Integrated Size and Energy Management Design of Battery Storage to Enhance Grid Integration of Large- scale PV Power Plants Ye Yang, Qing Ye, Student Member, IEEE, Leonard J. Tung, Michael Greenleaf, Member, IEEE, Hui Li, Senior Member, IEEE d Design parameter of EMS, the ratio of Pref to Abstract— Battery storage controlled by energy P management system (EMS) becomes an enabling PPV technique to enhance solar farm integration. In this paper, PPG Battery power generation for peak load the EMS controls battery storage to shape the fluctuated PV plant output into a relatively constant power and EB Battery energy capacity support the peak load. The proposed integrated design method considers both battery size and EMS impacts on SOH State of health the utility benefits and cost. The utility benefits include SOC State of charge power generation, peak power support, and reduced line losses. The cost of battery storage is determined by size DOD Depth of discharge and lifetime based on the developed battery models. Accordingly, the utility revenue change due to the battery ܥܮ௖௬௖௟௔௧௜௢௡ Cyclation-based irreversible capacity loss storage controlled by EMS can be evaluated. Therefore, ܥܮ Calendrical-aging-based irreversible the integrated design of battery size and EMS can be ௖௔௟௘௡ௗ௥௜௖௔௟ determined by managing the change of utility revenue to capacity loss gain economic benefits for the large-scale PV power plant application. Finally, the lithium-ion phosphate (LiFePO4) T Nonoperation time battery and lead-acid battery are compared to demonstrate BG Benefit of annual energy generation the proposed method on a utility system model respectively. BPPG Benefit of annual peak power generation BPL Benefit of annual power line losses reduction Index Terms— Battery storage, energy management system, large-scale PV plant, grid integration. CB Battery levelized cost EP Electricity price NOMENCLATURE R Utility revenue based on curtailed PV curtail EMS Energy management system generation ݋ݑ݈݋ܾ݉௧௢௧௔௟ Total available coulomb under 100% DODܥ Pref Power generation reference PPPV PV peak power generation of an unused battery ݋ݑ݈݋ܾ݉௨௦௘ௗ Used coulomb of an batteryܥ ܮܥ஼் Levelized cost of gas combustion turbine Manuscript received Aug., 2016; revised Dec., 2016, Feb., 2017, May, 2017; accepted Jun., 2017. This work was supported in part by. ܴܲ௉௅ Reduced line losses National Science Foundation under Grant ECCS-1001415 and the Department of Energy—Sunshine State Solar Grid Initiative LB Battery lifetime (SUNGRIN) under Grant DE-EE0002063. Ye Yang is with the National Institute of Clean-and-Low-Carbon ܲீ௥௜ௗ Power fed into the grid Energy, Beijing, China (email: [email protected]). Michael Greenleaf is with the U.S. Nuclear Regulatory Commission, ܲ௉ீ Battery power generation during peak load Atlanta, Georgia, USA (email: [email protected]). Qing Ye, Leonard J. Tung, and Hui Li are with the Department of ܲ஻ Power of battery Electrical and Computer Engineering, Florida State University, ܲ Battery power rating Tallahassee, FL. USA(e-mail: [email protected], [email protected], ஻ெ௔௫ [email protected] ). 'LJLWDO2EMHFW,GHQWL¿HU7,( ,(((7UDQVODWLRQVDQGFRQWHQWPLQLQJDUHSHUPLWWHGIRUDFDGHPLFUHVHDUFKRQO\ 3HUVRQDO XVH LV DOVR SHUPLWWHG EXW UHSXEOLFDWLRQUHGLVWULEXWLRQ UHTXLUHV ,((( SHUPLVVLRQ 6HH KWWSZZZLHHHRUJSXEOLFDWLRQV VWDQGDUGVSXEOLFDWLRQVULJKWVLQGH[KWPO IRU PRUH LQIRUPDWLRQ IEEE TRANSACTIONS ON INDUSTRIAL ELECTRONICS PCS Power conditioning system high cost of batteries. In order to achieve an effective and economical design of ܥ Unit cost of PCS ௉஼ௌ battery storage size, several research works have been ܥௐ Unit cost of battery capacity developed [6-11]. In [6], the battery storage size is determined ߟ Battery power conversion efficiency to maintain constant power production in PV plants according to the system requirement, however, the selected battery size ܥܨ௜௡௦௧௔௟௟ Installation cost factor has not been proved to be economical. A few battery sizing N Interest rate strategies have been developed by minimizing the investment on battery storage as well as the net purchased power for a FR The annual power fluctuation rate residential or a commercial building with a rooftop PV system T Temperature [7-11]. These methods are not suitable for large-scale PV plant applications, and the benefits to the utility company have not ܲ Curtailed PV generation ஼௨௥௧௔௜௟̴௉௏೔ been detailed. ܨܴ஼௨௥௧௔௜௟ Annual power fluctuation rate when the PV The battery EMS design has great impacts on the PV plant grid integration performance, which could affect the battery output is curtailed size selection as well. An energy management system (EMS) ܨܴ஻௔௧௧௘௥௬ Annual power fluctuation rate when the for PV power plants with energy storage was proposed in [12] to minimize the capacity requirement of energy storage, but no battery is deployed economic analysis was presented. In [13], an optimal power L Battery wire inductance