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      Power and Energy Management in Microgrid

       Jayesh J. Joglekar

       MIT World Peace University, Pune, India

       Abstract

      The microgrid voltage management has a significant concern during unstable system condition due to limited power to frequency ratio (MW/Hz). The selection of sources for microgrid would play an essential role and power management techniques could save the microgrid from the complete blackout. The modification in the power flow controller could achieve desirable results with an appropriate position of the power flow controller.

      Keywords: BESS, fuel cell, energy storage, microgrid, renewable source

2.1 Introduction

The power system in the modern world is restructured based on source, nature of load and geographical space availability. The grid size also depends on the need of society and consumers. The concept of microgrid (MG) emerges from the traditional grid. But like the traditional grid, MG has a limited area to serve and hence the transmission lines could be replaced by underground cables. Depending on the application at the consumer end, MG could be with Alternating Current or with Direct Current or mixed one. Due to limited size, capacity and consumer base, power flow in MG could be a critical issue. For the interconnected AC transmission line network, transfer capacity is an economical operational constraint. It forces to use the available infrastructure to its maximum limit. The increased usability of the transmission limit handled by the FACTS controllers. These controllers are known for their applications in improving power transfer capacity as well as stability using the existing infrastructure of a transmission utility. In addition to transmission capacity enhancement and power flow control, FACTS controllers have other advantages like transient stability improvement, power oscillation damping, voltage stability and control. The transmission line capacity is enhanced by around 40 to 50% by installing a FACTS controller in comparison to conventional mechanically-driven devices, as FACTS controllers are not subject to wear and tear and require a lower maintenance [1].

2.2 Microgrid Structure

The Microgrid (MG) broadly comprises of source, load and controller, as shown in Figure 2.1. The choice of the source depends on the geographical location of MG and the type as well as the demand of the load. The emerging technologies such as fuel cell could be suitable for supplying the base load and proves advantageous over batteries. The working of a fuel cell is similar to the battery. The batteries contain the limited capacity of support chemicals. They have a fixed life cycle, but a fuel cell is supplied with fuel externally and operates continuously as long as fuel supplied. An electrolyte separates an anode and a cathode in the fuel cell. The type of fuel cell decided by electrolyte used. A fuel cell is a static energy converter from chemical to electrical energy. It is a modular, efficient and very low emission power source for a distributed system. It is clear that fuel cell is an upcoming option for conventional power generation resources [2–5]. Fuel cell produces electricity from external supplies of hydrogen fuel (on the anode side) and oxidant (on the cathode side) in the presence of an electrolyte. Generally, the reactants flow in and reaction products flow out while the electrolyte remains in the cell. Fuel cells can operate almost continuously as long as the necessary fuel flows are maintained. There are different types of fuel cell based on base chemical or membrane used. Those are Phosphoric Acid Fuel Cell (PAFC), Solid Oxide Fuel Cell (SOFC), Molten Carbonate Fuel Cell (MCFC) Proton Exchange Membrane Fuel Cell (PEMFC), etc.