Abstract
This is the second part of a companion paper on variable reverse power flow (VRPF) in active distribution networks (ADNs) with wind stations (WSs). Here, we propose an electricity market model considering agreements between the operator of a medium-voltage active distribution network (MV-ADN) and the operator of a high-voltage transmission network (HV-TN) under different scenarios. The proposed model takes, simultaneously, active and reactive energy prices into consideration. The results from applying this model on a real MV-ADN reveal many interesting facts. For instance, we demonstrate that the reactive power capability of WSs will be never utilized during days with zero wind power and varying limits on power factors (PFs). In contrast, more than 10% of the costs of active energy losses, 15% of the costs of reactive energy losses, and 100% of the costs of reactive energy imported from the HV-TN, respectively, can be reduced if WSs are operated as capacitor banks with no limits on PFs. It is also found that allocating WSs near possible exporting points at the HV-TN can significantly reduce wind power curtailments if the operator of the HV-TN accepts unlimited amount of reverse energy from the MV-ADN. Furthermore, the relationships between the size of WSs, VRPF and demand level are also uncovered based on active-reactive optimal power flow (A-R-OPF).
Highlights
We have presented the relationships and the interplay between wind generation curtailment, variable reverse power flow (VRPF), varying power factors (PFs) of wind stations (WSs), different demand levels, and active/reactive energy prices in an electricity market model under different scenarios
It is shown that the extended active-reactive optimal power flow (A-R-OPF) allows
We derived based on computation results clear rules for power system planners when VRPF is allowed
Summary
The reactive power dispatch (Qdisp.w) of the WS, see Figure 2, the wind active power generation to prevent violations of system constraints (detailed mathematical which is to be optimized to minimize energy losses in the MV‐ADN and minimize the formulation is given in Part-I [1]). The curtailment factor and reactive which is to be optimized to minimize energy losses in the MV-ADN and minimize the power dispatch are used to balance all the terms in the objective function F (1) using an active energy reactive import from the HV-TN [19,20]. After solving the problem different operating direction at slack bus S1 denoted by αP1.rev (0 ď αP1.rev ď 1), the lower power factors (PFs) of WSs points can be obtained and their features distinguished: denoted by PFmin.w (0 ď PFmin.w ď 1) under different WS-sizes and WS-locations. We consider the situation that an operating point in the gray quadrants (i.e., quadrants 3 and 4) should be avoided to minimize charging costs for reverse reactive energy [3]
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