Design and implementation of power converter minigrids for embedded generation

Abstract

Supplying energy to off-grid and remote areas has always been a challenge despite the penetration of micro and minigrids in those areas. Challenges include the implantation costs of minigrids compared to the community low-income, the scarcity of skilled workers required to operate the plants, as well as issues pertaining to the reliability of solar and wind sources that are dependent on the time of the day, the weather, and the annual season. . As such, the operation of these minigrids not only requires a meticulous design but also autonomous management and control to ensure continuous service to the community in an operation mode known as an islanded mode. The literature survey conducted on the management and control of the energy in an islanded minigrid highlighted the need for further study to contribute to this area. Therefore, the focus of this study was on energy management and control systems for a multivariable energy system consisting of solar and wind plants backed up with a diesel generator and battery storage. The proposed algorithm referred to possible scenarios relating to the behaviour of the major energy sources when either one or more are at their lowest levels, as well as the variable levels of the load demand to establish the rules that will govern the response of the minigrid. In addition, the study worked on addressing issues related to the quality of power received by the variable or nonlinear load by designing a control system aiming at eliminating the harmonic distortions resulting from the presence of reactance in the load together with the presence of a voltage source inverter to process the power coming to the photovoltaic (PV) plant. Through meticulous modelling of the output network consisting of an LC filter and an RL load, a proportional–integral control was designed and tuned to ensure that the variable load would receive a harmonic-free output voltage and current. Finally, the study implemented the energy management strategy incorporating the power quality aspect to supply electricity in a rural area. This was completed using real-time software such as Typhoon HIL (Hardware In the Loop) to illustrate the functionality of an islanded minigrid where worst-case levels for the solar and wind plants were catered for. Overall, the aim of this study, which was to bring about a solution to control multivariable sources and make them successfully operate in an islanded mode, was achieved.