New method for calculating the susceptances of a balancing capacitive compensator for a three-phase four-wire distribution network

摘要

Nowadays, there is an increasing development of equipment type Custom Power Devices (CPDs) designed to ensure a high level of electrical power quality at the Point of Common Coupling (PCC). Most of these devices are built as advanced power electronics applications, such as the Switching Power Converters (SPCs) category. However, for a wide range of applications in consumer installations and electricity distribution operators, such as power factor correction, load balancing, voltage regulation, or flicker mitigation, the reactive power compensators based on passive circuit elements, Reactive Power Compensators (RPCs) are successfully used. The most efficient RPCs are those built so that they may adapt to variable regimes, known as Static Var Compensators (SVCs). Two of the usual functions of a SVC, namely power factor improvement and load balancing in a three-phase distribution network, can be achieved simultaneously by using an unbalanced SVC built in the version of Adaptive Balancing Reactive Compensator (ABRC). The paper briefly-outlines the mathematical model and operation of a Balancing Reactive Compensator (BRC) for a three-phase four-wire network. Then, moves on to develop a direct method of sizing based on equations that directly link the susceptances' values of the compensator with the real and imaginary components of load sequence currents. The problem is to determine the weight of these components, meaning their degree of compensation, by requiring only capacitive or null susceptances and avoiding capacitive over-compensation of positive sequence currents. Thus, a particular case of BRC, i.e. a Balancing Capacitive Compensator (BCC) is obtained, which keeps the same functions, but has the advantage of reducing costs by eliminating high-power single-phase coils and by simplifying the compensation control system. The paper also presents the numerical results and the conclusions of a case study on the application of the method, performed using two computational and modeling software tools. Experimental laboratory determinations and modeling under nonsinusoidal conditions complete the analysis. The results demonstrate the correctness of the new method of solving the sizing problem and once again validate the unbalanced capacitive compensation as an efficient method of power factor improvement and load balancing at a PCC belonging to a three-phase four-wire distribution network.