Electrical Mobility and Ultra Grid Implementation Problems in Emerging Countries

Abstract
Smart grids have important challenges for incorporating electrical mobility, especially in emerging countries. Due to new requirements associated with ultra-grid penetration, electrical mobility, and the new aspects of the medium voltage grids; it could be a limit for this technology without a new infrastructure or changes in the grid. In this research, a new methodology is proposed with seven steps. For electrical mobility in Perú, the electrical networks with Photo-voltaic Solar panels and fast-charging stations for emerging countries have new effects as overload in transformers, inverter control and modeling for chargers and distribution transformers should be reviewed, due to loads transfer, voltage sag, and losses, the impact is high in a short term. These results provide challenges for government, industry, and prosumers. Results have demonstrated voltage sag are from 5.68% to 3.81%, losses from 0.112kW to 0.12kW, voltage transformer from 1.21% to 1.09%, and transformers rotations with a detailed load density analysis with 20% penetration with fast charging stations and 40% of ultra grid penetration with photo-voltaic generators, with original mitigation associated to control in inverters and seven steps in the methodology.

 1. Introduction

Peruvian grid has increased in the wind and solar technology in a distributed energy grid, this technology allows to develop the electrical mobility, due to low energy cost and complimentary of renewable energy, according to Fig. 1. Each country around the world has experimented with electrical failures associated with power transformers with new renewable energy such as photovoltaic solar [7] panels and electrical cars, this phenomenon has been demonstrated especially in Germany [1]. One cause is for the inverter control in the transition from standby operation into working mode regime, each inverter in the middle of the city, will affect the transformers and medium voltage grid [2]. The power flows are different with ultra grids, transition at 5:00 pm and the detection of failures in cloudy conditions affect the medium voltage, so, it requires a grid manager to control and supervise all that is happening along the electric power grid [3].

2. Grids after and before smart grid implementation

Fig. 2, describes two high voltage substations: Tacna with seven distribution lines and Parque Industrial with six distribution lines, the implementation of the new smarts grid will require a special analysis, The methodology implemented in this research is according to the following characteristics:

• Load flow, short circuit, and protection of the medium voltage grids, in all the city, Fig. 2.
• Density load for the city allows for detection the chargers points around the city [8], and inverter impacts in the ultra grid, Fig. 3.
• To identify impacts in load distribution transformers.
• To identify impacts in the voltage in each transformer
• To identify loads in MV lines. To identify business-as-usual with 20%, 40%, 60%, 80%, and 100% photo-voltaic penetration; with and without reduction of taps +50% and -50%; we recommend the evaluation with distributed parameters similar to Fig. 6.
• To identify business-as-usual with inverter contribution for Volt-Watt or Volt-var technique for the voltage control [4].

 3. Discussion

In an emerging country like Perú, the first step for electrical mobility is the connection and protection architecture. In this case, to connect these two high voltage substations with medium-voltage grids, besides, the protection control should be improved with 67 and 67N protection schemes. Besides, the impact of the electrical chargers has increased the load in the distribution system [5], especially with fast charger stations [6], for the load variations [9]. On the other hand, The problems grew with 40% photo-voltaic penetration, due to overload in the transformer for the effect of the voltage and the inverter action, as Fig. 4, in this stage, the system required to change the taps two, besides, the inverters, should adequate an extra oversized of 10%, with a Volt-var instead of Volt-Watt for control voltage in the inverter, the control and load are controlled with Volt-var control, as Fig. 5. The simulation has considered 15 fast-charging stations for 7,500 vehicles. Associated with 10% of the vehicle available, The investment required is USD 0.78 million. Finally, this research helps to establish the necessary procedure to determine the fast charging infrastructure in urban centers and ultra grid influences with photo-voltaic generation in a Peruvian grid, considered an emerging country.


Figure 1: Peruvian wind (green) and solar (orange) production from 2019 to 2020.

Figure 2: High voltage distribution for Tacna

Figure 3: high voltage substations grid and the medium-voltage circuit.

