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With the development of urban and rural infrastructure, the power system is enforced to operate nearly at its full capacity which result in heavily stressed power grid operation, greater loss, peak generation, security threat and instability of the electrical network. The performance of the legacy electric network can be enhanced by solving optimal reactive power dispatch (ORPD) problems such as, tuning of the grid voltages, transformers tap setting, capacitor bank rating, allocation and sizing of flexible AC transmission system (FACTS) through computational intelligence tools. In last few decades, several optimization strategies are developed to solve ORPD problems but still research is in progress to leverage the performance of power system. In this line of thought, this paper provides a comprehensive literature of major optimization tools designed for the solution of ORPD problems with aim of improving the power system performance. The purpose of this study is to document up to date information on the optimal reactive power dispatch (ORPD), ORPD incorporating FACTS, mathematical model of ORPD problems with corresponding constraints, mathematical model of FACTS in ORPD, and applications of ORPD. At the end, a new computational tool based on fractional calculus has also been introduced for performance improvement of traditional swarming techniques to support researchers in field of energy/power sector and carry out further research.

Optimal reactive power dispatch (RPD) for reducing the real power losses of the transmission system is one of the paramount concerns for the research community to investigate the efficiency of power systems. In this paper, strength of meta-heuristic computing paradigm based on fractional-order Darwinian particle swarm optimization (FO-DPSO) is exploited for optimization of RPD problems in energy sector. The fitness functions including line loss minimization and voltage deviation (voltage profile index) are constructed to find the optimal reactive power flow for IEEE 30- and 57-bus test systems. The rich heritage of fractional evolutionary computing through variants of FO-DPSO is applied to minimization problem of optimal power flow by determination of control variables in terms of VAR compensators, bus voltages and transformer tap settings. Comparison of the results shows that fractional swarming intelligence outperformed the state-of-the-art counterparts by means of both line loss minimization and voltage deviation. Superiority of the proposed scheme is also validated for different degrees of freedom in the optimal RPD problems.

Reactive power dispatch is a vital problem in the operation, planning and control of power system for obtaining a fixed economic load expedition. An optimal dispatch reduces the grid congestion through the minimization of the active power loss. This strategy involves adjusting the transformer tap settings, generator voltages and reactive power sources, such as flexible alternating current transmission systems (FACTS). The optimal dispatch improves the system security, voltage profile, power transfer capability and overall network efficiency. In the present work, a fractional evolutionary approach achieves the desired objectives of reactive power planning by incorporating FACTS devices. Two compensation arrangements are possible: the shunt type compensation, through Static Var compensator (SVC) and the series compensation through the Thyristor controlled series compensator (TCSC). The fractional order Darwinian Particle Swarm Optimization (FO-DPSO) is implemented on the standard IEEE 30, IEEE 57 and IEEE 118 bus test systems. The power flow analysis is used for determining the location of TCSC, while the voltage collapse proximity indication (VCPI) method identifies the location of the SVC. The superiority of the FO-DPSO is demonstrated by comparing the results with those obtained by other techniques in terms of measure of central tendency, variation indices and time complexity.

Due to increasing power demand, incorporation of prosumers, continuous expansion, competitive market and inherent limitations of alternating current, the management and operation of power system has become very complex. For economical, reliable and secure operation, the use of emerging technologies is unavoidable. Flexible AC transmission system (FACTS) is one of the emerging technologies which does not only solve the problems but also gives new directions in existing high voltage AC (HVAC) and high voltage DC (HVDC) power systems. However, allocation of FACTS controllers i.e., determination of optimal location, size, number and type of these devices with minimized cost is a difficult problem. This paper, in broader sense, discusses FACTS allocation for the solution of issues of power system. The benefits and objectives of optimal allocation of FACTS have been reviewed from view point of objective functions, decision variables, constraints and recent optimization algorithms.