استراتژی عملیات بهینه و تجزیه و تحلیل اقتصادی یک منبع تغذیه اضطراری مرکب از فتوولتائیک، دیزل، باتری

This paper presents the optimum operation strategy and economic analysis of a photovoltaic-diesel-battery-mains hybrid uninterruptible power supply (UPS). The system involves a photovoltaic, battery and bi-directional inverter that is connected in parallel to the grid. A diesel generator is required when the grid is not available for a longer time. The optimum operation strategy of the system is proposed for the diesel-connected mode (when the grid fails for several hours), while the economic analysis is evaluated for the grid-connected mode. The optimum strategy determines the ‘set point’ value for starting and stopping the diesel generator, resulting in a lower system operation cost within its lifetime. The optimum value is obtained by comparing the cost of the diesel fuel consumption and the battery wear. The economic analysis includes the system operation as UPS and demand side management. The system will reduce the power flow from the mains by increasing the power from the inverter to the load when the tariff is high. However, when the grid tariff is low, the power from the mains is used to charge the battery and to meet the load simultaneously.

Uninterruptible power supplies (UPS) are used to interface critical loads such as computers and communication equipment to a utility power grid. A new UPS topology that involves photovoltaic, diesel and battery/converter has been presented by Nayar et al. [2]. This system has also been tested and implemented in India [3]. The configuration of the PV/Battery/Mains hybrid UPS is presented in Fig. 1. When the grid suddenly fails, the inverter will take over to supply the load without any interruption of power. The diesel generator (DG) may be used if the grid is not available for a longer-term e.g., for several hours.

Optimum operation strategy and economic analysis of a PV-diesel-battery-mains UPS system have been presented. The system uses set points to control the overall system operation providing a wide operation combinations. During the DG-connected mode, where the grid fails for a long time, the optimum value for starting and stopping the DG has been determined based on the DG fuel cost and battery wear cost. The economic analysis when the grid is normal presents that the lowest energy cost is found when the system operates as grid-PV UPS. The battery is set as the minimum size for the UPS operation only, typically for 30 min. This calculation excludes the effects of a weak grid system such as the loss of revenue, the damage of equipment and reducing the efficiency.