Elimination of the Impact Produced by DG Units on the Voltage Profile of Distribution Networks

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.

Active Power Management for PV Systems under High Penetration Scenario

“…In recent years, different techniques associated with voltage regulation and control methods to mitigate the effect of high PV penetration have been proposed. These solutions include studies to determine the maximum loads connected to the grid [23], grid layout and loads residential design [24], variable tap transformers [25] and smart transformers applications [26], battery bank systems [27][28][29], inverters with reactive power capability [30][31][32][33], and the interconnectivity of external devices with the grid as smart electrical vehicles [34]. Additionally, the theoretical use of a communication network that allows making decisions based on grid variations has been suggested [35].…”

“…Inverters with reactive power capability are an interesting option [30][31][32][33]; however, the main disadvantages are not only the increase in the inverter nominal power to offer good performance but also an increment in the grid power losses and in the semiconductor stress, which entails a reduction in the useful life of the inverter.…”

“…In [31,32], a static reactive power compensator is suggested and an analysis to select the best connection point is detailed. The main drawback of this work is that the proposal is no longer valid if the grid parameters change, like new loads and distribution transformer replacements.…”

“…In terms of cost (including power devices and controllers), it can be observed in Table 3 that the two best alternatives use a smart inverter with reactive power compensation [30][31][32][33] and the proposed strategy in this work. This is because no extra elements or devices or modifications on the infrastructure are required, just software modifications.…”