Читать книгу Microgrid Technologies - Группа авторов - Страница 31

In Ref. [6], the authors have represented a cost minimization EMS of GC–HKT system with a storage system, which consists mainly of three types of costs. The energy purchasing cost from the grid satisfies the load requirement and also the battery charging is the initial cost. The second cost is during the high costing time the revenue comes from exporting electricity to the primary grid. The third one is wearing cost or maintenance cost in the system. The authors choose power balance, limitations of HKT’s production and SOC of the battery as optimization constraints.

The authors in Ref. [46] have optimized GC MG with generators, Energy Storage System and electrical load. The generators maybe detachable or not. The overall energy charges are assumed as the goal function. Such as the fuel utilization cost, cost of charging the battery, cost of discharging the battery, the energy cost generated by detachable and non-detachable generators, the energy cost generated by trading power in between MG and the main grid network, and the cost of conveying energy demand all over the arrangement. The authors have incorporated environmental and technological factors as constraints to get the optimized result. The total quantity of energy produced by the end of the generator should be the same as the total quantity of energy at the consumption. The consumer and supplier of electricity are taken as technical constraints. Energy storage constraints include charging/discharging limitations of battery, the energy balance of battery, energy storage limitations and SOC of battery. In the end, the constraint was grid limitations that the quantity of exchanged energy in between the main grid network and MG.

Figure 1.7 Microgrid in Grid Connected mode.

The authors of Ref. [47] have given an optimized resolution for a mixed PV/WT/FC/HPC system, which is operating in the mode of grid connection. The authors have minimized the operational/running cost and maximized the system profits as system working cost includes (i) the fuel cost, (ii) the energy purchasing cost from the main gird, (iii) the installation cost of the system, (iv) the operation & maintenance cost of power generators. The authors have considered the system profits as the revenue in selling surplus energy (thermal and electrical) to the main grid when the net production of the distributed generation system go beyond the overall energy demand by the load.

The MSE for grid-connected HPC with both battery and thermal SSE, heat only boiler (HOB), thermal loads and electrical loads has evolved in Ref. [48]. This MSE technique has minimized the expenditure of the system operation. The authors have considered the expenditure of energy from HPC, HOB, CDG units, cost of importing energy from main grid and exporting back to the grid, and installation cost of different components of micro-grid. Now electrical power and thermal power balance are the main constraints for the optimization. The balancing of power guaranteed the electrical energy production and charging or discharging of the battery must be same as the consumption in electric load and energy tariff with the main grid. The thermal balance system is that when the amount of thermal energy produced at local thermal generators must be equivalent to local load (thermal) requirement and the energy (thermal) mutually shared with any other units of MGs. Other constraints are such as the capacity of the components of each MG. HPC, HOB and CDG must operate in their specified limitations. The quantity of energy exchanged with the main grid is limited by the capacity of the electric line. Also, the quantity of heat energy exchanged between two units of MG is limits with the thermal line capacity. The heat energy exchanged between thermal networks, and MGs is another constraint, which reduces thermal energy wastage when production of local thermal energy exceeds the demand of the local thermal load.