International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056 Volume: 07 Issue: 06 | June 2020 www.irjet.net p-ISSN: 2395-0072 © 2020, IRJET | Impact Factor value: 7.529 | ISO 9001:2008 Certified Journal | Page 1940 Protection of smart DC Micro Grid using Parameter Estimation Approach K. Praveen Kumar Yadav 1 , K.S.S.N. Murthy 2 , K. Sai Ganesh Varma 2 , Ch.Mohan 2 1 Assistant Professor, Dept. of EEE, Lendi institute of Engineering and Technology, Andhra Pradesh, India 2 Student, Dept. of EEE, Lendi institute of Engineering and Technology, Andhra Pradesh, India ---------------------------------------------------------------------***--------------------------------------------------------------------- Abstract - In a smart DC micro grid, power electronic devices limit the current during fault and therefore, an overcurrent based relaying scheme cannot provide required sensitivity and selectivity for such a system. For a DC micro grid with ring configuration having bidirectional power flow, the protection design is further complicated. The project main objective is to design protection system for the DC micro grid. For reliable supply to customers and to avoid unwanted disconnection of renewable resources, selectivity of a protection scheme is important. Using the direction of fault information of both ends of a line segment in a ring system, internal and external faults are discriminated for network protection. This project proposes the protection model for DC micro grid. Using MATLAB simulations for a ring system, proposed method is tested for various fault situations including high resistance fault, close in fault, signals with noise and considering different modes of distributed generation (DG) operations. Key Words: DC micro grid, transient’s analysis, local measurements, fault direction, carrier-aided directional comparison. 1. INTRODUCTION Recently significant research and development are being carried out to integrate renewable energy sources(RESs); photovoltaic and wind turbines into existing distribution networks. Growth of energy demand and environmental concern urge for RESs in smart grid initiatives. Today energy policy of many countries envisages increased penetration of RES. Based on the connection of equipment types, networks in the micro grid can be AC, DC or a combination of the two. DC network is more feasible for a demarcated power system, for example, rural power systems, office buildings and ships where the majority of loads are sensitive electronic equipment and electric vehicles. Further advantages with DC micro grid are high efficiency, easy connection of sources to DC bus, negligible transmission loss due to small and localized system, enhanced power transfer capability and interfacing through more efficient power electronic devices. As there are differences in patterns of voltage and current during fault in DC systems compared to AC, the methods for protecting AC network cannot be copied directly to DC systems. Thus, there is scope of development for improved protection for DC micro grid. Power electronic converters are required to connect both AC and DC sources and loads to a common bus (AC or DC type) in a micro grid system. Moreover, DC network uses less stages of conversion. Internal faults in converter include failure of switches such as insulated-gate bipolar transistor(IGBT). In a DC network, the common fault is of pole-to-ground type and this is because of physical damage, aging or severe electrical stress in cables. Differential current based protection schemes for cable fault in DC network are proposed in that require reliable communication channel for instantaneous data transfer between protective devices placed at both ends of the cable. Chances of communication failure and loss of data result in performance limitation of differential scheme. The cost of such protection scheme is also a concern in micro grid. unit and non-unit protection schemes are investigated for DC network faults. High rate of rise of fault current and its large steady state value demand for fast operation of DC network protection. The challenge is to avoid damage to the power electronics devices and keep the fault current within interruptible limit, the fault must be cleared in a timely manner. A non-unit protection scheme is proposed for DC network fault detection. The capacitor present in the DC side of the converters supplies current for short duration during a fault in the line. The main drawback of this method is that it shutdowns the system completely for a fault. A fast and selective protection scheme based on direction of current information only for DC network is proposed. During high resistance fault, flow of current direction may not be indicative of fault direction for a protection system. With increased number of sensors and communication infrastructure, the concept of smart micro grid is being realized for automatic network monitoring and management, increase the usage of intermittent sources and decrease the network congestion. Protection action can be performed utilizing this advanced communication infrastructure of future smart DC micro grid. In this paper, a protection scheme for smart DC micro grid with ring configuration is proposed. Using local intelligent electronic device (IED), voltage and current data during fault, a LS based technique estimates the inductance of the fault path which is able to discriminate forward and reverse faults with respect to the IED. This fault direction information is communicated to the other end IED of a line