Abstract
In this paper, an alternative strategy for real-time control of active distribution network voltage is developed, not by controlling the bus voltage as in the various centralized, decentralized, and local approaches presented in literature but rather by only eliminating the impact produced by active and reactive power of distributed generation (DG) units on the voltage of all network nodes and keeping the traditional voltage control systems dealing with the same constraints of passive systems. In literature, voltage deterioration introduced by DGs has been reported as one of the main obstacles for the interconnection of large amounts of DG units to the existing networks. In this paper, the novel control strategy is based on a sensitivity formula developed to calculate the compensation needed for additional distributed flexible AC transmission system (D-FACTS) devices to push and pull the exact reactive power and to eliminate the impact produced by DGs on the network voltage profile. The criteria of the allocation of the var devices and the required network reinforcement are developed in this paper, considering all possible topology structures, and an innovative codification method is introduced to reduce the needed computation time and communication data to actualize the sensitivity coefficients and get the proposed control approach flexible with network topology reconfiguration. The risk of the conflict of the proposed control system with the traditional voltage equipment is reduced due to the fast capability of D-FACTS devices to regulate their reactive power in finer granularity. A case study of two meshed IEEE 15-bus feeders is introduced to compare the voltage behavior with and without the presence of DG units and to evaluate the total system losses. The proposed method could be used for the interconnection of the first generation units in emerging networks, which does not yet have an active voltage control strategy, as it could be used for DG units not able to be connected to existing centralized control systems and it could also be used as the principal voltage control strategy, with the extension for several neighboring units and the preservation of the traditional voltage control systems.
Highlights
Without the presence of a distributed generation unit in low and medium voltage distribution systems, the network voltage magnitudes fall along the feeders, depending only on cable characteristics and the demanded load at each node [1]
We propose an alternative solution to mitigate the voltage profile in active distribution systems: the suppression of the impact of the active and reactive power produced or consumed by distributed generation units on the network voltage, in a fast way to avoid the risk of any conflict of the proposed tool with the conventional voltage control devices
By the elimination of the impact of a distributed generation (DG) unit on the voltage of some certain nodes, the voltage of all network points will become independent of the small variation of the active and reactive power introduced by the DG unit; an analytical approach based on the work presented in [17] is discussed, with an improvement by considering all the possible network topology structures
Summary
Without the presence of a distributed generation unit in low and medium voltage distribution systems, the network voltage magnitudes fall along the feeders, depending only on cable characteristics and the demanded load at each node [1]. The efforts presented in literature focus on adapting, improving, or even totally changing the traditional devices and systems Those modifications lead to wasting conventional voltage control equipment and methods and to abandoning all the practical experiments and good practices collected over generations by the utility personnel, in terms of network control operation and development. (i) An efficient control strategy able to avoid as much as possible both disconnection and curtailment of distributed generation (ii) A control strategy that saves the traditional voltage regulation equipment and keeps the utility personnel dealing with the same constraints (iii) Ease of implementation, with no need for load demand data or powerful electric meter infrastructure (iv) With the proposed codification method and with no requirement of any load flow analysis, the proposed approach is able to get implemented for real-time application. The changes in voltage at each node will depend on the variation of the two new variables of introduced DG: PDG and QDG, as demonstrated in equation (5): dV1 ⋯ dVi ⋯ dVn dPn+⋯
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