Robust tuning of power system stabilizer for small signal stability enhancement using metaheuristic bat algorithm

CIGRE WG C4.605 : “Modelling and aggregation of loads in flexible power networks”

A comprehensive review of dynamic voltage restorers

The parameters of electrical energy such as voltage amplitude are very important, particularly from the viewpoint of the final consumer and sensitive loads connected to the grid. The dynamic states in the power grid-deep voltage sags and swells-might cause faults and defects in sensitive loads. This paper deals with a three-phase hybrid transformer (HT) without dc energy storage to compensate voltage sags and swells and to protect sensitive loads against the rapid and extensive changes in supply voltage amplitude. The analyzed HT contains two main units: the first one is the conventional electromagnetic transformer, realizing an electromagnetic coupling, and the second one is the buck-boost matrix-reactance chopper, realizing an electrical coupling in the HT unit. In the presented solution, output voltage is transformed in two ways-electromagnetically and electrically. This paper presents an operational description, the theoretical analysis, and the experimental test results from a 2-kVA laboratory model. On the basis of the authors' research, it can be stated that the HT makes it possible to compensate deep voltage sags (deeper than 50% of nominal source voltage) and overvoltages (up to 140% of nominal source voltage) while maintaining good dynamic properties. The main advantages of the proposed solution, in comparison to other conventional solutions, are the ability to control the output voltage in the range of 0.66-3.5 US, good dynamics (transient state during source voltage uS amplitude change is shorter than 10 ms), and galvanic separation between source and load (such as in the case of the conventional electromagnetic transformer).

AC Voltage Sag/Swell Compensator Based on Three-Phase Hybrid Transformer With Buck-Boost Matrix-Reactance Chopper

Dynamic genetic algorithms for robust design of multimachine power system stabilizers

This paper analyzes the structure of an 84-pulse voltage source converter (VSC), assembled by combining one twelve-pulse VSC, in conjunction with an asymmetric singlephase seven-level converter plus an injection transformer. With this arrangement, the VSC output's total harmonic distortion in voltages is reduced, allowing it to be used in especial applications or as the basement of flexible A.C. transmission systems (FACTS) devices. The proposed strategy allows savings in the number of employed switches. Simulations and experimental results are provided to show the proposal appropriateness.

Rosa E. Correa

Papers

A new 84-pulse VSC configuration using multi-level DC voltage reinjection for especial applications