A Novel Switching Methodology for Low Voltage Static Regulators

Abstract

This paper presents a new switching methodology for low voltage static regulators. The switching method proposed in this paper differs from those found in the literature due to it not needing a measurement of the current signal in the transformer tap windings and/or in the static switches. This method simplifies the control, reduces the cost of implementation, and allows safe application onto grids with low loading and high harmonic current distortion. In order to analyze and evaluate the performance of the proposed methodology, the static voltage regulator presented in this article was implemented in a computer simulation and, later, a laboratory prototype was built. The topology, the operational principles, and the specifications of its constituent components are discussed and presented in this paper. In addition, the prototype of the equipment was tested under three different load conditions: operating under no-load conditions, supplying a purely resistive load and supplying a nonlinear load. For each of the three types of loads considered, the static voltage regulator’s performance was evaluated using specific measurements, which considered the occurrence of both long and short duration voltage variations imposed on the input of the equipment by a programmable power source. The obtained results show that—in the worst-case scenario—the tap changing process takes less than 4 cycles of the fundamental frequency to be concluded. In light of the obtained performance, the proposed switching methodology for low voltage static regulators is a promising solution for large scale use under varied applications.

Keywords

• Static voltage regulator
• on-load tap changing
• long duration voltage variations
• short duration voltage variations
• power quality