inversed based control»
- Objectives - 13 3 mains objectives Control of the speed of the elevator Control of the charge/discharge current for the accumulator Control of the current in the braking resistors 2 additional constraints Energy dissipated in braking resistor must be minimized Power fluctuations in the grid must be minimized
Answers to the objectives - Independent control loops - 3 tuning parameters for 3 objectives 3 independent control loops 14 Caution: as they are controlled, each sub-system will impact on the DC bus voltage. Each current reference must be set in harmony with each other.
DC bus voltage control - Strategy - Each reference current is not set directly, but from distribution elements (inversion of coupling elements) Distribution element need weight factor (k w ): strategies 15
- Synthesis - 16 3 mains objectives Control of the speed of the elevator Control of the charge/discharge current for the accumulator Control of the current in the braking resistors Allowed by the control as defined by the IBC, but not set independently 2 additional constraints Energy dissipated in braking resistor must be minimized Power fluctuations in the grid must be minimized Can be obtained depending on the strategy that is implemented
EMR 12 Madrid June 2012 Joint Summer School EMR 12 Energetic Macroscopic Representation «Back to the system»
Simulation results - Considerations on strategies - Based on datas from an industrial partner System controlled as defined by the IBC Simple strategy, for a given supercapacitive tank 18 Braking resistors used during energy recovering mode. Elevator needs are covered by the Scaps only, recovering of energy is possible. Elevator needs are covered by the Scaps, a reduced power (P ref ) is taken on the grid, recovering of energy is possible. Energy reserve in case of grid black-out, Elevator needs are covered by the grid only.
- Simulation results - P ref =100W P ref =2000W 19
Parameters of the strategy - Needs for adaptations - Power from the grid P ref Voltage limits for the supercapacitive accumulator 20 System itself For the same strategies, the supercapacitive tank can be re-sized Strategy System sizing
EMR 12 Madrid June 2012 Joint Summer School EMR 12 Energetic Macroscopic Representation «Conclusion»
- Conclusion - 22 EMR and IBC are powerful tools for representing a system and identifying some possible controls Once an IBC has been establish The most difficult part of the implementation is the identification of the correct strategy There is a strong link between the strategies and the physical system itself From my point of view EMR and IBC are not only tools dedicated for the control of systems EMR and IBC are also open doors for an optimal sizing of the system itself
- References - 23 [1] A Supercapacitor-Based Energy-Storage System for Elevators With Soft Commutated Interface. A. Rufer and P. Barrade. in IEEE Transactions on Industry Applications, vol. 38, num. 5, p. 1151-1159, 2002. [2] Design of a supercapacitor based storage system for improved elevator applications. Luri, S.; Etxeberria-Otadui, I.; Rujas, A.; Bilbao, E.; Gonza lez, A.Energy Conversion Congress and Exposition (ECCE), 2010 IEEE, Digital Object Identifier: 10.1109/ECCE.2010.5618424 Publication Year: 2010, Page(s): 4534 4539 [3] W. L'Homme, P. Delarue, P. Barrade, A. Bouscayrol, A. Rufer, "Design and Control of a Supercapacitor Storage System for Traction Applications", IEEE Industry Applications Conference, 2005.