Three-phase static series voltage regulator control algorithms for dynamic sag compensation

Abstract

Momentary interruptions and voltage sags are responsible for many of the power quality problems found in typical industrial plants. A common solution to this problem is the installation of uninterruptible power supplies (UPS). However, these are costly and require maintenance. A cost-effective alternative is the use of static series regulators rated a fraction of the load power. The regulators provide voltage support by injecting a voltage in series with the load. The structure presented in this paper consists in transformer coupled voltage source inverters fed from a diode bridge rectifier converter connected to the AC supply. The paper discusses implementation and control issues. Steady state compensation capability curves are presented. Are proposed control algorithms that ensure a fast dynamic voltage restoration and are insensitive to the type of faults, disturbances and harmonics present on the power network. Performance is illustrated for typical single and three-phase faults. The dynamic performance is verified on DSP based prototype power compensators.