UPFC is considered and known as one of the best FACTS devices. It is a combination of series and parallel quick compensation, and can therefore provide active and reactive control to achieve maximum power transfer, system stability and improve power quality and reliability. Therefore, presenting a suitable model for UPFC which enables studying the network and load flow in energy transmission lines, has gotten the experts' attention. This paper presents a new model of UPFC in steady state based on circuit elements in an exact transmission line model. Considering the fact that the elements like UJT and tunnel diode in negative resistance region cause power increase, the model determines the value of the active and reactive power injected by the series converter into the network, and then the series converter of UPFC is simulated by means of a negative resistor and an induction or capacitor reactance. Resistance and reactance are expressed as functions of voltage of buses, load angle, voltage injection and fire angle of series converter. The relations of this model have been achieved in a two-bus system and have been simulated in 14and 30-bus standard.
Reactive power dispatch (RPD) is an optimization problem that determines variables, such as reactive power outputs of generators, output of shunt capacitors/reactors, etc., and minimizes the transmission losses, satisfying a given set of constraints. To solve the optimal reactive power dispatch (ORPD), this article proposes a new method, called hybrid multiagent-based particle swarm optimization, which does not allow the search to struck at local optima and search in different zones of the search space. Simulation results show that the proposed approach converges to better solutions faster than the earlier approaches when evaluated on IEEE 30-bus and IEEE 118-bus systems.
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