Designing Power Electronic Interfaces and Microsource Controllers for a MicroGrid

No Thumbnail Available



Journal Title

Journal ISSN

Volume Title


Addis Ababa University


Developing a Microgrid (MG) system supplied with feasible integrated microsources, such as renewable energy sources and fuel cell, is one of the major solutions to be envisaged in terms of the current trend of power demand, i.e. efficient, environmentally friendly and relatively cheap means of power generation. In a Microgrid the most indispensible devices are the Power Electronic Interfaces and Controllers which regulate electrical parameters of the microsources. This research provides comprehensive overview, design and modelling of Power electronic interface (PEI) and Microsource Controllers (MCs) for a Microgrid supplied with Photovoltaic (PV) and Integrated Solid Oxide Fuel Cell/Gas Turbine (ISOFCGT). The PEIs to be designed includes Inverters and DCDC boost converter for the three microsources, PV, SOFC and GT, and rectifier for the Gas Turbine (GT) unit. To avoid use of transformer in the MG, two-stage DC-DC boost converter is used. For the ease of controlling and reduction of THD, SPWM technique of inversion is applied. In designing Microsource Controller a control technique known as Droop control, in which active and reactive powers are controlled during gridconnected mode of operation of the Microgrid, and voltage and frequency are controlled in island mode, is considered as a better option. By doing so the control of microsources is distributed and proportional power sharing among microsources is facilitated so that reliability of control is ensured as there is no central control unit which needs communication facilities. In the Microgrid the PV is not dispatchable unless it is backed by battery storage system due to the intermittent nature of the solar power. But the cost of battery for PVs is very expensive and makes the system sophisticated due to power electronic interface for charging and other ancillary devices like charge controller. There is the possibility of not to use the battery and the ancillary devices by using the SOFC microsource instead of the battery storage system when the solar power is reduced or completely unavailable. So this thesis also considers the possible mechanism of sensing the intermittency of the solar power in such a way that the SOFCGT can take over the PVs in partial or completely. The designed PEIs could make the microsources to be integrated in to the proposed MG by converting their original DC and high frequency AC sources in to standard three phase AC wave forms of 380 V and 50 Hz. Also using the designed Microsource Controller it is possible to control V, f, P and Q by ensuring proportional power sharing among the microsources. MATLAB/SIMULINK-Simpowersystem is used to simulate the designed PEIs and the MCs based on a model Microgrid so that the performance characteristics of the two systems can be demonstrated practically.



Microgrid, Microsource, Microsource Controller, Power Electronic Interface, Inverter, DC-DC converter, Rectifier, Droop Control, Photovoltaic, Integrated Solid Oxide Fuel cell/Gas Turbine