## 4 Conclusions  
The paper addressed the OPF problem in the electric networks integrating wind farms. The main objective aimed to determine an as constant as possible voltage level at each bus, if possible, in a variation interval as narrow as possible, such that the power losses have the lowest value. An SQP-CC methodology of the OLTCs was proposed, such that the optimal voltage level at the buses led to the minimum active power losses. Their practical implementation has, as the starting point, the ability of the TSOs to hold the control capability of the transformers with OLTC due to the advanced technologies based on the automatic voltage control (AVC). It can work in both operation modes (real-time and off-line). The methodology works in real-time with input data collected from the SCADA system at different periods by sampling steps (1, 5, 10, 15, 30, or 60 min). Using the same sampling steps, having the lowest possible value for all RTUs, represents a solution adopted at the level of the SCADA system, which includes the frequent changes in the wind generation. The effectiveness of the proposed SQP-CC methodology was tested on a 10-bus network, representing a zone of a real transmission and distribution system, with two wind farms connected. Two scenarios were analyzed, without and with wind farms connected, to quantify the benefits on the operation of the network with the wind power sources integrated overlapping the coordinated control of the OLTCs. Three specific cases were considered in the second scenario: Case 1: Wind Farm 1 is ON, Wind Farm 2 is OFF; Case 2: Wind Farm 1 is OFF, Wind Farm 2 is ON; Case 3: both wind farms are ON. The energy-saving, calculated by formula (32), was 33.5% in the scenario without wind farms connected and applying the SQP-CC methodology. Higher values were obtained in the three cases of the second scenario, 36.8% (Case 1), 37.42% (Case 2), and 41.27% (Case 3). The optimal tap positions of the transformers led to the very close voltage variations between the 110 kV buses of the network compared to not using the SQP-CC methodology. The average voltage drop between Bus 2 and Bus 10 in the three cases was by 0.008, 0.009, and 0.004 p.u., respectively, compared to 0.038, 0.034, and 0.031 p.u., without the SQP-CC methodology. From the point of view of DNOs and TSOs, the considered scenarios, without and with wind farms connected (together with the three cases analyzed within the second scenario), cover all of the situations associated with the steady-state of the electrical networks. Of course, the results will be different when new wind farms are connected, but the benefits on the operation of the network with the wind power sources integrated overlapping the coordinated control of the OLTCs will always be positive. The performance associated with the average time computing obtained in the analyzed cases was better compared with the RG-CC (0.24 versus 0.35 s). All results emphasized the effectiveness of the proposed control methodology. The implementation of the proposed methodology can be limited by the following technical features: the OPF module integrated into the software has a fast processing speed, the wide-area communication network has a high-speed data transmission, and the OLTC of the transformer performs quick changing of the taps. The authors now work with an improved variant of the OPF model, which considers a new constraint regarding minimum turns of the tap to avoid the overuse of the contact wear of the OLTC. Moreover, the influence of the changes in the wind generation, which can occur within the time interval associated with the sampling step, and the missing data due to a technical failure at the communication network of the SCADA system, represent another future work to evaluate the impact on the obtained solutions.