Figure 4: 40% penetration of ultra grid with photo-voltaic generators with taps on 0 position.


Figure 5: 50% photo-voltaic penetration with 15 chargers for electrical cars.

 
Figure 6: Distributed parameter for the high penetration evaluation.

 Acknowledgments
Thanks to Universidad Tecnológica del Perú, Universidad Nacional de San Agustín de Arequipa and IEEE Power & Energy Society Peru.

References
[1] Benjamin Bayer, Adela Marian, “Innovative measures for integrating renewable energy in the German medium-voltage grids”, Energy Reports, Volume 6, November 2020, Pages 336-342 
[2] Mihovil Ivas, Ante Marušić, Juraj George Havelka, Igor Kuzle, “P-Q capability chart analysis of multi-inverter photovoltaic power plant connected to medium voltage grid”, International Journal of Electrical Power & Energy Systems, Volume 116, March 2020, Article 105521. 
[3] Eduardo F. Ferreira, J. Dionísio Barros, “Faults Monitoring System in the Electric Power Grid of Medium Voltage”, Procedia Computer Science, Volume 130, 2018, Pages 696-703.
[4] Izzah A fandi, Philip Ciufo, Ashish Agalgaonkar, Sarath Perera, “A holistic approach for integrated volt/var control in MV and LV networks”, Electric Power Systems Research, Volume 165, December 2018, Pages 9-17.
[5] Matjaz Knez, Gašper Kozelj Zevnik, Matevz Obrecht, “A review of available chargers for electric vehicles: United States of America, European Union, and Asia”, Renewable and Sustainable Energy Reviews, Volume 109, July 2019, Pages 284-293. 
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[7] Ricardo Manuel Arias Velásquez, “Root cause analysis for inverters in solar photo-voltaic plants”, Eng. Fail. Anal., 118, 2020, 104856, 1-18. 
[8] Ricardo Manuel Arias Velásquez, Yovitza Lucia Romero Ramos, Ian Meldrum, César Díaz, Julien Noel, “Dynamic model for transmission lines maximum disconnection time on wind farm”, Ain Shams Engineering Journal, 2020, 1-13. 
[9] R. A. Velásquez and J. M. Lara, “E-mobility and PV Solar challenge in Peruvian radial distribution feeders”, 2020 IEEE Engineering International Research Conference (EIRCON), 2020, pp. 1-4.

Authors 

Jennifer Vanessa Mejía Lara: IEEE Senior Member, PMP®, She is a Colombian engineer and Project Manager for Renewable Energy in ENEL, She got her electrical engineer degree, and MSC in project manager degree, with Andean membership. Solid certified knowledge in projects and operation of Electrical Systems (power systems, high and extra-high voltage substations and transmission, conventional and unconventional generation, mining, hydrocarbons and distribution). PhD in engineering and Master's degree in control and management of projects for the planning and development of businesses in large mining, hydrocarbons, and energy. Currently, mainly in project management and commissioning management for EPC projects in mining, substations, and energy, ranging from design, planning, and construction to commissioning in Chile, Peru, Colombia, Venezuela, Ecuador, Spain, Germany, and Algeria. Advanced bilingual knowledge of English - Spanish.

Ricardo Arias Velásquez: IEEE Senior Member, Dr. Aruas is known for his contributions to Renewable energy solutions, artificial intelligence in energy design & engineering failure analysis. He did eleven postdoctoral research for MIT, UTEC, and UNSA. Furthermore, he holds a Ph.D. in Engineering from the Pontificia Universidad Católica del Perú, Master's Science degree in Engineering, and three Bachelor's degrees in electrical engineering, Project engineering & Computer Science from UNSA. Besides, Dr. Arias is IEEE PES PERU executive chairperson 2021-2022, Editor Associate in IEEE Latin America Transactions. As a professor, he is an Operational Efficiency Specialist in ENEL for the biggest renewable power plants in hydro, solar, and wind technology.