New Topologies for Static Reactive Power Compensator Based on PWM AC Choppers

Abstract

Nowadays, static reactive power control is widely used in electrical power networks. The former solution based on Thyristor Controlled Reactors is progressively replaced by PWM Voltage Source Inverters. The first solution is quite simple but requires bulky shunt passive filters whereas the second solution shows higher semiconductor losses and requires a significant cooling system. In this paper, the authors present new topologies which show a good compromise in comparison to the classical solutions. Single phase AC Choppers are used to achieve controlled impedances (capacitive or inductive) at the fundamental frequency and thus adjust the reactive power level. This concept is applied for medium or high power applications and multi-converter structures based on step down or step up AC choppers are proposed. An example of design concerning reactive power compensation in a 25 kV/50 Hz AC traction line is presented. Finally, experimental results obtained for a 1.2 MVAR prototype demonstrate the feasibility of these novel topologies.