A New Proposed Hierarchy for Renewable Energy Generation to Distribution Grid Integration Muhammad Umair Khan 1 , Khan Wali 2 , Kh. S. Karimov 3 , Muhammad Ahsan Saeed 4 1 2 3 4 Faculty of Electronic Engineering 1 2 3 4 Ghulam Ishaq Khan Institute of Engineering Sciences and Technology, Pakistan Emails: 1 m.umair72001@gmail.com, 2 khanwali909@gmail.com, 3 khasansangink@gmail.com, 4 ahsansaeed@giki.edu.pk Abstract—This paper presents a new hierarchy about the study of renewable energy generation, its transmission, energy storage and adding this power to distribution grid level. Simulation are verifying the feasibility and working. The main purpose of this study is to propose a feasible solution to replace fossil fuel energy sources to renewable energy sources without changing current working distribution grids setup. This paper will describe main components of this hierarchy including DC-DC converters, DC transmission, energy storage devices and grid integration. DC- DC converters are converting generated voltages to high voltages to transmit them on DC transmission line. Similarly a DC-DC step down converter is being used for step down purpose for using transmission line voltage to low level voltage for energy storage purpose and for grid integration on distribution side. DC-AC inverter is using old distribution grid signal as sample and converter DC into AC according to it. Simulation results verify the efficient working of all converters and completely stable system. Index Terms—Renewable Energy, Grid integration, grid hierarchy, DC-DC converter, Distribution grid I. INTRODUCTION From last few decades renewable energy generation have paid very great attention because of many well known disadvantages of fossil fuel energy generation. Energy need is rapidly increasing day by day and fossil fuel resources will not last forever so renewable energy is feasible solution to this problem. Main issue from renewable energy sources is their unpredictable fluctuation because of their sources like sun, wind etc. Also it is difficult to integrate these energy sources to our current grid network because currently working distribution grids were built without considering integration with other energy sources. Integrating them with more energy sources could cause serious problem with respect to frequency and voltage fluctuation. Researchers are working to get a proper solution and an easy way to integrate these sources to distribution grid. Many renewable sources like solar power and wind power generations have uncertainty even at their natural working condition so they cannot provide constant output power. This issue can be controlled be installing energy storage devices at large scale so that their fluctuation can be controlled. So it is difficult to provide fluctuation free power supply from renewable sources with backup power and to integrate these sources together and then integrate different energy sources to old distribution grid network to overcome the power need [1]- [3]. Many renewable energy resources are DC based such as photovoltaic (PV) Fuel cells (FC) etc. On the other hand few resources are AC based such as wind power, hydroelectric power etc. Those DC and AC sources cannot be added to grid directly and need to process their signals. DC sources (PV, FC etc.) needs to stabilize their output and then proper inverters are required to convert their signals into AC and also synchronize this signal to old grid network. Same as AC sources (Wind power, hydroelectric power etc.) also need to adjust according to distribution requirement. AC sources have variation in their output like frequency and amplitude. Their output needs to convert to DC because of two reasons, in this design DC transmission system is being used, secondly to match the amplitude, frequency and phase with distribution grid. Why DC transmission is preferred and other details are explained in DC Transmission section. Then at grid side these transmission voltages are converted to 3-phase AC voltages that are synchronized with old distribution grid. In fact these days many home appliances are working on DC such as Air conditioner, refrigerator, illumination lights and many other office devices. So this new integration network can be considered as DC in future. It can be transmitted as DC on distribution network also having backup energy storage support [4]-[6]. Recently many researches were carried in favor of grid integration but most of them were for specific type of renewable energy source such as for solar power or wind power [11]-[14]. Many of them don’t support backup energy storage system that is much more important as already discussed. Bidirectional converter is needed to charge batteries but this design eliminate bidirectional converter from this design which will be cost efficient and power efficient. Some researchers did their work for both AC and DC network for distribution level. But currently DC distribution is not so much important because not all appliances can support DC and it will be difficult to replace them all of a sudden. So currently AC network should be carried but this AC network’s replacement should be in mind. While constructing currently working distribution grids, other energy source power integration was not considered and we are still paying the price for that mistake so we don’t want to repeat this mistake again and will keep in mind about DC network at distribution level for future. 978-1-5090-0436-2/15/$31.00 ©2015 IEEE