100 Years of Symmetrical Components

Abstract

28 June 2018 was the 100th anniversary of the first presentation on symmetrical components made by Charles LeGeyt Fortescue at the 34th Annual Convention of the American Institute of the Electrical Engineers in Atlantic City (NJ, USA). The introduction of the symmetrical component concept was immediately seen as a milestone for electrical system studies, and many applications have been developed during the ensuing years. Today, refined or advanced contributions to conceptual and practical aspects of electrical applications are still being proposed based on the powerful structure of symmetrical components. This paper recalls the most significant steps made in the electrical engineering field after the introduction of the symmetrical component theory, and indicates recent developments concerning the studies on electrical machines, harmonics and interharmonics in different applications, and the operation of power and distribution systems with distributed energy resources.

Optimal Network Reconfiguration in Active Distribution Networks with Soft Open Points and Distributed Generation

“…Traditionally, power loss was minimized via several methods, such as using power quality (PQ) devices to enhance the PQ performance of a system by limiting inefficiencies in the way power is transferred and reducing harmonic distortion, which results in increased loss in distribution networks [4]; reducing network imbalance, as an unbalanced power system will have higher currents in one or more phases compared to balanced power systems [5]; improving power factor (PF), where low PF circuits suffer from a significant increase in current at the same power delivered [6]; configuring power system networks to provide a flexible framework to transfer electrical loads between feeders, resulting in minimized loss and improved balancing of loads [7]; upgrading networks to higher voltage levels, while expanding reinforcement plans to guarantee significant loss savings [8,9]; considering enhanced demand response programs to reschedule energy usage and improve the reliability and efficiency of electrical networks, and consequently reduce losses [10]; and allocating DG units and power electronic devices in the distribution network [11] to control power delivery between interlinked feeders and reduce power loss efficiently. However, it is prudent to ensure that DGs or electronic devices are optimally sized and connected to suitable locations in power systems to take full advantage of their positive benefits [1,7].…”

“…The reactive power limits [16] are given in (5) and the SOP capacity limit [16] is shown in (6). Thus:…”

“…In addition to the radiality requirements described in Section 2. A, power flow equality given in (4), SOP reactive power limits given in (5), SOP capacity limit given in (6), SOP active power loss given in (8), DG capacity limit given in (11) for the first type and (12) for the second type, and DG reactive power limits given in (13), the following constraints regarding voltage magnitudes, lines thermal capacities and the total reactive power injected by DGs and/or SOPs into the system are expressed, respectively, as follows:…”

“…The IEEE 33-node base configuration consists of 32 sectionalized lines and 5 tie-lines as shown in Figure 3. The number of SOPs that can be installed ranges from 1 to 5, i.e., N SOP ∈ [1,5] First, the results obtained for the system in the first three scenarios with no SOPs installed are given in Table 2. On the one hand, the results clarify that optimizing the NR and DGs allocation strategies separately cannot satisfy the voltage requirements in either the normal or heavy loading conditions, and only a sub-optimal performance can be achieved in the light loading case.…”

“…In order to validate the effectiveness of Scenario 9 proposed in this work, it was examined on an 83-node balanced distribution system from a power company in Taiwan, in which the 83-node base configuration consisted of 83 sectionalized lines and 13 tie-lines, as shown in Figure 7. The number of SOPs that can be installed ranges from 1 to 5, i.e., N SOP ∈ [1,5], where the individual SOP rating (S SOP I = S SOP J ) is 1.5 MVA and A SOP loss equals 0.02 [33,40,41]. N DG is set to 8 with S DG equal to 3 MVA and PF ranges from 0.95 lagging to unity.…”