The cyclical nature and high investment costs of the wind and photovoltaic renewable energy sources are the two critical issues seeking attention for the use of such systems in backup or isolated applications. This paper aims to present the experimental and economic analysis of a wind–photovoltaic-based hybrid direct current microgrid (DCMG) system for backup power and off-grid isolated power generation system for emergency purposes. The two distributed generating units comprising photovoltaic panels and wind generator were designed and developed for the experimental study. A lead-acid battery is also added as an energy storage system to enhance the system supply. The electric load of this system comprise of 42 DC light emitting diode (LED) lamps of 12 Watt each and a 25 Watt DC fan. The charge controller provides the control and protection features for the designed system. The complete system design and fabrication of this system have been undertaken at Mehran University of Engineering & Technology (MUET, Jamshoro, Pakistan). The compatibility of the designed system has been analysed by comparing the Levelized Cost of Energy (LCOE) with a conventional gasoline generator system of the same capacity. The capital, running and lifetime costs of DCMG are found to be 1.29, 0.15 and 0.29 times those of the gasoline generator, respectively. Moreover, it is found that per unit cost of gasoline generator is $0.3 (i.e., PKR 31.4) which is almost 3.4 times higher than that of the hybrid DCMG system. The performance and cost evaluation of the designed system indicate its broad potential to be adopted for commercialisation to meet backup power and off-grid power requirements. This study concludes that proposed DCMG system is a not only low cost, but also a pollution-free alternative option compared to the existing traditional small gasoline generator system.

Active power and DC voltage regulation is the key control challenge in a voltage source converter based multi-terminal high voltage direct current system (VSC-MTDC), particularly when integrating renewable energy sources. In such a system, the droop control may result in VSC overloading, leading to unequal power distribution and DC voltage instability following a major disturbance. To enhance the control performance, this paper presents an adaptive droop control technique based on the headroom of VSC (HR-ADC). The designed approach uses the headroom of rectifying and inverting converters to adaptively adjust values of droop coefficient, thereby avoiding converter overloading when significant power interruptions occur. The planned strategy is adopted for the rectifying and inverting converters. To validate its effectiveness, the HR-ADC is compared with the variable droop control using the four terminal ± 400 kV MTDC transmission system in PSCAD. Simulation results demonstrate that the designed HR-ADC is autonomous and resilient, ensuring stable system operation even during significant disturbances such as converter outage or fault conditions in the MTDC grids.