Hybrid solar PV–hydro controller for an autonomous dc microgrid

Abstract

The negative impact of global warming and general environmental pollution associated with the use of fossil fuel as a source of energy has become more visible in the past decade. Hence, the need to operate a more sustainable electrical grid network using renewable resources such as wind, solar PV, hydroelectric, biofuel and biomass. Solar PV is a reliable source of energy to solve the energy crisis and environmental pollution associated with it. This is mostly informed by the advancement in technology and reduced cost of solar PV panels. The power supply and consequent power output from a microgrid network with high solar-PV penetration is normally unstable due to the intermittent nature of solar PV supply. Hence, the need to incorporate a pumped hydro storage system as the energy storage system of choice. In this study, a control method for an off-grid hybrid DC microgrid that consists of solar PV and pumped hydro storage system was developed to provide sustainable, reliable, flexible and accessible energy for a remote community. The developed off-grid DC microgrid system consists of a solar PV system of 100 kWp as a distributed energy resource and a pumped hydro storage system as energy storage system (ESS). an energy management system (EMS) was designed and developed using a fuzzy logic controller (FLC) in the MATLAB/Simulink environment. A pumped hydro storage system (PHSS) is used as an energy storage system to improve the DC microgrid system stability and also operates as a backup power system. A load shedding scheme is part of the system to bring support to the supply by automatically disconnecting or re-connecting the secondary load to ensure reliability and continuous supply of power to the primary load and secondary load depending on the available power and the water level in the reservoir. A DC-DC boost converter connects the solar PV to the rest of the DC microgrid system thereby improving the quality of power generated and allow the flow of power in the system. The performance analysis of the research design considered the intermittent power supply of the solar PV and the flexibility of the load demand under different circumstances and time of the day. The study developed different scenarios using the energy management system algorithm to evaluate the performance of the system. The results showed that the adopted EMS ensured DC microgrid stability, improved reliability, increased system flexibility and effective power distribution. In addition, the developed algorithm provided adequate power distribution between the solar PV and the PHSS and maintained the charging and discharging of the reservoir within acceptable level. The results also showed that the PHSS was able to augment power shortage in the system based on the different scenarios that were implemented. The developed energy management system also provides an opportunity to remodel and change any parameter within the DC microgrid system. The results obtained were compared with other similar DC microgrid system’s and the results proved that the EMS was effective and the load demand was adequately met.