This paper presents a new approach for estimating and improving VOLTAGE stability margin from phase and magnitude PROFILEs of bus VOLTAGEs using sensitivity analysis of VOLTAGE Stability Assessment Neural Network (VSANN). Bus VOLTAGE PROFILE contains useful information about system stability margin including the effect of loadgeneration pattern, line outage and reactive power compensation, so it is adopted as input pattern of VSANN. In fact, VSANN establishes a functionality for VSM with respect to VOLTAGE PROFILE. Sensitivity analysis of VSM with respect to VOLTAGE PROFILE and reactive power compensation extracted from information stored in the weighting factor of VSANN is the most dominant feature of the proposed approach. Sensitivity of VSM helps one to select the most effective buses for reactive power compensation aimed enhancing VSM. The proposed approach has been applied to IEEE 39-bus test system which demonstrated applicability of the proposed approach.

Improving transient VOLTAGE stability is one of the most important issues that must be provided by doubly fed induction generator (DFIG)-based wind farms (WFs) according to the grid code requirement. This paper proposes adjusted DC-link chopper based passive VOLTAGE compensator and modified transient VOLTAGE controller (MTVC) based active VOLTAGE compensator for improving transient VOLTAGE stability. MTVC is a controller-based approach, in which by following a VOLTAGE dip (VD) condition, the VOLTAGE stability for the WF can be improved. In this approach, a VOLTAGE dip index (VDI) is proposed to activate/deactivate the control strategy, in which, two threshold values are used. In the active mode, the active and reactive power are changed to decrease the rotor current and boost the PCC VOLTAGE, respectively. Based on the control strategy, in a faulty grid, DFIG not only will be able to smooth DC-link VOLTAGE fluctuations and reduces rotor overcurrents but also it will increase the VOLTAGE of point of common coupling (PCC). Therefore, it improves transient VOLTAGE stability. The simulation results show the effectiveness of the proposed strategy for improving VOLTAGE stability in the DFIG.

Distributed Generations (DGs) are utilized to supply the active and reactive power in the transmission and distribution systems. These types of power sources have many benefits such as power quality enhancement, VOLTAGE deviation reduction, power loss reduction, load shedding reduction, reliability improvement, etc. In order to reach the above benefits, the optimal placement and sizing of DG is significant. In this regard, this paper gets use of the Bacteria Foraging Algorithm (BFA) and Binary Genetic Algorithm (BGA) to investigate the DG placement with the purpose of power loss and VOLTAGE deviation reduction. The proposed method is applied on the 33-bus and 69-bus IEEE test systems and the optimal place and size of DGs from the power losses and VOLTAGE deviation minimization are assessed. Also, the performance of the above two algorithms are compared with each other.

The use of photovoltaic-static compensators (PV-STATCOM) to improve the system VOLTAGE PROFILE has recently received much attention. This paper proposes coordinated control of multiple PV-STATCOM systems using fuzzy logic. The main feature of the proposed controller is that it can be operated in different modes: full-PV, partial-STATCOM and full-STATCOM in both capacitive and inductive compensation. In this strategy, when a disturbance occurs, depending on its severity, one or more PV-STATCOM systems go to the partial-STATCOM or full-STATCOM modes to optimize the reactive power compensation at the load bus. Then, after fixing the problem, the system returns to the full-PV power generation mode. To evaluate the system performance, different operating conditions were simulated with EMTDC/PSCAD software. The results confirm that the proposed fuzzy controller can improve the VOLTAGE PROFILE dynamics.

Nowadays, energy supplied by the reliable manner is one of the important challenges of the distribution company in the radial distribution system. Therefore, this paper considers these challenges by the optimal DG placement to minimize power losses with considering the analysis related to the reliability and VOLTAGE PROFILE. In this paper, exchange market algorithm (EMA) is used as a powerful tool to solve the optimization problem. In order to extract the global optimum point, EMA uses two searching operators and two absorbent operators based on the generation of random numbers. To evaluate the goals of this paper, EMA is successfully implemented on 10, 33, and 69 bus IEEE test systems. Simulation results have illustrated that power losses are reduced by the optimal DG placement and size. Finally, the analysis of obtained results has shown the system’ s reliability; VOLTAGE PROFILE can be improved if the DGs are allocated optimally in the radial network.