in the leads management strategy was presented for grid-connected PV systems with storage. The objective was to help intensive RS Battery cell ohmic contact and solution penetration of PV production into the grid by proposing peak resistance shaving service at the lowest cost. Similarly, a price-based EMS was presented for roof-top PV installations with battery ROX Oxidation layer resistance formed at battery and local load [14]. The power output of the PV and battery cathodes systems are scheduled based on the time-varying price signals COX Oxidation layer capacitance formed at corresponding to the demand in the electricity networks. A co- optimization method for battery sizing and control strategy in battery cathodes a PV plant application was proposed in [15]. The operation RCT Charge transfer resistance formed at the and maintenance (O&M) cost and market penalties cost were considered. The proposed method in [15] has been applied in a electrolyte/electrode interface PV plant. However, the system level related aspects such as CDL Effective double layer formed at the annual power fluctuation rate of PV plant as well as the line power losses have not been analyzed. In addition, the electrolyte/electrode interface preformation evaluation of different types of batteries has not ZW Ionic diffusion through porous electrodes been compared. In this paper, an integrated approach to design the battery storage size and EMS for the grid-tied PV plant application is I. INTRODUCTION presented considering meeting system requirement and HE market for solar energy has been expanding rapidly gaining economic benefits. The 1-minute interval PV plant T worldwide, and the fastest growing sector within the solar output with load data from one utility company in Florida and market is the large-scale PV plant with outputs over 1 MW the actual temperature data are applied to achieve more [1]. These grid-tied megawatt PV plants generally cause realistic results. EMS is developed to maintain the constant considerable power variation due to the weather conditions. power generation and support peak load. The utility benefits The intermittent power generation of solar farms can perturb including the improved power production, the peak power the supply and demand balance of the whole power system, generation, and the reduced line losses are analyzed based on and further cause stability issues such as voltage fluctuation different battery size and EMS designs. The cost of battery and frequency variations [2]. Besides, the PV farms do not storage is determined by the size and lifetime. As a result, the generate power at night, so they cannot support peak loads in utility revenue change can be obtained under all possible residential applications. To maintain system frequency battery sizes and EMS selections. Finally, an integrated design stability during the peak load period, spinning reserve is of battery size and EMS can be derived by managing the always adopted which inevitably increases system cost [3]. revenue to gain economic benefits using the method of Recent research works have demonstrated that the battery exhaustion. The LiFePO4 battery and lead-acid battery are storage can be used in PV farms to solve the above issues selected to demonstrate the proposed design method because of its flexible real power control [4-6]. Unfortunately, respectively due to the good performance of the former and this technique has not been applied extensively, due to the the lower cost of the latter. Accordingly, by comparing the analysis results of these two batteries, the suitable battery type IEEE TRANSACTIONS ON INDUSTRIAL ELECTRONICS 8 9101112 13 7 0.00021 0.00063 0.00021 0.00014 0.00049 0.00049 Battery OLTC 0.00028 0.00063 0.00069 0.00028 0.00049 0.00098 Storage 1 23456 0.00118 0.00027 0.00035 0.00014 0.00021 0.00007 0.00035 PV PV (0.25MW) (2.06MW) 0.00076 0.00076 0.00076 0.00056 0.00028 0.00090 14 15 16 17 18 19 Substation 0.00354 OLTC: On-Load Tap Changer Vbase = 12kV 0.00021 0.00028 0.00028 0.00014 0.00021 0.00021 R PV: Photovoltaic Sbase = 1MVA 0.00083 0.00083 0.00083 0.00042 0.00063 0.00063 X SC: Switched Capacitor Zbase = 144ohm PV 0.9 MVar SC (0.25MW) Fig.1. The utility system model. WWWs= 2.06MW WƌĞĨс100%ÂWWWs PV Power Generation PV Power Generation Daily Power Generation WƌĞĨс60%ÂWWWs Daily Power Generation Charging Charging Power Power WW' Light Load Discharging Charging Discharging 0 Time (h) 0 Time (h) 246810 12 14 16 18 20 22 24 246810 12 14 16 18 20 22 24 (a) Ě = 60%; = 6MWh (b) Ě = 100%; = 6MWh WWWs= 2.06MW WƌĞĨс100%ÂWWWs PV Power Generation PV Power Generation WƌĞĨс60%ÂWWWs Daily Power Generation Daily Power Generation Charging Charging Power Power WW' Light Load Discharging Charging Discharging 0 Time (h) 0 Time (h) 246810 12 14 16 18 20 22 24 246810 12 14 16 18 20 22 24 (c) Ě = 60%; = 4MWh (d) Ě = 100%; = 4MWh Fig. 2. The impact of EB and d on daily generation.