Murdoch University Faculty of Science & Engineering Lead Acid Batteries Modeling and Performance Analysis of BESS in Distributed Generation Heng Teng Cheng (30471774) Supervisor: Dr. Gregory Crebbin 11/19/2012 A thesis report submitted to the School of Engineering and Energy, Murdoch University, in partial fulfilment of the requirements for the degree of Bachelor of Engineering
Acknowledgement I would like to acknowledge my thesis supervisor, Dr. Greg Crebbin for providing guidance and for helping me to define my research topic, constantly asking me the tough questions. Authors, who have made past contribution to this topic of research and in turn, helped me to formulate my own thesis understanding. Finally, to my family and friends who have provided much needed moral support at a difficult and challenging time of my life. Completing my thesis is for you. Stand on the shoulders of giants 2
Abstract In this thesis, a methodology to accurately determine the state of charge (SOC) of a lead acid battery is proposed by calculating the integration of the net current flow through the battery at given time, t. Using an electrical circuit diagram of the lead-acid battery model; will run a simulated model of a lead acid battery and its charging or discharging characteristics are estimated based on the input values provided by manufacturers or user specifications. Using the data found, an optimum state of charge (SOC) was determined and a battery energy storage system (BESS) was sized accordingly. A simulation of a peak load scenario was conducted and a system performance analysis was carried out on the BESS connected to a micro-grid system. An investigation into the transient voltage stability at a peak load condition was conducted to compare the response of the battery bank and a diesel powered generator in ability to cope with increase in the load demand. Furthermore, an investigation into four types of control strategies for a distributed generation system was proposed with some predicted outcomes analyzed. It was found that operating the BESS as a secondary control mechanism to a primary diesel generator was the optimum control set-up. Further investigation into the levelized cost of energy (COE) would be required to conclusively determine these findings. Contents Chapter 1... 1 1.1 Introduction... 1 1.2 Thesis Objective... 1 1.3 Thesis Layout... 2 Chapter 2... 3 2.1 Modeling the Battery... 3 2.2 Chemical Operation of a Lead Acid Battery... 4 2.3 Dynamic equations of the circuit model... 5 2.4 Electrical Circuit Model... 6 2.5 Model Validation Process... 11 3
2.6 Parameters from manufacturers data-sheet... 12 2.7 Discussion on Simulink Model and Simulation Results... 13 2.8 Analysis of Simulation Results... 14 Chapter 3: Detailed analysis of Matlab Simscape TM Lead Acid Battery Demo... 19 3.1 Simulink Model Structure of a lead-acid battery cell... 19 3.2 Battery Equivalent Circuit... 20 3.3 Parameters for the circuit... 21 3.4 Results... 21 3.5 Discussion on ICAPS and SimScape TM models... 23 Chapter 4... 24 4.1 What is a battery bank?... 24 4.2 Introduction to the Battery Energy Storage System... 26 4.3 Definition of Distributed Generation... 27 4.4 Modeling Battery bank in power systems... 27 Chapter 5... 28 5.1 PowerFactory Simulation of Battery in micro grid conditions: Modeling and Control... 28 5.2 Model Validation: Performance analysis and testing... 33 5.3 Coordination between BESS and Microgrid... 33 5.4 Investigating Peak Power Loads... 35 5.5 Investigation of Transient Voltage Stability... 36 5.6 Dispatch Strategy of a Wind-Diesel Hybrid System with an attached BESS... 37 5.7 Control Strategy proposed methodology of testing... 38 Chapter 6... 39 6.1 Conclusion... 39 6.2 Future Work... 40 References... 41 Appendices... 43 Appendix A: Manufacturer Data-Sheets... 43 Appendice B: Tutorial on how to use Lead Acid Battery model in Simulink/Matlab.... 45 Appendix C: ICAPS PWM & Inverter Model... 53 4
Tables & Figures Figure 1: Simple Battery Model 6 Figure 2: Battery Model with Internal Resistance 7 Figure 3: Battery Model with Capacitor 8 Figure 4: Battery Model with Voltage Control 9 Figure 5: Battery Model with Charging & Discharging 10 Figure 6: Graph of Voltage and State of Charge 12 Figure 7: Simulink Lead Acid Battery Model 13 Figure 8: Nominal Charge Discharge Characteristics 16 Figure 9 : Puekert Effect 18 Figure 10: Simscape TM Battery Cell Model 19 Figure 11: ICAPS circuit diagram of Battery Cell 20 Figure 12: SimScape Battery Model Scope 22 Figure 13: PowerFactory Diesel Generator model 29 Figure 14: PowerFactory PWM Converter Model. 30 Figure 15: PowerFactory Battery Model 32 Figure 16 BESS and Microgrid Model for simulating Peak Power 34 Figure 17: Simulation results of the Diesel Generator with a load step increase of 10% 35 Figure 18: Circuit Diagram of PWM converter 53 Figure 19: ICAPS Circuit Diagram of Inverter 55 Table 1: Simulink Simulation Process 11 Table 2: Battery Parameters 12 Table 3: Parameters for SimScape & ICAPS model 21 Table 4: Components of BESS 26 Table 5: PowerFactory Diesel Generator Parameters 29 Table 6: PowerFactory PWM Inverter Converter Parameters 31 Table 7: PowerFactory Parameters of the Battery Model 32 Table 8: PowerFactory Parameters of the Load Profile 33 Table 9: FullRiver 12V 150Ah 43 Table 10: Trojan 12V 44 5