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a hybrid hydrokinetic system HKT battery is used in GC mode. The surplus power of HKT is utilized for charging a battery or trade to the grid. Whether the power will be sold to the main grid or not is determined by the charge condition of the battery and the principle of the utility grid network. The power requirement of the load is provided by the HKT. The excess power is utilized to charge the storage body. Then also, if there is an excess quantity of power, that can return back to the utility grid network. However, the utility grid supplies the load directly when the distributed generation system and the battery can’t entirely meet the load demand.

The universally used energy storage system is the battery. The battery system also has some limitations, as some charging and discharging current issues and unreliability according to the lifespan of the battery. So, techno-electronic indexes of micro-grid-based hybrid renewable energy resources are significantly increased by applying the distributed system of the generation with the storage system of energy [7]. Ref. [8] is a study of hybrid solar power as PV and diesel power in a distributed system supplying a load of a rural school in Ethiopia. The paper has compared the hybrid PV/Diesel distributed system with the storage system to the distributed generation system without storage as the net instantaneous rate of energy. Here a software named Homer is applied for analysis. The result was concluded that the hybrid distributed generation system with storage is having technical and economic advantages than that without storage. In Ref. [9] the authors proposed that the energy management system for hybrid micro-grid consist of photovoltaic and wind power as renewable energy sources (RES) and fuel cell (Hydrogen cell), ultracapacitor or battery as storage system of energy (SSE).

      1.2.2 Incorporation of Electric Car in Micro-Grid as a Device for Backup

      Nowadays the incorporation of an electric vehicle with micro-grid is viral because of its effect of low emission, inexpensive charging and decreased usage of conventional fuels. The electric car with MG can function in car-to-grid (C2G) mode or grid-to-car (G2C) mode. In Ref. [10] planned power management is proposed in the MG, including storage systems categorized into two types: regenerative fuel cell (RFC) and electric car (EV). That paper approaches with multi-goal optimization to minimize operational cost, line losses and maximise the value of energy stored in terms of RFC and EC. There are two functioning schemes planned for EC working in C2G mode to decrease the net running cost of the system. The combination of particle swarm skim of optimization as well as front and back sweep algorithm is used to solve complication, non-linear action and multidimensional property of the objective function. In Ref. [11] a large-scale electric vehicle charging station is proposed by the author, in which the required power is supplied by solar and wind power. Here both the PV and wind work with a unified MPPT technique. In Ref. [12] the author incorporated the plug-in charger of the electric vehicle in the distribution grid in both directions by using various converters. The bidirectional converters are coupled to the capacitor at the link with DC. The grid voltage may be regulated in the C2G configuration using the capacitor at the link with DC, which provides compensation for reactive power, which avoids the risk of voltage sag in the main. The mixed charging electrical car battery is used for peak load shaving and load levelling. Ref. [13] illustrates a real application of electric vehicle charging station along with a storage system of energy, which is a battery of Lithium polymer. Investigational research is done in Italy at the power and Sustainable Economic Development labs for innovative Technologies. The outcome shows the new performance of the ECs in the height of energy shaving action, as compared to the utility grid.

A resiliency-based Energy Management System of islanded operation of micro-grid is presented in Ref. [14]. Here the case studied is about micro-grid (MG) consisting of PV generation farms and WT generation farms both having storage system of energy (SSE) and distributed generation system. Based on the study, the researchers used 25 plug-in hybrid electric cars as adaptable load and supply to replicate the scheme of demand response in an optimal way, so the ECs in G2V manner are used as adaptable load, while in V2G manner is applicable as adjustable supply. Ref. [15] is a discussion on systematic energy management of a home with the smart system using PV panels as the source and plug-in EC (PEC) as storage of energy. It reduces payment for energy demand under using time tariff while supplying energy requirements to PEC and home load. A Lithium-ion battery is used in the PEC as storage and is controlled by DC–AC inverter, which allows the bidirectional flow of power. The plugs-in and plug-out of the PEC can be done once a day. The PEC mobility model is modeled by the Markov Chain model. The predictive models are used by the author to design solar power supply and home as load. The researchers proposed that the system may possibly be a significant cost savings system for the consumers. The proposed Management System of Energy manages the flow of power in between the PEC as storage, building or home as loads, and an array of PV panels and utility supply grid as supply.

      1.2.3 Power and Heat Integration in Management System

The heat or thermal energy can be generated concurrently with electricity in HPC systems. The heat can be used for some other purposes such as space heating, water heating, etc. The efficiency can be enhanced with the help of HPC, in which the waste energy as heat is used for various thermal utilizations, therefore minimizing energy loss during distribution or transmission. The Cooling–Heating-Power-Combination (CHPC) is further called as tri-generation micro-grid. It is capable of providing heat, cooling and power to the consumer as required. In Ref. [16] an optimized model of a tri-generation micro-grid (CHPC) is discussed. In this case, the CHPC deals with the uncertainty of energy demand such as heating, cooling and electricity. An MSE for HPC of a GC Micro-grid optimally operates the grid and dispatches the HPC. The micro-grid supplies electrical and thermal energy requirements. In Ref. [17], the author discussed a management system of energy for HPC for a micro-grid connected to the grid, which can plan grid operation and HPC send-off optimally. The MG is taken as supply of electricity and thermal energy as required. The given methods have been concluded that V2G operation achieves a minimum rate of the objective function as compared to the operating strategies of MG with no V2G and the micro-grid with a conventional vehicle. A large-scale electric vehicle charging station is proposed in Ref. [11], where solar and wind energy is combined to supply the total power required. Here both arrays of solar panels and wind power generators work through a combined MPPT technique. The author combined the plug-in hybrid electric vehicle charger working in V2G mode with the distribution grid by the converters like rectifiers and choppers [12]. They are connected to the DC-link with the capacitor. This DC-link capacitor offers compensation of reactive power. So, this V2G charger is able to adjust the voltage of the grid by employing a capacitor at the link of dc. So, the problem of voltage drop can be avoided in the grid. This energy could be used to level the load and to shave the peak load. The authors presented an actual execution of EV charging station in the company, including an energy storing system like Li-polymer battery. The authors of Ref. [14] offered an idea about resiliency-based MSE for a micro-grid working in islanded condition. That case study was on a micro-grid consisting of PV farm, WT farm, and battery. The researchers applied 25 plug-in hybrid EC as the controllable design of supply and demand, which are optimized to show the conception of demand–supply relation. In V2G mode the plug-in EV can be considered as adjustable generation and in G2V mode the plug-in EV can be considered as adjustable demand. The authors of Ref. [15] discussed systematic management of energy for a smart home including plug-in EV (PEV) and PV panels to minimize costs during a time of use tariff, which supplies the home load and energy required to charge the PEV. A Li-ion battery is used in the PEV, which is controlled by a bidirectional converter. It allows power flow in both directions. Here the Markov Chain model is applied to design the mobility of PEV. The predictive model is used to design a home as a load and the dispersed power generation. This guaranties the cost-saving at the consumer’s end. The total power flow is managed by the proposed energy management system.

      1.2.4 Combination of Heat and Electrical Power System

      The thermal energy also simultaneously can be generated with the electrical energy in the HPC systems, which can offer heat or thermal energy for diverse uses, like residential heating, cooling and water heating, etc. The power efficiency can be enhanced by HPC, in which the unused heat can be utilized for different heat applications, so distribution or transmission losses can be minimized.

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